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.

No abstract

Apparent molal heat capacities as a function of the degree of neutralization have been determined for dilute aqueous solutions of poly(acrylic acid) (PAA), poly(methacrylic acid) (PMA), copoly(maleic acid‐ethylene) (MAEt), and copoly(maleic acid‐styrene) (MASt) using direct flow microcalorimetry. Apparent molal volumes were measured as well. Both molal heat capacity and molal volume decrease with increasing ionization of the polymer. The effect of the hydrophobic interactions of the methyl group or phenyl group was obtained from the difference in the molal quantities of PMA and PAA, or MASt and MAEt. No evidence of hydrophobic effects, as determined from the heat capacity, was found for the conformational transition of PMA, but the hydration of the phenyl groups in MASt was found to be changed significantly at a degree of neutralization of 0.4.

No abstract