剪切力誘導PS—PLLA團聯共聚合物奈米微結構定向―奈米圖案成形模板之製備

• Main Author: 范慧雯
• Other Authors: 鄭紀民
• Format: Others
• Language: zh-TW
• Published: 2003
• Online Access: http://ndltd.ncl.edu.tw/handle/24335420261716884021

碩士 === 國立中興大學 === 化學工程學系 === 91 === A series of biodegradable block copolymers, polystyrene-poly(L-lactide) (PS-PLLA), with PLLA hexagonal cylinder (HC) morphology has been synthesized in this study. By selecting appropriate solvent for spin coating, the formation of large-size, oriented microdomains of PS-PLLA thin films where the axis of HC morphology is perpendicular to the substrate ( i.e., flat-on morphology ) was successfully achieved. The oriented microdomains can be as large as several cm2 in area. Furthermore, the effects of sample thickness and coated substrate on thin-film morphology were also examined in order to identify the limits and variations for practical applications. Different PS-PLLA thin films having uniform thickness ranging from tens nanometers to hundreds nanometers were obtained by spin coating at different spin rates. Topographic nanopatterns having periodic arrays of cylindrical nano-channels were successfully created after the treatment of NaOH aqueous solution where the PLLA component was hydrolytically degraded. By controlling molecular weight of block copolymers, topographic nanopatterns having various dimensions of nano-channels were prepared so as to establish a wonderful platform technology for nanopatterning. The large-size, well-oriented, topographic nanopatterns with tunable film thickness on different substrates give promising opportunities for block copolymer applications in the fields of nano-sciences. The mechanisms of shear-induced orientation for a series of biodegradable block copolymers by spin coating were systematically studied. By selecting appropriate solvent for spin coating, well-oriented microstructure where the axis of HC morphology is perpendicular to the substrate was obtained. The evaporation rate of solvent is the primary concern for the formation of oriented microdomains due to the consideration of building up steady state shearing field for orientation. Similar to the behavior of shear-induced orientation by oscillatory shear, the alignment of HC axes was achieved by interplaying with microphase separation and shear-induced orientation by spin coating. At steady state, viscous resistant force is balanced by centrifugal force so as to generate specific shear field. Meanwhile, the block copolymer solution gradually condenses so that induced order-disorder phase transition occurs under shearing. Besides the effect of solvent evaporation, the effect of solvent miscibility is also critical to the formation of oriented microdomains. To accomplish microstructure alignment, selective solvent for PS blocks in PS-PLLA is necessary. By contrast, well-developed, microphase-separated PS-PLLA morphology has not been identified by using mutual solvent for spin coating. Consequently, the critical role of solvent selection on induced orientation results from the effects of solvent evaporation and its miscibility with constituted blocks of block copolymers.