Aromatic Segments Research Articles

Synthesis and Study of Poly(ether-amide)s Containing Aromatic and Aliphatic Ether-Amine Segment and Isophthalic Acid

The paper describes some physical properties of poly(ether-amide)s (PEAs) prepared by solution polycondensation reaction of ether-amines such as 2,7-bis(4-aminophenoxy) naphthalene, 2,2-bis[4-(4-aminophenoxy)phenyl] propane, 1,4-bis(4-aminophenoxy methyl) cyclohexane and isophthalic acid. Resulting PEAs are high yield and have inherent viscosity ranging between 0.68–0.75 dL/g. The etheramines containing wholly, semi aromatic and aliphatic-aromatic segments were prepared by using two steps reaction. FTIR, 1H NMR, and elemental analyses were used for characterization of synthetic ether-amines and poly(ether-amide)s. PEAs films were prepared by solution casting technique then their thermal stability and mechanical properties were measured. TGA in nitrogen atmosphere shows that the PEAs are thermally stability, so 10% weight will be lost in the range of 335–358°C. Tensile strength and elongation at break of the PEA films ranged from 71.1–65.0 MPa and 6.48–8.41%, respectively.

Thermal degradation of polymer systems having liquid crystalline oligoester segment

Block copolymers and blends comprised by liquid crystalline oligoester and polystyrene were prepared and their thermal stability were characterized by thermogravimetric analysis (TGA). The samples have shown three main decomposition temperatures due to (1) lost of flexible chain and decomposition of mesogenic segment, (2) decomposition of polystyrene and (3) final decomposition of oligoester rigid segment. Both copolymers and polymer blends presented lower thermal stability compared to polystyrene and oligoester. The residual mass after heating at 600 °C in copolymers and polymer blends were lower than those found in the oligoesters. A degradative process of aromatic segments of oligoester induced by decomposition of polystyrene is suggested.

MOLECULAR DOCKING OF ANTIMYCIN A3 ANALOGS AND ITS AROMATIC SEGMENTS AS INHIBITORS OF APOPTOSIS PROTEIN MARKER BCL-XL AND MCL-1

Objective: Apoptosis is an important cellular process that causes the death of damaged cells. Its malfunction can lead to cancer development and poor response to conventional chemotherapy. Cellular proteins from the B-cell lymphoma 2 (BCL-2) family are crucial for apoptosis. Breast cancer is the most commonly diagnosed cancer among women worldwide. The aim of this work was to design using in silico docking antimycin A3, antimycin analogs, and its aromatic segments as inhibitors of Bcl-xl and Mcl-1.Methods: In silico molecular docking approach has been utilized to find the potential anticancer from antimycin A3 analogs and its aromatic segments. Antimycin A3 analogs and its aromatic segments were modeled into three-dimensional (3D) structures using Marvin Sketch. Based on Protein Data Bank, 3ZLN for Bcl-xl, and 5IEZ for Mcl-1 were selected as apoptosis protein marker from BCL-2 family. Geometry optimization and minimization of energy 3D structure of antimycin A3 analogs and segments (ligands) using the AutoDock software. Docking process and amino acid residue analysis were executed using AutoDock software. The best docking score was shown by the lowest binding energy and also checked with Lipinski rule of five.Results: In silico molecular docking showed antimycin A3 analogs, amide 5 and aromatic segment 14 have the best interaction and activity for Bcl-xl receptor inhibition. Moreover, amide 5 and segment 15 showed the best interaction and activity for Mcl-1 receptor inhibition.Conclusion: Our results clearly demonstrate that amide 5, segment 14, and segment 15 of antimycin A3 analog have a strong inhibitory activity against Bcl-xl and Mcl-1, and should be further developed as a promising candidate for the new anti-apoptosis agents.

