bluuebunny/crossref_metadata_2025_split huggingface dataset:
Liquid‐phase microextraction combined with liquid chromatography‐mass spectrometry. Extraction from small volumes of biological samples
Authors: Halvorsen Trine Grønhaug , Pedersen‐Bjergaard Stig , Reubsaet J. Léon E. , Rasmussen Knut E. 
Published: November 2003

AbstractLiquid‐phase microextraction (LPME) is a sample preparation technique based on disposable polypropylene hollow fibres, which results in efficient sample clean‐up and high preconcentration. The present paper describes the combination of LPME with LC‐MS utilising electrospray ionisation for high sensitivity. Nine antidepressant drugs were extracted from 50 or 500 μL of plasma or whole blood samples, through a thin layer of dodecyl acetate immobilised in the pores of the hollow fibre, and into 15 μL of 200 mM formic acid as acceptor solution inside the hollow fibre. Analyte recoveries in the range 12–68% and 9–52% were obtained from 50 μL of plasma and whole blood respectively. The acceptor solution (15 μL) was diluted with 60 μL of 5 mM ammonium formate pH = 2.7 prior to injection into the LC‐MS system. The system was qualitatively investigated for matrix effects utilising a post‐column infusion system. Whole blood from 5 different persons was cleaned‐up by LPME and injected onto the analytical column while a solution of the 9 model compounds was continuously infused post‐column. No signs of ion suppression were seen for any of the model compounds. Limits of quantification (S/N = 10) were in the low ng/mL range for 6 of the 9 model compounds utilising a whole blood sample volume of only 50 μL. The repeatability of the extractions was investigated utilising paroxetine as internal standard. Acceptable RSDs (%) were obtained (< 20%) for 5 of the antidepressants. By increasing the sample volume from 50 to 500 μL of whole blood RSDs below 20% (3–16%) were observed for all 8 antidepressants.
Adsorption of polyethylene from thermodynamically good solvents on a zeolite stationary phase
Authors: Macko Tibor , Denayer Joeri F. , Pasch Harald , Baron Gino V. 
Published: November 2003

AbstractAdsorption of linear polyethylene and isotactic polypropylene on columns packed with zeolites ZSM‐5, Y, and silicalite was studied using high‐temperature liquid phase chromatography. Linear polyethylene was fully retained on a column packed with ZSM‐5 zeolite from non‐polar solvents, such as 1,1,2,2‐tetrachloroethane and 1,3,5‐trimethylbenzene at a temperature of 140°C. Partial adsorption on ZSM‐5 zeolite was found for polyethylene in 1,2,4‐trichlorobenzene and on silicalite from 1,2,4‐trichlorobenzene and 1,3,5‐trimethylbenzene. On the other hand, adsorption of polyethylene was not found from polar liquids, such as 2‐ethylhexyl acetate, cyclohexyl acetate, and cyclohexanone. Isotactic polypropylene was not adsorbed on any tested sorbent.
Evaluation of surfactant‐assisted pressurized hot water extraction for marker compounds in Radix Codonopsis pilosula using liquid chromatography and liquid chromatography/electrospray ionization mass spectrometry
Authors: Ong Eng Shi , Len Shea Mei 
Published: November 2003

