基于计算机模拟的两嵌段高分子运动研究

以往计算机模拟高分子的模型相对简单,其准确度存在较大偏差,研究结果相对单一,影响实际材料的应用,故提出基于随机吸附表面的两嵌段高分子链模型。该模型选用自回避无规行走链模型和Monte Carlo方法,研究高分子链在随机表面上的运动行为,并通过数值分析和构象观察,发现表面吸附基块的临界比例与链段吸附力存在关联,且两嵌段高分子链存在双螺旋和环状两种新构象。实验结果表明,该模型具有良好的现实模拟效果。

两嵌段高分子链在周期管道内扩散的Monte Carlo模拟

高分子链在纳米管道内的静态和动态特性与许多生物技术和生命过程相关.采用Monte Carlo方法模拟研究了两嵌段高分子链(ANABNB)在周期管道内的扩散过程.管道由长度相等的α和β两部分周期排列而成,其中α部分与高分子链A嵌段间存在吸引相互作用,而其他情形均为纯排斥作用.模拟结果表明,高分子链的扩散过程显著依赖于A嵌段长度,且扩散系数随A嵌段长度呈周期变化.通过对链与管道间的吸引作用能图像分析发现,在扩散系数峰位置,A嵌段的投影长度为管道周期长度的整数倍,同时高分子链的扩散规律与均质链在均质管道内的扩散规律一致;在扩散系数谷附近,A嵌段的投影长度为管道周期长度的半整数倍,同时扩散过程存在一系列明显的受限阶段,高分子链在不同的受限位置间跳跃转移.研究结果有助于嵌段高分子链的序列分离和可控输运.

星形两嵌段共聚高分子薄膜微相分离的耗散粒子动力学模拟

利用耗散粒子动力学模拟研究两类典型的星形两嵌段共聚高分子薄膜的微相分离行为,观察到一系列有序结构,并获得相应的相图.结果表明:(Ax)4(By)4体系的相图比(AxBy)4体系具有更明显的对称性,且前者比后者更易发生相分离,这与体相中的情况相近,而同等条件下,后者比前者更易形成岛状结构;组成相同的星形共聚高分子体系在体相与薄膜中所形成的介观结构之间存在对应关系,且一维受限能够使得该体系所形成的微相分离结构更为多样化;较小的薄膜厚度与较强的A-B组分间的排斥作用均有利于增强所形成结构的有序性.

受限薄膜中不对称两嵌段共聚高分子的微相形态

用强分凝理论方法研究了组分不对称 (f≈ 0 2 5 )的两嵌段共聚高分子在受限薄膜中的微相形态———层状相、平行柱状相和垂直柱状相 .发现对中性基底 ,无论薄膜厚度为多少 ,垂直柱状相总是最稳定的相 ;而对亲少数相的基底 ,嵌段高分子的平均组成以及基底和两嵌段之间的相互作用能对薄膜体系的相行为有决定性影响 .随着薄膜厚度的增加 ,层状相 (包括奇数和偶数层数 )。

两嵌段共聚高分子链通过薄膜上纳米孔隙输运的研究

针对两嵌段高分子链的跨膜输运过程,分别给出与不同输运次序相对应的高分子链的自由能,进而通过求解Fokker-Planck方程并在不同条件下对平均首次通过时间进行了数值计算.计算结果表明,当共聚高分子链由良溶剂区向不良溶剂区输运时,不能发生线团-链滴转变的链首先输运总是有利于整个高分子链的输运.而在给定输运次序的情况下,化学势、线团-链滴转变、共聚链的组成以及输运速率等因素对输运时间可产生显著影响.相关研究结果可为调控实际生物高分子链的输运时间提供可能的理论线索.

Microphase Separation of Star-diblock Copolymer Films： a Dissipative Particle Dynamics Simulation

The microphase-separating behaviors of two types of star-diblock copolymers （Ax）4（By）4 and （A^Bg）4 in thin films are studied using the simulation technique of dissipative particle dynamics. A variety of ordered mesostructures have been observed and the simulated phase diagrams show obvious symmetries for the （Ax）4（By）a films and asymmetries for the （AxBy）4 films, besides, it is easier for the （Ax）4（By）4 than for the （A^By）4 to carry out microphase separation under the same conditions, which has been recognized in bulk and can be ascribed to the structural difference between the two types of star copolymers. There are some correspondences between the mesostructures formed in the film and those formed in bulk at the same composition fraction. Decreasing the thickness of film and strengthening the A-B repulsion both help the mesostructures enhance the degree of order. Composition fraction dependences of the mean-square radius of gyration in the two types of star copolymer films are almost contrary, which can be attributed to the differences in their respective structures. These findings can provide a guide to designing novel microstructures involving star-diblock copolymers via geometrical confinement.

Dissipative Particle Dynamics Simulation of Microscopic Properties in Diblock Copolymer Films

Mean-square bond length, root-mean-square end-to-end distance and gyration radius in diblock copolymer films have been studied by dissipative particle dynamics simulations. Results show evident linear trends of any property separately with the thickness of film, the interaction between particles of different types, the repulsion between particle and boundary, except for the dependence of the variations of mean-square bond length on the thickness of film, which exhibits as a wave trend. What＇s more, the varying trends of mean-square bond length and root-mean-square end-to-end distance can correspond to each other. The density distribution of either component in diblock copolymer film can be controlled and adjusted effectively through its interaction with boundary.