This thesis explores new and existing cellulose nanocrystal (CNC) production methods and evaluates their effects on CNC properties, with emphasis on their thermal performance. CNCs produced from industrial and lab-scale processes possess a wide range of surface chemistries, surface charge contents, as well as structural and morphological properties which affect their performance in CNC-based applications. Despite the broad range of available CNC properties, some challenges persist, particularly in the incorporation of CNCs into hydrophobic matrices, high brine liquid formulations, and high temperature applications. Herein, sulfated and carboxylated CNCs produced from large-scale processes were thoroughly characterized and key differences in their thermal performance and self-assembly and rheological behaviors were identified. Furthermore, an optimization study on phosphoric acid hydrolysis parameters and a novel surface modification method which deposits cellulose phosphate oligosaccharides onto CNC surfaces were proposed. The optimization study revealed that CNCs with high colloidal stability could not be produced with phosphoric acid alone; however, the weak acid hydrolysis allowed for precise control over CNC length. The deposition of oligosaccharides onto CNCs, however, resulted in highly colloidally stable CNCs possessing both phosphate and sulfate functional groups. Furthermore, this surface modification method altered CNC surface charge content, water interactions, and the viscosity of their aqueous suspensions. In these studies, however, changes in CNC thermal performance were difficult to elucidate. As such, to further understand the effects of CNC properties on both their dried and aqueous form thermal performance, a systematic comparison of sulfated, phosphated, and carboxylated CNCs was performed. CNCs were produced with new acid blend hydrolyses (i.e., combining sulfuric and phosphoric acid) as well as existing organic acid hydrolyses and oxidation routes. The combined effects of surface chemistry and counterion profoundly affected the thermal performance of dried CNCs, whereby sulfated and carboxylated CNCs were less thermally stable with proton and sodium counterions, respectively. Additionally, dried CNCs with more surface charge groups, shorter cellulose chains, and higher specific surface areas were found to be less resistant to high temperatures. As such, the new CNCs produced with acid blends exhibited superior thermal performance in their dried form due to their lower charge contents and longer cellulose chains. In their aqueous suspension form, carboxylated CNCs far outperformed both sulfated and phosphated CNCs at high temperatures; their suspensions remained colloidally stable at temperatures up to 150°C for extended time periods. Overall, this thesis equips CNC users and researchers with knowledge and tools to expand the usage of CNCs in commercial applications, particularly those which require high temperatures such as melt-processed polymer composites and oil and gas extraction fluids. / Thesis / Doctor of Philosophy (PhD) / This thesis contributes to a broader effort in replacing non-renewable and emissions intensive materials with sustainable alternatives such as nanocellulose. Nanocelluloses are nanometer-sized (where one nanometer is one billionth of a meter) cellulose particles manufactured from wood, cotton, or other natural resources. Nanocelluloses are made within Canada on a tonne-per-day scale; this value-added wood product presents an opportunity to refresh the Canadian forest industry. While nanocelluloses have many potential applications, their usage is somewhat limited by their inability to resist heat. This thesis examines changes in nanocellulose properties at high temperatures and evaluates how nanocellulose production methods affect their particle properties and thermal performance. New production methods are explored that increase nanocellulose resistance to heat, alter their dimensions, and change their interactions with water. Overall, this work aims to expand the usage of nanocellulose in commercial products such as coatings, plastics, industrial fluids, food products, and cosmetics (to name a few) by helping researchers select the right kind of nanocellulose for their intended applications.

