The major drawbacks of PLA are its poor toughness and lack of readily reactable groups. Unfortunately, typical methods of PLA toughening are associated with significant modulus and/or ultimate tensile strength UTS) loss. The main objective of this research was to toughen PLA, with minimal modulus and/or UTS loss, and introduce reactive groups into the PLA matrix in one step. Initially, this objective was divided into two separate parts: PLA surface modification followed by toughening. PLA film was solvent cast from chloroform solution and was surface modified using a sequential two-step photografting approach. Benzophenone was photografted onto the film surface in Step 1 followed by photopolymerization of hydrophilic monomers, acrylic acid and acrylamide, from the film surface. The resultant films were characterized using ATR-FTIR spectroscopy, water contact angle goniometry, transmission FTIR microspectroscopy, and tensile testing. The effect of the reaction solvent ethanol and water) in Step 2 on PLA film surface and bulk properties was also studied. There was significant penetration of monomers into the films when ethanol was used as the reaction solvent, resulting in significant toughness loss. This monomer penetration into the films was successfully reduced by using water instead of ethanol as the reaction solvent in Step 2 and resultant films showed higher toughness than films surface-modified using ethanol as the reaction solvent in Step 2. It was also observed that solvent cast PLA film retained approximately 13 wt% chloroform, as characterized using thermogravimetric analyses TGA). The presence of residual chloroform in the film specimens is undesirable from a biocompatibility standpoint. Therefore, further work was conducted on melt-processed films where residual solvent from the film-formation method would not be an issue. Addition of a small amount of poly[3-hydroxybutyrate)-co-3-hydroxyhexanoate)] PHBHHx) to PLA improved the toughness of the resultant melt-processed blend from 4 ＋/- 2 MPa for neat PLA to 175 ＋/- 35 MPa for PLA-PHBHHx blend 90 wt% PLA). PLA-PHBHHx blend films were melt-processed using a single screw extruder. These polyblend films appeared to be non-compatible as characterized using dynamic mechanical analyses DMA). PLA-PHBHHx blend films underwent rapid physical aging losing their toughness from 175 ＋/- 35 MPa right after extrusion) to 68 ＋/- 34 MPa day 3). The blend films were surface modified using the sequential two-step photografting protocol using water as the reaction solvent in Step 2. PLA-PHBHHx blend films lost approximately 95% of their toughness on surface modification due to UV-assisted solvent induced crystallization as characterized using wide angle X-ray diffraction WAXD) analyses. A novel reactive blending approach was developed to toughen PLA with minimal modulus and UTS loss and introduce reactive groups into the PLA matrix. PLA was reactive blended with a stiffening polymer, polyacrylic acid) PAA), followed by physical blending with a toughening polymer, polyethylene glycol) PEG), in solution. The modified PLA was extruded into films using a co-rotating twin-screw extruder and characterized using tensile testing, differential scanning calorimetry DSC), DMA, and toluidine-blue-surface-staining. This material exhibited, for the first time, approximately 10 fold increase in PLAs toughness without significant modulus and/or UTS loss and also introduced a controlled concentration of surface modifiable reactive acid groups into the PLA matrix in one step.

In this work we have developed a facile highly scalable two step method for templating hollow silica nanospheres using catanionic vesicles as templates. The template consisted of equilibrium unilamelar catanionic vesicles formed from mixtures of cationic and anionic surfactants. A thorough investigation of the template’s behavior was necessary in order to proceed in templating synthesis. The template’s (catanionic vesicles) structure, phase and stability were characterized by independent techniques such as cryo-Transmission Electron Microscopy, Small Angle Neutron Scattering and Dynamic Light Scattering. Hollow silica spheres were synthesized using catanionic vesicles as a template and tetramethoxysilane (TMOS) as the silica precursor under acidic conditions. Transmission Electron Microscopy, Scanning Electron Microscopy, Atomic Force Microscopy and Dynamic Light Scattering were the techniques that helped us to characterize the hollow silica nanospheres, further understand and face the challenges of the particular templating sol-gel process. The competition between the adsorption of the hydrolyzed silica precursor onto the vesicular surface and the homogeneous nucleation in the bulk (resulting in gel formation and particle trapping-caging into the gel) was never faced as an optimization challenge. We find that by introducing a second step, under conditions close to the Stober synthesis, non adsorbed silicate species condense resulting in solid particle formation and produce two distinctly different particle size populations of hollow and solid silica beads, which can easily be separated due to their significant density difference. Thus, the second step maximizes the yield of the templated synthesis and optimizes the sol-gel batch process.

