Complex epidemiological situation, nosocomial infections, microbial contamination, and infection risks in hospital and dental equipment have led to an ever-growing need for prevention of microbial infection in these various areas. Macromolecular systems, due to their properties, allow one to efficiently use them in various fields, including the creation of polymers with the antimicrobial activity. In the past decade, the intensive development of a large class of antimicrobial macromolecular systems, polymers, and copolymers, either quaternized or functionalized with bioactive groups, has been continued, and they have been successfully used as biocides. Various permanent microbicidal surfaces with non-leaching polymer antimicrobial coatings have been designed. Along with these trends, new moderately hydrophobic polymer structures have been synthesized and studied, which contain protonated primary or secondary/tertiary amine groups that exhibited rather high antimicrobial activity, often unlike their quaternary analogues. This mini-review briefly highlights and summarizes the results of studies during the past decade and especially in recent years, which concern the mechanism of action of different antimicrobial polymers and non-leaching microbicidal surfaces, and factors influencing their activity and toxicity, as well as major applications of antimicrobial polymers.

Antimicrobial activity of secondary and tertiary poly(diallylammonium) salts (PDAAs) had not been reported before. Due to difficulties with preparation of polymers from the monomers of the diallylamine (DAA) series in the nonquaternary form, up to recently it was not possible to obtain PDAAs with a sufficiently high molecular mass. Here, we describe the investigations of antimicrobial activity of novel water-soluble cationic polyelectrolytes of the PDAA series, namely secondary poly(diallylammonium trifluoroacetate) (PDAATFA) and tertiary poly(diallylmethylammonium trifluoroacetate) (PDAMATFA), in synthesis of which we have recently succeeded, against gram-positive and gram-negative bacteria, and fungi. We have studied the effect of molecular weight (polymeric chain length) and ionic strength of solution on the biocidal efficiency of those polymers; in addition, the concentration dependences of PDAATFA reduced viscosity in salt-free and KCl aqueous solutions have been investigated. The antimicrobial properties of polybase polydiallylamine (BPDAA), which was obtained in an aqueous solution of PDAATFA in presence of alkali, have been also studied as well as biocidal activity of commercial open-chain polybase branched PEI. Those PDAATFA, BPDAA and PEI polymers served as the systems to study the structure-activity relationships. Transmission electronic microscopy study was carried out to characterize the mode of antimicrobial action of PDAATFA using E. coli . It was shown that the synthesized PDAATFA and PDAMATFA exhibit, unlike the quaternary polymers of this series, a rather high biocidal efficiency that is comparable with the activity of known effective cationic polymer biocides or exceeds it. Novel polyelectrolytes exhibit quite strong biocidal properties at different conditions including aqueous solutions of moderate ionic strength (serum, 0.01 M/0.1 M) and aqueous-alkaline solutions (pH 10.5) until the macrochain retains some positive charge, but complete neutralization of the polyelectrolyte in a 1 M salt solution results in the loss of its biocidal activity. The obtained results evidence that the structure of links, which combine the hydrophobic pyrrolidinium rings with the hydrophilic secondary/tertiary ammonium groups, is responsible for the high biocidal activity of the PDAAs. Polymeric nature of the synthesized compounds is one of the most significant factors of their bactericidal efficiency, unlike their high fungicidal activity, which is evidently related to the secondary/tertiary pyrrolidinium cycle.

The potential energy profdes of reactions of diallylmethylamine and its protonated and quaternary forms with their own radicals were calculated by the semiempirical MNDO-PM3 method taking into account electrostatic solvation effects in the framework of the selfconsistent reaction field model. The reactions studied simulate chain propagation and chain transfet to monomer in radical polymerization of the above monomers in dilute solutions with different dielectric permittivities of the solvents. The conformations of monomers in the gas phase and in solvent were studied. It was found that protonatioa and quaternization lead to successive increase in the activation energy of mobile allyl hydrogen atom abstraction and to increase in the difference between the activation barriers to competing reactions of chain transfer and propagation. The remits obtained make it possible to predict the conditions of the synthesis of high-molecular-weight polymers based on diallylamine monomers. The mechanisms of reactions studied are discussed.Key words: diallylmethylamine, diallylmethylammonium, radical polymerization, chain propagation, degradative chain transfer, solvent, free electrostatic solvation energy, potential energy profile, activation energy, quantum--chemical calculations, MNDO-PM3 method.The problem of radical polymerization of allyl monomers has long been studied, t-7 It was established that polymerization of these compounds is to a great extent controlled by the reaction of degradative chain transfer to the monomer occurring with abstraction of the a-hydrogen atom of the allyl group of the monomer by the propagation radical to form a stable low-reactive allyl radical. This results in the kinetic chain termination, formation of low-molecular weight oligomeric produets, and complete inhibition of polymerization because of the low reactivity of the allyl radical that formed, t-7 It was established in the studies of polymerization kinetics that the polymerization rate of allyl monomers and the molecular weight (MW) of low-molecular weight oligomers substantially increase in complex-forming and acidic media, viz., they increase as proton-donor properties of acid (solvent) and the basicity of allyl monomers increase) -7 This effect is explained by an increase in the strength of the a-C--H bonds in the allyl group upon protonation (or complexation) and by increase in the reactivity of allyl radical, i.e., by partial transformation of degradative chain transfer into effective one in this type of media. 3-7All said above is also true for compounds of the diallyl series including diallylmethylamine (1) and monomers of the diallylamine series (2). 6-8 Only on going to quaternary forms of compounds 2, viz., salts of disubstituted N, N-dialkyI-N,N-diallylammonia (3), the degradative chain transfer to monomer can be inhibited to a great extent and converted into effective chain transfer to monomer, ~,i~ which makes it possible to solve thus the problem of synthesizing high-molecular weight products based on monomers of the type 3 ...