Rozprawy doktorskie na temat „Polystyrene Latexes”

Les particules à patchs magnétiques ont pris une importance toute particulière dans l’étude des assemblages vers de nouvelles structures colloïdales. L’état de l’art nous a montré que la majorité des systèmes synthétisés et étudiés concerne des particules à un seul patch magnétique limitant ainsi les possibilités de structures accessibles par assemblage. Notre objectif s’est donc centré sur l’obtention de nanoparticules sphériques de polystyrène (PS) porteuses de plusieurs nanoparticules superparamagnétiques à leur périphérie. La voie multi-étapes retenue a consisté à préparer par polymérisation en émulsion ensemencée des particules Janus magnétiques (MJPs) présentant un nodule de PS qui a ensuite été rendu « collant » dans un mélange de bon/mauvais solvant pour fusionner avec celui d’un nombre limité de particules similaires. Pour servir de patchs magnétiques d’environ 100 nm, nous avons préparé des supraparticules colloïdales de nanoparticules d’oxyde de fer superparamagnétiques par un procédé incluant des étapes d’évaporation d’une phase émulsifiée, de consolidation par la silice et de resserrement de la distribution de taille par purification. Les paramètres optimaux de la polymérisation en émulsion ensemencée (composition du mélange de tensioactifs, nature et taux de greffage de l’agent de couplage) et de l’assemblage (nature et fraction du bon solvant, concentration particulaire, température et durée d’incubation) ont été préalablement déterminés avec des nanoparticules-modèles de silice présentant un diamètre et un état de surface similaires. L’application de ces conditions aux MJPs s’est avérée plus compliquée que prévue notamment en raison de la faible quantité de supraparticules disponible et cela a notamment conduit à définir de nouvelles conditions de polymérisation en émulsion ensemencée. Finalement, des lots de nanoparticules de latex à deux ou trois patchs magnétiques ont été obtenus, mais nécessiteront des étapes de purification avant d’envisager des études d’assemblage sous champ magnétique
Magnetic patchy particles are of great interest for assembly into novel colloidal structures. The state of the art showed us that the vast majority of synthesized and studied systems concerns particles with a single magnetic patch, thus limiting the structures accessible by particles assembly. Therefore, the main goal of the present study was to develop spherical polystyrene (PS) nanoparticles with two or many superparamagnetic nanoparticles on their surface. Our multistep process involved first the fabrication of Magnetic Janus particles (MJPs) by seeded-growth emulsion polymerization and subsequent incubation in suitable mixtures of good and bad solvents to make their polystyrene lobe “sticky”. MJPs are then ready to coalesce into self-assembled structures with small aggregation numbers. In order to obtain magnetic patches with a size range of 100 nm, we prepared colloidal supraparticles highly loaded with superparamagnetic iron oxide nanoparticles through a multistep procedure, including evaporation-induced emulsion, silica coating and purification, leading to a narrowing of the size distribution. The optimal parameters of the seeded-growth emulsion polymerization (surfactant mixture composition, coupling agent type, surface grafting density) and of the assembly (solvent quality, good solvent content, particle concentration, temperature and incubation time) were previously determined with silica nanoparticles as models with similar particle diameter as well as surface chemistry. We demonstrated that under the same conditions MJPs synthesis became trickier, mainly because of the small amount of available supraparticules. This led us to implement new seeded-growth emulsion polymerization conditions. Finally, batches of latex nanoparticles with two or three magnetic patches were obtained, but required further purification steps before investigating their assembly behavior under magnetic field

With great strides in neuroscience that have been made in the past decade, further understandings of complex neural systems require extensive neural information from chronic implantation of biocompatible neural devices. Polyimide-based flexible microelectrode arrays were one of the earlier biocompatible neural devices due to its mechanical impedance matching with brain tissue. In this work, we propose to incorporate non-conventional laser ablation method for fabrication of flexible biocompatible microelectrodes. We also present a novel approach to modifying flexible microelectrodes with macroporous platinum film using latex polystyrene sphere template. Maskless laser ablation was used to pattern the electrode, and probe definition as well creating the contact openings of flexible polyimide electrodes. Laser ablation is a non-photolithographic method which does not require conventional cleanroom environment and is ideal for rapid prototyping of devices. An ordered polystyrene bead template was deposited by simple pipetting of bead solution over gold contact openings and evaporating in ambient room setting. Pulsed-potentiostatic mode electrochemical deposition of platinum through the polystyrene bead template resulted in increase in effective surface area of electrodes. The impedance of the platinum modified electrodes increased by two orders of magnitude compared to unmodified electrodes. Synergetic modification of microelectrodes with macroporous platinum film and polymer-brush coating can lead to fabrication of highly biocompatible microelectrode with low impedance characteristics.
Applied Science, Faculty of
Electrical and Computer Engineering, Department of
Graduate

In this thesis various physicochemical factors which determine the characteristics of latex agglutination immunoassays are examined. A model of antibodies reacting with antigen (bovine serum albumin; BSA) adsorbed to the surface of polystyrene latex (PSL) beads was examined. The adsorption studies of BSA to PSL showed that the mass of BSA adsorbed at saturation depends on the type of polystyrene latex. Latexes with highly hydrophobic surfaces adsorbed more BSA molecules than those with lower hydrphobicity. Desorption studies showed that latexes that maximize adsorption lost the lowest fraction of their bound BSA molecules following extensive buffer wash. Partial desorption of BSA from PSL was achieved by the addition of detergent, whereas the addition of more BSA molecules or other macromolecules such as PEG or IgG did not displace the adsorbed BSA molecules. Examination of the material removed from the surface of the latexes by SDS-PAGE analysis showed that the composition of the adsorbed layer was enriched in the higher molecular weight oligomers of BSA, relative to their concentrations in the stock solution. A model in which adsorbed protein is assumed to undergo a polymerization reaction provides a general explanation of the observed results. Studies of polyclonal antibody (anti-BSA IgG) binding to antigen-coated PSL showed that the surface concentration of bound antibody depends on the surface concentration of antigen on the latex particles and on the availability of PSL surface area not occupied by antigen. Analysis of shear induced aggregation results show that for low surface coverage of latex particles by protein antigen in stable suspension, relatively low concentrations of specific antibodies are required to cause agglutination. Increasing surface density of antigen requires significantly higher concentrations of specific antibodies to produce agglutination. For a given surface coverage of antigen, results show that increasing the shear rate decreases the antibody concentration necessary to produce a given degree of agglutination. A remarkable structure formation and long range ordering exhibited by floes of latex coagulating in salt under intermediate shear rates was observed. This structure formation was not observed during antibody-induced agglutination under shear.
Science, Faculty of
Chemistry, Department of
Graduate

Fonctionnalisation superficielle du polystyrene par bis 2-chloro ethyl-itaconate. Determination des constantes cinetiques et physicochimiques. Etude de la copolymerisation avec le styrene et l'acrylate de butyle

