Notre thèse s’inscrit dans le cadre de la compréhension des mécanismes d’inactivation de microorganismes, principalement des spores bactériennes, suite à un traitement à l’ozone. Les objectifs généraux, au départ, étaient de mettre en place une stratégie expérimentale dans le but de déterminer les espèces et les phénomènes impliqués dans les mécanismes d’inactivation des spores en combinant diverses techniques pluridisciplinaires. Rappelons que les récentes avancées en stérilisation par plasma sont principalement dues aux études menées sur les mécanismes d’inactivation des microorganismes. Dans ce contexte, en nous appuyant sur une synthèse des études publiées dans la littérature scientifique, nous avons élaboré une étude expérimentale en deux étapes : l’étude de la stérilisation à l’ozone en milieu sec puis en milieu humide. Au cours de ces études, nous avons principalement étudié la cinétique d’inactivation des microorganismes, les dommages occasionnés à ces derniers par de tels traitements et nous avons identifié les espèces responsables de l’inactivation pour, enfin, proposer un mécanisme d’inactivation en spécifiant le rôle et l’importance des différents phénomènes en jeu. L’originalité de notre approche s’appuie sur la corrélation faite entre ces deux types de traitement (ozone sec et humidifié) ainsi que la diversité et la complémentarité des moyens de caractérisation utilisés. Dans un second volet, nous avons mis en évidence pour la première fois la possibilité de conférer à une surface de Pétri de polystyrène (PS) une importante activité biocide suite à un traitement à l’ozone. Nous avons mené une étude de caractérisation des propriétés de ces surfaces démontrant, principalement, leur grande efficacité biocide sur une large gamme de microorganismes, l’importance de l’interaction microorganismes/surface traitée, l’existence de la rémanence biocide, les modifications physico-chimiques induites en surface… L’étude des modifications physico-chimiques et microbiologiques nous a permis d’approcher les mécanismes d’inactivation en identifiant, de manière non exhaustive, les phénomènes impliqués. Enfin, nous avons examiné l’applicabilité de cette méthode à divers types de polymères montrant que le degré d’activité biocide induite dépend de la nature du substrat. / The thesis deals with the inactivation mechanisms of microorganisms (mainly endospores) after an ozone treatment. The general objective of this work was to provide an experimental strategy to identify the phenomena and chemical species involved in microorganism inactivation mechanism using multidisciplinary techniques. Recall that the recent advances in plasma sterilization are mainly due to comprehensive studies dealing with the inactivation mechanisms of microorganisms. In this context, based on a review of published studies, we proposed a two-step experimental study of ozone sterilization in both dry and humid media. In the course of this work, we have examined the inactivation kinetics of some microorganisms, their damage after treatments; we have also identified the chemical species responsible for inactivation, and proposed an inactivation mechanism (for each type of ozone treatment) by describing the importance and role of the different implicated phenomena. The originality of our approach rests on the correlation achieved between the dry and humid ozone treatment, and by the diversity and complementarity of the characterization techniques used. In a second part, we show for the first time the possibility to confer biocide activity to surfaces of polystyrene (PS) Petri dishes after their exposure to ozone. A characterization study of these treated surfaces mainly shows a high inactivation efficacy on various microorganisms, the importance of the microorganisms/treated-surface interaction, the biocide persistence of the treated surfaces and physico-chemical modifications. The study on physico-chemical and microbiological changes gives us elements for identifying the phenomena involved in the inactivation mechanisms. Finally, we have shown the possibility to confer biocide properties to polymeric surfaces in general with the same experimental process observing that the biocide efficacy depends on the nature of the polymer. / Une partie du travail a mené a un dépôt de brevet.

Laser-Induced Breakdown Spectroscopy (LIBS) is an analytical technique that has the potential to detect all the elements present in the periodic table. The limit of detection can go below a few ppm and this regardless of the physical phase of the analyzed sample (solid, liquid or gas). Its simplicity of use, its rapidity to get results and its versatility provide this technique with attractive features. The technique is currently developed for applications in a large number of domains such as online control, spatial explorations and the environment. However the weakness of the LIBS technique, compared to other more conventional ones, is still its difficulty in providing reliable quantitative results, especially for inhomogeneous and complex matrix such as organic or biological materials. The work presented in this thesis includes a study of the properties of plasma induced from different organic materials. First, a study of the plasma induced on the surface of a Nylon sample at short time delays (~ns) was carried out using the time-resolved shadowgraph technique for different experimental parameters (laser energy, pulse duration, wavelength). Then, a complete diagnostics of the plasma was performed using the plasma emission spectroscopy. A detailed analysis of the emission spectra at different detection delays allowed us to determine the evolution of the temperatures of the different species in the plasma (atoms, ions and molecules). The homogeneity and the local thermodynamic equilibrium within the plasma was then experimentally checked and validated. We demonstrated that the optimisation of the signalto- noise ratio and a quantitative procedure, such as the calibration-free LIBS, can be put in place within a properly chosen detection window. In our experiments, such optimised detection configuration was further employed to record LIBS spectra from different families of polymer in order to identify and classify them. For this purpose, the chemometrics procedure of artificial neural networks (ANN) was used to process the recorded LIBS spectroscopic data. The promising results obtained in this thesis makes LIBS stand out as a potentially useful tool for real time identification of plastic materials. Finally, this work can also be considered as a base for the further studies of more complex materials such as biological tissues with LIBS.

