Molar Ratio Of Styrene Research Articles

Electrospun Poly(Styrene-Co-Vinylbenzyl Chloride-Co-Acrylonitrile) Nanofiber Mat as an Anion Exchange Membrane for Fuel Cell Applications.

A nanofiber mat of styrene−co−vinylbenzyl chloride−co−acrylonitrile copolymer as an anion exchange membrane (AEM) was synthesized via the electrospinning of organic reaction mixtures. The synthesized membranes were characterized using FT-IR spectroscopy for structural analysis. The AEM demonstrated a high ionic conductivity mainly due to the phase segregation in the membrane structure, as analyzed by transmission electron microscopy (TEM). The membrane properties such as water uptake, swelling ratio, and ion exchange capacity, as well as ionic conductivity, varied with the chemical composition. With the molar ratio of styrene, vinylbenzyl chloride, and acrylonitrile at 3:5:2, the highest ionic conductivity of 0.214 S cm−1 at 80 °C was observed. Additionally, the AEM retained 94% of original conductivity after 72 h of soaking in 1 M KOH solution.

Synthesis and sorption properties of organo-mineral sorbents based on poly(styrene-b-4-vinylpyridine) copolymer

New organo-mineral composites SiO2/poly(styrene-b-4-vinylpyridine) were obtained by adsorption of block- copolymers poly(styrene-b-4-vinylpyridine) with molar ratios of styrene (St) and 4-vinylpyridie (4-VP) St:4-VP = 1:4 and St:4-VP = 1:5 from THF solution onto silica gel surface. Block-copolymers were synthesized by controlled radical polymerization of styrene with RAFT agent and further copolymerization with 4-vinylpyridine. Also blok-copolymer with thiol end-group was obtained and has been employed for preparation of the composite. Composition of the block-copolymers and surface morphology of composites obtained were determined using 1H NMR and FT-IR spectroscopy, differential scanning calorimetry, thermogravimetric analysis and scanning electron microscopy. It was established that sorption capacity of the organo-mineral composites toward Pb(ІІ), Fe(ІІІ) and Cu(ІІ) ions is in 2–4 times higher in comparison with parent silica gel.

Perovskite LaSrCoFeO6 Oxide Enabled Visible Light Catalytic Aerobic Epoxidation of Styrene

AbstractIn the search for a highly efficient heterogeneous catalyst for the epoxidation of styrene, it is still a challenge to develop a system that simultaneously possesses superior catalytic activity and selectivity under aerobic conditions. Herein, we report the use of perovskite LaSrCoFeO6 (LSCF) as a heterogeneous and visible‐light catalyst, and determine that LSCF acts as a highly efficient catalyst for the epoxidation of styrene under aerobic conditions. The formation of 1O2 species transformed from O2⋅− species were proposed as reactive oxygen species for the epoxidation of styrene over the LSCF catalyst, where the directional generation of O2⋅− species on the LSCF catalyst is the key step to yield highly selective epoxidation of styrene. The experimental results of styrene epoxidation show that when the molar ratio of styrene and LSCF catalyst is 150 : 1 and the reaction is under the conditions of visible light (440 nm) and 100 °C for 6 h, the conversion of styrene and selectivity of styrene oxide reached 99.9 % and 80.3 %, respectively. The reaction rate over LSCF catalyst is as high as 50 mmol ⋅ gcat−1 ⋅ h−1. In addition, the reaction kinetics of the epoxidation of styrene over LSCF catalyst was systematically studied.

MCM-41 modified heterogeneous catalysts from rice husk for selective oxidation of styrene into benzaldehyde

This study examined the preparation of MCM-41, Ni-MCM-41 and Co-MCM-41 from silica extracted from rice husk ash (RHA) via sol–gel technique. The materials were characterized by X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM), Fourier Transform Infrared Spectroscopy (FT-IR), Diffuse reflectance UV–Vis (DR/UV–Vis),Energy Dispersive X-ray Spectrometry (EDX), N 2 adsorption–desorption and NH 3 TPD. XRD and TEM analyses showed reduction in the long range order upon the introduction of heteroatoms into MCM-41 framework. Successful substitution of Si 4 + with metal cations was verified by the shifting in the siloxane (Si-O-Si) bond. Presence of nickel phyllosilicates was evidenced from the FT-IR and DR/UV–Vis investigations. Mesoporous behavior with capillary condensation was unchanged even after the incorporation of Ni and Co species into the MCM-41 matrix. MCM-41 and modified MCM-41 catalysts were evaluated in the liquid-phase oxidation of styrene for 4 h under the influence of reaction parameters such as reaction temperature, catalyst loading, types of solvent and molar ratio of styrene : H 2 O 2 . Under the optimum condition of 343 K, 0.20 g catalyst, 1:4 molar ratios and DMF as the reaction medium, the activity was found to increase following the trend: Ni-MCM-41 (79.9%) >Co-MCM-41(56.6%) > MCM-41 (40.7%). Benzaldehyde was the sole product over Ni-MCM-41 and Co-MCM-41 while MCM-41 gave benzaldehyde (96.0%) and styrene oxide (4.0%). Surface characteristics and TPD acidity strength was found to govern the catalysis. Negligible leaching (0.448 ppm) and exceptional activity during successive reruns demonstrates that Ni-MCM-41 was beyond doubt, heterogeneous in nature. This research signifies a successful conversion of waste biomass into value added products. • Cobalt and nickel supported MCM-41 catalysts were synthesized from rice husk. • The catalyst was active in the oxidation of styrene at mild condition. • Benzaldehyde was the sole product over the modified MCM-41 catalysts. • The catalysis of Ni-MCM-41 was heterogeneous in nature with minor leaching. • Successful conversion of waste biomass into benign product.

