Linear Alkyl Chains Research Articles

Free-standing flexible and biomimetic hybrid membranes for ions and ATP transport

The transport of metabolites across robust, flexible and free-standing biomimetic membranes made of three perforated poly (lactic acid) (pPLA) layers, separated by two anodically polymerized conducting layers of poly (3,4-ethylenedioxythiophene-co-3-dodecylthiophene), and functionalized on the external pPLA layers with a voltage dependent anion channel (VDAC) protein, has been demonstrated. The three pPLA layers offer robustness and flexibility to the bioactive platform and the possibility of obtaining conducing polymer layers by in situ anodic polymerization. The incorporation of dodecylthiophene units, which bear a 12 carbon atoms long linear alkyl chain, to the conducting layers allows mimicking the amphiphilic environment offered by lipids in cells, increasing 32% the efficiency of the functionalization. Electrochemical impedance measurements in NaCl and adenosine triphosphate (ATP) solutions prove that the integration of the VDAC porin inside the PLA perforations considerably increases the membrane conductivity and is crucial for the electrolyte diffusion. Such results open the door for the development of advanced sensing devices for a broad panel of biomedical applications.

Influence of surfactant chain length, counterion and OrMoSil precursors on reversibility and working interval of pH colorimetric sensors

An in-depth study was conducted to determine the influence of some important parameters to produce a pH colorimetric sensor characterized by long-term stability, lack of leaching, high reversibility, repeatability and extended working range. Bromothymol Blue (BB) was used as pH sensitive molecule. Its performance was monitored while tailoring the concentration of some added cationic surfactants, together with the organic fraction of the sol-gel composition to avoid leaching phenomena, low homogeneity and to increase reversibility. Five cationic surfactants with different linear alkyl chain length (from C8 to C18) were added to a sol-gel containing BB. The C16 was chosen as optimal. The effect of the surfactant counterion was also investigated. The C16 surfactant had a pH working interval of 3 pH unit by using chloride, 1.5 with bromide and 1 pH unit with p-toluenesulfonate as counterions, respectively. Chloride was characterized by a larger inhomogeneity while p-toluenesulfonate gave homogeneity and high repeatability. The hexadecyltrimethylammonium p-toluenesulfonate was therefore chosen as the best surfactant. Leaching in alkaline medium was avoided by using the dodecyl moiety among three organic groups linked to the OrMoSil matrix (dodecyl, phenyl and methyl). Colorimetric sensor arrays made with these specifications remained stable and reversible for months.

C6–O-alkylated 7-deazainosine nucleoside analogues: Discovery of potent and selective anti-sleeping sickness agents

African trypanosomiasis, a deadly infectious disease caused by the protozoan Trypanosoma brucei spp., is spread to new hosts by bites of infected tsetse flies. Currently approved therapies all have their specific drawbacks, prompting a search for novel therapeutic agents. T. brucei lacks the enzymes necessary to forge the purine ring from amino acid precursors, rendering them dependent on the uptake and interconversion of host purines. This dependency renders analogues of purines and corresponding nucleosides an interesting source of potential anti-T. brucei agents. In this study, we synthesized and evaluated a series of 7-substituted 7-deazainosine derivatives and found that 6-O-alkylated analogues in particular showed highly promising in vitro activity with EC50 values in the mid-nanomolar range. SAR investigation of the O-alkyl chain showed that antitrypanosomal activity increased, and also cytotoxicity, with alkyl chain length, at least in the linear alkyl chain series. However, this could be attenuated by introducing a terminal branch point, resulting in the highly potent and selective analogues, 36, 37 and 38. No resistance related to transporter-mediated uptake could be identified, earmarking several of these analogues for further in vivo follow-up studies.

Stabilization of Grignard reagents by a pillar[5]arene host - Schlenk equilibria and Grignard reactions.

