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Electronic structure of aromatic conjugated polymers: Influence of ring torsions on the electronic properties of polyanilines and polyparaphenylene sulfide in the undoped and doped states
3450
Synthetic Metals, 41-43 ( 1991) 3450
ELECTRONIC STRUCTURE OF A R O M A T I C CONJUGATED POLYMERS: INFLUENCE OF RING TORSIONS ON THE ELECTRONIC PROPERTIES OF POLYANILINES AND POLYPARAPHENYLENE SULFIDE IN THE UNDOPED AND DOPED STATES J.L. Br6das, C. Quattrocchi, J. Libert, and F. Meyers Service de Chimie des Matdriaux Nouveaux, Universit6 de Mons, avenue Maistriau 21, B-7000 MONS (BELGIQUE).
Recently, it was pointed out that in aromatic polymers, torsions along the polymer chains could: (i) in the neutral (undoped) state, induce rin~-torsionaI dimerization (i.e., twists of unequal magnitude between adjacent rings) which might influence the bandgap value, in addition to the more conventional effect due to bond-length dimerization [1]; and (ii) in the doped state, produce the trapping of charged defects such as polarons, leading to high polaron effective masses and the possibility of memory effects [2,3].
In this contribution, we investigate the influence on the electronic properties, of torsions occurring along ring containing conjugated chains. Band structure calculations are performed at the Valence Effective Hamiltonian level for various ring-torsional dimerization values whereas the total energies involved by ring twists are calculated at the ab initio double zeta and AM1 semi-empirical levels for both undoped and doped states. The polymers under consideration are: (i) two members of the polyaniline family: on the one hand, the leucoemeraldine base polymer, (-C6H4-NH-), which is the fully reduced form and, on the other hand, the pemigraniline polymer, (-C6H4-N=C6H,=N-), which corresponds to the fully oxidized form; (ii) polyparaphenylene sulfide, (-C6Ha-S-), which is the sulfur analog of leucoemeraldine.
The results of these calculations provide a reliable framework to discuss the influence of ring-torsional dimerization in aromatic polymers and to interpret the memory effects reported for polyaniline compounds.
REFERENCES
[1] J. Ginder and A.J. Epstein, Phys. Rev. Lett., in press. [2] B. Villeret and M. Nechtschein, Phys. Rev. Lett. 6_._33,1285 (1989). [3] M.E. Jozefowicz et al., Phys. Rev. B39, 12958 (1989). Elsevier Sequoia/Printed in The Netherlands
Synthetic Metals, 41-43 ( 1991) 3450
ELECTRONIC STRUCTURE OF A R O M A T I C CONJUGATED POLYMERS: INFLUENCE OF RING TORSIONS ON THE ELECTRONIC PROPERTIES OF POLYANILINES AND POLYPARAPHENYLENE SULFIDE IN THE UNDOPED AND DOPED STATES J.L. Br6das, C. Quattrocchi, J. Libert, and F. Meyers Service de Chimie des Matdriaux Nouveaux, Universit6 de Mons, avenue Maistriau 21, B-7000 MONS (BELGIQUE).
Recently, it was pointed out that in aromatic polymers, torsions along the polymer chains could: (i) in the neutral (undoped) state, induce rin~-torsionaI dimerization (i.e., twists of unequal magnitude between adjacent rings) which might influence the bandgap value, in addition to the more conventional effect due to bond-length dimerization [1]; and (ii) in the doped state, produce the trapping of charged defects such as polarons, leading to high polaron effective masses and the possibility of memory effects [2,3].
In this contribution, we investigate the influence on the electronic properties, of torsions occurring along ring containing conjugated chains. Band structure calculations are performed at the Valence Effective Hamiltonian level for various ring-torsional dimerization values whereas the total energies involved by ring twists are calculated at the ab initio double zeta and AM1 semi-empirical levels for both undoped and doped states. The polymers under consideration are: (i) two members of the polyaniline family: on the one hand, the leucoemeraldine base polymer, (-C6H4-NH-), which is the fully reduced form and, on the other hand, the pemigraniline polymer, (-C6H4-N=C6H,=N-), which corresponds to the fully oxidized form; (ii) polyparaphenylene sulfide, (-C6Ha-S-), which is the sulfur analog of leucoemeraldine.
The results of these calculations provide a reliable framework to discuss the influence of ring-torsional dimerization in aromatic polymers and to interpret the memory effects reported for polyaniline compounds.
REFERENCES
[1] J. Ginder and A.J. Epstein, Phys. Rev. Lett., in press. [2] B. Villeret and M. Nechtschein, Phys. Rev. Lett. 6_._33,1285 (1989). [3] M.E. Jozefowicz et al., Phys. Rev. B39, 12958 (1989). Elsevier Sequoia/Printed in The Netherlands