Flexible Alkyl Chains Research Articles

Molecular Tetrahedrons as Selective and Efficient Ion Transporters via a Two-Station Swing-Relay Mechanism

The traditional approach to utilizing an ion-relay mechanism for ion transport requires three or more ion-relay stations. Herein, we describe a novel strategy, incorporating a swing action to reali...

Ab-Initio Investigation on Dye Conformer Structures and the Interplay between Conformation and Multilayer Aggregation on TiO2 toward Solar Cell Application

Self-assembled monolayers (SAMs) have many applications such as the solar cells and water-spitting systems, which mimic the photosynthetic process in the plants and serve as an effective alternative to provide clean energy from the sun. Dye molecules that are self-assembled on semiconductor substrates (usually TiO2) play essential roles in the photon-to-electron conversion process. However, many structural aspects and structure-properties of dyes in SAMs remain elusive, and the conformer structures of dye molecules and their effects on the properties of SAMs are frequently neglected. In fact, dye molecules can adopt multiple conformer structures on the TiO2 substrate due to the existence of flexible alkyl chains and non-rigid backbones, which might affect the structures and properties of the dye-sensitized systems. In this research, we investigate the structures and effects of different conformers via the first principles calculations, employing an organic azo dye 4-[2-[4-(diethyl-amino)phenyl]diazenyl]-benzoic acid, which combines good transparency, aesthetic quality and electricity-generation properties. We find that various conformers of the organic dye could reside stably on the TiO2 substrate, and the conformer effects are especially dominant when the dye aggregation model is considered. The relationship between the azo dye conformation and the azo dye aggregation is explained. Our calculations demonstrate that including the conformer effects leads to diverse structures and properties of the azo dye/TiO2 systems, which could be important for the devices containing the dye/TiO2 systems such as the dye-sensitized solar cells, smart windows and dye-sensitized water splitting systems.

One-Pot Synthesis of Proton Exchange Membranes from Anion Exchange Membrane Precursors.

Proton exchange membranes (PEMs) play a critical role in many electrochemical devices that could solve the shortcomings of current energy storage and conversion systems. Hydrocarbon-based PEMs are an attractive alternative for replacing the state-of-the-art perfluorosulfonic acid PEMs; however, synthetic routes are generally limited to sulfonation of aromatic units (pre- or postpolymerization functionalization). Here we disclose a facile and scalable one-pot synthetic method of converting an alkyl halide functionality to a sulfonate in polymer systems. With this method, sulfonated hydrocarbon PEMs can be conveniently prepared from a precursor polymer of anion exchange membranes which have recently experienced significant advances. Polyphenylene type PEMs (BPSA and mTPSA in this report) were generated in one-pot SN2 reaction of bromoalkyl side chains of polymers followed by oxidation. These PEMs showed excellent proton conductivity with BPSA showing 250 mS/cm in water at 80 °C, nearly 1.5 times higher than that of Nafion 212. Furthermore, the separation of the sulfonic acid group from the rigid backbone with a flexible alkyl chain mitigates excessive water uptake and in-plane swelling ratio of the polymer, despite having a high ion exchange capacity of 2.6 mequiv/g. Oxidative stability was also shown to be superior for hydrocarbon-based PEMs with negligible changes in mass, NMR, and proton conductivity.

Synthesis, characterization, thermal and band gap values of poly(azomethine-ether)s containing aromatic and aliphatic group

