Rozprawy doktorskie na temat „Molecular weight distribution”

To fully understand the properties of Long Chain Branched Metallocene Polyethylene (LCB mPE), we need to understand its molecular structure and Molecular Weight Distribution (MWD). Gel Permeation Chromatography (GPC) is the most important and widely applied technique to measure the MWD. In this analytical technique, polymer molecules are fractionated by their hydrodynamic volume (i.e. the sizes of polymer molecules in dilute solution). This work is focused on the simulation of GPC for the MWD of LCB mPE.<br>The polymerization reaction mechanism of LCB mPE provides a method to simulate the generation of LCB mPE molecules thus allowing the development of a statistical model of the structure and molecular weight distribution of LCB mPE by previous researchers. This statistical model gives a theoretical MWD. In this work after simulating the generation of one million LCB mPE molecules, we calculate the sizes (i.e. radii of gyration) of molecules at both theta and good solvent conditions to obtain the molecular size distributions. Then we simulate the fractionation in GPC and the different GPC detector responses to obtain simulated GPC MWDs. The simulated MWDs are compared to real GPC results provided by the Dow Chemical Company. We analyze the performance of GPC for long chain branched polyethylene and relate the results to the theoretical MWD.

An important characteristic of a polymer is its molecular weight distribution (MWD). The MWD affects both the processing and solid state performance properties of polymeric materials. Currently the analytical method for evaluating MWD involves the use of gel permeation chromatography (GPC). This is a labor and time intensive procedure, with the accuracy of the results depending strongly on the skill and experience of the equipment operator. Furthermore, GPC is not sensitive to small amounts of high molecular weight material that can have an important effect on processing and product properties. Thus GPC is far from ideal as a tool for industrial quality control. It is known that the rheological properties depend on the MWD, and it has been proposed that complex viscosity data be used to infer the MWD for commercial polymers. There has been some degree of controversy as to whether this is feasible, but recent results of Shaw, Tuminello and their coworkers indicate that for linear polymers this is, in theory, possible. However limitations in the accessible range of frequency, as well as inevitable experimental errors pose serious barriers to the use of such a procedure. We have investigated the severity of these baniers and have shown that within certain, reasonable constraints complex viscosity data can be used to infer a realistic MWD and that this procedure could be used for routine quality control in a production facility.

This thesis concerns the investigation of polymer pyrolysis by a combined approach of ' . , mathematical modelling and experimentation. This 'is done as a contribution towards better understanding how' materials behave in fire' situations. Thermogravimetric analysis has been investigated with regard to the accurate determination of kinetic parameters from thermogravimetric traces. This investigation has focused on various numerical methods that can determine the kinetic parameters from the curves and on correcting the buoyancy effect of the gas flowing through the analyser~ These mathematical techniques have then been applied to the thermogravimetric analysis of real plastics. The plastics investigated are; polystyrene, polymethyl methacrylate, polyvinyl chloride and flame retarded high impact polystyrene. Variations in kinetic parameters with heating rate are investigated in order to determine the ooent to which thermogravimetric analysis can shed light on fundamental chemical processes' occurring during pyrolysis. It is found that thermogravimetric analysis by itself is not realistically capable of shedding much' light on the chemistry occurring dl:lring pyrolysis. An alternative approach. that is subsequently considered is' to investigate polymer decomposition through variations in molecular weight distribution. This has allowed the description of polymer decomposition to be undertaken in terms of scission processes. In the cases of polystyrene and polymethyl methacrylate, it has been found (in agreement with the general literature) that the variations of molecular weight distribution are reminiscent of end-chain scission processes with small contributions of random scission. That said, it is also clear that there are features in both materials' decomposition profiles that requires further modelling. In the case of multi-component mixtures such as the flame retardant HIPS this modelling approach is unable to cope with the experimental observation in its current form.

Commercial polymers are typically classified according to their melt flow indices, measures of their viscosities. These properties are known to depend on a material’s molar mass distribution, on its averages and its degree of polydispersity. In determining a polymer’s performance, both the molar mass distribution and the process employed to produce the part are highly relevant, since the balance in the mass fractions from its distribution will determine the flow characteristics in the mould, and influence the material’s performance. The compromise polymer manufacturers have to make is to maintain the mechanical properties known to improve with increased molar mass at the same time as a sufficiently low viscosity, known to reduce with decreasing molar mass, to enable part production. This is often achieved by judicious blending of homopolymers. This thesis examines how varying molar mass and distribution in blends leads to changes in the thermal, rheological, and mechanical properties in polystyrene, and discusses and develops physical models to capturing the observed experimental responses. Chromatographic and calorimetric studies were carried out on monodisperse, bimodal blends of monodisperse, polydisperse, and blends of polydisperse polystyrenes. They revealed that changes in molar mass distributions and glass transition temperatures, Tg, could be directly attributed to the blending procedure of choice. In polydisperse blends, higher contents of low molar mass fractions, and corresponding lower Tgs were observed in the blends produced using a melt mixing method compared with solution-blended equivalents. Thermal degradation, accelerated by the large number of chain ends, was suggested as the cause for the increase in low molar mass fractions in the melt-mixed blends. The filtration and precipitation stages characteristic of solution blending instead promoted oligomer loss and evaporation, resulting in reductions in the low molar mass tails of the distributions. Craze initiation stress was measured in 3-point bending isochronal creep tests on the same polymers and blends, and was found to in-crease rapidly with additions of a higher molar mass component, reaching a plateau at 20 wt%. A simple model based on a weighted addition of the crazing stress contributions of individual weight fractions was developed from an established piecewise linear crazing law in order to enable predictions of the crazing stress in the blends, using a power law exponent of 2.59 (90% CI [1.75 17.34]). In highly poly-disperse systems, where short unentangled chains dilute the polymer, it was necessary to include dynamic tube dilution theory. Dilution leads to a change in the entanglement length and hence in the molar mass at which transitions in the crazing mechanisms (disentanglement and chain scission) occur. With the improved model, crazing stress could be predicted even for highly polydisperse blends with wide and bimodal distributions. Linear and non-linear rheological measurements were carried out in shear and extensions on the same materials. Existing rheological models for linear viscoelasticity including Likhtman-McLeish (L-M), Rubinstein-Colby (R-C) and polydisperse double reptation (pDR) theory were applied to the linear experimental data, exposing some of the fundamental difficulties of modelling the structure of systems where multiple chain-lengths interact. R-C was found applicable to bi-modal blends of monodisperse, whereas pDR was better able to model broad polydisperse blends. New non-linear shear and extensional rheology was recorded experimentally on all polymers and blends, and should enable future non-linear theories to be compared to experiment.

Thesis (Ph.D.)--University of Florida, 2004.<br>Typescript. Title from title page of source document. Document formatted into pages; contains 139 pages. Includes Vita. Includes bibliographical references.

The effect of the molecular weight distribution of both the soluble and the insoluble blocks on the solution self-assembly of the amphiphilic block copolymer polystyrene-block-poly(acrylic acid) was studied. Copolymers of a variety of block lengths but with narrow molecular weight distributions were synthesized by sequential anionic synthesis. Mixing two or more copolymers of differing block length (while the second block length was identical) artificially increased the polydispersity index (PDI) of one block. Self-assembly was induced by adding water slowly to a copolymer solution until a desired solvent composition was attained. The resulting aggregates were compared using transmission electron microscopy and dynamic light scattering.<br>The first experiments, presented in chapter 2, studied the effect of the corona (PAA) polydispersity on the size of vesicular aggregates. For a constant solvent composition and copolymer concentration, the size of the vesicles was generally found to decrease with increasing PAA polydispersity. In chapter 3, a partial phase diagram of morphology as a function of water content and PAA polydispersity is presented. The phase boundaries between spheres and rods, and rods and vesicles were found to shift to lower water contents with increased PAA polydispersity.<br>While chapters 2 and 3 show that the PAA polydispersity affects both the morphology and the size of vesicles, chapter 4 presents work that indicates that the shape of the PAA molecular weight distribution plays an important part in determining the degree to which the PAA polydispersity affects the morphology. A subsequent study also shows that the molecular weight distribution effect only occurs when the relative PAA/PS block length ratio is low.<br>The polystyrene molecular weight distribution studies, presented in chapter 5, show that the opposite effect to that of the PAA molecular weight distribution occurs with an increase in the PS PDI. The morphological boundary from spheres to rods was found to move to higher water contents with an increase in PS PDI. Even at very high water contents, where vesicles are usually found for low molecular weight distribution samples, only spherical micelles were found for the samples with increased PS PDI.

Thesis (Ph. D.)--Earth and Atmospheric Sciences, Georgia Institute of Technology, 2006.<br>Michael Bergin, Committee Member ; E. Michael Perdue, Committee Chair ; Ching-Hua Huang, Committee Member ; Ellery Ingall, Committee Member ; Martial Taillefert, Committee Member. Vita. Includes bibliographical references.

There are two main goals of this thesis: to investigate the flow-induced crystallization behaviour of Polybutene-1 (PB-1 samples, and to study the effects of molecular parameters on the crystallization behaviour While flow-induced crystallization is not a new area in polymer research, well-defined experimental methods that allow access to high flow rate range comparable to that encountered in real processing are still lacking. Two types of flow are considered: shear and uniaxial elongational. Regarding the second aim, several molecular parameters considered are: molecular weight, molecular weight distribution, isotacticity, presence of nucleating agents, and copolymer content. For this purpose an array of PB-1 samples were used. It is found that each of these parameters can have significant effect on the crystallization behaviour. Mainly rheological methods were utilized to conduct the flow-induced crystallization experiments. Crystallization onset time is define d from the change in viscosity or other related parameters. The experiments begin with low shear rate range, to ensure that the results are comparable with literature data. In this range we encounter the quasi-quiescent onset time at very small. shear rates, which draws an interesting comparison with another physical parameter, the gel time. Beyond a critical flow rate a decrease in the onset time is seen, and a plateau-and-slope trend is evident for a curve of onset time vs. shear rate. Using a combination of three experimental methods, shear rates ranging from Q0001 - 500 s-1 are successfully achieved, and a good agreement between these methods is observed. Furthermore, a normalization procedure is introduced, which yields temperature-invariant curves for the mentioned range of shear rate. For the uniaxial elongation flow, the Elongational Viscosity Fixture (EVF) is employed, with the strain rate ranging from 0.0001 - 10 s'. A greater reduction in onset time as compared to shear (at the same shear/strain r ate) is observed, and the difference in the onset times for shear and elongation already reaches more than one decade for a flow rate of 10 5. This quantitative comparison is particularly important; since not so many data on elongation-induced crystallization are available in the literature. Finally, the thesis compares several flow induced crystallization models that can be useful as prediction tools and selects one of these models to be compared with the experimental data. A qualitative agreement is found, however, for better quantitative prediction the model still needs to be.

