<p>The papermaking industry uses a large amount of starch each year, both as a wet-end additive and as a rheological modifier in surface sizing and coating colors. It is important to be able to reduce the amount of chemicals used in the papermaking and surface treatment process, to reduce costs and to make the process even more efficient. Interest in new high-performance starches is great. By using these new types of starches, improved recycling of barrier products may be obtained as well as a reduction in the use of synthetic sizing agents. The objectives of this work were to understand the behavior of temperature-responsive hydrophobically modified starches, where the solubility in water simply can be adjusted by temperature or by polymer charge, to improve the barrier properties, like the water vapor permeability, mechanical properties and water resistance (Cobb and contact angle) of papers surface sized by starch-containing solutions, and to investigate the potential for industrial use of these temperature-responsive starches. It was demonstrated that the temperature-responsive starches phase separate upon cooling and, depending on the charge density of the starch, a particulate precipitation or a gel-like structure was obtained. The starch with zero net charge showed a larger increase in turbidity than the starch with a cationic net charge, indicating that particulate precipitation is favored by a zero net charge and that the formation of a gel network is favored by charged starch molecules. Further, the starches formed inclusion complexes with surfactants, giving stabilization to the starches in the presence of surfactants. The net charge density of the starch and the charge of the surfactant determined whether or not an inclusion complex would form between them. Important mechanisms for the stability of the starch seemed to be formation of mixed micellar-like structures between the hydrophobic chain of the starch and the surfactant along the starch backbone in addition to formation of inclusion complexes between the starch and the surfactant. The hydrophobically modified starches showed higher hydrophobic surface character when applied to the paper surface above the critical phase separation temperature than with application at room temperature. Free films of the temperature-responsive starches showed good barrier against oxygen, but no barrier against water vapor. The mechanical properties decreased with addition of glycerol to the films.</p>

Ce travail avait pour principal objectif la synthèse de nouveaux systèmes amphiphiles à base de polysaccharides neutres (guar, hydroxyéthyl guar) ou chargés (acide hyaluronique), par greffage de groupements hydrophobes le long de la chaîne polysaccharidique. La stratégie de synthèse proposée pour ces dérivés amphiphiles repose sur des réactions d'éthérification en milieu basique des polysaccharides à partir d'éthers de glycidyle (époxydes) hydrophobes commerciaux (hexadécyl éther de glycidyle, phényl éther de glycidyle) et non commerciaux (Brij 56 époxyde, OP10 époxyde). Des dérivés de type Brij56® ont été sélectionnés en raison de leur structure chimique particulière, présentant un bloc oligo(éthylène glycol) (OEG) associé à une chaîne alkyle hydrophobe, susceptibles de conduire en milieu aqueux à des propriétés différentes par rapport à des dérivés alkylés classiques du fait de l'hydrophile du bloc OEG. Plusieurs conditions de greffage ont été testées et appliquées également à un dérivé de la cellulose disponible commercialement (hydroxyéthyl cellulose) afin de comparer l'efficacité des réactions en fonction de la nature du polysaccharide. L'analyse du comportement en milieu aqueux des polysaccharides hydrophobiquement modifiés par des mesures de viscosité met en évidence soit des augmentations de viscosité, soit des diminutions. Des analyses plus approfondies combinant la diffusion de la lumière et la spectroscopie de fluorescence en utilisant des sondes hydrophobes ont montré que de telles diminutions pouvaient être expliquées dans certains cas (acide hyaluronique) par la formation de particules de taille nanométrique. / The main aim of this work was the synthesis of new amphiphilic systems from neutral polysaccharides (guar, hydroxyethyl guar) or charged polysaccharides (hyaluronic acid), based on the grafting of hydrophobic groups along the polysaccharide backbone. The synthetic strategy proposed for these derivatives relies on etherification reactions of the polysaccharides in alkaline media from commercial hydrophobic alkyl glycidyl ethers (epoxides) (glycidyl hexadecyl ether, phenyl glycidyl ether) or non commercial glycidyl ethers (Brij 56 epoxide, OP10 epoxide). Derivatives of Brij 56 have been selected due to their peculiar chemical structure consisting of an oligo(ethylene glycol) (OEG) block associated to a hydrophobic alkyl chain, expected to lead to different properties in aqueous media compared to classical alkylated derivatives as a result of the hydrophilic character of the OEG block. Several grafting conditions have been tested and also applied to a commercially available cellulose derivative (hydroxyethyl cellulose) in order to compare the efficiency of reactions as a function of the nature of the polysaccharide. The analysis of the behavior in aqueous media of hydrophobically modified polysaccharides by viscosity measurements demonstrated either increases of viscosity or decreases. Deeper investigations combining dynamic light scattering and fluorescence spectroscopy showed that such viscosity decreases was related to some cases (hyaluronic acid) to the formation of nanosized particles.

