The reaction between a hydrogenated hydroxyl-functionalized polyisoprene (H-HTPI) and isophorone diisocyanate isocyanurate (I-IPDI) is followed by using direct FTIR spectroscopy. The reaction kinetics is studied using a simple model taking into consideration the I-IPDI structure. The rates of individual isocyanate groups are described by a second order equation. Influence of dibutyltin dilaurate (DBTL) concentration and temperature on selectivity, defined as the ratio between the rate constant of secondary isocyanate group and the rate constant of the primary isocyanate group, is investigated. It is observed that selectivity decreases when temperature or DBTL concentration increases. Eyring parameters are determined for the catalyzed [DeltaH*=77/35 (kJ mol(-1)), DeltaS*= 12/-100 (J mol(-1) K-1)] and uncatalyzed reactions [DeltaH*=48/43 (kJ mol(-1)), DeltaS* = -179/-167 (J mol(-1) K-1)] primary and secondary isocyanate groups being differentiated. (C) 2004 Elsevier Ltd. All rights reserved.