INVESTIGATION OF SHORT-RANGE ORDERING IN POLYMERS .3. STUDIES OF LOW-MOLECULAR WEIGHT ALKANES AND MOLTEN POLYETHYLENE

Radial distribution function methods have been used to compare the short range ordering (SRO) in molten polyethylene, with that in a number of n-alkanes. The SRO as monitored by the number and amplitude of intermolecular peaks increases with the number of carbon atoms in the alkane to C16, which has a similar degree of SRO to hexatriacontane (C36). The observed ordering decreases with increasing temperature, but the higher alkanes show less temperature dependence than the lower alkanes. For none of the measured systems do the intermolecular correlations persist over distances greater than ∼20 A ̊, and the SRO observed in molten polyethylene is similar to that for the lower alkanes. The data does not support suggestions in the literature that the SRO should increase progressively with chain length to give a substantially parallel arrangement of chain segments in molten polyethylene over regions 50-100 Å in size. © 1979.