1
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Roth CB. Polymers under nanoconfinement: where are we now in understanding local property changes? Chem Soc Rev 2021; 50:8050-8066. [PMID: 34086025 DOI: 10.1039/d1cs00054c] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Polymers are increasingly being used in applications with nanostructured morphologies where almost all polymer molecules are within a few tens to hundreds of nanometers from some interface. From nearly three decades of study on polymers in simplified nanoconfined systems such as thin films, we have come to understand property changes in these systems as arising from interfacial effects where local dynamical perturbations are propagated deeper into the material. This review provides a summary of local glass transition temperature Tg changes near interfaces, comparing across different types of interfaces: free surface, substrate, liquid, and polymer-polymer. Local versus film-average properties in thin films are discussed, making connections to other related property changes, while highlighting several historically important studies. By experimental necessity, most studies are on high enough molecule weight chains to be well entangled, although aspects that connect to lower molecule weight materials are described. Emphasis is made to identify observations and open questions that have yet to be fully understood such as the evidence of long-ranged interfacial effects, finite domain size, interfacial breadth, and chain connectivity.
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Affiliation(s)
- Connie B Roth
- Department of Physics, Emory University, Atlanta, Georgia 30322, USA.
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2
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Jiang N, Chen J, Yu T, Chao A, Kang L, Wu Y, Niu K, Li R, Fukuto M, Zhang D. Cyclic Topology Enhancing Structural Ordering and Stability of Comb-Shaped Polypeptoid Thin Films against Melt-Induced Dewetting. Macromolecules 2020; 53:7601-7612. [PMID: 32952217 PMCID: PMC7498153 DOI: 10.1021/acs.macromol.0c01205] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2020] [Revised: 07/21/2020] [Indexed: 12/03/2022]
Abstract
We investigated the effect of cyclic chain topology on the molecular ordering and thermal stability of comb-shaped polypeptoid thin films on silicon (Si) substrates. Cyclic and linear poly(N-decylglycine) (PNDG) bearing long n-decyl side chains were synthesized by ring-opening polymerization of N-decylglycine-derived N-carboxyanhydrides. When the spin-coated thin films were subjected to thermal annealing at temperatures above the melting temperature (T > T m), the cyclic PNDG films exhibited significantly enhanced stability against melt-induced dewetting than the linear counterparts (l-PNDG). When recrystallized at temperatures below the crystallization temperature (T < T c), the homogeneous c-PNDG films exhibit enhanced crystalline ordering relative to the macroscopically dewetted l-PNDG films. Both cyclic and linear PNDG molecules adopt cis-amide conformations in the crystalline film, which transition into trans-amide conformations upon melting. A top-down solvent leaching treatment of both l/c-PNDG films revealed the formation of an irreversibly physisorbed monolayer with similar thickness (ca. 3 nm) on the Si substrate. The physisorbed monolayers are more disordered relative to the respective thicker crystalline films for both cyclic and linear PNDGs. Upon heating above T m, the adsorbed c-PNDG chains adopt trans-amide backbone conformation identical with the free c-PNDG molecules in the molten film. By contrast, the backbone conformations of l-PNDG chains in the adsorbed layers are notably different from those of the free chains in the molten film. We postulate that the conformational disparity between the chains in the physically adsorbed layers versus the free chains in the molten film is an important factor to account for the difference in the thermal stability of PNDG thin films. These findings highlight the use of cyclic chain topology to suppress the melt-induced dewetting in polymer thin films.
