Potential Applications of Polyphosphazenes

As noted earlier the contact angle of [NP(OCH2CF3)2]n is comparable to that of Teflon. Thus, many applications that require hydrophobicity can be met by this class of polymers. In addition, polymers of this type have been noted for their biocompatibilty. In view of this, [NP(OCH2CF3)2]n along with [NP(OPh)2] are being looked upon as candidates for body parts such as cardiovascular parts or as coatings for pacemakers. 

Another type of application can arise from the hydrolytic instability of certain poly(aminophosphazene)s such as those that contain amino acid ester side-groups (Fig. 3.55). 

Transport of ions is facilitated through a medium which is known as an electrolyte. This process leads to ionic conduction. Conventionally, the electrolyte is a liquid which mediates ion-transport [36, 37]. However, in reeent years there is considerable interest in designing solids in general and polymers in particular that can function as electrolytes. The main idea is that if solids can be used as electrolytes, the weight and volume occupied by the liquid electrolyte can be avoided. Several solids such as p-alumina have been used as solid electrolytes. 

Polymers can be cast into thin films and can be sandwiched between electrodes. This will allow retention of contact since polymers are flexible and can adapt to the dimensional changes that occur at the electrode. 

Polyphosphazenes have an intrinsic skeletal flexibility and therefore can be designed as polymer electrolytes. Reaction of poly(dichlorophosphazene), [NPCy, with the sodium salt of methoxyeth-oxyethanol affords the etheroxy-side-chain containing polymer (see Eq. 3.64). 

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