Steric Hindrance Effect Research Articles

PDMS membrane incorporated by zeolites with tunable pore chemistry for dimethyl carbonate/methanol azeotropic mixture separation

The separation of organic-organic azeotropic mixtures is important in the petrochemical, agrochemical, and pharmaceutical industries, which is energy-intensive by using the current distillation technology. Pervaporation process is energy-efficient for azeotropic separation, while lacks of high-performing membrane materials. In this work, to realize efficient separation of dimethyl carbonate/methanol azeotropic mixtures, a benchmarked membrane, polydimethylsiloxane (PDMS), was incorporated by zeolites with tunable pore chemistry. Specifically, MFI-type zeolite was grafted by alkyl chains with different carbon numbers (C1, C4, C8), thereby providing tunable transport channels for organic molecules. Based on systematic characterizations (e.g., sorption and LF-NMR) and permeation test, we found that the organophilic alkyl chain can trap organic molecules into the zeolitic pores while may also hinder the organic diffusion through the zeolite due to the steric hindrance effect. The PDMS mixed-matrix membrane (MMM) with optimized C1-grafted MFI loading as high as 50 wt% exhibited separation factor of 3.6, and permeation flux of 11.5 kg m-2 h-1 for 30 wt% DMC-methanol azeotropic mixture at 40 °C. With slightly higher separation factor, the flux of PDMS MMM is 1.5-fold higher than that of the pure PDMS membrane. This work highlights the critical role of filler pore chemistry on the solution-diffusion transport and thus performance enhancement of MMM.

Monosaccharide coatings on nanoparticles affect protein corona formation but not the interaction with their binding receptor

Surface coatings with polyethylene glycol (PEG) polymers have often been employed to improve nanoparticles (NPs) biocompatibility and extend circulation time by reducing protein adsorption. PEGylated NPs benefit from steric hindrance and repulsion effects, which are influenced by PEG molecular weight, density, and chain conformation. However, repetitive exposure to PEG can trigger acute and chronic immunological responses as a result of the development of Immunoglobulin G anti-PEG antibodies. NPs functionalisation with glycans has become an emerging approach to increase their biocompatibility as these biomolecules are highly hydrophilic, biocompatible interact with biological receptors expressed in the body, and can be conjugated, controlling their orientation. In this study, we developed a series of gold NPs (AuNPs) coated with PEG linkers of different lengths and conjugated with mannose (Man) or sialic acid (Sia) glycans, and we carried out a detailed characterisation prior to and after exposure to biological fluids to study their behaviour and protein corona formation. Our findings show that the glycan-coated NPs exhibit stabilisation after protein interaction, with Man coatings showing the lowest protein affinity and that the glycans are biologically active and capable of binding to glycan receptors (such as Concanavalin A) despite the presence of a complex protein environment. Results indicate that glycan modification of PEGylated NPs reduces nonspecific interactions while preserving active targeting properties, underscoring their potential for therapeutic applications.

Sterically Induced Enhancement in the Electrochemical Stability of Salen-Type Cathode Materials.

This study investigates the electrochemical degradation mechanisms of nickel-salen (NiSalen) polymers, with a focus on improving the material's stability in supercapacitor applications. We analyzed the effects of steric hindrance near the nickel center by incorporating different bulky substituents into NiSalen complexes, aiming to mitigate water-induced degradation. Electrochemical performance was assessed using cyclic voltammetry, operando conductance, and impedance measurements, while X-ray photoelectron spectroscopy (XPS) provided insights into molecular degradation pathways. The results revealed that increased steric hindrance from methyl groups significantly reduced the degradation rate, particularly in water-containing electrolytes, by hindering water coordination to the Ni center. Among the studied polymers, the highly substituted poly[Ni(Saltmen)] exhibited superior stability with minimal capacity loss. Density functional theory (DFT) calculations further supported that steric protection around the Ni atom effectively lowers the probability of water coordination. These findings suggest that sterically enhanced NiSalen polymers may offer a promising path toward durable supercapacitor electrodes, highlighting the route of molecular engineering to enhance material stability.

