Thermophysical characterization of a reversible dynamic polymer network based on kinetics and equilibrium of an amorphous furan-maleimide Diels-Alder cycloaddition

Publication date: 30 June 2017
Source:Polymer, Volume 120
Author(s): M.M. Diaz, G. Van Assche, F.H.J. Maurer, B. Van Mele
The equilibrium and kinetics of the furan-maleimide Diels-Alder (DA) reaction for the formation of a reversible network were studied by calorimetry between 25 °C and 90 °C using an amorphous bismaleimide eliminating solvent use. The relationship between the equilibrium conversion xeq with temperature and the effect of dilution were simulated. The glass transition-conversion relationship of the reversible network was established.The thermophysical properties of the reversible network were linked to the kinetics and equilibrium of the DA system, and studied by dynamic mechanical analysis (DMA), dielectric analysis (DEA) and rheometry. Below Tg the reversible network behaves like an irreversible network; however, above Tg, a decrease in the rubber tensile storage modulus was observed due to a reduction of cross-link density caused by the retro DA reaction. DEA revealed that above Tg, an interface is formed between released bismaleimide molecules and the remaining network. The rheological behavior is related to xeq and the lifetime of the reversible covalent bonds. When xeq is higher than the gelation conversion xgel (below 90 °C), the system gels at constant xgel. An elastic strengthening effect is observed in a transition region between 90 °C and 115 °C. Above 115 °C the system is reaching a viscous melt behavior. These observations are important for the application of this network as a self-healing material and as a recyclable elastomer or thermoset.

Graphical abstract

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