Effects of amylose content on property and microstructure of starch-graft-sodium acrylate copolymers

•Superabsorbent St-g-SA copolymers based on starches with different amylose content.•Water absorbent capacity of copolymers increased as amylose content decreased.•Microstructure of waxy St-g-SA copolymer was homogeneous.•Starch aggregates were observed in maize and high amylose St-g-SA copolymer.•Property and microstructure were related to gelatinization behaviors of starches. Starch-graft-sodium acrylate (St-g-SA) copolymers were synthesized with ammonium persulfate as an initiator. This work focused on the effects of amylose content of corn starch on the water absorbent capacity and microstructure of the St-g-SA copolymers. The water absorbent capacity of waxy, maize and high amylose St-g-SA copolymers was 1800g/g, 1300g/g and 1100g/g respectively. The grafted copolymers were characterized by FTIR and solid state 13C NMR confirming that the graft reaction had taken place between sodium acrylate and corn starch. The surfaces and cross sections of St-g-SA copolymers were observed by SEM. Incomplete gelatinized starch aggregates increased with increasing amylose content on surfaces and cross sections of copolymers, which accorded with the water absorbent capacity and grafting ratio. DMTA results showed that the waxy St-g-SA copolymer had the highest transition temperature which indicated waxy starch had high grafting ratio.