Improved synthesis of poly (MAA)-starch graft copolymers

Abstract

Graft copolymerization of methacrylic acid (MAA) onto starch using a potassium persulfate/sodium thiosulfate redox initiation system was investigated. Emphasis was placed on the promotion of graft formation while minimizing homopolymerization. This could be achieved through a thorough investigation into the major factors affecting the polymerization reaction such as the state of the starch, redox ratio of the initiator, monomer and initiator concentrations, time and temperature of polymerization, and material-to-liquor ratio. The results obtained imply that the magnitude of the polymer yield including total conversion, graft yield, and homopolymer are determined by these factors. The yield is favored under the influence of higher temperature, longer time, short liquor, and increased monomer and initiator concentrations. A poly-(MAA)-starch graft copolymer is the main product of the polymerization reactions only when starch was preswelled (through cooking prior to grafting). Moreover, this grafted product could be precipitated by more dilution with water and easily separated by filtration. Hence, the results of the current work formed the basis of a novel method for the synthesis of poly (MAA)-starch graft copolymers. The mechanisms involved in the synthesis are reported. © 1998 John Wiley & Sons, Inc.