Study of neutral polyacetylene by multifrequency EPR method

Summary form only given. A great number of EPR studies of polyacetylene (PA) was performed at /spl lambda/ /spl ges/ cm wavebands EPR during the last years. However, the low spectral resolution and strong cross relaxation processes do not allow one to separate the lines of paramagnetic centers of different mobility at this wavelength range. This leads to ambiguity of the data concerned with soliton dynamics and content of mobile solitons in trans-PA. In order to obtain more correct and complete information, neutral cis- and trans-PA samples have been studied in 30-0.7-mm wave length range EPR. A higher spectral resolution allows one to determine the main values of g-tensor of localized paramagnetic centers in as-prepared cis-PA, which were attributed to neutral solitons pinned on short trans-PA segments. The cis-trans-isomerization induces the increase of a number of such centers and the appearance of /spl sim/6% solitons fast diffusing along the polymer chains. The /spl Delta/H/sup mob//spl sim/(/spl Delta/H/sup loc/)/sup i.3/ dependency obtained for the linewidths of mobile and localized solitons also evidences the existence of 1D soliton diffusion in trans-PA. Another dependency, /spl Delta/H/sup loc/ /spl equiv/ /spl lambda//sup -2/ indicates the sufficient decrease of a cross-relaxation rate at magnetic fields H/spl ges/1.2 T.