published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

Chan Siu Wai = 利用二次諧波比較應用在非線性光學聚合材料上不同的極化技術 / 陳兆偉. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2003. / Includes bibliographical references (leaves 105-106). / Text in English; abstracts in English and Chinese. / Chan Siu Wai = Li yong er ci xie bo bi jiao ying yong zai fei xian xing guang xue ju he cai liao shang bu tong de ji hua ji shu / Chen Zhaowei. / Anknowledgements --- p.ii / Abstract --- p.iii / Chinese Abstract --- p.iv / List of figures --- p.v / Contents --- p.ix / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Formulation of nonlinear optics --- p.2 / Chapter 1.2 --- Relationship between microscopic and macroscopic nonlinear susceptibility for a poled polymer --- p.4 / Chapter 1.3 --- Generation of electromagnetic radiation by nonlinear polarization --- p.7 / Figure --- p.9 / Chapter Chapter 2 --- Poling of NLO polymer --- p.10 / Chapter 2.1 --- Doped NLO polymeric system --- p.10 / Chapter 2.2 --- Poling techniques --- p.13 / Chapter 2.2.1 --- Thermal´ؤassisted poling (TAP) --- p.14 / Chapter 2.2.2 --- Photoassisted poling (PAP) --- p.16 / Chapter 2.2.3 --- All-optical poling (AOP) --- p.20 / Chapter 2.3 --- Relaxation studies of poled NLO polymers --- p.22 / Figures --- p.26 / Chapter Chapter 3 --- Experimental methods --- p.32 / Chapter 3.1 --- Laser system --- p.32 / Chapter 3.2 --- Detection system --- p.33 / Chapter 3.3 --- Reference arm --- p.33 / Chapter 3.4 --- Experimental setup --- p.34 / Chapter 3.5 --- Samples preparation --- p.35 / Figures --- p.37 / Chapter Chapter 4 --- Growth and decay of optical nonlinearity In poled polymer --- p.42 / Chapter 4.1 --- Reliability and validity of the data acquisition procedures --- p.42 / Chapter 4.1.1 --- Temperature calibration and the voltage supply --- p.42 / Chapter 4.1.2 --- Possibilities of damage or degradation of the samples during the experiment --- p.43 / Chapter 4.1.3 --- Effect of probing beam intensity and the duration on the growth and decay of x(2) in A〇P --- p.44 / Chapter 4.2 --- Basic features of the different poling techniques --- p.45 / Chapter 4.2.1 --- Below Tg electric poling (EP) in the glassy state --- p.45 / Chapter 4.2.2 --- Thermal assisted poling (TAP) --- p.47 / Chapter 4.2.3 --- Photoassisted poling (PAP) in the glassy state --- p.49 / Chapter 4.2.3.1 --- Effects of polarization of the pumping light on photoinduced poling --- p.50 / Chapter 4.2.3.2 --- Comparison of photoassisted poling at 50°C and 75°C --- p.51 / Chapter 4.2.3.3 --- Can photoassisted poling work on DANS/PMMA sample? --- p.52 / Chapter 4.2.4 --- All-optical poling (AOP) in the glassy state --- p.53 / Chapter 4.3 --- Comparison of the relaxation of X(2) poled by the four poling techniques --- p.54 / Chapter 4.3.1 --- Methods in defining the relaxation curves --- p.54 / Chapter 4.3.2 --- "X(2) relaxation of DR-1/PMMA sample poled by EP, TAP, PAP and AOP" --- p.55 / Chapter 4.3.3 --- Comparison of the fitting of the relaxation data by different models --- p.57 / Figures --- p.59 / Chapter Chapter 5 --- Physical aging and its effect on the Poling stability --- p.73 / Chapter 5.1 --- Aging effect of samples poled by EP --- p.73 / Chapter 5.2 --- Aging effect of samples poled by TAP --- p.74 / Chapter 5.3 --- Aging effect of samples poled by PAP --- p.75 / Figures --- p.78 / Chapter Chapter 6 --- Results and discussions on other Observations --- p.86 / Chapter 6.1 --- Poling with TAP and PAP successively --- p.86 / Chapter 6.2 --- Secondary poling of EP/TAP processed NLO polymer --- p.88 / Chapter 6.3 --- Effect of a pumping green light on NLO polymer (DR-1/PMMA) in the glassy state --- p.90 / Chapter 6.4 --- Depoling effect by a pumping green light --- p.91 / Figures --- p.93 / Chapter Chapter 7 --- Conclusions --- p.102 / References --- p.105

