Piezoelectric materials are very useful for applications in sensors and actuators. In addition to traditional ferroelectric ceramics and ferroelectric polymers, ferroelectrets have recently become a new group of piezoelectrics. Ferroelectrets are functional polymer systems for electromechanical transduction, with elastically heterogeneous cellular structures and internal quasi-permanent dipole moments. The piezoelectricity of ferroelectrets stems from linear changes of the dipole moments in response to external mechanical or electrical stress. Over the past two decades, polypropylene (PP) foams have been investigated with the aim of ferroelectret applications, and some products are already on the market. PP-foam ferroelectrets may exhibit piezoelectric d33 coefficients of 600 pC/N and more. Their operating temperature can, however, not be much higher than 60 °C. Recently developed polyethylene-terephthalate (PET) and cyclo-olefin copolymer (COC) foam ferroelectrets show slightly better d33 thermal stabilities, but usually at the price of smaller d33 values. Therefore, the main aim of this work is the development of new thermally stable ferroelectrets with appreciable piezoelectricity. Physical foaming is a promising technique for generating polymer foams from solid films without any pollution or impurity. Supercritical carbon dioxide (CO2) or nitrogen (N2) are usually employed as foaming agents due to their good solubility in several polymers. Polyethylene propylene (PEN) is a polyester with slightly better properties than PET. A “voiding + inflation + stretching” process has been specifically developed to prepare PEN foams. Solid PEN films are saturated with supercritical CO2 at high pressure and then thermally voided at high temperatures. Controlled inflation (Gas-Diffusion Expansion or GDE) is applied in order to adjust the void dimensions. Additional biaxial stretching decreases the void heights, since it is known lens-shaped voids lead to lower elastic moduli and therefore also to stronger piezoelectricity. Both, contact and corona charging are suitable for the electric charging of PEN foams. The light emission from the dielectric-barrier discharges (DBDs) can be clearly observed. Corona charging in a gas of high dielectric strength such as sulfur hexafluoride (SF6) results in higher gas-breakdown strength in the voids and therefore increases the piezoelectricity. PEN foams can exhibit piezoelectric d33 coefficients as high as 500 pC/N. Dielectric-resonance spectra show elastic moduli c33 of 1 − 12 MPa, anti-resonance frequencies of 0.2 − 0.8 MHz, and electromechanical coupling factors of 0.016 − 0.069. As expected, it is found that PEN foams show better thermal stability than PP and PET. Samples charged at room temperature can be utilized up to 80 − 100 °C. Annealing after charging or charging at elevated temperatures may improve thermal stabilities. Samples charged at suitable elevated temperatures show working temperatures as high as 110 − 120 °C. Acoustic measurements at frequencies of 2 Hz − 20 kHz show that PEN foams can be well applied in this frequency range. Fluorinated ethylene-propylene (FEP) copolymers are fluoropolymers with very good physical, chemical and electrical properties. The charge-storage ability of solid FEP films can be significantly improved by adding boron nitride (BN) filler particles. FEP foams are prepared by means of a one-step procedure consisting of CO2 saturation and subsequent in-situ high-temperature voiding. Piezoelectric d33 coefficients up to 40 pC/N are measured on such FEP foams. Mechanical fatigue tests show that the as-prepared PEN and FEP foams are mechanically stable for long periods of time. Although polymer-foam ferroelectrets have a high application potential, their piezoelectric properties strongly depend on the cellular morphology, i.e. on size, shape, and distribution of the voids. On the other hand, controlled preparation of optimized cellular