SAXS analysis of the order-disorder transition and the interaction parameter of polystyrene--poly(methyl methacrylate)

Zhao, Y.; Sivaniah, E.*; Hashimoto, Takeji

In this study, the order-disorder transition (ODT) for two symmetric polystyrene-b-poly(methyl methacrylate) diblock copolymers was investigated by a high temperature-resolution Small Angle X-ray Scattering (SAXS) experiments with small decreases of temperature (T) across the ODT. The characteristic ODT temperature was determined from the discontinuity of 1/Im and q2 vs 1/T, confirming the fluctuation-induced weakly first-order transition for this block copolymer. In the disordered state, far above ODT temperature, the interaction parameter for PS-b-PMMA was also extracted, and found to be slightly larger than that in the deuterated systems having the similar molecular weight and compositions. PS-b-PMMA is a promising technological system that is able to be manipulated to provide nanostructural templates and scaffolds. Hence our precise determination of the interaction parameter and the order-disorder characteristics of a non-deuterated system will be invaluable to future works.