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Affiliation(s)
- Naisheng Jiang
- Department of Chemistry
and Macromolecular Studies Group, Louisiana
State University, Baton
Rouge, Louisiana 70803, United States
- School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, China
| | - Jianxia Chen
- School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, China
| | - Tianyi Yu
- Department of Chemistry
and Macromolecular Studies Group, Louisiana
State University, Baton
Rouge, Louisiana 70803, United States
| | - Albert Chao
- Department of Chemistry
and Macromolecular Studies Group, Louisiana
State University, Baton
Rouge, Louisiana 70803, United States
| | - Liying Kang
- School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, China
| | - Ying Wu
- School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, China
| | - Kangmin Niu
- School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, China
| | - Ruipeng Li
- National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, New York 11973, United States
| | - Masafumi Fukuto
- National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, New York 11973, United States
| | - Donghui Zhang
- Department of Chemistry
and Macromolecular Studies Group, Louisiana
State University, Baton
Rouge, Louisiana 70803, United States
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3
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Yang F, Presto D, Pan Y, Liu K, Zhou L, Narayanan S, Zhu Y, Peng Z, Soucek MD, Tsige M, Foster MD. Proximity to Graphene Dramatically Alters Polymer Dynamics. Macromolecules 2019. [DOI: 10.1021/acs.macromol.9b00317] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Affiliation(s)
| | | | | | | | | | - Suresh Narayanan
- Advanced Photon Source, Argonne National Laboratory, Lemont, Illinois 60439, United States
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4
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Thees MF, Roth CB. Unexpected Molecular Weight Dependence to the Physical Aging of Thin Polystyrene Films Present at Ultra‐High Molecular Weights. ACTA ACUST UNITED AC 2019. [DOI: 10.1002/polb.24797] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
| | - Connie B. Roth
- Department of Physics Emory University Atlanta Georgia 30322
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5
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Zhang F, Quirk RP, Gerislioglu S, Wesdemiotis C, Bekele S, Tsige M, Koh YP, Simon SL, Foster MD. Synthesis and Characterization of Well-Defined, Tadpole-Shaped Polystyrene with a Single Atom Junction Point. Macromolecules 2018. [DOI: 10.1021/acs.macromol.8b01384] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
| | | | | | | | | | | | - Yung P. Koh
- Department of Chemical Engineering, Texas Tech University, Lubbock, Texas 79409, United States
| | - Sindee L. Simon
- Department of Chemical Engineering, Texas Tech University, Lubbock, Texas 79409, United States
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6
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Zhang F, He Q, Zhou Y, Narayanan S, Wang C, Vogt BD, Foster MD. Anomalous Confinement Slows Surface Fluctuations of Star Polymer Melt Films. ACS Macro Lett 2018; 7:834-839. [PMID: 35650756 DOI: 10.1021/acsmacrolett.8b00278] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The unusually large film thickness at which confinement effects manifest themselves in surface fluctuations of unentangled four-arm star polymers has been defined using film thicknesses from 10Rg to 107Rg. For 15k four-arm star polystyrene (SPS), confinement appears at a thickness between 112 nm (40Rg) and 72 nm (26Rg), which is remarkably larger than the thicknesses at which confinement appears for unentangled 6k linear (<15 nm, <7Rg) and 6k and 14k cyclic (24 and 22 nm, respectively) polystyrenes. Data for 15k star films can be rationalized using a two-layer model with a 17 nm (6Rg) thick highly viscous layer at the substrate, which is significantly thicker than the 1Rg thick "irreversibly adsorbed" layer. For a 29 nm (10Rg) thick film, more striking confinement occurs due to the combined influence of both interfaces. These results underscore the extraordinary role long-chain branching plays in dictating surface fluctuations of thin films.
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Affiliation(s)
| | | | | | - Suresh Narayanan
- X-ray Science Division, Argonne National Laboratory, Argonne, Illinois 60439, United States
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7
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Glynos E, Johnson KJ, Frieberg B, Chremos A, Narayanan S, Sakellariou G, Green PF. Free Surface Relaxations of Star-Shaped Polymer Films. PHYSICAL REVIEW LETTERS 2017; 119:227801. [PMID: 29286814 PMCID: PMC5839106 DOI: 10.1103/physrevlett.119.227801] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/16/2017] [Indexed: 06/07/2023]
Abstract
The surface relaxation dynamics of supported star-shaped polymer thin films are shown to be slower than the bulk, persisting up to temperatures at least 50 K above the bulk glass transition temperature T_{g}^{bulk}. This behavior, exhibited by star-shaped polystyrenes with functionality f=8 arms and molecular weights per arm M_{arm}
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Affiliation(s)
- Emmanouil Glynos
- Institute of Electronic Structure and Laser, Foundation for Research and Technology-Hellas, P.O. Box 1385, 711 10 Heraklion, Crete, Greece
| | - Kyle J. Johnson
- Department of Material Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA
- Biointeraces Institute, University of Michigan, Ann Arbor, Michigan 48109, USA
| | - Bradley Frieberg
- Biointeraces Institute, University of Michigan, Ann Arbor, Michigan 48109, USA
