bluuebunny/crossref_metadata_2025 huggingface dataset:
Overexpression of caveolin‐1 induces alteration of multidrug resistance in Hs578T breast adenocarcinoma cells
Authors: Cai Chuanxi , Chen Jianwen
Published: May 2004

Caveolin‐1 is a major caveolae‐coat protein involved in a variety of cell signaling processes. Some studies have suggested that the level of caveolin‐1 expression positively correlates with multi‐drug resistance in cancer cells. We demonstrated for the first time that Hs578T doxorubicin resistant cells (Hs578T/Doxo), which contain low levels of endogenous caveolin‐1 and high levels of P‐glycoprotein, are rendered drug‐sensitive by overexpression of exogenous caveolin‐1. MTT assays showed that after overexpressing caveolin‐1, the drug resistance of Hs578T/Doxo cells to doxorubicin and cisplatin was reduced from 25.4 ± 1.5 and 65.3 ± 2.5 μg/ml to 0.8 ± 0.15 and 23.2 ± 2.1 μg/ml, respectively (i.e. reduced by 97% and 64%, respectively). Furthermore, using rhodamine‐123 efflux assays, we observed a significant decrease in P‐glycoprotein activity in caveolin‐1 overexpressing cells, similar to that observed with 5 μM cyclosporine A or 10 μM verapamil, 2 inhibitors of P‐glycoprotein activity. Using confocal microscopy, subcellular fractionation and co‐immunoprecipitation assays, a possible physical interaction between caveolin‐1 and P‐glycoprotein in the caveolae membrane was observed in Hs578T/Doxo cells overexpressing caveolin‐1. These results suggest that overexpression of caveolin‐1 changes the state of the cells from drug‐resistant to drug‐sensitive by inhibiting P‐glycoprotein transport activity. © 2004 Wiley‐Liss, Inc.
Bone formation in polymeric scaffolds evaluated by proton magnetic resonance microscopy and X‐ray microtomography
Authors: Washburn Newell R. , Weir Michael , Anderson Paul , Potter Kimberlee
Published: May 2004

Magnetic resonance microscopy (MRM) and X‐ray microtomography (XMT) were used to investigate de novo bone formation in porous poly(ethyl methacrylate) (PEMA) scaffolds, prepared by a novel co‐extrusion process. PEMA scaffolds were seeded with primary chick calvarial osteoblasts and cultured under static conditions for up to 8 weeks. Bone formation within porous PEMA scaffolds was confirmed by the application of histologic stains to intact PEMA disks. Disks were treated with Alizarin red to visualize calcium deposits and with Sirius red to visualize regions of collagen deposition. DNA analysis confirmed that cells reached confluence on the scaffolds after 7 weeks in static culture. The formation of bone in PEMA scaffolds was investigated with water proton MRM. Quantitative MRM maps of the magnetization transfer ratio (MTR) yielded maps of protein deposition, and magnetic resonance (MR) relaxation times (T1 and T2) yielded maps of mineral deposition. The location of newly formed bone and local mineral concentrations were confirmed by XMT. By comparing MRM and XMT data from selected regions‐of‐interest in one sample, the inverse relationship between the MR relaxation times and mineral concentration was validated, and calibration curves for estimating the mineral content of cell‐seeded PEMA scaffolds from quantitative MRM images were developed. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res 69A: 738–747, 2004
The effect of production regime and crucible materials on the thermal properties of sodium phosphate glasses produced from salts
Authors: Parsons A.J. , Burling L.D. , Rudd C.D. , Scotchford C.A. , Walker G.S.
Published: May 2004

Changes in the thermal properties of sodium phosphate glasses during melt production have been investigated using Pt/Au and fused alumina crucibles. Glasses were produced from NaH2PO4 as a starting material, providing an intrinsic Na2O:P2O5 ratio of 1:1 and giving an O/P = 3, that is, a metaphosphate. In Pt/Au crucibles, glass transition temperatures rose to a plateau value of 295°C at a rate determined by melt temperature. No contamination of the glass by platinum or gold was detected or indicated in the results. Ea for the reaction was found to be 66.4 kJ mol−1. In fused alumina crucibles, glass transition temperatures rose to over 450°C, with these values showing some convergence at higher furnace temperatures. Extensive erosion of the alumina crucibles was observed. The amount of alumina incorporation within the glasses correlated well with the rise in glass transition temperature up to a maximum of 15.5 mol % Al2O3 content. Al2O3 incorporation above this value caused a reduction in the value of the Tg. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 71B: 22–29, 2004
Three‐dimensional topographic scanning electron microscope and Raman spectroscopic analyses of the irradiation effect on teeth by Nd:YAG, Er: YAG, and CO2 lasers
Authors: Yamada Magda K. , Uo Motohiro , Ohkawa Shoji , Akasaka Tsukasa , Watari Fumio
Published: May 2004

