Controlled formation of isocyanate-terminated star polyethers avoiding chain extension

Star polymers with reactive isocyanate end groups were prepared via the end capping of hydroxy-terminated star polyether polyols with toluene diisocya nate (TDI; 80% = 2,4 TDI, 20% = 2,6 TDI). The multifunctional polyols and T DI were reacted in bulk without a catalyst. This procedure was optimal in r egard to the product yield, minimizing unfavorable coupling side reactions and avoiding crosslinking reactions. The experimental results were based on theoretical studies of the reaction kinetics. (C) 2000 John Wiley & Sons, Inc.