In this thesis, we show using mass-spectrometry temperature-programmed-desorption MS-TPD) that the product of heating high-silica H-zeolites is predominantly hydrogen. Using electronicstructure calculations we also show a plausible path for the formation of hydrogen from zeolite Bronsted acid sites and propose that the reaction should lead to the formation of [AlO4/ h]0 sites in the zeolite. These [AlO4/h]0 sites can act as nonacidic one-electron acceptors of adsorbed molecules and could react further to form a more stable species. As such these sites could play an important role in the catalytic chemistry of hydrocarbons at high temperatures. It is proposed that the disappearance of hydrogen from the hydroxyl nests is accompanied by the formation of bisperoxysilyl groups Si-O-O-Si). Electronic structure calculations are also employed to support the energetic feasibility of this reaction mechanism. Silicalite-1 samples made with tetraethyl-orthosilicate show a number of differences in their IR and UV-Vis spectra compared to samples made with other silica sources, and it appears that the source of silica plays an important role in the structure of the internal defects. Nitrogen oxides NOx) are a major atmospheric pollutant produced through the combustion of fossil fuels in internal combustion engines. Copper-exchanged zeolites are promising as selective catalytic reduction SCR) catalysts for the conversion of NO into N2 and O2. Previously, it has been shown that when fresh, Cu-ZSM-5 has high NH3-SCR activity, however, ZSM-5 zeolites are highly susceptible to dealumination during steaming, which results in a lost of SCR activity. Whereas, recent reports have shown the enhanced performance of Cu-CHA catalysts over other zeolite frameworks in the NO decomposition of exhaust gas streams. In the present study, Rietveld refinement of variable-temperature XRD synchrotron data obtained for Cu-SSZ-13 and Cu-SSZ-16 is used to investigate the location of copper cations in the zeolite pores and the effect of temperature on these sites and on framework stability. The XRD patterns show that the thermal stability of the zeolite SSZ-13 is increased significantly when copper is exchanged into the framework compared with the acid form of the zeolite, H-SSZ-13. Cu-SSZ-13 is also more thermally stable than Cu-SSZ-16. From the refined diffraction patterns, the atomic positions of framework atoms, copper locations and occupancies, and thermal displacement parameters were determined as a function of temperature for both zeolites. Copper is found in the cages coordinated to three oxygen atoms of the six-membered rings. These results lead us to investigate the NH3-SCR activity of the small-pore zeolites, Cu-SSZ-13, Cu-SSZ-16, and Cu-SAPO-34. These copper exchanged smallpore zeolites have high SCR activity between 150-500&deg；C and are shown to be much more hydrothermally stable than the medium-pore zeolite, Cu-ZSM-5. The degree of copper exchange, the dimensionality of the framework, and heteroatom framework substitution all impact the SCR activity and hydrothermal stability of the materials. Of the small-pore zeolites tested, Cu-SSZ-13 and Cu-SAPO-34 display superior SCR performance, both before and after high-temperature hydrothermal treatment. Overall, the results of this thesis bring about new ideas as to what happens to zeolite systems at high-temperatures. The decomposition of Bronsted acid sites and hydroxyl nests within zeolite frameworks are startling finds that reevaluate previously held decomposition mechanisms within zeolites. By exchanging copper into small-pore zeolites, we showed that there is a resulting increase in the thermal stability of the material. The findings here also provide evidence that the pore size of the zeolite framework plays a crucial role in the stability of the material. Lastly, future recommendations are given for ways in which to utilize the properties of these unique materials. Abstract shortened by UMI.)