The papermaking industry uses a large amount of starch each year, both as a wet-end additive and as a rheological modifier in surface sizing and coating colors. It is important to be able to reduce the amount of chemicals used in the papermaking and surface treatment process, to reduce costs and to make the process even more efficient. Interest in new high-performance starches is great. By using these new types of starches, improved recycling of barrier products may be obtained as well as a reduction in the use of synthetic sizing agents. The objectives of this work were to understand the behavior of temperature-responsive hydrophobically modified starches, where the solubility in water simply can be adjusted by temperature or by polymer charge, to improve the barrier properties, like the water vapor permeability, mechanical properties and water resistance (Cobb and contact angle) of papers surface sized by starch-containing solutions, and to investigate the potential for industrial use of these temperature-responsive starches. It was demonstrated that the temperature-responsive starches phase separate upon cooling and, depending on the charge density of the starch, a particulate precipitation or a gel-like structure was obtained. The starch with zero net charge showed a larger increase in turbidity than the starch with a cationic net charge, indicating that particulate precipitation is favored by a zero net charge and that the formation of a gel network is favored by charged starch molecules. Further, the starches formed inclusion complexes with surfactants, giving stabilization to the starches in the presence of surfactants. The net charge density of the starch and the charge of the surfactant determined whether or not an inclusion complex would form between them. Important mechanisms for the stability of the starch seemed to be formation of mixed micellar-like structures between the hydrophobic chain of the starch and the surfactant along the starch backbone in addition to formation of inclusion complexes between the starch and the surfactant. The hydrophobically modified starches showed higher hydrophobic surface character when applied to the paper surface above the critical phase separation temperature than with application at room temperature. Free films of the temperature-responsive starches showed good barrier against oxygen, but no barrier against water vapor. The mechanical properties decreased with addition of glycerol to the films.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第19234号 / 工博第4069号 / 新制||工||1628(附属図書館) / 32233 / 京都大学大学院工学研究科分子工学専攻 / (主査)教授 渡辺 宏, 教授 古賀 毅, 教授 金谷 利治 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

The effect of hydrophobically modified hyaluronan on surfactants aggregation has been studied in this master’s thesis. The value of critical micelle concentration of anionic surfactant SDBS (sodium dodecylbenzensulfonate), cationic surfactant CTAB (cetyltrimethylamonnium bromide) and nonionic surfactant Triton X-100 (octylphenol ethoxylate) was determined by fluorescence spectroscopy using pyrene probe. Aggregation behavior of surfactants was performed with addition of hydrophobically modified hyaluronan of two molecular weights (17 kDa, 206 kDa) in aqueous solution. The greatest influence of hydrophobized hyaluronan on aggregation behavior was observed in system with cationic surfactant CTAB. Stability of system containing cationic surfactant and hydrophobically modified hyaluronan was established through zeta potential. Last part of thesis deals with size determination using dynamic light scattering.

