The viscosities of poly(acrylic acid) (PAA) and poly(methacrylic acid) (PMA) have been measured in aqueous 0.25 M NaCl solutions at 5, \5, 25, 35, and 45oC as a function of various degrees of neutralization. The potentiometric titration data for these polycarboxylic acids in water at 5, 25, and 45°C are also reported. Both results indicate that the compact conformation of PMA at low degree of dissociation is more stabilized at lower temperatures. The origin of the hydrophobic interaction has been discussed and it has been suggested that any change of water structure around hydrophobic groups is not required to account for the pH-induced conformational transition of PMA.

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