AbstractIn the move towards the elimination of organic solvents in the extraction process in botanicals, a new method combining surfactant and pressurized hot water extraction (PWHE) with an applied temperature below the boiling point and lower pressure from 10 to 20 bar was developed for the analysis of marker compounds that are reasonably hydrophobic such as tetradeca‐4E,12E‐diene‐8,10‐diyne‐1,6,7‐triol and tetradeca‐4E,12E‐diene‐8,10‐diyne‐1,6,7‐triol‐O‐β‐D‐glucoside in Radix Codonopsis pilosula (DangShen). Because reference substances for the proposed botanicals were not available, a method was developed to isolate the marker compounds in Radix Codonopsis pilosula. Other than surfactant‐assisted PHWE, the marker compounds present in Radix Codonopsis pilosula were extracted using pressurized liquid extraction (PLE) with methanol and PHWE with a mixture of water/ethanol (80:20). The extracts were analyzed using liquid chromatography and liquid chromatography/electrospray ionization mass spectrometry. With surfactant‐assisted PHWE, the effects of different added surfactants such as sodium dodecyl sulfate and Triton X‐100 was studied. Surfactant assisted PHWE with Triton X‐100 proved to be at least equivalent or better compared to Soxhlet extraction in terms of quantitative analysis of marker compounds in Radix Codonopsis pilosula. The method precision was less than 8% (RSD, n = 6). The presence of surfactants in PHWE was found to enhance the solubility of target compounds naturally occurring in medicinal plants.
Physical Properties of PBMA‐b‐PBA‐b‐PBMA Triblock Copolymers Synthesized by Atom Transfer Radical Polymerization
Authors: Martín‐Gomis Luis , Fernández‐García Marta , de la Fuente José Luis , Madruga Enrique López , Cerrada María L. 
Published: November 2003

AbstractThe physical properties of well‐defined poly(butyl methacrylate)‐block‐poly(butyl acrylate)‐block‐poly(butyl methacrylate) (PBMA‐b‐PBA‐b‐PBMA) triblock copolymers synthesized by atom transfer radical polymerization (ATRP) are reported. The glass transition and the degradation temperature of copolymers were determined by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). DSC measurements showed phase separation for all of the copolymers with the exception of the one with the shortest length of either inner or outer blocks. TGA demonstrated that the thermal stability of triblock copolymers increased with decreasing BMA content. Dynamic mechanical analysis was used for a preceding evaluation of adhesive properties. In these block copolymers, the deformation process under tension can take place either homogeneously or by a neck formation depending on the molecular weight of the outer BMA blocks and on the length of the inner soft BA segments. Microindentation measurements were also performed for determining the superficial mechanical response and its correlation with the bulk behavior.Stress‐strain curves for the different PBMA‐b‐PBA‐b‐PBMA specimens at room temperature and at 10 mm/min.magnified imageStress‐strain curves for the different PBMA‐b‐PBA‐b‐PBMA specimens at room temperature and at 10 mm/min.
Additive Effect of Triphenylphosphine on the Living Polymerization of 1,3‐Butadiene with a Cobalt Dichloride‐Methylaluminoxane Catalytic System
Authors: Nath Dilip Chandra Deb , Shiono Takeshi , Ikeda Tomiki 
Published: November 2003

AbstractThe additive effect of triphenylphosphine (Ph3P) was investigated in 1,3‐butadiene polymerization with cobalt dichloride (CoCl2) activated by methylaluminoxane (MAO); the catalytic system resulted in slowly‐initiated living polymerization with a high cis‐1,4 content (about 99%) at 0 °C. The polymerization behavior, such as the relationship of polymer yield and number‐average molecular weight ($\overline M _{\rm n}$) with polymerization time, was dependent on the amount of Ph3P added. In the presence of a small amount of Ph3P (Ph3P/Co = 0.025), the kinetic behavior qualitatively resembled that observed in the absence of Ph3P, which indicated that the catalytic system conducted slowly‐initiated living polymerization. An increase in the amount of Ph3P (Ph3P/Co > 0.025), however, caused chain transfer reaction. The 1H NMR analysis of the produced polymers showed that Ph3P changed the microtacticity from 99% of cis‐1,4 to 88% of 1,2‐unit, depending on the amount of Ph3P added. At the maximum amount of Ph3P (Ph3P/Co = 0.025) necessary for maintaining the livingness of the propagating species, 14% of the 1,2‐inserted unit was incorporated at the expense of the cis‐1,4‐inserted unit. The addition of Ph3P (Ph3P/Co = 0.025) during the polymerization did not affect the livingness and gave a regio‐block copolymer of 1,3‐butadiene.Number‐average molecular weight as a function of polymerization time.magnified imageNumber‐average molecular weight as a function of polymerization time.
Chemically Amplified Photolithography of a Copolymer Containing Phenolphthalein
Authors: Lee Chan‐Woo , Yuan Zhongzhe , Kim Young‐Bum , Lee Suck‐Hyun 
Published: November 2003

