Fillers are often incorporated in polymer matrices in order to improve cost, mechanical, thermal, and transport properties. This work explores the hypothesis that pollen, a natural particle, has the potential to be an effective biorenewable reinforcing filler due to its unique surface architectures, high strength, chemical stability, and low density. Pollens from sources such as ragweed plants are ubiquitous natural materials that are based on sustainable, non-food resources. Pollen is a remarkable example of evolutionary-optimized microscale particle with structures and/or chemistries tailored for effective adhesion to a variety of surfaces and protection of genetic material under different dynamic and environmental conditions. The pollen shell is perhaps the most chemically resistant naturally occurring material. As many pollens achieve pollination simply by being carried by wind, they are very light-weight. These properties make pollen an attractive option as a natural filler for polymers. This research aims to characterize pollen interfacial properties and utilize pollen as an effective reinforcing filler in polymer materials. In this work, interfacial properties are characterized using Fourier transform infrared spectroscopy (FTIR), the BET method, and inverse liquid chromatography (ILC). These techniques were useful in determining the effect of surface treatments and further chemical modifications on pollen interfacial properties. Characterizing these properties allowed for improved understanding and utilization of pollen as a filler by revealing the enhanced surface interactions and surface properties of acid-base treated pollens when compared to as received untreated pollens. Epoxy and polyvinyl acetate (PVAc) matrices were used to demonstrate the effectiveness of pollen as a filler, as a function of pollen loading and surface treatments/chemical modifications. Scanning electron microscopy (SEM) was used to determine interfacial morphology, a high throughput mechanical characterization device (HTMECH) was used to determine mechanical properties, and differential scanning calorimetry (DSC) was used to determine glass transition behavior. In epoxy, pollen was an effective load bearing filler only after modifying its surface with acid-base hydrolysis. In PVAc, pollen was an effective load bearing filler only after an additional functionalization with a silane coupling agent. Finally, the species of pollen incorporated in PVAc matrices was varied in order determine the effect of the size of surface nano- and micro- structures on wetting, adhesion, and composite properties. Composites containing pollen displayed enhanced wetting and interfacial adhesion when compared to composites with smooth silica particles. Additionally, it was observed that pollen with smaller surface structures were wetted more effectively by the polymer matrix than pollen with larger structures. However, mechanical properties did not suggest significant changes in interfacial adherence with varied pollen microstructure size. The results of this work highlight the feasibility and potential of utilizing pollen as a natural filler for creating high strength, light-weight polymer composites with sustainable filler.

The use of desiccant materials is crucial in many applications, such as dehumidification rotors, in OLED screen and as desiccant materials in dish washers, for example. Upsalite® is a novel, anhydrous, micro-mesoporous, and large surface area structure consisting of amorphous magnesium carbonate which has been shown to exhibit a good water sorption capacity. Depending on the heat treatment of Upsalite® after synthesis, the material exhibits different sorption capacity and hydrolytic stability. Calcined Upsalite® has a higher sorption capacity compared to as-synthesized, but crystallizes into nesquehonite when stored in a relative humidity of 100 % for several days. The need to stabilize the material arises and the use of two different aminosilanes as surface stabilizers has been evaluated. Two different deposition techniques from gas phase have been used, atomic layer deposition and vapor phase grafting, which are evaluated and compared.   The results of the functionalization show an increase in decomposition temperature by ~25 °C of the functionalized materials compared to non-functionalized. The initial water sorption capacity of the functionalized material increases by up to 80 %, when stored in a relative humidity of 100 % for 24 h and shows a stabilizing effect after five cycles of repeated exposure to high humidity. The long term stability seems to have decreased due to pore collapse, when the functionalized material is cycled 5 times for one week in a repeated relative humidity of 100 %. The stability of the material when exposed to two liquids of different pH was also evaluated and the functionalized material exhibits a slower increase of the pH in the buffer solution, implying a retardation of Upsalite® dissolution. The conclusion is that a functionalization of the material with aminosilane increases the initial sorption capacity and has a stabilizing effect.

