Studies on micellar behavior of anionic and surface-active monomers with acrylamide type in aqueous solutions

Abstract

Two kinds of anionic surface-active monomers of acrylamide-type, sodium 2-acrylamido-tetradecane sulfonate (NaAMC 14S) and sodium 2-acrylamido-dodecane sulfonate (NaAMC 12S), have been synthesized. Their micellar behaviors were researched, correlative micellar parameters were determined, and the relationships between their chemical structures and micellar behaviors were more thoroughly explored. The solubilities of NaAMC 14S, NaAMC 12S and sodium dodecyl sulfonate (SDS) in water were determined, and their Krafft temperatures were measured. Their critical micelle concentrations (CMC) were determined with surface tension measurements, the surface activities ( γ CMC) were obtained, the surface absorption amounts ( Γ m) and the molecular areas ( A m) at the interface of air–water were gained by using Gibbs equation. Their micellar aggregation numbers ( N agg) at different concentrations were obtained by steady-state fluorescence probe method. In addition, under the condition of adding electrolyte NaCl the critical micellar concentrations (CMCs) and aggregation numbers of NaAMC 12S and NaAMC 14S were also examined, and the effects of the addition of electrolyte on their micellar behaviors were studied. The experiment results show that because two hydrophilic head groups are present in their molecules, sulfonic acid group and acrylamide group, the anionic surface-active monomers of acrylamide-type have characteristic micellar behaviors: their solubility in water are larger, so Krafft temperatures are lower; the surface absorption amounts are lower, so the abilities to decrease surface tension are poorer; the micelles are looser, so CMC is higher in contrast with common anionic surfactant with the same hydrocarbon chain and anionic head group as them; besides, the effects of the length of the hydrophobic hydrocarbon chain and the addition of electrolyte on the micellar behaviors for the anionic surface-active monomers of acrylamide-type are similar to common anionic surfactants.