Polymer hydrogels of 2-hydroxyethyl acrylate and acrylic acid obtained by frontal polymerization.

In this work, we report on the synthesis and characterization of homopolymers and copolymers of acrylic acid and 2-hydroxyethyl acrylate prepared by the use of the frontal polymerization (FP) technique. Tetraethyleneglycoldiacrylate was used as a crosslinker and benzoyl peroxide as an initiator. The maximum temperatures reached by the front were in the range between 214 °C and 296 °C. Besides, front velocities ranged between 3.9 and 10.8 cm/min, the latter being one of the highest values reported so far in the FP literature. Differential scanning calorimetry was used to estimate the conversion degree, which was always comprised between 90% and 96%, and to determine the glass transition temperatures, which were found to be dependent on the composition, with values ranging from 13 °C to 168 °C. Moreover, the obtained materials were allowed to swell in aqueous solutions at various pH. The samples exhibit a moderate increase of the swelling ratio percentage (SR%) at pH ? 5-6, and a sudden and larger SR% increase at pH ? 12-13 depending on the composition, thus indicating the obtainment of pH-responsive polymer hydrogels. © 2012 Wiley Periodicals, Inc.