In the recent past it has been found that a considerable pressure drop occurred during the extrusion of linear polyethylene in the course of capillary flow. The pressure drop resides within a narrow temperature window of one to two degrees Celsius. In this research the hydrodynamic condition and molecular origin of the extrusion window of linear polymer were investigated further. The advantage of the extrusion window, viz. smooth extrudate with less die swell ratio attained at low extrusion pressure and temperature, has potential in industrial applications. However, the extrusion window, corresponding to linear polyethylene (PE) with relatively low polydispersity (<7), has a narrow window temperature interval, circa 1~2°C, thus it could not be applied to industrial scale processing at the industrial scale. To have a fundamental insight and make the process industrially viable, research in this thesis was devoted to broaden the extrusion window to tolerate the thermal fluctuations in conventional processing. To achieve this goal molecular weight dependence of window temperature and flow criticalities is revealed. The hydrodynamic conditions of the extrusion window observed in a rate-controlled rheometer and stick-slip flow studied in a stress-controlled rheometer could be traced back to the same origin, viz. slip flow arises due to the disentanglement of adsorbed chains on capillary wall from free chains in the bulk. Secondly, a dual window effect was uncovered in the course of capillary flow of a bimodal PE, which is consistent with the window temperature dependence on molecular weight. Moreover, it was found that flow induced orientation within the window effect is even less than that observed in steady state flow at a relatively low shear rate. This implies that in the window region only relaxed free chains are extruded through the capillary die and most of the adsorbed chains, which could be disengaged from the entangled melt, remain sticking to the inner capillary wall. This observation is consistent with the hydrodynamic origin of high-surface-energy-die slip flow. Finally, a unimodal linear PE with extremely broad molecular weight distribution, i.e. polydispersity (PDI) is 27, showed a broad window effect, circa 8°C, at an appropriate apparent shear rate. The molecular origin of such a broad window effect is due to its broad molecular weight distribution. These results have further implications for energy efficient processing.

A distribuição de massa molar (DMM) e seus parâmetros são de fundamental importância na caracterização dos polímeros. Por este motivo, o desenvolvimento de técnicas que permitam a determinação da DMM de forma mais rápida e a menor custo é de grande importância prática. Os principais objetivos deste trabalho foram a implementação de alguns dos modelos baseados da teoria da reptação dupla propostos na literatura para descrever o mecanismo de relaxação das cadeias poliméricas, a avaliação dessas implementações e a análise de dois passos fundamentais na obtenção da DMM a partir de dados reológicos que são a metodologia de cálculo do espectro de relaxação baseado no modelo de Maxwell e a estratégia para a avaliação numérica das integrais que aparecem nos modelos de relaxação. Foi resolvido o problema denominado problema inverso, ou seja, a determinação da DMM a partir de dados reológicos usando um modelo de relaxação especificado e uma função de distribuição imposta. Foi usada a função Exponencial Generalizada (GEX) para representar a probabilidade de distribuição, sendo consideradas duas abordagens: i) cálculo explícito do espectro de relaxação e ii) aproximações paramétricas de Schwarzl, que evitam a necessidade do cálculo explícito do espectro de relaxação. A metodologia de determinação da DMM foi aplicada para amostras de polietileno e foram estimadas distribuições com boa representação dos dados experimentais do GPC, ao considerarem-se amostras com polidispersões inferiores a 10. Com relação a metodologia de cálculo do espectro de relaxação, foi realizado um estudo comparativo da aplicação de espectros de relaxação discreto e contínuo, com o objetivo de estabelecer critérios para especificação do número ótimo de modos de Maxwell a serem considerados. Ao efetuar-se a comparação entre as técnicas, verificou-se o espectro discreto apresenta como um sistema melhor condicionado, permitindo assim obter maior confiabilidade dos parâmetros estimados. Também é proposta uma modificação da metodologia de determinação da DMM, em que é aplicada a quadratura de Gauss-Hermite para a resolução numérica da integral dos modelos de relaxação.<br>The molecular weight distribution (MWD) and its parameters are of the fundamental importance in the characterization of polymers. Therefore, the development of techniques for faster and less time consuming determination of the MWD is of great practical relevance. The goals of this work were the implementation of some of the relaxation models from double reptation theory proposed in the literature, the evaluation of these implementations and the analysis of two key points in the recovery of the MWD from rheological data which are the methodology for calculation of the relaxation spectrum based on the Maxwell model and the numeric strategy for the evaluation of the integrals appearing in the relaxation models. The inverse problem, i.e., the determination of the MWD from rheological data using a specified relaxation model and an imposed distribution function, was solved. In the analysis of the inverse problem, the Generalized Exponential (GEX) was used as distribution function and two approaches were considered: i) explicit calculation of the relaxation spectrum and ii) use of the parametric method proposed by Schwarzl to avoid the explicit calculation of the relaxation spectrum. In the test of commercial samples of polyethylene with polidispersity less than 10, the application of this methodology led to MWD curves which provided good fit of the experimental SEC data. Regarding the methodology for calculation of the relaxation spectrum, a comparison between the performance of discrete and continuous relaxation spectrum was performed and some possible a criteria to determine the appropriate number of relaxation modes of Maxwell to be used were evaluated. It was found that the technique of discrete spectrum leads to better conditioned systems and, consequently, greater reliability of the estimated parameters. With relation to the numeric strategy for the evaluation of the integrals appearing in the relaxation models, the use of Gauss-Hermite quadrature using a new change of variables was proposed.

Kyoto University (京都大学)<br>0048<br>新制・課程博士<br>博士(農学)<br>甲第20449号<br>農博第2234号<br>新制||農||1050(附属図書館)<br>学位論文||H29||N5070(農学部図書室)<br>京都大学大学院農学研究科森林科学専攻<br>(主査)教授 矢野 浩之, 教授 木村 恒久, 教授 髙野 俊幸<br>学位規則第4条第1項該当

O impacto da oxidação com ozônio na transformação de compostos orgânicos de elevada massa molar (HMW) para o aumento da biodegradabilidade dos efluentes da indústria de celulose e papel foi investigado sob diferentes doses de ozônio. Os experimentos foram realizados utilizando-se os efluentes primário e de extração alcalina de duas indústrias de celulose sob dois valores iniciais de pH (12 e 7). Utilizou-se um reator em escala de laboratório equipado com um difusor de bolhas finas para a aplicação do ozônio. Os resultados revelaram o potencial da aplicação de ozônio como uma etapa de tratamento anterior ao processo biológico convencional. Para o efluente primário, a aplicação de 0,70 mg\'O IND.3\'/mL efluente elevou a razão DBO5/DQO de 0,18 para 0,35 e foi alcançada uma remoção de cor na ordem de 87%. Para o efluente de extração alcalina da indústria Howe Sound, a razão DBO5/DQO foi elevada de 0,07 para 0,15 (pH inicial 12) e para 0,20 (pH inicial 7) e obteve-se uma remoção de cor por volta de 44% com a aplicação de 0,80 mg\'O IND.3\'/mL efluente. Para o efluente de extração alcalina da indústria Catalyst Paper, obteve-se uma remoção de cor por volta de 78% e a razão DBO5/DQO foi elevada de 0,07 para 0,16 após a aplicação de uma dose de ozônio de 0,80 mg\'O IND.3\'/mL efluente. Essas modificações foram alcançadas por uma redução nas frações de elevada massa molar durante a aplicação de ozônio. Para o efluente primário, observou-se uma elevada redução da faixa de maior massa molecular ( > 2kDa) após a aplicação de 0,72 mg\'O IND.3\'/mL efluente. Alcançaram-se 85% e 61% de remoção da faixa superior a 5 kDa para os efluentes de extração alcalina da indústria Howe Sound sob pH inicial 7 e 12, respectivamente, com a aplicação de cerca de 0,72 mg\'O IND.3\'/mL efluente. A faixa de maior massa molar ( > 10 kDa) dos efluentes de extração alcalina da indústria Catalyst Paper foi removida com a aplicação de aproximadamente 0,80 mg \'O IND.3\'/mL efluente. O papel do ozônio molecular disponível sob pH neutro parece ser de fundamental importância quando o objetivo é a redução dos compostos de elevada massa molecular.<br>The impact of ozone oxidation in transforming high molecular weight (HMW) organic compounds in order to improve the biodegradability of pulp and paper effluents was investigated under different ozone doses. The experiments were conducted uppon a primary treated effluent and an alkaline bleach plant effluent taken from two pulp mills. The effluents were investigated under different initial pH (7 and 12). Ozone was applied using a semi-batch reactor equipped with fine bubble diffuser. The results showed the potential for using ozone as a pre-treatment to the conventional biological process. Applying 0.70 mg\'O IND.3\'/mLww to the primary treated effluent enhanced the ratio of BOD5/COD was from 0.18 to 0.35 and decreased the colour by 87%. The ratio of BOD5/COD was increased from 0.07 to 0.15 (initial pH 12) and to 0.20 (initial pH 7) and colour was reduced by 44% after applying 0.80 mg\'O IND.3\'/mLww to the alkaline bleach effluent from Howe Sound\'s mill. A similar behavior was observed after 0.80 mg\'O IND.3\'/mLww was applied to the alkaline bleach effluent from Catalyst\'s mill. The ratio of BOD5/COD was increased from 0.07 to 0.16 and the effluent colour decreased by 78%. These changes were primarily driven by reductions of the HMW fractions of the effluent during ozonation. Organics with molecular range higher than 2 kDa were completely removed from the primary treated effluent. Aproximately 85% and 61% of the organics higher than 5 kDa were removed from the Howe Sound\'s alkaline bleach effluent under initial pH 7 and 12, respectively, after applying 0.72 mg\'O IND.3\'/mLww. Organic compounds with molecular weight higher than 10 kDa were completely removed from the Catalyst\'s alkaline bleach effluent after applying 0.80 mg\'O IND.3\'/mLww. Molecular ozone available under neutral conditions seems to play an important role when the removal of the high molecular weight organic compounds is the main objective.

