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Monegro R, Graham SR, Steele J, Robertson ML, Henderson JA. Hands-On Activity Illustrating the Sorting Process of Recycled Waste and Its Role in Promoting Sustainable Solutions. J Chem Educ 2024; 101:1899-1904. [PMID: 38764940 PMCID: PMC11097386 DOI: 10.1021/acs.jchemed.3c01128] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 11/04/2023] [Revised: 02/20/2024] [Accepted: 02/22/2024] [Indexed: 05/21/2024]
Abstract
Effective recycling is not merely a matter of collecting waste; it also requires meticulous categorization to maximize the potential for reusing material and minimizing waste sent to landfills. Education and awareness of the sorting and recycling process bottlenecks need to be emphasized and extended beyond higher educational contexts (e.g., in multiple stages of educational pathways, such as middle or high school). Hence, this project introduces a hands-on plastic sorting activity where students use recycled waste to be sorted based on their physical properties. Several tools were provided to perform the separation, such as water, sieves, magnets, and manual/visual separation while considering the time and cost associated with each tool. The activity was evaluated by pre- and post-evaluations based on Likert-scale and open-ended questions grouped in several categories related to the sorting process. In several categories, we observed that the activity enhanced student knowledge (e.g., general sorting understanding), while in other categories, there was no growth. From open-ended questions, students expressed an understanding of how to sort recycled waste and an appreciation for the trade-offs in developing sorting solutions. This activity effectively enhanced students' awareness of the sorting process of recycled waste. It lays the foundation for future inquiry and outreach project design.
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Affiliation(s)
- Ronard
Herrera Monegro
- William
A. Brookshire Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204, United States
| | - Savannah R. Graham
- William
A. Brookshire Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204, United States
| | - Jaiah Steele
- Texas
A&M College of Engineering, College
Station, Texas 77843, United States
| | - Megan L. Robertson
- William
A. Brookshire Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204, United States
| | - Jerrod A. Henderson
- William
A. Brookshire Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204, United States
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2
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Hansgen JP, Robertson ML, Verzino EM, Manning LM. Increasing Naloxone Access and Prescribing for Patients on High-Dose Opioids From a Managed Care Pharmacy Health Plan Perspective. J Pharm Pract 2024:8971900241247598. [PMID: 38685768 DOI: 10.1177/08971900241247598] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/02/2024]
Abstract
Background: Opioid overdoses decrease when communities have access to naloxone. Clinicians play a key role in offering naloxone to high-risk chronic opioid patients. Managed care pharmacists within our health plan noted disproportionate processing for claims of opioid utilizers compared to claims of naloxone prescriptions. Objective: To increase naloxone access and prescribing to members who classify at a dosage with a higher risk for opioid overdose, defined as over 90 morphine milligram equivalents (MME). Methods: Multiple system-wide initiatives were implemented to improve naloxone access. A claims file was pulled monthly to identify members on opioids meeting MME criteria >90 MME per day excluding members with cancer, sickle cell disease, or on hospice. A separate report was then matched to naloxone claims and prescribing percentages calculated. Results: 12 444 utilizing members on opioids were identified from June 2019 prescription claims data. Of these, 131 were on opioids exceeding 90 MME per day, or 1.05% of utilizers, and the percentage of members exceeding 90 MME per day prescribed naloxone was 6.87%. By May 2023, the percentage of opioid utilizers exceeding 90 MME per day decreased to 0.58%. Naloxone prescribing increased to 41.18%. Conclusion: A multi-pronged approach to improve access to naloxone and continued educational efforts by our health plan increased naloxone prescribing in members on opioids exceeding 90 MME per day.
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Affiliation(s)
- Jodi P Hansgen
- Pharmacy Services, Baylor Scott & White Health Plan, Temple, TX, USA
| | - Megan L Robertson
- Pharmacy Services, Baylor Scott & White Health Plan, Temple, TX, USA
| | - Ellen M Verzino
- Pharmacy Services, Baylor Scott & White Health Plan, Temple, TX, USA
| | - Lindsay M Manning
- Pharmacy Services, Baylor Scott & White Health Plan, Temple, TX, USA
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3
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Ammar A, Smith JD, Aslan U, Balan V, Robertson ML, Karim A. Pressure Indicator Composite Films via Compressive Deformation of a Translucent Matrix Containing a Contrasting Filler. ACS Appl Mater Interfaces 2024; 16:19432-19441. [PMID: 38588483 DOI: 10.1021/acsami.3c18380] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/10/2024]
Abstract
A neglected mechanism for pressure-responsive color change is demonstrated using cellulose acetate composites prepared by direct (solvent) immersion annealing (DIA), with different loadings of activated charcoal filler. Namely, compressive plastic deformation of the translucent cellulose acetate leads to a decrease in the optical path length and a concomitant increase in the visibility of the opaque contrasting filler. Composites bearing 1-7 wt% activated charcoal exhibited a linear relationship between applied pressure and resulting pressure mark brightness in the range of 12-56 MPa. Comparison of pressure mark patterns with cross-sectional scanning electron microscopy (SEM) supports the importance of the porous morphology arising from DIA for the tuning of the pressure indicator sensitivity. A simple ball drop test is used to illustrate the robustness and utility of these indicators in optical impact assessment.
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Affiliation(s)
- Ali Ammar
- William A. Brookshire Department of Chemical and Biomolecular Engineering, Cullen College of Engineering, University of Houston, Houston, Texas 77204, United States
| | - Justin D Smith
- William A. Brookshire Department of Chemical and Biomolecular Engineering, Cullen College of Engineering, University of Houston, Houston, Texas 77204, United States
| | - Ugur Aslan
- William A. Brookshire Department of Chemical and Biomolecular Engineering, Cullen College of Engineering, University of Houston, Houston, Texas 77204, United States
| | - Venkatesh Balan
- Department of Engineering Technology, Cullen College of Engineering, University of Houston, Sugarland, Texas 77479, United States
| | - Megan L Robertson
- William A. Brookshire Department of Chemical and Biomolecular Engineering, Cullen College of Engineering, University of Houston, Houston, Texas 77204, United States
| | - Alamgir Karim
- William A. Brookshire Department of Chemical and Biomolecular Engineering, Cullen College of Engineering, University of Houston, Houston, Texas 77204, United States
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4
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Qiu J, Chen X, Le AN, López-Barrón CR, Rohde BJ, White RP, Lipson JEG, Krishnamoorti R, Robertson ML. Thermodynamic Interactions in Polydiene/Polyolefin Blends Containing Diverse Polydiene and Polyolefin Units. Macromolecules 2023. [DOI: 10.1021/acs.macromol.2c01866] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/09/2023]
Affiliation(s)
- Jialin Qiu
- William A. Brookshire Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204, United States
| | - Xuejian Chen
- William A. Brookshire Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204, United States
| | - Amy N. Le
- William A. Brookshire Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204, United States
| | | | - Brian J. Rohde
- ExxonMobil Technology and Engineering Company, Baytown, Texas 77520, United States
| | - Ronald P. White
- Department of Chemistry, Dartmouth College, Hanover, New Hampshire 03755, United States
| | - Jane E. G. Lipson
- Department of Chemistry, Dartmouth College, Hanover, New Hampshire 03755, United States
| | - Ramanan Krishnamoorti
- William A. Brookshire Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204, United States
| | - Megan L. Robertson
- William A. Brookshire Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204, United States
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5
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Conrad JC, Robertson ML. Shaping the Structure and Response of Surface-Grafted Polymer Brushes via the Molecular Weight Distribution. JACS Au 2023; 3:333-343. [PMID: 36873679 PMCID: PMC9975839 DOI: 10.1021/jacsau.2c00638] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/22/2022] [Revised: 01/17/2023] [Accepted: 01/18/2023] [Indexed: 05/31/2023]
Abstract
Breadth in the molecular weight distribution is an inherent feature of synthetic polymer systems. While in the past this was typically considered as an unavoidable consequence of polymer synthesis, multiple recent studies have shown that tailoring the molecular weight distribution can alter the properties of polymer brushes grafted to surfaces. In this Perspective, we describe recent advances in synthetic methods to control the molecular weight distribution of surface-grafted polymers and highlight studies that reveal how shaping this distribution can generate novel or enhanced functionality in these materials.
