Step-growth polymerization provided an effective method for the preparation of several high performance polymers. Step-growth polymerization was used for syntheses of poly(siloxane imides), polyesters, poly(triazole esters), poly(triazole ether esters), and epoxy networks. Each of these polymeric systems exhibited novel structures, and either photoreactive capabilities, or high performance properties. There is an increasing trend towards the development of photoactive adhesives. In particular these polymers are often used in flip bonding, lithography, stimuli responsive polymers, drug delivery, and reversible adhesives. The ability to tailor polymer properties carefully with exposure to light allows for very unique stimuli responsive properties for many applications. This dissertation primarily investigates photoreactive polymers for reversible adhesion for use in the fabrication of microelectronic devices. In particular cyclobutane diimide functionality within polyimides and poly(siloxane imides) and o-nitro benzyl ester functionality within polyesters acted effectively as chromophores to this end. Thermal solution imidization allowed for the effective synthesis of polyimides and poly(siloxane imides). 1,2,3,4-Cyclobutane tetracarboxylic dianhydride acted as the chromophore within the polymer backbone. The polyimides obtained exhibited dispersibility only in dipolar, aprotic, high boiling solvents such as DMAc or NMP. The obtained poly(siloxane imides) demonstrated enhanced dispersibility in lower boiling organic solvents such as THF and CHCl₃. Dynamic mechanical analysis and tensile testing effectively measure the mechanical properties of the photoactive poly(siloxane imides) and confirmed elastomeric properties. Atomic force microscopy confirmed microphase separation of the photoactive poly(siloxane imides). ¹H NMR spectroscopy confirmed formation of maleimide peaks upon exposure to narrow band UV light with a wavelength of 254 nm. This suggested photo-cleavage of the cyclobutane diimide units within the polymer backbone. Melt transesterification offered a facile method for the synthesis of o-nitro benzyl ester-containing polyesters. ¹H NMR spectroscopy confirmed the structures of the photoactive polyesters and size exclusion chromatography confirmed reasonable molecular weights and polydispersities of the obtained samples. ¹H NMR spectroscopy also demonstrated a decrease in the integration of the resonance corresponding to the o-nitro benzyl ester functionality relative to the photo-stable m-nitro benzyl ester functionality upon exposure to high-intensity UV light, suggesting photo-degradation of the adhesive. ASTM wedge testing verified a decrease in fracture energy of the adhesive upon UV exposure, comparable to the decrease in fracture energy of a commercial hot-melt adhesive upon an increase in temperature. Click chemistry was used to synthesize polyesters and segmented block copolyesters. Triazole-containing homopolyesters exhibited a marked increase (~40 °C) in Tg, relative to structurally analogous classical polyesters synthesized in the melt. However, the triazole-containing homopolyesters exhibited insignificant dispersibility in many organic solvents and melt-pressed films exhibited poor flexibility. Incorporation of azide-functionalized poly(propylene glycol) difunctional oligomers in the synthesis of triazole-containing polyesters resulted in segmented block copolyesters which exhibited enhanced dispersibility and film robustness relative to the triazole-containing homopolyesters. The segmented triazole-containing polyesters all demonstrated a soft segment Tg near -62 °C, indicating microphase separation. Dynamic mechanical analysis confirmed the presence of a rubbery plateau, with increasing plateau moduli as a function of hard segment content, as well as increasing flow temperatures as a function of hard segment content. Tensile testing revealed increasing tensile strength as a function of hard segment, approaching 10 MPa for the 50 wt % HS sample. Atomic force microscopy confirmed the presence of microphase separated domains, as well as semicrystalline domains. These results indicated the effectiveness of click chemistry towards the synthesis of polyesters and segmented block copolyesters. Click chemistry was also used for the synthesis of photoactive polyesters and segmented block polyesters. The preparation of 2-nitro-p-xylylene glycol bispropiolate allowed for the synthesis of triazole-containing polyesters, which exhibited poor dispersibility and flexibility of melt-pressed films. The synthesis of segmented photoactive polyesters afforded photoactive polyesters with improved dispersibility and film robustness. ¹H NMR spectroscopy confirmed the photodegradation of the o-nitro benzyl functional groups within the triazole-containing polyesters, which indicated the potential utility of these polyesters for reversible adhesion. Synthesis of the glycidyl ether of 2,2,4,4-tetramethyl-1,3-cyclobutane diol (CBDOGE) allowed for the subsequent preparation of epoxy networks which did not contain bisphenol-A or bisphenol-A derivatives. Preparation of analogous epoxy networks from the glycidyl ether of bisphenol-A (BPA-GE) provided a method for control experiments. Tensile testing demonstrated that, dependent on network Tg, the epoxy networks prepared from CBDOGE exhibited similar Young's moduli and tensile strain at break as epoxy networks prepared from BPAGE. Dynamic mechanical analysis demonstrated similar glassy moduli for the epoxy networks, regardless of the glycidyl ether utilized. Tg and rubbery plateau moduli varied as a function of diamine molecular weight. Melt rheology demonstrated a gel time of 150 minutes for the preparation of epoxy networks from CBDO-GE and 78 minutes for the preparation of epoxy networks from BPA-GE, with the difference attributed to increased sterics surrounding CBDO-GE. These results indicated the suitability of CBDO-GE as a replacement for BPA-GE in many applications. / Ph. D.

