Glass transition in gels

Recent works have shown that gels with a large amount of solvents can still exhibit a glass transition behavior with the thermomechanical properties exhibiting tremendous change over a narrow temperature region. Similar to dry polymers, the rheological behaviors of gels also show a broad distribution of relaxation times. However, so far the effects of solvents on the relaxation spectrum have rarely been studied. In this work, we first develop a viscoelastic model to relate the rheological properties of gels and the corresponding properties in the dry state. We then apply the theoretical model to analyze the complex modulus of gels measured in the small strain dynamic tests. The results show that the breadth of relaxation spectrum has been expanded by increasing the swelling ratio. The physical mechanism behind this observation needs a deep investigation in further study and also raises a significant challenge for developing constitutive models for gels.