<p>The interactions between polymers and components of biological systems are an important area of interest within the fields of tissue engineering, polymer chemistry, medicine and biomaterials. In order to create such a biomimetic material, it must show the inherent ability to reproduce or elicit a biological function. How do we design synthetic materials in order to direct their interactions with biological systems?</p><p>This thesis contributes to this research with aspects of how polymers interact with biological materials with the help of ionic interactions. Polyesters, biodegradable or not, may after a hydrolytic cleavage interact ionically with protonated amines by the liberated carboxylate functions. Amines are found in proteins and this fact will help us to anchor proteins to polyester surfaces. Another type of interaction is to culture cells in polymeric materials, i.e. scaffolds. We have been working on compliant substrates, knitted structures, to allow cell culture in three dimensions. A problem that arises here is how to get a high cell seeding efficiency? By working on the interactions between polymers, proteins and finally cells, it is possible to create a polarized protein membrane that allows for very efficient cell seeding, and subsequent three dimensional cell cultures. Finally a synthetic route to taylor interaction was developed. Here a group of polymers known as ionomers were synthesized. In our case ionic end groups have been placed onto biodegradable polycarbonates, we have created amphiphilic telechelic ionomers. Functionalization, anionic or cationic, changes the properties of the material in many ways due to aggregation and surface enrichment of ionic groups. It is possible to add functional groups for a variety of different interactions, for example introducing ionic groups that interact and bind to the complementary charge of proteins or on the other hand one can chose groups to prevent protein interactions, like the phosphorylcholine zwitterionomers. Such interactions can be utilized to modulate the release of proteins from these materials when used in protein delivery applications. The swelling properties, Tg, degradation rate and mechanical properties are among other things that will easily be altered with the choice of functional groups or backbone polymer.</p>

The acceptance of blood contacting implants creating favorable conditions in vivo is decisively determined by their interaction with proteins that mediate inter cellular interactions with synthetic substrates. Adsorbed proteins can activate blood cascade systems like coagulation and complement that may result in serious blood clots, and/or immunological reactions. Poly (ethylene glycol) (PEG), heparin, and phosphoryl choline (PC) functional poly (methacrylates) are previously used polymers with known non-adhesive properties in blood contacting events. This thesis contributes to this extensive research by introducing a novel type of biomaterial that equips biodegradable polymers with biomimetic functionalities. The phospholipid mimetic material is synthesized by combining biodegradable polymers with various functional polar end-groups consisting of zwitterionic phosphoryl choline (PC), anionic succinates, and cationic quaternary ammonium. The polymer backbone provides mechanical stability and biodegradability whilst the various head groups provide a variety of functions. The careful evaluation of the synthesis has allowed reaction conditions to be optimized leading to complete conversion at each step and subsequently high yields. Initially, poly (e-caprolactone) (PCL) was used since it provided a suitable synthetic starting point. However, the synthesis has also included poly (trimethylene carbonate) (PTMC) to provide a material that allows spontaneous surface enrichment of the polar PC group. This was achieved with an added hydrophilic environment. Through the synthesis of multi PC functional PTMC, additional bulk organisation by the formation of zwitterionomers (PC ionomer) was achieved. Low modulus elasticity and water uptake were some of the properties of the formed material. As a result it was shown that the PC ionomer could be used for protein/drug loading and subsequent release. Furthermore, the material possessed non-adhesive properties in different biological environments. Importantly, the result suggests that a versatile synthetic platform has been established that may provide a smorgasbord of different functional polymers, or combinations of such. This is indeed important since it was shown that the polymer in many ways dictates how the material may take advantage of an added functionality. Such materials should be interesting for a variety of biomedical applications including the production of soft hemocompatible tissue.

