MELTING TEMPERATURE OF THE N-ALKANES AND THE LINEAR POLYETHYLENES

The melting behavior of n-alkanes up to carbon number 390 and molecular weight fractions of linear polyethylene up to Mn = 5600 have been analyzed. Surprisingly, it is found that the melting temperature-molecular weight relation is the same for both types of chain molecules. The results are explainedin terms of premelting of the n-alkanes, with the disordering of sequences of end units, so that the structure prior to melting is the same as that of the polymer. Support of this conclusion is given by theoretical considerations and experimental results. The difficulties in extrapolating the present data base to the equilibrium melting temperature of the infinite molecular weight chain are discussed. © 1990, American Chemical Society. All rights reserved.