| 학회 | 한국고분자학회 |
| 학술대회 | 2003년 가을 (10/10 ~ 10/11, 부경대학교) |
| 권호 | 28권 2호, p.43 |
| 발표분야 | 특별 심포지엄 |
| 제목 | Scattering Studies on the Transitions in Block Copolymer Solutions |
| 초록 | The phase behavior of a symmetric styrene-isoprene (SI) diblock copolymer in a styrene-selective solvent was investigated by in-situ small angle X-ray scattering on shear-oriented solutions. A remarkable new feature in our block copolymer solutions is the peculiar coexistence of both bcc and hcp phases between cp and hex in the concentration range of Φ = 0.33 ~ 0.45. In present study, the interplay among the cp, bcc/hcp mixture, and hex phases was investigated in detail. By focusing on the transition relationship among these various ordered phases in terms of heating and cooling, we observed hysterisis between the heating scan and cooling scan: super-cooled cylinders were formed during the cooling scan. The stability of the super-cooled cylinders is quite dependent on block copolymer concentration and for Φ > 0.40, the super-cooled cylinders do not return to the spheres even the annealing time for one month. This is to say that by increasing the polymer concentration, the spontaneous formation of spheres by way of the dissociation of cylinders during the cooling scan is kinetically not favored since the hex phase is large in size as well as in number and any pre-transitional fluctuation of cylinders prior to the cylinder-to-sphere transition is suppressed. We also examined nondilute block copolymer solutions in the vicinity of order-disorder transition (ODT). In order to understand morphological changes in more detail, one of the blocks is deuterated, i.e., PS-dPI and dPS-PI, and the contrast matching technique, in which scattering length density (SLD) of solvent used is identical to the SLD of corona chains was applied. We found that with the increase in temperature, the aggregation number is decreased, and the core radius is thus offset by the increased solvent swelling of the core. Notably, the change in G’ and G” as a function of frequency clearly represents the solid-like transient behavior immediately after ODT from cylindrical microdomain. This implies that the ODT is induced by the spontaneous formation of spheres due to the dissociation of cylinders. The temperature range of the transient phase is found to be quite dependent on the solvent-selectivity, which is confirmed by three kinds of solvents. |
| 저자 | 차국헌, 박문정 |
| 소속 | 서울대 |
| 키워드 | order-disorder transition; block copolymer solution |
