玻璃化转变
聚合物
链条(单位)
工作(物理)
热力学
化学物理
分子动力学
稀释
高分子
转变温度
线型聚合物
化学
材料科学
统计物理学
高分子化学
物理
计算化学
凝聚态物理
有机化学
量子力学
超导电性
生物化学
作者
William F. Drayer,David Simmons
标识
DOI:10.1021/acs.macromol.4c00419
摘要
The immense dependence of the glass transition temperature Tg on molecular weight M is one of the most fundamentally and practically important features of polymer glass formation. Here, we report on molecular dynamics simulations of three model linear polymers of substantially different complexity demonstrating that the 70-year-old canonical explanation of this dependence (a simple chain end dilution effect) is likely incorrect at leading order. Our data show that end effects are present only in relatively stiff polymers and, furthermore, that the magnitude of these end effects diminish on cooling. We find that Tg(M) trends are instead dominated by shifts in Tg throughout the entire polymer chain rather than through a chain end effect. We show that these data can be rationalized via a generic two-barrier model of Tg and its M-dependence, motivated by the Elastically Collective Nonlinear Langevin Equation theory. More broadly, this work indicates need to reopen the question of the origin of the Tg(M) dependence in linear polymers (and macromolecules at large), as well as an opportunity to reveal new glass formation physics with renewed study of M effects on Tg.
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