The synthesis of new ?-phosphonic acid-terminated poly(ethylene oxide) (PEOs) monomethyl ethers was investigated by the combination of AthertonTodd or KabachnikFields reactions and the click copper-catalyzed 1,3-dipolar cycloaddition of azides and terminal alkynes. The AthertonTodd route fails to give the corresponding phosphonic acid-terminated PEOs due to competitive cleavage of the P?N bond during the dealkylation step. In contrast, the KabachnikFields route leads with very good yields to ?-phosphonic acid-PEO through click reaction of azido-PEO onto dimethyl aminopropargyl phosphonate prepared by KabachnikFields reaction between propargylbenzylimine and dimethyl phosphonate, followed by acidic hydrolysis. The reported methodology, precluding the use of anionic polymerization of ethylene oxide, leads to novel well-defined phosphonic acid-terminated PEOs from commercially available products in good yields. Moreover, such a strategy can be adapted to anchor phosphonic acid functionality onto a wide range of polymers. (c) 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013