MICROSTRUCTURE OF COPOLYMERS OF METHACRYLONITRILE N-ALKYL METHACRYLATE MIXTURES GRAFTED ONTO AMYLOMAIZE BY C-13-NMR SPECTROSCOPY

The microstructure and stereochemical configuration of copolymers of m ethacrylonitrile (MAN) with methyl methacrylate (MMA), ethyl methacryl ate (EMA), and butyl methacrylate (BMA) grafted onto amylomaize are an alyzed by C-13-NMR spectroscopy. The graft copolymers were prepared at high conversion by free radical copolymerization in aqueous medium in itiated by a redox mechanism with the amylomaize/Ce(IV) system. The co mposition and distribution of comonomeric units of these copolymers ar e compared with those of the bulk copolymerization at low conversion u sing AIBN as initiator. The results obtained indicate that random copo lymers with a statistical distribution of comonomeric sequences are ob tained at low conversion, but BMA-MAN copolymers prepared at high conv ersion seem to have relatively long sequences of BMA units in a wide f eed composition interval. This behavior is explained taking into consi deration the relative solubility of the corresponding alkyl methacryla te and methacrylonitrile in the reaction medium.