Synthesis,Properties And Applications Of Ethylene Glycol-Based Gemini Surfactants

Gemini surfactant is a novel surfactant in which two conventional single hydrophilic heads and two single hydrophobic alkyl chains are connected with a linking group at the hydrophilic group or near the hydrophilic group.Compared with traditional single-chain surfactants,Gemini surfactants have higher surface activity and lower critical micelle concentration?cmc?.Gemini surfactants are now widely used in various areas including gene delivery,drug targeting technology,preparation of new materials and molecular self-assembly,etc.In recent years,with the increase of production of ethylene glycol and the maturity of domestic coal-based ethylene glycol technology year by year,it is very necessary to carry out relevant basic and applied research on the refinement of ethylene glycol downstream products.The synthesis of Gemini surfactants is one of the effective ways to achieve fine derivation of ethylene glycol.Based on the above reasons,a series of new ethylene glycol-based Gemini surfactants have been synthesized with the ethylene glycol as a starting material.The main work contents are as follows:Synthetic routes to ethylene glycol-based Gemini surfactants with ethylene glycol ester-based quaternary ammonium salt Gemini surfactant,ethylene glycol hydroxyl-based quaternary ammonium salt Gemini surfactant and ethylene glycol sulfonate-based Gemini surfactant were rationally designed,and the preparation of a series of products were explored.Through the corresponding experiments,six kinds of ethylene glycol ester-based quaternary ammonium salt Gemini surfactants were successfully synthesized.On the basis of the synthetic route,reaction conditions of ethylene glycol ester-based quaternary ammonium salt Gemini surfactant were optimized.The structures of products were determined by nuclear magnetic resonance.The surface tension(?_cmc)of the series of ethylene glycol ester-based quaternary ammonium salt Gemini surfactant solutions was measured by surface tension meter,and the properties of the surfactants were evaluated by parameters such as cmc and?_cmc.It was found that the surface tension of the series of ethylene glycol ester-based quaternary ammonium salt Gemini surfactant solutions decreased first and then stabilized with the increase of concentration.However,the critical micelle concentration decreased as the hydrophobic chain became longer.The length of the hydrophobic chain hasd a certain influence on the surface tension.When the hydrophobic alkyl carbon chain was 14,surfactants had the smallest?_cmc and highest surface activity.The equilibrium contact angles of the series of ethylene glycol ester-based quaternary ammonium salt Gemini surfactant solutions on the surface of paraffin,PTFE and metaplexis leaves were measured by balance contact angle measuring instrument,and the adhesion work,wetting work,spreading coefficient and other parameters were obtained by data such as cmc,?_cmcmc to evaluate the wetting properties of the series of surfactants on three solid surfaces.The equilibrium contact angles of the series of ethylene glycol ester-based quaternary ammonium salt Gemini surfactant solutions on the surface of paraffin,PTFE and metaplexis leaves decreased fisrtly with the increase of surfactant concentration,and finally stabilized.The changes of contact angle of the series surfactant solutions on the surface of the PTFE and the metaplexis leaves were not too much,but the 14-2-14 ethylene glycol-based Gemini surfactant solution can change the surface properties of the metaplexis leaves from hydrophobic to hydrophilic;The contact angle of the series of surfactants on the paraffin surface varied greatly,and all of the six types can change the surface of the paraffin from hydrophobic to hydrophilic.Among the six ethylene glycol ester-based quaternary ammonium salt Gemini surfactant solutions,the 14-2-14 one gave the best results.The dynamic contact angles of the series of ethylene glycol ester-based quaternary ammonium salt Gemini surfactant solutions on paraffin,PTFE and lotus leaves surface were measured by dynamic contact angle measuring instrument.It was found the dynamic contact angles of the ethylene glycol ester-based Gemini surfactant solutions on three solid surfaces gradually decreased with time going,and finally stabilized.The 14-2-14 had the best wetting effect on PTFE and paraffin,while 12-2-12,14-2-14 had better wetting effect on the lotus leaves.