Effects of block length and structure of surfactant on self-assembly and solution behavior of block ionomer complexes

Several new families of materials have been synthesized on the base of complexes of poly(ethylene oxide)-b-poly(sodium methacrylate) (PEO-b-PMA) with single-, double-, and triple-tail surfactants. Cetylpyridinium bromide (CPB), didodecyldimethylammonium bromide (DDDAB), dimethyldioctadecylammonium bromide (DODAB), and trioctylmethylammonium bromide (TMAB) were used as the surfactant components. In contrast to complexes of homopolymer PMA with these surfactants, which precipitated from aqueous solutions, PEO-b-PMA complexes formed stable dispersions with particle size in the range 100-200 nm. The properties of these systems strongly depended on the lengths of the polyion and nonionic blocks of PEO-b-PMA and the structure of the surfactant. In particular, factors governing stability of these complexes in aqueous dispersion include lyophilizing effect of PEO block (increases with increase in PEO chain length), repulsion of PEO chains (increases with decrease in PMA chain length), and packing parameter of the surfactant. Potential applications of these systems include drug delivery.