In this study, we proposed to synthesize soluble poly(azomethine-ether)s derivatives containing aromatic rings and long alkyl groups. For this reason, long alkyl groups containing double bromide or chloride atoms were chosen to synthesize diamines monomers (DIAMs). Seven different poly(azomethine-ether)s were synthesized from the condensation reaction of DIAMs with 4,4′-[1,4-phenylenebis(methyleneoxy)]dibenzaldehyde (PBMODB). The structures of compounds were confirmed by FT-IR, UV–Vis, 1H-NMR and 13C-NMR techniques. The molecular weight distributions of synthesized poly(azomethine-ether)s were determined by size exclusion chromatography (SEC). The synthesized compounds were characterized by solubility tests, TG-DTA and DSC. Optical band gaps of poly(azomethine-ether)s (Eg) were also calculated by UV–Vis spectrophotometer. Electrical conductivities of synthesized poly(azomethine-ether)s were measured by four-point probe technique using a Keithley 2400 electrometer. It was stressed that synthesized poly(azomethine-ether)s were found to be insulators which have a potential for electronic and optoelectronic applications, with fairly high band gaps. Thermal stability properties of synthesized poly(azomethine-ether)s were found to be stable up to 300 °C. The chars of them were observed between 33 and 45% at 1000 °C. Poly(azomethine-ether)s containing flexible ether groups and long alkyl chains showed good solubility in aprotic organic solvents.

Woven Polymer Networks via the Topological Transformation of a [2]Catenane.

Weaving technology has been widely used to manufacture macroscopic fabrics to meet the artistic and practical needs of humanity for thousands of years. However, the fabrication of molecular fabrics with fascinating topologies and unique mechanical properties represents a significant challenge. Herein, we describe a topological transformation strategy to construct woven polymer networks (WPNs) at the molecular level via ring-opening metathesis polymerization (ROMP) of a zinc-template [2]catenane. The key feature of this approach is the exploitation of the pre-existing catenane crossing points that maintain the dense woven structure and the flexible alkyl chains on the [2]catenane that synergistically work with the crossing points to modulate the physicochemical and mechanical properties of the woven materials. As a result, the WPN possesses a certain degree of flexibility and stretchability, as well as high thermostability and mechanical robustness. Furthermore, we could remove the zinc ions to endow the WPN with more degrees of freedom and then enhance its mechanical behaviors by remetalation. This study not only provides a novel strategy toward woven materials with intriguing structural features and emergent mechanical adaptivities, but also highlights that mechanically interlocked molecules could offer unique opportunities for the construction of smart supramolecular materials with peculiar interlaced topologies at the molecular scale.

Enhanced performances of fully solution-processed OLEDs via introducing flexible chains into thermally cross-linked thermally activated delayed fluorescent materials

Solution-processable thermally activated delayed fluorescent (TADF) materials have received tremendous attentions due to high exciton utilization, easily scalable large-scale applications. Herein, Thermal cross-linking technology is used to process carbazolyl cyanobenzene (CzCB) derivatives to construct solution-processable thin film networks. We synthesized two novel materials 3CzCN-DV and 3CzCN-O-DV, which could be tightly or loosely cross-linked through varying introduction of flexible alkyl chains. For 3CzCN-O-DV with core-dendron structure, thermal cross-linking in the dendrons was found to preserve the emissive color integrity compared to 3CzCN-DV and allowed for facile solution processing owing to more uniform film morphology. Furthermore, the decreased cross-linking temperature was shown to be advantageous for fabrication of solution-processed OLEDs whose performance was far beyond cross-linked devices based on 3CzCN-DV. This provides a novel method for systematic design of low-temperature cross-linkable luminescent materials, which pave the way for fabrication of fully solution-processed OLEDs that require solution-processable multilayer thin films.

Self-assembly, phase behaviour and ion-conducting property of pyridinium-based ionic liquid-crystalline oligomers

ABSTRACT Series of oligomeric ionic liquid crystals (OILCs) based on various anions including bromide (Br−), tetrafluoroborate (BF4 −), dodecylbenzenesulphonate (A-SO3 −) and (+)-10-camphorsulphonate (D-SO3 −) are synthesised by use of pyridine-containing monomers, terminal bromo-substituted alkanes and anion replacement reagents. The effect of anions on the chemical structure, liquid-crystalline behaviour, and ionic conductivity is investigated. The OILCs show various mesophases including smectic, hexagonal columnar and bicontinuous cubic phase due to the change in anions. These mesophase types are determined by two incompatible segments derived from ionic mesogens and flexible alkyl chains in the microstructure. For the OILCs based on A-SO3 − and D-SO3 − anions, a curvature of the interfaces between the layers arises due to the increased size of one segment, resulting in columnar and cubic mesophases. The ionic conductivity is investigated in the way that a lithium ion solution passing through the oriented OILC films at room temperature. For the OILC films with various anions, ionic conductivities of the measuring system increase a little in the order A-SO3 − > D-SO3 − > BF4 −> Br−. The values based on A-SO3− anion films show nearly twofold increase compared with those based on Br- anions, which can be attributed to the effects of both ion migration and ionic channels in the microstructures.

