Grafted Alkyl Chains Research Articles

Regulatory mechanism of grafted alkyl chain length of carbon quantum dots as additives on the tribological properties of lithium greases

Carbon quantum dots (CQDs) exhibit exceptional structural properties and minimal environmental impact, garnering significant interest in the field of lubrication. In this study, four types of modified CQDs with varying alkyl chain lengths were synthesized through hydrothermal methods and subsequently mixed with lithium grease (LG) to formulate mixed greases. The influence of the alkyl chain length on the CQDs used as additives in the mixed greases was investigated with a four-ball friction and wear tester, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). Specifically, compared to pure LG, the modified CQDs with the shortest alkyl chain length reduced the coefficient of friction (COF), the diameter of abrasive spots, and the depth of abrasive scars by 33.65%, 42.11%, and 51.87%, respectively. This improvement can be attributed to the ease of these shorter-chain CQDs entering the contact area and forming a stable film containing carbon, nitrogen, and oxygen elements through friction. The tribological properties of modified CQDs can be effectively controlled by adjusting the length of the carbon chain, providing a theoretical basis for the design of environmentally friendly and sustainable grease additives in engineering applications.

Fabrication of a modified bacterial cellulose with different alkyl chains and its prevention of abdominal adhesion

Abdominal hernia mesh is a common product which is used for prevention of abdominal adhesion and repairing abdominal wall defect. Currently, designing and preparing a novel bio-mesh material with prevention of adhesion, promoting repair and good biocompatibility simultaneously remain a great bottleneck. In this study, a novel siloxane-modified bacterial cellulose (BC) was designed and fabricated by chemical vapor deposition silylation, then the effects of different alkyl chains length of siloxane on surface properties and cell behaviors were explored. The effect of preventing of abdominal adhesion and repairing abdominal wall defect in rats with the siloxane-modified BC was evaluated. As the grafted alkyl chains become longer, the surface of the siloxane-modified BC can be transformed from super hydrophilic to hydrophobic. In vivo results showed that BC-C16 had good long-term anti-adhesion effect, good tissue adaptability and histocompatibility, which is expected to be used as a new anti-adhesion hernia repair material in clinic.

Enhanced adsorption of polystyrene nanoplastics by cetyltrimethylammonium bromide surface-modified magnetic rice straw biochar: Efficient performance and adsorption mechanisms

Nanoplastics, characterized by their small size, high diffusion, and stability, have attracted wide attention worldwide as a new potentially threatening pollutant. In this study, magnetic rice straw biochar modified with cetyltrimethylammonium bromide (CTAB) was prepared and utilized for the adsorption removal of polystyrene nanoparticles (PSNPs, <100 nm). The characteristics and adsorption performance of CTAB modified magnetic biochar (MBC-CTAB) were systematically investigated using characterization techniques and batch adsorption experiments. The grafting of alkyl chains onto the biochar surface through surfactant modification improved the surface activity and adsorption capacity of the magnetic biochar towards nanoplastics. Moreover, the application of an external magnetic field facilitated the rapid separation and recovery of MBC-CTAB. MBC-CTAB exhibited a removal efficiency of 99.56 % for 20 mg/L PSNPs, with a maximal adsorption capacity of 54.07 mg/g at 298 K. The presence of anions such as HPO42− and CO32− as well as dissolved organic compounds like humic acid creates significant competition between PSNPs, thereby inhibiting the adsorption capacity of MBC-CTAB towards PSNPs. The mechanism of MBC-CTAB for nanoplastics adsorption can be attributed to electrostatic interaction, hydrophobic interactions, pore filling, and surface complexation. This study demonstrates the feasibility of using surfactant-modified biochar for the adsorption of nanoplastics, providing a promising option for the development of new pollutant treatment technologies and the mitigation of the adverse impacts of nanoplastics on the environment and ecosystems.

