High-Rate Dynamics and Fracture Behavior of Model Swollen Polymer Network Characterized by Seeded Laser-Induced Cavitation*

Mechanical characterization of soft materials at high strain rates is challenging due to their high compliance, slow wave speeds, and rate-dependent viscoelasticity. Swollen polymer networks are attractive model materials as they can be tuned to simulate the high-rate dynamics and damage mechanisms of soft tissues, such as the brain, under extreme mechanical stimuli. In this study, seeded laser induced cavitation (SLIC) is performed within polydimethylsiloxane gels containing a significant amount of solvent (50 - 80 wt.%), levels similar to those of soft tissues. Ultrafast stroboscopic observation of a laser-induced microscale cavity is exploited to characterize the viscoelastic response of the gels at strain rates of 10⁶ s^-1. By varying the molecular weight between crosslinks from 1.2 to 12 kg/mol, fracture initiation and post-cavitation characteristics of the gels are systematically controlled. The demonstrated SLIC framework can guide the development of tailored synthetic systems that precisely mimic the high-rate plastic behavior of soft tissues.