Graft Polymerization of Acrylamide and 2-Acrylamido-2-methylpropanesulfonic Acid onto Starch

TL;DR: In this article, a mixture of acrylamide and 2-acrylamido-2-methylpropanesulfonic acid (AASOsH) was graft polymerized onto starch by cobalt-60 irradiation, and the water absorbency and water solubility of the resulting products were determined.

Abstract: Mixtures of acrylamide and 2-acrylamido-2-methylpropanesulfonic acid (AASOsH) were graft polymerized onto starch by cobalt-60 irradiation, and the water absorbency and water solubility of the resulting products were determined. The conversion of monomers to polymer was nearly quantitative when pregelatinized wheat starch and a water solution of the two monomers were si­ multaneously irradiated (simultaneous irradiation conditions). Products with high \vater absorbency were obtained with equal weights of starch and total monomers when acrylamide:AASOsH ratios ranged from 9:1 to 1:3. Water solubility of these polymers was over 50%. Neither of the two monomers gave absorbent polymers when graft polymerized individually onto starch. Although highly absorbent products were also obtained at a total monomer:starch ratio of 2:5, ratios of 1:5 and lower gave products with poor absorbency. Neutralization of AASOsH with sodium hydroxide before graft polymerization drastically reduced both the water solubility and absorbency of the final products. A reaction with granular starch was also carried out under simultaneous irradiation with a total monomer:starch ratio of 2:5 and with equal weights of the two monomers. Conversion of monomers to polymer was once again nearly quantitative. To obtain good water absorbency from this granular product, it was necessary to first neutralize the AAS03H portion with alkali, then disperse the polymer in hot water, and finally dry the resulting water dispersion. Graft copolymers with good water absorbency were also obtained by adding preirradiated starch to a water solution of acrylamide and AAS03H, although only partial conversions of monomers to polymer were realized. Selected products from the various graft polymerizations were fractionated by extractiqn with either water or a 1% solution of sodium chloride. The synthetic polymer content of the resulting fractions and the percentage of AAS03H in the synthetic portion of each polymer were determined. The M n of some of the synthetic polymers was also determined after removal of carbohydrate by enzymatic hydrolysis.