Preparation of hydrophobic association polyacrylamide in a new micellar copolymerization system and its hydrophobically associative property

This paper describes for the first time the combination of a polymerizable surfactant, sodium 2-acrylamido-dodecane sulfonate (NaAMC(12)S), and a hydrophobic monomer to prepare water-soluble associating polymer via a new micellar process. In this method, the hydrophobic monomer, N-dodecylacrylamide (C(12)AM) or N,N-didodecylacrylamide (DiC(12)AM), was first solubilized within NaAMC(12)S micelles, whereas the hydrophilic monomer acrylamide (AM) was dissolved in the aqueous continuous medium. The micellar copolymerization, therefore, resulted in a ternary hydrophobic association polyacrylamide (HAPAM), namely, C(12)AM/NaAMC(12)S/AM or DiC(12)AM/NaAMC(12)S/AM. The chemical structures of these ternary copolymers were characterized with Fourier transform infrared (FTIR) spectroscopy, and their hydrophobic associative behavior as well as the relationship between microstructure and hydrophobic associative property was studied by a combination of the fluorescence probe technique and viscosimetry. The experimental result shows, with the presented polymerizable surfactant or surface-active monomer NaAMC(12)S, the micellar copolymerization of AM and hydrophobic monomer can be favorably realized. In addition, the surface-active monomer can be incorporated into the polymer backbone to result in the ternary copolymers, which show a much stronger hydrophobic associative property in comparison with the binary copolymer obtained in the conventional micellar copolymerization system with common surfactants. More importantly, this new micellar copolymerization system is simple because the complicated process to remove the surfactant is avoided. We found that the hydrophobic associative property of the obtained ternary HAPAM is strongly affected by the hydrophobe content and the length of hydrophobic microblocks in the polymer backbone.