Investigation Of Surfactant/Macromolecule Interaction By Means Of Interfacial Dilational Rheology

Interfacial dilational rheology plays a key role in acquiring the information of molecule orientation, molecule interaction and characteristics of mixed surfactant/macromolecule films etc. Moreover, the data of dilational rheology has been proven to be related to the stabilities of foams and emulsions. Therefore, the measurement of dilational property is a powerful tool for detecting the nature of adsorption film.On the basis of previous studies, we have investigated the interfacial dilational rheology properties of ionic liquid-type surfactant/protein mixed system on the liquid/liquid interface, and the effect of pesticide adjuvant on the interfaicl film.1、The interfacial tension and interfacial dilational properties of a series of ionic liquid-type imidazolium surfactants solutions,[Cnmim]Br(n=12,14,16), at the decane-water interface are reported. The dilational rheology properties are measured by means of oscillating drop method. The influences of dilational frequency, bulk concentration and structure on dilational rheology properties have been investigated. The results reveal that the interfacial dilational elasticity of the imidazolium surfactants with longer hydrophobic chain is larger than that with shorter hydrophobic chain at lower concentration, but the opposite is observed at high [Cnmim]Br surfactants solution concentrations. At lower concentrations, with the length of hydrophobic chain increasing, the dilational modulus increase resulting from the greater hydrophobic interaction. However, at higher concentration,[CnmimjBr surfactants with longer hydrophobic chain turned to be more difficult to resist the interface deformation.2、The dynamic interfacial properties of mixed solutions of bovine serum albumin (BSA) and ionic-liquid type surfactant ([Cnmim]Br) were measured as a function of the interface age, surfactant concentration and solutions pH. Three BSA conformers were investigated:the normal N form as well as the fast F and aged A forms, corresponding to the different solutions pH, respectively. The results indicate that the addition of [C16mim]Br to the different structure of BSA isomers influence the properties of the adsorption layer at the decane/water interface. The addition of [C16mim]Br does not influence the structure of the protein at pH below the isoelectric point of BSA, but at higher solution pH, the additions of surfactants significantly influence the dynamic interfacial properties of BSA solutions due to the electricity interaction between the components.3、The interfacial behavior of β-casein and lysozyme solutions has been investigated in the presence of an ionic liquid-type imidazolium surfactant ([Cnmim]Br) at the decane/water interface. The interfacial tension isotherms for the mixed adsorption layers indicate that the increased addition of [C16mim]Br to a pure protein changes the properties of the complex formed at the decane/water interface. Whereas the interfacial tension data of the protein/surfactant mixed layers do not clearly show differences with changing bulk composition, the dilational rheology provides undoubted evidence that the structure and, in particular, the dynamics of the adsorbed layers depend on the bulk surfactant concentration. The experiment data for β-casein/[C16mim]Br solutions indicate that at higher bulk [C16mim]Br concentrations, β-casein in the interfacial layer is subject to conformational changes where it gives space to [C16mim]Br molecules in the form of co-adsorb rather than replacement; in contrast, lysozyme/[C16mim]Br solutions some lysozyme molecules desorb from the interface due to the competitive adsorption of free [C16mim]Br molecules. Experimental results related to the interfacial dilational properties of the protein/surfactant solutions show that the dilational modulus turns out to be more sensitive to the conformation of protein/surfactant mixture at the liquid interface than the interfacial tension.4、The interfacial behavior of cypermethrin, Tween60and Arabic gum systems have been investigated at the solvent/water interface. The results show that the interfacial activity turns to be better after the addition of cypermethrin, however, Arabic gum has not influence the interfacial properties significantly.The results show that the interfacial dilational rheology measurement is a powerful tool to investigate the interfacial adsorption film.