Vitrimers: Permanently crosslinked polymers with dynamic network topology

Abstract

The study of synthetic organic polymers rapidly expanded since Staudinger's recognition of the covalent structure of macromolecules. Today, these materials are far from just an academic concept-they are produced industrially and have become ubiquitous in everyday life because of their low cost and desirable physical properties. Nevertheless, a difficult choice between durability and reprocessability continues to hamper efforts to design synthetic organic polymers to be more recyclable. A new class of materials, vitrimers, has emerged as an intriguing approach to circumvent this tradeoff. Vitrimers are permanent networks of polymer chains connected via dynamic covalent bonds, which allow the network to change its topology while maintaining a constant number of chemical bonds at all temperatures. Characterized by both high mechanical performance and facile processing, vitrimers are well positioned to transition from academic labs to industrial production. The aim of this Trend article is to review the concept of vitrimers, describe their most unique properties, and present our outlook on outstanding challenges that must be met to realize vitrimers as a next generation solution for recyclable high performance materials.

Vitrimers: directing chemical reactivity to control material properties

“…A selection of chemistries is provided in our original mini-review and other related overviews and perspectives that recently appeared. [18][19][20][21] Very recently, Winne, Leibler and Du Prez also published a mechanistic perspective on the chemistry underlying vitrimers and dynamic covalent networks in general, with the attempt to clarify the sense and nonsense of distinguishing different types of bond exchange mechanisms, and their relation to mechanical properties. 22 Having established a broad toolbox of building blocks and chemistries that can be used to design vitrimers, researchers are now facing the challenge of gaining control over the reactivity prole, in order to rationally design materials with desired properties in terms of processability and recyclability.…”

Scalable upcycling of thermoplastic polyolefins into vitrimers through transesterification

“…12 Vitrimers are permanently crosslinked polymer networks, insoluble in solvents, but unlike thermosets they can plastically flow at high temperatures, allowing their reprocessing and making a true multi-use plastic. [13][14][15] Importantly, due to the associative nature of their bond exchange, vitrimers retain the same degree of crosslinking even in the stress-induced plastic-flow regime, so the total connectivity remains constant. This means that insolubility remains in force, and contamination on reprocessing is not such a problem as with molten thermoplastics.…”

The Impact of Vitrimers on the Industry of the Future: Chemistry, Properties and Sustainable Forward-Looking Applications

“…Further explanation provided in the text. Sketch based on considerations published by Denissen et al in [6] and Van Zee et al in [15].…”

“…Another potential weakness of point 4 is the insolubility requirement: Breuillac and coworkers designed a polybutadiene vitrimer based on dioxaborolane chemistry, which involves the spontaneous and highly dynamic metathesis of boron-heterocyclic cross-links [50]. Due to the promptness and low activation energy of the dioxaborolane units [3,51], the network was fully dissolved in tetrahydrofuran after 120 h [15,50]. This proves that a prolonged exposure to a good solvent may ultimately lead to the dissolution of a vitrimer, if the conditions are such that they favour dynamic exchanges of bonds.…”