Preparation and Moisture Absorption Behavior of PAM/CS/GO Hydrogels

Using acrylamide (AM) as monomer, chitosan (CS) and graphene oxide (GO) as functional components, N, N'-methylene bisacrylamide (MBA) as crosslinking agent, a series of PAM/CS/GO composite hydrogels with three-dimensional network structure were prepared by free radical polymerization. The chemical composition, structure, morphology, and mechanical properties of the composite hydrogels were analyzed using Fourier transform infrared (FT-IR) spectroscopy, X-ray diffractometer (XRD), scanning electron microscope (SEM), and universal testing machine. The experimental results show that GO is uniformly dispersed in the PAM/CS hydrogel matrix. Compared with PAM/CS hydrogels, PAM/CS/GO hydrogels have a tighter porous structure with an average pore diameter of about 55.7 μm. In addition, the mechanical properties of PAM/CS/GO hydrogels have been significantly improved, the largest elongation at break is 2 039%, and the maximum breaking stress reaches 237 kPa. This is due to the fact that GO acts as a physical crosslinking agent in the PAM/CS hydrogel to form good interface bonds. The hydrogel with cross-linked network structure and plenty of hydrophilic groups can be used as the sensing coating of the quartz crystal microbalance (QCM), and the QCM humidity sensor based on the functional hydrogel film is prepared. The moisture absorption behavior of composite hydrogel films was studied using QCM technology under different humidity conditions. As the air relative humidity (RH) increases from 33% to 85%, the frequency response of the composite hydrogel film modified QCM sensor increases from 12.2 Hz to 22.3 Hz. This research work provides valuable reference for the application of the hydrogel coating in the field of QCM humidity sensors.