STUDY OF THE REACTION BETWEEN 1,5-NAPHTALENE DIISOCYANATE AND POLYCAPROLACTONE IN DIFFERENT SOLVENTS

The reaction between polycaprolactone and 1,5-naphtalene diisocyanate has been investigated in solvents with different dielectric constants and hydrogen bonding powers (toluene, ethyl acetate, ethyl methyl keto ne), and in the same solvents with the addition of a catalytic amount of dimethyl sulfoxide (DMSO). The reaction was considered to proceed o ver two steps, the reaction of the first NCO group being faster. The c ourse of the reaction was measured by titration of the unreacted NCO g roups, H-1- and C-13-NMR spectroscopy, and size exclusion chromatograp hy. By titration only the overall reaction order and reaction rate con stants could be determined. DMSO accelerated the reaction in all three solvents, which was explained by the stabilization of the activation complex by DMSO. Both steps of the reaction could be specified by NMR spectroscopy. The ratio between the reaction rate constants for the fi rst and the second step decreased with the increased hydrogen bonding strength of the solvent and with DMSO. By SEC only the reaction of the first NCO group could be determined due to the low resolution for hig her molar mass reaction products with a broad distribution. The values obtained for the first step reaction rate constants were in good agre ement with NMR values. (C) 1995 John Wiley and Sons, Inc.