Diffusion-controlled self-healing of reversible Diels-Alder networks

Description

Intrinsic self-healing polymer networks were developed based on dynamic covalent bonding by means of thermoreversible Diels-Alder (DA) cycloadditions. The DA bonds are preferentially broken in case of damage, but also reversibly reform, leading to a repeatable healing cycle and an increased lifetime for many applications, such as sustainable coatings [1], [2]. However, thermo-mechanical robustness is requiring a network in the (partially) vitrified state, with a sufficient-ly high Tg.
This work focuses on the effect of vitrification on DA reaction kinetics, using fully reversible model systems of furan and maleimide compounds. In bulk, using (MT)DSC, vitrification is followed through (non-)isothermal heat capacity meas-urements, while non-isothermal microcalorimetry provides heat flow information.
These results are used to optimize the parameters of a kinetic model, consid-ering the DA endo−exo stereochemistry. In addition, dynamic rheometry allows the construction of time-temperature-transformation (TTT) and continuous-heating-transformation (CHT) diagrams for both reversible elastomers and thermo-sets [3]. A double asymptotic behavior of the isoconversion lines is revealed, and also two subsequent gelation/degelation events can occur during non-isothermal curing.
This bulk study was extended towards thin films through AC chip calorime-try, yielding preliminary results to compare vitrification in bulk and thin layers.
This work is the first systematic study of diffusion-controlled reversible DA network formation. The DA reaction was proven to proceed in diffusion-controlled conditions, allowing self-healing in mobility-restricted applications [2], [4].

Period	29 Aug 2021 → 2 Sep 2021
Event title	ICTAC 2020 17th International Congress on Thermal Analysis and Calorimetry: 8th Joint Czech-Hungarian-Polish-Slovakian Thermoanalytical Conference (V4 8) and 14th Conference on Calorimetry and Thermal Analysis of the Polish Society of Calorimetry and Thermal Analysis (CCTA 14)
Event type	Conference
Degree of Recognition	International