No description available.

In this work, methylmethacrylate, MMA was polymerized by ATRP method to obtain low molecular weight living polymers. The initiator was p-toluenesulfonylchloride and catalyst ligand complex system were CuCl-4,4&rsquo / dimethyl 2,2&rsquo / bipyridine. Polymers with controlled molecular weight were obtained. The polymer chains were shown by NMR investigation to be mostly syndiotactic. The molecular weight and molecular weight distribution of some polymer samples were measured by GPC method. The K and a constants in [h]=K Ma equation were measured as 9.13x10-5 and 0.74, respectively. FT-IR and X-Ray results showed regularity in polymer chains. The molecular weight-Tg relations were verified from results of molecular weight-DSC results.

Surgical masks are intended to be used to prevent transmission of disease from a health care worker to a patient. Often times, they are relied upon by health care workers for their own protection. In light of recent developments regarding preparation for health care worker response to global infectious diseases such as H1N1 Influenza, health care workers may experience a false sense of security when wearing surgical masks. The goal of this study was to evaluate the filtration efficiency of a double strap tie-on surgical mask. The manufacturer asserts a >95% efficiency with a 0.1 um challenge aerosol under FDA testing procedures. The NIOSH Title 42 CFR Part 84 certification criteria call for testing at a rate of 85 lpm representing a human moderate to heavy work load breathing rate. Three sizes of monodispersed aerosols (polystyrene latex beads: 0.5 um, 1.0 um, 2.0 um) were used. The specific aims were to measure the collection efficiencies of this mask for the various particle sizes. Two tests were performed. In the first, masks were affixed to a dummy head and the edges of the mask were not sealed. In the second, the edges of the masks were sealed to the head using silicone sealant, so all penetration was through the filtering material of the mask. Differences in upstream and downstream particle concentrations were measured. Thus, penetration by leakage around the mask and through the filtering material was measured. The experimental set up involved passing the aerosol from the nebulizer through a diffusion dryer and Kr-85 charge equilibrator ensuring a dry charge neutralized aerosol cloud for detection by a LASAIR particle counter. The analysis revealed that the filtration efficiency for 0.5 um particles ranged from 3% to 43% for the unsealed masks and 42% to 51% for the sealed. For 1.0 um particles, the efficiency was 58% to 75% for unsealed and 71% to 84% for sealed masks. For 2.0 um, the efficiency was 58% to 79% for unsealed masks and 69% to 85% for the sealed masks. The data were statistically significant and indicated that surgical masks were associated with very low filtration efficiency. This suggests that they may be inadequate against airborne viruses and bacteria.

This research is divided into three major parts. In part I, the critical supersaturations required for the homogeneous nucleation of 2,2,2-trifluorothanol (TFE) vapor have been measured over a temperature range (266-296 K) using an upward thermal diffusion cloud chamber (DCC). The measured supersaturations are in agreement with the predictions of both the classical and the scaled theory of nucleation. Moreover, the condensation of supersaturated TFE vapor on laser-vaporized magnesium nanoparticles has been studied under different experimental conditions, such as the supersaturation, the pressure and the electric field. In part II, the laser vaporization controlled condensation (LVCC) technique was used to prepare Au-Ag alloy nanoparticles in the vapor phase using designed targets of compressed Au and Ag micron-sized powder mixtures of selected composition. The results showed that the optical properties of these nanoparticles could be tuned depending on the alloy composition and the laser wavelength. Different intermetallic nanoparticles (FeAl and NiAl) from the vapor phase has also been prepared, using the same approach.In this work, the fraction of the charged particles generated during the laser vaporization process was used to prepare a new class of nanoparticle assemblies in the LVCC chamber under the influence of an electric field. The results showed that the electric field required to induce the formation of these nanoassemblies is material and field dependent. By coupling the LVCC chamber with the differential mobility analyzer, size-selected nanoparticles have been prepared in the vapor phase. The prepared nanoparticles were characterized by different techniques such as scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM) and UV-visible spectroscopy. In part III, new methods were developed to prepare nanoparticle-polymer composites from the vapor phase. In the first method, the LVCC method was used to prepare a carbonaceous cross-linked resin, with different nanoparticles (Ni, Pt and FeAl) embedded inside. In the second method, free radical-thermally initiated polymerization was used to polymerize a monomer vapor of styrene on the surfaces of activated Ni nanoparticles.

