Further discussion on the estimation of primary polymer chain length of vinyl-type network polymers based on the thermal decomposition of azo crosslinks

2,2′-Azobis[N-(2-propenyl)-2-methylpropionamide] (APMPA) having two carbon–carbon double bonds and an azo group was copolymerized with vinyl benzoate (VBz) at 60 °C, providing an azo groups containing VBz/APMPA prepolymer or crosslinked polymer which acts as a soluble or insoluble polymeric azo initiator, respectively. The gelation in VBz/APMPA (90/10 mol/mol) copolymerization was discussed briefly in order to reveal the characteristic polymerization behavior of APMPA as a novel crosslinker. Then, the resulting poly(VBz-co-APMPA)s as prepolymers or crosslinked polymers were thermally decomposed at elevated temperatures in the presence of lauryl mercaptan (LM) as a chain transfer agent; thus, the polymeric radicals generated through the cleavage of azo crosslinks would undergo the chain transfer reaction with LM to give primary polymer chains. This will provide a new approach to estimate the primary polymer chain length of vinyl-type network polymers by cutting all crosslinks in the network at the gel point as defined for the derivation of Stockmayerʹs equation.