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Products made from light olefins play an important role in our daily lives. Traditional light olefins production based on steam cracking and fluid catalytic cracking suffer from high energy consumption and CO2 emissions. Thereby, the continually increasing demand for light olefins needs to be met through more environmentally sustainable procedures. On‐purpose production routes are preferred choice among petrochemicals manufacturers, being energy efficient and having lower carbon footprint. Among them, oxidative dehydrogenation (ODH) of light paraffins is a thermodynamically favourable exothermic process as compared to non‐oxidative routes. They can be operated at lower temperatures and have propensity of low coke deposition on catalyst, thereby resisting rapid catalyst deactivation. Herein, we have analysed various catalytic systems utilised in the oxidative dehydrogenation process. We have reviewed role of support, chemical composition of catalyst, presence of dopant, oxidation state of active metal, controlled surface modification by oxidative and reductive pretreatments, and reaction factors for each system. The performance of various catalytic systems for ODH of ethane, propane and butane in the presence of O2, CO2, N2O and special oxidants have been reviewed. A short critical overview on emerging on‐purpose routes for the production of renewable 1,3 butadiene has also been discussed. [ABSTRACT FROM AUTHOR]

Block copolymers based on polyethylene (PE) and ethylene butadiene rubber (EBR) were obtained by successive controlled coordinative chain transfer polymerization (CCTP) of a mixture of ethylene and butadiene (80/20) and pure ethylene. EBR‐b‐PE diblock copolymers were synthesized using the {Me2Si(C13H8)2Nd(BH4)2Li(THF)}2 complex in combination with n‐butyl,n‐octyl magnesium (BOMAG) used as both the alkylating and chain transfer agent (CTA). Triblock and multiblock copolymers featuring highly semi‐crystalline PE hard segments and soft EBR segments were further obtained by the development of a bimetallic CTA, the pentanediyl‐1,5‐di(magnesium bromide) (PDMB). These new block copolymers undergo crystallization‐driven organization into lamellar structures and exhibit a variety of mechanical properties, including excellent extensibility and elastic recovery in the case of triblock and multiblock copolymers. [ABSTRACT FROM AUTHOR]

The copolymerization techniques of ethylene and conjugated diene, such as butadiene and isoprene, were summarized. The structure and performance characteristics of polymers obtained from different catalytic systems were reviewed with 26 references. The guidance and suggestions for the subsequent development of efficient catalytic systems of ethylene/conjugated diene copolymerization were previewed.

Block copolymers based on ethylene (E) and butadiene (B) were prepared using the ansa‐bis(fluorenyl) complex {Me2Si(C13H8)2Nd(BH4)2Li(THF)}2 in combination with (n‐Bu)(n‐Oct)Mg (BOMAG) as a chain‐transfer agent. The diblock copolymers incorporating a soft poly(ethylene‐co‐butadiene) segment, called ethylene butadiene rubber (EBR), and a hard polyethylene (PE) one were obtained by simply adjusting the different feeds of monomers during the polymerization. The soluble EBR block was formed first by feeding the catalytic system dissolved in toluene at 70 °C with a mixture of ethylene and butadiene (E/B molar ratio 80 : 20). Then the feeding was stopped leading to the consumption of a large part of the residual monomers. The reactor was finally fed with ethylene to form the PE block. By varying the molar mass of the latter, it is shown that the resulting soft‐b‐hard block copolymers can self‐assemble simultaneously to the growth of the PE block in agreement with a polymerization‐induced self‐assembly (PISA) mechanism. The self‐assembly is discussed considering the reaction conditions, the crystallization of the PE block, and the polymerization mechanism involved. [ABSTRACT FROM AUTHOR]

