Phenolic Polymers Research Articles

Bifunctional Phenol-Enabled Sequential Polymerization Strategy for Printable Tough Hydrogels.

Hydrogels are promising material candidates in engineering soft robotics, mechanical sensors, biomimetic regenerative medicine, etc. However, developing multinetwork hydrogels with high mechanical properties and excellent printability are still challenging. Here, a bifunctional phenol-enabled sequential polymerization (BPSP) strategy is reported to fabricate high-performance multinetwork hydrogels under the orthogonal catalysis of efficient ruthenium photochemistry. Benefiting from this bifunctional design, phenols can sequentially polymerize with typical monomers and themselves to fabricate various phenol-containing polymers (Ph-Ps) and Ph-Ps-based multinetwork tough hydrogels, respectively. The as-prepared hydrogels have maximum stress of 0.75MPa and toughness of 2.2MJ m- 3 under the critical strain of 800%. These property parameters are a maximum of 16 times higher than those of the phenol-postmodified and phenol-free hydrogels. Moreover, the rapid coupling polymerization of phenols can shorten the gelation times of hydrogels to as low as ≈4 s, which enables its printable property for customizable applications. As a proof of concept, a 3D scaffold-like structure is optimized as highly sensitive mechanical sensors for detecting various human motions.

Dual Mechanisms of Coniferyl Alcohol in Phenylpropanoid Pathway Regulation.

Lignin is a complex phenolic polymer that imparts cell wall strength, facilitates water transport and functions as a physical barrier to pathogens in all vascular plants. Lignin biosynthesis is a carbon-consuming, non-reversible process, which requires tight regulation. Here, we report that a major monomer unit of the lignin polymer can function as a signal molecule to trigger proteolysis of the enzyme L-phenylalanine ammonia-lyase, the entry point into the lignin biosynthetic pathway, and feedback regulate the expression levels of lignin biosynthetic genes. These findings highlight the highly complex regulation of lignin biosynthesis and shed light on the biological importance of monolignols as signaling molecules.

Impact of the Acetaldehyde-Mediated Condensation on the Phenolic Composition and Antioxidant Activity of Vitis vinifera L. Cv. Merlot Wine.

Acetaldehyde is a critical reactant on modifying the phenolic profile during red wine aging, suggesting that the acetaldehyde-mediated condensation can be responsible for the variation of antioxidant activity during the aging of this beverage. The present study employs exogenous acetaldehyde at six levels of treatment (7.86 ± 0.10–259.02 ± 4.95 mg/L) before the bottle aging of Merlot wines to encourage phenolic modification. Acetaldehyde and antioxidant activity of wine were evaluated at 0, 15, 30, 45, 60 and 75 days of storage, while monomeric and polymeric phenolics were analyzed at 0, 30 and 75 days of storage. The loss of acetaldehyde was fitted to a first-order reaction model, the rate constant (k) demonstrated that different chemical reaction happened in wines containing a different initial acetaldehyde. The disappearance of monomeric phenolics and the formation of polymeric phenolics induced by acetaldehyde could be divided into two phases, the antioxidant activity of wine did not alter significantly in the first phase, although most monomeric phenolics vanished, but the second phase would dramatically reduce the antioxidant activity of wine. Furthermore, a higher level of acetaldehyde could shorten the reaction time of the first phase. These results indicate that careful vinification handling aiming at controlling the acetaldehyde allows one to maintain prolonged biological activity during wine aging.

Ultrastrong underwater adhesion on diverse substrates using non-canonical phenolic groups

Robust underwater adhesion is challenging because a hydration layer impedes the interaction between substrates and adhesives. Phenolic adhesives inspired by marine creatures such as mussels were extensively studied, but these adhesives have not reached the adhesion strength and substrate diversity of Man-made dry adhesives. Here, we report a class of ultrastrong underwater adhesives with molecular phenolic designs extending beyond what nature has produced. These non-canonical phenolic polymers show versatile adhesion on various materials, with adhesion strengths exceeding 10 MPa on metal. Incorporating even just a small amount (<10%) of non-canonical phenolic groups into a polymer is sufficient for dramatically enhancing underwater adhesion, suggesting that this new class of phenolic materials will be incorporated into various industrial polymer systems in the future.

