Preparation and characterization of anti-freezing conductive organohydrogel based on carboxyl modified polyvinyl alcohol and polypyrrole

Abstract

Functional hydrogels have many excellent properties and many potential applications. However, hydrogels are easy to lose certain moisture or solvent in open environment, which makes volume shrinkage and hardness enhancement, even failure to possess use value. In addition, hydrogels usually lose their flexibilities at lower temperature due to water freezing. Therefore, the study of gels with low temperature flexibility and water retention are of great significance. In this paper, a kind of anti-freezing conductive organohydrogel was prepared from carboxyl modified polyvinyl alcohol which was dissolved in water and dimethyl sulfoxide (DMSO) (molar ratio = 3:1), pyrrole was added to the solution and polymerized, then gels were obtained by freeze-thawing method. It was found that the mixed solvent shows excellent low temperature freezing resistance, the carboxyl groups give favorable water retention property, polypyrrole makes the gel conductivity. The gels show good flexibility even at −60 °C. In open environment the mass loss of gels is only 30% after 17 days at room temperature. When the pyrrole content is 10%, the gel conductivity reaches the maximum value of 1 S/m. However, the introduction of pyrrole brought two changes, on one hand, when the pyrrole content increased from 0% to 10%, the mass retention dropped from 83% to 70%. On the other hand, with the content of pyrrole increased, the fracture stress of the organohydrogel first increased and then decreased. When the pyrrole content was 2%, the fracture stress reached the maximum value of 0.50 MPa. The gels can be further crosslinked by Fe3+, which was helpful for improving the mechanical properties. It is of great importance for recording intricate deformational signals in advanced flexible sensors.