Abstract: A series of long-chain fatty amido tertiary amine-based CO₂ switchable surfactant N-(3-(dimethyl amino) propyl) alkyl amide (C_nAMPM,n=12,14 and 16) was synthesized with fatty acids separately and N,N-dimethyl-1,3-propanediamine as starting materials.Its performance was verified to be CO₂-responsive via ¹H NMR spectra and conductivity measurement.Results showed that,C_{nAMPM display as cationic surfactants after bubbling CO2.With increasing the length of hydrophobic group,their critical micellar concentration (cmc) decreases linearly and foaming power,emulsifying power as well as wetting power all decrease.As CO2 is replaced with N2,the foaming power of CnAMPM decreases to a great extent.For C12AMPM,the emulsifying power keeps unchanged,while the wetting power is better than that of C14AMPM and C16AMPM.C14AMPM and C16AMPM display poor emulsifying power and wetting power.}

Key words: switchable surfactant, tertiary amine-based, CO₂-responsive, foaming, emulsifying, wetting