A three‐dimensional analyzer installed in a scanning electron microscope was used to evaluate the morphology and surface roughness using noncontact profilometry. Observations were carried out on the enamel and dentin surface irradiated by three different lasers: Nd:YAG (wavelength 1.06 μm), Er:YAG (2.94 μm), and CO2 (10.6 μm). Spectroscopic analysis was done by Raman spectroscopy for nonirradiated and laser‐irradiated surfaces. The lasers were applied perpendicularly to vertically sectioned and polished human extracted caries‐free molars. The tooth was sectioned at each cavity for cross‐section analysis after laser irradiation. Irradiation by Nd:YAG and CO2 lasers of the enamel surface showed an opaque white color, different from dentin where the surface turned black. The Er:YAG laser induced no changes in color of the dentin. Numerous cracks associated with thermal stress were observed in the CO2 laser‐irradiated dentin. Noncontact surface profile analysis of Er:YAG laser‐irradiated enamel and dentin showed the deepest cavities, and direct cross‐sectional observations of them showed similar cavity outlines. The CO2 laser‐irradiated dentin had the least surface roughness. Raman spectroscopic analysis showed that fluorescence from the laser‐irradiated tooth was generally greater than from nonirradiated teeth. Bands in dentin attributed to organic collagen matrix were lost after Nd:YAG and CO2 laser irradiation, and a broad peak due to amorphous carbon appeared. The Er:YAG laser‐irradiated dentin showed no sign of a carbon band and had more suitable results for dental ablation. Noncontact surface profile analysis was effective to evaluate the structural change in the tooth in the microarea of study after laser irradiation. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 71B: 7–15, 2004
Human microvascular endothelial cell prostaglandin E1 synthesis during in vitro ischemia–reperfusion
Authors: Watkins Michael T. , Al‐Badawi Hassan , Russo Andrea L. , Soler Hiram , Peterson Brian , Patton George M.
Published: May 2004

Ischemia–reperfusion injury is a microvascular event documented in numerous in vivo animal models. In animal models, prostaglandin and prostaglandin analogues have been found to ameliorate reperfusion injury. These studies were undertaken to evaluate human microvascular endothelial PGE1 synthesis during in vitro ischemia followed by reperfusion. Human (neonatal) microvascular endothelial cell (MEC) cultures (n = 6) were subjected to sequential 2 h periods of normoxia (20% O2), ischemia (1.5% O2), and reperfusion (20% O2). Prostaglandin E2 synthesis in conditioned media was determined by ELISA. Steady state levels of MEC prostaglandin H synthase (PGHS)‐1 and ‐2 mRNA were assessed at the end of each 2‐h period using RT‐PCR and a quantitative mRNA ELISA. MEC PGHS protein levels were analyzed using an ELISA. PGE1 release increased significantly during the initial 30 min of ischemia, but rapidly fell below normoxic levels by 90 and 120 min. During reperfusion, PGE1 release returned to normoxic levels at 30, 60, and 90 min, and exceeded normoxic levels at 120 min. PGHS‐1 mRNA levels were undetectable during all experimental conditions. PGHS‐2 mRNA levels were unchanged by ischemia, but were decreased by reperfusion. In contrast, PGHS‐2 protein levels increased 3‐fold during ischemia, and remained elevated during reperfusion. Human MEC do not express PGHS‐1 mRNA in vitro. Prolonged ischemia decreases MEC PGE1 synthesis, and stimulates increased PGHS‐2 protein levels without altering the steady state levels of COX‐2 mRNA. During reperfusion, increased PGHS‐2 protein levels persist and are associated with stimulated PGE2 secretion, despite relative decreases in PGHS‐2 mRNA. J. Cell. Biochem. 92: 472–480, 2004. Published 2004 Wiley‐Liss, Inc.
Secretions of MMP‐9 by soluble glucocorticoid‐induced tumor necrosis factor receptor (sGITR) mediated by protein kinase C (PKC)δ and phospholipase D (PLD) in murine macrophage
Authors: Lee Hee‐Sook , Park So‐Yun , Lee Hyeon Woo , Choi Hye‐Seon
Published: May 2004

The secretion of matrix metalloproteinase (MMP‐9) is stimulated by the glucocorticoid‐induced tumor necrosis factor receptor (GITR), a new tumor necrosis factor receptor (TNFR) family, in murine macrophages via an activation of protein kinase C (PKC)δ and phospholipase D (PLD). Secretions of MMP‐9 are stimulated by the phosphatidic acid (PA), a product of PLD activity and an inhibition of PA production by a 1‐propanol inhibited secretion of MMP‐9 by soluble GITR (sGITR). MMP‐9 is not secreted by diacylglycerol (DAG) and an inhibitor of PA phosphatase has no effect on the secretion induced by sGITR, indicating that PA is responsible for MMP‐9 secretion in murine macrophages. Our data indicates that sGITR‐induced activation of PKCδ and PLD increases MMP‐9 secretions in macrophages. © 2004 Wiley‐Liss, Inc.
Variability of the recent climate of eastern Africa
Authors: Schreck Carl J. , Semazzi Fredrick H. M.
Published: May 2004

The primary objective of this study is to investigate the recent variability of the eastern African climate. The region of interest is also known as the Greater Horn of Africa (GHA), and comprises the countries of Burundi, Djibouti, Eritrea, Ethiopia, Kenya, Rwanda, Somalia, Sudan, Uganda, and Tanzania.

The analysis was based primarily on the construction of empirical orthogonal functions (EOFs) of gauge rainfall data and on CPC Merged Analysis of Precipitation (CMAP) data, derived from a combination of rain‐gauge observations and satellite estimates. The investigation is based on the period 1961–2001 for the ‘short rains’ season of eastern Africa of October through to December. The EOF analysis was supplemented by projection of National Centers for Environmental Prediction wind data onto the rainfall eigenmodes to understand the rainfall–circulation relationships. Furthermore, correlation and composite analyses have been performed with the Climatic Research Unit globally averaged surface‐temperature time series to explore the potential relationship between the climate of eastern Africa and global warming.

