Hydroxyl Research Articles

Comparison of the mechanical characteristics of biocomposites of unsaturated polyester resin with cellulose extracted from corn silk and treated corn silk

The purpose of this study is to extract cellulose from corn silk (CS) fiber and use it as a reinforcing filler in unsaturated polyester resin (UPR) matrix. In this study, the cellulose is characterized using a Fourier Transform Infrared Spectrometer (FTIR), and the resulting UPR/cellulose biocomposite's mechanical properties (such as flexural and impact testing) are assessed. Scanning electron microscopy (SEM) provided strong support for mechanical rather than a chemical bond between fiber and UPR. Additionally, the sodium hydroxide treated CS in UPR biocomposite and comparing it with neat UPR. The agricultural byproduct rich in cellulose corn silk is a natural polymer known for its structural strength and UPR has garnered attention as a biopolymer with notable flexibility, making it an appealing choice for plastic product manufacturing. However, the drawback of UPR lies in its inherent deficiency in both stiffness and strength. According to the FTIR data, extracted cellulose (CS) had fewer ketone (C = O) and hydroxyl (-OH) groups than virgin cellulose. It was shown that throughout the extraction process, hemicellulose and lignin were more eliminated, producing a more pure form of cellulose. When filled in UPR, cellulose and treated CS both caused the impact strength of UPR biocomposites to drop. For both treated CS and cellulose, it was shown that the flexural modulus and flexural strength increased as the filler amount increased to a definite percentage (12%) after which it decreased. The result revealed the tensile strength and tensile modulus achieved by 0% of fiber with 48 N/mm2 and 51 N/mm2 and highest at 12% of fiber with 54.3 N/mm2 and 68.8 N/mm2 for CS + UPR. And 53.4 N/mm2 and 69.6 N/mm2 for cellulose + UPR composite,, respectively. In comparison, the flexural characteristics of UPR/cellulose were marginally inferior to those of UPR/treated CS. However, the impact resistance showed a significant improvement, particularly with a cellulose loading of 12%. Hence, cellulose presents a greater potential for composite manufacturing due to its ability to maintain the ductile properties of UPR compared to treated CS. Moreover, processed CS and cellulose both can be used as reinforcing agents in polymers to increase their strength and stiffness.

A latent curing agent for rapid curing of phenolic epoxy resin at low temperature

AbstractDeveloping effective latent curing agent for rapid curing of epoxy resins at low temperatures remains challenging. This study reports a latent curing agent, ortho‐cresol phenolic epoxy resin‐bisphenol A (EOCN‐BPA), prepared through the addition reaction of o‐methyl phenolic epoxy resin with BPA. When blended with dicyandiamide (DICY) in a 1:3 molar ratio, EOCN‐BPA/DICY is used to cure a linear epoxy phenolic novolac (EPN) resin (epoxy equivalent: 550 g eq−1, softening point: approximately 82°C), at an onset curing temperature of 90°C, which is considerably lower than the onset curing temperature of DICY with EPN (160°C). However, EOCN‐BPA does not react with EPN without a catalyst. Therefore, this latent curing system is successfully applied in powder coatings, rapid curing at 120°C within 3 min without an additional catalyst, outperforming the EPN/EOCN‐BPA system using cocatalyst 2‐methylimidazole. Consequently, DICY catalyzes the curing reaction between the phenol hydroxyl group and epoxy resin and participates in it. The prepared powder coating exhibits excellent storage stability, maintaining its properties for over 3 months at room temperature. These findings demonstrate the excellent latent properties of EOCN‐BPA/DICY, highlighting its potential as a highly effective latent curing agent.

