Recyclable bio‐based crosslinked polyurethanes with self‐healing ability

Abstract

We report the synthesis of a linear bio-based polyurethane (bio-PU) containing furan ring by using renewable polylactide copolymer diol and 2,5-furandimethanol as a soft segment and chain extender, respectively, in which the reversible crosslinked covalent bonds between hard segments were incorporated via Diels-Alder (D-A) reaction between the furan ring of the chain extender and bismaleimide (BM) crosslinker. By simply controlling the amount of BM, mechanical properties of the obtained crosslinked bio-PUs (CBPUs) were varied widely. In particular, the CBPU100 sample shows the highest tensile strength of 10.8 MPa, Young's modulus of 193 MPa, and an elongation of 155%. The differential scanning calorimetry experiments verify the recycle property of the CBPUs by the D-A/retro-D-A reaction at the proper temperature. The thermal recyclability and remolding ability of these materials are demonstrated by two kinds of polymer processing methods, i.e., solution casting and hot-compression molding. The recycled CBPUs display almost identical elongation and slightly decreased tensile strength compared to the as-synthesized samples. Furthermore, the CBPUs also exhibit excellent self-healing ability. Therefore, the resulting CBPUs possess tunable mechanical properties, good thermal recyclability, re-mending, and self-healing ability, which makes the bio-based materials more eco-friendly. V C 2018 Wiley Periodicals, Inc. J.Appl. Polym. Sci. 2018, 135, 46272.

Self‐healing polyurethane based on a difuranic monomer from biorenewable source

“…Internal healing based on reversible chemical interaction between functional groups in a polymer are more attractive due to unlimited mending cycles, but external stimulus such as heat or light must be applied . There is a wide variety of internal self‐healing approaches based on photoactivated [2 + 2]‐cycloaddition, reversible formation of disulfide bridges and hydrogen bonds, radical reactions, pH‐dependent processes, and Diels–Alder (DA) reactions …”

“…[10][11][12] There is a wide variety of internal self-healing approaches based on photoactivated [2 + 2]cycloaddition, 13 reversible formation of disulfide bridges 14 and hydrogen bonds, 15 radical reactions, 16 pH-dependent processes, 17 and Diels-Alder (DA) reactions. 1,18 The DA reaction between furans and maleimides is a thermally reversible process. 19 Formation of a bicyclic DA-adduct usually occurs at 40-70 C, and at higher temperatures (>100 C), it undergoes cleavage (reverse DA-reaction, re-DA) which results in regeneration of starting components.…”

Recyclable biobased materials based on Diels–Alder cycloaddition

“…Several researchers have studied the application of the DA reaction to construct some reversible structures of linear polymers, and the kinetics of the simpler systems have been studied . In addition, a number of thermally reversible healing materials and biological materials have been constructed based on this DA reaction . Modified epoxy resin was chosen by some researchers to construct DA reversible materials .…”

Renewable Responsive Systems Based on Original Click and Polyurethane Cross‐Linked Architectures with Advanced Properties

“…Nevertheless, very few studies have explored the use of biobased PUs as a canvas to investigate reversibly cross‐linked polymers. Gu and Wu synthesized a biobased TPU backbone from a renewable polylactide copolymer diol and 2,5‐furandimethanol as a soft segment and chain extender, respectively . The reversible covalent bonds were located in the hard segments, at which the DA reaction took place between the furan ring of the chain extender and a bismaleimide (BMI).…”

“…Gu and Wu synthesized ab iobased TPU backbonef rom ar enewable polylactide copolymer diol and 2,5-furandimethanola sasoft segmenta nd chain extender,r espectively. [26] The reversible covalentb onds were located in the hard segments, at which the DA reaction took place between the furan ring of the chain extender and a bismaleimide (BMI). Wilson and Chen synthesized an original C 11 difuranic diol from furfural and 5-hydroxymethylfurufral, which they used to synthesize polyesters and reversibly crosslinked PUs networks with aBMI.…”