bluuebunny/crossref_metadata_2025_split huggingface dataset:
Coordination‐polymer films by reactive self‐assembly
Authors: Laurence D. , Iii Thomsen , Papadimitrakopoulos Fotios 
Published: March 2011

AbstractA novel self‐assembly technique for the growth of insoluble and intractable thin organic films is presently reported. Bifunctional 8,8′‐dihydroxy‐5,5′‐biquinoline (bisquinoline) is reactively self‐assembled with diethyl zinc to form a linear coordination polymer. FTIR, UV/VIS spectroscopy, profilometry, and photoluminescence measurements were used to characterize these new multilayer films. The growth of these films on glass substrates was monitored by increasing absorbance at 396.6 nm using UV/VIS spectroscopy and by profilometry. FTIR spectroscopy indicated that the self‐assembled films are polymeric in nature. The reduction of end‐group hydroxyls and a significant red‐shift of the photoluminescence emission spectrum with respect to zinc bisquinoline powder was attributed to an increase in conjugation length.
Organic polymer leds with mobile and immobile ions
Authors: Schoo Herman F.M. , Demandt Rob C.J.E. , Vleggaar Jeroen J.M. , Liedenbaum Coen T.H. 
Published: March 2011

AbstractThe syntheses of partially conjugated alkoxy substituted Poly(p‐phenylenevinylene) (PPV) materials with tertiary amines and cationic species covalently bound to the polymer backbone are described. The amine/cationic species are introduced via a polymer analogous reaction of a functional alcohol and the chloro‐precursor polymer. Single layer, polymer light emitting diodes (PolyLEDs), prepared with the modified polymer materials show a strong ‘burn‐in’ effect, leading to very high electroluminescence (EL) quantum efficiencies especially with higher workfunction cathodes.
Thermal stability of organic electroluminescent devices fabricated using novel charge transporting materials
Authors: Tokito Shizuo , Tanaka Hiromitsu , Noda Koji , Okada Akane , Taga Yasunori 
Published: March 2011

AbstractNovel hole and electron transporting materials have been synthesized to improve the thermal stability of organic electroluminescent (EL) devices. Molecular structures of such hole and electron transporting materials were designed based on triphenylamine (TPA) and oxadiazole (OXD) moieties, respectively. It has been found that the resulting materials have high glass transition temperatures (Tg) over 100°C and the vacuum‐deposited thin films are significantly thermally stable. For the two‐layer EL devices using the novel hole transporting materials and the typical emitting material, tris(8‐quinolinolato) aluminum, the thermal stability has been clearly seen to depend on the Tg of the hole transporting material; excellent thermal stability was achieved. For the three‐layer EL device using the novel electron transporting material, good emission efficiency and good stability were achieved. The electron transporting materials have been also applied to the polymeric system with polyvinylcarbazole matrix.
Studies of adhesion to molecularly engineered surfaces using contact mechanics methods
Authors: Kim Soojin , Choi Gun Young , Nezaj Jeff , Ulman Abraham , Fleischer Cathy 
Published: March 2011

AbstractWe synthesized a number of poly(dimethylsiloxane) (PDMS) polymers with different molecular weights, and prepared model PDMS networks with a systematic change of cross‐link density, and therefore elastic constant (K). Self‐adhesion studies of PDMS hemispheres using the JKR method—the contact mechanics of solids spreading their interfacial area under load—reveal that hysteresis which results from relaxation processes in the elastomer can be practically eliminated using stepwise loading and unloading protocols. The adhesion of crosslinked PDMS surfaces to self‐assembled monolayers with different chemical functionality was investigated. Interfacial H‐bonding was shown to be an important chemical interaction causing significant adhesion hysteresis. The number of H‐bonds between PDMS and silanol groups on SiO2/Si surfaces increased with time of the contact under a constant load, indicating pressure‐induced reorganization of the PDMS network near the interface. The interaction between PDMS and carboxylic acid groups showed somewhat smaller hysteresis which suggests weaker H‐bonding strength. The interaction between PDMS and functionalized biphenyl groups exhibited small hysteresis which is believed to be caused by dipolar interaction, whereas that between PDMS and nonpolar perfluorocarbon groups showed negligible hysteresis. The distinction in the behavior of the unloading data between H‐bonding related interaction and dipolar interaction seems to indicate the difference in the nature between non‐specific (van der Waals, dipolar) and specific (donor‐acceptor, H‐bond, acid‐base) interactions.
Absorption of ionic amphiphils by oppositely charged polyelectrolyte gels
Authors: Kabanov Victor A. , Zezin Alexander B. , Rogacheva Valentina B. , Khandurina Yulia V. , Novoskoltseva Olga A. 
Published: March 2011

