The Study Of Interactions Between Carboxymethylchitosan And Quaternary Ammonium Gemini Surfactants

Chitosan is an important macromolecule due to its intrinsic biocompati bility, biodegradability, nontoxicityd and broad array of sources. Gemini surfactant is made up of two hydrophobic chains and two polar headgroups covalently linked through a spacer group. For cationic Gemini surfacetants, this kind of unique molecular architectures can govern charge density on head group and the hydrophobic interaction between the alkyl tails. Therefore, the aqueous solutions of such systems often display high surface activity and strong interaction force which would promote the diversity of the packing geometry and enhance the mobility of the surfactant. The mixtures of them posses some intrigueing and fascinating features, which chitosan or Gemini surfactant alone does not have. So the mixed systems which are widely used in many applications such as life science, material science, energy science and other fields have attracted considerable attention. In this paper, the methods of fluorescent probe, turbidimetric, DLS, Zeta potential were used to systematically study their interactions between carboxymethylchitosan and quaternary ammonium Gemini surfactants. The investigation on the interaction of them has gone deep into the level of molecule and submolecule in order to guide well the application of the mixture system in practice. The main results are summarized as follows:1. The fluorescence data and turbidity curve display that the CMCh concentration plays a dominant role in the aggregation behavior of CMCh/Cm-s-Cm-2Br-systems. With increasing surfactant concentration at a certain CMCh concentration, surfactant forms complex with CMCh. While this kind of structure transformation cannot exist in pure surfactant aqueous. Note that the structural evolution of aggregates is entwined with CMCh concentration.2. It has been shown that the qualities of spacer group is of the great importance in determining the complex structure of mixed systems. Owing to the unique molecular structure, the attraction strength between CMCh and C12-6-C12-2Br-is significantly enhanced compared with ordinary surfactants. The ability to form aggregates between CMCh and C12-s-C12-2Br-would decrease with the increasing of s when s=2-6. When s≥6 the ability of aggregation appears an upward trend until 5=12.3. The influence of NaBr on the interaction between CMCh and Cm-s-Cm·2Br- hybrid system is complex. The degree of the effect depended on the concentration of NaBr. At low NaBr levels, the addition of salt reduces or completly screens the electrostatic attraction between CMCh and surfactant. So that the cac observed is essentially increased with increasing NaBr concentration. On the other hand, at high salt levels the cac decreases with increasing salt concentration.