| Summary: | 博士 === 國立交通大學 === 應用化學系碩博士班 === 105 === The thesis consists of two major parts: the first deals with the structure of semi-crystalline donor (D) - acceptor (A) conjugated copolymer (PTh4FBT) by X-ray 2D-fiber diffraction and the second deals with X-ray coherent diffraction imaging (XCDI) of single particle assembly (liposome) using X-ray free electron laser. In order to develop the sense for structure model building, first more than 40 crystal lattices of conjugated oligomers to identify the morphological influence of each building block on the D-A molecules are summarized. These lattice structures reveal not only the packing preferences of the conjugated oligomers but also the conformational disorder in the lattices. The presence of this disorder in slowly grown crystals implies that attaining total long-range conformational order is challenging for D-A oligomers, which are structurally complicated and readily distorted. The single crystal structure of Th2FBT confirms the low conformational preference of the FBT containing molecule. Since crystallization process does not assist to unify the conformation of Th2FBT, both intrachain conformation and interchain c-shifts in the crystalline state of PTh4FBT have to be scrutinized. Through comparing the X-ray 2D-fiber diffraction pattern of PTh4FBT, and the simulated patterns generated from Cerius2 molecular modeling, it was found that the diffration pattern generated from the lattice containing PTh4FBT with anti-conformation and limited interchain c-shift matches best with the experimental one. In the XCDI experiments, individual liposome particles in water, with or without inserted doxorubicin nanorods were studied at SACLA. In spite of the low X-ray scattering cross section, the diffracted intensity of blank (drug-free) liposomes was sufficient for spatial reconstruction to yield quantitative structural information. When the particles contained doxorubicin, the complex structural parameters of the nanorods can be clearly revealed. Finally, the simulation of single molecule DNA is performed. We show that the current photon flux at SACLA needs to be increased by 108 time in order to reach atomic resolution of the XCDI image.
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