Entropic barrier theory of polymer melting
Entropic barrier theory of polymer melting
复制标题
聚合物熔融的熵势垒理论
DOI：
10.1002/pol.20230576
复制
发表时间：
2023
影响因子：
3.4
通讯作者：
Muthukumar, Murugappan
中科院分区：
文献类型：
--
作者：
Muthukumar, Murugappan
通过考虑熔融过程中链的构象熵，提出了半晶聚合物在平衡熔融温度以上的熔融动力学理论。我们得到了单个链从片层逃逸到无定形相的自由能图景，它是初始片层的特征的函数，例如片层厚度、链折叠的数量、折叠和侧面自由能以及片层内单体的平均能量。我们发现薄片的熔化总是伴随着一个自由能垒，它的起源是完全的熵。根据表征晶片的参数和过热程度，给出了晶片的平衡熔化温度、结晶驱动力、自由能垒高度、平均单链从晶片中排出的时间和晶片的熔化速度的闭合公式。现有的熵势垒理论预测熔化速度与过热度的关系是非线性的、非Arrhenius的，这与文献中报道的实验结果定性一致。导出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。
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.
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影响因子：
4.4
作者：
Muthukumar, M.
通讯作者：
Muthukumar, M.
影响因子：
3.2
作者：
E. Hellmuth;B. Wunderlich
通讯作者：
E. Hellmuth;B. Wunderlich
影响因子：
1.8
作者：
Häfele, A;Heck, B;Strobl, G
通讯作者：
Strobl, G
聚合物晶体中的可逆局部熔化
影响因子：
4.6
作者：
I. Okazaki;B. Wunderlich
通讯作者：
B. Wunderlich