Effect Of Chain Length Research Articles

Understanding the Reaction Kinetics and Microdynamics between Methylimidazole and Alkyl Thiocyanate for Ionic Liquid Synthesis through Experiments and Theoretical Calculation

Ionic liquids (ILs) are usually prepared via the Menshutkin SN2 reaction. Herein, the effects of the alkyl chain length of the substrate on the reaction kinetics and microdynamics between 1-methylimidazole (MIm) and alkyl thiocyanate (RSCN, R = methyl, ethyl, and butyl groups) for the preparation of thiocyanate-based ILs were analyzed by time-dependent Fourier transform infrared (FTIR) spectroscopy, classical molecular dynamics (MD) simulation, and ab initio molecular dynamics (AIMD) simulation. Experimental results show that the longer chain length of thiocyanate leads to a significantly slower rate constant and much higher activation energy. The rate constant of the MIm/BuSCN system is reduced by a factor of 21 fold compared to that of the MIm/MeSCN system at 330 K. The activation energy of the MIm/BuSCN system is increased by 27.5 kJ/mol in the MIm/MeSCN system. Metadynamics calculations in the explicit solvent offer a consistent trend for transition state energy barrier with experiments. MD simulations indicate that the long alkyl chain of thiocyanate results in a weaker spatial distribution of reaction sites as well as slower diffusion and reorientation, which can reduce the intermolecular collision probability. Hopefully, the insights from this work would guide the industrial synthesis of ILs.

Strong red fluorescent probe for detecting chymotrypsin activity in vivo and in vitro

Chymotrypsin is a medication that is useful in treating inflammation, edema, expectoration, and corruption. It has a wide range of medical applications. Therefore, it is critical to create a chymotrypsin real-time drug tracking detection approach. The ester bond in the molecule can be severed by chymotrypsin. Intramolecular charge transfer (ICT) recovers when the ester bond in the probe breaks, resulting in fluorescence. As a result, in this research, we built and investigated the "turn-on" fluorescent probe NBD-1, NBD-2, and NBD-3, which are used to detect endogenous chymotrypsin, and explored the effect of molecular chain length on probe sensitivity through density functional theory (DFT) calculation and spectral testing, and screened the best probe NBD-3, which is a rare bright red fluorescence probe. The presence of endogenous chymotrypsin was subsequently discovered for the first time in the liver of mice with NBD-3 probe in confocal imaging of HeLa cells, in vivo imaging of mice, and in vitro imaging of organs in the experiment. This result confirmed that such probes could precisely detect the distribution of chymotrypsin in various organs of the organism. NBD-3's strong performance makes it possible to detect chymotrypsin medications in real time with a robust tool.

The effect of the polydimethylsiloxane chain length on the properties of four-arm siloxane stars

Five low-dispersity star-shaped polydimethylsiloxanes were synthesized. The macromolecules of the polymers contain the same branching-out center, a cis-tetraphenylcyclotetrasilsesquioxane moiety, and the same number of arms, but with different lengths (n = 15, 21, 48, 75, and 123 Si(Me)2O units). Their properties were studied by a set of physicochemical analytical methods. Viscometric studies showed that the macromolecules of the Ph4-15, Ph4-21, Ph4-48, and Ph4-75 polymers are small-sized dense balls both in solution and in melt. DSC studies identified an unusual effect of the cyclic core on the thermal behavior of the Ph4-15, Ph4-21, and Ph4-48 polymers. Its incorporation suppresses the crystallization of PDMS-arms (up to n = 48 Si(Me)2O units) at concentrations four times lower than those of known modifiers and does not affect the glass transition temperature (ca. -124 °С).

