Poly(n-butylisocyanates) were synthesized by anionic homopolymerization with the addition of sulfonate groups in the termination stage. Two types of functional polymers were obtained from different quantities of added 1,3-propanesultone (PrS). When a stoichiometric proportion of sultone is added, the reaction with poly(n-butylisocyanate) renders a mix of a nonfunctionalized (PBIC) and a telechelic polymer (PBICT). In the presence of an excess of PrS, the proportion of end-functionalized chains was higher, and a significant change in their thermal properties was observed. Polymers were characterized by FTIR and NMR, and measurements of intrinsic viscosity were made. Thermal degradation of the polymers was studied under nitrogen atmosphere for various heating rates. The kinetic parameters such as the activation energy and the reaction order were determined by using Ozawa's method. Thermal degradation analyses showed that the degradation processes depend strongly on the concentration of functional groups. (C) 2003 Wiley Periodicals, Inc.