Bio-Based Poly(Imine-Amide) Materials with Dynamic Covalent Adaptable Networks: Toward Conductive Composites and Thermally Moldable Microcellular Foams

Abstract

Covalent adaptable networks constructed in biobased cross-linked polymers are used for the thermal-loop process for thermoset materials and composites. In this study, bio-based poly(imine-amide)s (PIAs; biomass content >85%) were synthesized from the lignin-derived monomer vanillin, citrate ester (triethyl citrate), and 1,4-diaminobutane via a condensation reaction. The imide bonds accompanied by a dynamic covalent nature provided PIAs with a satisfactory catalyst-free thermally malleable polymer network. The synthesized PIAs unveil toughness and ductility due to the combined effect of amide and imide structures and become thermally malleable in a few seconds. These PIAs show advanced performance in recyclability (efficient reprocessing) and have excellent foamability (suitable for good sCO 2 compatibility and diffusion), as the foams produced via green sCO 2 batch foaming technology have an expansion ratio of up to 12.1. PIA/multiwalled carbon nanotube (MWCNT) nanocomposites exhibit high electric conductivity (10 −2 to 10 2 S cm −1 in the range of 1−10 wt % MWCNTs), low percolation threshold (0.43%), and excellent EM-shielding properties (above 70 dB at 10 wt % MWCNTs). More promisingly, the electrical conductivity and EM-shielding properties of these PIA/MWCNT nanocomposites are enhanced by forming microcellular structures. This study presents the molecular structure of a green covalent adaptable network with potential foamability and reprocessing ability, which can be used to prepare lightweight nanocomposites with excellent electrical conductivity and EMI-shielding properties.

Robust Biobased Vitrimers and Its Application to Closed-Loop Recyclable Carbon Fiber-Reinforced Composites

“…Composite materials in various industrial products, such as wind turbines, sports goods, and electronic systems, are prepared using thermosetting resins as the matrix; these materials account for 15% of the total plastic consumption . Because thermosetting resins form three-dimensional (3D) covalent crosslinks, they exhibit superior strength, thermal stability, and creep resistance. , However, because the 3D covalent crosslinks are permanent and irreversible, thermosetting resins can be neither melted nor depolymerized into their original monomers; consequently, these materials cannot be recycled and reprocessed. − Therefore, end-of-life waste CFRPs and thermosetting resins are either discarded in landfills or incinerated, causing serious environmental pollution and wasting energy and resources. ,,, …”

Reprocessable Polyurethane Foams Using Acetoacetyl-Formed Amides

“…Finally, a few studies have focused on the fabrication of a CAN that was foamed in a second step using supercritical CO 2. However, this method has economical drawbacks, and the produced foams generally possess reduced properties compared to standard PUFs. − …”

Chemically Recyclable Supramolecular Thermosets toward Strong and Reusable Hot-Melt Adhesives

“…Imine exchange reactions have been extensively used to construct chemically recyclable polyimine (PI)-based supramolecular thermosets. ,,,− These PI materials are widely used to fabricate electronic skins, − thin electrolyte membranes for solid-state lithium batteries, and fully recyclable carbon fiber-reinforced composites. − However, most of these PI materials lack enough mechanical strength, hindering their prospects of replacing traditional thermosetting plastics. ,− , An effective strategy to prepare high-performance PI thermosets is to introduce diverse cross-linking structures, such as metal coordination or aromatic structures, , into the polymer networks. For example, by integrating a metal complex into PI networks, mechanically robust PI thermosets with good creep resistance and thermal stability were developed .…”