title: Rheological and chemical analysis of reverse gelation in a covalently crosslinked Diels-Alder polymer network.
abstract: A network polymer, incorporating dynamic and reversible crosslinks, was synthesized using the Diels-Alder reaction. Fourier transform infrared (FTIR) spectroscopy was used to characterize the reaction rate and thermodynamic equilibrium over a broad temperature range. Equilibrium conversion of the furan and maleimide varied from 74% at 85°C to 24% at 155°C, demonstrating significant depolymerization via the retro-Diels-Alder reaction. The gel point temperature, as determined by rheometry using the Winter-Chambon criterion, was 92°C, corresponding to a gel-point conversion of 71%, consistent with the Flory-Stockmayer equation. The scaling exponents for the complex moduli, viscosity, and plateau modulus, in the vicinity of the gel-point, were determined and compared with experimental and theoretical literature values. Further, the material exhibited a low frequency relaxation owing to dynamic rearrangement of crosslinks by the Diels-Alder and retro-Diels-Alder reactions.
authors: Department of Chemical and Biological Engineering, University of Colorado, Boulder, CO 80309-0424, USA.
authors: Brian J
authors: BJ
authors: Adzima
authors: H Alan
authors: HA
authors: Aguirre
authors: Christopher J
authors: CJ
authors: Kloxin
authors: Timothy F
authors: TF
authors: Scott
authors: Christopher N
authors: CN
authors: Bowman