Octacosane (C28H58) and hexatriacontane (C36H74) obtained by crystallization at room temperature from light petroleum solutions are polytypic modifications of the monoclinic structures. Their structure is a stacking of alternate monoclinic layers, related one to the other by a twofold axis perpendicular to the (001) plane. Space group Pbca, Z= 4. Cell parameters a= 7.42, b= 5-59, e= 66.50 or 84.50 ,~ for C28Hs8 and C36H74 respectively. The paraffinic chains are regular with C-C and C-H mean distances of 1.526 and 1 "00 •. The mean C-C-C angle is 113.9 °. Thermal motion is anisotropic, weak in the direction of the chain. Lateral contacts between chains are the same in this structure as in the monoclinic structure.

We investigate the temporal dynamics of terrylene diimide molecule with four phenoxy rings (TDI) in a poly(styrene) (PS) matrix in the supercooled regime by use of single molecule spectroscopy. By recording both fluorescence lifetime and linear dichroism observables simultaneously, we show that the TDI dye molecule is a versatile probe of the local dynamics in the polymer. The molecule is able to undergo conformational changes, as indicated by lifetime fluctuations and/or reorientation jumps, as indicated by both observables on different time scales. Owing to molecular mechanics and quantum calculations, we could assign the conformational changes to folding/unfolding event(s) of one or more arms with respect to the conjugated core. We tentatively attribute the different spatial extents of the locally probed motions to the alpha and beta relaxation processes occurring in the PS matrix.

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