Influence of spacer in the formation of nanorings by templateless electropolymerization

In this original work, we want to control the shape of the resulting porous structures by templateless electropolymerization, by adjusting the spacer (flexible alkyl chains or rigid aromatic groups) between thieno[3,4-b]thiophene and carbazole used as the monomer and the substituent, respectively. A huge change is especially observed from ribbon-like structures to nanorings as the alkyl spacer increases. The presence of a significant amount of water is necessary for the formation of these porous structures because it allows releasing a high amount of gas bubbles. The size and number of nanorings are dependent on both the alkyl spacer and electrochemical parameters such as the number of deposition scans. These surfaces could be used in the future in various potential applications such as in water harvesting, oil/water separation membranes, optical devices, sensors or photocatalysis.

Elevating the triplet level of carbazolyl benzonitrile-based dendritic hosts by suppressing intramolecular charge transfer for solution-processed blue thermally activated delayed fluorescence OLEDs

Realizing appropriate and excellent solution-processed thermally activated delayed fluorescence host materials is of great consequence to the development of low-cost, large-area OLED displays, as the doped devices mostly yield better efficiency than the undoped devices. Herein, two carbazolyl benzonitrile-based dendritic host materials were designed and synthesized by inserting phenyl bridges to 2,4,6-tri(9H-carbazol-9-yl) benzonitrile (3CzBN) and encapsulating flexible alkyl chains. The phenyl bridge extended the backbone of acceptor unit and donor unit respectively, allowed for a better separation of the HOMO and LUMO orbital and weakened intramolecular charge transfer, which endowed high triplet level of 3.01 eV, 2.85 eV for 3CzPhCN-O-Cz and 3PhCzCN-O-Cz. The introduction of the peripheral alkyl chains resulted in better solubility and film-forming ability. These features made the host materials suitable for fabricating blue solution-processed devices. The experimental results proved that the device performance was better when the phenyl bridge was inserted between the accepter unit and the center benzene ring than when it was introduced between the donor unit and the center benzene ring, which paved the way toward achieving high triplet level host materials for solution-processed OLEDs.

Enhanced water solubility, stability, and in vitro antitumor activity of ferulic acid by chemical conjugation with amino-β-cyclodextrins

To improve the water solubility, stability and bioactivity of ferulic acid (FA), a series of conjugates (FA-NH-CD, FA-EDA-CD, and FA-HDA-CD) were synthesized by bonding FA with different amino-β-cyclodextrins (amino-β-CD, ACDs) through amidation reactions. The structures of the conjugates were characterized by nuclear magnetic resonance, high-resolution mass spectra, scanning electron microscope, and X-ray diffraction, and FA was successfully linked with the ACDs in 1:1 molar ratios. The study of self-assembling behaviors of the conjugates indicated that FA-NH-CD with short and rigid alkyl chains displayed an intermolecular assembly mode in which the appended FA was accommodated into the cavities of other ACDs, while FA-EDA-CD and FA-HDA-CD with flexible alkyl chains could form self-inclusion structures. The solubility of FA-EDA-CD and FA-HDA-CD was remarkably enhanced, which also supported the formation of self-inclusion complexes. Moreover, all the conjugates exhibited improved stability and in vitro cytotoxicity against HepG2 cells compared with the parent FA, suggesting that conjugation with ACDs offered a promising way in the exploitation and utilization of insoluble natural products such as FA.

