Abstract: The Krafft point and the critical micelle concentrations (cmc) at different temperatures for the surface active monomer, sodium 2-acrylamido-tetradecane (NaAMC14S), were determined. The copolymerizations of NaAMC14S and acrylamide (AM) were carried out in aqueous solution at above and below cmc of NaAMC14S, respectively. The compositions of the copolymers were characterized via conductometric titration method, the thermal behaviors of the copolymers were measured by DSC, and the properties of hydrophobic association of the copolymers were determined by using fluorescence probe technique. By the above investigations, the copolymerization mechanism was explored emphatically. The experiment results show that there are two kinds of copolymerization mechanisms depending on the concentrations of NaAMC14S. When the copolymerization of NaAMC14S and AM is performed above the critical micelle concentration of NaAMC14S, the copolymerization process keeps being a micro-block copolymerization mechanism, and a large compositional drift occurs during the copolymerization. Whereas when the copolymerization of NaAMC14S and AM is performed below the critical micelle concentration of NaAMC14S, the polymerization process is carried out in agreement with random copolymerization mechanism, and the variation of the copolymer composition with the conversion is slower. The DSC thermograms of the copolymers and the result determined by fluorescence probe technique confirm the above mechanisms.

Key words: Surfmer, Micellization behavior, Critical micelle concentration, Copolymerization mechanism, Acrylamide