Extrudable Vitrimeric Rubbers Enabled via Heterogeneous Network Design

Abstract

The state-of-the-art reprocessing of vitrimers still struggles in crude hot-compression processes. The highly cross-linked nature and glass-like viscoelastic behavior of vitrimers critically restrict the network chain mobility, which limits the application of continuous processing techniques during reprocessing. Herein, a multiphase design strategy is outlined through incorporating highly cross-linked vitrimeric powders into a polymer matrix, followed by cross-linking with dynamic covalent bonds (DCBs) containing cross-linkers to form multiphase DCB-based networks. Accordingly, inhomogeneous stress distribution can be achieved inside the networks during deforming. The resulting high interfacial stress significantly accelerates the network relaxation upon mechanical activation enabling extrudable reprocessability to the vitrimeric rubbers with ∼100% recovery of overall performance. Moreover, the inhomogeneous stress distribution also promotes the chain orientation of the networks, leading to a remarkably mechanical reinforcement of the samples without compromising the elasticity. We envisage that this design concept can indeed facilitate the vitrimers toward industrial applications, which is significant to the sustainable development of rubber industry.

Design of ester crosslinked rubber with high dynamic properties by increasing dynamic covalent bond density

“…46 As a result, rubber vitrimers often show significantly longer relaxation times than epoxy vitrimers. To obtain rubber vitrimers with favorable dynamic properties, several DCBs with high dynamic activity (such as the boronic ester bond 47,48 and disulfide bond [49][50][51] ) have been proposed for rubber networks. Wu and Huang et al 52 constructed a rubber vitrimer with ester bonds and disulfide bonds, which showed rapid relaxation ability and improved mechanical properties, by a self-strengthening strategy after network rearrangement.…”

Bio-Based, Self-Healing, Recyclable, Reconfigurable Multifunctional Polymers with Both One-Way and Two-Way Shape Memory Properties

“…The stability of the cross-linking network of EUG-OH-BDBA was confirmed by the swelling ratio in different solvents (Figure S4). After being immersed for 7 days, EUG-OH-BDDA-1 hardly swelled in water and ethanol, but the swelling rate in tetrahydrofuran and xylene is 653 and 632%, respectively, which is similar to vulcanized rubber …”

“…After being cured by BDBA, the stretching vibration peak of −OH at 3417 cm −1 decreased significantly, and the bending vibration peak of −OH at 1548 cm −1 disappeared, while a new absorption peak attributed to B−O stretching vibration appeared at 1263 cm −1 . 48 These results indicate that the −OH of EUG-OH reacts with BDBA to from borate ester bonds. The curing behavior was monitored by moving the die rheometer, and the increase in torque (elastic modulus) demonstrates the formation of a cross-linking network (Figure 2b).…”

“…After being immersed for 7 days, EUG-OH-BDDA-1 hardly swelled in water and ethanol, but the swelling rate in tetrahydrofuran and xylene is 653 and 632%, respectively, which is similar to vulcanized rubber. 48 The thermal properties of EUG-OH-BDBA were investigated by DSC. As shown in Figures 2d and S5, and summarized in Table S1, with the amount of BDBA increased from 0.5 to 1.5 phr, the glass transition temperature (T g ) of EUG-OH-BDBA increased from −59.1 to −58.5 °C.…”

Mechanically Robust, Self-Repairable, Shape Memory and Recyclable Ionomeric Elastomer Composites with Renewable Lignin via Interfacial Metal–Ligand Interactions

“…The polar ionic groups tend to aggregate into microphase-separated ionic-rich domains in the nonpolar elastomer matrix, acting as physical cross-links and reinforcing points. − The ionomeric elastomers can show shape memory behavior and self-healing ability due to the dynamic nature of ionic interactions. − In the past decades, dynamic covalent polymer networks have provided another avenue for recycling elastomers at end of life due to their thermoplastic-like properties. However, the researchers were still struggling in crude hot-compression processes for the reprocessing of dynamic covalent polymers. − Recently, TPEs have become the most rapidly growing elastomers as substitutes for nonrecyclable cross-linked rubbers due to the requirement for resource-saving and sustainable development. However, most commercially available TPEs are derived from petroleum-derived products; thus, it is highly desirable to find a nonfood, renewable feedstock alternative to petroleum derivatives.…”