Preparation, properties, and antibacterial application of dialdehyde carboxymethyl cross‐linked sesbania gum

AbstractSuitably modified sesbania gum as a biodegradable functional biomaterials was very attractive in many applications. Therefore, a combination of cross‐linking, carboxymethylation, and oxidation was chosen to modify sesbania gum (SG) to expand its use. The experimental results indicated that cross‐linking could be completed not only on SG particles, but also between different SG particles. The cross‐linking decreased the number of surface hydroxyl groups on SG. The sedimentation volume decreased with the increase of phosphorus content of cross‐linked sesbania gum (CLSG). The structure of SG particles was severely disrupted by carboxymethylation and oxidation, while the structure was less affected by cross‐linking. The viscosities of SG and modified SG paste in acidic medium were less than those in neutral medium, while their viscosities in alkaline medium were more than those in neutral medium. Cross‐linking, carboxymethylation, and oxidation could ameliorate the retrogradation of SG, but decrease its swelling power, freeze–thaw stability, acid, and alkaline resistance. The aldehyde groups had good antibacterial activity against Trichoderma harzianum, whereas the carboxymethyl groups and phosphate ester groups showed poor antimicrobial activity against T. harzianum.

An Organic Molecular Mimetic Metal-Free Heterogeneous Catalyst for Electrocatalytic Alkyne Semihydrogenation.

The direct construction of metal-free catalysts on conductive substrates for electrocatalytic organic hydrogenation reactions is significant but still unexplored. Here, learning from the homogeneous molecular catalysts, an organic molecular mimetic metal-free heterogeneous catalyst is designed and constructed in situ on a graphite flake electrode via a mild electrochemical oxidation‒reduction relay strategy. The as-prepared -COOH- and -OH-functionalized metal-free catalyst exhibits an electrocatalytic alkyne semihydrogenation performance with a 72% Faradaic efficiency, 99% selectivity and 96% yield of the alkene product, which is comparable to that of noble metal catalysts. The removal of these oxygen-containing groups leads to negligible activity. The experimental and calculation results reveal that the origin of the high activity can be assigned to the -COOH and -OH groups on graphite. A flow electrolytic cell delivers ten grams of hydrogenated products with 81% Faradaic efficiency. This metal-free catalyst is also suitable for gas-phase acetylene semihydrogenation and other electrocatalytic hydrogenation reactions.

An Organic Molecular Mimetic Metal‐Free Heterogeneous Catalyst for Electrocatalytic Alkyne Semihydrogenation

The direct construction of metal‐free catalysts on conductive substrates for electrocatalytic organic hydrogenation reactions is significant but still unexplored. Here, learning from the homogeneous molecular catalysts, an organic molecular mimetic metal‐free heterogeneous catalyst is designed and constructed in situ on a graphite flake electrode via a mild electrochemical oxidation‒reduction relay strategy. The as‐prepared –COOH‐ and –OH‐functionalized metal‐free catalyst exhibits an electrocatalytic alkyne semihydrogenation performance with a 72% Faradaic efficiency, 99% selectivity and 96% yield of the alkene product, which is comparable to that of noble metal catalysts. The removal of these oxygen‐containing groups leads to negligible activity. The experimental and calculation results reveal that the origin of the high activity can be assigned to the –COOH and –OH groups on graphite. A flow electrolytic cell delivers ten grams of hydrogenated products with 81% Faradaic efficiency. This metal‐free catalyst is also suitable for gas‐phase acetylene semihydrogenation and other electrocatalytic hydrogenation reactions.

One‐Pot Synthesis of 3‐Hydroxy‐1H‐Pyrrolo[3,4‐b]quinolin‐1‐one via Enaminamides

A multicomponent cascade cyclization reaction using aryl methyl ketones, aryl amines, and enaminamide reagents to construct 3‐hydroxy‐1H‐pyrrolo[3,4‐b]quinolin‐1‐one skeleton with good substrate compatibility (50 examples) has been reported. The one‐pot, metal‐free process formed two C‐C bonds, two C‐N bonds, and a tetrasubstituted carbon stereocenter containing a hydroxyl group. The reaction enabled modified transformation of drug molecules and derivatization of products.

Determination of bisphosphonate properties in terms of bioavailability, bone affinity, and cytotoxicity.