Synthesis of Metal Salen@MOFs and Their Catalytic Performance for Styrene Oxidation

A series of effective heterogeneous catalysts, Cu or Ni salen with various loadings encapsulated in amino functionalized MOFs, were synthesized successfully for the first time via a one-pot method and denoted as metal salen@NH2-MIL-101(Cr). On the basis of detailed characterization of the catalysts, the varying coordination abilities between the Cu or Ni salen and NH2-MIL-101(Cr) provided the as-prepared Cu or Ni salen@NH2-MIL-101(Cr) with distinct activities toward styrene oxidation. The catalytic results showed that the introduction of Cu or Ni salen can significantly promote the selectivity to epoxide. However, Cu salen@NH2-MIL-101(Cr) showed preferable activity for styrene oxidation, and phenylacetaldehyde was generated with increasing Cu salen content. The optimal conditions for the reaction were also discussed, including the types of oxidants present, molar ratios of styrene and TBHP, and temperature. In particular, the mechanism of the styrene oxidation in 70% TBHP over Cu salen@NH2-MIL-101(Cr) was...

Nitrogen and sulfur Co-doped microporous activated carbon macro-spheres for CO2 capture

Millimeter-sized nitrogen and sulfur co-doped microporous activated carbon spheres (NSCSs) were first synthesized from poly(styrene-vinylimidazole-divinylbenzene) resin spheres through concentrated H2SO4 sulfonation, carbonization and KOH activation. Styrene (ST) and N-vinylimidazole (VIM) were carbon and nitrogen sources, while the sulfonic acid functional groups introduced by the simple concentrated sulfuric acid sulfonation worked simultaneously as cross-linking agent and sulfur source during the following thermal treatments. It was found that the surface chemistries, textural structures, and CO2 adsorption performances of the NSCSs were significantly affected by the addition of VIM. The NSCS-4-700 sample with a molar ratio of ST: VIM = 1: 0.75 showed the best CO2 uptake at different temperatures and pressures. An exhaustive adsorption evaluation indicated that CO2 sorption at low pressures originated from the synergistic effect of surface chemistry and micropores below 8.04 Å, while at the moderate pressure of 8.0 bar, CO2 uptake was dominated by the volume of micropores. The thermodynamics suggested the exothermic and orderly nature of the adsorption process, which was dominated by a physisorption mechanism. The high CO2 adsorption capacity, fast kinetic adsorption rate, and great regeneration stability of the nitrogen and sulfur co-doped activated carbon spheres indicated that the as-prepared carbon adsorbents were good candidates for large-scale CO2 capture.

Researchers collaborate to produce formaldehyde from CO2

This study examined the preparation of MCM-41, Ni-MCM-41 and Co-MCM-41 from silica extracted from rice husk ash (RHA) via sol–gel technique. The materials were characterized by X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM), Fourier Transform Infrared Spectroscopy (FT-IR), Diffuse reflectance UV–Vis (DR/UV–Vis),Energy Dispersive X-ray Spectrometry (EDX), N2 adsorption–desorption and NH3 TPD. XRD and TEM analyses showed reduction in the long range order upon the introduction of heteroatoms into MCM-41 framework. Successful substitution of Si4+ with metal cations was verified by the shifting in the siloxane (Si-O-Si) bond. Presence of nickel phyllosilicates was evidenced from the FT-IR and DR/UV–Vis investigations. Mesoporous behavior with capillary condensation was unchanged even after the incorporation of Ni and Co species into the MCM-41 matrix. MCM-41 and modified MCM-41 catalysts were evaluated in the liquid-phase oxidation of styrene for 4 h under the influence of reaction parameters such as reaction temperature, catalyst loading, types of solvent and molar ratio of styrene : H2O2. Under the optimum condition of 343 K, 0.20 g catalyst, 1:4 molar ratios and DMF as the reaction medium, the activity was found to increase following the trend: Ni-MCM-41 (79.9%) >Co-MCM-41(56.6%) > MCM-41 (40.7%). Benzaldehyde was the sole product over Ni-MCM-41 and Co-MCM-41 while MCM-41 gave benzaldehyde (96.0%) and styrene oxide (4.0%). Surface characteristics and TPD acidity strength was found to govern the catalysis. Negligible leaching (0.448 ppm) and exceptional activity during successive reruns demonstrates that Ni-MCM-41 was beyond doubt, heterogeneous in nature. This research signifies a successful conversion of waste biomass into value added products.

