New Thermally Remendable Highly Cross-Linked Polymeric Materials

Abstract

Two new remendable highly cross-linked polymers, 2ME4F and 2MEP4F, were prepared without solvent. Solid-state NMR (nuclear magnetic resonance) was used to study the thermal reversibility of Diels−Alder (DA) cross-linking, and it was found that DA connections and disconnections of both polymers are thermally reversible. Differential scanning calorimeter and dynamical mechanical analysis were applied to study thermal and mechanical properties of these materials, and it is found that the glass transition temperature (T g) of 2ME4F is about 30−40 °C and that of 2MEP4F is about 80 °C. A qualitative study of the healing efficiency of 2MEP4F showed that cracks can be healed effectively with a simple thermal healing procedure. This process can be repeated to heal cracks multiple times.

Intrinsic self-healing polymers with a high E-modulus based on dynamic reversible urea bonds

“…[3][4][5] In contrast, intrinsic self-healing materials can recover their properties due to the presence of specific reversible chemical bonds, which is beneficial due to the possibility of multiple healing steps at the same location. 6 These binding motifs can be composed of either dynamic covalent bonds, [7][8][9] for example, the Diels-Alder reaction [10][11][12] or radical-based systems, 13 or supramolecular interactions, such as hydrogen or halogen bonds, [14][15][16] ionic interactions, 17 π-π interactions, 18 host-guest interactions 19 or metal-ligand interactions. [20][21][22][23] Often there is a trade-off between the mechanical properties and the healing efficiency (Figure 1).…”

Composites, Multifunctional

“…In this case, the polymer (a furan based monomer synthesized with 1.8-bis(maleimido)-3.6 dioxaoctane) was subjected to mechanical testing lead ing to fracture followed by heat treatment at 130°C for 30 min. In this case, there was no loss in the original strength when the structure was re-tested [24]. This ap proach to self-healing has the clear advantage that no ad ditional material is needed to be added: the material is in trinsically self-healing.…”

“…This idea is based on that the elevated temperature activates a chemical process that results in healing. For example, by utilizing a particular thermally reversible reaction (e. g., a selected Diels-Alder reaction) for cross linking linear polymer chains, a fractured ma terial can be healed, as demonstrated by Chen and co workers [23,24]. For one material system investigated, af ter fracture and subsequent heat treatment, the original strength was regained.…”

An empirical model for estimating fracture toughness using the DCDC geometry

“…The final specimen remains intact after unloading and contains large axial cracks. This is a desirable configuration, particularly for crack healing studies (Plaisted and Nemat-Nasser 2007), where the sample would otherwise have to be manually reassembled (Chen et al 2002).…”