<p dir="ltr">The frequency and intensity of wildfires occurring at the wildland-urban interface is increasing, and public drinking water systems operating in these communities are at risk. Widespread volatile organic compound (VOC) and semi-VOC (SVOC) contaminations have been detected in water distribution systems, often at concentrations above regulatory limits. Uncertainty about the source and fate of these contaminants has hindered recovery efforts. It is hypothesized that one source of the contaminants is the thermal degradation of plastic components within water distribution systems. Plastics are commonly used for water conveyance due to their low cost and ease of installation. However, plastics are vulnerable to thermal degradation, and have been shown to release VOC/SVOCs into the air when thermally degraded. Further, certain plastics such as polyethylene, are vulnerable to organic compound permeation, which could result in the contamination of otherwise undamaged components. This dissertation is comprised of four studies aimed at evaluating if plastic components within water distribution systems may be a source of contamination post-wildfire.</p><p dir="ltr">First, the aqueous leaching from commercial drinking water pipes was evaluated following thermal degradation in air. In this work, eleven plastic drinking water pipes were exposed to elevated temperatures (200°C to 400°C), and subsequently submerged in water or in <i>n</i>-hexane to observe the extent of VOC leaching. Results indicated that thermally damaged drinking water pipes can be sources of VOC leaching, with ten of the eleven materials leaching benzene, a carcinogen, into water. As exposure temperature increased, there was an increase in VOC leaching from the polyethylene plastics. Conversely, in the vinyl plastics the significant mass loss associated with high exposure temperature was inversely proportional to the amount of leaching that was observed.</p><p dir="ltr">The second study determined how the direct contact of water during plastic thermal degradation impacts the formation and aqueous leaching. Experiments were carried out using a continuously stirred tank reactor (CSTR) to expose plastics to a range of temperature (100°C to 300°C) in the presence of water. Five polyethylene materials were tested, including three cross-linked polyethylene (PEX) pipes, one high-density polyethylene pipe (HDPE), and one HDPE resin. Following degradation, clean water was pumped through the reactor to evaluate the efficacy of flushing to remove contaminants from thermally damaged plastics. Again, material type and exposure temperature impacted the leaching profile. Flushing removed contaminants from the thermally damaged plastics, however the removal rate varied based on chemical properties. Exhumed materials from wildfire impacted water systems were extracted in water to assess similarities and leached up to twelve different compounds, seven of which were also detected in laboratory experiments.</p><p dir="ltr">The third study investigated the impact of polyethylene formulation on aqueous leaching following thermal degradation to further understand the underlaying phenomenon causing the formation and leaching of contaminants. The impact of resin density, antioxidant type (Irganox 1010^® or Irgafos 168^®), antioxidant dose (0 to 10 wt. %), and impact of carbon black (0 or 2 wt. %) was investigated by compounding 12 different composites and thermally degrading them in the CSTR reactor described previously. Results found that all variables tested impacted the observed leaching. The addition of antioxidants decreased the observed leaching of polyethylene degradation products but increased the leaching of a variety of antioxidant degradation products. Carbon black was found to interact with the antioxidants during compounding, leading their consumption, and as a result decreased their effectiveness in protecting the polymer chain.</p><p dir="ltr">Lastly, the susceptibility of plastic water supply connectors such as ice-maker lines, faucet connectors, and washing machines hoses was assessed. The vulnerability of rigid plastic materials within water systems has been well studied, however, water supply connectors tend to be made of flexible plastics such as plasticized PVC and low-density polyethylene, and limited data exists on the susceptibility of these materials to contamination. In this study, seven connectors were exposed to hydrocarbon contaminated water, and subsequently decontaminated by water flushing. Following an initial 24 h contamination period, water samples were collected at three consecutive periods of 72 h. Results found that all materials sorbed more than 90% hydrocarbon contaminants. All materials released contaminants into the water during decontamination, at times above health-based limits. The majority of sorbed mass remained in the plastics at the end of the decontamination periods.</p>

Dimethacrylate monomers containing two cleavable tert-butyl ester groups were synthesized and utilized in the synthesis of star-shaped polymers. Star polymer coupling was achieved by reacting the living poly(alkyl methacrylate) using 2,5-dimethyl-2,5-hexanediol dimethacrylate (DHDMA) or dicumyl dimethacrylate (DCDMA). These starshaped polymers were cleaved under hydrolytic conditions, leading to significant reductions in molecular weights. The cleavable star-shaped polymers also underwent uncatalyzed degradation at elevated temperatures. Pressure-sensitive adhesive (PSA) copolymers based on 2-ethylhexyl acrylate (EHA) were synthesized containing cleavable branching comprised of either DHDMA or DCDMA. Extremely high molecular weight branched polymers were obtained, and these branched adhesives exhibited 180° peel strengths that displayed a strong dependence on the weight-average molecular weights. The PSA branching sites were cleaved via acid-catalyzed hydrolysis, drastically lowering the 1180° peel strengths of the cleaved linear polymers between 75 and 95 percent. Branched poly (EHA) PSAs containing 2-hydroxyethyl methacrylate (HEMA) and ethylene glycol dimethacrylate (EGDMA), as well as poly(EHA-co-HEMA), were synthesized and modified with photoactive functional groups. Cinnamate functionalized PSAs underwent photocrosslinking under UV light, leading to significant losses in 180° peel strengths. The acrylate functionalized PSAs were mixed with a photoinitiator, and following crosslinking under visible light, these PSAs exhibited excellent deactivation characteristics. Poly(methyl methacrylate) containing aliphatic diols were synthesized via anionic polymerization utilizing the novel protected functional co-initiator 1,1-bis-, 4'-(2-(tertbutyldimethylsilyloxy) ethoxy)phenylethylene (BTOPE). Following the coupling of BTOPE with sec-butyl lithium, methyl methacrylate was polymerized in living fashion at -78 °C in THF. A broad molecular weight range of BTOPE-initiated PMMA samples were synthesized, and molecular weight distributions were as low as 1.03 were observed. Hydrolytic deprotection of the protecting groups resulted in α,α-dihydroxy PMMA. The graft macromonomers poly(tert-butyl styrene-block-styrene) methacrylate and poly(styrene-block-tert-butyl styrene) methacrylate were synthesized from the corresponding diblock copolymer alcohols utilizing acid chloride chemistry. Excellent molecular weight control, narrow molecular weight distributions, and perfect crossover were observed in both types of diblock polymers. The macromonomers were copolymerized with methyl methacrylate via solution free-radical copolymerization. The styrene blocks in the purified graft copolymers were selectively sulfonated using acetyl sulfate. / Ph. D.

