The effect of casting temperature on morphology of poly(styrene-ethylene/butylene-styrene) triblock copolymer

The morphology of poly(styrene-ethylene/butylene-styrene) (SEBS) triblock copolymer films cast from the solution in xylene at different temperatures was investigated by transmission electron microscope. The SEBS solution was first heated to a certain temperature, which ranges from 20 to 140°C and then cast onto the surface of phosphoric acid at the same temperature to prepare specimen films. Three different kinds of morphologies including coexistence of a large number of branched cylinders and a small number of spheres, coexistence of cylinder region and near homogenous region, and coexistence of non-branched cylinders and spheres were observed corresponding to 20, 80–110, and 130–140°C temperature zones, respectively. Moreover, it was found that the diameter of cylinders increases with the casting temperature. All these show an obvious casting temperature dependence of the microphase separation phenomenon.