The influence of molecular weight and chemical structure of soft segment in reaction kinetics with tolyl isocyanate

The influence of molecular weight and chemical structure of several polycar bonate diols on the kinetics of condensation reaction with p-tolyl isocyana te has been studied. Size exclusion chromatography has been used to monitor the reaction. The condensation reaction kinetics is adequately described b y an autocatalysed third order rate equation. The values obtained for rate constants, using a Runge-Kutta mathematical model, suggest an association p henomena by hydrogen bonding implying hydroxyl groups but also urethane gro ups. In bulk and in stoichiometric conditions, the association phenomena ob served increases proportionally, on one hand to the decrease of molecular w eight of macrodiol, and on the other hand to the tendency to form intramole cular hydrogen bonds. (C) 2001 Elsevier Science Ltd. All rights reserved.