Dithiadiazolium salts as initiators for the cationic ring‐opening polymerization of tetrahydrofuran

Abstract

Mono‐, bis‐ and tris‐(1,3,2,4‐dithiadiazolium) salts [R‐(CNSNS+)n]n+[AsF‐6]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 13C‐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. © 1992 John Wiley & Sons, Inc.