New insight into the mechanism for the excellent gas properties of poly(ethylene 2,5-furandicarboxylate) (PEF): Role of furan ring’s polarity

-COOH & -OH Condensation Reaction Utilization for Biomass FDCA-based Polyesters

A green and sustainable -COOH & -OH condensation solution polymerization method was hereby reported for FDCA-based polyesters to avoid discoloration and toxic solvents. First, taking poly(ethylene 2,5-furandicarboxylate) (PEF) as the representative of FDCA-based polyester, enabling good white appearance PEF with Mn=6.51×103 g mol-1 from FDCA and ethylene glycol in green solvent γ-valerolactone (GVL), catalyzed by 4-dimethylaminopyridine (DMAP) and N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride (EDC). Additionally, the molecular weight of PEF was rapidly improved (Mn >2.5×104 g mol-1) via remelting polycondensation within minutes, with the dispersity still kept relatively low dispersity (Đ<1.40). Importantly, the -COOH & -OH condensation solution polymerization method was successfully applied for the synthesis of various FDCA-based polyesters, including diols with varying carbon chain lengths (3 to 11 carbons) and cycloalkyl diols, especially the applicability of this method to diols containing C=C double bonds, which was found to exhibit low heat resistance. Lastly, assisting with 13C labeled 1,4-succinic acid and in-situ 13C-NMR, an in-depth study of the possible catalytic mechanism was proposed, by which, EDC activated FDCA, and then DMAP catalyzed it with diol to yield macromolecular chain of polyester. Overall, the results provided a green and sustainable strategy for the synthesis of FDCA-based polyesters.

Synthesis of Biobased Poly(butylene Furandicarboxylate) Containing Polysulfone with Excellent Thermal Resistance Properties

A synthetic biopolymer derived from furandicarboxylic acid monomer and hydroxyethyl-terminated poly(ether sulfone) is presented. The synthesis involves 4,4'-dichlorodiphenyl sulfone and 4,4-dihydroxydiphenyl sulfone, resulting in poly(butylene furandicarboxylate)-poly(ether sulfone) copolyesters (PBFES) through melt polycondensation with titanium-catalyzed polymerization. This facile method yields segmented polyesters incorporating polysulfone, creating a versatile group of high-temperature thermoplastics with adjustable thermomechanical properties. The PBFES copolyesters demonstrate an impressive tensile modulus of 2830 MPa and a tensile strength of 84 MPa for PBFES55. Additionally, the poly(ether sulfone) unit imparts a relatively high glass transition temperature (Tg), ranging from 36.6 °C for poly(butylene 2,5-furandicarboxylate) to 112.3 °C for PBFES62. Moreover, the complete amorphous film of PBFES exhibits excellent transparency and solvent resistance, making it suitable for applications, such as food packaging materials.

Improvement of properties of polylactic acid/polypropylene carbonate blends using epoxy soybean oil as an efficient compatibilizer

Epoxidized soybean oil (ESO) was used as a compatibilizer and blended with polylactic acid (PLA) and polypropylene carbonate (PPC) resin to prepare a series of PLA/PPC/ESO blends with varying compositions. The influence of the variation in the amount of ESO added to the blend system on the thermal properties, optical properties, rheological properties, mechanical properties, and microscopic morphology of the blends was studied. The research indicates that ESO can react with PLA and PPC to form a chemical bond interface, which improves the compatibility of PLA and PPC to a certain extent. With the increase in the amount of ESO added to the blend (1- 5 phr), the complete decomposition temperature, storage modulus, loss modulus, complex viscosity, notched impact strength, and elongation at break of the blend all show a trend of continuous increase. At the same time, the melt flow rate, light transmittance, and tensile strength of the blend do not show significant fluctuations. When the amount of ESO in the system is 5 phr, compared with the PLA/PPC blend, the notched impact strength and elongation at break of the PLA/PPC/ESO blend increase from 4270.3 J/m2, 43.89 % to 8560.4 J/m2, 211.28 %, respectively, and its tensile strength and transmittance still remain around 63 MPa, 92 %. This improves the toughness of the blend while maintaining its rigidity, demonstrating excellent mechanical and optical properties. At this time, the microscopic morphology of the fracture surface of the impact sample also shows obvious characteristics of tough fracture. However, when the amount of ESO added to the blend is excessive (6 phr), the compatibility of the blending system decreases, which will degrade the performance of the blending material and ultimately destroy the phase morphology of the blend and reduce its mechanical properties.

