ANALYSIS OF IONIZATION EQUILIBRIA OF POLYACIDS IN TERMS OF SPECIES POPULATION-DISTRIBUTIONS - EXAMINATION OF A 2-STATE CONFORMATIONAL TRANSITION

The potentiometric titration curves of two hydrolyzed 1-1 copolymers of maleic anhydride and alkyl vinyl ethers are described in terms of successive ionization constants of appropriately chosen oligomeric subunits in order to follow the population distribution among the various deprotonation states of the subunits with the progress of the titration. For the methyl copolymer the species distribution functions behaved normally, but for the butyl copolymer they showed two distinct peaks in the pH range in which a transition from compact to random coil conformation is known to occur. The results provide a quantitative characterization of the two-state" nature of the conformational transition. © 1979 American Chemical Society."