Phenyl Side Groups Research Articles

Synthesis and properties of novel poly(ether ether ketone) copolymers with (3,5-ditrifluoromethyl)phenyl and (4-phenoxy)phenyl side groups

A new nonfluorinated bisphenol monomer 2-(4-phenoxyphenyl)-1,4-diphenol was prepared via a four-step synthesis process. A series of poly(ether ether ketone) copolymers (6FPOP-PEEKs) were derived from 4,4′-difluorobenzophenone via a nucleophilic aromatic substitution polycondensation with various molar feed ratios of bisphenol monomer, 2-(4-phenoxyphenyl)-1,4-diphenol to (3,5-ditrifluoromethyl)phenylhydroquinone. The molecular weights ( Mn values), polydispersities and Tg values of 6FPOP-PEEKs increase as the molar feed ratio of 6FPH/(6FPH+POPH) increases. These 6FPOP-PEEKs show very high thermal stability. At a wavelength of 1550 nm, the refractive indices of the 6FPOP-PEEKs films are in the range of 1.5992–1.6396 and birefringences are in the range of 0.0034–0.0043. The near-infrared spectra show that the 6FPOP-PEEK films have small light absorption at the telecommunication wavelengths of 1300 and 1550 nm.

Molecular insights into human monoamine oxidase (MAO) inhibition by 1,4-naphthoquinone: Evidences for menadione (vitamin K3) acting as a competitive and reversible inhibitor of MAO

Monoamine oxidase (MAO) catalyzes the oxidative deamination of biogenic and exogenous amines and its inhibitors have therapeutic value for several conditions including affective disorders, stroke, neurodegenerative diseases and aging. The discovery of 2,3,6-trimethyl-1,4-naphthoquinone (TMN) as a nonselective and reversible inhibitor of MAO, has suggested 1,4-naphthoquinone (1,4-NQ) as a potential scaffold for designing new MAO inhibitors. Combining molecular modeling tools and biochemical assays we evaluate the kinetic and molecular details of the inhibition of human MAO by 1,4-NQ, comparing it with TMN and menadione. Menadione (2-methyl-1,4-naphthoquinone) is a multitarget drug that acts as a precursor of vitamin K and an inducer of mitochondrial permeability transition. Herein we show that MAO-B was inhibited competitively by 1,4-NQ (Ki=1.4μM) whereas MAO-A was inhibited by non-competitive mechanism (Ki=7.7μM). Contrasting with TMN and 1,4-NQ, menadione exhibited a 60-fold selectivity for MAO-B (Ki=0.4μM) in comparison with MAO-A (Ki=26μM), which makes it as selective as rasagiline. Fluorescence and molecular modeling data indicated that these inhibitors interact with the flavin moiety at the active site of the enzyme. Additionally, docking studies suggest the phenyl side groups of Tyr407 and Tyr444 (for MAO-A) or Tyr398 and Tyr435 (for MAO-B) play an important role in the interaction of the enzyme with 1,4-NQ scaffold through forces of dispersion as verified for menadione, TMN and 1,4-NQ. Taken together, our findings reveal the molecular details of MAO inhibition by 1,4-NQ scaffold and show for the first time that menadione acts as a competitive and reversible inhibitor of human MAO.

Tris-cis-tris-trans-dodeca[organo(dimethylorganosiloxy)]cyclododecasiloxanes {RSi(O)[OSiMe2R′]}12. Self-Ordering Features

The molecular order and thermotropic transitions of tris-cis-tris-trans-dodeca- [organo(dimethylorganosiloxy)]cyclododecasiloxanes {RSi(O)[OSiMe(2)R']}(12) (R = Ph, R' = Me, CH(2)Cl, Vi; R = Me, Et, Vi, R' = Me) have been investigated using differential scanning calorimetry, thermogravimetric analysis, and X-ray scattering. The cyclododecasiloxanes with phenyl side groups (R = Ph) can form mesomorphic structures within a very wide temperature range. Compounds with R = Me and Vi are liquids and exhibit microphase separation above their glass transition temperature because of the different nature and structure of the organic R and trimethylsiloxy OSiMe(3) side groups. When the side group R = Et, a mesomorphic structure is formed in a substantially more narrow temperature region than that for cycles containing phenyl groups. Thus, the type of side group R in organocyclododecasiloxanes determines their ability for self-ordering into mesomorphic structures and the thermal stability of the mesomorphic state.

