bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sulfonated polypropylene ionomers
Authors: Dassaud J. P. , Gallot B. , Guyot A. , Spitz R. , Beautemps J. P. , Williams C. , Bourgaux C. , Eisenberg A. 
Published: April 2003

AbstractPolypropylene ionomers have been prepared by sulfonation of copolymers of propene and 7 methyl, 1‐6 octadiene, followed by neutralization to cesium salts. Both WAXS and SAXS were used to study the morphology of the samples, while their thermal properties were studied by DSC and their mechanical properties by DMTA. The sulfonation process is shown to cause a further drop in crystallinity in addition to the effect of comonomer incorporation. Ion clustering is observed when the extent of sulfonation is high enough, the limit being dependent on the copolymer composition. The ion pairs which are not incorporated into the cluster cause a small‐angle upturn in the WAXS pattern. The mechanical properties are strongly affected by the drop in crystallinity, but may be partly recovered due to ion clustering. No disruption of the ion clusters is observed before thermal decomposition of the polymer.
Densely crosslinked liquid single‐crystal elastomers
Authors: Küpfer Jürgen , Nishikawa Etsushi , Finkelmann Heino 
Published: April 2003

AbstractA series of liquid single‐crystal elastomers (LSCE) with different crosslinking densities were synthesized. The influence of the crosslinking density on the macroscopic properties (e.g. swelling, thermoelastic behavior and birefringence) and the phase behavior was studied. It is shown that densely crosslinked duromers are available which possess no clearing temperature and exhibit relatively high birefringence at high temperature.
Recent developments in polymeric charge transfer complexes
Authors: Natansohn Almeria 
Published: April 2003

AbstractThe recent literature on polymeric charge transfer complexes is reviewed with emphasis on the author's own work. After a definition of the area and a survey of investigations on the spatial arrangement of donor and acceptor sites in the solid state, a variety of applications of these complexes is presented. Electrically conductive polymers are excluded. These applications are: compatibilization of polymer blends, liquid crystalline supramolecular organization, new developments in photo‐conductivity, electroluminescence, nonlinear optical properties, photorefractivity and reversible optical storage.
Crosslinked poly(N‐isopropylacrylamide) gel for electrophoretic separation and recovery of substances
Authors: Yoshioka Hiroshi , Mori Yuichi , Tsuchida Eishun 
Published: April 2003

AbstractCrosslinked poly(N‐isopropylacrylamide) gel was tested on the feasibility for a preparative electrophoretic matrix. Horse heart myoglobin and bovine hemoglobin were well separated on the gel matrix electrophoretically by molecular sieving effect of the gel network. Relative mobilities of those proteins in the gel were larger than those in a crosslinked polyacrylamide gel of the same polymer concentration. After the separation, the protein‐containing portion of the gel underwent swelling at 4°C and deswelling at 37°C, alternatively. As a result of the deswelling, each protein was recovered in a discharged solution out of the gel at almost 100% yield.
Orientation of a chiral smectic C elastomer by mechanical fields
Authors: Semmler Klaus , Finkelmann Heino 
Published: April 2003

AbstractIt is well known that, with respect to the director, nematic elastomers can be macroscopically aligned by uniaxial mechanical fields. Extending this method to a chiral smectic C elastomer, depending on the experimental set‐up either smectic layer orientation or director orientation parallel to the stress axis occurs. In order to align the director and the smectic layers a biaxial mechanical field (e.g. shear field) consistent with the phase symmetry has to be used to achieve a macroscopically uniform orientation of the untwisted smectic C* structure.
Photoelectrical properties of Langmuir–Blodgett films of poly(methyl phenylsilane)s
Authors: Brynda E. , Koropecký I. , Kmínek I. , Nes̆pu̇rek S. , Schnabel W. 
Published: April 2003

AbstractLangmuir–Blodgett (LB) films were prepared from poly(methylphenylsilane) bearing electron acceptor π‐conjugated substituents. The small limiting area (0.078 nm2) per one repeating unit of polysilane (PSi) in monomolecular film and the large thickness of the film (6 nm) suggest that the polymer chains are not fully spread on water surface. The electrical and photoelectrical properties of Al/LB film/Au sandwich cells containing various numbers of the polysilane layers were studied. Holes were transported from the Al electrode through the LB film to the Au electrode when the light was absorbed by the polysilane. The highest photovoltaic effect occurred in the first monolayer of polysilane at the Al contact. The cell resistivity and the photovoltage were decreased by parallel conductance of defects in the films consisting of small numbers of PSi layers.
Cure behavior and thermal stability of an epoxy: new bismaleimide blends for composite matrices
Authors: Kim Dae Su , Han Mi Jung , Lee Jae Rock , Chang Ji Young 
Published: April 2003