Biobased Biodegradable Copolyesters from 2,5-Thiophenedicarboxylic Acid: Effect of Aliphatic Diols on Barrier Properties and Degradation

The demand for sustainable development has led to increasing attention in biobased polyesters due to their adjustable thermal and mechanical properties and biodegradability. In this study, we used a novel bioderived aromatic diacid, 2,5-thiophenedicarboxylic acid (TDCA) to synthesize a list of novel aromatic-aliphatic poly(alkylene adipate-co-thiophenedicarboxylate) (PAATh) copolyesters through a facile melt polycondensation method. PAAThs are random copolyesters with weight-average molecular weights of 58400 to 84200 g·mol-1 and intrinsic viscosities of 0.80 to 1.27 dL·g-1. All PAAThs exhibit sufficiently high thermal stability as well as the highest tensile strength of 6.2 MPa and the best gas barrier performances against CO2 and O2, 4.3- and 3.3-fold better than those of poly(butylene adipate-co-terephthalate) (PBAT). The biodegradability of PAAThs was fully evaluated through a degradation experiment and various experimental parameters, including residue weights, surface morphology, and molecular compositions. The state-of-the-art molecular dynamics (MD) simulations were applied to elucidate the different enzymatic degradation behaviors of PAAThs due to the effect of diols with different chain structures. The sterically hindered carbonyl carbon of the PHATh-enzyme complex was more susceptible to nucleophilic attack and exhibited a higher tendency to enter a prereaction state. This study has introduced a group of novel biobased copolyesters with their structure-property relationships investigated thoroughly, and the effect of diol components on the enzymatic degradation was revealed by computational analysis. These findings may lay the foundation for the development of promising substitutes for commercial biodegradable polyesters and shed light on their complicated degradation mechanisms.

In Vitro and In Vivo Trypanocidal Efficacy of Nitrofuryl- and Nitrothienylazines

African trypanosomiasis is a vector-borne disease of animals and humans in the tsetse fly belt of Africa. Trypanosoma congolense ("nagana") is the most pathogenic trypanosome in livestock and causes high morbidity and mortality rates among cattle. In the absence of effective preventative vaccines, the management of trypanosomiasis relies on chemoprophylaxis and/or -therapy. However, the trypanocides in clinical use exhibit poor oral bioavailability and toxicity, and therapeutic failures occur because of resistant strains. Because nitrofurantoin displayed, in addition to its clinical use, promising antiparasitic activity, the current study was conducted to evaluate the in vitro trypanocidal activity and preliminary in vivo treatment efficacy of previously synthesized nitrofuranylazines. The trypanocidal activity of these nitrofuran derivatives varied among the evaluated trypanosome species; however, T. congolense strain IL3000 was more susceptible than other animal and human trypanosomes. The nitrofurylazines 4a (IC50 0.04 μM; SI > 7761) and 7a (IC50 0.03 μM; SI > 9542) as well as the nitrothienylazine 8b (IC50 0.04 μM; SI 232), with nanomolar IC50 values, were revealed as early antitrypanosomal leads. Although these derivatives showed strong trypanocidal activity in vitro, no in vivo treatment efficacy was observed in T. congolense IL3000 infected mice after both oral and intraperitoneal administration in a preliminary study. This was attributed to the poor solubility of the test compounds in the in vivo testing media. Indeed, a challenge in drug discovery is finding a balance between the physicochemical properties of a drug candidate, particularly lipophilicity and water solubility, and maintaining adequate potency to provide an effective dose. Hence, future chemical modifications may be required to generate lead-like to lead-like nitrofuranylazines that possess optimal physicochemical and pharmacokinetic properties while retaining in vitro and, ultimately, in vivo trypanocidal efficacy.

Engineering a Carboxyl Methyltransferase for the Formation of a Furan-Based Bioplastic Precursor

FtpM from Aspergillus fumigatus was the first carboxyl methyltransferase reported to catalyse the dimethylation of dicarboxylic acids. Here the creation of mutant R166M that can catalyse the quantitative conversion of bio-derived 2,5-furandicarboxylic acid (FDCA) to its dimethyl ester (FDME), a bioplastics precursor, was reported. Wild type FtpM gave low conversion due to its reduced catalytic efficiency for the second methylation step. An AlphaFold 2 model revealed a highly electropositive active site, due to the presence of 4 arginine residues, postulated to favour the binding of the dicarboxylic acid over the intermediate monoester. The R166M mutation improved both binding and turnover of the monoester to permit near quantitative conversion to the target dimethyl ester product. The mutant also had improved activity for other diacids and a range of monoacids. R166M was incorporated into 2 multienzyme cascades for the synthesis of the bioplastics precursor FDME from bioderived 5-hydroxymethylfurfural (HMF) as well as from poly(ethylene furanoate) (PEF) plastic, demonstrating the potential to recycle waste plastic.

