Chan, Man Hon. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references (leaves 141-144). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts also in Chinese.

Semiconducting polymers had been well studied and applied in many research areas. They are such as electroactive actuators, electrochromic materials, microwave-absorbent coatings, polymer solar cells, polymer light-emitting diodes, etc. Traditional semiconductors are metals/oxides and they are expensive, toxic and harmful to the environment. Compared to the traditional n-conjugated main-chain polymers, side-chain conductive polymers have a lower volume percentage of the charge transport moieties yet they possess advantages such as excellent mechanical strength, good rheological properties, solubility in common organic solvents and purer emission hue. Furthermore, the performances of the side-chain semiconducting polymers can be engineered easily by changing their composition or by choosing an appropriate additional polymerization method. As a result, several series of soluble, semiconducting and luminescent side-chain homopolymers and copolymers have been synthesized and characterized. In this thesis, several series of vinyl conductive polymers have been prepared using the facile solution free radical, anionic and atom transfer radical polymerization methods. The novel polymers including the homopolymer P(ADN), two highly soluble homopolymers P(2ADN) and P(3ADQ), two series of ADN moities containing copolymer P(ADN-co-S) and P(ADN-co-VK), a series of pyrene moieties containing copolymer P(PyPA-co-VPy) and two novel amphiphilic BAB-type block copolymers, ADN-PEG3400-ADN and Py-PEG3400-Py which contain blue and greenish-blue fluorescent moieties. The chemistry and physical properties of the intermediates, the resulting polymers were characterized using nuclear magnetic resonance spectroscopy (NMR), matrix-assisted laser desorption ionization time-of-flight mass spectrum (MALDI-TOF MS), fourier-transform infrared spectroscopy (FT-IR), elemental analysis (EA), gel permeation chromatography (GPC), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), UV-Visible spectroscopy (UV-Vis), photoluminescence spectroscopy (PL), cyclic voltammetry (CV), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and fabrication of polymer light-emitting diodes (PLED) and their measurements.

In this study, fluorescent polymers with pendant quinoline groups were synthesized by reversible addition-fragmentation chain transfer polymerization (RAFT) from a fluorescent quinoline-based vinyl monomer, synthesized in multiple steps from p-nitroaniline and crotonaldehyde. The structures of the synthesized vinyl monomer and polymers were confirmed by NMR and FT-IR spectroscopy, X-ray studies and modeling stdies. The photophysical properties of the synthesized quinoline compounds and resulting polymers were investigated. In order to evaluate the binding potential of our quinoline-based polymer in the presence of transition metal ions, preliminary studies on a complexation of quinoline-based polymers with Zn, Cd, Hg, Fe, and Ni were carried out. The investigation of fluorescence properties of the complexes showed fluorescence quenching for Fe(II), and fluorescence enhancement for the remaining ions [Zn(II), Cd(II), Hg(II), and Ni(II)].

Click chemistry is one of the growing areas of research which is applied in the design and synthesis of a wide range of polymeric architectures. This investigation focuses on the synthesis of fluorescent coumarin based polymers by “click” A-B step growth polymerization process and evaluation of their photophysical properties. Non-fluorescent azide-alkyne functionalized coumarin-based monomers were synthesized in multiple steps from 2,4-dihydroxybenzaldehyde in reasonable yields. Polymers with coumarin backbone were synthesized from azide-alkyne functionalized coumarin monomers via the Cu(I) catalyzed 1,3-dipolar cycloaddition reaction between azides and alkynes, a typical click reaction, to form polymers whose repeating units are connected by a 1,2,3-triazole ring. The structures of the synthesized polymers were confirmed by NMR and FT-IR spectroscopy. Finally, the photophysical properties of the synthesized monomers and polymers were evaluated in DMF. All coumarin based monomers showed reduced fluorescent properties due to the quenching effect from the azido group. Although all polymers absorbed at maximum wavelength of 340 nm, a characteristic for coumarin chromophore, the homo-polymers emitted at a shorter wavelength of 413 nm as compared to the co-polymers which emitted at 421 nm.

This research project focuses on the synthesis of fluorescent polymers with pendant triazole-substituted coumarin side chain units. Copper(I)-catalyzed Huisgen’s 1,3-dipolar cycloaddition of alkynes with azides to form a 1,2,3-triazole ring, a typical example of “click” reaction, has been utilized for the synthesis of a novel vinyl monomer, 2-oxo-3-(4- vinyl-1H-1,2,3-triazol-1-yl)-2H-chromen-7-yl acetate 62. The monomer and its precursors were synthesised and characterized using 1D- and 2D-NMR and FT-IR. Coumarin-containing triazole polymers were synthesised using free radical polymerization. Reversible Addition-Fragmentation Chain Transfer (RAFT)-mediated polymerization was used to synthesise well defined coumarin-containing triazole polymers with moderate PDI values. The polymers were characterised using 1H-NMR and FT-IR. Modelling of the monomer precursor 61 and the monomer 62 at DFT level of approximation provided useful insights into possible conformations adopted by the monomer precursor 61 and the monomer 62. The photophysical properties of the novel monomer and the synthesised polymers were investigated in a polar solvent.

No description available.

The use of polymers in electro-optical devices, especially light-emitting diodes (OLEDs), has become very popular in recent years, due to their ease of processability. The major drawback of using polymers in these systems is their time-consuming synthesis when trying to improve upon their physical properties. For example, each time a new color or better conducting properties are desired, a new monomer must be synthesized. To circumvent these problems, the system described in this work is designed to connect the well-known chromophore aluminum tris(8-hydroxyquinoline) (Alq3) to a norbornene monomer unit, followed by polymerization using ring-opening metathesis polymerization (ROMP), thus allowing for the processability of a polymer while maintaining the fluorescent properties of the metalloquinolate. The benefit of this system is that the monomers can be easily altered in order to tune color emission or to enhance the polymer properties. Some of the alterations include changing the metal center from aluminum to zinc in order to improve electron injection, adding substituents to the 8-hydroxyquinoline ligand in order to tune the emission color, and copolymerizing the Alq3-monomer with other norbornene monomers containing either a hole- or an electron-transport material side-chain to improve conductivity. These alterations lead to improved device performance and, more importantly, to a new method of designing polymeric systems for use in electronic devices.

Oligo(ethylene glycol) groups have been used as substituents in poly(p-phenyleneethynylene)s (PPEs) to provide solubility, and to boost quantum yield. Properties such as water-solubility and increased quantum yield in aqueous solution make these conjugated systems promising for biosensory applications. In this thesis, a PPE containing a branched ethylene glycol side chain is synthesized as part of a polymer array for glycan biosensing. I also report that the same side chain can be put to use in a red-emissive polymer to lend water solubility. Another monomeric unit, containing ethylene glycol chains, is incorporated into a PPE to create an ampiphilic polymer. The versatility of these polymers allows them to be used for a variety of purposes, some of which will be described herein.

No description available.

This thesis examines the synthesis, photophysical properties, and sensory responses of hydroxy-substituted 1,4-distyryl-2,5-bis(arylethynyl)benzenes (Cruciforms, XFs). These two-dimensional cross-conjugated materials possess spatially separated frontier molecular orbitals (FMOs). This spatial separation allows the HOMO and LUMO to be addressed independently by analytes, which leads to significant changes in their absorption and emission. These properties allow XFs to be utilized for the detection of various analytes. These studies highlight the benefits of utilizing XFs for the development of advanced functional solid state materials for sensory applications.