M.Tech. (Biomedical Technology) / Please read abstract in the full-text document

To Chi Wing = 具非線性光學性質客體-主體聚合物系統的極化動力學研究 / 杜志榮. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references (leaves 102-104). / Text in English; abstracts in English and Chinese. / by To Chi Wing = Ju fei xian xing guang xue xing zhi ke ti-zhu ti ju he wu xi tong de ji hua dong li xue yan jiu / Du Zhirong. / Table of contents / 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 --- Fundamental of nonlinear optics --- p.2 / Chapter 1.2 --- Centrosymmetry and even-order nonlinear susceptibilities --- p.4 / Chapter 1.3 --- Generation of second harmonic radiation --- p.5 / Chapter 1.4 --- Tensor properties of the nonlinear susceptibilities --- p.7 / Chapter 1.5 --- Relationship between macroscopic and microscopic nonlinear susceptibility for a poled polymer --- p.8 / Chapter 1.6 --- Outline of the thesis --- p.12 / Figures --- p.13 / Chapter Chapter 2 --- Poling and Relaxation of Guest-host Polymeric System --- p.15 / Chapter 2.1 --- Guest-host nonlinear optical polymeric systems --- p.15 / Chapter 2.1.1 --- Photoisomerization of Azobenzene --- p.16 / Chapter 2.1.2 --- Disperse Red-1 --- p.17 / Chapter 2.1.3 --- Poly (methyl methacrylate) --- p.18 / Chapter 2.2 --- Poling techniques --- p.19 / Chapter 2.2.1 --- Thermal Assisted Electric-field Poling --- p.19 / Chapter 2.2.2 --- Photo-assisted Electric-field poling --- p.22 / Chapter 2.2.3 --- All-Optical Poling --- p.25 / Chapter 2.3 --- Relaxation of poled nonlinear optical polymers --- p.27 / Figures --- p.31 / Chapter Chapter 3 --- Experimental Methods --- p.36 / Chapter 3.1 --- Sample Preparation --- p.36 / Chapter 3.2 --- Experimental Setup --- p.38 / Chapter 3.2.1 --- Laser system --- p.38 / Chapter 3.2.2 --- The reference arm --- p.39 / Chapter 3.2.3 --- The sample arm --- p.40 / Chapter 3.2.4 --- Data acquisition (DAQ) system --- p.41 / Chapter 3.2.5 --- Temperature control --- p.42 / Chapter 3.3 --- Poling and the erasing of thermal history --- p.43 / Chapter 3.3.1 --- All Optical Poling --- p.43 / Chapter 3.3.2 --- Eecteic Poling --- p.44 / Chapter 3.3.3 --- Erasure of thermal history --- p.45 / Figures --- p.46 / Chapter Chapter 4 --- Experimental results and discussions --- p.51 / Chapter 4.1 --- Reliability and reproducibility --- p.51 / Chapter 4.2 --- Features of different poling techniques --- p.52 / Chapter 4.2.1 --- Sub-Tg electric Poling --- p.53 / Chapter 4.2.2 --- Thermal assisted electric Poling --- p.54 / Chapter 4.2.3 --- Photo assisted electric Poling --- p.55 / Chapter 4.3 --- Relaxation of poling induced x(2) --- p.56 / Chapter 4.4 --- Effect of physical aging on the relaxation of PAP induced x{2) --- p.58 / Chapter 4.4.1 --- Origin of physical aging and its effect on relaxation --- p.58 / Chapter 4.4.2 --- Effect of aging on the relaxation of a PAP sample --- p.59 / Chapter 4.5 --- Onset studies of photo-induced free volume --- p.61 / Chapter 4.6 --- Comparative studies of TAP and PAP induced x{2) --- p.62 / Chapter 4.6.1 --- Secondary Poling --- p.63 / Chapter 4.6.1.1 --- Model for describing the temporal behavior of secondary poling --- p.65 / Chapter 4.6.1.2 --- Experimental details of the secondary poling measurement --- p.68 / Chapter 4.6.1.3 --- Results and Discussion on secondary poling of sample poled by TAP or PAP --- p.69 / Chapter 4.6.2 --- Onset of second harmonic signal during electric poling --- p.71 / Chapter 4.7 --- Charge injection studies --- p.73 / Figures --- p.77 / Chapter Chapter 5 --- Conclusion --- p.98 / References --- p.101

No description available.