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6
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Khakzad F, Dewangan NK, Li TH, Safi Samghabadi F, Herrera Monegro R, Robertson ML, Conrad JC. Fouling Resistance and Release Properties of Poly(sulfobetaine) Brushes with Varying Alkyl Chain Spacer Lengths and Molecular Weights. ACS Appl Mater Interfaces 2023; 15:2009-2019. [PMID: 36533943 DOI: 10.1021/acsami.2c16417] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
We examined the effects of alkyl carbon spacer length (CSL) and molecular weight on fouling resistance and release properties of zwitterionic poly(sulfobetaine methacrylate) brushes. Using surface-initiated atom transfer radical polymerization, we synthesized two series of brushes with CSL = 3 and 4 and molecular weight from 19 to 1500 kg ·mol-1, corresponding to dry brush thickness from around 6 to 180 nm. The brush with CSL = 3 was nearly completely wet with water (independent of molecular weight), whereas the brush with CSL = 4 exhibited a strong increase in water contact angle with molecular weight. Though the two-brush series had distinct wetting properties, both series of brushes exhibited similarly great resistance against fouling by Staphylococcus epidermidis bacteria and Aspergillus niger fungi spores when submerged in water, indicating that neither molecular weight nor CSL strongly affected the antifouling behavior. We also compared the efficacy of brushes against fouling by fungi and silicon oil in air. Brushes grafted to filter paper were strongly fouled by fungi and silicon oil in air. Grafting the polymers to the filter paper, however, greatly enhanced removal of the foulant upon rinsing. The removal of fungi and silicon oil when rinsed with a salt solution was enhanced by 219 and 175%, respectively, as compared to a blank filter paper control. Thus, our results indicate that these zwitterionic brushes can promote foulant removal for dry applications in addition to their well-known fouling resistance in submerged conditions.
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Affiliation(s)
- Fahimeh Khakzad
- William A. Brookshire Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas77204, United States
| | - Narendra K Dewangan
- William A. Brookshire Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas77204, United States
| | - Tzu-Han Li
- William A. Brookshire Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas77204, United States
| | - Farshad Safi Samghabadi
- William A. Brookshire Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas77204, United States
| | - Ronard Herrera Monegro
- William A. Brookshire Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas77204, United States
| | - Megan L Robertson
- William A. Brookshire Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas77204, United States
| | - Jacinta C Conrad
- William A. Brookshire Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas77204, United States
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7
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Ding W, Hanson J, Burghardt WR, López-Barrón CR, Robertson ML. Shear Alignment Mechanisms of Close-Packed Spheres in a Bulk ABA Triblock Copolymer. Macromolecules 2022. [DOI: 10.1021/acs.macromol.2c01245] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Wenyue Ding
- William A. Brookshire Department of Chemical & Biomolecular Engineering, University of Houston, Houston, Texas 77204-4004, United States
| | - Josiah Hanson
- William A. Brookshire Department of Chemical & Biomolecular Engineering, University of Houston, Houston, Texas 77204-4004, United States
| | - Wesley R. Burghardt
- Department of Chemical and Biological Engineering, Northwestern University, Evanston, Illinois,60208, United States
| | | | - Megan L. Robertson
- William A. Brookshire Department of Chemical & Biomolecular Engineering, University of Houston, Houston, Texas 77204-4004, United States
- Department of Chemistry, University of Houston, Houston, Texas 77204-4004, United States
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8
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Abstract
We show that dispersity (D̵) markedly alters the conformation of spherical polymer brushes. The average lengths (lb) of poly(tert-butyl acrylate) (PtBA) brushes of varying D̵ grafted to nanoparticles were measured using dynamic light scattering. In the semidilute polymer brush (SDPB) regime, the lb of PtBA and polymers from earlier studies of various D̵ could be cleanly collapsed onto a master curve as a function of the scaling variable Nwσ1/3, where Nw is the weight-average degree of polymerization and σ is the grafting density. In the concentrated polymer brush (CPB) regime, however, lb collapsed onto a bifurcated curve as a function of the scaling variable Nwσ1/2, indicating D̵ more strongly affects the average length of brushes with low Nwσ1/2. We propose that the stretching of the stem near the particle surface due to interchain interactions in the CPB regime leads to greater lb in broad dispersity brushes of low but not high Nwσ1/2.
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Affiliation(s)
- Tzu-Han Li
- Materials Science and Engineering Program, University of Houston, Houston, Texas 77204, United States
| | - Vivek Yadav
- William A. Brookshire Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204, United States
| | - Jacinta C. Conrad
- William A. Brookshire Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204, United States
| | - Megan L. Robertson
- William A. Brookshire Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204, United States
- Department of Chemistry, University of Houston, Houston, Texas 77204, United States
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9
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Abstract
The pH-dependence of the conformation of annealed polyelectrolyte brushes can be tuned by varying the molecular weight distribution, as characterized via weight-average molecular weight and dispersity.
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Affiliation(s)
- Tzu-Han Li
- Materials Science and Engineering Program, University of Houston, Houston, Texas 77204, USA
| | - Megan L. Robertson
- William A. Brookshire Department of Chemical Engineering, University of Houston, Houston, Texas, 77204, USA
- Department of Chemistry, University of Houston, Houston, Texas 77204, USA
| | - Jacinta C. Conrad
- William A. Brookshire Department of Chemical Engineering, University of Houston, Houston, Texas, 77204, USA
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10
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Shen M, Vijjamarri S, Cao H, Solis K, Robertson ML. Degradability, thermal stability, and high thermal properties in spiro polycycloacetals partially derived from lignin. Polym Chem 2021. [DOI: 10.1039/d1py01017d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Spiro polycycloacetals were synthesized from vanillin and syringaldehyde, along with high-performance co-monomers, exhibiting high glass transition temperatures and thermal stabilities, and rapid rates of hydrolysis in acidic solutions.
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Affiliation(s)
- Minjie Shen
- William A. Brookshire Department of Chemical and Biomolecular Engineering, University of Houston, Houston, TX, 77204, USA
| | - Srikanth Vijjamarri
- William A. Brookshire Department of Chemical and Biomolecular Engineering, University of Houston, Houston, TX, 77204, USA
| | - Hongda Cao
- William A. Brookshire Department of Chemical and Biomolecular Engineering, University of Houston, Houston, TX, 77204, USA
| | - Karla Solis
- William A. Brookshire Department of Chemical and Biomolecular Engineering, University of Houston, Houston, TX, 77204, USA
| | - Megan L. Robertson
- William A. Brookshire Department of Chemical and Biomolecular Engineering, University of Houston, Houston, TX, 77204, USA
- Department of Chemistry, University of Houston, Houston, TX 77204, USA
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11
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Qiu J, Chen X, López-Barrón CR, Rohde BJ, Robertson ML, Krishnamoorti R. Effect of Copolymer Composition on Thermodynamic Interactions in Blends Containing a Diene–Olefin Copolymer and a Polyolefin. Macromolecules 2020. [DOI: 10.1021/acs.macromol.0c01659] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Jialin Qiu
- Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204, United States
| | - Xuejian Chen
- Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204, United States
| | | | - Brian J. Rohde
- ExxonMobil Chemical Company, Baytown, Texas 77520, United States
| | - Megan L. Robertson
- Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204, United States
| | - Ramanan Krishnamoorti
- Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204, United States
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12
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Abstract
The production of thermoset polymers is increasing globally owing to their advantageous properties, particularly when applied as composite materials. Though these materials are traditionally used in more durable, longer-lasting applications, ultimately, they become waste at the end of their usable lifetimes. Current recycling practices are not applicable to traditional thermoset waste, owing to their network structures and lack of processability. Recently, researchers have been developing thermoset polymers with the right functionalities to be chemically degraded under relatively benign conditions postuse, providing a route to future management of thermoset waste. This review presents thermosets containing hydrolytically or solvolytically cleavable bonds, such as esters and acetals. Hydrolysis and solvolysis mechanisms are discussed, and various factors that influence the degradation rates are examined. Degradable thermosets with impressive mechanical, thermal, and adhesion behavior are discussed, illustrating that the design of material end-of-life need not limit material performance.
