bluuebunny/crossref_metadata_2025_split huggingface dataset:
Holographic recording using visible‐light sensitive polymers based on cationic polycondensation
Authors: Hotta Tsuyoshi , Yamaoka Tsuguo 
Published: April 2003

AbstractNegative‐working photopolymers based on a cationic polycondensation mechanism were developed. The photopolymers are highly sensitive to 488 nm argon ion laser light, because they use a chemically amplified reaction and are not sensitive to ambient oxygen. These photopolymers are composed of a poly(p‐hydroxystyrene) matrix, a hexamethoxy methylmelamine crosslinker and a 2,4,6‐tris(trichloromethyl)‐1,3,5‐triazine–coumarin dye combination as a photo‐initiator. They exhibit 0.6 mJ/cm2 (D0.7g) sensitivity to 488 nm light, as well as a high resolution of 0.5 μm. Due to their high sensitivity and high resolution, a relief‐type hologram, larger than 50 × 50 cm, can be recorded in a short exposure time using them.
Radiation degradation of poly(arylene ether ketone)s
Authors: Heiland Kirstin , Hill David J. T. , O'Donnell James H. , Pomery Peter J. 
Published: April 2003

AbstractThe resistance of five poly(arylene ether ketone)s with related chemical structures to degradation by ionizing radiation has been studied by ESR spectroscopy and yields of volatile products. All of the polymers showed high resistance to radiation with low yields of radicals after irradiation in vacuum at 77 K (when up to 84% of the radicals were identified as radical anions) and much lower yields at 300 K. The yields of volatile products were much less than reported for poly(arylene sulfone)s [1, 2]. Methyl substitution on a main‐chain aromatic ring decreased the radiation resistance, but methane only comprised 10% of the volatile products from the methyl‐substituted polymers. A polymer containing an isopropylidene group in the main chain and a substituent aromatic carbonyl showed significantly decreased radiation resistance. Extremely low radical yields were obtained after irradiation in air at 300 K, contrary to many polymers. XPS analysis showed an increase in C–O bonds on the surface after irradiation in air.
Miscibility enhancement in blends of polystyrene and polyisoprene modified with electron donor–electron acceptor groups
Authors: Cowie John M. G. , Demaude Alexi 
Published: April 2003

AbstractThe use of electron donor–electron acceptor groups to enhance miscibility in polymer blends has been investigated, using the immiscible binary pair polystyrene and polyisoprene as the basic materials. These polymers have been modified by copolymerization with monomers that are either donor or acceptor groups. The copolymers synthesized were poly(styrene‐stat‐N‐itaconimidyl‐3,5‐dinitrobenzoate), which contains the electron acceptor, and poly[isoprene‐stat‐N‐(2‐hydroxyethyl) carbazole methacrylate], which contains the electron donor. Blends were examined using differential scanning calorimetry and dynamic mechanical thermal analysis. The criterion of miscibility was taken to be the presence of only one glass transition temperature in the binary blend, and it was established that at least 20 mol% of the donor–acceptor units had to be incorporated into each chain before a stable one‐phase blend was obtained. Miscible blends were observed to undergo a “decomplexation” reaction above the blend Tg, to form partially phase separated blends, with each phase rich in one component and diluted by the second. The value of the blend Tg was above that expected from a weighted average of those of the components, indicating that specific intermolecular interactions, probably charge‐transfer complexes, which led to nonbonding crosslinking were present in the blend and stabilized the one‐phase system.
Kinetics of formation of charge transfer complexes of poly(vinyl pyridines) with iodine, 7,7′8,8′‐tetracyanoquinodimethane and 2,3‐dichloro‐5,6‐dicyano‐1,4‐benzoquinone by electronic spectroscopic studies
Authors: Palaniappan Srinivasan , Sathyanarayana Dixit N. 
Published: April 2003

