Preparation Of Styrene-maleic Anhydride Random Copolymer By Stabilizer-free Dispersion Polymerization

Random copolymer of styrene （St） and maleic anhydride （MAH）were prepared by stabilizer-free dispersion polymerization in twodifferent systems. The effects of solvent, copolymerization temperatureand time, feed ratios of MAH to St, the initiator concentrations, monomerconcentrations and strong polarity solvent dioxane on polymerizationyields, compositions and number-average molecular weights of thecopolymers were investigated in detail. Furthermore, the sequentialstructure, microsphere morphology and thermal property of thecopolymers were characterized by13C-NMR, SEM and DSC,respectively.In n-heptane system, the results showed that the ratio of monomerswas one of the main influence factors on MAH molar content ofcopolymer, which range from25-46%. Number-average molecular weightof the copolymer range from6000-40000can be obtained by changingthe initiator and monomer concentrations. The R-SMA copolymer had thecharacteristic of good resistance to heat, and the glass transition temperature is about122Random copolymer of styrene and maleic anhydride was preparedby stabilizer-free dispersion polymerization, with dicumyl peroxide （DCP）as initiator and ethyl butyrate as solvent. The results showed that a stabledispersion of SMA random copolymer particles was formed when thefeed ratio MAH/St20/80. When the feed ratio of MAH/St was less than15/85, it was observed that the obtained copolymer could be partiallydissolved in the solvent. The molecular weight of the soluble fraction wassmaller than that of the precipitation part. In addition, the microspheremorphology and sequential structure of the copolymers werecharacterized by SEM and¹³C-NMR, respectively. The results showedthat when the molar feed ratio of MAH to St （MAH/St） was20/80, theoverall MAH content in the copolymer was about26%（molar） from the13C-NMR spectrum, and the three St-centred triads SSS, MSS+SSM, andMSM were about41%,44%, and15%, respectively.