AbstractA new bismaleimide (BMI) resin was synthesized to formulate epoxy(tetraglycidyl diaminodiphenyl methane; TGDDM) – bismaleimide thermoset blends for composite matrix applications. 4,4′‐diaminodiphenyl methane (DDM) was used as an amine curing agent for the TGDDM. A Fourier transform infrared (FTIR) spectroscopy was employed to characterize the new BMI resin. Cure behavior of the epoxy–BMI blends was studied using a differential scanning calorimeter (DSC). DSC thermograms of the thermoset blends indicated two exothermic peaks. The glass transition temperature of the thermoset blends decreased with BMI content. Thermogravimetric analysis (TGA) was carried out to investigate thermal degradation behavior of the cured epoxy–BMI thermoset blends. The new BMI resin reacted partially with the DDM and weak intercrosslinking polymer networks were formed during cure of the thermoset blends.
Use of functional microgels with vinyl groups to accelerate photopolymerization reaction
Authors: Sasa Nobumasa , Sato Akira , Yamaoka Tsuguo 
Published: April 2003

AbstractThree types of functional microgels with vinyl groups on their surface were prepared. For the first type, the counter anion from clorin was exchanged with β‐methacryloylethyl sulfonic acid, styrene sulfonic acid or allyl sulfonic acid in a microgel with ammonium anions. For the second and third types, a quaternization with N,N‐dimethylaminoethyl methacrylate of 3‐chloro‐2‐hydroxypropyl methacrylate in the presence of microgel particles was prepared by emulsion copolymerization of styrene, chloromethylstyrene or N,N‐dimethylamino‐methylbenzene, and divinylbenzene. The resulting samples show good dispersibility in organic solvents without an emulsifier.A functional microgel‐based photopolymer combined with an acrylate monomer and ultraviolet (UV) or visible (VIS) light‐absorbing photoinitiators provides oleophilic images when exposed to UV or VIS light and developed in tap water. This photopolymer has a higher sensitivity than those of photopolymers based on microgels with an analogous composition but without vinyl groups. Photopolymers pepared by using functional microgels with a methacryloyl group exhibited a higher rate of polymerization (Rp) than that of photopolymers based on microgels without a vinyl group. The Rp of photopolymers prepared by using a functional microgel with either an allyl group or vinylphenyl group was nearly equal to that of photopolymers based on microgels with ammonium ions. Their high sensitivities are attributed to the rapid photopolymerization in the methacryloyl group.To determine how the photoreaction mechanism enhances sensitivity, the photoreaction products were investigated using a model photopolymerization system. It was found that the gelation reactions enhancing sensitivity are predominantly the polymerization and crosslinking ones when a microgel with the methacryloyl group is used, and the graft copolymerization with acrylate monomers when a microgel with either the allyl group or vinylphenyl group is used.
High‐performances membranes for pervaporation I. Poly(vinyl alcohol)–poly(N‐vinyl pyrrolidone) blends
Authors: Nguyen Quang‐Trong , Ping Zhenghua , Néel Jean 
Published: April 2003

AbstractDense membranes were prepared from poly(vinyl alcohol)–poly(N‐vinyl pyrrolidone) (PVA–PVP) blends of different compositions and studied in swelling and dehydration by pervaporation of three organic solvents contaminated by 5 wt% water. The swelling generally increases with the PVP content. No extraction occurs in water–tetrahydrofuran (THF) and water–methyl ethyl ketone (MEK) mixtures. In ethanol containing 10 wt% of water, there is no extraction for blends containing less than 40 wt% PVP and an increasing extraction beyond this PVP content. The pervaporation flux of the water–ethanol mixture increases drastically at the same threshold whereas the water permselectivity falls to a low level. The values of the diffusion and permeability coefficients determined from transient permeation of the test water–ethanol mixture exhibit a similar sudden increase at the same PVP content threshold. This singular behavior of the blend membranes is interpreted by a strong affinity of the PVP component to ethanol, combined with a disappearance of crystallites in the blend at this threshold. Consequently the amorphous membrane can swell freely according to the affinity of the PVP component, leading to the observed behavior.
High‐performance membranes for pervaporation II. Crosslinked poly(vinyl alcohol)–poly(acrylic acid) blends
Authors: Ping Zhenghua , Nguyen Quang‐Trong , Essamri Azouz , Néel Jean 
Published: April 2003

