Gelation Behavior of Reversible Diels–Alder Networks based on Precursor Design and the Addition of Multifunctional Microspheres

Diels–Alder (DA) chemistry can be used to synthesize reversible networks that are removable and recyclable, which makes them desirable in additive manufacturing. A long post-curing time to reach full mechanical strength, however, is a challenge because it increases the overall processing time and it may change the final dimensions from the original settings. Accelerating the formation of the DA network can decrease the processing time and reduce the needs of a post-curing step. In this presentation, the gelation behavior of DA networks was investigated with respect to precursors of various architecture, functionality, and molecular weight using rheometry. Thermomechanical properties showed that DA networks formed from flexible precursors yielded a material with a lower glass transition temperature and hence a more elastomeric polymer. The reversibility of the DA network was confirmed by the moduli drop at ~120°C. The gelation time was shown to decrease with an increase in the rigidity of the network. The addition of a small fraction of high functionality molecules demonstrated an efficient acceleration of the formation of DA networks: inclusion of 5 wt.% poly(bismaleimide-co-styrene) microspheres gave a ~2.5 times shorter gelation time.