Nanocomposites and nanomaterials

Formation of hydrophilic nanolayers on the surface of polypropylene microfibers
Nosova N.G., Dron I.A., Varvarenko S.M., Voronov S.A., Samaryk V.J.
Lviv Polytechnic National University
S.Bandera Str., 12, Lviv-79013, Ukraine
E-mail: nnosova2121@gmail.com

Immobilization of macromolecules and formation of thin polymeric films on solid surfaces is a promising contemporary method of improving the properties of polymeric materials. Surface modification enhances conductivity, wettability, stability, adhesion, antithrombogenicity, and antibacterial properties of polymeric surfaces without impairing the material’s bulk properties. Polymer surface modification is conventionally achieved by targeted covalent polymer attachment (grafting), resulting in thin films with interesting properties. In many cases, radical polymerization is considered a useful approach for polymer grafting on a solid surface.
Polymeric surfaces were peroxidized by employing plasma treatment, UV-irradiation, oxygenation and ozonation, and radical initiators and then further modified by the grafting of surface polymer films. Alternatively, polyperoxide macromolecules can be used for substrate surface activation. 
Covalent attachment of polyperoxide macromolecules to a polypropylene surface occurs due to the radical processes initiated by thermolysis of the peroxide groups. Covalent bonds between polyperoxide and a polypropylene surface are formed by the reaction of chain transfer to the polymer surface macromolecules, followed by recombination between the surface macroradicals and polyperoxide macromolecules. Chemical functionalization of a polymeric substrate, as a rule, results in increasing surface energy. Peroxide groups of the grafted polyperoxide macromolecules on a polymeric substrate can be used for surface hydrophilization.
Modification of the peroxidized surface of polypropylene microfibers due to the polymerization of acrylic acid, acrylamide, initiated from the surface was performed in this study. The height of the grafted layer was 20-40 nm.
The process of surface modification of polypropylene microfibers was monitored at all stages by Fourier transform infrared spectroscopy, by changing the water retention value and by the ellipsometric method.
The results of the conducted research have shown that the possibility of activating the surface of polypropylene microfibers when using polyperoxides with subsequent modification of the peroxidized surface. The hydrophobic surface of polypropylene acquires hydrophilic properties due to the grafting of nanolayers.