Polycomponent Catalytic Systems Based on Amphiphiles and Polymers

5 Polycomponent Catalytic Systems Based on Amphiphiles and Polymers 

There is much evidence that the amines including polyamines accelerate hydrolyses of phosphoras acid esters via the general basic catalysis. In the unbuffered solution, a small amount of protonated amino groups are present in the PEI molecnles ( 0.5-5.0% depending on the PEI molecular mass PEI with the molecular mass from 800 (PEI-800) to 60000 (PEI-60) were studied). This means that under these conditions PEIs behave as neutral polymers rather than polyelectrolytes. The pH kinetic profile danonstrates that up to pH 9.2 the observed rate constant of hydrolyses of 1 and 3 in 0.05M solution of PEI-50 does not exceed the limits of 5 x 10 s, while a further increase in the pH results in a ca. tenfold increase in the hydrolysis rate of both phosphonates. This pH dependence is rather typical and reflects the growth of the rate constant in the field of accumulation of catalytic species, namely nonprotonated amino groups, hi addition, the contribution of basic hydrolysis to kobs values at high pH should also be taken into account. 

Eor substrate 1 the kinetics of hydrolysis is measured in the SDS/PEI-30 system at different temperatures, and then the activation parameters for the reaction in different pseudo phases are calculated. For micellar pseudo-phase the enthalpy of activation AH = 55.2 kJ mol and entropy of activation AS = -121.7 J mol K are calculated, which are in agreement with the bimolecular mechanism of the reaction. These values differ little from the activation parameters obtained for the reaction in the aqneons pseudophase (AHo = 56.6 kJ mol, ASS = -100.3 J mol K ). This probably provides evidence that the mechanism of catalysis remains unchanged when the process is transferred from water to aggregates, i.e. the general basic catalysis occnrs in both cases. 

The next stage of the study was on the kinetics of hydrolyses of 1, 3 and di-p-nitrophenyl phosphate 15 in the ternary SDS/PEI/La(in) systan at spontaneons solution pH (pH = 8.7). In this system there occurs a high performance in the reactivity of phosphonates and its growth. The maximum catalytic effect exceeding fonr orders of magnitude is found for the substrate 15 as compared to the single PEI solntion. Comparison with the basic hydrolysis of 15 reveals the rate effect over six orders of magnitnde. 

Unlike the SDS/PEI system the cmc value does not decrease markedly in the solutions of nonionic surfactant C12E10 and Triton-X-l(X) when the polymer is added. This is in line with the assumption on the weak affinity between the nonionic snrfactant and polymers. However, as will be shown below a rather high probability occnrs that the mixed nonionic 

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