The unsaturated metalloid germanium cluster Ge6{N(SiMe3)Dipp}42 with two ligand-free germanium atoms and only four amine substituents was obtained starting from the base-coordinated germylene {N(SiMe3)Dipp}GeCl·DMAP 1 in 50% yield (DMAP = 4-(dimethylamino)-pyridine). This cluster reacts as a masked digermyne in cycloadditions with ethylene, diphenylacetylene and 2,3-dimethyl-1,3-butadiene in toluene at 100 °C to yield 3–5. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ethylene can react at cryogenic temperatures with dinitrogen tetroxide, N 2 O 4. • Organic nitro compounds and organic nitrates were detected by IR spectroscopy. • The results are compared with the known reaction of N 2 O 4 with butadiene. • The temperature and time characteristics of the reaction have been found. The possibility of the reaction of ethylene at cryogenic temperatures with dinitrogen tetroxide (N 2 O 4), at least at –40 °C, has been demonstrated. An infrared (IR) spectroscopic analysis of the condensed reaction products was carried out, which showed the presence of substances containing organic nitro compounds and organic nitrates. The latter particularly means the possibility of the formation of explosive substances, as in the known explosive cryogenic reaction of N 2 O 4 with butadiene. The fundamental possibility of such a reaction is of importance for the organization of cryogenic production of gases from raw materials containing ethylene and nitrogen oxide impurities. The sensitivity of the experimental setup was demonstrated by using the example of the known reaction of N 2 O 4 with butadiene. The temperature and time characteristics of the latter reaction have been found. To determine the temperature range of possible reactions of ethylene with N 2 O 4 , thermograms of the process of heating the reactive mixture at a constant rate were analyzed. To ensure the sensitivity of the qualitative analysis of thermograms of the reaction of ethylene with N 2 O 4 in the linear heating mode, a quasi-differential method was proposed that uses the temperature of the cryo-thermostat coolant, which varies linearly with time, as the reference temperature. Some recently published theoretical results concerning the mechanisms of N 2 O 4 isomerization are discussed which may be useful for further studies in establishing the mechanisms and predicting the ratios of the products and their yields for the reaction of N 2 O 4 with olefins under particular experimental conditions. [ABSTRACT FROM AUTHOR]

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The equation-of-motion coupled-cluster (EOM-CC) method has been used to calculate the vertical excitation energies of ethylene, trans-butadiene, cis-butadiene, and cyclopentadiene. The approximations used were the EOM-CC singles-and-doubles (EOM-CCSD) method and EOM-CCSD with a noniterative treatment of triple excitations, EOM-CCSD(T), EOM-CCSD(T). The basis sets were atomic natural orbital sets augmented with diffuse functions. Comparisons have been made with a series of complete active space second-order perturbation theory (CASPT2) results, which used the same basis sets and geometries, and experiment. For the Rydberg states the EOM-CCSD results were in good agreement with experiment and CASPT2. The results for the valence states show more variation. For ethylene CASPT2 exaggerates the Rydberg character of the V state, while EOM-CCSD provides a better description. For the valence states of the other molecules the EOM-CCSD excitation energies tend to be too high, but considerable improvements are given by EOM-CCSD(T). For the 1 1Bu/1 1B2 states of butadiene and cyclopentadiene EOM-CCSD(T) agrees well with experiment and CASPT2. The agreement for the 1 1Ag→2 1Ag and 1 1A1→2 1A1 transitions for trans-butadiene and cis-butadiene, which are not known experimentally, is not so good, with the EOM-CC results significantly higher than the CASPT2 ones. However, the EOM-CCSD(T) and CASPT2 energies for the 1 1A1→2 1A1 transition in cyclopentadiene are in quite close agreement and both agree well with experiment. EOM-CCSD(T) shows an average error in vertical excitation energies for all states of all molecules of 0.12 eV, and improves those for valence states from an error of 0.26 eV for EOM-CCSD to 0.13 eV. © 1996 American Institute of Physics. [ABSTRACT FROM AUTHOR]