Thermodynamics and transport properties of valine and cysteine peptides in water

The study of thermodynamic and transport properties of amino acids gives access to knowledge about interactions between distinct molecules necessary to understand a variety of biological processes. In this work, we have performed molecular dynamics simulations of valine and cysteine peptides with lengths of (n) = 1, 2, 4, 8 & 16 monomers in an aqueous environment to estimate the solvation free energy and diffusion coefficients. We modeled our system using OPLS-AA parameter sets and TIP3P water at 310 K temperature. Solvation free energy of both the peptides have been reported using two thermodynamic integration (TI) based methods: TI and TI-CUBIC. The solvation free energy of both the peptides increases with the chain length. The estimated values using both methods are in good agreement with a statistical error of < 3%. The solvent accessible surface area (SASA) of solutes and hydrogen bonds between solute and solvent have also been presented to get more insights on solvation processes. The increase in solvation energy of both peptides with chain length is further corroborated by increase in the number of hydrogen bond (between peptide and water) and SASA with the chain length. In addition, the self diffusion coefficient of both solute and solvent along with their binary diffusion coefficient have been estimated for both the peptides. Furthermore, the effect of chain length on solvation free energy as well as diffusion coefficients have been studied.

Synthesis and Photophysical Properties of Anthracene Bisimide–butadiynylene Linear Dimer and Trimer

Linear dimer and trimer of anthracene bisimide (ABI) units linked by butadiynylene spacers were synthesized through Hay coupling of 9,10-diethynyl ABI derivatives. Chain length effects on π-conjugation were experimentally and computationally investigated using DFT. UV-vis spectroscopy revealed that increasing the number of ABI units caused a bathochromic shift of the absorption maxima. Fluorescence emission spectroscopy revealed that these ABI-based oligomers had higher fluorescence quantum yields than those of their anthrylene counterparts, which might be attributed to strong fluorescence properties of the ABI units.

Effect of Alkylation Chain Length on Inhibiting Performance of Soluble Ionic Liquids in Water-Based Drilling Fluids.

This work investigated the effect of the alkyl chain length of soluble methylimidazolium bromide ionic liquids (ILs) on their inhibition performance. The IL with a shorter alkyl chain length showed superior inhibition performance by suppressing clay swelling, mitigating clay dispersion, at room temperature. Particularly, the IL with an alkyl chain length of two (EmBr) reduced the sodium bentonite (Na-BT) swelling degree to 89% and achieved a cutting recovery of 81.9% after being rolled at room temperature, performing the best among all ILs. To systematically analyze the inhibition mechanism of ILs, X-ray diffraction (XRD), ζ potential, and particle size distribution have been carried out. The results revealed that the methylimidazolium with shorter alkyl chain length had better ability to enter the interlayer void by ion exchange and decrease interlayer distance, suppress the electrical double layer of the Na-BT particles and decrease the ζ potential, and promote the aggregation of Na-BT in water. It is also observed that high hot rolling temperature reduced the shale inhibiting performance of all ILs, and ILs with longer alkyl chain length had better ability to prevent cutting disintegration at high temperature. It is attributed to the variation of the hydrophilic characteristic of Na-BT at high temperature where EmBr no longer adsorbed the most on the surface and entered the interlayer voids of Na-BT. This study can be used as a reference to systematically explore the effect of the structure of shale inhibitors on their inhibiting performance and develop effective shale inhibitors.

The effect of alkyl chain length on imidazole chloroaluminate ionic liquid/Pt(1 1 1) interface and aluminum deposition: A DFT-D3 study

The structure, active sites, and adsorption mechanism of imidazole-based ionic liquids ([CnMIM]Al2Cl7) (n = 1, 2, 4, or 6) on the Pt(111) surface and their effects on aluminum electrodeposition were evaluated by first-principles approaches. The active sites of imidazolium ILs were on the cationic imidazole ring. The adsorption order was [HMIM]Al2Cl7 >[BMIM]Al2Cl7 >[EMIM]Al2Cl7 > [C1MIM]Al2Cl7. The electrostatic interaction, electrostatic induction, and the interfacial dipole effect made the ionic liquids with longer alkyl chain increase the coverage of cations on the Pt(111) surface as well as the number of charge transfers from ionic liquids to the Pt(111) surface, and decrease the distance between chlorine atoms and the Pt(111) surface. This is beneficial to suppress the dendrite formation during the electrochemical process and deposit aluminum in smaller sizes. These results will provide a basis for the selection of efficient ionic liquids of aluminum electrodeposition.

