形状记忆磁性润滑表面的制备及对超顺磁液滴的滑动操控

将磁性粒子与形状记忆聚合物复合,通过设计渐变式构型构筑了梯度形状磁性材料,并与润滑涂层相结合,制备了一种磁性润滑表面.在磁性梯度的作用下,超顺磁液滴在表面上能够自发定向运动.借助于材料形状记忆效应对表面区域形态进行可逆调控,进一步展示了超顺磁液滴自发定向运动过程中的启停开关式控制,实现了将液滴定向自发运输与启停控制相结合.考察了磁性粒子含量对材料形状记忆性能的影响,以及区域形态调控尺寸与液滴滑动性能间的相互关系.机理分析进一步阐明磁场梯度提供的定向驱动力促使液滴定向自发输运,表面区域形态控制的可逆调控则可以在液滴运动过程中增加/消除黏滞阻力,基于两种因素的协同作用,可以实现对超顺磁液滴运动的智能操控.     

Simulation of the Critical Adsorption of Semi-Flexible Polymers

The critical adsorption of semi-flexible pol.ymer chains on attractive surfaces is studied using Monte Carlo simulations.The results reveal that the critical adsorption point of a free polymer chain is the same as that of an end-grafted one.For the end-grafted polymer,we find that the finite-size scaling relation and the maximum fluctuation of adsorbed monomers are equivalent in estimating the critical adsorption point.The effect of chain stiffness on the critical adsorption is also investigated.The surface attraction strength for the critical adsorption of semi-flexible polymer chain decreases exponentially with an increase in the chain stiffness;In other words,lower adsorption energy is needed to adsorb a stiffer polymer chain.The result is explained from the viewpoint of the free energy profile for the adsorption.