Polyphosphazenes via the living cationic condensation polymerization of halophosphoranimines

This thesis investigates a new synthetic route to polyphosphazenes. Polyphosphazenes represent a broad class of polymers based on a flexible inorganic backbone with many possible side-group substituents. The inorganic-organic polymers were synthesized through the cationic condensation polymerization of halophosphoranimines at ambient temperatures. An advantage of the new route is that polymers with controlled molecular weights and low polydispersities are produced. Other synthetic routes to polyphosphazenes have utilized thermal polymerizations, which offer little control over the molecular weight resulting in polymers with large polydispersities. The polymers synthesized via the new route contained halogen side groups, which allowed the polymers to be tailored by macromolecular substitution to produce air-stable derivative polymers. Furthermore, the living active sites at the polymer chains ends allow for many different reactions such as end-functionalization and copolymerization. Thus, polyphosphazenes with controlled architectures were synthesized through the new route.Four major synthetic directions are the subject of this thesis: (1) the synthesis and polymerization of trichlorophosphoranimine, (2) the synthesis and polymerization of organophosphoranimines, (3) the formation of phosphazene block copolymers via phosphoranimines, and (4) the synthesis of organic-phosphazene block copolymers via organic end-functionalized polymers. Monomers were synthesized with halogeno and/or organo groups such as methyl, ethyl, and phenyl. The phosphoranimine polymerizations produced living polymers with controlled molecular weights up to 3 x 105, based on the monomer to initiator ratios, and low polydispersities (<1.3). Electron-withdrawing, electron-donating, and sterically bulky side groups dramatically affected the solution polymerizations of the organophosphoranimines. Sequential copolymerization of phosphoranimines: produced phosphazene block copolymers, but the direct polymerization of carbocation monomers with phosphoranimines did not produce organic-phosphazene block copolymers. Instead, alcohol-, amine-, and phosphine-terminated organic polymers were used as precursors for phosphoranimine polymerizations to produce organic-phosphazene block copolymers.