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Affiliation(s)
- Minjie Shen
- Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204-4004, USA;
| | - Hongda Cao
- Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204-4004, USA;
| | - Megan L Robertson
- Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204-4004, USA;
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13
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Liu M, Rohde BJ, Krishnamoorti R, Robertson ML, Dawood M. Bond behavior of epoxy resin–polydicyclopentadiene phase separated interpenetrating networks for adhering carbon fiber reinforced polymer to steel. POLYM ENG SCI 2019. [DOI: 10.1002/pen.25264] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Affiliation(s)
- Meng Liu
- Department of Civil and Environmental Engineering University of Houston Houston Texas 77204‐4004
| | - Brian J. Rohde
- Department of Chemical and Biomolecular Engineering University of Houston Houston Texas 77204‐4004
| | - Ramanan Krishnamoorti
- Department of Chemical and Biomolecular Engineering University of Houston Houston Texas 77204‐4004
| | - Megan L. Robertson
- Department of Chemical and Biomolecular Engineering University of Houston Houston Texas 77204‐4004
| | - Mina Dawood
- Department of Civil and Environmental Engineering University of Houston Houston Texas 77204‐4004
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14
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Rohde BJ, Culp TE, Gomez ED, Ilavsky J, Krishnamoorti R, Robertson ML. Nanostructured Thermoset/Thermoset Blends Compatibilized with an Amphiphilic Block Copolymer. Macromolecules 2019. [DOI: 10.1021/acs.macromol.8b02061] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Brian J. Rohde
- Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77004, United States
| | - Tyler E. Culp
- Department of Chemical Engineering and the Materials Research Institute, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Enrique D. Gomez
- Department of Chemical Engineering and the Materials Research Institute, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Jan Ilavsky
- Advanced Photon Source, Argonne National Laboratory, 9700 S Cass Avenue, Argonne, Illinois 60439, United States
| | - Ramanan Krishnamoorti
- Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77004, United States
| | - Megan L. Robertson
- Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77004, United States
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15
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16
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Shen M, Almallahi R, Rizvi Z, Gonzalez-Martinez E, Yang G, Robertson ML. Accelerated hydrolytic degradation of ester-containing biobased epoxy resins. Polym Chem 2019. [DOI: 10.1039/c9py00240e] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Biobased epoxy resins, derived from lignin, phenolic acids, and vegetable oils, exhibited rapid degradation through hydrolysis in basic solution.
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Affiliation(s)
- Minjie Shen
- Department of Chemical and Biomolecular Engineering
- University of Houston
- Houston
- USA
| | - Rawan Almallahi
- Department of Chemical and Biomolecular Engineering
- University of Houston
- Houston
- USA
| | - Zeshan Rizvi
- Department of Chemical and Biomolecular Engineering
- University of Houston
- Houston
- USA
- Houston Community College
| | - Eliud Gonzalez-Martinez
- Department of Chemical and Biomolecular Engineering
- University of Houston
- Houston
- USA
- Houston Community College
| | - Guozhen Yang
- Department of Chemical and Biomolecular Engineering
- University of Houston
- Houston
- USA
| | - Megan L. Robertson
- Department of Chemical and Biomolecular Engineering
- University of Houston
- Houston
- USA
- Department of Chemistry
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17
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Affiliation(s)
- Xiuli Li
- Department of Chemistry and Macromolecules Innovation Institute, Virginia Tech, Blacksburg, Virginia 24061, United States
| | - Tyler J. Cooksey
- Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77004, United States
| | - Bryce E. Kidd
- Department of Chemistry and Macromolecules Innovation Institute, Virginia Tech, Blacksburg, Virginia 24061, United States
| | - Megan L. Robertson
- Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77004, United States
| | - Louis A. Madsen
- Department of Chemistry and Macromolecules Innovation Institute, Virginia Tech, Blacksburg, Virginia 24061, United States
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18
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Qiu J, Mongcopa KI, Han R, López-Barrón CR, Robertson ML, Krishnamoorti R. Thermodynamic Interactions in a Model Polydiene/Polyolefin Blend Based on 1,2-Polybutadiene. Macromolecules 2018. [DOI: 10.1021/acs.macromol.7b02181] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Jialin Qiu
- Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204, United States
| | - Katrina I. Mongcopa
- Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204, United States
| | - Ruixuan Han
- Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204, United States
| | | | - Megan L. Robertson
- Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204, United States
| | - Ramanan Krishnamoorti
- Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204, United States
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19
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Yadav V, Hashmi N, Ding W, Li TH, Mahanthappa MK, Conrad JC, Robertson ML. Dispersity control in atom transfer radical polymerizations through addition of phenylhydrazine. Polym Chem 2018. [DOI: 10.1039/c8py00033f] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Phenylhydrazine is an effective modifier for conventional ATRP syntheses, providing systematic control over the dispersity of polymers with unimodal molecular weight distributions.
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Affiliation(s)
- Vivek Yadav
- Department of Chemical and Biomolecular Engineering
- University of Houston
- Houston
- USA
| | - Nairah Hashmi
- Department of Chemical and Biomolecular Engineering
- University of Houston
- Houston
- USA
| | - Wenyue Ding
- Department of Chemical and Biomolecular Engineering
- University of Houston
- Houston
- USA
| | - Tzu-Han Li
- Materials Engineering Program
- University of Houston
- Houston
- USA
| | - Mahesh K. Mahanthappa
- Department of Chemical Engineering and Materials Science
- University of Minnesota
- Minneapolis
- USA
| | - Jacinta C. Conrad
- Department of Chemical and Biomolecular Engineering
- University of Houston
- Houston
- USA
| | - Megan L. Robertson
- Department of Chemical and Biomolecular Engineering
- University of Houston
- Houston
- USA
- Department of Chemistry
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20
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Yadav V, Jaimes-Lizcano YA, Dewangan NK, Park N, Li TH, Robertson ML, Conrad JC. Tuning Bacterial Attachment and Detachment via the Thickness and Dispersity of a pH-Responsive Polymer Brush. ACS Appl Mater Interfaces 2017; 9:44900-44910. [PMID: 29215264 DOI: 10.1021/acsami.7b14416] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
We investigated the effect of two brush parameters, thickness and dispersity in the molecular weight distribution, on the adhesion of bacteria to pH-responsive poly(acrylic acid) (PAA) brushes synthesized using surface-initiated atom transfer radical polymerization. The attachment and detachment of Staphylococcus epidermidis to PAA brushes at pH 4 and pH 9, respectively, were examined with confocal microscopy. An optimal range of brush thickness, 13-18 nm, was identified for minimizing bacterial adhesion on PAA brushes at pH 4, and bacterial attachment did not depend on the brush dispersity. Increasing either the brush thickness or dispersity detached bacteria from the brushes when the pH was increased from 4 to 9. Bacterial detachment likely arose from an enhanced actuation effect in thick or high-dispersity brushes, as PAA brushes change conformation from collapsed to extended states when the pH is increased from 4 to 9. These results suggest that manipulating the molecular weight distribution provides a route to separately tune the attachment and detachment of bacteria.
