Dimethyl Biphenyl Research Articles

Storage Stability of 6FDA-DMB Polyamic Acid Solution Detected by Gel Permeation Chromatography Coupled with Multiple Detectors

Polyamic acid (PAA) is the precursor of polyimide (PI), and its solution's properties have a direct influence on the final performances of PI resins, films, or fibers. The viscosity loss of a PAA solution over time is notorious. A stability evaluation and revelation of the degradation mechanism of PAA in a solution based on variations of molecular parameters other than viscosity with storage time is necessary. In this study, a PAA solution was prepared through the polycondensation of 4,4'-(hexafluoroisopropene) diphthalic anhydride (6FDA) and 4,4'-diamino-2,2'-dimethylbiphenyl (DMB) in DMAc. The stability of a PAA solution stored at different temperatures (-18, -12, 4, and 25 °C) and different concentrations (12 wt% and 0.15 wt%) was systematically investigated by measuring the molecular parameters, including Mw, Mn, Mw/Mn, Rg, and [η], using gel permeation chromatography coupled with multiple detectors (GPC-RI-MALLS-VIS) in a mobile phase 0.02 M LiBr/0.20 M HAc/DMF. The stability of PAA in a concentrated solution decreased, as shown by the reduction ratio of Mw from 0%, 7.2%, and 34.7% to 83.8% and that of Mn from 0%, 4.7%, and 30.0% to 82.4% with an increase of temperature from -18, -12, and 4 to 25 °C, respectively, after storage for 139 days. The hydrolysis of PAA in a concentrated solution was accelerated at high temperatures. Notably, at 25 °C, the diluted solution was much less stable than the concentrated one and exhibited an almost linear degradation rate within 10 h. The Mw and Mn decreased rapidly by 52.8% and 48.7%, respectively, within 10 h. Such faster degradation was caused by a greater water ratio and less entanglement of chains in the diluted solution. The degradation of (6FDA-DMB) PAA in this study did not follow the chain length equilibration mechanism reported in literature, given that both Mw and Mn declined simultaneously during storage.

Comparison of 4,4′-Dimethylbiphenyl from Biomass-Derived Furfural and Oil-Based Resource: Technoeconomic Analysis and Life-Cycle Assessment

Replacing oil-based toluene with biomass-derived furfural for 4,4′-dimethylbiphenyl (DMBP) production can pave the way for sustainable polyester manufacture. This work compared the economic and environmental performances of two conceptual designs of 4,4′-DMBP production. The first toluene-based route consists of toluene alkylation to (methylcyclohexyl)toluene (MCHT), MCHT dehydrogenation to DMBP, and isomerization of lower-valued 3,3′-DMBP. The renewable furfural-based route includes hydrogenation of furfural to 2-methylfuran (MF), oxidative coupling of MF to 5,5′-dimethylfuran (DMBF), and tandem Diels–Alder dehydration of 5,5′-DMBF to 4,4′-DMBP. The reaction conditions are optimized to achieve a more economically feasible process using furfural feedstock. At a scale of 83 kmol/h feedstock, the 4,4′-DMBP minimum selling price of the furfural-based route is $3044/t, while that of the toluene-based route is $2488/t. The feedstock and 3,4′-DMBP isomer prices are identified as critical parameters for the economic evaluation by sensitivity analysis. A “cradle-to-gate” life-cycle assessment confirms that furfural-based DMBP production emits significantly fewer greenhouse gas (5.00 kg CO2 equiv/kg DMBP) as compared to the toluene-based counterpart (8.28 kg CO2 equiv/kg DMBP).

