Kanemoto Katsuichi, Muramatsu Kazumi, Baba Masaaki, Yamauchi Jun
Department of Physics, Graduate School of Science, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan.
J Phys Chem B. 2008 Sep 4;112(35):10922-6. doi: 10.1021/jp804065k. Epub 2008 Aug 13.
Electron spin resonance (ESR) features in heavily doped conjugated polymers are investigated through the comparison of temperature dependences of ESR spectra between head-to-tail coupled regioregular (RR) and regiorandom (RRa) poly(3-octylthiophenes) (P3OTs). RR-P3OT, used as a model of having crystalline grains in the solid film, is found to exhibit anisotropic ESR spectra, whereas RRa-P3OT gives almost isotropic ESR spectra similar to those of usual heavily doped conjugated polymers. This difference in the degree of spectral anisotropy primarily arises from a difference in their film morphology. Spectral simulations show the anisotropy observed in RR-P3OT to be caused by g-anisotropy. The presence of the g-anisotropy in RR-P3OT indicates that its polarons spend most of the time within a single crystalline grain that has some domains with a common direction of the g-tensor. The g-anisotropy turns out to decrease with increasing temperature. This result is explained by thermally activated hopping motions between crystalline grains. We emphasize that the decrease in the g-anisotropy with temperature should be associated with its activated type of temperature dependence of conductivity. In RRa-P3OT, its isotropic ESR spectra are suggested to be caused by the interchain motion as well as the intrachain one.
通过比较头对头耦合的区域规整（RR）和区域无规（RRa）聚（3-辛基噻吩）（P3OT）的电子自旋共振（ESR）谱的温度依赖性，研究了重掺杂共轭聚合物中的ESR特征。RR-P3OT用作固体薄膜中具有晶粒的模型，被发现表现出各向异性的ESR谱，而RRa-P3OT给出的几乎是各向同性的ESR谱，类似于通常的重掺杂共轭聚合物。光谱各向异性程度的这种差异主要源于它们薄膜形态的差异。光谱模拟表明，在RR-P3OT中观察到的各向异性是由g-各向异性引起的。RR-P3OT中g-各向异性的存在表明其极化子大部分时间处于单个晶粒内，该晶粒具有一些具有g张量共同方向的畴。结果表明，g-各向异性随温度升高而降低。这一结果可以用晶粒之间的热激活跳跃运动来解释。我们强调，g-各向异性随温度的降低应与其电导率的激活型温度依赖性相关。在RRa-P3OT中，其各向同性ESR谱被认为是由链间运动以及链内运动引起的。
