Engineering and Exploring Hydrolytic Degradation in 3D-Printed Liquid Crystalline Elastomers

Liquid crystalline elastomers (LCEs) are being increasingly explored as biomaterials; however, many LCE properties were not designed with biomedical use in mind. Here, we examine LCE hydrolytic degradation, including investigating approaches to accelerate degradation and whether thermal and mechanical properties change with degradation. Among 3D-printable LCE chemistries, we find that networks formed via thiol-Michael addition followed by thiol-ene photo-cross-linking degrade most rapidly. The integration of hydrophilic chain extenders (e.g., PEG) accelerates LCE degradation and demonstrates their potential tunability for various applications. We monitor representative LCEs throughout degradation and show that as samples undergo heterogeneous surface erosion, nematic-to-isotropic transition temperatures increase, while actuation potential, alignment, and mechanical anisotropy remain stable until failure. ¹H NMR, SAXS, and DSC studies reveal that thermal changes arise from retained degradation products enriched in liquid crystal mesogens, which increase mesogenic interactions per unit volume and require greater thermal energy to disrupt the nematic state.