Construction And Regulation Of Gemini Amphiphilic Ordered Assembly With Rigid Spacer Group

Gemini surfactants are a new series of surfactants with two or more monomolecular amphiphilic structures,which are connected by spacer group.Owing to this structure feature,Gemini surfactants,compared with traditional surfactants,have lower Krafft point,lower critical micelle concentration?CMC?,good solubilization ability,abundant aggregation morphology,unique rheological properties and good synergistic effects.They have become a hotspot in surface and colloid science and were widely used in biological,chemical,environment,mataerial and some other fields.The main content and conclusions are following.Three series of Gemini surfactants with different hydrophilic headgroup,hydrophobic tail chain,spacer group were synthesized.The structures were proved by ¹H-NMR spectra and the purity of products were high.G_m series surfactants were studied by surface tension measurements,conductivity measurements,steady-state fluorescence measurements,dynamic light scattering and transmission electron microscopy.The result of surface tension measurement shows the surface tension decrease with the increase of Gemini surfactants concentration,and the values of A_min increase at the same time.Conductivity method result implies premicelles formed in G₁₄ and G₁₆.Steady-state fluorescence measurement shows the micropolarity of pyrene changed from non-polar to polar as the increase of concentrations of surfactants.And large size aggregates vesicles are detected in aqueous solutions by DLS and TEM methods.R_mPi series surfactants were studied by surface tension measurements,conductivity measurements,steady-state fluorescence measurements,dynamic light scattering and transmission electron microscopy.The results shows the aggregation tendency are stronger with increase hydrophobic chain;premicelles are formed in R₁₄Pi and R₁₆Pi systems;large size aggregates vesicles are detected in aqueous solutions,which are similar with G_m.Compared with G_m,piperidine headgroup in R_mPi leads to larger A_min values.The micellization inhibition of piperdine headgroup is weaker than diethylamine.Compared with Gemini surfactants F_mPi with flexible spacer groups,the steric hindrance of rigid spacer groups increase the difficulty of incorporating the spacer into the hydrophilic outer region of the aggregation,so R_mPi has more difficulty in aggregating,which means higher CMC values,looser packing densities,weaker conbination with counterions and larger aggregates sizes than F_mPi with same tail chain length.