Flexible Aliphatic Chains Research Articles

Tough epoxy resin systems for cryogenic applications

This work presents the development of new epoxy systems that combine high fracture toughness at cryogenic temperatures (▪) with a slow curing reaction (long pot life) and a glass transition temperature between ▪ and ▪, ensuring good mechanical performance at room temperature. This was achieved by incorporating varying amounts and types of short-chain alkylamines into epoxy networks based on bisphenol A diglycidyl ether (DGEBA) crosslinked with metaphenylene diamine (MPD). This modification enhanced the cryogenic fracture toughness of the base system, DGEBA crosslinked with MPD, from 2 to ▪. It has been suggested that the significantly improved cryogenic fracture toughness in systems with flexible aliphatic chain extenders might result from nano- or micro-phase separation, but X-ray scattering and dynamic mechanical spectroscopy did not provide conclusive evidence for this hypothesis.The required slow curing reaction was achieved by using a sterically hindered alkylamine (2-heptylamine) as chain extender, which increased the pot life more than twofold, resulting in resin formulations that combine a high cryogenic fracture toughness, a low viscosity and a long processing window at room temperature.

Green bio-derived epoxidized linseed-oil plasticizer improves the toughness, strength, and dimensional stability of furfuryl alcohol-modified wood

Furfuryl alcohol (FA) modification represents a sustainable approach to wood modification; however, it significantly reduces the toughness of the wood, limiting its practical applications. This study introduced epoxidized linseed oil (ELO) as an environmentally friendly and bio-derived plasticizer to enhance the toughness and mechanical properties of FA-modified wood. Microstructural analyses confirmed the integration of FA and ELO into the cellular structure of the wood. The chemical interactions between the epoxy groups of ELO and hydroxyl groups of FA were characterized using Fourier-transform infrared spectroscopy and nuclear magnetic resonance spectroscopy, illustrating that a ring-opening reaction occurred that grafted the long flexible aliphatic chains of ELO onto the FA chains, thereby enhancing the chain mobility and flexibility. This interaction significantly decreased the crosslinking density, thereby achieving toughening. FA–ELO modification resulted in significantly enhanced dimensional stability and mechanical properties. Specifically, the anti-swelling efficiency exceeded 80 %, while the modulus of elasticity, modulus of rupture, and along-grain compressive strength increased by up to 35.0 %, 36.8 %, and 45.7 %, respectively. Additionally, significant enhancements in the elongation at break and impact strength were achieved, at 369.1 % and 72.4 %, respectively. The loss factor also increased. The optimal ELO content was 20 wt%. This study effectively demonstrated how ELO mitigates the brittleness of FA-modified wood and supports its application in high-value fields such as construction.

A novel salt-swelling nanofiltration membranes for drinking water purification: High mineral ions passage and efficient organic removal

BackgroundMunicipal drinking water treatment demands nanofiltration (NF) membranes with high removal efficiency for organics, high passage for mineral ions, and low operating pressure. The development of innovative and loose NF membranes is imperative. MethodsA loose-network-structured NF membrane (L-NF) was synthesized through interfacial polymerization (IP) on a PES substrate by utilizing lysine (with a flexible aliphatic chain) as standalone aqueous phase monomers. The separation performance for typical organics and mineral ions in water, as well as the permeability of the membrane were investigated. Significant findingsThe lysine-based NF membranes exhibit a reversible and appropriate salt-induced swelling effect. The increased salt concentration leads to a significant enhancement of both permeate flux and salt passage, while maintaining unaffected removal efficiency for organics. The optimized membrane (L-NF3), synthesized with a 1 % (w/v) concentration of lysine, demonstrated remarkable retention (>98 %) for organics (humic acid and sodium alginate), while concurrently displaying low retention (5.22 %-16.40 %) for mineral ions (Mg2+ / Ca2+). Furthermore, the salts in the feed led to a substantial improvement in permeate flux (239.61 %-385.70 %) compared to salt-free feed. The Lys-TFC membrane showcased outstanding performance of separation, permeability, and operational stability, underscoring its significant potential in municipal drinking water purification.

