Polyphosphazenes through the cationic polymerization of phosphoranimines: Telechelic, graft, and block copolymers

• Main Author: Powell, Eric Shawn
• Format: Dissertation
• Language: English
• Published: ProQuest Dissertations & Theses 01-01-2004
• Subjects: Polymer chemistry; Polymers
• ISBN: 9780496899630; 0496899635

The work described in this thesis focuses on the synthesis and characterization of polyphosphazene-based materials for a wide array of applications. The living, cationic polymerization of phosphoranimines was utilized to produce polyphosphazenes with controlled molecular weights and unique architectures. Chapter 2 discusses the synthesis and characterization of mono- and di-telechelic polyphosphazenes through the living, cationic polymerization. Chapter 3 details the synthesis of well-defined graft copolymers through the use of mono-telechelic polyphosphazenes. The next portion (Chapters 4–6) describes the preparation of several block copolymers that contain polyphosphazenes. Appendix A outlines a study that relates bulk properties of poly(fluoroalkoxyphosphazenes) to their chemical structure. Chapter 2 is a detailed synthetic method for the preparation of mono- and di-telechelic polyphosphazenes using the living, cationic polymerization of phosphoranimines. Several alkoxy- and aryloxy-functionalized phosphoranimines were synthesized for use as terminators for the living, cationic polymerization. The structure of the final polymers, as well as the presence of the desired end groups was studied and confirmed through several analytical techniques. Chapter 3 describes the synthesis and characterization of graft copolymers that contain poly(methyl methacrylate) backbones and poly[bis(trifluoroethoxy)phosphazene] grafts. Styrenyl-telechelic polyphosphazenes were prepared, as outlined in Chapter 1, and used as precursors for the graft copolymers. Copolymerization of the polyphosphazenes with methyl methacrylate under free radical conditions yielded graft copolymers, which were examined for the effects of polyphosphazene incorporation on their thermal and optical properties. Chapters 4–6 discuss the synthesis and characterization of hydrophilic and amphiphilic block copolymers that contain polyphosphazenes. Chapter 4 focuses on the thermoresponsive properties of poly[bis(methoxyethoxyethoxy)phosphazene]- block-poly(ethylene oxide) copolymers in aqueous media. The solution behavior of this system was studied and related to the lower critical solution temperature of the corresponding polyphosphazene homopolymer. Chapters 5 and 6 are discussions concerning amphiphilic block copolymers and their abilities to form micelles in aqueous media. The synthesis of polystyrene-block -poly[bis(methoxyethoxyethoxy)phosphazene] copolymers is detailed in Chapter 5. These block copolymers were shown to self-organize in aqueous media to form spherical micelles. Polystyrene-block-poly[bis(potassium carboxylatophenoxy)phosphazene] copolymers were also shown to form spherical micelles in Chapter 6. (Abstract shortened by UMI.)