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1.
Panagiota G. Fragouli Hermis Iatrou Nikos Hadjichristidis 《Journal of polymer science. Part A, Polymer chemistry》2004,42(3):514-519
A series of five tetrablock quarterpolymers of styrene, isoprene, dimethylsiloxane, and 2-vinylpyridine with molecular weights varying from 117 × 103 to 177 × 103 and having different compositions were synthesized. The synthesis was based on recent advances in the controlled high-vacuum anionic polymerization of hexamethylcyclotrisiloxane and on the selective linking of poly(dimethylsiloxane)lithium with the chlorosilane group of the heterofunctional linking agent chloromethylphenylethylene dimethylchlorosilane. Combined characterization results by size exclusion chromatography, membrane osmometry, and NMR spectroscopy suggested that the synthesized multiblock multicomponent polymers had a high degree of structural and compositional homogeneity. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 514–519, 2004 相似文献
2.
Panagiota G. Fragouli Hermis Iatrou Nikos Hadjichristidis Takuro Sakurai Akira Hirao 《Journal of polymer science. Part A, Polymer chemistry》2006,44(1):614-619
3‐Miktoarm star copolymers, 3μ‐D2V, with two poly(dimethylsiloxane) (PDMS) and one poly(2‐vinylpyridine) (P2VP) arm, were synthesized by using anionic polymerization–high vacuum techniques and (chloromethylphenylethyl)methyl dichlorosilane, heterofunctional linking agent, with two SiCl groups and one CH2Cl group. The synthetic strategy involves the selective reaction of the two ? SiCl groups with PDMSOLi living chains, followed by reaction of the remaining chloromethyl group with P2VPLi. Combined molecular characterization results (size exclusion chromatography, membrane osmometry, and 1H NMR spectroscopy) revealed a high degree of structural and compositional homogeneity. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 614–619, 2006 相似文献
3.
Iliopoulou D Mihopoulos N Vagias C Papazafiri P Roussis V 《The Journal of organic chemistry》2003,68(20):7667-7674
Five new brominated diterpenes, along with two known, have been isolated from the organic extract of the red alga Laurencia obtusa, collected from the coastal rocks of Preveza in the Ionean Sea, Greece. The novel metabolites prevezols B-E possess two new carbon skeletons, to the best of our knowledge, unprecedented in the literature. The structures and the relative stereochemistry of the new natural products were established by means of spectral data analyses. The new metabolites were tested for their cytotoxic activity against five human cell lines. Two metabolites have exhibited significant cytotoxicity. 相似文献
4.
The orientation of antibodies, employed as capture molecules on biosensors, determines biorecognition efficiency and bioassay performance. In a previous publication we demonstrated for antibodies attached covalently to silicon that an increase in their surface amount Γ, evaluated with ellipsometry, induces changes in their orientation, which is traced directly using Time-of-Flight Secondary Ion Mass Spectroscopy combined with Principal Component Analysis. Here, we extend the above studies to antibodies adsorbed physically on a 3-aminopropyltriethoxysilane (APTES) monolayer. Antibodies physisorbed on APTES (0 ≤ Γ ≤ 3.5 mg/m2) reveal the Γ ranges for flat-on, side-on, and vertical orientation consistent with random molecular packing. The relation between orientation and Γ is juxtaposed for silicon functionalized with APTES, APTES modified with glutaraldehyde (APTES/GA) and N-hydroxysuccinimide-silane (NHS-silane). Antibody reorientation occurs at lower Γ values when physisorption (APTES) is involved rather than chemisorption (APTES/GA, NHS-silane). At high Γ values, comparable proportions of molecules adapting head-on and tail-on vertical alignment are concluded for APTES and the NHS-silane monolayer, and they are related to intermolecular dipole–dipole interactions. Intermolecular forces seem to be less decisive than covalent binding for antibodies on the APTES/GA surface, with dominant head-on orientation. Independently, the impact of glutaraldehyde activation of APTES on vertical orientation is confirmed by separate TOF-SIMS measurements. 相似文献
5.
Panagiota Fragouli Hermis Iatrou David J. Lohse Nikos Hadjichristidis 《Journal of polymer science. Part A, Polymer chemistry》2008,46(12):3938-3946
Three linear pentablock quintopolymers (l‐SIDMV), where S is polystyrene (PS), I polyisoprene‐1,4 (PI), D poly(dimethylsiloxane) (PDMS), M poly(tert‐butyl methacrylate) (PtBuM), and V poly(2‐vinylpyridine) (P2VP), were synthesized by anionic polymerization high vacuum techniques. The approach involves the following: (a) The synthesis of living triblock terpolymer PS‐b‐PI‐b‐PDMSLi and diblock copolymer P2VP‐b‐PtBuMK by sequential polymerizations of the corresponding monomers with sec‐BuLi and benzyl potassium, respectively; and (b) The selective linking of the living triblock terpolymer with the chlorosilane group of 2‐(chloromethylphenyl)ethyldimethylchlorosilane (CMPDMS), followed by linking of the living block copolymer with the remaining chloromethyl group of CMPDMS. Molecular characterization carried out by size exclusion chromatography, membrane osmometry, solution (in CDCl3 or d8‐toluene) and solid‐state 1H‐NMR spectroscopy indicated a high degree of molecular and compositional homogeneity. Differential scanning calorimetry results on the precursors and final polymers were discussed. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3938–3946, 2008 相似文献
6.
