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Di Lisio V, Rocchi LA, Cangialosi D. Twofold Facet of Kinetics of Glass Aging. PHYSICAL REVIEW LETTERS 2024; 133:048201. [PMID: 39121415 DOI: 10.1103/physrevlett.133.048201] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/20/2024] [Accepted: 06/24/2024] [Indexed: 08/11/2024]
Abstract
We employ fast scanning calorimetry to monitor the isothermal aging kinetics in glassy polymers, complemented with measurements on other glasses. Apart from following the time evolution of the glass enthalpic state, we monitor the aging kinetics of the devitrification width on heating, ΔT_{dev}. We find that significantly below the glass transition temperature, T_{g}, the glass enthalpy attains equilibrium earlier than ΔT_{dev}, which evolves at long aging times toward enhanced heterogeneity. Hence, our results indicate that the description of time dependent evolution in glassy materials requires information beyond the mere description of its enthalpic state.
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Colaruotolo LA, Singh SS, Dobson S, Lim LT, Joye IJ, Rogers MA, Corradini MG. Mapping deterioration in electrospun zein nonwoven nanostructures encapsulating corn oil. Curr Res Food Sci 2024; 9:100801. [PMID: 39050407 PMCID: PMC11267021 DOI: 10.1016/j.crfs.2024.100801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2024] [Revised: 06/14/2024] [Accepted: 06/27/2024] [Indexed: 07/27/2024] Open
Abstract
Electrospun nonwovens of biopolymers are gaining popularity in filtration, coatings, encapsulation, and packaging materials. However, their applications are hindered by limited stability, particularly when loaded with lipids. This research aimed to apply a multiscale approach to gain insights into deteriorative processes, e.g., oxidation, limiting the shelf life of these complex materials, using corn oil-loaded electrospun zein nonwovens as a model system. Oil-doped zein electrospun nonwovens were stored in the dark at 23 °C and 33% relative humidity for 28 days and tested at selected intervals to monitor their morphology and mechanical properties. Lipid oxidation was assessed using the thiobarbituric acid reactive species (TBARS) assay. The photophysical properties of intrinsic, i.e., tyrosine (Tyr), and extrinsic, i.e., boron-dipyrromethene undecanoic acid 581/591 (BODIPY C11), lumiphores were also monitored to evaluate changes in local molecular rigidity, and oxidation, respectively. The protein secondary structure was determined with Fourier transform infrared spectroscopy (FTIR). Scanning electron microscopy (SEM) analysis of the oil-loaded electrospun nonwovens revealed that the diameter of the ribbon-like fiber significantly decreased during storage from 701 ± 23 nm to 620 ± 44 nm. Breakage of the electrospun fibers was observed and correlated with increased brittleness and molecular rigidity of the nonwoven material, reflected by an increase in Tyr emission intensity and phosphorescence lifetime. Changes in tensile strength, brittleness and matrix rigidity also correlated with a zein secondary structure transition from unordered to ordered β-sheets. Raman and luminescence micrographs showed oil migration during storage, thereby increasing lipid oxidation. The correlation between local rigidity and lipid distribution/oxidation suggests that reorganizing protein structures increased material brittleness and displaced encapsulated oils within the electrospun fiber. Understanding deteriorative mechanisms aids in developing innovative strategies to improve the stability of these novel food-grade materials.
