Preparation and Self-assembly Properties of Sodium Maleopimaric Acid Octadecamide Dicarboxylate Surfactant
Sodium maleopimaric acid octadecamide dicarboxylate(C18MPA2Na)was synthesized from rosin by D-A addition,amidation and acid-base neutralization reactions.The structure was characterized by FT-IR,1H NMR and mass spectrometry.Surface tension method and Nile red(NR)fluorescence probe method were used to study the surface activity of C18MPA2Na.The critical micelle concentration(cmc)of C18MPa2Na was 0.29 mmol/L,the surface tension value at cmc(γcmc)was 41.11 mN/m,and it showed good surface activity.A viscoelastic solutions were successfully prepared by combining C18MPA2Na with cetyltrimethyl ammonium bromide(CTAB).The microstructure and rheological behavior of the composite system were studied by in situ cryo-electron microscopy(Cryo-TEM)and rheology.The results showed that the aggregates of the C18 MPA2Na/CTAB viscoelastic solutions were wormlike micelles.When the CTAB concentration in the complex system was fixed at 80 mmol/L,the zero-shear viscosity(η0)first increased and then decreased with the increase of C18MPA2Na concentration.The maximum value of η0 was 5.67 × 104 mPa·s at the C18MPA2Na concentration of 15 mmol/L.When the ratio of C18MPA2Na to CTAB(3∶16)was fixed,η0showed a trend of rapid increase and then tended to be constant with the increase of C18MPA2Na and CTAB concentrations in the mixed system.The power index value of ηo to concentration was 11.7.At C18 MPA2Na concentration of 15 mmol/L and CTAB concentration of 80 mmol/L,with the decrease of pH values,η0 increased first and then decreased,and reached the maximum value(7.67 × 104mPa·s)at the pH of 7.13.This study demonstrated that the rigid skeleton of rosin could promote the self-assembly of surfactants.
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