Howard B. Yokelson

Preparation of an ester-terminated telechelic polybutadiene by a two-step olefin metathesis process

Abstract A two-step olefin metathesis process was devised and utilized to prepare an ester-terminated telechelic 1,4-polybutadiene of high difunctional purity using readily available olefin reactants (methyl undecylenate and 1,5-cyclooctadiene or 1,5,9-cyclododecatriene). In the first step of this process, methyl undecyclenate was self-metathesized in the presence of WCl6SnMe4 catalyst to yield an acyclic olefinic diester, dimethyl 10-eicosene-1,20-dioate (DMED), plus ethylene. In the second step, ring-opening metathesis polymerization (ROMP) of 1,5-cyclooctadiene or 1,5,9-cyclododecatriene with DMED as a chain transfer agent was carried out using WCl6SnMe4 catalyst to afford the polybutadiene product. The methanol-insoluble fraction of the product, which was isolated in yields of 70–80%, consisted primarily of acyclic ester-terminated 1,4-polybutadiene species. The use of highly pure 1,5-cyclooctadiene and a low catalyst charge in the ROMP reaction yielded product in which the acyclic component was determined to be purely ester-terminated (Fn = 2.0) telechelic 1,4-polybutadiene by high-sensitivity 13C-NMR analysis. Further evidence of the high difunctional purity was obtained through chain extension of the telechelic polybutadiene to a high molecular weight polyester material by transesterification with 1,6-hexanediol.