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Affiliation(s)
| | | | - Stacie Dobson
- Department of Food Science, University of Guelph, Guelph, ON, Canada
| | - Loong-Tak Lim
- Department of Food Science, University of Guelph, Guelph, ON, Canada
| | - Iris J. Joye
- Department of Food Science, University of Guelph, Guelph, ON, Canada
| | - Michael A. Rogers
- Department of Food Science, University of Guelph, Guelph, ON, Canada
| | - Maria G. Corradini
- Department of Food Science, University of Guelph, Guelph, ON, Canada
- Arrell Food Institute, University of Guelph, Guelph, ON, Canada
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Verde R, D’Amore A, Grassia L. A Numerical Model to Predict the Relaxation Phenomena in Thermoset Polymers and Their Effects on Residual Stress during Curing-Part I: A Theoretical Formulation and Numerical Evaluation of Relaxation Phenomena. Polymers (Basel) 2024; 16:1433. [PMID: 38794626 PMCID: PMC11124950 DOI: 10.3390/polym16101433] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2024] [Revised: 05/08/2024] [Accepted: 05/14/2024] [Indexed: 05/26/2024] Open
Abstract
This paper analyzes the effect of crosslinking reactions on a thermoset polymer's viscoelastic properties. In particular, a numerical model to predict the evolution of epoxy's mechanical properties during the curing process is proposed and implemented in an Ansys APDL environment. A linear viscoelastic behavior is assumed, and the scaling of viscoelastic properties in terms of the temperature and degree of conversion is modeled using a modified version of the TNM (Tool-Narayanaswamy-Mohynian) model. The effects of the degree of conversion and structural relaxation on epoxy's relaxation times are simultaneously examined for the first time. This formulation is based on the thermo-rheological and chemo-rheological simplicities hypothesis and can predict the evolution of epoxy's relaxation phenomena. The thermal-kinetic reactions of curing are implemented in a homemade routine written in APDL language, and the structural module of Ansys is used to predict the polymer's creep and stress relaxation curves at different temperatures and degrees of conversion.
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Affiliation(s)
| | | | - Luigi Grassia
- Department of Engineering, University of Campania “Luigi Vanvitelli”, via Roma, 29, 81031 Aversa, Italy; (R.V.); (A.D.)
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Luo J, Wang X, Tong B, Li Z, Rocchi LA, Di Lisio V, Cangialosi D, Zuo B. Length Scale of Molecular Motions Governing Glass Equilibration in Hyperquenched and Slow-Cooled Polystyrene. J Phys Chem Lett 2024; 15:357-363. [PMID: 38175163 DOI: 10.1021/acs.jpclett.3c03263] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2024]
Abstract
Polymer glasses attain thermodynamic equilibrium owing to structural relaxation at various length scales. Herein, calorimetry experiments were conducted to trace the macroscopic relaxation of slow-cooled (SC) and hyperquenched (HQ) polystyrene (PS) glasses and based on detailed comparisons with molecular dynamics probed by dye reorientation, we discussed the possible molecular process governing the equilibration of PS glasses near the glass transition temperatures (Tg). Both SC and HQ glasses equilibrate owing to the cooperative segment motion above a characteristic temperature (Tc) slightly lower than the Tg. In contrast, below the Tc, the localized backbone motion with an apparent activation energy of 290 ± 20 kJ/mol, involving approximately six repeating units, assists equilibrium recovery of PS glasses on the experimentally accessible time scales. The results possibly indicate the presence of an alternative mechanism other than the α-cooperative process controlling physical aging of materials in their deep glassy states.
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Affiliation(s)
- Jintian Luo
- School of Chemistry and Chemical Engineering, Key Laboratory of Surface & Interface Science of Polymer Materials of Zhejiang Province, Zhejiang Sci-Tech University, Hangzhou 310018, China
| | - Xiang Wang
- School of Chemistry and Chemical Engineering, Key Laboratory of Surface & Interface Science of Polymer Materials of Zhejiang Province, Zhejiang Sci-Tech University, Hangzhou 310018, China
| | - Ben Tong
- School of Chemistry and Chemical Engineering, Key Laboratory of Surface & Interface Science of Polymer Materials of Zhejiang Province, Zhejiang Sci-Tech University, Hangzhou 310018, China
| | - Zhiqiang Li
- School of Chemistry and Chemical Engineering, Key Laboratory of Surface & Interface Science of Polymer Materials of Zhejiang Province, Zhejiang Sci-Tech University, Hangzhou 310018, China
| | - Lorenzo Augusto Rocchi
- Department of Chemistry, University of Rome "La Sapienza", P.le A. Moro 5, 00185 Rome, Italy
| | - Valerio Di Lisio
- Donostia International Physics Center, Paseo Manuel de Lardizabal 4, 20018 San Sebastian, Spain
| | - Daniele Cangialosi
- Donostia International Physics Center, Paseo Manuel de Lardizabal 4, 20018 San Sebastian, Spain
