Hybrid materials based on polyvinylpyrrolidone (PVP) with silver nanoparticles (AgNps) were synthesized applying two different strategies based on thermal or chemical reduction of silver ions to silver nanoparticles using PVP as a stabilizer. The formation of spherical silver nanoparticles with diameter ranging from 9 to 16 nm was confirmed by TEM analysis. UV-vis and FTIR spectroscopy were also applied to confirm the successful formation of AgNps. The antibacterial activity of the synthesized AgNPs/PVP against etalon strains of three different groups of bacteria-Staphylococcus aureus (S. aureus; grampositive bacteria), Escherichia coli (E. coli; gram-negative bacteria), Pseudomonas aeruginosa (P. aeruginosa; nonferment gram-negative bacteria), as well as against spores of Bacillus subtilis (B. subtilis) was studied. AgNps/PVP were tested for the presence of fungicidal activity against different yeasts and mold such as Candida albicans, Candida krusei, Candida tropicalis, Candida glabrata, and Aspergillus brasiliensis. The hybrid materials showed a strong antimicrobial effect against the tested bacterial and fungal strains and therefore have potential applications in biotechnology and biomedical science.

A redox initiating system was developed in order to bypass 2,2‘-azobis(4-methoxy-2,4-dimethylvaleronitrile) (V70) as the initiator of the cobalt-mediated radical polymerization (CMRP) of vinyl acetate (VAc) in the presence of cobalt(II) acetylacetonate (Co(acac)2). It is indeed a problem to stock up with V70 because of needed storage at −20 °C during transportation. This paper reports on the controlled CMRP of VAc initiated by ascorbic acid combined with either lauroyl peroxide or benzoyl peroxide at 30 °C. Substitution of citric acid for ascorbic acid results in faster polymerization whereas the polymerization control is maintained. All these improvements facilitate the implementation of the vinyl acetate CMRP and open the door to the scale-up of the process.

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Well-defined poly(vinyl acetate) macroinitiators, with the chains thus end-capped by a cobalt complex, were synthesized by cobalt-mediated radical polymerization and used to initiate styrene polymerization at 30 8C. Although the polymerization of the second block was not controlled, poly(vinyl acetate)-b-polystyrene copolymers were successfully prepared and converted into amphiphilic poly(vinyl alcohol)-b-polystyrene copolymers by the methanolysis of the ester functions of the poly(vinyl acetate) block. These poly(vinyl alcohol)-b-polystyrene copolymers self-associated in water with the formation of nanocups, at least when the poly(vinyl alcohol) content was low enough.

The cobalt‐mediated radical polymerization of vinyl acetate was extended to copolymerization with 1‐alkenes (ethylene or 1‐octene). In agreement with the low amount of 1‐alkene that could be incorporated into the copolymer, a gradient structure was predictable, but a rather low polydispersity was observed. A poly(vinyl acetate)‐b‐poly(octene) copolymer was also successfully synthesized, leading to a poly (vinyl alcohol)‐b‐poly(octene) amphiphilic copolymer upon the methanolysis of the poly (vinyl acetate) block. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2532–2542, 2007

Summary: Poly(vinyl acetate) chains end‐capped by a Co(acac)2 complex [PVAc‐Co(acac)2] were prepared by bulk cobalt‐mediated radical polymerization (CMRP) of vinyl acetate and used for grafting fullerene (C60) with four PVAc arms at low temperature (30 °C). A photoactive water‐soluble poly(vinyl alcohol)/C60 nanohybrid was then prepared by hydrolysis of the PVAc arms of the nanohybrid. Because of photoactivity and very low cytotoxicity, this type of water‐soluble nanohybrid is very promising for the photodynamic cancer therapy.

Summary: Poly(vinyl acetate) macroinitiators end‐capped by a Co(acac)2 complex (PVAc–Co(acac)2), prepared in bulk by cobalt‐mediated radical polymerization (CMRP), are used for the controlled radical polymerization of vinyl acetate in miniemulsion to give high‐molecular‐weight polymers and high monomer conversion. Stable poly(vinyl acetate) latexes with solid contents ranging from 25 to 30 wt.‐% are prepared within unusually short reaction times (∼1 h) at low temperatures (0–30 °C).SEC chromatograms for the PVAc–Co(acac)2 macroinitiator and PVAc latex obtained under ultrasonication for 6 min at 0 °C (79% monomer conversion).magnified imageSEC chromatograms for the PVAc–Co(acac)2 macroinitiator and PVAc latex obtained under ultrasonication for 6 min at 0 °C (79% monomer conversion).

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