(250e) Characterization of the Temperature Dependent Chemical and Mechanical Properties of a Diels-Alder Based Crosslinked Polymeric Material
AIChE Annual Meeting
Tuesday, November 18, 2008 - 9:54am to 10:15am
A cross-linked polymeric material was formed by the Diels-Alder
reaction between trisfuran and bismaleimide monomers. At elevated
temperatures, chemical equilibrium shifts from the Diels-Alder
reaction to the retro-Diels-Alder reaction, resulting in
depolymerization. As a consequence, the material is both
reversibly gelled and vitrified, existing as a liquid, polymer gel, or
polymer glass, depending on the temperature and relative reaction progress. FTIR spectroscopy was used to characterize the
conversion of furan and maleimide functionalities to the
oxy-norbornene adduct. Equilibrium conversion of the furan and
maleimide varied from 74 % at 85 degrees Celsius to 24% at 45 degrees
Celsius, demonstrating significant reversion via the retro-Diels-Alder
reaction. At lower temperatures vitrification and the subsequent mass transfer restrictions limit the extent of reaction rather than equilibrium. As a consequence the
highest conversion realized was 87% at 45 degrees Celsius. The
thermomechanical properties of the material were characterized by
rheometry. Both the storage and loss moduli were found to decrease
with increased temperature due to decreasing crosslink density, a result
of the retro-Diels-Alder reaction. The gel point, as determined by
the Chambon-Winters criterion, occurs at 92 degrees Celsius,
corresponding to a 71% conversion of functional groups and consistent
with the Flory-Stockmeyer equation for a stoichiometric mixture of A3
and B2 monomers.
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