AbstractSlightly cross‐linked polyelectrolytes absorb oppositely charged surfactants in aqueous media. Transfer of amphiphilic ions from solution into the swollen network proceeds as a frontal heterogeneous cooperative reaction causing a collapse of the original polyelectrolyte gel. Small and wide angle X‐ray diffraction data show that electrostatic complex formed as a result of the reaction consists of lamellar type surfactant micelles embedded in a polyelectrolyte network. It is also shown that such complexes contain equimolar amount of surfactant ions and ionized polyelectrolyte units paired with amphiphil head groups. In other words a charged network is not able to bind surplus oppositely charged surfactant ions. However, it is still able to solubilize a substantial amount of a nonionized surfactant. Chemical structure of surfactants strongly affect internal structure of lamellae and stability of the complexes.
Polyelectrolyte adsorption and stabilization of silica‐suspensions
Authors: Bauer Doris , Killmann Erwin 
Published: March 2011

AbstractThe adsorption of cationic polyelectrolytes on colloidal silica‐particles is investigated. The polyelectrolytes poly(diallyl‐dimethyl‐ammoniumchloride) PDADMAC of different molar mass have been used. The adsorbed amount is influenced by the ionic strength and pH of the suspension and the molar mass of the macromolecule. The adsorption determines the zetapotential of the covered particles. The electrostatic interaction between the particles as well as the structure of the adsorbed polyelectrolytes play an important role in the stabilization and flocculation behaviour of the polyelectrolyte covered suspensions.
Polymers grafted from solid surfaces
Authors: Rühe Jürgen 
Published: March 2011

AbstractMonolayers of polymer molecules were generated at the surface of a solid substrate in situ by using self‐assembled monolayers of initiator molecules. The layers were characterized by IR‐spectroscopy, surface plasmon resonance measurements, ellipsometry, X‐ray reflectometry, AFM and neutron reflectometry. Several novel techniques for the photolithographic patterning of the attached films are described. As a potential application for the attached layers the control of adhesion of biological cells to solid substrates is studied.
On the mechanism of adsorption of a cationic surfactant on quartz
Authors: Churaev N. V. , Sergeeva I. P. , Sobolev V. D. 
Published: March 2011

AbstractExperimental data on surface charge of quartz in dependence on concentration of CTAB solution and pH were obtained using capillary electrokinetic method. The results are compared with the developed theory of the Langmuir‐type adsorption that takes Into account adsorption both on charged and noncharged surface centers. Computer optimization procedure results in adsorption potential values −15 kT and −11 kT, respectively. A ratio between surface concentrations of the centers was also estimated.
A study on the adhesion of anchoring groups to pigment surfaces
Authors: van Den Haak Henk J. W. , Schöps Matthias , Adler Hans‐Jürgen P. , Fietzek Christopher , Montagut Judit 
Published: March 2011

AbstractA method is described for the comparison of the adhesion of anchoring groups to pigment or filler surfaces, using simple model compounds. Energies of adsorption and the amount of anchoring groups per gram of pigment can be estimated.
Electrochemical polymerization of functionalized thiophene derivatives for the immobilization of proteins
Authors: Welzel Hans‐Peter , Kossmehl Gerhard , Engelmann Gunnar , Neumann Barbara , Wollenberger Ulla , Scheller Frieder , Plieth Waldfried 
Published: March 2011

