We carried out experiments examining the impact that solvent selection and reaction conditions have on the radical initiated graft polymerization reaction of acrylamide onto starch. We have also evaluated the rheological properties of the starch graftpolyacrylamide product when a gel is formed in water. It was found that when the reaction was carried out in DMSO, the molecular weight and the number of anhydroglucose units in between grafting sites (AGU/site) decreased. For example, when conducted in water, the number average molecular weight of the polyacrylamide grafts could be as high as 448822 with 6723 AGU/graft, when DMSO was the solvent the molecular weight could be as low as 14013 with 136 AGU/graft.  Polyacrylamide content could be measured by %N or by IR (Figure). These differences could be observed in the rheological properties of the resulting gels in water. The linear range rheological property analysis of the two types of gels (water and DMSO) suggested that water-made starch-polyacrylamide graft copolymers should be 'weak' gels at lower concentrations (<7%), but be 'strong' gels at higher concentrations (=9%); however, the DMSO-made starch-polyacrylamide graft copolymer should be 'weak' gels at all measured concentrations. The ability to control and generate starch graft polymers with dramatically different architecture may allow starch to be tuned to deliver improved properties for current or new applications.

Impact of reaction conditions on architecture and rheological properties of starch graft polyacrylamide polymers

247th National Meeting (2014)

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