AbstractA convenient, low cost micro‐patterning method using a new side group polymer containing phenolphthalein is reported. A random copolymer of t‐BOC‐protected phenolphthalein methacrylate (t‐BMPP) with methyl methacrylate (MMA) was prepared by radical copolymerization in dioxane. The negative‐tone patterns of this polymer could be obtained by photo‐deprotection of the t‐BOC groups due to the effect of dissolution inhibition by the phenolic group of the phenolphthalein. The chemical and optical properties of the polymer were, as anticipated, very close to those of the corresponding phenolphthalein and the pH controlled colorimetric transition was reproducibly observed. The contrast in solubility and chromism upon alkaline treatment makes this polymer a promising candidate for investigating spatially‐directed chromism and selective deposition of pH sensitive polymers.SEM image of parallel lines of P(MMA/PPT) generated by contact UV exposure.magnified imageSEM image of parallel lines of P(MMA/PPT) generated by contact UV exposure.
Novel Light Emitting Diode Using Organic Electroluminescence Microcapsules
Authors: Heo Jae‐Seok , Park No‐Hyung , Ryu Jee‐Hyun , Choi Gyung‐Hyun , Suh Kyung‐Do 
Published: November 2003

AbstractNovel light emitting diodes (LEDs) were prepared using electroluminescence (EL) material/polymer microcapsules (ELC). N‐vinylcarbazole as a hole‐transporting component and methyl methacrylate (MMA) were copolymerized for producing the seed particles using dispersion polymerization. An oxadiazole derivative, synthesized as a electron‐transporting component, and tris(8‐hydroxyquinolinato) aluminium(III) (Alq3) were incorporated into the polymer particles by using the solute co‐diffusion method (SCM). The LEDs for the EL characterization were fabricated in a thin sandwich configuration: Al anode/ELC/ITO cathode. The surface imaging of the LED prepared using ELC was performed by atomic force microscopy (AFM). The EL characteristics of the ELC were investigated by UV, photoelectron and luminescence spectroscopy, and the current‐voltage and the light‐voltage characteristics for the LED were determined.Encapsulation procedure using solute co‐diffusion method (SCM).magnified imageEncapsulation procedure using solute co‐diffusion method (SCM).
Synthesis and Characterization of Segmented Poly(ether ester)s Containing H‐Bonding Units
Authors: Signori Francesca , Solaro Roberto , Chiellini Emo , Lips Priscilla A. M. , Dijkstra Pieter J. , Feijen Jan 
Published: November 2003

AbstractA series of poly(ether ester)s containing different H‐bonding units (amide, carbamate, urea) was prepared by polycondensation in bulk, using Ti(OBu)4 as a catalyst. The copolymers were obtained starting from PEG1000, 1,4‐butanediol, and a symmetrical, bis‐ester terminated monomer carrying H‐bonding units. These materials were designed for biomedical applications, in which ultimate biodegradability of the materials is required. The influence of the nature of the H‐bonding unit and of the length of the methylene spacer between H‐bonding groups on the thermal and solubility properties of copolymers was investigated. Amide containing copolymers were more thermally stable than ones containing carbamate, consistent with the observed behavior of the corresponding monomers. In most cases, differential scanning calorimetry (DSC) traces were quite complex because of phase separation and dependent on the applied cooling rate. Copolymers containing urea bonds were less soluble in most organic solvents, but their thermal properties were not significantly different than their amide containing counterparts.Synthesis of amide‐based diester monomers.magnified imageSynthesis of amide‐based diester monomers.
Preparation and Characterization of Acetoacetoxyethyl Methacrylate‐Based Gels
Authors: Boyko Volodymyr , Lu Yan , Richter Andreas , Pich Andrij 
Published: November 2003