Polyaniline nanocomposites doped with poly(vinylsulphonate) (PV-SO3 &minus
) and nanostructured polystyrene (PSNP) latex beads functionalized with amine (PSNP-NH2) and sulphate (PSNP-OSO3 &minus
) were prepared and characterised for use as nitrite electro-catalytic chemosensors and ochratoxin A immunosensors. The resultant polyaniline electrocatalytic chemosensors (PANI, PANI|PSNP-NH2 or PANI|PSNP-OSO3 &minus
) were characterized by cyclic voltammetry (CV), ultraviolet-visible (UV-Vis) spectroscopy and scanning electron microscopy (SEM). Brown-Anson analysis of the multi-scan rate CV responses of the various PANI films gave surface concentrations in the order of 10&minus
8 mol/cm. UV-vis spectra of the PANI films dissolved in dimethyl sulphoxide showed typical strong absorbance maxima at 480 and 740 nm associated with benzenoid p-p* transition and quinoid excitons of polyaniline, respectively. The SEM images of the PANI nanocomposite films showed cauliflower-like structures that were <
100 nm in diameter. When applied as electrochemical nitrite sensors, sensitivity values of 60, 40 and 30 &mu
A/mM with corresponding limits of detection of 7.4, 9.2 and 38.2 &mu
M NO2 &minus
, were obtained for electrodes, PANI|PSNP-NH2, PANI and PANI|PSNP-SO3 &minus
, respectively. Immobilisation of ochratoxin A antibody onto PANI|PSNP-NH2, PANI and PANI|PSNPSO3 - resulted in the fabrication of immunosensors.

The use of 153Sm-incorporated polystyrene latex particles for the external image scanning of tumors was simulated in four murine strains. Reticuloendothelial blood clearance and tissue localization of 0.5 mum and 1.0 mum fluorescent PSL was evaluated in RE-competent and RE-depressed mice following IV injection and oral particle administration. Intravenous injection of PSL revealed differences in blood clearance rates and tissue distribution patterns with respect to strain and particle size; an explanation based on genetic strain derivation is offered. RE depression in the Balb/c resulted in higher circulating blood levels of both particle sizes without affecting tissue distribution patterns; the use of dissimilarly sized particles for blocking and testing resulted in dramatic decreases in organ PSL concentrations and alterations in apparent kinetic rate constants. Balb/c blood levels of orally administered particles were increased and remained temporally constant while tissue concentrations were generally lower than IV-injected levels.

Les latex magnetiques, isodisperses en taille, hydrophiles, thermosensibles, fonctionnalises peuvent etre utilises comme support de tests de diagnostic. Afin d'obtenir de telles particules, un procede en plusieurs etapes a ete envisage. Ces microspheres composites ont ensuite ete utilisees pour etudier l'immobilisation d'un anticorps. Des particules de polymere isodisperses en taille, cationiques, hydrophobes ou hydrophiles ont d'abord ete synthetisees. L'etude de la copolymerisation en emulsion du styrene et du monomere fonctionnel amine, l'hydrochlorure de methacrylate d'aminoethyle (mae), sans tensioactif, a mis en evidence notamment la diminution des tailles et de la densite de charges par unite de surface des particules en presence de mae ainsi que son role actif comme agent de transfert. Les latex hydrophiles amines core-shell poly(styrene/n-isopropylacrylamide) (nipam) ont ete synthetises en deux etapes selon diverses formulations ; ceux contenant seulement du polynipam ont ete obtenus en reacteur ferme. Le materiau magnetique est apporte par le ferrofluide compose de nanoparticules d'oxyde de fer superparamagnetiques et chargees negativement. L'adsorption des particules de ferrite a ensuite ete menee en presence de differents latex cationiques. Les valeurs du plateau des isothermes d'adsorption sont les plus elevees dans le cas des microspheres hydrophiles et dependent a la fois de l'epaisseur et de la composition de la chevelure a base de polynipam. L'encapsulation des ferrites, presentes a la surface des differents latex synthetises, a ete finalement effectuee par polymerisation du nipam en utilisant l'acide itaconique comme monomere fonctionnel. Dans tous les cas, des particules hydrophiles et isodisperses ont ete obtenues. La quantite de ferrites incorporees et la stabilite des microspheres sont principalement influencees par le milieu reactionnel, la formulation, le procede de polymerisation. Enfin, des conditions de ph et de force ionique favorables a l'adsorption de l'anticorps anti--ftoproteine sur les latex magnetiques carboxyliques ont ete determinees. Le couplage covalent, effectue dans ces memes conditions, a ensuite permis une detection specifique de l'-ftoproteine et presentant une faible limite de sensibilite.

Différents dérivés hydrophobisés du dextrane (dextrane-phenoxy, dexph) et des copolymères dextrane-phenoxy-poly(oxyethylene) (dexph POE) ont été utilisés pour modifier les propriétés de surface de nanoparticules de polystyrène. Les dérivés dexph se déposent sous la forme de couches interfaciales relativement denses, tandis que les copolymères dexph POE forment une double-couche moins compacte, constituée d'un coeur de dextrane et d'une couronne externe de POE. La structure des couches adsorbées est essentiellement déterminée par le nombre de points de contact entre le dextrane et la surface du polystyrène, ainsi que par les répulsions des chaines de POE entre elles et avec celles de dextrane. Elle joue un rôle déterminant sur la stabilité des suspensions, en présence de sels ou sous l'effet de la température. Pour éviter la désorption de polymère en présence d'espèces hydrophobes telles que les protéines, les couches déposées ont été réticulées par voie chimique. Concernant les particules recouvertes des copolymères dexphpoe, les protéines sont capables de déformer et de pénétrer la couche épaisse de POE, puis de s'adsorber à la surface du polystyrène en déplaçant certains segments de dextrane. Au contraire, les recouvrements à base des dérivés dexph sont moins perméables aux protéines, à condition que le nombre de points d'ancrage entre le dextrane et le polystyrène soit suffisamment élevé. Nous avons également montre que la concanavaline a (cona), qui présente des sites de fixation spécifiques du glucose, s'adsorbe de façon spécifique sur les particules dont la surface externe est constituée de dextrane. Enfin, les dérivés du dextrane ont également été utilisés comme stabilisants pendant la polymérisation en émulsion du styrène. Les résultats préliminaires montrent qu'il est ainsi possible d'obtenir des particules dont la surface est hydrophile et non-attractive vis-à-vis des protéines. Comme précédemment, le nombre de points de contact entre le dextrane et la surface du polystyrène est un paramètre déterminant.

