Phase Behavior of Polystyrene-block-Poly(n-alkyl-ran-n'alkyl methacrylate) Copolymers

The phase behavior of polystyrene-block-poly(n-butyl-ran-n- hexyl) methacrylate copolymers and polystyrene-block-poly(n- octyl-ran-methyl) methacrylate copolymers were investigated by using small angle X-ray scattering, birefringence and rheometry. When the total molecular weight and the composition of the random copolymers were judiciously controlled, the closed-loop phase behavior with both a lower disorder-to-order transition and an upper order-to-disorder transition was observed. These block copolymers exhibited excellent baroplasticity. The observed phase behavior was explained by a compressible mean field approach.