Self‐Healable, Malleable, Ecofriendly Recyclable and Robust Polyimine Thermosets Derived from Trifluoromethyl Diphenoxybenzene Backbones

Abstract

Dynamic covalent chemistry opens up great opportunities for a sustainable society by producing reprocessable networks of polymers and even thermosets. However, achieving the closed-loop recycling of polymers with high performance remains a grand challenge. The introduction of aromatic monomers and fluorine into covalent adaptable networks is an attractive method to tackle this challenge. Therefore, we present a facile and universal strategy to focus on the design and applications of polyimine vitrimers containing trifluoromethyl diphenoxybenzene backbones in applications of dynamic covalent polymers. In this study, fluorine-containing polyimine vitrimer networks (FPIVs) were fabricated, and the results revealed that the FPIVs not only exhibited good self-healability, malleability and processability without the aid of any catalyst, but also possessed decent mechanical strength, superior toughness and thermal stability. We hope that this work could provide a novel pathway for the design of high-performance polyimine vitrimers by recycling of plastic wastes.

High-Performance Poly(imide-imine) Vitrimers Derived from Semiaromatic Bisimide Diamines

“…After optimizing the healing conditions, the healing efficiency for tensile strength, tensile modulus, and elongation at break can be, respectively, further improved to 98.9, 98.1, and 118.6%. Besides, similarly to a few reported imide-free polyimines, ,– the resulting PIIH s can also be rapidly degraded in acid solution (H 2 O/DMF, v/v = 1:1, 1 M HCl) and thermally reprocessed at 180 °C. The proposed strategy has thus been proven efficacious in improving the physical properties of vitrimers and is promising to construct thermostable and robust vitrimers for engineering applications.…”

“…However, 16 h later, all solutions turned faint yellow, and Un -PIIH film fragments decomposed into small pieces (Figure S40b, Supporting Information). When further prolonging the soaking time to 24 h (Figure S40c, Supporting Information) and even 60 h (Figure S40d, Supporting Information) at room temperature, all PIIH film fragments broke into small pieces but still did not totally dissolve and gave a clear faint yellow solution rather than a turbid suspension with small film pieces sinking to the bottom of the vial, which is different from those reported imide-free polyimines. ,,,,– We speculate that it is the imide linkages accompanying the aliphatic structures that impede the resulting PIIH s rapid degradation in acid solution, since the aliphatic structures are hydrophobic and the imide linkages are water- and acid-stable, which makes it difficult for H + to enter into the polyimine network in aqueous solution to attack the imine bonds. Moreover, the hydrolyzed products have poor solubility in water.…”

“…More specifically, the tensile strength of m -MPIIH and o -DMPIIH , respectively, reaches 94.3 and 97.0 MPa with tensile modulus as high as ∼2.6 GPa when m -MHBIDA and o -DMHBIDA are used as diamine monomers. These tensile properties are significantly higher than those of a majority of reported polyimines whose tensile strength is typically in the range of 20–50 MPa with tensile modulus less than 1.5 GPa, ,,,,,,, and are even comparable to those of some traditional high-performance polyimides (tensile strength: 90–120 MPa, tensile modulus: 2–3 GPa). – ,– On the one hand, the prepared PIIH films contain rigid and large polar imide linkages (Figure S39, Supporting Information), which increases the polymer backbone rigidity and the intermolecular interactions as well as the cohesive energy density, thus endowing the resulting PIIH films with high tensile modulus and tensile strength. On the other hand, the as-synthesized bisimide-containing diamines possess flexible ether linkages, and the cross-linker, tri­(2-aminoethyl) amine, also contains elastic methylene units (Figure S39, Supporting Information), which could facilitate the single bond rotation and conformational rearrangement of the polymer network when subjected to external stress, consequently increasing the toughness and robustness of the PIIH networks. ,,,, By contrast, when o -MHBIDA and m -3FBIDA are used to fabricate polyimines, the tensile strength slightly decreases to 88.3 MPa for o -MPIIH and 83.6 MPa for m -3FPIIH .…”

“…It can be seen that T g of the prepared PIIHs (211−306 °C) is significantly improved compared with those reported in the literature (T g = 25− 120 °C). 13,14,44,55,57,61,62 It is worth noting that m-MPIIH and o-MPIIH show two obvious glass transitions, respectively, at 211−216 and 270−280 °C, which usually appears in polymers or composites with two incompatible phases, 27 while this phenomenon is significantly restrained for o-DMPIIH and m-3FPIIH. Additionally, an evident subglass transition appears at around 200 °C for o-DMPIIH and Un-PIIH, whereas it shifts to a much higher temperature (∼270 °C) for m-3FPIIH.…”

“…49−52,64−66 On the one hand, the prepared PIIH films contain rigid and large polar imide linkages (FigureS39, Supporting Information), which increases the polymer backbone rigidity and the intermolecular interactions as well as the cohesive energy density, thus endowing the resulting PIIH films with high tensile modulus and tensile strength. On the other hand, the as-synthesized bisimide-containing diamines possess flexible ether linkages, and the cross-linker, tri(2aminoethyl) amine, also contains elastic methylene units (FigureS39, Supporting Information), which could facilitate the single bond rotation and conformational rearrangement of the polymer network when subjected to external stress, consequently increasing the toughness and robustness of the PIIH networks 11,57,64,67,68. By contrast, when o-MHBIDA and m-3FBIDA are used to fabricate polyimines, the tensile strength slightly decreases to 88.3 MPa for o-MPIIH and 83.6 MPa for m-3FPIIH.…”