Novel pH- and temperature-responsive polymer: Tertiary amine starch ether

A novel double pH- and temperature-responsive tertiary amine starch ether (TAS) has been developed. Synthesis was performed by grafting dipropyl or dibutyl epoxypropylamine onto hydroxyethyl starch. The cloud point temperatures (TC) of TAS could be tuned to a wide range from 26 to 72.8 °C by changing the alkyl chain length, their average molar substitution (MS), and pH value of the solution. The TC of TAS increases with decreasing the alkyl chain length, MS, and pH value of the solution. A linear relationship occurs between the TC and the pH, indicating well-tunable TC. These TAS also showed single pH-sensitive property due to the existence of tertiary amino and hydrophobic alkyl groups. The synthetic strategy presented here could be employed in the preparation of other novel biomaterials with dual pH- and temperature-responsive properties from a variety of polysaccharides.