Splitting of the disulfide bonds in polysulfide polymers by hydrazine

Abstract

AbstractThe action of hydrazine on desulfurized tetrasulfide polymer obtained from bis‐2‐chloroethyl formal leads to SS bond splitting and depolymerization. Our studies show that successful depolymerization can be initiated only in a strong alkali medium at 95–98°C. During this process cleavage of the disulfide bonds and the formation of polymers of lower molecular weight with SH end groups takes place. From the results of the experiments performed it can be seen that the degree of depolymerization increases with an increase in the amount of hydrazine, in the mole ratio of sodium hydroxide, and in the time of reaction. When 0.7–1.0 mole of hydrazine per segment of polymer and 4 mole of sodium hydroxide per mole of hydrazine are used, a polymer of low average molecular weight in the form of water‐soluble sodium salt (fraction I) and a polymer in dispersion form (fraction II) are obtained. Similar results could be attained if the amount ot hydrazine were decreased and the mole ratio of sodium hydroxide were simultaneously increased to more than 4 mole per segment of hydrazine used. In a constant amount of sodium hydroxide with a smaller quantity of hydrazine or a shorter reaction time the amount of water‐soluble polymer (as a sodium salt) decreases and the amount of polymer in dispersion form increases. If a portion of the polymer in dispersion is coagulated with a portion of the polymer in the mother liquid, the yield of the depolymerized product is higher, but the average molecular weight is also higher than those of fraction I. The influence of the average contents of sulfur on the efficiency of the depolymerization is tested in polymers that contain 2.5 (i.e., 3) atoms of sulfur per segment of polymer. The result is that the depolymerization of the polysulfide polymer could be carried out without previous desulfurization, but the molecular weights of the products obtained with an equivalent quantity of hydrazine are much higher than those obtained by depolymerization of the disulfide polymer.