- Centro de Física de Materiales, Paseo Manuel de Lardizabal 5, 20018 San Sebastian, Spain
| | - Biao Zuo
- School of Chemistry and Chemical Engineering, Key Laboratory of Surface & Interface Science of Polymer Materials of Zhejiang Province, Zhejiang Sci-Tech University, Hangzhou 310018, China
- Zhejiang Provincial Innovation Center of Advanced Textile Technology, Shaoxing 312000, China
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Seo Y, Zuo B, Cangialosi D, Priestley RD. Physical aging of hydroxypropyl methylcellulose acetate succinate via enthalpy recovery. SOFT MATTER 2022; 18:8331-8341. [PMID: 36300535 DOI: 10.1039/d2sm01189a] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Amorphous solid dispersions (ASDs) utilize the kinetic stability of the amorphous state to stabilize drug molecules within a glassy polymer matrix. Therefore, understanding the glassy-state stability of the polymer excipient is critical to ASD design and performance. Here, we investigated the physical aging of hydroxypropyl methylcellulose acetate succinate (HPMCAS), a commonly used polymer in ASD formulations. We found that HPMCAS exhibited conventional physical aging behavior when annealed near the glass transition temperature (Tg). In this scenario, structural recovery was facilitated by α-relaxation dynamics. However, when annealed well below Tg, a sub-α-relaxation process facilitated low-temperature physical aging in HPMCAS. Nevertheless, the physical aging rate exhibited no significant change up to 40 K below Tg, below which it exhibited a near monotonic decrease with decreasing temperature. Finally, infrared spectroscopy was employed to assess any effect of physical aging on the chemical structure of HPMCAS, which is known to be susceptible to degradation at temperatures 30 K above its Tg. Our results provide critical insights necessary to understand better the link between the stability of ASDs and physical aging of the glassy polymer matrix.
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Affiliation(s)
- Yejoon Seo
- Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08540, USA
| | - Biao Zuo
- Department of Chemistry, Zhejiang Sci-Tech University, Hangzhou, 310018, China
| | - Daniele Cangialosi
- Donostia International Physics Center (DIPC), Paseo Manuel de Lardizábal 4, 20018, San Sebastián, Spain
- Centro de Fisica de Materiales (CSIC-UPV/EHU), Paseo Manuel de Lardizábal 5, 20018, San Sebastián, Spain
| | - Rodney D Priestley
- Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08540, USA
- Princeton Institute for the Science and Technology of Materials, Princeton University, 41 Olden St, A215 Chemical and Biological Engineering, Princeton, New Jersey 08540, USA.
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Odarchenko Y, Kaźmierczak-Bałata A, Bodzenta J, Ferrari E, Soloviev M. AC/DC Thermal Nano-Analyzer Compatible with Bulk Liquid Measurements. NANOMATERIALS (BASEL, SWITZERLAND) 2022; 12:3799. [PMID: 36364575 PMCID: PMC9655476 DOI: 10.3390/nano12213799] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/31/2022] [Revised: 10/16/2022] [Accepted: 10/25/2022] [Indexed: 06/16/2023]
Abstract
Nanocalorimetry, or thermal nano-analysis, is a powerful tool for fast thermal processing and thermodynamic analysis of materials at the nanoscale. Despite multiple reports of successful applications in the material sciences to study phase transitions in metals and polymers, thermodynamic analysis of biological systems in their natural microenvironment has not been achieved yet. Simply scaling down traditional calorimetric techniques, although beneficial for material sciences, is not always appropriate for biological objects, which cannot be removed out of their native biological environment or be miniaturized to suit instrument limitations. Thermal analysis at micro- or nano-scale immersed in bulk liquid media has not yet been possible. Here, we report an AC/DC modulated thermal nano-analyzer capable of detecting nanogram quantities of material in bulk liquids. The detection principle used in our custom-build instrument utilizes localized heat waves, which under certain conditions confine the measurement area to the surface layer of the sample in the close vicinity of the sensing element. To illustrate the sensitivity and quantitative capabilities of the instrument we used model materials with detectable phase transitions. Here, we report ca. 106 improvement in the thermal analysis sensitivity over a traditional DSC instrument. Interestingly, fundamental thermal properties of the material can be determined independently from heat flow in DC (direct current) mode, by using the AC (alternating current) component of the modulated heat in AC/DC mode. The thermal high-frequency AC modulation mode might be especially useful for investigating thermal transitions on the surface of material, because of the ability to control the depth of penetration of AC-modulated heat and hence the depth of thermal sensing. The high-frequency AC mode might potentially expand the range of applications to the surface analysis of bulk materials or liquid-solid interfaces.
