Dynamic covalent chemistry enables temperature-stimulated recycling and self-healing properties of polymeric materials. Specifically, the Furan/Maleimide Diels-Alder (FMDA) reaction offers a wide range of Diels-Alder (TDA) and retro-Diels-Alder (TrDA) reaction temperatures, depending on the nature of the substituents enabling the design of a variety of temperature-sensitive polymeric systems. This study proposes to systematically investigate the impact of furan substituent on TDA and TrDA of Exo and Endo adducts from their reaction with the commercially available 1,1′-(methylenedi-4,1-phenylene)bismaleimide (BMI) through 1H-NMR monitoring. The nature of the chemical groups beared by the furan substituent (esters, ether, amide or sulfide bridge), their number and position were also studied to determine the thermal stability of each FMDA adducts.
As an example, 2-furfuryl acetate (FOM) having an electron-donating effect exhibits a completely different reactivity from methyl 2-furoate (FAM). At 30 °C, FOM reached 80 % conversion rate after 24 h while FAM only reached 30 % after 14 days. Moreover, two distinct TrDA were measured for the FOM-based adducts. The TrDA-Endo was around 40 °C and allowed the formation of the more stable Exo-adduct, for which a TrDA-Exo was measured at 90 °C.
This approach was then applied to more sterically hindered systems, in order to simulate the FMDA reaction of functional polycondensates, with the objective to identify the best structures to be used in the development of reversible polymer networks.