New Random Aromatic/Aliphatic Copolymers of 2,5-Furandicarboxylic and Camphoric Acids with Tunable Mechanical Properties and Exceptional Gas Barrier Capability for Sustainable Mono-Layered Food Packaging

High molecular weight, fully biobased random copolymers of 2,5-furandicarboxylic acid (2,5-FDCA) containing different amounts of (1R, 3S)-(+)-Camphoric Acid (CA) have been successfully synthesized by two-stage melt polycondensation and compression molding in the form of films. The synthesized copolyesters have been first subjected to molecular characterization by nuclear magnetic resonance spectroscopy and gel-permeation chromatography. Afterward, the samples have been characterized from a thermal and structural point of view by means of differential scanning calorimetry, thermogravimetric analysis, and wide-angle X-ray scattering, respectively. Mechanical and barrier properties to oxygen and carbon dioxide were also tested. The results obtained revealed that chemical modification permitted a modulation of the abovementioned properties depending on the amount of camphoric co-units present in the copolymers. The outstanding functional properties promoted by camphor moieties addition could be associated with improved interchain interactions (π-π ring stacking and hydrogen bonds).

Recent advances in the development of green furan ring-containing polymeric materials based on renewable plant biomass

Fossil resources are rapidly depleting, forcing researchers in various fields of chemistry and materials science to switch to the use of renewable sources and the development of corresponding technologies. In this regard, the field of sustainable materials science is experiencing an extraordinary surge of interest in recent times due to the significant advances made in the development of new polymers with desired and controllable properties. This review summarizes important scientific reports in recent times dedicated to the synthesis, construction and computational studies of novel sustainable polymeric materials containing unchanged (pseudo)aromatic furan cores in their structure. Linear polymers for thermoplastics, branched polymers for thermosets and other crosslinked materials are emerging materials to highlight. Various polymer blends and composites based on sustainable polyfurans are also considered as pathways to achieve high-value-added products.

Bio-based poly(hexamethylene 2,5-furandicarboxylate-co-2,6-naphthalate) copolyesters: a study of thermal, mechanical, and gas-barrier properties

A series of poly(hexamethylene 2,5-furandicarboxylate-co-2,6-naphthalate) copolyesters were synthesized using various amounts of poly(hexylene 2,5-furandicarboxylate) (PHF) and poly(hexylene 2,6-naphthalate) (PHN) via melt polymerization. The effects of introducing 2,6-naphthalene dicarboxylic acid (NDCA) on the thermal, mechanical, and gas-barrier properties were investigated. When the NDCA content was less than 30 mol%, the temperatures of crystallization (T_c) and melting (T_m) decreased as the amount of NDCA was increased owing to disturbance of the polymer-chain regularity. When the NDCA content was above 50 mol%, the T_c and T_m of the materials increased as the NDCA content was increased, showing that the dominant crystallization behavior varied from 2,5-furandicarboxylic acid to NDCA. Hence, the glass transition temperature (T_g) increased as the NDCA content was increased, which was attributed to the incorporation of NDCA with a more rigid naphthalate structure compared with the furan ring. The gas-barrier properties of the samples were observed to improve with the introduction of NDCA; this tendency could be explained by the β-relaxation behavior and free volume values of the samples in the amorphous state. The activation energy (E_a) of β-relaxation increased with the NDCA content, indicating that higher amounts of energy were needed to trigger the onset of long-range molecular motions. Free-volume calculations of the polymer structure showed that the introduction of NDCA hindered the space for gas penetration. For these reasons, the gas-barrier properties were improved and evaluated.