Model Catanionic Vesicles from Biomimetic Serine-Based Surfactants: Effect of the Combination of Chain Lengths on Vesicle Properties and Vesicle-to-Micelle Transition

Mixtures of cationic and anionic surfactants often originate bilayer structures, such as vesicles and lamellar liquid crystals, that can be explored as model membranes for fundamental studies or as drug and gene nanocarriers. Here, we investigated the aggregation properties of two catanionic mixtures containing biomimetic surfactants derived from serine. The mixtures are designated as 12Ser/8-8Ser and 14Ser/10-10Ser, where mSer is a cationic, single-chained surfactant and n-nSer is an anionic, double-chained one (m and n being the C atoms in the alkyl chains). Our goal was to investigate the effects of total chain length and chain length asymmetry of the catanionic pair on the formation of catanionic vesicles, the vesicle properties and the vesicle/micelle transitions. Ocular observations, surface tension measurements, video-enhanced light microscopy, cryogenic scanning electron microscopy, dynamic and electrophoretic light scattering were used to monitor the self-assembly process and the aggregate properties. Catanionic vesicles were indeed found in both systems for molar fractions of cationic surfactant ≥0.40, always possessing positive zeta potentials (ζ = +35-50 mV), even for equimolar sample compositions. Furthermore, the 14Ser/10-10Ser vesicles were only found as single aggregates (i.e., without coexisting micelles) in a very narrow compositional range and as a bimodal population (average diameters of 80 and 300 nm). In contrast, the 12Ser/8-8Ser vesicles were found for a wider sample compositional range and as unimodal or bimodal populations, depending on the mixing ratio. The aggregate size, pH and zeta potential of the mixtures were further investigated. The unimodal 12Ser/8-8Ser vesicles (<DH> ≈ 250 nm, pH ≈ 7-8, ζ ≈ +32 mV and a cationic/anionic molar ratio of ≈2:1) are particularly promising for application as drug/gene nanocarriers. Both chain length asymmetry and total length play a key role in the aggregation features of the two systems. Molecular insights are provided by the main findings.

Fatty acid modified zein films: Effect of fatty acid chain length on the processability and thermomechanical properties of modified zein films

Fatty acid modified zein films: Effect of fatty acid chain length on the processability and thermomechanical properties of modified zein films

Effects of Chain Length, Stretching, and Molecular Groups on the Thermal Conductivity of Single Crosslinked Epoxy Resin Chains

Effects of Chain Length, Stretching, and Molecular Groups on the Thermal Conductivity of Single Crosslinked Epoxy Resin Chains

Effect of fatty acid chain length on physicochemical properties of starch nanocomposites obtained via nanoprecipitation

To evaluate the effect of elaborate difference in the hydrophobicity of core material on encapsulation process and physicochemical properties of the composites, composites of starch and FA with various chain lengths (C:12–22) were prepared via nanoprecipitation. X-ray diffraction analyses revealed that all composites had a Vh-amylose crystalline unit cell, but the chain length of FA did not induce a clear change in crystallinity or the hydrodynamic mean diameter of the composites. As the chain length of FA increased from 12 to 22, FA content in the composites increased from 1.69 to 14.85 mg/g composite. The absorption analyses of Rose Bengal on the composite surfaces revealed that their hydrophobicity increased with increasing chain length of FA. The incorporation of FA enhanced the emulsification activity of the composites, and this result revealed that the composites could be applied as an emulsification agent. For longer FA, composite storage stability increased, but the release of FA by in vitro digestion was delayed.

Effects of macromonomer chain length, solvent and concentration on the cyclization kinetics during AB-type step-growth polymerization

For the first time, this work has explored the cyclization kinetics of multi-mers during step-growth polymerization by using alkyne-PS-azide (l-PS-N3) as model macromonomer, where PS represents polystyrene. First, three AB-type PS macromonomers with different chain lengths have been prepared by atom transfer radical polymerization (ATRP), namely, l-PS77-N3, l-PS240-N3 and l-PS380-N3. Second, the polymerization and cyclization kinetics has been monitored in dimethylformamide (DMF), tetrahydrofuran (THF) and cyclopentane (CyP). Third, by size exclusion chromatography (SEC) and liquid chromatography at the critical condition (LCCC) methods, we have quantified how the macromonomer chain length, solvent type and reaction concentration affect the intra-chain cyclization process. The analysis results have demonstrated that, for macromonomer l-PS77-N3 with shorter chain length, the reaction rate of macromonomer cyclization, multi-mer cyclization and inter-chain coupling, is significantly faster than that for l-PS240-N3 and l-PS380-N3 with longer chain lengths. The total percentage of final cyclic product (wtcyclic) slightly decreases with the increase of macromonomer chain length, namely, 33%, 25% and 23% for l-PS77-N3, l-PS240-N3 and l-PS380-N3, respectively. At the same time, we found that, solvent with lower solvent viscosity and relatively poor solvent quality is more conducive to the cyclization reaction of PS chains. In addition, we also found that the inter-chain and intra-chain reaction rate are both faster than that at other reaction concentrations when the reaction concentration is near the critical overlapping concentration.

