bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hyperbranched thermolabile polycarbonates derived from a A2+B3 monomer system
Authors: Scheel Arnulf , Komber Hartmut , Voit Brigitte 
Published: May 2004

AbstractHyperbranched 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

AbstractNitroxide 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

AbstractHydroxy‐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

AbstractResins 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

AbstractA 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

AbstractArylene 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

AbstractMain 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

AbstractAn 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

AbstractIn 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

AbstractSwitchable 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

AbstractCrystallization 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

AbstractA 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

AbstractPolymer 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

AbstractThe 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

AbstractChemical 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

AbstractThe 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

AbstractStable 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

AbstractThis 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

AbstractTemperature‐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

AbstractThis 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

AbstractThe 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

AbstractTri‐ 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

AbstractMacromonomer 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.