The aggregation behavior and catalytic activity toward nucleophilic substitution in p-nitrophenyl acetate of the polyethyleneimine (PEI) + cationic surfactant systems is studied. The values of the critical aggregation concentrations are shown to be much lower as compared to critical micelle concentrations of single solutions. A decrease in the self-diffusion coefficient of surface-active ions is observed within the concentration range limited by the tensiometry critical points. The data obtained provide evidence for mixed aggregation in the PEI + cationic surfactant systems. Due to the contribution of specific interactions, surfactants with hydroxyethylated head groups cetyldimethyl(2-hydroxyethyl)ammonium bromide and cetylmethylbis(2-hydroxyethyl)ammonium bromide demonstrate a higher affinity toward PEI as compared to cetyltrimethylammonium bromide. The systems studied show catalytic activity toward the cleavage of p-nitrophenyl acetate, which increasees with the number of hydroxyethyl fragments in their head groups and reaches more than 2 orders of magnitude.

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The aggregation of 2 hydroxybenzylated derivatives of polyethyleneimine in a water-DMF medium in the absence and in the presence of cationic surfactants was studied. The catalytic activity of modified polyethyleneimines in hydrolysis of phosphorus acid esters depends on the pH of the medium and increases with the formation of polymer colloidal complexes. The polymer colloidal complexes based on surfactants with two hydroxyethyl substituents in the head group have the maximum catalytic activity (increase in the reaction rate by up to three orders of magnitude).The modern level of technical progress provides the development of new approaches to the solution of prob lems in the field of catalysis. One of the promising trends is the use of supramolecular systems, whose biomimetic character allows one to achieve high efficiency and selec tivity of catalysts under mild conditions. 1-3 A tendency to the development of polycomponent compositions, whose catalytic activity can be controlled by varying the nature and ratio of reactant concentrations, is observed in the recent time. 4,5 Nowadays the study of the properties of polymer colloidal solutions is an intensely developing area of supramolecular chemistry. Interest to the systems based on surfactants and polymers is defined by their wide appli cation in the production of detergents, oil regeneration, cosmetic industry, etc. 6 From the viewpoint of biomi metics, surfactant-polymer systems are models of pro tein-lipid interactions. Among many polymers, we no ticed polyethyleneimines (PEI), which are of practical in terest because of their use as corrosion inhibitors, demul sifiers, 7,8 biologically active substances, 7 complexing agents, 9 and carriers of drugs. 10 It is known that polyethyleneimines can form aggre gates in individual solutions, and polymer colloidal com plexes (PCC) are formed in the presence of surfactants. 11,12 In addition, it is shown that PEI and polymer colloidal complexes based on them act as catalysts of hydrolysis of phosphorus acid esters. 12,13 Many works are devoted to the study of systems consisting of PEI and anionic surfac tants (for example, PEI-sodium dodecyl sulfate 13-17 ).The works on studying the interactions in systems based on polyethyleneimines (including those hydrophobically modified) and cationic surfactants have appeared in the recent time. 12,18-21 In aqueous solutions of such systems, electrostatic interactions exert an unfavorable effect on the formation of PCC, and combined structures are formed due to ion dipole and hydrophobic interactions. 18,21Modified polyethyleneimines are of certain interest. For instance, additional hydrophobic fragments (benzyl, alkyl) in a PEI molecule enhance their aggregation activi ty and ability to complex formation toward molecules and ions of low molecular weight organic compounds, as well as the catalytic activity in hydrolysis of carboxylic and phosphorus acid esters. 22, 23 In the present work, we investigated the self organi zation and catalytic activity of 2 hydroxybenzylated polyeth...