Multiresponsive Azobenzene End-Cap for Self-Immolative Polymers

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• 作者：Andrew D. Wong ; Thomas M. G眉ng枚r ; Elizabeth R. Gillies
• 刊名：ACS Macro Letters
• 出版年：2014
• 出版时间：November 18, 2014
• 年：2014
• 卷：3
• 期：11
• 页码：1191-1195
• 全文大小：295K
• ISSN：2161-1653

文摘

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 polycarbamates. An activated azobenzene derivative was then prepared, allowing for its incorporation as an end-cap for polycarbamates based on alternating N,N鈥?/i>-dimethylethylene diamine and 4-hydroxybenzyl alcohol. Upon treatment with hydrazine, depolymerization proceeded. To demonstrate the versatility of this end-cap, the chemistry was also applied to polycarbamates based on 4-aminobenzyl 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鈥揷is isomerization in response to UV light, providing multiple functions in a single end-cap.