Il est reconnu que le benzène, le toluène, l’éthylbenzène et les isomères du xylène, composés organiques volatils (COVs) communément désignés BTEX, produisent des effets nocifs sur la santé humaine et sur les végétaux dépendamment de la durée et des niveaux d’exposition. Le benzène en particulier est classé cancérogène et une exposition à des concentrations supérieures à 64 g/m3 de benzène peut être fatale en 5–10 minutes. Par conséquent, la mesure en temps réel des BTEX dans l’air ambiant est essentielle pour détecter rapidement un danger associé à leur émission dans l’air et pour estimer les risques potentiels pour les êtres vivants et pour l’environnement. Dans cette thèse, une méthode d’analyse en temps réel des BTEX dans l’air ambiant a été développée et validée. La méthode est basée sur la technique d’échantillonnage direct de l’air couplée avec la spectrométrie de masse en tandem utilisant une source d’ionisation chimique à pression atmosphérique (APCI-MS/MS directe). La validation analytique a démontré la sensibilité (limite de détection LDM 1–2 μg/m3), la précision (coefficient de variation CV < 10%), l’exactitude (exactitude > 95%) et la sélectivité de la méthode. Des échantillons d’air ambiant provenant d’un site d’enfouissement de déchets industriels et de divers garages d’entretien automobile ont été analysés par la méthode développée. La comparaison des résultats avec ceux obtenus par la technique de chromatographie gazeuse on-line couplée avec un détecteur à ionisation de flamme (GC-FID) a donné des résultats similaires. La capacité de la méthode pour l’évaluation rapide des risques potentiels associés à une exposition aux BTEX a été prouvée à travers une étude de terrain avec analyse de risque pour la santé des travailleurs dans trois garages d’entretien automobile et par des expériences sous atmosphères simulées. Les concentrations mesurées dans l’air ambiant des garages étaient de 8,9–25 µg/m3 pour le benzène, 119–1156 µg/m3 pour le toluène, 9–70 µg/m3 pour l’éthylbenzène et 45–347 µg/m3 pour les xylènes. Une dose quotidienne environnementale totale entre 1,46 10-3 et 2,52 10-3 mg/kg/jour a été déterminée pour le benzène. Le risque de cancer lié à l’exposition environnementale totale au benzène estimé pour les travailleurs étudiés se situait entre 1,1 10-5 et 1,8 10-5. Une nouvelle méthode APCI-MS/MS a été également développée et validée pour l’analyse directe de l’octaméthylcyclotétrasiloxane (D4) et le décaméthylcyclopentasiloxane (D5) dans l’air et les biogaz. Le D4 et le D5 sont des siloxanes cycliques volatils largement utilisés comme solvants dans les processus industriels et les produits de consommation à la place des COVs précurseurs d’ozone troposphérique tels que les BTEX. Leur présence ubiquitaire dans les échantillons d’air ambiant, due à l’utilisation massive, suscite un besoin d’études de toxicité. De telles études requièrent des analyses qualitatives et quantitatives de traces de ces composés. Par ailleurs, la présence de traces de ces substances dans un biogaz entrave son utilisation comme source d’énergie renouvelable en causant des dommages coûteux à l’équipement. L’analyse des siloxanes dans un biogaz s’avère donc essentielle pour déterminer si le biogaz nécessite une purification avant son utilisation pour la production d’énergie. La méthode développée dans cette étude possède une bonne sensibilité (LDM 4–6 μg/m3), une bonne précision (CV < 10%), une bonne exactitude (> 93%) et une grande sélectivité. Il a été également démontré qu’en utilisant cette méthode avec l’hexaméthyl-d18-disiloxane comme étalon interne, la détection et la quantification du D4 et du D5 dans des échantillons réels de biogaz peuvent être accomplies avec une meilleure sensibilité (LDM ~ 2 μg/m3), une grande précision (CV < 5%) et une grande exactitude (> 97%). Une variété d’échantillons de biogaz prélevés au site d’enfouissement sanitaire du Complexe Environnemental de Saint-Michel à Montréal a été analysée avec succès par cette