Cyclic acetal-photosensitized polymerization. VIII. Photopolymerizations of diallylidene pentaerythritol and its derivatives

The photopolymerization of diallylidene pentaerythritol (DAPE) was carried out in benzene at 40°C without the use of the usual initiator. DAPE was polymerized with the ester radical generated from DAPE by photoirradiation. To investigate the effect of dimethyl groups at the α,α- or β,β-positions of vinyl groups on the polymerization, photopolymerizations of dimethallylidene pentaerythritol (DMPE) and dicrotylidene pentaerythritol (DCPE) were carried out and kinetically studied from the standpoint of the degradative chain transfer by the allylidene group and cyclization by two double bonds. The results can be summarized as follows: (1) The relation between the rate of polymerization, R_p, and the monomer concentration M] can be expressed as M]/R_p = (AM] + B)/(2M] + C), where A, B, and C are constants. (2) The ratios of the rate constant of unimolecular cyclization to the total rate constants of bimolecular propagation and the chain transfer of uncyclized radical were estimated as 1.12, 0.26, and 0.16 mole dm^?3 for DAPE, DMPE, and DCPE, respectively; the cyclizations hardly took place. (3) The rate of polymerization and the molecular weight of the polymer were small because of the degradative chain transfer by the allylidene group.