A comparative study on the photocatalytic activity was done for TiO2/poly(acrylamide-co-potassium acrylate) composite hydrogels with varying content of potassium acrylate monomer units. The presence of the acrylate units led to the increase in the swelling ratio of hydrogel and to the enhancement of the diffusion of the methyl orange probe dye to the surface of the embedded TiO2 particles. However, the photocatalytic activity was not improved. Microcalorimetry data showed that while the enthalpy of polymer adhesion to the TiO2 particles surface was positive in the case of polyacrylamide and it became negative if acrylate units were included in the polymer network. Likely, the adhesion enhancement occurred due to the electrostatic interaction among acrylate monomer units and surface of TiO2 particles. As a result of polymer adhesion to the active surface of the catalyst particles was partly blocked and the photocatalytic activity of the composite hydrogel diminished. © 2022 Wiley-VCH GmbH.