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Conformations of end-labeled alkanes in a rigid polymer matrix were investigated using the pulsed double electron-electron resonance (DEER) method. To this end, dipolar spectra of a series of aliphatic dicarbonic acids with 8−20 methylene units and chain ends bifunctionalized with nitroxide radicals were recorded in a polystyrene matrix. The biradicals are derived from hindered amine light stabilizers (HALS), used as polymer additives. Analysis of the dipolar spectra allows the determination of the end-to-end distances of the oligomer biradicals. The experiments show that the “flexible” alkane chains are almost completely stretched. This observation is consistent with the results of force field calculations.

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Pulsed EPR measurements of the transverse and longitudinal relaxation times of the C« -anion radical in crystalline C«-tetraphenylphosphoniumchloride were done at temperatures from 4 to 40 K. Above 40 K to room temperature the longitudinal relaxation time was taken from the cw-EPR linewidth. The low-temperature data are explained in terms of local magnetic fluctuations, slow C«motion, and localized two-level states related with the local disorder. The relaxation data at higher temperatures reveal experimental evidence for the Jahn-Teller distortion of the C6p -anion radical and allow to determine the Jahn-Teller splitting between the az"electronic ground state and the excited el"state of the unpaired electron.