Facile One-Pot Synthesis of Furan Double Schiff Base from 5-Hydroxymethylfurfural via an Amination–Oxidation–Amination Strategy in Water

Bio-based plastics potentially have several positive impacts on the environment; however, in order to make a real difference, they need to have managed and sustainable end of life. This means they should from the start be designed for chemical, mechanical, and/or organic (biological) recycling. Development of energy-efficient and selective chemical recycling processes is a necessary part in reaching truly circular plastic flows. Polyesters are generally well suited for chemical recycling due to the presence of reversible ester bonds. Utilization of dynamic covalent chemistry to include a second, even more easily reversed bond, such as Schiff base (SB, imine bond), could further facilitate chemical recycling, enabling depolymerization back to monomeric products under mild conditions. Here, we present the synthesis of three vanillin-derived SB monomers SBM1, SBM2, and SBM3 and the corresponding polymers SBP3a–b, SBP4a–b, and SBP5a–b. Three different diamines and two potentially bio-sourced diesters were utilized to yield altogether six different polyester-imines with different aliphatic/aromatic contents. All the obtained SB-based polyesters were thermally stable at ∼290–330 °C and had a high char yield during the pyrolysis, which may indicate inherent flame resistance. All the polyesters were amorphous with glass transition temperatures from 36 to 76 °C. The chemical recyclability and hydrolytic degradation of the synthesized polyesters was evaluated by using real-time 1H NMR spectroscopy. Finally, the susceptibility of the synthesized polyester-imines to enzymatic degradation by PETase was demonstrated. The experimental results were further supported by induced-fit docking experiments to theoretically evaluate the potential productive binding of the produced polyester-imines and intermediates thereof to the active site of PETase.

Section: Introductionmentioning

confidence: 99%

Designed for Circularity: Chemically Recyclable and Enzymatically Degradable Biorenewable Schiff Base Polyester-Imines

Sathiyaraj

Najjarzadeh

Vanga

et al. 2023

“…Increasingly severe warming of the global climate and swift depletion of fossil fuels have stimulated the development of sustainable and renewable bioresources to replace the current fossil energy economy. − Cost-effective utilization of available renewable lignocellulose (LC) to manufacture valuable chemicals may alleviate the resource/energy crisis and environmental pollution. − Hemicellulose is an important polysaccharide in biomass, which can be used as feedstock for furfural (FAL) production . FAL is a versatile molecule that not only can be used to manufacture a series of furan derivatives, fine chemicals, biofuels, fuel additives, resins, plastics, fungicides, and nematicides , but also can be utilized as an industrial solvent for lubricating oil refining .…”

Section: Introductionmentioning

confidence: 99%

Improved Synthesis of Furfurylamine from a High Titer of Biomass-Derived Furfural by a Thermostable Triple Mutant ω-Transaminase in a Three-Component Deep Eutectic Solvent ChCl/Lactic Acid/Malonic Acid System

et al. 2023

Furfurylamine (FLA) is widely utilized in manufacturing polymers, food additives, fibers, fuel additives, flavors, and pharmaceuticals. Lignocellulose was tandemly transformed to furfurylamine by combining chemocatalysis with biocatalysis in a three-component deep eutectic solvent (3c-DES)–H2O in this work. Biomass-derived d-xylose (300 mM) was transformed with 3c-DES ChCl/MA/LA (15 wt %) [choline chloride (ChCl), malonic acid (MA), and lactic acid (LA)] at 190 °C for 45 min to produce furfural (70.6% yield). A robust triple mutant Aspergillus terreus ω-transaminase HNILQE with high biocatalytic activity and thermostability was obtained through a consensus strategy [Q97E (glutamine to glutamic acid), H210N (histidine to asparagine), I77L (isoleucine to leucine)]. HNILQE could aminate d-xylose-derived furfural to furfurylamine (97.6% yield), reaching a productivity of 0.98 g furfurylamine/g furfural (cal. 0.44 g furfurylamine/g d-xylose). High titer of biobased furfural (500 mM) was transformed to FLA (95.8% yield, >99% selectivity) in ChCl/MA/LA–H2O. A highly efficient manufacture of furfurylamine from high loading of furfural by this robust triple mutant HNILQE biocatalyst was successfully realized in the established eco-friendly medium. This established chemoenzymatic process can be utilized for efficient manufacture of biobased furans in the green and sustainable approach.

“…Therefore, such resin is not suitable for application as wood adhesive, but different resins will be obtained by combining MH polymer with glyoxal. It is known that aliphatic amines can react with aldehydes to form Schiff base, but stable Schiff base is generally formed between amines and aromatic aldehydes (like benzaldehyde − or furfural , ) as such Schiff bases are conjugated species. A recent study on tannin-MH system has shown that MH polymers are reactive toward quinone species .…”

Section: Introuctionmentioning

confidence: 99%

Long-Chain Polyamine-Glyoxal Wood Adhesive: Formaldehyde-Free, Green Synthesis, and Ultra-Performances

Jiang,

Duan,

Liu

et al. 2023

Formaldehyde emission from wood-based products has been a threat to human health and the environment due to the use of formaldehyde-based adhesives. Glyoxal (G) was once regarded as a promising substitute for formaldehyde due to its formaldehyde-like reactivity and low toxicity. However, many studies have indicated that the urea-glyoxal (UG) and melamine-glyoxal (MG) reactions did not lead to the desired adhesion property due to cyclization reactions. To prevent cyclization, in this study, a long-chain melamine-1,6-hexanediamine (MH) polymer was used with glyoxal to fabricate wood adhesive via a facile and clean strategy. In contrast to previously reported glyoxal-related wood adhesives, the MHG adhesive exhibited a lower cure temperature, much higher bonding strength, and far superior water resistance. Particularly, when a low hot-press temperature of 80 °C was applied, a dry bonding strength above 2.42 MPa (100% wood failure) and a wet bonding strength (boiling in water for 3 h) of 1.62 MPa were achieved for plywood. With a higher cure temperature of 120 °C applied, a bonding strength above 1.50 MPa was retained with 100% wood failure even after boiling for 72 h. Structural characterizations suggested that the outstanding performances of the MHG adhesive can be attributed to easy formation of highly stable conjugated imine bonds (−N�C−C�N−).