El propósito de la presente tesis doctoral es estudiar el efecto de la degradación térmica, biológica y fotolítica en la polilactida (PLA) para contribuir a la caracterización de este polímero biodegradable bajo diferentes condiciones o entornos. Este polímero procede de fuentes renovables y está considerado un excelente candidato para sustituir a otros materiales poliméricos con escasa degradabilidad. En este estudio se describen los mecanismos que regulan cada tipo de degradación y, lo que es más importante, cómo cada uno de ellos afecta a la variación de la masa molar del PLA. La monitorización del descenso de masa molar de polilactida se realizó tanto mediante Cromatografía de Permeación en Gel (GPC) como por Viscosimetría. Adicionalmente se utilizó la Espectroscopía Infrarroja con Transformada de Fourier (FTIR) para establecer los mecanismos que controlan la degradación y su efecto en la estructura química de la polilactida. Asimismo, se ha determinado el impacto de cada tipo de degradación en la morfología y en las propiedades térmicas y mecánicas del PLA. La Termogravimetría (TGA) permitió monitorizar los cambios en la estabilidad térmica del material debidos a los diferentes tipos degradación, ulilizando parámetros como la temperatura de máxima velocidad de degradación térmica o la energía de activación. El resultado de la bio y la foto degradación en la superficie del material fue evaluado mediante Microscopía Electrónica de Barrido (SEM), observándose únicamente cambios debidos a la degradación biológica. Las propiedades viscoelásticas y térmicas se analizaron mediante Análisis Dinámico-Mecánico-Térmico (DMTA), Calorimetría Diferencial de Barrido (DSC) y Microscopía Óptica (OM). Se ha obtenido que los parámetros más relevantes para discernir las diferencias entre los tres procesos de degradación son los relativos al fenómeno de cristalización. Los resultados muestran que cada degradación está controlada por un mecanismo que afecta de diferente forma a la / Santonja Blasco, L. (2012). Contribution to the study of thermal, biological and photo degradation of polylactide [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/16470

A combinação de excelentes propriedades mecânicas aliadas à biocompatibilidade torna a borracha natural um material amplamente empregado na fabricação de artefatos voltados à saúde, tais como bicos de chupetas e de mamadeiras, e luvas cirúrgicas e de procedimentos não-cirúrgicos. Esses artefatos são processados a partir de látices de poli(cis-isopreno) extraído de seringueiras. Entretanto, o grande número de insaturações presentes na cadeia polimérica, mesmo após a vulcanização, resulta em uma baixa resistência desse material ao envelhecimento, causado principalmente pela associação de fatores como temperatura, oxigênio, ozônio e radiação. Outro inconveniente associado à aplicação da borracha natural é a presença de proteínas no látex, com potencial alergênico, podendo promover reações fisiológicas em alguns usuários. Por esse motivo artefatos comerciais à base de material sintético também são encontrados no mercado. Esses artefatos também não são isentos dos processos naturais de desgaste e decomposição. Esta Dissertação teve como objetivo realizar um estudo comparativo de propriedades dos produtos comerciais à base de borracha natural e à base de material sintético (bicos de chupeta e de mamadeiras e luvas) de diferentes fabricantes, como adquiridos e após sofrerem envelhecimento acelerado. O estudo foi feito empregando-se as técnicas de espectroscopia na região do infravermelho com transformada de Fourier (FTIR) e termogravimetria (TG). Uma avaliação mecânica com métodos padronizados foi também realizada / By combining the excellent mechanical properties as well as biocompatibility, natural rubber is a suitable material to be applied in the manufacture of commercial articles as pacifiers, nursing bottles and gloves. Those products are processed from lattices of poly(cis-isoprene) extracted from rubber-trees. Nevertheless, the expressive amount of insaturations present along the polymeric chains, even after the vulcanization process, leads to degradation mainly caused by an association of factors as heat, oxygen, ozone and radiation. Another inconvenience in the application of natural rubber is the presence of some proteins in the latex, which causes allergic problems in a few usuaries. Thus synthetic materials are also employed in the production of such articles that are not free from degradation problems as well. The objective of this Dissertation was to carry out a comparative study of some properties of commercial products (nipples, of pacifiers and nursing bottles, and gloves) from different manufacturers. The materials were characterized, as received and after being submitted to accelerated degradation, by infrared spectroscopy (FTIR) and thermogravimetry (TG). Some mechanical properties were also evaluated by employing standard methods