The interactions between polymers and components of biological systems are an important area of interest within the fields of tissue engineering, polymer chemistry, medicine and biomaterials. In order to create such a biomimetic material, it must show the inherent ability to reproduce or elicit a biological function. How do we design synthetic materials in order to direct their interactions with biological systems? This thesis contributes to this research with aspects of how polymers interact with biological materials with the help of ionic interactions. Polyesters, biodegradable or not, may after a hydrolytic cleavage interact ionically with protonated amines by the liberated carboxylate functions. Amines are found in proteins and this fact will help us to anchor proteins to polyester surfaces. Another type of interaction is to culture cells in polymeric materials, i.e. scaffolds. We have been working on compliant substrates, knitted structures, to allow cell culture in three dimensions. A problem that arises here is how to get a high cell seeding efficiency? By working on the interactions between polymers, proteins and finally cells, it is possible to create a polarized protein membrane that allows for very efficient cell seeding, and subsequent three dimensional cell cultures. Finally a synthetic route to taylor interaction was developed. Here a group of polymers known as ionomers were synthesized. In our case ionic end groups have been placed onto biodegradable polycarbonates, we have created amphiphilic telechelic ionomers. Functionalization, anionic or cationic, changes the properties of the material in many ways due to aggregation and surface enrichment of ionic groups. It is possible to add functional groups for a variety of different interactions, for example introducing ionic groups that interact and bind to the complementary charge of proteins or on the other hand one can chose groups to prevent protein interactions, like the phosphorylcholine zwitterionomers. Such interactions can be utilized to modulate the release of proteins from these materials when used in protein delivery applications. The swelling properties, Tg, degradation rate and mechanical properties are among other things that will easily be altered with the choice of functional groups or backbone polymer.

No description available.

Wo und wie schnell nehmen Wurzeln Wasser auf? Obwohl diese Frage in Pflanzen- und  Bodenwissenschaften von großer Bedeutung ist, gibt es nur wenige experimentelle Daten darüber, an welcher Stelle der Wurzeln eine transpirierende Pflanze das Wasser aus dem Boden erhält. Die Antwort auf diese Frage erfordert direkte und in-situ Messungen des lokalen Wasserflusses in die Wurzel hinein. Ziel dieser Arbeit war es, eine neue Methode zu entwickeln und anzuwenden, um den lokalen Wasserfluss in unterschiedliche Segmente der Pflanzenwurzeln zu quantifizieren. Dabei wurde Neutronenradiographie eingesetzt um den Transport von deuteriertem Wasser (D2O) in die Wurzel von Lupinen zu untersuchen. Die Lupinen wuchsen in Aluminium Containern, die mit sandigem Boden gefüllt waren. Der sandige Boden wurde mit Hilfe von 1cm-dicken Schichten groben Sandes in verschiedene Bereiche eingeteilt. Diese Schichten reduzierten die Diffusion von D2O zwischen den verschiedenen Bereichen.  D2O wurde in ausgewählte Bereiche tagsüber (transpiriende Pflanzen) und nachts (nicht transpiriernde Pflanze) injiziert. Transport von D2O in die Wurzeln hinein wurde durch Neutronenradiographie mit einer räumlichen Auflösung von 100 µm in Intervallen von 10 Sekunden aufgezeichnet. Die Messungen zeigten: i) Transport von D2O in die Wurzel hinein war tagsüber schneller als nachst; ii) D2O wurde tagsüber schnell entlang der Wurzel in Richtung Spross transportiert, während dieser axiale Fluss nachts vernachlässigbar war. Die Unterschiede zwischen Tag- und Nachtmessungen wurden durch konvektiven Transport von D2O in den Wurzeln erklärt. Um den effektiven Wasserfluss in die Wurzeln hinein zu quantifizieren, wurde ein einfaches Konvektions-Diffusions Modell