Research on the preparation and performance of acrylic acid/methyl acrylate-modified starch catalyzed by an HRP binary initiation system

Abstract

Acrylic acid (AA)/methyl acrylate (MA)-modified starch was prepared via a catalytic process involving horseradish peroxidase (HRP)/acetylacetone (ACAC) as an initiation system. The structural analysis results demonstrated that the grafting of AA and MA onto starch was successful. Furthermore, the impact of the grafting reaction conditions on the grafting effect and the characteristics of the resulting grafted products were also examined. The results demonstrated that AA and MA were successfully grafted onto starch. The optimal conditions for starch grafting with AA/MA were identified as a reaction time of 4 h, an HRP enzyme concentration of 12 U/mL, a total monomer/starch ratio of 4:6, and a molar ratio of AA/MA feeding of 3:7. The viscosity and viscoelasticity of the modified starch slurry increased, and the film-forming property was enhanced. Compared with the original starch film, the modified film markedly increased the flexibility and tensile strength. Furthermore, an increased acrylic acid content maintained the original hydrophilicity of the modified starch film. The horseradish peroxidase (HRP)/acetone peroxide (ACAC) binary system serves as an initiator to stimulate the generation of free radicals from starch, acrylic acid (AA), and methyl acrylate (MA). Simultaneously, while AA and MA undergo self-polymerization and copolymerization, they also get grafted onto starch chains through self-polymerization and alternating copolymerization. A substantial number of branched small-molecule chains are uniformly grafted onto the primary chain of starch with a low molecular weight.