Preparation of soluble poly(phenylenevinylenes) by ring opening metathesis polymerisatioN

• Main Author: Spring, Andrew
• Other Authors: Turner, Michael
• Published: University of Manchester 2010
• Subjects: 547.7
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.520705

This thesis describes the synthesis and characterisation of a selection of ring functionalised cyclophanediene monomers. The strained monomers can be polymerised by ring opening metathesis polymerisation (ROMP) using the third generation Grubbs initiator to yield soluble and narrow polydispersity poly(phenylenevinylene) (PPV) polymers which display an alternating cis-trans microstructure. The Polymers were synthesised by microwave irradiation and the polymerisation method allows a precise control over the molecular weight. The functionalisation of the PPV backbone with solubilising groups enables the polymers to be dissolved in common organic solvents, facilitating both the polymerisation from monomer and the processing of the polymer from solution, which is important for applications such as organic light emitting diodes (OLEDs), organic field effect transistors (OFETs), and organic photovoltaics (OPVs). The electronic properties of the polymer can be tuned by altering the energy gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO). Introduction of electron releasing groups such as alkyl and alkoxy groups result in a narrowing of the energy gap and a red shift in the emission wavelength. Functionalisation with electron withdrawing groups such as cyanide result in an increase of the energy gap and a blue shift in the emission wavelength. Chapter 1 presents an overview of organic semiconducting polymers as well as the aims of the project, whilst chapter 2 describes an in depth study of the synthesis and characterisation of cyclophanediene monomers. Chapter 3 describes the polymerisation of these monomers to yield a range of PPV polymers which are characterised using nuclear magnetic resonance (NMR) spectroscopy and matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF-MS). The energy levels of these polymers is probed using cyclic voltammetry (CV) and ultraviolet-visible (UV-vis) spectroscopy. Chapter 4 presents the conclusions of the project and gives suggestions of how to further advance the results achieved. Finally chapter 5 presents the experimental conditions.