Designing Optical Anisotropy: Silver-Aminoalkylpyridine Nitrate Complexes with Tunable Structures.

To introduce a design strategy for improving optical properties, two silver-amino alkylpyridine nitrate complexes, AgC6H8N3O3 and Ag2C14H20N6O6, were successfully synthesized using a recrystallization method. By employing polarizable π-conjugated [NO3-] ions, two types of pyridine ligands, and silver cations with a high affinity for pyridine, we obtained a one-dimensional chain structure with 4-aminomethylpyridine (AgC6H8N3O3) and a zero-dimensional molecular compound by introducing a relatively flexible aliphatic chain with 4-(2-aminoethyl)pyridine (Ag2C14H20N6O6). The compounds crystallize in the triclinic crystal system with the centrosymmetric P-1 space group, exhibiting a change in orientation between the π-conjugated system and the silver ion. Despite similar optical band gaps (3.69 eV for AgC6H8N3O3 and 3.73 eV for Ag2C14H20N6O6), AgC6H8N3O3 shows higher absorption in the 350-600 nm range. Electronic structure calculations support the ultraviolet absorption findings, suggesting that charge transfer with π-conjugated systems influences birefringence. Ag2C14H20N6O6 exhibits experimental birefringence (0.261@546.1 nm) surpassing that of AgC6H8N3O3 (0.212@546.1 nm), placing it among the highest recorded values within metal-pyridine incorporating nitrate complexes. The nonconventional orientation of π-conjugated [NO3-] ions contributes to this phenomenon, enhancing the action of free π-conjugated orbitals. This design strategy for micromodulating the alignment of the π-conjugated system promises to be an effective approach for enhancing optical properties, such as birefringence.

A novel multifunctional phosphorous and nitrogenous reactive flame retardant toward epoxy resins by one‐pot method

AbstractEpoxy resin (EP) has attracted considerable attention in packaging, electronic devices, aerospace, and coatings fields owing to its remarkable chemical and physical performance. However, the inherent flammable performance and unfavorable brittle nature seriously restricted its application in sophisticated industry. Herein, an efficient reactive 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO)‐based flame retardant (DB‐DAD) was prepared by a facile “one‐pot” method. Due to their synergistic gas‐phase and solid‐phase flame‐retardant effects, DB‐DAD modified EP composites (EP/DB‐DAD composite) easily achieved UL‐94 V‐0 ratings, and an EP/DB‐DAD composite with a 0.32 wt% phosphorus content had an excellent (30.2%) limiting oxygen index. In addition, the amounts of heat and smoke decreased by 28.1% and 24.8%, respectively. Due to the introduction of long and flexible aliphatic chains, the EP/DB‐DAD composites exhibited satisfactory mechanical properties, the flexural and tensile toughness of EP/6% DB‐DAD were 82.5% and 62.2% higher than those of neat EP, respectively. Furthermore, EP/DB‐DAD composite showed good transparency (>85%) and favorable UV shielding performance. The EP/DB‐DAD composite with good comprehensive performance is extremely promising to accelerate EP application in high‐tech industries.

A new bio-based thermosetting with amorphous state, sub-zero softening point and high curing efficiency

In this work, bio-based tyramine was exploited to prepare a novel phthalonitrile monomer (L-CN) with amorphous characteristics, sub-zero softening point (−16 °C) and high curing reactivity. Compared with the control compounds, it showed that amorphous structure and low softening point of L-CN cannot be simply attributed to the introduction of flexible aliphatic chain. It is proposed that the inhibited crystallization of the PN monomer can be understood by the multi-competitive supramolecular interactions as suggested by 1HNMR, in-situ FTIR and molecular dynamics simulation. Furthermore, the cured resin exhibited excellent thermal and thermomechanical properties at relatively low post-cured temperature due to the strong nucleophilicity and mobility of the aliphatic amine.

Structural basis for the substrate specificity switching of lysoplasmalogen-specific phospholipase D from Thermocrispum sp. RD004668.

