Li Yongliang, Jiang Tao, Lin Shaoliang, Lin Jiaping, Cai Chunhua, Zhu Xingyu
Shanghai Key Laboratory of Advanced Polymeric Materials, State Key Laboratory of Bioreactor Engineering, Key Laboratory for Ultrafine Materials of Ministry of Education, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237, China.
Sci Rep. 2015 May 12;5:10137. doi: 10.1038/srep10137.
Self-assembly behavior of a mixture system containing rod-coil block copolymers and rigid homopolymers was investigated by using Brownian dynamics simulations. The morphologies of formed hierarchical self-assemblies were found to be dependent on the Lennard-Jones (LJ) interaction εRR between rod blocks, lengths of rod and coil blocks in copolymer, and mixture ratio of block copolymers to homopolymers. As the εRR value decreases, the self-assembled structures of mixtures are transformed from an abacus-like structure to a helical structure, to a plain fiber, and finally are broken into unimers. The order parameter of rod blocks was calculated to confirm the structure transition. Through varying the length of rod and coil blocks, the regions of thermodynamic stability of abacus, helix, plain fiber, and unimers were mapped. Moreover, it was discovered that two levels of rod block ordering exist in the helices. The block copolymers are helically wrapped on the homopolymer bundles to form helical string, while the rod blocks are twistingly packed inside the string. In addition, the simulation results are in good agreement with experimental observations. The present work reveals the mechanism behind the formation of helical (experimentally super-helical) structures and may provide useful information for design and preparation of the complex structures.
通过布朗动力学模拟研究了含有棒-线圈嵌段共聚物和刚性均聚物的混合体系的自组装行为。发现形成的分级自组装的形态取决于棒状嵌段之间的 Lennard-Jones（LJ）相互作用εRR、共聚物中棒状和线圈状嵌段的长度以及嵌段共聚物与均聚物的混合比例。随着εRR值的降低，混合物的自组装结构从算盘状结构转变为螺旋结构，再到普通纤维，最终分解为单聚物。计算棒状嵌段的序参数以确认结构转变。通过改变棒状和线圈状嵌段的长度，绘制了算盘、螺旋、普通纤维和单聚物的热力学稳定区域。此外，发现在螺旋中存在两级棒状嵌段有序排列。嵌段共聚物螺旋缠绕在均聚物束上形成螺旋链，而棒状嵌段在链内扭曲堆积。此外，模拟结果与实验观察结果吻合良好。本工作揭示了螺旋（实验上为超螺旋）结构形成背后的机制，并可能为复杂结构的设计和制备提供有用信息。
