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551.41 --- 551.25 --- Theses

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It is often not realised that a wide variety of intermediate phases can be foundbetween the solid state and liquid phase. The liquid-crystalline phase is oneof the possible states of matter that a substance can take on. Hence, liquidcrystals are sometimes referred to as the fourth state of matter. The fact thatliquid crystals combine the anisotropic properties of the crystalline solidstate and the liquid-like nature of the isotropic liquid phase has renderedthem of great interest for technological applications. Among them the liquidcrystal display (LCD) has proven to be one of the most important and profitable ones. Ionic liquid crystals are soft, ordered materials that consist solely of ions. Closely related to ionic liquid crystals are the so-called ionic liquids. These low-melting salts have received a great deal of attention thanks to their negligible vapour pressure. The advances made in the field of ionic liquids has greatly influenced liquid crystal research. One of the advantages of the incorporation of ionic species is that their physicochemical properties can be tuned straightforwardly by the proper choice of cations and anions. Until recently, most studies on ionic liquid crystals have been restricted to a limited number of cationic cores.Imidazolium and pyridinium salts have been by far the most popular classes of ionic liquid crystals. It has been realised that variation of the type of cationic core is a very valuable approach for tuning the mesophase behaviour of these compounds. In this PhD dissertation new ionic liquid crystals based on N-heterocyclic cores have been investigated.In the first part the thermal behaviour of the first series of ionic liquid crystals based on piperidinium, morpholinium and piperazinium has been investigated. These compounds showed a rich mesomorphism, including highly ordered smectic phases (crystal smectic T and E phases), disordered smectic A phases and hexagonal columnar phases. The formation of highly ordered smectic phases was attributed to the presence of a localised positive charge on the nitrogen atom. It was shown for the piperidinium core that a minimum alkyl chain length of fourteen carbon atoms was necessary in order to induce mesomorphism. In general, both the cationic core and the anion type have a great influence on the mesomorphic behaviour. For the piperidinium compounds, only high-ordered crystal smectic phases were observed (except for the dodecylsulfate salt of the piperidinium compound with two tetradecylchains, which showed a hexagonal columnar phase). For the piperazinium compounds, only disordered smectic A phases were observed (except for the dicyclohexylsulfosuccinate salt, which also showed a high-ordered crystalsmectic phase below the smectic A phase). The best results were obtained for the morpholinium compounds, which all showed liquid crystal phases (except the bistriflimide salt). For the large sulfosuccinate salts of the morpholiniumcompounds, hexagonal columnar phases were observed at room temperature and were stable over a wide temperature range. Via powder X-ray diffraction and molecular modelling, it was shown that via self-assembly of three molecules, a disc-like shape is obtained, which is suitable for the formation of hexagonal columnar phases. Secondly, we tried to give a better insight in the driving forces for mesophase formation of (iso)quinolinium salts. Although N-alkylquinolinium and N-alkylisoquinolinium salts with bromide, tetrafluoroborate, hexafluorophosphate, dodecyl sulphate and sulfosuccinate anions exhibit smectic A phases as many other ionic liquid crystals, the thermal behaviour of these ionic liquid crystals is atypical in the sense that these compounds only exhibit liquid-crystallinity when the alkyl chain is very long. However, for the analogue with a short alkyl chain a smectic A phase was observed at room temperature, given a proper choice of the anion was made. It can be concluded that the key factor for mesophase formation in these ionic liquid crystals is a delicate equilibrium between microphase segregation and the relative size of areas occupied by incompatible units (aliphatic/ionic) at the interface rather than the number of carbon atoms present in the alkyl chain.The third part of this PhD dissertation concerned the synthesis and characterisation of a new class of ionic liquid crystals based on the 1,10-phenanthrolinium core. The combination of an organic cation (with or without alkyl chains) with a dialkyl sulfosuccinate anion is proposed as a facile and general approach for the synthesis of ionic liquid crystals. The 1,10-phenanthrolinium dioctylsulfosuccinate salts can be considered to be genuine ionic liquids according to the definition of ionic liquids being organic salts with a melting point below 100 °C. Although the melting points of the dodecyl sulphate salts are much higher than those of the dioctylsulfosuccinate salts, an interesting feature of the dodecyl sulphate salts is the presence of the highly ordered smectic E phase (E phase). The molecular packing of the latter in the smectic E phase was elucidated using the data obtained from powder X-ray diffraction.Although the compounds exhibit a greenish or whitish fluorescence in the solid state and dissolved in methanol, the fluorescence intensities are weak at room temperature. The differences in the positions of the emission bands and quantum yields can be related to the nature of the substituents on the 1,10-phenanthroline ring and to the planarity of the heterocyclic ring. Given the high temperatures at whichmost mesophases occur, no measurable fluorescence is expected for the compounds in the mesophase. In the last part a slightly different approach towards the design ionic liquid crystals was developed. Here, a cationic imidazolium core was incorporated into the rigid part of the mesogen. In order to lower the transition temperatures of these aromatic, conjugated structures, the following strategies were applied: (i) exchange of the anion, (ii) variation of the end standing alkyl chain length, (iii) the use of laterally attached alkyl chains and (iv) the introduction of a fatty acid chain. It was shown that the presence of a charged moiety is crucial for the formation of liquid-crystalline phases. All the imidazolium iodides showed smectic A phases, as well as the tetrafluoroborate salt. For the latter, the widest mesophase range was observed. On the other hand, exchange of the halide anion with a bis(trifluoromethylsulfonyl)imide or a dodecyl sulphate anion did not result in mesomorphic compounds. Probably these anions are too bulky to be incorporated in a structured liquid-crystalline organisation. For the iodide salts, the influence of the alkyl chain length was investigated. It seems to be that a certain amount of fluidity, i.e. alkyl chains, is needed to form stable, enantiotropic mesophases. In contrast to what was found in earlier investigations, the introduction of a fatty acid (oleyloxy) did not result in a sharp decrease of the melting temperatures. Moreover, the synthesised liquid crystals proved to be good chromophores in solution. The quantum yield of the decyloxy-subsituted derivatives were significantly higher than similar ionic copolymers based on imidazolium. Compared to the neutral precursor a significant bathochromic shift was observed, which was attributed to the elongation of the conjugated rigid core.