The study aimed to evaluate the therapeutic potential of fourteen newly synthesized bisphosphonates by assessing their bioavailability, bone affinity, and cytotoxicity. These bisphosphonates included a series of aminomethylenebisphosphonates and standard compounds such as risedronate and tiludronate. Drug permeability was determined using Parallel Artificial Membrane Permeability Assays (PAMPA), while bone affinity was assessed by sorption on hydroxyapatite. Bacterial cell response to the bisphosphonates was also examined using Lactobacillus paracasei cells as a model. Several tested compounds, including BP3 to BP8 and BP11, which feature substituents in the pyridine ring such as methyl groups, iodine, bromine, chlorine, or hydroxyl groups, demonstrated potentially more beneficial therapeutic properties than commercially used bisphosphonates. These compounds showed stronger bone affinity and higher gastrointestinal absorption with comparable or lower cytotoxic effects. Specifically, BP11 exhibited the highest bone affinity, while BP8 and BP11 showed the greatest permeability. The findings suggest that BP3 BP8, and BP11 are promising candidates for further research. These results highlight the importance of comprehensively evaluating bisphosphonates' therapeutic properties to identify effective treatments for osteoporosis and other bone diseases.

Biodegradable MXene Quantum Dots with High Near-Infrared Photothermal Performance for Cancer Treatment.

Photothermal therapy (PTT) offers significant potential in cancer treatment due to its short, simple, and less harmful nature. However, obtaining a photothermal agent (PTA) with good photothermal performance and biocompatibility remains a challenge. MXenes, which are PTAs, have shown promising results in cancer treatment. This study presents the preparation of Ti3C2 MXene quantum dots (MXene QDs) using a simple hydrothermal and ultrasonic method and their use as a PTA for cancer treatment. Compared to conventional MXene QDs synthesized using only the hydrothermal method, the ultrasonic process increased the degree of oxidation on the surface of the MXene QDs. This resulted in the presence of more hydrophilic groups such as hydroxyl groups on the MXene QD surfaces, leading to excellent dispersion in the aqueous system and biocompatibility of the prepared MXene QDs without the need for surface modification. The MXene QDs showed great photothermal performance with a photothermal conversion efficiency of 62.5%, resulting in the highest photothermal conversion efficiency among similar materials reported thus far. Both in vitro and in vivo experiments have proved the potent tumor inhibitory effect of the MXene QD-mediated PTT, with minimal harm to mice. Therefore, these MXene QDs hold a significant promise for clinical applications.

Hierarchically porous carbon confined cobalt nanoparticles for highly efficient oxidative esterification of 5‐hydroxymethylfurfural

AbstractHerein, we report a controllable and versatile strategy for the synthesis of highly dispersed Co nanoparticles embedded in open‐channel hierarchically porous N/O‐doped carbon skeleton. Moreover, the pore sizes of the hierarchical structures can be easily tuned by adjusting the size of precursors. The as‐obtained Co@NC‐2ST exhibits unprecedented activity and selectivity in the oxidative esterification of 5‐hydroxymethylfurfural (HMF) to dimethyl furan‐2,5‐dicarboxylate under base‐free and atmospheric conditions. In particular, the achieved turnover frequency value is an order of magnitude higher than that of the state‐of‐art heterogeneous catalysts reported to date. A combination of experimental and density function theory studies reveals that the unique features of Co@NC‐2ST enable a novel reaction route, that is, the CHO group of HMF is preferentially esterified instead of the OH group. This can be attributed to the nucleophilic addition reaction caused by the attack of methoxy anion on the CHO group of HMF.

Unraveling the Mechanism of the Oxidative C-C Bond Coupling Reaction Catalyzed by Deoxypodophyllotoxin Synthase.

Deoxypodophyllotoxin synthase (DPS), a nonheme Fe(II)/2-oxoglutarate (2OG)-dependent oxygenase, is a key enzyme that is involved in the construction of the fused-ring system in (-)-podophyllotoxin biosynthesis by catalyzing the C-C coupling reaction. However, the mechanistic details of DPS-catalyzed ring formation remain unclear. Herein, our quantum mechanics/molecular mechanics (QM/MM) calculations reveal a novel mechanism that involves the recycling of CO2 (a product of decarboxylation of 2OG) to prevent the formation of hydroxylated byproducts. Our results show that CO2 can react with the FeIII-OH species to generate an unusual FeIII-bicarbonate species. In this way, hydroxylation is avoided by consuming the OH group. Then, the C-C coupling followed by desaturation yields the final product, deoxypodophyllotoxin. This work highlights the crucial role of the CO2 molecule, generated in the crevice between the iron active site and the substrate, in controlling the reaction selectivity.

Cross-Linkable Binders for Si Anodes in High-Energy-Density Lithium-Ion Batteries.

