This research mainly investigated how the hydrophilic and hydrophobic properties of gas diffusion layer, and the different open ratio of the flowfield may affect the performance of the micro proton exchange membrane fuel cell (£gPEMFC). The flow plate used in this experiment was made through deep UV lithography manufacturing processes and micro-electroforming manufacturing processes. Four different open ratios, 52.8 %, 50.8 %, 75.2 % and 75.75 %, of the flowfield were designed for the flow plate composed of serpentine-parallel and serpentine geometrical micro configurations. Acrylic (PMMA: Polymethylmethacrylate) was used to make the terminal plate placed on both sides of the micro proton exchange membrane fuel cell. By varying values of the hydrophilic and hydrophobic properties of the anode gas diffusion layer, the effects of these two parameters on the polarization curve and power density of the cell were explored. All results obtained in the experiment are presented by P-I curve and V-I curve. The experiment results show that, with 1: 5 flow ratio of anode to cathode, a design with the gas diffusion layer made of the material with hydrophobic factor 20 wt.% and with open ratio of 50.8 % for anode flow channel as well as open ratio of 75.75 % for cathode flow channel may have the best performance.

The interaction of a bubble with solid surfaces, hydrophobic and hydrophilic, was investigated. When a bubble approaches towards a solid surface, a thin liquid film forms between them. The liquid in the film drains until an instability forms and film ruptures resulting in a three phase contact (TPC). Following rupture, the TPC line spreads on the solid surface. In the present study, glycerol-water solutions with varying percentages of water were used to investigate the effect of viscosity. Experiments were carried out with varying bubble size. The rupture and TPC line movement were recorded by high-speed digital video camera. The dependence of the TPC line movement on different parameters was investigated. The experimental results were compared with the existing theories for the TPC line movement. An empirical equation was developed to predict the TPC line movement. Formation or rupturing of the intervening film in case of a hydrophilic surfaces, which were glass surface cleaned by six cleaning techniques, was investigated. It was shown that a stable film forms for acid or alkali cleaning.

No description available.

The practical applications of surfactant solutions in confined geometries require a thorough understanding of the system properties. Coarse-grained simulation techniques are useful for studying the qualitative behaviour of these systems, whereas the atomistic molecular dynamics (MD) technique can be used to obtain a molecular-level description. In this work, canonical MD simulations were performed using GROMACS version 4.0 to investigate the self-assembling behaviour of sodium octanoate (SO) confined between two parallel walls. In particular, the effects of gap size, wall type, and surfactant concentrations on the morphology of the surfactant aggregates were studied to gain in-depth knowledge of the system. The simulation results reveal that the morphology of the micelles formed between two parallel walls are affected not only by the gap size and surfactant concentration, but also by the nature and characteristics of the confining walls. With the graphite walls, most octanoate molecules are adsorbed at lower concentrations, but they form micellar aggregates as the surfactant concentration increases. Spherical micelles were found in the larger gaps (4 nm and 5 nm) but not in the smaller gap (3 nm), and the micellar shape also changes with increasing surfactant concentration. SO forms bilayer structures instead of spherical micelles between two silica walls. Interestingly, in the hydrophilic silica confinement, the orientation of these bilayers changes with gap sizes, whereas in the hydrophobic silica confinement, these bilayers remain perpendicular to the wall in all cases. Potentials of mean force between different molecules and atomic groups were determined under different conditions in order to develop a better understanding of the simulation results. It reveals, the presence of the confinement can alter the intermolecular interactions among the surfactant molecules, which, in turn, directly affects the self-assembling process, particularly the size and shape of the aggregates. Indeed, the formation of bilayers in silica wall confinement, as opposed to spherical micelles in graphite confinement, is caused by the enhanced electrostatic interactions between the charged atoms in the solution. The results of this study are expected to provide further insight into the self-assembling behaviour of confined surfactant systems, and may ultimately lead to the development of novel nanomaterials.

In this thesis, we are making a new approach to fabricate silicon on insulator (SOI). By replacing the buried silicon dioxide and the silicon handling wafer with silicon carbide through hydrophilic wafer bonding, we have achieved silicon on crystalline silicon carbide for the first time and silicon on polycrystalline silicon carbide substrates at 150 mm wafer size. The conditions for the wafer bonding are studied and the surface and bond interface are characterized. Stress free and interfacial defect free hybrid wafer bonding has been achieved. The thermally unfavourable interfacial oxide that originates from the hydrophilic treatment has been removed through high temperature annealing, denoted as Ox-away. Based on the experimental observations, a model to explain the dynamics of this process has been proposed. Ox-away together with spheroidization are found to be the responsible theories for the behaviour. The activation energy for this process is estimated as 6.4 eV. Wafer bonding of Si and polycrystalline SiC has been realised by an intermediate layer of amorphous Si. This layer recrystallizes to some extent during heat treatment. Electronic and thermal testing structures have been fabricated on the 150 mm silicon on polycrystalline silicon carbide hybrid substrate and on the SOI reference substrate. It is shown that our hybrid substrates have similar or improved electrical performance and 2.5 times better thermal conductivity than their SOI counterpart. 2D simulations together with the experimental measurements have been carried out to extract the thermal conductivity of polycrystalline silicon carbide as κpSiC = 2.7 WK-1cm-1. The realised Si-on-SiC hybrid wafer has been shown to be thermally and electrically superior to conventional SOI and opens up for hybrid integration of silicon and wide band gap material as SiC and GaN.

