Interactions Between Hydrophobic Associating Poly(sodium acrylate)and a Zwitterionic Surfactant in Non-aqueous Media and Low Temperature Environment

Hydrophobic associating polymers and surfactants are the main materials used to fabricate visco-elastic fluids. The interaction between these polymers and surfactants exerts significant effect on the fluids properties, so it has been a popular research topic in this field. However, previous studies only focused on aqueous systems at room temperature or above, there was few researches related to the extremely low temperature environment. In this paper, the interactions between the neutralized salt of hydrophobically modified polyacrylate acid (HMPA) and zwitterionic surfactant erucyl dimethyl amidopropyl betaine (EDAB) in mixed ethylene glycol/water at 20 degrees C and -20 degrees C were studied, and the effects on the rheological properties were examined. The rheological behavior of HMPA in pure water and in the mixed ethylene glycol/water were first investigated, and the rheological response of HMPA-EDAB in ethylene glycol/water and their self-assembly morphology were then studied. It is found that the introduction of ethylene glycol in aqueous solution, on one hand, inhibits the association of hydrophobic chains on HMPA, resulting in the reduction on viscosifying ability. On the other hand, it also largely reduces the freezing point of the mixture. In the HMPA-EDAB system, the hydrophobic chains of HMPA go into EDAB micelles to form mixed micelles whose morphology is dependent on the concentrations of HMPA and EDAB as well as temperature, and thus affecting the fluid rheological properties. The sub-zero low temperature is beneficial for EDAB forming wormlike micelles, so that the synergistic effect between HMPA and EDAB becomes more obvious in this case.