Lysoplasmalogen-specific phospholipase D (LyPls-PLD) hydrolyzes choline lysoplasmalogen to choline and 1-(1-alkenyl)-sn-glycero-3-phosphate. Mutation of F211 to leucine altered its substrate specificity from lysoplasmalogen to 1-O-hexadecyl-2-hydroxy-sn-glycero-3-phosphocholine (lysoPAF). Enzymes specific to lysoPAF have good potential for clinical application, and understanding the mechanism of their activity is important. The crystal structure of LyPls-PLD exhibited a TIM barrel fold assigned to glycerophosphocholine phosphodiesterase, a member of glycerophosphodiester phosphodiesterase. LyPls-PLD possesses a hydrophobic cleft for the binding of the aliphatic chain of the substrate. In the structure of the F211L mutant, Met232 and Tyr258 form a "small lid" structure that stabilizes the binding of the aliphatic chain of the substrate. In contrast, F211 may inhibit small lid formation in the wild-type structure. LysoPAF possesses a flexible aliphatic chain; therefore, a small lid is effective for stabilizing the substrate during catalytic reactions.

Graphene nanosheets dispersed hydrophobic and flexible aliphatic chain containing multifunctional poly(benzoxazines) nanocomposites for medium temperature proton exchange membrane fuel cell applications

Graphene nanosheets dispersed hydrophobic and flexible aliphatic chain containing multifunctional poly(benzoxazines) nanocomposites for medium temperature proton exchange membrane fuel cell applications

Crystallizable Aliphatic Chains Enhanced Covalent Adaptable Networks: Fast Reprocessing and Improved Performance.

Covalent adaptable networks (CANs) exhibit recyclability such as reprocessing, but it's a challenge to address the contradiction between reprocessing rate and performance. Here, pendent aliphatic chain anhydride monoesters are innovatively introduced into epoxy CANs based on transesterification, which efficiently accelerates the reprocessing without sacrificing thermal and mechanical properties. The transesterification rate is raised on account of the flexible aliphatic chain-promoted segment movement and dynamic transfer auto-catalysis. When the carbon number reflecting the length of the pendent chain is 12, the epoxy CAN exhibits the fastest stress relaxation or reprocessing. Computation via molecular dynamics simulation demonstrates that the increased segmental mobility from the pendent aliphatic chains contributes to enhanced reprocessability. Interestingly, the crystallization of the pendent aliphatic chains maintains or even improves the thermal and mechanical properties. Thus, introducing a flexible and crystallizable aliphatic side chain is an innovative and efficient approach to accelerate dynamic reactions and network arrangement while improving performance.

Molecular dynamics simulations reveal the selectivity mechanism of structurally similar agonists to TLR7 and TLR8.

TLR7 and TLR8 are key members of the Toll-like receptor family, playing crucial roles in the signaling pathways of innate immunity, and thus become attractive therapeutic targets of many diseases including infections and cancer. Although TLR7 and TLR8 show a high degree of sequence homology, their biological response to small molecule binding is very different. Aiming to understand the mechanism of selective profiles of small molecule modulators against TLR7 and TLR8, we carried out molecular dynamic simulations on three imidazoquinoline derivatives bound to the receptors separately. They are Resiquimod (R), Hybrid-2 (H), and Gardiquimod (G), selective agonists of TLR7 and TLR8. Our MD trajectories indicated that in the complex of TLR7-R and TLR7-G, the two chains forming the TLR7 dimer tended to remain "open" conformation, while the rest systems maintained in the closed format. The agonists R, H, and G developed conformational deviation mainly on the aliphatic tail. Furthermore, we attempted to quantify the selectivity between TLR7 and TLR8 by binding free energies via MM-GBSA method. It showed that the three selected modulators were more favorable for TLR7 than TLR8, and the ranking from the strongest to the weakest was H, R and G, aligning well with experimental data. In the TLR7, the flexible and hydrophobic aliphatic side chain of H has stronger van der Waals interactions with V381 and F351 but only pick up interaction with one amino acid residue i.e. Y353 of TLR8. Unsurprisingly, the positively charged side chain of G has less favorable interaction with I585 of TLR7 and V573 of TLR8 explaining G is weak agonist of both TLR7 and TLR8. All three imidazoquinoline derivatives can form stable hydrogen bonds with D555 of TLR7 and the corresponding D543 of TLR8. In brief, the set of total 400ns MD studies sheds light on the potential selectivity mechanisms of agonists towards TLR7 and TLR8, indicating the van der Waals interaction as the driving force for the agonists binding, thus provides us insights for designing more potent and selective modulators to cooperate with the hydrophobic nature of the binding pocket.

