Strong Polar Groups Research Articles

Geometric structures, vibrational spectroscopic and global reactivity descriptors of nematogens containing strong polar group- A comparative analysis using DFT, HF and MP2 methods

The present article deals with the geometric structures and vibrational spectroscopic studies of 4’-n-alkyl-4-cyanobiphenyl (nCB), with propyl (3CB), pentyl (5CB), and heptyl (7CB), strong polar groups that are of commercial and application interest. The computations have been carried out using the Density Functional Becke3-Lee-Yang-Parr (B3LYP) level with the basis set 6-31++G(d.p), Hartree Fock (HF), and second order Moller-Plesset perturbation (MP2) theory with the same basis set. The observed vibrational spectra has been resolved and assigned in detail for comparision with molecules. These results indicate that DFT, HF, and MP2 values are slightly different at three levels. Further, the global reactivity descriptors such as HOMO (EHOMO), LUMO (ELUMO), energy gap (Eg), ionization energy (I), electron affinity (A), electro negativity (χ), chemical hardness (η), electronic chemical potential (μ), electrophilicity index (ω), and softness (S) for higher homologous, namely; 7CB has been reported. It has been observed that the substitution of strong polar group with increment in alkyl chain length has profound control on vibrational bands that makes it possible to identify the liquid crystal phases and calculate the orientational order parameters.

Poly(arylene ether nitrile) anion exchange membranes with dense flexible ionic side chain for fuel cells

To resolve the excessive swelling and undesirable alkaline stability of densely functionalized type anion exchange membranes (AEMs) and to obtain high performance AEMs, quaternary ammonium-functionalized poly(arylene ether nitrile) (QPAEN) AEMs with dense flexible ionic side chain are prepared via nucleophilic substitution polycondensation, demethylation reaction and Williamson reaction. The densely pendent flexible long side chains with QA groups at the end provide a high conductivity and the introduced strong polar nitrile groups result in lower water uptake, excellent dimensional stability and strong alkali resistance of the AEMs. The QPAEN membrane with IEC of 1.78meqg−1 exhibits the highest hydroxide conductivity of 116.0 mScm−1 at 80°C. The high conductivity is attributed to the well-developed hydrophilic/hydrophobic phase separated morphology that constructs efficient ion conducting pathways in the membranes. High retention of hydroxide conductivity (80.2%) and ionic exchange capacity (IEC) (86.0%) was observed for the QPAEN-0.4 membrane in the degradation test in a 2M aqueous KOH solution for 480h. Moreover, the single cell performance of the as-prepared AEMs was greatly enhanced and a high peak power density of 251.3mWcm−2 at 60°C was observed.

Silk-sericin degummed wastewater solution-derived and nitrogen enriched porous carbon nanosheets for robust biological imaging of stem cells

Appreciated raw materials like silk-sericin can be recovered from silk-textile industrial waste for the production of novel functional nanomaterials. In this study, highly fluorescent sericin based carbon nanosheets (SCN) were produced from industrial wastewater containing silk-sericin as a precursor, and was applied as bio-imaging application for oral fat stem cells. A simple one-pot, hydrothermal carbonization method was used to produce SCN at a 180°C. The obtained hydrothermal carbons exhibited strong fluorescence properties due to the presence of strong polar groups, such as carboxyl, amino and amide groups in the surface. Heteroatom functionalization of the SCN leads to the property of fluorescence due to enriched nitrogen and was confirmed by X-ray photoelectron and Fourier transform infrared spectroscopy. The plate-like morphology of SCN about 35nm in size was evaluated by transmission electron microscopy. The carbon 13 nuclear magnetic resonance results revealed that nano-sized fluorescent SCN formed during carbonization and functionalization occurred through dehydration of the sericin protein. Moreover, the prepared SCNs demonstrated low toxicity and their suitability for bio-imaging applications was demonstrated to the oral fat stem cells. Overall, sericin degumming wastewater from the silk textile industry can be utilized for the production of SCNs for stem cells bio-imaging applications.

