Concentration boundaries within which polymer-colloid structures exist in a sodium dodecyl sulfate-polyethyleneimine-water system were determined. The catalytic effect of this composition was found for the hydrolysis of phosphonic acid esters. The found accelera tion of hydrolysis up to 25 fold is caused by reagent concentrating in a catalytic complex.Mixed systems surfactant-polymer are objects of a promising interdisciplinary scientific area that attract great researchers´ interest. 1-6 The development of this avenue of investigation is stimulated by a wide scope of practi cally useful properties of mixed solutions and a possibility of their purposeful control by the variation of the compo nent ratio in the system. In addition, the study of regulari ties of the formation of polymolecular ensembles extends potentialities of self assembly modelling in biological sys tems. The main goal of fundamental studies of aqueous surfactant-polymer solutions is to prove the combined aggregation, find concentration boundaries for the exist ence of mixed structures, estimate their stability, and char acterize the nature of intermolecular interactions. The reactivity of compounds in mixed polymer-colloid sys tems is poorly studied and, therefore, is one of the main tasks of the present work.We have previously 7,8 studied the physical and cata lytic properties of polymer-colloid systems based on the cationic surfactant cetyltrimethylammonium bromide (CTAB) and polyethyleneimine (PEI). Different points of view about the possible cooperative binding of cationic surfactants with nonionic and likely charged polymers can be found in the literature. 9 The published results 7,8 favor the hypothesis on the self organization and forma tion of supramolecular structures in the CTAB-PEI sys tem. These structures efficiently catalyze the hydrolysis of phosphorus esters. Taking into account that the electro static interaction contributes unfavorably to the free en ergy of formation of complexes of the likely charged sur factant and polymeric species, it should be assumed that combined aggregates are formed in these systems mainly due to hydrophobic interactions. To gain more compre hensive information on the contribution from differ ent types of intermolecular interactions in the surfac tant-polymer systems, we continued to study the cata lytic properties of PEI based compositions, using an un likely charged surfactant, sodium dodecyl sulfate (SDS). The hydrolysis of phosphonates 1-3 was studied as a model process (Scheme 1). Scheme 1 1 2 3 X NO 2 NO 2 Br R Et n С 6 Н 13 Et ExperimentalCompounds 1-3 were synthesized by a known procedure. 10 Sodium dodecyl sulfate (Sigma) and branched PEI (Aldrich, molecular weight 30000) containing the primary, secondary, and tertiary nitrogen atoms in a ratio of 1 : 2 : 1 were used. Molar concentrations of PEI presented in the work are based on the

No abstract

No abstract

No abstract

The kinetics of hydrolysis of bis (p-nitrophenyl] methylphosphonate in the presence of prima/3' aliphatic amines in aqueous micellar solutions of cetylpyridinium bromide was studied. Tile reaction proceeds via tv, o routes, alkaline hydrolysis and amine-catalyzed hydrolysis according to the general basic catalysis mechanism. The contributions of these routes and the catalytic effect of mieelles depend on the hydrophobicity of the amines. The formation of different types of miceltes was found, and their characteristic parameters were determined by tensiometr7 and high-resolution t H N M R spectroscopy with a magnetic field pulse gradient.Key words: kinetics, hydrolysis, bistp-nitrophenyl) methylphosphonate, amines, micetles. cetytpyridinium bromide. ~|t NMR spectroscopy, diffusion.Micellar catalysis is a nontraditional method of affecting the reactivity of org~mic compounds.l'2 Elucidation of the factors that determine the efficiency of micellar catalysis is a topical task. The line of investigation of micelle formation and micellar catalysis is tightly connected with the problems of enzymology, because most processes involving enzymes cxzcur in highly organized systems, namely, cell membranes and subceflular species. Micellar solutions can ser~'e as convenient models for the investigation of it/ vitro processes occurring in a living cell) Functionalization of micelles of cationic suffactants by incorporation of long-chain amines (i.e., the /brmation of mixed aggregates bearing a fixed active site responding to the variation of the medium pH and the component ratio) can result in the design of biomimetic systems. These systems exhibit catalytic activity in nucleophilic cleavage processes, in particular, in the transfer of acyl and phospho~t groups.This work is a continuation of our study dealing with the catalytic properties of micellar systems consisting of a surfactant and a primary' aliphatic amine. 4,5 It is aimed at elucidating the relationship between the structures of microaggregates and their influence on the rate and mechanism of cleavage of ester bonds. For this purpose. using bis(ao-nitrophenyt) methylphosphonate (1) as the sttbstrate, we studied the kinetics of hydrolysis of esters of tetracoordinated phosphorus in the presence of primar7 amines with nonbranched chains in aqueous micellar solutions of cetylpyridinium bromide (CPB). A number of characteristic parameters of the system confirming the fomaation of micellar aggregates of various types were determined by independent physical methods (tensiometry" and high-resolution ~H NMR spectroscopy with a magnetic field pulse gradient). ExperimentalThe solvents and amines were purified by standard procedures. CPB samples were twice reprecipitated with ether from ethanol. Phosphonatc 1 was synthesized and purified by a procedure reported previously. 6The formation of tile O-(p-nitrophenyl) methylphosphonic acid monoanion upon hydrolysis of compound 1 in solutions of CPB in the presence of decylamine is proved by the fact that its chemical shift in the 3t...