Parmi les bio-polymères issus des ressources renouvelables, les polysaccharides fournissent une alternative intéressante aux polymères de synthèse. Dans ce contexte, l’objectif de ce travail de thèse est basé sur la conception des copolymères amphiphiles pour la préparation de nouveaux biomatériaux. Ainsi, l’hydroxypropylméthylcellulose (HPMC) a été étudiée en raison de ses propriétés remarquables, dont la biocompatibilité, la biodégradabilité, la rétention d'eau et la gélification thermoréversible. Ces propriétés sont utiles pour de nombreuses applications telles que le relargage de médicament, la préparation des membranes et la formation de biomatériaux. L'hydrolyse enzymatique avec des endo cellulases issues de Trichoderma reesei a été étudiée pour produire des fragments d'HPMC ayant une masse molaire (Mw) entre 6000 et 30000 g mol-1. Les paramètres de l’activité enzymatique ont été étudiés en fonction de : la nature de substrat, le temps de réaction et la concentration de l'enzyme. Les polymères obtenus ont été comparés à ceux produits par hydrolyse acide. Il a été constaté que la structure des polymères issus d’un procédé d’hydrolyse, varie en termes de degré de substitution pour un même Mw. Cet effet donne lieu à différentes propriétés de gélification thermoréversible. Des copolymères amphiphiles tels que HPMC-b-poly (propylène glycol) et HPMC-b-PLA ont été préparés par amination réductrice et par couplage click thiol-ene, respectivement. Les propriétés d’agrégation ont été caractérisées par la diffusion de la lumière (DLS), le microscope électronique en transmission (TEM) et par la séparation de phase obtenue par la mesure du point de trouble. / Following the concept of bio-refinery, we propose to produce small fragments of biopolymers that can be used further as building blocks to prepare novel polymeric architectures. In the case of polysaccharides, enzymatic hydrolysis enables to form reducing end groups after each cleavage on the polymer chain. Reaction by reductive amination affords the possibility to introduce polysaccharides fragments in a large variety of materials going from amphiphilic copolymers to more sophisticated devices. Hydroxypropyl methylcellulose (HPMC) was used in this work because of its remarkable properties including biocompatibility, biodegradability, water retention and thermoreversible gelation beneficial for many applications such as drug delivery, film and biomaterial formation. Enzymatic hydrolysis using endo cellulases from Trichoderma reesei was investigated to produce a library of HPMC fragments with molecular weight (Mw) from 6000 to 30000 g mol-1. Mw control was carried out by varying the procedure conditions including the nature of starting HPMC, reaction time and enzyme concentration. The obtained polymers were compared to those produced by acidic hydrolysis.According to the preparation conditions, the structure of short chain polymers regarding substitution degrees varied for the same Mw giving rise to different clouding temperature and thermoreversible gelation properties. Amphiphilic block copolymers HPMC-b-poly(propylene glycol) and HPMC-b-PLA were prepared by reductive amination and by the thiol-ene click reaction, respectively. Self-assembly properties of these novel block copolymer were characterized by dynamic light scattering (DLS), transmission electron microscope (TEM), and clouding point temperature.

Ce manuscrit est consacré à l'élaboration de phases stationnaires monolithiques organiques pour lesmicrosystèmes électrochromatographiques plastiques. La partie bibliographique situe d'abord l'intérêt destechniques électrocinétiques en microsystème. Ensuite, l'état de l'art sur l'utilisation des monolithes dans cestechniques séparatives est présenté en portant une attention particulière à la description du processus dephotopolymérisation. La fonctionnalisation de surface du copolymère d'oléfine cyclique (COC) est ensuitedétaillée afin d'envisager l'ancrage du monolithe aux parois du canal.La partie expérimentale a porté tout d'abord sur le développement et la caractérisation de deux monolithesacrylates dédiés à la chromatographie à polarités des phases inversées. Le travail expérimental s'est ensuiteorienté vers le développement d’un nouveau procédé permettant la synthèse et l’ancrage du monolithe dansles microcanaux en COC, ceci en une seule étape et à partir des photoinitiateurs de type I. Ce protocolepermet l'obtention d'efficacités intéressantes qui restent cependant inférieures à celles obtenues en capillaire.Des adaptations des conditions d'irradiation ont alors été apportées pour la synthèse de ces monolithes àl’intérieur des microsystèmes afin d'obtenir des efficacités de l’ordre de 250 000 plateaux/m. Pour terminer,les domaines d'applications et la longévité du dispositif ont été illustrés par la séparation de différentesfamilles de solutés (PAH, mycotoxines, catécholamines, acides aminés, amines biogènes) et l'analysed'échantillons réels tels que les vins (pour déterminer la teneur en certaines amines biogènes : histamine ettyramine). / This manuscript is dedicated to the synthesis of organic monolithic stationary phases in plasticelectrochromatographic microchips. The bibliography part shows the benefit of electrokinetic techniques formicrosystems. After an overview on the use of monoliths in separation techniques, the manuscript is focusedon the description of photopolymerization process. Finally, a detailed review of the different protocols offunctionnalization of cyclic olefin copolymer (COC) surface to allow anchoring of the monolith to thechannel walls is produced.The experimental study firstly deals with the development and characterization of two acrylate monolithsdedicated to the reversed phase mode in chromatography. Then, the experimental part focus on a new onestepmethod for the simultaneous synthesis and anchoring of organic monolith inside COC microchipchannel, thanks to the use of type I photoinitiators. This protocol improves efficiencies which neverthelessstay below those obtained in capillary. Further, the adjustment of the irradiation conditions allows to reachup to 250 000 plates/m. Finally, the field of applications and the durability of microsystem have beenillustrated by the separation of different kinds of solutes (HAP, mycotoxins, catecholamines, biogenicamines) and the analysis of real matrices such as wine samples (for the quantitative determination of twobiogenic amines : histamine and tyramine).

