Copolymerization of diethyl 2‐(methacryloyloxy) ethyl phosphate with alkyl acrylates: Reactivity ratios and glass transition temperatures

Soluble copolymers of diethyl 2‐(methacryloyloxy) ethyl phosphate (DMP) with methyl methacrylate (MMA), methyl acrylate (MA), ethyl acrylate (EA) and butyl acrylate (BA) were synthesized by radical copolymerization in benzene solution using azobis(isobutyronitrile) (AIBN) as initiator. The monomer reactivity ratios of these systems at 60°C were determined by the conventional schemes using the methods of Fineman–Ross, Joshi‐Joshi, and Kelen–Tüdos. DMP underwent a completely random and azeotropic copolymerization with MMA whereas in its reaction with the other acrylates DMP entered preferentially into the polymer chain. The reactivities of DMP‐terminated polymer radicals towards the acrylate monomers were found to be in the order: MMA > EA > MA > BA. An increase in solvent polarity decreased the relative reactivity of DMP for the DMP‐MMA pair. An examination of the molecular weights of the copolymers revealed the occurrence of chain transfer caused by DMP. The copolymer glass transition temperatures were determined and the variations of Tg with copolymer compositions were discussed according to the theory of Johnston, taking into account the effect of the sequence distributions of the comonomers on Tg. The Tgs of the alternating copolymers of DMP with the four alkyl acrylates were calculated.