C-13 NMR AND X-RAY-DIFFRACTION STUDIES OF THE MORPHOLOGY OF ALKANES AND LINEAR POLYETHYLENES

C-13 n.m.r. spin-lattice relaxation times have been determined for carbons in a number of solid alkanes and in two linear polyethylenes. C-13 spin-lattice relaxation times, T1S, for the internal methylene carbons of the linear alkanes depend upon structure and chain length. There is almost a 100-fold increase in T1 in going from orthorhombic C21H44 to C60H122. The central methylene carbons in the two polyethylenes give rise to two exponential decays. Analysis of the methyl resonances in one of these polyethylenes suggests that 60% of the methyl ends are in a crystalline environment. Low molecular weight orthorhombic alkanes are more mobile than expected from the 1/T1 versus a dimension of the unit cell relationship observed for linear and branched polyethylenes.