Synthesis and characterization of photoactive columnar liquid crystals containing azobenzene and quinoxaline moieties

Abstract In this study, we report the synthesis and characterization of thermal and optical properties of photoactive molecules containing both quinoxaline and azobenzene moieties. Two series of molecules in which the quinoxaline is connected to the azobenzene without a flexible alkyl chain were accessed via esterification reactions between the 4-(hydroxy)-4′-substituted-azobenzenes (substituents on azobenzene ring: -ODecyl, -NO2, -Cl, -OMe and -O(2-Et-Hexyl)) and 2,3-bis(4-methoxyphenyl)quinoxaline-6-carboxylic acid or 2,3-bis(3,4-bis(dodecyloxy)phenyl)quinoxaline-6-carboxylic acid. The other two series of molecules containing an alkyl chain spacer of six carbon atoms between both aromatic systems were obtained via O-alkylation reactions of the same quinoxaline acids mentioned above with 4-(6-bromohexyloxy)-4′-substituted-azobenzenes. The absence of long alkyl chains on the quinoxaline side led to glassy materials and some of them showed a calamitic type mesophase, mostly monotropic. On the other hand, a considerable increase of side-chain density in compounds containing the long alkyl chains on the quinoxaline ring gave materials with hexagonal columnar phases (Colh). In these materials, the incorporation of small polar substituents such as nitro or chlorine on the azobenzene system increased the stability of the Colh. The presence of alkyl chain spacer was responsible for lowering the melting points and room temperature Colh phases were observed for some of these compounds. The molecular arrangement of molecules on the Colh is different from the analogous without the alkyl spacer between the aromatic systems. The absorption and fluorescence properties, as well as the photoisomerization of the azo group in solution were investigated. Colh phase was able to be destroyed under UV light and this process was found to be reversible.

Transition in nanoscale electrical conductivity in the Langmuir-Blodgett film of a novel liquid crystalline oligomer

We have studied the nanoscale electrical conductivity of a monolayer film of a novel star shaped liquid crystalline molecule, hexatriphenylene substituted anthraquinone (AQD6). The molecule has a central core of electron deficient anthraquinone moiety connected to six electron rich triphenylene moieties by flexible alkyl chains. The monolayer formed at air-water interface was transferred onto the solid substrates by Langmuir-Blodgett (LB) technique and its surface topography was imaged using an atomic force microscope (AFM). The limiting area obtained from the surface pressure-area per molecule isotherm and the topography of the AFM images suggest that the anthraquinone moiety of the AQD6 molecule is organized in face-on configuration on the substrate and the triphenylene moieties are in edge-on configuration extended away from the substrate. We have studied the electrical conductivity of the AQD6 monolayer deposited on gold coated silicon substrate using a current sensing AFM. Analysis of current (I) − voltage (V) characteristics of the metal-monolayer film-metal junction showed a transition from direct tunneling to an injection tunneling. Further, we have estimated the barrier height and the effective mass of electron in the metal-monolayer film-metal junction.

Supramolecular organic frameworks with ultralong phosphorescence via breaking π-Conjugated structures

Development of crystalline porous materials with luminescent properties have gradually attracted attention for their potential applications in drug delivery, bioimaging, photoelectronic and so on. To date, it is a formidable challenge to rationally design porous phosphorescent materials. Herein, we have reported a chemical strategy of breaking π-conjugated structures of phosphorescent molecules by alkyl chain to achieve supramolecular organic framework (SOFs) with visible ultralong phosphorescence (lifetime > 600 ms). The molecules having broken π-conjugation by flexible alkyl chain will be beneficial to produce short-range π-π stacking for forming luminescent SOFs. Effective π-π stacking between chromophores stabilized triplet excitons to contribute to ultra-long phosphorescence. This work demonstrates a new approach to design porus materials with ultralong phosphorescence and will expand the potential applications of organic phosphorescent crystals with diverse pores.

A Facilely Synthesized Dual-State Emission Platform for Picric Acid Detection and Latent Fingerprint Visualization.