Grignard reagents (RMgX) are widely used in organic synthesis. However, these highly reactive compounds are supplied in inflammable solvents, which causes extra complexity in their transportation. Herein we report that Grignard reagents with linear alkyl chains can be entrapped and stabilized by the macrocyclic host pillar[5]arene while preserving their reactivity.

Hexahydrofarnesyl as an original bio-sourced alkyl chain for the preparation of glycosides surfactants with enhanced physicochemical properties.

Five new bio-based surfactants have been synthetized by coupling hexahydrofarnesol with mono and di-saccharides. Hexahydrofarnesol (3,7,11-trimethyl-dodecan-1-ol) is a by-product of the industrial production of farnesane, a sustainable aviation fuel obtained by a fermentation process from sugar feedstocks. Using hexahydrofarnesol as the lipophilic starting material allows obtaining 100% bio-based surfactants while valorizing an industrial by-product. Moreover, the C15-branched alkyl chain brings unique properties to the surfactants. This paper presents a physicochemical characterization of these new surfactants including their behaviors in water (water solubility, critical micellar concentration and surface tension) and in oil/water systems (interfacial tension against model oil and ternary phase behavior). Their hydrophilicities have been determined thanks to the PIT-slope method and compared to the ones of standard surfactants with linear alkyl chains, in order to distinguish the contributions of the sugar polar heads and of the branched hexahydrofarnesyl lipophilic chain. This novel class of surfactants combines the properties of sugar-based surfactants (low sensitivity to temperature and salinity, ability to form Winsor III microemulsion systems over a wide range of salinity), along with specificities linked to the branched alkyl chain (lower Krafft temperature, low surface tension).

The Synthesis, Self-Assembled Structures, and Microbicidal Activity of Cationic Gemini Surfactants with Branched Tridecyl Chains

Cationic gemini surfactants with polymethylene spacer and linear alkyl chains containing an even number of carbon atoms have been extensively studied in the recent past, with the emphasis put on the determination of their aggregation behaviour in aqueous solution and their biological properties. However, the information on the aggregation of branched gemini surfactants with an odd number of carbon atoms in their alkyl chains is only sparsely reported in the literature. To help cover this gap in the research of cationic gemini surfactants, a series of branched bisammonium cationic gemini surfactants with an odd number of carbon atoms in alkyl chains (tridecane-2-yl chains) and a polymethylene spacer with a variable length ranging from 3 to 12 carbon atoms have been synthesized and investigated. Critical micelle concentration, which was determined by three methods, was found to be in the order 10−4 mol/L. A comparison of the obtained data of the novel series of tridecyl chain geminis with those of gemini surfactants with dodecyl chains and an identical spacer structure revealed that structural differences between both series of gemini surfactants result in different aggregation and surface properties for surfactants with 6 and 8 methylene groups in the spacer (N,N’-bis(tridecane-2-yl)-N,N,N’,N’-tetramethylhexane-1,6-diaminium dibromide and N,N’-bis(tridecane-2-yl)-N,N,N’,N’-tetramethyloctane-1,8-diaminium dibromide) with the cmc values 8.2 × 10−4 mol/L and 6.5 × 10−4 mol/L, respectively, as determined by surface tension measurements. Particle size analysis showed the formation of small stable spherical micelles in the interval between 2.8 and 5 nm and with zeta potential around +50 mV, which are independent of surfactant concentration and increase with the increasing spacer length. Microbicidal activity of 13-s-13 gemini surfactants was found to be efficient against Gram-positive, Gram-negative bacteria and yeast.

Roles of linear alkyl chain alkylation on reinforcement of graphene based polypropylene nanocomposites

Alkylation becomes one of the alternatives to cope with mixing compatibility issue that arises during melt mixing between graphene oxide (GO) and polypropylene (PP) by grafting linear alkyl chains onto GO surface. Alkylated (AGO-PP) and alkylated reduced (ARGO-PP) nanocomposites showed improvement in tensile strength and Young’s modulus values than neat PP as nanofillers loadings increased. However, the elongation at break for both AGO-PP and ARGO-PP nanocomposites displayed lower values than neat PP. This indicates that the interfacial interaction between nanofillers and PP was enhanced. On the contrary, the decrement in elongation at break in both nanocomposites than neat PP was found which caused by the restriction of movement at the interface layer between nanofillers and PP matrix.

