THE SYNTHESIS OF FUNCTIONAL POLYPHOSPHAZENES AND THEIR SURFACES

The macromolecular substitution approach for the synthesis of polyphos phazenes provides access to many different polymers. However, it precl udes the use of reagents that contain two or more functional groups be cause such compounds would cause extensive crosslinking of the chains. This presents a problem because many of the uses for which polyphosph azenes seem ideally suited require the presence of-OH, -COOH, -NH2, -S O3H, -PR2 and other functional units in the side-chain structure. We h ave developed two approaches to introduce such active sites: (1) prote ction-deprotection reactions; and (2) direct reactions of active reage nts with the organic side-groups of non-functional poly(organophosphaz enes), These methods have been applied both at the molecular level and in the form of reactions carried out only at polymer surfaces. The re sultant polymers have special properties that are valuable in the micr oencapsulation of sensitive biological agents; in the formation of hyd rophobic, hydrophilic, or adhesive surfaces; in crosslinking reactions ; and in the development of solid polymer electrolytes, bio-erodible p olymers, pa-triggered hydrogels, polymer blends and interpenetrating p olymer networks. Overall, more than 700 different polyphosphazenes are now known, and a large number of these are functional macromolecules targeted for specific property combinations and uses. (C) 1998 John Wi ley & Sons, Ltd.