Conjugated polymers for sensing biologically relevant molecules.

PhD Theses.The ability to detect and quantify biological molecules with specificity is of critical importance due to the many health problems that can arise from their dysregulation; deviation from a normal concentration of sodium can affect blood pressure, nerve impulses, and muscle control, while the continuous monitoring of glucose levels is vital to the management of diabetes mellitus. This thesis explores the development of covalently modified organic semiconductors which may be used to this effect. Chapter 2 discusses the relative merits and drawbacks of poly(3,4-ethylenedioxythiophene) (PEDOT) in the context of biological sensing, and presents the development of a novel PEDOT-based material functionalised with pendant 15-crown-5 moieties. PEDOT-Crown is demonstrated to improve upon many of the disadvantages associated with PEDOT, including substrate adhesion, control of surface morphology, stability to physical duress, and electrochemical behaviour, with an additional preliminary response to Na+ observed in long-term electrochromic experiments. Chapter 3 explores the synthetic strategy behind the creation of a boronic-acid functionalised PEDOT species, PEDOT-B(OH)2, and the subsequent optimisation of its deposition alongside novel bis-EDOT linkers, to use this material in a molecularly imprinted polymer to sense glucose. Chapter 4 applies the successes from the previous Chapters to present analogous materials based on dithienopyrrole (DTP), a monomer whose synthetic adaptability overcomes many of the known difficulties associated with EDOT modification. Corresponding analyte-binding DTP monomers featuring 15-crown-5 and boronic acids are synthesised alongside a bridged bis-DTP linker, and investigations into the polymerisation of these materials is conducted. Finally, Chapter 5 presents a range of relevant small molecules associated with the development of conjugated systems for biological sensing, including carboxylic acid functionalised EDOT and DTP analogues, applied to improve polymer adhesion to ITO-glass substrates; and pyrene and naphthalene/perylene diimide species modified with 15-crown-5, to open the door to ion sensing in a range of alternative device types