La spectrométrie de plasma induit par laser, plus connue sous le nom de LIBS (l’acronyme du terme en anglais Laser-Induced Breakdown Spectroscopy) est une technique analytique qui permet la détection de l’ensemble des éléments du tableau périodique avec des limites de détection de l’ordre du ppm et ceci sur tous types d’échantillons qu’ils soient liquides, solides ou gazeux. Sa simplicité de mise en œuvre, sa rapidité et sa versatilité en font une technique très attractive avec un fort potentiel en termes d’applications que ce soit pour le contrôle en ligne, l’environnement ou l’exploration spatiale. Son point faible reste cependant son manque de fiabilité dans l’analyse quantitative, en particulier lors de l’étude d’échantillons hétérogènes ou de matrices complexes telles que les matrices organiques. Ce travail de thèse propose une étude des propriétés des plasmas induit par laser sur différentes familles de polymères. Une étude du plasma au temps court (~ns) par ombroscopie est tout d’abord présentée, ceci pour différents paramètres expérimentaux (énergie laser, durée d’impulsion, longueur d’onde). Un diagnostic complet du plasma par spectrométrie d’émission est ensuite détaillé pour différents délais de détection et montre que la mesure des températures des différentes espèces du plasma (atomique, ionique et moléculaire) permet de vérifier, dans certaines conditions, les hypothèses d’homogénéité et de l’équilibre thermodynamique local. Ceci permet alors la mise en place de procédures quantitatives telles que la méthode dite sans calibration (calibration free LIBS) tout en optimisant le rapport signal sur bruit de la mesure LIBS. Dans nos expériences cette optimisation est mise à profit pour l’identification de différentes familles de polymères en utilisant, pour le traitement des données de la spectroscopie LIBS, la méthode chimiométrique des réseaux de neurones artificiels. Les résultats obtenus, très prometteurs, permettent d’envisager l’utilisation de la LIBS pour l’identification en temps réel des matières plastiques sur chaine de tri. Par ailleurs et de manière plus générale, ce travail pourrait constituer une base solide pour aller étudier d’autres matériaux organiques plus complexes tels que des tissus biologiques. / Laser-Induced Breakdown Spectroscopy (LIBS) is an analytical technique that has the potential to detect all the elements present in the periodic table. The limit of detection can go below a few ppm and this regardless of the physical phase of the analyzed sample (solid, liquid or gas). Its simplicity of use, its rapidity to get results and its versatility provide this technique with attractive features. The technique is currently developed for applications in a large number of domains such as online control, spatial explorations and the environment. However the weakness of the LIBS technique, compared to other more conventional ones, is still its difficulty in providing reliable quantitative results, especially for inhomogeneous and complex matrix such as organic or biological materials. The work presented in this thesis includes a study of the properties of plasma induced from different organic materials. First, a study of the plasma induced on the surface of a Nylon sample at short time delays (~ns) was carried out using the time-resolved shadowgraph technique for different experimental parameters (laser energy, pulse duration, wavelength). Then, a complete diagnostics of the plasma was performed using the plasma emission spectroscopy. A detailed analysis of the emission spectra at different detection delays allowed us to determine the evolution of the temperatures of the different species in the plasma (atoms, ions and molecules). The homogeneity and the local thermodynamic equilibrium within the plasma was then experimentally checked and validated. We demonstrated that the optimisation of the signalto- noise ratio and a quantitative procedure, such as the calibration-free LIBS, can be put in place within a properly chosen detection window. In our experiments, such optimised detection configuration was further employed to record LIBS spectra from different families of polymer in order to identify and classify them. For this purpose, the chemometrics procedure of artificial neural networks (ANN) was used to process the recorded LIBS spectroscopic data. The promising results obtained in this thesis makes LIBS stand out as a potentially useful tool for real time identification of plastic materials. Finally, this work can also be considered as a base for the further studies of more complex materials such as biological tissues with LIBS.

No description available.

