Poly(Ïμ-caprolactone) by combined ring-opening polymerization and polycondensation

Numerous water-initiated polymerizations of ÏμCL are conducted in bulk with variation of catalyst, reaction time, and temperature. The conversions are determined by ¹H NMR and the molar masses by SEC measurements. For polymerizations at 100 °C, Bi triflate and Hf triflate are used as catalysts, whereas at 140 °C, Al triflate, Sn(II) triflate, SnCl ₂, HfCl₄, BiCl₃, and LaCl₃ are used. In addition to a closed reaction vessel, experiments are also performed with stirring in a vacuum. Under these conditions, the best catalyst (SnCl ₂) yields 2-3 times higher molar masses and mass spectra indicate a significant higher fraction of cyclic polymers. The results prove that a modification of the procedure may stimulate a polycondesation process without change of catalyst, time, and temperature. The water-initiated polymerization of Ïμ-caprolactone is catalyzed by various metals salts. The resulting macromers are subjected to polycondensation in vacuo. The catalysts are optimized for a "one-pot procedure".