Supramolecular Catalytic Systems Based on Alkyltriphenylphosphonium Bromides and Polyethyleneimine

The critical aggregation concentration values for aqueous binary systems of alkyltriphenylphosphonium bromides (TPPB-n) and polyethyleneimine (M = 50000 Da) were obtained by tensiometry and conductometry. In addition to the aggregation thresholds, the solubilization capacity of the mixed polymer–colloid aggregates toward the hydrophobic dye Orange OT was evaluated by spectrophotometry. It was established that the formation of mixed aggregates probably occurs only for the higher homologues of the phosphonium surfactants. The catalytic activity of the polymer–colloid aggregates was investigated in the hydrolysis of O-alkyl-O-(4-nitrophenyl)chloromethylphosphonates. The experimental dependences were analyzed within the framework of the pseudophase micellar catalysis model. For the more hydrophobic phosphonate, increasing the hydrocarbon tail length led to higher binding constants for both reagents and, consequently, to an increase in the factor of concentration. Analysis of the catalytic effect of the mixed TPPB-n–PEI system revealed a trend analogous to that observed for the aggregation behavior: the properties of the system depend on whether the surfactant belongs to the lower or higher members of the homologous series.