Microstructural Defects of Epoxy–Phenolic Polymers on Metal Substrates during Acidic Corrosion

This study uses confocal microscopy and image processing to investigate the microstructural changes of coating–metal systems immersed in a heated acidic bath. Unlike standard optical microscopy techniques, 3D confocal microscopy images can quantitatively reveal microscopic defects formed at early stages of cathodic delamination. The coatings are made of fluorescent epoxy–phenolic resins cured at high temperatures onto tinplate (T23) and tin-free steel (TFS) substrates. When the coated metal substrates are immersed in acetic acid, a series of microscopic corrosion events occur at the polymer–metal interface. These events are quantified by changes in the thickness distribution of the degraded samples relative to that of intact coatings. The degradation rate is highest for epoxy–phenolic polymers on TFS substrates, represented by multiple orders of magnitude increase in the number density of defect sites. Higher molecular weight coatings provide slightly better resistance against delamination. The coating thickness dictates the rate of oxygen diffusion and ion transport along the polymer–coating interface, where raised asperities serve as localized sites for metal oxidation and formation of alkaline species, leading to subsequent delamination of the cured polymers from the surfaces. The results show that the metal surface topology is as important as chemistry when designing the corrosion resistance of products containing acidic liquids, and that confocal microscopy is useful in quality control through early detection of mesoscale polymer failure.

Oxidation of bromide by heat-activated persulfate – Effects of temperature and the organic matter surrogate phenol on kinetics and stoichiometry

• Oxidation of persulfate by sulfate radical affects persulfate decomposition kinetics. • Bromide oxidation to bromate was hindered by phenol. • Sulfate radicals reacting with Br-species decreased at higher temperature. • Insoluble phenol oxidation byproducts formation is favored at high temperature. Reaction mechanisms of sulfate radical with bromide and organic substances can be largely altered at elevated temperature in heat-activated persulfate process due to different activation energies. This study investigated kinetics and stoichiometry of bromide oxidation in the heat-activated persulfate process. We postulated that reaction of sulfate radical with persulfate, which has relatively low reaction rate (6.3 × 10 5 M −1 s −1 ), may become an important reaction at elevated temperatures. Persulfate decomposition was inhibited in the presence of sulfate radical scavenger phenol at low temperature (40 °C) whereas phenol affected persulfate decomposition only at < 50 °C but not at higher temperatures. This was because the second order reaction rate constant of sulfate radical with persulfate became higher (assumed as 10 10 M −1 s −1 ) than with phenol at a temperature > 50 °C, which can be explained by a high activation energy (estimated activation energy: 311 kJ/mol). Bromate formation was inhibited in the presence of phenol. However, phenol oxidation was not affected by the presence of Br − , even though Br − reacts faster with sulfate radicals than phenol and was present in excess. This indicated that formed reactive bromine species such as Br and Br 2 − oxidize phenol under reformation of bromide. Formation of insoluble products was also observed indicating polymerization of phenol. This can be explained by lack of dissolved oxygen under conditions of heat-activation.

Systematic Approach to Mimic Phenolic Natural Polymers for Biofabrication.

In nature, phenolic biopolymers are utilized as functional tools and molecular crosslinkers to control the mechanical properties of biomaterials. Of particular interest are phenolic proteins/polysaccharides from living organisms, which are rich in catechol and/or gallol groups. Their strong underwater adhesion is attributed to the representative phenolic molecule, catechol, which stimulates intermolecular and intramolecular crosslinking induced by oxidative polymerization. Significant efforts have been made to understand the underlying chemistries, and researchers have developed functional biomaterials by mimicking the systems. Owing to their unique biocompatibility and ability to transform their mechanical properties, phenolic polymers have revolutionized biotechnologies. In this review, we highlight the bottom-up approaches for mimicking polyphenolic materials in nature and recent advances in related biomedical applications. We expect that this review will contribute to the rational design and synthesis of polyphenolic functional biomaterials and facilitate the production of related applications.

