Phase diagrams come alive: understanding how to create, destroy or change ordered surfactant structures by polymerizing the counterions

Free radical polymerization of acrylate counterions to cationic alkyltrimethylammonium surfactant ions was performed in aqueous media. The results of the reactions were either formation, destruction or change of liquid crystalline surfactant structures, depending on the starting conditions such as the surfactant concentration, the content of inert counterions and the monomer-to-initiator ratio. The results were consistent with predictions inferred from equilibrium phase diagrams recently established for aqueous mixtures of the cationic surfactants alkyltrimethylammonium acetate or bromide (C_nTAAc/Br; n = 12, 16) with the “complex salts” C_nTAPA_m, in which the counterions to the surfactant ions were polyacrylate polyions (PAs) of different degrees of polymerization (m = 25, 30 or 6000). Appropriate pathways, at constant water content, through the latter ternary phase diagrams show what happens, at equilibrium, when monomeric counterions to the surfactant ions are replaced by polymeric counterions. These pathways through the equilibrium phase diagrams thus “come alive” in the counterion polymerization processes performed here.