Bio-effects of bio-based and fossil-based microplastics: Case study with lettuce-soil system

Bio-based plastics have been developed as alternative materials to solve the energy crisis brought by plastic production, but their impacts on soil ecosystems (e.g. plant and microorganisms) remain largely unknown. Here, we conducted study on the impacts of polyethylene 2,5-furan-dicarboxylate (PEF), a new bio-based plastic, on the plant-soil ecosystem, with comparison of fossil-based plastic polyethylene terephthalate (PET). Our investigation showed that, after 21 days exposure to microplastics (MPs) at doses of 0.5%, 1% and 2%, both PEF and PET MPs inhibited the growth of lettuce, where chlorophyll was found to be the most sensitive index. According to the comprehensive stress resistance indicators, PET MPs showed more severe phytotoxicity than PEF MPs. Although both PEF and PET MPs could inhibit soil enzyme activities, PET MPs exhibited significantly reduction on the diversity of rhizosphere soil bacterial community and changed the relative abundance of dominant species. Our study gave insights into the effects of PEF and PET MPs on the plant-soil system, where bio-based PEF MPs showed more friendly interaction with plant and soil than fossil-based PET MPs. Our results provided scientific data for risk assessment and useful information for the prospective application of bio-based plastics.

Recent Progress on Bio-Based Polyesters Derived from 2,5-Furandicarbonxylic Acid (FDCA)

The big challenge today is the upgrading of sustainable materials to replace miscellaneous ones from petroleum resources. Thus, a generic bio-based building block lays the foundation of the huge bio-market to green economy. 2,5-Furandicarboxylic acid (FDCA), a rigid diacid derived from lignocellulose or fructose, represents a great potential as a contender to terephthalic acid (TPA). Recently, studies on the synthesis, modification, and functionalization of bio-based polyesters based on FDCA have attracted widespread attention. To apply furanic polyesters on engineering plastics, packaging materials, electronics, etc., researchers have extended the properties of basic FDCA-based homo-polyesters by directional copolymerization and composite preparation. This review covers the synthesis and performance of polyesters and composites based on FDCA with emphasis bedded on the thermomechanical, crystallization, barrier properties, and biodegradability. Finally, a summary of what has been achieved and the issues waiting to be addressed of FDCA-based polyester materials are suggested.

Effects of Nonhydroxyl Oxygen Heteroatoms in Diethylene Glycols on the Properties of 2,5-Furandicarboxylic Acid-Based Polyesters

With regard to polyesters based on biobased 2,5-furandicarboxylic acid (FDCA), our work presents a new strategy, heteroatom substitution, to adjust the thermal and gas barrier properties. The effects of nonhydroxyl oxygen heteroatoms in the diols on the properties of FDCA-based polyesters were first investigated by a combination of an experiment and molecular simulation. The results demonstrated that the introduction of oxygen heteroatoms significantly influenced the thermal and gas barrier properties. As for the two model polymers with a very similar skeleton structure, poly(pentylene 2,5-furandicarboxylate) (PPeF) and poly(diethylene glycol 2,5-furandicarboxylate) (PDEF), their T_g exhibited an obviously increasing order. Moreover, they showed similar thermal stability and thermal oxidative stability. Dynamic mechanical analysis, positron annihilation lifetime spectroscopy, and molecular dynamics simulation indicated that the gas barrier properties followed the sequence of PDEF > PPeF mainly due to the decreased chain mobility and smaller fractional free volume. In-depth analysis of the effects of heteroatom substitution has an important directive significance for the design and preparation of new high glass transition temperature or novel excellent gas barrier materials. Through the manipulation of different heteroatoms in the diols, the polyesters with varied properties can be expected.

Polyimides from 2,5-bis[4-(4-aminophenoxy)benzoyl]furan and their thermal crosslinking reaction

Several polyimides were prepared via two-step polycondensation from novel 2,5-furandicarboxylic acid–based diamine, 2,5-bis[4-(4-aminophenoxy)benzoyl]furan, with commercial dianhydrides. The chemical structures of the monomers and polymers were characterized by FT-IR and NMR in detail, respectively. The polyimides exhibited high performances with 5 wt% weight loss temperatures of over 410 oC, glass transition temperatures of over 214 oC, and tensile strengths and Young’s moduli of up to 130 MPa and 3.2 GPa, respectively. The thermal crosslinking mechanism was studied by FT-IR, Raman spectroscopy, and model reaction analysis, which showed the Diels–Alder reaction between the furan group and diphenylethylene group was the main reaction. The crosslinked polyimide films showed improved solvent resistance, and thermal and mechanical properties.

