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Nano and micro-fibres can exhibit properties which enhance their performance at certain tasks due to their high surface-to-volume ratio, porosity, and tailorable characteristics. Structuring these fibres into a gradient form, in which one or more of their properties gradually changes over the membrane superstructure, can enhance their performance at certain tasks and grant them the ability to perform new functions. Electrospinning is the most commonly used fabrication method for these materials, but this method has limitations in the rate of material fabrication, the forms it can produce, and the surfaces it can spin fibres on. The aim of this thesis is to investigate the application of an alternative fibre fabrication technique to overcome these limitations and produce new forms of gradient fibre membranes which exhibit novel functions. This is developed by a literature review examining alternative fibre fabrication techniques, the use of fillers to enhance the properties of the membranes, and the form and function of existing functional gradient nanofibres (FGNFs). Solution blow spinning (SBS), an emerging nanofibre fabrication technique which uses blown air to fabricate fibre membranes on a wide range of surfaces, was chosen to fabricate a novel FGNF. Two material pairs were chosen as FGNF candidates. The first pair, poly(vinylidene fluoride) (PVDF)/ graphene oxide (GO), was chosen due to its high performance at multiple functions, in particular its piezoelectric energy harvesting capability. The second pair, poly(methyl methacrylate) (PMMA)/PVDF, was chosen due to the miscibility of the two polymers and their tailorable wettability. To fabricate high performance FGNFs, three separate experiments were performed. The first experiment was designed to reduce the incidence of beads which are pervasive in SBS PVDF membranes, which detrimentally effect the mechanical integrity and morphological homogeneity of the material. This was achieved by adding controlled heating elements to the SBS apparatus to prevent the formation of PVDF microgels, resulting in bead-free SBS PVDF for the first time. In the second experiment a PVDF membrane which contained a GO gradient was fabricated and characterized, resulting in a membrane with a gradient in electroactive crystalline phase. Though the membranes did not exhibit any significant piezoelectric output when spun either via conventional SBS or with an assisting electrostatic field, the material produced is an attractive candidate for wastewater treatment, irradiation protection and membrane antifouling applications. The third experiment investigated the production of a PMMA/PVDF membrane with a gradient in oil and water permeation rates to fractionate a mixture of oil and water. This was achieved by spinning PMMA/PVDF membranes of gradually increasing thickness over an open-sided container, resulting in a FGNF membrane which fractionated oil and water. The ability to fabricate a functional gradient nanofibre membrane on any surface which fibres will form on via SBS presents the potential to fabricate large-scale FGNFs on almost any surface.

Since the turn of the century interest in tissue scaffolds has grown at an ever increasing rate. A tissue scaffold is a structure designed to support an existing tissue when it is damaged, and to facilitate the healing process wherever possible. Hydrogels are an ideal material from which tissue scaffolds are formed, as they are easily processed into a wide array of structures and, with judicious selection of the materials used to form them, can be used to directly stimulate cell growth. Gelatin is used extensively in this work as it is a naturally occurring polypeptide which is both biocompatible and contains the RGD peptide (cell adhesion) motif making it bioactive. The material properties and functionality of hydrogels are affected by both the architecture of the hydrogel, and the structure it is formed into. Three main architectures (molecular arrangement within the hydrogel) are investigated in this thesis: single networks (SNs), interpenetrating networks (IPNs), and inorganic-organic hybrids (IOHs). The structure of the hydrogel refers to the shapes the architectures are formed into, such as fibres or monoliths. Whilst there are numerous shapes, this thesis focuses on micro- and nano-fibres, and the benefits they bring to tissue scaffolds through their large surface area and their cell signalling ability. The work presented in this thesis aimed to develop a range of gelatin based hydrogel micro- and nano-fibres, from which complex tissue scaffolds can be developed. This was achieved through the production of multiple fibre types, including wet spun IPN fibres based on gelatin and alginate, and the solution blow spun IOH fibres from gelatin and silica. For each fibre type characterisation of fibre precursors, intermediary structures (designed to allow simple testing of material properties) and the fibres themselves were carried out. This led to an understanding of the processing parameters and the effect they have on the fibres themselves. In the course of the fibre development a method for functionalising gelatin to allow for photo-crosslinking was also developed to help prevent premature dissolution.

The work embodied in this thesis: • The identification of scalable method for the preparation of graphene from readily available feed stocks currently represents a major challenge which limits the application of this material in device manufacture. The production of supported thin films of pristine graphene is a key objective for a potential solution to this impasse. Here we present a systematic study of amphiphilic graphene dispersing agents, together with a rational approach to their design for use in liquid-phase exfoliation processes. • The development of a robust preparative procedure for the synthesis of a small library of sodium n-(pyren-1-yl)alkyl-1-sulfonates and sodium n-(perylen-3-yl)alkyl-1-sulfonates has been achieved and their utility in the aqueous graphene exfoliation has been investigated. The availability of these materials has enabled a systematic study of the effect of structural features (size of PAH footprint and length of spacer between the PAH and water stabilizing polar substituent) on the exfoliation process to be investigated. In particular the effect of these structural features on monolayer content, lateral flakes size and graphene concentration has been possible. In addition 1-hroxypyrene and 1-(hydroxyl)methypyrene derivatives have been incorporated into polylactides using the ring-opening polymerisation of L-lactide enabling the preparation of submicron-sized fluorescent fibres. These materials are currently being investigated for heir opto-electronic properties. • An investigation into the Scholl dehydrogenative coupling reaction is also presented. This reaction is commonly used in the synthesis of large, polycyclic, aromatic hydrocarbons (PAHs) where we find that hitherto unreported modes of reaction are observed. This investigation sheds light onto the mechanism of this reaction and has also resulted in the synthesis of 2,4,10,12-tetramethoxytetrabenzo[a,cd,h,jk]pyrene, a new scaffold for PAH synthesis. C-H Marder borylation of this material afforded 7,15-bis(4,4',5,5'-tetramethyl-1,3,2-dioxaborolan-2-yl)-2,4,10,12-tetramethoxytetrabenzo [a,cd, h,jk]pyrene which on Suzuki cross-coupling with aryl halides afforded a series of PAHs with tunable electronic properties. Overall, this thesis describes the synthesis and derivatisation of polycyclic aromatic core structures (chrysene, pyrene and perylene) to develop π-functional materials for use as aqueous graphene stabilizing agents and fluorescent markers together with applications in inkjet printing and potential organic electronics.