Interactions Of Alkyl Chains Research Articles

Hyaluronan nanoplatelets exert an intrinsic anti-inflammatory activity in a rat model of bladder painful syndrome/interstitial cystitis.

Glycosaminoglycan (GAG) replenishment therapy consists of the instillation of GAG solutions directly in the bladder to alleviate Bladder Painful Syndrome/Interstitial Cystitis (BPS/IC). However, several issues were reported with this strategy because the GAG solutions are rapidly eliminated from the bladder by spontaneous voiding, and GAG have low bioadhesive behaviors. Herein, GAG nanomaterials with typical flattened morphology were obtained by a self-assembly process. The formation mechanism of those nanomaterials, denoted as nanoplatelets, involves the interaction of α-cyclodextrin cavity and alkyl chains covalently grafted on the GAG. Three GAG were used in this investigation, hyaluronan (HA), chondroitin sulfate (CS), and heparin (HEP). HA NP showed the best anti-inflammatory activity in an LPS-induced in vitro inflammation model of macrophages. They also exhibited the best therapeutic efficacy in a BPS/IC rat inflammation model. Histological examinations of the bladders revealed that HA NP significantly reduced bladder inflammation and regenerated the bladder mucosa. This investigation could open new perspectives to alleviate BPS/IC through GAG replenishment therapy.

Thermodynamics of glyme-sodium dodecyl sulfate (SDS) mixed micelle formation via isoperibol solution calorimetry: Temperature, and concentration effects

The enthalpies of mixed micelle formation (ΔmicH) for a number of sodium dodecyl sulfate (SDS)/glycol ether (glyme) systems were determined as a function of the concentration of the glycol ether in the mixed solvent systems and temperature via isoperibol solution calorimetry. The glycol ethers investigated in the present work were diethylene glycol dimethyl ether (DEGDME), triethylene glycol dimethyl ether (TEGDME), tetraethylene glycol dimethyl ether (TetraEGDME), and diethylene glycol diethyl ether (DEGDEE). The data from the isoperibol solution calorimeter was also used to directly determine the CMC values of the SDS/glyme mixed micelles. The entropies and Gibbs energies of mixed micellization (ΔmicSandΔmicG) were calculated by the application of the charged pseudo-phase separation model to the calorimetric enthalpies and CMC values. In general, CMC values and mixed micelle formation enthalpies depended strongly on the glyme structure and its concentration in the mixed solvents. The relative contributions to micelle thermodynamics by the ethylene oxide groups and the alkyloxy chain endcaps, and how the locus of solubilization influences the intramicellar surfactant/cosurfactant interactions, are interpreted in terms of alkyl chain interactions, hydrophobic effects, and electrostatic contributions.

Luminous Self-Assembled Fibers of Azopyridines and Quantum Dots Enabled by Synergy of Halogen Bond and Alkyl Chain Interactions

Herein, a simple approach for the fabrication of luminous self-assembled fibers based on halogen-bonded azopyridine complexes and oleic acid-modified quantum dots (QDs) is reported. The QDs uniformly align on the edge of the self-assembled fibers through the formation of van der Waals force between the alkyl chain of oleic acid on the QD surface and the alkyl chain of the halogen-bonded complexes, 15Br or 15I. Furthermore, the intermolecular interaction mechanism was elucidated by using Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, and density functional theory (DFT) calculations. This approach results in retention of the fluorescence properties of the QDs in the fibers. In addition, the bromine-bonded fibers can be assembled into tailored directional fibers upon evaporation of the solvent (tetrahydrofuran) when using capillaries via the capillary force. Interestingly, the mesogenic properties of the halogen-bonded complexes are preserved in the easily prepared halogen-bonded fluorescent fibers; this provides new insight into the design of functional self-assembly materials.

