Novel direct synthetic approach to thiol-functionalized poly(ε-caprolactone) by highly chemselective and low costly rare earth phenolate catalysts

The synthesis of thiol-functionalized poly(ε-caprolactone) by highly chemselective and low costly rare earth phenolate (REP) catalysts was reported. A series of REP including dysprosium, lanthanum, and yttrium tris(2,6-di-tert-butyl-4-methyl phenolate)s and yttrium triphenolate can efficiently catalyze controlled ring-opening polymerization (ROP) of caprolactone (CL) initiated by hydroxyl end of 6-mercaptohexanol (MH). The ROP of CL was carried out at 60 °C to yield over 90% for 3 h. The characteristic plasmon absorption band of silver nanoparticles (SNP) at 455 nm was observed differing from a maximum at 390 nm of the absorption of uncapped silver colloids, which suggested that the S-Ag bond formation of the nanoparticles. The well-separated SNP with an average size of 3 nm were characterized by TEM, which were smaller than those encapped by C₁₂H₂₆S and C₉H₂₀S.