Multiresponsive Azobenzene End-Cap for Self-Immolative Polymers

Azobenzene was introduced as a new multiresponsive end-cap for self-immolative polymers Using small-molecule model compounds, it was demonstrated that reducing agents including hydrazine and dithiothreitol could reduce the azobenzene to the corresponding hydrazobenzene, resulting in a 1,6-elimination reaction with the potential to initiate the depolymerization of self-immolative polycarbaniates. An activated azobenzene derivative was then prepared, allowing for its incorporation as an end cap for Polycarbamates based on alternating N,N'-climethylethylene diamine and 4-hydroxybenzyl alcohol. Upon treatment with hydrazine, depolymenzation proceeded. To demonstrate the versatility of this end cap, the chemistry was also applied to polycarbamates based on 4-anunobenzyl alcohol In addition to allowing triggered depolymerization, the azobenzene end cap also provides a visual signal upon triggering owing to the strong visible absorption of the azobenzene, which shifts to the UV range upon reduction. Furthermore, azobenzene is capable of undergoing trans-cis isomerization in response to UV light, providing multiple functions in a single end cap.