Aromatic End Research Articles

Non-migrating PVC plasticizers based on oligocaprolactones obtained by ring-opening polymerization

Oligomeric plasticizers for PVC were synthesized using ring-opening-polymerization of caprolactone (CL) initiated by aromatic and heteroaromatic thiol compounds containing hydroxy groups. The obtained plasticizers were chemically bound to the polymer both, in solution and in the melt, with different PVC/plasticizer weight ratios and their efficiency with respect to the degree of anchorage, resistance to migration and plasticization were studied.Thiolates from heteroaromatic thiol plasticizers were too strongly basic and produced partial hydrolysis and transesterification side reactions during the anchorage reaction to the polymer. On the other hand, oligomers carrying an aromatic thiol end group could be bound selectively and without hydrolysis to the PVC chains. The most suitable system was produced on a 50 kg scale and the plasticized materials obtained were analysed showing good degrees of anchorage and excellent plasticizing properties.

Sufficient driving force for quinoidal isoindigo-based diradicaloids with tunable diradical characters.

Stable organic π-conjugated diradcialoids with tunable diradical characters can profoundly affect emerging technology. Over the past years, great efforts have been devoted to studying the structure-diradical character relationship in diradicaloids. Herein, a series of quinoidal isoindigo (IID) compounds with different attached terminal end groups were designed. Detailed analysis focuses on elucidating the driving force for evoking and enhancing the diradical character in the quinoidal IID systems. The arylene units of the IID core and the bridged aromatic units determine the contribution of the open-shell diradical form in the ground state. Diradical character y0 correlates well with bond length alternation (BLA), the total HOMA, and the total NICS(1)zz, and it is tuned by bridged aromatic units and terminal end groups in symmetric systems. The zwitterionic character weakens the diradical character in asymmetric systems to different extents. This work contributes to the deep understanding of evoking and enhancing the diradical character in quinoidal IID-based diradcialoids, providing useful guidelines to produce new molecules with desirable properties.

High-sensitivity sensor array base on molecular design and machine learning for amine differentiation in exhaled vapor

• A sensor array which can classify pathological biomarkers of amines is provided. • By molecular backbone rigidity together with multiple hydrogen-bonding acceptor and aromatic terminal structure tuning, the difference interactions between molecules and multiple amines are realized. • Through molecular design and machine learning, the detection and recognition of ppb concentration of amine/ammonia at room temperature with an accuracy of 90% by the sensor array are achieved. Nowadays, the studies on the diagnosis of diseases by exhaled gas mostly focus on single markers. In fact, there are biomarkers with similar properties but corresponding to different diseases. The present sensing techniques still cannot achieve the multi-label classification of the targets simultaneously. Through introducing multiple hydrogen bond receptors and adjusting of the aromatic ring end group, the interaction strength modulation between target molecules and sensor array was realized. The sensor responses related to molecular structure can be used as the characteristic of the detection. By the machine learning, the different types of amines are well identified. It is worth mentioning that this method can also distinguish mixed amines ranging any concentration in ppm-ppb, which can be used in breath analyzer. The recognition of the mixed ammonia / amine gases is achieved at room temperature with an accuracy of 90%. The combination of molecular design and machine learning strategy can improve the selectivity of sensor array, which also provides a new idea for the design of sensor array that can be used in rapid, convenient, non-invasive and cost-effective exhalation diagnosis.

Self-assembly of Fmoc-diphenylalanine in water above the critical pH for gelation

The dipeptide, fluorenylmethyloxycarbonyl- di- phenylalanine (FmocFF), has displayed the self-assembly characteristics of short peptides in a way to induce hydrogel formation. The biocompatibility of these hydrogels makes them an important material to study. The underlying fibrils of the gel phase are built of β-sheets stabilized by ππ stacking between respective aromatic side chains and end group of the peptide. Gel formation can be triggered by adding water to dimethysulfoxide or by dissolving the peptide at a pH greater than 10.0 and subsequently titrating with HCl.

