Graft copolymers from cobalt-60 pre-irradiated starch and mixtures of acryl-amide with N,N,N-trimethylaminoethyl methacrylate methyl sulfate

Starch was preirradiated with cobalt-60 and then allowed to react with mixtures of acrylamide and N,N,N-trimethylaminoethyl methacrylate methyl sulfate (TMAEMA·MS) in a water solution. The graft copolymers resulting were purified and characterized, and the influence of a number of irradiation and reaction variables on graft copolymer composition was determined. Although the reaction of irradiated starch with monomers must be carried out with a monomer solution purged with nitrogen to remove dissolved oxygen, a nitrogen atmosphere over the starch sample during irradiation is not necessary to achieve graft polymerization. With monomer mixtures containing 2, 5, 10, 15, and 50 mol% TMAEMA·MS, the mole percentage of TMAEMA·MS in grafted branches was less than that in the initial monomer mixture, whereas ungrafted polymer generally contained a higher percentage of the cationic monomer than was present initially. A tenfold variation in irradiation dose (0.5–5.0 Mrad) caused only small variations in percent add-on; however, intrinsic viscosities of grafted branches decreased with increasing irradiation dose. Substituting aqueous ethylene glycol for water as the reaction medium produced more frequent grafts of lower molecular weight. Graft polymerization onto partially degraded starches gave graft copolymers with better water solubility.