The present study demonstrates in sitn real-time attenuated total reflection (ATR)-FTIR spectroscopy as a powerful tool for monitoring and analyzing different polymerization and polymer modification reactions. Thus, a metallocene catalyzed copolymerization of propene and 10-undecene-1-ol, a polycondensation reaction towards polysulfone, and a modification reaction of OH end groups of hyperbranched poly(urea-urethane) were investigated successfully. The interpretation of the development of FTIR spectra was carried out on the basis of typical vibration bands of chemical groups of the corresponding monomers and polymers in each case, e.g. of the C=C double bond of 10-undecene-1-ol during the copolymerization, the new C-O-C group of polysulfone, and the new urethane end group of poly(urea-urethane). Kinetics prediction is also under consideration. (c) 2006 Wiley Periodicals, Inc.