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R. Yamanaka, N. Shimizu, N. Igarashi, H. Takagi, S. Sakurai

Orienting cylindrical microdomains in polystyrene-b-poly(ethylene-co-butylene)-b-polystyrene
triblock copolymer/diluent sheet by application of temperature gradient (in English)

Polimery 2017, No 11-12, 812


DOI: dx.doi.org/10.14314/polimery.2017.812

Summary

The cylinder-forming polystyrene-b-poly(ethylene-co-butylene)-b-polystyrene (SEBS) triblock copolymer with a volume fraction of polystyrene (PS) equal to 0.16 was investigated. The orientation of cylindrical microdomains in SEBS/diluent sheet by application of temperature gradient were studied using small-angle X-ray scattering (SAXS). Dioctyl phthalate (DOP) was used as a diluent, which selectively dissolves SEBS, being a good solvent for PS but a poor solvent for poly(ethylene-co-butylene) (PEB). Due to this selectivity, a lamellar morphology was found at lower temperature (Tcold) for specimens with ­SEBS/DOP ratio of 6/4 and 7/3. It was further revealed that the morphology changed to be cylindrical at higher temperature (Thot). The order-order transition temperature (TOOT) was found to be 100 °C for both compositions, although a coexistence of lamellae and cylinders in a much wider temperature range was observed for the composition with SEBS/DOP = 7/3 as compared to the composition with SEBS/DOP = 6/4. These results indicate that the diluent selectivity of solubility at lower temperatures is suppressed at higher temperatures. For the specimen with SEBS/DOP = 6/4 the order-disorder transition temperature (TODT) was found to be 152.0 °C. The cylindrical morphology was found near the cold wall of the sample holder, even though the lamellar phase should be stable because the cold temperature was below TOOT. This result implies that the temperature gradient may destabilize the lamellar phase. The cylinders in the confined space under the temperature gradient are considered to accommodate well. Both of the spacing and the cylinder radius was found to be larger as the position of the specimen irradiated by the incident X-ray beam was closer to the cold sidewall of the temperature gradient sample cell.
Keywords: polystyrene-b-poly(ethylene-co-butylene)-b-polystyrene triblock copolymer, diluent, cylindrical microdomains, perpendicular orientation, temperature gradient, small-angle X-ray scattering
e-mail: shin@kit.ac.jp
R. Yamanaka, N. Shimizu, N. Igarashi, H. Takagi, S. Sakurai (1.24 MB)
Orienting cylindrical microdomains in polystyrene-b-poly(ethylene-co-butylene)-b-polystyrene triblock copolymer/diluent sheet by application of temperature gradient (in English)