Doping of cis-polyacetylene films with metal hexafluorides: Conductivity, E.S.R. and ENDOR measurements

• Published in: Synthetic metals 1987, Vol.20 (3), p.323-331
• Main Authors: Baker, Gareth J., Holloway, John H., Raynor, J.Barrie, Selig, Henry
• Format: Article
• Language: English
• Subjects: Applied sciences; Electrical, magnetic and optical properties; Exact sciences and technology; Organic polymers; Physicochemistry of polymers; Properties and characterization
• ISSN: 0379-6779; 1879-3290
• DOI: 10.1016/0379-6779(87)90829-0

Polyacetylene (70% cis) has been doped with MoF 6, WF 6, UF 6 and ReF 6 and electrical conductivity and electron spin resonance measurements made. The total magnetic susceptibility increases to a maximum at about 1 mol.% dopant, and then decreases to a low value. This can be accounted for by the generation of positive polarons followed by annihilation to form bipolarons. From the e.s.r. spectra, there is no evidence for paramagnetic metal fluoride anions, which suggests that dimerization or higher polymerization of the metal fluoride anions is possibly taking place to yield diamagnetic or antiferromagnetically coupled states. ENDOR measurements at 4.2 K on undoped 100% trans-polyacetylene and undoped and doped 70% cis-polyacetylene show pairs of lines with hyperfine couplings typical of that of a π-radical. From these it can be deduced that the unpaired electron is delocalized over about 70 carbon atoms.