nouvelle méthode. Les concentrations mesurées étaient de 131–1275 µg/m3 pour le D4 et 250–6226 µg/m3 pour le D5. Ces résultats représentent les premières données rapportées dans la littérature sur la concentration des siloxanes D4 et D5 dans les biogaz d’enfouissement en fonction de l’âge des déchets. / It is known that benzene, toluene, ethylbenzene and xylene isomers, volatile organic compounds (VOCs) commonly called BTEX, have toxic health effects on humans and plants depending on duration and levels of exposure. Benzene in particular is classified carcinogenic, and exposure to benzene at concentrations above 64 g/m3 can be fatal within 5–10 minutes. Therefore, real-time monitoring of BTEX in ambient air is essential for the early warning detection associated with their release and in estimating the potential exposure risks to living beings and the environment. In this thesis, a real-time analysis method for BTEX in ambient air was developed and validated. The method is based on the direct-air sampling technique coupled with tandem mass spectrometry using atmospheric pressure chemical ionization (direct APCI-MS/MS). Validation of the method has shown that it is sensitive (limit of detection LOD 1–2 μg/m3), precise (relative standard deviation RSD < 10%), accurate (accuracy > 95%) and selective. Ambient air samples from an industrial waste landfill site and various automobile repair shops were analyzed by the developed method. Comparison of results with those obtained by online gas chromatography coupled with a flame ionization detector (GC-FID) technique exhibited similar results. The capacity of the method for the fast evaluation of potential risks associated with an exposure to BTEX has been demonstrated through a field study with health risk assessment for workers at three automobile repair shops and through experiments under simulated atmospheres. Concentrations measured in the ambient air of the garages were in the ranges of 8.9–25 µg/m3 for benzene, 119–1156 µg/m3 for toluene, 9–70 µg/m3 for ethylbenzene, and 45–347 µg/m3 for xylenes. A total environmental daily dose of 1.46 10-3–2.52 10-3 mg/kg/day was determined for benzene. The estimated cancer risk due to the total environmental exposure to benzene was between 1.1 10-5 and 1.8 10-5 for the workers studied. A novel APCI-MS/MS method was also developed and validated for the direct analysis of octamethylcyclotetrasiloxane (D4) and decamethylcyclopentasiloxane (D5) in air and biogases. D4 and D5 are cyclic volatile siloxanes widely used in industrial processes and consumer products as replacement solvents for the tropospheric ozone forming VOCs, such as BTEX. Their ubiquitous presence in ambient air samples, due to the growing consumption, raises the need for toxicity studies which require qualitative and quantitative trace analysis of these compounds. Furthermore, the presence of trace amounts of these substances in a biogas hampers its use as a source of renewable energy by causing expensive damages to the equipment. Thus, siloxane analysis of the biogas is essential in determining if purification is needed before the use for energy production. The method developed in this study for these aims has good sensitivity (LOD 4–6 μg/m3), good precision (RSD < 10%), good accuracy (> 93%) and high selectivity. It was also shown that by using this method with hexamethyl-d18-disiloxane as an internal standard, detection and quantification of D4 and D5 in real biogas samples can be done with a better sensitivity (LOD ~ 2 μg/m3), high precision (RSD < 5%), and high accuracy (> 97%). Various biogas samples collected from the landfill site of the Complexe Environnemental de Saint-Michel in Montreal have been successfully analyzed by this new method. Concentrations measured were in the ranges of 131–1275 µg/m3 for D4 and 250–6226 µg/m3 for D5. These results represent the first primary-literature-reported data on siloxanes D4 and D5 contents of landfill-derived biogases as a function of the refuse age.

