Furan Polymers Research Articles

Supramolecular Polymer Network based on Electrophilic Substitution (ES) Adduct of Furan-Triazolinedione.

Polymers with furan functionality have been the subject of extensive research on developing sustainable materials applying a limited number of dynamic covalent approaches. Herein, we introduce a facile, dynamic non-covalent approach to make a furan polymer readily accessible for self-healing applications based on its electrophilic substitution (ES) with a commercially available 1,2,4-triazoline-3,5-dione (TAD) derivative, 4-phenyl-TAD (PTAD). A tailor-made furan polymer, poly(furfuryl methacrylate) (PFMA), considering it an initial illustrative example, was rapidly ES modified with PTAD to produce furfuryl-tagged triazolidine that subsequently associated via inter-molecular hydrogen (H-) bonding to produce a thermally reversible supramolecular polymer network under ambient conditions. The H-bonded network was experimentally quantified via ATR-IR analysis and theoretically rationalized via the density functional theory (DFT) study using smaller organic model compounds analogous to the macromolecular system. Thermoreversible feature of the H-bonded triazolidine-derived supramolecular polymer network enabled the solution reprocessing and self-healing of the polymer material.

Maleimidophenyl isocyanates adducts as versatile post‐polymerization modification agents for biobased furan polymers

AbstractBiobased furan polymers (BFPs) derived from 5‐hydroxymethylfurfural (HMF) are eco‐friendly polymers obtained from inedible biomass resources. Modification of such polymers is expected to expand their practical uses. BFPs have furan moieties that can react as dienophiles with maleimide, facilitating well‐designed polymer reactions. Herein, we report the preparation of various maleimides using p‐maleimidophenylisocyanate (PMPI), which has a highly reactive isocyanate group and a maleimide group, to modify BFP through the Diels–Alder reaction of the maleimide group. Two reactive sites in PMPI exhibit orthogonal reactivity, enabling us to achieve tailor‐made modification agents. The Tg values and rheological properties of modified polymers can be tuned according to the structure of maleimide and their reaction conversion, which demonstrates the practical usability of BFP derived from furfural. The strategy proposed herein can be applied to obtain biobased materials with desirable functions and physical properties.

Organic Heterocyclic Strategy for Precisely Regulating Electronic State of Palladium Interface to Boost Alcohol Oxidation

AbstractExploring highly‐efficient palladium (Pd)‐based electrocatalysts for the alcohol oxidation reaction (AOR) is crucial yet challenging for chemists due to the vague Pd interface with an uncontrollable electronic environment. Herein, an organic heterocyclic strategy is used for the first time to modulate the electronic state of Pd electrocatalysts by anchoring Pd nanoparticles to conjugated microporous polymers (CMPs) with varied S‐, N‐, O‐, or S, N‐heterocycles. Among these CMPs, the S, N‐containing thiazole heterocyclic polymer SNC with Pd catalyst exhibits highly‐efficient current densities of 1575.0 mA mgPd−1 for methanol oxidation and 1071.0 mA mgPd−1 for ethanol oxidation, which are among the highest performance in the heterocyclic modulated Pd systems and surpass the commercial Pd black catalyst. Detailed theory calculations suggest that although the furan (O‐heterocycle) polymer OC has the strongest charge transfer (0.057 |e|) with the Pd cluster, the moderate electron transfer (0.041 |e|) of the Pd/SNC heterojunction with an S···N···Pd noncovalent interaction shows the best catalytic reaction kinetics. Moreover, the d‐band of the Pd/SNC system is closer to the volcano vertex than its counterparts. These results indicate that appropriate electron transfer intensity regulation of Pd electronic state by well‐defined heterocyclic structures may significantly improve AOR activity.

Furan Polymers: State of the Art and Perspectives

AbstractThis contribution provides an outlook on the topic of furan polymers, dealing with both its main achievements and the salient recent contributions, together with a critical assessment of their most promising perspectives. Following a brief account of the relevant chemical properties of the furan heterocycle, the main monomers from furfural and hydroxymethylfurfural and their respective polymerization mechanisms are discussed. Chain‐growth polymerizations concentrate on free‐radical and cationic systems, whereas step‐growth polymerizations describe the polycondensation of furfuryl alcohol, polyesters, polyamides, polyurethanes and polyureas, poly(Schiff base)s, epoxy resins, and the polycondensation of 5‐methylfurfural. Finally, the use of the Diels–Alder reaction applied to furan polymer synthesis and modification is reviewed.

