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Diels
Alder Based Polymers
We have used the thermally reversible
Diels Alder reaction as the polymerization/depolymerization system for our
removable materials. The Diels Alder reaction most often involves the (4
+ 2) cycloaddition of a (4 p electron) diene with a (2 p electron) dienophile
to give a cycloadduct. The reaction is widely used synthetically because
it allows the formation of complex rings with two new bonds being formed
and multiple stereocenters being generated in a predictable fashion. The
reaction is thermodynamically reversible with, in many cases, the cycloaddition
reaction occurring at room temperature. The reverse or “retro Diels Alder”
reaction occurs at higher temperatures. The furan-maleimide Diels Alder
reaction was used in our materials because of the 1) readily available starting
materials, 2) one step monomer or oligomer synthesis, 3) polymerization
under ambient to 60 °C and 4) depolymerization at 90-120 °C. A resin based
on the polymer of a bisfuran and a bismaleimide cures at 60 °C to form an
acceptable encapsulant or foam for electronics that can be easily removed
at 120 °C. We have also successfully used the furan-maleimide DA adduct
as a weak link in a variety of materials including polyurethanes, epoxies,
and silicones.
Contact: Doug Loy
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