L'objectif de ce travail a consiste a synthetiser et caracteriser des latex polystyrene amines, afin d'etudier l'adsorption et le couplage d'oligodeoxyribonucleotides (odn) sur ces supports. Dans un premier temps, la synthese de latex a ete effectuee par copolymerisation en emulsion, sans tensioactif, du styrene et d'un monomere derive amine sous forme protonee, l'hydrochlorure d'aminomethylstyrene, en presence d'un amorceur egalement cationique, le dihydrochlorure de 2,2' azobis (2-amidino propane). L'ajout de monomere fonctionnel en debut de polymerisation a permis le controle de la taille des particules, alors qu'un second ajout a forte conversion a conduit a une meilleure incorporation de surface. La caracterisation moleculaire et colloidale de ces latex a aide notamment a comprendre les mecanismes de polymerisation. En complement, des mesures d'angles de contact sur ces latex ont montre le caractere assez hydrophobe de l'interface particulaire. Dans une seconde partie, l'etude d'adsorption d'un odn modele a ete menee en fonction de divers parametres (ph, force ionique, presence d'un tensioactif non ionique. . . ). Une forte affinite entre le latex amine et l'odn a ete mise en evidence, les interactions etant majoritairement electrostatiques. Une adsorption non specifique, due a des interactions dispersives, a egalement ete demontree en rendant hydrophile la surface du latex par adsorption d'un tensioactif non ionique, le triton x 405. Enfin, le couplage de differents odn a ete realise par l'intermediaire d'une molecule bifonctionnelle, le 2,4 phenylene diisothiocyanate. Le couplage s'est avere favorise soit lorsque les bases nucleiques de l'odn reagissaient avec cet agent de couplage, soit en presence d'une adsorption residuelle. Une etude de conformation de surface par diffusion de neutrons a montre que l'odn adoptait une conformation etalee sur la surface, ce qui a ete confirme par une etude d'hybridation de l'odn suivie par transfert d'energie de fluorescence.

Ce travail a consisté à élaborer des supports magnétiques particulaires fonctionnalisés à partir d'émulsions directes de ferrofluide pour des applications dans le domaine du diagnostic médical. Cela a d'abord nécessité la préparation d'émulsions magnétiques de type huile-dans-eau obtenues par émulsification d'un ferrofluide organique. Ce ferrofluide a été synthétisé par voie chimique, puis caractérisé à l'aide de nombreuses techniques afin de déterminer sa composition, la nature et la taille des nanoparticules d'oxyde de fer ainsi que ses propriétés magnétiques. Les émulsions magnétiques obtenues ont également été caractérisées afin de mettre en évidence la composition et la morphologie des gouttelettes ainsi que les propriétés colloi͏̈dales. Les particules de latex magnétiques ont ensuite été préparées par polymérisation à l'intérieur des gouttelettes d'émulsion gonflées par le styrène. Deux principaux systèmes de polymérisation ont été étudiés, le premier faisant intervenir un amorceur organosoluble (AIBN), le second un amorceur hydrosoluble (KPS). L'utilisation d'un polymère amphiphile, dont l'adsorption à la surface des gouttes d'émulsion a été préalablement étudiée, a permis d'obtenir des particules de latex fonctionnalisées. Différents mécanismes de polymérisation ont également été proposés en fonction de la nature de l'amorceur utilisé. La morphologie des particules de latex magnétiques a été discutée en détail sur la base d'une approche thermodynamique et cinétique du phénomène. Finalement, des conjugués particules/ODN ont été préparés puis étudiés à l'aide de la technique de mesure de forces colloi͏̈dales, qui a montré l'évolution de la nature des forces répulsives s'exerçant entre les particules en fonction du pH et de la force ionique du milieu. L'épaisseur de la couche d'ODN immobilisée en surface a également été déterminée par cette méthode.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 1999.
Includes bibliographical references (leaf 50).
The dynamics of polystyrene latex spheres [650 A radius] suspended in glycerol have been studied using the techniques of dynamic light scattering in the single scattering limit and diffusing wave spectroscopy in the multiple scattering regime using a charge coupled device [CCD] camera as our detector. Our experiments, which investigated suspensions of various concentrations [0.001by Bradley R. Plaster.
S.B.

Le caractère vivant et contrôlé de la polymérisation anionique nous a permis de synthétiser différents polymères amphiphiles à base de polystyrène et de poly(oxyde d'éthylène) porteurs d'une entité polymérisable à l'extrémité du bloc hydrophobe. Leur efficacité comme stabilisants lors de polymérisations en milieu dispersé a été évaluée sur le plan cinétique et colloi͏̈dal. La modification de paramètres intrinsèques au stabilisant, masse molaire, architecture, nature de l'insaturation ou propres au procédé de polymérisation, polymérisation en émulsion en discontinue et en dispersion, a permis d'obtenir des particules stables, isométriques et fonctionnalisées. L'utilisation d'un tel latex comme support d'entités biologiques en vue de réaliser des tests immunologiques est abordée dans cette thèse.

Certain models of NIOSH-approved filtering facepiece air purifying respirators are manufactured with stapled head straps. Depending on the manufacturer, these head straps may be stapled to the filter media itself. This may cause leakage through the filter media of the respirator, potentially exposing the user to an unacceptable level of contaminant. In this study, monodisperse polystyrene latex (PSL) spheres were generated to challenge four replicates of a N95 single use respirator model made by the same manufacturer. Nominal particle sizes of the PSL spheres used to challenge the respirators were 0.5, 1, and 2 micrometers in diameter. All respirators were sealed onto a custom built testing assembly and tested in a sealed chamber. Particle sizes of interest were generated using a nebulizer, and passed through a diffusion dryer and a Krypton-85 radioactive source prior to entering the test chamber. The dryer reduces the humidity of the aerosol generating by the nebulizer, while the radioactive source neutralizes the charge of the aerosol cloud. The test chamber was constructed using a glass aquarium measuring 32 x 53 x 122 centimeters. Three stainless steel air diffusers were placed above the testing compartment to evenly distribute the aerosol in the chamber. An exhaust manifold was placed at the lower part of the chamber beneath another stainless steel diffuser below the area where test respirators were placed. The respirators were challenged as received from the manufacturer with 0.5, 1 and 2 micrometer-sized (PSL) spheres. The same procedure was repeated for each respirator after sealing the areas where the head straps were stapled with silicon rubber. Testing was conducted at a flow rate of 85 liters per minute, as specified in the NIOSH respirator testing protocol. A laser particle counter was used to measure the concentration inside and outside of the respirator. The results showed unsealed efficiencies for particle sizes 0.5, 1, and 2 micrometers of 96.68%, 99.72%, 99.88% and sealed efficiencies of 97.35%, 99.82%, 99.93% respectively. There were no differences for particle size or sealing at 1.0 and 2.0 micrometers. A significant drop in efficiency was observed when testing with 0.5 micrometer PSL spheres. The drops in efficiency are not sufficient to reduce the integrity of the respirator for N95 certification. However, the leakages detected will have a cumulative effect when added to other sources of single use respirator leakage in the field.

