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BACKGROUND: Styrene trimers (STs) are polystyrene-container-eluted materials that are sometimes detected in packaged foods. Although the possible endocrine-disrupting effects of STs, such as estrogenic activities, have been reported, their potential [...]

Several polystyrene polymers were prepared by reversible addition fragmentation chain-transfer (RAFT) polymerization of styrene, using two different RAFT agent-initiator systems, and then further characterized by NMR and SEC as well as MALDI-TOF-MS techniques. The data indicate that most of the polymer chains are terminated by the active groups (Ph-C(=S)-S--) derived from RAFT agents, and few of the polymer chains bear initiator fragments at one end. Most importantly, the structures arising from the intermediate RAFt radicals and their cross-termination adducts were detected. Also, the MALDI-TOF-MS analysis shows that the combination termination between two macromolecular radicals is minor, and the amount of dead chains is quite low. Thus, narrow molecular weight distribution is obtained. This analysis confirms the operation of the Rizzardo mechanism including the Monteiro intermediate radical termination model for the RAFT polymerization.

In this paper, the preparation and performance of long, high-efficiency poly(styrene-divinylbenzene) (PS-DVB), 10-[micro]m-i.d. porous layer open tubular (PLOT) capillary columns are described. PLOT capillaries (~3% RSD column-to-column retention time), with relatively high permeability, were prepared by in-situ polymerization. Relatively high loading capacities, ~100 fmol for angiotensin I and ~50 fmol for insulin, were obtained with a 4.2 m x 10-[micro]m-i.d. PLOT column. Low detection levels (attomole to sub-attomole) were achieved when the column was coupled on-line with a linear ion trap MS (LTQ). Analysis of human epidermal growth factor receptor (EGFR), a large transmembrane tyrosine kinase receptor with heterogeneous phosphorylation and glycosylation structures, was obtained at the 25 fmol level. The PLOT column yielded a peak capacity of ~400 for the separation of a complex tryptic digest mixture when the sample preparation included a 50-[micro]m-i.d. PS-DVB monolithic precolumn and ESI-MS detection. As an example of the power of the column, 3046 unique peptides covering 566 distinct Methanosarcina acetivorans proteins were identified from a 50 ng in-gel tryptic digest sample combining five cuts in a single LC/MS/MS analysis using the LTQ. The results demonstrate the potential of the PIA)T column for high-resolution LC/MS at the ultratrace level.

Propene monooxygenase is cloned from Mycobacterium sp. strain M156, based on hybridization with the amoABCD genes of Rhodococcus corallinus B276. The results suggest that changing the volume occupied by the side chain at V188 leads to a systematic alteration in the stereoselectivity of styrene oxidization, presumably by producing different orientations for substrate binding during catalysis.

Pseudomonas sp. VLB120 uses styrene as a sole source of carbon and energy. The first step in this metabolic pathway is catalyzed by an oxygenase (StyA) and a NADH-flavin oxidoreductase (StyB). Both components have been isolated from wild-type Pseudomonas strain VLB120 as well as from recombinant Escherichia coli. StyA from both sources is a dimer, with a subunit size of 47 kDa, and catalyzes the enantioselective epoxidation of C[??]C double bonds. Styrene is exclusively converted to S-styrene oxide with a specific activity of 2.1 U [mg.sup.-1] ([k.sub.cat] = 1.6 [s.sup.-1]) and [K.sub.m] values for styrene of 0.45 [+ or -] 0.05 mM (wild type) and 0.38 [+ or -] 0.09 mM (recombinant). The epoxidation reaction depends on the presence of a NADH-flavin adenine dinucleotide (NADH-FAD) oxidoreductase for the supply of reduced FAD. StyB is a dimer with a molecular mass of 18 kDa and a NADH oxidation activity of 200 U [mg.sup.-1] ([k.sub.cat] [NADH] = 60 [s.sup.-1]). Steady-state kinetics determined for StyB indicate a mechanism of sequential binding of NADH and flavin to StyB. This enzyme reduces FAD as well as flavin mononucleotide and riboflavin. The NADH oxidation activity does not depend on the presence of StyA. During the epoxidation reaction, no formation of a complex of StyA and StyB has been observed, suggesting that electron transport between reductase and oxygenase occurs via a diffusing flavin.

Asymmetric epoxidation of various styrenes using carbocyclic oxazolidinone-containing ketone 3 has been investigated. High enantioselectivity (89-93% enantiomeric excess) has been attained for this challenging class of alkenes. Mechanistic studies show that substituents on the ketone catalyst can have electronic influences on secondary orbital interactions, which affects the competition between spiro and planar transition states and, ultimately, enantioselectivity. The results described herein not only reveal the potential of chiral dioxirane catalyzed asymmetric epoxidation as a viable entry into this important class of olefins but also further enhance the understanding of the mechanistic aspects of chiral ketone-catalyzed asymmetric epoxidation.

