bluuebunny/crossref_metadata_2025_split huggingface dataset:
Radiation resistance and molecular structure of poly(arylene ether sulfone)s
Authors: Hill David J. T. , Lewis David A. , O'Donnell James H. , Pomery Peter J. , Hedrick James L. , McGrath James E. 
Published: April 2003

AbstractThe radiation resistance of a series of aromatic polysulfones comprising alternating units of diphenyl sulfone and various aromatic diols has been investigated by measuring volatile products, soluble fractions and electron spin resonance (ESR) spectra. The yields of radicals at 77 K observed by ESR and of SO2 at 423 K have indicated that biphenol gives enhanced resistance to Y radiation, and tetramethyl bisphenol‐A decreased resistance, relative to bisphenol‐A, bisphenol‐S and hydroquinone. The protective effect of bisphenol was confirmed by lower scission and crosslinking yields determined from the soluble fractions after high doses.
Mechanical properties of solvolysis lignin‐derived polyurethanes
Authors: Nakamura Kunio , Mörck Roland , Reimann Anders , Kringstad Knut P. , Hatakeyama Hyoe 
Published: April 2003

AbstractIn order to study the tensile properties of solvolysis lignin polyurethanes, polyurethane (PU) films were prepared from the solvolysis lignin (SL)–polyethylene glycol (PEG)–diphenylmethane diisocyanate (MDI) system, and in addition to this further PU films were also prepared from the SL–MDI system. In the SL–PEG‐MDI system, the SL content, the molecular weight of PEG and the NCO:OH ratio were varied in order to control the physical properties. The tensile stress and Young's modulus of the PUs of the SL–PEG–MDI type increased with increasing SL content and NCO:OH ratio. The tensile properties of the PUs from the SL–MDI system showed no NCO:OH ratio dependency; i.e. the mechanical properties of PUs are not influenced by the change in crosslinking. It is possible to control the tensile properties of PUs of the SL–PEG–MDI type by changing the content of PEG and SL at a constant NCO:OH ratio.
Processable polyisoimide polymer blends for application as thermally stable adhesives for composites and advanced metal alloys
Authors: Boschan R. H. , Landis A. L. , Lau K. S. Y. , Quezada S. , Tajima Y. A. 
Published: April 2003

AbstractPolyimides are effective thermally stable bonding agents for substrates including titanium, aluminum alloys, steel alloys, metal matrix composites, and polymer/fiber composites with good tolerance toward elevated temperature and humidity.Problems associated with polyimide adhesives, including high processing temperatures and pressures and high melt viscosity, can be partially or totally alleviated by use of blends of polyisoimides. During thermal processing, the polyisoimides are isomerized to their polyimide modifications.
Fluorescence characteristics of europium ions stabilized in solid polymer electrolytes containing polyether structure
Authors: Ohno Hiroyuki , Lau Sim Peng 
Published: April 2003

AbstractPolyethylene oxide (PEO) oligomers can dissolve lanthanide salts. The terminal hydroxyl groups of PEO affect the solubility of the lanthanide salts in the PEO considerably. However, no intensive fluorescence was observed from Eu3+ dispersed in PEO or other ion‐conductive polymers containing terminal hydroxyl groups, because of the quenching effect of the terminal hydroxyl groups. Copolymer of ω‐methoxy oligo(oxyethylene) methacrylate and methyl methacrylate (P(MEOM‐co‐MMA)) could dissolve small amount of Eu(NO3)3, but the copolymer film containing Eu3+ shows intensive fluorescence (Ex = 269.0 nm, Em = 570.0 nm). This was prepared as a soft film, and there was a clear dependence of the Eu3+ concentration on the fluorescence intensity. A linear relation between the film thickness and the fluorescence intensity was also observed. Little fluorescence was found for Eu3+ in the blend of the corresponding two homopolymers, i.e. poly‐(ω‐methoxy oligo (oxyethylene) methacrylate) (PMEOM) and poly(α‐methyl methacrylate) (PMMA). This strongly suggests that intensive fluorescence requires a mixed state of MEOM and MMA units at molecular level.
Effect of substituent groups of diphenyl disulfide on novel cationic oxidative polymerization: examination of the electrophilic reaction of the cation by computational calculation
Authors: Shouji E. , Yamamoto K. , Katoh J. , Nishide H. , Tsuchida E. 
Published: April 2003