To achieve a highly efficient, dual-state emission platform for picric acid (PA) detection and latent fingerprint (LFP) visualization, flexible alkyl chains have been facilely attached to the commercial organic dye 3,4,9,10-perylenetetracarboxylic dianhydride to provide the target perylenetetracarboxylate molecules PTCA-C4, PTCA-C6, and PTCA-C12. Interestingly, all these molecules exhibited impressive fluorescence characteristics with high photoluminescence quantum yields (PLQYs) of around 93.0 % in dilute solution. Also, emissive features were observed in the solid state because close molecular packing is prevented by the alkyl chains, especially for PTCA-C6, which has a high PLQY value of 49.0 %. Benefiting from its impressive fluorescence performance in both solution and as aggregates, PTCA-C6 was used as a dual-state emission platform for PA detection and also LFP visualization. For example, double-responsive fluorescence quenching in solution was observed in PA detection studies, resulting in high quenching constants (KSV ) and also low limit-of-detection values. Furthermore, the fingerprint powder based on PTCA-C6 also presented an impressive performance on various substrates in terms of fluorescence intensity and resolution, clearly providing the specific fine details of latent fingerprints. These results demonstrate that the facilely synthesized PTCA-C6 with efficient dual-state emission exhibits great potential in the real-world applications of PA detection and LFP visualization.

2D Conjugated Polyelectrolytes Possessing Identical Backbone with Active-Layer Polymer as Cathode Interlayer for Organic Solar Cells.

A 2D conjugated polyelectrolyte (CPE), PBDTTh-TT-NBr, having the same backbone as the highly efficient donor polymer PTB7-Th and the quaternary ammonium pendant, is synthesized as a cathode interlayer (CIL) material for PTB7-Th-based fullerene and non-fullerene solar cells. The quaternary ammonium group is connected to the 2D conjugated backbone by a long, flexible alkyl chain, facilitating the modification of cathode via forming interface dipoles. Moreover, compared with another CPE analogue to PTB7, PBDT-TT-NBr, without the 2D conjugated backbone, the PBDTTh-TT-NBr presents a higher similarity in polymer structure to the donor polymer PTB7-Th. This feature makes it more compatible with the PTB7-Th-based active-layer film, improving the electron transport. With the PBDTTh-TT-NBr as the CIL, devices afford higher performances than those using the PBDT-TT-NBr in both fullerene and non-fullerene systems. This work offers guidance on choosing the CIL material that ought to possess a highly similar structure to the active-layer component.

Conformational impact of aliphatic side chains in local anaesthetics: benzocaine, butamben and isobutamben.

We studied the impact of aliphatic side chains on the stability and conformational landscape of the local anaesthetics benzocaine, butamben and isobutamben, combining high-resolution rotational spectroscopy in the microwave and millimetre regions and molecular modelling. The study reveals the connections between alkyl chain flexibility and molecular conformations.

Highly Loaded Cellulose/Poly (butylene succinate) Sustainable Composites for Woody-Like Advanced Materials Application.

We report the manufacturing and characterization of poly (butylene succinate) (PBS) and micro cellulose (MCC) woody-like composites. These composites can be applied as a sustainable woody-like composite alternative to conventional fossil polymer-based wood-plastic composites (WPC). The PBS/MCC composites were prepared by using a melt blending of 70 wt% of MCC processed from bleached softwood. MCC was modified to enhance dispersion and compatibility by way of carbodiimide (CDI), polyhydroxy amides (PHA), alkyl ester (EST), (3-Aminopropyl) trimethoxysilane (APTMS), maleic acid anhydride (MAH), and polymeric diphenylmethane diisocyanate (PMDI). The addition of filler into PBS led to a 4.5-fold improvement of Young’s modulus E for the MCC composite, in comparison to neat PBS. The 1.6-fold increase of E was obtained for CDI modified composition in comparison to the unmodified MCC composite. At room temperature, the storage modulus E′ was found to improve by almost 4-fold for the APTMS composite. The EST composite showed a pronounced enhancement in viscoelasticity properties due to the introduction of flexible long alkyl chains in comparison to other compositions. The glass transition temperature was directly affected by the composition and its value was −15 °C for PBS, −30 °C for EST, and −10 °C for MAH composites. FTIR indicated the generation of strong bonding between the polymer and cellulose components in the composite. Scanning electron microscopy analysis evidenced the agglomeration of the MCC in the PBS/MCC composites. PMDI, APTMS, and CDI composites were characterized by the uniform dispersion of MCC particles and a decrease of polymer crystallinity. MCC chemical modification induced the enhancement of the thermal stability of MCC composites.

