The reaction of phenyl propynyl ether and diphenyl disulfide in the presence of 1 mol % tetrakis(triphenylphosphine)palladium as a model reaction of the polymerization of bis(4-prop-2-ynyloxyphenyl) disulfide (1a) gave a Z-substituted dithioalkene. No E-substituted dithioalkene was formed in this reaction. The palladium-catalyzed bisthiolation polymerization of a diethynyl disulfide derivative, 1a, in benzene, was carried out to give a hyperbranched polymer (5a) containing a Z-substituted dithioalkene unit after reaction for 4 h at 70 degrees C. From the gel permeation chromatography analysis (chloroform, PSt standards), the number-average and weight-average molecular weights of 5a were found to be 8,100 and 57,000, respectively. The structure of 5a was confirmed by H-1 and C-13 NMR spectra. The obtained polymer was soluble in common organic solvents such as benzene, acetone, and CHCl3. Polymerization for more than 5 h gave insoluble products. (C) 2007 Wiley Periodicals, Inc.