Year

2010

Degree Name

Doctor of Philosophy

Department

University of Wollongong. School of Chemistry

Abstract

The production of conducting composite fibres via wet-spinning is studied in this thesis. The main objectives pursued are (1) to develop the knowledge and understanding of such materials, (2) to create new composites based on biopolymers or synthetic polymers and conducting materials such as carbon nanotubes (CNTs) or conducting polymers (CPs) for possible use in medical and bionic applications and (3) study the effects of pre- and post- processing parameters on the electrical and mechanical characteristics of the composite fibres.

Two wet-processing techniques are used to produce composite fibres, i.e. polyelectrolyte complexation and solvent / non-solvent wet spinning. These methodologies are adapted for the fabrication of electrically conducting composite fibres by incorporating conducting fillers such as CP and CNTs.

Fibres made of gellan gum or carrageenan combined with chitosan can be produced using polyelectrolyte complexation. The mechanical properties of these fibres are found to be influenced by processing conditions such as polyelectrolyte pH as well as the order in which the anionic and cationic biopolymer solutions are added. Using a facile method for mechanical reinforcement fibres, consisting on wetting the fibres and let them dry under tension, results in increased Young’s modulus, tensile strength, and toughness. Nevertheless, the ability to spin fibres is found to be dependent on the sonolysis regime (conditions employed to disperse CNT).

The addition of CNT to spinning solution improves the conductivity of fibres by up to 6 orders of magnitude and, typically, it also results in mechanical reinforcement.

Stretchable composite fibres based on poly (styrene-ß-isobutylene-ß-styrene) are produced via solvent / non-solvent wet spinning. Conducting fibres are produced by incorporating conducting fillers such as CNTs or CP. In all cases fibres can be stretched above 700% and some instances reaching up to almost 1200% of their original length. In addition, these composite fibres show interesting reversible electrical properties.

In summary, the work developed in this thesis increases the knowledge available in wet-spinning techniques (including pre- and postprocessing) in addition to produce new composite materials which may lead to exciting new applications in tissue engineering or bionic applications, such as flexible stretchable electrodes for cell stimulation or as neural prosthetic electrodes.

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