乙醇水溶液表面张力系数的微观机理

Microscopic Mechanism Research of Surface Tension Coefficient of Ethanol-aqueous Solution

采用拉脱法测量了不同质量百分比浓度乙醇水溶液的表面张力系数,结果表明:乙醇水溶液表面张力系数随着浓度的增加而减小,且减幅由大变小。分别建立了分子质点模型、胶团模型和键合作用模型:将液体分子视作质点,从表面分子受力和表面能角度论证了分子质点密度的增加使表面张力系数增大的机理;从乙醇分子内部微观结构的角度,结合表面活性原理,分析了分子结构的两亲性使其在溶液表面富集及在溶液内部自聚成胶团的过程,阐述了该过程使乙醇溶液表面张力系数随浓度增加而减小的机理;考虑到乙醇分子与水分子的水合作用,溶液中形成的不同团簇中氢键作用力不同,氢键作用的减弱导致了溶液表面张力系数变小。研究证明,3种理论模型的作用同时存在于乙醇水溶液中,不同程度地影响着乙醇水溶液的表面张力系数。

In this paper,the relationship between the surface tension coefficient and the concentration of ethanol-water was introduced,and the mechanism was explained from the molecular level.The surface tension coefficient of the ethanol-water solution in different quality percentage concentrations was measured by using haul escape method.The experimental results show that the surface tension coefficient of the ethanol-water solution decreases with the increase of concentration,and the reduction amplitude zooms out.The molecular particles model,micelle model and bonding effect model were used to analyze the law above.The liquid molecular was regarded as the particle first.From the angle of the surface molecules,force and the surface energy,the mechanism was demonstrated that the increase of the molecule density enlarged the surface tension coefficient.From the internal microstructure of the ethanol molecule and the principle of surface activity,the process was analyzed that the amphiphilic of the ethanol molecular structure made the molecular enrich in the surface of the solution and gathered internally into the micelle,for finding the influence of surface tension.Considering the different hydration form of ethanol molecular and water,the hydrogen bonding force in the molecular cluster become weaker,which caused the decrease of surface tension in the solution.The study proves that there exist three theoretical models in the ethanol-aqueous solution,which influence the surface tension coefficient differently.