bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polymer‐drug conjugates: Manipulation of drug delivery kinetics
Authors: Pitt Colin G. , Wertheim Jason , Wang C. T. , Shah Subodh S. 
Published: March 2011

AbstractThree methods of manipulating the kinetics of hydrolysis of polymer conjugates were evaluated. It was demonstrated that either first‐order, zero‐order or S‐shaped kinetic profiles could be achieved by systematic changes in the chemical composition of several series of model side‐chain substituted polyacrylates. The changes in kinetics were shown to arise from an increase in the rate constant during solvolysis, resulting from predictable changes in either the water content, secondary structure, or LCST of the polymer conjugate.
Interactions between flow and superstructure of liquid crystalline polymers
Authors: Marrucci G. , Maffettone P. L. , Crescitelli S. 
Published: March 2011

AbstractThe monodomain equation for rigid rodlike polymers in the nematic phase is here extended, in a simple form, to the polydomain situation. The mathematical problem is further simplified by considering a two‐dimensional restriction. Preliminary results are presented for simple shear flows, showing the formation of a superstructure along the sample thickness.
The state of high global chain orientation but nearly random segmental orientation of amorphous polymers
Authors: Fan Qingrong , Qian Renyuan 
Published: March 2011

AbstractIn the rubbery state of amorphous polymers under uni‐axial drawing the global chain orientation will relax in orders of magnitude slower than the relaxation of local segmental orientation. When this state of hot drawn sample is frozen at temperatures lower than its glass transition, Tg, an amorphous state with high global chain orientation but nearly random segmental orientation (GOLR) could result. Experimentally the GOLR state of amorphous polymers is easily realized by uni‐axial drawing the polymer at temperatures 20–30°C above its Tg. The characteristic features of a GOLR state are i) large recovery of the elastic deformation of global chain on being heated to temperatures above Tg, ii) very small birefringence and IR dichroism, iii) nearly isotropic sonic and ultrasonic velocity of propagation, iv) nearly isotropic WAXD pattern, while it shows v) pronounced anisotropy in stress‐strain behavior for large deformations and vi) appreciable anisotropy of thermal conductivity and of microwave dielectric properties. Concrete examples with detailed experimental results will be reviewed.
Photonic materials for electroluminescent, laser and photovoltaic devices
Authors: Hilberer A. , Moroni M. , Gill R. E. , Brouwer H.‐J. , Krasnikov V. V. , Pham T.‐A. , Malliaras G. G. , Veenstra S. , Werts M. P. L. , van Hutten P. F. , Hadziioannou G. 
Published: March 2011

AbstractThis article presents an overview of the work that has been done recently in our laboratory concerning the development and application of new conjugated materials with tunable properties. We have designed polymers containing oligo(phenylenevinylene)‐type conjugated segments of well defined size and structure isolated either in their main‐chain or in the side‐chains. Model oligomers corresponding to the conjugated parts of the polymers have also been studied. We show how these materials perform in light‐emission applications (light‐emitting diodes, lasers) or photovoltaic cells.
Thermally stable organic electroluminescent device using novel amorphous molecular charge‐transport materials, 4,4′,4“‐tris[bis(4′‐tert‐butyl‐biphenyl‐4‐yl)amino]triphenylamine and 4,4,4“‐tri(n‐carbazolyl)triphenylamine
Authors: Ogawa Hiromitsu , Inada Hiroshi , Shirota Yasuhiko 
Published: March 2011

AbstractFor the purpose of developing an amorphous molecular material with a high glass‐transition temperature (Tg) and a low ionization potential for use as a charge‐transport layer in organic electroluminescent (EL) devices, a novel starburst molecule, 4,4′,4“‐tris[bis(4′‐tert‐butylbiphenyl‐4‐yl)amino]triphenylamine (t‐Bu‐TBATA), was designed and synthesized. t‐Bu‐TBATA was found to form readily a stable glass with a Tg of 203 °C. A multilayer EL device consisting of double hole‐transport layers of t‐Bu‐TBATA and 4,4′,4“‐tri(N‐carbazolyl)triphenylamine and an emitting layer of tris(8‐quinolinolato)aluminum was fabricated and its performances were examined. The device was found to exhibit good performances and to be thermally stable, operating even at 170 °C.
Phenylated poly(P‐phenylene vinylenes) prepared via the chlorine precursor route (CPR)
Authors: Wan Wai Chou , Gao Yongli , Goodwin Thomas E. , Gonzalez Stevan A. , Feld William A. , Hsieh Bing R. 
Published: March 2011