Effect of Various Diamines on the Mechanical, Thermal, and High‐Frequency Dielectric Properties of Polyimide and Their Composites With Functionalized Hollow Silica Fiber

ABSTRACTIn this study, three different series of polyimides (PIs) and their composites fabricated using various chemical structure of diamines and functionalized hollow silica fiber (FHSF) were synthesized. The experimental results of three PIs indicate that the addition of fluorine atoms into the pending groups of PI can decrease the glass transition temperature (Tg) with increase in the chain flexibility and this can lower the dielectric constant of PI. The high‐frequency dielectric constants of the composite materials decrease with increase in the loadings of FHSF. These phenomena are possibly accredited to the steric hindrance effect caused by the presence of trifluoromethyl groups of PI polymer chain and FHSF, which can interrupt the PI chain packing and increase their free volumes, resulting in the decrease of Tg and the dielectric properties of PIs. The high‐frequency circuit transmission loss properties of fabricated composite materials measured using the Test Methods Manual IPC‐TM 650 2.5.5.14 are lower than those of pure polymer matrix, recommending that the prepared materials could be selected as interlayer dielectrics for nano‐level electronic.

Effects of polycarboxylate superplasticizers with different functional groups on the adsorption behavior and rheology of cement paste containing montmorillonite

The dispersing effectiveness of polycarboxylate superplasticizer (PCE) in cement paste is dramatically reduced as a result of the sorption of PCE by montmorillonite (MMT) clay. To improve the dispersing effectiveness of PCE in MMT-containing cement paste, three PCEswere synthesized by copolymerizing isopentenyl polyoxyethylene ether (TPEG) with trans-2-butenedioic acid (FA) (FA-TPEG), FA and methacryloxyethyltrimethyl ammonium chloride (FA-DMC-TPEG), FA and sodium p-styrene sulfonate (FA-SSS-TPEG), respectively. Their molecular structures were characterized by gel permeation chromatography, specific charge density , Fourier transform infrared spectrum, and 1H nuclear magnetic resonance spectroscopy. X-ray diffraction and adsorption analysis were used to reveal the interactions between PCEs and MMT, and their dispersing performance in cement-MMT paste was evaluated using mini-cone and rheology measurements.. Results indicate that the difference in flowability caused by PCEs is primarily attributed to their different affinity for MMT in cement paste. Among them,, FA-SSS-TPEG showed excellent flowability due to its high affinity for cement particles and strong steric hindrance effect.

Efficient room temperature afterglow in nitrogen doped carbon dots triggered by steric hindrance effect

Efficient room temperature afterglow in nitrogen doped carbon dots triggered by steric hindrance effect

Regioselective Late-stage Functionalization of Tetraphenylenes: Rapid Construction of Double Helical Architectures and Potential Hole Transport Materials

Herein we report a novel approach for diversification of tetraphenylene via regioselective late-stage iodination follow by atom(s) insertion to the resulted cyclic iodonium salts. Thus, steric hindrance effect of tert-butyl...

Polyhydroxy starch with abundant hydroxyls and a unique structure enables uniform Zn deposition.

Zinc metal is a promising anode material for zinc-ion batteries (ZIBs), but severe side reactions and dendrite formation hinder its commercialization. In this study, starch is introduced into the ZnSO4 electrolyte for stabilizing the Zn anode. With abundant hydroxyl groups, starch can reconstruct the H-bond system in the electrolyte, suppressing side reactions. Moreover, the unique ring and double-helix structures of starch show strong interactions with Zn2+ ions. The large molecule structure also exhibits a steric hindrance effect, regulating the diffusion and reduction of Zn2+. Additionally, starch molecules can adsorb onto the Zn anode, promoting the formation of a solid-electrolyte interphase (SEI) and resulting in uniform Zn deposition along the (002) plane. Consequently, this approach enhances the stability and reversibility of the Zn anode.

The steric hindrance effect of Co porphyrins promoting two-electron oxygen reduction reaction selectivity.