Il est reconnu que le benzène, le toluène, l’éthylbenzène et les isomères du xylène, composés organiques volatils (COVs) communément désignés BTEX, produisent des effets nocifs sur la santé humaine et sur les végétaux dépendamment de la durée et des niveaux d’exposition. Le benzène en particulier est classé cancérogène et une exposition à des concentrations supérieures à 64 g/m3 de benzène peut être fatale en 5–10 minutes. Par conséquent, la mesure en temps réel des BTEX dans l’air ambiant est essentielle pour détecter rapidement un danger associé à leur émission dans l’air et pour estimer les risques potentiels pour les êtres vivants et pour l’environnement. Dans cette thèse, une méthode d’analyse en temps réel des BTEX dans l’air ambiant a été développée et validée. La méthode est basée sur la technique d’échantillonnage direct de l’air couplée avec la spectrométrie de masse en tandem utilisant une source d’ionisation chimique à pression atmosphérique (APCI-MS/MS directe). La validation analytique a démontré la sensibilité (limite de détection LDM 1–2 μg/m3), la précision (coefficient de variation CV < 10%), l’exactitude (exactitude > 95%) et la sélectivité de la méthode. Des échantillons d’air ambiant provenant d’un site d’enfouissement de déchets industriels et de divers garages d’entretien automobile ont été analysés par la méthode développée. La comparaison des résultats avec ceux obtenus par la technique de chromatographie gazeuse on-line couplée avec un détecteur à ionisation de flamme (GC-FID) a donné des résultats similaires. La capacité de la méthode pour l’évaluation rapide des risques potentiels associés à une exposition aux BTEX a été prouvée à travers une étude de terrain avec analyse de risque pour la santé des travailleurs dans trois garages d’entretien automobile et par des expériences sous atmosphères simulées. Les concentrations mesurées dans l’air ambiant des garages étaient de 8,9–25 µg/m3 pour le benzène, 119–1156 µg/m3 pour le toluène, 9–70 µg/m3 pour l’éthylbenzène et 45–347 µg/m3 pour les xylènes. Une dose quotidienne environnementale totale entre 1,46 10-3 et 2,52 10-3 mg/kg/jour a été déterminée pour le benzène. Le risque de cancer lié à l’exposition environnementale totale au benzène estimé pour les travailleurs étudiés se situait entre 1,1 10-5 et 1,8 10-5. Une nouvelle méthode APCI-MS/MS a été également développée et validée pour l’analyse directe de l’octaméthylcyclotétrasiloxane (D4) et le décaméthylcyclopentasiloxane (D5) dans l’air et les biogaz. Le D4 et le D5 sont des siloxanes cycliques volatils largement utilisés comme solvants dans les processus industriels et les produits de consommation à la place des COVs précurseurs d’ozone troposphérique tels que les BTEX. Leur présence ubiquitaire dans les échantillons d’air ambiant, due à l’utilisation massive, suscite un besoin d’études de toxicité. De telles études requièrent des analyses qualitatives et quantitatives de traces de ces composés. Par ailleurs, la présence de traces de ces substances dans un biogaz entrave son utilisation comme source d’énergie renouvelable en causant des dommages coûteux à l’équipement. L’analyse des siloxanes dans un biogaz s’avère donc essentielle pour déterminer si le biogaz nécessite une purification avant son utilisation pour la production d’énergie. La méthode développée dans cette étude possède une bonne sensibilité (LDM 4–6 μg/m3), une bonne précision (CV < 10%), une bonne exactitude (> 93%) et une grande sélectivité. Il a été également démontré qu’en utilisant cette méthode avec l’hexaméthyl-d18-disiloxane comme étalon interne, la détection et la quantification du D4 et du D5 dans des échantillons réels de biogaz peuvent être accomplies avec une meilleure sensibilité (LDM ~ 2 μg/m3), une grande précision (CV < 5%) et une grande exactitude (> 97%). Une variété d’échantillons de biogaz prélevés au site d’enfouissement sanitaire du Complexe Environnemental de Saint-Michel à Montréal a été analysée avec succès par cette nouvelle méthode. Les concentrations mesurées étaient de 131–1275 µg/m3 pour le D4 et 250–6226 µg/m3 pour le D5. Ces résultats représentent les premières données rapportées dans la littérature sur la concentration des siloxanes D4 et D5 dans les biogaz d’enfouissement en fonction de l’âge des déchets. / It is known that benzene, toluene, ethylbenzene and xylene isomers, volatile organic compounds (VOCs) commonly called BTEX, have toxic health effects on humans and plants depending on duration and levels of exposure. Benzene in particular is classified carcinogenic, and exposure to benzene at