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PubMed2006

Silica particles encapsulated poly(styrene-divinylbenzene) monolithic stationary phases for micro-high performance liquid chromatography.

In the paper we demonstrate a new approach for the preparation and application of continuous silica bed columns that involve encapsulation (entrapment) of functionalized silica microparticles, which can be used as packing material in micro high performance liquid chromatography (micro-HPLC) and capillary electrochromatography (CEC). Like traditional packed columns, these capillaries possess characterized silica particles that offer high phase ratio and narrow pore size distribution leading to high retention and separation efficiency, respectively. More importantly, immobilization of the microparticles stabilizes the separation bed and eliminates the need for retaining frits. The developed capillary columns were fabricated in exactly the same way as a packed capillary column (slurry packing) but with an additional entrapment step. This immobilization of the packed bed was achieved by in situ polymerization of styrene and divinylbenzene in presence of decanol as a porogen and azobisisobutyronitrile as thermal initiator. Silica particles with different particle sizes and pore sizes ranging from 60 to 4000 A were studied. In addition different modified silica was used, including C-18 reversed phase, anion exchange and chiral stationary phases. Efficient separation of polyphenolic compounds, peptides, proteins and even DNA mutation were achieved using the developed technique depending on the properties of the silica particles used (particles pore size). For example, using 3 microm ProntoSIL C-18 particles with 300 A pore size, separation efficiencies in the range of 120,000-200,000 plates/m were obtained for protein separation, in a 6 cm x 200 microm i.d. capillary column. Using encapsulated silica C-18 with 1000 A pore size, separation of DNA homo and hetero duplexes were achieved under denaturing HPLC conditions for mutation detection. In addition, nucleotides were separated using anion exchange material encapsulated with poly(styrene-divinylbenzene) (PS/DVB), which indicated that the chromatographic properties of the silica packing material were still active after polymerization. The prepared capillary columns were found to be stable and could easily be operated continuously up to a pressure of 350 bar without column damage and capillary can be cut to any desired length.

Chromatography, High Pressure Liquid↗
PubMed2006

Use of new generation poly(styrene-divinylbenzene) resins for gas-phase trapping-thermal desorption. Application to the retention of seven volatile organic compounds.

Two new generation polymeric resins, Bond Elut ENV (styrene-divinylbenzene) from Varian and LiChrolut EN (ethylvinylbenzene-divinylbenzene) from Merck, commonly used in liquid--solid-phase extraction (SPE) were evaluated as sorbents for gas-phase sampling followed by thermal desorption and compared to Tenax TA, a reference sorbent in this kind of applications. The three resins were tested against seven volatile organic compounds (VOCs): 1-octene, ethylbenzene, (p-, m-, o-)xylenes, styrene and 1,4-dichlorobenzene. Elution curves for all compounds were determined at temperatures from 120 to 180 degrees C, and from such curves, different parameters, such as retention factor (k), distribution coefficient (K), height equivalent to a theoretical plate (H), asymmetry factor (Fa) and breakthrough volume (VB) were calculated and extrapolated at room (25 degrees C) and desorption (220 degrees C) temperatures in order to estimate breakthrough and elution volumes. In average, retention in LiChrolut EN is 10 and 200 times stronger than in Bond Elut ENV and Tenax TA, respectively, but its chromatographic behavior is rather poor giving quite asymmetric elution profiles (Fa >1.8 at 120 degrees C). Bond Elut ENV exhibited the best chromatographic behavior, with H values two or five times lower than those of LiChrolut EN or Tenax TA. An additional advantage of the new sorbents is that retention decreases with T much faster than it does in Tenax (8 or 20 times for Bond Elut ENV or LiChrolut EN). Modeling has finally shown that beds with 60-80 (for Bond Elut ENV) or 300-400 (for LiChrolut EN) times less of sorbent have the same retention properties than standard Tenax TA tubes and similar (LiChrolut EN) or five to six times smaller (Bond Elut ENV) elution volumes. These predictions have been experimentally confirmed.

Organic Chemicals↗
PubMed2005

Novel interface-binding chloroperoxidase for interfacial epoxidation of styrene.

