RING-CLOSING DEPOLYMERIZATION OF POLY(EPSILON-CAPROLACTONE)

Ring-closing depolymerization of poly(epsilon-caprolactone) in toluene solution with catalytic amounts of Bu(2)Sn(OMe)(2) results in a mixture of cyclic oligomers, the equilibrium concentration of which corresponds to the concentration predicted according to the Jacobson-Stockmayer theory. epsilon-Caprolactone, however, is absent from this reaction mixture. When poly(epsilon-caprolactone) is depolymerized in the melt at 260 degrees C in the presence of a catalyst, beside epsilon-caprolactone its cyclic dimer and trimer are distilled off. The composition is dependent on the catalyst used, e.g., Bu(2)Sn(OMe)(2) produces 95,4 wt.-% of epsilon-caprolactone and 3,7 wt.-% its dimer while with Ti(OiPr)(4)(iPr: isopropyl) 51,4 wt.-% epsilon-caprolactone and 49,6 wt.-% of its dimer are obtained. Block copolymers containing poly(epsilon-caprolactone) result in a similar product distribution, however, the second block may influence the rate of decomposition. The activation energy of the catalysed (0,5 mol-% Bu(2)Sn(OMe)(2)) and uncatalysed ring-closing depolymerization were determined to be 63 kJ/mol and 87 kJ/mol, respectively.