academic collection --- 544.25 --- Liquid crystals --- Theses

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33.25 thermodynamics. --- Binaire systemen. --- Ontmenging.

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347.25 --- Bijzondere zakelijke rechten: vruchtgebruik, erfpacht, opstal, woonrecht --- 347.25 Bijzondere zakelijke rechten: vruchtgebruik, erfpacht, opstal, woonrecht --- #RBIB:gift.2005 --- Theses

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Le consentement peut-être conceptualisé de différentes manières : le consentement en tant qu’état interne, le consentement en tant qu’accord explicite d’entreprendre une action et le consentement en tant que comportement que quelqu’un interprète comme une volonté (Muehlenhard et al., 2016). Notre étude recherche les représentations qu’ont les personnes entre 18 et 25 ans du consentement et cela à travers l’administration d’un questionnaire mesurant les représentations du consentement. Nous pensons qu’il y aura une différence de représentations entre les filles et les garçons. Les comportements utilisés afin d’indiquer le consentement seront également investigués, ainsi que l’effet du sexe et de l’orientation sexuelle sur ces comportements. Des vignettes cliniques seront administrées, dans le but de savoir si une confirmation du consentement est nécessaire pour certains actes, mais également si cette confirmation semble plus nécessaire en fonction de la cible. Nous pensons que les femmes, de manière générale, jugeront une confirmation du consentement comme étant plus nécessaire que les hommes.
Nous cherchons plus particulièrement à mettre en lumière la résolution de conflit positive, ainsi nous cherchons si elle a un lien avec les représentations du consentement. Nous pensons qu’une résolution de conflit positive favoriserait la négociation du consentement au sein du couple. 
Nous n’avons pas trouvé d’effet du sexe sur les représentations lorsqu’elles sont mesurées par la Sexual Consent Scale-Revised. Cependant, il y avait un effet du sexe sur les vignettes cliniques. Ainsi, les femmes jugeraient de manière générale qu’une confirmation du consentement est plus importante que les hommes. La confirmation du consentement semblerait plus importante pour tout le monde lorsque la cible est une femme. 
Nous avons trouvé des différences dans les fréquences d’utilisation de certains comportements pour le genre et pour l’orientation sexuelle. Il y avait cependant plus de similarités que de différences. 
Nous avons observé un lien entre la résolution de conflit positive et les représentations du consentement. Cependant, ce lien allait dans le sens opposé de notre hypothèse. Ainsi, au plus les personnes feraient preuve de stratégies de résolution de conflit au sein de leur couple, au moins leurs représentations du consentement seraient favorables. 
Le consentement n’a pas été pris en compte pendant longtemps, cependant il a été mis en lumière ces dernières années, notamment avec la campagne de prévention #BalanceTonPorc, qui a été l’une des plus marquantes de ces dix dernières années. Nous avons postulé que nos résultats ont probablement été influencés par les campagnes de prévention de ces dernières années.

Consentement - Résolution de conflit - 18-25 ans - Représentation consentement --- Sciences sociales & comportementales, psychologie > Traitement & psychologie clinique