Hydrophobic interaction of V12 bowl-type dodecavanadates with alkyl ammonium cations

The V12 dodecavanadate, [V12O32]4−, that is one of a dominant polyoxovanadate species in non-aqueous media, was investigated focusing on the interaction of alkyl chains on its counter cations. Although the presence of such a species is not reported in any biological system, the unique V12 bowl anions have exhibited a host-guest property to accommodate a biologically active anion such as a halide, a cyanide or an azide for its delivery to the system. The nonpolar interactions between alkyl chains and the surface oxygen atoms on the V12 is of significance in the host-guest property and the reactivity of the V12. In the solid state, a tetraethyl ammonium (TEA) cation approached 3 Å above the cavity of the V12 via non-covalent interaction showing the lid effect. This interaction induces a distortion of its flexible framework even in a solution state. From the solution state 51V NMR and IR spectra, the orientation of an azide in the cavity was altered between TEA and tetra-n-butyl ammonium (TBA) salts. The modification of the non-covalent interaction also affected an oxidative catalytic performance with H2O2. The rate of the formation of active species of a TEA salt of [V12O32(Br)]5− was shorter than that of a TBA salt.

Stabilization of CO2-foams in brine by reducing drainage and coarsening using alkyldimethylamine oxides as surfactants

Producing CO2-foams in saline environments can be a great challenge in many industrial applications, since fast gas diffusion and reduction of electrical double layer promote fast coarsening and coalescence of bubbles. Amine oxides are zwitterionic surfactants that have been shown to improve foam stability by intermolecular hydrogen bonding, but have not been investigated for CO2-foams yet. This paper reports a study on the use of commercial alkyldimethylamine oxides (CxDAO) as foaming agents in brine for CO2-foams, based on the interactions present at the low pH imposed by the dissolution of the CO2 and the presence of salts. Despite the presence of salt and CO2 increased the protonation degree of amine oxide molecules, favoring hydrogen bonding, a significant improvement in foam stability was only observed when using the long chain surfactant (C14DAO). This behavior was attributed to the synergy between increased attractive hydrophobic interactions of alkyl chains and reduced repulsion among ionic surfactant heads, which led to formation of large surfactant aggregates in bulk, as demonstrated by the significant increase in viscosity of the aqueous phase. There was also a decrease in foam drainage and coarsening rates for the foams using C14DAO in brine, compared to results in deionized water, suggesting that formation of hydrogen bonds is not enough to arrest the destabilization in CO2-foams. Moreover, the linear rate of bubble growth obtained for these foams (∝t) was higher than that reported for N2– or air-foams (∝t1/2), likely due to the high solubility of CO2 in the aqueous phase, which accelerated the coarsening phenomena. The results of this work offer insight on the future design of foaming formulations for stabilizing CO2-foams in applications that require the use of high salinity brines, such as carbon sequestration and oil recovery.

Amine-β-cyclodextrin-based nanosponges. The role of cyclodextrin amphiphilicity in the imidacloprid uptake

This paper describes the synthesis, characterization and sorption performance of cyclodextrin nanosponges (NSs). Cyclodextrins are cyclic oligosaccharides with remarkable amphiphilic properties, allowing for a vast range of applications. The synthesis of nanosponges of β-cyclodextrins was carried out using two uncommon cross-linkers: hexane-1,6-diamine (am6) and dodecane-1,12-diamine (am12). It has been found that the physico-chemical properties of the nanosponges are highly influenced by the chain length of the crosslinker. Nanosponge with crosslinker with shorter chain length is characterized by a higher active surface area (21.8 m2 cm−1), pore size (24.3 nm) and structural disorder; on the other hand, the use of am12 leads to a higher thermal stability but lower porosity (7.5 nm), suggesting the occurrence of intermolecular alkyl chain interactions. It can also be concluded that by increasing the crosslinker alkyl chain length, the CD gains additional degrees of freedom and, consequently, a higher structural organization is favored. The more compact structure of the CD-am12-CD led to less available amine groups, consequently it shows a more pronounced response to pH variation. Such properties make the am6–containing NS a better sorbent for imidacloprid – an active substance used as systemic foliar insecticide and veterinary substance. A preliminary factorial study was performed to determine the effect of several parameters (IMD concentration, amount of sorbent, volume of solution and pH) on sorption abilities of the NSs. Hence, the sorption analysis were performed at the optimal experimental conditions pH 3.8, s/l ratio 5 and 25 °C in which CD-am6-CD shows the ability for an efficient sorption of the active substance. From the application perspective, the maximum adsorption capability is 68 ± 5 mg g−1 and the removal efficiency is 95%.