AbstractThe synthesis of several highly phenylated PPV derivatives by a chlorine precursor route (CPR) was investigated in order to understand its scope. Three 1,4‐bis(chloromethyl)benzene monomers were prepared via a robust and versatile synthetic procedure involving the Diels‐Alder reaction. The monomers were then polymerized to the corresponding precursor polymers with about 1.0 equivalent of potassium t‐butoxide in THF. Only one monomer gave a soluble precursor polymer while the other two gave insoluble precursor polymers. The soluble precursor polymer was deposited as thin films and then converted to the corresponding PPV derivative, which showed green photoluminesence and electroluminesence.
Modification and characterization of thin polymer films for electrochemical applications
Authors: Brack Hans‐Peter , Scherer Günther G. 
Published: March 2011

AbstractProton‐conducting polymer membranes are utilized as the solid electrolyte in low temperature polymer electrolyte fuel cells (PEFC), which are efficient energy converters. We have selected the process of radiation grafting and subsequent sulfonation to prepare novel membranes because of its feasibility as a low cost production method. Investigations of the two first preparations steps, i.e., irradiation and grafting, lead to insight concerning the optimization of these two steps and the dependence of the final membrane properties on the various preparation parameters.
Power‐law exponent in the central region of a polymer layer adsorbed from dilute solution: Comparison between scaling and SCF results
Authors: Fleer G. J. , Leermakers F.A.M. 
Published: March 2011

AbstractDe Gennes predicted the self‐similar structure φ(z) ∞ z−α for adsorbed polymer layers in the semi‐dilute (central) region of the adsorption profile of homopolymers. This power‐law behaviour is recovered in mean‐field SCF calculations. In this case the exponent is α = 2 in good solvents provided D «z «d, where D is the proximal length and d the distal length. We use a ground‐state approximation (GSA) to derive expressions for the two lengths D and d, and show that in the central region the profile is in good approximation given by φ = 1/3(z + D)−2exp(‐(z + D)2/3d2). Unless the chains are extremely long the condition D«z«d is difficult to obtain and corrections on the exponent are necessary. For most chain lengths in the experimental range, the central region is quite narrow. It is shown that for high adsorption energies (small D) α = 2 + 2d−1 in leading order, where d = R/, with R the radius of gyration and φb the bulk solution concentration. For weak adsorption the proximal length D is larger, which leads to a smaller exponent α. The d−1 correction is in excellent agreement with numerical self‐consistent‐field calculations. In poor solvents we have φ = 1/2(z + D)−1exp(‐2(z + D)2/3d2) and α = 1 + 4d−1 in the strong adsorption limit, which implies a larger correction in this case. Our analysis suggests that in a polymer adsorption profile with excluded‐volume correlations (where α = 4/3) non‐universal aspects would also be present if the chain length is finite.
Interpolyelectrolyte complexes formation in dependence on the nature of polyelectrolytes
Authors: Cristea Mariana , Dragan Stela , Dragan Demetra , Simionescu Bogdan C. 
Published: March 2011

AbstractInterpolyelectrolyte complexes (PECs) were obtained starting from polycations with (N,N‐dimethyl‐2‐hydroxypropylenammonium chloride) units in the main chain and sodium salts of the poly(acrylic acid), on one hand, and poly (2‐acrylamido‐2‐methylpropane sulfonic acid), on the other hand, as polyanions. The polycations were different as concerns both the content of the quaternary ammonium salt groups and the degree of branching. The polyanions were different both by their structure and molecular weight. The complex formation was followed through the variation of the reduced viscosity and of the conductivity of the reaction medium vs. the unit molar ratio polyanion/polycation in two ranges of concentration.
Salt effect on surface modification of silica by interpolyelectrolyte complexes
Authors: Buchhammer Heide‐Marie , Lunkwitz Klaus , Pergushov Dmitry V. 
Published: March 2011