The structures, energetics, and growth pattern of styrene (Methanol)(sub n) clusters with n = 2-9 are investigated using a search technique that employs Monte Carlo procedures. The results indicate that the spectral shifts correlate with the interaction energies between styrene and M(sub n) within the SM(sub n) clusters.

Electrochemiluminescence (ECL) can be obtained directly from the reaction of guanine bases in oligonucleotides in ultrathin films with the catalytic metallopolymer [Ru(bpy)(sub 2)-(PVP)(sub 10)(super 2+) without using a sacrificial reluctant. ECL and catalytic SWV peaks are sensitive to oligonucleotide hybridization and chemical DNA damage.

Experiments conducted on styrene to examine its adsorption, desorption and molecular conformation are presented. The experiments include temperature programmed desorption and X-ray photoelectron spectroscopy.

Storage-stable styrene-butadiene-styrene triblock copolymer (SBS)-modified asphalt was prepared by dynamic vulcanization. The vulcanization characteristics of the asphalt/SBS/sulfur blend were studied using a strain-controlled rheometer. The vulcanization of SBS in the asphalt resulted in a marked increase in the torque of the blend. In addition, the vulcanization of a butadiene rubber (BR)/sulfur blend was significantly influenced by the addition of asphalt through a curemeter. The existence of asphalt can accelerate the vulcanization of BR/sulfur blend and reduce its reversion. The preparation process of storage-stable SBS-modified asphalt by dynamic vulcanization was identified by a plot of the electric current versus time. The addition of sulfur to the SBS-modified asphalts resulted in the formation of chemically vulcanized network structures in the modified binders. The physical properties of the SBS-modified asphalt containing sulfur were compared to those of the modified binders without sulfur. The sto rage stability of the SBS-modified asphalt was effectively Improved by the addition of sulfur. The rheological properties of the SBS-modified asphalts before and after adding sulfur were characterized by using dynamic shear rheometry and a rotational viscometer. As indicated by the monitored morphology, the compatibility and high-temperature storage stability of SBS-modified asphalts were improved by the addition of sulfur., INTRODUCTION The use of SBS as an asphalt modifier was developed by the Shell Chemical Company (1, 2). It has been recognized that the physical and mechanical properties and rheological [...]

Bacteria that degrade styrene in biofilters have a Pseudomonas-like fatty acid profile rather than a methyl-branched fatty acid profile. This indicates that Xanthomonas, Bacillus, Streptomyces, or Gordonia are not present.

The consecutive chain transfer reaction to p-methylstyrene and to hydrogen during polymerization is reported.

Poly(3,4-ethylenedioxy)thiophene - poly(styrene sulfonate) (PEDOT-PSS) was used as the conductive component in a matrix of chemically different insulating polymers to form an array of vapor detectors. Such composites produced larger relative differential resistance responses when exposed to polar analytes than did the corresponding carbon black filled polymer composite detectors. However, the PEDOT-PSS composites produced smaller responses than carbon black composites when exposed to nonpolar analytes. The resolving power of a PEDOTPSS detector army was compared to that of a carbon black composite array for a broadly construed set of organic vapors. The PEDOT-PSS array exhibited better, on average, discrimination between pairs of polar analytes and polar/nonpolar analytes than did the carbon black composite array. The carbon black composite array outperformed the PEDOT-PSS array in discriminating between nonpolar compounds. The addition of PEDOT-PSS composites to an array of carbon black composite detectors therefore can produce improved overall discrimination in a vapor sensor system when used in tasks to differentiate between of a broad set of analyte vapors.

Research has been conducted on the synthesis of bis-isoxazolo substituted piperidinones. Michael addition of the unsaturated alkoxide to beta-nitrostyrene is discussed.

The first study of the reactivity of the aromatic compounds pyrimidine and styrene with the excess electrons in supercritical ethane is reported.

A study of the aggregation behavior and self-assembly of fatty acid and phospholipid derivatives containing the styrylnaphthalene chromophore is reported.

Research has been conducted on the generation of 1,4-diphenyl-1,4-butanediyl biradical from 2,5-diphenylcyclopentanone under irradiation. Results indicate that the resulting products are styrene.

A methyl group in the alpha position of styrene stabilizes the transition state during methoxymercuration. However, the solvent also plays a role in the transition state, and is more important than the structure of the alkene.

