Ce travail, en amont du projet WIBIO portant sur le développement de films d’emballage alimentaire partiellement biosourcés, a pour but de caractériser et de comprendre les relations entre la structure et les propriétés thermomécaniques de l’amidon et du Gaïalène, mélange à base d’amidon et de polyoléfine. L’étude des amidons natifs souligne l’influence de l’eau sur leurs propriétés thermiques ainsi que la difficulté de les déstructurer sans induire de recristallisation. La caractérisation thermomécanique des amidons thermoplastiques plastifiés par l’eau ne permet pas de trancher entre les effets de masse moléculaire et de composition. Malgré un taux d’étirage élevé, aucun phénomène significatif d’orientation n’a cependant pu être mis en évidence. L’étude de tri-esters d’amidon, obtenus par substitution des groupements OH de l’amidon par des chaînes alkyles, montre que ces matériaux hydrophobes présentent une structure en feuillets dans laquelle les chaînes amylacées sont confinées dans des zones planaires séparées par les chaînes alkyles. La composition des amidons n'affecte pas les propriétés thermiques. La longueur des chaines alkyles induit par contre une réduction drastique de la ductilité, dès lors qu'elles ont la capacité de cristalliser. Le suivi par diffraction X in-situ de l’évolution structurale sous étirage des matériaux amorphes révèle une orientation progressive des chaînes amylacées selon l’axe de sollicitation durant l’étirage. / The present work, carried out in the frame of the WIBIO project which deals with the development of partly bio-based food packaging, is aimed at understanding relationships between structure and thermo-mechanical properties of starch based films.The study of native starches underlines the influence of water on the thermal properties and the difficulty to achieve destructuration without promoting recrystallization. Mechanical characterization of water plasticized thermoplastic starch does not enable to conclude on the respective influences of molar mass and composition. Also, in spite of achieving a fairly large draw ration, no significant orientation phenomenon is revealed from X-ray analysis. Structural investigations of starch triesters, obtained by full substitution of starch OH groups by alkyl chains, show that these hydrophobic materials display a sheet-like structure in which the amylaceous chains are confined in planar zones separated by extended alkyl chains. Starch composition has no influence on the thermal properties of these materials. On the contrary, alkyl chain length induces a drastic reduction in drawability, as soon as the chains are long enough to interpenetrate and crystallize. In-situ X-ray diffraction experiments reveal the gradual orientation of amylaceous chains towards the draw axis during the stretching of fully amorphous compositions.

M.Sc. / Molecules containing a long saturated carbon chain are present in many natural and commercial products. Due to the conformational flexibility of the carbon chain, different molecular conformations of these molecules are possible resulting in polymorphism. The crystal structure of a material greatly influences its chemical and physical properties, leading to different properties for different polymorphs. Designing materials with specific properties requires the understanding of the underlying fundamental parameters and forces influencing the packing of molecules in the crystal. A thorough literature study was conducted to determine the crystallographic research that has been done long chain compounds. Not only did this literature study lead to the identification of possible research fields, but also provided a solid background concerning the crystallographic behavior of these systems. In this project we investigated the polymorphism of simple molecules containing a saturated carbon chain with seventeen or eighteen carbons. Two systems are investigated namely n-alkylammonium halides and esters of fatty acids. By varying crystallization conditions different polymorphs of each compound can be obtained. Various experimental techniques were employed to shed light on the structure and packing of the long chain molecules in the different polymorphs. The crystal structure of the low temperature polymorph of n-octadecylammonium bromide was determined, as well as the cell dimensions of the low temperature form of noctadecylammonium chloride. The unit cell dimensions of n-octadecylammonium iodide monohydrate was also determined. The structures of the methyl and ethyl esters of noctadecanoic acid and the symmetrical -ester heptadecyl-heptadecanoate was investigated. In this project a young, dynamic research field was investigated. This led to the identification of other possible fields of study. Because there are not many reports in the literature on the crystallographic characteristics of these compounds, the evolving of the project required a lot of creativity.

