Impact Of Photolabile Counterion On The Nature Of Choline-derived Surfactant

With the growing use of cationic surfactants,their importance is more and more obvious,the study is more and more in-depth.Quaternary ammonium surfactants are with a favorable performance and a low cost,being a kind of most studied cationic surfactant.When the functionalized hydroxyethyl group is introduced to molecular structure,it can significantly improve the solubility,compatibility,designability of surfactant,which not only broadens the types of cationic surfactants,but also provides potential possibility for the preparation of new material.This subject takes the structure of choline chloride as model,new quaternization agent N,N-dimethyl ethanolamine and haloalkane as raw materials,a series of cholinederived surfactants was synthesized through quaternization reaction: decdecyl-(2-hydroxyethyl)-dimethylammonium bromide(C10HDAB),dodecyl-(2-hydroxyethyl)-dimethylammonium bromide(C12HDAB),tetradecyl-(2-hydroxyethyl)-dimethylammonium bromide(C14HDAB).Firstly,we determined the properties of the aqueous solution and calculated related parameters,then discussed the effects of alkyl chain length on parameters.Further we studied the interaction between choline-derived surfactants and methyl orange,using spectroscopy and surface tension methods,initially explored the interaction mechanism.Surfactant solution was mixed with methyl orange solution,counterions were replaced through precipitation reaction,introducing azobenzene groups into the surfactant molecules.The precipitate generated from the mixing solution can be considered as new cationic surfactants,which has a low solubility.Then studied the thermal stability,Krafft point,surfactivity(60 ℃)of precipitated complex by methods such as thermal analysis,conductivity,surface tension.Along with the growth of the hydrophobic group chain,Krafft point sequentially turns up,following by 40 ℃,45 ℃,52 ℃.At 60 ℃,along with the growth of the hydrophobic group,the values of CMC,γCMC,Amin become smaller,while Γmax becomes larger.Take one of the precipitation compounds as research object,there were myelins structures forming at the edge of the solid-liquid contact phases at40 ℃ in the phase permeability experiment.The temperature when myelins structures form is consistent with the Krafft point measured by DSC.Finally the photosensitivity tran-cinnamic counterions were introduced to the surfactant molecules through ion exchange reaction,a photosensitive surfactant tetradecyl-(2-hydroxyethyl)-dimethylammonium cinnamate(C14HDACin)was synthesized.C14 HDACin aqueous solution at a low concentration shows good viscoelasticity and spinnability,wormlike micelles were formed in the solution.Tran-Cin-counterion has optically active,it can isomerize from trans isomer to cis form under the irradiation of UV light,the hydrophobic between isomers is different,resulting in the change of integration degree to the cationic micelles,affecting the nature of the solution system.A change induced by light from viscoelastic fluid to Newtonian fluid can be observed in the rheological test,a corresponding change in molecular aggregates form was observed by freeze-fracture electron microscopy,wormlike micelles to spherical micelles.This paper systematically studied the photosensitive aqueous surfactant solution,such as rheological properties and changes in microstructure before and after UV irradiation,providing some experimental data and theoretical basis for the research and practical application in the future of the photosensitive surfactant.