entwickelt, wobei die Zunahme der D2O Konzentration in Wurzeln vom konvektiven Transport abhängt und von the Diffusion des D2O in die Wurzeln. Die Ergebnisse zeigten, dass die Wasseraufnahme nicht gleichmäßig entlang der Wurzel stattfindet. Die Wasseraufnahme war in den oberen Bodenschichten höher als in den tieferen. Entlang einzelner Wurzeln war der radiale Fluss in nahen Teilen der Wurzel höher als in den weiter entfernten Teilen der Wurzel. In Lupinen fand die Wasseraufnahme im Wesentlichen in den lateralen Wurzeln statt. Die Funktion der Pfahlwurzel war es, das Wasser der lateralen Wurzeln zu sammeln und zum Spross zu transportieren. Diese Funktion wird durch eine geringe radiale und eine hohe axiale Leitfähigkeit sichergestellt.  Wir haben diese Technik auch angewandt um den Einfluss der Rhizosphäre auf die Wasseraufnahme zu untersuchen. Wie vor Kurzem auch in der Literatur berichtet wurde, wurde auch in dieser Arbeit beobachtet, dass der Boden in der unmittelbaren Nähe der Wurzeln, der sogenannten Rhizosphäre, hydrophob wird, wenn der Boden trocken wird. Zum ersten Mal konnte gezeigt werden, dass durch die Hydrophobizität der Rhizosphäre die Wasseraufnahme nach Trocknung und folgender Bewässerung reduziert wird. Es wurde die Schlussfolgerung gezogen, dass nach Trocknung die Rhizosphäre einen entscheidenden Wiederstand für den Wasserfluss zur Wurzel darstellt. Das beeinflusst vermutlich auch die Ausdehnung des Bereiches der Wurzeln, in dem Wasser aufgenommen wird. Die Bedeutung dieser Arbeit ist die Entwicklung einer neuen Methode, um Wasseraufnahme durch Wurzeln lebender Pflanzen lokal zu quantifizieren. Diese Methode macht es möglich quantitativ zu messen, wo und wie schnell Wurzeln Wasser im Boden aufnehmen. Diese Technik wird es erleichtern, die Funktionsweise der Wurzeln verschiedener Pflanzen zu verstehen und den Einfluss von Wurzelwachstum und wechselnder äußerer Bedingungen, wie Wassergehalt, Transpiration und Verfügbarkeit von Nährstoffen und vieler weiterer Faktoren zu untersuchen.  Die Antwort auf diese Fragen könnten einen weiten Bereich für landwirtschaftliche Anwendungen eröffnen, die darauf abzielen, Bewässerungsmethoden zu verbessern.

Diss. (sammanfattning) Umeå : Sveriges lantbruksuniv. / Härtill 4 uppsatser.

O déficit de irrigação tem sido utilizado como uma das mais vantajosas estratégias de economia de água, redução dos custos com irrigação e custo de oportunidade de água. O objetivo principal deste trabalho foi avaliar o efeito da irrigação plena e com déficits em duas épocas distintas, no crescimento da planta, nas relações hídricas e parâmetros de produção e qualidade da pimenta cv. Tabasco (Capsicum frutescens). Como objetivo secundário avaliar o método da sonda de dissipação térmica (SDT) na estimativa da transpiração da pimenta Tabasco. O experimento foi desenvolvido em ambiente protegido, no Departamento de Engenharia de Biossistemas na Escola Superior de Agricultura Luiz de Queiroz ESALQ-USP, em Piracicaba-SP, de setembro de 2009 a agosto de 2010. O delineamento foi em blocos casualizados, com quatro repetições, lâminas de irrigação de 40, 60, 80 e 100% da evapotranspiração da cultura (Etc), inicializadas aos 39 dias após o transplantio - DAT (E1) e aos 59 DAT (E2). Aferiu-se a altura da planta (AP) e o comprimento de fruto (CF), o diâmetro do fruto (DF) e do caule da planta (DCP). Mediu-se a temperatura da folha aos 176 DAT, com termômetro de infravermelho e o potencial da água na folha antes do amanhecer falv, aos 59, 96 e 110 DAT, com câmara de pressão. O número de frutos (NF), a massa fresca de frutos por planta (MFFP) e a massa total de frutos por planta (MTFP) foram quantificados. Calculou-se a taxa de incremento de crescimento (TMICP) e do diâmetro do caule da planta (TMIDCP). Os dados foram submetidos à análise de variância para testar a significância das lâminas de irrigação (plena e com restrição) diferenciadas na E1 e E2 e, quando significativo, determinou-se a tendência por meio de análise de regressão. Foram instaladas sondas de dissipação térmica - SDT em 29 plantas com 8 