Design, preparation and properties of novel flame retardant thermosetting vinyl ester copolymers based on castor oil and industrial dipentene

Abstract A novel bio-based flame-retardant thermosetting vinyl ester resin monomer was synthesized from castor oil. The chemical structures of the monomer was characterized by FTIR and 1H-NMR. In order to improve its rigidity and expand its application in the field of bio-based materials, it was mixed with certain proportions of another reactive bio-based VER monomer, which had rigid and strong polar groups, and then a series of copolymers were prepared with thermal curing method. Then their tensile property, hardness, morphology of fractured surface, flame retardant property, DMA and thermostability were all investigated. The results indicated that the copolymers had relatively high tensile strength of 11.2 MPa, and the limiting oxygen index is above 23% in all prepared copolymers. DMA demonstrates that the glass transition temperature of the cured resins is up to 56.1°C. Thermogravimetric analysis shows that the copolymers have excellent thermal stability.

Synthesis and characterisation of asymmetrical mesogenic materials based on 2,5-disubstituted-1,3,4-oxadiazole

ABSTRACTNew mesogenic homologous series bearing 1,3,4-oxadiazole ring with a nitro terminal group, 4-(5-(4-nitrophenyl)-1,3,4-oxadiazol-2-yl)phenyl 4-((4-methoxybenzylidene)amino)benzoate (G1–G11), were synthesised. Their chemical structures are identified by fourier transform infrared spectroscopy (FT-IR), proton nuclear magnetic resonance (1H-NMR) and elemental analysis. The liquid crystalline properties of the series Gn and their precursory Fn were screened by differential scanning calorimetry and optical polarising microscopy (OPM). The compounds of the series Gn were screened by thermogravimetric analysis to observe their thermal stability. The target compounds (Gn) in this study, were displayed different liquid crystalline mesophase, the first two homologous (G1 and G2) did not show any liquid crystalline behaviour, the homologous (G3–G10) which have an alkoxy terminal group (n = 3–10) exhibited nematic phase, whilst the last derivative of the series (G11), n = 12, displayed SmA phase. The mesomorphic properties of these derivatives were affected by the presence of the nitro group at the end of the molecules which was classified as a strong polar group. Also, the role of alkoxy terminal chain and the bent heterocyclic ring (1,3,4-oxadiazole) in the liquid crystalline properties of these molecules were debated.

Study on the Preparation and Tribological Properties of Fly Ash as Lubricant Additive for Steel/Steel Pair

Fly ash, generated during the combustion of coal for energy production, has been regarded as an environmental pollutant if not properly disposed of. Many aggressive efforts have been evaluated to recycle the fly ash. In this paper, a new approach was developed to prepare lubricant additive based on fly ash and the tribological properties were investigated in detail. The results show that fly ash modified with oleic acid not only performs favorable dispersive ability, but also significantly improves the friction-reducing and anti-wear abilities for steel/steel contact. Based on the characterization of the wear scars by scanning electron microscopy, Raman spectroscopy and energy-dispersive X-ray spectroscopy, the excellent tribological properties are attributed to the synergies of fly ash and oleic acid because fly ash can act as spacer and bearing and deposit on the worn surfaces to significantly improve the friction-reducing and anti-wear abilities, and the introduction of strong polar groups can make fly ash easily form a stable and successive tribofilm on the rubbing surfaces throughout the sliding process.

Synthesis and characterization of poly(siloxane–ether–urethane) copolymers

Poly(siloxane–ether–urethane) (PSEU) copolymer materials were successfully synthesized from 4,4-diphenylmethane diisocyanate (MDI), 2,2-dimethylol propionic acid (DMPA) chain extender, and poly(siloxane–ether) copolymer (PSE) soft segments formed by hydrosilation of hydride-terminated polydimethylsiloxane (PDMS) and polyalkyl glycol allyl epoxyl ethers (PAGAEEs). The morphology, structure, and surface wettability of PSEU copolymer materials were characterized by FT-IR, XPS, TG, SEM, GPC, and contact angle measurements. It was demonstrated that the introduction of hard (urethane) segments can improve the thermal stability of PSEU materials. Moreover, due to the existence of strong polar groups originating from MDI segment, PSEU copolymer materials was superhydrophilic with water contact angle of 2.1°, which was possibly useful for surfactants and coatings applications.

