Mesoporous Zeolite as a New Class of Catalyst for Controlled Polymerization of Lactones

Polymerization of lactones such as δ-valerolactone (VL) and ε-caprolactone (CL) with protic compounds proceeded in the presence of an aluminosilicate mesoporous zeolite Al−MCM-41 (pore diameter of 27 Å, surface area = 1010 m2 g-1, and Si/Al = 17), to give polyesters with a narrow molecular weight distribution. A sequential two-stage polymerization of VL and CL with Al−MCM-41/butanol gave a block copolymer. NMR and GPC studies showed that the produced polymer carries a terminal group originating from the protic compound. In contrast with Al−MCM-41, pure silicate MCM-41, an MCM-41 with masked SiOH functionalities, and a “microporous” aluminosilicate with much narrower pores (zeolite-Y; pore diameter = 8 Å) were not effective for the polymerization under similar conditions. Infrared spectroscopy of an inclusion adduct of Al−MCM-41 with VL suggested a possible interaction of the monomer onto the aluminosilicate surface. Al−MCM-41, isolated from the polymerization mixture, could be used again for the polymerization.