Telechelic poly(epsilon-caprolactone)s or poly(D,L-lactide)s were prepared by SnOCt(2)-initiated polymerization of E-caprolactone (epsilon CL) Or D,L-lactide (D,L-LA) coinitiated with 1,4-butane diol or tetra(ethylene glycol). These telechelic polyesters were in situ functionalized with 3-isocyanatopropyl trimethoxysilane (IPTMS) by SnOct(2)-catalized addition of the OH-endgroups. Analogously, star-shaped polyesters were synthesized and functionalized using 1,1,1-trishydroxymethyl propane or pentaerythritol as coinitiators. All functionalized polymers were characterized by H-1 NMR and MALDI-TOF mass spectra. In crosslinking experiments with oligo(ethylene-glycol)s the trimethoxysilyl groups proved to be 10-30-fold more reactive than triethoxysilyl end-capped polyesters. (c) 2005 Elsevier Ltd. All rights reserved.