Selective Dispersion of Porphyrin Metal Complex into Styrene-(Ethylene-co-butylene)-Styrene Triblock Copolymer

Porphyrin metal complex covered with polystyrene (PS) arm chains was synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization of styrene from the porphyrin metal (Cu) complex with chain transfer agents (CTA) in the presence of AIBN at 80 °C (PDI < 1.2). Obtained PS covered porphyrin metal complex was then mixed with different molar ratio of styrene-(ethylene-co-butylene)-styrene (SEBS) triblock copolymer to give well-defined morphologies such as cylinder and lamella structures, where the porphyrin metal complex was selectively dispersed into the PS domain of the SEBS triblock copolymer. These materials could be expected to show interesting electroactive properties, because of high dielectric constant (k) and elastomeric property from the porphyrin metal complex and the SEBS triblock copolymer elastomer, respectively.

Ni 2+-containing ionic liquid immobilized on silica: Effective catalyst for styrene oxidation with H 2O 2 at solvent-free condition

In this work we synthesized Ni 2+-containing ionic liquid (IL) 1-methyl-3-[(triethoxysilyl)propyl]imidazolium chloride (TMICl) immobilized on silica to catalyze styrene oxidation with H 2O 2 for producing benzaldehyde. The catalyst was characterized by Fourier transform infrared (FT-IR) spectroscopy, UV–vis spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and nitrogen sorption techniques. The effects of reaction time, reaction temperature, and molar ratio of styrene and H 2O 2 on the conversion and selectivity were studied at solvent-free condition and in acetonitrile. It was demonstrated that the catalyst was very effective for the reaction. The unique advantage of the catalyst was that the reaction could be carried out at solvent-free condition. This advantage resulted mainly from the fact that both of the reactants, styrene and H 2O 2, are miscible with the IL, and the Ni 2+ was coordinated by the immobilized IL that allowed both reactants to access to active sites of the catalyst effectively.

The Effect of Feed Composition of Styrene and Acrylic Acid on the Properties of Modified Low Density Polyethylene

AbstractSummary: Low density polyethylene (LDPE) was functionalized with different molar ratios of styrene (St) to acrylic acid (AA) in the presence of dicumyl peroxide (DCP) in the molten state. The resultant LDPE was characterized by gel content and torque analysis. The results showed that the gel content of polymers grafted with small molar ratios (St/AA = 0.5) was always higher than those grafted with the equimolar St/AA ratio. The effect of DCP amount and AA concentration on the grafting degree of AA was investigated. The suitable DCP amount and AA concentration was obtained. Functionalized LDPE [LDPE‐g‐(AA‐St)] was characterized by Fourier transform infrared spectroscopy (FTIR), melt flow rate (MFR), water contact angle and capillary rheometry. The results showed that both MFR and grafting degree of AA of LDPE‐g‐(AA‐St) was the highest when an equimolar AA/St ratio was used, but when mixtures of St and AA (St/AA = 1/10) were loaded, the water contact angle of the film prepared from the LDPE‐g‐(AA‐St) was the smallest, which indicated that the hydrophicity of the film surface not only depended on the grafting degree, but also the molar ratios of the hydrophobic/hydrophilic groups.

RAFT Polymerization of Styrene in the Presence of 2‐Nonyl‐benzoimidazole‐1‐carbodithioic Acid Benzyl Ester

A novel dithiocarbamate, 2‐nonyl‐benzoimidazole‐1‐carbodithioic acid benzyl ester ( 1a ), was synthesized and successfully used in RAFT polymerization of styrene in bulk with thermal initiation. The effect of molar ratio of styrene to RAFT agent on the polymerization was investigated. The linear relationship between ln([M]0/[M]) and polymerization time indicated that the polymerization was first‐order with respect to monomer concentration. The molecular weights increased linearly with monomer conversion and were close to corresponding theoretical values. The molecular weight distributions (M w /M n ) kept very narrow (M w /M n <1.1) at a wide range of conversions of 14.2% to 73.3%. The obtained polymer had a strong ultraviolet absorption at 329 nm, which indicated that the 1a moiety remained at the end of polymer chain.