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Affiliation(s)
- Yaroslav Odarchenko
- Department of Biological Sciences, Royal Holloway University of London, Egham, Surrey TW20 0EX, UK
| | - Anna Kaźmierczak-Bałata
- Institute of Physics, Center for Science and Education, Silesian University of Technology, Konarskiego 22B, 44-100 Gliwice, Poland
| | - Jerzy Bodzenta
- Institute of Physics, Center for Science and Education, Silesian University of Technology, Konarskiego 22B, 44-100 Gliwice, Poland
| | - Enrico Ferrari
- Department of Life Sciences, University of Lincoln, Lincoln LN6 7TS, UK
| | - Mikhail Soloviev
- Department of Biological Sciences, Royal Holloway University of London, Egham, Surrey TW20 0EX, UK
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Cangialosi D, Alegría A, Colmenero J. Comment on “Anomalous structural recovery in the near glass transition range in a polymer glass: Data revisited in light of temperature variability in vacuum oven‐based experiments”. POLYM ENG SCI 2022. [DOI: 10.1002/pen.26054] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Daniele Cangialosi
- Centro de Fisica de Materiales (CSIC‐UPV/EHU) Sebastián Spain
- Departamento de Polímeros y Materiales Avanzados: Física, Química y Tecnología (UPV/EHU) San Sebastián Spain
| | - Angel Alegría
- Departamento de Polímeros y Materiales Avanzados: Física, Química y Tecnología (UPV/EHU) San Sebastián Spain
- Donostia International Physics Center San Sebastián Spain
| | - Juan Colmenero
- Centro de Fisica de Materiales (CSIC‐UPV/EHU) Sebastián Spain
- Departamento de Polímeros y Materiales Avanzados: Física, Química y Tecnología (UPV/EHU) San Sebastián Spain
- Donostia International Physics Center San Sebastián Spain
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8
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Niss K. A density scaling conjecture for aging glasses. J Chem Phys 2022; 157:054503. [DOI: 10.1063/5.0090869] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The aging rate of glasses has traditionally been modeled as a function of temperature, T , andfictive temperature, while density, ρ, is not explicitly included as a parameter. However, this de-scription does not naturally connect to the modern understanding of what governs the relaxationrate in equilibrium. In equilibrium it is well known that the relaxation rate, γeq , depends on tem-perature and density. In addition a large class of systems obey density scaling which means therate specifically depends on the scaling parameter, Γ = e(ρ)/T , where e(ρ) is a system specificfunction. This paper present a generalization of the fictive temperature concept in terms of a fic-tive scaling paramter, Γfic , and a density scaling conjecture for aging glasses in which the agingrate depends on Γ and Γfic .