With the overall goal of advancing nano-scale encapsulation technology, two companion problems in the controlled release of small hydrophobic molecules have been studied: equilibrium partitioning and colloidal transport, each within nanostructured matrices. In the first research focus, a solid phase microextraction SPME) method was developed to measure air–water–surfactant micelle partitioning of hydrophobic analytes. Vapor–liquid partitioning Kv &ell；) measurements were performed independently in the headspace HS-SPME) and via direct immersion in the liquid DI-SPME), and the results were compared. The method involves varying the total amount of analyte as well as the ratio of vapor to liquid in the closed, static system, such that the need for an external calibration is eliminated. The compounds studied cover four orders of magnitude in Kv &ell；, and agreement between DI-SPME and HS-SPME results was good, showing that these two methods were capable of providing accurate, complementary measurements. Equilibrium partitioning of limonene to sodium dodecyl sulfate SDS) micelles was also measured using HS-SPME by varying the concentration of SDS. By fitting the data to a simple model, the cmc was accurately measured and the micelle–liquid partition coefficient was determined. In the second research focus, the diffusion of SDS in solution and in agarose gel was measured and compared with an a priori model for colloidal transport which invokes hydrodynamic and statistical thermodynamic arguments to account for micelle–micelle and micelle–gel fiber interactions. Experimental results show that the concentration effect is enhanced considerably by the strong charge associated with SDS micelles. At high ionic strength, this concentration effect is further enhanced in 1% agarose gel, but in 2% gel the trend reverses, strongly suggesting a decrease in the micellar aggregation number. At low ionic strength, a concentration effect with a pronounced second order dependence is evident. Results show that the diffusion coefficient does not change appreciably with gel concentration up to 2%, and theoretical analysis suggests that this is due to partial canceling between the effects of solute–gel and solute–solute interactions. The pronounced second-order dependence is explained qualitatively by the changing Debye length and its influence on the thermodynamic driving force.

Membrane fluidity refers to the rate of translational, rotational, and trans-leaflet lipid diffusion in bilayer lipid membranes BLMs). It is an important physical property of the BLM that can affect the rate at which molecules diffuse across the membrane, the signaling and communication between cells, and the activity and function of membrane proteins. Membrane fluidity often depends on the interactions between constituent lipids in the BLM or between lipids and other membrane-bound molecules or macromolecules. This dissertation focuses on four studies that involved the use of optical techniques to measure the dynamics of fluorescently-tagged lipids in synthetic model BLM systems that mimic the behavior of cell membranes. The primary tools used for characterization were fluorescence recovery after pattern photobleaching FRAPP), which measures translational diffusion in two-dimensional supported bilayer lipid membranes sBLMs), and time-correlated single photon counting TCSPC), which measures rotational diffusion in three-dimensional spherical liposomes in solution. Our results showed that the diffusion of lipid fluorophores in model BLMs can significantly increase or decrease upon the addition of molecules or macromolecules to the bilayer. For example, both sonicated and extruded 1,2-dioleoyl-sn-glycero-3-phosphocholine DOPC) liposomes were less fluid upon incorporation of cholesterol, likely to the result of cholesterol molecules interacting with the hydrophobic acyl chains of the bilayer and causing the membrane to become more rigid. Addition of the lipid 1,2-dioleoyl- sn-glycero-3-[phospho-rac-1-glycerol)] DOPG) to DOPC sBLMs again resulted in a decrease in membrane fluidity. In this case, however, the reduced fluidity likely resulted from hydrogen bonding between constituent lipid head groups in the membrane. When single acyl chain lysophospholipids were added to DOPC sBLMs, the membrane fluidity increased. This is likely due to a reduction in van der Waals interactions between hydrophobic acyl chains. However, the fluidity decreased when a fraction of the lysophospholipids was converted to fatty acids by enzymatic activity of NEST NTE esterase domain), the catalytic domain of neuropathy target esterase NTE). The observed decrease in fluidity is attributed to the enhanced packing of fatty acids, relative to lysophospholipids, in the hydrophobic region of the bilayer. A maximum NEST protein concentration in fluid sBLMs formed from proteoliposome reconstitution was estimated and it was demonstrated qualitatively that microsomal membrane proteins at sufficiently high concentrations can decrease the fluidity of sBLMs reconstituted from microsomes. The results of these studies give a fundamental understanding of some of the important interactions that influence the fluidity of model BLM interfaces. The results may be useful in the design of BLM-based biosensor devices, the performance of which may depend upon BLM properties such as fluidity. They may also provide insight into the interactions that affect fluidity in cell membranes.