Exploring London Dispersion and Solvent Interactions at Alkyl-Alkyl Interfaces Using Azobenzene Switches.

Interactions on the molecular level control structure as well as function. Especially interfaces between innocent alkyl groups are hardly studied although they are of great importance in larger systems. Herein, London dispersion in conjunction with solvent interactions between linear alkyl chains was examined with an azobenzene‐based experimental setup. Alkyl chains in all meta positions of the azobenzene core were systematically elongated, and the change in rate for the thermally induced Z→E isomerization in n‐decane was determined. The stability of the Z‐isomer increased with longer chains and reached a maximum for n‐butyl groups. Further elongation led to faster isomerization. The origin of the intramolecular interactions was elaborated by various techniques, including 1H NOESY NMR spectroscopy. The results indicate that there are additional long‐range interactions between n‐alkyl chains with the opposite phenyl core in the Z‐state. These interactions are most likely dominated by attractive London dispersion. This work provides rare insight into the stabilizing contributions of highly flexible groups in an intra‐ as well as an intermolecular setting.

Sequence-Defined DNA Amphiphiles for Drug Delivery: Synthesis and Self-Assembly.

DNA nanotechnology has been used to create DNA containing nanostructures with well-defined sizes and shapes-properties highly applicable to drug delivery. By appending sequence-defined hydrophobic segments to DNA, DNA amphiphiles are created whose structures and modes of self-assembly mimic specialized biomacromolecules such as proteins. Automated, solid-phase DNA synthesis is a scalable and robust technique that has been optimized for several decades to make DNA oligomers. Using the same method and with minimal additional cost, DNA amphiphiles are synthesized with total control of monomer sequence. A variety of synthetic monomers may be appended to DNA depending on the application, but of particular interest is a linear twelve-carbon alkyl chain (C12). This chapter describes the synthesis, purification, and characterization of a DNA amphiphile consisting of twelve C12 units covalently attached to a 19mer DNA sequence (C1212-DNA19). These DNA amphiphiles self-assemble into spherical nanoparticles with potential applications for nucleic acid delivery. Methods common to chemistry and molecular biology are employed, including high-performance liquid chromatography and gel electrophoresis, as well as the more specialized imaging technique of atomic force microscopy.

Sequence-Defined Dendrons Dictate Supramolecular Cogwheel Assembly of Dendronized Perylene Bisimides.

A dendronized perylene bisimide (PBI) that self-organizes into hexagonal arrays of supramolecular double helices with identical single-crystal-like order that disregards chirality was recently reported. A cogwheel model of self-assembly that explains this process was proposed. Accessing the highly ordered cogwheel phase required very slow heating and cooling or extended periods of annealing. Analogous PBIs with linear alkyl chains did not exhibit the cogwheel assembly. Here a library of sequence-defined dendrons containing all possible compositions of linear and racemic alkyl chains was employed to construct self-assembling PBIs. Thermal and structural analysis of their assemblies by differential scanning calorimetry (DSC) and fiber X-ray diffraction (XRD) revealed that the incorporation of n-alkyl chains accelerates the formation of the high order cogwheel phase, rendering the previously invisible phase accessible under standard heating and cooling rates. Small changes to the primary structure, as constitutional isomerism, result in significant changes to macroscopic properties such as melting of the periodic array. This study demonstrated how changes to the sequence-defined primary structure, including the relocation of methyl groups between two constitutional isomers, dictate tertiary and quaternary structure in hierarchical assemblies. This led to the discovery of a sequence that self-organizes the cogwheel assembly much faster than even the corresponding homochiral compounds and demonstrated that defined-sequence, which has long been recognized as a determinant for the complex structure of biomacromolecules including proteins and nucleic acids, plays the same role also in supramolecular synthetic systems.

