The tacticity to triad and partial pentad resolution, of a commercial sample of poly(acrylic acid) was determined by 1H and 13C NMR. Curve deconvolution of the 13C NMR spectrum for the methine resonances gave relative areas of 27, 50, and 23% for the rr, mr, and mm sequence, respectively, based on Schaefer's peak assignments. The use of Bernoullian statistics gave the corresponding probabilities of r and m configuration as 52% and 48%, respectively, establishing the atactic character of the polymer. This was confirmed by the 1H NMR spectrum of the methylene protons. The simulated pentad spectrum was constructed on the basis of these probabilities and the experimental spectrum. The changes in chemical shift of the methine resonance for each tacticity and for the carbonyl resonance with changing pH were treated as typical polyelectrolyte titrations and analyzed by the extended Henderson-Hasselbalch and Mandel's equations. We found a small tacticity effect on the acid dissociation behavior of poly (acrylic acid). © 1985, American Chemical Society. All rights reserved.