Les propriétés hydrophobes des polymères extracellulaires (PEC) exercent l’influence profonde sur les propriétés de la surface cellulaire. Cependant, de nombreux facteurs tels que les méthodes d'extractions, le type de substrat influencent les caractéristiques des PEC et les informations concernant des caractéristiques hydrophobes sont rarement documentées. L'objectif principal de cette étude est de développer une méthode appropriée pour étudier l'hydrophobicité des PEC, puis d'étudier les caractéristiques hydrophobes des PEC.Le fractionnement hydrphobe par la résine Supelite™ DAX-8 a d'abord été appliqué sur les PEC extraits de boues granulaires anaérobies, deux conditions de pH d'élution (pH 2 et 5) ont été testées. L'impact de sept méthodes d'extraction sur les caractéristiques hydrophobes des PEC a été évalué. Les résultats ont montré que les méthodes d'extraction et le pH de la solution extraitante ont influencé la composition des PEC et leur hydrophobicité. En outre, les extraitants des PEC, par exempe le formaldéhyde, l'éthanol, le dodécylsulfate de sodium (SDS) et Tween 20, ont non seulement introduit une teneur supplémentaire en carbone pendant la mesure du carbone organique total (COT), mais ils ont également interagit avec la résine DAX-8. En comparant la répartition du poids moléculaire apparent (aMW) des échantillons des PEC non traités et ajustés au pH détectés par chromatographie d'exclusion stérique (en anglais SEC), l’information plus complète d’aMW a été préservée à pH 5. Ainsi, le fractionnement hydrophobe par la résine DAX-8 à pH 5 et les méthodes physiques d'extraction PEC ont été préférés dans cette étude.Une analyse qualitative détaillée des caractéristiques hydrophobes des EPS a été étudiée par la technique de la matrice de fluorescence d’excitation-emission (EEM). Les résultats ont montré que les substances de type humique (HS-like) représentaient la majorité des composés organiques des PEC extraits de la boue granulaire anaérobie, et constituaient également le principal support moléculaire de l'hydrophobicité des extraits. Ces composés hydrophobes de type HS étaient essenciellement des molécules petites tailles de 8 kDa à &lt;1 kDa. L’hydrophobité contributée par les protéines (PN) et les polysaccharides (PS) présentait un moindre rapport.Afin d’explorer les propriétés hydrophobes de PN et de PS, ainsi évaluer l'impact de l'addition de Ni(II) sur l'hydrophobicité des extraits des champignons, fongi Phanerochaete chrysosporium a été choisi. Les résultats ont montré que la teneur de PN et de PS dans les PEC extrait de ce type de fongi variait en fonction de la concentration de Ni(II). Avec une augmentation de la concentration de Ni de 0 mg/L à 25 mg/L, la teneur en PN a diminué alors que celle de PS a été augmentée. L'hydrophobicité des PEC du fongi, déterminée par le traitement de la résine DAX-8, a diminué lors que la concentration de Ni augmentait. Par ailleurs, l'intensité du pic de SEC correspondant aux molécules PN-like (Ex/Em = 225/345 nm) de 1,9 × 103 à 10 kDa a été augmentée par l'addition Ni; en même temps, la distribution d’aMW des composés organiques totaux (UV/210) dans les PEC restait presque stable. Ces résultats ont indiqué que les composés de type PN-like peuvent avoir déterminé l'hydrophobicité des PEC fongique dans des conditions de stress.Dans l’extrait plus hétérogène des PEC de boues granulaires anaérobies, des composés HS-like représentaient le composant organique majeur, ainsi le principal support moléculaire de l'hydrophobicité des PEC. En étudiant les caractéristiques hydrophobes des PEC extrait du champignon Phanerochaete chrysosporium, le PN et le PS des PEC jouaient un rôle actif dans la protection du champignon sous le Ni. La concentration élevée de Ni a diminué l'hydrophobicité des PEC fongique, mais elle a augmenté l'hydrophobicité de la surface cellulaire du champignon. Il semble que la présence de Ni favorise l'apparition d'un champignon plus hydrophobe<br>The hydrophobic properties of extracellular polymeric substances (EPS) exert a profound influence on the cell surface properties. However, many factors such as EPS extractions methods, substrate type influence EPS characteristics, and limited information regarding to the hydrophobic features of EPS can be found. The main aim of this study is to develop a proper method to study EPS hydrophobicity, and then investigate the hydrophobic features of EPS.The hydrophobic fractionation by Supelite™ DAX-8 resin was first applied on the EPS extracted from anaerobic granular sludge, two elution pH conditions i.e. pH 2 and 5 were tested. The impact of seven EPS extraction methods on the hydrophobic features of EPS was assessed. The results showed that the extraction methods and bulk solution pH dramatically influenced the EPS composition and their hydrophobicity. Besides, the EPS extracting reagents namely formaldehyde, ethanol, sodium dodecyl sulfate (SDS) and Tween 20 not only introduced extra carbon content during total organic carbon (TOC) measurement, but also interacted with the DAX-8 resin. By comparing the apparent molecular weight (aMW) distribution of the untreated and pH-adjusted EPS samples detected by size exclusion chromatography, more complete EPS aMW information was preserved at pH 5. Thus, the hydrophobic fractionation by DAX-8 resin at pH 5 and physical EPS extraction methods were preferred in this study.After identifying the proper conditions for DAX-8 resin fractionation, detailed qualitative analysis of the EPS hydrophobic features was further investigated. The results showed that the humic-like substances (HS-like) were the major organic constituent of the EPS extracted from the anaerobic granular sludge, and they were also the main molecular support of the EPS hydrophobicity. Those hydrophobic HS-like compounds were mainly small molecules ranging from 8 kDa to &lt;1 kDa. Proteins (PN) and polysaccharides (PS) contributed to the EPS hydrophobicity to a lesser extent.The role of PN and PS in the EPS hydrophobicity was difficult to be shown. It is known that the major organic constituents of the EPS extracted from bacteria, algae and fungi are PN and PS. Therefore, to explore the hydrophobic features of PN and PS, as well as to investigate the impact of Ni(II) addition, on the EPS hydrophobicity, the fungus Phanerochaete chrysosporium was chosen. The results showed that the contents of PN and PS in the extracted fungal EPS varied with the Ni(II) concentration. With an increase in the Ni concentration from 0 mg/L to 25 mg/L, the PN content was decreased whereas the PS content was increased. The fungal EPS hydrophobicity, determined by the DAX-8 resin treatment, was decreased as the Ni concentration increased.Besides, the peak intensity on the size exclusion chromatography (SEC) corresponding to the PN-like molecules (Ex/Em = 225/345 nm) ranging from 1.9×103 to 10 kDa were intensified by the Ni addition, while the aMW distribution of the total organics (UV/210) in the EPS remained almost stable. These results indicated that those PN-like compounds may determine the hydrophobicity of fungal EPS under stress conditions.For the more heterogeneous EPS extracted from anaerobic granular sludge, HS-like compounds were identified as the major organic component, as well as the main molecular support of the EPS hydrophobicity. By studying the hydrophobic features of the EPS extracted from the fungus Phanerochaete chrysosporium, it showed that the PN and PS in the EPS played an active role in protecting the fungus under Ni stress. The increased Ni concentration decreased the hydrophobicity of fungal EPS, but it increased the cell surface hydrophobicity of the fungus. It seems that the presence of Ni promoted the fungus becoming more hydrophobic

Um modelo matemático da reação de copolimerização em emulsão de acrilato de butila e estireno em reator batelada e semi-batelada isotérmico foi desenvolvido e apresentou bons resultados quando comparado a experimentos disponíveis em literatura científica. O modelo contemplou a solução do balanço populacional, tanto para a distribuição de tamanho de partículas quando para a distribuição média de radicais por partícula. Contemplou-se também a solução do balanço de momentos, para obtenção da massa molar média numérica e mássica. O problema descrito foi resolvido através da solução numérica de um conjunto de equações algébricodiferenciais e o balanço populacional foi resolvido pelo método dos pivots fixos. Foi possível validar com boa aderência a conversão dos monômeros, o diâmetro médio de partículas, número de partículas por litro de emulsão, número médio de radicais por partícula, a distribuição de tamanho de partículas e a massa molar média numérica e mássica ao longo do tempo para um conjunto de experimentos.<br>A mathematical model of emulsion copolymerization reaction of styrene and butyl acrylate for batch and semi-batch isothermal reactor was developed and presented good results when compared to experiments available in the scientific literature. The model included the solution of the population balance for both particle size distribution and average number of radicals per particle. The balances of moments of the molecular weight distribution are solved to obtain the weight- and numberaveraged molecular weight of the polymer. The problem described was solved by numerical solution of a set of algebraic-differential equations and the population balance was solved by the method of fixed pivots. The model prediction were validated with a set of experiments with respect to the changes of monomer conversion, average particle diameter, number of particles per liter of emulsion, average number of radicals per particle, particle size distribution, number- and weight-average molecular weight during process time.

Cette étude est consacrée à la modélisation de la copolymérisation en émulsion du styrène et de l'alpha-méthylstyrène. L'homopolymérisation de ce dernier, par voie radicalaire, est quasiment impossible à cause de sa faible réactivité, de sa température plafond faible et principalement des réactions de dépropagation dont il est le siège. Ce monomère est cependant susceptible de copolymériser avec d'autres monomères, par exemple le styrène, et dans ce cas la température de transition vitreuse du matériel obtenu est supérieure à celle du polystyrène seul. Dans le cadre de cette étude, la copolymérisation a permis de montrer l'influence de la composition initiale des monomères et de la température de la réaction. De même, nous avons étudié l'effet de l'alpha-méthylstyrène sur les principaux phénomènes intervenant dans le procédé, notamment la nucléation des particules de polymère et la capture des radicaux par celles-ci. À cette fin, un modèle cinétique, fondé sur la théorie de Smith et Ewart, a été d'abord élaboré pour l'homopolymérisation en émulsion du styrène. Ce modèle a permis de prédire la cinétique et les caractéristiques des macromolécules produites. Il a ensuite été étendu à la copolymérisation du styrène et de l'alpha-méthylstyrène. Dans les deux cas les coefficients cinétiques correspondants ont été déduits des données expérimentales. Ainsi, le modèle cinétique final a permis de prédire les masses molaires moyennes et leur distribution, de même que la composition chimique et la température de transition vitreuse du copolymère obtenu. Ces caractéristiques ont été validées à l'aide des techniques expérimentales telles que: la chromatographie d'exclusion stérique couplée à la diffusion dynamique de la lumière aux multi-angles, la résonance magnétique nucléaire du proton (¹H-RMN) et l'exploration par calorimétrie différentielle (ou DSC)

