Synthesis, properties, and applications of novel polyphosphazenes and phosphazene-functionalized polyolefins

This thesis deals with two types of phosphazene containing polymer systems: (1) poly(organophosphazenes), and (2) phosphazene-functionalized polyolefins. In the first example, a number of stable, degradable, and pH-sensitive polyphosphazenes were synthesized for potential use in biomedical applications. In the second example, functionalized polyolefins were synthesized with controlled molecular weights via the ring-opening metathesis polymerization (ROMP) of phosphazene-functionalized cyclic olefins. The ROMP-derived polymers were studied for (a) their ability to promote the conduction of ions, (b) their thermal and flame resistance properties, and (c) their use in polymer electrolyte applications. In addition, a novel graft copolymer system was developed that utilizes coupled ROMP and living cationic polymerization methods.;A wide range of polyphosphazenes were synthesized for prospective use in tissue engineering applications. The polymers were hydrophilic, hydrophobic, amphiphilic, biodegradable, biostable, or contained a combination of these properties. The degradation kinetics of select polymers were evaluated. Cell interactions upon the surfaces of select polymers were also evaluated. The effect of gamma-irradiation on the polymers was studied. Finally, contact angle measurements were carried out to determine the wettability of the polymer surfaces.;Tyrosine-derived polyphosphazenes were synthesized and their hydrolytic stabilities, pH-sensitive behavior, and hydrogel forming capabilities were studied. The tyrosine units were attached to the polymer via the amino group to yield biodegradable polymers, or via the oxygen atom of the phenolic group to yield materials with pH-dependent solubility behavior.;Ring-opening metathesis polymerization (ROMP) of phosphazene functionalized norbornenes was demonstrated with the use of (PCy3)2Cl 2Ru=CHPh as initiator. This allowed the incorporation of a wide range of functionalized cyclic phosphazenes as side groups linked to the organic polymer backbone. The polymers were obtained in moderate yields with the properties being dependent on the side groups attached to the phosphazene moiety and on the molecular weight. When alkyl ether side groups were used, the polymers showed high conductivities when complexed with lithium salts. Conductivities were ∼2--3 orders of magnitude higher at room temperature than commercially available poly(ethylene oxide).