Crystalline Cyclodextrin Inclusion Compounds Formed with Aromatic Guests: Guest-Dependent Stoichiometries and Hydration-Sensitive Crystal Structures

A series of solid inclusion complexes (ICs) containing the aromatic guests aniline, benzene, ethylbenzene, phenol, p-xylene, styrene, and toluene were formed with host γ-cyclodextrin (γ-CD). IC stoichiometry was observed to depend on the nature of the included aromatic guest. The molar ratio of styrene, aniline, and phenol guests to γ-CD host was ∼2:1 in their individual IC crystals, whereas ethylbenzene, p-xylene, and toluene guests formed ∼1:1 inclusion complexes with γ-CD. Thermogravimetric analysis showed that the thermal stabilities of these volatile aromatic guest molecules increased due to guest−host interactions once they were included in their γ-CD-ICs. X-ray diffraction (WAXD) observations performed on the aromatic guest−CD-IC crystals showed that all of them have channel-type crystalline structures. Moreover, it was observed that the presence of guest molecules inside the γ-CD cavities stabilized the channel structure of stacked γ-CDs. However, a solid-phase transition from tetragonal to hexago...

Polymers from renewable resources. II. A study in the radio chemical grafting of poly(styrene-alt-maleic anhydride) onto cellulose extracted from pine needles

A binary mixture of styrene and maleic anhydride has been graft copolymerized onto cellulose extracted from Pinus roxburghii needles. The reaction was initiated with gamma rays in air by the simultaneous irradiation method. Graft copolymerization was studied under optimum conditions of total dose of radiation, amount of water, and molar concentration previously worked out for grafting styrene onto cellulose. Percentage of total conversion (Pg), grafting efficiency (%), percentage of grafting (Pg), and rates of polymerization (Rp), grafting (Rg), and homopolymerization (Rh) have been determined as a function of maleic anhydride concentration. The high degree of kinetic regularity and the linear dependence of the rate of polymerization on maleic anhydride concentration, along with the low and nearly constant rate of homopolymerization suggest that the monomers first form a complexomer which then polymerizes to form grafted chains with an alternating sequence. Grafting parameters and reaction rates achieve maximum values when the molar ratio of styrene to maleic anhydride is 1 : 1. Further evidence for the alternating monomer sequence is obtained from quantitatively evaluating the composition of the grafted chains from the FT-IR spectra, in which the ratio of anhydride absorbance to aromatic (CC) absorbance for the stretching bands assigned to the grafted monomers remained constant and independent of the feed ratio of maleic anhydride to styrene. Thermal behaviour of the graft copolymers revealed that all graft copolymers exhibit single stage decomposition with characteristic transitions at 161–165°C and 290–300°C. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1763–1769, 1999

Radiation‐initiated copolymerization of styrene with unsaturated esters

AbstractThe kinetics of the γ‐ray‐initiated, gel‐forming copolymerization of styrene with the unsaturated ester containing 1.5 double bonds per molecule of number‐average molecular weight of 890 (derived from maleic anhydride, phthalic anhydride, and propylene glycol) have been studied with initial ester concentrations ranging from 65% to 2.4%. From experimentally determined gel fractions, rates of disappearance of styrene and ester unsaturation (measured up to complete conversion of ester unsaturation), and the degree of polymerization of the growing chains, a model is suggested based on a free radical copolymerization, assuming a single effective propagation and termination rate constant (kp and kt, respectively), and bimolecular chain termination except between a pair of immobile gel radicals. Three ester concentration ranges were considered. At high ester concentrations (≥ 50%), styrene and ester enter the gel at a constant rate (molar ratio of styrene:ester double bond of 2:1), precluding application of conventional copolymer composition theory. The rate at which overall unsaturation, α, disappears, is given by dα/dt = (kp2/kt)M2° where M2° is the initial molar concentration of ester unsaturation. The rate at which styrene, α1, disappears is given by dα1/dt = 2/3(kp2/kt)M2°(M1° + M2°)/M1°. The rate at which styrene is consumed in the dilute esterstyrene solutions (⩽4.6%), where M2° is negligibly small, is given by dα1/dt = kp(k1/2kt)1/2. Polymerization rates of the intermediate ester concentration ranges (10% to 30%) are higher than predicted from the simple model. An empirical rate expression is presented which describes these systems to 40% conversion of styrene: dα1/dt = (kp2/kt)M2° {[(1 + m)(r1 + M)]/(r1 + 2M)}, where M is the ratio of ester unsaturation to styrene in the starting mixture and r1 is the reactivity ratio for styrene, defined in the usual manner. For initial conversions of ester unsaturation (to 10%) dα/dt = (kp2/kt)M2°.