The Rheological Properties Of Quaternary Ammonium Cationic Surfactants And Its Distribution System Formed By Orderly Aggregate

Quaternary ammonium cationic surfactants are extensive applyed in food, cosmetics,medicine, etc. The rheological properties of the solution or dispersion system is closely related to their microstructure and the interaction among them, its important physical and chemical properties in the process of their application must be clear. As a result, the rheological properties of surfactant micelles become an important basic theory and widely used in all aspects of the actual articles for daily use and industrial. In the surfactant solution, surfactant molecules combined in ordered molecular aggregation by hydrophobic,such as micelle, vesicle, lamellar liquid crystal and cubic crystal, etc. The worm-like micelles which due to its surface activity, viscosity and excellent shear dilution performance, become the focus of the research area. In addition, the shape and their microstructure of the aggregate is decided by the composition of surfactant system,molecular structure and the concentration, the rheological properties of surfactant solution can greatly improve by joining additives, such as cosurfactant, organic salt, inorganic salt,polymer.As a part of the project supported by National Natural Science Foundation(No.21073081,21001061), our work is as follows:(一)A 2-hydroxypropoxy group was inserted at the junction between the headgroup and the alkyl chain of quaternary ammonium salts. This group promotes a bent configuration for the alkyl chain relative to the ammonium headgroup, as compared to those without the 2-hydroxypropoxy group. We examines the rheological behavior of different concentrations of pure surfactant 3- alkoxy- 2- hydroxypropyl trimethyl ammonium bromide(referred to as Rn HTAB, Scheme 2-1 shows its chemical structure)and aqueous rheological properties after joining the organic salt by rheological method.We observed different transformation between orderly aggregations by changing different concentration in the solution. The mixed solution in low concentrations which is formed of quaternary ammonium salt type surfactant and sodium salicylate showed a high viscosity and viscoelasticity. In addition, the surfactants are studied by FF-TEM is simple and microscopic structure change after adding sodium salicylate, shows that the system hasformed a reticular structure worm-like micelles.(二) A class new Gemini cationic surfactant, its linking group have hydroxyl substituents, N, N ’- long chain alkyl- 2- hydroxy- N, N, N’, N ’- dichloride methyl have been synthesized. The formulas for these compound are [Cn H2n+1-N+(CH3)2-CH2CH(OH)CH2-N+(CH3)2-Cn H2n+1Cl2,n= 12, 14, Shorthand for n-3(OH)-n(2Cl)],the rheological properties of the pure Gemini surfactant and its mixed solutions have been investigated by rheology and FF-TEM. The study found that 12-(OH) 3-12(cl) 2 pure solution only generate rod micelle in a large range of concentration.After joining sodium salicylate a worm-like micelles and network structure i s easily formed and its rheological property can enhance greatl(三) The effects of the added organic salt(sodium salicylate, Na Sal; sodium3-hydroxynaphthalene-2-carboxylat, SHNC; paratoluenesulfonic acid sodium salt, P-TAS)on the viscoelastic solutions of surfactants(Rn HTAB and n-3(OH)-n(2Cl))have been systematically investigated. Studies shown that the addition of salt significantly enhanced the viscoelastic of pure surfactant solution. The organic salts mainly follow the next functions with the surfactants:(1) the salting out effect;(2) the hydrogen bonding interaction;(3) the electrostatic interaction;(4) the Space effect;(5) The hydrophobic effect among long hydrophobic chains. Moreover, with changing concentration of salt solution, a complex rheological curve has formed, which is conformed to the Maxwell fluid type. The systems show a Maxwell type of single relaxation and rheological behavior which can be explained by the formation of a three-dimensional network built up from rodlike micelle. It is explained the macroscopic and microscopic properties of the solution according to the interaction between surfactants and additives, in combination with other measures method.