Evolution of surface chemistry and physical properties during thin film polymerization of thermotropic liquid crystalline polymers

Kui Xiang Ma, Tai-Shung Chung*, Pramoda K. Pallathadka, Si Shen Feng

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

1 Scopus citations

Abstract

By applying a novel thin film polymerization technique, X-ray photoelectron spectroscopy (XPS), and the Lifshitz-van der Waals acid-base (LWAB) theory, we have determined the time evolution of surface chemistry and surface free energy during the polymerization of liquid crystalline poly(p-oxybenzoate/2,6- oxynaphthoate) at a molar ratio of 50/50. The surface free energy components of these main-chain liquid crystalline copolyesters were calculated from contact angle measurements using a Ramé-Hart goniometer and a three-liquid procedure (water, glycerol, and diiodomethane). The experimental data suggest that the Lewis base parameter (γ -) during thin film polymerization decreases rapidly with the progress of polymerization, while the Lewis acid parameter (γ +) and the Lifshitz-van der Waals parameter (γ LW) are almost invariant. The surface roughness data measured by atomic force microscopy (AFM) suggested that the increase in water contact angle (or the decrease in y-) was not caused by the change in surface roughness, but by the change in surface chemistry, i.e. due to the reaction of acetoxy and carboxy groups to release acetic acid during the polymerization reaction. In addition, the XPS results coincide with our previous Fourier transform infrared spectroscopy results showing that the condensation polymerization is much faster in the beginning than in the later stages. Consequently, the decrease in y-in the early stages of the polymerization is well explained.

Original languageEnglish (US)
Pages (from-to)1193-1208
Number of pages16
JournalJournal of Adhesion Science and Technology
Volume13
Issue number10
DOIs
StatePublished - Dec 1 1999

Keywords

  • Contact angles surface free energy
  • acid-base interactions
  • liquid crystalline polymers
  • roughness
  • thin film polymerization

ASJC Scopus subject areas

  • Chemistry(all)
  • Mechanics of Materials
  • Surfaces and Interfaces
  • Surfaces, Coatings and Films
  • Materials Chemistry

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