AbstractSubstituent groups of the diphenyl disulfides (DPSs) influence the cationic oxidative polymerization in the formation of polyphenylene sulfides (PPSs). A semiempirical MO calculation (AM1) was performed on the model compounds of PPS, such as thioanisoles (TAs) and diphenyl sulfides (PSs), in order to elucidate the reactivity of the cation. Linear PPS is formed on polymerization because of the high electron density of the carbon in the para position. The ratios of the frontier electron density of the carbon in the para position on the disulfide to the sulfur atom are ordered as follows; 3,5‐dimethyl‐PS>2,5‐dimethyl‐PS‐3‐methyl‐PS>nonsubstituted PS>2‐methyl‐PS>2,6‐dimethyl‐PS. The formation energies of the σ‐complex, which is the intermediate of the reaction, also shows the same order. The theoretical calculation indicates that 3,5‐dimethyl disubstituted disulfide and 3‐methyl one are most preferable monomers of this cationic oxidative polymerization.
Study of the carbon fiber–Poly(Ether–Ether–Ketone) (PEEK) interfaces, 4: influence of fiber–matrix adhesion on the mechanical properties of unidirectional composites
Authors: Nardin M. , Asloun E. M. , Schultz J. , Brandt J. , Richter H. 
Published: April 2003

AbstractThe aim of the last part of this general study is to analyze the influence of the interfacial properties and, more precisely, the adhesion energy, between carbon fibers and PEEK on the final performance of unidirectional composites. A set of mechanical properties, i.e. interlaminar shear strength, longitudinal tensile and compressive and transverse tensile properties, of different unidirectional laminates with the same content (60% by volume) of carbon fibers is determined. It is first shown that the interlaminar shear strength is constant, whatever the type of materials. Therefore, this test is not appropriate to characterize the strength of the fiber–matrix interface in PEEK‐based composites. On the contrary, in agreement with previous work on other systems, it appears that the ultimate properties (longitudinal tensile and compressive as well as transverse tensile strengths and strains) of the laminates increase with the interfacial adhesion energy, whereas the stiffness of these composites remains unaffected in all cases.
Temperature diffusivity and heat conductivity of Langmuir–Blodgett–Kuhn and thin spun‐on polymer films
Authors: Fischer Thomas M. , Knoll Wolfgang 
Published: April 2003

AbstractThe temperature diffusivity β and heat conductivity κ of thin polymer films were measured at room temperature. Temperature waves were excited at one side of the film and detected at the other side with a pyroelectric foil (PVDF). The dependence of β and κ on chemical and structural parameters have been studied. For the first time, Langmuir–Blodgett–Kuhn multilayer assemblies prepared from “hairy rod” polymers were characterized: μm thin films of stiff polyamides prepared by spincoating exhibit heat conductivities an order of magnitude larger than “classical” polymers.
Adsorption of anti‐human IgG to plasma‐polymerized allylamine film formed on a silver plate
Authors: Kurosawa Shigeru , Kamo Naoki , Muratsugu Makoto 
Published: April 2003

AbstractIncrease in the sensitivity of an immunosensor or biosensor requires the immobilization of a large amount of proteins. Good materials must be developed for this protein adsorption. Allylamine thin film was formed on a flat silver plate by plasma polymerization; this plate is referred to as Ag(ALAM). Ag(ALAM) films were characterized by SEM, FT–IR and ESCA. Investigations on adsorption and desorption of F(ab')2 anti‐human IgG (hIgG) on to Ag and Ag(ALAM) revealed the following: (1) The adsorption isotherm of F(ab')2 anti‐hIgG on to AG(ALAM) or Ag was of a Langmuir type. The binding constant (Kb) and saturation binding (Ab) for this protein on to Ag(ALAM) were 8.93 l/mol and 181.8 nmol/m2, respectively, and for Ag, were 7.71 l/mole and 87.9 nmol/m2. (2) The extent of desorption of labeled F(ab')2 anti‐hIgG absorbed on the two plates was the same. (3) Ag(ALAM) and Ag were used as solid phases in a two‐site immunoradiometric assay of human serum IgG. The dose‐response on AG(ALAM) occurred at lower concentration, and was of greater magnitude than that on Ag.
Kinetics of swelling of polyacrylamide gels: concentration profiles and effect of an imposed strain
Authors: Peters Arsène , Hocquart Roger , Candau Sauveur J. 
Published: April 2003

AbstractThe time course of the concentration profile of a spherical gel has been measured during a swelling experiment, and compared to the theoretical expressions. The swelling of a cylindrical gel under imposed strain has been studied both theoretically and experimentally. This provides a new method of determination of the ratio of the shear modulus over the osmotic longitudinal modulus.
Ion dissociation and conduction of Nafion/modified oligo(oxyethylene) composite films
Authors: Wang Yun Pu , Feng Han Yu , Fu Zheng Sheng , Tsuchida Eishun , Takeoka Shinji , Ohta Tomoyuki 
Published: April 2003