A distribuição de pesos moleculares (DPM) de um polímero afeta as propriedades mecânicas, térmicas e reológicas do material. Além disso, a análise em tempo real de uma reação de polimerização é uma tarefa complicada e, consequentemente, os procedimentos de controle devem ser baseados em valores gerados pelos modelos. Por isso, é extremamente importante ter dados confiáveis sobre distribuições de pesos moleculares, melhorar a eficiência dos métodos existentes e desenvolver novos métodos capazes de prever as heterogeneidades das reações de polimerização. Experimentalmente, a DPM pode ser obtida usando técnicas como a cromatografia de permeação em gel. Para predizer a DPM, vários métodos foram desenvolvidos nas ultimas décadas. Um dos principais é o dos momentos estatísticos, baseado em conceitos puramente estatísticos, que não conseguem descrever completamente a DPM. Além disso, as aproximações com método de Galerkin usam polinômios ortogonais - no caso especifico polinômios de Laguerre - cujos coeficientes são calculados empregando os momentos estatísticos e a distribuição é gerada resolvendo um número de equações definido pelo usuário, relacionado à precisão desejada. Enfim, o método das funções geradoras de probabilidades foi utilizado para prever as DPMs, porém necessitando uma inversão da transformada de Laplace, que introduz problemas numéricos nem sempre possíveis de serem resolvidos. No presente trabalho, o sistema rigoroso de equações diferenciais ordinárias foi resolvido, com objetivo de reduzir as imprecisões e as limitações introduzidas pelas aproximações. Obter diretamente a DPM completa requer a resolução de um sistema contendo cerca de 2Nmax até 3Nmax equações diferenciais ordinárias rígidas, tarefa que há alguns anos era inviável devido a limitações relacionadas à capacidade de cálculo. Foi modelada a DPM para uma reação de polimerização radicalar livre de estireno e de metacrilato de metila. Um interesse especial foi dado à taxa de terminação que é, no momento, um dos temas mais investigados em polimerização por radicais livres. Os resultados das simulações foram comparados com dados experimentais tirados de reatores convencionais e, subsequentemente, com dados experimentais provenientes de um millireactor não convencional.<br>It is well known that the molecular weight distribution (MWD) of a synthetic polymer affects its mechanical, thermal and rheological properties. Furthermore, the on-line analysis for polymerization reaction is a difficult task and, consequently, the control procedures must rely on values given by models. As such, it is extremely important to have reliable data on the MWD, improve the efficiency of existing methods and develop new ones to predict the heterogeneities of polymerization reactions. Experimentally, the MWD can be obtained using techniques such as Gel Permeation Chromatography (GPC). To predict the MWD, many methods have been developed over the last decades. One of the main methods is the statistical moment treatment, which is based on a pure statistical concept and do not describe the whole MWD. Moreover, Galerkin approximation uses orthogonal polynomials -in general Laguerre polynomials- whose coefficients are calculated exploiting the statistical moment definition and the distribution is generated by solving a user-defined number of equations based on the desired precision. Finally, probability-generating functions that have been used to predict MWDs require Laplace transforms inversions, introducing numerical issues that must be bypassed and are not always solvable. It has been decided to base the approach without adopting any of these methods but directly solving the rigorous ordinary differential equation (ODE) system in order to reduce the inaccuracies and the limitations introduced by approximations. The direct obtention of the MWD requires the resolution of a system containing approximately 2Nmax up to 3Nmax stiff ODE equations that, a few years ago, was unfeasible due computational time limitations. The MWDs for a free radical styrene polymerization system and a methyl methacrylate system have been modeled. A special focus was given to the termination rate constant, which is, at the present, one of the most investigated topics in free radical polymerization. The results of the simulations were compared to experimental data taken from conventional reactors and, subsequently, to experimental data coming from an unconventional millireactor.

Characterization of cellulose by its molecular weight distribution is afforded after polymeranalogeous dissolution. Additionally, a molecular dispersion of the polymer is a prerequisite. Common processes are dissolution of cellulose in dimethylacetamide-lithiumchloride, nitration and carbanilation. Degradation of the polysaccharide chains can occur in each of the mentioned processes. It is shown that degradation in pyridine occurs via beta-elimination at carbonyl groups along the cellulose chains. Carbanilierung in DMSO is much more pronounced. It comprises oxidation along the Pfitzner-Moffatt-mechanism and subsequent beta-elimination at the thus formed carbonyl-groups. This was elucidated with model systems and by investigation of the carbanilation in different media. Carbonyl groups of cellulose are masked through reaction with phenylisocyanate. This was shown with model. Therefore, the determination of carbonyl groups in cellulose-tricarbanilates is not possible. The separation of low-molecular weight byproducts was optimised. The influence of pretreatment and preactivation of cellulose-samples on the completeness of the conversion was studied. A standard protocol for the carbanilation of cellulose is provided<br>Cellulose wird u.a. durch ihre Molmassenverteilung charakterisiert, deren Ermittlung ein polymeranaloges Verfahren zur molekulardispersen Auflösung des Polymers erfordert. Hierfür sind die Direktlösung, die Nitrierung und die Carbanilierung in Gebrauch. Bei allen Prozessen kann es zum Abbau der Polysaccharidketten kommen, wobei diesen Prozessen wenig Beachtung geschenkt wurde. In der Arbeit wird gezeigt, daß der Abbau bei der Carbanilierung in Pyridin durch Beta-Eliminierung an vorhandenen Carbonylgruppen erfolgt. Die Carbanilierung in DMSO fällt stets stärker aus als bei Einsatz von Pyridin und umfasst die Prozesse Oxidation nach dem Pfitzner-Moffatt-Mechanismus und anschließende Beta-Eliminierung an den neu gebildeten Carbonylgruppen. Dies wird durch Untersuchungen an Modellsystemen und am Polymer herausgearbeitet. Carbonylgruppen an Cellulose werden durch die Umsetzung mit Phenylisocyanat maskiert, was an Modellverbindungen gezeigt wurde (Bildung von Endioldicarbanilaten und carbanilierten Halbacetalen). Ihre Bestimmung in Cellulosecarbanilaten ist daher nicht möglich. Die Abtrennung von niedermolekularen Nebenprodukten der Umsetzung wurde optimiert. Der Einfluss der Vorbehandlung und Voraktivierung von Celluloseproben auf die Vollständigkeit der Umsetzung wurde eingehend untersucht. Es wird ein Standardverfahren zur Carbanilierung von Cellulose angegeben

<p>SARAF, Manish Kumar. Polymerization of Vinylidene Fluoride in Supercritical Carbon Dioxide: Molecular Weight Distribution (Under the direction of Drs. George W. Roberts and Joseph M. DeSimone)Conventional vinylidene fluoride polymerizations require the use of large amounts of water. Therefore, energy and cost-intensive drying and separation steps are required to isolate the polymer. Additionally, some conventional polymerizations use fluorosurfactants that belong to 3M?s ?Scotchgard? family of surfactants, which are being phased out due to environmental concerns. In this research, we investigate a "green" process for the continuous polymerization of vinylidene fluoride by free-radical precipitation polymerization in supercritical carbon dioxide (scCO2). Significant technological and environmental improvements can be achieved by this technology, such as: 1) elimination of waste streams generated by conventional suspension, and emulsion processes; and 2) achievement of major energy savings, as the polymer is isolated in a dry form with no water or solvent to evaporate. The experimental system used in this research consisted of a continuous stirred tank reactor (CSTR) for polymerization, and a polymer withdrawal system where polymer was collected, and continuously ejected to ambient conditions. The polymer was collected as a dry "free-flowing" powder, and was characterized by GPC (gel permeation chromatography), DSC (differential scanning calorimetry), and Fluorine-19 NMR (nuclear magnetic resonance spectroscopy). Experiments were carried out to study the effect of different parameters such as inlet monomer concentration ([M]in= 0.78 to 3.5 M), pressure (P=3050 to 4400 psig) , temperature (T=65 to 85 oC) , and average residence time (t = 12 to 50 mins.), on the polymerization rate and the average molecular weights. A homogeneous model based on classical free radical kinetics predicted the polymerization rate very well at the lower rates. However, this could not predict an inhibition in the rate that was observed at higher monomer concentrations. A bimodal molecular weight distribution was obtained at inlet monomer concentrations greater than around 1.9 M. The second (high molecular weight) mode was more prominent at higher monomer concentrations, higher residence times, and lower temperatures. Two hypothesis, poor mixing and long chain branching, were investigated to explain these broad and bimodal molecular weight distributions (MWDs). Agitation studies showed that poor mixing can account for the slower rate of polymerization at high monomer concentrations, but does not to bimodal MWDs. End group analysis using NMR showed that chain transfer occurs, probably to polymer. A homogeneous kinetic model was developed to investigate the effect of chain branching arising from chain transfer to polymer. This model showed that broad MWDs with large polydispersity indices (PDIs) are obtained at high monomer concentrations and at high residence times. These predictions matched very well with experimental data. However, the model predicted a unimodal MWD even at very high values of the rate constant for chain transfer to polymer.Batch polymerization studies were carried out to develop alternate low temperature initiators, which could reduce operating and equipment costs and potentially produce high molecular weight polymer with reasonable yields. A fluorinated initiator obtained from hexafluoropropynl oxide dimer produced PVDF with very high molecular weights (~90 K) at reasonable yields. <P>

Thesis (M.S.) -- University of Maryland, College Park, 2004.<br>Thesis research directed by: Dept. of Chemical Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.

In recent years there have been many reports of methods for inferring the molecular weight distribution (MWD) of linear polymers from either viscosity data or dynamic data. This subject is of great interest in the polymer industry, since MWD affects the processing and final properties of polymers, and gel permeation chromatography (GPC), normally used for determining MWD, has several limitations. There are two main types of method for inferring the MWD from rheological data. The first one involves empirical transformations that lead directly to a MWD, whereas the second type involves the inversion of an integral that gives the relaxation modulus G(t) of a polydisperse polymer in terms of its MWD. A comparison of the reliabilities of these methods for use with samples having a wide variety of polydispersities is lacking, especially for materials with high polydispersities. This study presents a comparison of the MWD predictions of four of these techniques in terms of their performance with groups of HDPEs, LLDPEs and polypropylenes having polydispersities from two to six and various molecular weights. It was found that the viscosity transform (as modified by Wood-Adams) and a modified time-dependent diffusion reptation model proposed by des Cloizeaux (TDD-DR model) are, to a certain extent, satisfactory methods for use with polymers having moderate to high polydispersities, whereas the modulus transform is reliable only for narrow distributions.

Dilute solution properties of three difficult-to-analyze macromolecular systems were investigated and clarified. Two were notorious for having highly time-in-solution dependent properties, nitrocellulose and lignin, while the third was an ideal model branched methacrylate polymer with which to examine unanswered questions in polymer hydrodynamic behavior. Gel permeation chromatography with a differential viscosity detector (GPC/DV) was employed to study the dilute solution properties of various polymers, specifically their absolute molecular weight distributions and hydrodynamic behavior. The study was divided into three parts. The first part focused on the time dependent change in molecular weight of nitrocellulose. Samples having 12.58% and 13.5% levels of nitration were investigated in THF and EtOAc. GPC/DV, LALLS, FT-IR and intrinsic viscosity experiments revealed that the materials existed as associated molecules in solution which decreased in molecular weight upon storage to extents dependent on the solvent. The second part was an examination of the hydrodynamic behavior of hydroxypropylated lignins using GPC/LALLS/DV and VPO. These materials were found to increase in molecular weight upon storage in solution due to association. Special precautions had to be taken in running experiments to obtain the correct molecular weights and molecular weight distributions. The last part involved a fundamental study of PMMA-g-PMMA's having similar molecular weights but containing different levels of branching. Variable temperature GPC/LALLS/DV was employed to obtain molecular weight distributions, branching parameters, average chain dimensions and information on the hydrodynamic behavior of these branched systems. Samples containing up to 40% of long chain branching were found to obey the universal calibration analytic scheme of GPC.<br>Ph. D.