concentrations above 64 g/m3 can be fatal within 5–10 minutes. Therefore, real-time monitoring of BTEX in ambient air is essential for the early warning detection associated with their release and in estimating the potential exposure risks to living beings and the environment. In this thesis, a real-time analysis method for BTEX in ambient air was developed and validated. The method is based on the direct-air sampling technique coupled with tandem mass spectrometry using atmospheric pressure chemical ionization (direct APCI-MS/MS). Validation of the method has shown that it is sensitive (limit of detection LOD 1–2 μg/m3), precise (relative standard deviation RSD < 10%), accurate (accuracy > 95%) and selective. Ambient air samples from an industrial waste landfill site and various automobile repair shops were analyzed by the developed method. Comparison of results with those obtained by online gas chromatography coupled with a flame ionization detector (GC-FID) technique exhibited similar results. The capacity of the method for the fast evaluation of potential risks associated with an exposure to BTEX has been demonstrated through a field study with health risk assessment for workers at three automobile repair shops and through experiments under simulated atmospheres. Concentrations measured in the ambient air of the garages were in the ranges of 8.9–25 µg/m3 for benzene, 119–1156 µg/m3 for toluene, 9–70 µg/m3 for ethylbenzene, and 45–347 µg/m3 for xylenes. A total environmental daily dose of 1.46 10-3–2.52 10-3 mg/kg/day was determined for benzene. The estimated cancer risk due to the total environmental exposure to benzene was between 1.1 10-5 and 1.8 10-5 for the workers studied. A novel APCI-MS/MS method was also developed and validated for the direct analysis of octamethylcyclotetrasiloxane (D4) and decamethylcyclopentasiloxane (D5) in air and biogases. D4 and D5 are cyclic volatile siloxanes widely used in industrial processes and consumer products as replacement solvents for the tropospheric ozone forming VOCs, such as BTEX. Their ubiquitous presence in ambient air samples, due to the growing consumption, raises the need for toxicity studies which require qualitative and quantitative trace analysis of these compounds. Furthermore, the presence of trace amounts of these substances in a biogas hampers its use as a source of renewable energy by causing expensive damages to the equipment. Thus, siloxane analysis of the biogas is essential in determining if purification is needed before the use for energy production. The method developed in this study for these aims has good sensitivity (LOD 4–6 μg/m3), good precision (RSD < 10%), good accuracy (> 93%) and high selectivity. It was also shown that by using this method with hexamethyl-d18-disiloxane as an internal standard, detection and quantification of D4 and D5 in real biogas samples can be done with a better sensitivity (LOD ~ 2 μg/m3), high precision (RSD < 5%), and high accuracy (> 97%). Various biogas samples collected from the landfill site of the Complexe Environnemental de Saint-Michel in Montreal have been successfully analyzed by this new method. Concentrations measured were in the ranges of 131–1275 µg/m3 for D4 and 250–6226 µg/m3 for D5. These results represent the first primary-literature-reported data on siloxanes D4 and D5 contents of landfill-derived biogases as a function of the refuse age.

No description available.

The acid and base catalyzed simultaneous twin polymerization (STP) of various 2,2′-disubstituted 4H-1,3,2-benzodioxasiline derivatives 2a–d with 2,2′-spirobi[4H-1,3,2-benzodioxasiline] (1) are presented in this paper. The products are nanostructured ternary organic–inorganic hybrid materials consisting of a cross-linked organic polymer, silica and a disubstituted polysiloxane. It can be demonstrated whether and in which extent the copolymerization of the two inorganic fragments of 1 and 2 takes place among the STP and how the molar ratio of the two components determines the structure formation of the resulting hybrid material. Steric and electronic effects of the substituents at the silicon center of 2 on the molecular structure formation and the morphology of the resulting hybrid material were investigated by means of solid state CP MAS 29Si and 13C NMR spectroscopy as well as high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). The mechanical properties (hardness and Young's modulus) of the hybrid materials were analyzed by means of nanoindentation measurements. / Dieser Beitrag ist aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.

