Plasma modification copolymerization

Cell adhesion on a nonfunctional scaffold is mediated dominantly by nonspecific, entropically favored adsorption of a layer of cell adhesion proteins, excreted by the cell itself [61]. In order to obtain and retain the native function of these proteins, attempts are being made to tune the hydrophilicity or hydrophobicity of the scaffold surfaces [62], Different methods of surface activation are commonly applied, e.g., blending, copolymerization, plasma treatment, etching, radiation, chemical surface modification, coatings, and combinations of those. 

Surface modification of a fiber can be accomplished by chemical treatment, graft copolymerization, ion implantation, or plasma treatment. Surface modification usually targets improvements in antistatic properties, moisture regain, dyeing, printing, adhesion, abrasion, antibacterial properties, and so forth. 

However, lack of good interfacial adhesion, low melting point, and poor resistance towards moisture make the use of natural fibre-reinforced composites less attractive. Pre-treatments of the natural fibre can clean the fibre surface, chemically modify the surface, stop the moisture absorption process and increase the surface roughness. Among the various pre-treatment techniques, graft copolymerization and plasma treatment are the best methods for surface modification of natural fibres. Graft copolymers of natural fibres with vinyl monomers provide better adhesion between matrix and fibre. 

The non-equilibrated, low-temperature plasma which is generated by glow discharge in gases is very suitable for the modification of polymer surfaces. Examples are plasma polymerization and plasma treatment In comparison with these plasma applications, plasma-induced graft copolymerization has attracted the attention of only very few researchers. 

There are three basic processes which are utilized for preparing new or modilled polymeric biomaterials. They are (1) surface modification via radiation graft copolymerization or plasma gas discharge (2) radiation polymerization of pure monomeifs) in solution, or an emulsion, or in the solid state (e.g., below Tq) and (3) radiation crosslinking, in a solution or swollen state, or in the solid state. 

The section on the chemical modification of PHAs is divided into different topics such as carhoxylation, hydroxylation, epoxidation, halogenations and graft copolymerization. The section on the physical modification of PHAs is divided into different topics such as PHA blending and coating, PHA irradiation, ion implantation, plasma treatment, electrospinning. To conclude, the authors discuss the modification of PHAs with enzymes. 

Along with physical modification, chitosan is most commonly modified by a number of chemical techniques including traditional chemical modification techniques such as photochemical, enzymatic, radiation, and plasma-induced graft copolymerization. Figure 1.6 summarizes some of the commercially used modification techniques for surface modification of chitosans. 

Modification of lignocellulosic materials surface by copolymerization with vinyl monomers has been reported. The polymerization reaction is initiated at the surface of the fibers by incorporation of peroxides or oxidation-reduction agents, or by treatment with gamma radiation or cold plasma [49]. These reactions form free radicals on the fibers, which initiates the free chain reaction with the vinyl monomers. Different types of properties can be conferred to the fibers using different vinyl monomers, such as increased hydrophilicity with poly(vinyl alcohol), increased hydrophobicity with polystyrene or polyvinylacetate, increased reactivity with polyvinylamine etc. 

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