<p>In this thesis, regioregularpoly( 3-hexylthiophene) (rr-P3HT) polymer was used as a light absorption and electron donating material, while the C60 fullerene and its derivative [6,6]-phenyl C61-butyric acid methyl ester (PCBM) were used as electron acceptor materials. The effect of solvent to control the degree of mixing of the polymer and fullerene components, as well as the domain size and charge transport properties of the blends were investigated in detail using P3HT:C60 films. The photo-physical, structural and electrical transport properties of the polymer blends were carried out according to their ratios. A distinctive photoluminescence (PL) quenching effect was observed indicating a photo-induced electron transfer. In this thesis, the effect of solvents on the crystallization and interchain interaction of P3HT and C60 fullerene films were studied using XRD, UV-vis, PL, Raman and FTIR spectroscopy. The polymer blends formed with non-aromatic solvents exhibited an improved crystallinity and polymer morphology than that formed with aromatic solvents. An improved ordering was demonstrated in the polymer films spin coated from non-aromatic solvents. This indicates that the limited solubility of rr P3HT in a marginal solvent such as non-aromatic solvents can offer a strategy to obtain highly ordered crystal structures and lead directly to optimal morphologies on the films.</p>

In this study, polymerization mechanisms of aromatic (C6H5 or C6F5) and alkyl (CH3, C2H5, C3H7, C6H13, C12H25 or C18H37) amine based naphthoxazine monomers (15-Na, 15Na-C1, 15Na-C2, 15Na-C3, 15Na-C6, 15Na-C12 and 15Na-C18) and thermal degradation mechanisms of polynaphthoxazines synthesized by curing the naphthoxazine monomers (P-15-Na, P-15NaF, P-15Na-C1, P-15Na-C2, P-15Na-C3, P-15Na-C6, P-15Na-C12 and P-15Na-C18) were studied by direct pyrolysis mass spectrometry. During the curing process, the evolutions of monomer and low mass aromatic or alkyl amines were detected below the curing temperature. The mass spectrometry findings indicated that the monomers were subjected to evaporation and degradation to a certain extent but also to polymerization during the curing process. It has been determined that the polymerization of aromatic amine based naphthoxazine monomer proceeded through the aniline units, either by coupling of the radicals produced by the ring opening of the side chains or by substitution to the benzene ring of aniline. However, even if no direct evidence to confirm polymerization by attack of &ndash / NCH2 groups to naphthalene ring was detected, it is not possible totally eliminate its existence. The evolution of aniline, the main thermal degradation product for this polymer was observed at relatively low temperatures indicating that thermal decomposition started by elimination of aromatic amine involving linkages. Coupling of &ndash / CH2 groups generated by loss of aniline, yielded naphthoxazines with unsaturated linkages that can recombine and form a crosslinked structure with higher thermal stability. Similarly, the polymerization of naphthoxazines based on alkyl amines followed opposing paths. The mass spectral data indicated that the coupling of alkyl amine radicals was the main polymerization pathway. Again, thermal decomposition of alkyl amine based naphthoxazines was started by loss of alkyl amines and diamines. The crosslinked structures produced by coupling of the radicals generated by lose of alkyl amines decomposed at relatively high temperatures.