Tröger's base polymer blended with poly(ether ketone cardo) for high temperature proton exchange membrane fuel cell applications

Developing membrane electrolyte materials with high performance and low cost is a key factor in promoting the application and commercialization of the high temperature proton exchange membrane fuel cell (HT-PEMFC). In this work, a Tröger's base (TB) polymer is synthesized from commercially available and low-cost 4,4′-diamine-3,3′-dimethyl-biphenyl (DMBP) and dimethoxy methane in trifluoroacetic acid via a one-pot TB polymerization reaction under mild conditions. The obtained polymer is composited by TB unit and DMBP moiety (named as DMBP-TB), which occupies a good organic solubility, high thermal stability and excellent chemical resistance. Due to the built-in bicyclic amine rings and intrinsic microporous structure, the pure DMBP-TB membrane exhibits a remarkable phosphoric acid (PA) doping content as high as 1077% in 85 wt% PA solution at room temperature. However, the excessive swelling and poor mechanical integrity hinder the PA doped DMBP-TB membrane as the HT-PEM. Thus, the commercial and low-cost engineering thermoplastic of poly(ether ketone cardo) (PEKC) is employed as the enhanced material to prepare DMBP-TB blend membranes. The DMBP-TB/50%PEKC/149%PA membrane displays an anhydrous conductivity of 0.061 S cm−1 at 180 °C and a tensile strength of 8.7 MPa at room temperature, which enables H2–O2 fuel cell with a peak power density of 536 mW cm−2 at 180 °C without backpressure, suggesting the utility for HT-PEMFCs.

Desulphurisation of dibenzothiophene and 4,6–dimethyl dibenzothiophene via enhanced hydrogenation reaction route using RePd–TiO2/SiO2 aerogel catalysts: kinetic parameters estimation and modelling

Re/Pd-TiO2/SiO2 aerogel catalysts were synthesized by using a sol-gel method and supercritical drying in excess solvent and investigated in the reaction of hydrodesulphurisation (HDS) of dibenzothiophene (DBT) and 4,6-dimethyl dibenzothiophene (4,6-DMDBT). Both Re/Pd catalysts, obtained with and without the use of mesitylene in the synthesis step, have shown increased conversions of up to 70 % in the desulphurization of 4,6-DMDBT, when compared to conventional Co/Mo hydroprocessing catalysts. This observation is of importance for conversion of highly refractory 4,6-DMDBT and hydroprocessing to produce ultra-low sulphur diesel fuels, ULSD. In order to quantify the extent of desulphurisation, which proceeds via a hydrogenation route, conversions of DBT and 4,6-DMDBT along with evolution of reaction products characteristic for the direct desulphurisation route and the hydrogenation route were monitored by using a gas chromatography?mass spectrometry (GC-MS) analytical technique. The reaction was performed at 630 K and 6 MPa in a batch catalytic reactor. The experimental results were used in the Hougen-Watson kinetic model describing DBT and 4,6-DMDBT desulphurisation on ? and ? active sites. Kinetic parameters of this complex catalytic kinetics were determined by using a Genetic Algorithm method and minimum deviation function. Values of calculated kinetic parameters and values of the ratio of 3-methylcyclohexyltoluene (MCHT and dimethyl biphenyl (DMBPH) expressed as the MCHT/(MCHT+DMBPH) ratio ranging between 0.66 and 0.94, have confirmed that the hydrogenation route is the dominant route for desulphurisation of 4,6-DMDBT.

Polymer Electrolyte Membranes from Microporous Troger’s Base Polymers for Fuel Cells

Fuel cells (FCs) have attracted much attention because of their high energy conversion efficiency and cleanliness. However, polyelectrolytes are a key component of FCs, and their cost and performance are not ideal at present, which is an obstacle to the development of FCs. Polymers of intrinsic microporosity (PIM) have attracted much attention as a class of membrane materials due to their three-dimensional pore structure, which can provide channels for ion transport. However, it remains challenging to prepare PIM membranes due to their poor solubility and brittleness. A novel soluble Troger’s base (TB)-PIM polymer is proposed in this paper. The prepared TB-based membranes with rigid and contorted backbones exhibit excellent dimensional stability (<8% swelling ratio at 60 °C), mechanical properties, and thermal stability and form subnanometer cavities to allow rapid ion transport. Therefore, the proton conductivity of the 4-(2-hydroxyethoxy)-1,3-phenylenediamine dihydrochloride (HEPD)/4,4′-diamine-3,3′-dimethyl-biphenyl (DMBP)-TB membrane is 58.3 mS/cm at 80 °C. The OH– conductivity of the HEPD/DMBP-QTB anion exchange membrane (AEM) is 105.9 mS/cm at 80 °C. Moreover, the single cell assembled with an HEPD/DMBP-QTB AEM showed a peak power density of 76.6 mW/cm2 in H2 air (CO2-free) at 60 °C.

