The Study Of Preparation And Rheological Properties Of Fluorocarbon/Hydrocarbon Surfactant Vesicle Gel

Vesicle gel is a supramolecular structure with self-assembly of surfactant molecules in solution with great application prospect.It is very important to find a simple structure of the gel factor to control the structure of different vesicle gel and explore its formation mechanism,which is very important for expanding the application of the gel in various fields.Based on this,this paper intends to study a class of simple and widely used perfluorinated fatty acid surfactants,and cationic surfactant tetradecyldimethylamine oxide(C₁₄DMAO)complex,through the construction of fluorocarbon/hydrocarbon surface Active agent mixture system,to explore the preparation of vesicular gel and the formation mechanism,and to study the rheological properties of the vesicle gel.In this paper,perfluorononanoic acid(C₈F₁₇COOH)and C₁₄DMAO were selected and the formation of vesicle gel was found in a certain range.In addition,L₁ micellar phase,L_αvesicle phase,L₁/L_αmixed phase,precipitation and other phase phase.The gel phase was observed by a freeze-etch microscope,and it was found that the gel phase consisted of polyhedral vesicles in a size-dispersed manner.Differential scanning calorimetry results show that the vesicle gel has a chain transition temperature,and the vesicle bilayer is present in crystalline form at room temperature,which is different from the traditional Lαvesicle phase.The results of X-ray diffraction（XRD）have also proved the existence of crystalline structure.At the same time,the results of Fourier transform infrared spectroscopy showed that the fluorocarbon chain existed in the gel phase with high regular all-transconformation,which also prove the crystal structure of the bilayer.Therefore,the formation of polyhedral vesicle gel is due to the co-crystallization of the hydrocarbon chain,which is the result of the interaction between the hydrocarbon and the hydrogen bond.Through the determination of the rheological properties of the vesicle gel,it was found that the vesicle gel had high viscoelasticity,its elastic modulus and viscous modulus were large,and its viscoelasticity was affected by the temperature,the total concentration of the surfactant and the mixing ratio of two surfactant.In order to investigate the effect of carbon chain length on the formation and rheological properties of vesicle gel,we selected perfluorooctanoic acid(C₇F₁₅COOH)and perfluorodecanoic acid(C₉F₁₉COOH)with C₁₄DMAO respectively.It was found that C₇F₁₅COOH/C₁₄DMAO/H₂O system could not form the vesicle gel,and the C₉F₁₉COOH/C₁₄DMAO/H₂O system,like the C₈F₁₇COOH/C₁₄DMAO/H₂O system,can also form a polyhedral vesicle gel,thus demonstrating that the vesicle gel can be formed only when the length of the fluorocarbon chain is 8 or more.In addition,the study found that the length of the fluorocarbon chain vesicle gel rheology has a certain impact,the longer the length of the fluorocarbon chain,the higher the viscoelasticity of the vesicle gel.