Macroscopic and Microscopic Acid Dissociation of the 1 : 1 Copolymer of Acrylic Acid and 4-Vinylpyridine

Acrylic acid and 4-vinylpyridine were copolymerized at 40 °C without any catalysts. The copolymer with 1 : 1 molar ratio of monomeric units was obtained over a wide range of the monomer ratios in the feed. Macroscopic and microscopic acid dissociation equilibria of the copolymer with 1 : 1 composition were determined in aqueous ethanol by potentiometric titration at 25 °C. The zwitterion and neutral molecule forms coexist over a wide range of pH, and the latter form is predominant. There exists only 10% of the zwitterion form in the neutral region.