Electrospun Conducting Polymer Rubber Fibres: Synthesis and Applications

Abstract

Conducting polymers are versatile, stimuli responsive materials with many desirable properties. They are easily chemically modified, possess tunable conductivities and are more processable in regards to other conductors. However, there are a few drawbacks that have limited their use, preventing conducting polymers from reaching their full potential. These drawbacks include poor mechanical properties and poor solubility. These two drawbacks make conducting polymers less processable than their conventional polymer counterparts. There are thus numerous methods that are being developed to overcome these limitations and this thesis in part makes use of some of that research and further develops it. One such method is the creation of semi-interpenetrated polymer networks with a conducting polymer as a component and a mechanically superior polymer as another component. Forming semiinterpenetrated polymer networks combines the properties of the polymer components in a synergistic manner, allowing the creation of materials with tailored properties. In this thesis, PEDOT is embedded into a NBR/PEGDM composite forming a semi-interpenetrated polymer network. The NBR adds elasticity and strength to the material while PEDOT’s electroactivity and conductance is maintained. The result is a conducting elastic actuator. This has been done before, however this thesis offers a new method. The novelty of the work discussed in this thesis is how such a material is presented, thus enters electrospinning. Electrospinning is a well-developed technique used to create 3D porous fibre networks with diameters in the range of nanometres to microns. Electrospinning has had many publications and has even entered the commercial space effectively. Electrospinning a rubber however, is much rarer with several complications, particularly involving the loss of fibre formation due to fibre coalescences as a result of the low Tg’s of uncrosslinked rubbers. In this thesis, NBR/PEGDM composites are electrospun. This is achieved through in-situ crosslinking of the rubber during electrospinning through the use of a UV light source and a photoinitiator. These electrospun fibres are then embedded with PEDOT, resulting in a highly porous, flexible, conducting fibre mat. The thesis starts with the establishment of the fabrication and processing steps and the detailed characterisation of the resulting materials. An application of such fibres is then explored, specifically using the conducting fibres as a scaffold for cardiac cell tissue engineering. During the development of this cardiac patch, producing aligned fibres is also demonstrated, with the affects the anisotropy has on the mechanical and electrical properties deliberated. Further enhancements of the fibre mats are then explored with the introduction of poly(acrylic acid) brushes from the fibres surface. These brushes impart hydrophilicity and pH responsiveness and the resulting fibres are then used for a lymphoma DNA sensor with an ultra low detection limit and impressive selectivity. In another example of application for the fibres with poly(acrylic acid) brushes, the fibres are used as a platform to grow and stabilise gold nanoparticles for catalysis purposes. Finally conclusions are drawn and future work and prospects are discussed.