Characterizing electroactive polymer films : from fundamentals to fingerprints

Abstract

Visualisation of latent fingerprints present on metallic surfaces has been demonstrated by means of spatially selective deposition of conducting copolymers. This novel technique utilises the inhibition of electrochemical processes on areas that have been masked by the fingerprint. This results in electropolymerisation between the ridges, generating a negative image of the fingerprint. The efficiency of recovery in forensically challenging scenarios of the copolymers was compared with the corresponding homopolymers. An extension of this electrochromic enhancement to include fluorescence has been developed using a novel synthetic pathway aiming to create more free volume to aid the inclusion of bulky fluorophore moieties. The unique selectivity of neutron reflectivity (NR), with isotopic contrast variation, permitted the diagnosis of chemical and structural changes within the depth profile of the polymer during the incorporation of the fluorophore moieties. The properties of conducting polymer films are determined by film composition and structure which, this thesis will show, can lead to different routes to electroneutrality maintenance during electrochemically controlled redox switching (doping/undoping). NR was used to quantify the diverse permeation characteristics of conventional solvents and ionic liquids into an electroactive copolymer. It revealed how the availabilities of these mechanisms are dictated by anion and cation sources and sinks in the film and liquid phases where molecular solvent is/is not present. In multi-layered systems, the nature of the polymer/polymer interface is central to the rectifying (segregated) or capacitive (interdiffused) characteristics of the films, such that the spatial distribution of the different polymer components determines the optical and electronic properties of the films. These properties are important for the potential applications of these multi-component systems in energy storage. NR was used to probe the extent of segregation and solvation properties of multi-layer films and revealed the order the components are deposited has a great effect on the final film properties