HEAT-CAPACITIES OF PERFLUOROPOLYETHERS

The heat capacities at constant pressure of liquid perfluoropolyethers with different chain structures were determined above the glass trans ition temperature up to 480 K by means of differential scanning calori metry (DSC). The group contributions of the - O -, - CF2 -, and - CF(C F3) - were calculated as a function of the temperature. Anomalous beha vior of ethereal oxygen in a perfluorinated chain, as previously found for group contributions to the glass transition and to the vaporizati on energy, was observed also for heat capacity where the oxygen contri bution is consistently lower for perfluorinated polyoxides in comparis on to the hydrogenated homologous. The jump in c(p) at the glass trans ition follows a regular behavior in the sense that Delta C-p/beadmole is within the average range found by Wunderlich for the majority of po lymers. Moreover, data obtained in the present work allow the predicti on of c(p) of perfluoropolyethers of whatever structure between T-g an d 480 K. (C) 1997 John Wiley & Sons, Inc.