Programmed Macromolecular Assembly by Dipole-Dipole Interactions with Aggregation-Induced Enhanced Emission in Aqueous Medium.

Self-assembling polymers by bioinspired directional supramolecular interactions currently hold great scientific and technological interests. Herein, we report an unorthodox strategy based on a dipole-dipole interaction-mediated extended antiparallel dipolar assembly of a model merocyanine (MC) dye for maneuvering the self-assembly of a highly water-soluble MC-functionalized block copolymer (P2). Unlike traditional amphiphilic block copolymers featuring distinct hydrophobic segments (flexible aliphatic hydrocarbon chains or rigid nonpolar aromatic scaffolds), P2 comprises polyethylene glycol monomethyl ether (PEG) as a hydrophilic block and an unconventional structure-directing acrylate block functionalized with polar MC-dyes in the side chains of every repeat unit. In the absence of any additional hydrophobic assistance, P2 spontaneously self-assembles in water through the continuous opposite alignment of its pendant MCs by multiple dipole-dipole interactions to cancel out their ground state dipole moments, which initially generates an H-aggregated species with ill-defined morphology (Aggregate 1). Upon thermal annealing, Aggregate 1 reorganizes into higher-order core-shell nanodisc-like structures (Aggregate 2) driven by the orthogonal π-stacking interactions of the rigid aromatic framework derived from the extended cofacial MC-stacks. The aromatic interiors of the nanodiscs gain colloidal stability from the externally decorated hydrophilic PEG chains. While the initially formed Aggregate 1, predominantly by dipole-dipole interactions, showed remarkable thermal stability due to the cooperative effect of the polymer chain, the hierarchical assembly guided by relatively weaker dispersion forces of the MC-stacked π-surfaces could be tailored by dilution or thermal treatment. Such organized packing of pendant MCs by the dual effect of dipole-dipole interactions and π-stacking conferred several exciting properties to the P2 assembly in water. Long-range ordered antiparallel stacking of the pendant MCs rendered outstanding aggregation-induced enhanced emission (AIEE) properties to the resultant nanostructures in water with increased fluorescence lifetime, quantum yield, and Stokes shift compared to nonaggregating P2 in CHCl3. The remarkable thermal and kinetic stability of the nanodiscs, their guest loading ability, and very low critical aggregation concentration (CAC) were demonstrated by Förster resonance energy transfer (FRET) studies with an encapsulated donor-acceptor dye pair.

A novel intrinsic semi-aromatic polyamide dielectric toward excellent thermal stability, mechanical robustness and dielectric performance

The development of aliphatic polyamide as dielectric polymer is limited due to relatively high dielectric loss, low breakdown strength and low servicing temperature. Different from the traditional ways for enhancing the dielectric properties of aliphatic polyamides by compositing with inorganic materials, here an alternative strategy is reported via random copolymerizing aliphatic polyamide with semi aromatic polyamides as functional segments. The designed co-polyamide shows decreased dielectric loss of 0.04 and enhanced breakdown strength of 319 MV/m with a low content of semi aromatic polyamides. Moreover, taking advantage of the inherent rigid benzene ring and flexible aliphatic chain, high glass transition temperature and great toughness are achieved simultaneously in the prepared semi aromatic polyamides. The introduction of aromatic segments has also improved dielectric and mechanical properties of co-polyamide at elevated temperature (150 °C), which is desirable and crucial for polymer dielectrics. The strategy provides new possibilities for the development of high-performance intrinsic polymer dielectrics.