- Macromolecular Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA
| | - Alexandros Chremos
- Materials Science and Engineering Division, National Institute of Standards and Technology, Gaithersburg, MD, 20899, USA
| | - Suresh Narayanan
- Department of Chemistry, National and Kapodistrian University of Athens, Panepistimiopolis, Zografou, 15771, Athens Greece
| | | | - Peter F. Green
- Department of Material Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA
- Biointeraces Institute, University of Michigan, Ann Arbor, Michigan 48109, USA
- Macromolecular Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA
- National Renewable Energy Laboratory (NREL), Golden, Colorado 80401, USA
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8
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Zhou Y, He Q, Zhang F, Yang F, Narayanan S, Yuan G, Dhinojwala A, Foster MD. Modifying Surface Fluctuations of Polymer Melt Films with Substrate Modification. ACS Macro Lett 2017; 6:915-919. [PMID: 35650890 DOI: 10.1021/acsmacrolett.7b00459] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Deposition of a plasma polymerized film on a silicon substrate substantially changes the fluctuations on the surface of a sufficiently thin melt polystyrene (PS) film atop the substrate. Surface fluctuation relaxation times measured with X-ray photon correlation spectroscopy (XPCS) for ca. 4Rg thick melt films of 131 kg/mol linear PS on hydrogen-passivated silicon (H-Si) and on a plasma polymer modified silicon wafer can both be described using a hydrodynamic continuum theory (HCT) that assumes the film is characterized throughout its depth by the bulk viscosity. However, when the film thickness is reduced to ∼3Rg, confinement effects are evident. The surface fluctuations are slower than predicted using the HCT, and the confinement effect for the PS on H-Si is larger than that for the PS on the plasma polymerized film. This deviation is due to a difference in the thicknesses of the strongly adsorbed layers at the substrate which are impacted by the substrate surface energy.
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Affiliation(s)
- Yang Zhou
- Department
of Polymer Science, The University of Akron, Akron, Ohio 44325, United States
| | - Qiming He
- Department
of Polymer Science, The University of Akron, Akron, Ohio 44325, United States
| | - Fan Zhang
- Department
of Polymer Science, The University of Akron, Akron, Ohio 44325, United States
| | - Feipeng Yang
- Department
of Polymer Science, The University of Akron, Akron, Ohio 44325, United States
| | - Suresh Narayanan
- X-ray
Science Division, Argonne National Laboratory, Argonne, Illinois 60439, United States
| | - Guangcui Yuan
- Center
for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
| | - Ali Dhinojwala
- Department
of Polymer Science, The University of Akron, Akron, Ohio 44325, United States
| | - Mark D. Foster
- Department
of Polymer Science, The University of Akron, Akron, Ohio 44325, United States
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9
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He Q, Mao J, Wesdemiotis C, Quirk RP, Foster MD. Synthesis and Isomeric Characterization of Well-Defined 8-Shaped Polystyrene Using Anionic Polymerization, Silicon Chloride Linking Chemistry, and Metathesis Ring Closure. Macromolecules 2017. [DOI: 10.1021/acs.macromol.7b01121] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Affiliation(s)
- Qiming He
- Department
of Polymer Science and ‡Department of Chemistry, The University of Akron, Akron, Ohio 44325, United States
| | - Jialin Mao
- Department
of Polymer Science and ‡Department of Chemistry, The University of Akron, Akron, Ohio 44325, United States
| | - Chrys Wesdemiotis
- Department
of Polymer Science and ‡Department of Chemistry, The University of Akron, Akron, Ohio 44325, United States
| | - Roderic P. Quirk
- Department
of Polymer Science and ‡Department of Chemistry, The University of Akron, Akron, Ohio 44325, United States
| | - Mark D. Foster
- Department
of Polymer Science and ‡Department of Chemistry, The University of Akron, Akron, Ohio 44325, United States
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10
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Wang L, Xu L, Liu B, Shi T, Jiang S, An L. The influence of polymer architectures on the dewetting behavior of thin polymer films: from linear chains to ring chains. SOFT MATTER 2017; 13:3091-3098. [PMID: 28393155 DOI: 10.1039/c7sm00379j] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The dewetting behavior of ring polystyrene (RPS) film and linear polystyrene (LPS) film on silanized Si substrates with different grafting densities and PDMS substrate was investigated. Results showed that polymer architectures greatly influenced the dewetting behavior of the thin polymer film. On the silanized Si substrate with 69% grafting density, RPS chains exhibited stronger adsorption compared with LPS chains, and as a result the wetting layer formed more easily. For LPS films, with a decreased annealing temperature, the stability of the polymer film changed from non-slip dewetting via apparent slip dewetting to apparently stable. However, for RPS films, the polymer film stability switched from apparent slip dewetting to apparently stable. On the silanized Si substrate with 94% grafting density, the chain adsorption became weaker and the dewetting processes were faster than that on the substrate with 69% grafting density at the same experimental temperature for both the LPS and RPS films. Moreover, on the PDMS substrate, LPS films always showed non-slip dewetting, while the dewetting kinetics of RPS films switched from non-slip dewetting to slip dewetting behaviour. Forming the wetting layer strongly influenced the stability and dewetting behavior of the thin polymer films.
