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Investigation and Construction of Self-oscillating SystemsWang, Guanqun 2010 May 1900 (has links)
Self-oscillating reactions have been widely observed and studied since the last century because they exhibit unique behaviors different from the traditional chemical reactions. Self-oscillating systems, such as the Belousov-Zhabotinsky (BZ) reaction, oxidation reaction of CO on single crystal Pt, and calcium waves in the heart tissue, are of great interest in a variety of scientific areas. This thesis contributes to the understanding of wave transition in BZ reaction, and to possible applications of non-equilibrium behaviors of polymer systems. In BZ reaction, two types of wave patterns, target and spiral, are frequently observed. The transition from one to another is not fully understood. Hence, a systematic investigation has been performed here to investigate the mechanism by which heterogeneity affects the formation of wave patterns. A BZ reaction catalyst was immobilized in ion exchange polystyrene beads to form active beads. Then active and inactive beads with no catalyst loading were mixed together with various ratios to achieve various levels of heterogeneity. In the same reaction environment, different wave patterns were displayed for the bead mixtures. We observed a transition from target patterns to spiral patterns as the percentage of the active beads in the beads mixture decreased. The increase of the heterogeneity led to wave pattern transition. Heterogeneity hindered the propagation of target waves and broke them into wavelets that generated spiral waves. In an effort to develop practical applications based on non-equilibrium phenomena, we have established a novel drug delivery system. A proton generator Zirconium Phosphate (ZrP) was imbedded inside a pH sensitive polymer matrix, poly acrylic acid (PAA). Through the ion exchange with sodium cation (Na+), ZrP generates protons to control the swelling/shrinking behaviors of PAA. The drug encapsulated in the matrix can be released in a controlled manner by adjusting the supply of Na+. This system might be developed into vehicles to deliver drugs to specific targets and release at a proper time. This new delivery technique will be convenient and significantly increase the efficiency of medicines.
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Integrated motions of light driven molecular motors at macroscopic scale / Mouvements macroscopiques intégrés de moteurs moléculaires activés par la lumièreLi, Quan 03 February 2015 (has links)
Dans la nature, des moteurs moléculaires tells que l'ATP synthase ou la kinésine peuvent consommer de l'énergie pour générer du mouvement et ainsi assurer des fonctions essentielles comme le transport ou la synthèse de molécules. La préparation de moteurs artificiels capables de fournir un travail à différentes échelles est un défi important pour les chimistes. Dans ce travail, nous avons conçu et synthétisé de manière stéréosélective un moteur moléculaire unidirectionnel et hautement fonctionnalisé à l'échelle du gramme. La fonctionnalisation orthogonale du moteur permet de l'intégrer dans des matériaux polymères. Grâce à une réaction de "click" réalisée sous différentes conditions de dilution, nous avons pu obtenir soit une macromolécule bicyclique en forme de 8 soit un gel de polymers dont les moteurs constituent les points de réticulation. Sous irradiation UV, les moteurs tournent ce qui enroule les chaines de polymers. Pour le bicycle, la taille caractéristique de la macromolécule diminue tandis que la morphologie évolue vers une pelote étirée. Dans le cas du gel, suite à la rotation des moteurs, l'enroulement des chaines conduit à une contraction du gel de l'ordre de 80% en volume. C'est le premier exemple d'intégration de mouvements moléculaires hors équilibre résultant en une réponse observable à l'échelle macroscopique. Ce travail ouvre des perspectives intéressantes dans le domaine des nanotechnologies ainsi que dans celui de l'énergie. / Natural molecular motors such as ATP synthase, myosin, kinesin and dynein can convert conformationalchanges, due to chemical energy input, into directed motion for catalysis and transport. Preparing artificial molecular motors and making them work at different scales (from nano to macroscopic scale) have been long-term challenges. Herein we designed and synthesized a light driven rotary molecular motor in highly enantiopure form and in gram scale. This motor is featured by two orthogonal functionalities on its upper and lower part, allowing its further integration into polymeric materials. By performing click reaction under different concentration conditions, either an eight shaped motor-polymer conjugate or a gel containing motors as reticulation units could be obtained. Upon UV irradiation, the polymer chains could be entangled due to the rotation of this motor. For eight shaped polymer, the dimension was changed towards smaller dimension, and the morphology was changed from cycle to collapsed coils (spherical or more elongated). For the gel, due to the twisting of polymer chains induced by the rotation of the motor, it could be contracted significantly (80 %) compared with its original volume. The integration of machines which display motions out of equilibrium at nanoscale to movement in the macroscopic world which is extensively used in natural systems will open very interesting prospects in nanotechnology for further developments.
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