Fluorinated polyphosphazenes,

In fact, fluorinated polyphosphazenes are usually considered to be extremely stable towards chemical agents and aggressives due to the presence of C-F bonds in the side phosphorus substituents. PTFEP, for instance, appears to be completely insensitive to several, most common, solvents (aliphatic and aromatic hydrocarbons, alcohols and water), to acids (e.g. acetic acid), and to bases (e.g. pyridine and concentrated NaOH solutions), although some decomposition could be observed in triethylamine and in concentrated H2SO4 [41]. Phos-phazene fluoroelastomers, moreover, are known to be completely insoluble in aromatic solvents [533] and petroleum-resistant materials [502-506,552]. 

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). 

Zumbulyadis et al. [86] selected a fluorinated polyphosphazene, containing CF3CF2CF2CF2CH2O side chains (attached to phosphorus atoms in the polymer backbone) to explore the potential of F MAS/NOESY experiments. MAS at 3.82 kHz sufficed to resolve all four F sites, though effects of isotropic indirect coupling were obscured by the linewidths. Cross peaks are seen in the two-dimensional NOESY spectrum. The authors argue that these arise from NOE processes and not from spin diffusion. 

Anomalous changes are frequently noted for fractions across the broad molecular weight distribution(s). For example, k + k" / 0.5 —see references (3) and (4). Intrinsic viscosity parameters as a function of percent acetone in E2 solvent are plotted in figure 3 of reference (3) for several PNF fractions. Many other values are tabulated by Hagnauer and Schneider in this reference along with many other solution parameters. Recently, the solution properties of polyphosphazenes have been critically reviewed. Besides polymer quality, there have been problems with tailing" in the fractionation of fluorinated polyphosphazenes as pointed out in reference (15). The quality polymers s)mthesized since the should... 

The high hydrophobicity of soluble fluorinated polyphosphazenes has drawn attention to their possible use as surface coatings in applications where insoluble fluoropoly-mers like Teflon cannot be used. This also applies to PNF-type elastomers that, in the uncross-linked state, are highly adhesive. One application that has shown promise is as ice-phobic coatings on helicopter rotor blades. Another reported application is the use of trifluoroethoxy-substituted polyphosphazenes for coating biomedical devices. 

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