Synthesis of performance-advantaged polyurethanes and polyesters from biomass-derived monomers by aldol-condensation of 5-hydroxymethyl furfural and hydrogenation

Functional polyurethanes and polyesters with tunable properties were synthesized from biomass-derived 5-hydroxymethyl furfural (HMF)-Acetone-HMF (HAH) monomers. HAH can be selectively hydrogenated over Cu and Ru catalysts to produce partially-hydrogenated (PHAH) and fully-hydrogenated (FHAH). The HAH units in these polymers improve the thermal stability and stiffness of the polymers compared to polyurethanes produced with ethylene glycol. Polyurethanes produced from PHAH provide diene binding sites for electron deficient C=C double bonds, such as in maleimide compounds, that can participate in Diels-Alder reactions. Such sites can function to create crosslinking by Diels-Alder coupling with bismaleimides and can be used to impart functionality to PHAH (giving rise to anti-microbial activity or controlled drug delivery). The symmetric triol structure of FHAH leads to energy-dissipating rubbers with branched structures. Accordingly, the properties of these biomass-derived polymers can be tuned by controlling the blending ratio of HAH-derived monomers or the degree of Diels-Alder reaction. The polyester produced from HAH can be used in packaging applications.

Melt-Spun Fibers from Bio-Based Polyester-Fiber Structure Development in High-Speed Melt Spinning of Poly(ethylene 2,5-furandicarboxylate) (PEF)

Poly(ethylene 2,5-furandicarboxylate) (PEF) is regarded as a bio-based alternative or complementary polyester for the widely used fossil resource-based polyester, poly(ethylene terephthalate) (PET). High-speed melt spinning of PEF of low and high molecular weight (L-PEF, H-PEF) was conducted, and the structure and properties of the resultant as-spun fibers were investigated. The occurrence of orientation-induced crystallization was confirmed for the H-PEF at the take-up velocity of 6.0 km/min, the highest speed for producing PET fibers in the industry. Molecular orientation and crystallinity of the as-spun fibers increased with the increase of take-up velocity, where the H-PEF fibers always showed a higher degree of structural development than the L-PEF fibers. The tensile modulus of the high-speed spun H-PEF fibers was relatively low at 5 GPa, whereas a sufficiently high tensile strength of approximately 500 MPa was measured. These values are adequately high for the application in the general semi-engineering fiber field.

Catalytic strategy for conversion of fructose to organic dyes, polymers, and liquid fuels

We report a process to produce a versatile platform chemical from biomass-derived fructose for organic dye, polymer, and liquid fuel industries. An aldol-condensed chemical (HAH) is synthesized as a platform chemical from fructose by catalytic reactions in acetone/water solvent with non-noble metal catalysts (e.g., HCl, NaOH). Then, selective reactions (e.g., etherification, reduction, dimerization) of the functional groups, such as enone and hydroxyl groups, in the HAH molecule enable applications in organic dyes and polyether precursors. High yields of target products, such as 5-(hydroxymethyl) furfural (HMF) (85.9% from fructose) and HAH (86.3% from HMF) are achieved by sequential dehydration and aldol-condensation with a simple purification process (>99% HAH purity). The use of non-noble metal catalysts, the high yield of each reaction, and the simple purification of the target product allow for beneficial economics of the process. Techno-economic analysis indicates that the process produces HAH at minimum selling price (MSP) of $1958/ton. The MSP of HAH product allows the economic viability of applications in organic dye and polyether markets by replacing its counterparts, such as anthraquinone ($3200-$3900/ton) and bisphenol-A ($1360-$1720/ton).

Influence of asymmetric substituent group 2-methyl-1,3-propanediol on bio-based poly(propylene furandicarboxylate) copolyesters

A series of bio-based poly(propylene-co-2-methyl-1,3-propanediol 2,5-furandicarboxylate) (PPMF) copolyesters, with various compositions from poly(propylene 2,5-furandicarboxylate) (PPF) to poly(2-methyl-1,3-propylene 2,5-furandicarboxylate) (PMePF), were synthesized by conventional melt polymerization. The effects of the substituent group to PPF on the thermal properties, mechanical properties, and gas barrier properties were analyzed by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), tensile testing, and the oxygen permeation test. The introduction of the methyl group with a hydrogen atom altered the thermal behavior and gas barrier properties of copolyesters, suggesting that the glass temperature (Tg) and the melting temperature (Tm) were decreased as the 2-methyl-1,3-propanediol (MPO) content increased. PPF exhibited the highest Tm and Tg of 175.9 °C and 83.0 °C with a melting enthalpy (ΔHm) of 38.6 J g-1, and poly(2-methyl-1,3-propylene 2,5-furandicarboxylate) formed as an amorphous polyester. Moreover, the effect of a substituent methyl group on the barrier properties was attributed to β relaxation and fraction free volume, which could be raised by replacing the methyl group with a hydrogen atom for PPF, weakening the barrier properties.