L’objectif de ce travail était d’élaborer un copolymère biodégradable dans le but de développer une endoprothèse biorésorbable. Ainsi, des copolymères de lactide et de glycolide ont été synthétisés par copolymérisation par ouverture de cycle, dans des conditions permettant le contrôle de leurs paramètres macromoléculaires. Après plastification et mise en forme des copolymères par extrusion, l’étude des propriétés mécaniques, à l’état sec et après immersion en milieu aqueux, a été réalisée. Les essais de traction ont permis de vérifier l’importance de la vitesse de sollicitation et d’accéder à certaines grandeurs caractéristiques du matériau. L’étude de la dégradation des copolymères, sous forme de jonc, a mis en évidence un mécanisme de dégradation hétérogène sur une durée en accord avec l’application visée. La plastification par des molécules acides a permis d’accélérer la vitesse d’hydrolyse des copolymères. En conclusion, les propriétés mécaniques et de dégradation des copolymères PDLGA synthétisés sont donc en adéquation avec le cahier des charges de l’application biomédicale. / This work describes the synthesis of biodegradable copolymer to design a bioabsorbable endoprosthesis. Lactide and glycolide-based copolymers were synthesized by ring opening polymerization. Experimental conditions were chosen to produce controlled structures. The study of mechanical properties was performed in dry and wet states. During the tensile experiments, the effect of strain rate was noticed and some characteristics parameters were determined. Hydrolytic degradation of materials was fast and revealed a heterogeneous mechanism. Addition of acidic molecules for plasticizing increased the degradation rate of the copolymers.Mechanical properties and degradation of the PDLGA copolymers are indeed in good agreement with the specifications of this biomedical application.

Les agents d'embolisation liquides utilisés dans le traitement endovasculaire ont de nombreuses limitations. Des polymères, tels que l’Onyx et les cyanoacrylates sont disponibles. L’alcool est un agent puissant, mais non radio-opaque. Les cyanoacrylates entrainent une réaction inflammatoire significative. Leur polymérisation rapide est responsable d’un comportement mal prévisible.Il existe une possibilité de traitement incomplet.L’Onyx est efficace pour le traitement des MAV.Une pénétration plus distale est obtenue avec l’alcool, mais associée à un risque de migration systémique. Nous avons évalué les propriétés d'un nouvel agent embolique (Alconyx) composé d'un mélange d'alcool et d'Onyx. Cet agent devrait cumuler les avantages respectifs de l'alcool et de l'onyx avec une visualisation adéquate sous fluoroscopie, une meilleure pénétration distale que l'Onyx seul et moins de toxicité systémique liée à la réduction de quantité d’alcool injecté. Divers mélanges ont été testés avec différentes concentrations d'Onyx 18 et d’alcool absolu. Alconyx 25 (75% Onyx 18; 25% d'éthanol) est la formulation la plus prometteuse. Nous avons démontré sa facilité d'injection in vivo, sa nature cohésive sans fragmentation ainsi que sa bonne visualisation sous fluoroscopie. En raison de sa moindre viscosité démontrée in vitro, Alconyx a été capable de pénétrer profondément dans le lit artériel.. L'occlusion proximale par Alconyx 25 devrait permettre d'améliorer le contact entre l'éthanol et la paroi vasculaire et donc augmenter son pouvoir sclérosant et limiter son passage systémique. Les propriétés occlusives d’Alconyx 25 sont similaires à celle de l’Onyx 18 sous haute pression in vitro. / Commercially available liquid embolization agents used in endovascular treatment have many limitations. Polymeric agents as Onyx and cyanoacrylate are available. Ethanol also is a potent sclero-embolic agent. Cyanoacrylates are effective liquid embolic agents, however, their rapid polymerization makes their behaviour unpredictable with possibility of incomplete treatment. These properties render their use challenging.Onyx is easy to use. However, in very small arterial niduses, Onyx, is unable to penetrate deeply. Deep penetration is obtained with ethanol, associated with risk of systemic migration.Poor visualization of ethanol under fluoroscopy is major drawback. Mixing Onyx with ethanol had never been described in the literature till now. In this work, various mixtures have been tested with different concentrations of Onyx 18 and absolute ethanol. Alconyx 25 (75% Onyx 18; 25% ethanol) seems to be a promising product. We proved its ease of injection in vivo and in vitro, its cohesive nature showing no fragmentation or interruption of the injected column as well as its good visualization under fluoroscopy. It was able to penetrate deeply in the arterial bed. The occlusive properties of Alconyx 25 were rated as good as Onyx 18 under high pressure in vitro. Further investigation is needed to better understand the behavior of ethanol in the suspension and its effect on tissues compared to Onyx diluted simply with an equivalent amount of DMSO. Studies on other commercially available concentrations of Onyx would certainly be interesting.