Effect of the chain lengthening on transport properties of imidazolium-based ionic liquids

The objective of this work is to study the effect of the lengthening of the linear alkyl chain of the imidazolium cation on some transport properties. We focused on hydrophobic ionic liquids based on bis(trifluoromethanesulfonyl)imide anion. Among the different properties, we measured at the viscosity and ionic conductivity of four different 1-alkyl-3-methylimidazolium ionic liquid in the temperature range between 293 and 333K. Thus, Electrochemical windows of these ionic liquids and the diffusion coefficient of ferrocenemethanol (FcMeOH) in the four ionic liquids were studied using cyclic voltammetry at 298K. The FcMeOH diffusion coefficient was found to be higher in shorter alkyl chain ionic liquids.

Solvent-Free Synthesis of Amidated Carboxymethyl Cellulose Derivatives: Effect on the Thermal Properties.

The present work explores the possibility of chemically modifying carboxymethyl cellulose (CMC), a widely diffused commercial cellulose ether, by grafting of hydrophobic moieties. Amidation of CMC, at high temperature and in heterogeneous conditions, was selected as synthetic tool for grafting on CMC a panel of commercially available amines (bearing long aliphatic chains, alkyl aromatic and heteroaromatic groups, more or less spaced from the cellulose backbone). The reaction was successfully carried out in absence of solvents, catalysts and coupling agents, providing a promising and more sustainable alternative to conventional amidation procedures. Relationships between the chemical structure of the obtained CMC derivatives and their thermal properties were carefully studied, with a particular attention to the thermal behavior. Grafting of aromatic and heteroaromatic alkyl amines, presenting a linear alkyl chain between CMC backbone and a terminal bulky moiety, allowed for efficiently separating the polysaccharide chains, improving their mobility and resulting in a consequent lowering of the glass transition temperature (Tg). The Tg values obtained (90–147 °C) were found to be closely dependent on both the size of the aliphatic spacer, the structure of the aromatic ring and the extent of amidation.

Retooling Asymmetric Conjugate Additions for Sterically Demanding Substrates with an Iterative Data-Driven Approach.

The development of catalytic enantioselective methods is routinely carried out using easily accessible and prototypical substrates. This approach to reaction development often yields asymmetric methods that perform poorly using substrates that are sterically or electronically dissimilar to those used during the reaction optimization campaign. Consequently, expanding the scope of previously optimized catalytic asymmetric reactions to include more challenging substrates is decidedly nontrivial. Here, we address this challenge through the development of a systematic workflow to broaden the applicability and reliability of asymmetric conjugate additions to substrates conventionally regarded as sterically and electronically demanding. The copper-catalyzed asymmetric conjugate addition of alkylzirconium nucleophiles to form tertiary centers, although successful for linear alkyl chains, fails for more sterically demanding linear α,β-unsaturated ketones. Key to adapting this method to obtain high enantioselectivity was the synthesis of modified phosphoramidite ligands, designed using quantitative structure–selectivity relationships (QSSRs). Iterative rounds of model construction and ligand synthesis were executed in parallel to evaluate the performance of 20 chiral ligands. The copper-catalyzed asymmetric addition is now more broadly applicable, even tolerating linear enones bearing tert-butyl β-substituents. The presence of common functional groups is tolerated in both nucleophiles and electrophiles, giving up to 99% yield and 95% ee across 20 examples.