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Affiliation(s)
- Vivek Yadav
- Department of Chemical and Biomolecular Engineering, ‡Department of Chemistry, and §Materials Engineering Program, University of Houston , Houston, Texas 77204, United States
| | - Yuly Andrea Jaimes-Lizcano
- Department of Chemical and Biomolecular Engineering, ‡Department of Chemistry, and §Materials Engineering Program, University of Houston , Houston, Texas 77204, United States
| | - Narendra K Dewangan
- Department of Chemical and Biomolecular Engineering, ‡Department of Chemistry, and §Materials Engineering Program, University of Houston , Houston, Texas 77204, United States
| | - Nayoung Park
- Department of Chemical and Biomolecular Engineering, ‡Department of Chemistry, and §Materials Engineering Program, University of Houston , Houston, Texas 77204, United States
| | - Tzu-Han Li
- Department of Chemical and Biomolecular Engineering, ‡Department of Chemistry, and §Materials Engineering Program, University of Houston , Houston, Texas 77204, United States
| | - Megan L Robertson
- Department of Chemical and Biomolecular Engineering, ‡Department of Chemistry, and §Materials Engineering Program, University of Houston , Houston, Texas 77204, United States
| | - Jacinta C Conrad
- Department of Chemical and Biomolecular Engineering, ‡Department of Chemistry, and §Materials Engineering Program, University of Houston , Houston, Texas 77204, United States
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21
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Affiliation(s)
- Jeannette M. Garcia
- IBM Almaden Research Center, Chemistry and Materials, 650 Harry Road, San Jose, CA 95120, USA
| | - Megan L. Robertson
- University of Houston, Department of Chemical and Biomolecular Engineering, Houston, TX 77204, USA
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22
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Kidd BE, Li X, Piemonte RC, Cooksey TJ, Singh A, Robertson ML, Madsen LA. Tuning Biocompatible Block Copolymer Micelles by Varying Solvent Composition: Dynamics and Populations of Micelles and Unimers. Macromolecules 2017. [DOI: 10.1021/acs.macromol.6b02579] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- Bryce E. Kidd
- Department
of Chemistry and Macromolecules Innovation Institute, Virginia Tech, Blacksburg, Virginia 24061, United States
| | - Xiuli Li
- Department
of Chemistry and Macromolecules Innovation Institute, Virginia Tech, Blacksburg, Virginia 24061, United States
| | - Rachele C. Piemonte
- Department
of Chemistry and Macromolecules Innovation Institute, Virginia Tech, Blacksburg, Virginia 24061, United States
| | - Tyler J. Cooksey
- Department
of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77004, United States
| | - Avantika Singh
- Department
of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77004, United States
| | - Megan L. Robertson
- Department
of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77004, United States
| | - Louis A. Madsen
- Department
of Chemistry and Macromolecules Innovation Institute, Virginia Tech, Blacksburg, Virginia 24061, United States
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23
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Cooksey TJ, Singh A, Le KM, Wang S, Kelley EG, He L, Vajjala Kesava S, Gomez ED, Kidd BE, Madsen LA, Robertson ML. Tuning Biocompatible Block Copolymer Micelles by Varying Solvent Composition: Core/Corona Structure and Solvent Uptake. Macromolecules 2017. [DOI: 10.1021/acs.macromol.6b02580] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Affiliation(s)
- Tyler J. Cooksey
- Department
of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204-4004, United States
| | - Avantika Singh
- Department
of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204-4004, United States
| | - Kim Mai Le
- Department
of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204-4004, United States
| | - Shu Wang
- Department
of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204-4004, United States
| | - Elizabeth G. Kelley
- Department
of Chemical Engineering, University of Delaware, Newark, Delaware 19716, United States
- National
Institute
of Standards and Technology Center for Neutron Research, Gaithersburg, Maryland 20899-6100, United States
| | - Lilin He
- Biology
and Soft Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, United States
| | - Sameer Vajjala Kesava
- Department
of Chemical Engineering and the Materials Research Institute, The Pennsylvania State University, State College, Pennsylvania 16801, United States
| | - Enrique D. Gomez
- Department
of Chemical Engineering and the Materials Research Institute, The Pennsylvania State University, State College, Pennsylvania 16801, United States
| | - Bryce E. Kidd
- Department
of Chemistry and Macromolecules Innovation Institute, Virginia Tech, Blacksburg, Virginia 24061, United States
| | - Louis A. Madsen
- Department
of Chemistry and Macromolecules Innovation Institute, Virginia Tech, Blacksburg, Virginia 24061, United States
| | - Megan L. Robertson
- Department
of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204-4004, United States
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24
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Affiliation(s)
- Brian J. Rohde
- Department of Chemical and
Biomolecular Engineering, University of Houston, Houston, Texas 77204-4004, United States
| | - Kim Mai Le
- Department of Chemical and
Biomolecular Engineering, University of Houston, Houston, Texas 77204-4004, United States
| | - Ramanan Krishnamoorti
- Department of Chemical and
Biomolecular Engineering, University of Houston, Houston, Texas 77204-4004, United States
| | - Megan L. Robertson
- Department of Chemical and
Biomolecular Engineering, University of Houston, Houston, Texas 77204-4004, United States
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25
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Affiliation(s)
- Guozhen Yang
- Department
of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204-4004, United States
| | - Samantha L. Kristufek
- Department of Chemistry, Department of Chemical Engineering, Department of Materials Science & Engineering, Texas A&M University, College Station, Texas 77842-3012, United States
| | - Lauren A. Link
- Department of Chemistry, Department of Chemical Engineering, Department of Materials Science & Engineering, Texas A&M University, College Station, Texas 77842-3012, United States
| | - Karen L. Wooley
- Department of Chemistry, Department of Chemical Engineering, Department of Materials Science & Engineering, Texas A&M University, College Station, Texas 77842-3012, United States
| | - Megan L. Robertson
- Department
of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204-4004, United States
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26
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Ganewatta MS, Ding W, Rahman MA, Yuan L, Wang Z, Hamidi N, Robertson ML, Tang C. Biobased Plastics and Elastomers from Renewable Rosin via “Living” Ring-Opening Metathesis Polymerization. Macromolecules 2016. [DOI: 10.1021/acs.macromol.6b01496] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Affiliation(s)
- Mitra S. Ganewatta
- Department
of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208, United States
| | - Wenyue Ding
- Department
of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204, United States
| | - Md Anisur Rahman
- Department
of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208, United States
| | - Liang Yuan
- Department
of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208, United States
| | - Zhongkai Wang
- Department
of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208, United States
| | - Nasrollah Hamidi
- Department
of Biological and Physical Sciences, South Carolina State University, Orangeburg, South Carolina 29115, United States
| | - Megan L. Robertson
- Department
of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204, United States
| | - Chuanbing Tang
- Department
of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208, United States
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27
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Kristufek SL, Yang G, Link LA, Rohde BJ, Robertson ML, Wooley KL. Synthesis, Characterization, and Cross-Linking Strategy of a Quercetin-Based Epoxidized Monomer as a Naturally-Derived Replacement for BPA in Epoxy Resins. ChemSusChem 2016; 9:2135-2142. [PMID: 27415143 DOI: 10.1002/cssc.201600392] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/23/2016] [Revised: 04/27/2016] [Indexed: 06/06/2023]
Abstract
The natural polyphenolic compound quercetin was functionalized and cross-linked to afford a robust epoxy network. Quercetin was selectively methylated and functionalized with glycidyl ether moieties using a microwave-assisted reaction on a gram scale to afford the desired monomer (Q). This quercetin-derived monomer was treated with nadic methyl anhydride (NMA) to obtain a cross-linked network (Q-NMA). The thermal and mechanical properties of this naturally derived network were compared to those of a conventional diglycidyl ether bisphenol A-derived counterpart (DGEBA-NMA). Q-NMA had similar thermal properties [i.e., glass transition (Tg ) and decomposition (Td ) temperatures] and comparable mechanical properties (i.e., Young's Modulus, storage modulus) to that of DGEBA-NMA. However, it had a lower tensile strength and higher flexural modulus at elevated temperatures. The application of naturally derived, sustainable compounds for the replacement of commercially available petrochemical-based epoxies is of great interest to reduce the environmental impact of these materials. Q-NMA is an attractive candidate for the replacement of bisphenol A-based epoxies in various specialty engineering applications.