The synthesis of Gemini-type sulfobetaine based hybrid monolith and its application in hydrophilic interaction chromatography for small polar molecular

In this work, a novel Gemini-type sulfobetaine-based hybrid monolith was fabricated by co-polymerization of a homemade Gemini-type sufobetaine, 1,3-bis (N-(3-sulfopropyl)-N-(methacrylic acid-2-hydroxy propyl ester)-N-methyl ammonium)-propane (BSMMP) with vinyltrimethoxysilane (VTMS) and tetramethoxysilane (TMOS) in the presence of 2′-azobis (2-methylpropionamidine) dihydrochloride (V50) as initiator. The recipe of pre-copolymerization solution for monolith preparation was optimized carefully, and the resulting monolith was characterized by scan electron microscope (SEM), fourier transform infrared spectroscopy (FT-IR) and thermal gravimetry analysis (TGA). The results indicated that the optimized monolith possess homogeneous bio-continue pore structure, and a relatively high proportion of the sulfobetaine groups was successfully introduced into the monolith. The results from permeability test shows that the proposed monoliths have excellent permeability within both water rich mobile phase and acetonitrile rich mobile phase, due to the rigid inorganic framework of hybrid monolith. Results showed that the relative standard deviations (RSDs) of run-to-run, column-to-column and batch-to-batch were less than 1.9%, 3.7% and 6.2%, respectively. The lowest plate height value of the column for thiourea was less than 10µm. Furthermore, separating the polar small molecules including nucleosides, the base species, the phenols and the amides were performed within 14min, 22min 18min and 9min on the prepared monolith, respectively, good separation effect on these polar small molecules was found, and remarkable hydrophilic retention behavior was observed when an acetonitrile rich mobile phase was applied, attributing to the existence of strong polar Gemini-type sulfobetaine groups. Finally, the potential application of the resulting monolith in complex sample was successfully demonstrated by separating a BSA digest in gradient elution mode.

Simple Synthesis of Eco-Friendly Multifunctional Silk-Sericin Capped Zinc Oxide Nanorods and Their Potential for Fabrication of Hydrogen Sensors and UV Photodetectors

The present investigation describes a new eco-friendly, low cost material-based approach for sensor device fabrication. In this study, sericin capped zinc oxide nanorod (ZNR)-based H2 gas sensors and UV photodetectors were fabricated by incorporating silk-sericin with ZnO. The proposed sensors have higher sensitivity to H2 and greater photoresponsivity. The sericin capped ZNRs were fabricated from a degummed waste sericin solution using an inexpensive hydrothermal method. The sericin capped ZNRs show excellent H2 gas response (17.8%) and photoresponse with a fast response time under UV illumination due to sericin coating on the surface of the ZnO. Sericin is a water-soluble protein with strong polar groups as side chains, such as carboxyl, amino, and hydroxyl groups, which can easily interact with zinc particles through electrostatic interactions, resulting in the unique and improved ZnO sensor behavior. This interaction was characterized by various analytical techniques and compared with as-grown ZNR. Th...

Surface Polarity and Self-Structured Nanogrooves Collaboratively Oriented Molecular Packing for High Crystallinity toward Efficient Charge Transport.

