On 14 January 2021, Audrey Cuvellier successfully defended her PhD thesis titled "Combining reversible and permanent bonds in interpenetrating and partially reversible polymer networks for toughening and healing of thermosets", being awarded the highest distinction and receiving felicitations from the jury. Congratulations Audrey!
Abstract of the PhD research
Materials get damaged during use. To prevent or at least postpone failure, the size of the structure is taken larger than needed for expected use. However, this safety factor makes objects larger, heavier and more taxing on nature than necessary. Lately, researchers have focussed on damage recovery and various self-healing strategies have been developed. Amongst these, healing capability has been introduced in polymers through the use of reversible chemical bonds that can reform after being broken, restoring the material’s properties. The reformation of these bonds can be autonomous or requiring activation through e g heat or light.
In this PhD, reversible bonds were used in stiff polymer networks, to improve energy dissipation and increase the elongation before fracture. These stiff polymer networks consist of a combination of two materials that each have their own function. One of the materials is stiff and contains reversible bonds, while the other one is rubbery and has permanent bonds only. When a certain deformation is exceeded, the weaker reversible bonds in the stiff material break, while the rubbery material remains intact and stretches, preventing failure and making sure the broken bonds will come back together after removal of the deformation stresses. As such the broken reversible bonds can reform. The reversible Diels Alder chemistry was combined with an epoxy amine chemistry into two network designs interpenetrating polymer network and partially reversible polymer network. Various compositions were used and the influence on the mechanical properties was studied. The energy dissipation capacity of both network design strategies was compared. In addition, the reaction kinetics of this thermally reversible Diels Alder reaction was studied using calorimetry.