The aggregation of branched polyethylenimine and cationic surfactants in aqueous systems

The aggregation of binary mixtures of branched polyethylenimine with a molecular mass of 30 000 and cationic surfactants, such as cetyltrimethylammonium bromide, cetyldimethylethylammonium bromide, or cetyldimethyl(2-hydroxyethyl)ammonium bromide, in aqueous solutions is studied. The critical micellization concentrations, as well as the sizes and shapes of aggregates, are determined by conductometry, small-angle neutron scattering, and dynamic light scattering methods. Catalytic activity of cationic surfactant-polyethylenimine compositions in the hydrolysis of tetracoordinated phosphorus acid 4-nitrophenyl esters is studied via spectrophotometry. The influence of spatial characteristics of aggregates on the catalytic activity and selectivity of nanostructured polymeric systems is revealed.