AbstractDense membranes made by crosslinking of poly(vinyl alcohol) (PVA) with poly(acrylic acid) (PAA) were prepared and tested in pervaporation and differential permeation of water–alcohol mixtures. Instead of a decrease of permeation flux as generally observed with most crosslinking agents, an increase in the permeability was observed with PAA crosslinked membranes at low PAA contents. The permeation flux increases with PAA contents in the polymer with no selectivity reduction for membranes containing less than 15 wt. % PAA. The membranes show good performances to water–2‐propanol and water–ethanol mixtures, i.e. high fluxes and high selectivities to pure water. The membranes were stable and highly permeable to water. The enhancement of the permeability of PVA can be explained by a reduced crystallinity and an improved diffusivity due to the presence of PAA.
Poly(butylene terephthalate)–polyarylate blends
Authors: Runt J. , Miley D. M. , Gallagher K. P. , Zhang X. , Barron C. A. , Kumar S. K. 
Published: April 2003

AbstractIn this paper we focus on miscible blends of two engineering polymers: poly(butylene terephthalate) (PBT) and a polyarylate (PAr). The issue of transesterification in these blends will be addressed, followed by a discussion of the crystallization kinetics of PBT, poly(ethylene terephthalate) and several PBT/PAr blends. The ability to estimate polymer–polymer interaction parameters in blends from melting point depression will also be discussed. The amorphous phase behavior of the PBT/PAr blends has been explored primarily using dielectric spectroscopy. For blends in which PBT has crystallized, we observe two relaxations associated with Tg‐like motion, and this behavior is interpreted in light of our recent work on order–disorder interphases in crystalline blends.
Study of the copper electrodeposition process from low molecular weight polymer electrolyte media
Authors: Panero S. , Bardanzellu L. , Scrosati B. 
Published: April 2003

AbstractThe characteristics of the copper deposition process from electrochemical cells using a solution of Cu(CF3SO3)2 in low molecular weight poly(ethylene glycol), PEG, have been investigated by cyclic voltammetry, potential steps and impedance spectroscopy. The results suggest that under non‐equilibrium at the cathodic side the process mainly involves the reduction of Cu(II) ions to copper metal while at the anodic side a chemical reaction competes with the electrochemical dissolution.
Preparation and properties of soluble polyamideimides containing oligo(tetrafluoroethene) segments and application in gas separation
Authors: Steinhauser Norbert , Mülhaupt Rolf , Hohmann Marcus , Springer Jürgen 
Published: April 2003

AbstractA series of PMDA‐, BTDA‐ and 6F‐polyamideimides containing well‐defined oligo(tetrafluoroethene) segments were derived from N,N′‐bis(aminophenyl)perfluoroalkane‐α, ω‐dicarboxamides with n =1,2,3 tetrafluoroethene units. The influence of the fluorine content, microstructures and the oligo(tetrafluoroethene) segment lengths on phase transition temperatures, thermal degradation, contact angles, pure gas permeabilities and permselectivities was studied.
Interdiffusion of polymer chains during latex coating
Authors: Pekcan Önder , Canpolat Murat 
Published: April 2003

AbstractThe fluorescence method was used to study the interdiffusion of polymer chains during annealing of latex above its glass transition temperature (Tg). The latex film was prepared from mixture of naphthalene (N) (donor) and pyrene (P) (acceptor)‐labeled poly(methyl methacrylate) (PMMA) latex particles. Heptane was used as the coalescent agent. A steady‐state fluorescence technique was employed to measure the amount of direct nonradiative energy transfer from N to P during the interdiffusion of polymer chains across the particle–particle junction. Various latex films with different latex contents were used to measure the percentage critical occupation for the reliable steady‐state fluorescence measurements. Diffusions activation energies in these latex films were measured and found to be around 30 kcal/mol, which was attributed to the backbone motion of PMMA chains.
Approaches to molecular composites from fluorine‐containing bis‐maleimides: Part I
Authors: Tesoro G. C. , Pendharkar S. M. 
Published: April 2003

