High molecular weight polyacrylonitrile (PAN) was obtained by the free-radical suspension copolymerization of itaconic acid (IA) and acrylonitrile (AN) which was carried out in DMSO／H2O using azodiisobutyronitrile(AIBN) as initiator．Orthogonal design method was used to study the effect of polymerization parameters

such as the reaction temperature

monomer concentration

DMSO／H2O ratio

initiator content and so on

on the conversion of polymerization．The reaction temperature is the most important factor determining the conversion of copolymerization. The effect of DMSO／H2O ratio on the conversion and viscosity-average molecular weight was specially introduced．The copolymerization reaction rate and the viscosity-average molecular weight of copolymers may decrease as the result of the high chain transfer constant of DMSO．For copolymerization of AN and IA

with the inclusion of good solvent DMSO

the solution degree of AN in DMSO／H2O is higher than in water

as a result

the resulting copolymer pellets becomes porous．The structure and properties of PAN homopolymer and P(AN-co-IA) copolymer were also studied by using DSC

TG and IR measurements．It was shown that the conversion of polymerization could be increased by increasing reaction temperature

decreasing monomer concentration and decreasing the IA content in the feed AN／IA ratio．The results also demonstrated that the conversion of copolymerization of IA and AN decreased with the increase of DMSO content in the feed DMSO／H2 ratio．For the same IA content in the feed AN／IA ratio

the high molecular weight P(AN-co-IA)copolymers have the lower start exothermal reaction temperature and wider DSC exothermal peak as compared to the convertional low molecular weight P(AN-co-IA) copolymers

and these phenomena are consistent with the result of IR studies．