structures is still a technical challenge. Consequently, new ferroelectrets based on polymer-layer system (sandwiches) have been prepared from FEP. By sandwiching an FEP mesh between two solid FEP films and fusing the polymer system with a laser beam, a well-designed uniform macroscopic cellular structure can be formed. Dielectric resonance spectroscopy reveals piezoelectric d33 coefficients as high as 350 pC/N, elastic moduli of about 0.3 MPa, anti-resonance frequencies of about 30 kHz, and electromechanical coupling factors of about 0.05. Samples charged at elevated temperatures show better thermal stabilities than those charged at room temperature, and the higher the charging temperature, the better is the stability. After proper charging at 140 °C, the working temperatures can be as high as 110 − 120 °C. Acoustic measurements at frequencies of 200 Hz − 20 kHz indicate that the FEP layer systems are suitable for applications at least in this range. / Piezoelektrische Materialien haben große technische und wirtschaftliche Bedeutung für Anwendungen in Sensoren und Aktuatoren. Neben den traditionellen ferroelektrischen Keramiken und Polymeren bilden Ferroelektrete eine neue Gruppe der Piezoelektrika. Ferroelektrete sind reversible funktionelle Polymersysteme zur Umwandlung von elektrischer in mechanische Energie und umgekehrt. Sie zeichnen sich aus durch eine elastische zelluläre Struktur mit internen quasi-permanenten Dipolen. Der Mechanismus der Piezoelektrizität in Ferroelektreten wird dominiert von der Änderung der einzelnen Dipolmomente bei Einwirkung einer äußeren mechanischen Kraft. Insbesondere zelluläres Polypropylene (PP) war in den vergangenen zwei Jahrzehnten Gegenstand intensiver Forschung und Entwicklung im Hinblick auf die grundlegenden Eigenschaften und Anwendungen von Ferroelektreten. Einige bereits erhältliche kommerzielle Produkte nutzen die in geladenem zellulären PP erreichbaren hohen piezoelektrischen d33-Koeffizienten von 600 pC/N und mehr, sind aber durch eine relativ geringe maximale Betriebstemperatur von ungefähr 60 °C eingeschränkt. Die kürzlich entwickelten Ferroelektrete aus zellulärem Polyethylenterephthalat (PET) und zellulären Cyclo-Olefin-Copolymeren (COC) zeigen eine bessere Temperaturbeständigkeit (vor allem COC), allerdings gewöhlich auf Kosten von geringeren d33-Koeffizienten. Das Ziel der vorliegenden Arbeit ist es, temperaturbeständige Ferroelektrete mit für den Markt geeigneten piezoelektrischen Eigenschaften zu entwickeln. Physikalisches Schäumen ist eine beliebte Methode, um besonders reine Polymerschäume herzustellen. Häufig werden, wegen ihrer guten Löslichkeit in vielen Polymeren, Kohlenstoffdioxid (CO2) und Stickstoff (N2) im superkritischen Zustand als Treibmittel eingesetzt. Der Polyester Polyethylennaphtalat (PEN) hat ähnliche Eigenschaften wie PET, ist jedoch temperaturbeständiger. Ein Dreistufenprozess (Schäumen, Aufblähen und Strecken) wurde entwickelt, um PEN-Schäume für hochwertige Ferroelektrete herzustellen. Ungeschäumte PEN-Folien werden mit superkritischem CO2 unter hohem Druck gesättigt und anschließend unter geringem Druck bei Temperaturen nahe der Glastemperatur geschäumt. Um die Hohlräume zu vergrößern, wird der Schaum anschließend mittels Gasdiffusionsexpansion (GDE) aufgebläht. Nach zusätzlichem biaxialen Verstrecken erhält man die optimalen linsenförmigen Zellen, welche zu einer minimalen mechanischen Steifigkeit und einem maximalen piezoelektrischen d33-Koeffizienten des Ferroelektrets führen. Sowohl Korona- als auch Kontaktaufladung werden an zellulärem PEN erfolgreich eingesetzt. Die Lichtemission der dielektrisch behinderten Entladungen (DBDs) kann klar beobachtet werden. Korona-Aufladung in Gasen mit hohen dielektrischen Durchbruchsfestigkeiten, wie z.B. Schwefelhexafluorid (SF6), ermöglicht es, das Paschen-Durchbruchsfeld in den Hohlräumen und damit die erzielbare interne Ladungsdichte zu erhöhen. Dadurch können für zelluläres