Abstract
The samarium(II) aryloxide complexes Sm(OAr)2(THF)3 and [(C5Me5)Sm(μ-OAr)]2 (Ar = C6H2tBu2-2,6-Me-4) showed an extremely high activity for the ring-opening polymerization of e-caprolactone (CL) and δ-valerolactone (VL). By using Sm(OAr)2(THF)3 as an initiator, polyesters with very high molecular weight (Mn up to 6 × 105) and relatively narrow molecular weight distributions (Mw/Mn < 1.65) could be quantitatively obtained within a few minutes at room temperature. γ-Butyrolactone (BL) did not polymerize under the similar conditions. However, the copolymerization of BL with CL took place under the coexistence of both monomers, which gave CL−BL copolymers in which the BL units all exist in an isolated form, and the CL units all in blocks, as confirmed by the two-dimensional 1H−13C HMQC and HMBC NMR studies. Part of the previously reported 13C NMR spectrum of poly(e-caprolactone) was reassigned on the basis of the two-dimensional 1H−13C HMQC NMR study. In all these polymerization reactions, incorporation of the...
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