AbstractThe kinetics of formation of charge transfer complexes of poly(4‐vinyl pyridine), poly(2‐vinyl pyridine), and poly(2‐vinyl pyridine‐co‐styrene) with iodine, 7,7′,8,8′‐tetracyanoquinodimethane and 2,3‐dichloro‐5,6‐dicyano‐1,4‐benzoquinone has been studied using electronic absorption spectroscopy. The charge transfer complexes of analogous low molecular weight donors, namely 2‐ and 4‐picolines with the same set of acceptors have also been investigated for comparison. The composition and the equilibrium constants of the charge transfer complexes have been obtained. The equilibrium constant of the polymeric complexes is found to be higher than that of analogous complexes of the low molecular weight donors. A new method for determining the rate constants of the association and dissociation of the equilibrium involving the charge transfer complex formation has been proposed. The rate constants vary with the concentration of the acceptor. It indicates that the charge transfer complexes undergo a further reaction and hence the observed rate constants are not true but apparent rate constants. The charge transfer complexes have also been investigated by electron paramagnetic resonance spectroscopy.
Photoelectrodes based on acceptor–donor assemblies in functionalized polypyrrole films
Authors: Deronzier Alain 
Published: April 2003

AbstractThe capability to act as molecular photoelectrodes under visible light irradiation of optically transparent electrodes (ITO) modified by thin films of polypyrrole containing several kind of electron acceptor–donor assemblies has been examined. Photolysis of electrodes coated by thin films of polypyrrole substituted by a reversible electron donor (phenothiazine) in the presence of an irreversible electron acceptor (tropylium cation) in acetonitrile gives weak photocurrents. In contrast, appreciable photocurrents can be obtained using a symmetrical arrangement; viologen as reversible electron acceptor, benzilate anion as irreversible donor. The photoresponses result from the photo‐induced charge separation of the charge transfer complexes created in the film. The measured photocurrents are markedly larger (up to five times), with films of polypyrrole substituted by a reversible electron acceptor (viologen) covalently linked with a donor (phenothiazine, triphenylamine or benzidine) than with the unimolecular immobilized system in similar experimental conditions. The greater efficiency of these materials is attributed to the formation of an intramolecular charge transfer complex occurring inside films between the two molecular entities. Markedly weaker photocurrents are obtained with polypyrrole films based on bilayers of the two independent components than those with the unimolecular design, while films based on copolymers arrangements give moderately weaker photoresponses.
Synthesis and thermal properties of side‐chain liquid crystalline polyethers with racemic and chiral backbone
Authors: Taton Daniel , Borgne Alain Le , Spassky Nicolas , Friedrich Claude , Noël Claudine 
Published: April 2003

AbstractRacemic and chiral [(4‐cyano‐4′‐biphenyl)oxy] and [(4‐methoxy‐4′‐biphenyl)oxy]methyloxiranes were prepared from racemic epichlorohydrin or racemic and chiral glycidols and polymerized in dimethylsulfoxide (DMSO) with ButOK as the initiator system. Initial phase identifications were made by differential scanning calorimetry (DSC) and optical microscopy techniques and confirmed by X‐ray diffraction measurements. Upon heating, all the monomers show only a crystal–isotropic phase transition. The racemic and chiral [(4‐cyano‐4′‐biphenyl)oxy]methyloxiranes exhibit a nematic and a cholesteric monotropic phase, respectively. Methoxybiphenyl substituted polyethers are crystalline and insoluble in virtually all common solvents. Cyanobiphenyl substituted polyethers are soluble under the same experimental conditions and show enantiotropic liquid crystalline properties. The racemic polymer exhibits a nematic phase, while the optically active polymer forms a cholesteric phase.
Synthesis of poly(2,5‐dimethylphenylene sulfide) through oxidative polymerization of sulfur chloride with p‐xylene
Authors: Miyatake Kenji , Jikei Mitsutoshi , Katoh Junya , Yamamoto Kimihisa , Nishide Hiroyuki , Tsuchida Eishun 
Published: April 2003

AbstractPoly(2,5‐dimethylphenylene sulfide) was prepared by oxidative polymerization of sulfur chloride with p‐xylene using 2,3‐dichloro‐5,6‐dicyano‐p‐benzoquinone (DDQ) as an oxidizing agent. The reaction proceeded efficiently under atmospheric pressure and at room temperature. The polymer formed had a high melting temperature and linear structure which was confirmed by spectroscopies. The effects of reaction time, solvent, temperature and oxidizing agent on polymerization are also discussed.
Composition and spectral studies of polyaniline salts
Authors: Palaniappan S. , Narayana B. H. 
Published: April 2003