AbstractThe hydroxy group of 3‐(2‐hydroxyethyl)thiophene was protected as methyl ether 1 and as dimethyl tert‐butyl silyl ether 5 before anodic polymerization. The poly[3‐(2‐methoxyethyl)thiophene] 2 was prepared by electrochemical homopolymerization of 1. Ether cleavage was carried out in the polymer film 2 and the resulting poly [3‐(2‐hydroxyethyl)thiophene] (3) was activated with cyanogen bromide to immobilize alcohol dehydrogenase. Silylether 5 did not undergo homopolymerization but copolymerization of 5 with 3‐methylthiophene (4) was successful. After cleavage of the protecting group the resulting copolymer 7 was activated by cyanuric chloride, and chymotrypsin was immobilized. Electrocopolymerization of thiophene‐3‐acetic acid (8) and 3‐methylthiophene (4) under various conditions produces copolymer 9. By activation of the carboxylic groups with N,N'‐dicyclohexylcarbodiimide (DCC) lactate oxidase (LOD) was bond to the surface of the electrode to form a lactate sensor.
Interfacial tension in polymer blends
Authors: Luciani André , Champagne Michel F. , Utracki Leszek A. 
Published: March 2011

AbstractTheoretical models of the interfacial tension coefficient in polymer blends, v12, were evaluated. A new working relation was derived that makes it possible to compute v12 from the chemical structure of two polymers. The calculations involve determination of the dispersive, polar and hydrogen‐bonding parts of the solubility parameter from the tabulated group and bond contributions. The computed values of v12 for 46 blends were found to follow the experimental ones with a reasonable scatter of ± 36%.Next, the experimental methods of v12‐measurements were critically examined. Although many have been developed for low viscosity Newtonian fluids, most are irrelevant to industrial polymeric systems. For the present studies two were selected. Values of v12 were measured using the so‐called “capillary breakup method,” and a newly developed method based on the retraction rate of deformed drop.
Tem‐ and neutron reflection studies on surfaces and interfaces with block copolymers
Authors: Stark Bernhard , Scherble Jonas , Ganter Markus , Kressler Jörg , Stühn Bernd , Lauter Jochen 
Published: March 2011

AbstractThe behavior of block copolymers at various interfaces is studied by transmission electron microscopy and neutron reflection. A thin film of a symmetric diblock copolymer of styrene and methyl methacrylate forms layer structures when in contact with air and a random copolymer of styrene and acrylonitrile containing 35 wt% acrylonitrile. When the random copolymer has an acrylonitrile content of 25 wt%, a competition between layer formation and diffusion of disordered micelles takes place. Driving force for these processes are different interfacial tensions and a changing miscibility behavior as a function of acrylonitrile contents of the random copolymers. The ordering behavior of a symmetric diblock copolymer of deuterated styrene and isoprene in contact with poly(3,5‐dimethyl phenylene ether) is studied by neutron reflection. Polystyrene‐block‐poly(ethene‐co‐but‐1‐ene)‐block‐polystyrene with cylindrical PS microdomains shows an interfacial phase transition to lamellae near to the interface with different polymers. The morphological studies are in agreement with adhesion data obtained by peel tests on different bilayer specimens.
Neutron reflectivity studies of hot polymer melt interfaces
Authors: Hermes Helen E. , Bucknall David G. , Butler Simon A. , Higgins Julia S. 
Published: March 2011

AbstractNeutron reflectivity data have been obtained using a specially designed cell that allows the investigation of the interfaces between polymers in the melt state. Systems which are semicrystalline at room temperature can be investigated for the first time. Example results from a polystyrene (PS)/ polyethylene (PE) interface (both with and without copolymer) and an isotactic polypropylene (PP)/ high density polyethylene interface are presented.
How green are petro‐polymers going to be?
Authors: Put Jos 
Published: March 2011

AbstractThe controversy between “petro‐polymers” and “green polymers” is a false one. Polymers synthesized by organisms, manipulated or not, are seen as green. Polymers based on cracker products, so called petro‐polymers, are considered to be environmentally unfriendly. Arguments used in favour of “natural” polymers are: biodegradability, renewable resources, recyclability, non waste producing etc. We think that several of these arguments are incorrect or irrelevant. Furthermore, we are convinced that petro‐polymers might move substantially towards a sustainable situation. It might seem strange, but the most important steps towards such a situation have to be made not in the field of petro‐polymers themselves but in the domain of energy supply.
Structure and mechanical properties of polysaccharides
Authors: Ross‐Murphy Simon B. , Wang Qi , Ellis Peter R. 
Published: March 2011

AbstractThis article serves both as a review of polysaccharides as gelling and thickening agents and as an introduction to polysaccharides, other than starch and cellulose, their source and extraction, and how molecular detail is reflected in their macromolecular and supramolecular properties. The whole is summarised for workers in the synthetic polymer area interested in new “green” polymers. We also introduce results for a new polysaccharide extracted from a Nigerian tree pod, and describe details of its structural and physicochemical characterisation including light scattering and rheological measurements.
Starch alkanoates as models for thermoplastic polysaccharides
Authors: Pellegrini Claudio , Tomka Ivan 
Published: March 2011