The total amount of plastic wastes produced by our society has been growing rapidly. The low biodegradability of these wastes creates a serious environmental problem that is directing the governments and environmental agencies to take serious measures to solve the problem of the plastic wastes. Landfilling or incineration of these wastes are not the right solutions, because the former has the danger of leaching and soil impregnation of its degradation products and the latter produce air pollution problems due to the possible emissions of toxic and acid gases. An alternative approach to the solution of problem caused by these wastes is the recycling of them by chemical recovery. In this method, the waste plastics are thermally non-catalytically or catalytically degraded into gases and oils. In this study, pure and aluminum containing ordered mesoporous materials MCM-type and SBA-type, were synthesized using different aluminum sources and aluminum loadings in order to be tested in catalytic degradation of polypropylene. These catalysts, except aluminum containing SBA-type catalysts, were synthesized by hydrothermal synthesis method. Aluminum containing SBA-type catalysts were synthesized by impregnation method. Tetraethyl orthosilicate was used as the Si source and aluminum nitrate, aluminum sulphate and aluminum isopropoxide were used as the Al source. It was observed that these materials had high surface areas and exhibited Type IV isotherms. In MCM-type materials, the aluminum incorporated more effectively into the structure at low concentrations but not effectively at high concentrations. On the other hand, in SBA-type catalysts, the aluminum incorporation into structure was very effective. 27Al MAS NMR spectra of the catalysts exhibited a mixture of tetrahedral and octahedral aluminum. TEM images showed well-ordered hexagonal arrays of mesopores. As an initial step, the activation energy value of polypropylene pyrolysis reaction in the presence of synthesized catalysts was determined by the help of a thermal analyzer and these TGA results showed a marked reduction in the degradation temperature. In the case of using aluminum containing MCM-type materials, the activation energy values decreased to about 68-126 kJ/mol. On the other hand, when aluminum containing SBA-type catalysts were used, the activation energy values decreased from 172 kJ/mol to a value in the range of 51 &ndash / 89 kJ/mol. Heavier molecules degraded into lighter hydrocarbons in the presence of catalysts and they gave high ethylene selectivity among the gaseous products. Additionally, butane selectivity increased with the use of catalysts. SBA-type catalysts showed higher selectivity to lighter hydrocarbons (&lt / C14). C7 selectivity among the liquid products was high when aluminum isopropoxide was used in the synthesis of catalysts and C18 selectivity increased significantly when aluminum nitrate was used in the synthesis of MCM-type catalysts.

<p>In this thesis, regioregularpoly( 3-hexylthiophene) (rr-P3HT) polymer was used as a light absorption and electron donating material, while the C60 fullerene and its derivative [6,6]-phenyl C61-butyric acid methyl ester (PCBM) were used as electron acceptor materials. The effect of solvent to control the degree of mixing of the polymer and fullerene components, as well as the domain size and charge transport properties of the blends were investigated in detail using P3HT:C60 films. The photo-physical, structural and electrical transport properties of the polymer blends were carried out according to their ratios. A distinctive photoluminescence (PL) quenching effect was observed indicating a photo-induced electron transfer. In this thesis, the effect of solvents on the crystallization and interchain interaction of P3HT and C60 fullerene films were studied using XRD, UV-vis, PL, Raman and FTIR spectroscopy. The polymer blends formed with non-aromatic solvents exhibited an improved crystallinity and polymer morphology than that formed with aromatic solvents. An improved ordering was demonstrated in the polymer films spin coated from non-aromatic solvents. This indicates that the limited solubility of rr P3HT in a marginal solvent such as non-aromatic solvents can offer a strategy to obtain highly ordered crystal structures and lead directly to optimal morphologies on the films.</p>

Since the achievement of the first results from the Cassini Huygens mission, Titan's aerosols present an astrobiological interest as their characterization enables to evaluate the prebiotic chemistry that occurred on the primitive Earth. To better understand the physical chemistry of the aerosols of Titan is important for scientists. The laboratory via analyzing the properties of tholins (analogues of Titan's aerosols) overcomes the difficulties for analyzing Titan's aerosols directly. In this thesis work, the research object is tholins produced by the PAMPRE experiment. Pyr-GC-MS analysis technique was used to characterize the composition and structure of tholins. The thermal stability and the properties change with the temperature have been realized by thermal degradation study. Finally, the evolution of organic aerosols after precipitation on the surface of Titan was also investigated through GC-MS analysis of tholins. The results obtained can be used to interpret data collected by observations of Titan from Earth or by the Cassini-Huygens probe, to better characterize the satellite and its evolution.