Conformational transition of block copolymers in dilute solution and their morphology in the solid state

Abstract

AbstractBlock copolymers poly(methyl methacrylate)‐block‐polystyrene‐block‐poly(methyl methacrylate) and polystyrene‐block‐poly(tert‐butyl methacrylate) were prepared by anionic polymerization and were studied in dilute solution as well as in the bulk state. The viscometric study revealed that the block copolymers exhibit a conformational “transition” occurring in a narrow temperature range. Films were obtained with the same copolymers by casting at different temperatures, chosen below and above the “transition”. From the investigation of these films by differential scanning calorimetry, using the entropy relaxation method, and by dynamic mechanical measurements, it was shown that the block copolymers exhibit a rather segregated structure if they are obtained below the “transition” temperature, and that they adopt a quasi‐Gaussian conformation (implying a better miscibility of the two kinds of blocks) if the solvent is evaporated above the “transition” temperature.