Surface energy of thermotropic liquid crystalline polyesters and polyesteramide

Abstract

We have determined the surface energies (γs) of two liquid crystalline polyesters (Vectra™ A-950 [Hoechst Celanese, NJ] and Xydar™ [Amoco, GA]) and one polyesteramide (Vectra™ B-950 [Hoechst Celanese, NJ]) using contact angle techniques at room temperature. These LCPs were dissolved in bis-trifluoromethyl phenol and spin coated upon glass slides to form thin films. The contact angle measurements were carried out employing a Ramé-Hart Contact Angle Goniometer (Ramé-Hart, NJ). Pure water, glycerol, formamide, and diiodomethane were chosen as the testing liquids. Various surface energy calculation models were utilized to analyze the surface energies of these LCP films. Experimental data suggest that surface energy values did match between two-liquid geometric and three-liquid acid-base approaches if the correct combinations of testing liquid were used. However, the three-liquid Lifshitz-van der Waals acid-base method is more suitable for the surface energy calculation of these three LCPs, and provides much more information (e.g., acidity and basity of LCP surfaces). The average surface energies of Vectra™ A-950, Vectra™ B-950, and Xydar™ are 41.0, 41.9, and 42.3 mJ/cm2, respectively. In addition, all these three LCPs should be classed as monopolar Lewis bases because their Lewis acid components, γ+, are negligible. © 1998 John Wiley & Sons, Inc.