This diploma thesis investigated thermal stability and the degradation of hyaluronan (HA) in HA with a molecular mass of 90–130 kDa and in HA with a molecular mass of 1 500–1 750 kDa. The following methods were used for the research: rheology, SEC-MALLS, TGA and DSC. Low-molecular HA was subject to time dependency of degradation investigation, where it was dried at a temperature of 90 °C for a period of 30 minutes and 60 minutes prior to the preparation of the solutions itself. High-molecular HA was investigated not only from the point of view of time but from the point of view of temperature dependency of degradation as well. In the case of investigating the time dependency of degradation, high-molecular HA was dried at a temperature of 75 °C at a time range from 15 minutes to 120 minutes prior to the preparation of the solutions. During the preparation of the solutions for discovering the temperature dependency of degradation, the high-molecular HA was then dried for a period of 30 minutes at a temperature range from 60 °C to 90 °C. For low-molecular HA, thermal stability was proven. Therefore, there is no decrease in the molecular mass and the solutions did not demonstrate a significant decrease of viscosity. For high-molecular HA, thermal stability was not proven. Degradation due to the temperature of drying as well as the time of drying occurred, which was demonstrated by a significant decrease in molecular mass and viscosity of the solutions. While in the case of using a drying temperature of 60 °C, a decrease in the molecular mass occurred by approximately 5 %, the molecular mass decreased by approximately 20 % at a drying temperature of 90 °C compared to undried HA. Due to this reason, high-molecular HA was also further investigated by means of the TGA method, where the decrease of humidity of HA samples in relation to the drying temperature was observed. The DSC method was also used. The objective of the DSC method was to find out temperatures, at which evaporation of humidity contained in an HA sample in relation to its form (undried HA, dried HA and lyophilized HA) occurs. This method further finds out the heat necessary to evaporate humidity from an HA sample. To conclude this research, the results obtained for high-molecular HA were compared with the results of other drying processes – lyophilized proved to be a very gentle drying method because a decrease in the molecular mass for lyophilized HA compared with undried HA almost did not occur.

<p>Transport of gasses and liquids through polymers and composites is an important factor to be considered when designing a material for structure and packaging applications. For structural engineering applications, more focus has been given to the transportation of water, vapor and organic liquids rather than gases as diffusion of these liquids into the polymers and polymer-based composites can significantly lower service life. In addition, much attention has been given to the leaching of unreacted reactant molecules, solvents, additives, degradation products from the polymers and composites to the atmosphere (water, soil etc.). We studied the transport of volatile organic compounds and water in cured-in-place-pipe (CIPP) (a representative of FRPC) and gas permeability of highly engineered cellulose nanocrystals (CNC) films.</p> <p>Cured-in-place-pipe (CIPP) is a popular technology which uses fiber reinforced polymer composite to repair sanitary sewer, stormwater, and drinking water pipe. The liner is installed in the field and exposed to flowing water immediately after installation (curing of the liner) is done. Curing conditions dictate liner properties as undercured liners can contain unreacted styrene monomers, additives, degradation products. These agents can leach out and enter the environment (soil, water, air). The objective of this work was to investigate the curing behavior, volatile content, thermal stability of steam-cured and UV-cured CIPP liners collected from Indiana and New York installation sites. The liner specimens were also exposed to water and other aggressive environmental conditions (saltwater, concrete pore solution at 50 °C) to explore the leaching of unreacted styrene and other organic chemicals from the liners. The influence of transportation of water, salt solution and pore solution through liners on mechanical and thermo-mechanical properties was also examined to study the durability of the liners. Study suggested that the durability of the liners depends on the curing condition and exposed environment conditions.</p> <p>The function of polymer packaging materials is mainly to inhibit gas and moisture permeation through the films. Cellulose nanocrystals (CNCs) have drawn growing interest for the packaging due to their non-toxicity, abundance in nature, biodegradability and high barrier properties. The objective of this work was to corelate the alignment of CNC with free volume and barrier performance of the film. Furthermore, citric acid (CA) was added to the CNC suspensions with varying quantity to explore the effect of CA on coating quality and barrier performance of CNC coated polypropylene (PP) film. Study revealed that CA addition in CNC suspension can enhance the hydrophobicity and gas barrier performance of coated PP films while retaining the high optical transparency. </p>

