PHOTO-DIFFERENTIAL SCANNING CALORIMETRY STUDIES OF CATIONIC POLYMERIZATIONS OF DIVINYL ETHERS

Photo-differential scanning calorimetry experiments were used to deter mine effective kinetic constants for propagation and termination for a series of unsteady-state divinyl ether polymerizations at different t emperatures and light intensities. For these cationic photopolymerizat ions the reaction rate and limiting conversion were both found to incr ease as the reaction temperature was increased. At all temperatures ex hibited a dramatic increase at the start of the reaction, the profile for the propagation rate constant k(p) plateaued at a value between 5 and 301 mol(-1)s(-1) (depending upon temperature) and then decreased a s the reaction reached a limiting conversion owing to trapping of the active centres. The effective termination rate constant k(t) was very low, with active centre lifetimes approaching 20 min. The overall acti vation energy for polymerization was found to be 26.5 +/- 3.2 kJ mol(- 1).