Chain Folding in Polyethylene and Cyclic Paraffins

With a view to a study of fold configurations, the crystal and molecular structure of a large cyclic paraffin (CH2)34 was determined by x-ray diffraction. Three-dimensional data were collected and the structure refined using a structure-factor least-squares computer program. The standard deviations in the final carbon atom coordinates were 0.02 Å. The configuration of the molecule was that of a ``collapsed'' ring, with two parallel linear chains linked by two terminal carbon atoms at either end. The chains packed together to give a triclinic subcell with dimensions a=4.246 Åα=60∘30′b=5.470 Åβ=74∘08′c=2.564 Åγ=96∘47′.Restraints imposed by the fold configuration gave rise to a departure from optimum packing of the chains at some distance from the fold. A rough estimate of the surface free energy of polymer faces containing similar folds was made.