L'objectif de ce travail a consiste a elaborer des latex hydrophiles fonctionnalises et thermosensibles, afin d'envisager de nouvelles methodes d'immobilisation orientee des proteines. La premiere partie de cette etude a ete consacree a la synthese de differents modeles de particules : des latex cur-couronne poly(styrene/n-isopropylacrylamide) fonctionnalises par un monomere cationique l'aminoethylmethacrylate (aem) ont ete obtenues par polymerisation en emulsion an l'absence de tensioactifs. Des latex hydrogels ont ete prepares a partir du n-isopropylmethacrylamide (nipmam) par polymerisation par precipitation en presence d'un reticulant (n, n'-methylene bisacrylamide, mba). Ces particules microgels dont la temperature de transition (lcst = lowest critical solubility temperature) est superieure a celle du poly(nipam) (i. E. 32\c) ont ete fonctionnalisees a l'aide d'un monomere prealablement synthetise (l'acide n-(vinylbenzylimino)-diacetique) capable de complexer les ions metalliques. La deuxieme partie traite de la caracterisation physico-chimique et colloidale de ces latex en termes de taille, de comportement electrocinetique, de stabilite colloidale, de degre de reticulation, de degre de gonflement, etc cette etude a contribue non seulement a la comprehension des mecanismes de polymerisation, mais aussi a mieux apprehender les phenomenes d'interactions gouvernant l'adsorption des proteines par une meilleure connaissance des systemes synthetises. Dans une derniere partie, l'adsorption de deux proteines modeles a ete etudiee en fonction de divers parametres (ph, force ionique, temperature, etc). La temperature qui permet de moduler la balance hydrophile-hydrophobe de la surface des particules thermosensibles est le parametre majeur gouvernant l'adsorption des proteines sur ce type de supports, celle-ci s'adsorbant preferentiellement par des interactions hydrophobes. Enfin l'immobilisation d'une proteine recombinante genetiquement modifiee (rh24k) provenant de la capside du virus du sida a ete exploree selon deux nouvelles voies : (i) en utilisant un copolymere reactif le poly(anhydride maleique-co-methyl vinyl ether) ou poly(amve) comme agent de couplage et directement par complexation via un ion metallique d'une sequence de six histidines introduite par genie genetique.

Much of the aerosol research completed at the University of South Florida has revolved around evaluating industrial hygiene equipment and instrumentation in environmental chambers. Data collected during these studies has provided valuable baseline data on equipment and instrument performance under calm air conditions. A newly constructed wind tunnel now allows researchers to evaluate industrial hygiene instruments under moving air conditions. Because the wind tunnel is capable of producing wind velocities that a worker could encounter in the occupational setting, researchers may gain insight into instrument performance under simulated field conditions. Because aerosols can be introduced into the new wind tunnel testing section, researchers can also challenge industrial hygiene equipment and instrumentation with aerosols in sizes ranges that are of interest in public health. The purpose of this dissertation research was to develop a new wind tunnel to be used for aerosol research at the University of South Florida. Three specific aims had to be met for this study to be successful. They included: (1) designing a wind tunnel based on best practice information outlined in scientific literature, (2) constructing an operable wind tunnel to be used for aerosol research, and (3) characterizing wind tunnel performance by examining the wind tunnel velocity profile, turbulence intensity, and aerosol introduction/collection. The actual wind tunnel was constructed to a length of approximately 20 feet, a height of approximately 2 feet at its tallest point, and includes an entrance filter housing, a settling chamber, a contraction, a testing section, a diffuser, an exit filter housing, a fan, and exhaust duct. All components were designed and constructed using guidelines and best practices reported in the scientific literature. Velocity profile measurements were the first way that this wind tunnel was characterized. In order to successfully obtain measurements, the wind tunnel cross section was divided into 16 equal quadrants. Five measurements were taken for each quadrant at each wind velocity. Target wind velocities for this research were 0.5 m/s, 1.0 m/s, and 2.0 m/s. Actual average wind velocities of 0.48 m/s, 1.00 m/s, and 2.04 m/s. All were within established limits reported in the scientific literature. Turbulence intensity measurements were the second way that this wind tunnel was characterized. In order to successfully obtain measurements, the wind tunnel cross section was divided into 16 equal quadrants. Five measurements were taken for each quadrant at each wind velocity. Wind tunnels are typically designed to have the lowest turbulence intensity possible, generally below 10%. The overall average turbulence intensities for this wind tunnel at wind velocities of 0.5 m/s, 1.0 m/s, and 2.0 m/s were 9%, 10%, and 8% respectively. Overall turbulence intensity measurements were at or below 10%. Isokinetic sampling was the final method used to characterize this wind tunnel by collecting and detecting aerosols traveling through the wind tunnel testing section. The wind tunnel was operated at wind velocities of 0.5 m/s, 1.0 m/s, and 2.0 m/s with isokinetic sampling flow rates of 15.4 L/min, 30.9 L/min, and 61.7 L/min respectively. Monodisperse fluorescent polystyrene latex spheres were used as the test aerosol because they are uniform in size and shape and can be detected by fluorometry. The Blaustein Multi-Jet Atomizer (BLAM) was used to generate monodisperse fluorescent polystyrene latex aerosol 0.5 µm and 2.0 µm particles from liquid suspensions. The Vilnius Aerosol Generator (VAG) was used to generate monodisperse fluorescent polystyrene latex aerosol of 6.0 µm and 12.0 µm particles from dry powders. Nitrogen gas was used for delivering test aerosols into the wind tunnel. Five experimental runs were completed for each particle size and wind velocity for a total of 60 experimental runs. Fluorescence was detected in all 60 samples with average mass concentrations ranging from 0.000050 ng/ml to 0.002703 ng/ml. Based on velocity profile measurements, turbulence intensity measurements, and isokinetic sampling, the performance of University of South Florida wind tunnel was found to be excellent, indicating that it was designed and constructed appropriately. The wind tunnel can now successfully be used by researchers interested in evaluating industrial hygiene sampling equipment with aerosols ranging from 0.5 µm to 12.0 µm in moving air with velocities ranging from 0.5 m/s to 2.0 m/s.

Les copolymères blocs, qui comportent dans une même molécule deux ou plusieurs séquences de nature chimique différente, peuvent se prêter à la stabilisation d'émulsions lorsque ces séquences présentent une hydrophilie différente. Comme exemple typique, on peut citer les copolymères poly(styrène-b-oxyde d'éthylène), qui ont été utilisés lors de cette étude pour stabiliser des particules de latex à base de styrène et d'acrylate de butyle. Après avoir synthétisé une gamme de copolymères bi et triblocs par voie anionique, l'étude des propriétés émulsifiantes de solutions aqueuses de ces tensio-actifs a montré que leur CMC est très faible, de l'ordre de 10-7 M/l. La partie principale de ce travail a été consacrée à l'étude de la polymérisation en émulsion de styrène et d'acrylate de butyle en présence de tels tensio-actifs macromoléculaires. L'étude cinétique du processus a tout d'abord permis d'élaborer un schéma réactionnel, qui suit globalement celui décrit par Harkins. Lors de cette étude, la présence d'une chevelure de Poe à la surface des particules, de même qu'un phénomène de piégeage du tensio-actif macromoléculaire ont été démontrés. Finalement, l'étude des différentes étapes de la filmification et des propriétés thermomécaniques des films ont montré l'existence d'eau structurée, et une coalescence incomplète des latex

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.

