Methyl methacrylate photopolymerization during

Problems associated with unsensitized thermal and photopolymerizations are still not completely resolved. Oligomers are produced during the thermal polymerization of methyl methacrylate, notably the unsaturated dimer CHj C(COOCH3) CH2 CH2-CH(COOCHj) CH3 its polymerization and copolymerization have been studied. The direct photopolymerization of styrene and possible pathways for radical production have received further consideration. ... 

Mathias et al. studied the photopolymerization of methyl methacrylate on parabolic airplane flights and reported a variation in the molecular weight with g level (34) consistent with a report from a drop tower experiment by Sturm et al. (55). This phenomenon is most likely an effect of mixing caused by composition gradients created during photopolymerization that affects the average rate of initiation throughout the sample. 

Like benzoin ethers, benzilketals undergo a-cleavage whereby a benzoyl radical and a dialkoxybenzyl radical is formed. Whereas the benzoyl radicals are, as explained earlier, vigorously reacting with olefinic bonds of vinyl monomers, dialkoxybenzyl radials were found to be of low reactivity. Actually, one of seven dialkoxy benzyl radicals formed is found to be incorporated into the polymer chain during the photopolymerization of methyl methacrylate initiated by DMPA [41]. However, to what extent this portion of dialkoxy benzyl groups is caused by termination rather than initiation remains unclear. 

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