Copolymerization Studies of Urethane Methacrylate and Ladder-Like Polysilsesquioxane Containing Side Chain Methacrylate Groups

Abstract

Urethane methacrylate (UMA) prepolymer was prepared by reacting 2 mole tolylene diisocyanate with 1 mole polyethylene glycol (molecular weight 400) followed by end-capping with 2 mole 2-hydroxyethyl methacrylate in N, N-dimethylformamide (DMF) solvent using stannous octoate as a catalyst. It took 72 h for complete reaction at ambient temperature as determined by monitoring the isocyanate peak at 2269 cm-1. Ladder-like polysilsesquioxane (LPS) containing side chain methacrylate groups was prepared by stepwise coupling polymerization. Different weight fractions of UMA and LPS in DMF were copolymerized using 1% (w/w) dibenzoyl peroxide at 80°C for 24 h followed by post curing at 100°C for 4-5 h in a nitrogen atmosphere. The copolymers were characterized by Fourier transform infrared analysis, solid-state 13C NMR spectroscopy, differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD) and thermogravimetric analysis. No glass transition temperatures were observed for the copolymers by DSC. The WAXD patterns of copolymers showed a broad peak corresponding to the width of double chain of LPS, indicating the incorporation of LPS in copolymers. These copolymers were more resistant to acid medium. The temperature of 5% weight loss increased with increasing silsesquioxane content in both air and nitrogen atmospheres, and verified the incorporation of LPS in the copolymers.