Self‐Immolative Polymers Derived from Renewable Resources via Thiol–Ene Chemistry**

The development of polymers from renewable resources is a promising approach to reduce reliance on petrochemicals. In addition, depolymerization is attracting significant attention for the breakdown of polymers at their end-of-life or to achieve specific stimuli-responsive functions. However, the design of polymers incorporating both of these features remains a challenge. Herein, we report a new class of self-immolative polymers based on lignin-derived aldehydes via a simple thiol-ene polymerization. These self-immolative polymers undergo cascade degradation in response to specific stimuli through alternating 1,6-elimination and cyclization reactions. The two methoxy substituents on the syringaldehyde monomer accelerated the desired depolymerization reaction, while enhancing stability against undesired backbone hydrolysis. Moreover, diverse responsive end-caps could be introduced through post-polymerization functionalization from a single polymer precursor.