TEMPERATURE AND MOLECULAR-WEIGHT EFFECT OF STYRENE-ISOPRENE DIBLOCK COPOLYMERS ON THE INTERFACIAL-TENSION BETWEEN POLYSTYRENE AND POLYISOPRENE

The effect of styrene-isoprene diblock copolymers on the interfacial t ension between polystyrene (PS) and polyisoprene (PI) has been investi gated by direct measurement of the interfacial tension using a pendant drop interfacial tension apparatus. The interfacial tension is nearly independent of the temperature when the diblock copolymers are added, although the interfacial tension of PS/PI without copolymers decrease s with increasing the temperature. A decrease in interfacial tension i s observed with the addition of a small amount of copolymer, followed by a leveling off when the copolymer concentration exceeds a critical micelle concentration. The critical micelle concentration increases wi th temperature. The effect of the molecular weight of block copolymers on the interfacial tension is not significant.