Copolymerization of styrene and methyl methacrylate with nickel acetylacetonate/methylaluminoxane catalyst system

The present work deals with copolymerization of styrene (STY) and methyl methacrylate (MMA) catalysed by nickel acetylacetonate - Ni(acac)2, employing methylaluminoxane (MAO) as cocatalyst. This catalyst system presented low catalyst activities for STY homopolymerization and very high activities for MMA. It seems that the catalyst system based on Ni(acac)2/MAO is effective for the copolymerization of MMA and STY to give block copolymer but it also produced polystyrene and poly(methyl methacrylate) homopolymers. The polymers were characterized by 13C NMR, GPC and FTIR. The polystyrene homopolymer was identified by IR and NMR analyses of the cyclohexane soluble fraction. The presence of absorption bands correspondent to carbonyl group and aromatic ring was observed in the IR spectrum of the acetic acid soluble part. This result is a clue that STY-MMA copolymer with low molecular weight was produced. The high molecular weight copolymer (acetic acid insoluble fraction) was also characterized by IR analysis which indicated the presence of characteristic absorption bands of carbonyl group and aromatic ring. These results were confirmed by 13C NMR analysis.