by Chan Sung-Chun = 具有二階非線性光學性質的主體-客體多聚物系統中的載色體的動力學研究 / 陳崇真. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2004. / Includes bibliographical references (leaves 107-109). / Text in English; abstracts in English and Chinese. / by Chan Sung-chun = Ju you er jie fei xian xing guang xue xing zhi de zhu ti--ke ti duo ju wu xi tong zhong de zai se ti de dong li xue yan jiu / Chen Chongzhen / Acknowledgements --- p.ii / Abstract --- p.iii / Chinese Abstract --- p.iv / Table of Contents --- p.v / List of Figures --- p.viii / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Interaction of light with a medium --- p.2 / Chapter 1.2 --- Tensor properties and Inversion symmetry --- p.3 / Chapter 1.3 --- Relationship between microscopic and macroscopic nonlinear susceptibility for a poled polymer --- p.5 / Chapter 1.4 --- Second Harmonic Generation by nonlinear polarization --- p.9 / Chapter 1.5 --- Outline of this thesis --- p.11 / Figures --- p.13 / Chapter Chapter 2 --- Poling and relaxation of Nonlinear Optical Polymeric systems --- p.14 / Chapter 2.1 --- Guest-Host nonlinear optical polymeric systems --- p.14 / Chapter 2.2 --- Poling of NLOP systems --- p.16 / Chapter 2.2.1 --- Thermal-assisted Electric Poling --- p.17 / Chapter 2.2.2 --- Photo-assisted Electric Poling --- p.19 / Chapter 2.2.3 --- All-Optical Poling --- p.22 / Chapter 2.3 --- Relaxation study of NLOP systems --- p.24 / Figures --- p.29 / Chapter Chapter 3 --- Experimental Method --- p.32 / Chapter 3.1 --- Sample Preparation --- p.32 / Chapter 3.2 --- Poling and Thermal history of samples --- p.35 / Chapter 3.3 --- Experimental Setup --- p.37 / Chapter 3.3.1 --- Laser system --- p.37 / Chapter 3.3.2 --- Data acquisition system --- p.37 / Chapter 3.3.3 --- Reference arm --- p.38 / Chapter 3.3.4 --- Optical Path --- p.39 / Figures --- p.43 / Chapter Chapter 4 --- Poling and relaxation studies of second order optical nonlinearity in a guest-host system --- p.50 / Chapter 4.1 --- Reliability and Reproducibility of the experimental result --- p.50 / Chapter 4.1.1 --- Temperature control --- p.50 / Chapter 4.1.2 --- Poling voltage --- p.51 / Chapter 4.1.3 --- Degradation of the sample --- p.52 / Chapter 4.1.4 --- Possible light induced decay by the probing laser beam --- p.53 / Chapter 4.2 --- Poling and relaxation in the Guest-Host system of DR-1/PMMA --- p.54 / Chapter 4.2.1 --- Poling in DR-l/PMMA --- p.54 / Chapter 4.2.2 --- Relaxation of polar orderin DR-l/PMMA --- p.58 / Chapter 4.3 --- Comparison of different relaxation models --- p.60 / Figures --- p.61 / Chapter Chapter 5 --- Investigation of chromophores dynamicsin poled nonlinear optical polymers by secondary poling --- p.69 / Chapter 5.1 --- Methods for studying the mobility of chromophores at sub-Tg temperature --- p.69 / Chapter 5.2 --- Experimental details --- p.71 / Chapter 5.3 --- Experimental results and discussion --- p.72 / Chapter 5.3.1 --- Free relaxation of chromophores --- p.72 / Chapter 5.3.2 --- Forced decay and further poling of chromophores --- p.73 / Chapter 5.4 --- Model for describing the temporal behavior of secondary poling --- p.76 / Chapter 5.4.1 --- Derivation of the model --- p.76 / Chapter 5.4.2 --- Quantitative description of the experimental results --- p.79 / Figures --- p.83 / Chapter Chapter 6 --- Results and observations on Photo-assisted electric poling --- p.89 / Chapter 6.1 --- Re-poling of the sample after PAP --- p.89 / Chapter 6.2 --- Other observations on Photo-assisted electric poling --- p.92 / Figures --- p.96 / Chapter Chapter 7 --- Conclusions --- p.103 / References --- p.107