A series of systematic approximations is applied within the correlated, size-extensive, ab initio effective valence shell Hamiltonian (Hν) formalism to test such basic assumptions of π-electron theory as the zero-differential-overlap (ZDO) approximation and the transferability of semiempirical matrix elements (called parameters). The systematic approximations (tested in paper I) involve the use of π-electron valence orbitals that are constructed from a set of localized, transferable pπ functions and the neglect of three- and four-body Hν parameters. Our approximate ab initio Hν explicitly contains correlation contributions to all its parameters, and some fundamental differences exist between the ab initio Hν and the standard semiempirical π-electron methods. Correlation contributions are shown to be essential in justifying the ZDO approximation, but some violations of this approximation appear. Transferability of Hν parameters is often excellent between ethylene, trans-butadiene, and cyclobutadiene provided that the local geometries are made as similar as possible. The Hν parameters with the largest correlation contributions display the greatest sensitivity to molecular environment, while orbital orthogonalization provides another mechanism inhibiting exact transferability. [ABSTRACT FROM AUTHOR]

Ab initio results for the low-lying 1B1u states of ethylene are used to discuss size-inconsistency effects on calculated molecular properties for states where valence-Rydberg mixing is important. Results for the expectation value of x2, x being the coordinate perpendicular to the plane of the molecule, are presented from quasidegenerate variational perturbation theory and multireference configuration-interaction calculations. These results are compared with values from previous studies. It is argued that size inconsistency in configuration-interaction studies can have a significant effect on estimated molecular properties. Calculations on several low-lying states of butadiene are also reported where similar size-inconsistency effects are found. [ABSTRACT FROM AUTHOR]

Equilibrium structures and in-plane harmonic force fields of ethylene, trans 1,3-butadiene, and all-trans 1,3,5-hexatriene were investigated with the aid of ab initio Hartree–Fock (SCF) calculations applying basis sets of DZ+P and TZ+P quality. The most interesting parts of the force fields, namely those involving stretching vibrations of the conjugated carbon backbone, were subsequently reevaluated including electron correlation at the coupled pair functional (CPF) level. We demonstrate that electron correlation has a significant influence not only on the degree of bond alternation in the ground state equilibrium structure but simultaneously leads to an increase in absolute value of all off-diagonal stretch–stretch coupling constants within the carbon backbone. [ABSTRACT FROM AUTHOR]

Computes the kinetic and thermodynamic properties for the Diels-Alder reactions of butadiene with ethylene, formaldehyde and thioformaldehyde. Quantum chemical principles included in the properties; Presence of heteroatoms; Extension of basis sets and inclusion of most of the dynamical correlation.

We have quantum chemically explored the Diels–Alder reactivities of a systematic series of hetero‐1,3‐butadienes with ethylene by using density functional theory at the BP86/TZ2P level. Activation strain analyses provided physical insight into the factors controlling the relative cycloaddition reactivity of aza‐ and oxa‐1,3‐butadienes. We find that dienes with a terminal heteroatom, such as 2‐propen‐1‐imine (NCCC) or acrolein (OCCC), are less reactive than the archetypal 1,3‐butadiene (CCCC), primarily owing to weaker orbital interactions between the more electronegative heteroatoms with ethylene. Thus, the addition of a second heteroatom at the other terminal position (NCCN and OCCO) further reduces the reactivity. However, the introduction of a nitrogen atom in the backbone (CNCC) leads to enhanced reactivity, owing to less Pauli repulsion resulting from polarization of the diene HOMO in CNCC towards the nitrogen atom and away from the terminal carbon atom. The Diels–Alder reactions of ethenyl‐diazene (NNCC) and 1,3‐diaza‐butadiene (NCNC), which contain heteroatoms at both the terminal and backbone positions, are much more reactive due to less activation strain compared to CCCC. Go forth and cyclize! A comprehensive account detailing the reactivity of a series of aza‐ and oxa‐dienes in hetero‐Diels–Alder reactions with ethylene is presented. The combined activation strain and energy decomposition analyses elucidate the factors governing reaction rates and highlight the delicate interplay between orbital interactions and strain, depending on the position of the heteroatom. [ABSTRACT FROM AUTHOR]