The effect of structural variations on aromatic polyethers for high‐temperature PEM fuel cells

AbstractThree series of new aromatic polyether sulfones bearing phenyl, p‐tolyl or carboxyl side groups, respectively, and polar pyridine main chain groups were developed. Most of the polymeric materials presented high molecular weights and excellent solubility in common organic solvents. More importantly, they formed stable, self‐standing membranes that were thoroughly characterized in respect to their thermal, mechanical and oxidative stability, their phosphoric acid doping ability and ionic conductivity. Particularly, the copolymers bearing side p‐tolyl or carboxyl groups fulfill all necessary requirements for application as proton electrolyte membranes in high temperature fuel cells, which are glass transition temperatures higher than 220 °C, thermal stability up to 400 °C, oxidative stability, high doping levels (DLs) and proton conductivities of about 0.02 S/cm. Initial single fuel cell results at high temperatures, 160 °C or 180 °C, using a copolymer bearing p‐tolyl side groups with a relatively low DLs around 200 wt % and dry H2/Air feed gases, revealed efficient power generation with a current density of 0.5 A/cm2 at 500 mV. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

Thiophene-2-aryl-2H-benzotriazole-thiophene Oligomers with Adjustable Electronic Properties

The synthesis and the optical and electrochemical properties of 2-aryl-2H-benzotriazole based thiophene oligomers with chemical modifications either on the phenyl side group or on the backbone are presented. All data, supported by DFT calculations, show that modification on the backbone has a major impact on the electronic properties while the side groups can fine-tune the electronic properties. In addition, one compound exhibits a thermotropic mesophase.

Brightly fluorescent red organic solids bearing boron-bridged π–conjugated skeletons

Two π-conjugated organoboron complexes 1 and 2 with highly efficient red (632 nm) and deep red (670 nm) solid-state fluorescence have been constructed and qualified as potential non-doped red emitters accompanied by excellent electron-transport ability. X-ray crystal analysis demonstrated that the two side phenyl groups coordinated to each boron atom effectively keep the luminescent units apart. As a result, these red fluorophores are brightly fluorescent in the solid state (fluorescence quantum yields: 0.30 for 1 and 0.41 for 2). In addition, these boron complexes possess good thermal stability and high electron-transport ability. Organic light-emitting diodes employing 1 or 2 as non-doped emitters with simple device configuration exhibit bright red and near-infared electroluminescence.

Alternating copolymers of carbon dioxide with glycidyl ethers for novel ion-conductive polymer electrolytes

To overcome the low ionic conduction of existing poly(ethylene oxide)-based polymer electrolytes, we consider polycarbonates obtained from the copolymerization of CO2 and epoxy monomers. We synthesized four types of polycarbonates possessing phenyl, n-butyl, t-butyl and methoxyethyl side groups using zinc glutarate, and measured the ionic conductivity of their electrolytes, including 10 mol% of LiTFSI. The electrolyte possessing methoxyethyl side groups had the highest conductivity, of the order of 10−6 S cm−1 at room temperature. The activation energy (Ea) for ionic conduction in the polycarbonate electrolytes was estimated from the VTF equation, and the Ea of the electrolyte possessing n-butyl side groups was almost the same with the polyether-based electrolytes. An interesting feature of our study is that the polycarbonate is a unique candidate for ion-conductive polymers because of its flexible and hydrophobic properties.

Molecular motion and mobility in an organic single crystal: Raman study and model

We report Raman spectra of the organic semiconductor 5,6,11,12-tetraphenyltetracene (rubrene) in the temperature range 30--300 K. The linewidths of certain low-frequency peaks increase significantly, especially in the range 150--200 K. These peaks correspond to the vibrations of the phenyl side groups of the rubrene molecules, and their couplings to intermolecular vibrational modes. We propose a model in which the strong increase in mobility observed with increasing temperature between 30 and 150 K results from disorder as the phenyl groups exchange sides of the backbone plane and break the symmetry. This model explains previous experimental observations of structural and calorimetric changes near 150 K.

Synthesis and Langmuir Monolayer Characterisation of Some Nitro Derivatives of Polyphenyl Carboxylic Acids

Derivatives of 5′-phenyl-1,1′:3′,1″-terphenyl-4-carboxylic acid (PTCA), each with 4′-nitro-substituents (2 and 5) have been synthesised and characterised as Langmuir monolayers at the air/water interface. Surface pressure and electric surface potential measurements of the monolayers under a variety of experimental conditions have been made. The presence of the nitro-substituent (in 2 cf 2′) was found to change the sign of the measured surface potential, indicating that the nitro-derivative is oriented with the -NO2 group towards the air side, while the carboxylic group is anchored into the water subphase. Upon introducing two more side phenyl groups into the hydrophobic core of the nitro derivative 2 to give 5, the measured surface potential (and the resulting apparent dipole moment) change sign to positive, indicating the prevalence of the dipolar contribution from the hydrophobic moiety over that of the hydrophilic part of the molecule. Our results show that the contribution of the double layer potential arising from ionisation of the carboxylic group of the investigated molecules is | 0.1 | V.

