Undecyltin Trichloride Grafted onto Cross-Linked Polystyrene: An Efficient Catalyst for Ring-Opening Polymerization of ϵ-Caprolactone

Abstract

The activity, recyclability, and chemical stability as a catalyst of undecyltin trichloride grafted to cross-linked polystyrene, [P-H](1−t)[P-(CH2)11-SnCl3]t, with [P-H] the monomeric unit of the nonfunctionalized polymer and t the organotin-functionalized monomer fraction, are assessed in the ring-opening polymerization (ROP) of ϵ-caprolactone. Quantitative conversion is obtained within 2 h under conditions in which conversion is by far incomplete for two other organotin grafts, [P-H](1−t)[P-(CH2)11-SnBuCl2]t and [P-H](1−t){[P-(CH2)11-SnBuCl]2O}t/2. Even after 15 min of reaction, conversions of at least 70% are achieved for the grafted tin trichloride. The catalytic reactions of the grafted undecyltin trichloride, more particularly its chemical integrity and recycling ability, are monitored, in situ, at the solid–liquid interface, using high-resolution magic angle spinning (HR-MAS) 1H and 119Sn NMR. Residual tin contents in the reaction products were assessed by inductively coupled plasma/atomic emission spectroscopy (ICP/AES). The polydispersity index of the synthesized poly(ϵ-caprolactone), investigated with size exclusion chromatography, is closer to unity than for grafted tin dichloride catalysts.