Mesomorphic behaviour, optical and quantum computational study: Effect of electron density on newly synthesized liquid crystalline positional isomers

Effect of position isomer in newly synthesized two liquid crystalline series having nitro and chloro groups at terminal and lateral position, with imine and cinnamoyloxy linkages was studied. The nitro and chloro groups in the aromatic end of the molecule are interchanged with each other at terminal and lateral position, giving rise to positional isomers. All synthesized compounds were characterized with standard spectroscopic techniques, Infrared, Ultra-Violet and Proton magnetic resonance spectroscopy. The mesophase behaviour was observed by a Polarizing optical microscope equipped with a heating stage and was confirmed by Differential scanning calorimetry with respective transition enthalpies of mesophase transition. The mesogenic derivative of both prepared series showed nematic and smectic A mesophase. DFT method was used to obtain optimized geometry of the molecules. The optimized geometry was used to obtain the Molecular electrostatic potential map, dipole moment, HOMO-LUMO and twist angle of the prepared series. The interaction between the molecules was studied on the base of electrostatic potential and HOMO-LUMO. The phase transition of the present two series is compared with each other and with three structurally related compounds to evaluate the effect of planarity, central linkage and position of substitution on their mesophase behaviour.

Carotenoid Biosynthesis in the Phylum Actinobacteria.

Actinobacteria is the phylum that has the biggest genome in the Bacteria domain and includes many colored species. Their pigment analysis revealed that structurally diverse carotenoids are responsible for their pigmentation. This chapter reviews the biosynthesis of the diverse carotenoids of Actinobacteria. Its carotenoids belong to three different types: 1) carotenoid of C50 chain length, 2) carotenoids with aromatic end groups, and 3) keto carotenoid like canthaxanthin (β,β-carotene-4,4'-dione) or monocyclic keto-γ-carotene derivatives. Species from the genus Rhodococcus are the only known Actinobacteria with a simultaneous pathway to aromatic and to keto carotenoids.

Management of local anesthetic toxicity and importance of lipid infusion

Local anesthetics (LA) are one of the groups that block the transmission of sensory, motor and autonomic nerve impulses commonly used in clinical anesthesia. All local anesthetic molecules in clinical use consist of three parts: a lipophilic (aromatic) end, a hydrophilic (amine) end, and a chain that provides the connection between the ends. Physicochemical properties determine the clinical efficacy of local anaesthetics The part that determines the lipid solubility of local anesthetics is the aromatic ring. A higher dose of local anesthetics is required for cardiovascular system (CVS) toxicity. Hypertension, tachycardia and ventricular arrhythmia are the first of the diseases of CVS. Hypotension, arrhythmia, bradycardia and cardiac arrest develop as local anesthetics increase in blood. The symptoms of central nervous system (CNS) toxicity associated with LA are related to the plasma levels of drugs. Initially, there are drowsiness, dizziness, sedation, disorientation, tinnitus, nystagmus, metallic taste, nausea and vomiting. Then, restlessness, irritability, tremors and muscle twitches occur. After this, the tonic-clonic seizure and loss of consciousness develops, finally, apnea, cardiovascular collapse and coma. In the treatment of local anesthetic toxicity, it is recommended to provide airway, avoid the propofol if seizure occurs and treat with benzodiazepine. If cardiac arrest develops, it is recommended to switch to advanced life support, to reduce the given dose of adrenaline, to administer lipid emulsion (20%) and to respond to treatment if cardiopulmonary bypass is not provided.

Enhancing the strength, toughness, and electrical conductivity of twist-spun carbon nanotube yarns by π bridging

The weak interfacial interactions between carbon nanotube (CNT) always results in low stress load transfer efficiency in CNT yarns, herein we fabricated strong, highly conducting CNT yarns at room temperature using molecules having aromatic end groups, π bridging neighboring CNTs. The resulting CNT yarns have high tensile strength with 1697 ± 24 MPa, toughness with 18.6 ± 1.6 MJ/m3, and electrical conductivity with 656.2 S/cm, which are 3.9, 2.5, and 3.5 times, respectively, as high as that of the neat CNT yarn. The specific tensile strength of the resulting CNT yarn is higher than that for previously reported CNT yarns fabricated at room temperature, even that for some CNT yarns fabricated using corossive environments or extreme temperature. This π bridging strategy provides a promising avenue for fabricating high performance CNT yarns under ambient conditions.

Development of Organo-Dispersible Graphene Oxide via Pseudo-Surface Modification for Thermally Conductive Green Polymer Composites.

