Polymerization and structure of poly(sulphur nitride) prepared under high pressure

Abstract

Poly(sulphur nitride)was prepared by spontaneous solid state polymerization of disulphur dinitride crystals immersed in perfluoro(methyl cyclohexane). The polymerization was carried out at hydrostatic pressures of up to 3.5 kbar in order to eliminate the lattice strain due to the mismatch in the monomer and the polymer lattice in the polymerization direction.It was observed that the pressure had no marked effect on the polymerization rate.The structure of the (SN)x samples polymerized at high hydrostatic and at atmospheric pressure was examined by electron microscopy and electron diffraction techniques.They were complemented by the measurements of (SN)x densities and electrical conductivities in the direction along and across the polymer chains. The results show that there is no significant difference in the structure and in the density of the high and the low pressure polymerized (SN)x. A modest increase in the electrical conductivity parallel to the polymer chains observed in the high pressure polymerized (SN)x is explained by a pressure induced increase in the average chain length. It is concluded that the long range lattice strain originating from the monomer-polymer lattice mismatch in the polymerization direction is less important for the solid state polymerization of (SN)x than the nearest-neighbour interactions in the direction across the chain.