良溶剂中环形高分子单链的结构与动力学性质的模拟研究

本文采用多粒子碰撞动力学与分子动力学耦合的模拟方法研究了环形高分子单链在良溶剂中的静态与动态性质,并与线形分子进行了对比.研究发现,环形高分子链内粒子之间的平均距离小于线形链,即粒子排列得更加紧密;相应的均方回转半径也小于线形链,线形链与环形链的均方回转半径的比值为1.77;同时,环形链扩散的速度也比线形链快,两者比值为1.10.模拟结果揭示了扩散行为是排斥体积作用和流体力学相互作用耦合的结果,在扩散过程中,流体力学相互作用消减了排斥体积作用对扩散行为的贡献.此外,通过对有和没有流体力学相互作用的多粒子碰撞动力学得到的结果作对比,研究了流体力学相互作用对高分子静态和动态行为的影响,结果表明,流体力学相互作用使高分子链在极稀溶液中的扩散速度变快.

Simulation study on conformational and dynamical properties of individual ring polymers in good solution

The conformational and dynamical properties of individual linear and ring polymers in good solution were studied by mesoscale simulations which combining multi-particle collision dynamics and molecular dynamics simulations. The excluded volume interactions play a more significant role for ring polymers than for linear polymers because of the smaller average distance among monomers of rings without ends. The ratio of mean-square radius of gyration between the linear and ring polymer with a same molecular weight in the presence of excluded volume interactions is 1.77, which is slightly smaller than the theoretical estimation （2） in theta solvents, indicating that ring polymers swell more in good solvents than their linear counterparts. Correspondingly, the ratio of diffusion coefficients between the ring and linear polymer was estimated as 1.10. The diffusion properties are dominated by the interplay between excluded volume interactions and hydrodynamic interactions. Furthermore, in order to elucidate the role of hydrodynamic interactions, we also compared these results with those without hydrodynamic interactions. The results showed that the diffusion coefficients with hydrodynamic interactions are larger than those without hydrodynamic interactions.