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Affiliation(s)
- Samantha L Kristufek
- Department of Chemistry, Department of Chemical Engineering, Departments of Materials Science & Engineering, Texas A&M University, College Station, Texas, 77842-3012, United States
| | - Guozhen Yang
- Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas, 77204-4004, United States
| | - Lauren A Link
- Department of Chemistry, Department of Chemical Engineering, Departments of Materials Science & Engineering, Texas A&M University, College Station, Texas, 77842-3012, United States
| | - Brian J Rohde
- Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas, 77204-4004, United States
| | - Megan L Robertson
- Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas, 77204-4004, United States
| | - Karen L Wooley
- Department of Chemistry, Department of Chemical Engineering, Departments of Materials Science & Engineering, Texas A&M University, College Station, Texas, 77842-3012, United States.
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28
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Xie M, Wang S, Singh A, Cooksey TJ, Marquez MD, Bhattarai A, Kourentzi K, Robertson ML. Fluorophore exchange kinetics in block copolymer micelles with varying solvent-fluorophore and solvent-polymer interactions. Soft Matter 2016; 12:6196-205. [PMID: 27383924 PMCID: PMC4973472 DOI: 10.1039/c6sm00297h] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Fluorescence spectroscopy was employed to characterize the kinetics of guest exchange in diblock copolymer micelles composed of poly(ethylene oxide-b-ε-caprolactone) (PEO-PCL) diblock copolymers in water/tetrahydrofuran (THF) mixtures which encapsulated fluorophores. The solvent composition (THF content) of the micelle solution was varied as a means of modulating the strength of interactions between the fluorophore and solvent as well as between the micelle core and solvent. A donor-acceptor fluorophore pair was employed consisting of 3,3'-dioctadecyloxacarbocyanine perchlorate (DiO, the donor) and 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (DiI, the acceptor). Through the process of Förster resonance energy transfer (FRET), energy was transferred from the donor to acceptor when the fluorophores were in close proximity. A micelle solution containing DiO was mixed with a micelle solution containing DiI at t = 0, and the emission spectra of the mixed solution were monitored over time (at an excitation wavelength optimized for the donor). In micelle solutions containing 5 and 10 vol% THF in the bulk solvent, an increase in the acceptor peak intensity maximum occurred over time in the post-mixed solution, accompanied by a decrease in the donor peak intensity maximum, indicating the presence of energy transfer from the donor to the acceptor. At long times, the FRET ratios (acceptor peak intensity divided by the sum of the acceptor and donor peak intensities) were indistinguishable from that determined from pre-mixed micelle solutions of the same THF content (in pre-mixed solutions, DiO and DiI were encapsulated within the same micelle cores). In the micelle solution containing 20 vol% THF, the fluorophore exchange process occurred too quickly to be observed (the FRET ratios measured from the solutions mixed at t = 0 were commensurate to that measured from the pre-mixed solution). A time constant describing the guest exchange process was extracted from the time-dependence of the FRET ratio through fit of an exponential decay. An increase in the THF content in the micelle solution resulted in a decrease in the time constant, and the time constant varied over five orders of magnitude as the THF content was varied from 5-20 vol%.
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Affiliation(s)
- Michelle Xie
- Department of Chemical and Biomolecular Engineering, University of Houston, 4726 Calhoun Road, S222 Engineering Building 1, Houston, TX 77204-4004, USA.
| | - Shu Wang
- Department of Chemical and Biomolecular Engineering, University of Houston, 4726 Calhoun Road, S222 Engineering Building 1, Houston, TX 77204-4004, USA.
| | - Avantika Singh
- Department of Chemical and Biomolecular Engineering, University of Houston, 4726 Calhoun Road, S222 Engineering Building 1, Houston, TX 77204-4004, USA.
| | - Tyler J Cooksey
- Department of Chemical and Biomolecular Engineering, University of Houston, 4726 Calhoun Road, S222 Engineering Building 1, Houston, TX 77204-4004, USA.
| | - Maria D Marquez
- Department of Chemical and Biomolecular Engineering, University of Houston, 4726 Calhoun Road, S222 Engineering Building 1, Houston, TX 77204-4004, USA.
| | - Ashish Bhattarai
- Department of Chemical and Biomolecular Engineering, University of Houston, 4726 Calhoun Road, S222 Engineering Building 1, Houston, TX 77204-4004, USA.
| | - Katerina Kourentzi
- Department of Chemical and Biomolecular Engineering, University of Houston, 4726 Calhoun Road, S222 Engineering Building 1, Houston, TX 77204-4004, USA.
| | - Megan L Robertson
- Department of Chemical and Biomolecular Engineering, University of Houston, 4726 Calhoun Road, S222 Engineering Building 1, Houston, TX 77204-4004, USA.
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29
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Wang S, Xie R, Vajjala Kesava S, Gomez ED, Cochran EW, Robertson ML. Close-Packed Spherical Morphology in an ABA Triblock Copolymer Aligned with Large-Amplitude Oscillatory Shear. Macromolecules 2016. [DOI: 10.1021/acs.macromol.6b00505] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Shu Wang
- Department
of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204-4004, United States
| | - Renxuan Xie
- Department
of Chemical Engineering and the Materials Research Institute, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Sameer Vajjala Kesava
- Department
of Chemical Engineering and the Materials Research Institute, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Enrique D. Gomez
- Department
of Chemical Engineering and the Materials Research Institute, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Eric W. Cochran
- Department
of Chemical and Biological Engineering, Iowa State University, Ames, Iowa 50011, United States
| | - Megan L. Robertson
- Department
of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204-4004, United States
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30
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Yadav V, Harkin AV, Robertson ML, Conrad JC. Hysteretic memory in pH-response of water contact angle on poly(acrylic acid) brushes. Soft Matter 2016; 12:3589-3599. [PMID: 26979270 DOI: 10.1039/c5sm03134f] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We investigated the pH-dependent response of flat polyacid brushes of varying length and dispersity in the extended brush regime. Our model system consisted of poly(acrylic acid) brushes, which change from hydrophobic and neutral at low pH to hydrophilic and negatively charged at high pH, synthesized on silicon substrates using a grafting-from approach at constant grafting density. We observed three trends in the pH-response: first, the dry brush thickness increased as the pH was increased for brushes above a critical length, and this effect was magnified as the dispersity increased; second, the water contact angle measured at low pH was larger for brushes of greater dispersity; and third, brushes of sufficient dispersity exhibited hysteretic memory behavior in the pH-dependence of the contact angle, in which the contact angle upon increasing and decreasing pH differed. As a consequence, the pKa of the brushes measured upon increasing pH was consistently higher than that measured upon decreasing pH. The observed pH response is consistent with proposed changes in the conformation and charge distribution of the polyelectrolyte brushes that depend on the direction of pH change and the dispersity of the brushes.