Tuning the length of aliphatic chain segments in aromatic poly(arylene ether sulfone) to tailor the micro-structure of anion-exchange membrane for improved proton blocking performance

Proton blocking anion exchange membrane (AEMs) can be used to treat various of acidic wastewater (i.e., enrich the recovered acid from acidic wastewater). In this work, four AEMs based on aliphatic chain segment imbedding poly(arylene ether sulfone)s bearing salt-terminated side-chains have been prepared for acid enrichment by electrodialysis (ED). In particular, the length of flexible aliphatic chain segments (methylenes of –(CH2)3–), –(CH2)6–, –(CH2)9–, and –(CH2)12–) in aromatic poly(arylene ether sulfone) was tuned to tailor the micro-structure. Our investigation demonstrates that the AEM with aliphatic chain segments of –(CH2)12– shows the strongest surface hydrophobicity (water contact angle: 107°) and has the smallest ion clusters (0.75 nm, relative to the other three AEMs with 0.78 nm, 0.80 nm, and 0.81 nm). In ED process, at the current densities of 10 mA cm−2, the maximum concentration of H+ enriched by the AEM is 2.06 M (initial concentration: 1.0 M). The investigations demonstrate that the optimized AEM with stronger hydrophobicity and smaller ion clusters shows the superior capacity of acid concentration relative to commercial AEM (AMX, Astom Japan). This work should be certain guiding significance for designing advanced proton blocking AEMs.

Ag immobilized lignin-based PU coating: A promising candidate to promote the mechanical properties, thermal stability, and antibacterial property of paper packaging

A lignin-based PU coating was prepared for paper-based green packaging. Two representative diisocyanate were used to prepare the coatings. Due to the rigid aromatic, the physical properties of the TDI system reached the maximum below the lignin content of 40%. The HDI that contains flexible aliphatic chains alleviated the brittleness of coating, and it showed physical advantages when the lignin content was more than 50%. Owing to the high lignin content, the coating presented enhanced thermal stability. After coated with the lignin-based PU coatings, the dry tensile strength of coated paper was improved by 126%. Amazingly, the wet strength was increased from 0.31 to 12.6 MPa with an improvement nearly 40 times. Based on the coordination of lignin, Ag+ was introduced into the PU matrix, which imparted the coating with excellent antibacterial ability. The colony forming units of E. coli and S. aureus were both less than 1. However, no inhibition halo was observed, which indicated that the Ag was firmly anchored on the coating and the antibacterial ability is only available when the bacterial contact the coating surface. The lignin-based PU coating with favorable sustainability and properties shows great potential in paper-based green packaging fields.

Formation of highly crosslinked polymer films in the presence of bio-based epoxy by photoinitiated cationic polymerization

Oleic acid was used as bio-based starting material for manufacturing of bis-(9,10-epoxystearic acid) 1,2-ethanediyl ester (EEDE). In contrast to epoxidized triglycerides, which contain also saturated structures, EEDE comprises exactly two epoxy groups that is advantageous for comparison with commercial diepoxides such as 1,4-butanediol diglycidylether (BDDE), 3,4-epoxycyclohexylmethyl-3′,4′-epoxycyclohexane carboxylate (EEC), and diglycidylether of bisphenol-A (DGEBA). Although 9,10-epoxystearic acid methyl ester (EME) and EEDE using bis-(t-butyl)-iodonium-tetrakis(perfluoro-t-butoxy)aluminate and isopropylthioxanthone as photoinitiator system are less reactive compared to the commercial diglycidylethers BDDE and DGEBA, the crosslinked films made from EEDE alone or a stoichiometric EEDE-DGEBA mixture showed higher hydrophobicity compared to crosslinked films derived from the commercial monomers as shown by both contact angle measurements and surface free energy calculation. Furthermore, DMA analysis resulted in detection of a secondary relaxation (β relaxation) in addition to the glass transition in case of poly-DGEBA and networks made from EEDE DGEBA mixtures using DGEBA excess. Although the glass transition temperature determined by both DSC and DMA decreases for the networks containing EEDE segments in comparison with pure DGEBA networks, the crosslink density is nearly not affected by the EEDE segments. This may be attributed to the structure of EEDE containing exactly two epoxy groups that is the case for DGEBA as well. The more flexible aliphatic chain causes the lower glass transition temperature. In addition, crosslink density and Mc value of poly-EEDE-DGEBA made from a 1:5 M ratio of EEDE: DGEBA by photoinitiated cationic polymerization show a nearly ideal crosslinked polymer network structure. The crosslinked poly-EEDE-DGEBA films may be interesting for application in coatings because of their high crosslink density.

