THE INFLUENCE OF SALICYLATE COUNTERIONS ON THE AGGREGATION BEHAVIOR OF A POLYMERIZABLE CATIONIC SURFACTANT

The aggregation behaviour of the cationic polymerizable surfactant dim ethylhexadecyl-(2-acrylamidoethyl)ammonium bromide (AM16) has been stu died with time-resolved fluorescence quenching (TRFQ) and viscometry. The quencher-averaged aggregation number N-q was determined in the abs ence and presence of strongly binding salicylate ions using TRFQ. In t he absence of sodium salicylate (NaSal) AM16 behaves very much like ot her cationic surfactants with an aggregation number increasing with su rfactant concentration and decreasing with increasing temperature. In the presence of NaSal at constant temperature, N-q first increases slo wly with NaSal concentration C-Sal, until the critical concentration C -Sal above which N-q increases sharply. At constant C-Sal, with incre asing temperature N-q decreases more strongly at C-Sal > C-Sal than a t C-Sal < C-Sal. Viscosity measurements have confirmed the trends obs erved with TRFQ. The values of C-Sal, as determined with the two diff erent techniques, agree well. The copolymerization of the surfactant w ith acrylamide leads to water-insoluble copolymers, because of the lar ge compositional drift during copolymerization. (C) 1998 Elsevier Scie nce B.V.