A theoretical interpretation of free volume at glass transition |
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| Authors: | Yi-kun Ren Yun-tao Li Liang-bin Li |
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| Institution: | 1. State Key Lab of Oil & Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu 610500, China;School of Material Science and Engineering, Southwest Petroleum University, Chengdu 610500, China;National Synchrotron Radiation Lab, Key Laboratory of Soft Matter Chemistry, Chinese Academy of Sciences, University of Science and Technology of China, Hefei 230029, China;2. State Key Lab of Oil & Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu 610500, China;School of Material Science and Engineering, Southwest Petroleum University, Chengdu 610500, China;3. National Synchrotron Radiation Lab, Key Laboratory of Soft Matter Chemistry, Chinese Academy of Sciences, University of Science and Technology of China, Hefei 230029, China |
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| Abstract: | We device a relaxed lattice model (RLM) to study the mechanism of glass transition,which unifies the cageeffects from particle-particle interaction and entropy.By analyzing entropy in RLM with considering the influence of interactions on equilibrium,we demonstrate that glass transition is a second-order phase transition.For a perfect onedimensional linked particle system like linear polymer under normal pressure,the free volume at glass transition is rigorously deduced out to be 2.6％,which provides a theoretical basis for the iso-free volume of 2.5％ given by Willian,Landel and Ferry (WLF) equation.Extending to system with dead particles linked with higher dimensions like branched or cross-linked chains under positive or negative pressure,free volume at glass transition is varied,based on which we construct a phase diagram of glass transition in the space of free volume-dead particle-pressure.This demonstrates that free volume is not the single parameter determining glass transition,while either dead particles like cross-linked points or external force fields like pressure can vary free volume at the glass transition. |
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| Keywords: | Glass transition Iso-free volume Relaxed lattice model Predicted phase diagram |
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