Measurement of the interfacial tension between polyethersulfone and a thermotropic liquid-crystalline copolyester

Due to the increasing interest in forming blends of liquid-crystalline polymers with conventional thermoplastics, it becomes important to determine the interfacial tension between two such polymers. A method for evaluating the interfacial tension between a thermotropic copolyester based on hydroxybenzoic and hydroxynaphthoic acid residues, and polyethersulfone is presented, based on the Fort and Patterson method. It is found that the value of the interfacial tension in the melt is much higher than is the case between conventional polymer pairs. It is suggested that this high value reflects an entropic effect due to the strong exclusion of the flexible coil polymer from the nematic melt. © 1993 John Wiley & Sons, Inc.