A new Co 5,10,15,20-tetrakis(2',6'-dipivaloyloxyphenyl)porphyrin (1) with eight ester groups in all ortho and ortho' positions of phenyl groups was designed, which displayed significantly improved 2e oxygen reduction reaction (ORR) selectivity compared with a 5,10,15,20-tetrakis(para-dipivaloyloxyphenyl) porphyrin (2) without large steric groups. This work is significant to reveal the steric hindrance effect of metal porphyrins on electrocatalytic ORR selectivity.

Impact of meta- and para-Direction External Side Chains in Y-Series Acceptors on the Molecular Packing and Charge Carrier Dynamics of Organic Photovoltaics.

The side-chain directions in nonfullerene acceptors (NFAs) strongly influence the intermolecular interactions in NFAs; however, the influence of these side chains on the morphologies and charge carrier dynamics of Y6-based acceptors remains underexplored. In this study, we synthesize four distinct Y6-based acceptors, i.e., meta-HOP-Y6-F (mF), meta-HOP-Y6-Cl (mCl), para-HOP-Y6-F (pF), and para-HOP-Y6-Cl (pCl), with outer side chains of alkoxy-2-ethylhexyl attached at the meta or para positions. Devices containing the meta-position acceptors blended with the polymer donor PM6 achieve power conversion efficiencies (PCEs) at least 1.27-fold higher than those of devices containing para-position acceptors. The enhanced performance can be attributed to the formation of donor-acceptor domains that are advantageous for charge carrier generation, transport, and collection. This is due to variations in phase aggregation that result from steric hindrance effects at the meta- and para-position acceptors. As a result, meta-position acceptors with lower steric hindrance improved π-π and lamellar stacking, whereas the para-position acceptors encountered excessive steric hindrance, reducing their photovoltaic efficiencies. Additionally, the meta-position acceptors demonstrate long charge carrier lifetimes, which suppress recombination in the charge transfer state and promote efficient charge separation. These results underline the critical role of side-chain direction in optimizing Y6-based acceptors for improving photovoltaic performance.

Diluting Ionic Liquids with Small Functional Molecules of Polypropylene Carbonate to Boost the Photovoltaic Performance of Perovskite Solar Cells.

It is necessary to overcome the relatively low conductivity of ionic liquids (ILs) caused by steric hindrance effects to improve their ability to passivate defects and inhibit ion migration to boost the photovoltaic performance of perovskite solar cells (PSCs). Herein, we designed and prepared a kind of low-concentration 1-butyl-3-methylimidazolium tetrafluoroborate (BMIMBF4) diluted with propylene carbonate (PC) via an ultrasonic technique (PC/IL). The decrease in the decomposition temperature related to the IL part and the increase in the sublimation temperature related to the PC part facilitated the use of PC/IL to effectively delay the crystallization process and passivate the defects in multiple ways to obtain high-quality perovskite films. Moreover, the increased conductivity of PC/IL and the more matched band alignment accelerated electron transport and collection. Finally, the MAPbI3- and CsMAFA-based PSCs achieved PCE values of 20.87% and 23.29%, respectively, and their stabilities were greatly improved. This work provides a promising approach to optimizing ILs to achieve multiple functions and boost the performance of PSCs.

Weakly Solvating Electrolytes for Safe and Fast-Charging Sodium Metal Batteries.

Electrolytes for high-performance sodium metal batteries (SMBs) are expected to have high electrode compatibility, low solvation energy, and nonflammability. However, conventional flammable carbonate ester electrolytes show high Na+ desolvation energy and poor compatibility with sodium metal anodes, leading to slow Faradaic reactions and significant degradation of SMBs. Herein, we report a weakly solvating electrolytes (WSEs) design developed by an ionized ether-induced solvent molecule polarization strategy. The steric hindrance and electron-withdrawing effect of the pyrrolidine cation weaken the solvation ability of the ionized ether and enable carbonate ester with low solvation energy through intermolecular polarization interactions. It enables WSEs with fast Na+ migration kinetics and electric-field-reinforced cationic electrode/electrolyte interface, thereby promoting the stability and reversibility of SMBs even under high-charge-rate conditions. The Na||Na3V2(PO4)3 battery with ionized ether-based WSEs exhibits a capacity retention of 83.5% with an average Coulombic efficiency (CE) of 99.69% after 500 cycles at 10C. Furthermore, the Na||Na2Fe2(SO4)3 cells maintained 92.8% capacity retention after 1000 cycles at 5C with an average CE of 99.77% at a cutoff voltage of 4.5 V. The ionized ether also eliminates the fire and safety risks associated with WSEs. This work offers valuable insights into the design of WSEs for safe and high-performance sodium metal batteries.