Surface modification boosts dispersion stability of nanoparticles in dielectric fluids

Achieving stable dispersion of nanoparticles in dielectric fluids is a challenging task, as there are complex and diverse influencing factors, requiring molecular-level understanding of the nanoparticle aggregation. In this paper, we conducted long-time molecular simulations of dielectric nanofluids containing fifteen SiO2 nanoparticles, systematically varying the length of alky chains grafted onto their surface to explore their impact on the aggregation process. Our results reveal that appropriate surface modification can dramatically increase the dispersion stability of nanoparticles in dielectric fluids. SiO2 nanoparticles lacking alkyl chains exhibit a strong tendency to approach each other, and form aggregates in natural esters, because of the Coulombic energy from heteroatoms of SiO2 nanoparticles. Despite the differences in the length of grafted alkyl chains on the surface of SiO2 nanoparticles, all of them, regardless of their length, are capable of effectively shielding the Coulombic interactions and increasing the van der Waals interaction with natural esters, thereby reducing the aggregation tendency of nanoparticles. Furthermore, the smaller diffusion ability, caused by the steric hindrance effect, of surface-modified SiO2 nanoparticles also inhibits their collision and subsequent aggregation.

Synergistically enhancing hydrogen bonding, hydrophobic interaction and electrostatic association of collagen fiber to flavonoid aglycones for their effective separation by polyethyleneimine modification

Compared with flavonoid glycosides, flavonoid aglycones are difficult to be separated since they have less hydroxyls. Collagen fiber (CF), a natural polymer, was once used as packing material for separation of kaempferol and quercetin (the typical flavonoid aglycones) after crosslinking by glutaraldehyde mainly based on hydrogen bonding and hydrophobic interaction in column length-diameter ratio of 60:1. Hydrophobic modification by grafting alkyl chains was then employed to enhance the hydrophobic interaction between CF and flavonoid aglycones, which can improve the separation efficiency and decrease column length-diameter ratio to 19:1. In order to further improve the adsorption capacity and separation efficiency, the strategy of simultaneously grafting hydrophobic alkyl chains (–CH2–CH2–) and alkali groups (–NH2) was adopted in this work to enhance hydrophobic interaction, hydrogen bonding and electrostatic association to flavonoid aglycones at the same time through grafting polyethyleneimine (PEI). PEI modified CF (PEI-CF) maintained the fiber structure of CF, and had higher adsorption extent and rate to flavonoid aglycones through the enhanced synergetic effect of hydrophobic interaction, hydrogen bonding and electrostatic association. As a result, PEI-CF presented a satisfactory column separation efficiency for kaempferol and quercetin even the length-diameter ratio of column was decreased to 11:1, which was much better than previously developed glutaradehyde-crosslinked collagen fiber and isobutyl-grafted collagen fiber, as well as commonly used polyamide and Sephadex LH-20.Graphical abstract

Effectively recovering catechin compounds in the removal of caffeine from tea polyphenol extract by using hydrophobically modified collagen fiber

Previous research had proved that collagen fiber can be used as separation material for removing caffeine from tea polyphenol extract effectively. But the recovery rate of catechin compounds from collagen fiber column was quite low by using water and ethanol as eluent because of excessively strong hydrogen bond interaction between collagen fiber and polyphenols. To solve the problem, collagen fiber was hydrophobically modified in this work by using silane coupling agents with alkyl chains (butyl, octyl, dodecyl and octadecyl). FT-IR, DSC, SEM and EDS Mapping proved the successful grafting of alkyl chains on collagen fiber, leading to the significantly enhanced hydrophobicity of collagen fiber. Static adsorption showed that the adsorption capacity of EGCG decreased when the grafted alkyl chain length increased mainly relying on the weakened hydrogen bond interaction. Dynamic adsorption and elution behavior also indicated less retention capacity of EGCG on collagen fiber with higher hydrophobicity. In column separation of simulated tea polyphenol extract containing caffeine and catechin compounds, the collagen fiber grafted with octadecyls (CF(C18)) presented excellent separation efficiency for caffeine and catechin compounds, and simultaneously the catechin compounds were highly recovered. The recovery rates of EGC and EGCG were 2–7 times higher than those separated by pristine collagen fiber column and glutaradehyde crosslinked collagen fiber column developed in our previous work. In the reusing round of CF(C18) column, the chromatogram was almost the same as the first round, showing excellent reusability. In fact, the separation performance of CF(C18) to caffeine and catechin compounds was comprehensively superior to Sephadex LH-20, presenting great practical application potential in effectively removing caffeine from tea polyphenol extract and recovering catechin compounds.