The exponential increase in the demands of world’s energy and the devastating effects of current fossil fuels based sources has forced us to reduce our dependence on the current sources as well as finding cleaner, cheaper and renewable alternates. Being abundant, efficient and renewable, hydrogen can be opted as the best possible replacement of the diminishing and harmful fossil fuels. But the transformation towards the hydrogen-based economy is hindered by the unavailability of suitable storage medium for hydrogen. First principles calculations based on density functional theory has been employed in this thesis to investigate the structures modelling and thermodynamics of various efficient materials capable of storing hydrogen under chemisorption and physisorption mechanisms. Thanks to their high storage capacity, abundance and low cost, metal hydride (MgH2) has been considered as promising choice for hydrogen storage. However, the biggest drawback is their strong binding with the absorbed hydrogen under chemisorption, which make them inappropriate for operation at ambient conditions. Different strategies have been applied to improve the thermodynamics including doping with light and transitions metals in different phases of MgH2 in bulk form.  Application of mechanical strain along with Al, Si and Ti doping on MgH2 (001) and (100) surfaces has also been found very useful in lowering the dehydrogenation energies that ultimately improve adsorption/desorption temperatures. Secondly, in this thesis, two-dimensional materials with high surface area have been studied for the adsorption of hydrogen in molecular form (H2) under physisorption. The main disadvantage of this kind of storage is that the adsorption of H2 with these nanostructures likes graphane, silicene, silicane, BN-sheets, BC3 sheets are low and demand operation at cryogenic conditions. To enhance the H2 binding and attain high storage capacity the above-mentioned nanostructures have been functionalized with light metals (alkali, alkaline) and polylithiated species  (OLi2, CLi3, CLi4). The stabilities of the designed functional materials for H2 storage have been verified by means of molecular dynamics simulations.

Membrane bioreactors (MBRs) show great promise for productivity improvement and energy conservation in conventional bioprocesses for wastewater reclamation. In order to attain high productivity in a bioprocess, it is crucial to retain the microorganisms in the bioreactors by preventing wash out. This enables recycling of the microorganisms, and is consequently saving energy. The main feature of MBRs is their permeable membranes, acting as a limitative interface between the medium and the microorganisms. Permeation of nutrients and metabolites through the membranes is thus dependent on the membrane characteristics, i.e. porosity, hydrophilicity,and polarity. The present thesis introduces membranes for MBRs to be used in a continuous feeding process, designed in the form of robust, durable, and semi-hydrophilic films that constitute an effective barrier for the microorganisms, while permitting passage of nutrients and metabolites. Polyamide 46 (polytetramethylene adipamide), a robust synthetic polymer, holds the desired capabilities, with the exception of porosity and hydrophilicity. In order to achieve adequate porosity and hydrophilicity, bulk functionalization of polyamide 46 with different reagents was performed. These procedures changed the configuration from dense planar to spherical, resulting in increased porosity. Hydroxyethylation of the changed membranes increased the surface tension from 11.2 to 44.6 mJ/m2. The enhanced hydrophilicity of PA 46 resulted in high productivity of biogas formation in a compact MBR, due to diminished biofouling. Copolymerization of hydrophilized polyamide 46 with hydroxymethyl 3,4-ethylenedioxythiophene revealed electroconductivity and hydrophilic properties, adequate for use in MBRs. To find either the maximal pH stability or the surface charge of the membranes having undergone carboxymethylation, polarity and the isoelectric point (pI) of the treated membranes were studied by means of a Zeta analyzer. The hydroxylated PA 46 was finally employed in a multilayer membrane bioreactor and compared with hydrophobic polyamide and PVDF membranes. The resulting biogas production showed that the hydroxylated PA 46 membrane was, after 18 days without regeneration, fully comparable with PVDF membranes.

No description available.

