کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
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5191660 | 1381236 | 2005 | 8 صفحه PDF | دانلود رایگان |
In this study, theoretical analysis on the geometries and electronic properties of various conjugated poly(azomethine)s is reported. The theoretical ground-state geometry and electronic structure of the studied poly(azomethine)s are optimized by the hybrid density functional theory (DFT) method treated in periodic boundary conditions at the B3LYP level of theory with 6-31G basis set. The geometry and electronic structure of poly(1,4-phenylenemethylidyneitrilo-1,4-phenylene-nitrilomethylidyne) (PPI) are compared with those of poly(p-phenylene vinylene) (PPV) or polyazine (PAZ). The theoretical results suggest the non-coplanar conformation of PPI but PPV and PAZ with a coplanar conformation. The electronic properties of PPI are in the intermediate between PPV and PAZ. The non-coplanar conformation of PPI could be released if the phenylene ring is replaced by the five-member ring of 3,4-ethylenedioxythiophene (PEEI), pyrrole (PYYI), thiophene (PTTI), furan (PFFI), or thiadiazole (PThThI). The theoretical Eg of PEEI, PYYI, PFFI, and PTTI are in the range of 1.11-1.67Â eV, which is due to the coplanar configuration or donor-acceptor intrachain charge transfer. However, the large bond length alternation or lack of charge transfer characteristic makes the PThThI with a larger Eg of 2.47Â eV than others. The trend on the IP or EA of the studied conjugated poly(azomethine)s are consistent with the electronic characteristic of the aromatic ring. The upper valence bandwidth of the studied five-member ring based poly(azomethine)s except PThThI is in the range of 562-613Â meV, which is larger than that of PPI (247Â meV) or PPV (373Â meV). The results suggest that the electronic properties of conjugated poly(azomethine)s could be varied through various ring structure. The proposed new coplanar conjugated poly(zomethine)s can be potentially used as transparent conductors or thin film transistors.
Journal: Polymer - Volume 46, Issue 13, 17 June 2005, Pages 4950-4957