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The Electronic and Lattice Structures of the Ground and the Polaron States of Polymer Poly (Phenylene Vinylene) (PPV)

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Communications in Theoretical Physics 2001年第7期36卷 109-114页

作者： YAO Kai-Lun HAN Si-En DUAN Yong-Fa Physics Department and National Lab of Laser Technology Huazhong University of Science and Technology Wuhan 430074 China International Center of Material Physics The Chinese Academy of Sciences Shenyang 110015 China Physics Department and National Lab of Laser Technology Huazhong University of Science and Technology Wuhan 430074 China Physics Department and National Lab of Laser Technology Huazhong University of Science and Technology Wuhan 430074 China

The electronic and lattice structures of poly (phenylene vinylene) (PPV) are studied theoretically. Both the electron-electron and electron-phonon interactions are taken into account in the Pariser-Parr-Pople model. The electronic band and the lattice structure of the ground state and the polaronic state are calculated by means of the unrestricted Hartree-Fock method. In the ground state, there exist eight bands in PPV including four valence bands and four conduction bands, and the benzenes can be considered to be rigid. The polaron induces the split of energy bands. There are four localized electronic states within the energy gap. The defect of the polaron appears to extend over about 5 units. The benzenes are strongly affected by the electron-phonon interaction. Our calculation for the energy band structure of the ground and polaron states are consistent with experimental absorption spectra. The results of our calculation show that the electron-phonon and inter-site electron-electron interactions play an important role in determining the electronic and lattice structures.

关键词： electronic structure, polaron state, PPV, benzenes

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A Study of the Behavior of Alkyl Side Chains Phenols and Arenes in Polar and Nonpolar GC Stationary Phases

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American Journal of Analytical Chemistry 2011年第3期2卷 324-331页

作者： Pavel Straka Petr Buryan Institute of Rock Structure and Mechanics Academy of Sciences of the Czech Republic Prague Czech Republic.

Gas chromatographic measurements of the relative retention times of alkyl-substituted arenes and phenols on capillary columns at temperatures of 125 – 140°C have shown that logarithms of retention times increase bilinearly with the number of carbon atoms in the molecule. It was found that in a high density stationary phase, the longer alkyl side chains of compounds in question are subject to cyclization as a result of the resistance force of this phase affecting molecules during their thermal and diffusion motion. Consequently, common conventional aromatic-aliphatic molecules become new molecules with quasi-alicyclic rings. In comparison with the conventionally conceived molecules, the resulting aromatic–quasi-alicyclic molecules are characterized by rather different, possibly even completely different non-covalent interactions between the molecules, which then affect the retention characteristics. Moreover, cyclization facilitates the mixing of n-alkyl arenes and n-alkyl phenols with high-molecular stationary phases, because the thermodynamic condition for mixing is better fulfilled.

关键词： Alkyl Phenols Alkyl benzenes Retention Times Molecular Mechanics Van der Waals Forces

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