PEN piezoelektrische d33-Koeffizienten bis zu 500 pC/N erzielt werden. Piezoelektrischen Resonanzmessungen der Ferroelektrete liefern Steifigkeiten c33 im Bereich von 1 – 12 MPa, Antiresonanzfrequenzen von 0.2 – 0.8 MHz und elektromechanische Kopplungsfaktoren zwischen 0.016 und 0.069. PEN-Ferroelektrete zeigen eine bessere Temperaturstabilität als solche aus PP und PET. Der Anwendungsbereich von unbehandeltem PEN reicht bis etwa 80 – 100°C, jener von getemperten oder bei 120°C geladenen Proben bis etwa 110 – 120 °C. Akustische Messungen im Frequenzbereich von 2 Hz – 20 kHz zeigen die Eignung von PEN-Ferroelektretwandlern für Luftschallanwendungen. Fluoriertes Ethylen-Propylen (FEP) ist ein Fluorpolymer mit sehr guten physikalischen, chemischen und elektrischen Eigenschaften. Die Ladungsspeichereigenschaften von ungeschäumtem FEP können durch die Beimengung von Bornitrid deutlich verbessert werden. In dieser Arbeit wird zelluläres FEP mittels eines einstufigen Prozesses, dem schon erwähnten Schäumen mit überkritischem CO2, hergestellt. Die geladenen FEP-Proben weisen d33-Koeffizienten von bis zu 40 pC/N auf. Ermüdungstests zeigen eine sehr gute mechanische Stabilität von PEN- und FEP-Ferroelektreten. Zelluläre Polymerferroelektrete haben großes Potenzial für Anwendungen, und die Suche nach geeigneten zellulären Morphologien ist eng verknüpft mit dem technischen Aufwand ihrer Herstellung. Alternativ wurden Ferroelektrete mit Sandwich-Strukturen aus FEP-Folien entwickelt. Durch Laserverschmelzen eines FEP-Foliengitters mit zwei umgebenden FEP-Folien wird eine definierte, einheitliche zelluläre Struktur gebildet. Aus dielektrischen Resonanzspektren können effektive piezoelektrische d33-Koeffizienten bis zu 350 pC/N, effektive mechanische Steifigkeiten um 0.3 MPa, Antiresonanzfrequenzen um 30 kHz und elektromechanische Kopplungsfaktoren von etwa 0.05 abgeleitet werden. Proben, welche bei erhöhter Temperatur geladen werden, zeigen höhere Ladungsstabilitäten. Nach geeigneter Aufladung bei 140 °C kann die Arbeitstemperatur bis auf 110 – 120 °C gesteigert werden. Akustische Messungen im Frequenzbereich von 2 Hz – 20 kHz zeigen die Eignung von FEP-Sandwich-Strukturen für Luftschallanwendungen.

The dual-writing process of holographic technique was applied to fabricate the two-dimensional surface relief gratings on azo-dye doped polymer film in this study. The structure of two-dimensional grooves was investigated under the various polarization state of writing beam, the various angle between two stages of writing, and the adoption of nematic liquid crystals as the interface. The results revealed that the depth of two-dimensional surface relief gratings produced by the writing beams with P-polarization and the interface of nematic liquid crystals in contact with azo-dye polymer film was about 2~3 times of that without nematic liquid crystals as the interface. As the angle between two stages of writing increases, the first order diffraction efficiency and the depth of surface relief structure in the second writing becomes smaller for the writing beam with S polarization; while the first order diffraction efficiency and the depth of surface relief structure becomes larger for the writing beam with P polarization.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第20406号 / 工博第4343号 / 新制||工||1673(附属図書館) / 京都大学大学院工学研究科高分子化学専攻 / (主査)教授 大北 英生, 教授 辻井 敬亘, 教授 竹中 幹人 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