AbstractIn order to improve the ionic conductivity of solid polymer electrolyte by controlling ion(alkali metal ion)–dipole(ether oxygen) interaction, two kinds of modification were adopted on oligo(oxyethylene) (OOE). One is the capping of terminal hydroxyl groups of OOE with methyl or acetyl groups. The other is the replacement of the center ethylene group of OOE with methylene or propylene group. Ion–dipole interaction was analyzed by measuring the ion dissociation, ion conduction and Tg of Nafion/modified OOE composite films. The modification of the end groups was more effective than that of the center group in increasing ionic conductivity. The methyl group is superior to the acetyl group as the end group of OOE for lithium ion conduction.
Preparation of dehydrated powder of hemoglobin vesicles
Authors: Wang Lin , Takeoka Shinji , Tsuchida Eishun , Tokuyama Satoru , Mashiko Takahiro , Satoh Tadashi 
Published: April 2003

AbstractThe carbonyl hemoglobin (CO‐Hb), which was used to prevent denaturation (metHb) during the preparation of samples, was encapsulated into lipid vesicles constituted from unsaturated phospholipid, cholesterol and unsaturated fatty acid. Unsaturated components were polymerized by γ‐irradiation to enhance the stability of bilayer membrane. An aqueous dispersion of resulting Hb vesicles was freeze‐dried in the presence of saccharides (50–200 mM) to obtain a dehydrated powder of Hb vesicles. Change in the vesicle size, the leakage of encapsulated Hb and the oxidation of Hb to metHb were not observed. Therefore, the long‐term storage of Hb vesicles can be realized as a dry powder.
Shear flow experiments in an assembly of gel beads and modelling of bingham behavior
Authors: Lequeux François , Grosshans Daniel , Hocquart Roger 
Published: April 2003

AbstractIn this paper, we present a rheological study of a compact layer of highly swollen gel beads. The flow regimes of these systems are modelled by an elastic sinusoid moving in a Newtonian fluid. This model predicts a yield stress varying with the square root of the elastic modulus of the gel bead. The slope at the origin (at zero velocity) of the flow curve is expected to depend only on geometrical parameters and on the solvent viscosity. The experimental data are in qualitative agreement with the theoretical predictions.
Positive working photoresists sensitive to visible light, II: poly{2‐arylpropyl‐2 and bis(p‐methoxyphenyl)methyl methacrylates}
Authors: Ohe Yasushi , Ichimura Kunihiro 
Published: April 2003

AbstractAcid‐labile polymers of methacrylates of 2‐(p‐substituted phenyl)propanol‐2 and bis(p‐methoxyphenyl)methanol were evaluated as visible light sensitive positive‐type resists. The chemistry to form images is based on the cleavage of esters catalysed by an acid generated by photodecomposition of diphenyliodonium hexafluorophosphate sensitized by 2‐benzoyl‐3‐(p‐dimethylaminophenyl)‐2‐propenenitrile. A copolymer of bis(p‐methoxyphenyl)methyl methacrylate‐phenyl methacrylate exhibited a high photospeed upon exposure to 488 nm light when coupled with the iodonium salt and the dye, and was applicable to relief holography.
FT–IR microspectroscopy study of blends of ester functionalized ethylene–propylene copolymer with (vinylidene fluoride‐hexafluoropropene) elastomer
Authors: Benedetti E. , D'Alessio A. , Tong S. Y. , Ruggeri G. , Ciardelli F. , Moggi G. , Pianca M. 
Published: April 2003

AbstractAn ethylene—propylene (EPR) copolymer functionalized with (1,2‐dicarboethoxy)ethyl groups has been blended with a vinylidene fluoride—hexafluropropene elastomer (NML). The existence of intermolecular interactions involving mainly the carbonyl groups of the side chains of the functionalized copolymer and the methylene hydrogens of the fluoroelastomer through hydrogen bonding was shown by means of FT—IR spectroscopy. The structure and composition of some microdomains in the mixture was examined by means of FT—IR microspectroscopy.
Fast‐switching ferrolectric liquid crystalline polymers containing one or two centres of chirality in the side chain
Authors: Scherowsky Günter 
Published: April 2003

