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The electrospinning of blended polyaniline Nano-fibres and their application in an ion- selective electrode

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Newman, NJ (2007) The electrospinning of blended polyaniline Nano-fibres and their application in an ion- selective electrode. PhD thesis, University of Tasmania.

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Abstract

Polyaniline (PAni) is a conducting polymer that has shown promise in the field of
composite sensors, including ion-selective and biomedical sensors. Sub-micron fibres of
PAni/poly(vinyl chloride) (PVC) and PAni/poly(acrylonitrile) (PAN) have been
electrospun from THF/DMF and DMSO/DMF respectively. Quaternary ammonium
salts (QAS) were incorporated into these polymer blends in an attempt to produce
electrospun solid-state conducting polymer ion-selective electrodes for the detection of
nitrate in aqueous solutions.
The electrospinning process relies on a number of different parameters for successful
fibre production, including solution viscosity, solution surface tension and solution
conductivity. The role of these parameters on the electrospinning of PVC from
THF/DMF solution and PAN from DMSO/DMF solution, both with and without the
addition of PAni and QAS, was studied. In addition to this study, the morphology of the
resultant fibres was determined by Scanning Electron Microscopy (SEM). SEM
morphology and fibre-sizing analysis revealed significant changes in the morphological
properties of the electrospun fibres, including bead formation and alteration of the fibre
diameters with varying solution viscosity, solution surface tension and solution
conductivity. It is believed this is the first time that the influences of the conducting
properties of PAni on these essential electrospinning parameters have been documented.
Electrospun fibrous mats of conducting and non-conducting blends, in addition to
blends incorporating QAS were analysed by Raman spectroscopy to determine the
degree of doping of PAni, the influence of QAS on the chemical properties of the
electrospun fibres and also the degree of dispersion of PAni throughout the electrospun fibres. PAni was found to be relatively well dispersed throughout the underlying fibre
mat. Raman spectra of PAni/PAN electrospun fibres indicated that PAN influenced the
doping of PAni significantly. It produced characteristic peaks similar to those observed
in the ‘secondary doping’ of PAni associated with increases in free-charge carriers and
changes in the PAni chain conformation. This phenomenon also occurred for PAni/PVC
electrospun fibres in the presence of the QAS, tetradodecylammonium bromide (TDAB)
and triallylethylammonium bromide (TAEAB). It is believed that this is the first time
that ‘secondary doping’ of PAni was induced by the normally electro-inactive species
PAN or TDAB. If this is so, it indicates a strong interaction between PAni and these
species which is not based on the use of dopant solvents for ‘secondary doping’.
Mechanical strength measurements of electrospun fibres of these polymer blends were
also carried out, indicating that the support polymer, the degree of orientation and also
the components of the polymer blend significantly influence the tensile strength of these
materials. However the overall tensile strength of these samples was relatively low
compared with literature values for other electrospun fibres.
Cyclic voltammetry (CV) analysis of electrospun composite PAni fibres showed that
PAni retains its electroactivity and produced the characteristic oxidation/reduction
responses expected of PAni. It is believed that this is the first time electrochemical
responses have been recorded for fibres electrospun from PAni/PVC and PAni/PAN
blends. Amperometric responses for nitrate, chloride and tetrafluoroborate were
observed, indicating that whilst these fibre mat electrodes were sensitive to changes in
solution composition, they were not selective towards nitrate in solution, regardless of the QAS employed.

Item Type: Thesis (PhD)
Date Deposited: 24 Jun 2011 00:59
Last Modified: 15 Sep 2017 01:06
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