AbstractThe effect of a low‐molecular‐mass salt on the properties of interpolyelectrolyte complexes formed as a result of interactions between poly(diallyldimethylammonium chloride) and copolymers of maleic acid with propylene or α‐methylstyrene in their salt containing non‐stoichiometric mixtures has been studied. Properties of such interpolyelectrolyte complexes were found to be determined by the chemical nature of the polyelectrolytes and by the salt concentration. The effect of salt on the surface modification of silica particles via their interactions with interpolyelectrolyte complexes has been examined. Two different ways of the surface modification of silica particles were used: (i) silica particles were contacted with previously prepared interpolyelectrolyte complexes and (ii) silica particles were contacted with cationic polyelectrolyte at first and then anionic polyelectrolyte was added. The efficiency of the surface modification was shown to be also dependent on the salt concentration and the chemical nature of polyelectrolytes. Turbidimetry, quasi‐elastic light scattering, laser microelectrophoresis, and polyelectrolyte titration were used to characterize studied systems.
Investigation of polyelectrolyte adsorption by means of a novel concept based upon the use of model surfaces and model polyelectrolytes
Authors: Oertel Ulrich , Nagel Jürgen , Hänel Brigitte , Pilch Bettina 
Published: March 2011

AbstractA concept to study the influence of molecular parameters in the adsorption of polyelectrolytes is presented. Characteristic for this approach is the use of model surfaces and model polyelectrolytes. The properties of both the surfaces and polyelectrolytes can be varied in a well defined way and over a broad range. First experiments show that the method is able to give structural information about the adsorbed polyelectrolytes. The method is very sensitive, adsorption experiments with polyelectrolyte concentrations in the region of micromoles per litre are possible.
Importance of surface tension for physical paint properties
Authors: Osterhold Michael , Armbruster Kornelia 
Published: March 2011

AbstractSurface tension is a parameter of decisive importance for characterizing painted and unpainted surfaces related to wetting and adhesion phenomena. This article presents measurements of the surface tension of solids by means of an automatic contact angle measurement device. The evaluation of the surface tension is based on a separation into polar and disperse components. In addition, this paper briefly touches on other, more far‐reaching approaches (acid/base) and discusses a method for the determination of dynamic surface tension of liquids.
The “green” image of polyolefins
Authors: Galli Paolo , Addeo Antonio 
Published: March 2011

AbstractPolyolefins, because they are produced by non‐toxic monomers such as ethylene and propylene and due to the minimum pollution impact during production and use and low‐thermal capacity during processing, have achieved a recognized “Green image”.This environmentally friendly image is founded also on the ability of replacing a number of materials and the possibility of contributing to solve the growing problem of recycling plastic parts at the end of their life.
Modelling of θ‐conditions for bisphenol—A polycarbonate single chains
Authors: Özgün Numan , Knopp Birgitta , Jung Bernd , Wortmann Franz‐Josef , Hǒcker Hartwig 
Published: March 2011

AbstractAssessing conformational dimensions of macromolecules is a topic of long‐standing interest. Because of its simplicity, it is attractive to investigate the chain properties in θ‐conditions. Under these special conditions, the effects of excluded volume of the segments of the polymer chain vanish. The molecular chain is only subject to local constraints resulting from the bond structure and the hindrance to rotations about bonds. To model θ‐conditions a contour length dependent cutoff is introduced ensuring that only nonbonded interactions of atoms of neighbouring monomeric units are taken into account for energy calculations. Using this energy model we will show that it is possible to model θ‐conditions of a single bisphenol‐A polycarbonate (BPA‐PC) chain in vacuum by two different methods: (i) (Pseudo‐) Langevin dynamics simulations and (ii) regular reassignment of randomly generated atom velocities during a molecular dynamics simulation. Both methods can be used to avoid oscillative dynamic behaviour of the chain. Calculations of the end‐to‐end vector and the radius of gyration of the equilibrium ensembles derived from simulations at different temperatures show good agreement with experimental data. Thus our model techniques are well suited to simulate θ‐conditions with small computational expense.
Amphiphilic copolymers in aqueous medium: Characterization of the structure of the hydrophobic microdomains
Authors: Benjelloun Abdesselam , Dorion Catherine , Brembilla Alain , Viriot Marie‐Laure , Adrian Marc 
Published: March 2011

