bluuebunny/crossref_metadata_2025_split huggingface dataset:
Production of micron‐sized monodispersed cross‐linked polymer particles having hollow structure
Authors: Okubo Masayoshi , Minami Hideto , Yamashita Tsuyoshi 
Published: March 2011

Abstract4 μm‐sized monodispersed cross‐linked polymer particles having hollow structure were produced as follows. First, 1.7 μm‐sized monodispersed polystyrene (PS) seed particles produced by dispersion polymerization were dispersed in ethanol/water (7/3, w/w) solution in which divinylbenzene (DVB), benzoyl peroxide (BPO), poly(vinyl alcohol), and toluene was dissolved. The PS seed particles were swollen with DVB, toluene and BPO maintaining high monodispersity throughout the dynamic swelling process where water was slowly added continuously. And then, the seeded polymerization of the (toluene/DVB)‐swollen PS particles was carried out.
Designs of latex particles' morphologies for toughening polymer matrices
Authors: El‐Aasser Mohamed S. , Segall Iris , Dimonie Victoria L. 
Published: March 2011

AbstractThe performance of the designed structured core/shell latex particles in toughening polycarbonate (PC) matrix was examined. The influence of parameters related to the core/shell latex particles on toughening PC such as: the particle size and levels of crosslinking of the core rubber particles, composition and molecular‐weight of the shell polymer, the weight ratio of shell and core polymers as well as the particle morphology was evaluated. Core/shell structured latex particles with thinner shells of higher molecular‐weight polymers were found to improve the impact resistance of PC. The role of chain entanglements in increased adhesion between the discrete rubbery phase and the continuous glass matrix are discussed.
Photoresponsive liquid crystalline and amorphous polymers
Authors: Anderle K. , Bach H. , Fuhrmann TH. , Wendorff J. H. 
Published: March 2011

AbstractIsomerization processes of azobenzene dyes dissolved in a glassy polymeric matrix or attached in glassy amorphous or liquid crystalline polymers to the backbone as side groups are induced by light. The isomerization process, in turn, causes the dye to reorient provided that polarized light is used: the long axis of the dye is oriented perpendicular to the polarization direction in the stationary case. Such a reorientation gives rise to strong modifications of the optical properties. This contribution is concerned with the analysis of the correlation between the nature of the azobenzene dyes, the isomerization, reorientation and modulations discussed above and with possible applications in the optical holographic storage. Considered are, in particular, dye/matrix combinations giving rise to nonlinear holographic responses, two photon holography, transient holographic modes applicable for holographic displays and the optical switching of other than optical properties.
Development of new cyclic olefin polymers for optical uses
Authors: Kohara Teiji 
Published: March 2011

AbstractNew cyclic olefin polymers (COP) with a better balance of properties than those of conventional optical plastics have been developed by using norbornene monomers. The COP are prepared by ring‐opening metathesis polymerization of norbornene monomers followed by complete hydrogenation of double bonds. The COP have practically been applied for optical uses such as lenses, prisms and optical discs.
Towards supramolecular polymers
Authors: Huff Jürgen , Preece Jon A. , Fraser Stoddart J. 
Published: March 2011

AbstractThe natural phenomenon of self‐assembly has been used to make complex unnatural products. These new compounds have taken the form of catenanes and rotaxanes. We have identified several polymeric architectures containing the catenane and rotaxane motifs, and then described how the model structures, which we have identified and actually realized as chemical compounds, can be employed to assess the feasibility of introducing mechanical linkages into novel polymers by means of self‐assembly processes.
Bengal rose@dendritic box
Authors: Jansen Johan F.G. A. , Meijer E. W. , De Brabander ‐ Van Den Berg Ellen M. M. 
Published: March 2011

AbstractBengal Rose was succesfully encapsulated and liberated from a dendritic box. Bengal Rose@DAB‐dendr‐(NH‐t‐BOC‐L‐Phe)64 was investigated with several different techniques such as ultraviolet, circular dichroism and fluorescence spectroscopy.
Degradable dendritic polymers — A template for functional pores and nanocavities‐
Authors: Muzafarov Aziz M. , Rebrov Evqueniy A. , Gorbacevich Olga B. , Golly Monika , Gankema Harold , Möller M. 
Published: March 2011