Cell‐Mediated Biointerfacial Phenolic Assembly for Probiotic Nano Encapsulation

AbstractThe use of cell‐mediated chemistry is an emerging strategy that exploits the metabolic processes of living cells to develop biomimetic materials with advanced functionalities and enhanced biocompatibility. Here, a concept of a cell‐mediated catalytic process for forming protective nano‐shells on individual probiotic cells is demonstrated. This process is leveraged by the cell environment to induce oxidative polymerization of phenolic compounds, and simultaneously these phenolic polymers assemble to form nano‐coatings around individual cell surfaces. The detailed analysis reveals that the oxidation process is triggered by an essential nutrient (manganese) of the probiotic cells, which significantly increases the oxidation rate of phenolic compounds. The phenolic coatings, encapsulating each cell in nanometre scale, demonstrate excellent biocompatibility and biodegradability. Additionally, the in situ encapsulated probiotic cells display an improved gastric tolerance of up to ≈1.4 times higher than the native cells and enhanced adhesion as high as ≈1.6 times onto a model of intestinal epithelial cells. Finally, the coated probiotic cells exhibit a high antioxidant activity as an advanced feature. Overall, this method provides a unique approach to improve the probiotic delivery using the cell machinery to engineer encapsulating nanocoatings with protective benefits and new functionalities.

Rerouting of the lignin biosynthetic pathway by inhibition of cytosolic shikimate recycling in transgenic hybrid aspen.

Lignin is a phenolic polymer deposited in the plant cell wall, and is mainly polymerized from three canonical monomers (monolignols), i.e. p-coumaryl, coniferyl and sinapyl alcohols. After polymerization, these alcohols form different lignin substructures. In dicotyledons, monolignols are biosynthesized from phenylalanine, an aromatic amino acid. Shikimate acts at two positions in the route to the lignin building blocks. It is part of the shikimate pathway that provides the precursor for the biosynthesis of phenylalanine, and is involved in the transesterification of p-coumaroyl-CoA to p-coumaroyl shikimate, one of the key steps in the biosynthesis of coniferyl and sinapyl alcohols. The shikimate residue in p-coumaroyl shikimate is released in later steps, and the resulting shikimate becomes available again for the biosynthesis of new p-coumaroyl shikimate molecules. In this study, we inhibited cytosolic shikimate recycling in transgenic hybrid aspen by accelerated phosphorylation of shikimate in the cytosol through expression of a bacterial shikimate kinase (SK). This expression elicited an increase in p-hydroxyphenyl units of lignin and, by contrast, a decrease in guaiacyl and syringyl units. Transgenic plants with high SK activity produced a lignin content comparable to that in wild-type plants, and had an increased processability via enzymatic saccharification. Although expression of many genes was altered in the transgenic plants, elevated SK activity did not exert a significant effect on the expression of the majority of genes responsible for lignin biosynthesis. The present results indicate that cytosolic shikimate recycling is crucial to the monomeric composition of lignin rather than for lignin content.

Optimization and modelling of the fracture inhibition potential of heat treated doum palm nut fibres in phenolic resin matrix polymer composite: a Taguchi approach

The chemical treatment of natural fibres for its surface modification for the development of polymer composites is popular but it comes with an adverse effect of a chemical change of the fibres. In this study, the surface modification of natural fibres (doum palm nut (DPN) fibres) with low-temperature heat treatment (30 °C–75 °C) has been reported as an alternative method to the treatment of natural fibres for the development of polymer composites. Taguchi method of the design of experiment was employed to determine the effect of temperature and fibre content on the mechanical properties (hardness and fracture toughness) of DPN fibre-reinforced phenolic resin polymer composite. The process showed that the best combination of fibre content and fibre treatment temperature for optimum hardness and fracture toughness and results proved to be at 5% and 75 °C respectively. Statistical analysis established the significance of heat treatment in improving the fracture toughness of DPN fibre reinforced phenolic resin composites. Physical observation with scanning electron microscope and Fourier-transform infrared spectroscopy confirmed the improvement in interfacial bonding between the fibre and the matrix with the increase in fibre treatment temperature without a change in the chemical properties of the treated fibres. The study concludes that the treatment of fibres with temperature is an alternative and effective method to the chemical treatment.