Dans cette étude, nous avons cherché à développer de nouvelles formulations pour améliorer la stabilité thermique et le comportement au feu de trois matrices polymères de grande diffusion: le polyéthylène (PE), le polystyrène (PS) et le polyamide 66 (PA66). Le système intumescent employé consiste à combiner des retardateurs de flammes classiques (polyphosphate d’ammonium (APP) et pentaérythritol (PER)) avec une faible quantité de nanooxydes métalliques dont les propriétés auraient été ajustées sur mesure de façon à améliorer la compatibilité du mélange à l’état fondu, ou encore pour changer le mécanisme de dégradation d’un point de vue chimique (effets catalytiques) ou physiques (effet barrière, viscosité etc…). Une partie importante de cette étude a donc été d’abord consacrée à la synthèse d’oxydes à morphologie, porosité, structure ou fonctionnalités particulières. A cet égard, les silices mésoporeuses possèdent l’avantage de présenter des surfaces spécifiques élevées (700-1400 m²/g) et une taille de pores compatible avec les chaines polymères. En adaptant les conditions de synthèse, nous avons cherché à établir des relations entre certains paramètres relatifs aux silices préparées (tels que la (1) surface spécifique (2) la taille des particules (3) la taille des pores (4) la morphologie et (5) le type de structure (en général SBA-15)) sur la stabilité thermique et le comportement au feu du polyéthylène. Préalablement, les propriétés texturales, structurales et chimiques de ces silices ont été caractérisées par porosimétrie à l’azote à 77K, DRX et FTIR. Globalement, les améliorations apportées par les silices mésostructurées restent modestes par rapport à celles induites par les RF classiques seuls et ceci particulièrement pour les polymères non charbonnants (PE et PS). Ceci est dû probablement à la très grande disparité des teneurs respectives en silice et RF dans les composites testés (1 et 24% en masse, respectivement). L’effet du taux de silice SBA-15 (0,5-10wt%) à taux de charge constant et égal à 25% massique a été également étudié pour les trois matrices polymères. Les valeurs maximales d’IOL (indice limite d’oxygène) sont toujours obtenues pour 1-2% de SBA-15. Les modifications de surface des silices SBA-15 par greffage des différentes fonctions organiques (CTAB, amine, thiol, phénol, phosphonate, acide benzoïque et diphénylphosphate), inorganiques (aluminium, acide phosphorique et acide tungstophosphorique) ou métalliques (cuivre, nickel) ont fait l’objet de caractérisations poussées afin d’évaluer la quantité et la stabilité thermique des espèces greffées ainsi que la nature des liaisons de surface. D’autres types de nanooxydes synthétiques (aluminophosphates, phosphate de zirconium et nanotubes de type titanates) ou commerciaux (CeO2, ZrO2, CeZr et CePr) ont également été étudiés. La plupart de ces échantillons a montré un effet légèrement positif sur la stabilité thermique et le comportement au feu des polymères. De point de vue mécanistique, les analyses réalisées en Py-GC-MS montrent que les oxydes greffés par des acides catalysent la transformation des alcènes et des diènes issus de la décomposition du PE en aromatiques. En présence de SBA-15, l’analyse des résidus carbonés (par DRX, FTIR) montrent la formation de nouvelles phases cristallines phosphosiliciques qui renforcent la couche protectrice. Les phases condensées et gazeuses de quelques formulations performantes en IOL ont été analysée par cône calorimètre et microcalorimètre (PCFC). La substitution d'une fraction d'APP/PER par de la silice SBA-15 a un effet plus marqué sur la stabilité thermique et le comportement au feu de la matrice PA66 (IOL= 48,5 (+10 par rapport au PA66/APP/PER), comparé aux matrices PE (IOL=25 (+0,5 par rapport au PE/APP/PER) et PS (IOL= 24,1 (+0,8 par rapport au PS/APP/PER). De plus, la fonctionnalisation [...] / In this study, we have tried to develop new formulations to improve the thermal stability and fire behavior of three polymer matrices widely used: the polyethylene (PE), the polystyrene (PS) and the polyamide 66 (PA 66). The intumescent system used consists to combine a classical flame retardants (ammonium polyphosphate (APP) and pentaeryhthritol (PER)) with a small amount of nanooxides whose properties can be adjusted in order to improve the compatibility of the melting mixture, or to change the degradation mechanism by a chemical (catalytic effect) or physical (insulating layer, viscosity, etc …) process. The total amount of additives has been set at 25wt%. An important part of this study was consecrated to the synthesis of oxides with different morphologies, porosities, structures and functionalities. In this regard, the mesoporous silica has an advantage of having a high surface area (700-1400 m²/g) and a pore size compatible with the polymer chains. By adapting the synthesis conditions, we have aimed to correlate between some parameters related to the prepared silicas (such as (1) the specific surface area (2) particle size (3) pore size (4) morphology and (5) the type of structure (usually SBA-15)) on the thermal stability and fire behavior of different polymer matrices. A comprehensive study has been conducted globally, regardless of the matrix, that the improvements provided by the mesostructured silicas are modest compared to those elicited by classical FR. However, the fire behavior has been improved (particularly LOI) by combining APP/PER system with 1-2wt% of SBA-15. The surface modification of SBA-15 by grafting a different organic functions (CTAB, amine, thiol, phenol, phosphonate, benzoic acid and diphenylphosphate), inorganic species (aluminum, phosphoric acid and tungstophosphoric acid) or metals (copper, nickel) have been the subject of an advanced characterizations in order to assess the amount and the thermal stability of the grafted species, well as the nature of the surface bonds. Other types of synthetic nanooxides (aluminophosphates, zirconium phosphate and titanate nanotubes) or commercial (CeO2, ZrO2, CeZr and CePr) have been also studied. Most of these particles in combination with APP/PER system have shown a slightly positive effect on the thermal stability and fire behavior of polymers. In mechanistic terms, the nanooxides have mainly an effect on enhancing the barrier effect. The analyses carried out by Py/GC/MS showed that the grafted oxides by acidic species catalyze the conversion of alkenes and dienes (resulting from the decomposition of PE) to aromatics. In the presence of SBA-15, the analysis of char (by XRD and FTIR) shows the formation of new crystalline phases which enhance the protective layer.

Scaffolds are proteins with high conformational stability, allowing us to implement multiple mutations into specific parts of the protein. Even with these mutations, the structural integrity of the protein is maintained as well as its physical-chemical properties. These mutations give the specific scaffold new properties. In most cases it is the binding specificity towards previously chosen target. The biggest advantages of scaffolds are their small size, stability, low-cost manufacturing, and easiness of preparation. Scaffold utilized in this thesis is unique for having two binging surfaces designed on which it can be mutated. Each of those two surfaces can be separately mutated to develop a binging site for two different proteins. In our case these mutations led to binding two nonidentical receptors of a human cytokine. Mutations are made with a use of yeast display, one of the methods of directed evolution. The main focus of this thesis is changing an expression system of the binding proteins from the yeast system to a bacterial one, their production and purification followed by characterization of those binding proteins using biophysical methods. These methods were used to evaluate structural and thermal stability, and binding affinity to both receptors of the beforementioned binding proteins....

Recent experimental advances for the fabrication of various borophene sheets introduced new structures with a wide range of applications. Borophene is the boron atom analogue of graphene. Borophene exhibits various structural polymorphs all of which are metallic. In this work, we employed first-principles density functional theory calculations to investigate the mechanical properties of five different single-layer borophene sheets. In particular, we analyzed the effect of the loading direction and point vacancy on the mechanical response of borophene. Moreover, we compared the thermal stabilities of the considered borophene systems. Based on the results of our modelling, borophene films depending on the atomic configurations and the loading direction can yield a remarkable elastic modulus in the range of 163–382 GPa nm and a high ultimate tensile strength from 13.5 GPa nm to around 22.8 GPa nm at the corresponding strain from 0.1 to 0.21. Our study reveals the remarkable mechanical characteristics of borophene films.