Rigid Polyurethane Foam Fabrication Using Medium Chain Glycerides of Coconut Oil and Plastics from End-of-Life Vehicles

Polycarbonate and polyurethane scraps from end-of-life vehicles were converted into liquid recycled polyols with hydroxyl number around 300 mgKOH·g–1 by using medium chain glycerides of coconut oil. The obtained polyols were used for preparation of low-density rigid polyurethane foams. It was found that up to 50 wt % of the virgin petrochemical polyol can be replaced by the recycled polyols without any negative effect on the foaming process. The obtained foams exhibited the apparent density of 40–44 kg·m–3, the homogeneous cellular structure with a high content of closed cells (>91 vol %) and the beneficially low value of lambda coefficient (∼23 mW·m–1·K–1). The exceptionally high compressive strength (>350 kPa in parallel to foam rise direction) of the rigid PUR foams with 50 wt % of recycled polyol derived from polycarbonate scrap resulted probably from the unique structure of recycled polyol combining rigid aromatic segments together with flexible coconut oil glyceride units. In conclusion, this approa...

Synthesis, Characterization, and Application Studies of Polyurethane Acrylate Thermoset Coatings: Effect of Hard Segment

ABSTRACTThe waterborne polyurethane acrylate coatings are smart option to reduce the environmental hazards. To evaluate the structure–property relationship, polyurethane acrylate coating dispersions were synthesized with aromatic and aliphatic hard segments. Furthermore, to evaluate the performance, dispersions were used to finish the cotton fabric. The dispersions were prepared by prepolymer method followed by emulsion polymerization in aqueous medium. The characterization of dispersions was performed by Fourier transform infrared, dynamic light scattering, atomic force microscopy, differential scanning calorimetry, and thermogravimetric analysis. In general, aliphatic hard segment has shown more appreciable results. But, thermal stability of aromatic polyurethane acrylate was more pronounced as inherent rigidity of aromatic diisocyanate dominates.

Nonlinear Optical Properties of Novel Polypyrrole Derivatives Bearing Different Aromatic Segments

Polypyrrole (PPy) and its derivatives containing different were synthesized by the interfacial polymerization reaction using ammonium per sulfate as oxidant, and were characterized by using Fourier transform infrared, Ultraviolet/visible absorption, and Raman spectroscopic techniques. The third-order nonlinear optical properties of all samples were measured by using nanosecond Z-scan measurements at 532 nm. At the identical mass concentration of 0.15 mg·mL-1, all PPy derivatives exhibited an obvious reverse saturable absorption performance, while the saturable absorption response was observed for PPy. In addition, significant differences in their nonlinear optical performances were observed, highlighting the influence on optical nonlinearity of the aromatic segments of conjugated polymers.

Nanomorphological Diversity of Self-Assembled Cyclopeptisomes Investigated via Thermodynamic and Kinetic Controls

The physicochemical and biological characteristics of vesicles are dependent on the type of self-assembly building blocks and methods of preparation. In this report, we designed a vesicle-forming linear and cyclic peptide building blocks and investigated the effect of molecular topology and thermodynamic and kinetic controls on the stability and morphological features of the self-assembled vesicles. Comparison of topological effect on self-assembly revealed that the strong association of the aromatic hydrophobic segments is observed only in the cyclic peptide, which is most likely the results of constrained structure along with the restriction in the molecular degree of freedom. Consequently, the formation of stable vesicles could be observed only with the cyclic peptide. Further investigation with cyclic peptide building blocks revealed that depending on the control methods, vesicles with a variety of structural features, such as polygonal, wrinkled, round, round-patched, and round-fused vesicles, could ...

Metal-Free Sensitizers for Dye-Sensitized Solar Cells.

