Self-assembly of hydrophobically associating amphiphilic polymer with surfactant and its effect on nanoemulsion

A new scheme for controlling the rheological properties and stability of oil-in-water nanoemulsions is presented based on the polymer-surfactant self-assembly in solution. Specifically, amphiphilic property, hydrophobic association and thermo-responsive behavior is imparted to the polymer by using surfactant as a main function monomer to introduce hydrophilic and hydrophobic groups on the polymer. The polymer can cooperate with the surfactant to form oil-water interfacial film without compromising nanoemulsion formation based on its self-assembly properties. And there can be a moderate increase of the association between the hydrophobic groups on different polymers with increasing temperature based on their hydrophobicity. These behaviors will affect the rheological properties and stability of the nanoemulsion. The thermo-association mechanism of polymer, interaction between polymer and surfactant, and the effects of the polymer on nanoemulsions were analyzed. Test results show that, the thermo-association occurs when the polymer concentration is greater than 0.2%, and the association begins to be obvious when the temperature is higher than 50 °C, which would increase the viscosity of solution. The thermo-association may be attributed to the fact that the curled side chains of the polymer stretch and the hydrophobically association is intensified under higher temperature. The self-assembly of polymer and surfactant increase the interface film dilational modulus of the emulsions, which is conducive to the stability of nanoemulsion droplets. This polymer and the thermo-association mechanism could be applied in the study of smart emulsion and temperature-resistant emulsion.