Selective Synthesis of 4,4′-Dimethylbiphenyl from 2-Methylfuran

4,4′-Dimethylbiphenyl (DMBP) is a promising platform chemical for the production of polymer precursors, plasticizers, and metal–organic frameworks among other materials. We report a two-step proces...

Synthesis and crystal structure of peptide dimethyl biphenyl hybrid C52H60N6O10·0.25H2O.

The synthesis and crystal structure of peptide 6,6'-dimethyl biphenyl hybrid are described. The title compound was synthesized by reaction between 6,6'-dimethyl-[1,1'-biphen-yl]-2,2'-dicarbonyl dichloride in CH2Cl2, amine HN-proline-phenyl-alanine-alanine-COOMe and Et3N at 273 K under N2 atmosphere and characterized by single-crystal X-ray diffraction. The asymmetric unit contains one peptide mol-ecule and a quarter of a water mol-ecule. A disorder of a methyl and meth-oxy-carbonyl group of one alanine residue is observed with occupancy ratio 0.502 (6):0.498 (6). The structure is consolidated by intra- and inter-molecular hydrogen bonds.

Geometrical Optimization Approach to Isomerization: Models and Limitations.

We study laser-driven isomerization reactions through an excited electronic state using the recently developed Geometrical Optimization procedure. Our goal is to analyze whether an initial wave packet in the ground state, with optimized amplitudes and phases, can be used to enhance the yield of the reaction at faster rates, driven by a single picosecond pulse or a pair of femtosecond pulses resonant with the electronic transition. We show that the symmetry of the system imposes limitations in the optimization procedure, such that the method rediscovers the pump-dump mechanism.

“Cascade recognition” of Cu2+ and H2PO4− with high sensitivity and selectivity in aqueous media based on the effect of ESIPT

Organic molecular sensors have the advantage of being used through easy, fast, economical and reliable optical methods for detecting toxic metal ions in the environment. In the present work, a simple but specific organic ligand N,N-(3,3′-dimethyl biphenyl)-bis(4-diethylaminosalicyladimine) (Q2) was designed and synthesized according to the excited state intramolecular proton transfer (ESIPT). Q2 can be regarded as a colorimetric and fluorescent sensor for relay recognition of Cu2+ and H2PO4− in DMSO/H2O (8:2, v/v) HEPES buffer solutions. Moreover, sensor Q2 showed a highly sensitive and selective response towards Cu2+ and H2PO4− over other metal ions and anions. Particularly, the fluorescence “ON–OFF–ON” responding circle could be repeated over 4 times by the sequential addition of Cu2+ and H2PO4−. Notably, the actual usage of sensor Q2 was further demonstrated by test kits and silica gel plates. The fluorescence changes of Q2 upon the addition of Cu2+ and H2PO4− were utilized as an INHIBIT logic gate at the molecular level, using Cu2+ and H2PO4− as chemical inputs and the fluorescence intensity signal as the output.

A Herbal Formula, CGXII, Exerts Antihepatofibrotic Effect in Dimethylnitrosamine-Induced SD Rat Model.