Molecular Design and Mechanism Study of Non-Activated Collectors for Sphalerite (ZnS) Based on Coordination Chemistry Theory and Quantum Chemical Simulation.

Sphalerite flotation is generally achieved by copper activation followed by xanthate collection. This study aims to propose a design idea to find novel collectors from the perspective of molecular design and prove the theoretical feasibility that the collector can effectively recover sphalerite without copper activation. To address this, 30 compounds containing different structures of sulfur atoms and different neighboring atoms were designed based on coordination chemistry. Twelve potential collectors were screened, and their properties and interactions with a hydrated sphalerite (110) surface were evaluated. Compound 27 (C2H4S22-) showed the greatest reactivity, suggesting that the double-coordination structure of two sulfhydryl groups is an effective molecular structure for direct sphalerite flotation. The DFTB+ and MD results demonstrate that 1,2-butanedithiol (C4H10S2), having a similar coordination structure to compound 27, has the potential to replace the traditional reagent scheme of sphalerite flotation. The strong reagent-surface interaction is attributed to the overlap of Zn 3d with S 3p orbitals, the most negative electrostatic potential, the relatively high EHOMO and low average local ionization energy, and the eliminated steric hindrance effect. It is expected that this study can provide a design idea for the targeted design and development of novel reagents for complex sulfide ore flotation.

Hydrogen/Electron Amphiphilic Bi-functional Water Molecular Inactivator-Assisted Interface Stabilization in Highly Reversible Zn Metal Batteries.

Continuous hydrogen-bond-network in aqueous electrolytes can lead to uncontrollable hydrogen transfer, and combining the interfacial parasitic electron consumption cause the side reaction in aqueous zinc metal batteries (AZMBs). Herein, hydrogen/electron amphiphilic bi-functional 1,5-Pentanediol (PD) molecule was introduced to stabilize the electrode/electrolyte interface. Stronger proton affinity of -OH in PD can break bulk-H2O hydrogen-bond-network to inhibit the activity of water, and electron affinity can enhance electron acceptation capability, which ensures that PD is preferentially bound to electrode material over H2O. Besides, the participation of PD in the Zn2+ solvation structure reduces water content at the solid-liquid interface and promotes uniform deposition process by optimizing Zn2+ de-solvation energy. Accordingly, dense and vertical zinc texture based on intrinsic steric hindrance effect of PD and formed SEI protective layer to induce stable Zinc anode-electrolyte interface. Moreover, an organic-inorganic shielding water layer was formed at the cathode side to suppress vanadium dissolution in vanadium Oxide. Resultly, Zn//Zn symmetric cell could cycle for more than 5600 hours at 1 mAh cm-2@1 mA cm-2 (more than 250 hours at 50 ℃). Besides, the VO2 and I2 cathode all achieved stable cycling performance and former pouch cell could reach average capacity of 0.13 Ah.