First deep eutectic solvent-based (DES) stationary phase for gas chromatography and future perspectives for DES application in separation techniques

The paper presents the first application of deep eutectic solvents (DES) as stationary phases for gas chromatography. DES obtained by mixing tetrabutylammonium chloride (TBAC) as a hydrogen bond acceptor (HBA) with heptadecanoic acid being a hydrogen bond donor (HBD) in a mole ratio of HBA:HBD equal to 1:2 was characterized by its ability to separate volatile organic compounds (VOCs). The Rohrschneider – McReynolds constants determined reveal that the synthesized DES is a stationary phase of medium polarity. A detailed retention characteristic was determined for a number of groups of chemical compounds, including aromatic hydrocarbons, alcohols, ketones, sulfides and thiophene derivatives. The synthesized DES was found to have a high selectivity towards alcohols. At the same time, the investigated stationary phase was found to have specific interactions with some analytes. For example, a stronger retention was observed for 1-hexanol and 1-heptanol compared to other alcohols. Retention times of these two alcohols are longer by 191% and 300%, respectively, relative to the expected value based on their boiling point. Such an increased retention is caused by a synergistic effect of various kinds of interactions – the possibility of formation of hydrogen bonds between the DES and the hydroxyl group of alcohols and hydrophobic interactions of alkyl chains of the DES with the alkyl chain of alcohols. The ability to modify properties of DESs by replacement of HBA or HBD with a different chemical compound or by dissolving in DES macromolecular substances makes the proposed stationary phase highly flexible. In addition to using the developed DES in chromatographic techniques, the retention data collected indicate the possibility of its application to other separation techniques, i.e. extractive distillation.

Janus lamellar nanosheets fabricated at the air/liquid interface

Two-dimensional (2D) Janus nanostructures have attracted much interest due to their unique structure and properties, and researchers are making great efforts continuously to explore new preparation methods. Herein, we reported a facile method to fabricate Janus nanosheets with lamellar structures at the air/liquid interface of a water-miscible organic solution of fatty acids and an aqueous solution of metal ions. The organic solution spread on the subphase surface and diffuse into the subphase simultaneously, and the aqueous solution diffused into the organic solution at the same time. Thus, the fatty acid molecules and metal ions self-assembled into layered nanosheets with the aid of hydrophobic interaction of alkyl chains and coordination between carboxylic groups and metal ions in the mixed solution. The sides facing to air and the subphase are composed of alkyl chains and carboxylates, respectively, indicating that the nanosheets are Janus ones. Various organic solvents, metal ions and fatty acid molecules have been tried to fabricate such layered Janus nanosheets. This method is expected to be a useful way to assemble Janus nanostructures.

Ion Dissociation in Ionic Liquids and Ionic Liquid Solutions

The extent to which cations and anions in ionic liquids (ILs) and ionic liquid solutions are dissociated is of both fundamental scientific interest and practical importance because ion dissociation has been shown to impact viscosity, density, surface tension, volatility, solubility, chemical reactivity, and many other important chemical and physical properties. When mixed with solvents, ionic liquids provide the unique opportunity to investigate ion dissociation from infinite dilution in the solvent to a completely solvent-free state, even at ambient conditions. The most common way to estimate ion dissociation in ILs and IL solutions is by comparing the molar conductivity determined from ionic conductivity measurements such as electrochemical impedance spectroscopy (EIS) (which measure the movement of only the charged, i.e., dissociated, ions) with the molar conductivity calculated from ion diffusivities measured by pulse field gradient nuclear magnetic resonance spectroscopy (PFG-NMR, which gives movement of all of the ions). Because the NMR measurements are time-consuming, the number of ILs and IL solutions investigated by this method is relatively limited. We have shown that use of the Stokes-Einstein equation with estimates of the effective ion Stokes radii allows ion dissociation to be calculated from easily measured density, viscosity, and ionic conductivity data (ρ, η, λ), which is readily available in the literature for a much larger number of pure ILs and IL solutions. Therefore, in this review, we present values of ion dissociation for ILs and IL solutions (aqueous and nonaqueous) determined by both the traditional molar conductivity/PFG-NMR method and the ρ, η, λ method. We explore the effect of cation and anion alkyl chain length, structure, and interaction motifs of the cation and anion, temperature, and the strength of the solvent in IL solutions.