We aimed to evaluate the antihepatofibrotic effects of CGXII, an aqueous extract which is composed of A. iwayomogi, A. xanthioides, and S. miltiorrhiza, against dimethylnitrosamine- (DMN-) induced hepatofibrosis. Male Sprague Dawley rats were intraperitoneally injected with 10 mg/kg of DMN for 4 weeks (three consecutive days weekly). Rats were orally given distilled water, CGXII (50 or 100 mg/kg), or dimethyl dimethoxy biphenyl dicarboxylate (50 mg/kg) daily. DMN injection caused substantial alteration of total body weight and liver and spleen mass, whereas they were notably normalized by CGXII. CGXII treatment also markedly attenuated the elevation of serum aspartate aminotransferase and alanine aminotransferase levels, hepatic lipid peroxidation, and protein carbonyl contents. Collagen accumulation in hepatic tissue evidenced by histopathological analysis and quantitative assessment of hepatic hydroxyproline was ameliorated by CGXII. Immunohistochemistry analysis revealed decreased α-smooth muscle actin supporting the antihepatofibrotic effect of CGXII. The profibrogenic cytokines transforming growth factor-β, platelet-derived growth factor-β, and connective tissue growth factor were increased by DMN injection. Administration of CGXII normalized the protein and gene expression levels of these cytokines. Our findings suggest that CGXII lowers the levels of profibrogenic cytokines and thereby exerts antifibrotic effects.

Possible carcinogenic potential of dimethyl dimethoxy biphenyl dicarboxylate in experimental animals.

Dimethyl dimethoxy biphenyl dicarboxylate (DDB) has been extensively used in the treatment of liver diseases accounting for 1–6% of the global disease burden. Cell replication, DNA synthesis, and proliferation, providing significant information about behavior of cells were examined in mice exposed to subchronic administration with DDB. Conventional liver functions specifically gamma-glutamyltransferase (γ-GT), a marker expressing liver canceration was also investigated. Normal mice were allocated into two groups each of 10 mice. The 1st and 2nd groups were treated with DDB in a dose of 50 mg/kg/day, 5 days/week for 1 month and 3 months, respectively. Comparable groups of normal mice were left without treatment as controls. Compared to normal control group, animals receiving DDB for 3 months showed marked elevations of both alanine aminotransferase and γ-GT, significant inhibition in cytochrome P450, a significant increase in the mean ploidy and 4C with moderate to marked increase in S-phase populations and the number of proliferating cell nuclear antigen-positive cells. In conclusion, this is the first report on the potential relationship between the subchronic administration of DDB and the increase in the hepatocyte proliferation, cell replication and DNA synthesis that may raise an alarm regarding possible DDB insult on the biological behavior of cells.

High thermo-responsive shape memory epoxies based on substituted biphenyl mesogenic with good water resistance

In this work, a novel epoxy monomer denoted as 3,5′-di-t-butyl-5,3′-dimethyl biphenyl diglycidyl ether was synthesized and applied intoin situcomposites with 3,3′,5,5′-tetramethyl-4,4′-biphenyl diglycidyl ether, accompanied with curing agent aromatic amines.

Cancer preventive agents 11. Novel analogs of dimethyl dicarboxylate biphenyl as potent cancer chemopreventive agents†

Context: Dimethyl dicarboxylate biphenyl (DDB) is a clinically used hepatoprotectant and has also been found to have chemopreventive activity.Materials and methods: Sixteen novel analogs (5-20) were designed, synthesized, and evaluated for their cancer preventive activity. The 2,2′-bismethyl ester (5-18) and ether (19, 20) DDB analogs were synthesized by insertion of various linear alkyl, short fatty acid, polar, and aromatic groups. All synthesized analogs were evaluated in an in vitro short-term 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced Epstein Barr virus early antigen (EBA-EA) activation assay. Three of the most potent compounds were also tested for inhibitory effects on skin tumor promotion in an in vivo two-stage mouse-skin carcinogenesis test using 7,12-dimethylbenz[a]anthracene (DMBA) as an initiator and TPA as a promoter.Results: Compound 19 with bisprenyl ethers had the most significant cancer preventive activity (100% inhibition of activation at 1 × 103 mol ratio/TPA, 78.4%, 49.7%, and 10.9% inhibition at 5 × 102, 1 × 102, 1 × 10 mol ratio/TPA, respectively) in vitro. Compound 19 also exhibited a remarkable inhibitory effect on skin tumor promotion in the in vivo two-stage mouse-skin carcinogenesis test.Discussion and conclusions: Thus, DDB analog 19 could be a valuable candidate as a cancer preventive agent or as a lead for the development of new antitumor promoter drugs.