The most dominant mode of variability (EOF1) based on CMAP data over eastern Africa corresponds to El Niño–southern oscillation (ENSO) climate variability. It is associated with above‐normal rainfall amounts during the short rains throughout the entire region, except for Sudan. The corresponding anomalous low‐level circulation is dominated by easterly inflow from the Indian Ocean, and to a lesser extent the Congo tropical rain forest, into the positive rainfall anomaly region that extends across most of eastern Africa. The easterly inflow into eastern Africa is part of diffluent outflow from the maritime continent during the warm ENSO events. The second eastern African EOF (trend mode) is associated with decadal variability. In distinct contrast from the ENSO mode pattern, the trend mode is characterized by positive rainfall anomalies over the northern sector of eastern Africa and opposite conditions over the southern sector. This rainfall trend mode eluded detection in previous studies that did not include recent decades of data, because the signal was still relatively weak. The wind projection onto this mode indicates that the primary flow that feeds the positive anomaly region over the northern part of eastern Africa emanates primarily from the rainfall‐deficient southern region of eastern Africa and Sudan. Although we do not assign attribution of the trend mode to global warming (in part because of the relatively short period of analysis), the evidence, based on our results and previous studies, strongly suggests a potential connection. Copyright © 2004 Royal Meteorological Society.
Interannual variability of European extreme winter rainfall and links with mean large‐scale circulation
Authors: Haylock M. R. , Goodess C. M.
Published: May 2004

December–February (DJF) extreme rainfall was analysed at 347 European stations for the period 1958–2000. Two indices of extreme rainfall were examined: the maximum number of consecutive dry days (CDD); and the number of days above the 1961–90 90th percentile of wet‐day amounts (R90N). A principal component analysis of CDD found six components that accounted for 52.4% of the total variance. Six components of DJF R90N were also retained that accounted for 39.1% of the total variance. The second component of R90N has a very significant trend and the factor loadings closely resemble the observed linear trend in this index, suggesting that the analysis has isolated the mode of variability causing the trend as a separate component. The principal components of the indices were correlated with surface and upper‐air observations over the North Atlantic. The best correlations were generally found to be with sea‐level pressure (SLP) observations. A separate canonical correlation analysis of each of the two indices with SLP revealed several coupled modes of variability. The North Atlantic oscillation (NAO) was isolated as the first canonical pattern for R90N. For CDD the first two canonical coefficients of CDD were significantly correlated with the NAO index. Generally, the canonical coefficients with the highest correlations with the NAO had the most significant trends, suggesting that the observed trend in the NAO has strongly contributed to the observed trends in the indices. Two other important canonical patterns were isolated: a pattern of anomalous mean SLP (MSLP) centred over the North Sea, which seems to be related to local sea‐surface temperature over this region; and a dipole‐like pattern of MSLP with poles over the eastern Mediterranean and the central North Atlantic. Repeating the canonical correlation analysis with two other indices of extreme rainfall, the 90th percentile of wet day amounts and the maximum 10 day rainfall total, gives very similar coupled patterns. Copyright © 2004 Royal Meteorological Society.
Monolithic systems: from separation science to heterogeneous catalysis
Authors: Lubbad Said , Mayr Betina , Mayr Monika , Buchmeiser M.R.
Published: May 2004

Recent results that have been obtained in the ring‐opening metathesis polymerization (ROMP)‐based synthesis of monolithic supports are summarized. We have elaborated a synthetic concept that allows modifying monolithic supports in a way that they can be used both for applications in separation science, for SEC and as supports for catalytically active systems. In all cases, a tailor‐made microstructure was accessible due to the controlled character of the transition‐metal catalyzed polymerization. Taking advantage of the “living” catalytic sites, an “in situ” functionalization was accomplished by subsequently grafting a variety of functional monomers and catalyst precursors onto the rod. Their design and use as supports for high‐performance separation devices (e.g. for ds‐DNA) and catalytic supports (e.g. supported Grubbs‐type catalysts) is summarized.
Positron annihilation: a unique method for studying polymers
Authors: Dlubek Günter , Kilburn Duncan , Bondarenko Vladimir , Pionteck Jürgen , Krause‐Rehberg Reinhard , Alam M. Ashraf
Published: May 2004

Positron annihilation is a unique technique for studying the local free volume of polymers. Employing the positron annihilation lifetime spectroscopy (PALS) the size and size distribution of subnanometer size holes which constitute the excess free volume may be studied. In combination with macroscopic volume data the fractional free volume and the number density of holes may be estimated. After presenting the principles of the method, some examples typically for the investigation of the free volume in polymers will be given. Moreover, the study of interdiffusion in demixed polymer blends and further applications are shortly reviewed
Sulphonated poly(ether ether ketone): synthesis and characterisation
Authors: Lakshmi V.V. , Choudhary V. , Varma I.K.
Published: May 2004

The paper describes the sulphonation of commercially available poly(ether ether ketone) PEEK (GATONETM, Gharda Chemicals Limited, India and VICTREX®, ICI Limited, UK) by using concentrated sulphuric acid. The concentration of GATONE in conc. H2SO4 was varied from 4‐10% (w/v) whereas in VICTREX® the concentration was 4% (w/v). The temperature was varied from 35‐55°C and the duration of reaction was 3‐7 h. Structural characterisation of sulphonated polymers was done by elemental analysis, FT‐IR and 1H‐NMR spectroscopy. On the basis of elemental analysis, the extent of sulphonation of GATONE was found to be 57‐75%. The extent of sulphonation as determined by 1H‐NMR in case of GATONE was in the range of 53‐80% and for VICTREX 58‐87%. Thermal analysis, proton conductivity and water uptake of these samples were also studied. Proton conductivity of the films was comparable to the perflourinated polymer (Nafion).
Reactivity of supramolecular systems based on calix[4]resorcinarene derivatives and surfactants in hydrolysis of phosphorus acid esters
Authors: Ryzhkina Irina S. , Pashirova Tat'yana N. , Habicher Wolf D. , Kudryavtseva Ludmila A. , Konovalov Alexander I.
Published: May 2004

