Creep and Recovery Behavior of Vitrimers with Fast Bond Exchange Rate

Abstract

Vitrimers encompass the desirable mechanical properties of thermosets with the recyclability of thermoplastics. This ability arises from the rearrangement of the vitrimer covalent network upon heating via a bond shuffling mechanism while its cross‐link density remains preserved. This unique feature makes vitrimers interesting candidates for the design of materials that combine dimensional stability at high temperatures and solvent resistance with the ability to be reshaped and processed. Despite these advantages, vitrimer exhibits significant creep at operating conditions where thermosets show little or no creep. As the mechanical properties of vitrimers not only depend on their chemical composition but also on the dynamics of the polymer chains, molecular dynamics (MD) simulations can provide detailed molecular mechanisms of the system of interest under macroscopic stress‐induced deformations. In this regard, the recently developed MD/Monte Carlo simulation methodology capable of capturing the bond exchange mechanics in vitrimers is used to study the creep and recovery response of a coarse‐grained model thermoset and vitrimer with a fast bond exchange rate. The time‐stress superposition principle is then successfully applied to the creep response. The resulting universal curves enable us to predict the long‐time creep behavior of both systems extending the timescale from 4 to over 10 orders of magnitude.

Phase separation in supramolecular and covalent adaptable networks

“…As such, when a force is applied that leads to deformation of a CAN material, stress re- laxation via bond exchange will compensate for this deformation, leading to creep of the material. 149 To relieve the issue of creep in CANs, research has been focused on changing the reactivity and characteristics of the DC bonds, to tune the structural integrity and strength in the final materials. This has been done chemically, e.g., by changing local polarity 150 or sterics 144,151 near the DC bonds, by means of metal-coordination of dynamic covalent groups, 152,153 or by modifying the electronic behaviour of the DC bond, [154][155][156] .…”

“…As such, when a force is applied that leads to deformation of a CAN material, stress relaxation via bond exchange will compensate for this deformation, leading to creep of the material. 149 To relieve the issue of creep in CANs, research has been focused on changing the reactivity and characteristics of the DC bonds, to tune the structural integrity and strength in the final materials. This has been done chemically, e.g.…”

Vitrification: Versatile Method To Modulate Properties of Myrcene-Based Rubbers

“…However, CANs can undergo depolymerization under certain conditions and temperatures, limiting their applications . This has led to the development of vitrimers, first reported in 2011, as a new category of polymeric materials bridging the gap between thermosets and thermoplastics. , Vitrimers are permanently cross-linked networks with thermally induced “associative” dynamic covalent bonds. , This provides them with a unique ability to behave like thermosets at service temperatures but can change topology and be reprocessed without decreasing connectivity and dissolution at elevated temperatures. , Several catalyst-free chemistries, such as exchange of silyl ethers, imines, vinylogous urethanes, ,, disulfides, dioxaborolane metathesis, − hydroxy urethanes, and metathesis of cyclic acetals, have been reported, showing great potential for malleability, shape memory, and weldability. − Despite these advantageous properties, it has been commonly reported that vitrimers undergo substantially higher creep compared to their static thermosetting counterparts. , Improving the dimensional stability of vitrimers is still an evolving area of research. It has been shown that a vitrimer’s molecular architecture greatly influences its malleability and rheological properties. − …”

Harnessing Formamide Groups to Enhance the Heat‐Resistance of Poly(β‐amino esters) with Investigation into Reprocessability and Fluorescence

“…[12][13][14][15] To date, many kinds of dynamic covalent bonds such as ester bonds, [16] imine bonds, [17] disulfide bonds, [18,19] and siloxane bonds [20] have been used to prepare CANs to realize the reprocessing or recycling of thermosets. [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37] DOI: 10.1002/macp.202300278 Among the dynamic covalent bonds mentioned above, ester bonds are the most commonly used for CAN synthesis. [28] For example, ester bond-based epoxy resin CANs can be obtained by using anhydride and dicarboxylic acid as the crosslinkers, which can be reprocessed via transesterification.…”

“…[ 12–15 ] To date, many kinds of dynamic covalent bonds such as ester bonds, [ 16 ] imine bonds, [ 17 ] disulfide bonds, [ 18,19 ] and siloxane bonds [ 20 ] have been used to prepare CANs to realize the reprocessing or recycling of thermosets. [ 21–31,32–37 ]…”