In-depth analysis of reaction kinetics parameters of phenolic resin using molecular dynamics and unsupervised machine learning approach

Reaction kinetics parameters of a material depend on energy dynamics based on breaking and formation of all the types of bonds in the system. While employing molecular dynamics simulation, it can become tedious and a complicated job to use all the bond information for extracting reaction kinetics parameters. With this understanding, in the current study, the use of an unsupervised machine learning technique is demonstrated for extracting the reaction kinetics parameters from the molecular dynamics simulation of an ablative material. Molecular dynamics simulations are performed on crosslinked and non-crosslinked polymers in temperature regime where they would undergo pyrolysis decomposition. Non-negative Matrix Factorization (NMF) technique is used to reduce the bonding environment, obtained during the simulations, to the concentration profiles of a few principal components. A comparative analysis performed with polymers having different degrees of crosslinking reveals that the activation energy reduces with increase in the degree of crosslinking. The effect of heating rate on the reaction kinetics of phenolic polymers during the pyrolysis simulation is investigated in detail. The assumption of chemical equilibrium between gases and porous solid domain is frequently made in continuum level thermal response solvers. It is unknown if this assumption significantly affects the calculated reaction kinetics parameters. To understand the same, a molecular dynamics simulation, which eliminates the generated gas molecules in a systematic manner throughout the pyrolysis process, is carried out. Furthermore, to demonstrate the usefulness of reaction kinetics parameters extracted after manifestation of chemical equilibrium at microscale level, a one-dimensional heat conduction analysis is performed. The results obtained by not considering the gas particles in reaction modeling agree well with experiments. At the end, a multiscale thermal response analysis is performed over an axi-symmetric geometry for which, a relation is derived between pyrolysis gas species and solid material density evolution from MD simulations. Based on the relation, the axi-symmetric domain is segregated into different regions for their contribution in changing pyrolysis gas composition by either adding or consuming gas species.

Electrochemical Properties of Peat Particulate Organic Matter on a Global Scale: Relation to Peat Chemistry and Degree of Decomposition

AbstractMethane production in peatlands is controlled by the availability of electron acceptors for microbial respiration, including peat dissolved organic matter (DOM) and particulate organic matter (POM). Despite the much larger mass of POM in peat, knowledge on the ranges of its electron transfer capacities—electron accepting capacity (EAC), and electron donating capacity (EDC)—is scarce in comparison to DOM and humic and fulvic acids. Moreover, it is unclear how peat POM chemistry and decomposition relate to its EAC and EDC. To address these knowledge gaps, we compiled peat samples with varying carbon contents from mid to high latitude peatlands and analyzed their EACPOM and EDCPOM, element ratios, decomposition indicators, and relative amounts of molecular structures as derived from mid infrared spectra. Peat EACPOM and EDCPOM are smaller (per gram carbon) than EAC and EDC of DOM and terrestrial and aquatic humic and fulvic acids and are highly variable within and between sites. Both are small in highly decomposed peat, unless it has larger amounts of quinones and phenols. Element ratio‐based models failed to predict EACPOM and EDCPOM, while mid infrared spectra‐based models can predict peat EACPOM to a large extent, but not EDCPOM. We suggest a conceptual model that describes how vegetation chemistry and decomposition control polymeric phenol and quinone contents as drivers of peat EDCPOM and EACPOM. The conceptual model implies that we need mechanistic models or spatially resolved measurements to understand the variability in peat EDCPOM and EACPOM and thus its role in controlling methane formation.

Manganese-phenolic nanoadjuvant combines sonodynamic therapy with cGAS-STING activation for enhanced cancer immunotherapy

Dendritic cells (DCs) play a key role in the presentation of tumor antigens to initiate innate and adaptive immune responses. While the tumor microenvironment (TME) contains a network of immunosuppressive factors that inhibit the differentiation and maturation of DCs. Immunoadjuvants have been focusing on modulating DCs function to improve cancer immunotherapy. Herein, a phenolic nanoadjuvant was developed by self-assembly of the sonosensitizer polymer (PEG-b-IR), GSH inhibitor (sabutoclax), Mn2+ and TME acidic sensitive phenolic polymer (PEG-b-Pho) via metal–phenolic coordination. The combinational action of SDT-mediated ICD effect and Mn2+ promoted the activation of the cGAS-STING pathway significantly enhanced DCs maturation. Furthermore, this phenolic nanoadjuvant greatly sensitizes tumors to PD-L1 checkpoint blockade immunotherapy, resulting in efficiently inhibiting the growth of distant tumors and restraining lung metastasis. Therefore, our work provides the potential to remedy the therapeutic limitation of insufficient antitumor immunity for enhanced cancer immunotherapy.