Tethered polymer layers at solid-fluid interfaces are used widely in a variety of surface science applications. Although many of these applications require exposure to dynamic flow conditions, flow field penetration into densely grafted polymer brushes, is still a question open to debate despite the fact that it is a fundamental process crucial to mass transport through these polymer films. Although most theoretical work has indicated flow field penetration into polymer films, with varying predicted penetration depths predicted, the limited experimental attempts to investigate this phenomenon have resulted in inconsistent conclusions due to lack of a proper analytical method. To help resolve this controversy, in this Dissertation, a new spectroscopic method, FRET-TIRFM, based on a combination of Förster resonance energy transfer (FRET) and total internal reflectance fluorescence microscopy (TIRFM), is developed to provide the first direct, quantitative measurements on flow field penetration by measuring linear diffusion coefficients of small molecules through densely grafted, thin poly(N-isopropylacryl-amide) (pNIPAM) films. Decay curves from FRET of the acceptor with a donor covalently attached at the substrate surface were fit to a combined Taylor-Aris-Fickian diffusion model to obtain apparent linear diffusion coefficients of the acceptor molecules for different flow rates. These values can then be used to obtain quantitative estimates of flow field penetration depths. For a pNIPAM surface of 110 nm dry thickness, with a 0.6 chain/nm² grafting density, apparent diffusion coefficients ranging from 1.9-9.1 × 10-12 cm²/s were observed for flow rates ranging from 100 to 3000 μL/min. This increase in apparent diffusion coefficient with applied fluid flow rate is indicative of flow field penetration of the polymer film. The depth of penetration of the flow field is estimated to range from ~6% of the polymer film thickness to ~57% of the film thickness in going from 100 to 3000 μL/min flow rate of a good solvent. Factors other than flow rate that may impact flow field penetration were also investigated using this new FRET-TIRFM method. Solvent quality and polymer brush grafting density are the two most important parameters due to the fact that they influence changes in tethered polymer chain conformation. This work demonstrates that polymer films are most penetrable in a good solvent and least penetrable in a poor solvent under identical flow conditions. These findings are consistent with polymer chain conformational changes going from extended brushes to compact globules. For flow rates ranging from 100 to 3000 μL/min, flow field penetration depth ranges from ~6% of the film thickness to ~57% of film thickness for a good solvent compared to ~4% to ~19% for a poor solvent. Thus, by simply changing solvent quality from good to poor, flow field penetration decreases by about 38%. Grafting density has a less pronounced effect than solvent quality on penetration depth, probably due to the small range of grafting densities chosen for study. However, a roughly 10-20% difference in penetration depth was observed between high density (0.60 chain/nm²) and low density (0.27 chain/nm²) pNIPAM surfaces in the same solvent. Changes in grafting density have a less significant impact in a good solvent compared to a poor solvent. This is most likely caused by the fact that grafting density impacts polymer chain conformation mainly through polymer-polymer repulsion, which becomes less significant in a solvent that better solvates the polymer. For the two extreme cases studied here at flow rates ranging from 100 to 3000 μL/min, the penetration depth is estimated to range from ~4-19% of the original solvent-swollen film thickness for high density pNIPAM films in a poor solvent and from ~7-67% for low density films in a good solvent. One important assumption that underlies all of this work is that the dominant mass transport mechanism for small molecules in dense polymer brushes is diffusion. This assumption was further validated through the use of two different small molecule quenchers, RhB and 2-nitrobenzylalcohol. These molecules are significantly different in size, charge, and structure, and operate by different quenching mechanisms. Despite these differences, the results for flow field penetration are statistically the same for both. These observations validate the assumption of diffusive mass transport in these films.