AbstractThe low degree of internal molecular mobility of stiff polysaccharide chains prevent any thermal transition in the temperature range of their chemical stability. Substituted starches were synthesised to find the structural range, i.e. the necessary amount and length of mobile side chains which support the molecule with high enough level of internal degrees of freedom. Esterification and transesterification with hydroxy alkanoates, their polymers and lactones were used. The reaction was best catalysed with strong delocalised bases. The thermal properties of these model substances were characterised.
Starch ‐ polyvinylalcohol ‐ acetal: A watersoluble film
Authors: Keilbach Andreas , Tomka Ivan 
Published: March 2011

AbstractTo ensure more comfort, dosage units of active ingredients may be packed in water soluble film prior to application. In the mean time plasticised polyvinylalcohol (PVAL), with limited metabolitic degradability in common water epuration units, is used for present purpose. In this work we found that the reducing chain ends of degraded starch molecules form semi acetals with the hydroxyl moieties of (PVAL). Reaction conditions could be selected for processing in a twin screw extruder. Due to replacement of around 50% of the polyvinylalcohol by starch the production costs are significantly lower than that of pure PVAL‐films. The acetal films show better mechanical properties, seal easier, dissolve faster in water and mineralise at lower temperatures if compared with pure PVAL.
Polymers from pine gum components: Radical and coordination homo and copolymerization of pinenes
Authors: Ramos Ana Maria , Lobo Luís S. , Bordado João M. 
Published: March 2011

AbstractThe present work is aimed at studying the reactivity of α‐ and β‐pinenes in radical polymerization. The pinene homopolymers obtained were oligomers, showing both isomers similar reactivities. In order to achieve products of higher molecular weight, the radical copolymerization of α‐ and β‐pinene with methyl methacrylate and styrene was performed, giving rise to polymers with M̄w varying from 11 500 to 53 000. In radical copolymerization α‐pinene showed to be more reactive than β‐pinene. All the radical reactions performed were carried out with a Ziegler‐Natta catalyst, TiCl4/Et3Al, and with Et3Al. Under the conditions tested, β‐pinene did not undergo any polymerization reaction and the cocatalyst showed a pronounced catalytic effect. The coordination polymers obtained at 5 h had chain lenghts of the same order of magnitude of the corresponding radical copolymers obtained at 50 h, although for much lower overall conversion.
Investigations on homopolymerization and copolymerization of phenylacetylene and 1‐hexyne by iron‐based ziegler‐natta catalyst systems
Authors: Duc Sandrine , Petit Alain 
Published: March 2011

AbstractHomopolymerization and copolymerization of phenylacetylene (PA) and hex‐1‐yne (HX) were performed in the presence of two iron‐based catalysts having various ligands: an organic salt, iron tripropionate [Fe(prop)3] and a complex, iron triacetylacetonate [Fe(acac)3], both in combination with the triethylaluminum (AlEt3). The geometric structures of the resulting monosubstituted polyacetylene samples were investigated by 1H‐NMR, 13C‐NMR and IR spectroscopic techniques. The number‐average molecular weights were also determined. The compositions of the PA‐HX copolymers were obtained by 1H‐NMR analysis and the monomer reactivity ratios were calculated from these values using the Kelen‐Tüdös method and a nonlinear least squares curve‐fitting procedure. The proportions of cis and trans structural units in polyalkynes and the relative reactivities of two monomers PA and HX during the copolymerization were found to be strongly associated with the nature of the initiating system.
Polyfunctional polyisobutenes as building blocks for amphiphilic graft polymers
Authors: Grasmüller Martin , Rueda‐Sanchez Juan C. , Voit Brigitte I. , Nuyken Oskar 
Published: March 2011