Chemical Structures of Adhesive and Interphase Parts in Sucrose/Citric Acid Type Adhesive Wood-Based Molding Derived from Japanese Cedar (Cryptomeria japonica).

In sucrose/citric acid based wood adhesive, the detailed bonding mechanism has still been unknown. Here, we investigated the detailed chemical structures of this adhesive wood (Japanese cedar)-based molding by using heteronuclear single quantum coherence–nuclear magnetic resonance (HSQC-NMR). NMR peaks associated with the furan-type structure appeared, suggesting that the furan compound was formed from sucrose and converted to a furan polymer during the adhesive process and that some of the furan structures in the polymers were ester-bonded with citric acid. The secondary forces between the furan polymers and wood components were thought to contribute to the adhesive effect. In our analysis of the interphase structure, primary hydroxyl groups of both polysaccharides and of lignin substructures were found to be esterified with citric acid. Additionally, some of the glycosidic bonds in polysaccharides were cleaved during the acidic condition produced by citric acid. The above results provided evidence of the polymerization of sucrose-derived 5-HMF, the esterification of wood components, and the degradation of polysaccharides during the molding process. Citric acid functioned as a clamp between the obtained furan polymer and the wood components. The sucrose/citric acid based wood adhesive can be defined as a hybrid-type wood adhesive, involving both secondary forces and chemical bonding interactions.

Furan monomers and polymers from renewable plant biomass

Plant biomass is considered the main source of renewable carbon raw materials, which is a viable alternative to crude oil and natural gas and provides compounds with a low carbon footprint. The most promising direction for the conversion of biomass is the synthesis of 5-hydroxymethylfurfural, which is regarded as a platform chemical, the basis for the synthesis of valuable compounds, including monomers and polymers. The move of the polymer industry to renewable plant materials will contribute to solving global environmental problems and ensure the sustainability and environmental safety of plastics production. This review analyzes recent advances in the preparation of key C6-furan platform chemicals, such as 5-hydroxymethylfurfural, 2,5-furandicarboxylic acid, 2,5-diformylfuran, 2,5-bis(hydroxymethyl)furan, levulinic acid, and their use for the production of monomers and polymers based on renewable plant biomass. Production processes of widely known furan polyesters and polyamides, such as polyethylene-, polypropylene-, polybutylene furanoates, polyhexamethylene furanamide, are considered, as well as developments towards novel promising materials that are furan copolymers and polymer mixtures. For the first time, studies have been systematized aimed at converting liquid and solid wastes of the synthesis of platform chemicals, known as humins, into a range of value-added products, including organic compounds, porous carbon materials, thermosetting binders, and anticorrosive coatings that can replace similar materials based on fossil raw materials. Economic and environmental prospects and problems of production and consumption of furan polymers are considered.The bibliography includes 275 references.

Cell wall changes during brown rot degradation of furfurylated and acetylated wood

This study explores cell wall changes in Radiata pine (Pinus radiata) after modification with acetylation or furfurylation and subsequent prolonged subjection to the brown rot fungus R. placenta with the aim of better understanding the modus operandi of these two modifications. Both modifications have shown good durability in field tests, but in order to learn from their possible limitations, we used optimal environmental conditions for fungal growth, and extended the testing period compared to standard tests. Hyphae were found in acetylated wood after two weeks, and after 28 weeks of decay abundant amounts of encapsulated hyphae were present. In furfurylated wood, mass loss and a few hyphae were seen initially, but no further development was seen during weeks 18–42. The general degradation pattern was qualitatively the same for unmodified, acetylated and furfurylated wood: carbohydrates decreased relative to lignin. Acetyl groups were lost from acetylated wood during decay (earlier results), while the furan polymer did not seem to be altered by the fungus. Based on these findings it is hypothesized that modifications such as furfurylation that enhance moisture exclusion within the cell wall through impregnation polymerization offer better long term protection compared to modifications such as acetylation that depend on the replacement of hydroxyl groups with ether bound adducts that can be removed by fungi.

Renewable Cyclopentanol From Catalytic Hydrogenation-Rearrangement of Biomass Furfural Over Ruthenium-Molybdenum Bimetallic Catalysts.

