Synthetic functionalized biodegradable polymers and their composites with inorganics

The synthesis of a variety of biodegradable polymers incorporating ester and amide functional groups was the main focus of this research. Pendant hydrophilic functional groups were also introduced onto the polymer backbone. The objective here was to introduce cell attachment or nucleation sites on polymer substrates. Thus two major aspects are discussed in this dissertation. The first is the synthesis and characterization of novel biodegradable polymers, and this includes (i) polyureas containing leucine-tyrosine dipeptide linkages by step polymerization; (ii) polyesteramides containing poly(L-lactide) with pendant hydroxy functional groups by ring-opening copolymerization. Through the free hydroxy functional groups of the latter, polyethylene glycol was grafted onto the polyesteramides; and (iii) poly($\varepsilon$-caprolactone) copolymers with pendant phosphonic acid and dimethylphosphoester functional groups by free radical polymerization. Several critical issues are also discussed along with the synthesis of these polymers, viz., (i) preparation and investigation of polyesteramide microparticles with functional groups on the surface of the particles; (ii) a mechanistic study of the free radical ring-opening polymerization of 2-methylene-1,3-dioxepane, in which hydrogen transfer was observed during the polymerization.^ The second important integral aspect of this dissertation was the preparation and characterization of polymer-inorganic composite materials. The polymers are the synthetic poly($\varepsilon$-caprolactone) copolymers with pendant phosphonic acid and dimethylphosphoester groups. The phosphonic acid functional groups were observed to provide nucleation sites for the heterogeneous nucleation of hydroxyapatite. Biodegradability of the polymers was observed during the biomineralization process. In another approach, a polymeric-inorganic composite system with a multi-layered alternating structure of polymer, which has hydrophilic dimethylphosphoester functional groups, and synthetic nanosized hydroxyapatite was accomplished. These composites combining biodegradability and biocompatibility, have potential applications as implant materials.