Polymer complexes of poly(N-isopropylacrylamide) with poly(acrylic acid) and poly(methacrylic acid) partially neutralized have been isolated, for degrees of neutralization up to 15%, as a consequence of their mutual precipitation in aqueous solution. Blends of these polymers have been prepared for higher degrees of neutralization of the polyacids, where no insolubilization is observed in their aqueous mixtures. The obtained samples have been calorimetrically studied. All complexes present a single high T-g, while the blends present two T(g)s, one of them also very high. Thermal behavior of complexes and blends have also been studied.