A C-13 CP/MAS NMR INVESTIGATION OF POLY(ISOTHIANAPHTHENE)

The title polymer was prepared by several different approaches. C-13 CP/MAS NMR spectra of these insoluble powders are reported. The results have been obtained by cross-polarization with proton decoupling and magic angle spinning techniques. Using selective polarization, we have been able to separate the lines of inequivalent carbons and to estimate their chemical shift. In order to obtain more information about the geometry of these polymers, we used 1,3-diphenylisothianapthene (4) and 1,3-dibenzal-thiophthalan (5) as model compounds for an aromatic (3a) and a quinoidal structure (3b) of PITN. The results suggest a quinoidal structure for this narrow bandgap polymer.