Abstract: In order to study the effect of end groups on copolymerization activity of polyether macromers and consequent copolymer structure, methyl allyl poly(ethylene glycol) ether (MAPEG), isoprenyl oxy poly(ethylene glycol) ether (IPEG) and vinyloxyethyl ether poly(ethylene glycol) ether (VEPEG) were copolymerized with acrylic acid (AA) via aqueous free radical copolymerization. The monomer reactivity was obtained and explained through ¹H NMR spectra and Frontier Molecular Orbital Theory, and three copolymerization processes and consequent copolymer microstructure were compared. The results show that the chemical structure and copolymerization activity of MAPEG and IPEG monomers are similar but significantly different from VEPEG monomers as VEPEG monomers has different end groups. The macromonomer conversion trendency of the VEPEG-AA copolymerization system was opposite to that of the MAPEG-AA and IPEG-AA copolymerization systems. The side chain density and side chain distribution of MAPEG-co-AA and IPEG-co-AA copolymers were similar, while the side chain density of VEPEG-co-AA copolymers was low. As the feeding amount of macromonomer increased, the difference in macromonomer activity and copolymerization process resulted in less difference in side chain density of the three copolymers.