| 초록 |
Polystyrene-b-poly(methyl methacrylate) (PS-b-PMMA) thin films with various initial thicknesses are known to show the unusual hierarchical structures (i.e., fractal hole or hole-in-hole). In particular, the development of hole-in-hole structures turns out to be initiated by the lateral strain due to the evaporation of a small amount of residual solvent after the fast formation of parallel lamellae. In present study, in order to investigate the effect of homopolymers on hole formation, PS-b-PMMA/PPO and PS-b-PMMA/PS binary blend thin films: PPO denotes poly (2,6-dimethyl 1,4-phenylene oxide), were prepared and surface morphology was investigated using optical microscopy (OM) and atomic force microscopy (AFM). Notably, our experimental results revealed that homopolymers suppress the development of hole-in-hole structure in PS-b-PMMA thin films by the bridging between slipping planes above critical concentration. The hole formation was more effectively suppressed by adding PPO rather than PS since it is well known that ΧPPO-PS < 0, ΧPS-PS = 0 and ΧPPO,PS-PMMA > 0, namely, PPO is more miscible with PS domain. In addtion, the change in L0 (the equilibrium lamellar period) represents the wet brush in blending with PPO, however, the dry brush in blending with PS. Based on these results, schematics of the hierarchical topology of PS-b-PMMA/homopolymer binary blend thin films with different homopolymers were given.
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