- 9:54 AM
250e

Characterization of the Temperature Dependent Chemical and Mechanical Properties of a Diels-Alder Based Crosslinked Polymeric Material

Brian Adzima1, Christopher J. Kloxin2, Timothy F. Scott2, and Christopher N. Bowman2. (1) Dept. of Chemical and Biological Engineering, University of Colorado, ECCH 111, UCB 424, Boulder, CO 80309, (2) Chemical and Biological Engineering, University of Colorado, Boulder, CO 80309

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.