Background: Tissue engineering and its contribution to regenerative medicine has advanced through the years. It has proven its efficacy especially in the treatment of advanced full thickness burn wounds. Tissue engineering is the synergy between biology and engineering. This fairly young science has one common goal and that is to regenerate new tissue. Various commercially available products have appeared on the market and this due to the ground-breaking work of many. One such well known product is Integra® which is the brain child of Yannas and Burke. This is a collagen-glycosaminoglycan copolymer which serves as a bioactive regeneration template or extracellular matrix analogue. Advanced wound healing is promoted along with the prevention of scar tissue formation and consequent contractures. Aims:</p This study provides an extensive review on the development of this dermal regeneration matrix and also aims to develop an equivalent product. Attention will be paid to: the biological building blocks and the motivation for their use; the essential production steps; and the final processing required in order to deliver a sterile product. Materials and Methods: A collagen and chondroitin 6-sulphate coprecipitate was prepared and subjected to either controlled or uncontrolled freezing. The frozen slurry was dried under vacuum for 17 hours after which each sample was coated with a thin silicone film. Glutaraldehyde crosslinking followed after which the product was thoroughly rinsed. The packaged products were then subjected to terminal sterilisation via gamma irradiation under various conditions. Various tests were conducted to evaluate the newly formed regeneration matrices and included scanning electron microscopy, enzymatic degradation by collagenase, and a cytotoxicity assay. Scanning electron microscopic analysis was done in order to reveal the adequacy of the scaffold architecture. Collagenase degradation of the scaffolds was used to project the rate of degradation of each template. Integra® served as the gold standard for each test. Quantifiable data was statistically analysed and any comparison made included the calculation of means, standard deviations and p-values (confidence interval of 95%). Results: Results indicated that highly porous bioactive tissue engineering matrices were obtained by either controlled freezing or uncontrolled freezing. The average pore diameter of the most homogenous scaffolds ranged between 52.47 and 136.44 µm with a mean of 87.34 µm. These templates were formed by using a 0.5% collagen concentration and a controlled freeze rate of 0.92 °C/min. Uncontrolled freezing (1.3 °C/min) of a 0.5% collagen concentration resulted in the formation of an irregular scaffold with an average pore diameter of 174.08 µm. It was found that the architecture of the most equivalent scaffold compared well with that of Integra® with p = 0.424. Scaffolds prepared using higher collagen concentrations (1.0%) and controlled freezing resulted in dense sponges with average pore diameters of 56.51 µm. Statistical analysis upon comparison indicated a significant difference p = 0.000 in the micro architecture. The rate of degradation of the most equivalent scaffold was 1.9 times that of Integra®. This implicates that the crosslinking was insufficient and due to one of the following: poor collagen quality; method of crosslinking; and degradation due to terminal sterilization. The rate of scaffold degradation can be extended, either by additional crosslinking or the prevention of degradation induced by irradiation. Temperature vacuum dehydration crosslinking through esterification or amide formation can be used as an initial crosslinking method in further studies. This form of crosslinking will complete the conventional glutaraldehyde crosslinking that reacts with the free amine groups of lysine or hydroxylysine of the protein backbone of collagen. It should be stressed that the determination of an in vivo degradation rate, in the form of an animal study, will aid to confirm the efficacy of the biologically active regeneration matrix. / Dissertation (MSc)--University of Pretoria, 2008. / Anatomy / unrestricted

