Highly efficient condensation of hydroxyl-terminated polyethylene oxide with 3-mercaptopropionic acid catalyzed by hafnium salt

A general, highly efficient, one-step synthesis of thiol functionalized polymer was described. In the presence of 1-5 mol% of HfCl4 · 2THF, the hydroxyl group of polyethylene oxide monomether (MPEO) directly reacted with 3-mercaptopropionic acid to yield thiol functional MPEO. For MPEO with molecular weight from 550 to 5000, the degree of functionalization was almost quantitative (>96%), and the reaction proceeded without side reaction.