Water Solubilization of Phthalocyanine Derivatives via Interactions of Long Alkyl Chains and Cyclodextrins: Potential Complexes for Photodynamic Therapy

AbstractFive types of cyclodextrins, based on α‐cyclodextrin (α‐CDx) and β‐cyclodextrin (β‐CDx), were used to make hydrophobic phthalocyanine (Pc) derivatives with long alkyl chains soluble in water via a high‐speed vibration milling method. Aqueous solutions of DMe‐β‐CDx‐based complexes were found to be the most stable, for at least 1 week over those containing α‐CDx. Although DMe‐β‐CDx complexes containing a free‐base Pc and Zn−Pc with eight dodecyl chains showed greater solubility than their α‐CDx‐base counterparts, α‐CDx complexes containing a free‐base Pc and Zn−Pc with eight dodecyl chains show no self‐aggregation of the Pcs and, as a result, exhibit fluorescence signals. Overall, it was found that the α‐CDx−Zn−Pc complex exhibits higher photodynamic activity than that of the commercially available and widely used photosensitizer Photofrin.

Acceleration of Liquid-Crystalline Phase Transition Simulations Using Selectively Scaled and Returned Molecular Dynamics.

The molecular dynamics (MD) technique to accelerate simulation of phase transition to liquid-crystalline (LC) phases is demonstrated on the model LC system 4-octyl-4'-cyanobiphenyl (8CB) smectic A phase. Simulation of a phase transition to a smectic phase is challenging because an intrinsically long simulation time and large system size are required owing to the high order and low onset temperature. Acceleration of the simulated transition of 8CB to the smectic A phase was ultimately achieved by selectively weakening the intermolecular Lennard-Jones interaction of alkyl chains and then returning the scaled interaction to the unscaled one. The total time needed to form the smectic A phase using selectively scaled and returned molecular dynamics (ssrMD) was five times shorter than that when using unscaled MD. Formation of the smectic A phase occurred only when induced polarization from the antiparallel dipole dimer point charge was included in the simulation. The use of ssrMD presented herein is anticipated to accelerate the theoretical development of self-assembled organic materials containing both rigid and flexible moieties, including LC materials.

The aggregation induced fluorescence effect enhanced by a reasonable length of carbon chain

Six different barbituric acid derivatives using ethyl, propyl, butyl, pentyl, hexyl and heptyl groups as hydrophobic substituents were prepared. Molecular dynamics simulation was carried out to study the effect of different carbon chain lengths on the aggregation-induced emission process. Among the compounds, the CB-5 containing a hexyl substituent exhibited the strongest Aggregation induced emission (AIE) effect, not the CB-6 with longest carbon chain. The aggregates of CB-5 was used to detect the 2, 4, 6-trinitrotoluene (TNT) in aqueous media, exhibiting a maximum quenching constant of 3.1 × 105 M−1. The paper sensor based on CB-5 showed a superior sensitivity toward TNT both in vapor and solution. This provided a clear strategy for designing compounds that utilize the hydrophobic interaction of long-chain alkyl chains to enhance the AIE effect.

Calorimetric determination of the thermodynamics of alcohol-surfactant mixed micelle formation: Temperature and concentration effects

The thermodynamic parameters of surfactant/alcohol mixed micelles were determined in mixtures of sodium dodecyl sulfate (SDS) and dodecyltrimethylammonium bromide (DTAB) in a series of solvents composed of varying concentrations of n-propanol (C3OH), n-butanol (C4OH), and n-pentanol (C5OH). Conductivity studies were used to determine CMC values and the degrees of counterion binding. Isoperibol solution calorimetry was used to directly determine CMC values and enthalpy of micellization (ΔmicH). From these experimentally determined values, the Gibbs energy and entropy of micellization were calculated as a function of temperature and alcohol concentration. In general, CMC values decreased with increasing alcohol carbon chain length and concentration but increased with temperature. The effects of temperature, alcohol carbon chain length, and alcohol concentration on the energetics of these mixed micellar systems are explained in terms of the relative contributions to ΔmicH by alkyl chain interactions, hydrophobic effects, and electrostatic contributions.