Biomass furfural-like compounds are chemicals that cannot be extracted from fossil materials, through which a large number of fine chemicals and fuel additives can be opened up, but one big efficiency problem during the transformation is the accumulation of oligomers. Here, we propose a novel and efficient Ru-Mo bimetallic catalyst for selective hydrogenation-rearrangement of furfural-like compounds. The result showed that an unprecedented rearrangement product selectivity of 89.1% to cyclopentanol was achieved under an optimized reaction condition over a 1%Ru−2.5%Mo/CNT catalyst reduced at 600°C. Subsequent characterization suggested that the catalyst presented with weak acidity and strong hydrogenation activity for the reaction, which not only ensures the smooth hydrogenation-rearrangement reaction but also inhibits the accumulation of furan polymers. These findings provide a convenient strategy to tune the catalytic performance of Mo-based catalysts by controlling the reduction and carburization conditions, which appear to be versatile for the rearrangement of furans and similar compounds.

On the way to greener furanic-aliphatic poly(ester amide)s: Enzymatic polymerization in ionic liquid

The polymerization of 2,5-furandicarboxylic acid (FDCA), one of the key building blocks for the preparation of furan polymers, is often accompanied with side reactions (e.g. decarboxylation). Due to the mild reaction conditions, enzymatic polymerizations became an excellent candidate to address this issue. Here, we present a green and effective method to prepare different furanic-aliphatic poly(ester amide)s (PEAFs) by applying two different approaches. PEAFs with Mw‾ up to 21 kg mol−1 were successfully synthesized by a Novozyme 435-catalyzed polycondensation of dimethyl 2,5-furandicarboxylate (DMFDCA) with aliphatic diols, diamines or amino alcohols, using toluene at 90 °C. Additionally, we were able to enhance the sustainability of the entire process by performing the polymerization in ionic liquids – BMIMPF6 and EMIMBF4. Using the ionic liquids (ILs) BMIMPF6 and EMIMBF4 as solvents, we were able to produce PEAFs with Mw‾ up to 7 kg mol−1. The different polarity of the solvents affects the enzyme activity and product solubility, thus also the final molecular weight of the PEAFs. Despite the lower molecular weight, the tested ILs result products with similar characteristics. All obtained PEAFs are semi-crystalline materials and decompose at a temperature around 390 °C with a Tm of around 77–140 °C and Tg of around 11–46 °C. Although still exemplified on the proof-of-concept production of sustainable materials, these findings pave the way to promote the transition from fossil-to bio-based polymers, as well as more environmentally friendly synthetic routes.

Self-healing of biobased furan polymers: Recovery of high mechanical strength by mild heating

Bio-based self-healing polymers exhibiting recovery of high mechanical strength by mild heating are developed. A series of bio-based network polymers was prepared from furan copolymers, poly(2,5-furandimethylene succinate-co-propylene succinate)s, through the reversible Diels-Alder reaction with bismaleimide. By changing the comonomer composition of the copolymer and the amount of bismaleimide added to the copolymer, the network polymers with various glass transition temperature, Tg, covering from −19 to 37 °C were obtained. Healing test of these network polymers at r.t. and 50 °C revealed a clear relationship between healing ability and Tg: healing required a healing temperature Th > Tg+15 °C. Furthermore, the network polymers with r.t < Tg < 50 °C expressed recovery of quite high tensile strength of 11–18 MPa at 50 °C. This result indicates that setting Tg slightly above r.t. and Th above Tg+15 °C shoud be a good strategy to obtain a good balance between mild healing conditions and recovery of high mechanical strength.

Microstructure of chemically modified wood using X-ray computed tomography in relation to wetting properties

Abstract X-ray computed tomography (XCT) was utilized to visualize and quantify the 2D and 3D microstructure of acetylated southern yellow pine (pine) and maple, as well as furfurylated pine samples. The total porosity and the porosity of different cell types, as well as cell wall thickness and maximum opening of tracheid lumens were evaluated. The wetting properties (swelling and capillary uptake) were related to these microstructural characteristics. The data show significant changes in the wood structure for furfurylated pine sapwood samples, including a change in tracheid shape and filling of tracheids by furan polymer. In contrast, no such changes were noted for the acetylated pine samples at the high resolution of 0.8 μm. The XCT images obtained for the furfurylated maple samples demonstrated that all ray cells and some vessel elements were filled with furan polymer while the fibers largely remained unchanged. Furfurylation significantly decreased the total porosity of both the maple and pine samples. Furthermore, this was observed in both earlywood (EW) and latewood (LW) regions in the pine samples. In contrast, the total porosity of pine samples was hardly affected by acetylation. These findings are in line with wetting results demonstrating that furfurylation reduces both swelling and capillary uptake in contrast to acetylation which reduces mostly swelling. Furfurylation significantly increased the cell wall thickness of both the maple and pine samples, especially at higher levels of furfurylation.

