A New Approach to Preparing Bio-Synthetic Hybrid Materials Using Starch Nanoparticles
Starch nanoparticles (SNP) are a new class of innovative biopolymers that can be obtained from native starch using different methods. Interest in bio-synthetic hybrid materials based on polysaccharides has been increasing in academia and industry in recent years. Previous studies have explored the modification of polysaccharides using different techniques to broaden their applications. Grafting from and grafting to with synthetic polymers, as well as etherification with small molecules were chosen in this work to modify the SNP. This work demonstrates the first successful nitroxide-mediated polymerization (NMP) grafting of SNP using both, the grafting from and the grafting to approaches. To graft synthetic polymers from the surface of the SNP, three steps were followed: 1) functionalization of SNP with vinyl benzyl chloride (VBC); 2) reaction of SNP-VBC with BlocBuilder MA (BB) to form an SNP-macroinitiator (SNP-BB); and 3) graft copolymerization of methyl methacrylate (MMA) with styrene (S), acrylic acid (AA) and methyl acrylate (MA) with SNP-BB. To graft synthetic polymers to the surface of SNP, again three steps were followed: 1) similar to the grafting from, functionalization of SNP with VBC; 2) synthesis of SG1-capped copolymers (macroalkoxyamines) via NMP using BB: P(MMA-co-S), poly(2-(dimethylamino)ethyl methacrylate-co-styrene), P(DMAEMA-co-S), and poly(2-(diethylamino)ethyl methacrylate-co-styrene), P(DEAEMA-co-S); and 3) reaction of the double bond of SNP-VBC with SG1-terminated macroalkoxyamines. 1H NMR, FTIR, TGA and elemental analysis were used to characterize the grafted SNP and confirm the success of the grafting from and grafting to reactions. The grafting of synthetic polymers such as P(MMA-co-S), PAA, PMA, P(DMAEMA-co-S) and P(DEAEMA-co-S) on hydrophilic SNP yields new bio-synthetic hybrid materials that could find use in paper coating latexes and other industrial applications. SNP were also modified with small molecules, such as octenyl succinic anhydride (OSA) and styrene oxide (STO), to change their hydrophilic/hydrophobic balance to make them Pickering stabilizers. Miniemulsion stability tests, emulsion polymerizations and miniemulsion polymerizations were conducted with SNP-STO for the first time. These new modified SNP showed the ability to partition at the oil-water interface, thereby providing stabilization to the system, which was not possible without the modification.