Regular Formation of Chain Folding in Smectic Phase of Main-Chain BB-3(2-Ph) Polymer Followed by Columnar Association of Phenyl Side Group in Propane Spacer

The main-chain type of liquid crystal (LC) polymer was prepared with a combination of bibenzoate mesogen and 2-phenyl propane spacer. It forms the fluid smectic LC. However, the smectic phase has a two-dimensional frustrated structure with a (parallel to the layer) = 12.9 Å, c (along the polymer chain) = 20.6 Å and β = 70.0°. The occurrence of such a characteristic frustration is due to the bulky phenyl group sticking out of the propane spacer that is incompatible with a conventional smectic structure. The polymer assumes the regular chain folding conformation excluding the obstructive phenyl groups within a limited column-like space, and the resulting columns embedded in a smectic matrix are aligned with a two-dimensional positional order.

Orientation Relaxation of Triblock Copolymer with Cylindrical Microdomain by in situ Stress-Birefringence Measurements

The orientation relaxation behavior of polystyrene-block-hydrogenated polyisoprene-block-polystyrene (SEPS) with cylindrical microdomains of polystyrene (PS) dispersed in the rubbery segments was investigated by simultaneous measurements of stress and birefringence, and small angel X-ray scattering (SAXS) measurements. At short relaxation time, the stress σ and the birefringence Δn decreased at almost constant rate with time and temperature. At long relaxation time, however, the σ and Δn decreased steeply with time, and the decrease became larger with increasing time and temperature. The decrease of the Δn stopped and large Δn remained at high temperature, while the σ was close to zero. Such characteristic relaxation behavior is ascribed to the form birefringence induced by the orientation of the parallel arranged cylindrical microdomains and the conformational change of the phenyl ring side group associating with the orientation relaxation of PS. The analysis of these results suggest that the orientation relaxation of the rubbery segments occurs at short relaxation time during the stress relaxation after the uniaxial stretching, and then the orientation relaxation of the PS segments in the cylindrical PS microdomains occurs associating with the conformational change of the phenyl side group at long relaxation time at high temperature while the orientation of the cylindrical domain is not changed.

Low cost selective sensor for carbonyl compounds in air based on a novel conductive poly( p-xylylene) derivative

A novel poly( p-xylylene), PPX, derivative bearing phenyl side groups was electrochemically synthesized in 85% yield. The polymer, poly(2-phenyl- p-xylylene) (PPPX), presented a major fraction (88%) soluble in common organic solvents. It showed to be thermally resistant up to 140 °C. UV–VIS analysis revealed an Egap of ~ 3.0 eV. Gas sensors made from thin films of CSA doped PPPX deposited on interdigitated electrodes exhibited significant changes in electrical conductance upon exposure to five carbonyl compounds: acetaldehyde, propionaldehyde, benzaldehyde, acetone and butanone. Three-dimensional plots of relative response vs. time of half-response vs. time of half-recovery showed good discrimination between the five carbonyl compounds tested.

Irradiation of Atactic Polystyrene: Linear Energy Transfer Effects

Atactic glassy polystyrene (PS) has been irradiated in anoxic conditions by electron and ion beams. The induced modifications were followed, in situ, by Fourier transform infrared spectroscopy (FTIR). In-film modifications and hydrocarbon gas release were followed. In-situ measurements allowed one to avoid any spurious oxidation of the films after irradiation and also permitted studying in detail the evolution with dose of the FTIR spectra. The data were quantitatively analyzed, and we present a complete analysis of the effects of the Linear Energy Transfer (LET) on the radiation chemical yields of several radiation-induced modifications (alkynes, allenes, alkenes, benzene, and disubstituted benzenes). For a better understanding of the LET effects, the in-film modifications are compared to H2 release data from the literature and to our measurements of hydrocarbon gaseous molecule yields obtained by us. The overall destruction yield becomes very significant at high LET, and the radiation sensitivity of this aromatic polymer merges with typical values of aliphatic polymers: the radiation resistance conferred at low LET to polystyrene by the phenyl side groups is lost at high LET. This loss of radiation resistance equally affects the aromatic and aliphatic moieties. Monosubstituted alkynes are created above a LET threshold, whereas the other radiation-induced modifications are observed in the whole LET range. Several observations indicate that the phenyl ring is broken at high LET. Comparison of the alkyne yield in PS, polyethylene, and polycarbonate as well as the formation of nitrile bonds in poly(vinylpyridine- co-styrene) are consistent with a cleavage of the phenyl ring as the prominent source of alkynes. As the competing damage mechanisms do not have the same LET evolution, the relative importance of a specific modification on the global damage depends on LET. Some (benzene and disubstituted benzenes) dominate at low LET, while others (in-film alkyne and acetylene release) dominate at high LET.