Controllably Adjusting the Hydrophobicity of Collagen Fibers for Enhancing the Adsorption Rate, Retention Capacity, and Separation Performance of Flavonoid Aglycones.

Collagen fibers (CFs) were previously used as packing materials for the separation of flavonoids based on hydrogen bond and hydrophobic interactions. However, as for flavonoid aglycones, CFs presented unsatisfactory adsorption capacity and separation efficiency due to the fact that they include limited hydroxyls and phenyls. In order to improve the adsorption capacity and separation efficiency, the hydrophobic modification strategy was employed in this research to enhance the hydrophobic interaction of CF with flavonoid aglycones by using silane coupling agents with different alkyl chains (isobutyl, octyl, and dodecyl). FT-IR analysis, DSC, TG, SEM, EDS mapping, water contact angle, and absorption time of solvent proved the successful grafting of alkyl chains on the CF without disturbing its special fiber structure, leading to the significantly enhanced hydrophobicity of the CF. The dynamic adsorption and elution behavior of kaempferol and quercetin (the typical flavonoid aglycones) on the hydrophobic CF showed that the adsorption rate and retention rate were largely increased in comparison with the CF without modification. Molecular dynamic simulations indicated that the CF grafted with isobutyls could interact with flavonoid aglycones through the highest synergetic effect of hydrophobic and hydrogen bond interactions, which exhibited the strongest retention to flavonoid aglycones. On further increasing the alkyl length (octyl and dodecyl), the hydrophobic interaction was further enhanced, but the hydrogen bonds were significantly weakened by steric hindrance, which showed that the retention to flavonoid aglycones was appropriately increased but without causing peak tailing. In the column separation of kaempferol and quercetin, the CF with hydrophobic modification presented a greater separation efficiency, with the purity of kaempferol increased from 71.99 to 86.57-97.50% and the purity of quercetin increased from 82.69 to 88.07-99.37%, which was much better than that of polyamide and close to that of sephadex LH 20. Therefore, the hydrophobicity of the CF could be controllably adjusted to enhance the adsorption rate and retention capacity, specifically improving the separation efficiency of flavonoid aglycones.

Hydrophobically modified silica nanolaces-armored water-in-oil pickering emulsions with enhanced interfacial attachment energy

HypothesisAnisotropic particles with a high aspect ratio led to favorable interfacial adhesion, thus enabling Pickering emulsion stabilization. Herein, we hypothesized that pearl necklace-shaped colloid particles would play a key role in stabilizing water-in-silicone oil (W/S) emulsions by taking advantage of their enhanced interfacial attachment energy. ExperimentsWe fabricated hydrophobically modified silica nanolaces (SiNLs) by depositing silica onto bacterial cellulose nanofibril templates and subsequently grafting alkyl chains with tuned amounts and chain lengths onto the nanograins comprising the SiNLs. FindingsThe SiNLs, of which nanograin has the same dimension and surface chemistry as the silica nanospheres (SiNSs), showed more favorable wettability than SiNSs at the W/S interface, which was supported by the approximately 50 times higher attachment energy theoretically calculated using the hit-and-miss Monte Carlo method. The SiNLs with longer alkyl chains from C6 to C18 more effectively assembled at the W/S interface to produce a fibrillary interfacial membrane with a 10 times higher interfacial modulus, preventing water droplets from coalescing and improving the sedimentation stability and bulk viscoelasticity. These results demonstrate that the SiNLs acted as a promising colloidal surfactant for W/S Pickering emulsion stabilization, thereby allowing the exploration of diverse pharmaceutical and cosmetic formulations.