AbstractPolyfunctional polyisobutenes (PIB) have been synthesized by cationic copolymerization of isobutene and chloromethylstyrene. Their potential applications with focus on their use as macroinitiators (MI) for oxazoline polymerization were discussed. The “grafting from” reaction led to tailor‐made graft copolymers with various backbones and adjustable graft arm length. Graft copolymers with hydrophobic PIB backbone and poly(2‐methyloxazoline) graft arms have unusual viscosity properties due to their amphiphilic character and show aggregate formation.
Adhesive liquid‐crystalline polymers
Authors: Nieuwhof René P. , Marcelis Antonius T. M. , Sudhölter Ernst J.R. , van Der Wielen Maarten W.J. , Cohen Stuart Martien A. , Fleer Gerard J. 
Published: March 2011

AbstractThe synthesis and characterization of liquid‐crystalline polymers with possible good adhesive properties is reported. These polymers are prepared by alternating copolymerization of maleic anhydride and mesogenic alkenes. The spacer length m is varied (m = 2, 3, 4, 6, 8 and 9) and methoxybiphenyl is used as the mesogenic group. The glass transition temperature decreases and the isotropization temperature increases with spacer length. Depending on the spacer length and temperature, SB and SAd mesophases can be observed. After annealing, spin‐coated films of these polymers show very regular layered structures with a layer spacing similar to that in the bulk.
Electrospinning of ultra‐thin polymer fibers
Authors: Jaeger Raimund , Bergshoef Michel M. , Batlle Cristina Martín I. , Schönherr Holger , Julius Vancso G. 
Published: March 2011

AbstractThe electrospinning technique was used to spin ultra‐thin fibers from several polymer/solvent systems. The diameter of the electrospun fibers ranged from 16 nm to 2 μm. The morphology of these fibers was investigated with an atomic force microscope (AFM) and an optical microscope. Polyethylene oxide) (PEO) dissolved in water or chloroform was studied in greater detail. PEO fibers spun from aqueous solution show a “beads on a string” morphology. An AFM study showed that the surface of these fibers is highly ordered. The “beads on a string” morphology can be avoided if PEO is spun from solution in chloroform; the resulting fibers show a lamellar morphology. Polyvinylalcohol (PVA) dissolved in water and cellulose acetate dissolved in acetone were additional polymer/solvent systems which were investigated. Furthermore, the electrospinning process was studied: different experimental lay‐outs were tested, electrostatic fields were simulated, and voltage ‐ current characteristics of the electrospinning process were recorded.
Effects of recycling on mechanical and thermal properties of polystyrene
Authors: Djidjelli H. , Benachour D. 
Published: March 2011

AbstractA commercial Polystyrene (Mw = 2.5 105, MFI =14.80) was extruded repeatedly from one to eight times at 190 °C. The effects of extrusion process on physical and chemical properties of polystyrene were investigated using: ‐Average molecular weight
—Izod Impact strength;
—Thermal properties (TGA, DTA).
The results showed that processing of polystyrene leads to degradation. In fact, a decrease of 23% in the average molecular weight was observed for the 8th cycle sample and a reduction in impact strength by 34% was also noticed for the 4th cycle sample.
Polypropylene, modified with some oligoesters
Authors: Gorbunova Irina YU. , Kerber Michail L. , Vladimirova Svetlana I. , Musleh Reem R. , N. Avdeev Nickolay 
Published: March 2011

AbstractMiscibility of polypropylene with some oligoesters was evaluated by optical wedge interference microscopy. Mechanical, thermal, rheological and relaxation properties were studied. Compatibility between the polymers and modifying agents was shown to have a marked effect on stress‐strain properties as well as on the structure and melting characteristics of the modified polymers.
Abiotic and biotic degradation of aliphatic polyesters from “petro” versus “green” resources
Authors: Karlsson Sigbritt , Albertsson Ann‐Christine 
Published: March 2011

AbstractAliphatic polyesters are degradable by abiotic and/or biotic hydrolysis. The accessibility of a polymer to degradative attack by living organisms is not dependent on its origin, but on its molecular composition and architecture. Synthetic polymers with intermittent ester linkage (e.g. polyesters, polyurethanes etc.) are accessible to biodegradative attack of esterase. On the other hand aliphatic polyesters are also quickly degraded by a pure abiotic hydrolysis. The results from abiotic and biotic hydrolyses of polycaprolactone (PCL) (from “petro” resource), poly(L‐lactide) (PLLA) and polyhydroxyalkanoates (PHA) (from “green” resources) are presented and discussed with the respect to rate of degradation, molecular weight changes and degradation product pattern. For the environmental consequences, the type of formed degradation products are of importance and not the origin of the polymer.