Undecyl tin chloride grafted onto cross-linked polystyrene: an efficient catalyst for ring-opening polymerization of e-caprolactone

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 -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(-caprolactone), investigated with size exclusion chromatography, is closer to unity than for grafted tin dichloride catalysts.