CO2-responsive aliphatic tertiary amine-modified alginate and its application as a switchable surfactant

A new kind of hexyl diethyl tertiary amine-grafted amphiphilic alginate derivative (HDEA-Alg) was synthesized from (6-bromo-hexyl)-diethyl-amine (BHDEA) and sodium alginate (NaAlg) through esterification. The structure of HDEA-Alg was confirmed by FT-IR and NMR spectroscopies. The grafting ratio was calculated according elemental analysis and thermodynamic property was analyzed by TG. The CO 2 /N 2 -responsive performance of HDEA-Alg in aqueous solution was demonstrated by surface tension and conductivity measurements. Stable emulsions of liquid paraffin were easily prepared in the presence of the HDEA-Alg. These emulsions can be de-emulsified by bubbling CO 2 through the emulsions at 5   °C for 30   min, resulting in complete oil/water phase separations. They can be re-emulsified by bubbling N 2 through the solutions at 50   °C for 30   min with the aid of homogenization.