Among the chemical modification techniques developed to date, surface grafting has emerged as a simple, useful, and versatile approach to improve surface properties of polymers for a wide variety of applications.
Grafting has several advantages: (1) the ability to modify the polymer surface to have very distinct properties through the choice of different monomers, (2) the ease and controllable introduction of graft chains with a high density and exact localization of graft chains to the surface with the bulk properties unchanged, and (3) covalent attachments of graft chains onto a polymer surface assuring long-term chemical stability of introduced chains, in contrast to physically coated polymer chains [31,44].
Many different synthetic routes can be employed to introduce graft chains onto the surface of polymeric substrates depending on a system of interest. Surface modification can be achieved by two methods : graft coupling and graft polymerization. The former is applied when reactive groups are present on the polymer surface that can undergo a condensation reaction with a second polymer chain to be grafted onto its surface. The latter does not require any reactive functional groups on the surface; instead the surface of the polymer must be initiated in order for graft polymerization to occur.
Graft co-polymerization is one of the promising methods of modification for various polymers and polymer materials. Initiation of the surface can be achieved via direct chemical modification, ozone, gamma rays, electron beams, glow discharge, corona discharge, or UV irradiation . The general scheme of how the surface of polymer can be grafted is reflected in Figure 4.1. There are two main approaches to graft co-polymerization of particular interest to nanofibers: radiation-induced graft co-polymerization and plasma-induced graft co-polymerization.
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