The objective of this research is to investigate three classes of block copolymers, the vesicle structures they form, their response to stimuli in solution and their capabilities for use in biomimicry. The self-assembled structures of all classes of polymers will be used as a basis for templating hydrogel materials, in the interior of the vesicles, and the resulting particles will be designed to show the structural and mechanical properties similar to living cells. The synthetic block copolymers are a polyethylene glycol) and polybutadiene) PEO-b-PBd) copolymer, a polyethylene glycol) and a polydimethyl siloxane) PEO-b-PDMS) copolymer and the polypeptide block copolymer is a lysine and glycine K-b-G) copolymer. Investigation using the synthetic block copolymers will focus on whether the polymer can form vesicles, size limitations of vesicle structures, and the formation of internal polymer networks. Subsequent investigations will look at the needed steps for biomimicry. The PDMS copolymer is a novel entrant into amphiphilic block copolymers. Although characterization of the copolymer solution behavior is known, the mechanical properties of the polymer are not known. PDMS was investigated along with the PBd polymer due to the similar chemical structure and nature. The lysine-glycine copolymers are a new system of materials that form fluid vesicle structures. Therefore, characterization of how K-b-G assembly behavior and investigations of how K-b-G responds to solution conditions are needed before incorporating this copolymer into a cellular mimic. The size and mechanical behavior of the lysine-glycine vesicles are measured to compare and contrast to the synthetic systems. The goals in creating a biomimic are a hollow sphere structure with a fluid bilayer, a vesicle that has controllable mechanical properties, and with a controllable surface chemistry and density. Overall, these experiments were successful； the various properties are easily controllable: the size of vesicles created, the material properties of the vesicle interior and shell, as well as the surface chemistry of the vesicles. Investigations into the novel block copolymers were conducted, and the polypeptide block copolymer showed the ability to create vesicles that are responsive to changing salt and pH concentrations. The PDMS block copolymer system offers a new material system that will perform as well as the PBd system, but without some of the inherent drawbacks.

Podophyllotoxin is a natural medicine possessing an outstanding anti-tumour activity. It can be extracted from the rhizome of Podophillum peltatum American Podophyllum). Volumetric heating of a packed bed of particles including solvent during the extraction can eliminate the solvent pre-heating time and provide uniform and quick heating of the bed. RF-assisted extraction has a potential to be a promising extraction alternative over conventional methods. The characterization and assessment of RF-assisted extraction of podophyllotoxin is crucial. Thermal properties including specific heat capacity, thermal conductivity, and thermal diffusivity of a packed bed of P. peltatum with and without ethanol solutions were determined and the associated multiples regression equations were obtained for the purpose of thermal analysis of RF-assisted packed bed extraction process and related modeling investigations. The dielectric properties of the packed bed of rhizome particles were measured from 10 to 30 MHz using a precision LCR meter and a liquid test fixture. The effects of temperature, particle moisture content, volumetric concentration of ethanol and bed porosity on the dielectric constant, dielectric loss factor and power penetration depth were investigated. The dielectric loss factor significantly increased with the particle moisture content for the beds with 100% and 70% ethanol but not with 30% ethanol. The dielectric loss factor was proportional to temperature directly and to frequency inversely. With 30% ethanol and therefore 70% water), the dielectric loss factor of the bed dramatically increased compared to 70% and 100% ethanol. Porosity had a significant effect on the dielectric constant but not on the dielectric loss factor. The power penetration depth of a packed bed with 100% ethanol was significantly larger than those of the packed bed with 30% and 70% ethanol. Empirical regression equations were developed for simulation and design of an RF-assisted packed bed extraction of podophyllotoxin. A RF-transparent batch reactor was made of glass filled Teflon and the extraction kinetics of podophyllotoxin was characterized. The effects of temperature, ethanol