Cationic surfmers with benzyl groups: Synthesis and copolymerization with acrylamide

A series of cationic surfmers with benzyl groups (QARBCs) with different R groups on the benzene ring were synthesized and characterized by IR, ¹H-NMR, ¹³C-NMR. The aggregation of QARBCs was studied by the steady-state fluorescence technique. It turned out that QARBCs had surface activity and their critical micelle concentration (CMC) values varied in the range of 10⁻²–10⁻³ mol/L with slight increase with temperature. The copolymerization of acrylamide (M₁) and QARBCs (M₂) was studied below and above CMC, their reactivity ratios were determined by the Finemann-Ross method. It was found that below CMC, copolymerization took place in a homogeneous system and reactivity ratios of acrylamide and QARBCs were less than 1; while above CMC, reactivity ratios of QARBCs were greater than 1. The copolymerization mechanism of QARBC was observed to be similar to that of micellar polymerization. QARBCs tended to homopolymerization, which gave rise to micro-blocky sequences in the polymer backbone. The Q and e values of QARBCs were calculated according to the Alfrey-Price equation by using r _{1 (AM)} and r _{2 (QARBC)}. Samples of poly(AM-co-QARBC) were prepared above and below CMC and their hydrophobic associations were studied by the steady-state fluorescence spectra and 2D NOESY spectra, and their critical associating concentrations (CAC) were estimated. The results showed that samples of poly(AM-co-QARBC) prepared above CMC had stronger hydrophobic association in aqueous solution than those prepared below CMC.