By using the Lifshitz-Van der Waals-Acid-Base theory, we have determined the surface tensions (γs) of three commercially available liquid crystalline polymers (LCPs) from the measurement of contact angles on thin films. The values obtained are 43.1, 41.1 and 41.5 mJ/m2 (dyn/cm) for Vectra™ A-950, Vectra™ B-950 and Xydar™ SRT-900, respectively. Experimental data suggest that all the three LCPs are monopolar. The strength of Lewis base (tendency to donate a pair of electrons for the formation of a covalent bond) for these three LCPs is as follows: Vectra™ B-950 > Xydar™ SRT-900 > Vectra™ A-950. We also theoretically estimated γs from both parachor (Ps) and cohesive energy (Ecoh) utilizing the concept of molecular group contribution. It was found that γs's calculated from Hoftyzer & Van Krevelen and Hayes' Ecoh values are close to our experimental results obtained from contact angle measurements. This is especially true for Xydar™ SRT-900 LCP, where γs obtained from contact angle measurements is 41.5 mJ/m2, while from Hoftyzer and Van Krevelen, and Hayes it is 42.4 and 41.8 mJ/m2, respectively. However, more adequate group contributions for naphthalene and amide groups are urgently needed.
All Science Journal Classification (ASJC) codes
- Condensed Matter Physics
- Physical and Theoretical Chemistry
- Organic Chemistry
- Polymers and Plastics
- Materials Chemistry