Propargylic and Chromene Terminated Prepolymers. 3. Study of Homopolymerization and the Effect of the Chromene Content on Reaction Kinetics

We have chemically synthesized CTR (chromene terminated resin) prepolymers in order to more specifically study the homopolymerization reaction of chromene. Physicochemical data were used to show the value of working with dichromene prepolymers instead of propargylic monomers. In particular, the homopolymerization reaction is less exothermic than the thermally induced ring formation. So, when the homopolymerization reaction is predominant, the processability of the final thermoset material will be easier. Besides, the rate constant of the homopolymerization reaction is higher than that measured for dipropargylic monomers. This explains the interest in overcoming β stage formation which is the kinetically rate limiting step. On the other end, the presence of residual propargylic functions in dichromene prepolymers after synthesis has no considerable effect on reaction temperature or advancement of reaction.