Working towards a New Sustainable Rechargeable Battery; Zinc, Conducting Polymer and Deep Eutectic Solvent System

Electronically conducting polymers based on functionalised thiophenes and pyrroles have continued to stimulate academic interest as well as starting to be employed in practical applications and uses. This thesis describes studies of the electronic properties of mixed thiophene-pyrrole polymers (based on custom synthesised mixed monomer precursors) and polymers electrodeposited from commercially available monomers, pyrrole and 3,4-ethylenedioxythiophene, in respect to energy storage applications including batteries and ion selective membranes. In such applications the movement of ion and solvent through the polymer film during oxidation and reduction cycles is critical to application and function, e.g. charging rate, metal ion permeability or adhesion stability. Recently the unexpected behaviour of polypyrrole in choline chloride based ionic liquids has been described. These liquids are especially attractive because of their unique solubility profiles, high stability, low volatility and low toxicity. This thesis describes the electrochemical characterisation, DC capacitance behaviour and ion / solvent transport properties of conducting polymers using a range of electrochemical methodologies in combination with acoustic impedance electrochemical quartz crystal microbalance techniques (EQCM) and X-Ray Photo-electron Spectroscopy (XPS). The behaviour of several mixed thiophene-pyrrole films, polypyrrole and poly 3,4-ethylenedioxythiophene in different electrolyte media; deep eutectic solvents (DESs), conventional organic solvents and aqueous media are contrasted in this thesis. PEDOT and one of the mixed thiophene-pyrrole polymers (poly 2-(thiophene-2-yl)-1H pyrrole) gave the highest DC capacitances of the polymers investigated, with high values observed in both choline chloride based (Type III) and zinc based (Type IV) DESs. The ion dynamics of the polymers p-doping in the DESs, observed to fit gravimetric data recorded, was able to show a marked difference in the ion transfers between DES types and a conventional organic solvent, acetonitrile. Both polymers in acetonitrile and the zinc based DES (ZnCl2 / EG) satisfied the electro-neutrality condition through dominance of anion transfers. Whereas, polymers in the choline chloride based DES (Ethaline) satisfied the electro-neutrality condition through dominance of choline cation transfers (in the opposite direction to anion transfers). This research involved work towards the development of a new class of rechargeable batteries based on a Zinc-Polymer system incorporating a novel, inexpensive, environmentally sustainable solvent. This work is necessitated by the problems associated with petrol and diesel powered vehicles and the limitations of batteries available for electric vehicles

Nanoscale control of interfacial processes for latent fingerprint enhancement

Latent fingerprints on metal surfaces may be visualized by exploiting the insulating characteristics of the fingerprint deposit as a “mask” to direct electrodeposition of an electroactive polymer to the bare metal between the fingerprint ridges. This approach is complementary to most latent fingerprint enhancement methods, which involve physical or chemical interaction with the fingerprint residue. It has the advantages of sensitivity (a nanoscale residue can block electron transfer) and, using a suitable polymer, optimization of visual contrast. This study extends the concept in two significant respects. First, it explores the feasibility of combining observation based on optical absorption with observation based on fluorescence. Second, it extends the methodology to materials (here, polypyrrole) that may undergo post-deposition substitution chemistry, here binding of a fluorophore whose size and geometry preclude direct polymerization of the functionalised monomer. The scenario involves a lateral spatial image (the whole fingerprint, first level detail) at the centimetre scale, with identification features (minutiae, second level detail) at the 100–200 μm scale and finer features (third level detail) at the 10–50 μm scale. However, the strategy used requires vertical spatial control of the (electro)chemistry at the 10–100 nm scale. We show that this can be accomplished by polymerization of pyrrole functionalised with a good leaving group, ester-bound FMOC, which can be hydrolysed and eluted from the deposited polymer to generate solvent “voids”. Overall the “void” volume and the resulting effect on polymer dynamics facilitate entry and amide bonding of Dylight 649 NHS ester, a large fluorophore. FTIR spectra demonstrate the spatially integrated compositional changes. Both the hydrolysis and fluorophore functionalization were followed using neutron reflectivity to determine vertical spatial composition variations, which control image development in the lateral direction