Equilibrium Polymerization under Pressure: The Case of Sulfur

Abstract

A previously derived theory of equilibrium polymerization is generalized to take into account the effect of superposed hydrostatic pressure, and the results are applied to the equilibrium polymerization of sulfur. It is shown that the transition which at atmospheric pressure occurs at about 160°C is shifted with pressure toward lower temperatures; at ∼850 atm it intersects the melting line, so that above that pressure sulfur melts to a liquid of high viscosity consisting of S8 rings and diradical terminated chains. The effect of pressure on the equilibrium degree of polymerization and the equilibrium S8 concentration is also discussed.