AbstractIn a liquid crystalline side chain polyacrylate containing one center of chirality in the terminal alkyl chain of the mesogenic part, switching times of 200–400 μs were measured in the SmC* phase. Below this phase an unidentified phase exists, which shows electroclinic‐like switching. The phase transition between those two phases can be shifted by applying an electric field.At higher molecular weights three subphases emerge in the SmC* region. Variation of the spacer length revealed, for the first time, ferroelectric switching even at a spacer length of only two CH2 groups.By shifting the centre of chirality into the spacer of the side group a polymer resulted, which shows electroclinic switching in the SmC* phase, changing to ferroelectric switching when the voltage is increased.Incorporation of an oxirane ring as chiral building block into the spacer yielded a polymer that shows a sign inversion of the spontaneous polarization in the SmC* phase.A polymer containing a dioxolane carbonic ester as chiral unit exhibits three switching states, with the third state existing at a low or zero electric field. This phenomenon is known for antiferroelectric liquid crystals.By doping a racemic LC polymer with a chiral monomeric LC we induced a spontaneous polarization. Colored FLC polymers were obtained by two different approaches. In an FLC–dye copolymer, increasing switching speed in three different chiral smectic phases was observed when increasing the dye concentration.
Collective and molecular dynamics in ferroelectric liquid crystals: from low molar to polymeric and elastomeric systems
Authors: Kremer F. , Schönfeld A. , Hofmann A. , Zentel R. , Poths H. 
Published: April 2003

AbstractBroadband dielectric spectroscopy delivers in the frequency range from 10 Hz to 1010 Hz two collective dielectric loss processes (soft and Goldstone modes) and one molecular relaxation (β‐relaxation). The soft mode and Goldstone mode are assigned to the fluctuation of the amplitude and the phase of the helical superstructure. The β‐relaxation corresponds to the libration (hindered rotation) of the mesogene around its long molecular axis. At the SmA–SmC* phase transition this process does not split or broaden, and the temperature dependence of its relaxation rate does not show any deviation from an Arrhenius‐like behavior. Its dielectric strength does not decline at the SmA–SmC* phase transition. These experimental findings are in contrast to the common explanation of the origin of the saturation polarization (“induced spontaneous polarization”), which is based on the existence of a “free” rotation inside the SmA phase and its strong hindrance in the ferroelectric SmC* phase. Furthermore, the high frequency results require a reformulation for the (generalized) Landau theory as applied to the SmA–SmC* phase transition. In comparing low molar mass and polymeric (elastomeric) FLC, the collective and molecular dynamics are qualitatively similar, independent of the molecular architecture (e.g. side‐chain, combined main‐ and side‐chain or crosslinked systems).
A novel method to determine the molecular weight of the oligomers of biodegradable polymer
Authors: Maniar Manoj L. , Advant Siddharth J. , Kalonia Devendra S. , Simonelli Anthony P. 
Published: April 2003

AbstractThe biodegradable polymers used in controlled release applications are primarily insoluble polymers which undergo chemical or enzymatic hydrolysis to form soluble monomeric or oligomeric units. To determine the endurance of the polymer after implantation or injection into the body it is important to determine the rate of elimination of the intermediates formed upon the hydrolysis of the polymer. It is essential to identify these intermediates before its elimination rate can be determined. Identification of these intermediates is a problem because they are difficult to isolate, and are thermally and hydrolytically unstable.A new technique is proposed, taking advantage of the neighboring group effect on the hydrolysis of ionic and non‐ionic oligomers, to determine the molecular weight of unknown species that are formed upon hydrolysis of the polymer. The technique involves the determination of the specific acid and base catalytic rate constants. To demonstrate the technique, a time sequence synthesis was carried out to synthesize several oligomers that would be forming upon the hydrolysis of poly(butylene tartrate). Hydrolysis studies were conducted with these oligomers and the samples were analyzed by liquid chromtography. The observed rate constant for the hydrolysis under acidic and alkaline pH medium were calculated from the terminal slopes of the first order plot. The observed rate constants were further utilized to calculate the specific acid and base catalytic rate constants. These specific rate constants, along with the micro‐hydrogen and ‐hydroxyl ion catalytic rate constants, were used to determine the molecular weight of the intermediate species.The molecular weight obtained from the kinetic parameters was in excellent agreement with the results obtained from fast atom bombardment mass spectrometry. The same type of analysis can be extended to any multifunctional group compound which has repeat units and can undergo a specific reaction which can be accurately measured.
Targeting polysaccharide–methotrexate conjugates to the rat brain
Authors: Sanzgiri Yeshwant D. , Blanton C. Dewitt , Gallo James M. 
Published: April 2003