La miniaturisation des systèmes a montré qu’à l’échelle nanométrique, les matériaux possèdent des propriétés différentes de leur état massif. Aujourd'hui, la synthèse d’objets de taille nanométrique est en parfaite adéquation avec les systèmes biologiques pour des applications médicales. La possibilité pour les chimistes de combiner dans un même « nano-objet » différent types de matériaux aux propriétés complémentaires a ouvert la voie au développement de nanoparticules multifonctionnelles pour des applications biologiques. C’est dans ce domaine, en utilisant les propriétés remarquables des terres rares que le LPCML de l’Université de Lyon en collaboration avec le laboratoire MATEIS de l’INSA de Lyon a pu mettre au point des nanoparticules hybrides multifonctionnelles ayant une structure cœur/coquille en combinant un cœur inorganique d’oxyde de lanthanide protégé par une coquille organique composée de polysiloxanes. L’utilisation d’un cœur d’oxyde de terre rare permet de disposer à la fois d’outils de détection (optique avec Eu et Tb, IRM avec Gd, Dy et Ho ou en scintigraphie avec Ho) et d’agent thérapeutique avec Gd et Ho. Après avoir longuement étudié les propriétés comme agent de contraste et de thérapie par capture neutronique du gadolinium, nous nous sommes intéressés aux propriétés atomiques de l’holmium qui après irradiation neutronique émet des rayonnements  et - potentiellement intéressants pour un traitement en curiethérapie. Le travail de thèse présenté ici rend compte de l’étude réalisée d’une part sur les propriétés optiques et magnétiques de ces nanoparticules hybrides à base d’oxyde de terre rare et d’autre part sur les possibilités d’applications médicales avec l’utilisation d’holmium. / The everlasting search for the miniaturization of the processes has shown that at the nanometer scale materials exhibit different properties than from the bulk. Today, the synthesis of nano-sized objects is in perfect harmony with biological systems for medical applications. The opportunity for chemists to combine into a single nano-oject different kind of materials with complementary properties has opened the way for the development of multifunctional nanoparticles for biological applications. In this area, using the remarkable properties of rare earths, LPCML laboratory from Lyon University in collaboration with MATEIS laboratory from INSA-Lyon was able to develop multifunctional hybrid nanoparticles with a core/shell structure by combining an inorganic rare earth oxide core coated by a polysiloxane shell. The using of a lanthanide in the core enables the combination of detection tools (optical with Eu and Tb, MRI with Gd, Dy and Ho or scintigraphy with Ho) and therapeutic agents with Gd and Ho. After having studied the properties of gadolinium as a contrast and neutron capture therapeutic agent, we were interested in atomic properties of holmium after neutron irradiation which emits  and - radiations, potentially interesting for scintigraphic imaging and brachytherapy. The thesis presented here reports studies on the one hand on optical and magnetic properties of these hybrid nanoparticles and on the other hand the possibilities of medical applications by using holmium-based particles.

Carbon nanotubes (CNT) and graphene have been one of the noticeable research areas in science and technology. In recent years, the assembly of these carbon nanostructures is one of the most interesting topic to the scientific world due to its variety of applications from nano to macroscale. These bulk nanostructures to be applicable in shock absorbers, batteries, sensors, photodetectors, actuators, solar cells, fuel cells etc. The present work is motivated to study the detailed compressive behavior of three dimensional cellular assemblies of CNT and graphene. The CNT foams are synthesized by chemical vapor deposition method. It is interesting to study the compressive behavior of CNT foam in the presence external magnetic field applied perpendicular to CNT axis. The peak stress and energy absorption capability of CNT foam enhances by four and nearly two times in the presence of magnetic field as compared to the absence of the magnetic field. In the absence of magnetic field the deformation of CNT foam is obtained elastic, plateau and densification regions. Further CNT foam is loaded with iron oxide nanoparticles of diameter is ~ 40nm on the surface and detailed study of the compressive behavior of the foam by varying iron nanoparticles concentration. The peak stress and energy absorption capability of CNT foam initially decreases with increasing the intensity of the magnetic field, further increases the intensity of the magnetic field the maximum stress and energy absorption capability increases which is due to magnetic CNT and particles align in the direction of the magnetic field. CNT surfaces were further modified by fluid of different viscosities. The mechanical behavior of CNT foam filled with fluids of varying viscosities like 100%, 95% and 90% glycerol and silicone oil are 612, 237, 109 and 279 mPa-s respectively. The mechanical behavior of CNT foam depends on both the intensity of magnetic field and fluid viscosity. The non linear relation between peak stress of CNT and magnetic field intensity is σp(B, η) = σ0 ± α(B-B0) where σ0 is the peak stress at B = B0 , η is the fluid viscosity, parameter α depends on properties of the MR fluid and B0 is an optimum magnetic field for which peak stress is maximum or minimum depending on the fluid viscosity. Graphene is assembled into a three dimensional structure called graphene foam. The graphene foam is infiltrated with polymer and study the detailed compressive behavior of graphene foam and graphene foam/PDMS at different strains of 20, 40, 60 and 70%. The maximum stress and energy absorption capability of graphene foam/PDMS is six times higher than the graphene foam. Also the graphene foam/PDMS is highly stable and reversible for 100 cycles at strains of 30 and 50%. The mechanical behavior of CNT, graphene foam, CNT/PDMS and graphene foam/PDMS is compared. Among all the foams, graphene foam/PDMS has shown the highest elastic modulus as compared to other foams. This behavior can be attributed to the wrinkles formation during the growth of graphene and a coupling between PDMS and interfacial interactions of graphene foam. Therefore it suggests potential applications for dampers, cushions and electronic packaging. Furthermore, the interaction between nanoparticles and polymer in a novel architecture composed of PDMS and iron oxide nanoparticles is studied. The load bearing capacity of uniform composites enhanced by addition of nanoparticles, reaching to a maximum to 1.5 times of the PDMS upon addition of 5wt.% of nanoparticles, and then gradually decreased to 1/6th of PDMS upon addition of 20wt.% of nanoparticles. On the other hand, the load bearing capacity of architectured composites at high strains (≥40%) monotonically increased with addition of nanoparticles in the pillars.

