Graft copolymers of starch with mineral acid salts of dimethylaminoethyl methacrylate. Preparation and testing as flocculating agents

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Abstract
Mineral acid salts of dimethylaminoethyl methacrylate (DMAEMA) have been graft polymerized onto starch with ferrous ammonium sulfate–hydrogen peroxide initiation. The nitric acid salt was used in most reactions, and graft polymerizations were run in both water and aqueous–organic solvent systems. Increased monomer concentration in water led to an increase in both the percentage of poly(DMAEMA · HNO3) in the graft copolymer (percent add‐on) and the molecular weight of grafted branches. Variations in initiator concentration altered the percent add‐on only slightly but affected the molecular weight of grafted polymer significantly. When swollen starch, in contrast with unswollen starch was used in graft polymerization reactions run in water, the product had a higher per cent add‐on and a larger number of grafted branches of lower molecular weight. The efficiency of starch–poly(DMAEMA · HNO3) graft copolymers as flocculants for diatomaceous silica increased with per cent add‐on; however, variations in grafting frequency and graft molecular weight had less effect on the behavior of these materials as flocculants.