A unique interface-binding chloroperoxidase (CPO) was developed and examined for interfacial biocatalysis. Native CPO was conjugated with polystyrene (PS) to form a surfactant-like structure that self assembled at oil-water interfaces. While enantioselectivity of the enzyme was maintained, the interfacial assembly of the enzyme improved its overall catalytic efficiency as compared to that observed with the enzyme contained in the bulk aqueous phase. The PS conjugated CPO (PS-CPO) showed a 2.5-fold enhancement of enzyme productivity versus native CPO under batch reaction conditions for the epoxidation of styrene, whereas a 25-fold improvement was realized in a continuous feeding reaction to reach a productivity of 10 micromol h-1 mg protein-1. The interface-binding enzyme also demonstrated several other advantages such as suppressing unwanted side reactions including the hydrolysis of styrene epoxide products, stabilizing the enzyme by limiting its exposure to both the oxidant H2O2 and epoxide products, and alleviating the deactivating effect of interfacial stress on enzymes by functioning as a surfactant.

Ascomycota↗
PubMed2004

Characterization of surface NH3+Cl- groups on poly(styrene-co-Boc-aminostyrene) microspheres obtained by controlled acidic treatment.

Different samples of aminated latex of poly(styrene-co-Boc-aminostyrene) microspheres with mean diameters varying from 0.7 to 1.0 microm were prepared by dispersion copolymerization of styrene (ST) and Boc-aminostyrene (Boc-AMST). The copolymer compositions determined by nuclear magnetic resonance (1H NMR) were Boc-AMST/ST 6.9/93.1 mol/mol % (BOC7 sample) and Boc-AMST/ST 31.3/68.7 mol/mol % (BOC30 sample). The average molecular weights determined by gel permeation chromatography were 126 kDa (BOC7 sample) and 51 kDa (BOC30 sample). The latex containing NH-carbo-tert-butoxy groups (NH-Boc) were treated with 2 M HCl in isopropyl alcohol/water (1:1 vol/vol), at 50 degrees C for 3, 6, 9, 24, and 30 h, in order to control the extent of deprotection reaction of the NH-Boc. The deprotection reaction resulted in the formation of NH3+Cl- groups on the particle surfaces. The kinetic of the deprotection reaction was investigated by 1H NMR analyses and the yield varied from 20 to 40%. The resulting -NH3+Cl- groups on the microsphere surfaces were examined, in particular, by electron spectroscopy imaging (ESI) using an energy-filtered transmission electron microscope (EFTEM) that clearly demonstrated the presence of Cl on the particle surfaces. Scanning electron photomicrographs recorded for the above samples showed that the particle morphology was maintained after the acidic treatment.

Journal Article↗
PubMed2005

Analysis of oxidative stress in SK-N-MC neurons exposed to styrene-7,8-oxide.

Styrene-7,8-oxide (SO) is the main metabolite of styrene, a neurotoxic volatile organic compound used industrially. Here we report the novel observation that several markers of oxidative stress were affected in SK-N-MC cells exposed for 16 h to concentrations of SO that induce apoptotic cell death. The production of Thiobarbituric Acid Reactive Substances (TBARS), rose from 69.1 +/- 15.7 nmol/g protein (control) to 119.3 +/- 39.2 and 102.0 +/- 17.3 nmol/g protein after exposure to 0.3 and 1 mM SO, respectively. Carbonyl group levels were significantly enhanced by SO at both concentrations. The lower dose also decreased sulphydryl groups. SO caused a marked oxidative DNA damage, as shown by a fivefold increase in 8-hydroxy-2(')-deoxyguanosine (8-OHdG). In addition, SO exposure resulted in alterations of scavenging abilities, given the reduction of both glutathione (GSH) and glutathione-S-transferase (GST) activity. Induction of expression of the oxidative stress response gene heme-oxygenase-1 (HO-1) and an increased HO-1 activity were also observed. These data provide compelling evidence that oxidative stress significantly contributes to SO toxicity in neuronal cells.

8-Hydroxy-2'-Deoxyguanosine↗
PubMed2004

Styrene 7,8-oxide induces mitochondrial damage and oxidative stress in neurons.

Styrene 7,8-oxide (SO) is the main metabolite of styrene, a neurotoxic compound used industrially. Neurons exposed to SO undergo apoptosis with characteristic features including chromatin rearrangements and caspase activation. We report that the execution phase of apoptosis induced by SO (0.3 mM) in SK-N-MC neurons is triggered by translocation of apoptogenic factors (e.g., cytochrome c) into the cytosol. In addition, mitochondria exhibit lower Ca2+ capacity and loss of mitochondrial membrane potential (DeltaPsi). Lipid peroxidation, measured as thiobarbituric acid reactive substances (TBARS), is increased after 12 h. Pre-treatment with the antioxidant MnTBAP (100 microM) prevents the decrease of Ca2+ capacity, cytochrome c release, activation of caspases, exposure of phosphatidylserine and cell death. Hence, the neurotoxic effects of SO are related to mitochondrial damage and oxidative stress.