The formation of mixed micelles of amphiphilic calix[4]resorcinarenes with aminomethyl (AMC, PAMC), tris(hydroxymethyl)amide (THAC) fragments and the cationic surfactant cetyl trimethylammonium bromide (CTAB) in water and aqueous DMF solutions (10‐50% DMF) leads to the decrease of the critical micelle concentration of the systems and the increase of the size of the mixed micelles in comparison with CTAB micelles. The catalytic activity of the mixed systems in the hydrolysis of phosphorus acid esters is higher than those of CTAB micelle and AMC, PAMC or THAC aggregates.
Heterotelechelic poly(oxazolidine‐acetals) and their functionalization
Authors: Maślińska‐Solich Jolanta , Gibas Edyta
Published: May 2004

Telechelic poly(1,3‐oxazolidine‐acetal)s with ‐CH2OH and ‐CHO groups were synthesized by polycondensation of the 2‐amino‐2‐hydroxy‐1,3‐propanediol (1) (TRIS) with terephthaldehyde (2). The degree of polymerization (DP) was controlled by the ratio of 1 to 2 at the given reaction time. Characterization was achieved by 1H and 13C NMR and IR spectroscopy. The distribution of oxazolidine‐acetal units in the polymer chain has been performed using ESI‐MS. The activities of telechelic poly(oxazolidine‐acetal) were determined in reaction oxidation (4‐chloroperbenzoic acid), reduction (CH3MgCl) and nucleophilic substitution (acylation, alkylation).
Synthesis of functional polymers with acetal‐monosaccharide moieties
Authors: Maślińska‐Solich Jolanta , Kukowka Sylwia
Published: May 2004

The polycondensation of methyl α‐D‐mannopyranoside (1) with 1,n‐bis(formylphenoxy)alkanes (2), using acidic catalysts, leads to the formation of linear polymers and macrocyclic compounds. The structure of the polymer and macrocycles was determined by 1H, 13C NMR spectroscopy and ESI‐MS analysis.
ω‐substituted long chain alkylphosphonic acids – their synthesis and deposition on metal oxides and subsequent functional group conversion of the deposited compounds
Authors: Eschner Michael , Frenzel Ralf , Simon Frank , Pleul Dieter , Uhlmann Petra , Adler Hans‐Jürgen
Published: May 2004

The crystal structure and the surface of alumina layers on silicon wafers were investigated by means of GIWAXS, WAXS, and AFM. Self‐assembled monolayers of ω‐substituted long‐chain alkylphosphonic acids were deposited on alumina and the layer thickness and homogeneity were determined by ellipsometry revealing a dependency of thickness and homogeneity on the nature of the substituent. During the adsorption process surface etching by the phosphonic acid was observed causing an increase in surface roughness.

Furthermore, ex post functional group conversions were carried out yielding surface bound azides and rhodanides.
Reactive polymers on the basis of functional peroxides
Authors: Fleychuk R.I. , Kohut A.M. , Hevus O.I. , Voronov S.
Published: May 2004

The copolymerization constants of new monomer containing ditertiary peroxide groups with styrene have been determined. The peroxide monomers were prepared by the acylation of 3‐(tert‐butylperoxy)‐3‐methyl‐1‐butanol with methacryloyl chloride or maleic anhydride in the presence of tertiary amines. Peroxide containing copolymers were obtained by copolymerization of peroxyalkyl methacrylate and peroxyalkyl maleate with styrene.
Ring‐expansion polycondensation of 2‐stanna‐1,3‐dioxepane (or 1,3‐dioxepene) with dicarboxylic acid chlorides
Authors: Kricheldorf Hans R. , Chatti Saber , Schwarz Gert
Published: May 2004

2,2‐Dibutyl‐2‐stanna‐1,3‐dioxepane 1 (or 1,3‐dioxepene 2) were prepared from 1,4‐butane (or 1,4‐butene) diol and dibutyltin dimethoxide. They were polycondensed at 80°C in n‐heptane with adipoyl‐, suberoyl, sabacoyl chloride and with decane‐1,10‐dicarbonyl chloride. In the case of suberoyl chloride and 2,2‐dibutyl‐2‐stanna‐1,3‐dioxepane reaction time, temperature and stoichiometry were varied to optimize both the molecular weight and the fraction of cyclic polyesters. With a slight excess of the dicarboxylic acid chlorides, only macrocyclic polyesters were obtained in all cases. The resulting cyclic polyesters were characterized by viscosity measurements, by 1H and 13C NMR and by MALDI‐TOF mass spectrometry.
Hyperbranched thermolabile polycarbonates derived from a A2+B3 monomer system
Authors: Scheel Arnulf , Komber Hartmut , Voit Brigitte
Published: May 2004

Hyperbranched polycarbonates were synthesized successfully via the A2 + B3 route by the reaction of a bis(carbonylimidazolide) with triethanolamine. These polymers containing the carbonate group as thermolabile moiety are decomposing into volatile products at around 200°C. The polymers were characterized with 1H/13C NMR spectroscopy, SEC, DSC and TGA techniques.
Synthesis of Boc protected block copolymers based on para‐hydroxystyrene via NMRP
Authors: Messerschmidt Martin , Häußler Liane , Voit Brigitte , Krause Tilo , Habicher Wolf‐Dieter
Published: May 2004

Nitroxide mediated free radical polymerization (NMRP) was used for the preparation of orthogonally protected block copolymers based on para‐hydroxystyrene. The polymers have a low polydispersity and an active chain end. By a series of polymer analogous reactions, a partly deprotected block copolymer was synthesized consisting of a block with unprotected phenolic OH groups and a further block which is protected by the thermolabile Boc group.
High energy binders: glycidyl azide and allyl azide polymer
Authors: Varma I.K.
Published: May 2004

