Modeling study on theroles 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 effects of various molecules.We found that when the attrac-tion 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 poly-mer monomer is strong,with the weakening of the bridging between CNS and polymer monomer,the volume frac-tion of PG presents two step transitions,indicating 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 at-traction between CNS and polymer monomer has not been completely eliminated.The theoretical results are con-sistent with the experimental observations,which indicates that the phase transition behavior of PG can be con-trolled to a large extent by the co-nonsolvency.
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