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Electric Properties of Ladder Type Polymers BBB and BBL

Published online by Cambridge University Press:  26 February 2011

I. Belaish ,
C. Rettori ,
D. Davidov ,
M.R. Mclean ,
L. Dalton  and
H. Nalwa
I. Belaish
Affiliation:
Racah Institute of Physics, Hebrew University, Jerusalem, Israel
C. Rettori
Affiliation:
Racah Institute of Physics, Hebrew University, Jerusalem, Israel
D. Davidov
Affiliation:
Racah Institute of Physics, Hebrew University, Jerusalem, Israel
M.R. Mclean
Affiliation:
Department of Chemistry, University of Southern California Los Angeles, California 90089-0482, USA
L. Dalton
Affiliation:
Department of Chemistry, University of Southern California Los Angeles, California 90089-0482, USA
H. Nalwa
Affiliation:
Department of Chemistry, University of Southern California Los Angeles, California 90089-0482, USA
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Abstract

We report on ESR and electric conductivities of BBB and BBL ladder polymers with emphasis on the former. Both the ESR and the electrical conductivities are strongly anisotropic suggesting that the polymer backbones are plannar. The ESR data implies the existence of two different types of spin species. The hyperfine spectrum of one of these species is analyzed in terms of a Spin Hamiltonian and anisotropic transferred hyperfine interaction with the 14N nuclei (I = 1). We found that “annealing” the BBB and BBL films to high temperatures, To, increase the spin susceptibility for To ≤ 850K (BBB). However annealing to To ≥ 900K results in a dramatic reduction in the spin susceptibility and dramatic incise in the conductivity. The room temperature in-plane conductivity of annealed samples at To ≥ 900K exceeds σ = 1 Ω−1 cm−1. This high intrinsic conductivity is probably associated with the formation of cross-linked condensed aromatic structure. The 'phase transition” temperature to this structure is higher by 50K for BBB compared to BBL. The conductivity versus temperature of annealed samples (700K ≤ To) can be described by the onisotropic version of Mott's law for variable range hopping. We demonstrate that the anisotropic conductivity is due to the anisotropic localization lengths (ξ∥ and ξ⊥) of the wave function of the localized states.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 134: Symposium J – Materials Science and Engineering of Rigid-Rod Polymers , 1988 , 689
Copyright
Copyright © Materials Research Society 1989

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References

REFERENCES

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