신규 공액 고분자의 합성과 분석

Abstract

I designed and synthesized various conjugated copolymers for application of organic electronics and bio sensor. In the first part, control of energy level of electron donor polymer in organic solar cell was studied. Relation between electronic energy levels of electron donor and acceptor in organic solar cell is important factor which can influence performance of device. And these levels could be controlled by molecular engineering and optimized design. Herein, we present energy level control of silole-based polymer by attaching electron donation group-methoxy and electron withdrawing group-fluorine at the 3,6- position of dioctyl silafluorene in alternating copolymer of 2,7-silafluorene and 4,7-di(2-thienyl)-2,1,3-benzothiadiazole. The synthetic schemes for monomers -2,7-Bis(4′,4′,5′,5′-tetramethyl-1′,3′,2′-dioxaborolan-2′-yl)-3,6- dimethoxy-9,9-octylsilafluorene and 2,7-Bis(4′,4′,5′,5′-tetramethyl-1′,3′,2′-dioxaborolan-2-yl)-3,6-difluoro-9,9’-octylsilafluorene were designed for SUZUKI coupling polymerization and following intermediate molecules are synthesized. In the second part, a series of carbazole-based D-π-A copolymers was synthesized to investigate the influences of conjugation length and structural distortion on intramolecular charge transfer (CT) complexation between the donor (D) and acceptor (A) components. Carbazole presents two possible linkage sites, the 2,7- and 3,6-positions, which lead to significant differences in the thermal, photophysical, electrochemical, and electrical properties of the copolymers due to the positioning of the electron-rich nitrogen atom with respect to the copolymer backbone. The copolymers were comprehensively characterized using TGA, DSC, UV-Vis and photoluminescence spectroscopy, cyclic voltammetry, and DFT calculations. P(3,6C-DTBT), which was linked by a thienyl-2′,1′,3′-benzothiadiazole(DTBT) group at the 3,6-positions of the carbazoles so as to directly involve the electron-rich nitrogen atoms in conjugation, exhibited conjugation breaks in the middle of the carbazole units. The breaks resulted in a robust coplanar structure with an extraordinarily low oxidation potential and the ability to stably generate excitons, in contrast with P(2,7C-DTBT), which was linked by DTBT at the 2,7-positions of the carbazole. Two additional hexyl substituents at the 4-position of the thiophene in the DTBT groups of P(2,7C-HDTBT) and P(3,6C-HDTBT), which were identical to P(2,7C-DTBT) and P(3,6C-DTBT), respectively, except for the presence of the substituents, introduced steric hindrance between the D and A units, thereby breaking the coplanarity. Finally, the hole mobilities of the 3,6-carbazole-based copolymers were one order of magnitude higher than those of 2,7-carbazole-based copolymers, measured in hole-only devices. This result indicated the presence of stable radical cations and dications at the nitrogen atoms of the copolymers. This work deepens our understanding of carbazole-based D-π-A copolymers and provides insight into the design of novel materials for optoelectronic devices. In the third part, novel all conjugated diblock copolymers were synthesized and characterized. Even though several block copolymers connected with sp2 carbons, namely, all conjugated block copolymers have been synthesized, exhibiting distinctive optical and electrochemical characteristics, it is little attractive partially due to complicated synthetic schemes with low reaction yields and difficulty(or impossibility) in isolating pure block copolymers. Recently, it is successfully demonstrated that quasi living polymerization method using Grignard reagents (GRIM synthesis) is a promising method without synthetic difficulty of macro-monomers and purification problems to prepare all conjugated block copolymers. By emplolying GRIM method, we easily synthesized a class of all conjugated amphiphilic diblock copolymers applicable to bio theraphy diagnosis, especially, drug delivery system, and studied their phase separation behaviors and amphiphilic nature.