Excited States of [3.3](4,4′)Biphenylophane: The Role of Charge-Transfer Excitations in Dimers With π−π Interaction

The singlet and triplet electronic excitation manifold of [3.3](4,4')biphenylophane (BPP), an intramolecular dimer, and 4,4'-dimethylbiphenyl (DMBP), the corresponding monomer, has been analyzed by employing the approximate coupled-cluster singles and doubles model (CC2). The calculated triplet-triplet and singlet-singlet transient absorption spectra show good agreement with recent experimental results. The calculations suggest a strong interaction of the two biphenyl moieties of BPP in the first singlet and triplet excited states due to the overlapping pi-electron systems, and Forster-Dexter theory for weak coupling cannot be applied. Both the first excited singlet and triplet states of BPP can be characterized as excimeric states with a strong admixture of charge-transfer contributions.

Simultaneous HDS and HDN over supported PtSn catalysts in comparison to commercial NiMo/Al2O3

The performance of platinum-tin catalysts, supported on Al2O3 and SiO2 and subjected to reduction prior to use, has been studied. The catalysts were characterized in reduced forms by X-ray diffraction (XRD) and XPS. The surface properties were determined by N2 BET specific surface area and CO chemisorption. The model compounds were 4,6-dimethyldibenzothiophene (4,6DMDBT) and carbazole. The PtSn catalysts supported on either Al2O3 or SiO2 were characterised by high activity, but the catalyst PtSn/SiO2 was found the most effective, even more effective than the commercial KF848 catalyst. Both PtSn catalysts studied were more effective in the reaction of 4,6DMDBT hydrogenation, the dominant product obtained with the use of PtSn/Al2O3 was methyl-cyclohexyltoluene (MCHT) and with PtSn/SiO2 the dominant product was dimethylbicyclohexyl (DMBCH). The amount of dimethylbiphenyl (DMBPh) obtained was small and practically independent of the contact time. In the HDN reaction of carbazole the most active was PtSn/SiO2. It was also more active in the consecutive reaction of isomerisation of the main product of the HDN reaction, bicyclohexyl (BCH) to methylcyclopentylcyclohexane (MCPCH). The large differences shown in the hydrotreating activity specially in the HDN reaction between PtSn catalysts supported on Al2O3 and SiO2 result from the physicochemical properties of both samples. The significantly higher CO chemisorption for PtSn/SiO2 indicates the presence of larger amount of metallic species and better hydrogenation properties so important for deep hydrotreating process.

White organic light-emitting devices employing phosphorescent iridium complex as RGB dopants

Efficient phosphorescent white organic light-emitting diodes (WOLEDs) were realized by using a bright blue-emitting layer, iridium (III) bis-[(4,6- di-fluoropheny)-pyridinato-N, C2′] picolinate doped 4.4′-bis-(9-carbazolyl)-2, 2′-dimethyl–biphenyl doped, together with tris-(2-phenylpyridine) iridium and bis-(1-phenyl–isoquinoline) acetylacetonate iridium (III) are codoped into a 4,4′-N,N′-dicarbazole- biphenyl layer to provide blue, green and red emission for colour mixing. The device emission colour is controlled by varying dopant concentrations and the thicknesses of blue and green–red layers as well as tuning the thickness of an exciton-blocking layer. The maximum luminance and power efficiency of the WOLED are 42700 cd m−2 at 17 V and 8.48 lm W−1 at 5 V, respectively. The Commission Internationale de 1'Eclairage (CIE) chromaticity coordinate changes from (0.41, 0.42) to (0.37, 0.39) when the luminance ranges from 1000 cd m−2 to 30000 cd m−2.