First principles investigation on long alkyl chain-based surface anchoring for self-assembled bilayer

Bilayer assembly is important for energy conversion devices such as the photoelectrochemical water-splitting system, in which a second layer such as the catalyst is required to deposit onto a functional self-assembled monolayer. In this manuscript, we employ first principles calculations to reveal the nanoscopic structures and properties of a long alkyl chain stabilized bilayer assembly on metal oxide substrate. The calculation confirms the viability of employing the long alkyl chain as an effective anchoring method to stabilize the self-assembled bilayer. The calculation constructs the potential energy surface and identifies a charge transfer character induced by the long alkyl chain interactions. We expect that the long alkyl chains could facilitate the preparation of more advanced surface structures for energy conversion devices which rely on self-assembled multilayers. This study helps the fundamental understanding of photoelectrochemical photoelectrodes and optoelectronic devices with the multi-layer molecular assembly.

Interaction of alkyl chain containing pyrene derivatives with different micellar media: Synthesis and photophysical study.

The present work describes the synthesis and photophysical studies of four newly synthesized alkyl chain containing pyrene derivatives and their applications in micellization process of different types of surfactants e.g. CTAB and SDS. The fluorescent properties of these pyrene derivatives were utilized to understand the micellization process of CTAB and SDS. The length of alkyl chain affects the hydrophobicity of pyrene fluorophore which also affects the sensitivity of fluorophore towards the micellization of CTAB and SDS surfactants. The longest alkyl tail containing, PBBU showed more sensitivity whereas moderate alkyl chain containing, PABU and PBME showed moderate sensitivity and finally PAME contained smallest alkyl tail, showed no sensitivity towards the micellization of CTAB and SDS. The alkyl tail of fluorophore make it more hydrophobic and it could easily bind with the hydrophobic inner core of micelles. In both surfactants, PBBU showed LE emission at ~400 nm and aggregate emission at ~470 nm, whereas, PABU and PBME showed LE emission band at ~400 nm. Before CMC, the aggregates band of PBBU increased with increasing the surfactant concentrations, but after CMC the individual PBBU present into the water medium could binds with the inner core of micelles. Thus PBBU senses the formation of premicellar aggregates of CTAB and SDS. The LE emission of the fluorophore gradually increases while increasing the CTAB and SDS concentrations. The change in fluorescence emission of PABU, PBME and PBBU with increasing concentration of CTAB and SDS were used to calculate the CMC of CTAB and SDS surfactants.

1-nm-Wide Hydrated Dipole Arrays Regulate AuNW Assembly on Striped Monolayers in Nonpolar Solvent

Summary We show that striped phases of horizontally oriented phospholipids presenting 1-nm-wide orientable dipole arrays can order and straighten flexible 2-nm-diameter gold nanowires (AuNWs) with lengths (up to 1 μm) that greatly exceed the template pitch (∼7.5 nm). AuNW ordering can extend over areas > 100 μm2. Whereas wires bundle in solution, with contact between ligand shells, wires adsorbing to the template separate to much larger center-to-center distances (e.g., 12–30 nm) near multiples of the template pitch, consistent with repulsive interactions between wires emerging during interactions with dipole arrays in the template. AuNW assembly was carried out in cyclohexane, a nonpolar solvent. Interestingly, we found that wire ordering was contingent on the extent of phospholipid headgroup hydration and the presence of excess oleylamine, which assembled into hemicylindrical micelles around the hydrated headgroups. Together, these components generated a protected polar environment that enabled the phospholipid headgroups to function collectively to regulate AuNW assembly.

Co-assembly of gold nanocluster with imidazolium surfactant into ordered luminescent fibers based on aggregation induced emission strategy

Metal nanoclusters (NCs) with outstanding luminescent nature have been engineered as an emerging material, while the application of NCs in aqueous solution is subjected to major limitations because of their luminescence quenching in water. Herein, imidazolium surfactant 1-hexadecyl-3-methylimidazoliumbromide (C16mimBr) with opposite charge was used to overcome this issue based on aggregation induced emission (AIE) strategy through mild co-assembly of Au-NCs with C16mimBr. Of interest is that not only the luminescence of Au-NCs was enhanced but also fibers with strikingly regular layer-like periodic structures were obtained which is rarely prepared at room temperature. The underlying mechanism for the formation of ordered fibers was systematically investigated by a series of experiments. Firstly, the electrostatic interaction between Au-NCs and C16mimBr induces the aggregation of Au-NCs while the directional H-bonding facilitates the elongation of aggregates into 1D ordered structures. Besides, the hydrophobic interaction of alkyl chains is also crucial for the formation of fibers. Importantly, the emission of fibers exhibited reversible pH-responsiveness, i.e. when adding H+, the emission turns off meaning that the aggregates disintegrate along with fluorescence quenching. While with the addition of equal OH−, it turns on again. Such a type of optical materials with ordered structure will have potential applications in pH sensors and photoelectronic devices. It can be expected that this work will serve as a simple and low-cost platform for the preparation of ordered luminescent materials based on metal NCs.