Hydroxy‐terminated azido polymers such as poly(glycidyl azide), poly bis(azidomethyl oxetane) and poly(azidomethyl methyloxetane) have been investigated in the past in propellent formulations and as fuels in rocket technology. The high energy released upon the decomposition of the azido group is responsible for their specialized application as high‐energy binders. The present paper describes the synthesis and characterization of new low molecular mass azido polymer i.e. poly(allyl azide). The curing reaction was carried out by using 1,3‐cyclic dipolar addition reaction. The dipolarophiles, such as dimethylene glycol dimethacrylate (EGDMA) and addition polyimides (bismaleimides, bisnadimides and bisitaconimides) were used for curing of azido polymers. The curing reaction was monitored by FT‐IR and differential scanning calorimetry. Curing was carried out at 40°C for 16 h (EGDMA) or 2 days (bismaleimide) and then at 60°C by using different phr of dipolarophiles. The heat of exothermic transition, due to decomposition of azide groups and thermal polymerization of addition polyimides, was very high and an improvement in thermal stability of cured resins was observed.
Selective resins, synthesis and sorption for precious metals
Authors: Jermakowicz‐Bartkowiak Dorota , Kolarz Bożena N.
Published: May 2004

Resins based on vinylbenzyl chloride (VBC) and divinylbenzene (DVB) copolymer were synthesised and used for preconcentration and separation of Au, Pt and Pd from hydrochloric acid solutions. Resulted resins show functionality concentration up to 5,8 mmol/g. The acidity and interference of other ions on the resins sorption were discussed. The sorption capacities of gold, platinum and palladium from hydrochloric solutions reaches to 85, 100 and 60 mg/g and distribution coefficients achieve 50 000 value. Recovery of noble metals revealed average of 60‐98% from mulitcomponent solutions.
Creation of crosslinkable interphases in polymer blends
Authors: Sadhu Veera Bhadraiah , Pionteck Jürgen , Pötschke Petra , Jakisch Lothar , Janke Andreas
Published: May 2004

A new type of bi‐ and trifunctional coupling agents containing 2‐oxazoline and/or 2‐oxazinone as well as hydrosilane moieties has been prepared by hydrosilylation of the corresponding allyl ether containing precursors with poly(methylhydro)siloxanes. In heterogeneous model blends based on mono‐carboxylic acid terminated polystyrene (PS) and mono‐amine terminated polyamide 12 (PA), the oxazoline and oxazinone units can selectively react with the carboxylic groups or amino groups, respectively. Under this mixing conditions the hydrosilane partially crosslinks.

The morphology development of the three‐component blends under melt mixing conditions is a rather complex process. We have shown that the coupling agents are immiscible with the polymers and form their own phase. Under proper processing conditions they locate at least partially at the PS/PA interface and can be used for further modification of the blend interphase, e.g. for crosslinking by hydrolysis. This crosslinking can be accelerated by the addition of a Pt‐catalyst during the melt mixing.
Sulfonated multiblock copoly(ether sulfone)s as membrane materials for fuel cell applications
Authors: Taeger Antje , Vogel Claus , Lehmann Dieter , Lenk Wolfgang , Schlenstedt Kornelia , Meier‐Haack Jochen
Published: May 2004

Arylene ether multiblock copolymers of the (AB)n‐type with various degrees of sulfonation have been prepared by a two‐step polycondensation procedure. Multiblock copolymers in high yields and of high molecular weights were obtained. For comparison random copolymers with the same overall composition were synthesized. The theoretical ion‐exchange capacities (IEC) of the materials were ranging from 0.50 mmol/g to 1.25 mmol/g. The water‐uptake of the multiblock copolymers showed a linear dependency from the IEC and was increasing with increasing IEC. No differences were observed between random and block copolymers. Furthermore, the hydrolytic stability of aromatic sulfonic acid groups was investigated in this study. Aromatic sulfonic acids, having additional electron donating groups, especially in ortho‐ or para‐position to the sulfonic acid group are sensitive to hydrolytic desulfonation. On the other hand electron‐withdrawing groups in meta‐position showed a stabilizing effect.
Inorganic, polymeric and hybrid colloidal carriers with multi‐layer reactive shell
Authors: Novikov V. , Zaichenko A. , Mitina N. , Shevchuk O. , Rayevska K. , Lobaz V. , Lubenets V. , Lastukhin Yu.
Published: May 2004

Main experimental approaches for obtaining polymer, inorganic and hybrid colloidal particles as well as the tailored functionalization of their surface by oligoperoxide surfactants (OPS) and metal complexes (OMC) on their basis are discussed in the paper. The methods proposed enable to combine the stage of the formation of colloidal polymer, siliceous, metal and metal‐oxide particles with the stage of their surface modification by functional surface‐active oligoperoxides, which are sorbed irreversibly. Novel functional particles are studied by chemical, colloidal‐chemical, rheological methods and scanning electronic microscopy. The occurrence of metal and metal oxide particle formation in distinct zones correlates well with the particle size distribution. The availability of reactive ditertiary peroxidic fragments on the particle surface as a result of OPS or OMC sorption causes their reliable protection, hydrophobity and ability to form free radicals and participate in elementary stages of radical processes.
Peroxide‐containing compatibilizer for polypropylene blends with other polymers
Authors: Roiter Yuri , Samaryk Volodymyr , Varvarenko Sergiy , Nosova Natalya , Tarnavchyk Igor , Pionteck Jürgen , Pötschke Petra , Voronov Stanislav
Published: May 2004

An approach to synthesize interfacial active peroxide graft copolymers, so called precompatibilizers, which are suitable for the universal compatibilization of one special polymer with a number of other polymers, has been presented. As example, this approach is illustrated by the reactive fusion of a random peroxide copolymer (VO) with polypropylene (PP) resulting in a VOgPP precompatibilizer. A mathematical model of the process of the VOgPP synthesis and the conduction of a full‐factorial experiment have allowed both the optimization of the synthesis conditions and the prediction of its proceeding.