The intensity of the thermal oxidation has been followed through kinetic parameters. In styrene/butadiene copolymers, soft polybutadiene phase (PB) and hard polystyrene phase (PS) have different sensibilities to thermal degradation. The thermal oxidative stability of high-impact polystyrene (PS-HI), styrene/butadiene/styrene block copolymers (SBS), and PS-HI + SBS blends were investigated by isothermal DSC analysis. The kinetic parameters of the thermal oxidative degradative process: the reaction rate constants, the reaction orders and the activation energies have been determined. The total area under the exothermic curve was used to calculate the isothermal heats of degradation. The conversion ([Alpha]) and the rate of the thermal oxidative degradation (d[Alpha]/dt) have been derivated. The experimental data have been tested with a kinetic model for autocatalytic reactions: d[Alpha]/dt = k [[Alpha].sup.m] [(1 - [Alpha]).sup.n]. Activation energies have been determined from the Arrhenius equation and the order of the thermal oxidative stability evaluated. The extent of agreement of the experimental data with the autocatalytic model is discussed., 1. INTRODUCTION Stability of polymer materials under high temperatures is essential for their practical use and processing, hence the present investigation of thermal oxidative stability. Thermogravimetric analysis (TG) and Differential [...]

A study was conducted on the control of polymerization process relating to the development of macromolecular architectures with new and improved properties. It describes the use of a 'smart,' xanthate-derived photoinitiator that can differentiate methyl methacrylate and styrene based on the electron availability over the monomer's polymerization double bond. This photoinitiator is S-methacryloyl O-ethyl xanthate. Experimental methodology and results are discussed.

A novel biocatalyst for synthesizing optically pure aryl epoxides has been developed by cloning the styrene monooxygenase genes styA and styB from Pseudomonas fluorescens ST. Several aryl vinyl and aryl ethenyl derivatives were oxidized by recombinant Escherichia coli to their respective optically pure epoxides. The bioconversions suggest that styrene monooxygenase exhibits a broad substrate preference as well as a potential for the formation of different fine chemicals.

A study was conducted to analyze the discharge and tracking phenomena on polymer dielectric materials induced by acid rain. The accelerated aging of acrylonitrile-butadiene-styrene copolymer in artificial rainwater was utilized to carry out the analysis. The impact of hydrophobicity degradation on the surface discharge and tracking was examined. Experimental results indicated that decreases in the hydrophobicity promote the occurrence of surface discharges and tracking.

A study was conducted to analyze the asymmetric reactions of 2-methoxy-1,4-benzoquinones with styrenyl systems. A cycloaddition model was developed to rationalize the enantioselectivities in the products from reactions of the quinones with propenylbenzenes. The possibility of an in situ cyclobutane to dihydrobenzofuran rearrangement was also examined. In addition, reactions of 2H-chromenes with quinones were developed as expedient asymmetric syntheses of pterocarpans.

A study was conducted on the mechanism of cyclic osmate ether intermediate formation in olefin osmium-catalyzed dihydroxylation. The experiment provides a quantitative theoretical characterization of the origin of enantioselectivity in the osmium-catalyzed dihydroxylation of olefins by performing IMOMM calculations on the (DHQD)2PYDZ*OsO4 + H2C=CH(Ph) system. Experimental methodology and results of the study are discussed.

A study was conducted to analyze a synthetic model of determining dense polymer brushes on planar surfaces. A self-assembled monolayer of biphenyllithium moieties on gold substrates was utilized to promote the anionic polymerization of styrene. The gold substrates were obtained by thermal evaporation of titanium as an adhesive layer and gold onto planar microscope glass slides. Findings indicated that the method results in densely grafted polymer brushes.

A study was conducted to enforce near coplanarity associated with the conjugative interaction between phenyl group and olefin in styrenes by integrating phenyl group and double bond into a bicyclic system. The 1H and 13C nuclear magnetic resonance spectra were determined using a Bruker AM-500 instrument. Spin-lattice relaxation times were then obtained by the inversion-recovery technique with vacuum-sealed solutions.

Steady-state and pre-steady-state experiments were conducted to study the kinetics of styrene oxide conversion. The kinetic constants were resolved using stopped-flow fluorescence and rapid-quench techniques. A three-step mechanism involving reversible and rapid formation of an ester intermediate from a Michaelis complex and consequent slow hydrolysis as a rate-limiting step could describe the conversion of (S)-styrene oxide. The conversion of (R)-styrene oxide could be described by a four-step mechanism, which involves the formation of a Michaelis complex and rapid and reversible alkylation of the enzyme.