Catalytic synthesis of 1,3-butadiene from dimethyl ether (DME) has been carried out for the first time. It has been established that 1,3-butadiene forms via three possible routes of reactions between DME conversion products: by reaction of propylene with formaldehyde according to the Prins condensation mechanism, by DME isomerization of to ethanol followed by its conversion to 1,3-butadiene through acetaldehyde, and by dehydrogenation of butylenes. [ABSTRACT FROM AUTHOR]

An iridium complex is found to catalyze the selective dehydrogenative coupling of ethylene to 1,3-butadiene. The key intermediate, and a major resting state, is an iridacyclopentane that undergoes a surprisingly facile β-H elimination, enabled by a partial dechelation (κ³-κ²) of the supporting 3,5-dimethylphenyl-2,6-bis(oxazolinyl) ligand. [ABSTRACT FROM AUTHOR]

Over the last decade, increasing demand for olefins and their valuable products has prompted research on novel processes and technologies for their selective production. As olefins are predominately dependent on fossil resources, their production is limited by the finite reserves and the associated economic and environmental concerns. The need for alternative routes for olefin production is imperative in order to meet the exceedingly high demand, worldwide. Biomass is considered a promising alternative feedstock that can be converted into the valuable olefins, among other chemicals and fuels. Through processes such as fermentation, gasification, cracking and deoxygenation, biomass derivatives can be effectively converted into C2–C4 olefins. This short review focuses on the conversion of biomass-derived oxygenates into the most valuable olefins, e.g., ethylene, propylene, and butadiene. [ABSTRACT FROM AUTHOR]

The solubility of ethylene (H2C=CH2), propyne (CH3-C=C-H), 2-methyl-2-butene (CH3-CH=C(CH3)2), and isoprene or 2-methyl-1, 3-butadiene (H2C=C(CH3)-CH=CH2) in liquid argon has been measured using mid-infrared and nearinfrared (NIR) absorption. Spectra were recorded in the C-H infrared (IR) region. Spectra were obtained at increasing solution composition until the magnitude of the integrated absorption band reached a maximum value, indicating a saturated solution. The approximate experimental solubilities are: (600±100) ppm at 92 K for ethylene, (22±9) ppm at 100 K for propyne, (9±5) ppm at 100 K for 2-methyl-2-butene, and (12±2) ppm at 86 K for isoprene. The experimental solubility values at the corresponding temperature were used with solubility parameters of two separate models: the perturbed-chain statistical associating fluid theory (PC-SAFT) and the regular solution theory. Solvent-solute interaction parameters k12 (PC-SAFT) and i12 (RST) were obtained for each solute in the presence of argon as the solvent. Data from experimental measurements are important for more realistic simulations of solubility of solids in cryogenic liquids. [ABSTRACT FROM AUTHOR]

Introducing ethylene units into polybutadiene backbones is an approach to synthesize advanced rubber materials, which has been a research challenge because of distinct polymerization mechanisms of the two monomers. To date, only trans-1,4- and 1,2-regulated copolymers have been obtained. Herein, we reported the unprecedented cis-1,4 selective copolymerization of ethylene and butadiene by using the thiophene-fused cyclopentadienyl-ligated scandium complexes. The effects of the sterics and electronics of the catalytic precursors as well as the monomer loading mode on the activity and selectivity as well as the sequence lengths were investigated, and the mechanism was elucidated. Thus a novel ethylene-based rubber material possessing a high molecular weight, 80 % cis-1,4 regularity and a Tg=−94 °C without an obvious melting point owing to short polyethylene sequences even at its content up to 45 mol %, was isolated. This new rubber material exhibited excellent anti-flowing performance and strong tensile strength. [ABSTRACT FROM AUTHOR]