volumetric concentration, solid/liquid ratio, RF heating and particle moisture content on the extraction rate and yield of podophyllotoxin were investigated at different extraction conditions. A generalized diffusion mathematical model taking into account three major particle geometries was developed and coupled with genetic algorithm for determination of effective diffusivity and partition coefficient through an inverse simulation approach. The approach was first verified by reported experimental data of andrographolide extraction followed by determining the effective diffusivity and partition coefficient of podophyllotoxin for different conditions. The optimum batch extraction condition was achieved with 30% ethanol-water solution at 53&deg；C. A prototype was developed for RF-assisted extraction of podophyllotoxin using two optical and RF-transparent reactors with horizontal and vertical orientations. Applying the optimum conditions obtained from batch experiments, the potential of RF heating for providing a uniform temperature in the packed bed was evaluated. The effect of solvent dielectric loss factor on uniform RF heating was investigated and the chemical effect of NaCl used for increasing dielectric loss factor of the solvent on podophyllotoxin was assessed. The horizontal packed bed demonstrated a large temperature gradient across the thickness of the bed during RF heating； however, a uniform RF heating was achieved when the vertical packed bed reactor was used for RF-assisted extraction of podophyllotoxin. The concentration of 2.5 g NaCl/L of the solvent at the temperature controller set point of 40&deg；C provided a relatively good uniform temperature of 50&deg；C within the bed. Evaluating three flow rates of 130, 160 and 200 ml/min for the solvent of 30% ethanol with 2.5 g NaCl/L indicated that the flow rate of 160 ml/min could provide better temperature overlap of four positions of the bed height.

Fluidized bed dryers FBDs) are used in the pharmaceutical industry to remove excess moisture from granule prior to tablet formation. Currently, the hydrodynamics associated with FBDs are not fully understood and consequently a number of product quality and control issues still exist. To improve the understanding of FBDs, the hydrodynamics of drying and the influence of important fluidized bed design parameters, such as distributor design and vessel geometry, were studied using pressure fluctuation analysis and x-ray densitometry. As granule moisture content is reduced from its initial to final state, the velocity required to fully fluidize the granule decreases and the bed voidage increases. The changes in these fluidization properties are attributed to the decrease in the interparticle force load created by a reduction in liquid bridging as moisture is removed. During constant velocity drying in a conical FBD, these fluidization properties result in a bubbling fluidization state, which evolves into a bubble coalescing regime as drying proceeds. This behaviour was identifiable using pressure fluctuation time-series analysis techniques. This demonstrates the viability of using pressure fluctuation analysis as a monitoring tool for fluidized bed drying processes. Distributor design studies using dry and wet granule in a conical fluidized bed suggest that the punched plate design limits bubble coalescence when compared to the perforated plate and Dutch weave mesh designs. Furthermore, the Dutch weave results in extensive segregation, which is undesirable from a fluidization perspective. Local drying hydrodynamic measurements using x-ray densitometry found that the punched and perforated plates generate a centralized bubbling core region during drying with a defluidized bed periphery in a cylindrical FBD. This fluidized core region grows as drying proceeds until the defluidized region disappears. Under the same operating conditions, a porous plate distributor creates extensive channelling and defluidization across the entire bed cross-section during the constant rate period of drying. These poor fluidization characteristics result from the porous plate introducing the gas into the bed as a fine dispersion. Lastly, the hydrodynamics associated with the conical vessel geometry improves the circulation and mixing patterns in FBDs. This is especially the case in the entry region of the conical bed where the high inlet gas velocity prevents defluidization around the periphery of the bed. The straight walled geometry of the cylindrical bed resulted in defluidization in this area. As a result, the hydrodynamics associated with bubbling differ between the geometries over the course of drying.

