Development of novel functionalized bis-nitroxide initiators for the preparation of designed polymers

This work focuses on the synthesis and full characterization of a novel bis-N-alkoxyamine for use in nitroxide-mediated radical polymerization. Chapter 1 details the advantages of nitroxide-mediated radical polymerization. A review of existing bi-directional initiators and low-temperature N-alkoxyamines is provided. A brief survey of some of the applications of telechelic polymers includes attachment to surfaces and biomolecules.; Chapter 2 details the synthetic challenges encountered during the synthesis of the bis-N-alkoxyamine. Highlights include a modified Ritter reaction and a thermal rearrangement of a bis-oxaziridine to a bis-nitrone compound. Once synthesized, the polymerization capabilities of this novel bidirectional initiator were explored in Chapter 3. Symmetrical ABA triblock copolymers were easily prepared in an "outside-in" manner. Cleavage experiments that entailed decomposition of the central bis-nitroxide verified bidirectional growth.; During the polymerization studies of the bis-N-alkoxyamine, it was observed that the initiator effected polymerization significantly faster than the parent mono-directional version. This prompted low-temperature polymerization studies as well as an investigation into the kinetic properties of the bis- N-alkoxyamine. With the use of EPR, the kd , EA and A values were determined in Chapter 4. Using 1H NMR kdec was investigated, however the rate of decomposition of the bis-N-alkoxyamine does not follow a first order relationship as alpha-hydrogen nitroxides can undergo two types of decomposition: beta-hydrogen abstraction and disproportionation by single electron transfer. EPR of the bis-nitroxide revealed the existence of a half-field signal indicating an unusually strong spin-spin interaction. This suggests a novel delocalized mono-nitroxide as a key stabilized intermediate during polymerization.; Chapter 5 discusses the development of a number of functionalized mono-directional N-alkoxyamines. In Chapter 6, a yellow fluorescent protein was coupled to a carboxylic acid-functionalized bis-N-alkoxyamine and carried through a polymerization, highlighting the ability to prepare biomolecule/polymer hybrids under mild conditions.