Effect of molecular weight and film thickness on the crystallization and microphase separation in polystyrene-<Emphasis Type="Italic">block</Emphasis>-poly(L-lactic acid) thin films at the early stage |
| |
Authors: | Yu-han Wei Cai-yuan Pan Bin-yao Li Xin-hong Yu Yan-chun Han |
| |
Institution: | (1) Department of Chemistry, Key Laboratory of Advanced Textile Materials and Manufacturing Technology of Education Ministry, Zhejiang Sci-Tech University, Hangzhou, 310018, China; |
| |
Abstract: | We investigated the effects of molecular weight and film thickness on the crystallization and microphase separation in semicrystalline
block copolymer polystyrene-block-poly(L-lactic acid) (PS-b-PLLA) thin films, at the early stage of film evolution (when T
g < T < T
ODT) by in situ hot stage atomic force microscopy. For PS-b-PLLA 1 copolymer which had lower molecular weight and higher PLLA fraction, diffusion-controlled break-out crystallization
started easily. For PS-b-PLLA 2 with higher molecular weight, crystallization in nanometer scales occurs in local area. After melting of the two copolymer
films, islands were observed at the film surface: PS-b-PLLA 1 film was in a disordered phase mixed state while PS-b-PLLA 2 film formed phase-separated lamellar structure paralleling to the substrate. Crystallization-melting and van der Waals
forces drove the island formation in PS-b-PLLA 1 film. Film thickness affected the crystallization rate. Crystals grew very slowly in much thinner film of PS-b-PLLA 1 and remained almost unchanged at long time annealing. The incompatibility between PS and PLLA blocks drove the film
fluctuation which subsequently evolved into spinodal-like morphology. |
| |
Keywords: | |
本文献已被 万方数据 SpringerLink 等数据库收录! |
|