Zickler Martin F, Feist Florian A, Jacob Josemon, Müllen Klaus, Basché Thomas
Institut für Physikalische Chemie, Johannes Gutenberg-Universität Mainz, 55099, Mainz, Germany.
Max Planck-Institut für Polymerforschung, 55128, Mainz, Germany.
Macromol Rapid Commun. 2015 Jun;36(11):1096-102. doi: 10.1002/marc.201400739. Epub 2015 Mar 30.
Confocal fluorescence microscopy and spectroscopy are employed to investigate single poly(ladder-type pentaphenylene) (LPPentP) molecules dispersed in thin poly(methyl methacrylate) (PMMA) films at 1.2 K. Emission spectra of single chains show single as well as multi-chromophore emission indicating variegated communication along the chains. The vibronic structure in the emission spectra resembles the one found for other ladder-type polymers. Purely electronic zero-phonon lines in emission are substantially broadened, most probably due to fast spectral diffusion. By surmounting the limitations of emission spectroscopy, nonemitting donor chromophores, which transfer their excitation energy in a radiationless manner to emitting chromophores, are accessed by excitation spectroscopy. Remarkably, by comparing the data of emitting and nonemitting chromophores a contribution to the zero-phonon excitation line width has to be considered which places a lower limit on the estimated energy transfer time of several picoseconds between adjacent chromophores. Finally, the data indicate qualitatively a restricted flexibility of LPPentP compared to poly[2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV).
利用共聚焦荧光显微镜和光谱学研究了分散在1.2 K的聚甲基丙烯酸甲酯（PMMA）薄膜中的单个聚（梯形五苯撑）（LPPentP）分子。单链的发射光谱显示出单发色团和多发色团发射，表明沿链存在多样化的相互作用。发射光谱中的振动结构类似于其他梯形聚合物的结构。发射中的纯电子零声子线显著展宽，很可能是由于快速的光谱扩散。通过克服发射光谱学的局限性，利用激发光谱学研究了以无辐射方式将激发能转移到发射发色团的非发射供体发色团。值得注意的是，通过比较发射和非发射发色团的数据，必须考虑对零声子激发线宽的贡献，这对相邻发色团之间估计的几皮秒的能量转移时间设定了下限。最后，数据定性地表明，与聚[2-甲氧基-5-（2'-乙基己氧基）-1,4-亚苯基亚乙烯基]（MEH-PPV）相比，LPPentP的柔韧性受限。
