Synthesis of starch graft-copolymers via reactive extrusion: Process development and structural analysis

To promote the large-scale production of starch-based biomaterials, we developed a method of synthesis based on reactive extrusion that combines the benefits of continuous manufacturing with the use of green chemistry principles. This paper describes the grafting of four different types of starches with acrylamide monomers via free radical copolymerization using twin-screw extrusion technology. The elemental analysis confirmed the success of this method, with an average monomer conversion of 80% and grafting efficiency of 74% across all samples. The C-13-NMR/H-1-NMR and ATR-FTIR analysis revealed that the type of starch substrate used strongly influenced the mechanism of the grafting reaction. Thermal analysis (TG/DTG-DSC) indicated that the graft-copolymers thermal stability was influenced by the amylose-amylopectin content ratio. Swelling tests suggested that cationic modification of the substrate is a promising approach to produce stimuli-responsive graft-copolymers via reactive extrusion. The proposed method has proved to be a viable alternative for the production of starch-copolymers.