meses de idade. A equação para estimativa do fluxo de seiva foi calibrada tendo como padrão medidas lisimétricas em uma planta. Os volumes de irrigação totais aplicados variaram de 160 (E1L40) a 362 L planta-1 (L100), num ciclo de 208 DAT. Houve efeito significativo da irrigação plena e com déficit aplicado a partir da fase vegetativa e de floração sobre a AP, DCP, TMICP, TMIDCP, folha antes do amanhecer, temperatura média da folha, NFP, sendo o modelo linear o que melhor se ajustou. A MMFP não variou com o déficit, nem com as épocas de inicialização. O déficit de irrigação 40% Etc imposto na E2 permitiu economia de até 49,8% de água no ciclo de 208 DAT. O déficit de irrigação afetou a produção da pimenta, mas o mesmo não foi observado para a sua qualidade física. Há maior influência do déficit de irrigação na relação hídrica da pimenteira quando aplicado a partir da fase de floração. O método da SDT, com ajuste da calibração original, correção das diferenças térmicas naturais e uma correta amostragem na determinação da área do xilema, é eficaz na avaliação da transpiração de pimenta Tabasco. Palavras-chave: Capsicum frutescens; Restrição de irrigação; Estresse hídrico; Sonda de dissipação de calor / The deficit irrigation has been used as one of the most advantageous strategies for saving water, reducing costs witch irrigation and the opportunity cost of water. The main objective of this study was to evaluate the effect of full irrigation and with deficits in two different periods in plant growth, water relations, production parameters and quality of pepper cv. Tabasco (Capsicum frutescens). As a secondary objective method to evaluate the thermal dissipation probe (SDT) in the estimation of transpiration pepper \'Tabasco\'. The experiment was conducted in a greenhouse at the Biosystems Engineering Department at the Escola Superior de Agricultura \"Luiz de Queiroz\" - ESALQ-USP, Piracicaba-SP, from September 2009 to August 2010. The experiment was conduced as randomized block design with four replications and irrigation levels of 40, 60, 80 and 100% of crop evapotranspiration (Etc), beginning 39 days after transplanting - DAT (E1) and 59 DAT (E2) . The plant height (PH), fruit length (FL), fruit diameter (FD) and the stem diameter (SD) were measured. Leaf temperature was measured upon 176 DAT, with infrared thermometer, also the pre-dawn leaf water f predawn, at 59, 96 and 110 DAT, pressure chamber was measured. The fruit number (FN), average mass fruit per plant (AMFP) and the total mass of fruits per plant were (TMFP) are quantified. The rate growth increment (RGI) and the plant stem diameter (PSD), considering the current and previous evaluation were calculated. Data were subjected to analysis of variance to test the significance of irrigation (full and restricted) differentiated in E1 and E2, and when significant, the trend was determined by regression analysis. A heat dissipation probe - HDP were installed in 29 plants 8 months old. The equation to estimate the sap flow was calibrated using a lysimeter as a standard measure in a plant. The total volume of irrigation applied ranged from 160 (E1L40) to 362 L plant-1 (L100), in a cycle of 208 days from transplanting. There was a significant deficit and full irrigation started at vegetative stage and flowering on the PH, SD, RGI, PSD, f pre-dawn, average leaf temperature, FN been the linear model that best fitted. The average fruit plant mass did not vary with deficit neither with beginning time. The deficit irrigation 40% Etc in E2 allowed savings of up to 49.8% water consumption in a cycle 208 DAT. The deficit irrigation affected the pepper production witch was not observed for the physical quality of the fruits. There is greater influence of deficit irrigation on pepper water relation when applied from the flowering stage. It can be concluded the method of HDP, adjusting the original calibration, correction of the natural thermal differences and a correct sampling in determining the area of the xylem, is effective in evaluating the transpiration of pepper Tabasco.