Although silicon (Si) has a high theoretical capacity, the large volume expansion during lithiation has greatly hindered its application in high-energy-density lithium-ion batteries (LIBs). Among the strategies for improving the performance of Si anode, the role of binders should not be underestimated. Here, a novel strategy for designing a cross-linkable binder for Si anode has been proposed. The binder with hydroxyl and nitrile groups can be in situ covalently cross-linked through the amide group in the batteries. The cross-linked binder (c-POAH) shows high elasticity and strong adhesion to Si particles and the current collector. Si||Li half coin cells using the c-POAH binder have excellent cycle performance and the capacity retention ratio is 67.1% after 100 cycles at 0.2 C. Scanning electronic microscopy images show that the c-POAH binder can contribute to suppressing the pulverization of the Si anode. Moreover, the investigation with X-ray photoelectronic spectrum demonstrates that the decomposition of the liquid electrolyte on Si anode has been mitigated and the c-POAH binder can promote the formation of a more stable SEI film. Our strategy of endowing the binder with good elasticity through in situ cross-linking has opened up a new route for developing binders, which will definitely promote the application of Si anodes in high-energy-density LIBs.

Primary Allylic Amine Synthesis via Pd-Catalyzed Direct Amination of Allylic Alcohols with Ammonium Acetate.

Pd/DPEphos-catalyzed direct amination of allylic alcohols with readily available ammonium acetate as a nitrogen source provides access to convenient and scalable syntheses of primary allylic amines with high monoallylation selectivity. Mechanistic studies revealed that ammonium acetate functions as a Brønsted acid to activate the hydroxyl groups and inhibit overreaction.

Trifluoromethylation Strategies of Alcohols and Phenols

In this review, we present a comprehensive update on the latest trifluoromethylation protocols for alcohols, highlighting the significant advancements and innovative strategies in this rapidly evolving field. Given the prevalence of hydroxyl groups in pharmaceutical compounds, there is a heightened interest in synthesizing functionalized organic molecules through the ‐CF3 functionalization of parent alcohols. Recent developments have introduced intriguing methods such as O‐trifluoromethylation, dehydroxylative trifluoromethoxylation, deoxytrifluoromethylation, and oxytrifluoromethylation of readily available alcohols. These protocols enable the efficient single‐step construction of diverse structures featuring C‐CF3 and C‐OCF3 bonds. This review aims to encapsulate the significant progress, structural diversity, and mechanistic insights of these transformative reactions, emphasizing their substrate scope and the underlying reaction pathways that drive these advancements.

Itaconic anhydride functionalized cyanoethyl cellulose with crosslinked structure enabled improved dielectric properties

AbstractAs a type of cellulose ether, cyanoethyl cellulose (CEC) is considered to be a promising candidate for polymer dielectrics due to its sustainable nature and high dielectric constant induced by the cyano groups. However, the relatively high conduction loss of CEC arising from the charge motion across the polymer degrades its dielectric properties. In this work, we designed and synthesized an all‐organic polymer composite of CEC/itaconic anhydride (ITA) to improve dielectric properties. The CEC matrix was graft functionalized by ITA via an esterification reaction between the anhydride groups of ITA and hydroxyl groups of CEC. Meanwhile, crosslinking structure was also established in the composite by the generation of diester. Significantly improved dielectric constant (εr), elevated breakdown strength (Eb), restrained dielectric loss (tan δ) and decreased conductivity (σ) were observed in the composites compared with unmodified CEC. The εr increased from 17 for pure CEC to 32 for CEC/ITA at 1 kHz, and Eb also soared from 145 MV m−1 for CEC to 226 MV m−1 for the composite. The tan δ reduced from 0.24 for pure CEC to about 0.05 for the composite at 100 Hz. This should be attributed to the molecule trapping centers arising from the high electron affinity ITA and the formation of crosslinked networks as well as hydrogen bonding, which impeded the electric conduction. It also provided additional advantages of better dielectric properties for the CEC/ITA composites than pure CEC at high temperatures, which may offer inspiration for the design and preparation of bio‐based dielectrics for high temperatures. © 2024 Society of Chemical Industry.

