The phase behavior for the binary mixtures of a polystyrene-block-poly(n- pentyl methacrylate) (PS-b-PnPMA) and homopolystyrenes (PS) with various molecular weights was investigated by depolarized light scattering and small-angle X-ray scattering (SAXS) as a function of PS amount. A homopolymer-free PS-b- PnPMA, prepared by a high performance liquid chromatography (HPLC) technique, showed the entirely disordered (or homogeneous) state within experimental temperature range from the glass transition temperature (Tg) to the thermal degradation temperature (Td). By adding PS to this PS-b-PnPMA, the closed-loop phase behavior was observed for the binary mixtures where no macrophase separation occurred. With increasing molecular weight (chain length) of PS, the ordered range of the closed-loop extended remarkably and a critical amount of PS increased, resulting in the conservation of only lamellar morphology up to the overall PS volume fraction (fps) of 0.70 for a PS, having a chain length ratio (α) of 2 with respect to the PS chain length of PS-b-PnPMA.
All Science Journal Classification (ASJC) codes
- Organic Chemistry
- Materials Chemistry
- Polymers and Plastics
- Inorganic Chemistry