During blending PP with other polymers VOgPP localizes across the blend interphases and initiates radical processes leading to the in situ formation of final compatibilizer macromolecules, which are efficient just for the blends where they are formed. The universality of the precompatibilizer concept is demonstrated in PP blends of the thermoplastic/thermoplastic type (with polystyrene and polyethylene) and of the thermoplastic/thermoset type (with unsaturated polyester resin).
Adsorption of poly(vinyl formamide‐co‐vinyl amine) onto silica particle surfaces and stability of the formed hybrid materials
Authors: Bucatariu Florin , Simon Frank , Spange Stefan , Schwarz Simona , Dragan Stela
Published: May 2004

In order to produce silica/polyelectrolyte hybrid materials the adsorption of the polyelectrolyte poly(vinyl formamide‐co‐vinyl amine), P(VFA‐co‐VAm) was investigated. The adsorption of the P(VFA‐co‐VAm) from an aqueous solution onto silica surface is strongly influenced by the pH value and ionic strength of the aqueous solution, as well as the concentration of polyelectrolyte.

The adsorption of the positively charged P(VFA‐co‐VAm) molecules on the negatively charged silica particles offers a way to control the surface charge properties of the formed hybrid material. Changes in surface charges during the polyelectrolyte adsorption were studied by potentiometric titration and electrokinetic measurements.

X‐ray photoelectron spectroscopy (XPS) was employed to obtain information about the amount of the adsorbed polyelectrolyte and its chemical structure.

The stability of the adsorbed P(VFA‐co‐VAm) was investigated by extraction experiments and streaming potential measurements. It was shown, that polyelectrolyte layer is instable in an acidic environment. At a low pH value a high number of amino groups are protonated that increases the solubility of the polyelectrolyte chains. The solvatation process is able to overcompensate the attractive electrostatic forces fixing the polyelectrolyte molecules on the substrate material surface. Hence, the polyelectrolyte layer partially undergoes dissolving process.
Switching and structuring of binary reactive polymer brush layers
Authors: Ionov Leonid , Stamm Manfred , Minko Sergiy , Hoffmann Frank , Wolff Thomas
Published: May 2004

Switchable binary polymer brushes grafted to Si‐wafers were prepared from hydrophilic and hydrophobic polymer components. When exposed to solvents, either the hydrophobic or the hydrophilic component extends in to the liquid phase, depending on the polarity of the solvent. The hydrophilic component was poly‐2‐vinylpyridine; the hydrophobic component was made photocrosslinkable in that a polystyrene copolymer containing a photodimerizing chromophore was used. In this system surfaces differing in water contact angle between 60° and 100° can be produced by variation of the solvent. The chromophore was phenylindene, which forms crosslinks upon direct UV‐irradiation. Therefore, the polystyrene component can be fixed in the extended or collapsed state. It will be shown that by irradiation through an appropriate mask, surfaces can be structured and the structures fixed.

In both the systems structural patterns differing in surface properties were produced and fixed photochemically.
Crystallization behavior and thermal properties of blends of poly(3‐hydroxybutyate‐co‐3‐valerate) and poly(1,2‐propandiolcarbonate)
Authors: Chen Long , Zhu Meifang , Song Liyuan , Yu Hao , Zhang Yu , Chen Yanmo , Adler H.J.
Published: May 2004

Crystallization behavior of blends of poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV) and poly(1,2‐propandiolcarbonate) (PR(CO2)) has been investigated by polarized light microscopy (PLM). The spherulite growth rates (SGR) of all blends were faster than that of pure PHBV, and the spherulite growth rates of PHBV in the PHBV/PR(CO2) blends reduced with increasing PR(CO2) weight fraction. There are two melting peaks in both the pure PHBV and the PHBV/PR(CO2) blends. The melting peak of PHBV/PR(CO2) blends was reduced by lower temperature about 20K as compared to PHBV and the higher temperature melting peak was increased by about 10K in the blends.
Cooperative hydration effect on the binding of organic vapors by a cross‐linked polymer and beta‐cyclodextrin
Authors: Gorbatchuk Valery V. , Ziganshin Marat A. , Savelyeva Ludmila S. , Mironov Nikolay A. , Habicher Wolf D.
Published: May 2004

A cooperative hydration effect being favorable for the binding of organic vapors by cross‐linked poly(N‐6‐aminohexylacrylamide) and beta‐cyclodextrin was observed in ternary systems in the absence of liquid phase. For these systems the vapor sorption isotherms were determined by the static method of headspace gas chromatographic analysis at 298 K. The obtained isotherms show an increase of binding affinity for vapor of hydrophobic sorbates above a threshold value of receptor hydration. Further hydration gives a saturation of this affinity for the studied hydrophilic polyacrylamide derivative, while the affinity of beta‐cyclodextrin for the hydrophilic sorbate ethanol even decreases. A similar behavior of this polymer and beta‐cyclodextrin at the change of their hydration helps to explain the observed cooperative hydration effect in terms of clathrate formation.
Heteropolyacids dispersed within a polymer matrix as a new catalytic systems with controlled oxidative‐reductive and acid‐base active centers
Authors: Turek Wincenty , Lapkowski Mieczyslaw , Pron Adam , Debiec Joanna , Wolna Agnieszka , Domagala Wojciech
Published: May 2004