Apoptosis↗
PubMed2000

Adenine N3 is a main alkylation site of styrene oxide in double-stranded DNA.

Styrene 7,8-oxide (SO), a major metabolite of styrene, is classified as a probable human carcinogen. In the present work, salmon testis DNA was reacted with SO and the alkylation products were analysed after sequential depurination in neutral or acidic conditions followed by HPLC separation and UV-detection. A novel finding was that the N-3 position of adenine was the next most reactive alkylation site in double-stranded DNA, comprising 4% of the total alkylation, as compared to alkylation at the N-7 position of guanine, 93% of the total alkylation. Both alpha- and beta-products of SO were formed at these two sites. Other modified sites were N2-guanine (1.5%, alpha-isomer), 1-adenine (0.4%, both isomers) and N6-adenine (0.7%, both isomers) as well as 1-hypoxanthine (0.1%, alpha-isomer), formed by deamination of the corresponding 1-adenine adduct. The results indicated that in double-stranded DNA N-7 of guanine and N-3 of adenine account for 97% of alkylation by SO. However, these abundant adducts are not stable, the half-life of depurination in DNA for 3-substituted adenines being approximately 10 and approximately 20 h, for alpha- and beta-isomers, respectively, and 51 h for both isomers of 7-substituted guanines.

Adenine↗
PubMed1996

Molded continuous poly(styrene-co-divinylbenzene) rod as a separation medium for the very fast separation of polymers. Comparison of the chromatographic properties of the monolithic rod with columns packed with porous and non-porous beads in high-performance liquid chromatography of polystyrenes.

Gradient elution separations of polystyrene standards in a monolithic molded 50 x 8 mm I.D. poly(styrene-co-divinylbenzene) rod column and in 50 x 8 mm I.D. and 30 x 4.1 mm I.D. columns packed with porous and non-porous poly(styrene-co-divinylbenzene) beads has been carried out. All of these separation media differ in shape and porosity. Excellent separations of eight polystyrene standards were achieved with both the molded monolithic rod and porous beads at moderate flow-rates. However, the monolithic medium proved to be superior for high-speed separations using very steep gradients at a flow-rate of 20 ml/min. Three polystyrene standards were separated in the rod column within 4 s. The separation in the column packed with non-porous beads was poor at flow-rates of 2-8 ml/min, while higher flow-rates led to an unacceptably high back pressure.

Chromatography, High Pressure Liquid↗
PubMed2001

Isoprene-styrene copolymer elastomer and tetrahydrofurfuryl methacrylate mixtures for soft prosthetic applications.

Novel elastomer/methacrylate systems have been developed for potential soft prosthetic applications. Mixtures of varying compositions of an isoprene-styrene copolymer elastomer and tetrahydrofurfuryl methacrylate (SIS/THFMA) formed one-gel systems and were heat cured with a peroxide initiator. The blends were characterised in terms of sorption in deionised water and simulated body fluids (SBF), tensile properties and viscoelastic parameters of storage modulus and tan delta, as well as glass transition temperatures using dynamic mechanical analysis (DMA). DMA data gave two distinct peaks in tan delta, a lower temperature transition due to the isoprene phase in SIS and one at high temperature thought to be a combination of THFMA and the styrene phase in SIS. The tensile data showed a clear phase inversion within the mid range compositions changing from plastic to elastomeric behaviour. The sorption studies in deionised water showed a two stage uptake with an initial Fickian region that was linear to t 1/2 followed by a droplet growth/clustering system. The slope of the linear region was dependent on the composition ratio. The extent of overall uptake was osmotically dependent as all materials equilibrated at a much lower uptake in SBF. The diffusion coefficients were found to be concentration dependent.

Absorption↗
PubMed1997

Changes in high molecular weight DNA fragmentation following human blood exposure to styrene-7,8-oxide.