Au niveau académique et industriel, les nanocelluloses connaissent un engouement toujours grandissant. Ce projet de thèse explore la modification chimique des nanofibrilles de cellulose (CNF) pour des applications médicales. Des drogues et prodrogues de principes actifs (PA) ont été liées de manière covalente ou adsorbées sur des films ou des suspensions de CNF. Pour l’immobilisation covalente, une première stratégie d’estérification en milieu aqueux a été utilisée sur des films de CNF. Les propriétés antibactériennes contre des bactéries à gram positif et à gram négatif, ainsi que l’activité par contact prolongée de ces films, ont été démontrés. La seconde stratégie a porté sur la modification des suspensions de CNF au travers d’une procédure multi-étape (amidation puis chimie click), à nouveau en phase aqueuse. Des outils de caractérisation innovants comme la résonance magnétique nucléaire (RMN) dopée par polarisation dynamique nucléaire (PDN), ont permis de compléter les techniques classiques pour prouver le succès du greffage chimique. L’adsorption de PA sur les films et suspensions de CNF a été menée en parallèle de l’immobilisation covalente. Ensuite, les films de CNF avec des PA greffés ou adsorbés ont été utilisés pour développer des dispositifs médicaux pour application cutanée. Quant aux suspensions de CNF avec PA greffé ou adsorbé, elles ont été intégrées à des matrices de collagène pour créer de nouveaux prototypes de réparation pariétale. Leur activité antibactérienne et leurs propriétés de relargage contrôlé confirment l’intérêt de ces composites pour le design de dispositifs médicaux innovants.Mot-clés: nanocellulose, nanofibrilles de cellulose, fonctionnalisation, dispositif médical, activité antibactérienne, relargage contrôlé / In line with the ever-increasing academic and industrial interest for wood derived nanocellulose, the present work investigated the chemical surface modification of cellulose nanofibrils (CNFs) for biomedical application. Drugs and pro-drugs of active principle ingredients (APIs) were covalently immobilized or adsorbed onto CNFs films or suspensions. For covalent immobilization, the first strategy selected calls for water-based and single step esterification of CNF films. The resulting materials demonstrated antibacterial activity against both gram-positive and gram-negative bacterial strains, with a prolonged contact-active effect. In the second strategy, CNFs suspensions were modified through a multistep reaction, involving amidation and click chemistry, still water-based. Highly innovative characterization tools, such as dynamic nuclear polarization (DNP) enhanced nuclear magnetic resonance (NMR), complemented well-established techniques to confirm the success of grafting. In parallel to covalent immobilization, an adsorption strategy was also adopted, on both CNFs films and suspensions. Then, the CNF films with grafted or adsorbed APIs were used for preparing 100% CNF medical devices for topical applications. Another component of this work used CNF suspensions with grafted or adsorbed APIs were embedded in collagen matrices to prepare model medical device of soft tissue repair implants. Antibacterial activity against both aerobic and anaerobic bacteria, together with controlled release properties were assessed confirming that such composites present the expected active properties, and can be used for the design of innovative medical devices.Key words: nanocellulose, cellulose nanofibrils, functionalization, medical devices, antibacterial activity, drug release

Thesis advisor: Shih-Yuan Liu / Described herein are four projects focused on the elaboration of aromatic 1,2-azaborine core structures through late-stage functionalization strategies. In the first chapter, the gram scale, protecting group-free synthesis of the direct BN isostere of benzene is developed. This protocol is used to produce large quantities of pure 1,2-azaborine suitable for use in fundamental investigations. Second, the first general solution for the functionalization of the C4, C5, and C6 ring positions of 1,2-azaborines is described, featuring iridium catalyzed C-H borylation as the key strategy. Azaborine boronates produced via this method are successfully elaborated through cross coupling and oxidation to access azaborines that serve as N,N-ligands for electrophilic boron sources. The third project is an extension of the borylation/cross coupling project, and introduces the first polymer consisting of repeating azaborine units that displays highly efficient extension of conjugation along the azaborine chain. Finally, a copper catalyzed radical process is developed that enables removal of azaborine boron protecting groups during synthetic routes to simple azaborine targets of high interest. / Thesis (PhD) — Boston College, 2016. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

