Search results for "Styrene"
showing 10 items of 561 documents
Opals infiltrated with a stimuli-responsive hydrogel for ethanol vapor sensing
2013
We report on a novel class of optical materials for ethanol vapor sensing, based on polystyrene opals infiltrated with an innovative stimuli responsive hydrogel. We describe the fabrication process of the bare polystyrene opals and their subsequent infiltration. The optical characterization of the photonic crystal templates was performed to prove the good quality of the samples. Measurements on the infiltrated opals showed that the transmission spectra in the visible range strongly change at varying concentrations of ethanol vapor. The fabricated structures show a linear optical response in the visible range, for high values of ethanol concentration.
Polystyrene nanoparticles in the presence of (ethylene oxide)13(propylene oxide)30(ethylene oxide)13, N,N-dimethyloctylamine-N-oxide and their mixtur…
2008
Polystyrene nanoparticles were synthesized by emulsion polymerization of styrene. They were functionalized using the conventional surfactant N,N-dimethyloctylamine-N-oxide (ODAO), the tri-block copolymer (ethylene oxide)13(propylene oxide)30(ethylene oxide)13 (L64) and their mixtures. To this purpose, dynamic light scattering and calorimetric experiments were carried out and provided information consistent to each other. The L64 adsorption is Langmuir-type in the copolymer dilute regime and generates complex structures at larger concentrations. In the region where ODAO is in the unimeric state, the adsorption process is cooperative leading to hemi-micelle formation at the polystyrene nanopa…
Recombinant expression of human microsomal epoxide hydrolase protects V79 Chinese hamster cells from styrene oxide- but not from ethylene oxide-induc…
1997
Styrene 7,8-oxide and ethylene oxide are widely used genotoxic bulk chemicals, which have been associated with potential carcinogenic hazard for occupationally exposed workers. Both epoxides alkylate DNA preferentially at the N-7 position of guanine and consequently produce single-strand breaks and alkali labile sites in the DNA of exposed cells. In order to study the role of human microsomal epoxide hydrolase (hmEH) in protecting cells against genotoxicity of styrene 7,8-oxide and ethylene oxide, we expressed the cDNA of hmEH in V79 Chinese hamster cells. We obtained a number of cell clones that expressed functionally active epoxide hydrolase. Among these, the clone 92hmEH-V79 revealed an …
Enhancement of the Mutagenicity of Ethylene Oxide and Several Directly Acting Mutagens by Human Erythrocytes and its Reduction by Xenobiotic Interact…
1999
According to the present state of knowledge mutagenicity or genotoxicity of the ulti mate genotoxic agents ethylene oxide or styrene oxide cannot be increased by further me tabolism. However, in the present study we demonstrate that mutagenicity of several ultimate genotoxic substances is increased by human erythrocytes. For instance mu tagenicity of mafosfamide, N-nitroso-N-methylurea, ethylene oxide, and styrene oxide to Salmonella typhimurium TA 1535 was increased 5.5-, 5.1-, 2.7-, and 2.3-fold, respectively, by addition of human erythrocyte homogenate to the preincubation mixture in the Ames test. On the other hand, the mutagenicity of cumene hydroperoxide, benzo[a]pyrene-4,5-oxide, and…
Introducing an amine functionality at the block junction of amphiphilic block copolymers by anionic polymerization strategies
2011
A series of block copolymers bearing a single amino in-chain functionality was synthesized via anionic polymerization of styrene and ethylene oxide. By means of both a conventional and a continuous setup, living polystyrene was quantitatively end functionalized with an oxirane (DBAG) prior to the polymerization of the poly(ethylene oxide) segment. The in-chain amine was conjugated with a fluorescent dye.