This review focuses on our work on metal-free sensitizers for dye-sensitized solar cells (DSSCs). Sensitizers based on D-A'-π-A architecture (D is a donor, A is an acceptor, A' is an electron-deficient entity) exhibit better light harvesting than D-π-A-type sensitizers. However, appropriate molecular design is needed to avoid excessive aggregation of negative charge at the electron-deficient entity upon photoexcitation. Rigidified aromatics, including aromatic segments comprising fused electron-excessive and -deficient units in the spacer, allow effective electronic communication, and good photoinduced charge transfer leads to excellent cell performance. Sensitizers with two anchors/acceptors, D(-π-A)2 , can more efficiently harvest light, inject electrons, and suppress dark current compared with congeners with a single anchor. Appropriate incorporation of heteroaromatic units in the spacer is beneficial to DSSC performance. High-performance, aqueous-based DSSCs can be achieved with a dual redox couple comprising imidazolium iodide and 2,2,6,6-tetramethylpiperidin-N-oxyl, and/or using dyes of improved wettability through the incorporation of a triethylene oxide methyl ether chain.

Fluorescent Cross-Linked Supramolecular Polymer Constructed by Orthogonal Self-Assembly of Metal-Ligand Coordination and Host-Guest Interaction.

A new host molecule consists of four terpyridine groups as the binding sites with zinc(II) ion and a copillar[5]arene incorporated in the center as a spacer to interact with guest molecule was designed and synthesized. Due to the 120 ° angle of the rigid aromatic segment, a cross-linked dimeric hexagonal supramolecular polymer was therefore generated as the result of the orthogonal self-assembly of metal-ligand coordination and host-guest interaction. UV/Vis spectroscopy, (1) H NMR spectroscopy, viscosity and dynamic light-scattering techniques were employed to characterize and understand the cross-linking process with the introduction of zinc(II) ion and guest molecule. More importantly, well-defined morphology of the self-assembled supramolecular structure can be tuned by altering the adding sequence of the two components, that is, the zinc(II) ion and the guest molecule. In addition, introduction of a competitive ligand suggested the dynamic nature of the supramolecular structure.

Molecular dynamics simulation on adsorption of pyrene-polyethylene onto ultrathin single-walled carbon nanotube

The mechanism of the adsorption of pyrene-polyethylene (Py-PE) onto ultrathin single-walled carbon nanotube (SWNT) was studied by using all-atom molecular dynamics (MD) simulations. We found that solvent polarity and pyrene group are two critical factors in the Py-PE decoration on ultrathin SWNT. Combined MD simulations with free energy calculations, our results indicate that larger solvent polarity can decrease the contribution of conformation entropy, but contributes little to the interaction energy, moreover, larger SWNT diameter can decrease the contribution of conformation entropy but lead to the increasing of the interaction energy. In polar organic solvent (N, N-Dimethylacetamide), the pyrene group plays a key role in the adsorption of Py-PE onto ultrathin SWNT, not only facilitates the spontaneous adsorption of Py-PE onto ultrathin SWNT, but also helps to form compact structure between themselves in the final adsorption states. While in aqueous solution, pyrene group no longer works as an anchor, but still affects a lot to the final adsorption conformation. Our present work provides detailed theoretical clue to understand the noncovalent interaction between aromatic segment appended polymer and ultrathin SWNT, and helps to explore the potential application of ultrathin SWNT in the fields of hybrid material, biomedical and electronic materials.

Synthesis, Characterization and TFT Characteristics of Diketopyrrolopyrrole Based Copolymer.

A novel diketopyrrolopyrrole (DPP) based low band gap polymer, poly[4,8-bis(triisopropylsilylethynyl) benzo[1,2-b:4,5-b']dithiophene-2,6-diyl-alt-[2,5-di-hexyl-3,6-dithiophen-2-ylpyrrolo[3,4-c]pyrrole-1,4-dione] (PTIPSBDT-DPP) is synthesized by Stille polymerization for use in thin film transistor (TFTs). The new polymer contain extended aromatic π-conjugated segments alternating with the DPP units and are designed to increase the free energy for charge generation to overcome current limitations in photocurrent generation. In this study we describe the synthesis, thermal stability, optical, electrochemical properties and TFT characteristics.