Ce travail concerne les proprietes des gels de latex polystyrene-poly(acrylate de butyle-acide carboxylique) a l'etat pur et ceux additionnes de kaolin ou de carbonate de calcium. En vue d'explorer la structure des films de latex, nous avons fait appel a plusieurs methodes d'investigations: extraction de chaines libres, le gonflement, la relaxation magnetique nucleaire et la viscoelasticite. Chaque etat de gelification, caracterise par des parametres physico-chimiques, est identifie par une variable pertinente, fonction du taux d'acide carboxylique. De plus, la variation de la fraction de gel avec cette variable a ete decrite dans le cadre de la theorie de percolation. La caracterisation de ces gels complexes repose egalement sur l'analyse de la texture du reseau. Nous avons clairement mis en evidence que l'etat de gonflement a l'equilibre des milieux latex est assimile a un ensemble de systemes fonctionnalises aux extremites a la concentration de recouvrement. La rmn a permis d'affiner la description du reseau. En effet, par une analyse detaillee des signaux rmn, nous avons degage deux parametres fondamentaux: le premier est directement relie aux taux de gel, le second rend compte de l'anisotropie des mouvements d'isomerisation des unites monomeres. De plus, leur comparaison nous renseigne sur l'etat de coalescence des films de latex en temperature. Tous les resultats experimentaux conduisent finalement a une description globale et coherente de la structure statistique des etats de gelification de nos milieux

Filtration is the most efficient method of aerosol monitoring and control. A number of theories (Bradley, 1932); (Hamaker, 1937); (Johnson et al., 1971); (Wang and Kasper, 1991); (Dahneke, 1995); (Wall et al., 1990) have been developed to describe the particle interaction with surface of a filter and to estimate the probability of the particle adhesion onto a surface. A range of the particle, filter and process parameters could contribute to the strength of the adhesion. Some of them are: hardness and cross-sectional shape of the fiber, smoothness of either the fiber or particle, air humidity, the effect of particle shape and many others. Obviously, the particle size (and correspondingly the surface area) also plays a crucial role in the bouncing processes. However, despite its importance in the research field the detailed mechanisms of the particle-fiber collision and possibility for the particle to bounce or to be re-entrained have not been fully explored. Therefore, there is a need for a theoretical and experimental knowledge concerning the influence of particle bouncing on filtration and separation processes. Although, some work on the effect of particle shape on filtration process has been done, there is still need for further research regarding the influence of motion of the particles of different shape along a fiber...
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Engineering
Science, Environment, Engineering and Technology
Full Text

碩士
國立臺灣大學
材料科學與工程學研究所
90
Poly(styrene-b-sodium 4-styrenesulfonate) block copolymers were synthesized via living free-radical polymerization. First, the macroinitiator, PSSNa, was prepared by the use of styrene sulfonic acid as monomer, benzoyl peroxide as monomer, and 2,2,6,6-tetramethyl 1-piperidynyloxy as stable free radical in ethylene glycol-water mixture at 130℃. The second step, emulsion polymerizations were carried out at 125+5℃ in high pressure reactor using styrene as monomer and PSSNa as macroinitiator. Molecular weights characteristic and chemical structure of both macroinitiator and block copolymer were examined by GPC and NMR techniques, respectively. SEM was employed to study the shape and size of latex. Experimental results show the size of latexes are in the range of 0.1-0.5μm, the molecular weights are about ten millions and the polydispersity of PSSNa-PS copolymer latexes is narrow.

碩士
國立臺灣大學
材料科學與工程學研究所
91
Abstract The Polyaniline(PANi)-coated polystyrene(PS) core-shell latexes were synthesized. Electrically conductive films were made from core-shell latexes. Thermal analysis of the core-shell latexes were studied by DSC and TGA. In this study, the preparation and characterization of core-shell latex film formation were studied. The effects of the annealing temperature and atmosphere (air/N2) on the resistance of film were investigated. The film morphologies during the film formation were observed by Scanning electron microscopy (SEM). Furthermore, the relation among conductivity, annealing time and temperature was studied in order to characterize the PS-PANi film conduction transport mechanism.

碩士
國立臺灣大學
化學工程學研究所
89
A feasible route for preparing polystyrene/polyaniline core shell latex was developed . The monodisperse cationic polystyrene latex was synthesized by emulsifier-free emulsion polymerization method, using azobis(isobutylamidine hydrochloride)(AIBA) as an initiator, and then mixed with anionic surfactants overnight, to afford better stability. Polyaniline was grow on the PS seed from oxidation polymerization of aniline at pH 0.7 and 5℃ to form a core-shell structure. The purpose of this project is to discuss the effect of type and hydrophobic chain length of surfactants, adsorption amount, and aniline concentration on the latex stability and morphology. Moreover, the effect of shell thickness of these conductive particles on their electrical conductivity will be discussed. The result shows the type and hydrophobic chain length of surfactants, the adsorption amount of anionic surfactants on cationic PS spheres, and aniline concentration were identified as decisive factors affecting particle stability. Using anionic surfactants with longer hydrophobic chain length, to afford better stability. And the SEM micrographs indicate a fairy narrow size distribution in these conductive core-shell particles. The conductivity percolation threshold was found to be around 3wt% of polyaniline.

碩士
國立臺灣大學
藥學研究所
84
Valinomycin可促進陽離子通過細胞膜，尤其是促進鉀離子對細胞膜的通 透性。因此，valinomycin吸附在細胞膜上可能是一個很重要的過程，我 們選擇表面極性不同之聚苯乙烯(polystyrene,PS)與聚甲基丙烯酸甲酯( polymethyl methacrylate,PMMA)乳膠作為評估valinomycin吸附現象的固 體受質。合成方式為無乳化劑聚合法。掃瞄式電子顯微鏡與粒徑分析儀觀 察合成所得乳膠的粒子外形與粒徑及其粒徑分佈，可知所製備的聚合物乳 膠皆為圓球型，表面平坦並有高度單一分散性。每毫升PS與PMMA乳膠粒子 表面積分別為0.5854與1.4375平方公尺；電位與電導度滴定的方法所測得 乳膠粒子的表面電荷密度為每平方公分4.8483微庫侖與0.8917微庫侖。為 了測量valinomycin吸附在聚合物乳膠表面的量，我們發展出一個準確而 且精確性高之定量溶液中valinomycin含量的方法。首先將valinomycin水 解後，再以fluorescamine螢光法分析水解產物中valine的含量，進而推 算出valinomycin的含量。比較以HPLC的方式和fluorescamine螢光法定 量 valine的試驗結果，發現fluorescamine螢光法在低濃度範圍有較高的 靈敏度與準確度，螢光法之最低偵測濃度為每毫升1毫微克，而HPLC法則 為每毫升2微克 。吸附實驗係將固定量的聚合物乳膠與不同濃度的 valinomycin溶液在25度恆溫中振搖20小時，並利用溶液耗損法估算的吸 附量。吸附動態曲線中，可明顯地可以看出valinomycin對PS乳膠吸附達 到平衡所需時間較對PMMA乳膠來的短。類似的結果亦可在溶液中氯化鉀存 在吸附實驗結果觀察到。從吸附等溫曲線之高原期吸附量可以估算出吸附 在乳膠表面之分子於緊密排列時之每分子所佔表面積分別為183與163平方 埃。氯化鉀存在下，對PS及PMMA乳膠之吸附等溫曲線可觀察到有一不連續 之轉折點存在，而且會有較高之高原吸附量。以氯化鈉取代氯化鉀時，所 得吸附等溫曲線仍會有一轉折點，高原吸附量則與無鹽類存在下的結果相 近。吸附等溫曲線上的轉折點為溶液中離子所造成的影響，而於KCl存在 之溶液中，因部份 valinomycin可能與鉀離子形成錯合物，因為此錯合物 帶有部份正電性，因此對帶負電荷的乳膠粒子表面有較大之親和力，而且 由空間填充模型所得 valinomycin錯合物之分子截面積亦小於非錯合物之 分子截面積，因此在吸附等溫曲線上可觀察到valinomycin對二種乳膠皆 有較大之高原吸附量。 Valinomycin acts as acarrier of ions, especially potassium ion, to transport through the cell membrane. Two different types of latexes used were polystyrene (PS) and polymethyl methacrylate (PMMA). The preparation of the PS and PMMA latexes was non - emulsifier polymerization. The particle shape and diameter of latexes were determined by the scanning electron microscopy and the particle analyzer. Surface areas per unit volume of PS and PM MA latexes were 0.5854 and 1.4375 square meter per miniliter. The surface charge densities of the two latexes, was determined by the potentiometric and conductometric titrations. The quantitative method, in brief, valinomycin was first hydrolyzed by fumed HCl to give products of valine, lactic acid and alfa-hydroxyisovaleric acid. A fluorescamine fluorescence method was applied to determinethe amount of valine in the hydrolysate. Comparison of the fluorescamine fluorescence method and the HPLC method indicated that both methods provided highly accurate and precise assay for valine. Nevertheless, the fluorescence method seems to be more sensitive and precisely at a lower concentration range. The adsorption experiments were carried out by adding a fixed amount of polymer latex into valinomycin solutions. The equili- brium time of adsorption for the PS latex was much shorter than that of the PMMA latex. The areas occupied per valinomycin mole- cule were 183 and 163 square armstrone. In the presence of KCl, the discontinuity on the isotherm and a greater plateau adsorp- tion amount were observed for the adsorption isotherms of the two polymer latexes. It seems that the discontinuity on the iso- therm may be due to the existence of ions. The greater plateau adsorption is due to that part of valinomycin existed as complex with potassium ions.

