DITHIADIAZOLIUM SALTS AS INITIATORS FOR THE CATIONIC RING-OPENING POLYMERIZATION OF TETRAHYDROFURAN

Mono-,bis-and tris-(1,3,2,4-dithiadiazolium)salts[R-(CNSNS+)n]n+[AsF6]n(R aryl, n = 1, 2, 3) were found to initiate the cationic ring-opening polymerization of tetrahydrofuran (THF) at room temperature to give clear gels from which the pure polymer was precipitated. 1,3,2,4-Dithiadiazolium cations associated with the hard [ AsF6 ]- anion thus constitute a new class of cationic polymerization initiators. The poly(THF) formed by initiation with 1,3,2,4-dithiadiazolium cation was characterized by gel permeation chromatography, infrared spectrophotometry, and C-13-NMR spectroscopy. Number-average molecular weights of 198 700 g mol-1 (polydispersity 1.96) and 190 000 g mol -1 (polydispersity 1.61) were obtained using [PhCNSNS][AsF6] and [C6H3-1,3,5-(CNSNS)3][AsF6]3, respectively, as initiators. The use of multifunctional dithiadiazolium salts as initiators suggests that they may be useful in the preparation of starburst and dendritic polymers.