The Effect of Chain Length and Conformation on the Nucleation of Glycine Homopeptides during the Crystallization Process.

To explore the effect of chain length and conformation on the nucleation of peptides, the primary nucleation induction time of glycine homopeptides in pure water at different supersaturation levels under various temperatures has been determined. Nucleation data suggest that longer chains will prolong the induction time, especially for chains longer than three, where nucleation will occur over several days. In contrast, the nucleation rate increased with an increase in the supersaturation for all homopeptides. Induction time and nucleation difficulty increase at lower temperatures. However, for triglycine, the dihydrate form was produced with an unfolded peptide conformation (pPII) at low temperature. The interfacial energy and activation Gibbs energy of this dihydrate form are both lower than those at high temperature, while the induction time is longer, indicating the classical nucleation theory is not suitable to explain the nucleation phenomenon of triglycine dihydrate. Moreover, gelation and liquid-liquid separation of longer chain glycine homopeptides were observed, which was normally classified to nonclassical nucleation theory. This work provides insight into how the nucleation process evolves with increasing chain length and variable conformation, thereby offering a fundamental understanding of the critical peptide chain length for the classical nucleation theory and complex nucleation process for peptides.

Pendant Length-Dependent Electrochemical Performances for Conjugated Organic Polymers as Solid-State Polymer Electrolytes in Lithium Metal Batteries.

The development of solid-state polymer electrolytes (SPEs) has been plagued by poor ionic conductivity, low ionic transference number, and limited electrochemical potential window. The exploitation of ionized SPEs is a feasible avenue to solve this problem. Herein, conjugated organic polymers (COPs) with excellent designability and rich pore structures have been selected as platforms for exploration. Three cationic COPs with different chain lengths of quaternary ammonium salts (CbzT@Cx, x = 4, 6, 9) are designed and applied to SPEs for the first time. Meanwhile, the effects of chain lengths on their electrochemical performances are compared. Especially, CbzT@C9 shows the most attractive electrochemical performance due to its high specific surface area of 212.3 m2 g-1. The larger specific surface area allows more exposure of the long-chain quaternary ammonium cation groups, which is more favorable for the dissociation of lithium salts. Moreover, the flexible long-chain structure increases the compatibility with poly(ethylene oxide) (PEO) and reduces the crystallinity of PEO to some extent. The richer pore structure can accommodate more PEO, further disrupting the crystallinity of PEO and creating more channels for the ether-oxygen chain to transport lithium ions. At 60 °C, the SPE (CbzTM@C9) presents an excellent ionic conductivity (σ) of 8.00 × 10-4 S cm-1. CbzTM@C9 has a lithium-ion transference number (tLi+) of 0.48. Thus, the assembled Li/CbzTM@C9/LiFePO4 battery provides a good discharge capacity of 158.8 mAh g-1 at 0.1C. After 70 cycles, the capacity retention rate is 93.8% with a Coulombic efficiency of 98%. The excellent flexibility brings stable power supply capability under various bending angles to the assembled Li/CbzTM@C9/LiFePO4 soft-packed battery. The project uses conjugated organic polymers in SPEs and creates an avenue to develop flexible energy storage equipment.

