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无规共聚物的结晶

Crystallization of Random Copolymers.

作者信息

Sanchez Isaac C, Eby R K

机构信息

Institute for Materials Research, National Bureau of Standards, Washington, D.C. 20234.

出版信息

J Res Natl Bur Stand A Phys Chem. 1973 May-Jun;77A(3):353-358. doi: 10.6028/jres.077A.023.

Abstract

A theory of crystallization is formulated for random copolymers which crystallize with the non-crystallizable co-units incorporated into the crystalline lattice as defects. The appropriate melting point equation and other associated thermodynamic properties are derived for this model as a function of crystal thickness and comonomer concentration. The formation of lamellar type morphology is assumed to be a kinetically determined phenomena and nucleation theory is utilized accordingly. The isothermal lamella thickness is predicted to increase in a definitive manner as the noncrystallizable comonomer concentration increases, while the associated isothermal growth rate is predicted to decrease. The variation of lamella thickness with when the copolymer is quenched or cooled at a uniform rate is also qualitatively predicted. Under these conditions lamella thickness decreases with increasing , which is in accord with previous experimental observations on random copolymers of tetrafluoroethylene and hexafluoropropylene as well as other random copolymers. Theory also suggests how the surface free energy parameters σ and can be determined from isothermal crystallization experiments for a series of random copolymers of varying composition.

摘要

针对无规共聚物提出了一种结晶理论,这类共聚物结晶时,不可结晶的共聚单元作为缺陷并入晶格中。针对该模型,推导了合适的熔点方程以及其他相关的热力学性质,它们是晶体厚度和共聚单体浓度的函数。假定片层状形态的形成是由动力学决定的现象,并据此运用成核理论。预测随着不可结晶共聚单体浓度的增加,等温片层厚度会以确定的方式增加,而相关的等温生长速率预计会降低。还定性地预测了共聚物以均匀速率淬火或冷却时片层厚度随时间的变化。在这些条件下,片层厚度随时间增加而减小,这与先前关于四氟乙烯和六氟丙烯无规共聚物以及其他无规共聚物的实验观察结果一致。该理论还表明如何从一系列不同组成的无规共聚物的等温结晶实验中确定表面自由能参数σ和γ。

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