AbstractPrevious work in our laboratory has shown that covalent bonding of a semiflexible polymer in a bis‐imide matrix prior to thermal polymerization is a promising, although structure‐dependent, approach to the synthesis of molecular composites from organic solvents in thermosets. In the present investigation, the focus has been on the rapid amine‐catalyzed anionic polymerization and crosslinking of fluorine‐containing bis‐maleimides. The objective has been to provide physical entrapment of rigid polymer prior to aggregation. Results have shown that gelation of fluorine‐containing bis‐maleimides initiated by tertiary amines in organic solvent can occur in seconds at moderate temperatures, and thus affords a means of preventing aggregation of rigid polymer prior to crosslinking.
Fluorinated poly(benzoxazole–imide)s
Authors: Bruma Maria , Mercer Frank , Schulz Burkhard , Dietel Reinhard , Neumann Werner 
Published: April 2003

AbstractNew poly(benzoxazole–imide)s have been prepared by polycondensation of bis(o‐aminophenol)s, such as 3,3′ dihydroxybenzidine or 2,2‐bis(3‐amino‐4‐hydroxyphenyl)‐hexafluoropropane, with diacid chlorides containing both imide and hexafluoroisopropylidene groups. The soluble polymer precursor resulting from the first step of polycondensation in N‐methylpyrrolidinone (NMP) at low temperature was processed into thin flexible films, which were then thermally treated to reach the fully cyclized structure of poly(benzoxazole–imide)s, as observed by infrared spectra. An alternative way to produce the cyclization was by heating at reflux the solution of polymer precursor in NMP. Thermal stability, glass transition temperature, dielectric constant and its dependence on relative humidity have been studied and compared with those of related polybenzoxazoles and other heterocyclic Polymers.
Energetic polymers as binders in composite propellants and explosives
Authors: Colclough M. Eamon , Desai Hesmant , Millar Ross W. , Paul Norman C. , Stewart Malcolm J. , Golding Peter 
Published: April 2003

AbstractThe principles behind the use of polymeric binders in composite propellants and explosives are described with emphasis on the properties which they should possess in order to satisfy the requirements for inclusion in a composition. The desirability of using energetic polymers as binders in terms of both performance and safety, and the problems associated with their preparation and properties, are discussed. The contributions of chemical synthesis within DRA to overcome these problems will be shown. Preparation of energetic polymers both by polymer modification and by polymerization of an energetic monomer is described. We have developed three energetic polymers: poly‐3‐nitratomethyl‐3‐methyloxetane (polyNIMMO), polyglycidyl nitrate (polyG‐LYN) and nitrated hydroxy‐terminated polybutadiene (NHTPB). Two of these (polyNIMMO and polyGLYN) have shown excellent properties in propellant and explosive formulations and proved that low‐vulnerability, high‐performance compositions are possible. The properties of the products from our work are compared with those of other groups and a glimpse of the future in this area is given to show the potential for new energetic polymers.
Bimolecular photoinitiating systems of polymerization: photochemical behavior and radical efficiency
Authors: Mateo José Luis , Bosch Paula 
Published: April 2003

AbstractA key component in light‐induced radical polymerization is the photoinitiator which produces free radicals through a photochemical reaction. In the first part of this paper, a short analysis of the different steps that take place in the light‐induced radical polymerization using bimolecular photoinitiating systems is made. In the second part, the obtained results in the polymerization of acrylic monomers using conjugated and nonconjugated aminobenzophenones as photoinitiators are shown. A summary of the photochemical behavior of these photoinitiators together with several aspects related to the polymerization kinetics are described. The nature and efficiency of the produced radicals are studied as well as the reactivity of the radicals generated from the substituted dimethylanilines‐camphorquinone photoinitiation systems. Important mechanistic differences were found in the photochemical behavior and radical efficiency for the families of photoinitiators studied.
Approaches to molecular composites from fluorine‐containing bis‐maleimides: Part II
Authors: Pendharkar S. M. , Tesoro G. C. , Levon K. 
Published: April 2003