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Affiliation(s)
- Lina Wang
- School of Materials Science and Engineering, Tianjin University, Tianjin 300072, P. R. China.
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11
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Napolitano S, Glynos E, Tito NB. Glass transition of polymers in bulk, confined geometries, and near interfaces. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2017; 80:036602. [PMID: 28134134 DOI: 10.1088/1361-6633/aa5284] [Citation(s) in RCA: 244] [Impact Index Per Article: 34.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
When cooled or pressurized, polymer melts exhibit a tremendous reduction in molecular mobility. If the process is performed at a constant rate, the structural relaxation time of the liquid eventually exceeds the time allowed for equilibration. This brings the system out of equilibrium, and the liquid is operationally defined as a glass-a solid lacking long-range order. Despite almost 100 years of research on the (liquid/)glass transition, it is not yet clear which molecular mechanisms are responsible for the unique slow-down in molecular dynamics. In this review, we first introduce the reader to experimental methodologies, theories, and simulations of glassy polymer dynamics and vitrification. We then analyse the impact of connectivity, structure, and chain environment on molecular motion at the length scale of a few monomers, as well as how macromolecular architecture affects the glass transition of non-linear polymers. We then discuss a revised picture of nanoconfinement, going beyond a simple picture based on interfacial interactions and surface/volume ratio. Analysis of a large body of experimental evidence, results from molecular simulations, and predictions from theory supports, instead, a more complex framework where other parameters are relevant. We focus discussion specifically on local order, free volume, irreversible chain adsorption, the Debye-Waller factor of confined and confining media, chain rigidity, and the absolute value of the vitrification temperature. We end by highlighting the molecular origin of distributions in relaxation times and glass transition temperatures which exceed, by far, the size of a chain. Fast relaxation modes, almost universally present at the free surface between polymer and air, are also remarked upon. These modes relax at rates far larger than those characteristic of glassy dynamics in bulk. We speculate on how these may be a signature of unique relaxation processes occurring in confined or heterogeneous polymeric systems.
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Affiliation(s)
- Simone Napolitano
- Laboratory of Polymer and Soft Matter Dynamics, Faculté des Sciences, Université Libre de Bruxelles (ULB), Boulevard du Triomphe, 1050 Brussels, Belgium
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12
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Zhang L, Elupula R, Grayson SM, Torkelson JM. Suppression of the Fragility-Confinement Effect via Low Molecular Weight Cyclic or Ring Polymer Topology. Macromolecules 2017. [DOI: 10.1021/acs.macromol.6b02280] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Affiliation(s)
| | - Ravinder Elupula
- Department
of Chemistry, Tulane University, New Orleans, Louisiana 70118, United States
| | - Scott M. Grayson
- Department
of Chemistry, Tulane University, New Orleans, Louisiana 70118, United States
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13
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He Q, Narayanan S, Wu DT, Foster MD. Confinement Effects with Molten Thin Cyclic Polystyrene Films. ACS Macro Lett 2016; 5:999-1003. [PMID: 35614649 DOI: 10.1021/acsmacrolett.6b00497] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The surface fluctuations of a melt film of a low molecular weight cyclic polystyrene (CPS) manifest confinement effects for a film thickness (14Rg) much larger than that for which a melt film of the linear chain analog manifests confinement. This is true both in terms of absolute thickness and thickness relative to chain size, Rg. In fact, the linear analog polymer does not manifest confinement effects even at a thickness of 7Rg. Both types of films have a strongly adsorbed layer at the substrate that plays a role in slowing the surface fluctuations for the thinnest films. This layer is 70% thicker for the cyclic chains than for the linear chains. At the interface with the substrate the packing of the cyclic chains is perturbed much more strongly than is the packing of the linear chains.