Styrene-7,8-oxide (S7,8O) is the major in vivo metabolite of styrene and is a genotoxic agent potentially carcinogenic to humans. It is known to cause DNA strand breaks and adducts. We studied high molecular weight DNA fragmentation in white blood cells following incubation of blood with S7,8O from individuals with no previous exposure to this compound. To better understand the effects of S7,8O, we also examined blood exposed to hydrogen peroxide (H2O2) a typical oxidant that is linked to oxidative stress. All individuals in this study showed a variable reduction in high molecular weight DNA fragments determined by laser densitometry compared to untreated controls for both S7,8O and H2O2 treated samples. This decrease was independent of the concentration and length of exposure of blood to S7,8O and H2O2. An increase in low molecular weight DNA fragments from samples treated with S7,8O and H2O2, compared to untreated samples was also noted. Similarities in the reduction of HMW-DNA fragments after S7,8O and H2O2 exposure suggested a similar mechanism of HMW-DNA damage. It was surmised that S7,8O exposure in blood may induce high molecular weight DNA fragmentation due to oxidative stress.

Carcinogens↗
PubMed2002

DNA damage and repair in human leukocytes exposed to styrene-7,8-oxide measured by the comet assay.

Styrene-7,8-oxide (SO) is produced by cytochrome p450 monooxygenases as the main mammalian metabolite of styrene, an important industrial chemical present at high concentrations in the ambient air of fiberglass-reinforced plastic plants. Previous studies have shown positive results for SO in the induction of several cytogenetic endpoints in vitro. In this work we have evaluated, by means of the comet assay, the potential of SO to act as a DNA damaging agent in human peripheral leukocytes and the ability of white blood cells to repair the DNA damage induced by this compound. Our results show that SO induces DNA damage at concentrations higher than 50 microM in a dose-dependent manner, and that the lesions produced by SO are efficiently removed within a few hours after the end of treatment.

Adult↗
PubMed1998

S-(1,2-dichlorovinyl)-L-cysteine-induced dedifferentiation and p53 gene mutations in LLC-PK1 cells: a comparative investigation with S-(2-chloroethyl)cysteine, potassium bromate, cis-platinum and styrene oxide.

Exposure of cultured renal (LLC-PK1) cells for 7 weeks to non-cytotoxic concentrations of S-(1,2-dichlorovinyl)-L-cysteine had resulted in the induction of morphologically and biochemically dedifferentiated clones, which retained their altered properties after removal of the chemical. In this study we investigated by polymerase chain reaction-single strand conformational polymorphism (PCR-SSCP) analysis and direct sequencing if S-(1,2-dichlorovinyl)-L-cysteine-induced LLC-PK1 clones display mutations in the p53 gene in comparison with wild-type clones. In addition, the characteristics of S-(1,2-dichlorovinyl)-L-cysteine-induced clones were compared with clones induced by carcinogens/metabolites of carcinogens with different mechanisms of action: (i) The potent alkylating agent and bacterial mutagen chloroethylcysteine, the key metabolite of the carcinogen dichloroethane; (ii) potassium bromate, a nephrocarcinogen inducing reactive oxygen species, which give rise to the formation of 8OHdG and DNA strand-breaks; (iii) cis-platinum, a bifunctional cross-linking agent and strand-break inducer and (iv) styrene oxide, the main intermediate metabolite of styrene, an epoxide whose carcinogenicity is thought to be based on cytotoxicity. Three essential markers of the physiological integrity and renal tubule origin of the wild-type LLC-PK1 cells were disrupted in all chemical-derived clones: (i) the polarisation of the plasma membrane into a luminal and basolateral part; (ii) the sodium-dependent glucose uptake and (iii) the pH-dependent ammonia production. Compared with the wild-type clones, poly(ADP-ribosyl)ation, a posttranslational modification of nuclear proteins, was clearly increased in clones induced by S-(1,2-dichlorovinyl)-L-cysteine, potassium bromate and cis-platinum. These clones displayed also band shifts of p53 exon 7, indicating mutations, which were confirmed by sequencing: a double mutation consisting of a base substitution followed by one base insertion in the case of S-(1,2-dichlorovinyl)-L-cysteine and potassium bromate and a base substitution in the case of cis-platinum. The base insertions both lead to the formation of the stop codon UGA resulting in loss of protein function.

Ammonia↗
PubMed2000

Gas chromatography-electron capture determination of styrene-7,8-oxide enantiomers.

