Polymerization Of Benzene Research Articles

Investigation of different configurations of alumina packed bed reactor for coke free conversion of benzene

Conversion of producer gas tar without coke generation is a great challenge. This study investigates conversion of tar model benzene using different configurations of highly non-porous ɣ-Al2O3 packed bed reactor at 1000–1100 0C. The configurations comprised of different positions (relative to top (P1), center (P2) and bottom (P3) of reactor furnace), heights (5, 13 and 25 cm) and particles sizes (0.5, 3 and 5 mm) of alumina packed bed. Steam and CO2 were used as reforming media for tested benzene concentrations (0.4–1.8 vol%). The results showed benzene conversions of 48–91% with negligible steady thin coke generation using a packed bed (height: 25 cm, particles size: 3 mm) at P1. Whereas, relative high benzene conversions of 63–93 and 68–95% at P2 and P3 respectively with unsteady thick coke generation at benzene concentrations greater than 0.4 vol% increased differential upstream pressures (DUPs) of beds. Similar unsteady coke generation at benzene concentrations greater than 0.8 vol% and temperature of 1100 0C was observed with packed beds of heights of 5 and 13 cm, and particles size of 0.5 mm at P1. Generation of unsteady coke with condensed structure as evidenced by its characterization was attributable to increased benzene polymerization and reduced bed surface gasification reactions due to improperly installed packed bed. Developed kinetic model predicted well the generated coke. As conclusion, properly installed alumina packed bed pertaining to tar concentration and other experimental conditions may inhibit coke generation during tar conversion.

A combined experimental and computational study on the catalytic effect of aluminum nitride nanocrystal (AlN) on the polymerization of benzene, naphthalene, anthracene, phenanthrene, chrysene and tetracene

A combined experimental and computational study on the catalytic effect of aluminum nitride nanocrystal (AlN) on the polymerization of benzene, naphthalene, anthracene, phenanthrene, chrysene and tetracene

Deuterium Isotope Effects in Polymerization of Benzene under Pressure.

The enormous versatility in the properties of carbon materials depends on the content of the sp2 and sp3 covalent bonds. Under compression, if intermolecular distances cross a critical threshold, then unsaturated hydrocarbons gradually transform to saturated carbon polymers. However, the mechanism of polymerization, even for benzene, the simplest aromatic hydrocarbon, is still not understood. We used high-pressure synchrotron X-ray, neutron diffraction, and micro-Raman spectroscopy together with density functional calculations to investigate the isotope effects in benzene isotopologues C6H6 and C6D6 up to 46.0 GPa. Raman spectra of polymeric products recovered from comparable pressures show the progression of polymerization exhibiting a pronounced kinetic isotope effect. Kinetically retarded reactions in C6D6 shed light on the mechanism of polymerization of benzene. We find that C6D6-derived products recovered from P < 35 GPa actively react with moisture, forming polymers with higher sp3 hydrogen contents. Significant isotopic shift (≥7 GPa) in persistence of Bragg reflections of C6D6 is observed.

High Temperature Thermoplastic Elastomers Synthesized by Living Anionic Polymerization in Hydrocarbon Solvent at Room Temperature

We present the synthesis and characterization of a new class of high temperature thermoplastic elastomers composed of polybenzofulvene–polyisoprene–polybenzofulvene (FIF) triblock copolymers. All copolymers were prepared by living anionic polymerization in benzene at room temperature. Homopolymerization and effects of additives on the glass transition temperature (Tg) of polybenzofulvene (PBF) were also investigated. Among all triblock copolymers studied, FIF with 14 vol % of PBF exhibited a maximum stress of 14.3 ± 1.3 MPa and strain at break of 1390 ± 66% from tensile tests. The stress–strain curves of FIF-10 and 14 were analyzed by a statistical molecular approach using a nonaffine tube model to estimate the thermoplastic elastomer behavior. Dynamic mechanical analysis showed that the softening temperature of PBF in FIF was 145 °C, much higher than that of thermoplastic elastomers with polystyrene hard blocks. Microphase separation of FIF triblock copolymers was observed by small-angle X-ray scattering, even though long-range order was not achieved under the annealing conditions employed. In addition, the microphase separation of the resulting triblock copolymers was examined by atomic force microscopy.

