Atom Transfer Radical Polymerization of Acrylic and Methacrylic Acids: Preparation of Acidic Polymers with Various Architectures.

The preparation of poly(acrylic acid) (PAA) with tailored architecture and morphology is important for the design of advanced polymer materials. Cu-catalyzed atom transfer radical polymerization (ATRP) of AA is challenging due to the tendency of dormant chains to undergo an intramolecular lactonization reaction with consequent loss of chain-end functionalities, as previously reported for ATRP of methacrylic acid (MAA). In addition, AA can coordinate to the Cu catalyst. Moreover, the lower ATRP reactivity of AA relative to MAA enhances side reactions during polymerizations. These issues were overcome by adjusting the composition of the catalytic system, the polymerization setup, and the initiator nature. AA conversion >70-80% was obtained in 5 h, producing PAA with ≈1.4. Multifunctional water-soluble initiators provided PAA and PMAA with telechelic and star-shaped architectures. Block copolymers of MAA and AA confirmed the retention of chain-end functionalities during ATRPs.