Ultrahigh Thermoresistant Lightweight Bioplastics Developed from Fermentation Products of Cellulosic Feedstock

Abstract

Production of bioplastics from renewable biological resources is a prerequisite for the development of a circular and sustainable society. Current bioplastics are mostly heat‐sensitive aliphatic polymers, requiring thermoresistant aromatic bioplastics. Herein, 3‐amino‐4‐hydroxybenzoic acid (AHBA) and 4‐aminobenzoic acid (ABA) are produced from kraft pulp, an inedible cellulosic feedstock, using metabolically engineered bacteria. AHBA is chemically converted to 3,4‐diaminobenzoic acid (DABA); subsequently, poly(2,5‐benzimidazole) is obtained by the polycondensation of DABA and processed into an ultrahigh thermoresistant film. The copolymerization of DABA with a small amount of ABA dramatically increases the degradation temperatures of the resulting films (over 740 °C) to yield the most thermoresistant plastic on record. Density functional theory calculations indicate that the incorporation of ABA strengthens the interchain hydrogen bonds between aromatic imidazole rings. Thus, an alternative organic molecular design is proposed for thermoresistant plastics without using heavy inorganics, although continuous aromatic heterocycles are widely considered ideal for polymer thermoresistance. This innovative macromolecular design increases thermoresistance and can be widely applied to well‐processable plastics for the production of lightweight materials and is expected to contribute to the development of a more sustainable society.

Synergistic Effects of Polybenzimidazole and Aramide on Enhancing Flame‐Retardancy and Solubility

“…The incorporation of a small amount of simple non-𝜋-conjugated p-aramid component into ABPBI was very effective on enhancing the hydrogen bonding of imidazole ring to increase the thermal degradation temperatures but too high composition of aramid reduced the thermoresistance. [15] For all the compositions, ABPBI copolymers showed a solubility only in strongly acidic solvents such as TFA and concentrated sulfuric acid, to cast films over TFA solution with concerning safety under strict ventilation facility. Here, bio-derived 4-AHCA was selected as a comonomer to afford semirigid amide units including phenethyloyl group into PBI while expecting thermoresistant PBI films with a good solubility.…”

“…Previously, the conversion of a bio-derived precursor molecule 3,4-AHBA to 3,4-DABA was reported. [15] On the other hand, 4-aminocinnamic acid (4ACA) was derived from biomass through genetic engineering, and employed in the synthesis of polyamides and polyimides. [22,23] Hydrogenation of 𝛼, 𝛽 unsaturation in 4ACA through microbial technique produced another building block 4-AHCA with aromatic ring and flexible alkyl chain as reported by Kawasaki et al [24] 4-AHCA together with 3,4-DABA was decided to be used in a different molar ratio to obtain copolymers while maintaining the balance between rigidity and flexibility to tune various molecular properties.…”

“…The homopolymer PBI BA was prepared by the method as described in the previous research (Scheme 1a). [15] CH 3 SO 3 H along with P 2 O 5 was used as the polycondensation reagent (Eaton's reagent) to polymerize 3,4-DABA at 150 °C with continuous stirring for 24 h, followed by precipitation in water and dried. Obtained yellow granules were crushed and dispersed in KOH water (10 wt%) in order to reach neutral pH, followed by washing with water and dried at 100 °C.…”

“…[13,14] The copolymers of ABPBI have scarcely been explored and they were still insoluble so far. [15][16][17][18][19][20][21] We have reported the copolymerization of ABPBI with biobased comonomers para-aminobenzoic acid and 3-amino-4hydroxybenzoic acid. [15] The poly(benzimidazole-co-benzamide) showed the ultrahigh heat-resistance than any other thermoresistant polymers reported thus far, through enhancement of interchain H-bonding by incorporation of a small amount of benzamide units as calculated using density functional theory, although the para-aminobenzoic acid homopolymer has much lower thermoresistance temperature than ABPBI.…”

“…[15][16][17][18][19][20][21] We have reported the copolymerization of ABPBI with biobased comonomers para-aminobenzoic acid and 3-amino-4hydroxybenzoic acid. [15] The poly(benzimidazole-co-benzamide) showed the ultrahigh heat-resistance than any other thermoresistant polymers reported thus far, through enhancement of interchain H-bonding by incorporation of a small amount of benzamide units as calculated using density functional theory, although the para-aminobenzoic acid homopolymer has much lower thermoresistance temperature than ABPBI. [15] Thus, copolymerization of ABPBI with benzamide derivatives is worth investigating further to control the materials performances, where the solubility is a key character to be investigated for the application of PBI category polymers.…”