This report discusses the research and results of the study done to characterize total organic halide (TOX) distributions by apparent molecular weight (AMW) of combined effluents from a mill employing the Kraft pulp process. AMW distributions of TOX and total organic carbon (TOC) are examined at five locations within an aerated stabilization basin (ASB). An effort is made to explain experimental methods used for separation into AMW ranges and analysis for the described parameters. TOX and TOC results are tabulized and discussed. Degradation pathways of chlorinated organic compounds are examined using data from three sample sets. Analyses of the data for TOX and TOC are included and implications from this data discussed. Improvements for further analysis of future samples are incorporated in this report.

Synthese et polymerisation de diethoxy-1,1 epoxy-2,3 et diethoxy-1,1 epithio-2,3 propane racemiques en vue de preparer des polyethers et polythioethers ayant des fonctions aldehydes dans la chocine laterale

A new method, probability distribution of diffusivities (time scaled square displacements between succeeding video frames), was developed to analyze single molecule tracking (SMT) experiments. This method was then applied to SMT experiments on ultrathin liquid tetrakis(2-ethylhexoxy)silane (TEHOS) films on Si wafer with 100 nm thermally grown oxide, and on thin semectic liquid crystal films. Spatial maps of diffusivities from SMT experiments on 220 nm thick semectic liquid crystal films reveal structure related dynamics. The SMT experiments on ultrathin TEHOS films were complemented by fluorescence correlation spectroscopy (FCS). The observed strongly heterogeneous single molecule dynamics within those films can be explained by a three-layer model consisting of (i) dye molecules adsorbed to the substrate, (ii) slowly diffusing molecules in the laterally heterogeneous near-surface region of 1 - 2 molecular diameters, and (iii) freely diffusing dye molecules in the upper region of the film. FCS and SMT experiments reveal a strong influence of substrate heterogeneity on SM dynamics. Thereby chemisorption to substrate surface silanols plays an important role. Vertical mean first passage times (mfpt) in those films are below 1 µs. This appears as fast component in FCS autocorrelation curves, which further contain a contribution from lateral diffusion and from adsorption events. Therefore, the FCS curves are approximated by a tri-component function, which contains an exponential term related to the mfpt, the correlation function for translational diffusion and a stretched exponential term for the broad distribution of adsorption events. Lateral diffusion coefficients obtained by FCS on 10 nm thick TEHOS films, thereby, are effective diffusion coefficients from dye transients in the focal area. They strongly depend on the substrate heterogeneity. Variation of the frame times for the acquisition of SMT experiments in steps of 20 ms from 20 ms to 200 ms revealed a strong dependence of the corresponding probability distributions of diffusivities on time, in particular in the range between 20 ms and 100 ms. This points to average dwell times of the dye molecules in at least one type of the heterogeneous regions (e.g. on and above silanol clusters) in the range of few tens of milliseconds. Furthermore, time series of SM spectra from Nile Red in 25 nm thick poly-n-alkyl-methacrylate (PnAMA) films were studied. In analogy to translational diffusion, spectral diffusion (shifts in energetic positions of SM spectra) can be studied by probability distributions of spectral diffusivities, i.e. time scaled square energetic displacements. Simulations were run and analyzed to study contributions from noise and fitting uncertainty to spectral diffusion. Furthermore the effect of spectral jumps during acquisition of a SM spectrum was investigated. Probability distributions of spectral diffusivites of Nile Red probing vitreous PnAMA films reveal a two-level system. In contrast, such probability distributions obtained from Nile Red within a 25 nm thick poly-n-butylmethacrylate film around glass transition and in the melt state, display larger spectral jumps. Moreover, for longer alkyl side chains a solvent shift to higher energies is observed, which supports the idea of nanophase separation within those polymers.

Doutoramento em Bioquímica<br>Os polissacarídeos são os componentes maioritários dos grãos de café verde e torrado e da bebida de café. Os mais abundantes são as galactomananas, seguindo-se as arabinogalactanas. Durante o processo de torra, as galactomananas e arabinogalactanas sofrem modificações estruturais, as quais estão longe de estar completamente elucidadas devido à sua diversidade e à complexidade estrutural dos compostos formados. Durante o processo de torra, as galactomananas e arabinogalactanas reagem com proteínas, ácidos clorogénicos e sacarose, originando compostos castanhos de alto peso molecular contendo nitrogénio, designados de melanoidinas. As melanoidinas do café apresentam diversas atividades biológicas e efeitos benéficos para a saúde. No entanto, a sua estrutura exata e os mecanismos envolvidos na sua formação permanecem desconhecidos, bem como a relação estrutura-atividade biológica. A utilização de sistemas modelo e a análise por espectrometria de massa permitem obter uma visão global e, simultaneamente, detalhada das modificações estruturais nos polissacarídeos do café promovidas pela torra, contribuindo para a elucidação das estruturas e mecanismos de formação das melanoidinas. Com base nesta tese, oligossacarídeos estruturalmente relacionados com a cadeia principal das galactomananas, (β1→4)-Dmanotriose (Man3), e as cadeias laterais das arabinogalactanas, (α1→5)-Larabinotriose (Ara3), isoladamente ou em misturas com ácido 5-Ocafeoilquínico (5-CQA), o ácido clorogénico mais abundante nos grãos de café verde, e péptidos compostos por tirosina e leucina, usados como modelos das proteínas, foram sujeitos a tratamento térmico a seco, mimetizando o processo de torra. A oxidação induzida por radicais hidroxilo (HO•) foi também estudada, uma vez que estes radicais parecem estar envolvidos na modificação dos polissacarídeos durante a torra. A identificação das modificações estruturais induzidas por tratamento térmico e oxidativo dos compostos modelo foi feita por estratégias analíticas baseadas principalmente em espectrometria de massa, mas também em cromatografia líquida. A cromatografia de gás foi usada na análise de açúcares neutros e ligações glicosídicas. Para validar as conclusões obtidas com os compostos modelo, foram também analisadas amostras de polissacarídeos do café obtidas a partir de resíduo de café e café instantâneo. Os resultados obtidos a partir dos oligossacarídeos modelo quando submetidos a tratamento térmico (seco), assim como à oxidação induzida por HO• (em solução), indicam a ocorrência de despolimerização, o que está de acordo com estudos anteriores que reportam a despolimerização das galactomananas e arabinogalactanas do café durante a torra. Foram ainda identificados outros compostos resultantes da quebra do anel de açúcares formados durante o tratamento térmico e oxidativo da Ara3. Por outro lado, o tratamento térmico a seco dos oligossacarídeos modelo (individualmente ou quando misturados) promoveu a formação de oligossacarídeos com um maior grau de polimerização, e também polissacarídeos com novos tipos de ligações glicosídicas, evidenciando a ocorrência de polimerização através reações de transglicosilação não enzimática induzidas por tratamento térmico a seco. As reações de transglicosilação induzidas por tratamento térmico a seco podem ocorrer entre resíduos de açúcares provenientes da mesma origem, mas também de origens diferentes com formação de estruturas híbridas, contendo arabinose e manose como observado nos casos dos compostos modelo usados. Os resultados obtidos a partir de amostras do resíduo de café e de café instantâneo sugerem a presença de polissacarídeos híbridos nestas amostras de café processado, corroborando a ocorrência de transglicosilação durante o processo de torra. Além disso, o estudo de misturas contendo diferentes proporções de cada oligossacarídeo modelo, mimetizando regiões do grão de café com composição distinta em polissacarídeos, sujeitos a diferentes períodos de tratamento térmico, permitiu inferir que diferentes estruturas híbridas e não híbridas podem ser formadas a partir das arabinogalactanas e galactomananas, dependendo da sua distribuição nas paredes celulares do grão e das condições de torra. Estes resultados podem explicar a heterogeneidade de estruturas de melanoidinas formadas durante a torra do café. Os resultados obtidos a partir de misturas modelo contendo um oligossacarídeo (Ara3 ou Man3) e 5-CQA sujeitas a tratamento térmico a seco, assim como de amostras provenientes do resíduo de café, mostraram a formação de compostos híbridos compostos por moléculas de CQA ligadas covalentemente a um número variável de resíduos de açúcar. Além disso, os resultados obtidos a partir da mistura contendo Man3 e 5-CQA mostraram que o CQA atua como catalisador das reações de transglicosilação. Por outro lado, nas misturas modelo contendo um péptido, mesmo contendo também 5-CQA e sujeitas ao mesmo tratamento, observou-se uma diminuição na extensão das reações transglicosilação. Este resultado pode explicar a baixa extensão das reações de transglicosilação não enzimáticas durante a torra nas regiões do grão de café mais ricas em proteínas, apesar dos polissacarídeos serem os componentes maioritários dos grãos de café. A diminuição das reações de transglicosilação na presença de péptidos/proteínas pode dever-se ao facto de os resíduos de açúcares redutores reagirem preferencialmente com os grupos amina de péptidos/proteínas por reação de Maillard, diminuindo o número de resíduos de açúcares redutores disponíveis para as reações de transglicosilação. Além dos compostos já descritos, uma diversidade de outros compostos foram formados a partir dos sistemas modelo, nomeadamente derivados de desidratação formados durante o tratamento térmico a seco. Em conclusão, a tipificação das modificações estruturais promovidas pela torra nos polissacarídeos do café abre o caminho para a compreensão dos mecanismos de formação das melanoidinas e da relação estrutura-atividade destes compostos.<br>Polysaccharides are the major components of green and roasted coffee beans, and coffee brew. The most abundant ones are galactomannans, followed by arabinogalactans. During the roasting process, galactomannans and arabinogalactans undergo structural modifications that are far to be completely elucidated due to their diversity and complexity of the compounds formed. During the roasting process, galactomannans and arabinogalactans react with proteins, chlorogenic acids, and sucrose, originating high molecular weight brown compounds containing nitrogen, known as melanoidins. Several biological activities and beneficial health effects have been attributed to coffee melanoidins. However, their exact structures and the mechanisms involved in their formation remain unknown, as well as the structure-biological activity relationship. The use of model systems and mass spectrometry analysis allow to obtain an overall view and, simultaneously, detailed, of the structural modifications in coffee polysaccharides promoted by roasting, contributing to the elucidation of the structures and formation mechanisms of melanoidins. Based on this thesis, oligosaccharides structurally related to the backbone of galactomannans, (β1→4)-D-mannotriose, and the side chains of arabinogalactans, (α1→5)-Larabinotriose, alone or in mixtures with 5-O-caffeoylquinic acid, the most abundant chlorogenic acid in green coffee beans, and dipeptides composed by tyrosine and leucine, used as models of proteins, were submitted to dry thermal treatments, mimicking the coffee roasting process. The oxidation induced by hydroxyl radicals (HO•) was also studied, since these radicals seem to be involved in the modification of the polysaccharides during roasting. The identification of the structural modifications induced by thermal and oxidative treatment of the model compounds was performed mostly by mass spectrometry-based analytical strategies, but also using liquid chromatography. Gas chromatography was used in the analysis of neutral sugars and glycosidic linkages. To validate the conclusions achieved with the model compounds, coffee polysaccharide samples obtained from spent coffee grounds and instant coffee were also analysed. The results obtained from the model oligosaccharides when submitted to thermal treatment (dry) or oxidation induced by HO• (in solution) indicate the occurrence of depolymerization, which is in line with previous studies reporting the depolymerization of coffee galactomannans and arabinogalactans during roasting. Compounds resulting from sugar ring cleavage were also formed during thermal treatment and oxidative treatment of Ara3. On the other hand, the dry thermal treatment of the model oligosaccharides (alone or when mixed) promoted the formation of oligosaccharides with a higher degree of polymerization, and also polysaccharides with new type of glycosidic linkages, evidencing the occurrence of polymerization via non-enzymatic transglycosylation reactions induced by dry thermal treatment. The transglycosylation reactions induced by dry thermal treatment can occur between sugar residues from the same origin, but also of different origins, with formation of hybrid structures, containing arabinose and mannose in the case of the model compounds used. The results obtained from spent coffee grounds and instant coffee samples suggest the presence of hybrid polysaccharides in these processed coffee samples, corroborating the occurrence of transglycosylation during the roasting process. Furthermore, the study of mixtures containing different proportions of each model oligosaccharide, mimicking coffee bean regions with distinct polysaccharide composition, subjected to different periods of thermal treatment, allowed to infer that different hybrid and non-hybrid structures may be formed from arabinogalactans and galactomannans, depending on their distribution in the bean cell walls and on roasting conditions. These results may explain the heterogeneity of melanoidins structures formed during coffee roasting. The results obtained from model mixtures containing an oligosaccharide (Ara3 or Man3) and 5-CQA and subjected to dry thermal treatment, as well as samples derived from spent coffee grounds, showed the formation of hybrid compounds composed by CQA molecules covalently linked to a variable number of sugar residues. Moreover, the results obtained from the mixture containing Man3 and 5-CQA showed that CQA acts as catalyst of transglycosylation reactions. On the other hand, in the model mixtures containing a peptide, even if containing 5-CQA and subjected to the same treatment, it was observed a decrease in the extent of transglycosylation reactions. This outcome can explain the low extent of non-enzymatic transglycosylation reactions during roasting in coffee bean regions enriched in proteins, although polysaccharides are the major components of the coffee beans. The decrease of transglycosylation reactions in the presence of peptides/proteins can be related with the preferential reactivity of reducing residues with the amino groups of peptides/proteins by Maillard reaction, decreasing the number of reducing residues available to be directly involved in the transglycosylation reactions. In addition to the compounds already described, a diversity of other compounds were formed from model systems, namely dehydrated derivatives formed during dry thermal treatment. In conclusion, the identification of the structural modifications in coffee polysaccharides promoted by roasting pave the way to the understanding of the mechanisms of formation of melanoidins and structure-activity relationship of these compounds.