Interest in microemulsions as potential platforms for polymerization stems from the wide range of phase behaviour dependant morphologies and domain sizes that can be generated in a low viscosity environment. By introducing polymerizable components into the oil and aqueous phases of a microemulsion, we may essentially create a low viscosity, low interfacial tension, bicontinuous template with nanostructured morphologies and narrow domain size distributions analogous to those generated through conventional interpenetrating polymer network (IPN) synthesis and spinodal decomposition. The main objective of this dissertation is to test the application of bicontinuous microemulsion templates to the formulation and polymerization of a silicone-hydrogel IPN. In addition, the project expands on the classical definition of IPNs to a scale of entanglement at the level of groups of polymer chains, as opposed to molecular or chain-level entanglement. This study is divided into two main parts. In the first part, silicone microemulsions were developed and characterized according to the Hydrophilic-Lipophilic Difference (HLD) framework. The hydrophobicity of silicone oils, the characteristic curvature of silicone surfactants and the co-surfactant contribution of methacrylic acid (MAA) and hydroxyethyl methacrylate (HEMA) were quantified. These findings led to the successful formulation of bicontinuous microemulsions (μEs) containing silicone oil, silicone alkyl polyether and reactive monomers in aqueous solution. Ternary phase diagrams of these systems revealed the potential for silicone-containing polymer composites with bicontinuous morphologies. In the second part of this study, the formulation and simultaneous polymerization of polydimethylsiloxane-poly(methacrylic acid – hydroxyethyl methacrylate), (PDMS-P(MAA-HEMA) IPNs from bicontinuous microemulsions was demonstrated. Laser scanning confocal microscopy (LSCM) on swollen polymers highlights aqueous pathways, and indicates the formation of bicontinuous morphologies with domain sizes at equilibrium swelling ranging from ~100 nm to 1 μm. Incorporating polymerizable surfactants into the microemulsion aided in stabilizing the initial microemulsion structure during polymerization. The process developed demonstrates a simple, single-step polymerization approach to forming IPNs from low viscosity microemulsion templates, and could potentially be extended to a variety of hydrophilic and hydrophobic monomers.

Interest in microemulsions as potential platforms for polymerization stems from the wide range of phase behaviour dependant morphologies and domain sizes that can be generated in a low viscosity environment. By introducing polymerizable components into the oil and aqueous phases of a microemulsion, we may essentially create a low viscosity, low interfacial tension, bicontinuous template with nanostructured morphologies and narrow domain size distributions analogous to those generated through conventional interpenetrating polymer network (IPN) synthesis and spinodal decomposition. The main objective of this dissertation is to test the application of bicontinuous microemulsion templates to the formulation and polymerization of a silicone-hydrogel IPN. In addition, the project expands on the classical definition of IPNs to a scale of entanglement at the level of groups of polymer chains, as opposed to molecular or chain-level entanglement. This study is divided into two main parts. In the first part, silicone microemulsions were developed and characterized according to the Hydrophilic-Lipophilic Difference (HLD) framework. The hydrophobicity of silicone oils, the characteristic curvature of silicone surfactants and the co-surfactant contribution of methacrylic acid (MAA) and hydroxyethyl methacrylate (HEMA) were quantified. These findings led to the successful formulation of bicontinuous microemulsions (μEs) containing silicone oil, silicone alkyl polyether and reactive monomers in aqueous solution. Ternary phase diagrams of these systems revealed the potential for silicone-containing polymer composites with bicontinuous morphologies. In the second part of this study, the formulation and simultaneous polymerization of polydimethylsiloxane-poly(methacrylic acid – hydroxyethyl methacrylate), (PDMS-P(MAA-HEMA) IPNs from bicontinuous microemulsions was demonstrated. Laser scanning confocal microscopy (LSCM) on swollen polymers highlights aqueous pathways, and indicates the formation of bicontinuous morphologies with domain sizes at equilibrium swelling ranging from ~100 nm to 1 μm. Incorporating polymerizable surfactants into the microemulsion aided in stabilizing the initial microemulsion structure during polymerization. The process developed demonstrates a simple, single-step polymerization approach to forming IPNs from low viscosity microemulsion templates, and could potentially be extended to a variety of hydrophilic and hydrophobic monomers.

