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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

The Observation and Study of ELP V5-120 Conformational Changes

Zhou, Qian 14 March 2013 (has links)
Elastin-like polypeptides (ELPs) consist of simple pentapeptide repeats which can be easily modified by substituting various amino acid residues to control its properties. This provides an ideal platform for studying hydrophobic collapse and secondary/tertiary structure formation. In this thesis, the collapse process of ELP was studied with differential scanning calorimetry (DSC). In DSC thermal cycling, a clear conformational transition was observed. Also, a transiently stable state of ELP V5-120 was noted and it was found that the formation of this state was related to temperature, ramping rate and stabilization time. To explain this, a conformational redistribution model is proposed in which there are two conformations in the ELP solution below its transition temperature. However, after the system is heated up and cooled back down, one of the conformations remains the same while the other one changes to two new conformations. After the conformational distribution is done, the ELP stays in a transiently stable state before gradually shifting back to the original, pre-heat-treatment state. Bi-Gaussian fitting was used to fit DSC response curve and monitor the changes of the different conformations in the system. The influence of ramping rate on the process of conformational redistribution was explained through the equilibration time at each temperature point through heating and cooling. Overall, the ELP V5-120 system is in a dynamic conformational equilibrium, and the equilibration time is much longer than earlier expectations.
2

Structure property relationship and thermal stability of organic photovoltaic cells

Motaung, David Edmond January 2010 (has links)
<p>In this thesis, regioregularpoly( 3-hexylthiophene) (rr-P3HT) polymer was used as a light absorption and electron donating material, while the C60 fullerene and its derivative [6,6]-phenyl C61-butyric acid methyl ester (PCBM) were used as electron acceptor materials. The effect of solvent to control the degree of mixing of the polymer and fullerene components, as well as the domain size and charge transport properties of the blends were investigated in detail using P3HT:C60 films. The photo-physical, structural and electrical transport properties of the polymer blends were carried out according to their ratios. A distinctive photoluminescence (PL) quenching effect was observed indicating a photo-induced electron transfer. In this thesis, the effect of solvents on the crystallization and interchain interaction of P3HT and C60 fullerene films were studied using XRD, UV-vis, PL, Raman and FTIR spectroscopy. The polymer blends formed with non-aromatic solvents exhibited an improved crystallinity and polymer morphology than that formed with aromatic solvents. An improved ordering was demonstrated in the polymer films spin coated from non-aromatic solvents. This indicates that the limited solubility of rr P3HT in a marginal solvent such as non-aromatic solvents can offer a strategy to obtain highly ordered crystal structures and lead directly to optimal morphologies on the films.</p>
3

Liquid crystalline polyesters prepared by flexible spacers with rigid spiral moieties: synthesis and characterization.

Zheng, Weideng 10 July 2001 (has links)
Different monomeric diols, with a central rigid FD unit connected with two aliphatic chains of various length, were prepared to react with aromatic mesogenic triad, TOBC. In this manner, thermotropic polyesters with possible low thermal transition temperatures (including Tmand Ti) and high solubility in organic solvent can be generated in view of the non-linear polymeric chain imposed by the rigid, bent FD moieties. In addition to the effect of the aliphatic chain length, polyesters of different molecular weight will be obtained by different synthesis approach (or fractionation of the resulting polyester product) and therefore, the influence of molecular weight on liquid crystalline properties can be evaluated.
4

Structure property relationship and thermal stability of organic photovoltaic cells

Motaung, David Edmond January 2010 (has links)
<p>In this thesis, regioregularpoly( 3-hexylthiophene) (rr-P3HT) polymer was used as a light absorption and electron donating material, while the C60 fullerene and its derivative [6,6]-phenyl C61-butyric acid methyl ester (PCBM) were used as electron acceptor materials. The effect of solvent to control the degree of mixing of the polymer and fullerene components, as well as the domain size and charge transport properties of the blends were investigated in detail using P3HT:C60 films. The photo-physical, structural and electrical transport properties of the polymer blends were carried out according to their ratios. A distinctive photoluminescence (PL) quenching effect was observed indicating a photo-induced electron transfer. In this thesis, the effect of solvents on the crystallization and interchain interaction of P3HT and C60 fullerene films were studied using XRD, UV-vis, PL, Raman and FTIR spectroscopy. The polymer blends formed with non-aromatic solvents exhibited an improved crystallinity and polymer morphology than that formed with aromatic solvents. An improved ordering was demonstrated in the polymer films spin coated from non-aromatic solvents. This indicates that the limited solubility of rr P3HT in a marginal solvent such as non-aromatic solvents can offer a strategy to obtain highly ordered crystal structures and lead directly to optimal morphologies on the films.</p>
5

Structure property relationship and thermal stability of organic photovoltaic cells

Motaung, David Edmond January 2010 (has links)
Philosophiae Doctor - PhD / In this thesis, regioregularpoly( 3-hexylthiophene) (rr-P3HT) polymer was used as a light absorption and electron donating material, while the C60 fullerene and its derivative [6,6]-phenyl C61-butyric acid methyl ester (PCBM) were used as electron acceptor materials. The effect of solvent to control the degree of mixing of the polymer and fullerene components, as well as the domain size and charge transport properties of the blends were investigated in detail using P3HT:C60 films. The photo-physical, structural and electrical transport properties of the polymer blends were carried out according to their ratios. A distinctive photoluminescence (PL) quenching effect was observed indicating a photo-induced electron transfer. In this thesis, the effect of solvents on the crystallization and interchain interaction of P3HT and C60 fullerene films were studied using XRD, UV-vis, PL, Raman and FTIR spectroscopy. The polymer blends formed with non-aromatic solvents exhibited an improved crystallinity and polymer morphology than that formed with aromatic solvents. An improved ordering was demonstrated in the polymer films spin coated from non-aromatic solvents. This indicates that the limited solubility of rr P3HT in a marginal solvent such as non-aromatic solvents can offer a strategy to obtain highly ordered crystal structures and lead directly to optimal morphologies on the films. / South Africa
6

Systémy energeticky úsporných budov / Systems of energy efficient buildings

Šlampová, Kateřina Unknown Date (has links)
The topic of this diploma thesis is systems of energy efficient buildings with a focus on the building envelope. The first theoretical part describes the quantities that we consider when designing the building envelope. The second half of the theoretical part is with reference to the experimental part of the thesis focused on a special type of vertical perimeter structure, namely walls with live vegetation installed from the outside of the structure. The second, practical part of this work, deals with the design of heating and hot water supply for a multifunctional building. The design is elaborated in two variants - heating by means of radiators in the first variant and in the second variant by means of floor heating for residential units of the solved building. The third part define an experiment, which had the task of comparing the measured quantities on two types of vertical perimeter structures, namely a structure with growing greenery from the outside and an identical structure only without a layer of greenery. At the same time, the task was to check the possible influence of the applied greenery on heat losses, and thus the design of the heating system.

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