Graft copolymers of starch with mixtures of acrylamide and the nitric acid salt of dimethylaminoethyl methacrylate

摘要

AbstractMixtures of acrylamide and the nitric acid salt of dimethylaminoethyl methacrylate (DMAEMA·HNO3) have been graft polymerized onto unmodified wheat starch with ferrous ammonium sulfate–hydrogen peroxide initiation. Graft polymerizations were carried out with both unswollen starch granules and granules that had been swollen by heating in water to 60°C. Ungrafted synthetic polymers were removed from graft copolymers by cold‐water extraction and were characterized by their M̄nand DMAEMA·HNO3content. Graft copolymers were characterized with respect to per cent add‐on, M̄nand DMAEMA·HNO3content of grafted polymer, and grafting frequency. Ungrafted synthetic polymers contained a mole percentage of DMAEMA·HNO3equal to or greater than that present in the initial monomer mixtures; whereas in most grafted polymers the mole‐ DMAEMA·HNO3in the grafted branches was less than that in the starting monomers. At all monomer ratios examined, polymer grafted to swollen starch granules contained a higher percentage of DMAEMA·HNO3then polymer grafted to unswollen starch. The influence of starch granule swelling on the molecular weight and frequency of grafted branches was correlated with the composition of the initial monomer mixture. It was determined that the effect of granule swelling on graft copolymer structure would be minimal when 25–30 mole‐ DMAEMA·HNO3was used. In an acetonitrile–water solvent system, reactions with 20 and 50 mole‐ DMAEMA·HNO3produced graft copolymers with less DMAEMA·HNO3in grafted branches than corresponding graft polymerizations run in water. The flocculation of 3 aqueous suspensions of diatomaceous silica was examined with selec