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Affiliation(s)
- Vivek Yadav
- Department of Chemical and Biomolecular Engineering, University of Houston, Houston, TX 77204-4004, USA.
| | - Adrienne V Harkin
- Department of Chemical and Biomolecular Engineering, University of Houston, Houston, TX 77204-4004, USA.
| | - Megan L Robertson
- Department of Chemical and Biomolecular Engineering, University of Houston, Houston, TX 77204-4004, USA.
| | - Jacinta C Conrad
- Department of Chemical and Biomolecular Engineering, University of Houston, Houston, TX 77204-4004, USA.
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31
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Mauck SC, Wang S, Ding W, Rohde BJ, Fortune CK, Yang G, Ahn SK, Robertson ML. Biorenewable Tough Blends of Polylactide and Acrylated Epoxidized Soybean Oil Compatibilized by a Polylactide Star Polymer. Macromolecules 2016. [DOI: 10.1021/acs.macromol.5b02613] [Citation(s) in RCA: 95] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Sheli C. Mauck
- Department
of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204-4004, United States
| | - Shu Wang
- Department
of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204-4004, United States
| | - Wenyue Ding
- Department
of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204-4004, United States
| | - Brian J. Rohde
- Department
of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204-4004, United States
| | - C. Karen Fortune
- Department
of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204-4004, United States
| | - Guozhen Yang
- Department
of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204-4004, United States
| | - Suk-Kyun Ahn
- Center
for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
- Department
of Polymer Science and Engineering, Pusan National University, Pusan 609-735, Korea
| | - Megan L. Robertson
- Department
of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204-4004, United States
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32
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Wang S, Ding W, Yang G, Robertson ML. Biorenewable Thermoplastic Elastomeric Triblock Copolymers Containing Salicylic Acid-Derived End-Blocks and a Fatty Acid-Derived Midblock. MACROMOL CHEM PHYS 2015. [DOI: 10.1002/macp.201500274] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Shu Wang
- Department of Chemical and Biomolecular Engineering; University of Houston; 4726 Calhoun Road, S222 Engineering Building 1; University of Houston; Houston TX 77204-4004 USA
| | - Wenyue Ding
- Department of Chemical and Biomolecular Engineering; University of Houston; 4726 Calhoun Road, S222 Engineering Building 1; University of Houston; Houston TX 77204-4004 USA
| | - Guozhen Yang
- Department of Chemical and Biomolecular Engineering; University of Houston; 4726 Calhoun Road, S222 Engineering Building 1; University of Houston; Houston TX 77204-4004 USA
| | - Megan L. Robertson
- Department of Chemical and Biomolecular Engineering; University of Houston; 4726 Calhoun Road, S222 Engineering Building 1; University of Houston; Houston TX 77204-4004 USA
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33
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Yang G, Kristufek SL, Link LA, Wooley KL, Robertson ML. Synthesis and Physical Properties of Thiol–Ene Networks Utilizing Plant-Derived Phenolic Acids. Macromolecules 2015. [DOI: 10.1021/acs.macromol.5b01796] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- Guozhen Yang
- Department
of Chemical and Biomolecular Engineering, University of Houston, 4726 Calhoun Road S222 Engineering Building 1, Houston, Texas 77204-4004, United States
| | - Samantha L. Kristufek
- Department of Chemistry, Department of Chemical Engineering, Department of Materials Science & Engineering, Texas A&M University, College Station, Texas 77842-3012, United States
| | - Lauren A. Link
- Department of Chemistry, Department of Chemical Engineering, Department of Materials Science & Engineering, Texas A&M University, College Station, Texas 77842-3012, United States
| | - Karen L. Wooley
- Department of Chemistry, Department of Chemical Engineering, Department of Materials Science & Engineering, Texas A&M University, College Station, Texas 77842-3012, United States
| | - Megan L. Robertson
- Department
of Chemical and Biomolecular Engineering, University of Houston, 4726 Calhoun Road S222 Engineering Building 1, Houston, Texas 77204-4004, United States
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34
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35
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Wang S, Robertson ML. Thermodynamic Interactions between Polystyrene and Long-Chain Poly(n-Alkyl Acrylates) Derived from Plant Oils. ACS Appl Mater Interfaces 2015; 7:12109-12118. [PMID: 26020581 DOI: 10.1021/acsami.5b02326] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Vegetable oils and their fatty acids are promising sources for the derivation of polymers. Long-chain poly(n-alkyl acrylates) and poly(n-alkyl methacrylates) are readily derived from fatty acids through conversion of the carboxylic acid end-group to an acrylate or methacrylate group. The resulting polymers contain long alkyl side-chains with around 10-22 carbon atoms. Regardless of the monomer source, the presence of alkyl side-chains in poly(n-alkyl acrylates) and poly(n-alkyl methacrylates) provides a convenient mechanism for tuning their physical properties. The development of structured multicomponent materials, including block copolymers and blends, containing poly(n-alkyl acrylates) and poly(n-alkyl methacrylates) requires knowledge of the thermodynamic interactions governing their self-assembly, typically described by the Flory-Huggins interaction parameter χ. We have investigated the χ parameter between polystyrene and long-chain poly(n-alkyl acrylate) homopolymers and copolymers: specifically we have included poly(stearyl acrylate), poly(lauryl acrylate), and their random copolymers. Lauryl and stearyl acrylate were chosen as model alkyl acrylates derived from vegetable oils and have alkyl side-chain lengths of 12 and 18 carbon atoms, respectively. Polystyrene is included in this study as a model petroleum-sourced polymer, which has wide applicability in commercially relevant multicomponent polymeric materials. Two independent methods were employed to measure the χ parameter: cloud point measurements on binary blends and characterization of the order-disorder transition of triblock copolymers, which were in relatively good agreement with one another. The χ parameter was found to be independent of the alkyl side-chain length (n) for large values of n (i.e., n > 10). This behavior is in stark contrast to the n-dependence of the χ parameter predicted from solubility parameter theory. Our study complements prior work investigating the interactions between polystyrene and short-chain polyacrylates (n ≤ 10). To our knowledge, this is the first study to explore the thermodynamic interactions between polystyrene and long-chain poly(n-alkyl acrylates) with n > 10. This work lays the groundwork for the development of multicomponent structured systems (i.e., blends and copolymers) in this class of sustainable materials.