Graphene chemically synthesized from benzene at liquid–liquid interfaces

Herein, we report the total chemical synthesis of graphene assembled at a liquid–liquid interface through a chemical reaction starting from benzene as a monomer. The reaction occurs at the benzene/water liquid interface, taking advantage of the insoluble material (the growing graphene structures) assembling as a film, which allows a heterogeneous reaction with the precipitated material and a molecular construction of large graphene sheets (ca. 800nm2 or larger). A two-step polymerization mechanism has been proposed, involving the initial polymerization of benzene to poly-paraphenylene (PPP) and/or its oligomers, followed by subsequent Scholl reaction between disconnected aryl rings to graphene.

Calculated Nuclear Magnetic Resonance Spectra of Polytwistane and Related Hydrocarbon Nanorods

Polytwistane is an intriguing hydrocarbon nanorod that has not been experimentally realized to date. To facilitate its identification in complex reaction mixtures, the (1)H and (13)C nuclear magnetic resonance (NMR) spectra of idealized polytwistane were calculated using two distinct quantum chemical approaches. In addition, the NMR spectra of related hydrocarbon nanorods were determined. On the basis of these data, we speculate whether polytwistane and its congeners correspond to a crystalline one-dimensional sp(3) carbon nanomaterial formed by high-pressure solid-state polymerization of benzene.

Sequential deposition of hexamethyldisiloxane and benzene in non-thermal plasma adhesion to dental ceramic

According to the types of dental ceramic, various surface treatment techniques have been tried for adhesive cementation, but each treatment has its shortcomings. A simple and universal surface treatment for intraoral and chair-side adhesion promotion is needed for resin cements. This study investigated whether hexamethyldisiloxane (HMDSO) and benzene, when deposited using a low-power non-thermal atmospheric pressure dielectric barrier discharge jet, were effective precursor monomers in dental ceramic adhesion. Their effect on adhesion was evaluated with shear bond strength test (SBS), contact angle measurement, X-ray photoelectron spectroscopy, and Fourier transform infra-red spectrophotometer in an attenuated total reflectance mode. The bonded interfaces and fractured surfaces were evaluated using a scanning electron microscope. Plasma polymerization of HMDSO resulted in formation of a siloxane network (Si2 peak), but its surface hydrophobicity hindered adhesive wetting. Additional deposition of benzene onto the HMDSO-coated ceramic surface increased the C1 peak, which partly corresponded to the C=C double bonds, and the hydrophilic peaks (C-O, C=O and O-C=O bonds). Benzene deposition itself improved the adhesion between the ceramic and the overlying adhesive through the chemical interaction of C=C double bonds and the increased hydrophilic groups. Additional deposition of HMDSO before benzene mediated the chemical adhesion of benzene to the ceramic surface and led to an additional increase of bond strength. Plasma polymerization of benzene and HMDSO/benzene increased the bond strength of composite resin to dental ceramic by improving wettability and adaptation with hydrophilic ether, carbonyl and ester groups, and chemical bonding with active species, such as C=C double bonds and silanol groups. Open image in new window

Benzene under High Pressure: a Story of Molecular Crystals Transforming to Saturated Networks, with a Possible Intermediate Metallic Phase

In a theoretical study, benzene is compressed up to 300 GPa. The transformations found between molecular phases generally match the experimental findings in the moderate pressure regime (<20 GPa): phase I (Pbca) is found to be stable up to 4 GPa, while phase II (P4(3)2(1)2) is preferred in a narrow pressure range of 4-7 GPa. Phase III (P2(1)/c) is at lowest enthalpy at higher pressures. Above 50 GPa, phase V (P2(1) at 0 GPa; P2(1)/c at high pressure) comes into play, slightly more stable than phase III in the range of 50-80 GP, but unstable to rearrangement to a saturated, four-coordinate (at C), one-dimensional polymer. Actually, throughout the entire pressure range, crystals of graphane possess lower enthalpy than molecular benzene structures; a simple thermochemical argument is given for why this is so. In several of the benzene phases there nevertheless are substantial barriers to rearranging the molecules to a saturated polymer, especially at low temperatures. Even at room temperature these barriers should allow one to study the effect of pressure on the metastable molecular phases. Molecular phase III (P2(1)/c) is one such; it remains metastable to higher pressures up to ∼200 GPa, at which point it too rearranges spontaneously to a saturated, tetracoordinate CH polymer. At 300 K the isomerization transition occurs at a lower pressure. Nevertheless, there may be a narrow region of pressure, between P = 180 and 200 GPa, where one could find a metallic, molecular benzene state. We explore several lower dimensional models for such a metallic benzene. We also probe the possible first steps in a localized, nucleated benzene polymerization by studying the dimerization of benzene molecules. Several new (C(6)H(6))(2) dimers are predicted.