Ces travaux de thèse ont pour but d'obtenir une meilleure connaissance des mécanismes de dégradation, lors de l'exposition à un milieu agressif, de primaires de peinture en phase aqueuse (époxy-polyamino amide) utilisés dans l'industrie aéronautique pour la protection contre la corrosion de l'alliage d'aluminium 2024 à l'aide des techniques d'impédances globale et locale. Deux revêtements formulés soit avec du chromate de strontium soit avec un mélange de pigments non-chromatés ont été comparés. Les diagrammes d'impédance des deux revêtements, mesurés dans des conditions sèches (en contact avec Hg), présentent un comportement proche de celui d'une capacité pure, et ont été analysés à l'aide du modèle en loi de puissance, qui correspond à un comportement CPE (Constant Phase Element). Lors de l'immersion dans une solution chlorurée, le comportement des revêtements s'écarte progressivement de l'idéalité. Les données d'impédance électrochimique obtenues pour différents temps d'immersion ont été analysées avec un modèle qui suppose une variation exponentielle de la résistivité le long de l'épaisseur du revêtement (modèle de Young). Cette analyse a confirmé que la pénétration de l'eau et des ions dans le revêtement ne se fait pas de façon identique. La vitesse de pénétration de l'eau est plus rapide et celle-ci affecte plus fortement la permittivité que la résistivité, alors que la diffusion des ions Na+ et Cl- est plus lente et affecte exclusivement la résistivité du revêtement. L'utilisation de ces modèles permet non seulement d'expliquer les comportements CPE et pseudo CPE observés sur les diagrammes d'impédance mais aussi de déterminer la prise en eau des revêtements durant le test. Celle-ci est en accord avec des mesures gravimétriques. L'effet d'auto-cicatrisation des deux revêtements en présence de blessures artificielles a ensuite été étudié par spectroscopie d'impédance électrochimique locale. Les diagrammes locaux et les cartographies (2D ou 3D) ont permis de suivre les phénomènes d'auto-cicatrisation pour le système chromaté ou bien le développement de la corrosion pour le système non-chromaté. Ce travail de thèse propose une méthodologie qui servira de référence pour développer et caractériser les performances de peintures contenant des inhibiteurs écologiques et en particulier leur processus d'auto-cicatrisation. / The aim of this work is to obtain a better understanding of the degradation mechanisms, as a function of exposition time in an aggressive environment, of commercial coatings (epoxy-polyaminoamide waterborne paint) used in aeronautical industry for corrosion protection of 2024 aluminium alloy by global and local impedance techniques. The coatings formulated with either strontium chromate (SrCrO4) or Cr(VI)-free pigments were compared. The behavior of dry coatings (in contact with Hg) was close to that of an ideal capacitor and could be accurately modelled with the power-law model corresponding to a CPE (Constant Phase Element). Upon immersion in NaCl solution, the behavior of the wet coatings became progressively less ideal, i.e. farther from a capacitive behavior. The impedance data was analyzed with the Young model that take into account the exponential variation of the coating resistivity along its thickness. This analysis confirmed that penetration of water and ions occurs on different time scales. The former process is faster and affects permittivity more strongly than resistivity; the latter is slower and affects almost exclusively resistivity. The models allows to explain not only the CPE or pseudo-CPE behaviors observed on impedance diagrams but also to determine the coatings water uptake during the test which is in good agreement with gravimetric measurements. Then, the self-healing properties of artificially damaged coatings were studied by local electrochemical impedance spectroscopy (LEIS). The local diagrams and the mappings (2D or 3D) allowed self-healing processes for the chromated system or corrosion developments for the unchromated system to be observed. The present work proposed a methodology to develop and to characterize coatings containing environmentally friendly inhibitors, and particularly the self-healing process.

Fort d’une croissance annuelle de l’ordre de 6%, le secteur des matériaux composites est actuellement en pleine expansion et se doit de répondre aux exigences d’un marché en constante évolution. Dans le même temps, la raréfaction des ressources pétrolières et l’augmentation de la conscience environnementale, conduisent à une demande croissante en matériaux bio-composites. Le remplacement des fibres synthétiques (fibre de verre en particulier) par des fibres naturelles engendre un intérêt certain dont les motivations principales sont la réduction de l’impact environnemental, la diminution des coûts et l’obtention d’un matériau plus léger à volume égal. Néanmoins, la faible compatibilité existante entre les fibres de cellulose hydrophiles et les matrices polymères hydrophobes, est un des inconvénients majeurs qui nuit au bon développement de ces matériaux. L’objectif de cette thèse est de développer une alternative aux fibres de verre pour l’élaboration de matériaux composites à matrice thermoplastique. Pour ce faire, l’intégration de filaments de cellulose (FC), fournis par Kruger notre partenaire industriel, a été étudiée. En plus d’apporter un côté « vert » au matériau final, les FC permettent de réduire le poids