E.p.r. study of polyacetylene films

Magnetic Properties of cis- and trans- Polyacetylene as Studied by Electron Spin Resonance

“…16 Such a width has its origin partially in unresolved hyperfine interactions as stated by Snow et aC who compared the cases of (CH)x and (CD)x systems. We confirmed this conclusion, since spectra obtained on 13 (Table III).…”

“…This amount was isomerized quite rapidly when the sample heat from its polymerization temperature to room temperature. 13 Consequently, we suggest such an amount to be located on chain ends where the ability to rotate around C-C bonds is greater than in the middle of the chain. Using n = 1000 as a mean value of the number of carbon atoms in one chain, as estimated by shirakawa eta!., 18 Gauss which is compared reasonably with our experimental value of 8 Gauss (Table I), taking into account the crudeness of the assumptions model.…”

“…The heating of the pure cis-isomer was shown 13 to create unpaired electrons whose resonance g value could not be distinguished from the free electron value.…”

“…If observed at the polymerization temperature -78°C the ESR spectrum as described previously 13 showed no signal from the polyacetylene film while a very huge and broad signal centered near g = 1.95 came from the catalytic system. Such a catalyst signal has been studied by different authors 14 • 15 and a strong dependence of its shape with the molar ratio of Al/Ti was pointed out.…”

EPR study of the cis-trans isomerization process in polyacetylene films

“…The magnetic properties of undoped polyacetylene are largely dependent on the cis/trans content [2]. It is now well established that there are no unpaired electrons in the as-prepared pure cis-(CH)x (at -78 °C) as evidenced by the absence of any EPR signal [3]. The presence of unpaired electrons is directly related to the trans content, following for instance a thermal treatment.…”