Stimuli-responsive hydrogels swell or contract in response to external pH, ionic strength or temperature, and are of considerable interest as pharmaceutical controlled release devices. Alginate, a linear polysaccharide consisting of mannuronic and guluronic acids, was used as starting material in semisynthesis of pH-responsive hydrogel. Linear alginate was chemically modified with di-aldehyde via acid-catalyzed acetalization, forming a tetrafunctional acetal-linked semisynthetic network alginate polymer SNAP) with carboxylate moieties preserved as stimuli-responsive sensors. The kinetics of acetalization were found to undergo zero and second-order reaction with respect to dialdehyde and alginate respectively. With the determined rate constant of 19.06 microL&middot；mole -1&middot；s-1 at 40&deg；C and activation energy of 78.58 kJ&middot；mol-1, a proposed predictive reaction model may be used a priori to select reaction conditions providing specific polymer properties. Gel swelling and average pore size were then able to be kinetically or thermodynamically controlled between 80–1000 fold and 30 nm-1 microm respectively. As a proof of concept, SNAP hydrogel was fine-tuned with specific swelling and pore sizes for absorptive encapsulation and controlled release of a wide spectrum of molecular sizes of proteins ranging between 1.3 to 546 kDa. SNAP hydrogels/granules demonstrated limited swelling in the simulated gastric environment, protecting proteins from enzymatic and acid degradation, while swelling in alkaline media, releasing active therapeutics in a simulated intestinal lumen pH &sim；7.8), so is under the consideration as an oral delivery vehicle for protein therapeutics. A constitutive polyelectrolyte gel model based on non-Gaussian polymer elasticity, Flory-Huggins liquid lattice theory, and non-ideal Donnan-membrane equilibria was derived, to describe SNAP gel swelling in dilute and ionic solutions. The derived model accurately describes the SNAP hydrogel swelling in acid and alkaline solutions of wide range of ionic strength. The pore sizes of SNAP hydrogel were estimated by the derived model and were comparable to those determined experimentally by thermoporometry and protein diffusion. The derived model can characterize hydrogel structure such as molecular weight between crosslinks, or can be used as predictive model for swelling and pore size if gel structural information is known, and can potentially be applied to other point-link network polyelectrolytes such as hyaluronic acid gel.

Textile dyes are molecules designed to impart a permanent colour to textile fabrics. They pose an environmental problem because they are toxic and they decrease the aesthetic value of rivers and lakes. Current technologies for dye removal cannot remove all classes of dyes and two or more technologies are usually combined to achieve satisfactory decolourization efficiencies. Lignin-degrading enzymes like laccases are potential technologies for dye decolourization and decolourization with immobilized laccase has been intensively investigated. The majority of those studies however have focused on dye disappearance and several reported that significant dye adsorption had occured during the dye removal, making the role of the enzyme unclear. Moreover, textile wastewaters contain auxiliary chemicals that can impact enzymatic dye decolourization and very few studies have evaluated the impact of those substances on laccase. This research evaluated the feasibility of treating dye-contaminated textile wastewaters with an immobilized laccase system. The first sub-objective was to examined the decolourization of Reactive blue 19 (an anthraquinone dye) by Trametes versicolor laccase immobilized on controlled porosity carrier (CPC) silica beads and the second was to analyze the kinetic effects of a non-ionic surfactant Merpol, sodium sulfate, and sodium chloride on laccase decolourization of Reactive blue 19. Decolourization of Reactive blue 19 by immobilized laccase was mainly enzymatic although dye some adsorption occurred. Decolourization led to less toxic by-products from azo and indigoid dyes whereas increased toxicity was observed for anthraquinone dyes. The feasibility of immobilizing laccase on poly(methyl methacrylate) (PMMA) through its sugar residues with a simple procedure was demonstrated and the mass of enzyme immobilized compared well with other commercial acrylic supports. The decolorization of Reactive blue 19 by laccase was inhibited by the non-ionic surfactant, Merpol by substrate depletion. A model describing this inhibition was developed and was validated by a saturated equilibrium binding experiment. While sodium sulfate (ionic strength) had no effect on either ABTS oxidation or dye decolourization, sodium chloride inhibited laccase during dye decolourization and the type and nature of the inhibition depended on the substrate. With ABTS, the inhibition was hyperbolic non-competitive whereas it was parabolic mixed with Reactive blue 19.