Synthesis and characterization of electrically conducting copolymers based on benzene and biphenyl

AbstractPoly(p‐phenylene) (H‐PPP), which is one of the firstly investigated conducting polymer, has the disadvantage of difficult processability because it is infusible and insoluble. The use of biphenyl instead of benzene leads to ortho‐, meta‐, para‐polyphenylenes (H‐PP) which are more soluble and easier to be processed, however their electrical conductivity is lower. Copolymers of polyphenylenes (C1 and C2) and corresponding homopolymers (H‐PPP and H‐PP) were produced by the oxidative cationic polymerization of benzene and/or biphenyl. The soluble (‐S) and the insoluble (‐I) in chlorobenzene polyphenylenes were separated (H‐PP‐I, H‐PP‐S, C1‐I, C1‐S, C2‐I, and C2‐S) and they were doped with a solution of FeCl3. All polyphenylenes were studied by FTIR, XRD, TGA, and their electrical conductivity with constant current was determined. Pronounced differences between the copolymers and the homopolymers were observed, indicating the different structure of the former. The values of the electrical conductivity of doped insoluble copolymers (10−4 and 10−5 S/cm) are between that of H‐PPP (10−3 S/cm) and H‐PP‐I (10−6 S/cm). The values of the electrical conductivity of doped soluble copolymers (10−5 S/cm) are considerably higher than that of H‐PP‐S (10−9 S/cm). The new electrically conductive polyphenylenes that were produced differ significantly from the corresponding homopolymers and combine good electrical conductivity and solubility. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Side chain liquid crystal poly(fumarate)s bearing tolane‐based mesogens

AbstractCyanotolane or fluorotolane mesogens were for the first time introduced into the fumarate monomer under basic conditions. All fumarate monomers undergo radical polymerization in benzene in the presence of dimethyl 2,2′‐azobis(isobutyrate) as an initiator at 60 °C, affording the corresponding poly(fumarate)s with a molecular weight (Mn) of ∼ 104 and an exceptionally narrow polydispersity. The phase behaviors of the fumarate monomers and the correspoding poly(fumarate)s were comprehensively investigated by differential scanning calorimetry (DSC), polarized optical microscopy (POM), and X‐ray diffraction (XRD) analysis. For the fumarate monomers, fluorotolane derivatives were prone to form higher‐order liquid crystal phases such as a smectic phase, while cyanotolane derivatives tended to show a wide mesophase temperature range, depending on the alkyl chain spacer length. Very surprisingly, these features dramatically weakened when they were polymerized. The mesophase temperature ranges became narrow and completely disappeared for the poly(fumarate)s with a shorter alkyl chain spacer. A nematic phase representing lower‐order arrangements became a predominant liquid crystal phase for the poly(fumarate) carrying cyanotolane mesogens. Only the poly(fumarate) carrying fluorotolane mesogens with a longer alkyl chain spacer displayed the characteristic XRD patterns of the smectic B phase. The transient photocurrent measurements of the fumarate monomer with cyanotolane mesogens displayed a hole mobility of the order of 10−4–10−5 cm2 V−1 s−1 at room temperature. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5101–5114, 2008

Facile synthesis and characterization of novel pseudo-hypercrosslinked resin

A kind of pseudo-hypercrosslinked polymer resin was firstly synthesized via a continuous Friedel–Crafts alkylation polymerization of benzene, diphenyl and their dichloromethyl derivatives. And the micromorphology and adsorption properties of these resins were investigated. The results demonstrated that the novel resins have high-specific surface area (581.26–974.88 m 2/g), high-pore volume (0.56–1.65 mL/g), small average porous radius (1.93–3.67 nm) and excellent adsorption properties for small non-polar organic molecules.