Regioselective C-H arylation of imidazoles employing macrocyclic palladium(II) complex of organoselenium ligand

In this report we have presented synthesis of a new air stable bidentate selenium ligand (L1) by the reaction of 1,8-bis(2-(chloromethyl)phenoxy)octane with sodium salt of diphenyl diselenide. The reaction of bidentate selenium ligand (L1) with Pd(CH3CN)2Cl2 in acetonitrile under reflux conditions resulted nineteen membered ring macrocyclic palladium(II) complex. The structure of ligand precursors, ligand, and macrocyclic palladium(II) complex were authenticated by using 1H, 13C{1H} NMR spectroscopy and elemental analysis. The repeated attempts to obtain single crystals of macrocyclic palladium(II) complex were unsuccessful probably due to long flexible aliphatic chain in the molecule. The air and moisture stable, thermally robust macrocyclic palladium(II) complex was employed as catalyst to catalyze the regioselective arylation reaction of imidazole derivatives. The reaction works efficiently without any need of inert atmosphere. The current protocol works under mild reaction conditions with exclusive C-5 regioselectivity. Excellent yields (~73–95%) were obtained by using only 1.5 mol% of C1, with wide range of derivatives and large functional group tolerance. Homogeneous nature of catalysis process was confirmed with the help of mercury and triphenylphosphine poisoning tests. Further, the catalyst can be reused with significant loss (22%) in the efficiency.

Comparison of ultrasonic-treated rice husk carbon with the conventional carbon black towards improved mechanical properties of their EPDM composites

Because of depletion of fossil fuel from the earth curst and increase of environmental concerns, in search of an efficient alternative to the traditional carbon black (CB), a biochar known as rice husk carbon (RHC) has been examined here as a filler material to develop the EPDM composite. In this regard, the ball milled RHC was further treated with ultrasonic wave and used with or without its surface treatment by the silane coupling agent [i.e., 3-mercaptopropyl triethoxysilane (3-MPTMS)]. Among the RHC, ultrasonic treated RHC (UHC) and silane treated UHC (USHC), the EPDM composite of USHC showed nearly similar tensile strength to that of the CB (e.g., CB: 33.88 kgf/cm2, USHC: 31.38 kgf/cm2 at 20 wt% filler loading) with an enhanced elongation at break (e.g., CB: 206%, USHC: 342% at 20 wt% filler loading) and surprisingly much less compression set value (CB: 40.87%, USHC: 18.95% even after 40 wt% of filler loading). Compared to RHC, the UHC also showed its better performance next to the USHC. In addition to presence of both the carbon and silica in RHC and additional silica within the flexible aliphatic chain in USHC, the disintegration of RHC by ultrasonic treatment towards its narrow particle distribution, smaller particle size, and increased surface area is considered very much effective to develop the corresponding high performance EPDM composites. Thus, the use of waste material, i.e., rice husk through the ultrasonication of RHC followed by its surface treatment can be used as a potential filler material to prepare the environment friendly and cost effective high performing composites to be used in different efficient end products, and motivated further for industrial upscaling.

AIE-active polyelectrolyte based photosensitizers: the effects of structure on antibiotic-resistant bacterial sensing and killing and pollutant decomposition.