Mechanical forces have been observed to affect various aspects of life, for example, cell differentiation, cell migration, locomotion and behavior of multicellular organisms etc. Such forces are generated either by external entities such as mechanical touch, fluid flow, electric and magnetic fields or by the living organisms themselves. Study of forces sensed and applied by living organisms is important to understand the interactions between organisms and their environment. Such studies may reveal molecular mechanisms involved in mechanosensation and locomotion. Several techniques have been successfully applied to measure forces exerted by single cells and cell monolayers. The earliest technique made use of functionalized soft surfaces and membranes as substrates on which cell monolayers were grown. The forces exerted by the cells could be measured by observing deformation of the substrates. Atomic Force Microscope (AFM) is another sensitive instrument that allows one to exert and measure forces in pico-Newton range. Advances in micromachining technology have enabled development of miniature force sensors and actuators. Latest techniques for mechanical force application and measurement use micromachined Silicon cantilevers in single as well as array form and micropillar arrays. Micropillar arrays fabricated using soft lithography enabled the use of biocompatible materials for force sensors. Together, these techniques provide access to a wide range of forces, from sub micro-Newton to milli-Newton. In the present work, types of forces experienced in biological systems and various force measurement and actuation techniques will be introduced. This will be followed by in depth description of the two major contributions of this thesis, 1) ―Colored polydimethylsiloxane micropillar arrays for high throughput measurements of forces applied by genetic model organisms‖. Biomicrofluidics, January 29, 2015. doi: 10.1063/1.4906905 2) ―Air microjet system for non-contact force application and the actuation of micro-structures‖. Journal of micromechanics and microengineering, December 15, 2015. doi: 10.1088/0960-1317/26/1/017001 Device developed for force measurement consists of an array of micropillars made of a biocompatible polymer Poly Dimethyl Siloxane (PDMS). Such devices have been used by researchers to measure traction forces exerted by single cells and also by nematode worm Caenorhabditis elegans (C. elegans). C. elegans is allowed to move in between the micropillars and the locomotion is video recorded. Deflection of the micropillar tips as the worm moves is converted into force exerted. Transparent appearance of C. elegans and PDMS poses difficulties in distinguishing micropillars from the worm, thus making it challenging to automate the analysis process. We address this problem by developing a technique to color the micropillars selectively. This enabled us to develop a semi-automated graphical user interface (GUI) for high throughput data extraction and analysis, reducing the analysis time for each worm to minutes. Moreover, increased contrast because of the color also delivered better images. Addition of color changed the Young‘s modulus of PDMS. Thus the dye-PDMS composite was characterized using hyper-elastic model. The micropillars were also calibrated using commercial force sensor. Analysis of forces exerted by wild type and mutant C. elegans moving on an agarose surface was performed. Wild type C. elegans exerted a total average force of 7.68 µN and an average force of ~1 µN on an individual pillar. We show that the middle of C. elegans exerts more force than its extremities. We find that C. elegans mutants with defective body wall muscles apply significantly lower force on individual pillars, while mutants defective in sensing externally applied mechanical forces still apply the same average force per pillar compared to wild type animals. Average forces applied per pillar are independent of the length, diameter, or cuticle stiffness of the animal. It was also observed that the motility of the worms with mechanosensation defects, lower cuticle stiffness, and body wall muscle defects was reduced with worms that have defective body wall muscle having the largest degree. Thus, we conclude that while reduced ability to apply forces affects the locomotion of the worm in the micropillar array, the reduced motility/locomotion may not indicate that the worm has reduced ability to apply forces on the micropillars. We also used the colored micropillar array