Highly Coplanar Polythiophenes with –C≡CR Side Chains: Self-Assembly, Linear and Nonlinear Optical Properties, and Piezochromism
作者:Takakazu Yamamoto、Takao Sato、Takayuki Iijima、Masahiro Abe、Hiroki Fukumoto、Take-aki Koizumi、Motoaki Usui、Yoshiyuki Nakamura、Takehiko Yagi、Hiroyuki Tajima、Taku Okada、Shintaro Sasaki、Hideo Kishida、Arao Nakamura、Takashi Fukuda、Akira Emoto、Hirobumi Ushijima、Chisato Kurosaki、Hiroshi Hirota
DOI:10.1246/bcsj.82.896
日期:2009.7.15
Self-assembly of polythiophenes with –C≡CR (R = alkyl, phenyl, etc.) side chains has been investigated. Seven new polymers consisting of head-to-head and tail-to-tail 2,2′-bithiophenes with –C≡CR side chains were synthesized. The new polymers include alternating copolymers between bithiophenes with –C≡C–alkyl side chains and thiophene and those between bithiophenes with –C≡C–alkyl side chains and 2,2′-bithiophene. The polythiophene main chain is considered to be coplanar because of the absence of steric repulsion between the main chain and the –C≡CR side chain. Single-crystal X-ray crystallography and DFT calculations indicated that the head-to-head- and tail-to-tail-2,2′-bithiophenes with –C≡CR side chains were coplanar. The polythiophenes with –C≡CR side chains showed a strong tendency to self-assemble, and assumed edge-on alignment and side-on alignment on the surface of substrates. Self-assembly caused a decrease in the π–π* transition energy of the polymers by 0.3–0.4 eV. A copolymer of thiophene and dialkoxy-p-phenylene showed analogous self-assembly. The polythiophenes with –C≡CR side chains showed piezochromism, with a decrease in the π–π* transition energy by about 0.2 eV at 10 GPa. Head-to-head-P3(C≡C–Dec)Th with a –C≡C–decyl side chain gave a larger optical third-order nonlinear susceptibility χ(3) than regio-regular poly(3-hexylthiophene)s.
已研究了具有–C≡CR(R = 烷基,苯基等)侧链的聚噻吩的自组装。合成了由具有–C≡CR侧链的头对头和尾对尾2,2′-联噻吩组成的七种新型聚合物。这些新聚合物包括具有–C≡C–烷基侧链的联噻吩与噻吩之间的交替共聚物,以及具有–C≡C–烷基侧链的联噻吩与2,2′-联噻吩之间的交替共聚物。由于主链与–C≡CR侧链之间不存在空间排斥,因此聚噻吩主链被认为是共平面的。单晶X射线晶体学和DFT计算表明,具有–C≡CR侧链的头对头和尾对尾2,2′-联噻吩是共平面的。具有–C≡CR侧链的聚噻吩显示出强烈的自组装倾向,并在基底表面呈现出边缘对齐和侧面对齐。自组装导致聚合物的π–π*跃迁能量降低了0.3–0.4 eV。噻吩与二烷氧基-对苯二烯的共聚物显示了类似的自组装行为。具有–C≡CR侧链的聚噻吩显示出压致变色现象,在10 GPa下π–π*跃迁能量降低了约0.2 eV。具有–C≡C-癸基侧链的头对头-P3(C≡C-癸基)噻吩的光学三阶非线性极化率χ(3)大于区域规整聚(3-己基噻吩)。