The isothermal kinetic of the release of nicotine from a poly(acrylic acid) (PAA) hydrogel was investigated at temperature range from 26 degrees C to 45 degrees C. Specific shape parameters of the kinetic curves, the period of linearity and saturation time were determined. The change in the specific shape parameters of the kinetic curves with temperature and the kinetic parameters of release of nicotine E-a and ln A were determined. By applying the "model fitting" method it was established that the kinetic model of release of nicotine from the PAA hydrogel was [1 - (1 - alpha)(1/3)] = k(M)t. The limiting stage of the kinetics release of nicotine was found to be the contracting volume of the interaction interface. The distribution function of the activation energy was determined and the most probable values of activation energies of 25.5 kJ mol(-1) and 35 kJ mol(-1) were obtained. Energetically heterogeneity of the interaction interface was explained by the existence of the two different modes of bonding the nicotine molecules onto the hydrogel network by hydrogen bond and electrostatic forces. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 119: 1805-1812, 2011