for the first time to measure forces exerted by Drosophila larvae. Our device successfully captured the peristaltic rhythm of the body wall muscles of the larva and allowed us to measure the forces applied on each deflected pillar during this motion. Average force exerted by 1st instar wild type Drosophila larvae was measured to be ~ 1.5 µN per pillar. We demonstrated that a microjet of air can be used to apply forces in micro-Newton range. We developed a standalone system to generate a controlled air microjet. Microjet was generated using a controlled electromagnetic actuation of a diaphragm. With a nozzle diameter of 150 µm, the microjet diameter was maintained to a maximum of 1 mm at a distance of 5 mm from the nozzle. The force generated by the microjet was measured using a commercial force sensor to determine the velocity profile of the jet. Axial flow velocities of up to 25 m/s were obtained at distances as long as 6 mm. The microjet exerted a force up to 1 µN on a poly dimethyl siloxane (PDMS) micropillar (50 µm in diameter, 157 µm in height) and 415 µN on a PDMS membrane (3 mm in diameter, 28 µm thick). We also demonstrate that from a distance of 6 mm our microjet can exert a peak pressure of 187 Pa with a total force of about 84 µN on a flat surface with 8 V operating voltage. Next, we demonstrated that the response of C. elegans worms to the impinging air microjet is similar to the response evoked using a manual gentle touch. This contactless actuation tool avoids contamination and mechanical damage to the samples. Out of the cleanroom fabrication and robust design make this system cost effective and durable. Magnetic micropillars have been used as actuators. We fabricated magnetic micropillar arrays and designed actuation mechanisms using permanent magnet and a pulsed electromagnet. Force of about 19 µN was achievable using a permanent magnet actuation. In a pulsed electromagnetic field micropillar exerted a force of about 10 µN on a commercial force sensor. These techniques have promising applications when actuation needs to be controlled from long distances.

Im Rahmen der vorliegenden Arbeit werden die Synthese und Charakterisierung eines thermisch-kontrollierten und eines photochemisch-kontrollierten reversiblen Polymersystems vorgestellt. Weiterhin werden Poly(dimethyl)siloxan-Oberflächen mit Amino-, Isocyanat-, Furan-, Maleimid- und Cumarin-Gruppen funktionalisiert. Hierbei werden sowohl bekannte als auch neuartige Wege der Oberflächenmodifizierung vergleichend untersucht und bewertet. Ausgehend von den hergestellten Cumarin-funktionalisierten Poly(dimethyl)siloxan-Oberflächen wird eine Anbindung des synthetisierten photochemisch-kontrollierten reversiblen Polymersystems an diese Oberflächen untersucht. Des Weiteren wird die Anbindung des synthetisierten thermisch kontrollierten reversiblen Polymersystems sowohl an den hergestellten Maleimid- als auch an den Furan-funktionalisierten Poly(dimethyl)siloxan-Oberflächen analysiert. Basierend auf den vorgestellten Cumarin-Funktionalisierungen werden photoaktive Oberflächen beschrieben und mittels ATR-IR-spektroskopischer und UV/Vis-spektroskopischer Methoden analysiert.

Im Fokus dieser Arbeit stand die Methode Zwillingspolymerisation zur Synthese organisch-anorganischer Hybridmaterialien. Die simultane Zwillingspolymerisation wird als neues Konzept zur gezielten Herstellung homogener, nanostrukturierter Hybridmaterialien unterschiedlicher Zusammensetzung vorgestellt. Hierfür wurden die Zwillingsmonomere 2,2’-Spirobi[4H-1,3,2-benzodioxasilin] und 2,2 Dimethyl-4H-1,3,2-benzodioxasilin in einem Arbeitsschritt gemeinsam polymerisiert. Die erhaltenen Phenolharz-Siliciumdioxid/Dimethylsiloxan-Hybridmaterialien weisen aufgrund einstellbarer Syntheseparameter unterschiedliche Eigenschaftsprofile auf, die systematisch analysiert wurden. Die Charakterisierung der Produkte erfolgte mit Hilfe der Festkörper-NMR-Spektroskopie, Elektronenmikroskopie, DSC, TGA-MS, sowie durch Extraktionsversuche und die Erzeugung und Analyse poröser Materialien. Neben der simultanen Zwillingspolymerisation wird die Synthese, Charakterisierung und thermisch induzierte Polymerisation literaturunbekannter Silicium-Spiroverbindungen mit einfach- oder zweifach substituierter Salicylalkohol-Einheit beschrieben. Hierbei wurden nanostrukturierte Hybridmaterialien mit teils hohem löslichen Anteil erhalten. Die Produktbildung wird in Abhängigkeit von der Entstehung und Weiterreaktion gefundener Chinonmethid-Strukturen diskutiert.