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Affiliation(s)
- Qiming He
- Department
of Polymer Science, The University of Akron, Akron, Ohio 44325, United States
| | - Suresh Narayanan
- X-ray
Science Division, Argonne National Laboratory, Argonne, Illinois 60439, United States
| | - David T. Wu
- Chemical
Engineering and Chemistry Departments, Colorado School of Mines, Golden, Colorado 80401, United States
| | - Mark D. Foster
- Department
of Polymer Science, The University of Akron, Akron, Ohio 44325, United States
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14
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He Q, Yol AM, Wang SF, Ma H, Guo K, Zhang F, Wesdemiotis C, Quirk RP, Foster MD. Efficient synthesis of well-defined cyclic polystyrenes using anionic polymerization, silicon chloride linking chemistry and metathesis ring closure. Polym Chem 2016. [DOI: 10.1039/c6py01149g] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
An efficient method for the synthesis of well-defined cyclic polystyrenes using anionic polymerization, silicon chloride linking chemistry, and metathesis ring closure has been developed.
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Affiliation(s)
- Qiming He
- Department of Polymer Science
- The University of Akron
- Akron
- USA
| | - Aleer M. Yol
- Department of Chemistry
- The University of Akron
- Akron
- USA
| | - Shih-Fan Wang
- Department of Polymer Science
- The University of Akron
- Akron
- USA
| | - Hongwei Ma
- Department of Polymer Science
- The University of Akron
- Akron
- USA
- School of Chemical Engineering
| | - Kai Guo
- Department of Polymer Science
- The University of Akron
- Akron
- USA
- Department of Chemistry
| | - Fan Zhang
- Department of Polymer Science
- The University of Akron
- Akron
- USA
| | - Chrys Wesdemiotis
- Department of Polymer Science
- The University of Akron
- Akron
- USA
- Department of Chemistry
| | | | - Mark D. Foster
- Department of Polymer Science
- The University of Akron
- Akron
- USA
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15
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Zhang L, Elupula R, Grayson SM, Torkelson JM. Major Impact of Cyclic Chain Topology on the Tg-Confinement Effect of Supported Thin Films of Polystyrene. Macromolecules 2015. [DOI: 10.1021/acs.macromol.5b02474] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Affiliation(s)
| | - Ravinder Elupula
- Department
of Chemistry, Tulane University, New Orleans, Louisiana 70118, United States
| | - Scott M. Grayson
- Department
of Chemistry, Tulane University, New Orleans, Louisiana 70118, United States
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16
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Sinha SK, Jiang Z, Lurio LB. X-ray photon correlation spectroscopy studies of surfaces and thin films. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2014; 26:7764-7785. [PMID: 25236339 DOI: 10.1002/adma.201401094] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2014] [Revised: 06/24/2014] [Indexed: 06/03/2023]
Abstract
The technique of X-ray Photon Correlation Spectroscopy (XPCS) is reviewed as a method for studying the relatively slow dynamics of materials on time scales ranging from microseconds to thousands of seconds and length scales ranging from microns down to nanometers. We focus on the application of this technique to study dynamical fluctuations of surfaces, interfaces and thin films. We first discuss instrumental issues such as the effects of partial coherence (or alternatively finite instrumental resolution) and optimization of signal-to-noise ratios in the experiments. We then review what has been learned from recent XPCS studies of capillary wave fluctuations on liquid surfaces and polymer films, of nanoparticles used as probes to study the interior dynamics of polymer films, of liquid crystals and multilamellar surfactant films, and of metal surfaces, and magnetic domain wall fluctuations in antiferromagnets. We then discuss studies of non-equilibrium dynamics described by 2-time correlation functions. Finally, we briefly speculate on possible future XPCS experiments at new synchrotron sources currently under development including studies of dynamics on time scales down to femtoseconds.