AbstractNovel polymeric gels have been prepared by radical copolymerization of acetoacetoxyethyl methacrylate (AAEM) and hydroxyethyl methacrylate (HEMA) in water‐ethanol medium. The influence of the HEMA:AAEM ratio and crosslinker concentration on properties of gels was studied. Independently on gel composition the maximum swelling was detected in chloroform. It was found that PAAEM gels possess phase transition temperature or upper critical solution temperature (UCST) in alcohol‐water solutions. UCST decreases in linear order from 75 to 10 °C when HEMA content in gel structure increases. The minimal UCST of AAEM/HEMA gels in binary alcohol‐water mixtures is shifted toward lower temperatures and lower alcohol concentrations when the alkyl chain of alcohol increases.AAEM/HEMA gels prepared at different BIS concentrations (1:1 mol‐%, 2:2.5 mol‐%, 3:5 mol‐%).magnified imageAAEM/HEMA gels prepared at different BIS concentrations (1:1 mol‐%, 2:2.5 mol‐%, 3:5 mol‐%).
Chain Connectivity and Conformational Variability of Polymers: Clues to an Adequate Thermodynamic Description of their Solutions, 3
Authors: Stryuk Sergej , Wolf Bernhard A. 
Published: November 2003

AbstractA simple expression for the composition dependence of the Flory‐Huggins interaction parameter of polymer/solvent systems reported earlier is used to model the demixing of polymer solutions into two liquid phases. To this end, the system specific parameters ζ and ν of that approach are calculated as a function of temperature using the thermodynamic expressions resulting for the critical conditions on one side and from experimentally determined critical data for polymers of different molar mass on the other side. By means of data reported for the system cyclohexane/polystyrene it is demonstrated that binodal and spinodal lines are very accurately modeled at low temperatures (UCSTs) and at high temperatures (LCSTs). The parameters obtained from the demixing behavior match well with that calculated from the composition dependence of the vapor pressure at temperatures where the components are completely miscible. Information on the phase separation of the system trans‐decalin/polystyrene for different molecular weights and at different elevated pressures is used to show that the approach is also apt to model pressure influences. The thus obtained ζ(T;p) and ν(T;p) enable the prediction of the (endothermal) theta temperature of the system as a function of pressure in quantitative agreement with the data directly obtained from light scattering measurements with dilute solutions.Phase diagram for trans‐decalin/polystyrene.magnified imagePhase diagram for trans‐decalin/polystyrene.
Synthesis of Poly(ester amide)s Derived from Glycolic Acid and the Amino Acids: β‐Alanine or 4‐Aminobutyric Acid
Authors: Rodríguez‐Galán Alfonso , Vera Montserrat , Jiménez Katia , Franco Lourdes , Puiggalí Jordi 
Published: November 2003

AbstractThe polymerization of metal salts of N‐chloroacetyl‐β‐alanine and N‐chloroacetyl‐4‐aminobutyric acid was investigated. The former gives a mixture of polymer and a seven‐membered cyclic compound constituted of glycolic and β‐alanine units, and its reaction proceeds in the solid state. However, liquefaction is observed in the second case giving rise to a polymer with a moderate molecular weight. Condensation kinetics of both sodium and silver salts of N‐chloroacetyl‐β‐alanine have been studied by differential scanning calorimetry. Copolymers of glycolic acid and β‐alanine with a molar ratio of glycolic acid/β‐alanine varying from 0.5 to 1.0 have been synthesized by thermal reaction of co‐precipitated crystals of the sodium salts of chloroacetic acid and N‐chloroacetyl‐β‐alanine. NMR spectroscopy indicates that copolymers tend to have a random distribution. The resulting new poly(ester amide)s have been characterized by spectroscopy and thermal analysis.DSC heating runs corresponding to different mixtures of the sodium salts of chloroacetic acid and chloroacetyl‐β‐alanine.magnified imageDSC heating runs corresponding to different mixtures of the sodium salts of chloroacetic acid and chloroacetyl‐β‐alanine.
Synthesis and Characterization of Poly(arylene ether oxadiazole) Telechelics
Authors: Gomes Dominique , Nunes Suzana P. 
Published: November 2003