Tang Kwan-Yee.<br>Thesis submitted in: September 2002.<br>Thesis (M.Phil.)--Chinese University of Hong Kong, 2003.<br>Includes bibliographical references (leaves 86-94).<br>Abstracts in English and Chinese.<br>TABLE OF CONTENTS --- p.i<br>LIST OF FIGURES --- p.v<br>LIST OF TABLES --- p.viii<br>ABSTRACT --- p.ix<br>ACKNOWLEDGEMENT --- p.xiii<br>DECLARATION --- p.xiv<br>ABBREVIATIONS --- p.xv<br>Chapter CHAPTER ONE --- INTRODUCTION<br>Chapter 1.1. --- Structure and conformation of Curdlan --- p.1<br>Chapter 1.2. --- Important of Curdlan --- p.3<br>Chapter 1.3. --- Conventional methods on molecular weight and molecular weight distribution on polysaccharide --- p.4<br>Chapter 1.3.1. --- Laser Light Scattering --- p.4<br>Chapter 1.3.2. --- Size Exclusion Chromatography --- p.5<br>Chapter 1.3.3. --- Viscometry --- p.6<br>Chapter 1.4. --- Polysaccharide analysis using MALDI-TOF-MS --- p.7<br>Chapter 1.5. --- Matrix-Assisted Laser Desorption／Ionization Mass Spectrometry --- p.9<br>Chapter 1.6. --- Outline of project --- p.13<br>Chapter CHAPTER TWO --- INSTRUMENTATION AND EXPERIMENTAL<br>Chapter 2.1. --- Instrumentation --- p.14<br>Chapter 2.1.1. --- Vacuum system --- p.14<br>Chapter 2.1.2. --- Laser-based Ion Source --- p.14<br>Chapter 2.1.3. --- Time-of-flight Mass Analyzer --- p.18<br>Chapter 2.1.4. --- Detector and Data System --- p.22<br>Chapter 2.2. --- Experimental --- p.22<br>Chapter 2.2.1. --- Extraction of water-soluble and water-insoluble Curdlan --- p.22<br>Chapter 2.2.2. --- Fractionation of water-soluble Curdlan samples --- p.23<br>Chapter 2.2.3. --- Fractionation of water-insoluble Curdlan samples --- p.23<br>Chapter 2.2.4. --- Phenol-sulfuric acid test --- p.24<br>Chapter 2.2.5. --- Sample preparation in MS --- p.24<br>Chapter 2.2.6. --- Calibration of MALDI-TOFMS --- p.24<br>Chapter 2.3. --- Data Analysis --- p.25<br>Chapter CHAPTER THREE --- OPTIMIZATION OF MALDI EXPERIMENTAL CONDITIONS FOR ANALYSIS OF CURDLAN<br>Chapter 3.1. --- Introduction --- p.27<br>Chapter 3.2. --- Experimental --- p.28<br>Chapter 3.2.1. --- Sample preparation method for analysis of water-soluble Curdlan --- p.29<br>Chapter 3.2.2. --- Sample preparation method for analysis of water- insoluble Curdlan --- p.29<br>Chapter 3.2.2.1 --- Aqueous DHB matrix --- p.30<br>Chapter 3.2.2.2 --- Aqueous DHB/NH4F matrix --- p.30<br>Chapter 3.2.2.3 --- Non-aqueous DHB matrix (in DMSO) --- p.30<br>Chapter 3.2.2.4 --- Non-aqueous DHB/3AQ matrix (in DMSO) --- p.30<br>Chapter 3.2.2.5 --- Aqueous DHB/3AQ matrix --- p.31<br>Chapter 3.2.3. --- Fractionation of the water-soluble and water-insoluble Curdlan --- p.31<br>Chapter 3.3. --- Results and Discussion --- p.32<br>Chapter 3.3.1. --- Development of matrix system for analysis of water- insoluble Curdlan --- p.35<br>Chapter 3.3.2. --- MALDI analysis of water-soluble and water-insoluble Curdlans --- p.39<br>Chapter 3.3.3 --- MALDI analysis of fractionated water-soluble and water- insoluble Curdlans --- p.42<br>Chapter 3.4. --- Conclusion --- p.48<br>Chapter CHAPTER FOUR --- "EVALUATION OF MW AND MWD OF DMSO- SOLUBLE CURDLAN BY MALDI-TOF-MS, UV- VIS, REFRACTOMETRIC AND GC-MS ANALYSIS"<br>Chapter 4.1. --- Introduction --- p.51<br>Chapter 4.2. --- Experimental --- p.54<br>Chapter 4.2.1. --- Gel permeation chromatography of water-insoluble Curdlan --- p.54<br>Chapter 4.2.2. --- Matrix-assisted Laser Desorption/Ionization (MALDI) Mass Spectrometry --- p.55<br>Chapter 4.2.3. --- Ultraviolet Absorption Spectrometry (UV-VIS) --- p.55<br>Chapter 4.2.4 --- Refractometry Analysis (RI) --- p.56<br>Chapter 4.2.5 --- Gas Chromatography Mass Spectrometry (GC-MS) --- p.56<br>Chapter 4.3. --- Results --- p.57<br>Chapter 4.3.1 --- MALDI analysis --- p.57<br>Chapter 4.3.2 --- Ultra-violet Absorption Spectrometry (UV-VIS) --- p.61<br>Chapter 4.3.3 --- Refractometry Analysis (RI) --- p.62<br>Chapter 4.3.4 --- Gas chromatography Mass Spectrometry (GC-MS) --- p.66<br>Chapter 4.4. --- Discussion --- p.79<br>Chapter 4.5 --- Conclusion --- p.83<br>Chapter CHAPTER FIVE --- CONCLUDING REMARKS --- p.84<br>REFERENCES --- p.86<br>APPENDIX<br>Appendix A Chemical Structure of Curdlan --- p.95<br>Appendix B Structure of Universal Matrices Used in MALDI-TOF- MS --- p.96<br>"Appendix C Structure of Aniline Blue fluorochrome Sodium 4,4- [carbonyldis-(benzene-4,l-diyI)bis(imino)]bisbenzene- sulphonate" --- p.97<br>Appendix D Structure of common internal standard for GCMS analysis --- p.97<br>Appendix E Structure of Trim ethylsilylated reagent and Trimethylsilylated glucose --- p.98<br>Appendix F The table of raw data for graph plotting in RI analysis. --- p.99<br>Appendix G The table of raw data used for graph plotting in UV-VIS analysis. --- p.100<br>Appendix H The table of raw data used for graph plotting in GC-MS analysis. --- p.101