Polymer support such as polypyrrole was selected as a matrix for heteropolyacid H5PMo10V2O40 in an attempt to prepare heterogeneous catalysts containing two different active centers: protons and transition metal ions. Exchanging protons from heteropolyanions dispersed in polymer matrix into ferric or ferrous ions cause the modifications of their catalytic properties. It is manifested by decrease of activity of acid‐base centers and increase of activity of oxidative‐reductive centers. Oxidation state of iron in all samples before and after catalytic reaction is the same (Fe(III)), but their structure is not similar. For catalysts doped with ferric ions the structural order is much more pronounced than for these doped with ferrous ions.
Reactive compatibilization in phase separated interpenetrating polymer networks
Authors: Alekseeva Tatiana , Lipatov Yuri , Grihchuk Sergey , Babkina Natali
Published: May 2004

The effects of compatibilizing additives (monomethacrylic ester of ethylene glycol (MEG) and oligo‐urethane‐dimethacrylate (OUDM)) on the kinetics of interpenetrating polymer network (IPN) formation based on cross‐linked polyurethane and linear polystyrene and its influence on the microphase separation, viscoelastic and thermophysical properties have been investigated. It was established, that various amounts (3‐10 mass%) of the additive MEG and 20 mass% OUDM introduced into the initial reaction system prevent microphase separation in the IPN. In the course of the reaction the system undergoes no phase separation up to the end of reaction, as follows from the light scattering data. The viscoelastic properties of modified IPN are changed in such a way that instead of two relaxation maxima characteristic of phase‐separated system, only one relaxation maximum is observed, what is result of the formation of compatible IPN system. The position of this relaxation transition depends on the system composition and on the reaction conditions.
Dynamics of hyperbranched polymers and dendrimers: theoretical models
Authors: Blumen Alexander , Jurjiu Aurel , Koslowski Thorsten
Published: May 2004

Chemical reactions depend in many ways on the dynamics of the underlying reactants, and an important aspect is the distance covered by the reactants before the reaction act occurs. Hence, even diffusion‐limited reactions between point particles in confined geometries and in low‐dimensional systems display decay forms which are very different from those obtained from simple chemical kinetics. Clearly, even more complex decay forms hold for macromolecules, given their internal degrees of freedom. Here we discuss how the dynamics of macromolecules in solution relates to their topological structure and focus on the motion of macromolecular segments (monomers) under the influence of external fields. After a general survey of the method of generalized Gaussian structures (GGS) we recall the wealth of forms which are observed, depending on the topology and on the microscopic dynamics involved. Paradigmatic are the findings for the class of hyperbranched macromolecules; to these belong the dendrimers. While the dendrimers do not show a typical scaling behavior, as found, say, for linear chains, the situation is different for particular classes of regular hyperbranched polymers which are fractal. We end by discussing their pattern of motion in the GGS‐Rouse‐Zimm picture.
Investigation of surface and interfacial properties of modified epoxy films formed under different conditions
Authors: Magsumova Ayzada , Amirova Liliya , Ganiev Makhmoud
Published: May 2004

The surface free energies and their components of the modified amine‐cured epoxy polymers were estimated using the geometric mean and acid‐base approaches. The surface and interfacial properties of the modified epoxy films depend on the modifying agent percentage and on the conditions of the polymer formation.
Solid‐supported biomimetic membranes with tailored lipopolymer tethers
Authors: Förtig Anton , Jordan Rainer , Graf Karlheinz , Schiavon Giovanni , Purrucker Oliver , Tanaka Motomu
Published: May 2004

Stable lipid membranes with controlled substrate‐membrane spacing can be prepared using well‐defined lipopolymers as a tether. Based on the living cationic ring‐opening polymerization of 2‐methyl‐ or 2‐ethyl‐2‐oxazoline, lipopolymers can be synthesized bearing a lipid head group as well as a silanol reactive coupling end group. Using a “grafting onto” procedure these polymers can form dense, brush like monolayers, whose layered structures can be obtained by x‐ray reflectivity measurements. By transfer of a pre‐organized monolayer that is followed by vesicle fusion, stable polymer supported lipid membranes can be prepared. The substrate‐membrane spacing can be controlled via the degree of polymerization, while the lateral diffusion of lipids within the membrane depends on the density of polymer tethers. Preliminary experiments implied that the membrane with long (N = 40) polymer tethers could reside trans‐membrane receptors homogeneously, suggesting a large potential of this strategy.
Improvement in strength of the aluminium/epoxy bonding joint by modification of the interphase
Authors: Phung Lan H. , Kleinert Horst , Jansen Irene , Häßler Rüdiger , Jähne Evelin
Published: May 2004

This contribution describes the influence of different surface pre‐treatments including self‐assembly of phosphoric acid mono alkyl ester as adhesion promoter (AP) for adhesive bonding of aluminium alloy AlMg3. The investigations were performed using a cold hardening two components epoxy‐adhesive. The pre‐treated surfaces, the interphase structures and the joints were characterized by: SEM/EDX, surface tension, XPS, DMA and the determination of mechanical parameters. The results interestingly show that the test sample with three step pre‐treatment (degreasing in acetone, then anodic oxidation in phosphoric acid and adsorption of AP) has the highest adhesive strength and durability.
Preparation of filled temperature‐sensitive poly(N‐isopropylacrylamide) gel beads
Authors: Kuckling Dirk , Schmidt Thomas , Filipcsei Genovéva , Adler Hans‐Jürgen P. , Arndt Karl‐Friedrich
Published: May 2004

Temperature‐sensitive filled poly(N‐isopropylacrylamide) (PNIPAAm) gel beads with diameters in the range of millimeters were prepared using the alginate technique. The polymerization and cross‐linking reaction of NIPAAm in the presence of inorganic filling particles was performed in spherical networks of Ca‐alginate forming interpenetrating networks (IPN). Thermo‐sensitive gel beads could be obtained by washing these IPN with EDTA solution.