AbstractPoly(arylene ether oxadiazole) telechelics with fluorine and hydroxyl end groups were synthesized by nucleophilic substitution polymerizations of 2,5‐bis(4‐fluorophenyl)‐1,3,4‐oxadiazole monomer with bishydroxy compounds containing C(CH3)2, C(CF3)2 and SO2 groups. Fluorotelechelics were obtained with about 3 repeating units (molecular weight about 2 000 g · mol−1) using a rather excess (100 mol‐%) of bis(fluorophenyl) oxadiazole compound. On the other hand, hydroxytelechelics were synthesized with about 9 repeating units (molecular weight about 5 000 g · mol−1) using a small excess of bishydroxy compound (monomer molar ratio of 0.93). Sulfonated poly(arylene ether oxadiazole) hydroxytelechelics were also synthesized using sulfonated and unsulfonated bishydroxy compounds. All sulfonated hydroxytelechelics were partially water soluble, even when only 40 mol‐% of sulfonated monomers was used. The number of repeating units of hydroxytelechelics increased up to 12 (molecular weight about 9 000 g · mol−1) using sulfonated monomers, probably because of the higher reactivity of sulfonated phenoxide. The molecular weights estimated by 1H NMR were in agreement to the results obtained by SEC. The telechelics can be used as precursor for the synthesis of block copolymer.Structure of the hydroxytelechelics.magnified imageStructure of the hydroxytelechelics.
Study on Doping Behaviors of Vinyl Hydrogels with Pendant Terthiophenes
Authors: Chen Li , Gong Jian Ping , Ohsedo Yutaka , Osada Yoshihito 
Published: November 2003

AbstractThe water‐swollen poly(AA3T‐co‐NaSS) and poly(AA3T‐co‐PEG) gels were synthesized by radical copolymerization of the monomer, [(2,2′:5′,2″‐terthiophen‐5‐yl)methyl acrylate] (AA3T), containing pendant terthiophenes as an electron‐conducting material with a soluble monomer, sodium p‐styrenesulfonate (NaSS), or oligo(ethylene glycol) (PEG); their swelling, spectral, and doping behaviors were investigated. The degree of swelling of the poly(AA3T‐co‐PEG) gel was independent of the pH, whereas that of poly(AA3T‐co‐NaSS) gel increases abruptly below pH 3, which suggests self‐doping between the AA3T and NaSS groups. The self‐doping is not suppressed by cross‐linking. Both poly(AA3T‐co‐NaSS) and poly(AA3T‐co‐PEG) gels can be chemically doped with concentrated HCl or HClO4 solution.Concentration dependence of the absorbency of the copolymers and gel.magnified imageConcentration dependence of the absorbency of the copolymers and gel.
Polyelectrolyte‐in‐Ionic‐Liquid Electrolytes
Authors: Tiyapiboonchaiya Churat , Pringle Jennifer M. , MacFarlane Douglas R. , Forsyth Maria , Sun Jiazeng 
Published: November 2003

AbstractNovel polymer electrolyte materials based on a polyelectrolyte‐in‐ionic‐liquid principle are described. A combination of a lithium 2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid (AMPSLi) and N,N′‐dimethylacrylamide (DMMA) are miscible with the ionic liquid, 1‐ethyl‐3‐methylimidazolium dicyanamide (EMIDCA). EMIDCA has remarkably high conductivity (≥ 2 · 10−2 S · cm−1) at room temperature and acts as a good solvating medium for the polyelectrolyte. At compositions of AMPSLi less than or equal to 75 mol‐% in the copolymer (P(AMPSLi‐co‐DMAA)), the polyelectrolytes in EMIDCA are homogeneous, flexible elastomeric gel materials at 10 − 15 wt.‐% of total polyelectrolyte. Conductivities higher than 8 · 10−3 S · cm−1 at 30 °C have been achieved. The effects of the monomer composition, polyelectrolyte concentration, temperature and lithium concentration on the ionic conductivity have been studied using thermal and conductivity analysis, and pulsed field gradient nuclear magnetic resonance techniques.Comparison of the measured and calculated lithium conductivity at 30 °C.magnified imageComparison of the measured and calculated lithium conductivity at 30 °C.
Homolysis and Decomposition of Alkoxyamines Containing PROXYL and TEMPO Residues: A Comparison
Authors: Bacon Catherine A. , Cameron Neil R. , Reid Alistair J. 
Published: November 2003