Sun Baizhong.<br>Thesis (M.Phil.)--Chinese University of Hong Kong, 2004.<br>Includes bibliographical references (leaves 75-79).<br>Abstracts in English and Chinese.<br>ABSTRACT --- p.i<br>ABSTRACT (IN CHINESE) --- p.ii<br>TABLE OF CONTENTS --- p.iii<br>LIST OF FIGURES --- p.v<br>LIST OF TABLES --- p.vii<br>ABBREVIATIONS --- p.vi<br>ACKNOWLEDGEMENT --- p.ix<br>DECLARATION --- p.x<br>Chapter CHAPTER ONE --- INTRODUCTION<br>Chapter 1.1 --- Polysaccharides --- p.1<br>Chapter 1.2 --- Pharmacological importance of polysaccharides --- p.2<br>Chapter 1.3 --- Polysaccharides from Ganoderma Lucidum --- p.3<br>Chapter 1.4 --- Characterization of polysaccharides --- p.3<br>Chapter 1.5 --- Matrix-assisted laser desorption / ionization --- p.5<br>Chapter 1.6 --- Matrix-assisted laser desorption / ionization of polysaccharides --- p.8<br>Chapter 1.7 --- Outline of the project --- p.10<br>Chapter CHAPTER TWO --- INSTRUMENTATION AND EXPERIMENTAL<br>Chapter 2.1 --- Time-of-flight mass spectrometry --- p.12<br>Chapter 2.1.1 --- Instrumentation --- p.15<br>Chapter 2.1.1.1 --- Laser system --- p.16<br>Chapter 2.1.1.2 --- Ion source --- p.16<br>Chapter 2.1.1.3 --- Reflector --- p.19<br>Chapter 2.1.1.4 --- Detector --- p.19<br>Chapter 2.1.1.5 --- Data acquisition and manipulation --- p.20<br>Chapter 2.2 --- Ultraviolet-visible spectrometer --- p.21<br>Chapter CHAPTER THREE --- OPTIMIZATION OF MALDI CONDITIONS FOR POLYSACCHARIDE ANALYSIS USING DMSO AS SOLVENT<br>Chapter 3.1 --- Introduction --- p.22<br>Chapter 3.2 --- Experimental --- p.25<br>Chapter 3.2.1 --- Selection of matrix materials --- p.26<br>Chapter 3.2.2 --- Selection of co-matrix materials --- p.26<br>Chapter 3.2.3 --- Ratios of matrix-to-analyte --- p.26<br>Chapter 3.2.4 --- Effect of sample drying temperature --- p.27<br>Chapter 3.2.5 --- Sample loading methods --- p.27<br>Chapter 3.3 --- Results and discussion --- p.27<br>Chapter 3.3.1 --- Selection of matrix materials --- p.28<br>Chapter 3.3.2 --- Selection of co-matrix materials --- p.30<br>Chapter 3.3.3 --- Effect of matrix-to-co-matrix ratio --- p.32<br>Chapter 3.3.4 --- Effect of sample drying temperature --- p.37<br>Chapter 3.3.5 --- Effect of matrix-to-analyte ratio --- p.39<br>Chapter 3.3.6 --- Evaluation of sample preparation protocols --- p.43<br>Chapter 3.4 --- Conclusion --- p.46<br>Chapter CHAPTER FOUR --- MOLECULAR AND MOLECULAR WEIGHT DISTRIBUTION OF WATER-INSOLUBLE POLYSACCHARIDES FROM GANODERMA LUCIDUM<br>Chapter 4.1 --- Introduction --- p.47<br>Chapter 4.2 --- Experimental --- p.48<br>Chapter 4.2.1 --- Extraction of water-insoluble polysaccharides from Ganoderma Lucidum --- p.48<br>Chapter 4.2.2 --- Gel permeation chromatography of water-insoluble polysaccharides --- p.49<br>Chapter 4.2.3 --- Phenol sulfuric acid assay --- p.51<br>Chapter 4.2.4 --- MALDI-TOF analysis --- p.51<br>Chapter 4.2.5 --- Bradford assay --- p.52<br>Chapter 4.3 --- Results and discussion --- p.52<br>Chapter 4.3.1 --- Extraction of water-insoluble polysaccharides from Ganoderma Lucidum --- p.52<br>Chapter 4.3.2 --- Fractionation of water-insoluble polysaccharides using gel permeation chromatography (GPC) --- p.54<br>Chapter 4.3.3 --- MALDI-TOF analysis of fractionated polysaccharides --- p.57<br>Chapter 4.3.4 --- Carbohydrate content analysis of fractionated polysaccharides --- p.62<br>Chapter 4.3.5 --- MW and MWD of water-insoluble polysaccharides extracted from Ganoderma Lucidum --- p.69<br>Chapter 4.4 --- Conclusion --- p.71<br>Chapter CHAPTER FIVE --- CONCLUDING REMARKS<br>Chapter 5.1 --- Conclusion --- p.73<br>REFERENCES --- p.76<br>APPENDIX --- p.81<br>Appendix A Reaction scheme of carbohydrate with phenol in phenol-sulfuric acid assay --- p.81

碩士<br>淡江大學<br>水資源及環境工程學系<br>89<br>The wastewater samples studied in this paper were taken from the secondary effluent of a textile wastewater treatment plant. The experiments were conducted in a UV reactor under different conditions, including pH, H2O2 dosage, and UV intensity. At different time intervals, the treated wastewater samples were withdrawn for the analyses of residual DOC, color, and the size distribution of organic molecules. Results show that HO‧ reacts with the color-forming species much faster than with the carbonate species. Hence, if the color removal is the main focus, it appears that there’s no need to control the pH. But the pH controlled within acidic range is required to achieve a higher DOC removal. At a low H2O2 dosage of 50 mg/L and a low UV power of 64 watts, the DOC removal was only 30% for pH 4 and 5% for pH 7. The percentages of molecular weight (M.W.) distribution of DOC for the untreated water sample are 57% (0.45 μm-10 KD), and 28%(< 1 KD). Furthermore the portion with the M.W. of 0.45 μm-10 KD decreases from 11.7 (untreated sample) to 5.8 and 2.9 mg/L (treated at pH 7 and pH 4, respectively); the percentages of reduction were 50 and 75%. On the other hand, the portion with the M.W. than 1 KD increases from 5.7 (untreated sample) to 8.8 and 10.2 mg/L (treated at pH 7 and pH 4, respectively); the increasing percentages were 54 and 79%. In addition, the first order reaction constant of color (KC) increases with the increase of H2O2 doses. The KC value increases 3.6 times as the H2O2 doses increase from 50 mg/L to 100 mg/L. In contrast, the KC values increase 1.4 times as the UV intensity increase from 64 Watts to 128 Watts. Therefore, H2O2 doses is more improver treatment efficacy than ultraviolet. In conclusion, the use of H2O2/UV process is promising in treating the secondary effluent of textile wastewater, in terms of DOC and color, for the purpose of wastewater reclamation.

The objective of this work is to develop mathematical models to predict molecular weight distributions (MWDs) of ethylene copolymers produced in an industrial gas-phase reactor using a Ziegler-Natta (Z-N) catalyst. Because of the multi-site nature of Z-N catalysts, models of Z-N catalyzed copolymerization tend to be very large and have many parameters that need to be estimated. It is important that the data that are available for parameter estimation be used effectively, and that a suitable balance is achieved between modeling rigour and simplification. In the thesis, deconvolution analysis is used to gain an understanding of how the polymer produced by various types of active sites on the Z-N catalyst responds to changes in the reactor operating conditions. This analysis reveals which reactions are important in determining the MWD and also shows that some types of active sites share similar behavior and can therefore share some kinetic parameters. With this knowledge, a simplified model is developed to predict MWDs of ethylene/hexene copolymers produced at 90 °C. Estimates of the parameters in this isothermal model provide good initial guesses for parameter estimation in a subsequent more complex model. The isothermal model is extended to account for the effects of butene and temperature. Estimability analysis and cross-validation are used to determine which parameters should be estimated from the available industrial data set. Twenty model parameters are estimated so that the model provides good predictions of MWD and comonomer incorporation. Finally, D-, A-,and V-optimal experimental designs for improving the quality of the model predictions are determined. Difficulties with local minima are addressed and a comparison of the optimality criteria is presented.<br>Thesis (Ph.D, Chemical Engineering) -- Queen's University, 2009-05-28 20:43:58.37

碩士<br>國立高雄海洋科技大學<br>水產食品科學研究所<br>99<br>Protein hydrolysates from Achatina fulica foot muscle was extracted by high-temperature hydrolysis (121℃, 15-90 min) to obtain a retorted Achatina fulica protein hydrolysates (RAFPH). RAFPH obtained at 60 min was selected to further hydrolyzed with three enzymes (e.g. papain, tripsin, and alcalase) The RAFPH and enzymatic-treated RAFPH was analyzed for their degree of hydrolysis, molecular weight distribution, soluble protein, peptide content, antioxidant capacity, together with measurement of cholesterol-micelles disintegration , fat adsorption, emulsion capacity and foam capacity. The degree of hydrolysis of RAFPH obtained after 15−90 min hydrolysis reached about 74.4-78.0%. Using the gel filtration chromatography on a Superdex Peptide 10/300, the major molecule weight of protein hydrolysates was in the range of 686−6,511 Da. Soluble protein and peptide contents of the RAFPH were increased with prolonged hydrolysis time. For determination of In vitro disintegration of cholesterol in mixed micell, significant decreased concentrations of cholesterol-micelle was observed at high-temperature extraction as well as hydrolysis with papain, trypsin and alcalase, relative to control implying the ability to reduce cholesterol absorption. In the evaluation of physiochemical properties, fat absorption capacity, emulsifying capacity, foaming capacity of RAFPH obtained after hydrolysis for 15 min were better than the other, were as high as 2.27 g, 3.35 mL and 62.9%, respectively. The lower physicochemical properties of RAFPH digested with enzymatic hydrolysis relative to the RAFPH along is attributed to the excessive hydrolysis. This study revealed that all RAFPH was found to have a good antioxidant effect on 86.6-91.8% scavenging activity of DPPH radical, 94.1-98.2% inhibition ratio of linoleic acid oxidation, 95.9-97.0% trolox equivalent antioxidant capacity, and reducing power of 0.360-0.407 value (OD 700 nm). In addition, RAFPH treated with alcalase and papain had better antioxidant capacity than that trypsin treated RAFPH.

碩士<br>東海大學<br>化學工程學系<br>91<br>In this research, the submerged cultures of Ganoderma lucidium were carried out in shake flasks and a fermentor to study the effect of the medium composition and the environmental factors on the production of mycelia, extracellular polysaccharide and the mycelia morphology. In addition, the influence of different cultivation conditions on the molecular weight of polysaccharide was also investigated. Experimental items were divided into the different types and concentrations of C-sources and N-sources, initial pH, temperature, surface aeration and rotating speed, etc. The results indicate that the cultural medium containing glucose 5％, yeast extract 2.5％at initial pH4.5 and 30℃reached to a highest mycelial concentration of 1306.8mg/100ml. Yeast extract of 3.0% would be favorable to the formation of water-soluble extracellular polysaccharide. Some of medium composition and environmental conditions tested above were found to have an influence on the distribution of molecular weight of extracellular polysaccharide. Higher concentration of yeast extract in the medium caused the increase of molecular weight of polysacchride. In contrast, higher level of malt extract might lead to the reduction of molecular weight. Initial pH ranging from 4.5 to 6.5 could lower the molecular weight of polysaccharide formed. Lower rotation speed was beneficial to the formation of polysaccharide with higher molecular weight. In addition, the molecular weight of extracellular polysaccharide was strongly associated with mycelia morphology. In fermentor cultures, the results reveal that the molecular weight of polysaccharide could be lower than that obtained from shake flasks and the pellets formed were also incompact in nature.

碩士<br>國立中正大學<br>化學工程研究所<br>90<br>The traditional way of modeling the polymerization processes relies largely on empiricisms for obtaining the transport properties, such as viscosity and heat conductivity. In this work, we consider the polymerization of ethylene in a tubular reactor. While all other aspects in the modeling remain unchanged from traditional approaches, the polymer viscosity is estimated from a molecular, rheological theory using two different types of molecular weight distributions that bear the average number and weight molecular weights solved from traditional moment equations describing the mass balance during polymerization. The simulation results show that differential assumptions for the molecular weight distribution indeed have apparent effects on the predicted viscoelastic properties as well as the polymerization conditions, such as the yield and the temperature profile. The significance of the current finding is briefly discussed.

