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Queen Mary University of LondonQueen Mary University of London
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School of Engineering and Materials Science
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PhD Thesis: Synthesis and Novel Processing of Polyurethanes

Author: AHMAD, Zeeshan

Year: 2007

Supervisor(s): Ihtesham Rehman

This study focuses on a class of polymeric material, polyurethanes, and then to prepare a novel material through novel synthesis routes and electro-spinning, for fabricating porous structures from polyurethanes.

A selection of polyurethanes were synthesised using the two step solvent polymerisation methods without the use of a catalyst, as catalysts can cause premature degradation of the polymeric chain and act as fungicides within the biological environment. Characterisation was performed using Fourier Transform Infrared (FT-IR), Fourier Transform Raman (FT-Raman)/Raman, Differential Scanning Calorimetry (DSC) and Gel Permeation Chromatography (GPC). Degradation profile of the polymers was assessed through simple hydrolytic degradation and tensile properties of the materials were also evaluated.

A scaffold material was obtained by using Agar as a soft segment, as their hydrolysis ratio can be varied by changing the hard and soft segments of the resulting polyurethane. Agar has a number of hydroxyl groups within its structure and provides sufficient reaction sites for the isocyanate to react and form urethane linkages. The ratios of reactants were varied and the reaction conditions optimised. A series of co-polymers were also synthesised with Agar molecule.

A selection of the polymers prepared from the first section was electrospun to form scaffolds. Prior to electrospinning, polymers were assessed for pH, relative permittivity, viscosity, surface tension, conductivity and density to ascertain the properties of polymers that are required for the electrospinning process. Highly porous polymeric scaffold materials were obtained, which were analysed under the optical microscope and the scanning electron microscope (SEM).