Homopolymers and copolymers produced from aromatic based methacrylates, acrylates, and dimethacrylates are excellent materials with many applications in dentistry, microelectronics, and optics, including optical eye wear, fiber optics, and non-linear optics, such as holography. Carbazole based polymers have demonstrated good optical, photo-refractive, and charge-transporting properties, combined with ease of processing. The objective of this research was to design, synthesize, and characterize high refractive index polymers and copolymers for use in optical spectacle lenses of eyeglasses. Additionally, other interesting attributes were observed for selected carbazole based polymers, such as high thermal stability and birefringence, which could lend these materials to other uses, such as non-linear optics and electronic data storage. A family of novel, high refractive index homopolymers and copolymers were synthesized by incorporating carbazole, along with other aromatic substituents, into methacrylates, acrylates, and dimethacrylates. Subsequent free radical polymerizations provided for high refractive index materials well suited for lightweight optical spectacles and other applications. The refractive index of materials can be increased by increasing the polarizability of substituent groups. By incorporating oxygen, sulfur, or sulfoxide groups into polymers, high refractive index polymers have been attained. By reacting the phenol, aromatic diols, or aromatic thiols with 9-(2,3-epoxypropyl)-carbazole, the refractive index of the final polymer can be increased further. The reaction of the carbazole based intermediate with methacryloyl chloride or methacrylic anhydride eliminated any hydroxyl groups in the final methacrylate or dimethacrylate. Hydroxyl groups undergo intermolecular hydrogen bonding, which increases viscosity. The absence of hydrogen bonding in the final methacrylated monomers reduces viscosity, which is desirable for processing. Novel carbazole based monomers and polymers were characterized in terms of molecular composition and molecular weight, thermal properties, such as melting point, glass transition temperature, and decomposition, and in terms of optical properties, such as refractive index. The AIBN initiated carbazole-phenoxy based methacrylate polymerization was followed using in-situ FTIR, which showed the reaction to be completed within 40 minutes in DMAC at 90°C. Photo-DSC was used to determine the heat of polymerization (DHp) for the carbazole-phenoxy based methacrylate, which was found to be -39.4 kJ/mole. One and two dimensional 1H NMR was used to characterize the molecular structure of the carbazole-phenoxy based methacrylate monomer. The carbazole-phenoxy based methacrylate homopolymer had a surprisingly high decomposition temperature. 13C NMR spectroscopy experiments and molecular modeling were employed to explore the configuration of the polymerized carbazole-phenoxy based methacrylate. The lack of head-to-head linkages due to steric considerations could explain the higher thermal stability observed for the carbazole-phenoxy based methacrylate polymer. Refractive indices of these carbazole based methacrylates, acrylates, and dimethacrylate polymers ranged from 1.53 to 1.63. Statistical copolymers of carbazole based methacrylates with methyl methacrylate were also produced by solution polymerization in DMAC, and characterized. Using free radical polymerization techniques, homopolymers and copolymers of the carbazole functionalized methacrylates, acrylates, and dimethacrylates were readily obtained. This research demonstrated a variety of carbazole based chemistries which could produce controlled linear and cross-linked materials with high refractive index values and other interesting features. / Ph. D.

>Magister Scientiae - MSc / The growth of the Internet has led to many interesting developments for both educational and commercial purposes. In this project an attempt was made to use the Internet for a research purpose to facilitate the determination of the thermal stability of diffusion barriers. Another purpose of this thesis is to investigate the teaching and training use of the Internet through the development of online interactive tools and activities as well as materials. The training aspects are mentioned as it is hoped that this thesis can serve as a form of documentation of the use of the Internet, while the central part was the determination of thermal stability of TiN, TaN and TiW diffusion barriers on Ag. The fact that most advanced instruments are computer driven or can be interfaced with a computer was exploited to set up a virtual laboratory facility through which sophisticated and scarce instrumentation can be remotely accessed. The major piece of equipment that forms part of the laboratory is a four-point probe furnace at Arizona State University, Tempe, USA. The Internet made it possible to use the facility to perform an online experiment to determine the effectiveness of different diffusion barriers for silver metallisation. This was accomplished by measuring the resistance of the different samples remotely over the Internet through the control of the four-point probe furnace at Arizona State University. Four types of analysis were used to determine the thermal stability of the diffusion barriers, namely the Scanning Electron Microscopy, Rutherford Backscattering Spectrometry, X-Ray Diffraction and resistivity measurements. Similar facilities exist at Oak Ridge National Laboratory, Tennessee, USA, where a range of different electron microscopes can be accessed remotely via the Internet. The measurements of the diffusion barriers form the main part of this work. However, the other aspects required for the use of the Internet in such a system, such as the development of a website to receive and upload scanning electron microscopy (SEM) images, the development of the virtual scanning electron microscope and the learning of the Virtual Reality Markup Language are also included.

