Development of phosphazene-based materials for advanced applications

In Chapter 2, the synthesis of a new type of cyclolinear polymer, poly(phenylene vinylene-alt-cyclotriphosphazenes), is described. The synthesis occurs through a Heck-type coupling reactions to produce pi-conjugated macromolecules with excellent solubility and precise electronic control of the band gap energy. The resulting polymers are also capable of accommodating a wide variety of substituents on the cyclophosphazene rings with minimal effect on the electronic properties. The band-gap and electron affinities of the polymer were varied through the manipulation of the pi-conjugated unit located between the insulating phosphazene rings. Each chromophore matched the intended conjugation length consistently throughout the macromolecules. The polymers were good film-formers due to the chosen substituents on the phosphazene rings. The absorbance of the polymers indicated minimal spectral shift from the monomer absorbance. This suggests an effective insulation of each chromophore unit from it neighbors by the phosphazene rings. Solution photoluminescent efficiencies were found to be up to 44.1%.In Chapter 3, a new inorganic-organic macromolecular intermediate, poly(mono(5-norbornene-2-methoxy)pentachlorocyclotriphosphazene), is reported that is capable of being polymerized without halogen replacement on the phosphazene. It was found that ring opening metathesis polymerization occurs without initiator deactivation even in the presence of highly reactive phosphorus-chlorine bonds. This route can be utilized as a valuable one-pot synthesis to produce a variety of polymer architectures such as, diblock, multiblock, star, comb, and linear polymers. The ability to substitute after polymerization avoids any steric or polarity effects of the side groups on ring opening metathesis polymerization. This polymer intermediate is also capable of long-term storage in solution without significant degradation. Chapter 3 also illustrates three macromolecular products from the same "living" intermediate.In Chapter 4, three polymer systems were investigated in an attempt to produce lithium ion conductive polymers that resist the absorption of water. All were synthesized via ring opening metathesis polymerization (ROMP) to give a polynorbornene backbone with each repeat unit bearing a pendent cyclotriphosphazene ring. Each pendent inorganic ring carried either hydrophilic, ion conductive 2-(2-methoxyethoxy)ethoxy (MEE) and/or hydrophobic 2,2,2-trifluoroethoxy (TFE) side groups. The three systems were (a) composite blends of two polymers with all hydrophobic and all lithium ion conductive side groups, (b) homopolymers in which each polymer repeating unit bore both hydrophobic and ion conductive side groups, or (c) copolymers derived from two monomers one of which bore only hydrophobic side groups and the other with all ion conductive groups. Room temperature (25° C) ionic conductivities were measured by incorporating 7 mole % LiBF4 in each system. Hydrophobicity was estimated from water contact angles of the polymeric materials with and without LiBF 4. One of the homopolymer systems with two MEE and three TFE groups on every side group generated conductivities in the range of 1.2 x 10 -5 S/cm at 25° C in combination with a semi-hydrophobic surface with a water contact angle of 77.7°. The conductivity of this polymer was close to that of the highly hydrophilic, water soluble poly[bis(2-(2-methoxyethoxy)ethoxy)phosphazene] (MEEP) which is one of the most conductive solid polymer electrolytes (2.7 x 10-5 S/cm at 25° C).In Appendix A, the development of a biodegradable shape memory polymer is described. A novel shape memory material is described that has controllable degradation, transition temperature, and does not require physical crosslinks. A unique hydrogen bonding mechanism in poly(di(amino acid)phosphazene) provides a significant advantage over typical shape memory polymers. In the phosphazene-based materials, the permanent shape can be reprogrammed. These materials were found to have an unusually quick response time because of the unique mechanism. These materials are thought to be ideal for medical implants such as cardiac stents. Other applications may include: internal stitches that self-tighten, shrink-wrap, tightening band-aids, bone securing devices, thermal responsive applications, and automotive applications.In Appendix B work is focused towards the development of a blue emitting, electroluminescent phosphazene-based polymer. In this work two chromophores were synthesized and polymerized through a Heck-coupling reaction. This polymerization produced a perfectly alternating polymer capable of high-energy emission, along with a controllable band gap. The polymers formed were soluble in common organic solvents due to the substitution on the cyclotriphosphazene ring. This work showed that the cyclotriphosphazene could indeed be used to break the conjugation of even high energy chromophores to produce a blue emitting polymer.Appendix C is synthetic work towards the development of a 15 A diameter tunnel. This work focused first on the synthesis of tris(o-anthracenedioxy)phosphazene, then the formation of a single crystal. This single crystal would be utilized to investigate the inclusion behavior of polymers. The synthetic work is presented in this appendix, although the crystallization is ongoing. (Abstract shortened by UMI.)...