The PNIPAAm gel beads were analyzed by optical methods to observe there swollen diameter in dependence on the temperature. The diameters of the swollen gel beads were in the range of 0.1 ‐ 2 mm. The influence of the monomer to cross‐linker ratio (MCR) and the filling materials (ferrofluid, BaTiO3, TiO2, and Ni,) were studied. The phase transition temperature (Tpt) was only weakly influenced by the MCR and the filling material remaining at around 34°C.
Adjustable low dynamic pumps based on hydrogels
Authors: Richter Andreas , Klenke Christian , Arndt Karl‐Friedrich
Published: May 2004

This paper discusses the suitability of hydrogel actuators as drives of automatic pumps for long‐term drug release. We demonstrate that such actuators can execute a defined task if several functional units are connected serially. Investigated functions of this pump are the adjustability of the time‐delay from the initial operation up to the beginning of the drug release, opening the sterile drug ampoule, and the drug release at a specified timeframe. The described parameters to influence the pump behaviour are satisfying only for realization of continuous working devices. An outlook of the development of programmable pulsate pumps is given.
Electrostimulated shift of the precipitation temperature of aqueous polyzwitterionic solutions
Authors: Georgiev George , Tzoneva Anna , Lyutov Lyudmil , Iliev Stefko , Kamenova Irena , Georgieva Ventseslava , Kamenska Elena , Bund Andreas
Published: May 2004

The precipitation temperature (Tpr) value of aqueous poly(dimethylamino‐ethoxyacryloyl‐propylsulphonate) (PDMAPS) solutions decreases with the rise of electric field intensity both in the absence and in the presence of a low molecular salt. This electrostimulated Tpr shift is explained qualitatively by means of the model taking into account both the dominating intermacromolecular dipole‐dipole interaction and the dipole cluster formation.
Synthesis and aqueous solution properties of functionalized and thermoresponsive poly(D,L‐lactide)/polyether block copolymers
Authors: Porjazoska Aleksandra , Dimitrov Philip , Dimitrov Ivaylo , Cvetkovska Maja , Tsvetanov Christo B.
Published: May 2004

Tri‐ and pentablock amphiphilic copolymers containing hydrophobic poly(D,L‐lactide) block(s) and hydrophilic polyethers were synthesized in order to obtain new precursor architectures suitable for drug delivery systems. Polyglycidol‐6‐poly(ethylene oxide)‐b‐poly(D,L‐lactide) possess high hydroxyl functionality provided by the linear polyglycidol block. Thus very stable hydroxyl functionalized micelles in aqueous media were obtained. On the other hand poly(D,L‐lactide)‐b‐poly(ethylene oxide)‐b‐poly(propylene oxide)‐b‐poly(ethylene oxide)‐b‐poly(D,L‐lactide) form temperature sensitive aggregates. The copolymers obtained were analyzed by SEC and NMR, and their aqueous solution properties were followed by cloud point measurements and determination of critical micellization temperature. TEM was used for particles visualization.
Poly(ethylene oxide) macromonomer based hydrogels as a template for the culture of hepatocytes
Authors: Alexandre Eliane , Cinqualbre Jacques , Jaeck Daniel , Richert Lysiane , Isel François , Lutz Pierre J.
Published: May 2004

Macromonomer based poly(ethylene oxide) (PEO) hydrogels were tested with respect to their ability to serve as a template for the survival and the growth of hepatocytes. Two systems were considered : either the surface of preexisting hydrogels, with controlled structural parameters, were seeded with isolated rat hepatocytes or the hepatocytes were dispersed in physiological medium containing the macromonomer/initiator and heated to 37°C. In the first case, cells were examined at given times after spreading over two days. The results were compared to those observed for the dispersion of fibroblasts onto a surface of the same type of hydrogels. The effects of the structure of the hydrogels and its chemical nature on the extent of hepatocyte attachment (or encapsulation) and the morphology were investigated.
Structural characterization of temperature‐sensitive hydrogels by field emission scanning electron microscopy (FESEM)
Authors: Reichelt Rudolf , Schmidt Thomas , Kuckling Dirk , Arndt Karl‐Friedrich
Published: May 2004

The submicrometer structure of the temperature‐sensitive hydrogels was observed by field emission scanning electron microscopy (FESEM), using synthesized hydrogels of different outer size and shape. The hydrogel structure strongly depends on the homogeneity of the polymer chains during the crosslinking process. A porous structure of the poly(vinyl‐methyl‐ether) (PVME) bulkgel, synthesized by electron beam irradiation of a concentrated polymer solution, was observed in the swollen state because the phase transitions temperature is acquired through the crosslinking process. Photo‐crosslinking reaction of the poly(N‐isopropylacrylamide) (PNIPAAm) copolymer in the dry state to form PNIPAAm thin films leads to a rather homogeneous structure. In the shrunk state both gels possess structure being more compact than in the swollen state. We also synthesized PVME and PNIPAAm gels with small outer dimensions in the range of some 100 nm. Heating of the thermo‐sensitive polymer in diluted solutions collapses the polymer chains or aggregates. The crosslinking reaction (initiated by electron beam or UV irradiation) of these phase separated structures produces thermo‐sensitive microgels. These microgel particles of PVME and PNIPAAm are spherical shape having diameters in the range of 30 ‐ 500 nm.