Molecular mechanisms of cavitation nucleation in polymer networks

Cavitation initiation and growth are key precursors to debonding and failure in soft polymer networks, yet their connection to molecular cohesion and precursor size remains difficult to establish because the operative cavitation mechanism depends sensitively on the size and nature of the initiating precursor. Here, we develop a continuum theory that connects this pre-nucleation cohesive instability to post-nucleation cavity growth. The pre-nucleation response is modeled using a van der Waals-inspired free energy that couples entropic chain elasticity with cohesive resistance to volumetric dilation, yielding a large bulk-to-shear modulus contrast and a non-monotonic pressure-volume response with a well-defined stability limit. The post-nucleation regime is described using a modified Gent-Tompkins cavity-growth model in which the interfacial resistance includes both a baseline cohesive surface energy and a stretch-dependent stiffening contribution from finite-chain extensibility near the cavity wall. By matching the VW critical pressure to the instability of the modified cavity-growth branch, the theory maps molecular cohesion parameters onto an effective elasto-capillary resistance and precursor stretch. The matched framework predicts abrupt pressure-controlled cavity opening, stable growth on the stiffened branch, and discontinuous closure during unloading, thereby producing a hysteretic cavitation response. These results provide a physics-based route for connecting molecular cohesion, precursor activation, and macroscopic cavitation behavior in elastomers and soft adhesives.