An attempt has been made to develop a model for predicting the course of an asymmetric alkylation. Thus, by considering the influence of an asymmetric center upon a reaction center located in an adjoining plane, a preferred conformation of the intermediate anion is selected. This conformation is used to predict the stereochemistry of the product. The model correctly predicts the stereochemical result of several reactions known in the literature. The (-) isobornyl and (-) menthyl esters of 2-methylbutyric acid were alkylated with 1-bromobutane in 42% yield. Both of the alkylated esters were reduced with lithium aluminium hydride and the 2-methyl-2-ethylhexan-1-ol isolated by gas-liquid chromatography was shown to be optically inactive. The lack of an observable rotation does not permit a critical evaluation of the proposed model in these instances. The major impurities present in the alkylation of the aforementioned esters, namely the n-butyl ether of the optically active alcohol, have been identified by independent syntheses. / Science, Faculty of / Chemistry, Department of / Graduate

A series of isomeric, six-membered, cyclic phenyl phosphate esters has been obtained by column chromatography of the mixtures of isomers obtained by reaction of phenyl phosphorodichloridate with appropriate 1,3-diols. The conformational analysis of the isomers was undertaken using both ¹ʜ and ³¹p n.m.r.. The basic conformation of the 2 oxo-2-phenoxy-1,3,2-dioxaphosphorinane ring system is that of a "flattened-chair". The thermodynamic free energy difference between "chair" conformations is sufficiently large for the basic ring to exist essentially in one favoured conformation, rationalized to have an axial phenoxy substituent. The stereospecific nature of Jpoch has been confirmed by using ¹ʜ n.m.r. to determine conformations. Long-range, ⁴J, ³¹p- ¹ʜ coupling constants have been found to be stereospecific in nature and useful in facilitating assignment of conformations for methyl-substituted-2-oxo-2-phenoxy-l,3,2-dioxaphosphorinanes. Similar ring systems having different substituents at phosphorus have been studied and the conformations of these derivatives are seen to differ depending on the nature of the phosphorus substituent. The conformation of a cyclic nucleotide has been determined from its ³¹p n.m.r. spectrum. The use of computer programming techniques and hetero-nuclear double resonance techniques, greatly facilitated the analysis of the n.m.r. spectra discussed. An interesting deceptively-simple type of ABX n.m.r. spectrum has been found for many of these cyclic phosphate derivatives and the explicit analysis of this system is presented. / Science, Faculty of / Chemistry, Department of / Graduate

D.Sc. (Chemistry) / Please refer to full text to view abstract

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A series of macrocyclic ether-esters has been prepared by treating various glycols with adipoyl chloride and various substituted malonyl, succinyl and glutaryl chlorides. The prepared compounds include: 15-ethyl- and 15-phenyl-1,4,7,10,13-pentaoxacyclohexadecane-14,16-dione (5 and 6); 15-methyl-, 15-phenyl-, cis-cyclohexo-[o]-, and benzo-[o]-1,4,7,10,13-pentaoxacycloheptadecane-14,17-dione (7-10); trans,trans-1,4,7,10,13,18,21,24,27,30-decaoxacyclotetratriacontane-15,32-diene-14,17,31,34-tetraone (11); 1,4,7,10,13-pentaoxacyclooctadecane-14,18-dione (12); 15,15,16,16,17,17-hexafluoro- and 16-methyl-1,4,7,10,13-pentaoxacyclooctadecane-14,18-dione (13 and 14); 1,4,7,10-tetraoxacyclohexadecane-11,16-dione (15); and 1,4,7,10,13-pentaoxacyclononadecane-14,19-dione (16).

Reactions of different alcohols with 2-hydroxy - 1- trifluoromethyl -1,2,2-trifluoroethanesulfonic acid sultone were studied. Six new esters were prepared: C6F5OC(O)CF(CF3)SO2F, CH3CH2OC(O)CF(CF3)SO2F, CF3CH2OC(O)CF(CF3)SO2F, (CF3)2CHOC(O)CF(CF3)SO2F, CH2=CHCH20C(O)CF(CF3)SO2F, (CH2OC(O)CF(CF3)SO2F)2. Analytical data, infrared, nmr and mass spectra are presented supporting the proposed structures for these new compounds.

No description available.

No description available.