Targeted Synthesis of Interpenetration‐Free Mesoporous Aromatic Frameworks by Manipulating Catalysts as Templates

AbstractReticular chemistry allows the design and synthesis of mesoporous networks by extending the size of the building blocks. However, interpenetration of the nets easily happens against the designed mesoporous networks, thereby falling short of achieving the intended specific surface area and pore size. Controlling the framework interpenetration has always been a challenge in the synthesis section of reticular chemistry. In this work, based on our previously reported type of highly porous aromatic frameworks (named PAF‐1), we extended the tetrahedral building blocks to target an iso‐reticular mesoporous PAF‐333. A series of Ni(0) ligands with different sizes were employed to confirm that suitable‐sized catalyst ligands could successfully inhibit skeleton interpenetration in the coupling reaction through the steric hindrance effect. The obtained mesoporous PAF‐333 possessed a pore size of approximately 3.2 nm matching well with the value from the predicted non‐interpenetrated structure. PAF‐333 showed great high‐pressure hydrogen and methane storage potential with a 13.4 wt % H2 uptake at 77 K, 100 bar and a 0.537 g g−1 CH4 uptake at 298 K, 98 bar, ranking at the top of the reported porous adsorbents in the gas storage applications.

Materials Nanoarchitectonics for Advanced Devices.

Advances in nanotechnology have made it possible to observe and evaluate structures down to the atomic and molecular level. The next step in the development of functional materials is to apply the knowledge of nanotechnology to materials sciences. This is the role of nanoarchitectonics, which is a concept of post-nanotechnology. Nanoarchitectonics is defined as a methodology to create functional materials using nanounits such as atoms, molecules, and nanomaterials as building blocks. Nanoarchitectonics is very general and is not limited to materials or applications, and thus nanoarchitecture is applied in many fields. In particular, in the evolution from nanotechnology to nanoarchitecture, it is useful to consider the contribution of nanoarchitecture in device applications. There may be a solution to the widely recognized problem of integrating top-down and bottom-up approaches in the design of functional systems. With this in mind, this review discusses examples of nanoarchitectonics in developments of advanced devices. Some recent examples are introduced through broadly dividing them into organic molecular nanoarchitectonics and inorganic materials nanoarchitectonics. Examples of organic molecular nanoarchitecture include a variety of control structural elements, such as π-conjugated structures, chemical structures of complex ligands, steric hindrance effects, molecular stacking, isomerization and color changes due to external stimuli, selective control of redox reactions, and doping control of organic semiconductors by electron transfer reactions. Supramolecular chemical processes such as association and intercalation of organic molecules are also important in controlling device properties. The nanoarchitectonics of inorganic materials often allows for control of size, dimension, and shape, and their associated physical properties can also be controlled. In addition, there are specific groups of materials that are suitable for practical use, such as nanoparticles and graphene. Therefore, nanoarchitecture of inorganic materials also has a more practical aspect. Based on these aspects, this review finally considers the future of materials nanoarchitectonics for further advanced devices.

Cashew Phenol Modified Lignosulfonate Strategy for the Preparation of High-performance Dye Dispersants.

Lignin-based dye dispersants (LDD), as one of the most common lignin resource end-application product, is difficult to meet the rapidly developing needs of modern fiber dyeing due to their inherent structural defects. The efficient upgrading and modification of LDD is of great significance to the value-added application of lignin resources and the expansion of LDD sinking market. In this study, using industrial kraft lignin as raw material, cashew phenol was introduced into lignosulfonate in the form of CC bonds by ingenious utilizing the structural characteristics of lignin disordered condensation. Aromatic ring in cashew phenol could provide sufficient sulfonic acid group grafting sites, while C15 fatty chain could enhance steric hindrance effect. In the dispersibility test, the dispersing power showed 99.09%, and the low/high temperature dispersion (LTD/HTD) were 5s/4 and 6s/4, respectively, higher than the dispersibility level of LDD in the market, has great commercial value and industrial potential. Combined with FTIR, 1H NMR, GPC and ICP, the structural properties of lignin were analyzed in detail, and the degree of sulfonation-condensation was balanced-optimized. The CC bond condensation process between cashew phenol and lignin was revealed, and the mechanism of action on dye particles was elucidated.

Effects of interaction between wheat bran dietary fiber and gluten protein on gluten protein aggregation behavior.

