Copolymers of 3,5-dimethylphenyl acrylate and methyl methacrylate: synthesis, characterization and determination of monomer reactivity ratios

Copolymers of 3,5-dimethylphenyl acrylate (DMPA) and methyl methacrylate (MMA) having various compositions were synthesized using free radical solution polymerization in butane-2-one at 70 +/- 1 degreesC with benzoyl peroxide as initiator. The structure of the copolymer was confirmed by FTIR, H-1 NMR and C-13 NMR spectroscopic techniques. The polydispersity indices of the copolymers determined using gel permeation chromatography suggest that the chain termination by disproportion was predominant when the mole fraction of MMA in the feed is high and radical recombination was predominant when the mole fraction of DMPA was high in the feed. The glass transition temperature of the copolymer increases with increase in MMA content. The thermal stability of the copolymers increases with increase in DMPA content. The copolymer compositions were determined using H-1 NMR analysis. The monomer reactivity ratios were determined by application of conventional linearization methods such as the Fineman-Ross (r(1) = 0.3942; r(2) = 2.3250), the Kelen-Tudos (r(1) = 0.3848; r(2) = 2.2584), an extended Kelen-Tudos (r(1) = 0.3608; r(2) = 2.3384) and a non-linear error-in-variables model method using a computer program, RREVM (r(1) = 0.3879; r(2) = 2.2642). These values suggest that MMA is more reactive than DMPA and the copolymer will be richer in MMA units. (C) 2003 Society of Chemical Industry.