Generation of structural diversity in polyphosphazenes

Polyphosphazenes are macromolecules with a chain of alternating phosphorus and nitrogen atoms and with two (usually) organic side groups linked to each phosphorus. Although the earliest poly(organophosphazenes) were essentially linear polymers each bearing only one type of side group along the chain, research in our program in recent years has widened the scope to include mixed-substituent polymers with two or more different side groups, block copolymers, comb structures, stars, and dendrimers, all with a wide variety of different properties. In addition, supramolecular systems have also been synthesized including vesicles, microspheres, and a variety of composite systems. This review provides a summary of these developments together with an introduction to the widening array of developing uses.