abstract: Polyurea is a highly versatile material used in coatings and armor systems to protect against extreme conditions such as ballistic impact, cavitation erosion, and blast loading. However, the relationships between microstructurally-dependent deformation mechanisms and the mechanical properties of polyurea are not yet fully understood, especially under extreme conditions. In this work, multi-scale coarse-grained models are developed to probe molecular dynamics across the wide range of time and length scales that these fundamental deformation mechanisms operate. In the first of these models, a high-resolution coarse-grained model of polyurea is developed, where similar to united-atom models, hydrogen atoms are modeled implicitly. This model was trained using a modified iterative Boltzmann inversion method that dramatically reduces the number of iterations required. Coarse-grained simulations using this model demonstrate that multiblock systems evolve to form a more interconnected hard phase, compared to the more interrupted hard phase composed of distinct ribbon-shaped domains found in diblock systems. Next, a reactive coarse-grained model is developed to simulate the influence of the difference in time scales for step-growth polymerization and phase segregation in polyurea. Analysis of the simulated cured polyurea systems reveals that more rapid reaction rates produce a smaller diameter ligaments in the gyroidal hard phase as well as increased covalent bonding connecting the hard domain ligaments as evidenced by a larger fraction of bridging segments and larger mean radius of gyration of the copolymer chains. The effect that these processing-induced structural variations have on the mechanical properties of the polymer was tested by simulating uniaxial compression, which revealed that the higher degree of hard domain connectivity leads to a 20% increase in the flow stress. A hierarchical multiresolution framework is proposed to fully link coarse-grained molecular simulations across a broader range of time scales, in which a family of coarse-grained models are developed. The models are connected using an incremental reverse–mapping scheme allowing for long time scale dynamics simulated at a highly coarsened resolution to be passed all the way to an atomistic representation. / Dissertation/Thesis / Doctoral Dissertation Mechanical Engineering 2020

Diploma thesis deals with preparation and characterization of block copolymer PP/PE grafted with itaconic anhydride in melt. Experimental part deals with free radical iniciated grafting of polar monomers onto polyolefins and with potencial applications of grafted polyolefins. Samples of PP/PE grafted with itaconic anhydride were prepared under various conditions in the experimental part. 2,5-dimethyl-2,5bis(tert-buthylperoxy)hexane (Luperox 101) was used as radical iniciator. Grafting was performed in Brabender mixer under conditions: temperature 190-230°C, concentration of monomer 0,25-1 weight percent, concentration of iniciator 0,025 – 2 weight percent, screw speed 30 rpm. The influence of certain parameteres: iniciator concentration, monomer concentration and temperature upon conversion of monomer, value of MFI and homopolymerization of monomer extent was of interest. Presence of anhydride bonded to the polymer backbone was confirmed by FTIR spectroscopy. Concentration of grafted anhydride and conversion of monomer was determined by acid-base titration and confirmed by FTIR spectroscopy.

Impact E/P copolymer (ICP) is produced using gas-phase polymerization catalysed by Ziegler-Natta catalysts. This material with its excellent mechanical properties is used in many industries, for example in automotive industry to produce bumpers or instrument panels. Its properties depend on chemical structure which was analysed using DSC, 13C NMR and GPC. It was used 6 different samples of ICP for studies, the chosen samples have different ratio between ethylene and propylene in their copolymer phase. The samples were fractionated using preparative TREF and solvent extraction to obtain fractions, which composition depends on elution temperature. Obtained fractions and original samples were subsequently analysed using above-mentioned methods.

This thesis is focused on the study of the properties of mortars and pastes with active pozzolanic materials. It deals with monitoring cementitious composites which describes both the effect of compensation pozzolanic cement mortar admixtures active based on amorphous silica and the modifying polymeric additive. The main criteria for the assessment of these modified mortars and pastes are particularly adhesive and achieved strength compared with the reference mortar. The detailed work also examined the microstructure past through images from REM, records RTG, DTA and high pressure mercury porosimetry.

The Diploma thesis is adressing the issue of polymer-modified mortars (PMM) and theirs properties in dependence on curing conditions. The reasons of using polymer additives and some selected applications of PMM are described in theoretical part of this work. Cementitious composite (mortar) hardening is especially focused on mechanism of formation co-matrix system based on cement hydration products and polymer film in dependence on curing conditions. The knowledge of interaction of cement and ethylene-vinyl acetate (EVA) copolymer is presented in the latest paragraphs of theoretical work. Following practical part presents influence of EVA to physical and mechanic properties of PMM in dependence of dosage polymer additive and exogenous factors. The study of microstructure was investigated by scanning electron microscope and high-pressure mercury porosimetry. Tests and investigations are described and evaluated.