AbstractContinuing our research on molecular composites from fluorine‐containing bis‐maleimides (reported in this journal as Part I), we have prepared and characterized experimental composite films from a fluorine‐free bismaleimide (BMI) with Technora® fiber and from a fluorine‐containing system of BMI and rigid rod by rapid amine‐initiated anionic polymerization of the bis‐maleimide. We have also explored the effect of increasing amounts of initiator and of system composition on the film structure.
The first normal stress difference and viscosity in shear of liquid crystalline solutions of hydroxypropylcellulose: new experimental data and theory
Authors: Fried F. , Leal C. R. , Godinho M. H. , Martins A. F. 
Published: April 2003

AbstractThe constitutive equations for liquid crystalline polymers recently proposed by one of us [1] are applied here to interpret the behaviour of the shear viscosity η
$ \dot \gamma $ and the first normal stress difference N1($ \dot \gamma $) measured for liquid crystalline (LC) solutions of hydroxypropylcellulose in acetic acid. N1($ \dot \gamma $) is observed to change from positive to negative and again to positive, as the shear rate $ \dot \gamma $ increases, at lower concentrations, in the LC phase. The $ \dot \gamma $‐values at which N1 changes sign depend on the molecular mass (degree of polymerization) and on the concentration. η $ \dot \gamma $ shows a small Newtonian plateau at low shear rates and a strong shear‐thinning at higher values of $ \dot \gamma $. The rate of decrease of η $ \dot \gamma $ in this region shows an “hesitation” similar to one previously observed in LC solutions of poly‐γ‐benzyl‐L‐glutamate PBLG. All these observations can be rationalized within the frame‐work of Martins' theory. The expressions for N1($ \dot \gamma $) and η $ \dot \gamma $ derived from this theory fit very well (quantitatively) to the experimental data and some fundamental viscoelastic parameters of the system under study are thereby obtained for the first time.
Synthesis and properties of modified aramids
Authors: Berger Werner , Küchenmeister Frank 
Published: April 2003

AbstractThe purpose of this study was to determine the influence of different kinds of main chain modification of aramids on their thermal properties and solubility. The properties of polyamides synthesized by direct polycondensation using phosphorylation reaction depend strongly on the chemical architecture of the macromolecules. Polymers thus obtained were characterized by viscosity measurements, differential scanning calorimetry, thermogravimetry and solubility tests. These polyamides were distinguished by inherent viscosities in the range of 0.12–1.67 dl/g. The thermal transitions decrease in all cases of modification and the solubility is improved. Furthermore, the liquid crystalline properties of the polyamides were investigated. Thermotropic liquid crystalline behavior can be stated for a polyamide composed of 4,4′‐diaminodiphenylmethane (MDA) and sebacic acid (SEB) under shearing. Aromatic polyamides with kinks in their main chain exhibit lyotropic crystalline behavior whereas parallel displacement in the main chain prevent the formation of liquid crystals in solution.
Synthesis and thermal studies of heterocyclic siloxanes containing boron
Authors: Behbehani Haider S. J. , Brisdon Brian J. , McEnaney Brian 
Published: April 2003

AbstractEight‐ and six‐membered cycloborasiloxanes containing two and one boron atoms respectively are strained ring compounds which undergo ring opening polymerization and ring–ring transformation reactions on thermolysis. Prolonged heating at 200°C results in volatilization of the cyclic boroxine (PhBO)3, whereas rapid heating of either compound to 1500°C in an inert atmosphere does not result in loss of boron, but affords instead an amorphous residue containing silicon carbide, boron oxide and carbon. Upon further pyrolysis at 1700°C the final product consists of microcrystalline silicon carbide in which are embedded large crystals of boron carbide.
Adsorption of bovine serum albumin to acrylamide–itaconic acid hydrogels
Authors: Karadaǧ Erdener , Saraydin Dursun , Öztop H. Nursevin , Güven Olgun 
Published: April 2003

AbstractIn this study, acrylamide–itaconic acid hydrogels containing different amounts of itaconic acid prepared by irradiating with γ radiation are discussed. They have been used in experiments of swelling, diffusion and bovine serum albumin (BSA) adsorption. Maximum and minimum swellings were observed with water (1520%) and BSA (890%), respectively. Diffusion of water, NaCl and BSA within hydrogels were found to be non‐Fickian in character. In the experiments of BSA adsorption, type III adsorption was found. The hydrogel prepared with 60 mg itaconic acid and irradiated at 2.00 kGy was found to be the best adsorption system for BSA. The adsorption capacity of acrylamide–itaconic acid hydrogel was found to exceed that of acrylamide hydrogel by more than 80–100%.