Deep-Red Fluorescent Organic Nanoparticles with High Brightness and Photostability for Super-Resolution in Vitro and in Vivo Imaging Using STED Nanoscopy.

To achieve super-resolution imaging in biological research using stimulated emission depletion (STED) nanoscopy, organic luminescent materials and their corresponding fluorescent nanoparticles with high brightness and photostability are of great significance. Herein, donor-acceptor-typed DBTBT-4C8 bearing flexible alkyl chains was developed, not only to afford deep-red emission from 600 to 800 nm but also to obtain high fluorescent brightness with the absolute photoluminescence quantum yields of 25%. After that, well-defined and monodispersed spherical nanoparticles using DBTBT-4C8 with bright emission, excellent biocompatibility, and photostability, which can easily mix with amphipathic block polymers, were then produced for super-resolution in vitro and in vivo imaging using STED nanoscopy. The observations showed that in contrast to confocal microscopy with a full width at half-maximum (FWHM) value of ≈400 nm, superior resolution with a significantly improved FWHM value of only 100 nm was achieved in biomedical cell imaging, which was also used to reconstruct three-dimensional images of stained HeLa cells at an ultrahigh resolution. More importantly, by using the prepared fluorescent organic nanoparticles (FONPs) in STED nanoscopy, in vivo imaging in glass catfish with largely enhanced resolution was also successfully achieved, demonstrating that these developed deep-red FONPs here are highly suitable for super-resolution in vitro and in vivo imaging using STED nanoscopy.

Temperature evolution of the bulk nano-structure in a homologous series of room temperature ionic liquids

We present x-ray scattering measurements on a homologous series of a model room-temperature ionic liquid (RTIL), [CnC1mim][NTf2]. The measurements span a broad range of cation alkyl chain lengths, n = 4 − 22, and temperatures, T = 293 − 393 K, not hitherto available for any RTIL. Thus, they support significantly deeper insights into the RTILs' structure. Resolution of the scattering curves into individual lines yields an accurate description of the RTILs' nanoscale-segregated structure, and its n and T evolution. The results strongly support a lateral packing of partly-overlapping, interdigitated, flexible alkyl chains within the segregated apolar domains. The domain thickness, and effective chain and overlap lengths, are determined for all n and T. These reveal that the n- and T-increasing overlap drives the observed counterintuitive layer-spacing contraction upon increasing T, while the effective chain lengths hardly vary. An overlap length beyond 5–6 methylenes is found to accelerate the overlap's increase rate with n and T. This marks n ≈ 12 as the borderline between slow and fast overlap-increase regimes. Finally, the results highlight the importance of the reduced temperature, t = (T − Tm)/Tm, the “distance” from the melting temperature Tm, for comparing the variation with n of the structure's T-evolution.

Synthesis, anti-plasmodial and cytotoxic evaluation of 1H-1,2,3-triazole/acyl hydrazide integrated tetrahydro-β-carboline-4-aminoquinoline conjugates

A series of 1H-1,2,3-triazole/acylhydrazide-tethered tetrahydro-β-carboline-4-aminoquinoline conjugates was synthesized with an aim to study their anti-plasmodial structure-activity relationship. The presence of 1H-1,2,3-triazole-core along with a flexible alkyl chain length on aminoquinoline core has favourable influence on the anti-plasmodial activity against Chloroquine-resistant W2 strain of P. falciparum while the introduction of hydrazine core not only diminished the activities but also resulted in increased cytotoxicity against mammalian Vero cells.