Preparation and Characterization of a Small Library of Thermally-Labile End-Caps for Variable-Temperature Triggering of Self-Immolative Polymers

The
reaction between furans and maleimides has increasingly become
a method of interest as its reversibility makes it a useful tool for
applications ranging from self-healing materials, to self-immolative
polymers, to hydrogels for cell culture and for the preparation of
bone repair. However, most of these applications have relied on simple
monosubstituted furans and simple maleimides and have not extensively
evaluated the potential thermal variability inherent in the process
that is achievable through simple substrate modification. A small
library of cycloadducts suitable for the above applications was prepared,
and the temperature dependence of the retro-Diels–Alder processes
was determined through in situ 1H NMR
analyses complemented by computational calculations. The practical
range of the reported systems ranges from 40 to >110 °C. The
cycloreversion reactions are more complex than would be expected based
on simple trends expected based on frontier molecular orbital analyses
of the materials.

呋喃（furans）与马来酰亚胺（maleimides）之间的环加成反应因其可逆性而日益成为研究热点，其应用场景覆盖自修复材料、自降解聚合物、用于细胞培养的水凝胶以及骨修复制剂的制备。然而，现有此类应用大多仅采用简单的单取代呋喃与简单马来酰亚胺，尚未全面评估通过简单底物修饰即可实现的该反应内在的热变异性潜力。本研究制备了适用于上述应用的小型环加合物（cycloadducts）库，并通过原位1H核磁共振（in situ 1H NMR）分析结合计算模拟，测定了逆狄尔斯-阿尔德（retro-Diels–Alder）过程的温度依赖性。所报道体系的实用温度区间为40℃至110℃以上。该环逆转反应的复杂度高于仅通过材料前沿分子轨道分析得出的简单趋势预期。