Carbon nanotube (CNT) polymer composites have attracted much attention since the extraordinary electrical and mechanical properties of CNTs were realised. However research into biomedical applications of CNT/polymer composites has received little attention. The aim of this thesis was to fabricate an electrically conductive, biocompatible polymer based on a poly(ether)urethane (PEU) with multiwalled carbon nanotubes (MWNTs) as the conductive filler. Paramount to achieving this was to obtain good dispersion and integration of MWNTs within the host polymer matrix. A number of different strategies were investigated including high energy mixing of MWNTs in PEU and covalent functionalisation of MWNTs with long chain hydrocarbons, poly(tetramethylene oxide) (PTMO) and poly(acrylic acid) (pAA) for enhanced miscibility with PEU. The impact of these strategies was assessed by testing the tensile properties, electrical conductivity as well as cytotoxicity of resulting MWNT/PEU composites. It was found that high energy mixing in the presence of MWNTs caused severe degradation of PEU, resulting in significant cytotoxicity and reductions in composite tensile strength. Covalent functionalisation of MWNTs was achieved by utilising defect group chemistry to attach a range of molecules. PTMO covalently attached to MWNTs was found to cause significant nanotube aggregation in PEU composites. Long chain hydrocarbons covalently attached to MWNTs exhibited enhanced dispersability in PEU with increasing molecular weight, attributed to disrupting intertube Van der Waals forces and providing favourable hydrophobic interactions with PEU. Additionally these composites exhibited increased conductivity and decreased cytotoxicity with increasing hydrocarbon length. However increasing long chain hydrocarbon molecular weight also caused significant reductions in MWNT conductivity. MWNTs surface modified with carboxylic acid groups exhibited favourable hydrophilic interactions with PEU but did not retain tensile properties at nanotube loadings where electrical conductivity was significant. Successful polymerisation of acrylic acid monomer initiated from MWNTs using a reversible addition-fragmentation chain transfer polymerisation was demonstrated. Resulting pAA-MWNTs exhibited enhanced dispersability in water but not in PEU composites, resulting in severe degradation in composite tensile properties. PAA-MWNTs also exhibited decreased conductivity with increasing pAA molecular weight. Incorporating MWNTs in PEU composites has been demonstrated to impart multi-functionality to existing biomaterials for potential uses in a range of biomedical applications.
| Identifer | oai:union.ndltd.org:ADTP/187541 |
| Date | January 2008 |
| Creators | Williams, Charles, Graduate School of Biomedical Engineering, Faculty of Engineering, UNSW |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
| Rights | http://unsworks.unsw.edu.au/copyright, http://unsworks.unsw.edu.au/copyright |
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