A facile and effective multifunctional platform with high bacterial detection sensitivity, good antibacterial activity, and excellent dye decomposition efficiency holds great promise for wastewater treatment. To explore the design rationality and mechanism of material platforms with various integrated components into a single molecule for wastewater treatment applications, herein, four kinds of polyelectrolyte photosensitizers with aggregation-induced emission (AIE) fluorescent units are synthesized and systematically studied to investigate the structure-property relationship that influences the level of conjugation and the hydrophobicity-hydrophilicity balance. By improving the strength of the conjugation, the new AIE photosensitizers DBPVEs (including DBPVE-4 and DBPVE-6) generate a reactive oxygen species (ROS), and a decomposition efficiency of around 55% is obtained for dyes when they are exposed to DBPVEs under white light irradiation, which is higher than those of DBPEs (including DBPE-4 and DBPE-6). More importantly, owing to the longer and more flexible aliphatic chains of DBPVE-6 that facilitate efficient intercalation into cell membranes, the staining ability of DBPVE-6 for methicillin-resistant S. epidermidis (MRSE) is greatly enhanced as compared to that of DBPVE-4. It should be noted that the antibacterial experiment indicates that DBPVE-6 displays potent toxicity to MRSE with 99.9% killing efficiency under white light irradiation. This work provides essential theoretical and experimental guidance on the designing of new photosensitizers for wastewater treatment.

Flexible Aliphatic-Aromatic Polyamide Thin Film Composite Membrane for Highly Efficient Organic Solvent Nanofiltration.

Membranes with strong solvent resistance and efficient molecular separation are desirable in industries. Especially the fractionation of organic molecules in harsh organic solvents still remains a challenge in the pharmaceutical industry. Here, we report a flexible aliphatic-aromatic polyamide thin-film composite (TFC) membrane with high stability, permeability, and precise selectivity in mild solvents as well as in polar aprotic solvents. This composite organic solvent nanofiltration (OSN) membrane integrates a cross-linked sub-100 nm nanofilm and a nanofibrous sublayer. The flexible aliphatic chains in the polyamide network render the selective layer with a tunable free volume in different organic solvents. Consistent with the solvent swelling degrees, the membrane shows a cutoff in a sequence of dimethyl sulfoxide (DMSO, MWCO: 814 g mol-1) > N,N-dimethylformamide (DMF, MWCO: 648 g mol-1) > methanol (MWCO: 506 g mol-1, with DMF activation) > methanol (MWCO: 327 g mol-1). The membrane can precisely fractionate two molecules with difference in molar mass of <166 g mol-1 in a polar aprotic solvent, DMSO. Long-term filtration tests in DMF further demonstrate that the TFC membrane has an outstanding chemical stability and molecular selectivity in aggressive organic media. This work provides an efficient way to control OSN membrane separations by introducing flexible alkane chains into the rigid polymer structure followed by solvent activation. Additionally, the high permeance and excellent separation efficiency of the TFC membrane highlight its great potential for molecular separation in pharmaceutical and chemical industries.

Efficient and green approach for the esterification of lignin with oleic acid using surfactant-combined microreactors in water

A green, effective, and feasible reaction for esterification of lignin with oleic acid in water at room temperature was investigated. A surfactant-combined system (p-toluenesulfonic acid/4-dodecylbenzenesulfonic acid) was designed to simultaneously solubilize kraft lignin and disperse the oleic acid, producing microreactors for esterification. Esterification using a higher 4-dodecylbenzenesulfonic acid dosage at room temperature was found to be a good option, and an increasing oleic acid dosage had no effect on improving the degree of esterification. Structural characterization analyses confirmed the successful esterification of lignin with oleic acid, indicating the effectiveness and feasibility of esterification of macromolecules in water. Due to the introduction of a long flexible aliphatic chain, the lignin ester showed a noticeable decrease in glass transition temperature, an obvious increase in contact angle, and exhibited excellent thermoplasticity, processability, and hydrophobicity. Additionally, lignin-ester nanoparticles were prepared through the micellization of p-toluenesulfonic acid. Therefore, the method of esterification using surfactant-combined microreactors in water is promising for high value-added utilization of lignin.