Synthesis And Properties Of The Gemini Surfactants With Pyrrolidinium Head-groups

Gemini surfactants have a more superior surface activity and richer aggregates than traditional surfactants.Preparing new Gemini surfactants with different structures and studying the relationship between the structure and the morphology of their aggregates can lay the foundation for their applications in more fields.In this paper,seven kinds of Gemini surfactants with pyrrolidinum head groups were synthesized by using 1,3-dibromo-2-propanol,1,3-dichloro-2-propanol,long chain bromoalkane and pyrrolidine as materials.The main work and results are as follows:(1)Seven kinds of Gemini surfactants were synthesized and their structures were identified by IR,1H NMR,13C NMR and mass spectrometry.The results showed that the Gemini surfactants were consistent with the target products.(2)The surface activity was measured by surface tension method.Results showed that the cmc and C2O of the synthesized surfactants decreased with the increase of the number of carbon atoms in the tails and were an order of magnitude lower than that of the traditional surfactants.The values of cmc,C2O and Amin of Cn-3OH-nPB were lower than those of Cn-3OH-nPC,when the number of carbon atoms in the tails is same.It means that suface activity and behaviour of aggreation of Cn-3OH-nPB is wonderful.(3)The aggregation behavior of Cn-3OH-nPB in aqueous solution was studied by conductivity,steady-state fluorescence,dynamic light scattering and transmission electron microscopy.It was found that,Cn-3OH-nPB could form larger aggregates.Meanwhile,at 10cmc,the aggregates of C12-3OH-12PB and C10-3OH-10PB were larger than those of C14-30H-i4PB and C16-3OH-16PB,and C12-3OH-i2PB formed coral-like aggregation.When the concentration increased from 10cmc to 50cmc,the aggregates of C14-30H-14PB and C16-3OH-i6PB changed from spherical to long linear,and the aggregates of C12-3OH-i2PB changed from coral-like to a branch one,and for C10-3OH-10PB the aggregates turned from asymmetric spherical to short short chain beads aggregates.(4)Dendritic gold nanomaterials were prepared by simple one-step method using Cn-3OH-nPB as the inducer.The effects of the change of hydrophobic chain length,the concentration of surfactants,reducing agents and chloroauric acid on the morphology of products were studied.The morphologies of the products obtained in different time were observed,and the mechanism of formation of products was preliminarily speculated.The results showed that when the carbon number of the tail chain was 16,if the ratio of surfactant,reducing agent and chloroauric acid was appropriate,dendritic gold nanoparticles with secondary branch structure could be obtained.In addition,surfactant could selectively adsorpt on some specific crystal face of irregular crystal nucleus,so that unattached crystal face could growed,which resulting the formation of dendritic products.