The enantiomers of styrene-7,8-oxide (phenyloxirane, SO) were determined using a method based on base catalysed hydrolysis with sodium methoxide. The oxirane ring opening resulted in formation, without racemisation, of the enantiomeric pairs of the two regional isomers, 2-methoxy-1-phenylethanol and 2-methoxy-2-phenylethanol. The structure of these regional isomers was confirmed by gas chromatography-mass spectrometry (GC-MS) and proton nuclear magnetic resonance (1H-NMR). To improve sensitivity of determination, the formed methoxy alcohols were subsequently derivatised with pentafluoropropionic anhydride enabling electron capture detection. This derivatization proceeded also without racemisation and the formed pentafluoropropionyl derivatives were separated on two serially coupled columns, a non-chiral AT 1705 and a chiral CP Chirasil-Dex-CB. As internal standard 2S,3S-(-)-2-methyl-3-phenyloxirane was used. The limit of quantitation of the method was 0.2 microM. The repeatability of the method was assessed at two concentration levels (2.5 and 25 microM) and ranged from 6 to 9% for both enantiomers. The method was applied to the determination of the rate and enantioselectivity of the cytochrome P-450 dependent oxidation of styrene to SO enantiomers in human liver microsomes.

Calibration↗
PubMed2002

Gas-phase conformations of cationized poly(styrene) oligomers.

The gas-phase conformations of poly(styrene) oligomers cationized by Li+, Na+, Cu+, and Ag+ (M+ PSn) were examined using ion mobility experiments and molecular mechanics/ dynamics calculations. M+PSn ions were formed by MALDI and their ion-He collision cross-sections were measured by ion mobility methods. The experimental collision cross-sections of each M+PS n-mer were similar for all four metal cations and increased linearly with n. Molecular modeling of selected M+ PS oligomers cationized by Li+ and Na+ yielded quasi-linear structures with the metal cation sandwiched between two phenyl groups. The relative energies of the structures were approximately 2-3 kcal/mol more stable when the metal cation was sandwiched near the middle of the oligomer chain than when it was near the ends of the oligomer. The cross-sections of these theoretical structures agree well with the experimental values with deviations typically around 1-2%. The calculations also show that the metal cation tends to align the phenyl groups on the same side of the -CH2-CH- backbone. Calculations on neutral poly(styrene), on the other hand, showed structures in which the phenyl groups were more randomly positioned about the oligomer backbone. The conformations and metal-oligomer binding energies of M+PS are also used to help explain CID product distributions and fragmentation mechanisms of cationized PS oligomers. etry

Cations↗
PubMed1998

Comparison of ethylene, propylene and styrene 7,8-oxide in vitro adduct formation on N-terminal valine in human haemoglobin and on N-7-guanine in human DNA.

Epoxides react at various nucleophilic sites in macromolecules such as haemoglobin and DNA. To study the reaction rate constants of ethylene oxide (EO), propylene oxide (PO) and styrene 7,8-oxide (SO) towards two of these positions, i.e., the N-terminal valine in haemoglobin and N-7-guanine in DNA was the central aim of this investigation. These two reactive sites are the most studied haemoglobin and DNA adducts, respectively. Further attention, therefore, was also paid to the applicability in vivo of the in vitro determined reaction constants. The determination of the second-order rate constants between EO and PO and N-terminal valine in Hb [2.7 l (mol Hb h)-1 and 1.0 l (mol Hb h)-1, respectively] were consistent with the literature values. The constants for the reaction with N-7-guanine [16x10(-3) l (mol DNA nucleotide h)-1 and 7. 7x10(-3) l (mol DNA nucleotide h)-1, respectively] were lower than previously published values, probably due to differences in the methodology used. The use of the in vitro obtained values to model the in vivo situation lead to a consistent picture for EO and PO. In contrast, for SO the in vitro ratio between the adduct formation on N-terminal valine [1.5 l (mol Hb h)-1] and N-7-guanine [0.71x10(-3) l (mol DNA nucleotide h)-1] was about two orders of magnitude greater than for the in vivo situation. This was probably due to a lower than expected reactivity of SO towards N-terminal valine in vivo. Further research is needed to elucidate whether the use of SO in vitro, contrasting with the in vivo experiments in which SO was metabolically formed from styrene, could entail an explanation for this discrepancy. Concerning the methodological part, the use of dipeptide standards to replace the alkylated globins as standard lead to an improvement of the method. Especially the commercial availability of the standards, their stability and accurately known adduct content will make them to the standards of choice in the future.

Alkenes↗
PubMedDate not supplied

Copoly(styrene-maleic acid)-pirarubicin micelles: high tumor-targeting efficiency with little toxicity.

