| 학회 | 한국고분자학회 |
| 학술대회 | 2002년 가을 (10/11 ~ 10/12, 군산대학교) |
| 권호 | 27권 2호, p.36 |
| 발표분야 | 특별 심포지엄 |
| 제목 | Self-assembling Behaviors of Different Polystyrene-block-Poly(methyl methacrylate) Diblock Copolymers at Air/Water Interface |
| 초록 | Diblock copolymer (A-B) behaviors in quasi-two dimensional space have been examined where the A block is polystyrene (PS) and the B block is poly(methyl methacrylate) (PMMA). The length of the PMMA block was varied while that of the PS block was kept almost the same. The surface pressure isotherms were determined with the aid of a Langmuir film balance. The surface pressure isotherms exhibited two phase-transitions attributed to surface micelle formation at low surface pressure and to further assembly of surface micelles at high surface pressure. Atomic force microscope images are correlated with the aggregates of the chains forming the quasi-two dimensional surface micelles at low surface pressure. Chains having shorter PMMA block than PS block form the micelles with many block copolymer molecules (ca. 430 molecules) whereas chains having four times longer PMMA block than PS block form the micelles with several molecules. High compression led the micelles to have a more compact structure. New structure of crowds of micelles by further compression was observed by Brewster angle microscope. This is not corresponding to big aggregates formation since its structure appearance was reversible whereas the surface micelle formation was irreversible. All the block copolymers used in this study exhibited a hysteresis. In the slow expansion process, the surface pressure of the long chain showed a minimum. Because of the micelle formation in the first cycle of compression and expansion, the hyteresis was remarkably reduced in the consecutive cycles. Using surface quasi-elastic light scattering (SLS), the monolayer behaviors were also studied in terms of the surface viscoelasticity. Substantial changes in viscoelastic behavior accompany changes in surface concentration and can be attributed to differences in molecular packing resulting from micelle formation and surface phase behavior, which are consistent with atomic force microscopy images of monolayer films transferred from air/water interface to solid substrates. The ill-defined PS segment sits on top of PMMA segment without much contact with the water. As the concentration goes up, these systems show progressive surface viscoelastic behavior. Viscoelastic parameters, i.e. the dynamic dilational elasticity, ε, and viscosity, κ, deduced from the SLS data indicate that the rigidity of the liquid-like domains increases smoothly to ε and κ →∞, regardless of the PMMA molecular weight. |
| 저자 | 서용석 |
| 소속 | 한국과학기술(연) |
| 키워드 | |
| VOD | VOD 보기 |