Efficient charge transport in organic semiconductors is essential for construction of high performance optoelectronic devices. Herein, for the first time, we demonstrate that poly(amic acid) (PAA), a facilely deposited and annealing-free dielectric layer, can tailor the growth of organic semiconductor films with large area and high crystallinity toward efficient charge transport and high mobility in their thin film transistors. Pentacene is used as a model system to demonstrate the concept with mobility up to 30.6 cm2 V-1 s-1, comparable to its high quality single crystal devices. The structure of PAA has corrugations with OH groups pointing out of the surface, and the presence of an amide bond further allows adjacent polymer strands to interact via hydrogen bonding, leading to a self-rippled surface perpendicular to the corrugation. On the other hand, the strong polar groups (-COOH/-CONH) of PAA could provide repulsive forces between PAA and pentacene, which results in the vertical orientation of pentacene on the dielectric surface. Indeed, in comparison with its imidized counterpart polyimide (PI), PAA dielectric significantly enhances the film crystallinity, drastically increases the domain size, and decreases the interface trap density, giving rise to superior device performance with high mobility. This concept can be extended to more organic semiconducting systems, e.g., 2,6-diphenylanthracene (DPA), tetracene, copper phthalocyanine (CuPc), and copper hexadecafluorophthalocyanine (F16CuPc), demonstrating the general applicability. The results show the importance of combining surface nanogrooves with the strong polarity in orienting the molecular arrangement for high crystallinity toward efficient charge transport in organic semiconductors.

Differences in the viscoelastic features of white and grey matter in tension

Owing to its higher stiffness, white matter can absorb more energy than grey matter at strain rates of 0.025, 0.15 and 0.25 /s in tension. The reverse trend was observed at low strain rate (0.005 /s) due to the enhanced interactions between biomolecules in white matter, which may originate from the presence of strong polar groups and the stronger hydrogen bonding, as evidenced by differential scanning calorimetry and Fourier transform infrared spectrometer spectra.

Side-chain-type phenolphthalein-based poly(arylene ether sulfone nitrile)s anion exchange membrane for fuel cells

A series of phenolphthalein-based poly(arylene ether sulfone nitrile)s containing imidazolium groups on the side chains was synthesized to prepare anion exchange membranes (AEMs) for alkaline fuel cells. Strong polar nitrile groups were introduced into the polymer backbone with the intention of improving the dimensional stability of the AEMs. The content of nitrile groups was varied to study the effect of nitrile groups on the morphology and properties of the AEMs. With imidazolium groups locating on the cardo side chains, all the AEMs exhibited well-defined microphase-separated structures. Furthermore, the imidazolium groups tend to aggregate with increasing the nitrile group content resulting in the formation of larger and more interconnected ionic domains in the AEMs. The ionic conductivity in the range of 2.21–8.14×10−2Scm−1 increased with increasing the nitrile group content and temperature. The AEMs showed superb ratios of conductivity to IEC or swelling ratio at 60°C, good mechanical properties, and thermal and alkaline stability. A single H2/O2 fuel cell using the as-prepared AEMs showed an open circuit voltage of 0.95V and a peak power density of 50.6mWcm−2 at 60°C.

High quantum yield both in solution and solid state based on cyclohexyl modified triphenylamine derivatives for picric acid detection

Five triphenylamine derivatives containing cyclohexyl have been designed and synthesized with a solvent-free green procedure. The compounds possess high quantum yields both in solution and solid state. Our investigation shows that the steric effects of the chair conformation cyclohexyl and strong intramolecular hydrogen bond play a key role for the high emission. Moreover, a conjugated triphenylamine core and strong polar groups (pyridinyl and hydroxy) and their location in the molecule formed a typical non-planar push–pull electronic structure. This special chemical structure endows the molecules with solvatochromic effect and exhibit interesting fluorescent behavior in binary solvent systems of THF-H2O due to the strong intramolecular charge transfer (ICT), which has been confirmed by DFT calculation, absorption and fluorescence spectra of the compounds in different polar solvents. In addition, their high emission characters, both in solution and solid state are utilized for picric acid (PA) detection.

Phenolphthalein-based Poly(arylene ether sulfone nitrile)s Multiblock Copolymers As Anion Exchange Membranes for Alkaline Fuel Cells.

