Nanocomposites and nanomaterials

Silver-containing polymer nanocomposites obtained by the chemical and thermochemical reduction methods 
V.L. Demchenko, S.V. Riabov
Institute of Macromolecular Chemistry, National Academy of Sciences of Ukraine, 
48, Kharkiv highway, Kyiv, 02160, Ukraine. 
E-mail: dvaleriyl@ukr.net.

Structure, thermomechanical and antimicrobial properties of nanocomposites based on interpolyelectrolyte complex and Ag nanoparticles, which formed by the chemical and thermochemical reduction methods from interpolyelectrolyte–metal complexes (IMC) have been investigated. It is established that chemical reduction of Ag+ ions in the pectin – Ag+ – poly(4-vinylpyridine) IMC, involving sodium borohydride at molar ratio [BH4–] : [Ag+] ≥ 1.0 results in formation of the nanocomposite based on the „pectin–poly(4-vinylpyridine)“ interpolyelectrolyte complex (IPEC) and silver nanoparticles (Ag) as well. Applying small-angle X-ray method, we confirmed that at transformation from IMC to IPEC–Ag structure of nanocomposite, the relative heterogeneity level is augmented, while effective size of the region heterogeneity goes down. The nanocomposites pectin – poly(4-vinylpyridine)–Ag prepared are shown much higher Tg value and enhanced ability for deformation than those for IMC. Another type of nanocomposites on the base of interpolyelectrolyte complexes „pectin–polyethyleneimine (PEI)“ and Ag nanoparticles was obtained by both chemical and thermochemical reduction of Ag+ ions in the polyelectrolyte–metal complexes. Such type of nanocomposites with Ag nanoparticles incorporated into polymer matrix is obtained due to the chemical reduction of Ag+ ions by NaBH4 in the interpolyelectrolyte complex, and appearance of the silver metallic phase is observed in full extent while BH4– : Ag+ molar ratio is equal to 2.0. It is defined that thermochemical reduction of Ag+ ions in IMC bulk (while films are heated to the temperature around 100 °С and more) results in formation of silver-containing nanocomposites. In its turn, thermochemical reduction of silver ions is found out to take place owing to polyethyleneimine (namely, on account of electrons transfer from the amino groups’ nitrogen atoms of polyethyleneimine to Ag+ ions). The antimicrobial investigation of the elaborated nanocomposites revealed they possess a high antimicrobial activity against S. aureus and E. coli strains.