--Redox Transformations of the OX063 Radical in Biological Media: Oxidative Decay of Initial Trityl with Further Formation of Structurally-Modified TAM.

Being a low-toxic and hydrophilic representative of TAM, OX063 has shown its suitability for in-vivo and in-cell EPR experiments and design of spin labels. Using 13C labeling, we investigated the course of oxidative degradation of OX063 into quinone-methide (QM) under the influence of superoxide as well as further thiol-promoted reduction of QM into TAM radical, which formally corresponds to substitution of a carboxyl function by a hydroxyl group. We found these transformations being quantitative in model reactions mimicking specific features of biological media and confirmed the presence of these reactions in the blood and liver homogenate of mice in vitro. The emergence of the trityl with the hydroxyl group can be masked by an initial TAM in EPR spectra and may introduce distortions into EPR-derived oximetry data if they have been obtained for objects under hypoxia. 13C labeling allows one to detect its presence, considering its different hyperfine splitting constant on 13C1 (2.04 mT) as compared to OX063 (2.30 mT). The potential involvement of these reactions should be considered when using TAM in spin-labeling of biopolymers intended for subsequent EPR experiments, as well as in the successful application of TAM in experiments in vivo and in cell.

High Antifouling Performance of Weakly Hydrophilic Polymer Brushes: A Molecular Dynamics Study.

The antifouling performance of polymer brushes usually improves with increasing hydrophilicity of the grafted polymer. However, in some cases, less hydrophilic polymers show comparable or better antifouling performance than do more hydrophilic polymers. We investigate the mechanism of this anomalous behavior using molecular dynamics (MD) simulations of coarse-grained (CG) models of weakly and strongly hydrophilic polymers. The antifouling performance is evaluated from the potential of mean force of a model protein. The strongly hydrophilic polymer exhibits a better antifouling performance than the weakly hydrophilic polymer when the substrate of the polymer brush is repulsive. However, when the substrate is sufficiently attractive, the weakly hydrophilic polymer brush becomes more effective than the strongly hydrophilic brush in a certain range of grafting density. This is because the weakly hydrophilic polymer chains form a tightly packed layer that prevents the adsorbate molecule from contacting the substrate. We also perform all-atom (AA) MD simulations for several standard polymers to examine the correspondence with the CG polymer models. The weakly hydrophilic CG polymer is found to be similar to poly[N-(2-hydroxypropyl)methacrylamide] and poly(2-hydroxyethyl methacrylate), both of which have a hydroxyl group in a monomer unit. The strongly hydrophilic CG polymer resembles zwitterionic poly(carboxybetaine methacrylate). A discussion referring to the adsorption free energies of proteins on surfaces calculated in previous AA MD studies suggests that the higher antifouling performance of less hydrophilic polymer brushes can be realized for various combinations of protein and surface.

Thermal Behavior of Clinoptilolite

Understanding the thermal properties of zeolites is crucial for their industrial applications. This study explores the thermal stability and dehydration process of clinoptilolite using high-temperature X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). Clinoptilolite’s thermal decomposition was monitored from 25 °C to 1200 °C, with results analyzed based on its crystal structure. Principal components analysis (PCA) of the DRIFT spectra indicated progressive water removal and dehydration upon heating, leading to the formation of hydrogen bonds. Thermogravimetric analysis (TGA) revealed a two-step endothermic weight loss: initially, physically adsorbed water was lost up to 100 °C, followed by the removal of tightly bound water and hydroxyl groups until 800 °C. Clinoptilolite remained the dominant phase up to 800 °C, after which albite and cristobalite took over. Rietveld refinement showed that the sample initially contained 70% clinoptilolite, 24% albite, and 6% cristobalite. Above 800 °C, clinoptilolite disappeared, leaving 93% albite and 7% cristobalite. FT-IR spectra changes due to water loss were evident: drying of adsorbed water occurred up to 75 °C and minimal changes were observed from 75 °C to 135 °C, followed by further dehydration until 240 °C. Complete dehydration was confirmed by the disappearance of OH stretching vibration bands by 395 °C, consistent with TGA findings.

