Department of Chemistry, Laboratory of Macromolecular and Organic Chemistry, University of Louvain, B-3030 Heverlee, Belgium Received 4 September 1972 Thennostable poly-1,2,3-triazoles (7) were prepared by the regiospecific rt:action of bisazides with. keto-stabilhed bisalkylidenephosporanes (6) in DMSO solution. Ir spectroscopic analysis revealed the presence of terminal ylide functions in all polymeric samples and also azide functions in most of them, especially in the lower molecular weight fractions. The novel bisylides required in this work were prepared by two reaction routes, previously elaborated on for monofunctional systems. The first method consists of reacting bisacyl chlorides with 4 equiv. of alkylidenephosphoranes in benzene solution. The second method involves treatment of bisthioesters with two equiv. of alkylidenephosphoranes in refluxing toluene. '