Photodegradable hydrogels: Connecting network evolution and material properties by a photo-chemo-mechanical coupling model

Abstract

Degradable hydrogels possess excellent biocompatibility, controllable mechanical properties, and mass transfer capabilities, making them widely applicable in wound dressings, drug delivery, and tissue engineering. By incorporating photo-responsive components into the polymer network, degradable hydrogels can respond to precisely controlled light fields. However, mechanical modeling works on photodegradable hydrogels remain relatively limited. A finite deformation theory coupling photochemical principles is needed to comprehensively describe the mechanical behavior of photodegradable hydrogels. In this study, we developed a photo-chemo-mechanical coupling constitutive model of photodegradable hydrogels within the framework of continuum mechanics. The model involves the photochemical kinetics of the photo-induced degradation process and depicts the evolution of networks in the degradation process using sub-networks, providing a microscopic image more consistent with the degradation mechanism. The model characterizes the changes in mechanical properties and swelling deformation after photodegradation, and corresponding experimental validations are conducted. Building upon this theoretical model, specific recipe compositions and degradation conditions are systematically discussed, and the parameter-property relationships are bridged. This constitutive model reveals the photodegradation mechanism of the hydrogel network at the microscopic level and can predict mechanical behavior at the macroscopic level, guiding the synthesis and application of photodegradable hydrogels.