The Interaction Between Imidazolium Surface Active Ionic Liquids And Polymers In Aquous Solution

The surfactant/polymer mixed aqueous solution can play important role in detergency, foods, sensitive material, paint, cosmetics, pharmaceuticals, mining and oil recovery, etc. Simultaneously, this kind of system can be regarded as the simplified model of bioprocess which determines the corresponding complicated interaction. Thus this is helpful to find the novel "soft" material to obtain the important gel which has potential applications in drug release, environmental protection and artificial crgan, etc.This dissertation is focused on the interaction of surface active ionic liquid and polymer through changing the various influencing factors. Combining the isothermal titration microcalorimetry (ITC), conductivity, surface tension, turbidity and rheology measurements, the aggregation behaviour, the microstructures of the complexs and the corresponding thermodynamical parameters were obtained. There are three main parts in this dissertation as follows.1. The effect of NaBr and the polyelectrolyte concentration on the complex formation between 1-dodecyl-3-methylimidazolium bromide (C12mimBr) and sodium carboxymethylcellulose (NaCMC) has been studied. Following results were obtained.?The mechanism for surfactant/polyelectrolyte complex formation is found to be different at various salt concentrations. When the salt concentration is lower than the critical value, the surfactant/polyelectrolyte complex can be formed in this system. The binding process corresponding to surfactant monomers to polymer chain is endothermic. Then the micelle-like surfactant/polyelectrolyte aggregates begin to form and the turbidity increases accordingly. Further addition of surfactant, the formation of free micelles induces a second sharp endothermic peak in the enthalpy curves and the beginning of the plateau region of the surface tension curves. Thereafter, the polyelectrolyte chains are saturated with surfactant micelles as determined by the maximum values of the turbidity curve. When the salt concentration is higher than the critical value, no surfactant/polyelectrolyte complex forms in the solution and only surfactant free micelles can be formed due to the complete salt screening.?At the lower surfactant concentration, the monomeric surfactant adsorbs on the polyelectrolyte chains through electrostatic attraction, appearing as endothermic process. While at the higher surfactant concentration, surfactant monomers bind to the NaCMC chains to form micelle-like aggregates through the hydrophobic force and the surfactant micelles behave as a physical cross-linking to bind to polyelectrolyte chains corresponding to exothermic action. The rheological measurement verifies this interpolymer cross-linking network. With further increase of surfactant concentration, more surfactant/polyelectrolyte complexes are formed and lead to the phase separation. Increasing polymer concentration, the interaction of monomeric surfactant binds on the NaCMC chains becomes gradually stronger and the polymer-induced micelle-like aggregates formation is influenced, which resulted in larger CAC.2. The effects of different surfactant headgroup and alkyl chain, and the different polymer type and hydrophobicity on the interaction of a series of cationic surfactants 1-alkyl-3-methylimidazolium bromide (CnmimBr, n=8,10,12,14, 16) and N-alkyl-N-methylpyrrolidinium bromide (CnMPB, n=12,14,16) with nonionic triblock copolymers (PEOnPPOmPEOn) and NaCMC in aqueous solution have been investigated. Following results were obtained.The addition of CnmimBr or CnMPB (except C8mimBr) to L64 or F68 solutions induces the formation of surfactant-copolymer complexes by hydrophobic interaction between the surfactant monomers and the PPO segments. The intensity of surfactant-copolymer interaction increases with the increasing hydrophobicity of the surfactant or copolymer, and it is not affected by the different surfactant headgroup. In the presence of NaCMC, CnmimBr or CnMPB (except C8mimBr) monomers can strongly associate with NaCMC chains due to electrostatic attraction and hydrophobic interaction, but interacting characteristics are strongly dependent on the alkyl chain length of the surfactant. The electrostatic and binding interactions of CnMPB molecules on NaCMC chains are stronger than that of CnmimBr with the same alkyl chain. In the case of CgmimBr, except the monomers can bind to NaCMC chains through electrostatic attraction, the micelle-like surfactant-polymer clusters can not be formed and only surfactant micellization occurs.3. The enthalpy change of salt-induced wormlike micelle formation has been measured. The studied systems include C16mimBr/NaTos and C16mimBr/NaSal. Following results were obtained.The observed molar enthalpies of C16mimBr aqueous solutions as a function of NaTos or NaSal concentration not only allow the determination of the enthalpy of micelle dilution, but also the enthalpy change corresponding to the spherical to wormlike transition. The enthalpy change value of wormlike micelle formation (?Hw) was equal to the sum of the enthalpy of micelle formation (?Hm) and the transformation enthalpy (?Htra).The value of?Hw is negative in C16mimBr/NaTos system, and this exothermic phenomenon in the formation of wormlike micelles is mainly caused by the hydrophobic interaction between surfactant tails and the electrostatic attraction between Tos- and C16mim+; while the wormlike micelle formation is endothermic in the C16mimBr/NaSal system, attributing to the disruption and rebuilding of hydrogen bonds. In addition, the planar structure of Sal- induces the wormlike micelle a more tight structure with higher viscosity.