Crystalline polymer/salt complexes can conduct, in contrast to the view held for 30 years. The alpha-phase of the crystalline poly(ethylene oxide)₆:LiPF₆ is composed of tunnels formed from pairs of (CH₂-CH₂-O)ₓ chains, within which the Li⁺ ions reside and along which the latter migrate.¹ When a polydispersed polymer is used, the tunnels are composed of 2 strands, each built from a string of PEO chains of varying length. It has been suggested that the number and the arrangement of the chain ends within the tunnels affects the ionic conductivity.² Using polymers with uniform chain length is important if we are to understand the conduction mechanism since monodispersity results in the chain ends occurring at regular distances along the tunnels and imposes a coincidence of the chain ends between the two strands.² Since each Li⁺ is coordinated by 6 ether oxygens (3 oxygens from each of the two polymeric strands forming a tunnel), monodispersed PEOs with the number of ether oxygen being a multiple of 3 (NO = 3n) can form either “all-ideal” or “all-broken” coordination environments at the end of each tunnel, while for both NO = 3n-1 and NO = 3n+1 complexes, both “ideal” and “broken” coordinations must occur throughout the structure. A synthetic procedure has been developed and a series of 6 consecutive (increment of EO unit) monodispersed molecular weight PEOs have been synthesised. The synthesis involves one end protection of a high purity glycol, functionalisation of the other end, ether coupling reaction (Williamson's type ether synthesis³), deprotection and reiteration of ether coupling. The parameters of the process and purification methods have been strictly controlled to ensure unprecedented level of monodispersity for all synthesised samples. Thus obtained high purity polymers have been used to study the influence of the individual chain length on the structure and conductivity of the crystalline complexes with LiPF₆. The results support the previously suggested model of the chain-ends arrangement in the crystalline complexes prepared with monodispersed PEO² over a range of consecutive chain lengths. The synthesised complexes constitute a series of test samples for establishing detailed mechanism of ionic conductivity. Such series of monodispersed crystalline complexes have been studied and characterised here (PXRD, DSC, AC impedance) for the first time. References: 1. G. S. MacGlashan, Y. G. Andreev, P. G. Bruce, Structure of the polymer electrolyte poly(ethylene oxide)₆:LiAsF₆. Nature, 1999, 398(6730): p. 792-794. 2. E. Staunton, Y. G. Andreev, P. G. Bruce, Factors influencing the conductivity of crystalline polymer electrolytes. Faraday Discussions, 2007, 134: p. 143-156. 3. A. Williamson, Theory of Aetherification. Philosophical Magazine, 1850, 37: p. 350-356.

