Optimization of Methodology of Protonated Diallylammonium Monomers Free Radical Polymerization for the Obtaining Polymers with a Low Molecular Weight

Abstract

Protonated diallylammonium polymers attract attention due to a number of properties, in particular high antimicrobial activity, including activity against the mycobacterium M. tuberculosis. To reduce the cytotoxic effect of polymers in the case of practical use, samples with a low MW are required. The work investigated the free radical polymerization of protonated diallylammonium monomers, diallylammonium trifluoroacetates, in excess of the initiator ammonium persulfate (10^–1 M) and at average polymerization temperatures (40 and 50°C) to obtain polymers with a low degree of polymerization. It has been shown that under such conditions it is possible to obtain polymers with values suitable within the aim: 16000 < MW < 28000 g/mol. Using NMR and IR spectroscopy, it was shown that with an increase in the concentration of the initiator and, accordingly, a decrease in the molecular mass of polymers, the relative number of characteristic terminal vinyl groups decreases, and the terminal groups formed by the interaction of macroradicals with primary radicals of the initiator become predominant, in this case, sulphate groups of ammonium persulfate. The data obtained indicate that at high concentrations of the initiator, the characteristic reactions of chain transfer to the monomer are largely kinetically suppressed by the interactions of macroradicals with the primary radicals of the initiator. The approach used, which makes it possible to synthesize polymers with a low MW and terminal groups of the initiator, can be applicable in the future to vary the properties of antimicrobial activity and toxicity of polymers.