Structure of polyethylene sulfide

The structure of the polyether series expressed by the general formula [─(CH2)m─O─]n with m = 1-4, 6, 8-10, and 12 was previously determined [l]. The molecular structure of polyoxymethylene (m = 1) is a sequence of nearly gauche forms (9/5 o r 29/16 helix [a]). On the other hand, the conformation of polythiomethylene, the first member of the polythioether series [─(CH2)m ─S─]n, was found to also be a nearly gauche sequence (l7/9 helix) by Carrazzolo and Valle [3]. Both of these polymers have the highest melting point of each series (polyoxymethylene, 180°C; polythiomethylene, 245°C). Polyethylene oxide (m = 2) is a 7/2 helix consisting of nearly trans, trans, and gauche forms and has rather a low melting point (66°C). Polyethylene sulfide has a very high melting point (210°C) compared with polyethylene oxide. In this respect it is thus of much interest to investigate the structure of polyethylene sulfide. Boileau et al. [4] synthesized high molecular weight polyethylene sulfide and reported its unit-cell dimensions, but they did not determine its structure. In this note, the molecular and crystal structure of polyethylene sulfide is briefly reported.