Vitrimers is a relatively new term [1] for a class of polymers that have existed for decades. These class of polymers are special as they have properties of both thermosets and thermoplastics. Traditionally, thermoplastics can be recycled and reworked. Thermosets are generall known to not undergo any further reactions and chemical changes once they are formed and crosslinked. Usually thermosetting resins cannot be recycled and reworked like the thermoplastic counterpart.
Vitrimers have crosslinked structure like thermosets but they can be recycled like thermoplastics. This is made possible because of bond-exchange reactions. These bond exchange reaction happen even in the solid state - so the thermoset polymer has a mechanism of plasticity and adhesive bonding even in the solid-state.
The first vitrimer polymer was developed by James Economy’s group at UIUC in the 1990’s [3, 4]. The research group demonstrate a new class of thermoset polymer systems that were processable by virtue of topology changes within the covalent networks as mediated by bond exchange reactions. This class of polymers was called aromatic thermosetting copolyester. It was shown that composite laminae could be consolidated to make a dense composite structure. [5] The Economy group conducted studies employing secondary ion mass spectrometry (SIMS) on deuterated and undeuterated fully cured vitrimer layers to discriminate the length scales (<50 nm) for physical interdiffusion between vitrimers constituent atoms – providing evidence towards eliminating physical interdiffusion of the polymer chains as the governing mechanism for bonding between vitrimer layers [6]. Recent NASA-funded work on reversible adhesives for in-space assembly has used a high performance vitrimer system called aromatic thermosetting copolyester (ATSP) as the basis for coatings and composites reversibly bondable in the solid state – providing new possibilities for the assembly of large, complex structures for space exploration and development [7, 8].
The term vitrimer came after two decades of this work and it has drawn interest to this new field of polymers. Vitrimers were first termed as such in the early 2010s by French researcher Ludwik Leibler, from the CNRS[4]. Leibler and co-workers developed silica-like networks using the well-established transesterification reaction of epoxy and fatty dicarboxylic or tricarboxylic acids.[7]
Besides epoxy resins, other polymer networks have been used to produce vitrimers, such as aromatic polyesters [3, 4], polylactic acid (polylactide),[2] polyhydroxyurethanes,[10] epoxidized soybean oil with citric acid[12] and polybutadiene.[13]
Because of the ability to undergo these bond exchange reactions, vitrimers can emerging to be an important category in the polymer field. With vitrimers, you can get best of both worlds – you get a crosslinked network with high dimensional stability and other unique properties like elasticity while being able to reprocess and recycle into different shapes and forms.
ATSP innovations has taken the leap into commercializing vitrimers based on aromatic polymers on the foundational work by the Economy group in the 1990s. Check out our product offerings in the high Tg polymers, composites, low-wear materials and adhesives space at www.atspinnovations.com.
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12. Y-X, Lu. JACS. 134: 8424–8427. (2012)
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