Content removed due to copyright restrictions: E I-Sherbiny, I.M., Lins, R.l , Abdel-Bary, E.M., Harding, D.R.K. Preparation, characterization, swelling and in vitro drug release behaviour of poly[Nacryloylglycine- chitosan] interpolymeric pH and thermally-responsive hydrogels. Eur. Polym. J. 41 (2005) 2584. E I-Sherbiny, I.M., Abdel-Bary, E.M., Harding, D. R.K. Preparation and swelling study of a pH-dependent interpolymeric hydrogel based on chitosan for controlled drug release. Inl. J. Polym. Mater. 55 (2006) 789. El-Sherbiny, I.M., Abdel-Bary, E.M., Harding, D. R. K. Swelling characteristics and in-vitro drug release study with pH and thermo-sensitive hydro gels based on modified chitosan. J. Appl. Polym. Sci. 102 (2006) 977. Abdelaal, M.Y., Abdel-Razik, E . A , Abdel-Bary, E.M., El-Sherbiny, I.M. Study on chitosan-poly(vinyl alcohol) interpolymeric pH-responsive hydrogel films for controlled drug delivery. J. Appl. Polym. Sci. (2006) in press. El-Sherbiny, I. M., Abdel-Bary, E.M., Harding, D. R. K. In-vitro investigation of new biodegradable pH-responsive hydrogel beads for oral delivery of protein drugs in the small intestine. New Zealand Institute of Chemistry Conference (NZIC), (2006) Rotorua, New Zealand, 2-6 December. / Controlled drug release enhances the safety, efficacy and reliability of drug therapy. Regulation of the drug release rate results in a reduction in the frequency of drug administration and should encourage patients to comply with dosing instructions. Hydrogels are crosslinked, three-dimensional hydrophilic polymers, which swell without dissolving when brought into contact with water or other biological fluids. The number of polymers suitable for the controlled release of viable therapeutics is quite limited because of inherent toxicity or lack of certain properties such as biodegradability. In this thesis, chitosan was chosen as the base polymer for the development of new hydrogels that can be tailored for use in the site-specific delivery of drugs to the gastrointestinal tract. Chitosan is a non-toxic and biodegradable polymer obtained through the alkaline deacetylation of natural chitin. The interesting characteristics of chitosan make it an ideal candidate for use in controlled drug release formulations. However, chitosan exhibits some shortcomings such as hydrophobicity and a high pH-dependency for its physical properties. Hence, it is very difficult to control drug release with chitosan itself because of the various pH values of the internal organs of the human body. This may negatively affect the human body because of drug under- or over-release. In a structured programme, some new chitosan-based hydrogels have been prepared for controlled drug release investigations by applying three main approaches to overcome the shortcomings of chitosan. The first approach was the incorporation of chitosan into interpenetrating polymer network hydrogels with either a hydrophilic polymer or with hydrophilic monomers treated to bring about in situ copolymerization in the presence of chitosan and a suitable crosslinking agent. The second approach was the chemical modification of chitosan by grafting of a suitable vinyl macromer such as poly(ethylene glycol)-diacrylate, then crosslinking this modified chitosan. The equilibrium swelling studies were carried out for the hydrogels prepared using these two approaches at 37 °C at pH 2.1 (simulated gastric fluid, SGF) and at pH 7.4 (simulated intestinal fluid, SIF). The swelling results showed a pH-responsive nature of these hydrogels. They attained higher swelling values in SGF than in SIF. 5-Fluorouracil (5-FU), an anti cancer drug, was entrapped as a model drug in all the hydrogels prepared using these two approaches. The in-vitro drug release studies were carried out at 37 °C in SGF and SIF. From the preliminary investigations of the prepared hydrogels, they may be customized and used to expand the utilization of these systems in drug delivery applications. In the third approach, chitosan was modified in such a fashion that the hydrogels produced were also pH-responsive but attained limited swelling in SGF and higher swelling in SIF. Hence, the resulting hydrogels could be tailored for utilization for intestine-targeted delivery of peptide and protein drugs with a potential protection of the drugs from the harsh acidity of the stomach. In this third approach the ionotropic gelation was used for the preparation of the hydrogels based on the modified chitosan with another natural polymer (sodium alginate) in the presence of a divalent ion. Bovine serum albumin (BSA) was entrapped as a model protein drug and the in-vitro drug release profiles were established at 37 °C in SGF and SIF. The results showed promising release profiles of BSA. However, this hydrogel study requires more effort to limit the swelling and consequently the loss of drug in the SGF, to act as an excellent candidate for intestine-specific delivery of peptide and protein drugs.

