Polyphosphazenes surface reactions

Table 23 Surface implications in polyphosphazenes surface modification by chemical reactions...

The same fluoroalkoxy substituents, however, are able to enhance substitutional reactivity of fluorinated polyphosphazenes by originating methatetical exchange reactions on polymers in the presence of new nucleophiles and under appropriate experimental conditions. Thus, a series of exchange reactions at phosphorus atoms bearing the trifluoroethoxy substituents in PTFEP have been describedbyH.R. Allcock [508] (Fig. 13),Cowie [482,483] (Fig. 14), and Ferrar [509] (Fig. 15), while surface modification of PTFEP films were reported by Allcock [514,515] (Fig. 16 or 17) and by Lora [516] (Fig. 18). 

The surface of aryloxy-substituted polyphosphazenes can be modified by a variety of chemical reactions, such as ... 

The connection between hydrophobicity and tissue compatibility has been noted for classical organic polymers (19). A key feature of the polyphosphazene substitutive synthesis method is the ease with which the surface hydrophobicity or hydrophilicity can be fine-tuned by variations in the ratios of two or more different side groups. It can also be varied by chemical reactions carried out on the organo-phosphazene polymer molecules themselves or on the surfaces of the solid materials. 

Secondary reactions of these types are widely used to produce polyphosphazenes that are required for biomedical applications or for polymer grafting reactions. They are also used to modify the surfaces of poly(organophosphazene), as discussed in the following section. 

The surface character of a polymer often controls its technological and biological properties. In the past, new surface characteristics could be generated mainly by the synthesis of entirely new polymers. The most modem approach is to choose a polymer for its "internal" properties (elasticity, rigidity, etc.) and then modify the surface by chemical reactions. We have developed a number of approaches to achieving this for polyphosphazenes (16-20). 

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