Covalent grafting of alkyl chains on laser-treated titanium surfaces through silanization and phosphonation reactions

This work evaluates the efficiency of silanization and phosphonation reactions for the grafting of alkyl chains on the surface of titanium treated by nanosecond laser. The light blue squama-like oxide layers with dominating anatase and rutile were obtained. The silanization using alkoxysilanes with C12 and C18 alkyl chains was attempted in tetrahydrofuran, in pure liquid phase and in vapor phase. The phosphonation with octylphosphonic acid was performed in boiling water solutions. The obtained surfaces were characterized by Raman and X-ray photoelectron spectrometry, scanning electron microscopy and energy dispersive X-ray spectroscopy. Their hydrophobicity was evaluated using static contact angle measurements.The modification in pure liquid silane and in vapor phase allowed obtaining high loadings (6 and 10 at.% Si respectively) of grafted groups and the formation of polycondensed silane layers. The silanization in tetrahydrofuran resulted in partial monolayer coverage. The phosphonation in boiling water solutions allowed obtaining significant P loading (up to 7 at.%) and full monolayer coverage. Both silanization and phosphonation increased the hydrophobicity of laser-treated surfaces. However, the modification with octylphosphonic acid in water solutions is more appropriate since milder conditions of chemical functionalization and lower concentrations of the modifier are necessary to obtain similar organic loading and hydrophobicity.

Covalent Grafting of Alkyl Chains on Laser-Treated Titanium Surfaces Through Silanization and Phosphonation Reactions

Covalent Grafting of Alkyl Chains on Laser-Treated Titanium Surfaces Through Silanization and Phosphonation Reactions

Free‐energy calculations of the host–guest association in grafted supramolecular assemblies

AbstractHerein, we investigate the impact of grafting macrocyclic hosts with hydrophobic cavities onto a gold surface on the association with a guest molecule of particular importance to applications for molecular machines. We establish that the increase of the grafted alkyl chain length and number of anchor points strengthens the binding of the guest with the β‐cyclodextrin host. This is the opposite effect with the p‐sulfonatocalix[4]arene host for which the grafting considerably reduces the strength of the host–guest association. The structural and thermodynamic characterizations, carried out with free energy simulations, are combined to rationalize the differences in the association process in both heterogeneous and homogeneous conditions.

Fabrication of Ionic Liquid-Based Pickering Emulsion and Its Enhancement for Tri-isobutene Formation in Isobutene Oligomerization

Nanoparticles resistant to strong acid were prepared by grafting alkyl chains (i.e., C1–, C8–, and C18−) and alkyl sulfonic acid groups onto silica. The composition, morphology, and contact angles ...

Modification of Kraft Lignin with Dodecyl Glycidyl Ether.

Kraft lignin (KL) is extensively produced in industry but is mainly burned as fuel. To broaden its use, KL was grafted with dodecyl glycidyl ether to alter its thermal properties. The reaction of KL with dodecyl glycidyl ether (DGE) was analyzed using nuclear magnetic resonance (NMR), Fourier infrared spectroscopy (FT‐IR) and elemental analysis. Alternatively, KL was methylated to mask its phenolic hydroxy groups to investigate how phenolic hydroxy groups impact the grafting of the alkyl chain of DGE onto lignin (methylated Kraft lignin, MKL). The methylation facilitated the molecular weight enhancement and thermal stability reduction of Kraft lignin via grafting with DGE. The influence of grafting alkyl chains on the structural and thermal properties of KL and MKL was studied using thermogravimetric analysis and differential scanning calorimetry analysis. Our data suggest that, due to their high molecular weights and lower glass transition temperatures, the produced lignin derivatives may be promising feedstocks for composite production.

Interfacial Assembly Behavior of Alkylamine-Modulated Graphene Oxide with Different Oxidation Degrees.

