Effect of photoinitiator on the molar mass distribution obtained from a pulsed laser polymerization

The choice of the photoinitiator is not usually regarded as being as important consideration in attempting to determine the value of the propagation rate coefficient k_p from a pulsed laser-initiated polymerization (PLP). It is shown that in fact the choice of the photoinitiator can profoundly influence the success of such experiments. Specially, for a number of monomers it was found that the successful determination of k_p is essentially impossible when 1,1-azodicyclohexanecarbonitrile is employed as a photoinitiator. The likely reason for this phenomenon is discussed from which it would seem appropriate to be wary in using any azo compound as a PLP photoinitiator. From PLP experiments with a non-azo photoinitiator, ambient pressure k_p has been determined for bulk polymerization of methyl methacrylate over an extended temperature range.