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Affiliation(s)
- Shu Wang
- Department of Chemical and Biomolecular Engineering, University of Houston, 4800 Calhoun Road, S222 Engineering Building 1, Houston, Texas 77204-4004, United States
| | - Megan L Robertson
- Department of Chemical and Biomolecular Engineering, University of Houston, 4800 Calhoun Road, S222 Engineering Building 1, Houston, Texas 77204-4004, United States
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36
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Affiliation(s)
- Shu Wang
- Department of Chemical and Biomolecular
Engineering, University of Houston, Houston,
Texas 77204-4004, United States
| | - Sameer Vajjala Kesava
- Department of Chemical Engineering and the Materials Research Institute, The Pennsylvania State University, University Park,
Pennsylvania 16802, United States
| | - Enrique D. Gomez
- Department of Chemical Engineering and the Materials Research Institute, The Pennsylvania State University, University Park,
Pennsylvania 16802, United States
| | - Megan L. Robertson
- Department of Chemical and Biomolecular
Engineering, University of Houston, Houston,
Texas 77204-4004, United States
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37
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Abstract
Poly(l-lactide) (PLLA) is a renewable resource polymer derived from plant sugars with several commercial applications. Broader implementation of the material is limited due to its inherent brittleness. We show that the addition of 5 wt % castor oil to PLLA significantly enhances the overall tensile toughness with minimal reductions in the modulus and no plasticization of the PLLA matrix. In addition, we used poly(ricinoleic acid)-PLLA diblock copolymers, synthesized entirely from renewable resources, as compatibilizers for the PLLA/castor oil blends. Ricinoleic acid, the majority fatty acid comprising castor oil, was polymerized through a lipase-catalyzed condensation reaction. The resulting polymers contained a hydroxyl end-group that was subsequently used to initiate the ring-opening polymerization of l-lactide. The binary PLLA/castor oil blend exhibited a tensile toughness seven times greater than neat PLLA. The addition of block copolymer allowed for control over the morphology of the blends, and even further improvement in the tensile toughness was realized-an order of magnitude larger than that of neat PLLA.
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Affiliation(s)
- Megan L Robertson
- Department of Chemistry, University of Minnesota, 207 Pleasant St. SE, Minneapolis, Minnesota 55455-0431, United States
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38
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Nedoma AJ, Lai P, Jackson A, Robertson ML, Wanakule NS, Balsara NP. Phase Diagrams of Blends of Polyisobutylene and Deuterated Polybutadiene as a Function of Chain Length. Macromolecules 2011. [DOI: 10.1021/ma200258w] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Alisyn J. Nedoma
- Department of Chemical Engineering, University of California, Berkeley, Berkeley, California 94720, United States
| | - Peggy Lai
- Department of Chemical Engineering, University of California, Berkeley, Berkeley, California 94720, United States
| | - Andrew Jackson
- National Institute of Standards and Technology Center for Neutron Research, Gaithersburg, Maryland 20899, United States
- Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742, United States
| | - Megan L. Robertson
- Department of Chemical Engineering, University of California, Berkeley, Berkeley, California 94720, United States
| | - Nisita S. Wanakule
- Department of Chemical Engineering, University of California, Berkeley, Berkeley, California 94720, United States
| | - Nitash P. Balsara
- Department of Chemical Engineering, University of California, Berkeley, Berkeley, California 94720, United States
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
- Environmental Energy Technologies Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
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Affiliation(s)
- Alisyn J. Nedoma
- Department of Chemical Engineering, University of California, Berkeley, California 94720
| | - Peggy Lai
- Department of Chemical Engineering, University of California, Berkeley, California 94720
| | - Andrew Jackson
- National Institute of Standards and Technology Center for Neutron Research, Gaithersburg, Maryland 20899
- Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742
| | - Megan L. Robertson
- Department of Chemical Engineering, University of California, Berkeley, California 94720
| | - Nitash P. Balsara
- Department of Chemical Engineering, University of California, Berkeley, California 94720
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720
- Environmental Energy Technologies Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720
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Nedoma AJ, Lai P, Jackson A, Robertson ML, Wanakule NS, Balsara NP. Phase Behavior of Asymmetric Multicomponent A/B/A−C Blends with Unequal Homopolymer Molecular Weights. Macromolecules 2010. [DOI: 10.1021/ma1000354] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Alisyn J. Nedoma
- Department of Chemical Engineering, University of California, Berkeley, California 94720
| | - Peggy Lai
- Department of Chemical Engineering, University of California, Berkeley, California 94720
| | - Andrew Jackson
- National Institute of Standards and Technology Center for Neutron Research, Gaithersburg, Maryland, 20899
- Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742
| | - Megan L. Robertson
- Department of Chemical Engineering and Materials Science, Minneapolis, Minnesota, 55455
| | - Nisita S. Wanakule
- Department of Chemical Engineering, University of California, Berkeley, California 94720
| | - Nitash P. Balsara
- Department of Chemical Engineering, University of California, Berkeley, California 94720
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720
- Environmental Energy Technologies Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720
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Affiliation(s)
- William M. Gramlich
- Department of Chemistry, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455-0431
| | - Megan L. Robertson
- Department of Chemistry, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455-0431
| | - Marc A. Hillmyer
- Department of Chemistry, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455-0431
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42
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Affiliation(s)
- Megan L. Robertson
- Department of Chemistry, University of Minnesota, 207 Pleasant St. SE, Minneapolis, Minnesota 55455-0431
| | - Kwanho Chang
- Department of Chemistry, University of Minnesota, 207 Pleasant St. SE, Minneapolis, Minnesota 55455-0431
| | - William M. Gramlich
- Department of Chemistry, University of Minnesota, 207 Pleasant St. SE, Minneapolis, Minnesota 55455-0431
| | - Marc A. Hillmyer
- Department of Chemistry, University of Minnesota, 207 Pleasant St. SE, Minneapolis, Minnesota 55455-0431
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Chang K, Robertson ML, Hillmyer MA. Phase inversion in polylactide/soybean oil blends compatibilized by poly(isoprene-b-lactide) block copolymers. ACS Appl Mater Interfaces 2009; 1:2390-2399. [PMID: 20355877 DOI: 10.1021/am900514v] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Renewable composites were prepared by melt blending of polylactide and soybean oil. The blend morphology was tuned by the addition of poly(isoprene-b-lactide) block copolymers. Due to the extreme difference in the viscosities of soybean oil and polylactide, a critical block copolymer composition was found to induce a phase inversion point at which the minor soybean oil phase became the matrix surrounding polylactide particles. This transition was due to the thermodynamic interactions between the block copolymer and the two phases and shear forces acting on the mixture during blending. The size of the soybean oil droplets in the polylactide matrix was also highly dependent on the block copolymer composition. In binary polylactide/soybean oil blends, there was a limiting concentration of soybean oil that could be incorporated into the polylactide matrix (6% of the total blend weight), which could be increased up to 20% by the addition of block copolymers.