The stability and surface activity of environmentally responsive surface-modified silica nanoparticles: the importance of hydrophobicity

In this study, the effect of hydrophobicity of environmentally responsive surface-modified silica nanoparticles on the stability and surface activity of the nanoparticles is examined. To this end, n-propyl, n-hexyl, or n-octyl chains and methoxy poly(ethylene glycol) chains at various quantities were coated covalently on the surface of silica nanoparticles to regulate the hydrophobicity of the responsive nanoparticles. Various experimental tools such as stability analysis, interfacial-tension and contact-angle measurements, and emulsion formation were performed to investigate the effect of hydrophobicity. It became evident that the presence of the hydrophobic agents influences considerably the stability and surface activity of the responsive nanoparticles. To achieve the most stable nanofluids and the largest reduction in the oil-water interfacial tension, the hydrophobicity should be tuned at an optimum value, which would be at a lower amount with longer linear-alkyl chains. While our solely hydrophobic- or hydrophilic-silica nanofluids do not emulsify with n-hexane, the ability of the responsive-silica nanofluids to emulsify with n-hexane is more, with the ability being largely dependent on the length of the linear-alkyl chains. Furthermore, increasing the hydrophobicity has adverse effect on the wettability-alteration ability of the responsive nanoparticles.

The side chain effects on TPD-based copolymers: the linear chain leads to a higher jsc

Alkyl substituents appended to polymers play the determining role on self-assembly and film-forming properties, and on device performance. In this work, we highlight the effects of the linear and branched flexible chains appended to the acceptor moiety (A) in D-A type copolymers. Two thieno[3,4-c]-pyrrole-4,6-dione (TPD) based copolymers PT1 and PT2 with different alkyl chains, were designed and synthesized. By comparison their UV-vis absorptions, HOMO/LUMO energy levels, as well as the characters in polymer solar cells, the influences of alkyl chains were investigated. Both copolymers showed molecular weights of 21 kDa and similar optical properties with a medium band gap of 1.93 eV, while PT2 with the branched chain exhibited a lower HOMO than that of PT1 (−5.43 vs − 5.37 eV). In bulk heterojunction (BHJ) solar cells, PT1 with a linear chain presented a short circuit current (Jsc) of 6.76 mA cm‒2, open circuit voltage (Voc) of 0.89 V and power conversion efficiency (PCE) of 2.92%. To the contrary, PT2 showed a Jsc of 3.53 mA cm‒2, Voc of 0.99 V, delivering a relatively lower PCE of 2.05%. The result indicates that appending a linear alkyl chain to the TPD unit could sufficient enhance the Jsc value of the related polymer.

Organogel Formation Rationalized by Hansen Solubility Parameters: Shift of the Gelation Sphere with the Gelator Structure.

To rationalize how the gelation ability of a low molecular weight gelator is influenced by its molecular structure, we performed extensive solubility tests of a group of thiazole-based gelators and made use of Hansen solubility parameter formalism. We observe that the increase of a linear alkyl chain in these gelators promotes an increase of the radius of the gelation sphere as well as a gradual shift of its center to lower values of the polar (δP) and hydrogen bonding (δH) components. The molecular packing within the fibers and the crystal habit were determined by a combination of X-ray diffraction and molecular modeling. We attribute the gradual and linear shift of the gelation sphere to the fact that all of the studied gelators share the same molecular packing, so that an increasing length of the alkyl chain reduces the proportion of polar groups at the surface, resulting in a gradual increase in the contact between apolar parts of the fiber and the solvent.

Quaternary Ammonium Compounds: Simple in Structure, Complex in Application.

Quaternary ammonium compounds, referred to as QACs, are cationic substances with a structure on the edge of organic and inorganic chemistry and unique physicochemical properties. The purpose of the present work is to introduce QACs and their wide application potential. Fundamental properties, methods of preparation, and utilization in organic synthesis are reviewed. Modern applications and the use of QACs as reactive substrates, reagents, phase-transfer catalysts, ionic liquids, electrolytes, frameworks, surfactants, herbicides, and antimicrobials are further covered. A brief discussion of the health and environmental impact of QACs is also provided. The emphasis is largely on tetraalkylammonium compounds bearing linear alkyl chains.