Stimuli sensitive polymers and hydrogels respond with large property changes to small physical and chemical stimuli (e.g. temperature, pH, ionic strength). The bulk behavior of these polymers is widely studied and they show an isotropic swelling. However, thin hydrogel layers of polymers on a substrate show a swelling behavior, which is constrained in some way. Therefore, size, confinement, patternability, response time and transition temperature of thin hydrogel layers are the most important parameters in technological applications and this study focuses on the investigation of these above-mentioned parameters. The aim of this study involves synthesis, characterization and application of thin photo-crosslinked hydrogel layers. Dimethylmaleimide (DMI) moiety was incorporated in the polymers chains and was used to introduce photo-crosslinking by [2+2] cyclodimerization reaction in the presence of UV irradiation. The following photo-crosslinkers based on DMI group were synthesized ? - Acrylate photo-crosslinker (DMIAm) - Acrylamide photo-crosslinker (DMIAAm) - Polyol photo-crosslinker (DMIPA, DMIPACl) The conventional free radical polymerization of above listed photo-crosslinker with its respective monomer resulted in formation of photo-crosslinkable polymers of (a) HEMA, (b) DMAAm, (c) NIPAAm/DMAAm, (d) NIPAAm/Cyclam. The properties of these polymers were investigated by NMR, UV-VIS spectroscopy, GPC and SPR. Thin hydrogel layers were prepared by spin coating on gold-coated LaSFN9 glass. The covalent attachment to the surface was achieved through an adhesion promoter. Swelling behavior of the thin polymer layers was thoroughly investigated by Surface Plasmon Resonance (SPR) Spectroscopy and Optical Waveguide Spectroscopy (OWS). SPR and OWS gave a wide range of information regarding the film thickness, swelling ratio, refractive index, and volume degree of swelling of the thin hydrogel layer. For hydrophilic photo-crosslinked hydrogel layers of HEMA and DMAAm, it was observed that the volume degree of swelling was independent of temperature changes but was dependent on the photo-crosslinker mol-% in the polymer. These surface attached thin hydrogel layer exhibited an anisotropic swelling. For NIPAAm photo-crosslinked hydrogel layers with DMAAm as a hydrophilic monomer, it was observed that both transition temperature (Tc) and volume degree of swelling increases with increase in the mol-% of DMAAm. To study the effect of film thickness on Tc and volume degree of swelling, hydrogels with wide range of film thickness were prepared and investigated by SPR. These results provided vital information on the swelling behavior of surface attached hydrogel layer and showed the versatility of SPR instrument for studying thin hydrogel layers. Later part of project involved synthesis of multilayer hydrogel assembly involving a thermoresponsive polymer and a hydrophilic polymer. The combination of two layers with photo-crosslinkable DMAAm polymer as base layer and photo-crosslinkable NIPAAm polymer as top layer formulate a multilayer assembly where, the base layer only swells in response to temperature and the top layer shows temperature dependent swelling. Photo-crosslinked hydrogel layers of NIPAAm, DMAAm and HEMA shows a high-resolution patterns when irradiated by UV light through a chromium mask. At last this study focused on an important application of these hydrogel layers for cell attachment processes. Cell growth, proliferation and spreading shows a biocompatible nature of these hydrogel surfaces. Such thermoresponsive photo-crosslinkable multilayer structure forms bases for future projects involving their use in actuator material and cell-attachment processes.

Ce travail est axe sur l'etude des effets orientationnels induits par photo-isomerisation et de la relaxation de l'ordre cree. La methode que nous utilisons est basee sur la possibilite de certains materiaux de devenir dichroiques et birefringents lorsqu'ils sont eclaires par une lumiere polarisee et d'acquerir des proprietes non-lineaires du premier ordre, si un champ electrique est applique simultanement. Cette methode permet d'induire, par voie optique, un ordre orientationnel a partir de molecules photo-isomerisables. Cette orientation est la consequence de la superposition de plusieurs mecanismes: le pompage selectif des molecules paralleles a la polarisation de la pompe, la redistribution angulaire (non-centrosymetrique s'il y a un champ) et enfin, la relaxation angulaire. Ce modele a deja ete demontre sur la molecule de disperse red 1 (derivee de l'azobenzene), mais, du fait de la brievete de la duree de vie du photo-isomere, il est impossible de determiner les differentes etapes de la rotation des molecules. Une experience de dichroisme photo-induit a ete realisee pour observer l'anisotropie des deux isomeres de la molecule. Cette experience a montre que la rotation est faible a chaque cycle de pompage mais qu'il est pratiquement impossible de determiner a quel moment du cycle la molecule tourne. Nous montrons alors, sur le systeme spiropyrane-merocyanine, que la longue duree de vie du photo-isomere permet d'obtenir des informations sur les mecanismes d'orientation. Dans le cas du spiropyrane, l'orientation a lieu aussi bien pendant la photo-isomerisation que par diffusion thermique spontanee apres la photo-isomerisation. D'autre part, ces experiences ont permis d'etudier la mobilite angulaire des molecules de merocyanine dans le polymere: elle est d'autant plus faible que la concentration des echantillons est grande, elle diminue en fonction du temps apres le processus de photo-isomerisation et elle est plus faible dans le cas d'echantillons ages. Notre etude a permis une meilleure comprehension des mecanismes d'orientation lies a la photo-isomerisation et de relaxation de l'ordre orientationnel.