Thank you for your response and guidance. This is exactly what I want that the temperature of water changes as it interacts with the hydrogel and this part works fine. The only thing I was concerned about was whether the hydrogel volume would be fixed by only applying NVT to hydrogel and not the entire system. From your response, my understanding is that “V” in NVT will keep the volume of the entire simulation domain fixed and not the volume of the group to which NVT is being applied to. Is my understanding correct?
Thank you again for the help.