Aromatic polyesters with photosensitive side chains: Synthesis, characterization and properties

Abstract

New aromatic polyesters with photosensitive groups in their pendant chains were prepared from a diphenol carrying as substituent a cinnamoyl group extended with a flexible oxyethyleneoxy spacer and different aromatic dicarboxylic acids via direct polyesterification reaction in the presence of tosyl chloride/pyridine/dimethylformamide system as condensing agent. The resulting polyesters were characterized using Fourier-transform IR, proton and carbon nuclear magnetic resonance and ultraviolet spectroscopy, differential scanning calorimetry, thermogravimetric analysis, wide-angle X-ray diffractometry, gel permeation chromatography, viscosity measurement and solubility test. These polyarylates had moderate inherent viscosities ranging from 0.37 to 0.54 dL g-1, good solubility in polar aprotic solvents, and afforded transparent, colorless and apparently tough films by casting from their solutions. Their glass-transition temperatures ranged from 136 to 154?C. All of them did not show significant decomposition below 320?C and retained 38-47 % weight at 700?C in nitrogen atmosphere. The presence of cinnamoyl chromophore endowed these polymers with the ability to react to ultraviolet light which resulted in photodimerization between cinnamoyl side groups upon irradiation at l = 365 nm and cross-linking the polymers chains in the absence of photo-initiators or photo-sensitizers. As a consequence, the polymer films became insoluble in organic solvents.