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Entropic barrier theory of polymer melting
Journal of Polymer Science ( IF 3.9 ) Pub Date : 2023-10-04 , DOI: 10.1002/pol.20230576 Murugappan Muthukumar 1
Journal of Polymer Science ( IF 3.9 ) Pub Date : 2023-10-04 , DOI: 10.1002/pol.20230576 Murugappan Muthukumar 1
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We present a theory of melting kinetics of semicrystalline polymers at temperatures above the equilibrium melting temperature, by accounting for conformational entropy of chains during melting. We have derived free energy landscapes for escape of individual chains from a lamella into the amorphous phase as a function of the characteristics of the initial lamella, such as the lamellar thickness, number of chain folds, fold- and lateral-surface free energies, and mean energy of a monomer inside the lamella. We show that melting of lamellae is always accompanied by a free energy barrier which is entirely entropic in origin. In terms of the parameters characterizing the lamellae and the extent of superheating, closed-form formulas are presented for the equilibrium melting temperature, driving force for crystallization, free energy barrier height, average expulsion time of a single chain from a lamella, and the melting velocity of lamellae. The present entropic barrier theory predicts that the dependence of melting velocity on superheating is nonlinear and non-Arrhenius, in qualitative agreement with experimental observations reported in the literature. The derived formulas open an opportunity to further explore the role of various molecular features of semicrystalline polymers on their melting kinetics.
中文翻译：
聚合物熔融的熵势垒理论
通过考虑熔化过程中链的构象熵，我们提出了半结晶聚合物在高于平衡熔化温度的熔化动力学理论。我们导出了单个链从片层逃逸到无定形相的自由能景观，作为初始片层特征的函数，例如片层厚度、链折叠数量、折叠和侧表面自由能，以及片层内单体的平均能量。我们表明，片层的熔化总是伴随着自由能垒，该自由能垒本质上是完全熵的。根据表征片层的参数和过热程度，给出了平衡熔化温度、结晶驱动力、自由能垒高度、单链从片层中排出的平均时间以及熔化的闭式公式。片层的速度。目前的熵势垒理论预测熔化速度对过热的依赖性是非线性和非阿累尼乌斯的，与文献中报告的实验观察结果定性一致。推导的公式为进一步探索半结晶聚合物的各种分子特征对其熔融动力学的作用提供了机会。
更新日期：2023-10-04
中文翻译：
聚合物熔融的熵势垒理论
通过考虑熔化过程中链的构象熵，我们提出了半结晶聚合物在高于平衡熔化温度的熔化动力学理论。我们导出了单个链从片层逃逸到无定形相的自由能景观，作为初始片层特征的函数，例如片层厚度、链折叠数量、折叠和侧表面自由能，以及片层内单体的平均能量。我们表明，片层的熔化总是伴随着自由能垒，该自由能垒本质上是完全熵的。根据表征片层的参数和过热程度，给出了平衡熔化温度、结晶驱动力、自由能垒高度、单链从片层中排出的平均时间以及熔化的闭式公式。片层的速度。目前的熵势垒理论预测熔化速度对过热的依赖性是非线性和非阿累尼乌斯的，与文献中报告的实验观察结果定性一致。推导的公式为进一步探索半结晶聚合物的各种分子特征对其熔融动力学的作用提供了机会。
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