Preparation of starch-g-polystyrene copolymer by emulsion polymerization

Styrene was graft copolymerized onto native corn starch by emulsion polymerization, using potassium persulfate (KPS) as an initiator, sodium dodecylbenzenesulfonate (SDBS) as an emulsifier, and tetraethylthiuram disulfide (TETDS) as a chain transfer agent. As the reaction time and the emulsifier concentration increased, graft percent (GP) was increased. With the increase of TETDS concentration, GP was decreased. When the corn starch was pre-heated in water, or when the reaction mixture was post-reacted at 80°C, higher GP values were obtained. The molecular weight of the grafted polystyrene showed a certain relationship with the variation of GP. The particle size of the starch in the grafted starch was reduced by pre-heating or by post-reaction heating.