A study was conducted to analyze the sonochemical reactions of lead tetracarboxylates with styrene. The experiments were performed in the dark under an argon atmosphere. Potassium acetate and proponaote were dried before use. Experimental results indicated that carboxylate anions significantly affects the reaction associated with the conversion of styrene. Findings also showed a sonochemical effect in homogeneous solutions.

A study was conducted to characterize the preparation of a new type of polypyrrole films. Electropolymerization was carried out to integrate spherical styrene-methacylic acid block copolymer micelles supporting a hydrophobic core of 18 nm and a hydrophilic corona of 100 nm in polypyrrole films. Results indicated that charge compensation during electrochemicaloxidation or reduction of a copolymer micelle correlated with cation movements.

This paper reports the result of studies using a biotrickling filter with blast-furnace slag packings (sizes = 2-4 cm and specific surface area = 120 [m.sup.2]/[m.sup.3]) for treatment of styrene in an airstream. The effects of volumetric styrene loading L, superficial gas velocity [U.sub.o] and liquid recirculation rate [V.sub.L] on the styrene elimination capacity K, and the removal efficiency K/L were tested. Variations of styrene concentration with packing height as well as rates of nutrient utilization were also tested. The results show that for L < 30 g/[m.sup.3]. h, K/L was nearly independent of [U.sub.o] in the range of 29-67 m/h and was independent of [V.sub.L] in the range of 3.84-9.60 m/h. In this range, the rate of styrene removal was both reaction and diffusion limited and the reaction was of zero-order kinetics. For higher loadings, K/L decreased with increasing [U.sub.o] and increased with increasing [V.sub.L] and the system approached the condition of reaction limitation.

Research was conducted to examine the efficient and selective synthesis of crownopaddlanes having two cyclobutane rings and the exclusive complexation of lithium. Synthesization of crownopaddlanes was done conveniently through intramolecular (2 +2) photocycloaddition of the corresponding divinylbenzene derivatives. Results demonstrate that the host molecule with four ethereal oxygen atoms displayed great efficiency in solid-liquid extraction and excellent lithium selectivity due to its unique structure.

Research was conducted to study the styrene degradation pathway of Pseudomonas sp. strain VLB120. The DNA sequence of a genomic fragment of Pseudomonas sp. strain VLB120 was prepared from the deletion clones of pSPW1 while a Qiagen kit was utilized to determine the genomic DNA of VLB120 from styrene-grown cells. Results showed that Escherichia coli recombinants supporting styrene monooxygenase cloned genes from VLB120 transform styrene to (S)-styrene oxide.

Research was conducted to examine the rate of biohydrolysis and the regioselectivity of several styrene oxide derivatives. These oxides were catalyzed by an epoxide hydrolase activity located in the soluble cell extract of the 'Syncephalastrum racemosum' fungus. Results show that the electronic character of the para substituent affects regioselectivity to and from the terminal and the benzylic carbon atom.

Ductile thermoplastic N-phenylmaleimide-styrene copolymers (PMS) have been introduced into diglycidyl ether of bisphenol A (epoxy) by a simultaneous polymerization technique. The tens fie strength and fracture toughness increased with increasing PMS content and reached a maximum value at a PMS/epoxy ratio of about 20/80 (w/w). The mechanical properties decreased significantly beyond that ratio, because of phase inversion., INTRODUCTION Epoxy resins are important engineering materials possessing high elastic modulus and glass transition temperatures. Several studies have attempted to modify the epoxy structure in order to improve its fracture [...]

A study was conducted on the reaction of the complex of [Os(NH3)5(eta2-anisole)]2+ with acetals or Michael acceptors to produce 4-methoxystyrene complexes that are exclusively coordinated at the arene (eta2). These styrene complexes are active dienes and are involved in Diels-Adler reactions with electron-deficient olefins to form tetrahydronaphthalene complexes. The cycloadducts are produced as single diastereomers and are essential as precursors to functionalized tetralins and decalins.

Research was conducted to study the application of carbamate asymmetric aminohydroxylation process with a wide range of substituted styrenes. Styrenes make excellent substrates for the new carbamate-based AA reaction due to enantioselectivities of up to 99% and yields of up to 80% for the major regioisomer. Results demonstrate that catalytic asymmetric aminohydroxylation reaction proves to be an efficient tool for the enantioselective one-step synthesis of N-Cbz- or N-t-BOC-protected alpha-arylglycinols from styrenes.

Studies show that substituted phenylsulfonyl chloride promotes styrene, methacrylate and acrylate metal-catalyzed living radical polymerization at homogeneous conditions regardless of substituent nature. A different steady-state concentration of propagating radicals was found to influence an inversion from the absolute rate constant's classic dependence. The apparent rate constants of initiation were observed to be three or two orders of magnitude higher than those of propagation for acrylates and four orders of magnitude for styrene and methacrylates.

