Oriented Microstructures of Polystyrene-b-poly(L-lactide) Thin Films Induced by Crystallizable Solvents

详细信息    查看全文

• 作者：Wen-Hsien Tseng ; Ping-Yen Hsieh ; Rong-Ming Ho ; Bor-Han Huang ; Chu-Chien Lin ; Bernard Lotz
• 刊名：Macromolecules
• 出版年：2006
• 出版时间：October 3, 2006
• 年：2006
• 卷：39
• 期：20
• 页码：7071 - 7077
• 全文大小：716K
• 年卷期：v.39,no.20(October 3, 2006)
• ISSN：1520-5835

文摘

Polystyrene-b-poly(L-lactide) (PS-PLLA) diblock copolymers with high and low molecular weightswere synthesized to form strongly and weakly segregated thin-film morphologies, respectively (i.e., ordered lamellarand disordered textures). Large-sized, well-oriented lamellar microstructures of PS-PLLA thin films were producedfor both samples by using the crystallizable solvents: benzoic acid (BA) and hexamethylbenzene (HMB). Instrongly segregated (high M_n) PS-PLLA, the oriented microstructures were obtained through the PS-PLLAmicrophase separation due to directional crystallization of crystallizable solvents at the eutectic point (directionaleutectic solidification) regardless of the PLLA crystallization. Lattice matching between crystalline substratesand PLLA was found to be nonessential for inducing microstructure orientation although it may improve itsorientation order. In weakly segregated (low M_n) PS-PLLA, the oriented microstructures were formed throughthe directional crystallization of PLLA on the substrates (crystallization-induced orientation) regardless of thedirectional eutectic solidification and lattice matching. Two mechanisms: of directional eutectic solidificationand of crystallization-induced oriented microstructure have thus been identified. Oriented, defined lamellar trenchescan be prepared by hydrolysis of PLLA component, providing a possible path to prepare nanopatterned templateswith lamellar nanochannels.