Rational design of efficient polar heterogeneous catalysts for catalytic oxidative-adsorptive desulfurization in fuel oil

The rational design of efficient polar heterogeneous catalysts for oxidation adsorption desulfurization (OADS) is still a challenge. Herein, we fabricated a novel polar fingerprint-like heterogeneous catalyst (HPW-NH2-CPRNSs) by immobilizing phosphotungstic acid on amino grafted phenolic resin nanospheres prepared through gradient temperature hydrothermal method, which exhibits highly effective oxidative-adsorptive desulfurization (OADS) performance. The fingerprint-like nanospheres catalysts were formed when the F127 exposed on the surface of PRNSs was dissolved during the refluxing. Moreover, the polarity of the HPW-NH2-CPRNSs catalysts can be well adjusted by controlling the amount of amino grafting and calcination temperature, which plays an important role in OADS. The removal rate of DBT on optimal polar catalyst reached the highest 98.9% in 90 min. It is the first time that this work involving the phenolic resin polymers have been used as the carrier of desulfurization catalyst and the polarity of the catalyst has been artificially controlled for OADS.

Crystal structure of the plant feruloyl–coenzyme A monolignol transferase provides insights into the formation of monolignol ferulate conjugates

Lignin is a highly complex phenolic polymer which is essential for plants, but also makes it difficult for industrial processing. Engineering lignin by introducing relatively labile linkages into the lignin backbone can render it more amenable to chemical depolymerization. It has been reported that introducing a feruloyl-coenzyme A monolignol transferase from Angelica sinensis (AsFMT) into poplar could incorporate monolignol ferulate conjugates (ML-FAs) into lignin polymers, suggesting a promising way to manipulate plants for readily deconstructing. FMT catalyzes a reaction between monolignols and feruloyl-CoA to produce ML-FAs and free CoA-SH. However, the mechanisms of substrate specificity and catalytic process of FMT remains poorly understood. Here we report the structure of AsFMT, which adopts a typical fold of BAHD acyltransferase family. Structural comparisons with other BAHD homologs reveal several unique structural features of AsFMT, different from those of the BAHD homologs. Further molecular docking studies showed that T375 in AsFMT may function as an oxyanion hole to stabilize the reaction intermediate and also proposed a role of H278 in the binding of the nucleophilic hydroxyl group of monolignols. Together, this study provides important structural insights into the reactions catalyzed by AsFMT and will shed light on its future application in lignin engineering.

Hierarchical porous phenolic polymer for efficient adsorption of triazine herbicides: Novel preparation strategies and potential applications

Efficient removal of pollutants based on porous adsorbents is a research hotspot now. Triazine herbicides (TRZHs), a class of broad-spectrum, low-cost pesticides, have become an environmental concern owing to the widespread use and abuse these chemicals. In this study, an ionic liquid (IL)-functionalized porous m-aminophenol formaldehyde polymer (IL-PMAPFP) used to adsorb four TRZHs (simazine, cyanazine, atrazine, and terbuthylazine) in environmental water was synthesized. The role of the ethylene oxide/propylene oxide block copolymer (F127) and IL in pore formation was confirmed by microscopic morphology and specific surface area analysis of IL-PMAPFP. The specific surface area of IL-PMAPFP increased 13-fold after adding F127 and the IL. The adsorption of TRZHs on IL-PMAPFP conformed to the pseudo-second-order kinetic and Freundlich isotherm models. The adsorption process is spontaneous, endothermic, and has a strong anti-interference ability. The adsorption equilibrium of IL-PMAPFP could be reached within 1 h, and the adsorption capacities of the four TRZHs are 4.26, 4.82, 5.21, and 8.53 mg/g, respectively, which were higher than many reported adsorbents. Theoretically, the ability of the adsorbent to treat TRZH-contaminated water is 450–900 L/g. IL-PMAPFP is a powerful adsorbent owing to its large surface area, high adsorption amount, fast mass transfer, and good regeneration capability (>eight cycles). IL-PMAPFP combined with dispersive solid phase extraction/miniaturized pipette tip solid phase extraction-high performance liquid chromatography is expected to accurately quantify TRZHs. In addition, the synergistic pore formation strategy of F127 and IL present a new method for preparing of porous polymer. This study provides a new perspective for developing efficient purification techniques to monitor and remove pollutants.