O presente trabalho é parte de um projeto maior que abrange pesquisadores de áreas complementares em química que visam a elaboração de estratégias sintéticas voltadas para a síntese de monômeros fenilacetilênicos derivados de aminoácidos ou calcogenetos onde, a partir desses, deverão ser construídos polímeros helicoidais de estruturas planejadas passíveis de funcionalização em nanopartículas de ouro e/ ou prata (NPsAu e NPsAg, respectivamente), que sejam capazes de modificar suas conformações frente a estímulos externos, formando assim, sensores poliméricos suportados em superfície de nanopartículas metálicas. A dissertação de mestrado que apresentaremos se dedica a um fragmento desse todo que trata especificadamente de estudos envolvendo a organofuncionalização de NPsAu e NPsAg com compostos orgânicos de selênio, bem como o desenvolvimento de metodologias na preparação de entidades monoméricas fenilacetilênicas derivadas de aminoácidos e organoselenetos. Por fim, alguns dos monômeros preparados serão polimerizados e devidamente caracterizados. Sendo assim, o trabalho foi dividido em duas partes, onde a primeira trata da preparação e funcionalização de organoselenetos em NPs e a segunda discorre sobre a síntese e polimerização dos monômeros. No que diz respeito à funcionalização de NPs com organoselenetos, foi preparada uma série de disselenetos derivados de aminoálcoois e aminoácidos. A proposta síntética na preparação desses compostos foi baseada na reação de substituição nucleofílica de segunda ordem de mesilatos ou haletos orgânicos por disselenolato de dilítio, o qual é gerado pela redução de selênio elementar por trietilboroidreto de lítio. Os organoselenetos foram funcionalizados em NPsAu e NPsAg pela simples mistura em etanol, cujos materiais híbridos resultantes dessa reação foram caracterizados por espetroscopia Raman. No capítulo que trata da síntese de monômeros, procedeu-se primeiramente a preparação de blocos construtores fundamentais contendo a porção fenilacetilênica e na sequência a homologação com aminoácidos protegidos ou selenetos orgânicos munidos de grupos alquílicos. Alguns dos monômeros preparados foram submetidos a reações de polimerização e co-polimerização gerando polímeros helicoidais com sentido helicoidal predominante, o que pôde ser confirmado por dicroísmo circular. Os objetivos do projeto foram alcançados com êxito e a maioria dos problemas em potencial puderam ser solucionados. O presente trabalho foi a primeira empreitada do projeto maior ao qual este está vinculado e proporcionará subsídios para os demais estudantes envolvidos alcançarem resultados em termos de aplicação. / The present work is part of a bigger project involving researchers of complementary areas in chemistry concerned on development of new synthetic strategies towards phenylacetylenic monomers bearing amino acid and/or organoselenide derivatives, that will be used to prepare helical polymers with planned structure capable to functionalize gold and silver nanoparticles (AuNPs and AgNPs, respectively) which could modify their conformations when submitted to external stimuli, acting as a polymeric sensor supported in the surface of the metal nanoparticles. This master\'s dissertation is devoted to a fragment of the whole work which involves studies regarding the AuNPs and AgNPs organofunctionalization with selenium organic compounds, as well as the development of new methodologies for the preparation of phenylacetylenic monomers synthesis bearing amino acid and selenide derivatives. Some of the prepared compounds have been polymerized and characterized. In this way, the work was divided in two chapters, whereas the first deals with organoselenium compound preparation and NP functionalization, and the synthesis and polymerization of the monomers. Regarding the NPs functionalization with organoselenides, a series of amino alcohol and amino acid diselenide derivatives was prepared. The synthetic approach was based upon the second order nucleofilic substitution of organic mesylates and halides by dilithium disselenolate, wich way was generated reducing elemental selenium with lithium tryethylborohydride. The NPs were functionalized with the diselenides after the mixture of both in ethanol, and the resulting hybrid materials were characterized by Raman spectroscopy. In the second chapter, we report on the fundamental building blocks preparation containing the phenylacetylenic group and its homologation with amino acids or organic selenides. Some of the final monomers were submitted to polymerization reactions, generating one hand preferred helical polymers, which was confirmed by circular dichroism. The main goal of the project were successfully reached and the potential problems could be solved. The present work was the first step of the major project in which it is tied and will give subsidy to other students involved to reach some results application.

O estudo de nanopartículas plasmônicas de ouro sob o ponto de vista conceitual foi o foco desta tese, explorando principalmente os efeitos do envoltório molecular e a intensificação dos espectros SERS tendo em vista aplicações em sensoriamento químico. Como moléculas sonda, foram selecionadas espécies multifuncionais, como a 2,4,6-trimercapto-1,3,5-triazina (TMT), 4,5-diamino-2,6- dimercaptopirimidina (DadMcP ou Dad) e a mercaptoetilpirazina (PZT), que apresentam grupos tióis capazes de ancorar nas nanopartículas de ouro, deixando outros sítios livres para interagir com substratos e complexos metálicos. Observou-se que o envoltório molecular formado no método de Turkevich, é bastante dependente das condições de síntese, tendo sido possível detectar a presença do intermediário da reação de oxidação do citrato na superfície das nanopartículas, sob condições controladas, influenciando drasticamente o comportamento SERS. Foi feito um estudo sistemático da molécula sonda 2,4,6-trimercapto-1,3,5-triazina ancorada nas nanopartículas de ouro, tanto por troca da camada passivante (citrato), como por síntese in situ com e sem agente redutor. Esses sistemas foram investigados, sob diferentes condições, como sensores SERS para metais. Esse estudo foi ampliado para a molécula sonda 4,5-diamino-2,6-dimercaptopirimidina (DadMcP), explorando a influência do tempo na coordenação dessa espécie na superfície e o efeito de diferentes eletrólitos nos processos de agregação. Finalmente, foram apresentadas fortes evidências da ocorrência de processos fotoinduzidos envolvendo as nanopartículas funcionalizadas, com destaque para a mercaptoetilpirazina (PZT), cujo comportamento mostrou-se bastante inusitado, gerando filmes fotoagregados sob influência da luz UV com possível aplicação em fotolitografia. / The study of plasmonic gold nanoparticles under the conceptual point of view was the focus of this thesis, exploring mainly, the effects of molecular shell and the intensification of SERS spectra aiming at applications in chemical sensing. For the probe molecules, multifunctional species were selected, such as a 2,4,6-trimercapto- 1,3,5-triazine (TMT), 4,5-diamine-2,6-dimercaptopyrimidine (DadMcP or Dad) and mercaptoethylpyrazine (PZT) which present thiol groups able to anchor onto gold nanoparticles, leaving available sites for further interaction with substrates and metal complexes. It was observed that the molecular shell in Turkevich\'s method is very dependent on the synthesis condition, being possible to detect the intermediate product of citrate oxidation reaction in the nanoparticle surface, under controlled conditions, dramatically influencing the SERS behavior. A systematic study was conduct with the probe molecule 2,4,6-trimercapto-1,3,5-triazine anchored to gold nanoparticles either by changing the passivating layer (citrate), or for in situ synthesis with and without a reducing agent. These systems were investigated under different conditions as SERS sensors for metals. This study was extended to the probe molecule 4,5-diamine-2,6-dimercaptopyrimidine, exploiting the influence of time in the coordination of such species and also the effect of different kinds of eletrolytes in the aggregation process. Finally, it has been presented strong evidences for the occurence of photoinduced processes involving functionalized nanoparticles with emphasis on mercaptoethylpyrazine, whose bahavior has proved to be very unusual, generating photoaggregated films under UV light influence, with possible applications in photolithography.