Graphene has attracted lots of researchers attention because of its remarkable conductivity in both electrically and thermally. However, it has poor dispersibility in organic solvents which limited its applications. Polymers with aromatic end group which act as an intercalator were prepared by ring-opening polymerization with ε-caprolactone by utilizing 1-naphthalene methanol (1-NM) as an initiator. These intercalators will exist between graphene oxide (GO) sheets to prevent aggregation via interactions. The attachment of 1-NM on polymer chains was supported by ultraviolet–visible spectra, size exclusion chromatography profiles, and 1H nuclear magnetic resonance spectra. Exfoliated structured functionalized GO (fGO)/polycaprolactone (PCL) (synthesized fGO) nanocomposites that dispersed well in acetone, chloroform, N,N-dimethylformamide, dimethyl sulfoxide, tetrahydrofuran, and toluene were successfully synthesized. This agreed well with the enlarged interlayer spacing in the optimized fGO as compared to that of GO from density functional theory simulations using the DMol3 module that implemented in the Materials Studio 6.0. Furthermore, its potential to be applied as green electronics in electronics, aerospace, and automotive industries was presented, by trailering the thermal conductivity enhancement from the incorporation of fGO/PCL with commercialized biodegradable polymers, PCL, and poly[(R)-3-hydroxybutyric acid].

Schiff base complexes that form sandwich compounds.

In this article, we explore the capacity of formed Schiff base complexes to trap metal atoms or ions, using their aromatic ends. The intrinsic geometry of each complex defines the process of substitution. Two cases were studied; one involving a trans Schiff base complex and the other considering how a salen ligand, with nickel systems traps chromium. We also assessed the nature of the new bonds and the frontier molecular orbitals. Graphical abstract Two salen nickel compounds are joint by a Cr(0) atom forming an organometallic interaction.

Structure-property relationships of crosslinked disulfonated poly(arylene ether sulfone) membranes for desalination of water

Controlled molecular weight poly(arylene ether sulfone) oligomers with aromatic amine end groups and systematically varied degrees of disulfonation were synthesized by direct polymerization of disulfonated and non-sulfonated 4,4′-dichlorodiphenylsulfone. The oligomers were crosslinked with a tetrafunctional epoxy curing agent in the membrane casting process. Water uptake and IEC were investigated to understand how the structure and ion content affected the fixed charge concentrations (moles of ions/L of sorbed water). The hydrated mechanical properties of these copolymer networks were also studied in light of their ion contents and water uptake. At similar IECs, membranes with shorter ∼5000 Da oligomers absorbed less water than those with ∼10,000 Da blocks. The salt permeabilities correlated with water uptake and fixed charge density. Among the crosslinked membranes, the one with the 10,000 Da oligomer and with 50% disulfonation (mB5-10) had an excellent combination of water uptake, hydrated mechanical properties, fixed charge density, and low salt permeability.

Molecular design of organic small molecules based on diindole–diimide with fused aromatic heterocycles as donors for organic solar cells

A series of novel diindole–diimide based molecules with different aromatic end groups have been designed as charge transport and donor materials for organic solar cells (OSCs).

Steam – Air Conversion of Heavy Oil in the Presence of Nanosized Metal Oxide Particles

The effect of suspended nanosized magnetite and hematite particles on the thermal degradation of heavy oil at 360°C in a steamair atmosphere was studied at various pressures. The highmolecularweight components of the oil were found to undergo degradation, leading to reduced oil viscosity. The effect of aluminum and zinc oxides used as additives to initiate hydrocarbon bond dissociation on this process was also investigated. The mechanisms for how change in composition components alters the conversion products relative to the initial oil were studied. Carrying out the process in the presence of additives at 11 MPa leads to reduced yield of aromatic end products with increased yield of oil hydrocarbons and the formation of gaseous products. Asphalticresin materials are also found to be reduced due to conversion in the presence of the additives. Rheological curves were determined for the conversion products and were used to show the change in the viscositytemperature characteristics.

Encapsulation of dicinnamalacetone in β-cyclodextrin: A physicochemical evaluation and molecular modeling approach on 1:2 inclusion complex