AbstractDegradable dendrimers are prepared as a template to create utrasmall cells when they get embedded in a polymer resin and to obtain well‐defined cavities with particular chemical groups at their walls if the endgroups remain attached to the matrix. In a first approach cascade: (13‐oxa‐1‐methylsilaundecenylidene): undecene was synthesised by the polyaddition reaction of methyl‐di‐undecenoxysilane as basic repeat unit. A multimodal weight distribution was found which appeared to be selfcontrolled to a limited molecular weight. Degradation was done with dry methanol and methanol with aqueous hydrochloric acid. In the case of dry methanol, the degradation products yielded only low molecular weight compounds while siloxane bonds were formed in the case the degradation was performed with methanol and aqueous hydrochloric acid. In order to create films with nanocavities, the degradable dendritic macromolecules were embedded in a methacrylate resin. Hole formation was illustrated by transmission electron microscopy for the case of 0.5 wt.‐%, 5 wt.‐% and 30 wt.‐% of dendrimer content. However, aggregation of the dendritic molecules during the curing of the methacrylate resin could not be avoided. In order to suppress aggregation, cascade: (1‐methylsilapropylidene): propene with methacrylate endgroups have been prepared which can be covalently linked to the embedding resin molecules. In a first approach the compatibility with the methacrylate resin was indicated by the optical transparency, while microscopy techniques were not capable to resolve the fine structure.
Block copolymers and telechelic oligomers by end group reaction of polymethacrylates
Authors: Esselbom Eberhard , Fock Jürgen , Knebelkamp Arno 
Published: March 2011

AbstractBlock copolymers and telechelic oligomers bearing methacrylate moities were obtained by means of a new highly selective end group reaction. Starting from polymethacrylates that were prepared by radical polymerization in the presence of mercaptanes as chain transfer agents, the resulting ester end group linked to the terminal tertiary carbon atom of the polymer backbone can be either transesterified or saponified selectively. The selectivity of the end group reactions was determined by MALDI‐TOF‐mass spectrometry. Polymethacrylate‐b‐poly(ethylene oxide)‐, polymethacrylate‐b‐poly(methacrylic acid)‐ and polymethacrylate‐b‐polysiloxane‐b‐polymethacrylate‐copolymers as well as α,ω‐dihydroxy‐ and α,ω‐dicarboxy‐telechelic polymethacrylates were prepared by applying end group transesterification or end group saponification.
Synthesis and characterization of syndiotactic polystyrene and poly[styrene‐co‐(p‐methylstyrene)]
Authors: Cardi Nicoletta , Po′ Riccardo , Abbondanza Luigi , Abis Luigi , Conti Giuseppina 
Published: March 2011

AbstractSyndiotactic polystyrene and copolymers of styrene and p‐methylstyrene were synthetized in bulk by using a titanium tetraethoxide/methylaluminoxane catalytic system. The polymers were analyzed by 13C and 1H Nuclear Magnetic Resonance, Infrared Spectroscopy, Gel Permeation Chromatography and Differential Scanning Calorimetry and their properties were compared.
Measurement of interfacial adhesion between glassy polymers using the JKR method
Authors: Mangipudi Venkata S. , Huang Elbert , Tirrell Matthew , Pocius Alphonsus V. 
Published: March 2011

AbstractThe surface and interfacial energies of polymers are measured using the JKR‐type experiments. A novel method has been developed to prepare samples of glassy polymers for adhesion measurements. A thin layer of a polymer is coated on the surface of an O2‐plasma modified cross‐linked poly(dimethylsiloxane) [PDMS] spherical cap resulting in the formation of a composite. Using the JKR theory, the surface energies of polystyrene [PS] and poly(methyl methacrylate) [PMMA] are determined from the measurements of the contact radius as a function of applied load. The results of the JKR‐type experiments are compared to adhesion measurements done using the surface forces apparatus (SFA). Adhesion hysteresis was observed for PS‐PS contact as well as PMMA‐PMMA contact. However, no hysteresis was observed for PDMS‐PDMS, PDMS‐PS, and PDMS‐PMMA contacts. The exact origin of the hysteresis is not clear at present. The current evidence suggests that hysteresis is due to rearrangement of the interface during contact.
Approaches to supramolecular structures with various topologies in the crystal lattice
Authors: Valiyaveettil Suresh , Enkelmann Volker , Moeßner George , Müllen Klaus 
Published: March 2011

