The ring-opening polymerization of cyclic (aromatic disulfide) oligomers derived from 4,4’-isopropylidene bisthiophenol was studied both in diphenyl ether solution and in the melt. The polymers formed were soluble in solvents such as chloroform, tetrahydrofuran, DMF, NMP and characterized by n.m.r., g.p.c., d.s.c. and t.g.a. techniques. The ring-opening polymerization began at about 150 degrees C in solution, but did not begin until around 200 degrees C in the melt, as determined by the melting point of the cyclic oligomers. A C-13- n.m.r. study indicated that structurally regular polydisulfides were formed below 250 degrees C, however, structural irregularity occurred above this temperature. There were no cross-linking reactions observed below 300 degrees C for short times, although cross-linking was very serious above 300 degrees C.