Multitudinous studies have been carried out on the controllable functionalization and performance evaluation of graphene oxide (GO). In this study, the correlation between the amount of grafted alkylamine on GO and its interfacial assembly behavior at liquid-liquid and liquid-solid interfaces was studied. GO was modified with n-octylamine through basal functionalization (bGO). The grafting amount of alkylamines was regulated using two GOs varied in oxidation degree (GO_L and GO_H). A study on the oil-water interfacial behaviors shows that bGO_L has better ability to modulate the interfacial tension than that of bGO_H. Grafting alkylamine on GO will not only increase the interaction strength with oil while weaken that with water but also do damage to the graphene lattice and weaken the interaction of π-π stacking; therefore, bGO_L displays a broader capability to modulate interfacial tensions than that of bGO_H. The bGO-based Pickering emulsion was prepared, and the interfacial behavior at the liquid-solid interface was investigated. A study on the interfacial anti-rust performances demonstrates that grafted alkyl chains in bGOs can form more compact and ordered protective films on the metal surface and enhance the hydrophobicity as a result of the similar structure to oil in the emulsion system, which makes Pickering emulsions show better anti-rust abilities than water dispersions. Meanwhile, the bGO_H emulsion shows a better anti-rust property than that of the bGO_L emulsion. A study on the interfacial tribological behaviors shows that the lubricity of bGO_L is better than that of bGO_H. X-ray photoelectron spectroscopy analysis shows that a high content of C-O-C/C-OH in lubricating films contributes to the improvement of lubricity. The modulated interfacial assembly properties of GO at both liquid-liquid and solid-liquid interfaces suggest their potential applications in surface protection, lubrication, controllable drug deliveries, absorption and separation, nanocomposites, and catalyst fields.

Alkyl-Chitosan-Based Adhesive: Water Resistance Improvement.

A chemical modification by grafting alkyl chains using an octanal (C8) on chitosan was conducted with the aim to improve its water resistance for bonding applications. The chemical structure of the modified polymers was determined by NMR analyses revealing two alkylation degrees (10 and 15%). In this study, the flow properties of alkyl-chitosans were also evaluated. An increase in the viscosity was observed in alkyl-chitosan solutions compared with solutions of the same concentration based on native chitosan. Moreover, the evaluation of the adhesive strength (bond strength and shear stress) of both native and alkyl-chitosans was performed on two different double-lap adherends (aluminum and wood). Alkyl-chitosans (10 and 15%) maintain sufficient adhesive properties on wood and exhibit better water resistance compared to native chitosan.

Preparation of oil sorbents by solvent-free grafting of cellulose cotton fibers

Natural cellulose-based fibers, such as cotton, have been investigated as oil sorbent to remediate and recover oil spills. The unmodified fibers are hydrophilic and have a high capacity to absorb water. To circumvent this drawback, the hydrophobicity of fibers is usually enhanced by chemical modification using solution-based processes that produce significant amounts of chemical waste. In the present study, gas–solid solvent-free silylation reaction was used to graft alkyl groups on cotton fibers. The modified cotton fibers were characterized by IR-spectroscopy, TGA analysis and SEM–EDS. The degree of substitution varied between 0.1 and 0.3 per glucose residue. The ability of the fibers to remove oil from the surface of simulated sea-water was investigated and all the modified fibers have adsorption capacity at least five times that of unmodified cotton. To optimize the adsorption capacity, factors that affect oil adsorption were investigated, namely the effect of fiber–oil contact time, temperature, and length of the grafted alkyl chains. Cotton fibers grafted with dialkyl substituted silyl ethers, through solvent-free silylation reaction, were found to have the best adsorption capacity of ~ 18 g oil/g of modified cotton with a fiber–oil contact time of 10 min at 25 °C.

A Concentration-Dependent Insulin Immobilization Behavior of Alkyl-Modified Silica Vesicles: The Impact of Alkyl Chain Length.

The insulin immobilization behaviors of silica vesicles (SV) before and after modification with hydrophobic alkyl -C8 and -C18 groups have been studied and correlated to the grafted alkyl chain length. In order to minimize the influence from the other structural parameters, monolayered -C8 or -C18 groups are grafted onto SV with controlled density. The insulin immobilization capacity of SV is dependent on the initial insulin concentrations (IIC). At high IIC (2.6-3.0 mg/mL), the trend of insulin immobilization capacity of SV is SV-OH > SV-C8 > SV-C18, which is determined mainly by the surface area of SV. At medium IIC (0.6-1.9 mg/mL), the trend changes to SV-C8 ≥ SV-C18 > SV-OH as both the surface area and alkyl chain length contribute to the insulin immobilization. At an extremely low IIC, the hydrophobic-hydrophobic interaction between the alkyl group and insulin molecules plays the most significant role. Consequently, SV-C18 with longer alkyl groups and the highest hydrophobicity show the best insulin enrichment performance compared to SV-C8 and SV-OH, as evidenced by an insulin detection limit of 0.001 ng/mL in phosphate buffered saline (PBS) and 0.05 ng/mL in artficial urine determined by mass spectrometry (MS).