ABSTRACT A combination of microvolumetry, the rotating sector method, ESR, 1H NMR, and IR allowed to establish a detailed mechanism of liquid-phase oxidation of vinyl compounds X1CH=CHX2 and X1CH=CH-CH=CHX2 (X1 and X2-a polar substitute: С6Н5-, CO-, СOO-) initiated by azobisisobutyronitrile. A distinctive feature of the mechanism is the fact that the oxidation chain is carried out by a low-molecular hydroperoxide radical joining the π-bond. For nine compounds in the temperature range of 303-353 K, relative chain propagation and termination rate constants were measured ( k2• k3−0.5). Absolute values of k2 were obtained for diphenylethylene (110 L·mol−1·s−1), ethyl ether of trans-phenyl-pentadiene acid (13 L·mol−1·s−1), and methyl ether of trans-phenyl-pentadiene acid (14.2 L·mol−1·s−1) at T = 323 K. For the same conditions, 10−8 k3 were calculated for diphenylethylene (0.87 L·mol−1·s−1) and methyl ether of trans-phenyl-pentadiene acid (1.21 L·mol−1·s−1). A cyclic mechanism of the oxidation chain termination on introduced antioxidants (stable nitroxyl radicals of the piperidine series ( >NO●) and the transition metal compounds (Me n)) was established. The inhibition factor ( f) showing how many reaction chains are terminated by the one particle of the antioxidant is equal to 102. The cyclic chain termination is caused by the following reactions: HO2● + >NO● → NOH + O2, HO2● + NOH → >NO● + H2O2 (for >NO●) and HO2● + Me n → Me n+1 + HO2●−, HO2● + Me n+1 → Me n + H+ + O2 (for Me n). [ABSTRACT FROM AUTHOR]

In this study, acrylonitrile butadiene styrene/ethylene vinyl acetate-based melt blends were prepared using linear low-density polyethylene as modifier. Commercially available sodium montmorillonite clay was organically modified and incorporated in blends. Fourier transformed infrared was used to confirm the structure of the blend and composites. Morphology of acrylonitrile butadiene styrene / ethylene vinyl acetate blend showed two-phase structure that formed a well-aligned pattern with fine nanoclay distribution. Addition of organo-modified clay depicted increase in tensile strength (43%) and modulus (89%) in damage-free range. XRD results of sodium montmorillonite, organically modified Na-montmorillonite, and PNCs were compared to investigate the degree of dispersion in matrix. [ABSTRACT FROM PUBLISHER]

Ageing of bitumen is an important cause of reduced durability of asphalt pavements. Therefore, the polymer modified bitumens are recommended to increase the durability of the material. In the present work, rheology has been applied to evaluate the properties of Styrene-Ethylene- Butadiene -Styrene (SEBS) polymer modified bitumen (PMB) to compare to the 35 / 50 penetration grade bitumen, before and after ageing. The effects of ageing on the physical and rheological properties of (PMB) were evaluated using SARA analysis, penetration test, softening point test and dynamic shear rheometer test (DSR). The binders were aged by Rolling Thin Film Over Test (RTFOT) and Pressure Ageing Vessel (PAV). The results showed that use of SEBS polymer reduces the ageing effect on physical and rheological properties of the bitumen binder as illustrated through lower ageing index of complex modulus and an increase in tang δ indicating that the SEBS polymer improve the ageing resistance of bitumen binder. [ABSTRACT FROM AUTHOR]

