Vitrimers acmc_logo

Vitrimers, also known as Covalent Adaptable Networks (CAN), were first discovered and named by Ludwik Leibler [1, 2] in 2011.  They are a third class of polymers [3, 4] which, like the thermosets, have covalent molecular networks. However, thermally activated bond-exchange reactions mean they can be formulated to crosslink at certain temperatures like thermosets, but at elevated temperatures vitrimers can be softened and reformed like thermoplastics.  As flow is controlled by the chemical exchange reactions, the viscosity decrease has Arhennian characteristics similar to vitreous silica, making vitrimers the first reported strong organic glass formers [5].  Vitrimers have two transition temperatures: the classical glass transition temperature (Tg) and a topology freezing transition temperature (Tv).  The latter is characterised by a change from a viscoelastic solid to a viscoelastic liquid.  Tv recognises the increasing rate of the exchange reactions where vitrimers become processable but lose their resistance to creep [5].

Yue et al [6] have suggested that unrecyclable thermoset materials by vitrimisation of the permenent networks into dynamic netwroks.  The polymers can be reprocessed, and maybe even upcycled or healed, by swelling the thermoset network in solution with catalyst to enable a transesterification reaction exchange between the ester and the hydroxyl groups within the thermoset network.  Potential catalysts include tin (II) 2‐ethylhexanoate (Sn(Oct)2), zinc acetylacetonate, triazobicyclodecene, triphenylphosphine, zinc acetate and zinc octoate.  Solvents were dichloromethane (DCM) for polyurethane and dimethylformamide for epoxy.

Kloxin et al [7] discuss both thermoreversible and photoreversible (photochemically triggered) CAN with attributes including recyclability, healability, tunability, shape changes and low polymerisation stress.

Video

Review papers on vitrimers

References

  1. D Montarnal, M Capelot, F Tournilhac and L Leibler, Silica-Like malleable materials from permanent organic networks, Science, 2011, 334(6058), 965-968.
  2. M Capelot, D Montarnal, F Tournilhac and L Leibler, Metal-catalyzed transesterification for healing and assembling of thermosets, Journal of the American Chemical Society, 2012, 134(18), 7664-7667.
  3. J Sloan, Vitrimers: the reprocessable thermoset, CompositesWorld, October 2020, 6(4), 32-34.
  4. JL Meyer, Z Parkar and P Lan, Reinforced vitrimers: thermosets that process like thermoplastics, Reinforced Plastics, July/August 2021, 65(4), 190-194.
  5. W Denissen, JM Winne and FE Du Prez, Vitrimers: permanent organic networks with glass-like fluidity, Chemical Science, 2016, 7(1). 30-38.
  6. L Yue, VS Bonab, D Yuan, A Patel, V Karimkhani and I Manas‐Zloczower, Vitrimerization: a novel concept to reprocess and recycle thermoset waste via dynamic chemistry, Global Challenges, July 2019, 3(7), 1800076.
  7. CJ Kloxin, TF Scott, BJ Adzima and CN Bowman, Covalent Adaptable Networks (CANs): a unique paradigm in crosslinked polymers, Macromolecules, 23 March 2010, 43(6), 2643–2653.

Created by John Summerscales on 06 October 2020 and updated on 16-Sep-2021 9:28. Terms and conditions. Errors and omissions. Corrections.