Nanocomposites and nanomaterials

Graft copolymer-assisted synthesis of nickel nanoparticles in aqueous solutions 
Zheltonozhskaya Т.B.1, Permyakova N.М.1, Kunitskaya L.R.1, Klepko V.V.1, Grishchenko L.М.2, Klymchuk D.О.3
1 Department of Polymer Physics, Institute of Macromolecular Science of the NAS of Ukraine, 48 Kharkivske Shosse, 02160 Kyiv, Ukraine. 
E-mail: zheltonozhskaya@ukr.net 
2 Faculty of Chemistry, Taras Shevchenko National University of Kyiv, 60 Volodimirska St., 01033 Kyiv, Ukraine.
3 Laboratory of Electron Microscopy, M.G. Kholodniy Institute of Botany of the NAS of Ukraine, 2 Tereshchenkivska St., 01601 Kyiv, Ukraine.

A special hydrophilic graft copolymer with interacting poly(vinyl alcohol) backbone and grafted polyacrylamide chains (PVA-g-PAAm) was synthesized, characterized and used as a matrix for in situ synthesis of nickel nanoparticles (NiNPs) in aqueous media. The copolymer solutions contained individual macromolecules (monomolecular micelles) of ellipsoidal shape and length of ~18-64 nm, and their various fractal aggregates (Figure 1 a). To study the borohydride reduction of Ni2+-ions in PVA-g-PAAm solutions and pure water, an original method for monitoring the kinetics of the formation of metal nanoparticles was proposed and implemented for the cases where there is no a surface plasmon resonance band in UV-Vis spectra. An increase in the initial rate of accumulation and yield of NiNPs with an increase in the concentration of Ni-salt and a decrease in both parameters in copolymer solutions in comparison with pure water was established. The complex role of matrix concentration was also shown.
	Figure 1. TEM images of (a) PVA-g-PAAm matrices and (b) their compositions with NiNPs.  	
 In the final NiNPs/PVA-g-PAAm compositions (Figure 1 b), the emergence of new structures such as “hairy coils” and “hairy rods” with small individual spherical NiNPs and their chains was identified.