Structural stability and improved properties of poly(3-alkylthiophenes) synthesized in an acid medium

Poly(3-methylthiophene) (P3MT), poly(3-hexylthiophene) (P3HT) and poly(3-octylthiophene) (P3OT), with better chemical stability, efficiency and charge transfer properties for use in organic solar cells were synthesized on indium tin oxide (ITO) in LiClO4–acetonitrile (ACN) and in the presence of dyphenyl phosphate (DPHP), used as a Bronsted–Lowry acid. By means of cyclic voltammetry in the DPHP–LiClO4–ACN, we observed the displacement of two oxidation peaks, as well as the widening and definition of the second reduction peak in comparison to P3ATs synthesized in a neutral medium. Using electrochemical impedance spectroscopy, the Nyquist diagrams for the ITO/P3MT/DPHP–LiClO4–ACN system revealed a reduction in charge transfer resistance as the amount of DPHP was increased. However, for ITO/P3HT/DPHP–LiClO4–ACN and ITO/P3OT/DPHP–LiClO4–ACN this dependence was not observed. In the Bode-phase diagrams, the charge transfer processes were related to polaronic conduction in the ITO/P3MT/DPHP–LiClO4–ACN, and bipolaronic conduction in the ITO/P3HT/DPHP–LiClO4–ACN and ITO/P3OT/DPHP–LiClO4–ACN. These results were complemented by ex situ Raman spectroscopy, in which the charge transfer process in the ITO/P3MT/DPHP–LiClO4–ACN system was due to radical cation species stabilization in the P3MT as prepared, and in the ITO/P3HT/DPHP–LiClO4–ACN and ITO/P3OT/DPHP–LiClO4–ACN systems it occurred because of the stabilization of the dication on the P3HT and P3OT films obtained. The stability of these various species in the polymer matrix varied as time elapsed, leading to a disproportionate quantity of radical cation segments in aromatic and dication segments of the P3MT matrix, and the formation of a charge transfer complex with oxygen in the P3HT and P3OT. The radical cation segments stabilized 48 h after preparation.

π-π Stacking Mediated Chirality in Functional Supramolecular Filaments.

While a great diversity of peptide-based supra-molecular filaments have been reported, the impact of an auxiliary segment on the chiral assembly of peptides remains poorly understood. Herein we report on the formation of chiral filaments by the self-assembly of a peptide-drug conjugate containing an aromatic drug camptothecin (CPT) in a computational study. We find that the chirality of the filament is mediated by the π‒π stacking between CPTs, not only by the well-expected intermolecular hydrogen bonding between peptide segments. Our simulations show that π‒π stacking of CPTs governs the early stages of the self-assembly process, while a hydrogen bonding network starts at a relatively later stage to contribute to the eventual morphology of the filament. Our results also show the possible presence of water within the core of the CPT filament. These results provide very useful guiding principles for the rational design of supramolecular assemblies of peptide conjugates with aromatic segments.

Studies on homologous random and alternating segmented conjugated polymers with and without silicon synthesized by ADMET

Using acyclic diene metathesis (ADMET), we synthesized homologous luminescent conjugated polymers with two aromatic segments based on thiophene and substituted phenylene, either alternating or randomly distributed, and either directly connected or separated by Si-linkers.

Synthesis of a Tetrabenzotetraaza[8]circulene by a "Fold-In" Oxidative Fusion Reaction.

Tetrabenzotetraaza[8]circulene (1) has been synthesized in good yield by a "fold-in" oxidative fusion reaction of a 1,2-phenylene-bridged cyclic tetrapyrrole. X-ray diffraction analysis of 1 has revealed a planar square structure with a central cyclooctatetraene (COT) core that shows little alternation of the bond lengths. Despite these structural features, 1 shows aromatic-like character, such as sharp absorption bands, high fluorescence quantum yields (Φ(F)=0.55 in THF), and a single exponential fluorescence decay with τ(F)=3.8 ns. These observations indicate a dominant contribution of an [8]radialene-like π conjugation and hence aromatic character of the local aromatic segments in 1.