Autoassemblies of α-Cyclodextrin and Grafted Polysaccharides: Crystal Structure and Specific Properties of the Platelets.

Cyclodextrins (CDs) are a family of oligosaccharides with a toroid shape, which exhibit a remarkable ability to include guest molecules in their internal cavity, providing a hydrophobic environment for poorly soluble molecules. Recently, new types of inclusions of α CDs with alkyl grafted polysaccharide chains (pullulan, chitosan, dextran, amylopectin, chondroitin sulfate...) have been prepared which are autoassembled into micro- and nanoplatelets. We report in this paper an extensive investigation of platelets with different compositions, including their reversible hydration (thermogravimetric analysis), crystalline structure (powder X-ray diffraction), dimensions and shapes (scanning electron microscopy-field emission gun), thermal properties, solubility, and melting (micro-differential scanning calorimetry). The crystalline platelets exhibit layered structures intercalating the polysaccharide backbones and CD complexes hosting the grafted alkyl chains. The monoclinic symmetry of columnar-type crystals suggests a head-to-tail arrangement of the CDs. The platelets have a preferentially hexagonal shape with sharp edges, variable sizes, and thicknesses and sometimes show incomplete layers (terraces). The crystal parameters change upon dehydration. Melting temperatures of platelets in aqueous solutions exceed 100 °C. Finally, we discuss the potential relation between the platelet structure and applications for mucoadhesive devices.

Biodistribution and preliminary toxicity studies of nanoparticles made of Biotransesterified β–cyclodextrins and PEGylated phospholipids

BackgroundThe modification of β-cyclodextrins (βCDs) by grafting alkyl chains on the primary and/or secondary face yields derivatives (βCD-C10) able to self-organize under nanoprecipitating conditions into nanoparticles (βCD-C10-NP) potentially useful for drug delivery. The co-nanoprecipitation of βCD-C10 with polyethylene glycol (PEG) chains yields PEGylated NPs (βCD-C10-PEG-NP) with potentially improved stealthiness. The objectives of the present study were to characterize the in vivo biodistribution of βCD-C10-PEG-NP with PEG chain length of 2000 and 5000Da using nuclear imaging, and to preliminarily evaluate the in vivo acute and extended acute toxicity of the most suitable system. Research design and methodsThe in vivo and ex vivo biodistribution features of naked and decorated nanoparticles were investigated over time following intravenous injection of 125I-radiolabeled nanoparticles to mice. The potential toxicity of PEGylated βCD-C10 nanosuspensions was evaluated in a preliminary in vivo toxicity study involving blood assays and tissue histology following repeated intraperitoneal injections of nanoparticles to healthy mice. ResultsThe results indicated that βCD-C10-PEG5000-NP presented increased stealthiness with decreased in vivo elimination and increased blood kinetics without inducing blood, kidney, spleen, and liver acute and extended acute toxicity. ConclusionsβCD-C10-PEG5000-NPs are stealth and safe systems with potential for drug delivery.

Cells capture and antimicrobial effect of hydrophobically modified chitosan coating on Escherichia coli

Hydrophobically modified chitosan (HMCS), prepared by reacting alkyl aldehyde with chitosan was demonstrated to be an effective antimicrobial and transparent coating. The grafted alkyl chains exist as protruded hydrophobic tails on the HMCS coating surface. In contact with E. coli cells, HMCS coating captured and immobilized the cells via these hydrophobic tails. The hydrophobic tails could also kill the cells captured on the coating surface as visualized by fluorescence microscope. More than 50% of the initially loaded cells (2.5×104 CFU) could be killed after 2h contact with HMCS coating. The cells capture and killing effects of the coating surface could be completely neutralized by treating with α-cyclodextrin to sequester the protruded hydrophobic tails. The facile coating of antimicrobial HMCS on surface also enabled the easy fabrication of patterned E. coli cells arrays.