AbstractDelivery of drugs to brain tumors is difficult due to the impermeability, and variable nature of the blood/tumor barrier. Of the various strategies designed to improve drug uptake‐intracellularly and into the brain, cationic carriers seem to offer an advantage. In the current investigation cationic polysaccharide–methotrexate conjugates were examined in the rat. Conjugates were prepared from N,O‐carboxymethyl chitosan (NOCC) and 3H‐methotrexate (MTX) by two different synthetic schemes, resulting in NOCCMTX‐1 and NOCCMTX‐2. NOCCMTX‐1 appeared to have a higher degree of cross‐polymerization than NOCCMTX‐2. Each conjugate and free MTX were administered intra‐arterially in a retrograde manner in the external carotid artery at a MTX dose of 1 mg/kg as a constant rate infusion over 30 min. Animals were sacrificed at various times after administration, and blood and tissue samples collected, processed in a sample oxidizer, and then measured for radioactivity. Brain MTX concentrations were 18‐ and 12‐fold greater at 15 min and 3 hr, respectively, following NOCCMTX‐1 administration compared to free MTX treatment. However, NOCCMTX‐1 resulted in animal death at about 12 hr after administration. NOCMTX‐2 was found to be non‐toxic, yet did not increase brain MTX concentrations compared to free drug administrations after correction for MTX in residual blood. Further investigations are planned to combine the positive drug targeting effect of NOCCMTX‐1 with the safety of NOCCMTX‐2.
Stimulation of trigeminal motoneurons by in vivo implantation of glutamate‐impregnated microspheres
Authors: Byrd Kenneth E. , Domb Abraham J. , Sokoloff Alan J. , Hamilton‐Byrd Elizabeth L. 
Published: April 2003

AbstractThe objective of this study was to alter biomechanical forces generated by the muscles of mastication that affect the growth of the craniofacial skeleton through the implantation of neurotransmitter microspheres to stimulate trigeminal motoneurons (TMNe) in vivo. Polyanhydride microspheres containing L‐glutamate were stereotaxically implanted 170–920 μm rostral to the left‐side trigeminal motor nucleus (TMNu) in 17 Sprague–Dawley rats at 33–38 days old. Seven rats received blank‐microsphere implants and two rats had empty delivery system penetration as controls. All rats were killed 10–14 days postsurgical for dissection, brain histology, osteometric data, and SEM analyses. Dimensions of the facial skeletons of glutamate‐microsphere rats showed significant (P<0.01, P<0.05) differences when compared to control animals. Glutamate‐microsphere animals also demonstrated significant (P<0.01) differences between the dimensions of their implant‐and nonimplant‐side facial skeletons. SEM analyses indicated that glutamate‐microsphere rats had greater implant‐side wear of their mandibular incisors compared to blank‐microsphere or delivery system controls. The skeletal alterations in the glutamate‐microsphere rats are hypothesized to be due to increased implant‐side TMNe and masticatory muscle activity patterns.
The effect of fiber coating on the tensile properties of ionomer‐based composites
Authors: Papaspyrides Constantine D. , Poulakis John G. 
Published: April 2003

AbstractAsbestos fibers, of the chrysotile variety, were coated with a thin polyamide film by an in situ polycondensation technique. Ionomer‐based composites were prepared containing the so‐modified asbestos fibers in a random in‐plane orientation; results of testing the tensile properties of these asbestos/polyamide/ionomer composites are presented. Parameters investigated comprise the asbestos content in the composite and the polyamide content deposited on asbestos. A significant improvement in the tensile performance was established, especially at the intermediate polyamide content of 3.4 phr. The behavior is discussed in terms of possible interactions between the phases present in the composite material.
A new approach to the design of surface treatments for reinforcing agents
Authors: Economy James , Jung Holger , Andreopoulos Andreas G. 
Published: April 2003

AbstractA new approach for design of improved interfacial bonding between carbon fibers and polymeric matrices is described. In this method the affinity of surface‐treated carbon fibers to various polymer matrices is simulated by analyzing the adsorption characteristics of model compounds, typical of the polymer units, onto very high surface area carbon fibers. The affinity can be evaluated by the use of Thermogravimetric Analysis (TGA) to measure adsorption–desorption characteristics. Since high surface area, activated carbon fibers (ACF) can be chemically treated to obtain acidic, basic, nonpolar or highly polar surfaces, it should be possible to assess the interactions of chemically modified surfaces with model compounds such as methanol (MeOH), acetone, dimethylformamide (DMF), dimethylether, tetrahydrofuran (THF) and water. Some preliminary results are presented, indicating that surface treatments for carbon fibers other than oxidation may lead to enhanced bonding with polymeric matrices.