Open atmospheric processed perovskite solar cells using dopant-free, highly hydrophobic hole-transporting materials: Influence of thiophene and selenophene π-spacers on charge transport and recombination properties

We have synthesized three donor-π-acceptor polymers by crosslinking 4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b'] and pyrrolo[3,4-c]pyrrole-1,3-dione with thiophene, thieno[3,2-b]thiophene, selenophene as π-spacer. These polymers have been integrated successfully as dopant-free hole-transporting materials in fully open atmosphere solution-processed lead halide perovskite solar cells. Due to the synergistic impact of linear and long alkyl chains with different π-spacers, these hole transporters retard interfacial charge recombination and afford rich solubility and morphology resulting long carrier lifetime with uniform film coverage. In addition, these hole transporters possess a deeper highest occupied molecular orbitals (−5.40, −5.37 and −5.42 eV) and suitable over potential with perovskite valence band (−5.43 eV), favorable for efficient hole extraction. Further, the large number of S-based heterocycles helps to strengthen the interaction of the perovskite and hole transporting layer interface and high hydrophobicity (∼104°) facilitate enhanced stability with insignificant hysteresis. As a result, the power conversion efficiency has reached 14% under AM1.5 G without any additives in fully open atmospheric conditions. Our findings highlight the better energy transfer capabilities of additive-free hole transporters as a promising candidate for developing stable PSCs in the open air.

Self‐Assembly of Polyethylene Glycol Ether Surfactants in Aqueous Solutions: The Effect of Linker between Alkyl and Ethoxylate

AbstractThe aqueous self‐assembly behavior of two homologous series of poly(ethylene oxide) (PEO)‐containing nonionic surfactants based on a C10‐Guerbet hydrophobe is reported. The two families of surfactants, alkyl ethoxylates and alkyl alkoxylates, are commercially available from BASF under the trade name Lutensol® XP‐series and XL‐series, respectively. The latter incorporate propylene oxide (PO) units in the surfactant chain. Dye solubilization was used to determine the critical micellization concentration (CMC) of each surfactant at 22 and 50 °C. The PO‐containing alkyl alkoxylates displayed lower CMC values, which were also more sensitive to temperature. The Gibbs free energy, enthalpy, and entropy of micellization were computed from the CMC data and used to identify the contribution of each surfactant moiety (alkyl chain, PO unit, and PEO block) in controlling the CMC. The micellization properties are compared with compositionally similar surfactants with linear alkyl chains, yielding information about the effects of the Guerbet alkyl chain on micellization. Isothermal titration calorimetry was also used to characterize the CMC and enthalpy of micellization which generally compare well with the dye solubilization results. Cloud point data reveal nonmonotonic relationships for the Lutensol® surfactants with respect to composition, unlike linear alkyl chain surfactants. Finally, dilute solution viscosity measurements performed on some Lutensol® surfactants show a change in the slope, suggesting a structural change that tends to be more pronounced for surfactants with longer PEO blocks. The data presented herein enhance the understanding of surfactant structure–property relationships required for industrial formulation.

Amidophosphonate ligands as cerium extractants in supercritical CO2

Industrial-scale rare earth extraction is typically performed by liquid-liquid extraction with large amounts of solvents, acids and organophosphorus ligands. An alternative is to use these extractants in supercritical CO2 (SC-CO2), where the crucial operating parameter is their solubility. Different molecules with amidophosphonate backbones have been synthesized and investigated to improve their solubility in SC-CO2 and their capacity to extract cerium. The CO2-philicity of these extractants was adjusted by attaching branched or linear alkyl chains with four, six and eight carbons. Using a dynamic gravimetric setup, the solubility and cerium extraction capacity of these molecules were measured to vary from 1.56 to 2.47 47 mmolligand.molCO2−1 and 0.25 to 0.46 mmolCe.molligand−1, respectively. The two properties were correlated and in both cases the highest values were obtained with a diisobutylamine chain. Solubility measurements between 313 and 331 K and between 13 and 28 MPa shows that optimal condition is (320 K ; 28 MPa).