Bismuth‐Triflate‐Catalyzed Polymerizations of ε‐Caprolactone

Abstract

εCL was polymerized using the triflates of lanthanum, samarium, magnesium, aluminum, scandium, and bismuth as catalysts. Bismuth triflate proved to be extraordinarily reactive, and catalyzed polymerizations of εCL even at 20 °C. Adding DTBMP reduced the polymerization rate only slightly. Furthermore, no evidence of a cationic mechanism was found by end‐group analyses. Polymerization at 20 °C either in bulk or in solution only yielded polyesters of low or medium molecular weights ($\overline {M} _{{\rm n}} $ up to 30 000 Da). Yet addition of alcohols allowed for a proper control of molecular weight and end‐groups. Additionally, low catalyst concentrations and low temperature resulted in narrow molecular weight distributions and polylactones almost free of cyclic compounds.

(Co‐)Polyesters Derived from Isosorbide and 1,4‐Cyclohexane Dicarboxylic Acid and Succinic Acid

“…These results indicate that the direct calibration overestimates the real M n s by %30 and 45%, respectively in contrast to 80% in the case of poly(butylene succinate). [20] The DSC measurements of several homo-and copolyesters were conducted with a heating and cooling rate of 20 8C Á min À1 . All homo-and copolyesters were as expected, amorphous, and the glass transition temperatures (T g s) are listed in Table 1-3 and in the footnotes of Table 4.…”

Polymerization of Cyclosiloxanes by Means of Triflic Acid and Metal Triflates

“…Secondly, bismuth halide and bismuth triflate were found to be efficient catalysts of the ring-opening polymerization of oxazolies [32] and e-caprolactone. [33][34][35] Therefore, the present work should expand our systematic studies of bismuth-based catalysts.…”

Low‐Temperature Polymerization of ε‐Caprolactone Catalyzed by Cerium Triflates

“…Previously, for Bi 3+ ‐catalyzed polymerizations at room temperature, it was also observed that the Mn values increased upon prolonged storage, although the conversion of ϵ‐CL was completed within 2–4 d. (depending on the ϵ‐CL/water ratio) . This reproducible chain growth effect was speculatively attributed to condensation steps involving the CH 2 OH and the CO 2 H end groups.…”

“…Although this amount of water is very small, it may play a role for polymerizations with ϵ‐CL/water ratios >100. With regard to Mn and its dependence on the ϵ‐CL/water ratio, the results obtained here well agree with those found for Bi 3+ ‐catalyzed polymerizations …”

“…In a recent publication, we reported that bismuth triflate slowly catalyzes water or methanol‐initiated polymerizations of ε‐CL at 21–22 °C in bulk. Gel‐permeation chromatography (GPC) measurements obtained after prolonged reaction times also suggested that bismuth triflate catalyzed condensation steps of CH 2 OH and CO 2 H end groups.…”