Poly(Oxyalkylene) Block Copolymers in Aqueous Solution—Phase Behavior and Transition Kinetics

Abstract

A study into the liquid‐crystal mesophase of two triblock copolymers in aqueous solution has been reported, E17B14E17 and the reverse architecture, B11E47B11 were studied by polarized light microscopy, rheology, and time‐resolved small‐angle x‐ray scattering (SAXS) techniques. Two phase diagrams of composition vs. temperature have been constructed where three isolated morphologies are observed; body‐centered cubic‐packed spherical micelles, hexagonally packed cylindrical micelles, and a lamellar structure are formed on increasing concentration of block copolymer. It also was found that phase transitions could be induced thermally. Such phenomena were characterized by a change in scattering pattern or texture under polarized light microscopy, or by changes in storage modulus as the system was heated or cooled. The determination of phase boundaries was crucial in the next stage of the investigation, which was to quantify the kinetic parameters of each phase transition. Phase transitions were analyzed by the Avrami model. Initial results suggest that, on raising the quench depth, the transition is faster. In addition, systems with a higher block copolymer concentration were shown to transform slower.