Electrochemical performance of V-doped spinel Li4Ti5O12/C composite anode in Li-half and Li4Ti5O12/LiFePO4-full cell

This work reports the preparation of a V-doped Li4Ti5O12/C (donated as V-doped LTO/C) composite material, applying a solid-state method. Both metal doping and carbon coating are applied on the Li4Ti5O12 material, enhancing its rate capability and cycle stability. Furan polymer is used as a carbon source, and vanadium (V) is selected as a dopant. The properties of the materials are examined by X-ray diffraction (XRD), micro-Raman, scanning electron microscopy (SEM), high-resolution transmission microscopy (HR-TEM), the AC impedance method, and the galvanostatic charge/discharge method. For comparison, Li4Ti5O12/C composite materials with and without V doping are also examined. The Li4Ti4.90V0.10O12/C composite material achieves discharge capacities of 165.59 and 76.76 mAh g−1 at a 0.2/1C and 0.2/20C rate, respectively. A Li4Ti5O12/LiFePO4 full cell (LTO capacity-limited) is constructed and investigated. The full cell exhibits discharge capacities of 181, 178, 167, 142, 110, and 78 mAh g−1 at 0.2, 0.5, 1, 3, 5, and 10C, respectively. We determine that the Li4Ti4.95V0.05O12/C composite anode is an outstanding candidate for application in high-power Li-ion batteries.

Self-healing bio-based furan polymers cross-linked with various bis-maleimides

A series of bio-based self-healing polymers was prepared by cross-linking a furan polymer, poly(2,5-furandimethylene succinate), with bis-maleimide compounds by means of Diels–Alder reactions. In addition to the amount of the bis-maleimide linker, the molecular structure of the bis-maleimide played a key role in determining the extent of the Diels–Alder reaction and the mechanical and healing properties of the polymers. Bis-maleimides with phenylene rings markedly enhanced the tensile strength of the network polymers but hindered healing. In contrast, bis-maleimides with a flexible molecular structure tended to improve the polymer elongation, affording polymers with excellent healing ability. The efficiencies of self-healing (=healing without any external stimulus) and healing with an assistance of solvent (CHCl3) were over 70% and 80%, respectively, for the network polymer crosslinked by bis-maleimide with flexible long-alkyl segment. Thus, our results indicate that the choice of bis-maleimide linker is an important factor for designing furan-maleimide–based self-healing polymers.

Bio-Based Furan Polymers with Self-Healing Ability

We report the preparation of a furan polymer, poly(2,5-furandimethylene succinate) by means of a condensation reaction between bio-based monomers. A reversible Diels–Alder reaction between furan and maleimide groups allowed the formation of network polymers cross-linked by a bismaleimide. By controlling the amount of the bismaleimide, mechanical properties were varied widely. These network polymers healed well when their broken surfaces were activated by bismaleimide solutions or solvent. The polymers also displayed excellent self-healing ability without external stimulus. This polymer class offers a wide range of possibilities to produce materials from biomass that have both practical mechanical properties and healing ability. These materials have the potential to bring great benefits to our daily lives by enhancing the safety, performance, and lifetime of products.

Bisfuran‐s‐Tetrazine‐Based Conjugated Polymers: Synthesis, Characterization, and Photovoltaic Properties

AbstractBisfuran‐s‐tetrazine (FTz) and its copolymers with cyclopenta[2,1‐b:3,4‐b′]dithiophene (CPDT) and benzo[1,2‐b:4,5‐b′]dithiophene (BDT) (PCPDTFTz and PBDTFTz) are prepared with the alternating s‐tetrazine and CPDT or BDT units bridged by a furan ring. Their optical and electrochemical properties are studied and compared with their thiophene analogs (PCPDTTTz‐out and PCPDTTTz‐in), in which the bridging unit is 4‐hexylthiophene or 3‐hexylthiophene, respectively. Bulk heterojunction (BHJ) solar cells fabricated from these polymers with PC71BM have a power conversion efficiency (PCE) of 0.8%, which is much lower than that from the PCPDTTTz‐out analog (3.2%), due to the low steric hindrance of the furan polymers in the absence of alkyl substitution on the furan ring.