AbstractFive different polyaniline salts have been prepared by chemical polymerization of aniline in aqueous solution of different acids. The polyaniline base was obtained from the corresponding polyaniline salt by dedoping using aqueous ammonium hydroxide solution. Electron paramagnetic, electronic absorption, infrared spectral and conductivity measurements have been performed on the polyaniline salts and polyaniline bases. This composition and the extent of dopant in polyaniline salt systems have been determined. There is no definite correlation between the conductivity and the stoichiometric ratio between the polyaniline base and the acid, and also the spin concentration.
New photochromic inorganic/organic hybrid siloxane gels with chemically bonded spirobenzopyran moiety
Authors: Nakao Ren , Ueda Norikazu , Abe Yasuo , Horii Toyokazu , Inoue Hiroo 
Published: April 2003

AbstractTransparent photochromic inorganic/organic hybrid gels involving the Chemically bonded spirobenzopyran moiety have been prepared by the sol–gel reactions using tetraethoxysilane, the silanol‐terminated oligomeric poly(dimethylsiloxane), and spirobenzopyrans with the alcoxysilyl groups.
The moisture absorption characteristics of crosslinked vinyl terminated polyethers compared with epoxies
Authors: Barton Stephen J. , Pritchard Geoffrey 
Published: April 2003

AbstractProcessable and practically useful thermosetting resins are almost invariably highly polar. For this and other reasons they can absorb considerable moisture, which affects their physical, electrical and mechanical properties. Crosslinked vinyl terminated oligomeric polyethers (VTPs) of very low polarity are described and their moisture absorption characteristics are compared with those of a standard amine cured Epikote 828® epoxy resin cured with metaphenylene diamine (MPD). The equilibrium moisture absorption of the vinyl terminated polymers is about one‐tenth of that of the epoxy system, but their diffusivity is higher. The dependence of the equilibrium uptake on temperature, relative humidity, specimen thickness and oligomer proportions is discussed. The effect of moisture saturation on the d.c. volume resistivity is considered. Moisture prevents the resin from obeying Ohm's law.
Effect of carrier concentration on the facilitated oxygen transport in a polymer membrane
Authors: Suzuki Takayuki , Nishide Hiroyuki , Itakura Keita , Tsuchida Eishun 
Published: April 2003

AbstractFacilitated transport of oxygen in a solid Polymer membrane containing cobaltporphyrin (CoP) which carries oxygen specifically and reversibly, leads to permselectivity of oxygen against nitrogen in the membrane. The increase in concentration of the CoP carrier is expected to enhance the oxygen transport. The membranes of poly(octylmethacrylate‐co‐vinylimidazole) containing 0.8 ∼ 10 wt% CoP were prepared, and the effects of the CoP‐concentration on the transport and the diffusion constants of oxygen are studied. Although the induction period before the steady state of oxygen permeation was prolonged with the CoP concentration in the polymer membrane, the glass transition temperature (Tg) of the membrane was increased and the diffusion constants of oxygen were decreased with the CoP concentration to yield unexpected reduction of the oxygen permeation in the highly CoP loaded membrane.
Synthesis of unsaturated polyester resins for large sized composites
Authors: Abdel‐Azim A. A. , Mahmoud B. H. , Farhat M. S. 
Published: April 2003

AbstractA series of unsaturated polyesters based on phthalic anhydride (PHA), maleic anhydride (MA), ethylene glycol (EG), diethylene glycol (DG), triethylene glycol (TG), propylene glycol (PG), styrene (Sty) and acrylonitrile (AN) were prepared. The molecular weights of the prepared polyesters were determined by end‐group analysis. The effect of the structure of the resin on its curing behavior has been investigated. On the basis of the experimental study, the following were concluded: (1) The maximum curing temperature (Tmax) is related to the molecular weight of the glycol incorporated in these castings. In this context the Tmax was found to decrease with increasing the molecular weight. Meanwhile the time to peak temperature tmax was increasing. (2) The higher the percentage of AN in the crosslinking monomer system, the slower a resin cures. (3) The values of Tmax were found to be influenced to a large extent by the percentage of AN.
Thermostable poly(p‐phenylene sulfide sulfonic acid) as ion exchangers
Authors: Song H. Y. , Miyatake Kenji , Yamamoto Kimihisa , Tsuchida Eishun 
Published: April 2003