Este projeto tem como objetivo o estudo do recobrimento superficial de filmes poliméricos à base de látex e breu, com microbicida de prata em painéis multicamadas de bagaço de cana-de-açúcar, reforçados com partículas de bambu (PMBB), visando seu o uso como material isolante térmico em instalação agroindustrial sujeita a ambientes úmidos e com grande carga bacteriana. O projeto foi desenvolvido em quatro etapas. Na etapa 1 (Estudo dos painéis multicamadas), foi realizado o estudo de dois diferentes procedimentos de moldagem, sendo moldagem 1 (PMBB-M1) com prensagem nas camadas e a moldagem 2 (PMBB-M2) sem prensagens nas camadas. Na avaliação física e mecânica o painel PMBB-M2 apresentou melhor desempenho físico e mecânico, por conta da melhor interação entre as camadas, quando comparado ao painel PMBB-M1. A etapa 2 (Estudo do tratamento superficial dos painéis) consistiu na produção e caracterização dos filmes de breu, látex-LT e látex-LS, e na avaliação do recobrimento do painel PMBB e da sua durabilidade expostos às intempéries ambientais (sol, chuva, vento e orvalho). Os filmes apresentaram bom desempenho físico, dificultando a penetração de água no material, contudo, a exposição à radiação e as intempéries climáticas promoveram a degradação dos filmes, apesar disso o látex-LT e o breu apresentaram, até os três meses de envelhecimento natural, melhor desempenho mecânico. A etapa 3 (Estudo da impregnação de nanopartículas de prata (AgNPs) nos filmes) consistiu na preparação e avaliação dos filmes com AgNPs. Por meio da análise microbiológica constatou-se que os filmes de látex-LT e breu apresentaram caráter bacteriostático. Por fim, na etapa 4 (Aplicação dos painéis PMBB em Instalação Suinícola), foi analisado o potencial do painel PMBB-M2 como material isolante térmico, na forma de abrigo para leitão (escamoteador) em uma granja de suínos. Nessa etapa, foi avaliado o microclima gerado no interior dos escamoteadores aquecidos com lâmpada incandescente, por meio da coleta de dados ambientais e análise dos índices de conforte térmico. O painel apresentou bom desempenho, atendendo a faixa de temperatura e umidade de conforto térmico para os leitões na primeira semana de vida. Portanto, pode-se concluir que os filmes de breu e látex-LT no painel PMBB-M2, promoveram uma impermeabilização do material e por apresentarem caráter bacteriostático, evitaram a proliferação de bactérias quando em contato com os filmes, sendo assim, a aplicação deste material como isolante térmico em instalação para suíno apresenta um grande potencial, pois, o recobrimento no material propicia sua aplicação em um ambiente úmido e com grande carga bacteriana. / This project aims the study of surface coatings with polymeric films based on latex and rosin, by using a microbicide agent of\' silver in multilayer panels of sugarcane bagasse reinforced with bamboo particles (PMBB) to be used as an insulate material in agroindustrial facilities subject to humid environments with high bacterial load. This project was conducted into four steps. In the step 1 (Study of the multilayer panels), the evaluation of two different molding procedures was conducted, with molding 1 (PMBB-M1) with pre-pressing in the layers and molding 2 (PMBB-M2) without pre-pressing in the layers. Physical and mechanical properties of the PMBB-M2 panel presented better physical and mechanical performance due to the best interaction between the layers compared to the PMBB-M1 panel. In the step 2 (Study of the superficial treatment of panels), it was studied the production and characterization of the films of rosin, latex-LT and latex-LS, as well as the evaluation of the PMBB panel covering, and evaluation of the durability of these panels exposed to weather conditions (sun, rain, wind and dew). The films presented good physical performance, making it difficult to penetrate water in the material, on the other hand, by exposing the materials to radiation and weather conduction it was noticed the degradation of the films, despite the fact that latex-LT and rosin presented better mechanical performance until three months of age. In the step 3 (Study of impregnation of silver nanoparticles (AgNPs) in the films) it was conducted the preparation and evaluation of the films with AgNPs. By means of the microbiology analyses it was stated that the latex-LT and rosin presented bacteriostatic character. In the step 4 (Application of PMBB panels in Poultry facilities) it was evaluated the potential of the PMBB panel as an insulation material in a pig-farm as a piglet shelter. In this step, the microclimate generated inside of the pig shelter heated by incandescent lamps was evaluated through the collection of environmental data and evaluation of the thermal comfort indices. The panel presented good performance, taking into account the temperature and humidity range of thermal comfort for the piglets in the first week of life. Therefore, it can be concluded that the films of rosin and latex-LT in the PMBB panel, promoted a waterproofing of the materials and due to the bacteriostatic character, it was noticed that proliferation of the bacteria when in contact with the films was avoided, thus, the application of this material as thermal insulation in pig installation presents a great potential, due to the coating in the material and propitiates its application in a humid environment and with bacterial load.