碩士<br>國立臺灣海洋大學<br>食品科學系<br>100<br>The proximate composition of Oreochromis niloticus skin was analyzed. The contents of moisture, crude protein, lipid and ash of tilapia skin were 33.38%, 32.23%, 4.21% and 0.21%, respectively. Tilapia skin collagen was extracted with 0.5 M acetic acid at room temperature (20 ± 2℃) and 50℃ for 2 to 8 h to obtain acid - soluble collagen (ASC). The viscosity and Brix of room-tempeature extracted and 50℃-extracted ASC increased with extraction time. ASC hydrolyzed at room temperature had lower Brix than that at 50℃. Brix for ASC extracted at 50℃ (ASC-50℃) was from 3.4 to 3.6% and ASC extracted at room temperature (ASC-RT) was from 3.0 to 3.2% Brix. The viscosity of ASC solution was maximal at 777.67 cP after 6 h of extraction at room temperature. Conversely, the viscosity of collagen solution extracted for 2 h to 8 h from tilapia skin at 50℃ decreased slightly from 12.98 cP to 10.00 cP. The yield of acid-soluble collagen extracted at room temperature from 2 to 8 h increased from 19.28 % to 28.71% (on dry weight basis), respectively. The yield increased to about 30% after re-extraction. Differences in the yields of extraction at 50℃ from 2 to 8 h were insignificant (P>0.05). The molecular weight of ASC-RT ranged 105 kD to 295 kD, while that extracted at 50℃ had molecular distribution from 71 kD to 244 kD. The largest molecular weight band (295 kD) of ASC-RT decreased in concentration (mg/ ml albumin) from 1.67 to 1.54 mg/ ml. Similarly, concentration of ASC-50℃ of the largest molecular weight band (244 kD) decreased from 2.12 mg/ ml for 2 h and 1.53 mg/ ml for 8 h while the concentration of 71 kD showed an increased trend, enhancing from 1.45 to 1.56 mg/ml for 2 h and 8 h, respectively. The molecular weight (MW) of ASC in present research is much higher than those in commercial products and fish-scale collagen peptides, MW ≤ 50 kD for commercial products and 1.3 - 4.5 kD for fish-scale collagen peptides. Collagen hydrolyzed by collagenase had low molecular weight about 35 kD and less than 20 kD. ASC-RT of 2 h extraction might be more stable in structure than ASC-50℃due to higher hydroxyproline and hydroxylysine content in ASC-RT. Therefore, the molecular weight of ASC-RT was higher than that of ASC-50℃. Microscopic images of ASC-RT and ASC-50℃ were taken to compare differences in ASC microstructure. It seemed that microstructure of freeze-dried ASC-50℃ was fine and less porous than that of ASC-RT. There were presence of collagen fibers with thin strands and collagen sheets in both freeze-dried ASC-RT and ASC- 50℃.

碩士<br>東海大學<br>環境科學系<br>85<br>Chlorination is the most simple tool for disinfection in drinking water process. Due to the pollution of raw water, which contains high organic substance, may react with chlorine and form so-called disinfection by-products (DBPs). One of the most popular DBPs: Trihalomethane, is confirmed as cancengenic substance since 1974. The precursors of DBPs normally be identified as: humic or fulvic acids. The potential technique may obtain seven categories of either hydrophilic or hydrophobic contents in raw water. In this study, we attempt to apply three resins: XAD-8, AG-MP-50 and IRA-93 to classify different species of NOM from raw water taken from Te-Chi reservoir, which suffered from the excess farm cultivation and soil erosion. After obtaining different species NOM; we will utilize Sephadex gel to identify its MWD and select target size to cutoff by either ultrafilter (UF) or nanofilter (NF) technique. The items to examine the efficient of DBPs reduction are: DOC, UV absorbance, THMFP (formation potential), HAAFP, AOXFP.The result shows that hydrophobic substances predominate in the raw water ( about 58 %), especially hydrophobic neutrals (about 29 %). Hydrophobic substances also has the highest DBPs formation potential, THMFP/DOC, AOXFP/DOC can be reach to 16.48 and 137.32 ug/mg.With the molecular weight distribution for various species organics, for example: DOC of humic acids distributed over the range of several thousand daltons, and the DBPs mainly formed between 5,000~1,000 daltons, it*s because humic acids has more aromatic compounds and gets higher average molecular weight； Generally speaking, DBPs formation is related to molecular weight distribution of the organics.Membrane filtration can be an affective technology to reduce DBPs formation, with the <500 daltons filtered, the reduction of DBPs can be reached to 70 %, but hydrophobic neutrals is worse( about 50~60 %). To get the better removal rate of DBPs, the lower molecular weight cutoff should be used. According to the results, membrane filtration can removal the DBPs precursor in raw water directly, and reduce the DBPs formation.

abstract: Asphalt binder is a complex viscoelastic hydrocarbon, whose performance depends upon interaction between its physical and chemical properties, both of which are equally important to the successful understanding of the material. Researchers have proposed various models linking linear viscoelastic (LVE) and microstructural parameters. However, none of these parameters provide insight into the relationship in the non- linear viscoelastic NLVE domain. The main goals of this dissertation are two fold. The first goal is to utilize the technique of Laser Desorption Mass Spectroscopy (LDMS) to relate the molecular structure of asphalt binders to its viscoelastic properties. The second goal of the study is to utilize different NLVE characterization tools and analysis procedures to get a clear understanding of the NLVE behavior of the asphalt binders. The goals of the study are divided into four objectives; 1) Performing the LDMS test on asphalt binder to develop at the molecular weight distributions for different asphalts, 2) Characterizing LVE properties of Arizona asphalt binders, 3) Development of relationship between molecular structure and linear viscoelasticity, 4) Understanding NLVE behavior of asphalt binders through three different characterization methods and analysis techniques. In this research effort, a promising physico-chemical relationship is developed between number average molecular weight and width of relaxation spectrum by utilizing the data from LVE characterization and the molecular weight distribution from LDMS. The relationship states that as the molecular weight of asphalt binders increase, they require more time to relax the developed stresses. Also, NLVE characterization was carried out at intermediate and high temperatures using three different tests, time sweep fatigue test, repeated stress/strain sweep test and Multiple Stress Creep and Recovery (MSCR) test. For the intermediate temperature fatigue tests, damage characterization was conducted by applying the S-VECD model and it was found that aged binders possess greater fatigue resistance than unaged binders. Using the high temperature LAOS tests, distortion was observed in the stress-strain relationships and the data was analyzed using a Fourier transform based tool called MITlaos, which deconvolves stress strain data into harmonic constituents and aids in identification of non-linearity by detecting higher order harmonics. Using the peak intensities observed at higher harmonic orders, non-linearity was quantified through a parameter termed as “Q”, which in future applications can be used to relate to asphalt chemical parameters. Finally, the last NLVE characterization carried out was the MSCR test, where the focus was on the scrutiny of the Jnrdiff parameter. It was found that Jnrdiff is not a capable parameter to represent the stress-sensitivity of asphalt binders. The developed alternative parameter Jnrslope does a better job of not only being a representative parameter of stress sensitivity but also for temperature sensitivity.<br>Dissertation/Thesis<br>Doctoral Dissertation Civil, Environmental and Sustainable Engineering 2018

The microstructure of polyolefins determines their macroscopic properties. Consequently, it is essential to predict how polymerization conditions will affect polyolefin microstructure. The most important microstructural distributions of ethylene/alfa-olefin copolymers made with coordination catalysts are their molecular weight (MWD), chemical composition (CCD), and comonomer sequence length (CSLD). Several mathematical models have been developed to predict these microstructural distributions; reliable techniques to estimate parameters for these models, however, are still poorly developed, especially for catalysts that have multiple site types, such as heterogeneous Ziegler-Natta complexes. Most commercial polyolefins are made with heterogeneous Ziegler-Natta catalysts, which make polyolefins with broad MWD, CCD, and CSLD. This behavior is attributed to the presence of several active site types, leading to a final product that can be seen as a blend of polymers made on the different catalyst site types. The main objective of this project is to develop a methodology to estimate the most important parameters needed to describe the microstructure of ethylene/alfa-olefin copolymers made with these multiple site-type catalysts. To accomplish this objective, we developed the Integrated Deconvolution Estimation Model (IDEM). IDEM estimates ethylene/alf-olefin reactivity ratios for each site type in two-steps. In the first step, the copolymer MWD, measured by high-temperature gel permeation chromatography, is deconvoluted into several Flory’s most probable distributions to determine the number of site types and the weight fractions of copolymer made on each of them. In the second estimation step, the model uses the MWD deconvolution information to fit the copolymer triad distributions measured by 13C NMR and estimate the reactivity ratios per site type. This is the first time that MWD and triad distribution information is integrated to estimate the reactivity ratio per site type of multiple site-type catalysts used to make ethylene/alfa-olefin copolymers. IDEM was applied to two sets of ethylene-co-1-butene copolymers made with a commercial Ziegler-Natta catalyst, covering a wide range of 1-butene fractions. In the first set of samples (EBH), hydrogen was used as a chain transfer agent, whereas it was absent in the second set (EB). Comparison of the reactivity ratio estimates for the sets of samples permitted the quantification of the hydrogen effect on the reactivity ratios of the different site types present in the Ziegler-Natta catalyst used in this thesis. Since 13C NMR it is an essential analytical step in IDEM, triad distributions for the EB and EBH copolymers were measured in two different laboratories (Department of Chemistry at the University of Waterloo, and Dow Chemical Research Center at Freeport, Texas). IDEM was applied to both set of triad measurements to find out the effect of interlaboratory 13C NMR analysis on reactivity ratio estimation.

CHARLES UNIVERSITY IN PRAGUE FACULTY OF SCIENCE DEPARTMENT OF BIOCHEMISTRY PRAGUE 2010 Supervisor: Doc. MUDr. Jiří Gallo, PhD. Supervisor-consultant: Prof. RNDr. Gustav Entlicher, CSc. Eva Zolotarevová Summary of PhD Thesis POLYETHYLENE WEAR PARTICLES AROUND TOTAL JOINT REPLACEMENTS - THEIR PROPERTIES, DISTRIBUTION AND POSSIBLE MECHANISM OF THEIR ADVERSE BIOLOGICAL EFFECTS PRAGUE 2010 The research project was supported by the Grant project of National research program II. (no. 2B06096) of the Czech Ministry of Education, Youth and Sports named "Observation and minimization of UHMWPE wear in joint replacements". Front-page picture: Polyethylene wear particle isolated from granuloma tissue surrounding total hip replacement; Electron microscope microphotograph; particle size app. 90 x 80 µm; retouched Eva Zolotarevová Introduction Introduction For many people all over the world a replacement with an implant of irreversibly damaged joint is often the only way how to come back to normal life without pain and mobility limitation. Nowadays, greater and greater requirements are asked of quality of all replacement components, especially in terms of quality of used materials. Biomechanical properties of hip and knee replacements have been already solved. The most often used materials for manufacturing joint...