Content removed due to copyright restrictions: E I-Sherbiny, I.M., Lins, R.l , Abdel-Bary, E.M., Harding, D.R.K. Preparation, characterization, swelling and in vitro drug release behaviour of poly[Nacryloylglycine- chitosan] interpolymeric pH and thermally-responsive hydrogels. Eur. Polym. J. 41 (2005) 2584. E I-Sherbiny, I.M., Abdel-Bary, E.M., Harding, D. R.K. Preparation and swelling study of a pH-dependent interpolymeric hydrogel based on chitosan for controlled drug release. Inl. J. Polym. Mater. 55 (2006) 789. El-Sherbiny, I.M., Abdel-Bary, E.M., Harding, D. R. K. Swelling characteristics and in-vitro drug release study with pH and thermo-sensitive hydro gels based on modified chitosan. J. Appl. Polym. Sci. 102 (2006) 977. Abdelaal, M.Y., Abdel-Razik, E . A , Abdel-Bary, E.M., El-Sherbiny, I.M. Study on chitosan-poly(vinyl alcohol) interpolymeric pH-responsive hydrogel films for controlled drug delivery. J. Appl. Polym. Sci. (2006) in press. El-Sherbiny, I. M., Abdel-Bary, E.M., Harding, D. R. K. In-vitro investigation of new biodegradable pH-responsive hydrogel beads for oral delivery of protein drugs in the small intestine. New Zealand Institute of Chemistry Conference (NZIC), (2006) Rotorua, New Zealand, 2-6 December. / Controlled drug release enhances the safety, efficacy and reliability of drug therapy. Regulation of the drug release rate results in a reduction in the frequency of drug administration and should encourage patients to comply with dosing instructions. Hydrogels are crosslinked, three-dimensional hydrophilic polymers, which swell without dissolving when brought into contact with water or other biological fluids. The number of polymers suitable for the controlled release of viable therapeutics is quite limited because of inherent toxicity or lack of certain properties such as biodegradability. In this thesis, chitosan was chosen as the base polymer for the development of new hydrogels that can be tailored for use in the site-specific delivery of drugs to the gastrointestinal tract. Chitosan is a non-toxic and biodegradable polymer obtained through the alkaline deacetylation of natural chitin. The interesting characteristics of chitosan make it an ideal candidate for use in controlled drug release formulations. However, chitosan exhibits some shortcomings such as hydrophobicity and a high pH-dependency for its physical properties. Hence, it is very difficult to control drug release with chitosan itself because of the various pH values of the internal organs of the human body. This may negatively affect the human body because of drug under- or over-release. In a structured programme, some new chitosan-based hydrogels have been prepared for controlled drug release investigations by applying three main approaches to overcome the shortcomings of chitosan. The first approach was the incorporation of chitosan into interpenetrating polymer network hydrogels with either a hydrophilic polymer or with hydrophilic monomers treated to bring about in situ copolymerization in the presence of chitosan and a suitable crosslinking agent. The second approach was the chemical modification of chitosan by grafting of a suitable vinyl macromer such as poly(ethylene glycol)-diacrylate, then crosslinking this modified chitosan. The equilibrium swelling studies were carried out for the hydrogels prepared using these two approaches at 37 °C at pH 2.1 (simulated gastric fluid, SGF) and at pH 7.4 (simulated intestinal fluid, SIF). The swelling results showed a pH-responsive nature of these hydrogels. They attained higher swelling values in SGF than in SIF. 5-Fluorouracil (5-FU), an anti cancer drug, was entrapped as a model drug in all the hydrogels prepared using these two approaches. The in-vitro drug release studies were carried out at 37 °C in SGF and SIF. From the preliminary investigations of the prepared hydrogels, they may be customized and used to expand the utilization of these systems in drug delivery applications. In the third approach, chitosan was modified in such a fashion that the hydrogels produced were also pH-responsive but attained limited swelling in SGF and higher swelling in SIF. Hence, the resulting hydrogels could be tailored for utilization for intestine-targeted delivery of peptide and protein drugs with a potential protection of the drugs from the harsh acidity of the stomach. In this third approach the ionotropic gelation was used for the preparation of the hydrogels based on the modified chitosan with another natural polymer (sodium alginate) in the presence of a divalent ion. Bovine serum albumin (BSA) was entrapped as a model protein drug and the in-vitro drug release profiles were established at 37 °C in SGF and SIF. The results showed promising release profiles of BSA. However, this hydrogel study requires more effort to limit the swelling and consequently the loss of drug in the SGF, to act as an excellent candidate for intestine-specific delivery of peptide and protein drugs.

Thesis (Ph.D.)--University of Alabama at Birmingham, 2009. / Title from PDF title page (viewed on Sept 9, 2009). Includes bibliographical references (p. 120-125).