Este projeto tem como objetivo o estudo do recobrimento superficial de filmes poliméricos à base de látex e breu, com microbicida de prata em painéis multicamadas de bagaço de cana-de-açúcar, reforçados com partículas de bambu (PMBB), visando seu o uso como material isolante térmico em instalação agroindustrial sujeita a ambientes úmidos e com grande carga bacteriana. O projeto foi desenvolvido em quatro etapas. Na etapa 1 (Estudo dos painéis multicamadas), foi realizado o estudo de dois diferentes procedimentos de moldagem, sendo moldagem 1 (PMBB-M1) com prensagem nas camadas e a moldagem 2 (PMBB-M2) sem prensagens nas camadas. Na avaliação física e mecânica o painel PMBB-M2 apresentou melhor desempenho físico e mecânico, por conta da melhor interação entre as camadas, quando comparado ao painel PMBB-M1. A etapa 2 (Estudo do tratamento superficial dos painéis) consistiu na produção e caracterização dos filmes de breu, látex-LT e látex-LS, e na avaliação do recobrimento do painel PMBB e da sua durabilidade expostos às intempéries ambientais (sol, chuva, vento e orvalho). Os filmes apresentaram bom desempenho físico, dificultando a penetração de água no material, contudo, a exposição à radiação e as intempéries climáticas promoveram a degradação dos filmes, apesar disso o látex-LT e o breu apresentaram, até os três meses de envelhecimento natural, melhor desempenho mecânico. A etapa 3 (Estudo da impregnação de nanopartículas de prata (AgNPs) nos filmes) consistiu na preparação e avaliação dos filmes com AgNPs. Por meio da análise microbiológica constatou-se que os filmes de látex-LT e breu apresentaram caráter bacteriostático. Por fim, na etapa 4 (Aplicação dos painéis PMBB em Instalação Suinícola), foi analisado o potencial do painel PMBB-M2 como material isolante térmico, na forma de abrigo para leitão (escamoteador) em uma granja de suínos. Nessa etapa, foi avaliado o microclima gerado no interior dos escamoteadores aquecidos com lâmpada incandescente, por meio da coleta de dados ambientais e análise dos índices de conforte térmico. O painel apresentou bom desempenho, atendendo a faixa de temperatura e umidade de conforto térmico para os leitões na primeira semana de vida. Portanto, pode-se concluir que os filmes de breu e látex-LT no painel PMBB-M2, promoveram uma impermeabilização do material e por apresentarem caráter bacteriostático, evitaram a proliferação de bactérias quando em contato com os filmes, sendo assim, a aplicação deste material como isolante térmico em instalação para suíno apresenta um grande potencial, pois, o recobrimento no material propicia sua aplicação em um ambiente úmido e com grande carga bacteriana. / This project aims the study of surface coatings with polymeric films based on latex and rosin, by using a microbicide agent of\' silver in multilayer panels of sugarcane bagasse reinforced with bamboo particles (PMBB) to be used as an insulate material in agroindustrial facilities subject to humid environments with high bacterial load. This project was conducted into four steps. In the step 1 (Study of the multilayer panels), the evaluation of two different molding procedures was conducted, with molding 1 (PMBB-M1) with pre-pressing in the layers and molding 2 (PMBB-M2) without pre-pressing in the layers. Physical and mechanical properties of the PMBB-M2 panel presented better physical and mechanical performance due to the best interaction between the layers compared to the PMBB-M1 panel. In the step 2 (Study of the superficial treatment of panels), it was studied the production and characterization of the films of rosin, latex-LT and latex-LS, as well as the evaluation of the PMBB panel covering, and evaluation of the durability of these panels exposed to weather conditions (sun, rain, wind and dew). The films presented good physical performance, making it difficult to penetrate water in the material, on the other hand, by exposing the materials to radiation and weather conduction it was noticed the degradation of the films, despite the fact that latex-LT and rosin presented better mechanical performance until three months of age. In the step 3 (Study of impregnation of silver nanoparticles (AgNPs) in the films) it was conducted the preparation and evaluation of the films with AgNPs. By means of the microbiology analyses it was stated that the latex-LT and rosin presented bacteriostatic character. In the step 4 (Application of PMBB panels in Poultry facilities) it was evaluated the potential of the PMBB panel as an insulation material in a pig-farm as a piglet shelter. In this step, the microclimate generated inside of the pig shelter heated by incandescent lamps was evaluated through the collection of environmental data and evaluation of the thermal comfort indices. The panel presented good performance, taking into account the temperature and humidity range of thermal comfort for the piglets in the first week of life. Therefore, it can be concluded that the films of rosin and latex-LT in the PMBB panel, promoted a waterproofing of the materials and due to the bacteriostatic character, it was noticed that proliferation of the bacteria when in contact with the films was avoided, thus, the application of this material as thermal insulation in pig installation presents a great potential, due to the coating in the material and propitiates its application in a humid environment and with bacterial load.