AbstractThe behaviour of new cationic amphiphilic copolymers derived from 3‐vinylpyridine was studied in aqueous medium. The formation of hydrophobic microdomains was evidenced by fluorescence spectroscopy using a molecular rotor as a fluorescent probe and their structure was visualized by cryo‐transmission electron microcospy (Cryo‐TEM). The parameters (shape and size) obtained from Cryo‐TEM were discussed in relation to the copolymers composition and to the local viscosity defined by the rotor fluorescence quantum yield.
Composite material for medical application
Authors: Zamyslov E. V. , Klochkov V. I. , Ostrovidova G. U. 
Published: March 2011

AbstractComposite material for medical application on the basis of polydimethylsiloxane rubber (PDMS) and graphite was obtained. The physico‐chemical and mechanical properties of the material depending on the quantity, purity of the modifier and its preliminary treatment were studied. The established physico‐chemical properties of the material surface allow to make the preliminary prediction of its thromboresistance.
Broom fibers as reinforcement for thermoplastic matrices
Authors: Avella Maurizio , Casale Luca , Dell'Erba Ramiro , Martuscelli Ezio 
Published: March 2011

AbstractVegetable fibers deriving from the basts of broom plants have been used as reinforcement for two polypropylenic matrices: a conventional isotactic polypropylene (iPP) and a maleate modified one (iPPMA).Before mixing the fibers were subjected to two different extraction procedures: a conventional alkaline treatment and an innovative steam explosion process.Afterwards, the composites obtained by compression moulding were thermally, morphologically, and mechanically characterized. Moreover, water absorption tests, to examine the behaviour of these materials in wet conditions, were also performed.
Luminescence properties of PPV derivatives carrying anthracene pendent groups
Authors: Jin Jung‐Il , Chung Sung‐Jae , Yu Seong‐Han 
Published: March 2011

AbstractPhoto‐ (PL) and electroluminescence (EL) properties of three different PPV derivatives carrying the 9,10‐diphenylanthracene units are compared. One (polymer 1) of the polymers contains the 9,10‐diphenylanthracene structure as an integral part of the main chain, but the other two have it as the pendent group attached to the main chain through either oxyethyleneoxy (polymer 2) or oxyhexamethyleneoxy (polymer 3) spacer. Polymers 1 and 2 exhibit very similar PL and EL spectra that are more or less of superimposed feature of the spectra from the backbones and the anthracene pendents. In contrast, polymer 3 shows an EL spectrum that is completely different from its PL spectrum. Whereas the PL spectrum of polymer 3 appears to be a combination of the spectra from the main chain and the pendents, as for polymer 1 and 2, the EL spectrum of polymer 3, however, looks as if the lights were emitted only from the backbone. This difference is explained in terms of excited state electronic interactions between the main chain and the pendents.
New polymer architectures: Recent results with polyrotaxanes
Authors: Gibson Harry W. , Gong Caiguo , Liu Shu , Nagvekar Devdatt 
Published: March 2011

AbstractRecent results from our laboratory have shown that the formation of polyester and Polyurethane rotaxanes by polymerization in the presence of crown ethers is driven by hydrogen bonding of the OH groups with the oxygen atoms of the macrocycles. Here we summarize these findings. Then we describe the application of this type of self assembly for the production of polyrotaxanes by threading preformed macromolecules and for the controlled synthesis of branched and crosslinked systems. These latter protocols comprise a new and novel way to prepare mechanically linked, elastomeric materials. Rheological properties of main chain polyrotaxanes are compared to simple linear backbones; the rotaxanes display higher intrinsic viscosities and lower melt viscosities, reflecting larger hydrodynamic volumes and less entanglement, respectively; these are potentially useful aspects in terms of processability of this new class of polymeric materials.
Synthons as building blocks in the synthesis of liquid crystalline multiblock copolymers
Authors: Bilibin Alexander Y. , Girbasova Nina V. , Tenkovtsev A.V. 
Published: March 2011