Fabrication of naphthol-based phenolic polymer coated-silica for mixed-mode chromatography

This paper introduces a novel phenolic resin-coated silica stationary phase grafted from the surface of amino-functionalized porous silica microspheres through copolymerization of 1,5-dihydroxynaphthalene and 1,3,5-trioxane in the dispersed state, followed by low-temperature calcination at 200 °C. The new material was identified by scanning electron microscopy, elemental analysis, thermogravimetric analysis and Fourier-transform infrared spectroscopy. The new column has the capability to separate different types of compounds. When utilizing hydrophilic interaction liquid chromatography, sulfonamide drugs and nucleosides/nucleobases could be separated with good resolution even if there were no buffer salts in the eluent. In reversed-phase liquid chromatography, the column indicated satisfactory separation abilities for positional isomers, alkylbenzenes as well as polycyclic aromatic hydrocarbons (PAHs). The selectivity and retention of the new column for PAHs were higher than those for alkylbenzene, which may be affected by the π–π forces between the PAH analytes and naphthalene ring from the surface of the silica. Depending on the retention mode, the elution order can be reversed using this column. Thus, the stationary phase was intended as a novel mixed-mode column. Meanwhile, the retention and selectivity can be adjusted very flexibly by changing the chromatographic conditions.

Impact of the Phenolic Matrix in Terms of Phenolic Polymerization on the Bioaccessibility and Bioavailability of the Low Molecular Phenolic Compounds, and the Antioxidant Activity, of Pressurized Liquid Grape Stem Extracts

Impact of the Phenolic Matrix in Terms of Phenolic Polymerization on the Bioaccessibility and Bioavailability of the Low Molecular Phenolic Compounds, and the Antioxidant Activity, of Pressurized Liquid Grape Stem Extracts

Plant secondary cell wall proteome analysis with an inducible system for xylem vessel cell differentiation.

Plant cell walls are typically composed of polysaccharide polymers and cell wall proteins (CWPs). CWPs account for approximately 10% of the plant cell wall structure and perform a wide range of functions. Previous studies have identified approximately 1000 CWPs in the model plant Arabidopsis thaliana; however, the analyses mainly targeted primary cell walls, which are generated at cell division. In contrast, little is known about CWPs in secondary cell walls (SCWs), which are rigid and contain the phenolic polymer lignin. Here, we performed a cell wall proteome analysis to obtain novel insights into CWPs in SCWs. To this end, we tested multiple methods for cell wall extraction with cultured Arabidopsis cells carrying the VND7-VP16-GR system, with which cells can be transdifferentiated into xylem-vessel-like cells with lignified SCWs by dexamethasone treatment. We then subjected the protein samples to in-gel trypsin digestion followed by LC-MS/MS analysis. The different extraction methods resulted in the detection of different cell wall fraction proteins (CWFPs). In particular, centrifugation conditions had a strong impact on the extracted CWFP species, resulting in the increased number of identified CWFPs. We successfully identified 896 proteins as CWFPs in total, including proteases, expansins, purple phosphatase, well-known lignin-related enzymes (laccase and peroxidase), and 683 of 896 proteins were newly identified CWFPs. These results demonstrate the usefulness of our CWP analysis method. Further analyses of SCW-related CWPs could be expected to produce information useful for understanding the roles of CWPs in plant cell functions.

Comparative analysis of antioxidant activities between dried and fresh walnut kernels by metabolomic approaches

Fresh walnut kernel (FW) and dry walnut kernel (DW) are significantly different in antioxidant activity. However, the metabolomic mechanism underlying these differences remains to be explored. Here, we evaluated the antioxidant activities of FW and DW of four walnut varieties, and characterized their metabolites by GC-MS and LC-MS/MS. The influence of different metabolites on antioxidant activity of walnut kernel was investigated through a multivariate analysis. DW showed significantly higher antioxidant activities than FW. A total of 144 metabolites were detected in all samples. Pearson correlation analysis demonstrated that phenolic metabolites and polyunsaturated fatty acids significantly affect the antioxidant activity. A further network analysis of 21 target differential metabolites indicated that the higher antioxidant activity of DW may be mainly attributed to the higher content of phenolic acid polymers. This study reveals the potential mechanism for improving of antioxidant activity of walnut kernels by drying.