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Affiliation(s)
- Sunil K Sinha
- Dept. of Physics, University of California San Diego, 9500 Gilman Drive, La Jolla, CA, 92093-0319, USA
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17
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Frieberg B, Kim J, Narayanan S, Green PF. Surface dynamics of miscible polymer blend nanocomposites. ACS NANO 2014; 8:607-613. [PMID: 24358964 DOI: 10.1021/nn405233a] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Diverse processes that include energy conversion, wettability, lubrication, adhesion, and surface-directed phase separation in mixtures fundamentally depend on the structure and dynamics of materials' surfaces and interfaces. We report an unusual phenomenon wherein the surface viscosity of polymer nanocomposites of polystyrene (PS), polyvinyl methyl ether (PVME), and PS-coated gold nanoparticles (PS/PVME/PS-Au) is over an order of magnitude smaller than that of the neat miscible PS/PVME blend. Our X-ray photon correlation spectroscopy studies of the surface dynamics also reveal that the polymer chains manifest dynamics associated with two separate average compositional environments: a PVME-rich region, significantly in excess of its bulk concentration, and a separate PS-rich environment, where the dynamics are approximately 2 orders of magnitude slower. The unusually rapid surface dynamics in the PS/PVME/PS-Au nanocomposite are due largely to the excess PVME chains and the polymer/brush-coated nanoparticle interactions at the free surface.
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Affiliation(s)
- Bradley Frieberg
- Macromolecular Science and Engineering and ‡Department of Material Science and Engineering, University of Michigan , Ann Arbor, Michigan 48109, United States
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18
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Wang SF, Yang S, Lee J, Akgun B, Wu DT, Foster MD. Anomalous surface relaxations of branched-polymer melts. PHYSICAL REVIEW LETTERS 2013; 111:068303. [PMID: 23971618 DOI: 10.1103/physrevlett.111.068303] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/10/2012] [Indexed: 06/02/2023]
Abstract
The dynamics of thermally stimulated surface fluctuations of 100 nm thick films of long-branched polymers are measured for the first time. In contrast to comparable films of linear or cyclic chains that show no change in viscosity upon confinement, films of 6-pom, 6-star, and 6-end end-branched stars show viscosities, inferred from x-ray photon correlation spectroscopy, as much as 100 times higher than in the bulk. This difference varies in magnitude with chain architecture. Branching has a profound effect on confinement, even for these unentangled chains.
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Affiliation(s)
- Shih-fan Wang
- Department of Polymer Science, The University of Akron, Akron, Ohio 44325-3909, USA
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19
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Frieberg B, Kim J, Narayanan S, Green PF. Surface Layer Dynamics in Miscible Polymer Blends. ACS Macro Lett 2013; 2:388-392. [PMID: 35581844 DOI: 10.1021/mz400104p] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
In thin film A/B polymer/polymer mixtures, the formation of a layer at the free surface, with average composition that differs from the bulk, due to the preferential segregation of the lower cohesive energy density component, is well understood. While much is also understood about this surface layer formation and growth to date, virtually nothing is known about the surface dynamics of the chains in such mixtures. Questions about the surface chain dynamics in relation to the bulk have remained unanswered. With the use of X-ray photon correlation spectroscopy (XPCS) we show that the dynamics of poly(vinyl methyl ether) (PVME) chains at the free surface of polystyrene (PS)/PVME thin film mixtures can be orders of magnitude larger than the PVME chains in the bulk. These dynamics manifest from differences between the local compositions of the blend at the free surface and the bulk, as well as film thickness constraints.
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Affiliation(s)
| | | | | | - Peter F. Green
- Advanced Photon
Source, Argonne National Laboratory, Argonne, Illinois 60439, United States
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Liu B, Narayanan S, Wu DT, Foster MD. Polymer Film Surface Fluctuation Dynamics in the Limit of Very Dense Branching. Macromolecules 2013. [DOI: 10.1021/ma3022986] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Boxi Liu
- Department of Polymer Science, The University of Akron, Akron, Ohio 44325, United
States
| | - Suresh Narayanan
- X-ray Science Division, Argonne National Laboratory, Argonne, Illinois 60439,
United States
| | - David T. Wu
- Chemical Engineering
and Chemistry
Departments, Colorado School of Mines,
Golden, Colorado 80401, United States
| | - Mark D. Foster
- Department of Polymer Science, The University of Akron, Akron, Ohio 44325, United
States
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