Texas has the largest ambient air monitoring network in the country with approximately 83 monitoring sites that measure ambient air concentrations of volatile organic compounds (VOCs). The lower olefins, including 1,3-butadiene, ethylene, isoprene, and propylene, are a group of VOCs that can be measured in both 24 h/every sixth-day canister samples and continuous 1-h Automated Gas Chromatography (AutoGC) samples. Based on 2012 Toxics Release Inventory data, the total reported industrial air emissions in Texas for these olefins, as compared to total national reported air emissions, were 79% for 1,3-butadiene, 62% for ethylene, 76% for isoprene, and 54% for propylene, illustrating that Texas industries are some of the major emitters for these olefins. The purpose of this study was to look at the patterns of annual average air monitoring data from 2002 to 2012 using Texas Commission on Environmental Quality (TCEQ) data for these four lower olefins. It should be emphasized that monitors may not be located close to or downwind of the highest emitters of these lower olefins. In addition, air monitors only provide a snapshot in time of air concentrations for their respective locations, and may not be able to discriminate emissions between specific sources. In 2012, the highest annual average air concentration for 1,3-butadiene was 1.28 ppb by volume (ppbv), which was measured at the Port Neches monitoring site in Region 10-Beaumont. For ethylene, the highest 2012 annual average air concentration was 5.77 ppbv, which was measured at the Dona Park monitoring site in TCEQ Region 14-Corpus Christi. Although reported industrial emissions of isoprene are predominantly from the Houston and Beaumont regions, trees are natural emitters of isoprene, and the highest ambient air concentrations tend to be from regions with large areas of coniferous and hardwood forests. This was observed with TCEQ Region 5-Tyler, which had the two highest isoprene annual average air concentrations for 2012: 0.56 ppbv at the Karnack monitoring site and 0.47 ppbv at the Longview monitoring site. For propylene, the highest 2012 annual average air concentration was recorded at the HRM 7 monitoring site in TCEQ Region 12-Houston, which was 7.9 ppbv. A significant portion of the total 2012 industrial propylene emissions were also reported in TCEQ Region 12-Houston. Although some individual monitors showed increased annual averages from 2002 to 2012, there was a general decreasing trend present across the state for all four lower olefins examined. The annual average air concentrations of the four lower olefins were well below their respective Air Monitoring Comparison Values (AMCVs) and are not expected to cause long-term or chronic adverse health effects. [ABSTRACT FROM AUTHOR]

Themethods used in deriving the rate expressions from comparativerate single-pulse shock tube studies, recent direct shock tube studies,and high-pressure flow experiments bearing on the data for the reverseDiels–Alder decomposition of cyclohexene to form ethylene and1,3-butadiene are reviewed. This current interest is due to the increasingneed for accurate kinetics and physical data (particularly the temperature)for realistic simulations in practical areas such as combustion. Therate constants derived from the direct shock tube studies and high-pressureflow experiments are somewhat larger than those used in comparativerate single-pulse shock tube experiments. For the latter, it is shownthat they have been derived from a variety of independent experimentsthat include rate constants for unimolecular decomposition and isomerizationprocesses that are considered to be well understood. The possibilityof non-Arrhenius behavior in the unimolecular rate constants as aconsequence of the large range covered in rate constants (as muchas 12 orders of magnitude) for the comparative rate experiments hasbeen examined and ruled out as a source of the discrepancy. Our analysisshows that there is the need to consider the possibility of radical-induceddecompositions for verifying the correctness of the reaction mechanismsin studying unimolecular reactions. In the case of cyclohexene decomposition,recent experiments demonstrating the presence of residual amountsof H atoms in shock tube experiments suggest that addition to thedouble bond can also lead to the formation of ethylene and 1,3-butadieneand hence to rate constants larger than the true values. This possibilityis even more likely to occur in high-pressure flow experiments. Asa result, the internal standard method must be used with care anda radical inhibitor should always be present in sufficiently largequantities to suppress possible chain reactions. The present analysisresults have important implications for the determination of temperaturesin shock tubes. [ABSTRACT FROM AUTHOR]

In this article, 50/70 penetration graded TUPRAS bitumen was modified. Reactive elastomeric terpolymer (Elvaloy RET) from DuPont, ethylene vinyl acetate (EVA) and styrene butadiene styrene (SBS) polymers were used in the bitumen modification. Set hours of the tests were applied to samples taken from the obtained modified bitumen mixture, and 1 % reactive ethylene terpolymer, 1 % SBS and 0.5, 1, 1, 5, 2, and 2.5 % EVA (w/w) were added to the raw bitumen. Penetration, penetration index, softening point, ductility and % elastic recovery tests were performed with the modified bitumen and raw bitumen. The samples of raw bitumen and modified bitumen with 2 % RET, 1 % SBS and 1 % EVA were investigated by means of IR spectroscopy (FT-IR) and thermogravimetrical analysis/differential thermal analysis (TG/DTA). The raw bitumen was modified with RET, SBS and EVA, and it was determined that the penetration and ductility values were decreased while the penetration index, softening point and % elastic recovery were increased. The most important characteristics (such as softening point, penetration and % elastic recovery) of the new polymer-modified bitumen (NPMB) containing 2.5 % EVA, 1 % RET and 1 % SBS were compared with eight different types of polymer-modified bitumens in Turkey (TPMB). NPMB provided all the required parameters (softening point, penetration and % elastic recovery) for two different types of TPMBs (TPMB 70-16, TPMB 70-22). [ABSTRACT FROM AUTHOR]