Intramolecular electron transfer and exciplex formation were studied for a family of styrene-spacer-amine molecules in which the spacer is composed of a rigid amide group in the center of a flexible alkane chain. The amide is linked to the styrene by either one or two methylene units and to a trialkylamine by two to six methylene units. Intramolecular quenching of the styrene fluorescence intensity and lifetime was seen for all of the styrene-spacer-amine molecules. Quenching was accompanied by the emergence of intramolecular styrene-amine exciplex fluorescence in nonpolar solvents.

A study was conducted to characterize the stereoselective preparation of (Z)-alpha,beta-difluorostyrenes and their conversion to (E)-alpha,beta-difluoro-beta-iodostyrenes. n-BuLi was used to pregenerate vinyllithium reagents which were mixed with I2 while an Et3SiF mixture was treated with activated zinc metal. The stereochemistry of the compounds were assigned on the basis of 19F nuclear magnetic resonance coupling constants.

The Corynebacterium strain St-10 capable of gaseous styrene assimilation was used to purify a novel phenylacetaldehyde reductase 50-fold to homogeneity. The enzyme, which was observed to be vital in in vivo styrene metabolism, featured four identical subunits and had a 155,000 molecular weight. The decrease of several ketones, aldehydes and phenylacetaldehyde was achieved through the enzyme. However, the enzyme failed to promote the dehydrogenation of 2-phenylethanol.

The mechanism by which nitrogen dioxide and ozone react with styrenes was examined through the use of para-chlorostyrene as an intermediate in dichloromethane at -20 to 0 degrees Celsius. It was indicated that the olefinic bond was reversible through the electron transfer mechanism to produce unstable nitroso-nitrate adducts. Further rapid oxidation of the nitroso group to the nitro group yielded isomeric nitro-nitrato adducts in the presence of ozone.

The influence of structural recovery or physical aging on the craze initiation of amorphous polystyrene and a styrene-acrylonitrile copolymer has been examined in two states of stress/deformation and at different temperatures. Studies of craze initiation in equibiaxial creep were performed using a 'bubble' inflation test geometry while uniaxial elongation in stress relaxation conditions was studied by bending the specimen over a variable radius of a curvature test jig. All tests were performed by aging the specimen and testing it at the same temperature subsequent to a quench from above the glass transition to below it. The results are compared with expectations from three craze models: Sternstein and Ongchin (1), Argon (2), and Kambour (3). The results are most consistent with the model of Kambour, but discrepancies arise because, e.g., the impact of aging on the stress for crazing in the equibiaxial tests is different for the polystyrene than for the styrene-acrylonitrile copolymer. The results also suggest that there are two regimes of behavior for craze initiation under equibiaxial stresses, a behavior not manifested in the uniaxial stress relaxation experiments., INTRODUCTION The failure of amorphous polymers in the glassy state is often preceded by a dilatational deformation process referred to as crazing (1). Additionally, polymers are often subjected to thermal [...]

Steady-state modeling and simulation of thermally initiated bulk polymerization of styrene in a train of existing industrial reactors is presented. Two reactors of different geometry and flow arrangement, which operate in series, are modeled as plug flow reactors. The model of Arai et al. for the kinetics of thermal polymerization of polystyrene is used. The model predictions agree well with plant data for different operating conditions. A parametric study shows the feed rate, diluent (ethyl benzene) concentration and reactor temperatures to have a significant effect on final conversion and molecular weight., INTRODUCTION The bulk polymerization of styrene usually occurs with a high viscosity reaction mixture. Many industrial continuous polymerization reactors are thus motionless mixers, where the extent of backmixing is low [...]

This article describes the influence of the polymerization rate on the working domain of a counter-rotating twin-screw extruder used as a polymerization reactor. The rate of polymerization was varied by changing the maleic anhydride (Mah) content in the feed, which consisted of styrene, n-butylmethacrylate, and maleic anhydride. It appeared that the Mah content influenced the operating window of the extruder. Higher Mah percentages resulted in higher throughputs and a decreased dependence on the extruder parameters. On the basis of these results, a new theory concerning reactive extrusion was developed, which resulted in a diagram that is useful in optimizing the extruder, when it is used as polymerization reactor. In addition to the effect of Mah on the process, its effect on product properties was studied., INTRODUCTION The copolymerization of styrene with monomers, such as maleic anhydride and methacrylates, is studied thoroughly. The importance of the copolymerization with methacrylates stems from the fact that the polymer [...]