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Choy Kwok Wai = 利用全光極化在本體聚合物中產生準相匹配二次諧波 / 蔡國偉. / Thesis submitted in: August 2005. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references (leaves 132-133). / Text in English; abstracts in English and Chinese. / Choy Kwok Wai = Li yong quan guang ji hua zai ben ti ju he wu zhong chan sheng zhun xiang pi pei er ci xie bo / Cai Guowei. / Acknowledgements --- p.ii / Abstract --- p.iii / Chinese Abstract --- p.V / Table of Contents --- p.vi / List of Figures --- p.ix / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Principle and origin of nonlinear optics --- p.2 / Chapter 1.2 --- Tensor properties and Inversion symmetry --- p.3 / Chapter 1.3 --- Relationship between microscopic and macroscopic nonlinear susceptibility for a poled polymer --- p.5 / Chapter 1.4 --- Second Harmonic Generation by nonlinear polarization --- p.7 / Chapter 1.5 --- Outline of the thesis --- p.9 / Figures --- p.10 / Chapter Chapter 2 --- Poling and relaxation of nonlinear optical polymeric systems --- p.11 / Chapter 2.1 --- Guest-Host nonlinear optical polymeric systems --- p.11 / Chapter 2.2 --- Poling techniques --- p.13 / Chapter 2.2.1 --- Thermal-assisted Electric Poling --- p.13 / Chapter 2.2.2 --- Photo-assisted Electric Poling --- p.15 / Chapter 2.2.3 --- All-optical Poling --- p.17 / Chapter 2.3 --- Quasi-phase-matching in bulk polymers by All-optical Poling --- p.20 / Chapter 2.4 --- Photorefractive effect in polymers --- p.22 / Chapter 2.5 --- Relaxation study of NLOP system --- p.23 / Figures --- p.27 / Chapter Chapter 3 --- Experimental Method --- p.33 / Chapter 3.1 --- Experimental Setup --- p.33 / Chapter 3.1.1 --- Laser system --- p.33 / Chapter 3.1.2 --- Data acquisition system --- p.34 / Chapter 3.1.3 --- Reference arm --- p.34 / Chapter 3.1.4 --- Optical Path --- p.35 / Chapter 3.2 --- Sample Preparation --- p.36 / Chapter 3.2.1 --- Polymer Films Preparation --- p.36 / Chapter 3.2.2 --- Bulk Polymers Preparation --- p.38 / Chapter 3.3 --- Poling and Thermal history of samples --- p.41 / Figures --- p.43 / Chapter Chapter 4 --- Growth and decay of optical nonlinearity in all-optically poled polymers --- p.53 / Chapter 4.1 --- Poling profiles for DR-1 and DANS doped bulk polymer by All-optical poling --- p.53 / Chapter 4.1.1 --- Poling profiles for DR-1 doped bulk polymer and polymer films by All-optical poling --- p.53 / Chapter 4.1.2 --- Possibilities of degradation of the samples during the experiment --- p.56 / Chapter 4.1.3 --- Effects of probing beam intensity and the duration of probing on the growth and decay of X(2) --- p.57 / Chapter 4.1.4 --- Poling profiles for DANS doped bulk polymer by All-optical poling --- p.57 / Chapter 4.2 --- Dependence of the poling profiles on various parameters in all-optical poling --- p.59 / Chapter 4.2.1 --- Dependence on the temperature --- p.59 / Chapter 4.2.2 --- Dependence on the relative intensities between the two seeding beams --- p.60 / Chapter 4.2.3 --- Dependence on the relative phase between the two seeding beams --- p.64 / Chapter 4.2.4 --- Tensorial properties of X(2) --- p.67 / Chapter 4.2.5 --- Dependence on the thickness of the sample --- p.68 / Chapter 4.3 --- Comparison of different relaxation models --- p.69 / Figures --- p.71 / Chapter Chapter 5 --- Growth and decay of optical nonlinearity in poled polymers with charge-generating additives --- p.89 / Chapter 5.1 --- Orientational enhancement in NLOP systems --- p.89 / Chapter 5.2 --- Space-charge field by charge-transporting molecules and sensitizer --- p.89 / Chapter 5.3 --- Poling profile of the bulk DR-1 polymer with charge-generating ingredients --- p.91 / Chapter 5.4 --- Poling profile of the bulk DANS polymer with the presence of charge-transporting molecules and sensitizers --- p.100 / Figures --- p.107 / Chapter Chapter 6 --- Growth and decay of optical nonlinearity in a nano-structured composite system --- p.113 / Chapter 6.1 --- Historical background --- p.113 / Chapter 6.2 --- Preparation of the composites films --- p.116 / Chapter 6.2.1 --- Preparation of the silver nano-particles --- p.116 / Chapter 6.2.2 --- Preparation of the composite films --- p.117 / Chapter 6.3 --- Poling profiles of polymer films with silver nano-particles --- p.118 / Figures --- p.124 / Chapter Chapter 7 --- Conclusions --- p.129 / References --- p.132

