Phosphonated Polymers for Nanofibrous Tissue Scaffolds

This thesis, entitled “Phosphonated polymers for nanofibrous tissue scaffolds”, was written by Peter James Youle at the University of Manchester for the degree of Doctor of Philosophy and was submitted in 2016. The work contained within concerns itself with the synthesis and characterisation of phosphonated polymers intended for application as nanofibrous tissue scaffolds for improving the healing of bone; it is based on previous work performed in the University of Manchester that identified poly(ε-caprolactone) (PCL) nanofibres coated with poly(vinylphosphonic acid-co-acrylic acid) (PVPA-co-AA) as a promising material for enhancing bone healing. This thesis initially focuses on the characterisation of a commercially sourced PVPA-co-AA by defining its composition and molar mass using quantitative 31P NMR and aqueous gel permeation chromatography. A method of synthesising the copolymer by free radical polymerization, with controlled rates of monomer addition, was developed to produce PVPA-co-AA copolymers with a range of compositions. Additionally, nanofibres of PVPA-co-AA were then formed by electrospinning and crosslinked with ethylene glycol; the subsequent nanofibres were found to be water stable and retain their structure after hydration and subsequent drying. A block copolymer, polycaprolactone-b-poly(acrylic acid) (PCL-b-PAA), was synthesised by four-step ATRP and two-step NMP based approaches, with the block character of the resulting copolymer being demonstrated by GPC and dynamic light scattering. The PCL-b-PAA was subsequently used as a compatibiliser for PCL and PVPA-co-AA emulsions, which were used to create composite nanofibres by electrospinning. These nanofibre were in turn characterized by scanning electron microscopy and compared to nanofibres formed using a surfactant, Span® 80, and the original dip-coated nanofibres. Finally, a small portion of work was undertaken to develop phosphonated PCL analogues, by attempting to synthesise phosphonated ε-caprolactone monomers.