Chemical Modification of Starch via Etherification with Methyl Methacrylate

Reaction of starch with methyl methacrylate (MMA) via etherification was investigated under different conditions. Factors studied include sodium hydroxide concentration, methyl methacrylate concentration. reaction time and temperature, as well as the reaction medium. Results obtained indicate that the extent of etherification increases as the amount of sodium hydroxide increases, attains a maximum then decreases. Prolonging the reaction time up to 20 h is accompanied by enhancement in the extent of etherification. Longer reaction time has no effect on the extent of etherification since a stage of leveling off of the reaction is attained. 55 °C constitutes the optimal temperature for the etherification reaction. Higher or lower than 55°C causes a decrease in the percent of etherification and degree of substitution. Neither aqueous nor nonaqueous medium presents suitable media for carrying out the MMA/ starch etherification reaction. The reaction takes place easily when water/solvent medium at ratio 41ul/4ml was used. Higher ratios prevents etherification by virtue of their very favourable effect on the swelling of starch.