Non-bridged amido cyclopentadienyl complexes of titanium: synthesis, characterization, and olefin polymerization catalysis
2000
Alkylation of Ti(η 5 -C 5 Me 5 )(NMe 2 )Cl 2 gives thermally stable, crystalline dialkyl complexes Ti(η 5 -C 5 Me 5 )(NMe 2 )R 2 (R=Me, CH 2 Ph, Ph). The molecular structure of the dibenzyl complex reveals an unprecedented conformation of the doubly bonded NMe 2 group which is turned parallel to the η 5 -C 5 Me 5 ligand, according to single-crystal X-ray diffraction studies. Treatment of the dibenzyl complex with B(C 6 F 5 ) 3 in d 5 -bromobenzene solution results in the quantitative formation of a thermally (>10°C) unstable monobenzyl cation as solvent-separated ion pair [Ti(η 5 -C 5 Me 5 )(NMe 2 )CH 2 Ph] + [PhCH 2 B(C 6 F 5 ) 3 ] − which efficiently polymerizes styrene syndiospecifically…
Homopolymerization of styrenic monomers and their copolymerization with ethylene using group 4 non‐metallocene catalysts
2020
Homopolymerization of styrenic monomers (St, p ‐Me‐St, p ‐t Bu‐St, p ‐t BuO‐St) and their copolymerization with ethylene, with the use of [( t Bu2O2NN′)ZrCl]2(μ‐O) (1 ) and ( t Bu2O2NN′)TiCl2 (2 ), where t Bu2O2NN′ = Me2N(CH2)2N(CH2‐2‐O−‐3,5‐t Bu2‐C6H2)2, is explored in the presence of MMAO and (i Bu)3Al/Ph3CB(C6F5)4. The ethylene/styrenic monomers copolymerization with 1 /MMAO produces exclusively copolymers with high activity and good comonomer incorporation whereas the other catalytic systems yield mixtures of copolymers and homopolymers. The use of p ‐alkyl styrene derivatives instead of styrene raises the catalytic activity, comonomer incorporation and molecular weights of the copolyme…
Directed Assembly of Soft Colloids through Rapid Solvent Exchange
2015
We studied the directed assembly of soft nanoparticles through rapid micromixing of polymers in solution with a nonsolvent. Both experiments and computer simulations were performed to elucidate the underlying physics and to investigate the role of various process parameters. In particular, we discovered that no external stabilizing agents or charged end groups are required to keep the colloids separated from each other when water is used as the nonsolvent. Furthermore, the size of the nanoparticles can be reliably tuned through the mixing rate and the ratio between polymer solution and nonsolvent. Our results demonstrate that this mechanism is highly promising for the mass fabrication of un…
A fluorescent molecular sensor for pH windows in traditional and polymeric biocompatible micelles: comicellization of anionic species to shift and re…
2011
A new approach is presented to obtain fluorescent sensors for pH windows that work in water and under biomimetic conditions. A single molecule that features all-covalently linked components is used, thus making it capable of working as a fluorescent sensor with an OFF/ON/OFF response to pH value. The components are a tertiary amine, a pyridine, and a fluorophore (pyrene). The forms with both protonated bases or both neutral bases quench the pyrene fluorescence, whereas the form with the neutral pyridine and protonated amine groups is fluorescent. The molecular sensor is also equipped with a long alkyl chain to make it highly hydrophobic in all its protonated and unprotonated forms, that is,…
[The in vitro effect of the addition of ion exchange resins on the bioavailability of electrolytes in artificial enteral feeding formulas].
2008
Objective: To determine in vitro free ion concentration in 3 standard artificial enteral feeding formulas following the addition of ion exchange resins. Method: Three standard types of AEF were chosen: Osmolite HN®, Nutrison Standard®, and Isosource Standard®. The ion exchange resins used were: sodium polystyrene sulfonate and calcium polystyrene sulfonate. In a beaker were mixed 100 mL of AEF with 1.5 g or 3 g of ion exchange resins for 48 hours at 37oC. Subsequently, the samples were precipitated and the supernatant obtained was used for determining the concentrations of calcium, magnesium, sodium, and potassium ions. Results: The addition of sodium polystyrene sulfonate to different type…