Polymerization of poly(ε-caprolactone) using yttrium triflate

The ring-opening polymerization of epsilon-caprolactone (CL) has been initiated by yttrium triflate (trifluoromethanesulfonate) in air using simple glass vials at 60degreesC without desiccation steps and stirring. The number averaged molecular weight and molecular weight distribution of the obtained poly(epsilon-caprolactone) (PCL) was 5000-12000 and about 1.2, respectively. It was found that this polymerization reaction of CL was activated by the addition such as little water or 2-propanol. The copolymerization activities of comonomers such as L-lactide, gamma-butyrolactone, delta-octanolactone, delta-decanolactone, or omega-pentadecalactone with CL by yttrium triflate were very low at 60 degreesC. Direct molding method during polymerization of PCL at 40degreesC by yttrium triflate was developed. It was found that this direct molding PCL (M(n) = 2000, M(w)/M(n) = 3.07) was biodegraded very slowly in a buffer (pH 7.0) with a lipase produced by Rhizoupus arrhizus.