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Polymer based photovoltaic cells are being intensively investigated. In such cells three key processes need to occur; namely light absorption, charge separation of the exciton, and transport of the separated charges to the electrodes. Light absorption is reliant on the optical density of the polymer. In general charge separation is achieved by blending an electron acceptor with the polymer film. However, blending materials gives rise to potentially unreliable manufacturing and lifetime issues. This thesis describes the preparation of poly(l,4-phenylenevinylene) derivatives containing dipoles in which the process of charge separation can be achieved intramolecularly. The dipole was created with the use of electron donating alkoxy groups attached to the polymer backbone, and electron withdrawing nitro group attached to the fluorenyl side chains. These groups are believed to facilitate the dissociation of the photogenerated exciton, and potentially stabilise the holes and electrons that are formed when the exciton is separated. The fluorenyl side chains were attached to the polymer backbone via biphenyl or vinyl linkages. The polymers were primarily formed using the Gilch method and the conjugated polymers were obtained either via a soluble precursor route or directly from the monomer. The photophysical properties were studied for polymers with the fluorenyl side-chains as they were found to be more easily formed and stable. For poly[2-(7-nitro-9,9-dipropylfluorenyl)-5-(2'- ethylhexyloxy)-l,4-phenylenevinylene] it was found that the photoluminescence quantum yield dropped by a factor of eight relative to the polymer without the nitro group. It was further elucidated that this was due to the exciton being separated. Solar cells containing the polymers from this study showed modest performance.

This work involves the synthesis of two types of electro-optic monomers and their corresponding polymers. The first type of monomers contain the p-oxy-α-cyanocinnamate structure and were synthesized from ω-hydroxyalkoxy-substituted benzaldehydes and methyl cyanoacetate. These ω-hydroxy-α-cyanoester monomers show a high degree of electron delocalization. Copolyesters were synthesized by copolymerization of these monomers with methyl 12-hydroxydodecanoate by the standard two-stage, high-temperature polyesterification procedure. The copolyesters, incorporating dipolar units all pointing in the same direction, are soluble and solution- and melt-processable. Second harmonic generation (SHG) measurements on chloroform solutions of the copolymers showed enhancements of χ² as large as 20 relative to the dipolar monomers. These are the first known readily soluble main chain polymers that exhibit SHG behavior. The second type of monomers were acrylates containing substituted phenyl esters of benzoic acid as mesogenic (pendant) groups. Specifically, the mesogenic group contained an oxy-aryl-carboxy-aryl-carboxy-alkyl structure separated from the acrylate carbon-carbon double bond by a spacer group, which had a carboxyethyl-carboxyhexyl structure. A synthetic route was established by synthesizing a model monomer containing a 2-methylpropyl group as the alkyl group at the end of the mesogenic group. The model monomer was polymerized free radically and the resulting polymer found to possess a smectic liquid crystalline phase that became isotropic at 103° C. With the synthetic route established, an optically active monomer containing a (S)-2-methyl-1-butyl group as the alkyl group at the end of the mesogenic group was synthesized and polymerized. The optically active polymer was already in a smectic liquid crystalline phase at room temperature (≈25° C) and the phase persisted up to 72.6° C. These results indicate that it is possible to design polymers containing thermotropic liquid crystalline phases by fixing low molecular weight liquid crystalline molecules to a polymer main chain.