How starch molecular fine structure influences starch graft copolymerization with acrylamide

Fifteen starches with distinct molecular structures were used to synthesize starch-g-polyacrylamide copolymers via horseradish-peroxidase-catalyzed graft copolymerization. Starch fine structures, including amylose content and the chain-length distributions (CLDs) of both amylose and amylopectin, were quantitatively analyzed using size-exclusion chromatography, and the data interpreted with biosynthesis-based mathematical models. Successful grafting was confirmed by Fourier-transform infrared spectroscopy, while the degree of branching (DB), degree of substitution and grafting ratio (GR) were quantified by proton nuclear magnetic resonance spectroscopy. Statistically significant correlations revealed that parent starches with higher amylose content, or a greater proportion of short amylose chains, or more short branches in amylopectin, often resulted in substantially higher DB and GR. This study establishes structure-reactivity relationships, providing guidance for the synthesis of grafted starches with tailored architectures.