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Zhang R, Madhavi V, Shaffer TD, Androsch R, Schick C. Cyclic Olefin Copolymers (COC) – Excellent Glass Formers with Low Dynamic Fragility. MACROMOL CHEM PHYS 2022. [DOI: 10.1002/macp.202200065] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Rui Zhang
- Institute of Physics and Competence Centre°CALOR University of Rostock Rostock 18051 Germany
- Interdisciplinary Center for Transfer‐oriented Research in Natural Sciences (IWE TFN) Martin Luther University Halle‐Wittenberg Halle/Saale 06099 Germany
| | | | | | - René Androsch
- Interdisciplinary Center for Transfer‐oriented Research in Natural Sciences (IWE TFN) Martin Luther University Halle‐Wittenberg Halle/Saale 06099 Germany
| | - Christoph Schick
- Institute of Physics and Competence Centre°CALOR University of Rostock Rostock 18051 Germany
- Butlerov Institute of Chemistry Kazan Federal University 18 Kremlyovskaya Street Kazan 420008 Russia
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10
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Effects of Fiber Orientation on the Coefficient of Thermal Expansion of Fiber-Filled Polymer Systems in Large Format Polymer Extrusion-Based Additive Manufacturing. MATERIALS 2022; 15:ma15082764. [PMID: 35454459 PMCID: PMC9031978 DOI: 10.3390/ma15082764] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/03/2022] [Revised: 04/01/2022] [Accepted: 04/06/2022] [Indexed: 11/17/2022]
Abstract
Large format polymer extrusion-based additive manufacturing has been studied recently due to its capacity for high throughput, customizable bead size and geometry, and ability to manufacture large parts. Samples from three fiber-filled amorphous thermoplastic materials 3D printed using a Masterprint 3X machine from Ingersoll Machine Tools were studied, along with their neat counterparts. Characterization techniques included thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and thermo-mechanical analysis (TMA). TGA results showed that the fillers decreased the degradation temperature for most of the materials investigated, with a 30 °C decrease for polycarbonate (PC) and a 12 °C decrease for polyethylene terephthalate glycol (PETG). For all the materials used, heat capacity increases with increasing temperature. Moreover, results show that a highly conductive filler increases the heat capacity. In contrast, a material with a lower conductivity decreases the heat capacity indicated in the 15.2% and 2.54% increase for acrylonitrile butadiene styrene (ABS) and PC and a 27.68% decrease for PETG. The TMA data show that the printed bead exhibits directional properties consistent with an orthotropic material. Smaller strains and coefficient of thermal expansion (CTE) were measured along the bead direction and across the bead compared to the through bead thickness showing that fillers are predominantly oriented in the bead direction, which is consistent with the literature. CTE values through bead thickness and neat material are similar in magnitude, which corresponds to the CTE of the matrix material. The experimental results serve to characterize the effect of fiber filler on the part thermal strains in three principal directions and two-part locations during the extrusion and bead deposition of large-format polymer extrusion-based additive manufacturing technologies.
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Riechers B, Roed LA, Mehri S, Ingebrigtsen TS, Hecksher T, Dyre JC, Niss K. Predicting nonlinear physical aging of glasses from equilibrium relaxation via the material time. SCIENCE ADVANCES 2022; 8:eabl9809. [PMID: 35294250 PMCID: PMC8926348 DOI: 10.1126/sciadv.abl9809] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
The noncrystalline glassy state of matter plays a role in virtually all fields of materials science and offers complementary properties to those of the crystalline counterpart. The caveat of the glassy state is that it is out of equilibrium and therefore exhibits physical aging, i.e., material properties change over time. For half a century, the physical aging of glasses has been known to be described well by the material-time concept, although the existence of a material time has never been directly validated. We do this here by successfully predicting the aging of the molecular glass 4-vinyl-1,3-dioxolan-2-one from its linear relaxation behavior. This establishes the defining property of the material time. Via the fluctuation-dissipation theorem, our results imply that physical aging can be predicted from thermal-equilibrium fluctuation data, which is confirmed by computer simulations of a binary liquid mixture.
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Flores I, Pérez-Camargo RA, Gabirondo E, Caputo MR, Liu G, Wang D, Sardon H, Müller AJ. Unexpected Structural Properties in the Saturation Region of the Odd–Even Effects in Aliphatic Polyethers: Influence of Crystallization Conditions. Macromolecules 2022. [DOI: 10.1021/acs.macromol.1c02235] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Irma Flores
- POLYMAT and Department of Polymers and Advanced Materials: Physics, Chemistry and Technology, Faculty of Chemistry, University of the Basque Country UPV/EHU, Paseo Manuel de Lardizabal 3, Donostia-San Sebastián 20018, Spain
| | - Ricardo A. Pérez-Camargo
- Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Engineering Plastics, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