ABSTRACTThe aim of this research is to prepare and characterize the inclusion complex between Dicinnamalacetone (DCA) and β-CD. The inclusion complex of Dicinnamalacetone [DCA] and Beta-cyclodextrin [β-CD] was characterized both in solution and solid state by UV-visible spectroscopy, Fluorescence spectroscopy, Nano second time resolved fluorescence study, Fourier Transform Infra-red spectroscopy (FT-IR), Differential Scanning Calorimetry (DSC), Scanning Electron Microscopy (SEM), Powder X-ray diffractometry (XRD), Atomic Force Microscopy (AFM) and molecular modeling test. The 1:2 soichiometry of inclusion complex and binding constant values were determined by Benesi-Hildebrand plot and confirmed by Job's continuous variation method. FT-IR study indicated that the aromatic rings of the Dicinnamalacetone molecule were included in the β-CD cavities. The nano second time resolved fluorescence study revealed that DCA exhibits single exponential decay in aqueous medium and bi-exponential decay in β-CD medium indicating the formation of inclusion complex. From the DSC study it is observed that the thermal stability of the inclusion complex was significantly enhanced when compared with the pure compound due to strong interaction between DCA and β-CD. Furthermore, implementation of molecular modeling test confirmed that the complexation could reduce the energy of the system. The experimental studies revealed that the most predominant structure of 1:2 inclusion complex is the one in which the two aromatic ends of DCA were inserted into the cavities of two β-CD molecules.

End Groups of Functionalized Siloxane Oligomers Direct Block-Copolymeric or Liquid-Crystalline Self-Assembly Behavior.

Monodisperse oligodimethylsiloxanes end-functionalized with the hydrogen-bonding ureidopyrimidinone (UPy) motif undergo phase separation between their aromatic end groups and dimethylsiloxane midblocks to form ordered nanostructures with domain spacings of <5 nm. The self-assembly behavior of these well-defined oligomers resembles that of high degree of polymerization (N)–high block interaction parameter (χ) linear diblock copolymers despite their small size. Specifically, the phase morphology varies from lamellar to hexagonal to body-centered cubic with increasing asymmetry in molecular volume fraction. Mixing molecules with different molecular weights to give dispersity >1.13 results in disorder, showing importance of molecular monodispersity for ultrasmall ordered phase separation. In contrast, oligodimethylsiloxanes end-functionalized with an O-benzylated UPy derivative self-assemble into lamellar nanostructures regardless of volume fraction because of the strong preference of the end groups to aggregate in a planar geometry. Thus, these molecules display more classically liquid-crystalline self-assembly behavior where the lamellar bilayer thickness is determined by the siloxane midblock. Here the lamellar nanostructure is tolerant to molecular polydispersity. We show the importance of end groups in high χ–low N block molecules, where block-copolymer-like self-assembly in our UPy-functionalized oligodimethylsiloxanes relies upon the dominance of phase separation effects over directional end group aggregation.

Synthetic Curcumin Analogs as Inhibitors of β -Amyloid Peptide Aggregation: Potential Therapeutic and Diagnostic Agents for Alzheimer's Disease.

There is a crucial need to develop new effective drugs for Alzheimer's disease (AD) as the currently available AD treatments provide only momentary and incomplete symptomatic relief. Amongst natural products, curcumin, a major constituent of turmeric, has been intensively investigated for its neuroprotective effect against β-amyloid (Aβ)-induced toxicity in cultured neuronal cells. The ability of curcumin to attach to Aβ peptide and prevent its accumulation is attributed to its three structural characteristics such as the presence of two aromatic end groups and their co-planarity, the length and rigidity of the linker region and the substitution conformation of these aromatics. However, curcumin failed to reach adequate brain levels after oral absorption in AD clinical trials due to its low water solubility and poor oral bioavailability. A number of new curcumin analogs that mimic the active site of the compound along with analogs that mimic the curcumin anti-amyloid effect combined with anticholinesterase effect have been developed to enhance the bioavailability, pharmacokinetics, water solubility, stability at physiological conditions and delivery of curcumin. In this article, we have summarized all reported synthetic analogs of curcumin showing effects on β-amyloid and discussed their potential as therapeutic and diagnostic agents for AD.

Conducting polyaniline nanorods doped with aromatic carboxyl chain end functionalized polystyrene