The effect of cobalt addition to bulk MoP and Ni 2P catalysts for the hydrodesulfurization of 4,6-dimethyldibenzothiophene

Bulk metal phosphide catalysts with nominal composition Co x Ni 2P ( 0 ⩽ x ⩽ 0.34 ) and Co 0.07MoP were investigated for the hydrodesulfurization (HDS) of 4,6-dimethyldibenzothiophene (4,6-DMDBT) at 583 K and 3.0 MPa H 2. The selectivity for the direct desulfurization (DDS) of 4,6-DMDBT to the product dimethylbiphenyl (DMBP) increased to 49 and 31% over the Co 0.08Ni 2P and Co 0.07MoP catalysts, respectively, compared with the <3% DMBP selectivity obtained on bulk Ni 2P and MoP. Analysis by X-ray photoelectron spectroscopy (XPS) showed that the addition of the Co to MoP and Ni 2P resulted in a P enrichment of the catalyst surface. Among the Co x Ni 2P and Co 0.07MoP catalysts studied, the maximum DMBP selectivity occurred for the Co 0.08Ni 2P catalyst; this catalyst had the highest n-propylamine uptake and lowest CO uptake and the highest P/metal atom ratio, as determined by XPS. The increased selectivity to DMBP suggests that acid sites associated with phosphorous promote skeletal isomerization of 4,6-DMDBT to yield products that readily undergo DDS on the metal sites of the Co x Ni 2P ( 0 ⩽ x ⩽ 0.34 ) and Co 0.07MoP catalysts.

Characterization of Novel Nucleoside Analogs by Electrospray Ionization Mass Spectra

In this paper, we synthesized a novel nucleoside analog by coupling thymine with dimethyl dicarboxylate biphenyl (DDB). The structure of the target compound was determined using 1H nuclear magnetic resonance (NMR) and electrospray ionization tandem mass spectrometry (ESI-MS/MS). The fragmentation pathways were studied in details through ESI-MS/MS. By comparing with unsubstituted nucleosides, such as AZT, MCI, d4T and DDI, it was found that the nucleoside analog coupled with DDB would not yield the daughter ions corresponding to the fragments of the nucleoside base and arabinofuranose analogs, but would lose a neutral molecule HF and DDB easily. However, the unsubstituted nucleosides could lightly yield the fragment ions of the nucleoside base and sugar ring. Hence, electrospray ionization mass spectrometry combined with tandem mass spectrometry (MS/MS) provides a convenient method to recognize the substituted and unsubstituted nucleosides.

Twist Angles and Rotational Energy Barriers of Biphenyl and Substituted Biphenyls

Using B3LYP/6-311+G* and other methods, twist angles and torsional energies were obtained for biphenyl (BP), 2-halogen BPs, 2,2‘-dihalogen BPs, and 3,3‘-dihalogen BPs, the halogens ranging from F to I. The results were compared with available gas phase and X-ray data. 2,2‘-difluoro BP has a rotational double minimum, at 57.9 and 128.9°, whereas the other 2,2‘-dihalogen BPs have a single minimum at dihedral angles ranging from 84.9 to 94.8°. All 3,3‘-dihalogen BPs have a double minimum at about 45 and 135°. Optimized twist angles and energy barriers were also calculated for 2,2‘-dimethyl BP and for perfluoro as well as perchloro BP. Most structures are accounted for by steric effects. For 2,2‘-dihalogen BPs, however, attractive forces also appear to play a role, as evidenced by the dihedral angle of 2,2‘-dichloro BP lying well below 90°.

Effect of phosphorus addition on the behavior of CoMoS/Al 2O 3 catalyst in hydrodesulfurization of dibenzothiophene and 4,6-dimethyldibenzothiophene

The hydrodesulfurization (HDS) activity of phosphorus-added CoMoS/Al 2O 3 catalysts has been examined using dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) as reactants. Phosphorus modifies catalytic behavior in two ways: increase of active sites by enhanced metal dispersion and increase of Brönsted acidity. These effects yield a different distribution of products depending on the reactants. In thiophene HDS, phosphorus increases only the conversion. In DBT HDS, phosphorus increases the conversion and produces more cyclohexylbenzene (CHB) than biphenyl (BP). In 4,6-DMDBT HDS, the conversion also increases but more dimethylbiphenyl (DMBP) is produced than methylcyclohexyltoluene (MCHT), the opposite trend from the one observed in DBT HDS. This is due to enhanced acidity of the catalyst, which allows migration of the methyl groups in 4,6-DMDBT. Maximum conversions are obtained when the phosphorus content is proper, 0.5 wt.% in this study.