A new method to synthesize graft polymer with controlled graft density (?) through the coupling reaction between the appending β-keto ester and the terminal amine is proposed. Following this method, the backbone polymer of poly[2-(acetoacetoxy) ethyl methacrylate] (PAEMA) containing the appending β-keto ester is synthesized by reversible addition-fragmentation chain transfer polymerization and the side-chain polymer of poly(ethylene glycol) monomethyl ether containing the –NH₂ terminal group (MPEG–NH₂) is prepared, and then the side-chain polymer is covalently bonded to the backbone polymer by the CN bond through the coupling reaction between the appending β-keto ester and the terminal –NH₂. By changing the molar ratio of the side-chain polymer and the backbone polymer, the PAEMA-g-MPEG graft polymers with ? ranging from 0.07 to 0.85 are prepared. The solubility/dispersion of the graft polymers in water is studied and the ?-dependent solubility/dispersion is demonstrated. The proposed method is anticipated to be a valid method to prepare graft polymers.

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