AbstractSynthetic approaches which allow to insert rather long fragments with exactly definite sequence of several single structural units into polymer chains are considered and summarized. The procedure consists in preliminary formation of such sequences in a form of bifunctional “complex monomer” (synthons) which may undergo a polycondensation with other single or complex monomer to form macromolecule with definite alternation of several single monomers. These synthetic approaches were used for the synthesis of LC multi‐block copolymers with definite structure of rigid block.
Effect of component interaction on the melting and crystallization characteristics of pe/pib blends
Authors: Szabó Péter , Epacher Edina , Belina Károly , Pukánszky Béla 
Published: March 2011

AbstractLinear low density polyethylene/polyisobutylene blends were prepared in the entire composition range. Non‐isothermal and isothermal crystallization of the samples was carried out and melting behavior was studied as a function of composition and crystallization temperature. The equilibrium melting temperature of the neat PE and the blends was determined by the Hoffman‐Weeks extrapolation technique. Flory‐Huggins interaction parameters were calculated by the approach of Nishi and Wang. The decrease of melting temperature with increasing PIB content indicated the interaction of the polymers in the melt. Both irregular chain structure of the crystalline polymer and interaction lead to a decrease of the equilibrium melting temperature and maximum lamellar thickness. The results prove that even relatively weak dispersive forces can lead to the miscibility of two polymers.
Synthesis and physical properties of polyurethanes from saccharide‐based polycaprolactones
Authors: Hatakeyama Hyoe , Izuta Yoshinobu , Kobashigawa Ken , Hirose Shigeo , Hatakeyama Tatsuko 
Published: March 2011

AbstractPolyurethane (PU) sheets were prepared from glucose‐, fructose‐and sucrose‐based polycaprolactones (PCL). The obtained saccharide‐based PCL's were characterized by gel permeation chromatography, Fourier‐transform infrared spectroscopy and nuclear magnetic resonance spectroscopy. The glass transition temperature, thermal degradation temperature, tensile strength, elongation and Young's modulus of the PU sheets were measured. The obtained results suggest that the molecular motion of PU's is enhanced with increasing fraction of PCL chains in PU molecules, and that at the same time the saccharide components act as hard segments.
Biodegradation of polyorganosiloxanes
Authors: Rościszewski Paweł , Łukasiak Jerzy , Dorosz Agnieszka , Galiński Janusz , Szponar Maria 
Published: March 2011

AbstractBiodegradation of various polyorganosiloxanes (about 30 substances) under the influence of several biotype bacteria strain (16 types) were studied. A special procedure of biodegradation and analytical methods of evaluation the degree of degradation were applied. It was found that nearly all polysiloxanes tested are biodegradable but the degree of degradation depends on their composition and structure, as well as on the type of bacteria strain chosen.
A novel redox system consisting of π‐conjugated polymers and transition metals
Authors: Hirao Toshikazu , Higuchi Masayoshi , Yamaguchi Satoshi 
Published: March 2011

AbstractCoordination of π‐conjugated polymers to transition metals constructs a novel redox system due to interchangeable various oxidation states of the polymers, which permits transition metals to interact with each other through a π‐conjugate chain. The redox characteristics were found to depend on the electronic interaction with metals and the doping. A combination of copper(II) or iron(III) chloride and polyanilines afforded the complex catalysts with the higher oxidation capability for dehydrogenative oxidation. A catalytic system was also realized in the transition‐metal‐induced oxidation reaction, in which π‐conjugated polymers serve as redox‐active ligands participating in the reversible redox cycle. The Wacker oxidation of terminal olefins proceeded catalytically in the presence of a catalytic amount of polyaniline or polypyrrole derivative under oxygen.
Photoinduced water oxidation by polymeric iron cyanide complex
Authors: Abe Toshiyuki , Shiroishi Hidenobu , Kinoshita Kosato , Kaneko Masao 
Published: March 2011

AbstractIt was found that photoelectrochemical water oxidation takes place at a polynuclear iron‐cyanide complex‐coated electrode called Berlin Brown (BB; Fe4III[FeIII(CN)6]33 3X). The electrode‐coated BB showed electrocatalytic activity for water oxidation to produce O2 not only in the dark but also under illumination to result in photoinduced water oxidation. The amount of the photoelectrochemically produced O2 increased with the thickness of the BB film, indicating that the BB works as a bulk catalyst.