摘要
采用分子动力学（ＭＤ）模拟方法研究了真空状态下单链聚乙烯从伸直链开始的结晶过程。结果表明，整个模拟过程可以分成３个阶段。由于内聚能和熵的驱动，伸直链开始因各个σ键的内旋转和构象态跃迁而卷曲、聚集，渐渐形成具有一定密度的无规线团，这一阶段称为“内聚阶段”。从无规线团开始，通过分子链段的调整而形成结构比较规整的片晶（Ｌａｍｅｌａ）结构，是“有序化阶段”。该阶段可用通常处理结晶实验数据的Ａｖｒａｍｉ方程描述（在３００Ｋ，ｎ＝１４４，Ｋ＝４９２×１０－４ｓ－１４４），属于无热成核、受链段扩散控制的三维生长的结晶生长机制。在最后的“调整阶段”，模拟体系的能量和有序度基本稳定，但片晶的形状还在做动态调整。模拟过程的３个阶段与聚合物本体结晶过程中结晶成核、晶体生长和晶体完善不同但有相似之处。
A study using molecular dynamics has been done on a single chain crystallization from the extended chain under vacuum. The results show that this process consists of three stages. Since the cohesion energy and the entropy drive the extended chain crimpled with conformational state transitions on the backbone bonds. It is leading to a random coil, and ended “the cohesion stage”. In turn, “the ordering stage” starts, the chain segments of the coil are ordering and become a structure of lamella. It was found that the process under the second stage can be described by using Avrami equation (300 K, n=1 44,K =4 92×10 -4 s -1 44 ) which is extensively used in experiments. Therefore, the crystal growing mechanism belongs to the athermal nucleation and the chain defusion controled process. Finally, at “the adjusting stage”, the energy and the order of the system tend to be stable, and the shape of the lamella is fluctuating.
出处
《计算机与应用化学》
CAS
CSCD
1999年第2期81-88,共8页
Computers and Applied Chemistry
基金
国家自然科学基金
国家攀登计划---"高分子凝聚态物理"资助
关键词
分子动力学
单链聚乙烯
结晶过程
聚乙烯
Molecular dynamics, Single chain polyethylene, Crystallization