Experimental and simulated distribution and interaction of water in cellulose esters with alkyl chain substitutions

This study investigated the effect of the average length of substituted side chains in different cellulose esters on water sorption and the water association mechanism. For this purpose, a set of esters with a similar total degree of substitution was selected: cellulose acetate, cellulose acetate propionate, and cellulose acetate butyrate. Dynamic vapor sorption was used to determine the effect of the side chain length on sorption, desorption, and the occurrence of water clustering. Since water association in the structure was of interest, molecular dynamics simulations were performed on cellulose acetate and cellulose acetate propionate. This study showed that cellulose acetate appears to be water-sensitive and experiences hysteresis upon water sorption, which was attributed to structural changes. The simulations also showed that water is screened out by the side chains and forms intermolecular hydrogen bonds, primarily to the carbonyl oxygen rather than the residual hydroxyl groups.

Development of Low-Molecular-Weight Organogelators from Cyclic β-Amino Acid: Effect of Stereochemistry and their Application on Visual Chiral Recognition of Amines.

This study reports the formation of low-molecular-weight gelators based on carboxylic acids derived from chiral cyclicβ-amino acids. The effect of their stereochemistry on the gelation of organic solvents was investigated, and their assemblies with the intermolecular interactions in the xerogels were proposed via infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and crystallographic details of the related model compounds. The effect of the alkyl chain length on the gelators was studied, and they were applied to the chiral recognition of amines. Only one diastereomeric salt with amines afforded gels, whereas the others resulted in precipitates. Chiral recognition was also achieved in the gel state, and the appearance of the as-prepared gel changed upon the addition of each amine enantiomer, thus enabling the visual detection of their chirality.

Photo- and Thermoresponsive Liquid Marbles Based on Fatty Acid as Phase Change Material Coated by Polypyrrole: From Design to Applications.

Responsive liquid marbles (LMs), which can change their shape, stability, and motion by the application of stimuli, attract a growing interest due to their wide range of applications. Our approach to design photo- and thermoresponsive LMs is based on the use of micrometer-sized fatty acid (FA) particles as phase change material covered with polypyrrole (PPy) overlayers with photothermal property. The core-shell particles were synthesized by aqueous chemical oxidative seeded dispersion polymerization. First, we investigated the effect of the alkyl chain length of FA on the resulting FA/PPy core-shell particles by characterizing their size and its distribution, shape, morphology, chemical composition, and photothermal behavior. Then LMs were fabricated by rolling water droplets on the dried FA/PPy particle powder bed and their light and temperature dual stimuli-responsive nature was studied as a function of the FA alkyl chain length. For all FAs studied, LMs disrupted in a domino manner by light irradiation as the first trigger: the temperature of the FA/PPy particles on the LM surface increased by light irradiation, followed by phase change of FA core of the particles from solid to liquid, resulting in disruption of the LM and release of the encapsulated water. The disruption time was closely correlated to the melting point of FA linked to the alkyl chain length and light irradiation power, and it could be controlled and tuned easily between quasi instantaneous and approximately 10 s. Finally, we showed potential applications of the LMs as a carrier for controlled delivery and release of substances and a sensor.

Ring-chain equilibria of dynamic macrocycles with a bis(hindered amino)disulfide linker

The effect of chain length on ring-chain equilibria was investigated to both reveal their dynamic equilibrium reactions and expand the availability of bis(2,2,6,6-tetramethylpiperidin-1-yl)disulfide (BiTEMPS)-based macrocyclic monomers.

Narrowing down chain length effects on the antibacterial action of guanylated oligomers

Synthesis of discrete guanylated antimicrobial oligomers through reversible addition fragmentation chain transfer (RAFT) polymerization followed by flash chromatography is described.

Effects of chirality and side chain length in Cα,α-dialkylated residues on β-hairpin peptide folded structure and stability.

Strategic incorporation of achiral Cα,α-dialkylated amino acids with bulky substituents into peptides can be used to promote extended strand conformations and inhibit protein-protein interactions associated with amyloid formation. In this work, we evaluate the thermodynamic impact of chiral Cα,α monomers on folding preferences in such systems through introduction of a series of Cα-methylated and Cα-ethylated residues into a β-hairpin host sequence. Depending on stereochemical configuration of the artificial monomer and potential for additional hydrophobic packing, a Cα-ethyl-Cα-propyl glycine residue can provide similar or enhanced folded stability relative to an achiral Cα,α-diethyl analogue.