AbstractSimple molecular building blocks for creating supramolecular architectures in the crystal lattice are described. Combination of hydrogen bonding and alkyl chain crystallization is used to explore self‐assembly1 of molecular building blocks 1, 2, 3 and 4 in the crystal lattice. The crystal lattice of pure acids and its equimolar mixtures with bifunctional hydrogen bond acceptors are characterized by singe crystal analysis.
Investigation of α‐keratin intermediate filament structure by molecular dynamic simulation
Authors: Knopp Birgitta , Jung Bemd , Wortmann Franz‐Josef 
Published: March 2011

AbstractMolecular dynamic simulations are carried out in order to investigate the stability of the secondary and tertiary structure of the intermediate filaments monomer unit of wool. Based on the assumed secondary structure three segments of the primary structure are selected: 1A, L1,2 and a part of 2B. With the ideal α‐helix as start conformation, the simulations are carried out with the MD‐algorithm of DISCOVER 2.9.0 (BIOSYM, 1993) and the CFF91 force field for 500 ps at different temperatures in vacuum. In either simulation a destabilization of the helical structure with an increase of the simulation temperature is observed. By monitoring the length distribution of the axially oriented (O···H)‐hydrogen bonds, which stabilize the helical structure, transition temperatures for the α‐helical denaturation are determined. The supposedly α‐helical segments 1A and 2B show significantly higher transition temperatures than segment L1,2. This lower temperature confirms the expectation from the amino acid sequence that the linker segment shows more conformational flexibility and is nonhelical at room temperature.
Prospects and challenges of reactive processing
Authors: Joachim Rösch , Holger Warth , Philipp Müller , Rüdiger Schäfer , Christof Wörner , Christian Friedrich , Jörg Kressler , Rolf Mülhaupt 
Published: March 2011

AbstractChemical reactions during polymer melt processing afford a wide range of highly diversified polymers derived from well‐known polymers. This technology, especially functionalization, grafting, in‐situ formation of copolymers, segmented polymers, and compatibilizers, plays a key role in the development of novel thermoplastics including blends, composites, and polymers from renewable resources. Oxazolines are useful highly reactive and selective intermediates for polymer melt modification.
The processing and properties of conductive polypropylene/polypyrrole composites
Authors: Omastová Mária , Piontek Jürgen , Janke Andreas , Košina Stanislav 
Published: March 2011

AbstractPolypropylene (PP) particles were chemically coated with polypyrrole (PPy). The content of polypyrrole varied from 0.8 to 7.6 wt.‐%. Electrical conductivity of compression moulded samples depends on the concentration of polypyrrole and reached values from 4×10−10 to 5×10−3 S/cm, which is about 7 orders of magnitude higher than the conductivity in the blends prepared by mechanical mixing of PP and PPy in the same PPy concentration range. Highly conductive composites were also obtained from a mixture of coated and non‐coated PP particles.The PP/PPy composites were characterized by elemental analysis, SEM and mechanical testing. The antistatic properties of PP/PPy composites were demonstrated. The electrical and mechanical properties depend on processing of composites.
Homogeneous mixtures of polybetaines with low molecular weight salts
Authors: Bonte Nelly , Laschewsky André , Mayer# Bernd , Vermylen Valérie 
Published: March 2011

AbstractThe prepaparation of amorphous, homogeneous blends of zwitterionic polymers with various low molecular weight salts, and in particular with ionic dyes was studied. Homogeneous miscibility was achieved in many cases up to equimolar amounts of salt, even for bulky compounds. Whether miscibility is achieved, or not, depends in a subtle way on the chemical structure of the salt, but no obvious correlation between structure and miscibility could yet be revealed. Spectral shifts of the dye UV/Vis spectra in solution as well as in bulk suggest strong interactions between the polybetaines and the admixed salts.
On the interaction of the morphological structure and the LC behaviour of LC side group block copolymers
Authors: Fischer Hartmut , Arnold Manfred 
Published: March 2011