Reversible click chemistry at the service of macromolecular materials

The application of the reversible Diels–Alder (DA) reaction to the realm of furan polymers has recently bloomed, because of its potential for the preparation of a wide variety of novel macromolecular materials based on renewable resources, possessing, among other properties, thermoreversible, mendable and recycling features. In this study, the synthesis and characterisation of novel furan–maleimide monomers, viz. AB-type molecules, and their polycondensation by means of the DA reaction, are presented. These systems represent an interesting alternative to the traditional linear DA polycondensations, because they ensure the ideal initial stoichiometry. The behaviour of two A–B monomers was investigated with the maleimide group protected in the form of a furan–DA adduct in order to obtain a stable monomer and thus avoid premature polymerization. Their polycondensation was then followed after the in situ deprotection at high temperature, followed by the cooling to the appropriate temperature for the DA polymerization to occur.

Towards novel wood-based materials: Chemical bonds between lignin-like model molecules and poly(furfuryl alcohol) studied by NMR

Abstract Wood modification with furfuryl alcohol is a non-toxic alternative to conventional preservation treatments. A process in which furfuryl alcohol polymerises in situ was previously proposed for chemical modification of wood. In the present work, liquid model systems were investigated using compounds that resemble repeating units of lignin to verify whether chemical bonds form between the furfuryl alcohol polymer and wood. Using different NMR spectroscopic techniques we confirmed that these model compounds do form covalent bonds with the polymerising polymer. The results indicate that the furan polymer grafts to lignin, supporting observations in similar studies performed with genuine wood materials.

Carbons from furan-polymers prepared in the presence of a double-chain amphiphile

Furfuryl alcohol was polymerized in the presence of a double-chain amphiphile using malonic acid or phosphoric acid as the catalyst, leading to an aggregate of spherical particles with a long period of 2.6 nm. On calcination at 1000 °C in nitrogen gas, the polymer particles were converted into lamella-patterned carbons with a long spacing of some micrometers that are composed of carbon layers 0.4 nm in spacing. The lamella-patterned carbon particles were further developed into a highly ordered structure in an appreciable portion on calcination at 2800 °C in argon gas. The present results demonstrate that the presence of a double-chain amphiphile in the polymerization process is effective for the synthesis of such a structurally modified carbon from non-graphitizable furan polymers.

Novel Polymer Substrates for SFM Investigations of Living Cells, Biological Membranes, and Proteins

Extended studies were performed to prepare substrates for scanning force microscopy of biological samples with a surface roughness below 1 nm rms over an area of 500 × 500 nm2. The substrate smoothness and the lack of tip obscuring material are indispensable in order to visualize detailed structures of membrane surfaces, particularly when scanning the lamellipodia of mechanically sensitive goldfish glial cells where peripheral lamellipodia are only 20–30 nm in thickness. Appropriate substrates are poly(vinyl phenyl ketone) or furan polymers with corrugations of 0.3 and 0.15 nm rms, respectively, to which the growth-promoting protein laminin adsorbs directly with an acceptably increased roughness. Cells show normal growth behavior on these substrates and stick to the substrates in a stable fashion during several scans. Thus details of the membrane's surface may be resolved and are not obscured by the substrate texture. The uncoated furan polymer substrates are suitable for immobilization of membrane preparations such as purified membrane fragments containing bacteriorhodopsin or Na,K-ATPase and protein preparations such as antibodies.

Mass-spectrometric thermal analysis of polymers based on furyl alcohol

Mass-spectrometric thermal analysis of samples of furan polymers obtained by heating furyl alcohol in a closed volume at 200 °C, 250 °C and 300 °C permitted determination of the qualitative composition of the gas products evolved from the polymers upon non-isothermal temperature increase from 20 to 1200 °C. The degree of unsaturation of the samples was evaluated quantitatively. The main features of the formation, degradation, structurization and carbonization of furan polymers were considered.