Catechin and Furfurylamine Derived Biobased Benzoxazine with Latent‐Catalyst Effect

Abstract

Sustainable polybenzoxazines sourced from renewable feedstock has emerged as an area of interest due to the inherent presence of a high number of reactive and additional functionalities. Plants are a rich source of flavan-3-ol viz., catechin (CAT) with four phenolic-OH and one aliphatic secondary-OH that can be a viable substitute to petro-phenols. In this current work, a biobased benzoxazine monomer, viz. CAT-fa, is synthesized using CAT and carbohydrate sourced furfurylamine (fa). Interestingly, an unexpected tris-oxazine (instead of tetra-oxazine) benzoxazine monomer is obtained. The unreacted phenolic-OH is involved in intramolecular H-bonding with the neighboring oxazine ring. Upon heat treatment, H-bonded hydroxyl groups become free and initiate ring-opening polymerization reaction at a low temperature of ≈125 °C exhibiting the latent catalyst effect. The ring-opening polymerization of the monomer and the thermal stability of polybenzoxazine are analyzed by differential scanning calorimetry, thermal gravimetric analysis, rheometry, and Fourier transform infrared spectroscopy. The polymerization reaction is proposed to proceed by the ring-opening reaction by cleavage at the oxygen of the pyran ring and O─CH 2 -N bond in oxazine ring to generate multiple polar functionalities to enable extensive H-bonding interactions. This work supports the potential of catechin as a green synthon to form sustainable polymers to employ H-bonding interactions and latent-catalytic potential.

Synthesis of new biobased benzoxazine through green strategy and its polybenzoxazine resin with high thermal resistance and mechanical strength

“…Among the literature that reported benzoxazine resins based on green strategies, 9–27,29–31,47–72 only three of them reported static mechanical properties of the resins (Table S1), however, these resins do not show high thermal resistance ( T g ≤ 193 °C, T di ≤ 381 °C). Figure 10B shows the stress–strain curve of poly(CT‐fa) , from which poly(CT‐fa) is known to have excellent tensile strength (51.60 ± 0.27 MPa), tensile modulus (3.32 ± 0.03 GPa) and elongation at break (1.95 ± 0.02%).…”

The mechanochemical synthesis of environmentally benign fully biobased 4th generation benzoxazines and their polymers: mechanistic insights into the catalytic activity of latent catalysts

“…To mitigate this limitation, the incorporation of functionalities with an inherent latent catalytic effect in the phenolic and amine counterparts of BZ has been attempted. [20][21][22][23][24] Incorporating inactive structural motifs within the BZ monomer, which become activated upon an external trigger, is an interesting approach. In particular, functionalities involving intramolecular H-bonding lock the acidic labile hydrogen atoms and render them available once heat is applied to accelerate the polymerization reaction without compromising the shelf life of monomers.…”

“…Over the past few decades, the production of sustainable feedstock–derived polymeric materials including polybenzoxazines, 25 gained significant interest to overcome the challenges associated with the depletion of fossil reserves, fluctuation in petroleum prices, and environmental concerns. A wide variety of renewable phenolics and amines are explored in polybenzoxazines, including cardanol, 26,27 magnolol, 28 urushiol, 29 coumarin, 30 eugenol, 31 vanillin, 32,33 guaiacol, 34 isoeugenol, sesamol, 35 bisguaiacol-F, 36 resveratrol, 37 catechol, 38 catechin, 23 chavicol, 39 carvacrol, 40 ferulic acid, 41 peterostilbene, 42 chrysin, 43 anethole, 44 furfurylamine, stearylamine, 34 chitosan, 15 isomannide, 45 rosin, 46 and tyramine. 47 Biomass-derived derivatives of phenols and amines have proven successful as renewable resources, offering excellent opportunities to synthesize sustainable polymers capable of partially or fully replacing petroleum-based PBZs.…”

Thermal Stable and Flexible Bio‐Based Polybenzoxazine with Epoxy‐Functionalized Poly(dimethylsiloxane) Hybrids

“…In recent years, there has been significant research on benzoxazines (BZ) as the thermosetting resins ascribable to their exceptional properties such as good electrical resistance, flexible molecular design, excellent flame retardancy, high thermal and dimensional stability, and low surface free energy. [1][2][3][4][5][6][7][8][9][10][11][12][13][14] Derivatives of BZ, comprising six-membered heterocyclic rings, could be synthesized through the Mannich condensation process involving phenols, formaldehyde, and primary aromatic or aliphatic amines. [15][16][17] Epoxy resins are also widely reckoned as thermosetting polymers with excellent performance characteristics, making them suitable for a range of applications such as adhesives, automotive components, coatings, composites, semiconductor encapsulation, and paint.…”

“…In recent years, there has been significant research on benzoxazines (BZ) as the thermosetting resins ascribable to their exceptional properties such as good electrical resistance, flexible molecular design, excellent flame retardancy, high thermal and dimensional stability, and low surface free energy. [ 1–14 ] Derivatives of BZ, comprising six‐membered heterocyclic rings, could be synthesized through the Mannich condensation process involving phenols, formaldehyde, and primary aromatic or aliphatic amines. [ 15–17 ]…”