AbstractThe interaction between morphological structure and phase behaviour of a group of LC side group block copolymers have been investigated using DSC, TEM and small angle X‐ray diffraction. Generally, phase separation between the two blocks was observed. It was found that in the case of those samples, where the liquid crystalline sub‐phase is not continuous (spheres), only a nematic phase is seen, whereas in all samples in which there is a continuous liquid crystalline sub‐phase, the smectic A phase of the homopolymer is formed. On the other hand, the block copolymer seems to stabilise the LC‐phase and the polymer properties in general, no dependency of the clearing temperatures and of the glass transition temperatures from the molecular weight of the LC blocks has been detected.
Supramolecular polymer interactions using melamine
Authors: Lange Ronald F. M. , Meijer E. W. 
Published: March 2011

AbstractTriple‐hydrogen bonding between the imide containing polymers 1a‐c and melamine 2 is used to obtain supramolecular interactions between macromolecules. Melamine, known as a compound barely soluble in any organic solvent, is molecularly dissolved in the copolymers 1a‐c by meltprocessing. Maximum concentrations of 1 equivalent amount of melamine per 2.5 equivalent amounts of copolymer are obtained, indicating a 3:1 mol:mol superstructure with physical crosslinking by hydrogen bonding. Crystalline melamine is detected by powder diffraction X‐ray analysis at melamine concentrations exceeding the 3:1 imide‐melamine mole ratio.
Structure of crystals of nylon 6,3 and related polymers: Folding is stabilized by thermodynamic interactions
Authors: Subirana Juan A. , Aceituno Juana E. 
Published: March 2011

AbstractThe n,3 polyamides have the structure: [‐(CH2)n NHCOCH2CONH‐]×. Due to the stereochemistry of the malonamide unit, these polymers have a unique hydrogen bonding system with two different orientations at 120°: they do not form hydrogen bonded sheets as in conventional polyamides. We have obtained a very well oriented mat from crystals of this polymer which shows up to ten orders of the lamellar spacing. In this paper we analyze the structure of the fold in the crystal surface of nylon 6,3 and in related polyamides, including polyglycine. The thickness of these lamellar crystals is in agreement with the values determined for other polyamides. These results, taken together with some recent findings with other polymers, indicate that the thickness of polymer lamellar crystals may be thermodynamically controlled. An outline of this hypothesis is presented.
Role of the cure kinetics in morphology control at phase separation of curing multicomponent thermosets and a criterion of equilibrium
Authors: Rozenberg Boris A. , Sigalov Grigory M. 
Published: March 2011

AbstractThe formation of heterophase polymers via phase separation in the course of curing reaction in a blend of a thermosetting oligomer with a rubber modifier is considered. The interference of thermodynamic and kinetic factors that define the morphology of the material being formed is discussed. The need for a kinetic theory of cure‐induced phase separation is established, and an approach of this kind is proposed. On the basis of this approach a simple quantitative criterion of deflection of the phase‐separating system from the thermodynamic equilibrium is given.
Polymer bound chromogenic crown‐ethers as the cladding material for polymer optical waveguides
Authors: Klok Harm‐Anton , Möller Martin 
Published: March 2011

AbstractThe synthesis and spectroscopic characterization of the chromoionophoric poly(methyl methacrylate‐co‐N‐(9‐[10‐methacryloylmethyl]anthrylmethyl)monoaza‐18‐crown‐6) (4) copolymer is described. Complexation of K⊕ by extraction from aqueous medium with toluene solutions of (4) was found to enhance the intensity of fluorescence up to 40% compared to the situation in which no K⊕ was complexed. For low concentrations, the intensity of fluorescence was found to increase linearly with the concentration of K⊕ in the aqueous solution. The copolymer (4) might be used for the transduction of the chemical recognition of K⊕ into an optical signal in evanescent wave fluorescence chemical sensors based on poly(methyl methacrylate) optical waveguides.
Polymer light emitting diodes
Authors: Greczmiel Michael , Pösch Peter , Schmidt Hans‐Werner , Strohriegl Peter , Buchwald Elke , Meier Martin , Rieß Walter , Schwoerer Markus 
Published: March 2011