The chiroptical properties of isotropic solutions, cholesteric liquid crystals and solid films prepared from selected cellulose derivatives are investigated by optical rotary dispersion (ORD) and circular dichroism (CD). Optical activity from intrinsic molecular dissymmetry, polymer conformation and cholesteric reflection properties are considered. / The chiroptical properties of cholesteric liquid crystals are interpreted according to deVries' theory. Lyotropic liquid crystalline phases formed by (hydroxypropyl)cellulose in methanol display anomalously high optical rotation at low wavelengths. The anomalies disappear on the addition of a dipolar aprotic solvent, and are absent for the ethyl ether derivative of the polymer, indicating a chiral hydrogen bonded structure is contributing to the optical activity. / Investigation of the chiroptical properties of cellulosics by circular dichroism requires the presence of a suitable chromophore, either as a chain substituent or as an added dye. Congo red exhibits induced optical activity in dilute aqueous solutions of methylcellulose and cellulose oligomers, providing evidence for the presence of a helical conformation. CD spectra of two new biphenyl derivatives also exhibit exciton splitting characteristic of a helical arrangement of chromophores. Conformational dissymmetry is not indicated in spectra of cellulose acetate although the sign of carbonyl CD band is solvent dependent. The sign of this band is interpreted in terms of the orientation of the ester substituent relative to the anhydroglucose ring. Congo red, bound in cholesteric cellulose films prepared by the deacetylation of cellulose acetate cast from mesophase solution, shows induced optical activity which, in this case, reflects the cholesteric nature of the matrix. Similar results for cellulose gels regenerated from LiCl/N,N-dimethylacetamide solution indicate that cellulose adopts a supramolecular helicoidal arrangement on slow precipitation from solution. / The optical properties of the thermotropic cholesteric liquid crystalline phase formed by a new cellulose derivative, (ethoxypropyl)cellulose, are examined by circular reflectivity measurements. / The cholesteric reflection properties of mesophase solutions of cellulose acetate in trifluoroacetic acid are characterized. The polymer undergoes rapid trifluoroacetylation in this solvent and the presence of trifluoroacetate substituents alters the handedness and the magnitude of the pitch. Although the pitch is sensitive to the nature of achiral substituents, it is not influenced by the addition of chiral solvents. (Abstract shortened with permission of author.)

No description available.

The syntheses of novel poly(paraphenyleneethynylene)s, PPEs, and poly(aryleneeethynylene)s, PAEs, as well as hybrid poly(paraphenyleneethynylene)- poly(paraphenylenevinylene)s, PPE-PPVs, are presented. Fluorescent PPEs decorated with biologically relevant ligands are utilized in model biosensing schemes. PPE-PPV hybrids, as well as their highly emissive oligomeric, cruciform model compounds are studied in an effort to modify the bandgap of the parent PPE backbone. Improved hole and electron injection capabilities are demonstrated with these hybrid conjugated materials. Structural variation and morphological effects of PPEs, PPE-PPVs and model compounds are studied to elucidate the effects upon the photophysical properties of the emissive materials.

published_or_final_version / abstract / Chemistry / Doctoral / Doctor of Philosophy

This thesis is geared towards using hydrogel nanoparticles in various biotechnological applications. The polymer that was used in making these nanoparticles was poly(N-isopropylacrylamide), which is a thermoresponsive polymer. These particles were used in making fast responsive polymer films, which can be used in optics. It was observed that the rate of deswelling increased as the concentration of the nanoparticles in the film was increased. These particles were also used in making photoresponsive materials. In this case a photoresponsive dye (malachite green) was conjugated to these nanoparticles and in presence of light of appropriate wavelength the particles undergo a phase transition. A core/shell construct was synthesized where the core was composed of degradable cross-links and the shell of composed of non-degradable cross-links. The degradable cross-linker had vicinal diols, which can be cleaved by sodium periodate. Hence after degrading the core, hollow particles were obtained. Zwitterionic particles were made by incorporating a cationic and anionic comonomer. These microgels go from a positively charged state to zwitterionic to negatively charged state on increasing the pH. One of the important potential applications for these microgels is drug delivery. Microgels were used for targeting cancer cells. Folic acid was used as the targeting ligand. The microgels were conjugated with folic acid and were able to target cells that overexpress folate receptors. In one other application core/shell microgels were made which exhibit pore-size dependent permeation of proteins.

No description available.

The objective of this research is to investigate the use of laser direct writing to micro-pattern low loss passive optical channel waveguide devices using a new hybrid organic/inorganic polymer. Review of literature shows previous methods of optical waveguide device patterning as well as application of other non-polymer materials. System setup and design of the waveguide components are discussed. Results show that laser direct writing of the hybrid polymer produce single mode interconnects with a loss of less 1dB/cm.