Insights into Physical Aging of Thermally-Quenched and Solvent-Cast Polymers from Molecular Dynamics Simulation
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University of Akron / OhioLINK
2020
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| Online Access: | http://rave.ohiolink.edu/etdc/view?acc_num=akron1597238400716617 |
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ndltd-OhioLink-oai-etd.ohiolink.edu-akron15972384007166172021-08-03T07:16:12Z Insights into Physical Aging of Thermally-Quenched and Solvent-Cast Polymers from Molecular Dynamics Simulation Jaeger, Tamara D. Condensed Matter Physics Engineering Polymers physical aging molecular dynamics simulation polymer aging solvent-processing MD simulation glasses non-equilibrium dynamics non-Arrhenius dynamics The nature of glassy aging has been a topic of study for over half a century, and yet a number of open questions remain in the understanding of the glassy state. Since a polymer’s physical and mechanical properties are directly dependent on its molecular structure and changes in that structure alter the physical properties of the glass, considerable economic impact can result from aging-related physical changes. Characterization of aging dynamics in under-dense and over-dense glasses and a comparison of the aging response in solvent-processed vs thermally-quenched glasses are two important questions that are addressed here. This work reports on the development of a protocol for studying physical aging via molecular dynamics simulation after a near-instantaneous temperature quench. The resulting data display characteristic experimental signatures of glassy aging in both a pure polymer and a polymer-plasticizer system, indicating that this protocol can potentially be used to study aging in a variety of systems. Results indicate that aging dynamics in under-dense and over-dense glasses are fundamentally different in character. Unlike in under-dense glasses, translational dynamics in over-dense glasses are mechanistically different than relaxation in equilibrium glass-forming liquids, which is supported by the finding that relaxation in over-dense glasses occurs through an explosive burst of superdiffusive motion. Addition of a plasticizer appears to moderate this response compared to that of the pure polymer system, which can be attributed to a decrease in system fragility in the plasticized system. Higher additive loadings may have an even greater effect and further research would be beneficial in clarifying this. Aging relaxation time in over-dense glasses obeys a zero parameter dependence on purely equilibrium properties. This finding enables prediction of non-equilibrium relaxation time given knowledge only of the starting temperature and the in-equilibrium relaxation time curve and is likely to be of considerable value in predicting physical aging times of highly supercooled glasses. Relaxation in under-dense glasses exhibits a non-Arrhenius dependence on aging temperature in the form of a fractional power law relationship with equilibrium relaxation times, indicating that aging times after down jumps can be predicted from equilibrium relaxation time data with one system-dependent parameter. Results suggest that relaxation times do not depend strongly on initial solvent loading and that solvent-processed polymers respond qualitatively like a temperature down jump from the melt. Further, it appears that after an initial short-time response, aging after solvent removal can be directly equated to aging after a temperature quench for aging temperatures both above and below TA. Further research over a wider range of solvent concentrations would provide greater insight in this area. 2020-08-25 English text University of Akron / OhioLINK http://rave.ohiolink.edu/etdc/view?acc_num=akron1597238400716617 http://rave.ohiolink.edu/etdc/view?acc_num=akron1597238400716617 unrestricted This thesis or dissertation is protected by copyright: all rights reserved. It may not be copied or redistributed beyond the terms of applicable copyright laws. |
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NDLTD |
| language |
English |
| sources |
NDLTD |
| topic |
Condensed Matter Physics Engineering Polymers physical aging molecular dynamics simulation polymer aging solvent-processing MD simulation glasses non-equilibrium dynamics non-Arrhenius dynamics |
| spellingShingle |
Condensed Matter Physics Engineering Polymers physical aging molecular dynamics simulation polymer aging solvent-processing MD simulation glasses non-equilibrium dynamics non-Arrhenius dynamics Jaeger, Tamara D. Insights into Physical Aging of Thermally-Quenched and Solvent-Cast Polymers from Molecular Dynamics Simulation |
| author |
Jaeger, Tamara D. |
| author_facet |
Jaeger, Tamara D. |
| author_sort |
Jaeger, Tamara D. |
| title |
Insights into Physical Aging of Thermally-Quenched and Solvent-Cast Polymers from Molecular Dynamics Simulation |
| title_short |
Insights into Physical Aging of Thermally-Quenched and Solvent-Cast Polymers from Molecular Dynamics Simulation |
| title_full |
Insights into Physical Aging of Thermally-Quenched and Solvent-Cast Polymers from Molecular Dynamics Simulation |
| title_fullStr |
Insights into Physical Aging of Thermally-Quenched and Solvent-Cast Polymers from Molecular Dynamics Simulation |
| title_full_unstemmed |
Insights into Physical Aging of Thermally-Quenched and Solvent-Cast Polymers from Molecular Dynamics Simulation |
| title_sort |
insights into physical aging of thermally-quenched and solvent-cast polymers from molecular dynamics simulation |
| publisher |
University of Akron / OhioLINK |
| publishDate |
2020 |
| url |
http://rave.ohiolink.edu/etdc/view?acc_num=akron1597238400716617 |
| work_keys_str_mv |
AT jaegertamarad insightsintophysicalagingofthermallyquenchedandsolventcastpolymersfrommoleculardynamicssimulation |
| _version_ |
1719457772665307136 |