溶剂退火过程中嵌段共聚物薄膜形态的分子模拟研究

Controlling the morphology and long-range order in self-assembled nanostructures of block copolymers remains a considerable challenge. Solvent annealing technique has been applied for controlling microphase separation in block copolymer thin films. The controlling mechanisms, however, are not clear. In this proposal, we will investigate the mechanisms of solvent annealing technique for controlling the morphology and the domain orientation in self-assembled nanostructures of block copolymer thin films based on molecular modeling with a liquid-gas equilibrium model. We will examine the effect of the selectivity of the solvent, the property of the substrate, the copolymer composition, the swelling degree, and the solvent evaporating rate on the morphology and the domain orientation of the self-assembled nanostructures of block copolymer thin films. We will find out the conditions to form the various ordered structures, as well as the correlation and matching between the solvent vapor permeation into the film and the evaporation processes. We will illucidate the mechanisms of forming different morphologies. Based on the above studies, we will obtain the diagrams of the thin film in the space of different parameters. Furthermore, we will sum up the generic characteristic of the variations of the self-assembled morphology and its domain orientation with the swelling degree and the solvent evaporating rate, and finally predict and design thin film systems that can self-assemble to form some specific morphologies or with specific domain orientations. The results of this proposal will provide us deep understanding on the solvent annealing technique in controlling morphology and the domain orientation in self-assembled nanostructures of block copolymer thin films, and will provide guidelines to the technological applications, such as in nanolithography, of block copolymers.

调控嵌段共聚物自组装纳米结构的形态和长程序仍然是一个相当大的挑战。溶剂退火技术已被用于调控嵌段共聚物薄膜体系的微观相分离，然而对其调控机理还不清楚。本项目拟采用分子模拟方法结合可调节气液平衡的模型，围绕溶剂退火过程中调控嵌段共聚物薄膜自组装形态和微区取向的机理开展研究。考察溶剂的性质、衬底的性质、共聚物的组分、溶胀度和溶剂蒸发速率等对薄膜自组装形态及微区取向的影响；探索形成不同形态结构的条件，以及溶剂渗入薄膜和溶剂蒸发过程之间的关联与匹配性；揭示不同自组装形态形成的机制。获取薄膜自组装形态以及微区取向随不同参数演化的相图。总结、归纳薄膜溶胀程度和溶剂蒸发速率对自组装形态及微区取向调控的规律；并进一步预言和设计具有特定自组装形态或特定微区取向的嵌段共聚物薄膜体系。本研究的成果将提供溶剂退火对嵌段共聚物薄膜自组装形态调控的深入认识；并将为嵌段共聚物作为纳米刻蚀模板等技术应用提供理论指导。

在本项目的资助下，项目组成员使用格点蒙特卡洛模拟围绕溶剂退火过程中调控嵌段共聚物薄膜自组装形态和微区取向的机理开展了系统研究。考察了溶剂的性质、两种不同性质溶剂的混合比例、衬底的性质、共聚物的组分、溶胀度和溶剂蒸发速率等对薄膜自组装形态及微区取向的影响；找到了形成垂直取向的柱状相（垂直柱状相）和垂直取向的层状相（垂直层状相）的形成条件；揭示了各种形态的形成机制。获得了薄膜自组装形态以及微区取向随上述参数演化的相图。总结、归纳了上述参数对自组装形态及微区取向调控的规律。另外还对溶剂蒸发条件下嵌段共聚物在油/水乳化液滴中自组装形成多孔粒子的机制，平板接枝环形均聚物刷、接枝三嵌段共聚物刷、以及接枝AB两嵌段共聚物与A均聚物刷在溶剂中自组装行为，全亲水嵌段共聚物在水溶液中、嵌段共聚物在二元溶剂中、星形四元聚合物或巨分子在选择性溶剂中的自组装行为，以及聚电解质单链在显含不良溶剂的溶液中链构象转变等进行了系统研究。相关研究成果提供了对溶剂退火诱导的嵌段共聚物薄膜自组装行为及其自组装结构的深入认识；并将为嵌段共聚物作为纳米刻蚀模板等技术应用提供理论指导。