The copolymer of styrene-maleic acid (SMA) was used to construct micelles containing pirarubicin (4'-O-tetrahydropyranyladriamycin, or THP) as a new anticancer drug formulation. The procedure for the preparation of the micelles was simple, the component consisting of only SMA and pirarubicin in a noncovalent association, possibly by hydrophobic interaction between the styrene portion of SMA and pirarubicin chromophore. This method ensures more than 80% recovery of pirarubicin by weight, and 60% of drug loading (by weight) was achieved. The micelles obtained (SMA-THP) showed high solubility in water and a constant pirarubicin release rate of about 3-4%/day in vitro. SMA-THP micelles had an average molecular size of about 34 kDa according to gel chromatography; this size is a marked increase from the 627.6 Da of free THP, which suggests the formation of a micellar structure. When albumin was added, the molecular size of the micelles increased to about 94 kDa, which indicates binding to albumin, a unique characteristic of SMA. SMA-THP micelle preparation had a cytotoxic effect (93-101%) on MCF-7 breast cancer cells and SW480 human colon cancer cells in vitro that was comparable to that of free THP. An in vivo assay of SMA-THP at doses of 20 mg/kg in ddY mice bearing S-180 tumor revealed complete tumor eradication in 100% of tested animals. Mice survived for more than 1 year after treatment with micellar drug doses as high as 100 mg/kg pirarubicin equivalent. This marked antitumor activity can be attributed to the enhanced permeability and retention (EPR) effect of macromolecular drugs seen in solid tumors, which enables selective delivery of drugs to tumor and thus much fewer side effects. Complete blood counts, liver function test, and cardiac histology showed no sign of adverse effects for intravenous doses of the micellar preparation. These data thus suggest that intravenous administration of the SMA-THP micellar formulation can enhance the therapeutic effect of pirarubicin more than 50-fold.

Animals↗
PubMed2003

Hydroxy- and silyloxy-substituted TEMPO derivatives for the living free-radical polymerization of styrene and n-butyl acrylate: synthesis, kinetics, and mechanistic studies.

The synthesis of new 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO) styryl derivatives as mediators for the living free-radical polymerization is described. Two of the alpha-methyl groups at the 2- and 6-position of the parent TEMPO styryl alkoxyamine have been replaced by hydroxymethyl and silyloxymethyl groups. To further increase the steric hindrance around the alkoxyamine oxygen atom, the remaining two methyl groups have been substituted with larger ethyl groups. Styrene polymerizations using hydroxy-substituted TEMPO derivatives are fast, but are not well-controlled. As previously shown for other OH-substituted alkoxyamines, intramolecular H-bonding leads to an acceleration of the C-O bond homolysis and, hence, to an acceleration of the polymerization process. However, the OH groups also increase the alkoxyamine decomposition rate constant. The kinetics of the C-O bond homolysis have been determined using EPR spectroscopy. Decomposition studies have been conducted with the aid of 1H NMR spectroscopy. In contrast to the OH-substituted alkoxyamines, highly hindered silyloxy-substituted TEMPO alkoxyamines turned out to be excellent mediator/initiators for the controlled styrene polymerization. Polystyrene with M(n) of up to 80 000 g/mol and narrow polydispersities (PDI) has been prepared using the new alkoxyamines. Reactions have been conducted at 105 degrees C; however, even at 90 degrees C controlled but slow polymerizations can be achieved. Furthermore, and more importantly, poly(n-butyl acrylates) with narrow PDIs (<1.15) have been prepared at 105 degrees C with the new alkoxyamines. Controlled acrylate polymerization can be conducted at temperatures as low as 90 degrees C. The silylated alkoxyamines presented belong to the most efficient initiator/mediators for the controlled acrylate polymerization known to date. The effect of the addition of free nitroxide on the acrylate polymerization is discussed. Moreover, the synthesis of diblock copolymers with narrow PDIs is described.

Journal Article↗
PubMed2004

Directly probing the hybrid bonding of styrene on Cu111.

The interfacial electronic structure of chemisorbed styrene on Cu(111) was successfully investigated with two-photon photoemission spectroscopy. We observed unoccupied states 3.5 eV above the Fermi level and occupied states 2.0 eV below the Fermi level. Polarization results reveal that the occupied and unoccupied states arise from bonding and antibonding orbitals formed by hybridization of copper (surface state and d-band orbitals) and styrene (pi1* and pi2* orbitals).

Journal Article↗