A series of phenolphthalein-based poly(arylene ether sulfone nitrile)s (PESN) multiblock copolymers containing 1-methylimidazole groups (ImPESN) were synthesized to prepare anion exchange membranes (AEMs) for alkaline fuel cells. The ion groups were introduced selectively and densely on the unit of phenolphthalein as the hydrophilic segments, allowing for the formation of ion clusters. Strong polar nitrile groups were introduced into the hydrophobic segments with the intention of improving the dimensional stability of the AEMs. A well-controlled multiblock structure was responsible for the well-defined hydrophobic/hydrophilic phase separation and interconnected ion-transport channels, as confirmed by atomic force microscopy and small angle X-ray scattering. The ImPESN membranes with low swelling showed a relatively high water uptake, high hydroxide ion conductivity together with good mechanical, thermal and alkaline stability. The ionic conductivity of the membranes was in the range of 3.85-14.67×10(-2) S·cm(-1) from 30 to 80 °C. Moreover, a single H2/O2 fuel cell with the ImPESN membrane showed an open circuit voltage of 0.92 V and a maximum power density of 66.4 mW cm(-2) at 60 °C.

Molecular vibration mode assignment of nematic liquid crystal 5CB on Terahertz spectra

Using DFT/B3LYP/6-311++G** method, the molecular structure and absorption spectra in terahertz (THz) range of liquid crystal 5CB are investigated. In a frequency range 0–15 THz, an assignment of the vibrational modes corresponding to absorption frequencies is performed using potential energy distribution for the first time. It is found that the cyano group radical (–CN) do actively take part in the strongest THz absorption of 1.743, 3.942, 5.169 and 14.769 THz in different vibration modes. The results suggest that the strong polar group should be avoided in designing liquid crystal molecule and mixtures in order to reduce the absorption intensity in THz range.

Bifunctionalized conjugated microporous polymers for carbon dioxide capture

A novel kind of bifunctionalized conjugated microporous polymers containing sultone and hydroxyl groups has been synthesized via palladium-catalyzed Sonogashira–Hagihara cross-coupling reaction of bromophenol blue with 1,4-diethynylbenzene or 1,3,5-triethynylbenzene. The resulting polymers show high specific surface area up to 1470 m2 g−1 and good thermal stability. BFCMP-2 exhibits a hydrogen uptake ability of 156 cm3 g−1 (∼1.39 wt%) at 77 K/1.13 bar and a carbon dioxide uptake capacity of 2.77 mmol g−1 at 273 K/1.13 bar. Compared with most other reported non-functionalized conjugated microporous polymers, both of the bifunctionalized polymer networks show relatively high isosteric heat of CO2 adsorption (25 kJ mol−1) due to the introduction of the polar functional groups of sultone and hydroxy enhanced the binding affinity between the polymer networks and CO2 molecules. The results demonstrate that the introduction of strong polar groups into a polymer skeleton is an efficient strategy to produce CO2-philic microporous organic polymers with enhanced binding affinity with CO2 molecules.

Conformational Behavior and Influence of Organic Solvents on a Strong Polar Group Nematogen at Room Temperature—A Computational Model

The conformational behavior and influence of organic solvents on a nematogen, 4’-n-alkyl-4-cyanobiphenyl, with strong polar group propyl (3CB) that is of commercial and application interest has been studied with respect to the translational and orientational motions. The atomic net charge and dipole moment components at each atomic center have been evaluated using the complete neglect differential overlap (CNDO/2) method. The modified Rayleigh-Schrodinger Perturbation theory with the multicentered-multipole expansion method has been employed to evaluate the long-range interactions, and a “6-exp.” potential function has been assumed for the short-range interactions. The minimum energy configurations obtained during the different modes of interactions have been taken as input to calculate the configurational probability using the Maxwell–Boltzmann formula in nonpolar organic solvents, i.e., carbon tetrachloride (CCl4), and chloroform (CHCl3) at room temperature 300 K. It has been observed that the molecules show the interesting property in the organic solvents. The interaction energies of dimer complexes have been taken into consideration in order to investigate the most energetically stable configuration. An attempt has been made to develop an interesting computational model for nematogen at molecular level.