A series of co-pyrolysis tests of naphtha and methyl cyclohexane were carried out to study the products yield changes in pyrolysis of different proportions and at different temperatures. The result showed that comparing with the naphtha pyrolysis alone, the yield of co-pyrolysis ethylene decreased while the yield of butadiene substantially increased. Relatively high temperatures are benefit for high butadiene yield while smaller drop of ethylene yield. The co-pyrolysis of naphtha and methyl cyclohexane can optimize the pyrolysis gas product distribution and improve the comprehensive added value of products. It can fully rely on existing ethylene pyrolysis unit and subsequent separation system. Meanwhile, co-pyrolysis has the advantages of high feasibility, lower investment and stable operation, which can meet the requirements of industrial production. [ABSTRACT FROM AUTHOR]

This article presents an investigation about the polymer-modified bitumens (PMBs) containing styrene–butadiene–styrene (SBS) block copolymers with different structures, linear (SBS-L) and radial (SBS-R), semicrystalline copolymer ethylene–vinyl acetate (EVA), and terpolymer ethylene–butyl acrylate–glycidyl methacrylate, Elvaloy AM and Elvaloy 4170. The aim of the study was to establish the influence of the polymer type and content on the properties of PMBs for engineering applications and to evaluate the effectiveness of polymer modifiers. The results indicated that the polymer modification improved the rheological properties of bitumen, increased critical temperature, that is better resistance to permanent deformation was achieved as well as a wider temperature range in service. The degree of improvement generally increased with the polymer content but varied with the polymer type. [ABSTRACT FROM PUBLISHER]

The (DA) reaction is one of the most important reactions in organic chemistry. The controversy surrounding this reaction as to whether it follows a concerted or stepwise mechanism has existed for a long time. The reaction of 1,3-butadiene and ethylene is the paradigmatic example of the DA reaction. We have reinvestigated the mechanism of this reaction using density functional theory. The theoretical study considered all types of possible pathways for the reaction of 1,3-butadiene and ethylene using six functionals at different rungs of Jacob's ladder. Therefore, a complete picture is given for a thorough understanding of the iconic DA reaction, and a new stationary point during the reaction processes has been reported for the first time. The calculated results indicated that three functionals, ωB97X-D, M06-2X, and B2-PLYP, of the fourth and fifth rungs of Jacob's ladder performed well in the investigation of the mechanism of this reaction and that the reliable basis set should be larger than 6-311+G(2d,p). The cis-1,3-butadiene more easily reacted with ethylene compared with 1,3-butadiene in the trans conformation. The concerted mechanism was found to be energetically favorable, whose energy barrier is around 10 kcal/mol lower than that of the stepwise mechanism. Two investigated solvents, toluene and CH3CN, had little impact on this simple DA reaction. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

In this work, maleic anhydride grafted styrene-ethylene-butadiene-styrene copolymer (SEBS-g-MA) and carbon nanotubes (CNTs) were introduced into the immiscible polypropylene/polystyrene (PP/PS) blend. Among the three polymer components, SEBS-g-MA has the strongest affinity to CNTs; thus, it exhibits dual effects to adjust the phase morphology of the blends and the dispersion state of CNTs in the blends. The experimental observations obtained from morphology characterizations using scanning electron microscope and transmission electron microscope confirm the selective localization of CNTs at the interface of the immiscible PP/PS blend. As a consequence, largely decreased percolation threshold is achieved when most of CNTs are selectively localized at the interface region between PP and PS. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]