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Updated: Oct 9, 2025

Evaluation of the Curing of Adhesive Systems by Rheological and Thermal Testing
Published on: July 3, 2020
The role of crosslinking density in surface stress and surface energy of soft solids
Weiwei Zhao1, Jianhui Zhou1, Haitao Hu1
1Department of Physics, The Hong Kong University of Science and Technology, Hong Kong, China. qinxu@ust.hk.
Abstract:
Surface stress and surface energy are two fundamental parameters that determine the surface properties of any material. While it is commonly believed that the surface stress and surface energy of liquids are identical, the relationship between the two parameters in soft polymeric gels remains debatable. In this work, we measured the surface stress and surface energy of soft silicone gels with varying weight ratios of crosslinkers in soft wetting experiments. Above a critical density, k0, the surface stress was found to increase significantly with crosslinking density while the surface energy remained unchanged. In this regime, we can estimate a non-zero surface elastic modulus that also increases with the ratio of crosslinkers. By comparing the surface mechanics of the soft gels with their bulk rheology, the surface properties near the critical density k0 were found to be closely related to the underlying percolation transition of the polymer networks.
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