Phosphazenes are molecules containing a skeleton of alternating phosphorus and nitrogen atoms.  They can be joined together to make long chains or rings called polymers, some containing thousands of repeating segments linked end-to-end.  The polymer backbone can be designed according to the physical requirements of the application.  For example, linear high-molecular weight chains, block copolymers, organic-inorganic hybrid polymers, star, micelle and numerous other architectures are used for non-linear optics, controlled-drug delivery, biostability, bioerosion, high-performance elastomers and electronically conductive polymers have been synthesized at a major research university. Some examples are illustrated below.