High strength hydrogels with multiple shape-memory ability based on hydrophobic and electrostatic interactions.

Hydrogels with multiple shape-memory ability have aroused great interest due to their promising applications in various fields. Nevertheless, the weak mechanical performance of most shape-memory hydrogels seriously impedes the practical application in more complex environments. Herein, we reported a novel hydrogel with both high mechanical and multi-shape memory properties composed of stearyl methacrylate (SMA), acrylic acid (AA) and quaternary chitosan (QCH). The electrostatic interactions between AA and QCH together with the hydrophobic interactions of alkyl chains in SMA endowed the hydrogel with great strain-stress and fatigue resistance. Furthermore, due to the reversible destruction and construction of physical cross-links, the prepared hydrogels also exhibited the shape-memory ability in response to different stimuli, such as temperature, pH and NaCl solution. Additionally, the multiple shape-memory effect could be accomplished via programmable combination because of the relatively independent physical interactions in the hydrogels.

Pyrrolo[3,2-b]pyrrole-Based Quinoidal Compounds For High Performance n-Channel Organic Field-Effect Transistor

It is a very important and challenging topic to design high performance n-channel organic semiconductors with a new type conjugated skeleton. Herein, a new class of n-channel organic semiconductors, pyrrolo[3,2-b]pyrrole-based quinoidal molecules QBPBP and QFBPBP, was designed and synthesized. Both compounds have low-lying lowest unoccupied molecular orbital energy level and high thermal stability. Single crystal structures reveal they adopt unusual two-dimensional layer-type packing structures in single crystals. Multiple π–π and CN···H interactions are observed in the layer, and alkyl–alkyl chain interactions exist between layers. Transistors based on single ribbons displayed gate voltage-dependent electron mobility with an average of 4.0 cm2 V–1 s–1 and a peak over 6.0 cm2 V–1 s–1 under N2. These results demonstrate pyrrolo[3,2-b]pyrrole-based quinoidal molecules are a new prototype for high performance n-channel organic semiconductors.

Conformational explosion: Understanding the complexity of short chain para-dialkylbenzene potential energy surfaces.

The single-conformation ultraviolet and infrared spectroscopy of three short-chain para-dialkylbenzenes (para-diethylbenzene, para-dipropylbenzene, and para-dibutylbenzene) is reported for the jet-cooled, isolated molecules. The present study builds off previous work on single-chain n-alkylbenzenes, where an anharmonic local mode Hamiltonian method was developed to account for stretch-bend Fermi resonance in the alkyl CH stretch region [D. P. Tabor et al., J. Chem. Phys. 144, 224310 (2016)]. The jet-cooled molecules are interrogated using laser-induced fluorescence (LIF) excitation, fluorescence dip infrared spectroscopy, and dispersed fluorescence. The LIF spectra in the S1 ← S0 origin region show a dramatic increase in the number of resolved transitions with increasing length of the alkyl chains, reflecting an explosion in the number of unique low-energy conformations formed when two independent alkyl chains are present. Since the barriers to isomerization of the alkyl chain are similar in size, this results in an "egg carton" shaped potential energy surface. A combination of electronic frequency shift and alkyl CH stretch infrared spectra is used to generate a consistent set of conformational assignments. Using these experimental techniques in conjunction with computational methods, subsets of origin transitions in the LIF excitation spectrum can be classified into different conformational families. Two conformations are resolved in para-diethylbenzene, seven in para-dipropylbenzene, and about nineteen in para-dibutylbenzene. These chains are largely independent of each other as there are no new single-chain conformations induced by the presence of a second chain. A cursory LIF excitation scan of para-dioctylbenzene shows a broad congested spectrum at frequencies consistent with interactions of alkyl chains with the phenyl π cloud.