des composites par rapport à leurs homologues synthétiques. Néanmoins, la faible compatibilité entre les filaments polaires et la matrice apolaire ainsi que la grande capacité d’absorption d’eau des FC nous a conduit à développer différentes stratégies de modification chimique des FC, afin d’en accroitre le caractère hydrophobe. Ces modifications ont permis de renforcer les matériaux composites grâce à l’amélioration de l’adhésion entre les FC et la matrice, le tout en minimisant la perte de résistance mécanique causée par l’absorption d’eau. Les résultats obtenus après acétylation, alkylation et encollage sont décrits dans ce manuscrit. / Over the past two decades, the increase of environmental concerns and shortage of petroleum resources have provoked a growing interest in the use of natural fibers as an alternative to synthetic fibers for the reinforcement of composites. Natural fibers possess desirable specific properties including biodegradability, renewability and low-cost. In addition, they have densities much lower than synthetic fibers, which makes them interesting for different applications ranging from automotive parts to packaging. Despite their benefits, certain drawbacks such as incompatibility with the hydrophobic polymer matrix, a tendency to form aggregates during processing and a poor resistance to moisture absorption, reduce the potential of these fibers to be used as a reinforcement of hydrophobic thermoplastic matrices.This thesis aims to substitute glass fibers by cellulose fibers for their use in fiber-reinforced composites. Reinforcement of LDPE composites with cellulose filaments (CF), supplied by our industrial partner Kruger, was studied. CF appear to an interesting alternative to glass fibers because they possess desirable specific properties including biodegradability, low density, high tensile strength and modulus as well as providing a low-cost and renewable option. However, the weak interfacial adhesion between CF and LDPE, and the high moisture absorption of CF led us to carry out several chemical modifications of CF in order to increase their hydrophobicity. Modified CF-composites exhibit higher mechanical properties and lower water uptake than unmodified CF-composites. Results obtained from acetylation, alkylation and paper sizing are described in this manuscript.

Wood is a widely used construction material that has many advantageous properties, and some drawbacks. These drawbacks are mainly associated with the porous vascular structure of wood that makes it a high water-absorbent material. In addition, wood’s properties alter substantially with respect to the moisture content. Amongst the treatment techniques that limit the water uptake capacity of wood, vacuum-aided impregnation has exhibited promising results. However, little research has explored the effect of key parameters (such as the vacuum pressure) on the effectiveness of the impregnation. This study aims to optimize the performance of SiO2 impregnation of spruce wood under vacuum pressures. The main objective of this research is to overcome wood’s weakness by reducing its water uptake capacity through a vacuum-aided impregnation technique and study its effect on the physico-mechanical properties of wood under dry and saturated conditions. The study was conducted in two parts. In the first part, wood samples underwent impregnation under atmospheric and three vacuum pressures. Density measurements, water uptake tests, microscopy examination, thermogravimetric analysis, and dynamic mechanical analysis were conducted on non-treated and SiO2-treated samples. Quantitative and qualitative analyses demonstrated that SiO2 impregnation performed under -90 kPa was able to effectively enhance the wood’s properties compared to the other conditions. The SiO2 impregnation under high vacuum pressure demonstrated an effective increase in the density of the wood and achieved a significant reduction in the water uptake capacity. The analysis of the wood’s viscoelastic properties revealed that SiO2 impregnation under atmospheric and vacuum conditions triggered two different reinforcing mechanisms: a solid film, causing stick-slip oscillation, and particle diffusion, causing particle-particle and particle-lumen wall friction, respectively. For the second part, characterization methods such as Impact test, DMA, SEM, EDS, Porosity, and SAXS tests were conducted on non-treated and -90 kPa treated spruce wood samples in dry, saturated, and submerged states in order to reveal the synergistic effect of the SiO2 impregnation pressure and water uptake on the wood’s properties. The results showed that high vacuum impregnation pressure has a significant positive reinforcing effect on the wood’s properties. It increased the impact resistance of wood in dry and saturated conditions. A high vacuum impregnation was able to overcome the softening effect of water and caused a significant increase in the Storage modulus by strengthening the wood’s vascular structure, which accordingly increased the wood’s capacity to absorb energy. High vacuum impregnation was also able to counteract the plasticizing effect of water and significantly increased the Loss modulus by increasing the internal friction in the wood with the diffusion of the nanoparticles in the wood’s cell walls and vascular structure. This phenomenon increased the wood's capacity to absorb and dissipate energy under dry and submerged conditions.