<p>Ovaj rad je imao za cilj , razvoj postupka sinteze polimernih prekursora mreža na bazi<br />obnovljivih sirovina. Razvijen je postupak sinteze poli laktida u rastvoru dihlor metana. Vreme trajanja postupka sinteze je 6 h, a uspe&scaron;nost samog procesa je potvrđena metodama identifikacije i karakterizacije dobijenih polimera PLLA. U ovom radu, za ispitivanja dobijenih polimernih materijala, uzimajući u obzir ideju o krajnjoj nameni, kori&scaron;ćene su sledeće metode: GPC ( Gel Permeation Chromarography) za određivanje raspodele molekulske mase; IR spektrofotometrija, prikazuje vibraciju atomskih, molekulskih ili funkcionaknih grupa; i termička analiza TGA i DSC, za praćenje promena pri kontrolisanom zagrevanju i hlađenju.<br />Jedan od ciljeva rada je bio i da se da pregled postojećih teorija ojačanja elastomera punilima sa nano česticama, i ispita pona&scaron;anje nano-kompozitnih materiajala pod dejstvom visoko energetskog zračenja ( gama zračenja). U eksperimentalnom delu ispitivani su elastomerni materijale na bazi butadienakrilonitrilnog kaučuka (NBR) i hlorsulfonovanog polietilenskog kaučuka (CSM) . Me&scaron;anjem CSM i NBR formiraju se umreženi sistemi, koji se koriste kao prekursori mreža za dobijanje nano-kompozitnih materijala ojačanaih česticama aktivnih punilačađi i silicijum (IV) oksida. Kod tako dobijenih materijala ispitivane su karakteristike pre i posle ozračivanja &gamma; zracima. Dinamičko-mehaničkom analizom potvrđen je ojačavajući efekat punila.</p> / <p> This work was aimed at the development procedure for the synthesis of polymer precursors<br /> network based on renewable raw materials. Developed a procedure for synthesis of poly<br /> lactide in solution, dichloro methane. The duration of the synthesis procedure was 6 h, and<br /> the success of the process was confirmed by the methods of identification and<br /> characterization of the obtained polymer PLLA. In this paper, the investigation obtained<br /> polymer materials, taking into account the idea of final destination, following methods were<br /> used: GPC (gel permeation Chromarography) to determine the distribution of molecular<br /> weight, IR spectrophotometry, showing the vibration of atomic, molecular or funkcionaknih<br /> group, and thermal analysis TGA and DSC, to track changes in a controlled heating and<br /> cooling.<br /> One of the aims of this study was to be given to review of existing theories of reinforcement<br /> fillers elastomer with nano particles, and examine the behavior of nano-composite<br /> materiajala under the influence of high energy radiation (gamma radiation). In the<br /> experimental part of elastomeric materials have been studied on the basis of<br /> butadienakrilonitrilnog rubber (NBR) and chlorosulphonated polyethylene rubber (CSM). CSM NBR mixing and forming the network system, which are used as precursors for a<br /> network of nano-composite particles ojačanaih active fillers-carbon black and silicon (IV)<br /> oxide. With so obtained materials were investigated characteristics before and after<br /> irradiation with &gamma; rays. Dynamic-mechanical analysis confirmed the reinforcing effect of<br /> fillers.</p>

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