Electrosynthesis of Poly(para)phenylene in an Ionic Liquid: Cyclic Voltammetry and in Situ STM/Tunnelling Spectroscopy Studies

The electropolymerization of benzene in the air and water-stable ionic liquid 1-hexyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate (HMIm)FAP is investigated. The study comprises cyclic voltammetry, IR and in situ STM/tunnelling spectroscopy measurements. The IR results indicate that poly(para)phenylene is the end product of the electropolymerization of benzene in the employed ionic liquid. The resulting conjugation lengths of the product fall between 19 and 21. A polymer reference electrode is used successfully for the electrochemical polymerization of benzene. The first in situ STM results show that the electropolymerization of benzene in the ionic liquid can be probed on the nanoscale and the band gap of the prepared polymer can be determined. The electrodeposited polymer film obtained at a constant potential of 1.0 V vs PPP (polyparaphenylene) exhibits a band gap of 2.9+/-0.2 eV.

Basic Information on Nonsubstituted Polyphenylene and Polythiophene Obtained via Solubilization of Polymers

Basic information on the molecular weights and structures of poly(p-phenylene) PPP, poly(m-phenylene) PMP, poly(thiophene-2,5-diyl) PTh, and related copolymers has been obtained. PPPs prepared by a Ni-catalyzed dehalogenative polycondensation of p-C6H4Br2 with Mg (PPP(Ni)) and an oxidative polymerization of benzene using CuCl2 (PPP(Cu)) became soluble in DMF after nitration. The nitration proceeded essentially without crosslinking, and GPC analysis gave Mn values of 8300 and 6100 for nitrated PPP(Ni) and PPP(Cu), respectively. Light scattering analysis indicated that nitrated PPP(Ni) and PPP(Cu) assumed a rather stiff structure in DMF with ρv (degree of depolarization) in the range of 0.12−0.13. PMP and PTh also became soluble in DMF after nitration, and GPC analysis of nitrated PMP and PTh gave Mn values of 5500 and 8500, respectively. Light scattering analysis of nitrated PTh gave a ρv of 0.33, which indicated that the polymer had a stiff structure in DMF. Copolymers of p-phenylene (PP) and m-phenylene (MP) were soluble in organic solvents when the content of the PP unit was about 20%, and a soluble fraction with an Mn of 12 100 was obtained. Light scattering analysis indicated that the copolymer assumed an essentially random coil-like structure in THF. To the contrary, copolymers of 2,5-thienylene (2,5-Th) and 2,4-thienylene (2,4-Th) were insoluble in organic solvents presumably due to their essentially linear and stiff structure.

Electrochemical synthesis and characterization of conducting polyparaphenylene using room-temperature melt as the electrolyte

Freestanding polyparaphenylene films were obtained on polymerization of benzene at potential of 1.2 V versus Al wire on substrates like platinum/transparent conducting glass as an anode. The electrolyte used was chloroaluminate room-temperature melt, which was prepared by intimate mixing of a 1:2 ratio of cetyl pyridinium chloride and anhydrous aluminum chloride to yield a viscous liquid. This liquid was miscible in all proportions with benzene and other aromatic hydrocarbons in all proportions at room temperature. The polyparaphenylene films deposited on platinum anode exhibited a prominent cyclic voltammetric peak at 0.7 V versus Al wire as reference electrode in chloroaluminate medium. The impedance spectra gave low charge transfer resistance. The diffused reflectance electronic spectra of the film gave the peaks at 386 nm and 886 nm. The PPP films showed electronic conductivity around 3–4 × 10 4 S/cm by four probe method under nitrogen atmosphere. The polymer was also characterized by IR spectra, thermal studies, and SEM studies.

Electropolymerization of benzene in a room temperature ionic liquid

In this paper, we report on the electropolymerization of benzene in the room temperature ionic liquid 1-hexyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate. This liquid exhibits on platinum an electrochemical window of 4.5 V, furthermore it can easily be dried to water contents below 3 ppm. By potentiodynamic or potentiostatic polymerization of benzene a black deposit is obtained which has a spherulitic morphology with smallest grains of around 500 nm. IR spectrometry reveals that poly( para)phenylene was deposited to a certain extent. The polymer film is electroactive with a quasi-reversible electrochemical behavior and an electrode potential of around 1 V vs. ferrocene/ferrocinium. The importance of ionic liquids as mild solvents for the electropolymerization of benzene is pointed out.

