Reaction of poly(vinyl alcohol) with n‐butyl isocyanate. Chemical hydrolysis of the resulting polymers

Abstract

AbstractThis study is concerned with some kinetic features of the reaction of n‐butyl isocyanate with poly(vinyl alcohol) without any catalyst and using triethylene diamine as catalyst. The structure of the resulting polymers was determined by means of IR, 1H‐ and 13C‐NMR spectroscopy as well as by chemical analysis. Vinyl alcohol‐vinyl butyl urethane (VAL‐VBU) copolymers were obtained. It has been found a linear dependence of reaction rate on polymer, n‐butyl isocyanate, and triethylene diamine concentrations. Reaction rate constant decreases as reaction time increases. It can be explained by steric hindrance phenomena due to urethane groups incorporated along the polymeric chain. The activation energy was found to be 49.9 kJ/mol. A kinetic study of the homogeneous hydrolysis of VAL‐VBU copolymers has been made as a function of the base concentration, the temperature, and the VBU content. The homogeneous hydrolysis was found to be first order with respect to both hydroxyl ion and VBU contents. The activation energy for the base catalyzed homogeneous hydrolysis was found to be 79.3 kJ/mol. The heterogeneous hydrolysis of VAL‐VBU copolymers in basic medium showed that no hydrolysis takes place under the conditions employed.