| | - Elena Gabirondo
- POLYMAT and Department of Polymers and Advanced Materials: Physics, Chemistry and Technology, Faculty of Chemistry, University of the Basque Country UPV/EHU, Paseo Manuel de Lardizabal 3, Donostia-San Sebastián 20018, Spain
| | - Maria Rosaria Caputo
- POLYMAT and Department of Polymers and Advanced Materials: Physics, Chemistry and Technology, Faculty of Chemistry, University of the Basque Country UPV/EHU, Paseo Manuel de Lardizabal 3, Donostia-San Sebastián 20018, Spain
| | - Guoming Liu
- Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Engineering Plastics, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Dujin Wang
- Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Engineering Plastics, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Haritz Sardon
- POLYMAT and Department of Polymers and Advanced Materials: Physics, Chemistry and Technology, Faculty of Chemistry, University of the Basque Country UPV/EHU, Paseo Manuel de Lardizabal 3, Donostia-San Sebastián 20018, Spain
| | - Alejandro J. Müller
- POLYMAT and Department of Polymers and Advanced Materials: Physics, Chemistry and Technology, Faculty of Chemistry, University of the Basque Country UPV/EHU, Paseo Manuel de Lardizabal 3, Donostia-San Sebastián 20018, Spain
- IKERBASQUE, Basque Foundation for Science, Plaza Euskadi 5, Bilbao 48009, Spain
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Mansuri A, Münzner P, Feuerbach T, Vermeer AWP, Hoheisel W, Böhmer R, Thommes M, Gainaru C. The relaxation behavior of supercooled and glassy imidacloprid. J Chem Phys 2021; 155:174502. [PMID: 34742219 DOI: 10.1063/5.0067404] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Employing dielectric spectroscopy, oscillatory shear rheology, and calorimetry, the present work explores the molecular dynamics of the widely used insecticide imidacloprid above and below its glass transition temperature. In its supercooled liquid regime, the applied techniques yield good agreement regarding the characteristic structural (alpha) relaxation times of this material. In addition, the generalized Gemant-DiMarzio-Bishop model provides a good conversion between the frequency-dependent dielectric and shear mechanical responses in its viscous state, allowing for an assessment of imidacloprid's molecular hydrodynamic radius. In order to characterize the molecular dynamics in its glassy regime, we employ several approaches. These include the application of frequency-temperature superposition (FTS) to its isostructural dielectric and rheological responses as well as use of dielectric and calorimetric physical aging and the Adam-Gibbs-Vogel model. While the latter approach and dielectric FTS provide relaxation times that are close to each other, the other methods predict notably longer times that are closer to those reflecting a complete recovery of ergodicity. This seemingly conflicting dissimilarity demonstrates that the molecular dynamics of glassy imidacloprid strongly depends on its thermal history, with high relevance for the use of this insecticide as an active ingredient in technological applications.
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Affiliation(s)
- A Mansuri
- INVITE GmbH, 51368 Leverkusen, Germany
| | - P Münzner
- Department of Physics, TU Dortmund University, 44221 Dortmund, Germany
| | - T Feuerbach
- Chair of Solids Process Engineering, TU Dortmund University, 44227 Dortmund, Germany
| | | | | | - R Böhmer
- Department of Physics, TU Dortmund University, 44221 Dortmund, Germany
| | - M Thommes
- Chair of Solids Process Engineering, TU Dortmund University, 44227 Dortmund, Germany
| | - C Gainaru
- Department of Physics, TU Dortmund University, 44221 Dortmund, Germany
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14
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Ngai KL. The origin of the faster mechanism of partial enthalpy recovery deep in the glassy state of polymers. Phys Chem Chem Phys 2021; 23:13468-13472. [PMID: 34105553 DOI: 10.1039/d1cp01445e] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A novel finding made by Cangialosi and coworkers in the physical aging of several polymers way below the glass transition temperature Tg is that equilibrium recovery occurs by reaching a plateau in the enthalpy with partial enthalpy recovery. This observation points to the existence of a much faster mechanism capable of partial equilibrium recovery deep in the glassy state. A similar phenomenon was found in different glassy materials. The generality of the phenomenon indicates that the faster mechanism of equilibrium recovery is universal and fundamental. In this paper the faster mechanism is identified to be the universal JG β-relaxation having dynamic and thermodynamic properties analogous to the α-relaxation, and thus capable of effecting enthalpy and volume recovery far below Tg in several high-Tg polymers. The JG β-relaxation is also the mechanism responsible for the first step of two steps in the approach to equilibrium found in another polymer with much lower Tg. The Coupling Model is used to explain why the first step transpires far below Tg in some polymers but much closer to Tg in another polymer.
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Affiliation(s)
- K L Ngai
- CNR-IPCF, Largo B. Pontecorvo 3, I-56127, Pisa, Italy.
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