AbstractMonolayer light emitting diodes from poly(1,4‐phenylenevinylene) (PPV) usually exhibit relatively low quantum efficiencies. So the external efficiency of an ITO/PPV/Ca LED is typically 0.01%. In order to increase the quantum yield in bilayer devices, oxadiazole polymers have been used. The syntheses of a number of novel polymethacrylates with pendant oxadiazole groups and some aromatic polyethers with oxadiazole units in the main chain are described. These polymers with the electron withdrawing oxadiazole units facilitate electron injection and transport in bilayer LEDs with PPV as hole transport layer. Thus an LED with a top layer of the polyether 3a exhibits a tenfold increase of the external quantum efficiency to 0.1%. Compared to conventional PPV LEDs, the improved bilayer devices show intense emission at low current densities.
Gel template leaching: An approach to functional nanoporous membranes
Authors: Gankema Harold , Hempenius Mark A. , Möller Martin , Johansson Gary , Percec Virgil 
Published: March 2011

AbstractA novel preparation method for nanoporous structures, denoted “Gel Template Leaching”, is described. The approach is based on the gelation of solutions containing two low molecular weight compounds of which one is crystallizable and the other curable. Gelation of the solute upon cooling followed by curing of the solvent below the gelation temperature lead to the formation of a semi‐IPN consisting of a reversibly and a covalently crosslinked network. After leaching of the solute (the template) a well‐defined nanoporous architecture was formed. Functional pores could be obtained after charging the pore walls with ionic sites.
Organic thin film pyrosensors
Authors: Brehmer Ludwig , Kaminorz Yvette , Grasnick Gerd , Herkner Georg 
Published: March 2011

AbstractRecent developments in sensor technology show the suitability of thin pyroelectric films for the construction of pyroelectric sensor devices made from polymer materials. These materials are used for its advantageous thermal properties and also for its suitable frequency behaviour. Pyroelectrical measurements have been provided on thin films based upon poly(vinyl alcohol)s and poly(siloxane)s with azobenzene side chains. Relaxation behaviour and stability of poled pyroelectric polymers are discussed and related to the results of dipole relaxation measurements provided at our laboratories.
Preparation and properties of self‐reinforced polypropylene/liquid crystalline polymer composites
Authors: Postema Adri R. , Fennis Paul J. 
Published: March 2011

AbstractA fast and potentially economic method for creating a composite material of polypropylene (PP) with liquid crystalline polymers (LCPs) was explored. The LCPs were dispersed in the PP matrix in a conventional extrusion process and subsequently drawn in order to obtain a highly uniaxially molecular orientation of the LCP fibres. The strongest mechanical properties were found after rapid cooling of the blend, which was optimally exploited in thin filaments where cooling was fast enough to prevent fibre break‐up and/or orientation relaxation.To enable the production of extrudates which are thick enough to be cut into self‐reinforced pellets, a fused multi‐filament technology was developed. In this technology several thin filaments were extruded/drawn and rapidly cooled to a temperature between the crystallisation temperatures of the LCP and the PP. After solidification of the LCP, the single filaments were fused to a multifilament strand and further cooled to room temperature. The thick multifilament LCP reinforced PP strands were cut into pellets and used in injection‐and compression‐moulding processes. This processing took place between the melting temperature of the PP and the LCP, with retention of the aspect ratio and the molecular orientation of the LCP fibres.
Strategies for the development of haemocompatible dialysis membranes
Authors: Diamantoglou M. , Vienken J. 
Published: March 2011

AbstractHaemocompatibility is the number one target of membrane development for haemodialysis, because chronic renal failure and the subsequent dialysis‐treatment is affecting more and more patients. Two strategies are currently in use to achieve the goal of new blood compatible polymers: Firstly, existing cellulosic membranes are modified by introducing functional groups through ether and ester bonds and secondly, synthetic polymers are mixed with bulk additives or copolymerized with other polymers. Biological responses as a consequence of blood/material interaction are common observations. However, blood compatibility in general cannot be improved by a single membrane surface feature. The assessment of a series of surface properties shows that physiological defense systems, like complement and cell activation, or coagulation are differently stimulated by means of the same surface structures of biomaterials. Thus, a compromise has to be found, already during membrane development.We synthetized a series of modifications of cellulosic membranes with the aim to investigate whether the type of substituent and its degree of substitution has an influence on the blood compatibility of these dialysis membranes. Data indicate that alterations in the lipophilic/ hydrophilic balance (HLB) on the polymer surface may explain substituent‐related changes in haemocompatibility. Optimal degrees of substitution are characteristic for a given type of substituent and enables the membrane manufacturer to tailor materials for improved blood compatibility.