显式溶剂模型模拟嵌段共聚物在纳米微滴中的图案化结构

采用耗散粒子动力学(DPD)方法研究了嵌段共聚物在纳米微滴中的相分离行为.模拟是将共聚物纳米微滴置于溶剂环境中进行自发相分离,从而形成一些图案化结构.由于是受限体系,所形成的结构和在溶液或熔融体中形成的相分离结构有所差异,这些结构的形成与亲/疏溶剂嵌段比例(RH/T)有关系.随着亲/疏溶剂嵌段比例的增加,依次形成了枣糕球体、排球状相、多层囊泡(洋葱相)、笼状相、纳米杆状相和分散胶束等结构.我们对洋葱相的形成过程进行了详细的描述.溶剂粒子的集群属性有助于更加深入地了解洋葱相的结构衍化.采用密度曲线分析了洋葱相的结构.在较高的亲/疏溶剂嵌段的比例条件下,嵌段共聚物主要表现为亲溶剂性,通过吸收大量的溶剂溶胀形成疏松结构或瓦解形成分散的胶束悬浮在溶剂中.本文模拟结果与理论或实验结果基本吻合.

Simulating Patterned Structures in Block CopolymerNanodroplets Using Explicit Solvent Model

Dissipative particle dynamics(DPD)simulation technique is used to elucidate the microphase separation behavior of block copolymers in nanodroplets.The simulation is performed by relaxing disordered copolymer nanodroplets in a solvent bath.Microphase separation is then carried out inside the nanodroplet,which allows block copolymers self-assemble into many new morphologies differing from those formed in pure melts or in solution.These patterned structures depend on the volume ratio of solvophilic/solvophobic blocks(RH/T).As the value of RH/T increases,the following structures are formed: plum-pudding microsphere,volleyball-like structure,multilamellar vesicle,cage-like structure,nanorods, and discrete micelles.Density analysis is performed to characterize the onion’s structure.At high R H/T values,block copolymers exhibit mainly solvophilicity and form swollen loose structures or small micelles suspended in the solvent.The simulation results are in good agreement with experimental and theoretical results.