AbstractQuantitative ESR and 1H NMR spectroscopies have been used to study the homolysis and decomposition, respectively, of alkoxyamines derived from TEMPO and PROXYL nitroxides. It is shown that alkoxyamines substituted in the β position with a tert‐butoxy group have different activation parameters than those bearing a 1‐phenethyl fragment, however, there is compensation between transition state enthalpy and entropy, resulting in most cases in similar transition state free energies and homolysis kinetics. On the other hand, β‐substituted alkoxyamines show a much lower tendency to undergo decomposition, while species derived from TEMPO are more prone to decomposition than those from the substituted PROXYL derivative investigated. These findings are used to explain the observed differences in polymerisation behaviour of the various alkoxyamines.Alkoxyamines used in the present study.magnified imageAlkoxyamines used in the present study.
Electrical Conductivity of an Individual Polyaniline Nanotube Synthesized by a Self‐Assembly Method
Authors: Long Yunze , Zhang Lijuan , Ma Yongjun , Chen Zhaojia , Wang Nanlin , Zhang Ze , Wan Meixiang 
Published: November 2003

AbstractCamphor sulfonic acid (CSA) doped polyaniline (PANI) nanotubes (175 nm in outer diameter and 120 nm in inner diameter) were synthesized successfully by a self‐assembly method. It is found that the room‐temperature conductivity of an individual PANI nanotube is 30.5 S · cm−1; in particular, the intrinsic resistance of an individual nanotube (30 kΩ) is much smaller than the contact resistance of crossed nanotubes (500 kΩ).A SEM image of two crossed PANI‐CSA nanotubes and the attached Pt electrodes.magnified imageA SEM image of two crossed PANI‐CSA nanotubes and the attached Pt electrodes.
Probing Nanoscale Polymer Interactions by Forced‐Assembly
Authors: Liu Richard Y. F. , Jin Yi , Hiltner Anne , Baer Eric 
Published: November 2003

AbstractWhen two immiscible polymers are brought into intimate contact, highly localized mixing of polymer chains creates an “interphase” region. Materials that are entirely interphase are fabricated by forced‐assembly using layer‐multiplying coextrusion to form assemblies of thousands of nanolayers. Analysis of the interphase materials with conventional methods of polymer analysis confirms certain theoretical predictions for the first time. The unique properties of the new interphase materials result from lower free volume than the constituents.Atomic force microscopy phase image from the cross‐section of a PC/PMMA nanolayer film with 4096 layers and average layer thickness of 25 nm.magnified imageAtomic force microscopy phase image from the cross‐section of a PC/PMMA nanolayer film with 4096 layers and average layer thickness of 25 nm.
Encapsulation of Bovine Serum Albumin in Temperature‐Programmed “Shell‐in‐Shell” Structures
Authors: Jo Yun‐Suk , Kim Do‐Kyung , Jeong Young‐Keun , Kim Kyung‐Ja , Muhammed Mamoun 
Published: November 2003

AbstractA novel approach to load a hydrophilic bovine serum albumin into drug carriers was proposed in terms of temperature‐programmed “shell‐in‐shell” structures, which were fabricated with poly(N‐isopropylacrylamide), poly(lactide), poly(ethylene glycol), and Au nanoparticles. Spherically well‐defined “shell‐in‐shell” structures were constructed by a modified‐double‐emulsion method (MDEM). The lower critical solubility temperature of the structures was manipulated to 36.4 °C which was confirmed by UV/Vis spectroscopy and DSC (Differential Scanning Calorimetry).TEM image of the Au@PLLA‐PEG@PNIPAAm‐PDLA structure.magnified imageTEM image of the Au@PLLA‐PEG@PNIPAAm‐PDLA structure.