Synthesis and Characterization of Two-dimensional Thiophene-Based Conjugated Polymers and Macromolecules

• Main Authors: Chun-Yao Wang, 王俊堯
• Other Authors: Lee-Yih Wang
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/94275883293173280004

碩士 === 國立臺灣大學 === 高分子科學與工程學研究所 === 101 === This research focuses on two topics, whichincludes the synthesis and characterization of two-dimensional conjugated polymers and macromoleculesfor high-efficiency bulk-heterojunction solar cells application. At first,two-dimensional conjugated polymers, P(v-3EHT-BT) and P(h-3EHT-BT) in which a bithiophenewas employed as comonomer to reduce the crowdedness of side chains, and terthiophene units were bonded to the backbone vertically and horizontally, respectively, were designed, synthesized and characterized. The molecular structure of these polymers and the related intermediates were characterized using nuclear magnetic resonance(NMR) and mass spectrometry. Moreover, UV-visible spectroscopy was applied to examine how the side-chain architecture affects the light absorption properties of the polymers. Electrochemical analysis together with AC2 were used to determinethe band gap and energy levels, thermogravimetry analyzer (TGA) and differential scanning calorimeter (DSC) to investigate the thermal properties, and, finally, X-ray diffraction(XRD) spectrometer to study the crystallinity of the polymers. We found that the conjugation length of the side chains in P(v-3EHT-BT) is longer than that in P(h-3EHT-BT), causing the red-shift of the absorption band of side chains to visible region and the overlap with the absorption band of main chain that results in a substantial increase in the extinction coefficient of the polymer. Conversely, the thin film of P(h-3EHT-BT) possesses a strong X-ray diffraction peak, indicating the formation of orderly packed polymer chains, however, no such crystallization peak was observed for P(v-3EHT-BT). In the second topic, following the conclusion of the first part, i.e. horizontal orientation of side-chains along the polythiophene backbone can effectively promotethe formation of polymer crystallites, a series of two-dimensional conjugated macromolecules in which two linear conjugated moieties are connected by a vinyl bridge in parallel, was designed and developed. Similarly, the structure of these molecules were characterized by NMR, mass spectrometry and elemental analysis; their optical, electronic and thermal properties as well as crystallization behavior were investigated by UV-visible spectroscopy, electrochemical analysis, AC2, TGA, DSC, and XRD. Experimental results demonstrates all molecules developed herein have distinct crystallization peaks. More importantly, the absorption spectra, band-gap and energy levels of the molecules can be fine-tuned by controlling the conjugation length of two sides or by introducing proper electron-withdrawing units.