<p>The presence of <i>Escherichia coli</i> in water is an environmental indicator that the water is contaminated with faeces. Approximately, 30% of the world population drink water from sources contaminated with human faeces. Consequently, this percentage comprises of people that are highly vulnerable to <i>Escherichia coli</i> infection. While most strains of <i>Escherichia coli</i> are harmless or maintain a symbiotic relationship with humans, the pathogenic strains are responsible for injurious health effects, such as diarrhoea and kidney failure. The traditional method of detecting <i>Escherichia coli</i> takes about 24 – 48 hours, does not detect viable but non-culturable cells, and requires advanced equipment and great technical skills. Most other available detection techniques lack specificity, as observed with enzyme-based techniques, or are not very sensitive, as observed with most impedance-based techniques with clogged surfaces.</p> <p> </p> <p>As a result of the health effects due to this microorganism and the basic limitations of available detection techniques, there is need for a specific, sensitive and rapid detection technique to ensure a sustained and timely access to <i>E. coli</i>- free water. Therefore, the aim of this research work is to develop a detection technique devoid of the basic limitations of available methods. In this study, the antibody-antigen relationship was taken advantage of to ensure the specificity of the technique is guaranteed. This was achieved using <i>Escherichia coli</i> polyclonal antibodies that target the O and K antigens found in most pathogenic strains. These antibodies were functionalized on carboxyl group modified superparamagnetic fluorescent microparticles immobilized with streptavidin. The sensitivity of the technique was ensured by utilizing the low detection limit feature offered by the use of microfluidic devices. Two microfluidic devices, glass-based and PDMS-based, were fabricated with easily accessible materials. </p> <p> </p> <p>On introducing the sample reagents and test samples into the microfluidic devices, and passing an alternating current frequency through the system, the antibodies specifically isolated the target organisms from the pool of water contaminants and a drop in the device electric potential proportional to the bacteria concentration was observed. The success of this procedure depends on the identification of the alternating current frequency beyond which manipulation of the samples would not be easily carried out. As a result, the flow field analysis of the microparticles was carried out to study the particle behavior by varying the alternating current frequency from 15 kHz – 75 kHz. </p> <p> </p> <p>The optimum frequency observed was 35 kHz. Using the glass-based microfluidic device, the voltage drop observed for the serial dilutions, 10¹ to 10⁶ ranged from 200 mV to 420 mV while that for the serial dilutions, 10^-7 to 10^-1 ranged from 90 mV to 285 mV. To ascertain if a lower detection limit could be obtained, the PDMS-based microfluidic device, with a channel with of 300 µm, was used to analyze the response of the device to 10^-7 to 10^-1<b> </b>serial dilutions. The result ranged from 10 mV to 30 mV respectively. A comparative analysis with the conventional detection method showed that it was able to detect less than 300 <i>Escherichia coli</i> colony-forming units. This result indicates that an optimized PDMS-based microfluidic device with higher resolution microchannel could potential detect tens of bacteria colony-forming units. These results were obtained in about 60 secs of introducing the sample in the device.</p> <p> </p> <p>The rapidity and consistency of the results observed by the continuous increase in voltage drop with increasing concentrations of <i>Escherichia coli</i> indicate that this detection technique has great potential in addressing the time, specificity and sensitivity issues observed with most available detection methods.</p><br>