No description available.

The properties of materials, especially of solids, can be attributed mainly to the phenomena occurring at the surface. Surface engineering deals with altering the surface properties of materials to realize useful functionalities like wear and corrosion resistance, biocompatibility, hardening etc. Among the various methods adopted, plasma surface modification stands out, because of the inherent dry processing nature and little amount of left over chemicals. In conventional plasma systems, the process is carried out in a low pressure environment. This restricts its use in treating vacuum incompatible materials including tissues and bio-medical samples. Moreover, the batch processing nature and use of expensive vacuum pumps put a bottle-neck in the throughput of any production line. The subject matter of this thesis is about developing and optimizing an atmospheric pressure (760 torr) plasma system and to use it for surface modification of polymers. The experimental system developed, consists of two parallel electrodes facing each other, each of which is covered with a dielectric plate. A gap of 4mm exists between the dielectric surfaces, through which an axial flow of the working gas is maintained. When a high voltage is applied across the electrodes, the gas breaks down, creating plasma. The surface of the sample kept in this plasma, undergoes various phenomena, depending on the power applied, type of gas used and gas flow rate. To drive the plasma a high voltage power supply, which is able to generate 10 kV at 5.8 kHz, was developed in the laboratory. By varying the process parameters, the inherent filamentary nature of discharge can be converted to a diffuse uniform glow. The purity of plasma was studied and established by analyzing the optical emission from the plasma. After optimizing the system, it was used to modify the surface properties of polyester sheets. The wetting nature was altered using fluorocarbon and oxygen plasmas, realizing hydrophobic and hydrophilic surfaces. The contact angle of a water droplet made with the surface changed from 72° to 84° degree for hydrophobic and to 22° for hydrophilic surfaces respectively. Through this investigation, an insight to the procedure for developing an Atmospheric glow discharge system was developed. The details about system frame work, the power supply, electrical and optical characterization of the plasma, are well studied and recorded. The work establishes the various parameters to be varied to convert the filamentary discharge to a uniform glow. Purity of the plasma has been studied extensively and the system design and process values essential for maintaining the purity have been dealt with. Finally the plasma was put in use for surface modification of polymers, and the surface wetting nature alteration was studied and quantified.

No description available.

Cette thèse présente des résultats théoriques et expérimentaux portant sur des écoulements à l'échelle nanoscopique de polymères fondus. L'étude analytique et numérique de l'écoulement d'un film de polymère, préalablement nanostructuré par nanoimpression puis recuit au dessus de sa température de transition vitreuse, a permis de dégager différentes dynamiques de nivellement selon la topographie initiale du film. Certaines ont été appliquées à l'élaboration d'éléments optiques par recuit de nanostructures complexes. Une méthode de mesure de la viscosité Newtonienne et du temps terminal de relaxation d'un polymère déposé en film mince a également pu être développée. Enfin, un travail exploratoire portant sur un procédé de nanoimpression sans épaisseur résiduelle par démouillage est présenté. L'accent a porté sur le calcul précis de la pression de disjonction dans un milieu stratifié en utilisant la théorie moderne de Lifshitz basée sur les propriétés optiques des matériaux en interaction. / This thesis presents a theoretical and experimental work on nanoscale flows of polymer melts. Different leveling dynamics emerge from the analytical and numerical study of the reflow of a polymer film that is first nanoimprinted and then annealed above its glass transition temperature, depending on the initial topography of the film. These concepts were applied to the manufacturing of optical devices from the reflow of complex nanostructures. A method to measure the Newtonian viscosity and the terminal relaxation time of a thin polymer film was also developed. Finally, an exploratory work on a residual-layer-free nanoimprint process based on dewetting is presented. Emphasis was put on the accurate computation of the disjoining pressure in stratified media with the modern Lifshitz theory based on the optical properties of the interacting materials.