Effect of chemical structure and crosslinking density on the thermo-mechanical properties and toughness of (meth)acrylate shape memory polymer networks

The objective of this work is to characterize and understand structure–mechanical property relationships in (meth)acrylate networks. The networks are synthesized from mono-functional (meth)acrylates with systematically varying sidegroup structure and multi-functional crosslinkers with varying mole fraction and functionality. Fundamental trends are established between the network chemical structure, crosslink density, glass transition temperature, rubbery modulus, failure strain, and toughness. The glass transition temperature of the networks ranged from −29 to 112°C, and the rubbery modulus (Er) ranged from 2.8 to 129.5MPa. At low crosslink density (Er<10MPa) network chemistry has a profound effect on network toughness. At high crosslink densities (Er>10MPa), network chemistry has little influence on material toughness. The characteristic ratio of the mono-functional (meth)acrylates' components is unable to predict trends in network toughness as a function of chemical structure, as has been demonstrated in thermoplastics. The cohesive energy density is a better tool for relative prediction of network mechanical properties. Due to superior mechanical properties, networks with phenyl sidegroups are further investigated to understand the effect of phenyl sidegroup structure on toughness.

2-Naphthoxymethyl-Substituted Polystyrenes for Homeotropic Liquid-Crystal Alignment Layers

A series of 2-naphthoxymethyl-substituted polystyrenes (P2NAP) were prepared by the reaction of poly(chloromethylstyrene) with different amounts of 2-naphthol to investigate the liquid-crystal (LC) alignment properties of these polymer films. P2NAP with only 2-naphthoxymethyl side groups (100% conversion of chloromethyl to 2-naphthoxymethyl) was obtained when 180 mol-% of naphthol was used in the reaction at 80 °C for 12 h. LC cells fabricated with unrubbed P2NAP films exhibited a homeotropic LC alignment behavior with a pretilt angle of approximately 90°. The homeotropic LC alignment behavior of the unrubbed LC cell of the P2NAP film was ascribed to the head-on type incorporation of a nonpolar bulky 2-naphthoxymethyl group into the phenyl side group of the polystyrene.

Poly(thiophenylanilino) and poly(furanylanilino) polymers

Novel hybrid polymers with thiophenylanilino and furanylanilino backbones and substituted phenyl side groups are reported. The new monomers bis-(4-heterocyclic-2-yl-phenyl)-aryl-amine (heterocyclic = thiophen with aryl = 4-benzoyl (2a), 4-nitro-phenyl (2b) and furan with aryl = 4-benzoyl-phenyl (3a), 4-nitro-phenyl (3b)) were prepared by monosubstituting triphenylamine under electrophilic aromatic conditions affording 4-nitrotriphenylamine and 4-benzoyltriphenylamine. Di(bromination) of the latter compounds followed by Stille cross-coupling reactions with 2-tributylstannylthiophene or 2-tributylstannylfuran produces the new monomers 2a–b and 3a–b in high yield. The monomers are electrochemically polymerized at relatively low potentials (<0.8 V versus Ag+/AgCl) in acetonitrile electrolytes resulting in electroactive films. All the new polymers can be repeatedly oxidized and reduced with little loss of electrochemical activity. Vibrational spectroscopy reveals that the monomer units are connected predominately via coupling of the thiophenyl or furanyl rings yielding the novel polymers. Single-crystal molecular structure determinations of 4-nitrotriphenylamine and monomer 3b indicate the importance of the electron-withdrawing groups on the pendent phenyl groups in determining the extent of delocalization of the extended multi-ring systems. Molecular orbital calculations suggest that the HOMO of 2b is delocalized about both anilino and thiophenyl portions of the molecule.

