Electrocontrolled swelling and water uptake of a three-dimensional conducting polypyrrole hydrogel

Polypyrrole 3D hydrosponges of tubular structure were synthesized and electrochemically characterized. The Fourier transform infrared attenuated total reflection (FTIR-ATR) spectroscopy technique was employed to study the water uptake of the hydrosponges under different conditions. This technique presentsseveral advantages over conventional swelling measurements due to its specificity that allows analyzing the kinetics of water uptake at the molecular level. In combination with mathematical modeling, FTIR-ATR spectroscopy also enablesthe calculation of the water diffusion coefficients in the hydrogels. The experimental setup also allows electroswelling of the hydrosponges to be studied. The results presented herein are complementary to those obtained with the electrochemicalquartz crystal microbalance with dissipation (EQCM-D) technique and make it possible to determine the actual role played by water in the ionic exchange occurring in conducting polymers during their redox processes. Whereas EQCM-D showsthe whole mass change in the film provoked by injection/ejection of ions and solvent molecules, FTIR-ATR spectroscopy follows water flux only, which thus allows separation of the solvent contribution.