A semi-continuous synthesis of polystyrene/acrolein latex was carried out. The optimum addition time of acrolein monomer was determined to be 10 hours after addition of the initiator, giving a monodisperse polystyrene latex with aldehyde on the surface. A DNPH assay was used to assay the aldehyde group in the latex suspension; it was specifically a surface assay. It successfully detected aldehydes at concentrations above 1 x 10⁻⁶ mol/g but was limited at high surface concentrations of aldehyde probably due to the steric hindrance. Quantitative agreement with respect to surface concentration of aldehyde groups was obtained using freshly solubilized NaBT 4 reduction in a radiochemical assay. NMR was used to assay aldehydes present in dissolved latex and the same result as for the DNPH assay was obtained. NMR provided information on the environment of the surface aldehydes, the chemical shift showing the possible presence of polyacrolein chains on the latex with the seeded reaction. This was an important observation as the polyacrolein blocks are not favorable for the grafting reactions to be carried out later in this project. XPS provided strong evidence that aldehyde functions were present on the latex surface, were reactive with DNPH and were reduced by NaBH₄. The XPS spectra obtained were those expected based on the surface chemistry anticipated and no unexpected groups were detected.

碩士
國立臺灣大學
材料科學與工程學研究所
93
The purpose of this research is to discuss the mechanism of the PAni of PS/PAni core-shell is in a dedoping process in ammonium hydroxide and replaced with organic acids in a redoping process by using UV-Vis spectrum experiment. And PS/PAni chemical structure were changed after reaction were confirmed by the FTIR experiment. Three different feasible ways to remove dopant and dope acid of the PAni of PS/PAni core-shell particle. Dedoping and redoping process of the PAni were PS/PAni core-shell latex in solution, PS/PAni core-shell packing immersed in solution, and PS/PAni thin film immersed in solution. After redoping process PS/PAni core-shell thin film were made by heat. And the film formation were observed by SEM. Beside this, the conductivity of film was convert by measured resistance and the thermal stability of film after redoping process were discussed in the high temperature by measuring the change of the resistance. The result shows that redoping process in PS/PAni core-shell packing was developed higher conductivity and better thermal stability film. All of the reaction process still in water phase. And the preparation of PS/PAni conductive film is easily.

碩士
國立臺灣大學
高分子科學與工程學研究所
92
The cationic polystyrene and crosslinked polystyrene latexes synthesized by emulsifier-free emulsion polymerization method functions as seeds and polyaniline grows on the polystyrene/crosslinked polystyrene seeds. Thus, the conductive polyaniline–coated polystyrene core-shell latexes were synthesized. The coated morphology and latex particle were observed by SEM,TEM, and diameter analyzer .The chemical structure and thermal analysis were studied by the FTIR, DSC. Three types of conductive films (polystyrene-polyaniline , crosslinked polystyrene-polyaniline, and the blends) were made by casting and heating the latex particles above the glass transition temperature. The film formation is observed by SEM. Moreover, the conductivity of conductive films were degraded in different temperatures and environments. Relations between the conductivity and the characteristics of core material were studied.

碩士
國立臺灣大學
化學工程學研究所
91
This work is to prepare nanosized or submicron complex particles with silica as core and polymer as shell by using the method of emulsion polymerization. First, we prepared nanosized silica particles from the reaction of hydrolysis of tetraethoxysilane (TEOS) followed by a condensation reaction. After that﹐ the surface of silica particles are treated with the functional group C=C. On the surface of particles containing group of C=C, further polymerization reaction of styrene is carried out via the technique of emulsion polymerization. Polymers form over the surface of silica particles, thus the complex particles are of core-shell structure. A series of nanosized or submicron complex particles are prepared under different reaction conditions. The size distribution, morphology, and thermo-properties of the complex particles were tested and discussed. Moreover, we may introduce conductive polymers on the surface of the complex particles, such as polyaniline. Therefore the product can be used in many applications.

碩士
國立臺灣大學
高分子科學與工程學研究所
95
The purpose of the study is to discuss the effect of UV irradiation on the conductivity of conductive films based on polystyrene(PS)-polyaniline (PANI) core-shell latexes. Furthermore, conduction mechanism and aging effect on conductivity of conductive films after UV irradiation were investigated. The PS-PANI core-shell latexes were synthesized; conductive films were made by casting and heating the PS-PANI core-shell latex particles above the glass transition temperature of polystyrene. After exposure to UV irradiation, the conductivity of conductive films decreased slightly. In contrast, the conductivity decreased obviously after UV irradiation when photoinitiator was added to the PS-PANI film. The aging effect on conductivity of conductive films in different atmosphere was investigated. Among three types of conductive films (unexposed, exposed, and exposed with photoinitiator), the exposed conductive film with photoinitiator has the best thermal stability due to crosslinked structures formed during UV irradiation. Moreover, for all the conductive films, the temperature dependence of conductivity follows the law: σ/σ0＝exp[-(T0/T)0.5]. It indicated the conduction proceeds through hopping between small conducting grains separated by insulating barriers.

