软受限条件下嵌段共聚物薄膜缺陷消除的理论研究  

Theoretical Study on Defect Removal in Block Copolymer Thin Films under Soft Confinement

作　　者：宋俊清 刘一新 张红东[1] Jun-qing Song;Yi-xin Liu;Hong-dong Zhang(State Key Laboratory of Molecular Engineering of Polymers,Department of Macromolecular Science,Fudan University,Shanghai200438)

机构地区：[1]聚合物分子工程国家重点实验室复旦大学高分子科学系

出　　处：《高分子学报》2018年第12期1548-1557,共10页Acta Polymerica Sinica

基　　金：上海市浦江人才计划(项目号18PJ1401200);国家自然科学基金(基金号21004013);国家重点基础研究发展计划(973计划,项目号2011CB605701)资助

摘　　要：理解缺陷消除机理对于制备无缺陷的长程有序嵌段共聚物薄膜至关重要.本文利用弦方法结合自洽平均场理论研究了接枝均聚物高分子刷在AB两嵌段共聚物垂直层薄膜的偶极位错缺陷消除中发挥的作用.研究发现,高分子刷的“浸润效应”和“重排效应”能够降低胁的有效值,增大跳跃扩散的扩散系数,进而促进“桥连”结构的形成.并且,接枝高分子刷的基底表面的“硬度”越小,以上2种效应越显著,越能进一步降低缺陷消除过程中形成“桥连”结构这一关键步骤的能垒.Understanding the defect removal process is crucial for the fabrication of defect-free self-assembled structures in block copolymer thin films.In this study,the removal of the dislocation dipole defect in thin films of perpendicular lamellar block copolymers on substrates modified by grafting polymers has been extensively studied.As revealed in previous studies,the"bridge"structure,which converts the slow hopping diffusion of block copolymer chains to fast interfacial diffusion,is a key factor to understand the mechanism of the defect removal process.Polymer grafting onto substrates is a widely accepted way to control domain orientation and fabricate surface pattern for directed self-assembly(DSA).However,the role of the grafted polymers on defect removal is unclear.In this study,the string method coupled with the self-consistent field theory(SCFT)is used to explore the influence of grafted polymers on the removal of a dislocation dipole in lamellar-froming thin films assembled by symmetric AB diblock copoymers.It is found that the"immersion effect"and the"rearrangement effect"introduced by the grafted polymers can facilitate the hopping diffusion of the block copolymer chains through reducing the effective χAB,thus making the formation of the bridge structure easier.The decrease of the softness of the brush layer(γ)will enhance these two effects and reduce the energy barrier of the transition state of the defect removal process.In the limit of γ=0,the bridge structure is found to already exist in the dislocation dipole near the brush layer,leading to a diminishing energy barrier of the removal process.Using the symmetric PS-b-PMMA with a number-average molecular weight of≈5.1×10^4at195℃ as an example,we estimated the annealing time required to eliminate the dislocation dipole by assuming the diffusion coefficient of the hopping diffusion of block copolymers being D≈10^-13cm^2/s.The annealing time are estimated to be τ=91.4s and150.9s for extremely soft confinement(γ=0)and intermediate soft confinemen

关 键 词：嵌段共聚物 薄膜 高分子刷 缺陷消除 弦方法 自洽平均场理论方法 

分 类 号：O631[理学—高分子化学] TB383.2[理学—化学]