SURFACE-ENERGY OF THERMOTROPIC LIQUID-CRYSTALLINE POLYESTERS AND POLYESTERAMIDE

We have determined the surface energies (gamma(s)) of two liquid cryst alline polyesters (Vectra(TM) A-950 [Hoechst Celanese, NJ] and Xydar(T M) [Amoco, GA]) and one polyesteramide (Vectra(TM) B-950 [Hoechst Cela nese, NJ]) using contact angle techniques at room temperature. These L CPs were dissolved in bis-trifluoromethyl phenol and spin coated upon glass slides to form thin films. The contact angle measurements were c arried out employing a Rame-Hart Contact Angle Goniometer (Rame-Hart, NJ). Pure water, glycerol, formamide, and diiodomethane were chosen as the testing liquids. Various surface energy calculation models were u tilized to analyze the surface energies of these LCP films. Experiment al data suggest that surface energy values did match between two-liqui d geometric and three-liquid acid-base approaches if the correct combi nations of testing liquid were used. However, the three-liquid Lifshit z-van der Waals acid-base method is more suitable for the surface ener gy calculation of these three LCPs, and provides much more information (e.g., acidity and basity of LCP surfaces). The average surface energ ies of Vectra(TM) A-950, Vectra(TM) B-950, and Xydar(TM) are 41.0, 41. 9, and 42.3 mJ/cm(2), respectively In addition, all these three LCPs s hould be classed as monopolar Lewis bases because their Lewis acid com ponents, gamma(+), are negligible. (C) 1998 John Wiley & Sons, Inc.