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Polymerization of Cyclic Lactones at Nucleophilic Surfaces
A large fraction of bone substitute materials currently used to repair bone voids are sourced from two types of human bone. One type is called an autograft, which is often considered the ideal bone repair material. Autografts have low risks of rejection because the graft originated from the patient’s body and is histocompatible. Unfortunately the overall supply of autologous bone is limited, making some surgeries impractical or impossible to perform. Another type is called an allograft. Allograft bone is obtained from humans other than the ones receiving the graft. In many cases, the bone comes from a cadaver. Allografts, although significantly more abundant, have more limitations and lead to less consistent results than the autografts. Recent investigations have focused on using composite materials made from hydroxyapatite (HA) and bioresorbable polymers such as Poly-glycolide (PGA) and Poly-ϵ-caprolactone (PCLA) as potential replacements for autograft and allograft bone. This thesis demonstrates that HA derived from bovine bone can be used to initiate the ring opening polymerization (ROP) of cyclic lactones such as glycolide and ϵ-caprolactone. The kinetics of HA initiated, solvent-free, polymerization of glycolide was studied for the first time using GC-FID. Synthesized nonporous HA and PGA composite materials were found to have compressive strength 2 – 3 greater than that of living human bone and a comparable compressive modulus. Additionally, this thesis describes the preparation of a porous PCLA scaffold that not only mimics the structure of demineralized bone matrix (DBM), but also has mechanical properties superior to that of DMB. Porous PCLA scaffolds were obtained by first using the anorganic bovine bone as a template to shape the PCLA polymer, which than had its HA was etched away to obtain the porous PCLA structure. Finally nanocrystalline HA synthesized by me is not well suited to initiate the ROP of cyclic lactones. Slow rates of reactions are hypothesized to be due to the absence of carbonate substitution that is present in biological bone.
Chemistry|Analytical chemistry|Polymer chemistry
Gauza, Lukasz, "Polymerization of Cyclic Lactones at Nucleophilic Surfaces" (2016). ETD collection for University of Nebraska - Lincoln. AAI10248231.