模型化研究高分子凝胶体积相变中的共非溶性作用

基于Flory-Huggins理论，我们建立理论模型，研究在共非溶剂(CNS)中，高分子凝胶(PG)体积相变中的共非溶性作用.理论模型考虑PG中CNS的桥接作用、各种分子的混溶效应.研究发现，当CNS与高分子单体间的吸引强度较小时，CNS与高分子单体间桥接作用的减弱，会导致PG体积相变.当CNS与高分子单体间的吸引作用强度较大时，随着CNS与高分子单体间桥接作用的减弱，PG的体积分数呈现两次台阶式的转变，表明PG体系出现两次体积相变.这是由于桥接作用的减弱，虽然会有部分CNS分子被排挤出PG，但是并未完全消除CNS与高分子单体间的桥接吸引作用.所得理论结果符合实验观测，由此表明了共非溶性作用会在很大程度上调控PG的相变行为.

Modeling study on the roles of co-nonsolvency in volume transition of polymer gels

Based on the Flory-Huggins theory, we built a theoretical model to study the role of co-nonsolvency in the volume phase transition of polymer gel(PG) in co-nonsolvent (CNS). The theoretical model considers the bridging effect of CNS in PG and the miscibility effect of various molecules. We found that when the attraction strength between CNS and polymer monomer is low, the bridging effect between CNS and polymer monomer is weakened, which will lead to the volume phase transition of PG. When the attraction between CNS and polymer monomer is strong, with the weakening of the bridging between CNS and polymer monomer, the volume fraction of PG presents two step transitions. It indicates that the PG presents two volume transitions. Because of the weakening of the bridging effect, although some CNS molecules will be squeezed out of the gel, the bridging attraction between CNS and polymer monomer has not been completely eliminated. The theoretical results are consistent with the experimental observations, which indicates that the phase transition behavior of PG can be controlled to a large extent by the co-nonsolvency.