Coupling the Microscopic Healing Behaviour of Coatings to the Thermoreversible Diels-Alder Network Formation

Abstract

While thermally reversible polymer network coatings based on the Diels-Alder reaction are widely studied, the mechanisms responsible for the heating-mediated healing of damage is still not well understood. The combination of microscopic evaluation techniques and fundamental insights for the thermoreversible network formation in the bulk and coating shed light on the mechanisms behind the damage healing events. The thermomechanical properties of thermoset and elastomer coatings, crosslinked by the furan-maleimide Diels-Alder cycloaddition reaction, were studied in bulk and compared to the thermal behaviour applied as coatings onto aluminium substrates. The damage sealing of thermoset (Tg = 79 °C) and elastomer (Tg = −49 °C) coatings were studied using nano-lithography and atomic force microscopy (AFM). The sealing event is studied and modelled at multiple temperatures and correlated to the changes in the network structure and corresponding thermomechanical properties.

Re-usable thermally reversible crosslinked adhesives from robust polyester and poly(ester urethane) Diels–Alder networks

“…It is interesting to compare the creep failure temperatures observed for the adhesive networks reported here to the temperature required for self-healing of coatings from polyether networks recently reported elsewhere 41 also based on the reversible cycloaddition of maleimides and furans. Selfhealing of the coatings was possible starting at 70-80°C depending on cross-link density, quite similar to the upper limits of creep resistance observed here especially considering the different nature of the backbones.…”

“…The strong dependence of network properties on f g is similar to that observed by Van Assche et al on polyether networks based on furan functional prepolymers and BMI monomer cast from solution where materials were investigated in the range f g = 0.69-2.52. 41,42 The relative change in concentration of maleimide functional groups was also monitored as a function of time at ambient temperature after deposition from the melt (Fig. 4).…”

Modeling Self-Healing Mechanisms in Coatings: Approaches and Perspectives

“…Dynamic polymeric networks based on reversible chemistries lead to coating systems that actively react to externally applied stimulus such as changes in temperature [5,10] and exposition to UV light [12]. The incorporation of reversible bonds enhances polymer flow, but at the expense of its strength.…”

“…Barrier recovery can be achieved by means of the enhancement of polymer chain mobility, the production of continuous phases at the crack gap or by the expansion of dispersed phases. The increase of polymer mobility has been pursued by the implementation of reversible chemistries, such as those based on (retro) Diels-Alder reactions [3][4][5] and disulfide [6][7][8][9][10], hydrogen [11] and trithiocarbonate [12] bond reactions. Most of these approaches require the supply of an external trigger (such as an increase of temperature or photostimulation) to activate the healing response, but the self healing mechanism is repeatable.…”

Additive Manufacturing for Self-Healing Soft Robots

“…To this end, the in-house developed software toolbox MATKIN was used. 34,35 This toolbox also calculates the molecular weight of the polymer, and from these values, the viscosity is obtained. As a power law describes the relationship between molecular weight M W and viscosity g, experimental viscosity values obtained using rheometry are plotted against the simulated molecular weight.…”