AN INVESTIGATION OF POLYMERIZATION OF LIQUID SULFUR SULFUR-SELENIUM AND SULFUR-ARSENIC MIXTURES USING RAMAN SPECTROSCOPY AND SCANNING DIFFERENTIAL CALORIMETRY

Raman spectroscopy has been used to follow the polymerization of sulfur in the pure liquid and in mixtures with arsenic or selenium. These studies have been supplemented by observations of the variation of specific heat associated with the polymerization phenomenon. The relative monomer-polymer concentrations have been determined as a function of temperature from the contribution of the monomer vibrations to the Raman scattering. In the case of liquid sulfur the contribution of polymer vibrations to the Raman scattering was also determined. The polymer concentrations deduced from both observations are in good mutual agreement but are somewhat higher than suggested by earlier work. Addition of 2 at. % of arsenic to sulfur lowers the polymerization threshold temperature, Tφ, from 159 ± 3 to 122 ± 4°, a value which shows near invariance with further additions of arsenic up to 15%. This lowering of the polymerization temperature is attributed to the participation of an arsenic-sulfur polymer in the propagation reaction. Selenium additions to sulfur reduce the threshold temperature uniformly throughout the experimentally observable temperature range. The lowering of Tφ in this case is attributed to the introduction of monomeric species SxSe8-x which can undergo copolymerization with S8 monomer.