Nanocomposites and nanomaterials

Thermosensitive nanogels based on poly(N-vinylcaprolactam) 
Kernosenko L.O., Samchenko Yu.M., Pasmurtseva N.O., Poltoratska T.P., Kryklya S.O.
F. D. Ovcharenko Institute of Biocolloidal Chemistry of the NAS of Ukraine. 
42 Acad. Vеrnadskoho Blvd., Kyiv-03142, Ukraine.
Е-mail: kernosenko@ukr.net
Recently, researchers focus is on the creation of «smart» nano-hydrogels due to their unique properties such as high biocompatibility, low toxicity, ability to prolonged and controlled release of incorporated medicines, and sharp change of diffusion properties in response to small changes in their microenvironment (for example, minor physiologically acceptable changes in temperature or pH). 
The most promising seem thermosensitive nano-hydrogels composed of N-vinylcaprolactam (VCL) which posess the phase transition temperatures close to human body temperature, is non-toxic and stable against hydrolysis unlike another thermosensitive polymer N-isopropylacrylamide [1].
Synthesis of pVCL-based nanogels were carried out by radical polymerization in water solution at 70 °C. Ammonium persulfate was used as the initiator, and N,N'-methylene bisacrylamide – as crosslinking agent. Measurement of the nanoparticles size and their distribution was carried out at 25 °C, 37 °C and 50 °C using Malvern Zetasizer Nano ZS. 
	It has been demonstrated that the average nanoparticles radius of pVCL-based  hydrogels is about 130 nm and depends on temperature. When heated from 25 to 50 °C (Fig. 1), the nanoparticles size decreases in result of a thermally induced phase transition from swelled to collapsed state with a sharp change of physical and chemical parameters.
Consequently, pVCL-based synthesized nanogels are promissing for the development of «smart» controlled-release drug delivery systems of medicines. 

1.	Sun S., Wu P. Temperature-sensitive nanogels: Poly(N-vinylcaprolactam) versus poly(N-isopropylacrylamide) // Polymer Chem.-2012.-3-P. 852-856. 

Fig. 1 Particle Size Distributions 
of pVCL-hydrogel at 50 °C (1), 
37 °C (2), and 25 °C (3)