Year

2009

Degree Name

Doctor of Philosophy

Department

Intelligent Polymer Research Institute, Faculty of Engineering

Abstract

Polypyrrole (PPy) as a conducting polymer has potential applications in electrical and electronic devices because of its high electrical conductivity, environmental stability and redox activity. There have been many attempts to endow electrically PPy with processibility. Although some success has been achieved via synthesising soluble PPy, there have remained difficulties to fabricate this material through fibre spinning due to its low molecular weight and poor mechanical properties. Prior to this thesis, there was no report of the production of PPy fibres. This project therefore aimed to produce novel “polypyrrole fibres via the development of nanostructured conducting polypyrrole” by fibre spinning of PPy and to investigate the formed fibres for applications such as actuators, e-textiles, batteries, sensors and biomedical areas. As a result of the research conducted for this thesis, polypyrrole fibres have been produced for the first time. The initial wet-spinning process was enabled by the use of highly soluble non-functionalised PPy using di-(2-ethylhexyl)sulfosuccinate (DEHS) dopant, and the generation of a spinning solution of the PPy-DEHS in dichloroacetic acid (DCAA) solvent. Subsequent work sought to improve the properties of these first generation PPy-DEHS fibres by increasing the molecular weight, addition of carbon nanotubes (CNTs) and addition of a supporting polymer (alginate). The use of the host polymer also enabled a new fibre spinning method to be developed that included an in situ polymerization process. Carbon nanotubes additions were achieved in two ways: firstly by adding small amounts of CNTs to the spinning dope; and secondly, a completely novel approach was developed whereby PPy was polymerized onto and into a CNT yarn. viii Each of the methods used to generate PPy fibres gave different performances in terms of mechanical strength / stiffness; electrical conductivity and electroactivity. Generally, it was found that adding of carbon nanotubes to the PPy improved the strength, stiffness and conductivity. The highest conductivity and Young’s modulus of any conducting polymer based fibre reported to date was obtained by incorporating PPy into a CNT yarn. The more robust fibres were assessed as mechanical actuators and a maximum strain of 2.5% was produced from the high molecular weight PPy-DEHS fibre. In summary, a range of novel fibrous PPy materials have been developed for possible use in applications such as actuators, sensors, artificial muscles, batteries and biomedical applications. The main aim of the thesis was to develop methods for continuous production of doped PPy fibres. This aim was successfully completed with a variety of different fibre compositions and properties demonstrated using a range of different fibre processing methods. ix

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