Electric field responsive chitosan–poly(N,N-dimethyl acrylamide) semi-IPN gel films and their dielectric, thermal and swelling characterization

The electroresponsive, dielectric and swelling behavior of semi-interpenetrated polymer network (semi-IPN) gel films prepared from chitosan (CS) and N,N-dimethyl acrylamide (DA) were investigated and compared with those CS film. CS–DA semi-IPN films were also characterized by Fourier transform infrared, x-ray diffraction and differential scanning calorimetry measurements. The electrosensitivity of CS–DA films to an electric field was investigated by determining their bending at 8 V in (0.05 M/0.1 M/0.15 M) NaCl solution. Equilibrium swelling values of CS–DA films both in distilled water and buffer solution with pH = 2.2 decreased with poly-DA (PDA) content of the films. While the maximum decomposition of CS film took place at about 296 °C, the presence of PDA in CS–DA semi-IPN films reduced the thermal stability, and their maximum decomposition temperature shifted from 261 to 240 °C with the increase in PDA content. In addition, the PDA network led to a decrease in the dielectric constant (ε'), dielectric loss (ε'') and conductance (σ) of CS–DA semi-IPN films in the frequency range between 12 Hz and 100 kHz. The values of electric modulus and impedance, and Cole–Cole plots confirmed that the conductance values of CS–DA films are lower than that of CS film. The PDA network also led CS–DA films to respond more slowly to electric field. The increase in NaCl concentration in the bending medium increased the response rate of CS–DA films to an electric field. The final bending angle of all CS–DA films was 90°, and it was not dependent on either NaCl concentration or PDA content of the films.