Synthesis of Oligosaccharide-Based Block Copolymers with Pendent 蟺-Conjugated Oligofluorene Moieties and Their Electrical Device Applications

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• 作者：Han-Sheng Sun ; Yu-Cheng Chiu ; Wen-Ya Lee ; Yougen Chen ; Akira Hirao ; Toshifumi Satoh ; Toyoji Kakuchi ; Wen-Chang Chen
• 刊名：Macromolecules
• 出版年：2015
• 出版时间：June 23, 2015
• 年：2015
• 卷：48
• 期：12
• 页码：3907-3917
• 全文大小：679K
• ISSN：1520-5835

文摘

We report the synthesis and electric device applications of oligosaccharide-based diblock copolymers consisting of a maltoheptaose (MH) block and a poly(4-oligofluorenylstyrene) block (PStFl_n, n = 1 or 2), referred to as MH-b-PStFl_n. MH-b-PStFl_n was prepared by the Cu(I)-catalyzed click reaction of azido-terminated PStFl_n (PStFl_n-N₃), which was obtained from the azidation reaction of the bromo-terminated PStFl_n (PStFl_n-Br), with excess ethynyl-terminated MH in the THF/DMF mixture solvent. The resulting diblock copolymers self-assembled to spherical microdomains with sub-10 nm sizes in both bulk and thin film state after annealing process. Thereafter, the MH-b-PStFl_n thin film (鈭?0 nm) with the self-assembled nanoscale spherical aggregates was used as the charge storage layer for the pentacene-based field-effect transistor type memory devices. The MH-b-PStFl_n-based devices had the excellent hole mobility (0.25鈥?.52 cm² V^鈥? s^鈥?) and the high ON/OFF current (I_ON/I_OFF) ratio of 10⁷鈥?0⁸, of which the MH-b-PStFl₁-based one had the higher mobility than that of the MH-b-PStFl₂-based one because the pentacene crystal in the former device possessed the larger grain size and fewer boundaries. On the other hand, the MH-b-PStFl₂-based device showed a larger memory window than the MH-b-PStFl₁-based one because the stronger electron-donating effect of the difluorenyl group in MH-b-PStFl₂ increased the charge storage capability of its related device. All the memory devices showed a long-term retention time over 10⁴ s with the high I_ON/I_OFF ratio of 10⁶鈥?0⁸. Among these devices, the MH-b-PStFl₁-based device showed a good WRER endurance over 180 cycles. This work not only demonstrates the tunable electrical memory characteristics by adjusting the 蟺-conjugation length of the oligofluorenyl side chain in the polymer electret but also provides a promising approach for developing the next-generation 鈥済reen electronics鈥?using natural materials.