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Affiliation(s)
- Kwanho Chang
- Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, USA
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Nedoma AJ, Robertson ML, Wanakule NS, Balsara NP. Measurements of the Composition and Molecular Weight Dependence of the Flory−Huggins Interaction Parameter. Macromolecules 2008. [DOI: 10.1021/ma800698r] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Alisyn J. Nedoma
- Department of Chemical Engineering, University of California, Berkeley, California 94720; Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720; and Environmental Energy Technologies Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720
| | - Megan L. Robertson
- Department of Chemical Engineering, University of California, Berkeley, California 94720; Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720; and Environmental Energy Technologies Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720
| | - Nisita S. Wanakule
- Department of Chemical Engineering, University of California, Berkeley, California 94720; Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720; and Environmental Energy Technologies Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720
| | - Nitash P. Balsara
- Department of Chemical Engineering, University of California, Berkeley, California 94720; Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720; and Environmental Energy Technologies Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720
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Wanakule NS, Nedoma AJ, Robertson ML, Fang Z, Jackson A, Garetz BA, Balsara NP. Characterization of Micron-Sized Periodic Structures in Multicomponent Polymer Blends by Ultra-Small-Angle Neutron Scattering and Optical Microscopy. Macromolecules 2007. [DOI: 10.1021/ma701922y] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Nisita S. Wanakule
- Department of Chemical Engineering, University of California, Berkeley, California 94720; Othmer-Jacobs Department of Chemical & Biological Engineering, Polytechnic University, Brooklyn, New York 11201; NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899; Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742; Department of Chemical and Biological Sciences, Polytechnic University, Brooklyn, New York
| | - Alisyn J. Nedoma
- Department of Chemical Engineering, University of California, Berkeley, California 94720; Othmer-Jacobs Department of Chemical & Biological Engineering, Polytechnic University, Brooklyn, New York 11201; NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899; Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742; Department of Chemical and Biological Sciences, Polytechnic University, Brooklyn, New York
| | - Megan L. Robertson
- Department of Chemical Engineering, University of California, Berkeley, California 94720; Othmer-Jacobs Department of Chemical & Biological Engineering, Polytechnic University, Brooklyn, New York 11201; NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899; Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742; Department of Chemical and Biological Sciences, Polytechnic University, Brooklyn, New York
| | - Zhuangxi Fang
- Department of Chemical Engineering, University of California, Berkeley, California 94720; Othmer-Jacobs Department of Chemical & Biological Engineering, Polytechnic University, Brooklyn, New York 11201; NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899; Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742; Department of Chemical and Biological Sciences, Polytechnic University, Brooklyn, New York
| | - Andrew Jackson
- Department of Chemical Engineering, University of California, Berkeley, California 94720; Othmer-Jacobs Department of Chemical & Biological Engineering, Polytechnic University, Brooklyn, New York 11201; NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899; Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742; Department of Chemical and Biological Sciences, Polytechnic University, Brooklyn, New York
| | - Bruce A. Garetz
- Department of Chemical Engineering, University of California, Berkeley, California 94720; Othmer-Jacobs Department of Chemical & Biological Engineering, Polytechnic University, Brooklyn, New York 11201; NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899; Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742; Department of Chemical and Biological Sciences, Polytechnic University, Brooklyn, New York
| | - Nitash P. Balsara
- Department of Chemical Engineering, University of California, Berkeley, California 94720; Othmer-Jacobs Department of Chemical & Biological Engineering, Polytechnic University, Brooklyn, New York 11201; NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899; Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742; Department of Chemical and Biological Sciences, Polytechnic University, Brooklyn, New York
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Nedoma AJ, Robertson ML, Wanakule NS, Balsara NP. Measurements of the Flory−Huggins Interaction Parameter Using a Series of Critical Binary Blends. Ind Eng Chem Res 2007. [DOI: 10.1021/ie0710723] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Alisyn J. Nedoma
- Department of Chemical Engineering, University of California, Berkeley, California 94720, Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, and Environmental Energy and Technologies Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720
| | - Megan L. Robertson
- Department of Chemical Engineering, University of California, Berkeley, California 94720, Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, and Environmental Energy and Technologies Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720
| | - Nisita S. Wanakule
- Department of Chemical Engineering, University of California, Berkeley, California 94720, Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, and Environmental Energy and Technologies Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720
| | - Nitash P. Balsara
- Department of Chemical Engineering, University of California, Berkeley, California 94720, Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, and Environmental Energy and Technologies Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720
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Abstract
We use new data on the timing and extent of the early Pleistocene dispersal of Homo erectus to estimate diffusion coefficients of early Homo from Africa. These diffusion coefficients indicate more rapid and efficient dispersals than those calculated for fossil Macaca sp., Theropithecus darti, and Mesopithecus pentelicus. Increases in home range size associated with changes in ecology, hominid body size, and possibly foraging strategy may underlay these differences in dispersal efficiency. Ecological data for extant primates and human foragers indicate a close relationship between body size, home range size, and diet quality. These data predict that evolutionary changes in body size and foraging behavior would have produced a 10-fold increase in the home range size of H. erectus compared with that of the australopithecines. These two independent datasets provide a means of quantifying aspects of the dispersal of early Homo and suggest that rapid rates of dispersal appear to have been promoted by changes in foraging strategy and body size in H. erectus facilitated by changes in ecosystem structure during the Plio-Pleistocene.
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Affiliation(s)
- S C Antón
- Center for Human Evolutionary Studies, Department of Anthropology, Rutgers University, New Brunswick, NJ 08901, USA.
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48
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Affiliation(s)
- W R Leonard
- Department of Anthropology, Northwestern University, Evanston, Illinois 60208, USA.
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Robertson ML, Gleich LL, Barrett WL, Gluckman JL. Base-of-tongue cancer: survival, function, and quality of life after external-beam irradiation and brachytherapy. Laryngoscope 2001; 111:1362-5. [PMID: 11568569 DOI: 10.1097/00005537-200108000-00009] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
OBJECTIVE Base-of-tongue cancer has traditionally been treated by surgical resection followed by radiation therapy. Primary radiation therapy with brachytherapy has recently been proposed as an alternative. In a prior analysis, we found that patients with advanced tongue-base cancer treated by total glossectomy and postoperative radiation therapy can be cured while potentially maintaining good quality of life. Therefore, we designed the current study to assess survival, function, and quality of life in our patients with tongue-base cancer who were treated with primary radiation therapy and brachytherapy with neck dissection as indicated. STUDY DESIGN Consecutive case series. METHODS Twenty patients were treated between 1993 and 1997 using the approach just named. The T stages were T1 (3), T2 (10), T3 (6), and T4 (1). The N stages were N0 (3), N1 (3), N2 (11), and N3 (3). At the time of brachytherapy catheter placement, neck dissections were performed in all 14 patients with N2 or N3 disease. Surviving patients completed a functional status survey and quality of life questionnaire. RESULTS The 3- and 5-year Kaplan-Meier corrected actuarial survival rates were 57% and 38%, respectively. Eight patients remained alive at the time of this writing and completed the functional status survey and quality of life assessment. Function and quality of life were well maintained in patients treated with external-beam irradiation followed by brachytherapy and neck dissection. However, none of our patients with T3 disease had long-term survival. CONCLUSION Although we do not endorse external-beam irradiation and brachytherapy for advanced tongue-base cancers, this treatment should be strongly considered for patients with T1 or T2 tumors in whom preservation of function and quality of life is a priority.
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Affiliation(s)
- M L Robertson
- Department of Otolaryngology-Head and Neck Surgery, The University of Cincinnati Medical Center, 213 Bethesda Avenue, Cincinnati, OH 45267-0528, U.S.A
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Abstract
There is currently great interest in developing ecological models for investigating human evolution. Yet little attention has been given to energetics, one of the cornerstones of modern ecosystem ecology. This paper examines the ecological correlates of variation in metabolic requirements among extant primate species, and uses this information to draw inferences about the changes in energy demands over the course of human evolution. Data on body size, resting metabolism, and activity budgets for selected anthropoid species and human hunter-gatherers are used to estimate total energy expenditure (TEE). Analyses indicate that relative energy expenditure levels and day ranges are positively correlated with diet quality; that is, more active species tend to consume more energy-rich diets. Human foragers fall at the positive extremes for modern primates in having high expenditure levels, large ranges, and very high quality diets. During hominid evolution, it appears that TEE increased substantially with the emergence of Homo erectus. This increase is partly attributable to larger body size as well as likely increases in day range and activity level. Assuming similar activity budgets for all early hominid species, estimated TEE for H. erectus is 40-45% greater than for the australopithecines. If, however, it is assumed that the evolution of early Homo was also associated with a shift to a more "human-like" foraging strategy, estimated expenditure levels for H. erectus are 80-85% greater than in the australopithecines. Changing patterns of resource distribution associated with the expansion of African savannas between 2.5 and 1.5 mya may been the impetus for a shift in foraging behavior among early members of the genus Homo. Such ecological changes likely would have made animal foods a more attractive resource. Moreover, greater use of animal foods and the resulting higher quality diet would have been important for supporting the larger day ranges and greater energy requirements that appear to have been associated with the evolution of a human-like hunting and gathering strategy.
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Affiliation(s)
- W R Leonard
- Department of Anthropology, University of Florida, Gainesville 32611, USA
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