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Highly ordered microstructures of poly(styrene-b-isoprene) block copolymers induced by solution meniscus |
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| Authors: | Jiyoung Hwang Bumsuk Jung Min Park |
| Affiliation: | a Department of Materials Science and Engineering, Yonsei University, Seoul 120-749, South Korea b School of Materials Science and Engineering, Seoul National University, Seoul, South Korea c Department of Environmental Engineering and Biotechnology, Myongji University, san 38-2 Namdong, Yongin, Kyunggido 449-728, South Korea d Optoelectronic Materials Center, Korea Institute of Science and Technology, P.O. Box 131, Cheongryang, Seoul 130-650, South Korea e Polymer Hybrid Research Center, Korea Institute of Science and Technology, P.O. Box 131, Cheongryang, Seoul 130-650, South Korea |
| Abstract: | Microstructures of hundreds of micron thick poly(styrene-block-isoprene) copolymer films solution-cast in a cylindrical tube with the solvent evaporation controlled were investigated by transmission electron microscope (TEM), small angle X-ray scattering (SAXS) and optical microscope (OM). In a block copolymer with cylindrical polyisoprene microdomains, the orientation of the cylinders was varied along radial direction of the cylindrical tube. Highly aligned hexagonal arrays of in-plane polyisoprene cylinders were formed with their cylindrical axis parallel to the circumference of the tube in the regimes close to the wall edge. In contrast randomly ordered microdomains were observed at the center of the tube. We have also found that the orientation depends on the solvent evaporation rate and an intermediate rate (∼2.3 nL/s) provides the best orientation. In the case of a block copolymer with a bicontinuous double gyroid structure, we obtained a globally ordered microstructure where 111] crystallographic direction was parallel to the circumference of the tube. For both block copolymers, the area of highly ordered arrays of nanoscopic domains is over 1 mm2. Development of the orientation was explained by coupling two orthogonal fields: (1) The flow of a solution induced by strong capillary force at a meniscus between the cylindrical tube wall and the block copolymer solution and (2) the solvent evaporation. |
| Keywords: | Poly(styrene-b-isoprene) block copolymer Microstructure orientation Solution meniscus |
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