Intrinsic Conformational Preferences of Cα,α-Dibenzylglycine

The intrinsic conformational preferences of C (alpha,alpha)-dibenzylglycine, a symmetric alpha,alpha-dialkylated amino acid bearing two benzyl substituents on the alpha-carbon atom, have been determined using quantum chemical calculations at the B3LYP/6-31+G(d,p) level. A total of 46 minimum energy conformations were found for the N-acetyl- N'-methylamide derivative, even though only nine of them showed a relative energy lower than 5.0 kcal/mol. The latter involves C 7, C 5, and alpha' backbone conformations stabilized by intramolecular hydrogen bonds and/or N-H...pi interactions. Calculation of the conformational free energies in different environments (gas-phase, carbon tetrachloride, chloroform, methanol, and water solutions) indicates that four different minima (two C 5 and two C 7) are energetically accessible at room temperature in the gas phase, while in methanol and aqueous solutions one such minimum (C 5) becomes the only significant conformation. Comparison with results recently reported for C (alpha,alpha)-diphenylglycine indicates that substitution of phenyl side groups by benzyl enhances the conformational flexibility leading to (i) a reduction of the strain of the peptide backbone and (ii) alleviating the repulsive interactions between the pi electron density of the phenyl groups and the lone pairs of the carbonyl oxygen atoms.

Effect of phosphorous flame retardants on the thermal decomposition of vinyl polymers and copolymers

The effect of ammonium polyphosphate (APP) and tris(2,4-di- ter-butylphenyl)phosphite (TBP) flame retardants and polyphosphoric acid (PPA) was examined on the thermal decomposition reactions of polystyrene (PS), styrene-acrylonitrile copolymer (SAN), acrylonitrile-butadiene-styrene copolymer (ABS) and polyacrylonitrile (PAN) by pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) and thermogravimetry (TG) techniques. The effect of APP and PPA proved to be significant on the thermal decomposition of polymers investigated. The char formation from each polymer-APP and polymer-PPA mixture increases considerably. The thermal stability of PS increases in the presence of APP and PPA by 17 and 28 °C, respectively. Analogous and significant changes were observed in the pyrolysis product distribution of PS, SAN and ABS in the presence of APP and PPA, indicating, that the polyphosphoric residue of APP modifies the thermal decomposition mechanisms of these polymers even during fast pyrolysis when the chemical processes take place simultaneously. The presence of PPA promotes hydrogen shifts resulting in isomerisation and formation of indene compounds from PS, moreover, development of a conjugated ladder structure from PAN chain even during fast pyrolysis. This is the first time that a GC/MS evidence can be presented directly confirming the first step of carbonization reaction of PAN. The results also give an insight into the influence of PPA on the electron donating ability of phenyl side groups having a significant effect on the thermal decomposition product distribution of PS and styrene copolymers.

Photoisomerization mechanism of the cis isomers of 1,2-distyrylbenzene and two hetero-analogues

The radiative and reactive excited state relaxations of the ZE and ZZ geometrical isomers of 1,2-distyrylbenzene [1,2-(PhE) 2B] and two hetero-analogues, where the side phenyl groups were replaced by 4′-pyridyl or 2′-thienyl groups, were studied and compared with the photobehaviour of the EE isomers previously investigated. The ZE and ZZ isomers of the hydrocarbon photoisomerize by a predominant adiabatic mechanism (a “one photon – two bonds” process is also operative in the case of ZZ) whereas the contribution of the adiabatic pathway is reduced for the thienyl-analogues, which isomerize by a mixed (diabatic/adiabatic) mechanism, whereas a prevalent diabatic mechanism characterizes the behaviour of the pyridyl analogue.

Conformational degree and molecular orientation in rubrene film by in situ x-ray absorption spectroscopy

The conformation degree and molecular orientation during the growth of rubrene films on Si(111) and Au(111) have been studied by in situ x-ray absorption spectroscopy. The backbones of rubrene molecules on Au(111) are twisted at the first few layers; in contrast, no appreciable twisting is observed on Si(111) even at a thickness of approximately 1.5 nm. The planarization of the backbone in the first few layers is due to strong molecule–substrate interactions between rubrene and Si(111). The rubrene molecules on Au(111) have a backbone tilt angle of 41° and a phenyl side group tilt of 64° with respect to the substrate surface, suggesting the crystalline nature of the films. Ex situ atomic force microscopy measurements confirm that the rubrene film grown on Au(111) is crystalline and the growth direction is along its crystallographic c axis.