The preparation of new conducting polyaniline (PANI) derivatives with different nanostructures is described. PANI derivatives doped with aromatic carboxyl chain end functionalized polystyrene derivatives of different number average molecular weights between 18×103 and 3×103g/mol were prepared to determine the effect of the structure and number average molecular weights of the aromatic carboxyl chain end functionalized polystyrene dopant on the morphology of the resultant doped polyaniline derivatives. The aromatic carboxyl chain end functionalized polystyrene derivatives of different number average molecular weights were prepared by atom transfer radical polymerization (ATRP) methods using α-bromo-p-toluic acid as the aromatic carboxyl functionalized initiator. The chemical oxidative polymerization of aniline with ammonium persulphate as oxidant in the presence of aromatic carboxyl chain end functionalized polystyrenes as the dopants affords PANI derivatives as nanorods and nanosheets. The use of polymeric acids as dopants in the chemical oxidative polymerization of aniline leads to improved morphological control, eliminates dopant volatility, retains the electrical conductivity and promotes the processibility of the final polymeric carboxylic acid doped polyaniline derivatives. Also, the chemical oxidative polymerization of aniline with ammonium persulphate as oxidant in the presence of α-bromo-p-toluic acid as the dopant affords doped PANI derivatives as hollow microspheres. Furthermore, heating of the PANI nanorods doped with aromatic carboxyl chain end functionalized polystyrene under nitrogen atmosphere above 800°C affords carbon nanorods and nanosheets. The aromatic carboxyl chain end functionalized polystyrenes and the different PANI derivatives were characterized by size exclusion chromatography, 1H NMR and 13C NMR spectrometry, FTIR spectroscopy, UV–Vis spectroscopy, non-aqueous titrations, scanning electron microscopy, thermogravimetric analyses, transmission electron microscopy, X-ray diffraction and electrical conductivity measurements.

Encapsulation with the Protrusion of Cruciform 9,10‐Bis(arylethynyl)anthracene Derivatives in a Self‐Assembled Boronic Ester Cavitand Capsule: Photochemical and Photophysical Properties

The self-assembled boronic ester cavitand capsule 3 quantitatively and tightly encapsulates 2,6-diacetoxy-9,10-bis(arylethynyl)anthracene derivatives 4 a-4 c as highly fluorescent cruciform guests to form complexes 4 a@3, 4 b@3, and 4 c@(3)2. The structural features of capsule 3, which possesses two polar bowl-shaped aromatic cavity ends and four large equatorial windows connected by dynamic boronic ester bonds, made it possible to encapsulate cruciform 4 with protection of the reactive anthracene core inside the capsule and with two protruding arylethynyl groups, the π-conjugated arms of compound 4, through two of the equatorial windows of the capsule. Thus, complexes 4 a@3, 4 b@3, and 4 c@(3)2 show greater resistance to photochemical reactions in solution and fluorescence quenching in the powder state compared to free guests 4. In addition to the improved photostability, restriction of the free rotation of the arylethynyl groups of guests 4 upon encapsulation results in sharpening of the UV/Vis absorption peaks with a red-shift and a significant increase in some of the two-photon-absorption peaks of complexes 4 a@3, 4 b@3, and 4 c@(3)2 compared with free guests 4.

Plasma-chemical and photo-catalytic degradation of methyl orange

Non-thermal atmospheric humid air plasma is used to investigate chemical reactions mechanisms of predominantly produced neutral hydroxyl radicals by gliding arc discharges with Methyl Orange (MO). UV/Visible spectroscopy and electrochemical measurements were performed. Treated solutions show that highly reactive HOradicals interaction favours the creation of intermediate species followed by their degradation leading to one aromatic ring end product. Photocatalytic (UV/TiO2 and UV/H2O2) treatments lead to the complete decolourisation of MO within few minutes. The results obtained may confirm that the final product of air plasma MO interaction contains NO2 and NH2 groups, the consequence ofNO presence in plasma.

Three Sites and You Are Out: Ternary Synergistic Allostery Controls Aromatic Amino Acid Biosynthesis in Mycobacteriumtuberculosis

3-Deoxy-d-arabino-heptulosonate 7-phosphate synthase (DAH7PS) catalyzes the first step in the shikimate pathway, the pathway responsible for the biosynthesis of the aromatic amino acids Trp, Phe, and Tyr. Unlike many other organisms that produce up to three isozymes, each feedback-regulated by one of the aromatic amino acid pathway end products, Mycobacterium tuberculosis expresses a single DAH7PS enzyme that can be controlled by combinations of aromatic amino acids. This study shows that the synergistic inhibition of this enzyme by a combination of Trp and Phe can be significantly augmented by the addition of Tyr. We used X-ray crystallography, mutagenesis, and isothermal titration calorimetry studies to show that DAH7PS from M. tuberculosis possesses a Tyr-selective site in addition to the Trp and Phe sites, revealing an unusual and highly sophisticated network of three synergistic allosteric sites on one enzyme. This ternary inhibitory response, by a combination of all three aromatic amino acids, allows a tunable response of the protein to changing metabolic demands.