Synthesis of aluminium nitride nanocrystals and their catalytic effect on thepolymerization of benzene

Aluminium nitride (AlN) nanocrystals were prepared by the benzene thermalmethod at low temperature (110̂C) and low pressure (0.12–0.14 MPa). Owing tothe catalytic effect of AlN nanocrystals, 5–8% benzene was converted at 150̂C and0.1–0.3 MPa into several polymers, mainly cyclohexylbenzene, 1, 1′-biphenyl and1′, 1-methylenebisbenzene. In contrast, when the pure benzene without AlNnanocrystals was heated to 200̂C, no new product could be detected. Themechanism of the polymerization of benzene in the presence of AlN nanocrystalsis briefly discussed on basis of a model of the coordination chemistry.

Synteza i wlasciwosci polifenylenow

A review with 36 refs, covering the synthesis routes to polyphenylenes, e.g., the Friedel-Crafts reactions, oxidative cationic polymerization of benzene in the presence of AlCl 3 /CuCl 2 , anionic polymerization in the presence of BuLi, the Yamamoto reaction, Diels-Alder reactions, etc. The products show broad MWD, various isomeric forms, colors, etc. Physicochemical properties (crystallinity, solubility, thermal resistance, electric conductivity) are described in relation to chemical structure. Service properties of construction materials (pump and mixer parts, anticorrosive and ablative coatings) produced from poly(p-phenylene)s (I) are also characterized. As the chain length is increased, the solubility and the melting temperature of linear I decreases and increases, resp. Conventional processing procedures are inapplicable to I. Powdered I compacted at 520 MPa at room temperature and sintered in nitrogen at 500°C and 140 MPa for 1 h, yielded a product resistant to high-T hydrolysis and chemical agents. Polycondensation (300°C) of terphenyl with m-benzene disulfone chloride afforded soluble oligo(phenylene)s; these dissolved in organic solvents serve as adhesives in the production of laminates. Extremely pure I is applied as a (semi)conductor.

Preparation and Electrorheological Characteristics of Poly(p-phenylene)-Based Suspensions

Poly(p-phenylene) (PPP) particles were synthesized from a bulk polymerization of benzene and then doped with FeCl3 in aqueous solution to control their electrical conductivity for their electrorheological (ER) application. Various concentrations of the aqueous FeCl3 were implemented to investigate the effect of doping degree on ER performance, and the yield stress of an ER fluid, which is a typical characteristic of a Bingham fluid, was found to be related to both the applied electric field strength and the doping degree. A universal scaling function was introduced to collapse all of the data. From dynamic experiments, it was also found that the semiconducting PPP-based ER fluids exhibit characteristics of a viscoelastic solid, which increases with electric field strength and doping degree.

Electrochemical synthesis and behavior of polyparaphenylene films prepared in the presence of surfactant

By the anodic polymerization of benzene in sulfuric acid in the presence of sodium alkylbenzene sulfonate as surfactant the uniform layers of polyparaphenylene with linear chain structure and high degree of polymerization on the stationary Pt, graphite electrodes were prepared. Cyclic voltammetric curves in the inorganic and organic media show that the rate of charge-transport processes and redox-stability of PPP films depends on nucleophilic agents presence and electron-donor (acceptor) properties of solvents. The reversible electrochemical behavior is observed in sulfuric acid solution (C>10 M) and in organic solvents with donor number DN ≤15.

Incorporation of sulfonylurea into N-isopropylacrylamide as an extracellular matrix for an artificial pancreas.

High-molecular-weight N-isopropylacrylamide copolymers with small amounts of sulfonylurea (SU, typically 2-4 mol% in the feed) were synthesized by free radical polymerization in benzene. SU-incorporated polymer solutions (5, 6, 8, and 10% w/v) in a culture medium (pH 7.4, 0.15 M ionic strength) with islet cells were mixed and poured into Millicells which supported gel formation. In order to increase the gelation temperature, the SU-incorporated copolymer gel, p(NiPAAm-co-SU), was blended with the p(NiPAAm-co-AAc) polymer at a ratio of 4 to 96. Interaction between the islet cells and the synthetic matrix of SU-incorporated copolymer gel resulted in effective cell viability and such cell functions as insulin secretion. To verify the specific interaction between the SU (K+ channel closer)-incorporated copolymer and islet cells, the cells were pretreated with diazoxide, an agonist of the ATP-sensitive K+ channel (K+ channel opener), before interaction between the polymer and islet cells. This treatment suppressed the action of SU on the islet cells. The results from this study provide evidence that the SU-incorporated copolymer stimulated insulin secretion by specific interaction between SU moieties in the polymer and the islet cells.