Amphiphilic polymers, wherein two or more immiscible polymeric segments are connected covalently, form an interesting class of macromolecules that can self-assemble in block selective solvents as well as in bulk, to exhibit a variety of elegant nano-structures. In this context, simple block copolymers have been studied extensively. Graft copolymers, on the other hand, are a unique class that contains polymeric pendant chains of one type attached to backbone of a second type. Depending on the grafting density, the graft polymers can be broadly classified into two categories; these are comb polymers, where the distance between the two grafting segments is large and brush polymers, where the pendant chains are grafted densely at every repeat unit. The most striking feature of these graft copolymers is that, with increase in the grafting density of the pendant segments, the backbone of the graft copolymers begins to adopt a stretched conformation. This unique property of graft copolymers impart interesting solution and bulk properties which cannot be achieved in simple linear polymers. In the present thesis, we first studied various aspects of the self-assembly behaviour of two novel types of amphiphilic graft copolymers, namely, criss-cross polymers and double-brush polymers, as depicted in scheme 1. Amphiphilic criss-cross polymer Amphiphilic double-brush polymer Pendant amphiphilic polymers – Type I Amphiphilic double-brush polymers – Type II Scheme 1. Schematic representation of the two types of amphiphilic graft polymers studied in this thesis. Controlling conformation of synthetic polymer chains, both in solution and in solid state, has been long term challenge as it confronts the entropy driven random coil conformation. For the past two decades there have been a significant efforts to control folding of polymeric chains via H-bonding interactions, bond angle constrains, solvophobic interactions, donor acceptor interactions, and so on. More recently, our group has demonstrated the immiscibility driven folding of periodically grafted amphiphilic copolymers (PGACs), wherein the immiscibility of the pendant and the backbone forces the polyethylene-like backbone to adopt a folded zigzag conformation that is further stabilized by crystallization of one or both the segments. We first investigated the folding behaviour of an amphiphilic comb polymer, wherein two crystallizable hydrophobic alkyl chains are periodically grafted along a hydrophilic polyethylene glycol-like (PEG) backbone in a criss-cross orientation; implying that the alkyl chains lie across the backbone on either sides, as depicted in Scheme 2. The polymers were prepared by simple transesterification of dimethyl-2,5-didocosyloxy terephthalate with PEG diols of different molecular weights; thus, permitting a variation of the periodicity of the grafting along the backbone. DSC, WAXS and variable temperature-IR studies confirmed that, in spite of the presence of intervening PEG segments, the pendant alkyl chains crystallize. This is a direct consequence of immiscibility driven self-segregation of pendant docosyl units via folding of the PEG backbone to generate a Janus folded polymeric chain, as depicted in scheme 2; here the periodicity of grafting acts as a “folding regulator”. Studies of model criss-cross amphiphiles helped confirm the hypothesized Janus-type chain folding. Interestingly, SAXS studies revealed that the folded chains further organize to generate a lamellar morphology with sub-10 nm domain spacings. Conformational reorganization Scheme 2. Schematic representation of the amphiphilic criss-cross polymer and its immiscibility driven folding behaviour. Recently, there has been growing interests towards reducing the microphase separated nano-structures to sub-10 nm length scales for variety of potential applications. It is well known that, in case of block copolymers the microphase separation is governed by the degree of polymerization (N) and the Flory-Huggins interaction parameter (χ); for microphase separation to occur the value of χN must reach the threshold value of 10.5. Therefore, such small length scales cannot be readily achieved by the simple reduction of the total molecular weight of the polymer. Recently, block copolymers with high χ values have been studied which was found to compensate for the decrease in N. In this context, self-assembly of PGACs have proven to be a promising approach to reduce the domain sizes in microphase separated morphologies.1,2 In order to explore alternate strategies, we designed a series of amphiphilic double-brush polymers, wherein two immiscible pendant chains are anchored at the same point on every repeat unit. Such polymers were prepared via micellar polymerization of hetero-functionalized itaconic acid based surfmers that contain a reactive double bond at the junction of the two immiscible segments. The important revelation of this work is that, despite of the relatively short pendant chains (namely, cetyl-PEG, cetyl-glycerol, cetyl-fluoroalkyl chains), the mutual incompatibility between the pendant segments appears to drive self-segregation along the polymeric backbone to generate Janus polymeric chains. DSC, WAXS and variable temperature-IR studies confirmed that either one or both the pendant chains crystallize, which acts as the key parameter to reinforce the microphase separated morphology, apparently breaching the lower χN limit. Furthermore, SAXS studies revealed the formation of lamellar morphologies with ultrasmall interlamellar spacing in the range of 4-6 nm (scheme 3); and, most importantly, the domain spacing matches almost exactly with the estimated length of the pendant segments. Thus, we have successfully shown that sub-10 nm domains can be generated using a fairly simple strategy that could be further exploited for some interesting potential applications. Amphiphilic double-brush Lamellar organization with sub-10 nm size polymer Scheme 3. Schematic representation of the self-assembly of amphiphilic double-brush polymer. The amphiphilic double-brush polymer which contains hydrophobic cetyl groups and hydrophilic PEG chains exhibited an interesting behaviour, namely polymerization-induced gelation, when the concentration of the monomer exceeded 2.5 wt%. TEM images confirmed the presence of elongated fibrillar network possibly formed from cylindrical micellar aggregates, as shown in scheme 4; DSC and WAXS studies confirmed that the gel is formed via the collocation and crystallization of the pendant cetyl chains in water. Interestingly, heating the hydrogel beyond the DSC melting temperature (~40 oC) transformed it into a sol, while cooling it restored the gel; variable temperature rheological measurements helped confirm this thermally reversible gel-to-sol transition. These findings, apart from confirming that the gelation occurs because of crystallization of the cetyl chains, also opens up the possibility of encapsulating hydrophobic therapeutics by a simple heating-cooling process; since the transition temperature is fairly low, these systems could be of interest for the encapsulation of some temperature-sensitive drugs. These hydrogels also exhibit a shear-induced transformation from a gel-to-sol at shear stress of ~30 Pa, which makes it very attractive as an injectable hydrogel matrix. Amphiphilic double-brush polymer Scheme 4. Formation of hydrogel upon polymerization-induced self-assembly of amphiphilic double-brush polymer. Study of surface functionalized polymeric nanoparticles has gained momentum, especially in the context of biomedical applications, electronics and photonics, etc. Among different techniques that are used to prepare such nanoparticles, emulsion polymerization has been studied extensively as it provides good control over the particle size distribution and utilizes benign reaction conditions. Furthermore, the hydrophilic moieties present in the emulsifier used for the emulsion polymerization would decorate the surface of the particle; thus, providing ample opportunities to tailor the surface of the polymeric nanoparticles. In this context, various hetero-functionalized amphiphilic itaconates were investigated as non-ionic surfmers; the nature of the hydrophilic segment was varied from PEG, glycerol or even dopamine, while the hydrophobic segments were either cetyl or octyl chains. These surfmers were utilized for the emulsion polymerization of styrene to generate PEGylated PS, glycerol coated and dopamine coated “sticky” PS latexes, respectively, as depicted in scheme 5. Furthermore, using a fluorinated surfmer, containing fluoro-alkyl chain and cetyl chains as the two immiscible segments, the preparation of PS nanoparticles having a fluorous-rich surface was also explored. NMR, GPC and DSC studies confirmed the copolymerization of the surfmers with styrene and thereby confirmed the covalent surface functionalization of the latexes. DLS and SEM images showed the formation of uniform sized spherical particles in most of the cases. Interestingly, dopamine coated particles exhibited the anticipated adhesive property towards a variety of substrates. The PEGylated and fluorinated polystyrene copolymers were also examined for their ability to serve as coatings to modify the wetting behaviour of surfaces. PEGylated PS latex Glycerol coated PS latex Sticky PS latex Fluroinated PS latex Figure 5. Schematic depiction of the formation of functionalized PS latexes using hereto-functionalized itaconate based surfmers. In a more ambitious attempt, the potential for microphase separation of itaconate-based amphiphiles was explored as a basis for the preparation of cross-linked 2-D polymers; to accomplish this, ABA-type bola-amphiphilic systems were examined, wherein polymerizable units were placed at the two junctions of the A and B segments. It was anticipated that, upon self-segregation, such ABA-type amphiphiles would organize in a lamellar morphology with alternate A and B domains; here the double bonds, which are present at the junction of two immiscible segments, would collocate at two different planes. Therefore, upon polymerization, it can generate 2D nano-sheets. Evidently, in order to facilitate the polymerization, the double bonds in the self-assembled structure must have enough mobility. In this context, various cross-linkable bola-amphiphiles carrying terminal fluorocarbon segments with central hydrocarbon units, and those with central mesogneic biphenyl unit and terminal hydrocarbon segments, were examined; although polymerization was shown to occur, exfoliation to separate out the layers were unsuccessful. This was attributed to the inability to retain the layered morphology while at the same time maintain adequate mobility at the interfacial planes where polymerization was expected to occur; therefore, either polymerization did not occur or, if it did, a randomly cross-linked polymer was formed. In a final successful attempt, the polymerization was carried out in a vesicular dispersion of a suitably designed bola-amphiphile carrying two terminal PEG units and a central hydrocarbon segment; here, the polymerization occurred apparently forming a 2-dimensionally cross-linked layer, but one that is wrapped into a sphere. Figure 6. Schematic representation of polymerization of self-assembled structure of ABA-type amphiphile to generate 2D polymers.