In-situ chain extension of polymers used in the formulation of artificial tears and mild gelation are techniques to increase the residence time of eye drops on cornea. In-situ chain extension also helps to control the stability of ophthalmic emulsions both in the bottle and in the tear film. In this work, the interaction of hydrophobically modified guar and tear proteins as a method of polymer chain extension and mild gelation has been evaluated. Guar and its derivatives have been found to be very effective for ophthalmic applications. The ideal guar gelation agent is the one that turns on the gelation upon introduction onto the eye and that gelation chemistry is biocompatible and biodegradable. Controllable gelation is desirable to have relatively low viscosity eye drops for easy application and the drops form weak gels in the eye. One recent strategy to cure dry eye disease is to include emulsions in lubricant eye drops. The idea is to supplement the natural lipid layer on the exterior surface of the tear film. Formulating artificial tear emulsions is relatively complicated and must satisfy conflicting criteria. Emulsion droplets should be stable over the period of their shelf life without creaming or aggregate formation. On the other hand, in the tear film the emulsion droplets must cream fast enough and deposit onto the water/lipid film interface on the exterior surface of the tear film. Thus, the emulsion must be stable but not too stable. Initially, science-based design rules were proposed for the development of future generations of lubricant eye drops. The effect of guar molecular weight and concentration on emulsion stability was evaluated. According to the concentration-molecular weight plot, polymer solutions can be divided into stable and unstable regions. They are defined based on the critical flocculation concentration (CFC) and critical viscosity concentration (C*). Inverted QCM-D has been proposed as a simple and fast method to define the stability of oil in water emulsion systems. This technique is a promising alternative for time consuming conventional creaming experiments. Low molecular weight guar can be optimized to out-perform high molecular weight guars without the complications of formulating eye drops with high molecular weight polymers. Hydroxypropyl guar samples were oxidized and modified with linear alkyl amines to give a series of hydrophobically modified guars (MGuars). Lysozyme and human serum albumin (HSA), natural tear proteins, are able to extend the effective chain length of MGuar through polymer/protein complex formation. Hydrophobic modifications on guar enable efficient interaction with proteins, through their mutual hydrophobic characteristics. The interaction of proteins with various alkyl chain lengths, degrees of substitution and a range of molecular weights were examined. Binding and rheological measurements were employed to evaluate the interactions efficiency. Our results suggest that higher degrees of substitution and longer alkyl chain length give higher viscosity values. Lowering molecular weight allows for higher concentration, while keeping the initial viscosity constant. Higher viscosity was achieved as the chain extension occurred. The influence of hydrophobic modification and molecular weight variation on lubrication behavior of MGuars has also been determined. Hydrophobic modification enhanced the lubrication between hydrophobic surfaces. However, saturation of hydrophobes with protein abolished the lubricity. / Thesis / Doctor of Philosophy (PhD)

Made available in DSpace on 2014-12-17T15:41:48Z (GMT). No. of bitstreams: 1 Bruna Vital de Lima_DISSERT.pdf: 1526229 bytes, checksum: 072431027e1aefba9f0023f2f514ae5f (MD5) Previous issue date: 2010-02-02 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / The hydrolysis reaction in alkaline conditions of the commercial polymer poly(acrylamide-co-metacrylate of 3,5,5-trimethyl-hexane) called HAPAM, containing 0.75 % of hydrophobic groups, was carried out in 0.1 M NaCl and 0.25M NaOH solutions, varying the temperature and reaction time. The polymers were characterized by 1H and 13C Nuclear Magnetic Resonance (NMR), Elemental Analysis and Size Exclusion Chromatography (SEC). The values of the hydrolysis degree were obtained by 13C NMR. The viscosity of HAPAM and HAPAM-10N-R solutions was evaluated as a function of shear rate, ionic strength and temperature. At high polymer concentration (Cp), the viscosity of HAPAM solutions increased with the ionic strength and decreased with the temperature. The viscosity of HAPAM-10N-R solutions increased significantly in distilled water, due to repulsions between the carboxylate groups. At high Cp, with the increase of ionic strength and temperature, occurred a decrease of viscosity, due to mainly the high hydrolysis degree and the low amount of hydrophobic groups. These results indicated that the studied polymers have properties more suitable for the application in Enhanced Oil Recovery (EOR) in low salinity and moderate temperature reservoirs / A rea??o de hidr?lise em meio alcalino do pol?mero comercial poli(acrilamida-co-metacrilato de 3,5,5 trimetil-hexano) denominado HAPAM, contendo 0,75 % de grupos hidrof?bicos, foi realizada em solu??es de NaCl 0,1 M e NaOH 0,25 M, variando a temperatura e o tempo reacional. Os pol?meros foram caracterizados por Resson?ncia Magn?tica Nuclear (RMN) de 1H e 13C, An?lise Elementar e Cromatografia de Exclus?o por Tamanho (SEC). Os valores do grau de hidr?lise foram obtidos por RMN 13C. A viscosidade das solu??es de HAPAM e HAPAM-10N-R foi avaliada em fun??o da taxa de cisalhamento, for?a i?nica e temperatura. ? alta concentra??o polim?rica (Cp), a viscosidade das solu??es de HAPAM aumentou com a for?a i?nica e diminuiu com o aumento da temperatura. A viscosidade das solu??es de HAPAM-10N-R aumentou significantemente em ?gua destilada, devido ?s repuls?es entre os grupos carboxilato. ? alta Cp, com o aumento da for?a i?nica e da temperatura ocorreu uma diminui??o da viscosidade, devido, principalmente, ao alto grau de hidr?lise e ? baixa quantidade de grupos hidrof?bicos. Estes resultados indicaram que os pol?meros estudados apresentam propriedades mais adequadas para aplica??o na recupera??o avan?ada de petr?leo (EOR) em reservat?rios de baixa salinidade e temperatura moderada