Amino‐functionalized nano‐hydroxyapatite boosts the grafting efficiency of poly (l‐lactic acid) to enhance interfacial bonding in composite bone scaffold

AbstractNano‐hydroxyapatite (nano‐HAP)/poly (l‐lactic acid) (PLLA) bone scaffold is expected to overcome the deficiencies and achieve the complementary advantages of individual constituents, but the weak interfacial bonding due to their thermodynamic incompatibility is detrimental to the mechanical properties. Herein, the PLLA chains were grafted onto nano‐HAP with 3‐aminopropyltriethoxysilane (KH550) as a coupling reagent to enhance the interfacial bonding with PLLA. Specifically, the silicon hydroxyl group produced by KH550 hydrolysis could form covalent bonding with the hydroxyl group of nano‐HAP, and the amino group of KH550 initiated the ring‐opening polymerization of l‐lactide monomers to graft PLLA chains onto nano‐HAP more effectively, leading to a higher grafting ratio of 16.7% compared with 7.2% in direct grafting without KH550 modification. Consequently, the tensile and compressive strength of the modified nano‐HAP/PLLA scaffold were improved by 40.8% and 59.5% enhancement due to the enhanced interfacial bonding in the composite scaffold, respectively, compared to the original nano‐HAP/PLLA scaffold. Additionally, the bone scaffold was conducive to cell adhesion and proliferation, making it an ideal candidate for bone defect repair.Highlights Amino‐functionalized nano‐HAP boosted the grafting efficiency of PLLA chains. Interfacial bonding between nano‐HAP and matrix was enhanced. Bone scaffold showed better mechanical properties and benign cytocompatibility.

Removal of phenazopyridine from water, synthetic urine, and real sample by adsorption using graphene oxide: A DFT theoretical/experimental approach

Herein, graphene oxide was used as the highly efficient phenazopyridine adsorbent from aqueous medium, synthetic, and human urine. The nanoadsorbent was characterized by different instrumental techniques. The adsorption capacity (1253.17 mg g−1) was reached at pH 5.0, using an adsorbent dosage of 0.125 g L−1 at 298 K. The Sips and Langmuir described the equilibrium data well. At the same time, the pseudo-second order was more suitable for fitting the kinetic data. Thermodynamic parameters revealed the exothermic nature of adsorption with an increase in randomness at the solid-liquid interface. The magnitude of the enthalpy variation value indicates that the process involves the physisorption phenomenon. At the same time, ab initio molecular dynamics data corroborated with the thermodynamic results, indicating that adsorbent and adsorbate establish hydrogen bonds through the amine groups (adsorbate) and hydroxyl groups on the adsorbent surface (weak interactions). Electrostatic interactions are also involved. Additionally, the adsorption assays conducted in simulated medium and human urine showed the excellent performance of adsorbent material to remove the drug in real concentrations excreted by the kidneys (removal values higher than 60%).

Sugar derived hydrochar catalysts for enhanced biodiesel production via esterification

Sugars and sugar alcohols are renewable raw materials which can be used for char production. Their acid-catalyzed hydro-carbonization results in the formation of carbon materials with acidic functional groups on the surface, which makes them suitable to be used as heterogeneous catalysts in esterification reactions. Hydrochars materials were prepared by low-temperature slow carbonization of glycerol, xylitol, sucrose, and glucose in the presence of different amounts of H2SO4 (mass ratios from 1 to 4). The hydrochars were extensively characterized and tested in the methanolysis reaction of oleic acid. All the carbon materials were amorphous with features of polyaromatic sheets with hydroxyl (–OH), carboxylic acid (–COOH), and sulfonic (−SO3H) functional groups. The effect of the oleic acid water content on catalytic performance was studied, showing a strong inhibition effect due to the hygroscopic character of catalysts induced by sulfonic groups and other surface groups with oxygen. Under the conditions evaluated (5 % wt. of catalyst, methanol/oleic acid = 9 M ratio, methanol reflux temperature) the sucrose-derived catalyst prepared with the highest H2SO4 content showed the best performance, leading to methyl oleate yield > 90 % after 2 h of reaction, which is only achieved by the majority of analogous catalysts reported in the literature after 4 to 8 h of reaction. The data showed that there is a correlation between the methyl ester yield and the graphitization of the catalyst, as this makes the catalyst more hydrophobic, which is an advantage in esterification catalysts.