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.