Papoutsis I Nikolaou P Athanaselis S Pistos C Maravelias C Spiliopoulou C 《Journal of mass spectrometry : JMS》2011,46(1):71-76
Vardenafil (VDN) is one of the three commercially available phosphodiesterase type 5 inhibitors and it is mainly used in the treatment of erectile dysfunction. A sensitive and specific gas chromatography/mass spectrometry (GC/MS) method for the determination of VDN in blood has been developed and validated. Sample preparation included solid-phase extraction and derivatization with N-methyl-N-tert-butyldimethylsilyl-trifluoroacetamide (MTBSTFA) and 1% tert-butyldimethylsilylchloride (TBDMSCl). Protriptyline was used as the internal standard for this assay. Limits of detection and quantification for VDN were 0.70 and 2.00 μg/l, respectively. The calibration curves were linear within the dynamic range 2.00-200.0 μg/l with a correlation coefficient higher than 0.991. Absolute recovery ranged from 88.6% to 95.7% for the analyte of interest at three quality control levels. Intra- and inter-day accuracy was found to be between - 6.1% to 10.8% and - 9.3% to 11.6%, respectively, whereas intra- and inter-day precision was < 7.8% and 9.7%, correspondingly. The proposed method is the first fully validated GC/MS method for the determination of VDN in blood samples and it can be used in routine every day analysis by clinical and forensic laboratories for pharmacokinetic studies, for therapeutic drug level monitoring or for the investigation of related forensic cases. A few blood samples analyzed using the developed method is reported herein to demonstrate the suitability of the method. 相似文献
7.
Papoutsis I Nikolaou P Athanaselis S Alevizopoulos G Pistos C Paraskevopoulou C Spiliopoulou C 《Journal of separation science》2011,34(21):3037-3042
Sildenafil (SDL) is a phosphodiesterase type 5 inhibitor and it is approved for the treatment of erectile dysfunction and pulmonary hypertension. SDL is extensively metabolized to its pharmacologically active metabolite, desmethyl‐sildenafil (DSDL). A sensitive and specific GC/MS method for the determination of SDL and DSDL in whole blood was developed and validated to support therapeutic drug monitoring of SDL patients. The combination of solid‐phase extraction with derivatization using BSTFA with 1% TMCS in acetonitrile efficiently reduced matrix effect and improved sensitivity of the method. In this assay, protriptyline was used as internal standard for both analytes. The LODs were 1.50 and 5.00 ng/mL for SDL and DSDL, respectively, whereas the respective LOQs were 5.00 and 15.0 ng/mL. The calibration curves were linear up to 500.0 ng/mL (SDL: R2 0.992, DSDL: R2 0.990). Absolute recovery values for both analytes ranged from 83.1 to 93.2%. Within‐ and between‐batch accuracy was less than 11.8 and 10.2%, respectively, whereas within‐ and between‐batch precision was less than 8.1 and 10.8%, correspondingly. The developed method is suitable for the determination of SDL and DSDL concentrations in blood samples obtained from patients under Viagra® treatment, for pharmacokinetic studies or for the investigation of related forensic cases. 相似文献
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9.
In this paper, heavy crude oil–water flows are studied in a horizontal stainless steel test section with 25.4 mm ID and overall length of 50 m. Crude oil (viscosity = 628.1 mPa s, interfacial tension with water = 10.33 mN/m at 60 °C) and water, collected from an oilfield, were used as test fluids. Visual observations, local sampling and pressure drop measurements were used to identify the flow patterns and their transitions. It was found that in all conditions studied there was a water-in-oil emulsion present. At low mixture velocities and water fractions this occupied the whole pipe cross section. As the velocity or the volume fraction increased water appeared to segregate. At high water fractions and mixture velocities annular flow appeared with the water-in-oil emulsion in the core surrounded by a water layer. The results were compared with those from a model oil with the same viscosity. At low water fractions there was a similarity between the patterns observed with the two oil systems characterized by water segregation from an oil continuous dispersion with increasing water fraction or mixture velocity. However, at high water fractions an oil-in-water dispersion formed with the model oil that was not seen with the crude oil. Pressure drop was generally higher for the crude oil system compared to the model one, while in both cases it decreased when water started to segregate and form layers in contact with the pipe wall. The differences between the two oil systems are attributed to the natural surfactants present in the heavy crude oil (such as asphaltenes and resins), which tend to accumulate on the water/oil interface, retard film drainage and maintain the stability of water drops in oil. 相似文献
10.
Miguel Córdova Arnaldo T. Lorenzo Alejandro J. Müller Panagiota Fragouli Hermis Iatrou Nikos Hadjichristidis 《Macromolecular Symposia》2010,287(1):101-106
Summary: A set of melt miscible Poly(2-vinyl pyridine)-b-Poly(ethylene oxide) (P2VP-b-PEO) block copolymers of different compositions were studied. Transmission electron microscopy shows phase separation in the materials during the crystallization process of the PEO block as crystalline lamellae are observed for all compositions evaluated. The isothermal crystallization kinetics of PEO is progressively retarded as the P2VP content in the copolymer increases, since P2VP hinders molecular mobility in the miscible amorphous phase. Polarized light optical microscopy demonstrated that the glassy P2VP block has a negative effect on the secondary nucleation of the PEO. Finally, physical ageing experiments performed in the glassy state of the amorphous mixed phase, at different ageing times, demonstrated that a nucleating effect can be induced in the glassy state as a consequence of the reorganization of the amorphous regions. This nucleating effect significantly alters the cold crystallization rate upon subsequent heating above the glass transition temperature. 相似文献