Biocompatible materials can be defined as materials which can be introduced into a living organism without producing stress or traumatic response. When a solid material comes in contact with a biological medium, a layer of protein immediately binds to the surface. Subsequent defensive responses depend on the type and binding orientation of the protein on the surface. Therefore, primary surface protein binding is directly related to the type of physiological response observed in the body. Surfaces coated with grafted hydrophilic polymers can reduce non-specific protein adsorption. The hydrophilic nature of the grafted chain reduces the hydrophobic driving force. The long grafted chains extending out through the electrical double layer can reduce electrostatic driving forces. Non-specific protein can be excluded by the grafted chains and the solvent trapped between grafted chains. Polymer chains of hydrophilic poly(N,N -dimethylacrylamide) of different lengths were polymerized in situ by initiation from aldehyde groups on the surface of polystyrene latex. Using the techniques of particle electrophoresis, conductometric titration and elemental analysis, the surfaces of these latexes were analyzed. The adsorption isotherms of human serum albumin (HS A) to these latexes were measured. The results indicate that HSA has an affinity for the grafted poly(N,N -dimethylacrylamide). The exclusion effect of the grafted polymer in reducing HSA adsorption was greatest with the medium length grafted chains. The shorter or longer grafted chains on the latex did not reduce HSA adsorption compared with non-grafted latex.

碩士
國立臺灣科技大學
化學工程系
87
Two sub-topics are studied in this work: the first part involves is a project supported by EPA, Taiwan and the second one is determination of surface concentration of SDS adsorbed onto the polystyrene latex particles in aqueous solution. The first sub-topic, detailed in chapters 2 - 6, investigates automobile coatings and the ways of improvement for lowering the VOC emission. At present, there are many small automobile companies and the volume of the market is not large enough to adopt an automatic process or install a better pollution control equipment. From the technical point of view, automobile manufactures can use low VOC paints, but a new coating system is needed. The new system costs about 10 millions NT dollars and, therefore, the manufactures doe not want to see any changes in the near future. It is suggested that EPA should publish new VOC regulations with a higher standard on VOC release and assist the manufactures may thus have to start considering the low VOC paints. The surface concentrations of SDS molecules adsorbed on the polystyrene (PSt)-water interface is determined in the second part of this work. The surface concentration is obtained from the mass balance of SDS molecules among the water phase, liquid-solid interface, interface, and air-water interface via a surface tension measurement of the air-water interface. The surface coverage of SDS on the PSt latex particles increases as the SDS concentration in the water phase increases. The Langmuir adsorption isotherm describes the surface concentration vs bulk conc

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Nanoparticles are increasingly used in industry and medicine due to their unique physiochemical properties such as their small size, charge, shape, chemical architecture, large surface area, surface reactivity and media interactions, etc [1-5]. However, very little is still known on the interactions between nanoparticles and the biological system. This study aims to evaluate the cytotoxicity of polystyrene latex bead nanoparticles on HaCat and HeLa cell lines. Carboxyl-modified 20 nm polystyrene NPs core labelled with fluorophore were from Invitogen. We chose to use polystyrene NPs because this specific type of NP is being increasingly characterized for use in nanosensors and drug nanocarrier investigations. 1x 104 cells/100 μl of cell culture medium were plated into 96-well plates in triplicate, measuring activity post 24 hours at concentrations of 10, 50, 100 μg/ml of polystyrene NPs exposure. The extracellular lactate dehydrogenase release was measured by using a colorimetric CytoTox 96 nonradioactive assay kit from Promega and the absorbance were recorded at 450nm (FLUO-star) with Elisa micro plate reader. The MTT assay was used to evaluate mitochondrial activity. This was performed by inserting a premixed optimized dye solution in the culture wells. The Absorbance was recorded at 570 nm, from the recorded absorbance is directly proportional to the number of live cells. The cell lines were kept in a plastic T-75cm2 tissue culture flasks grown in DMEM. We found that cytotoxicity of polystyrene NPs on both cells was concentration dependent. For Hela cells, with exporesure of polystyrene NPs at concentrations of 10, 50, 100 μg/ml for 24 hrs, the percentage cytotoxicity of positive control for LDH assay was 35.9%, 49.5% and 73.4% respectively. With the MTT cell viability assay the percentage MTT reduction of negative control was 88.9%, 42.9% and 26.4% respectively. Cell toxicity increased with increasing polystyrene NPs concentration. For HaCaT cells, the cytotoxic effect is less significant than those on Hela cells. With MTT assay, when compared to HaCaT cells exposed to a negative control containing only PBS, the cell viability decreased as the concentrations of NPs increased. Cells exposed to 100μg/ml of polystyrene NPs for a period of 24 hours compared to those exposed to a positive control (100% cell viability) had an average cell viability of 49%, with those numbers decreasing from 59% for cells exposed to 10μg/ml of polystyrene NPs to 57% for cells exposed to 50μg/ml of polystyrene NPs. Our results indicated that polystyrene NPs acted differently in two different cell types and that cautions should be taken about its cytotoxicity. Further understanding of the mechanism involving the ROS generation could provide more information on how polystyrene NPs increase cytotoxicity.