Effects of wheat bran dietary fiber (WBDF) as a nutritional additive on flour products quality mainly depends on the interaction between WBDF and gluten protein. In this study, the effects and mechanisms of WBDF with different particle sizes and additive amounts on gluten protein aggregation behavior were investigated. The results showed that the addition of WBDF led to a decrease in free sulfhydryl content, particle size, molecular weight and gluten macromer (GMP) content, an increase in zeta potential and SDS-extractable protein content, and a deterioration in the gluten network morphology compared to the control group, suggesting that the aggregation behavior of gluten protein was inhibited. When WBDF was added at 3% and 6%, dilution effect, mechanical shear, steric hindrance, and non-covalent binding were the main mechanisms leading to depolymerization. Further addition of WBDF (9%, 12%) inhibited the depolymerization of gluten protein due to competitive hydration and non-covalent binding. However, when WBDF was added at 15%, the dilution effect, mechanical shear and steric hindrance of WBDF (88μm<particle size<150μm) dominated, and their inhibitory of aggregation induced the formation of a loose gluten network structure. In contrast, the weaker mechanical shear and steric hindrance effects of WBDF (particle size<88μm) mitigated the degradation of gluten network structures by WBDF.

Folic acid-coupled phosphorylated Fe2+ chelating peptide: The properties of Fe2+ chelating capacity and mechanisms of anti-gastrointestinal enzyme degradation

The aims of this study were to investigate the effect of precise phosphorylation of Ser in GL-Hyp-GPSGEEGKR on its Fe2+ chelating capacity, and the effects and mechanisms of folic acid coupling to GL-Hyp-GPS(PO4)GEEGKR on its resistance against degradation by gastrointestinal enzymes. The results demonstrated that GL-Hyp-GPS(PO4)GEEGKR exhibited significantly enhanced Fe2+ chelating capability compared to GL-Hyp-GPSGEEGKR. This was attributed to the phosphorylation of Ser introducing more Fe2+ chelating sites. Furthermore, the results of UV-Vis, FTIR, and 1H NMR showed that folic acid has successfully coupled with GL-Hyp-GPS(PO4)GEEGKR to generate folic acid-GL-Hyp-GPS(PO4)GEEGKR. Folic acid-GL-Hyp-GPS(PO4)GEEGKR demonstrated superior resistance against degradation by gastrointestinal enzymes. This may be attributed to the coupling of folic acid altering the original zeta potential of the peptide and the steric hindrance effect of folic acid hindering the interaction between enzymes and peptide. These findings can provide valuable insights for the production of high Fe2+ chelating peptides that resist gastrointestinal enzyme degradation.

CO2 capture and viscosity of metal chelate-based ionic liquids: Influence of the structure and substitution of the azole-based anion

In this work, the effect of the structure and substitution of azole-based anion on the CO2 capture and viscosity (η) of metal chelate-based dual functional ionic liquids (DFILs) with [K(DGA)2]+ cation was investigated. The CO2 absorption capacity of DFILs at 0.1 MPa and 333.2 K shows that methyl and nitro groups on the azole-based anion, such as pyrazolide ([Pyr]−) and imidazolide ([Im]−), attenuate their reactivity with CO2 through the steric hindrance and electron-withdrawing effects, respectively. Furthermore, the CO2 absorption capacity of [K(DGA)2][Pyr] is larger than that of [K(DGA)2][Im], which is due to the interaction of the two adjacent N atoms in the [Pyr]− anion with CO2, as confirmed by DFT calculations. The CO2 absorption mechanism shows that both [Pyr]− anion and [K(DGA)2]+ cation of [K(DGA)2][Pyr] can chemically interact with CO2, making its saturated uptake at 333.2 K as high as 1.47 mol CO2 per mole IL. Moreover, CO2 interacts preferentially with [Pyr]−, and the [K(DGA)2]+–CO2 interaction is enhanced when the CO2 uptake is greater than 0.5 mol CO2 per mole IL. η of pure [K(DGA)2][Pyr] is lower than that of pure [K(DGA)2][Im]. η of [K(DGA)2][Pyr] increases with the increase of CO2 absorption, and the rapid increase in η after CO2 uptake greater than 0.5 is attributed to the formation of [K(DGA)2]+–CO2 interactions.