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No description available.

No description available.

No description available.

No description available.

No description available.

The zirconia is one of the transition metal oxides with a wide band-gap, showing many good mechanical and physical properties. This study concentrates on the preparation of the polystyrene template and the characterization of the ordered mesoporous zirconia thus prepared. The polystyrene (PS) templates have been prepared by the emulsifier-free emulsion polymerization of styrene monomer (SM) in mixed solution of K2S2O8 and H2O, without any cross-linking agent. The PS spheres so prepared have diameters ranging from 50 ¡V 400 nm. These spheres are then arranged in array by sedimentation method; then the infiltration of zirconia sol solution is followed. After the sol has been transformed to the gel, calcinations under high temperature are proceeded to remove the PS template to obtain the ordered mesoporous zirconia with various pore sizes. Doping of the zirconia also is conducted by applying an AgNO3 solution to the mesoporous zirconia. Results from SEM indicate that with a fixed ratio of K2S2O8/styrene = 5.98 wt¢H, the PS size decreases with the SM concentration; PS as small as 66 nm can be obtained when SM/H2O = 0.05¢H by volume. The PS spheres forms a hexagonal close packing when using a solution of H2O/ethanol = 3¡G7 by wt during sedimentation. Shrinkage ranging from 60 ¡V 80% of the original PS size happens when the PS template is removed from the calcined zirconia. Results from XRD indicate the same tetragonal crystalline structure of zirconia after calcinations at 500oC, regardless of the different pore sizes. BET measurements show the specific surface area of the zirconia from 6.05 - 42.61m2/g. For Ag-doped zirconia under hydrogen atmosphere, it is found from EDS mapping that the AgNO3 can be reduced to the metallic silver without particles aggregation but random distribution on the pore walls or surfaces, while the tetragonal crystalline structure of zirconia remains unaltered.

A model is developed to describe the bulk thermally-initiated free-radical polymerization of styrene between 100 °C and 170 °C. This model incorporates a comprehensive thermal initiation mechanism including generation and consumption of a Diels-Alder adduct intermediate species. A semi-empirical break-point treatment of diffusion control on reaction kinetics is used to account for autoacceleration behaviour. Using recently-developed statistical techniques, parameters are ranked based on their influence on model predictions, uncertainty in their initial values and correlation between their effects. The four top-ranked parameters (of the 40 total model parameters) are chosen for estimation to improve the fit between model predictions and literature data. After estimation of these four parameters, and hand-tuning of two additional autoacceleration parameters, the model predicts conversion data with a standard error of 5 %. The model also provides an excellent fit to a single MWD curve obtained from a literature experiment performed at 100 °C. Simulations are used to show that chain-end degradation reactions are not important in the temperature range of interest. The model is then extended to include industrially-relevant dicumyl peroxide and biphenyl peroxide chemical initiation. Additional peroxide-induced mid-chain scission reactions are considered as they may have an important influence on the molecular weight of polystyrene. To improve trends in predictions of Mn and Mw, the stationary-state hypothesis is applied to the initial adduct concentration. Parameters are then ranked, and selected for estimation using recently-developed statistical techniques. While significant improvements in predictions of conversion data are obtained, it is necessary to manually tune several parameters and scrutinize the reaction scheme in detail. To improve trends in predictions of Mn and Mw, mid-chain scission reactions are turned off and chain-transfer to monomer is implemented. Nine of the 48 total parameters are selected for estimation, resulting in a 73 % decrease in the objective function value compared with predictions using literature values. The final step of this work will be to estimate parameters using a large, proprietary industrial data set. Using this data set, it may be possible to estimate additional parameters which may lead to improved model predictions. / Thesis (Master, Chemical Engineering) -- Queen's University, 2012-02-22 12:43:35.531

No description available.

The work herein describes efforts to improve the understanding of the structural and optical properties of molecules adsorbed to polymeric surfaces. The main emphasis was placed upon the determination of molecular orientation of adsorbed molecules by developing methods for extracting structural information from vibrationally-resonant sum frequency generation spectroscopy experiments. Through the comparison of electronic structure calculations to the acquired spectra, orientation distributions were determined for phenylalanine on polystyrene coated fused silica. The initial study was a single example of a method that is applicable to any surface for which the adsorbing species has a completely characterized infrared and Raman spectra. Predicted intensities for the symmetric and antisymmetric CH2 stretches were compared to their corresponding amplitudes extracted from the acquired spectra. In the second study, the method developed was more general, incorporating the addition of molecular dynamics simulations, which were used to discover various conformations present at the surface, allowing for fits to the acquired spectra to be determined based on the relative populations of these species. This approach was chosen as it is applicable to cases in which the adsorbing species has overlapping spectral features that will not allow for characterization of specific modes. As an example of this, leucine, which possesses highly coupled and overlapping absorptions in its infrared and Raman spectra, adsorption to a polystyrene surface was studied. A high speed Stokes polarimeter based on a dual photoelastic modulator was designed, assembled, and calibrated based on a novel method, capable of measuring the adsorption kinetics of molecules adsorbing to surfaces. The adsorption of bovine serum albumin (BSA) to a polystyrene coated fused silica surface was studied. The configuration of the polarimeter was amenable to the determination of Mueller matrices of equilibrated surfaces with minimal procedural modifications. / Graduate / 0495