Synthesis of a Tetrabenzotetraaza[8]circulene by a “Fold‐In” Oxidative Fusion Reaction

AbstractTetrabenzotetraaza[8]circulene (1) has been synthesized in good yield by a “fold‐in” oxidative fusion reaction of a 1,2‐phenylene‐bridged cyclic tetrapyrrole. X‐ray diffraction analysis of 1 has revealed a planar square structure with a central cyclooctatetraene (COT) core that shows little alternation of the bond lengths. Despite these structural features, 1 shows aromatic‐like character, such as sharp absorption bands, high fluorescence quantum yields (ΦF=0.55 in THF), and a single exponential fluorescence decay with τF=3.8 ns. These observations indicate a dominant contribution of an [8]radialene‐like π conjugation and hence aromatic character of the local aromatic segments in 1.

Synthesis and spectroscopic analysis of polydiphenylamine via oxidation with bentonite clay in the solid state

In this study, solids of polydiphenylamine (PDPA) synthesized mechanochemically by reaction with bentonite (PDPAOB) were studied using Raman spectroscopy. It was possible to identify the chemical species in the PDPA–bentonite compound. The spectra obtained were compared to the spectra of PDPA prepared chemically by oxidation of DPA with K2S2O8 in the solid state, and PDPA produced electrochemically, with the aim of studying the characteristic frequencies of the aromatic segments (DPB), radical cation (DPB+) and dication (DPB2+) of N,N-diphenylbenzidine (DPB) in the polymer structure of the PDPA. To analyze the segments present, the band characteristic of CC asymmetric stretching of the aromatic ring in the Raman spectra was deconvoluted because of the widening of the band and shifts observed by irradiation at wavelengths of 532 and 785nm. This procedure showed that there are three distinct contributions in the spectra which facilitate the monitoring of changes in the contributions of the segments in the materials doped with HCl (PDPAOBD) and de-doped with NH4OH, (PDPAOBR).

Mutagenesis and functional analysis of the pore-forming toxin HALT-1 from Hydra magnipapillata.

Actinoporins are small 18.5 kDa pore-forming toxins. A family of six actinoporin genes has been identified in the genome of Hydra magnipapillata, and HALT-1 (Hydra actinoporin-like toxin-1) has been shown to have haemolytic activity. In this study, we have used site-directed mutagenesis to investigate the role of amino acids in the pore-forming N-terminal region and the conserved aromatic cluster required for cell membrane binding. A total of 10 mutants of HALT-1 were constructed and tested for their haemolytic and cytolytic activity on human erythrocytes and HeLa cells, respectively. Insertion of 1–4 negatively charged residues in the N-terminal region of HALT-1 strongly reduced haemolytic and cytolytic activity, suggesting that the length or charge of the N-terminal region is critical for pore-forming activity. Moreover, substitution of amino acids in the conserved aromatic cluster reduced haemolytic and cytolytic activity by more than 80%, suggesting that these aromatic amino acids are important for attachment to the lipid membrane as shown for other actinoporins. The results suggest that HALT-1 and other actinoporins share similar mechanisms of pore formation and that it is critical for HALT-1 to maintain an amphipathic helix at the N-terminus and an aromatic amino acid-rich segment at the site of membrane binding.

ChemInform Abstract: Design of Nanostructures Based on Aromatic Peptide Amphiphiles

AbstractReview: 309 refs.

Aspects of Asphaltene Aggregation Obtained from Coarse-Grained Molecular Modeling

We have performed a molecular-simulation-based study to explore some of the underlying mechanisms of asphaltene aggregation. The daunting complexity of the crude oil + asphaltene system precludes any type of meaningful molecular simulation unless some assumptions are made with respect to the key physical and chemical properties that must be explicitly described. In the present work, we focus on molecular simulations of a coarse-grained model of asphaltene molecules in pure solvents, which are based on the assumption that the general size asymmetry and asphaltene morphology play a key role in the aggregation process. We use simple single isotropic Lennard-Jones sites to represent paraffinic and aromatic C6 segments, which are used as building blocks for the description of continental asphaltene models and solvent moieties. The energy and size parameters for the intermolecular models (e and σ) for solute and solvent molecules are chosen to reproduce the experimental density of the liquid phase for different...