Polymeric monodispersed nanocarriers with controlled shape and size have been fabricated in the literature primarily using top down processes such as imprint lithography. In this dissertation, the geometric and material property limits of imprint based techniques have been studied. The resulting insight has led to the creation of new processes that significantly extend the limits of imprint processes in several ways: (i) Ability to print nanocarriers with ultra-soft biomaterials (<1MPa modulus); (ii) Sub-50nm diameter cylindrical particles with >3:1 aspect ratio with >5x enhanced wafer yield; (iii) Creation of reentrant barrel shapes that have the potential to be valuable in cellular uptake, such shapes being significant as they lead to fundamental demolding challenges in prior imprint processes; and (iv) Multi-layer nanocarriers which can potentially provide sophisticated functionality such as tailored release kinetics of one or more drugs. By understanding the requirements of bio-functional nanocarriers and related manufacturing constraints, a previously explored Bio Jet and Flash Imprint Lithography (Bio J-FIL) process was refined to perform successful imprints and improve the nanocarrier fabrication scalability. Next, two new fabrication processes have been developed. The first process is called Decoupled Functional Imprint Lithography (D-FIL) which allows fabrication of ultra-soft bio-functional materials (modulus of <1 MPa), challenging sizes (sub-50nm diameter cylinders with aspect ratio > 3:1), and reentrant barrel shapes. The second decoupled process, Dual Removable Layer Lithography (DRLL), has been developed to specifically create multi-layered cylindrical nanocarriers. Nanocarriers fabricated with D-FIL and DRLL process have been shown to chemically bind with an imaging agent, and model anti-cancer drugs. Drug (siRNA) retention (>90% over 9 days) and stimuli triggered release studies were performed on sub-100nm cylindrical PEGDA nanocarriers. It was found that these nanocarriers show accelerated triggered drug release when exposed to a hydrolase, Cathepsin B. While the exact mechanisms causing the triggered release are not fully understood, a few possible explanations are provided based on the experiments reported. Finally, the D-FIL, the DRLL, and the refined Bio J-FIL processes have been successfully demonstrated at the prototype scale as well as at the pilot scale in collaboration with an industrial partner, Molecular Imprints Inc. / text

L’objectif de ce travail est d’élaborer des matériaux composites modèles nanotubes de carbone/polymères permettant de tirer profit des propriétés des nanotubes de carbone à l’échelle macroscopique. L’obtention de tels matériaux nécessitant une fonctionnalisation homogène entre les nanotubes de carbone et les polymères, les nanotubes de carbone utilisés doivent être individuels et de même réactivité chimique, donc de même diamètre. Ainsi, ils doivent être synthétisés par CVD par des nanoparticules catalytiques monodisperses et supportées. Dans la première partie, nous avons élaboré une nouvelle méthode générique de synthèse de nanoparticules d’oxydes métalliques supportées. Nous avons principalement détaillé la synthèse de nanoparticules de Fe2O3 dont la distribution en taille est de 1.1 ± 0.3 nm. Dans la deuxième partie, après avoir étudié la stabilité thermique de ces nanoparticules, nous les avons utilisées pour catalyser la croissance des nanotubes de carbone monofeuillets individuels par CVD. La caractérisation des nanotubes obtenus par Raman indique une distribution en diamètre exceptionnellement étroite de 1.27 ± 0.15 nm. Dans la troisième partie, nous avons tout d’abord étudié la mise en solution des nanotubes de carbone par fonctionnalisation non covalente avec un polymère hydrosoluble le POE portant un motif pyrène en bout de chaîne et mis en évidence un phénomène de déplétion qui limite la solubilisation des nanotubes. Nous avons ensuite élaboré des matériaux composites nanotubes de carbone/rrP3HT par fonctionnalisation covalente et non covalente et nous avons étudié l’efficacité de séparation de charge dans les deux cas de fonctionnalisations. / The aim of this work is to develop composite materials carbon nanotubes/polymers to take advantage of properties of carbon nanotubes at macroscopic scale. To get such materials, homogeneous functionalization between carbon nanotubes and polymers is required, carbon nanotubes must be individual with the same chemical reactivity, therefore the same diameter. Thus, they must be synthesized by CVD from monodispersed and supported catalyst nanoparticles. In the first part, we developed a new universal method for the synthesis of metal oxide supported nanoparticles. We mainly detailed the synthesis of Fe2O3 nanoparticles with size distribution of 1.1 ± 0.3 nm. In the second part, after studying the thermal stability of these nanoparticles, we used them to catalyze the growth of individual single wall carbon nanotubes by CVD. The caracterisation of the obtained nanotubes by Raman show exceptionally narrow diameter distribution of 1.27 ± 0.15 nm. In the third section, we first studied the dispersion of carbon nanotubes by noncovalent functionalization withhydro-soluble polymer POE with pyrene as end group and revealed depletion phenomena that limit the solubilization of nanotubes. Then we developed composite materials carbon nanotubes/rrP3HT by covalent and noncovalent functionalisation and we studied the efficiency of charge separation in both cases of functionalization.