Crystallization of short aliphatic chains. Part II. An example of even fold surface with adjacent fold reentry and of a transition to chain extension

As a continuation of the preceding study on the folding behavior of short polymer chains, an iodine-terminated paraffin having 156 A peak molecular length and a sharp molecular weight distribution was prepared. The paraffin could be crystallized in lamellae of two different thicknesses: (A) thickness close to half the chain length (the most readily obtained); (B) thickness intermediate between half chain length and fully extended chain. Case A corresponds to each chain folding once with equal stems and with ends at the surface. Degradation behavior revealed that the folds must be of closely equal length giving rise to an even fold surface. In case B the situation is more involved: here the chain ends must turn into the lattice. Adjacent reentry is a necessity throughout. In both cases the lamellar thickness could be increased by annealing up to complete chain extension.