| 초록 |
Amphiphilic diblock copolymers self-assemble at the air-water interface into a micro-phase separated structure, which is called as surface micelle. The hydrophobic blocks aggregate to form isolated structures of different shapes depending on relative block lengths and they are stabilized by surface-active hydrophilic blocks spread on the water surface. We report on the effect of subphase pH on the surface micelle behavior of diblock copolymer mixtures of PS-b-P2VP and PS-b-PMMA. PS-b-P2VP (Mw = 56 kg/mol, wPS = 50%) and PS-b-PMMA (Mw = 50 kg/mol, wPS = 50%) diblock copolymers used in this work were synthesized by sequential anionic polymerizaton. Langmuir films of the PS-b-P2VP and PS-b-PMMA were formed at the air-water interface by spreading chloroform solutions (0.5 mg/mL). The pH of the subphase was adjusted using sodium phosphate buffer (0.2 M). The surface micelle behavior of PS-b-P2VP is affected by subphase pH greatly due to the ionizable P2VP block while PS-b-PMMA is independent. We found that all the surface micelles are well isolated when the two block copolymers are premixed in the spreading solution. In contrast, the independent micelles of PS-b-PMMA and PS-b-P2VP coexist when PS-b-P2VP and PS-b-PMMA were spread sequentially. These results indicate that once the surface micelles are formed, there is no observable exchange of the block copolymers between the micelles in a reasonable time span. |