The Interesting Property of Strong Polar Group Nematogens in Organic Solvents – A Computational Study

The interesting property of strong polar group nematogens, 4′-n-alkyl-4-cyanobiphenyl (nCB) with pentyl (5CB), and heptyl (7CB), groups that are of commercial and application interest has been studied with respect to the translational and orientational motions. The atomic net charge and dipole moment components at each atomic center have been evaluated using the complete neglect differential overlap (CNDO/2) method. The modified Rayleigh–Schrodinger Perturbation theory with the multicentered–multipole expansion method has been employed to evaluate the long-range interactions, and a “6-exp.” potential function has been assumed for the short-range interactions. The minimum energy configurations obtained during the different modes of interactions have been taken as input to calculate the configurational probability using the Maxwell-Boltzmann formula in nonpolar organic solvents, that is, carbon tetrachloride (CCl4), and chloroform (CHCl3) at room temperature 300 K. It has been observed that the molecules show the remarkable property in the organic solvents. The interaction energies of dimer complexes have been taken into consideration in order to investigate the most energetically stable configuration. An attempt has been made to develop a new and interesting model for nematogens at molecular level.

Deep-blue luminescent compound that emits efficiently both in solution and solid state with considerable blue-shift upon aggregation

We have designed and synthesized a novel deep-blue luminescent compound (WuFDA), which can emit efficiently both in solution and in the aggregated state; the fluorescence emission maximum of WuFDA in the aggregated state shows a remarkable blue-shift from that shown in the dilute solution. Moreover, WuFDA shows interesting fluorescent behaviour in mixed solvent systems of THF–H2O, and a solvent effect in different polar solvents. These unusual phenomena have been interpreted by studies of the single crystalline structure of WuFDA and density functional theory (DFT) investigations. The special chemical structure (containing a planar conjugated fluorene core and strong polar groups (–NH and –F)) and their location in the molecule formed a typical non-planar D–π–A molecule with strong internal charge transfer (ICT). Such a polar molecule possesses the ability to form hydrogen bond interactions with itself, as well as with the polar solvents. Both the ICT effect and the intermolecular hydrogen bond interactions play very important roles in the geometrical manner of aggregation and the fluorescent behaviours of the WuFDA. In addition, WuFDA exhibited good thermal stability, with 5% and 10% weight-loss temperatures (Td) of WuFDA in nitrogen of 399 and 414 °C, respectively, and the glass transition temperature (Tg) was about 161 °C.

Design, preparation and properties of novel renewable UV-curable copolymers based on cardanol and dimer fatty acids

Abstract A cardanol-based UV-curable vinyl ester (VE) monomer was prepared via simple esterification, and its successful synthesis was demonstrated by FTIR and 1H-NMR. In order to improve its rigidity, it was mixed with certain proportions of another reactive bio-based VE monomer, maleic anhydride modified dimer fatty acids polymerized glycidyl methacrylate (MA-m-DA-p-GMA) which had rigid and strong polar groups, and then a series of UV-cured copolymers were prepared from the two VE monomers. The UV curing process was monitored by FTIR analysis. The tensile and thermal properties of the cured copolymer films were also investigated. UV curing analysis demonstrated that the double bonds in the mixed VE could be converted to ultimate curing level within 40 s. Tensile tests showed the prepared copolymers had a tensile strength of 8.86 MPa. Dynamic mechanical analysis (DMA) revealed the copolymers had relatively high glass transition temperature (Tg) from 40 to 60 °C. Thermogravimetric analysis (TGA) showed the copolymers containing higher content of CDMA had higher thermal stability, and all copolymers’ main thermal initial decomposition temperatures were above 410 °C, indicating the copolymers had certain thermal stability. These copolymer films can be used as eco-friendly materials in coatings and other applications to replace the currently used petroleum-based polymers.