AbstractPoly(p‐phenylene sulfide sulfonic acid) was thermally crosslinked for use as a cation exchange polymer with high thermal stability. The decomposition temperature (Td) of the polymer increases with an increase in the crosslinking temperature. The crosslinking reaction at 300°C in air resulted in the formation of a strongly acidic cation exchange polymer with a T = 467°C and having an SO2 bond, whose crosslinked structure was investigated using IR spectroscopy.
Synthesis and characterization of conductive polypyrrole grown on the sulfonated surface of polyethylene films
Authors: Berdjane Z. , Rueda D. R. , Balta‐Calleja F. J. 
Published: April 2003

AbstractChemical synthesis of polypyrrole (PPy) was carried out in the presence of FeCl3 aqueous solution. The grown PPy is fixed on the sulfonated surface of polyethylene (SPE) films, where the sulfonic groups act as counteranions to balance the positive charge of PPy, giving the composite material of PPy–SPE.For reasons of comparison, two types of polyethylene (PE) have been used, low and high densities with different degrees of sulfonation, SD (g/m2), defined as the ratio of weight increase to the area of the two surfaces of the sample. A series of reaction times was used to evaluate the variation of the electrical conductivity, σ (S/cm), of polypyrrole. It was found that σ increases as reaction time increases.To characterize the samples, Fourier transform infrared (FTIR) spectroscopy and conductivity measurements were performed.
Morphological modification of UHMPE fibers
Authors: Economy J. , Andreopoulos A. G. 
Published: April 2003

AbstractUHMPE fibers can display several morphological features, including skin‐core, microfibrillar and shish‐kebab structures. In this work, an attempt was made to eliminate these morphologies by treating the UHMPE in a two‐roll mill, at temperatures ranging from ambient to 145°C. Up to 130°C the tensile strength and modulus of the fiber were retained, and thermal analysis and crystallographic data showed that ordering in the fiber remained intact. The shish‐kebab and microfibrillar morphologies were greatly reduced and the fiber cross‐section was altered from circular to a flat ribbon.
The effect of electrochemical surface treatments of carbon fibers using scanning tunneling microscopy
Authors: Donnet Jean‐Baptiste , Park Soo‐Jin , Wang Wei‐Dong 
Published: April 2003

AbstractScanning tunneling microscopy (STM) has been applied to the study of the topography of polyacrylonitrile (PAN)‐based carbon fibers before and after electrochemical surface treatments. The results show that the electrical anodic oxidation only changes the surface aspects; at nanometric resolution; the nanostructure and nanotexture such as the step‐like crystallite stacking are decreased with increasing electric current densities.
Conformation and electrochemical reduction of myoglobin in PEO oligomers
Authors: Ohno Hiroyuki , Ohkubo Waki , Yamaguchi Natsue 
Published: April 2003

AbstractHorse‐heart myoglobin (Mb) was modified with poly(ethylene oxide) (PEO) to solubilize it in PEO oligomers. PEO‐modified Mb (PEO–Mb) showed a quasi‐reversible electrochemical redox reaction in PEO200 (molar mass of 200 g). PEO–Mbs, modified with lower molecular weight of PEO chains, were soluble in PEO oligomers with wider range of molecular weight. A conformation of PEO–Mb was studied with circular dichroism spectroscopy in phosphate buffer solution (PBS) or PEO oligomers. The α‐helix content of PEO–Mb, determined by the molar ellipticity at 222 nm, decreased from 71% to about 58% after PEO modification. However, the degree of PEO modification did not affect the α‐helix content of PEO–Mbs. On the other hand, the α‐helix content of PEO–Mbs was reduced by lowering the molecular weight of the modified PEO chains. Since the α‐helix content of PEO–Mb in PBS and that in the PEO oligomers were almost identical, the conformation of PEO–Mb in PBS was considered to be maintained even in PEO oligomers. Although the reduction rate constant of PEO–Mb in PEO oligomers depended on the total molecular weight of the PEO–Mbs, their relation did not obey the Stokes–Einstein equation. The reduction of the PEO–Mb was probably affected by the interfacial electron transfer process at the electrode surface rather than by diffusion in the PEO oligomer.
Molecular basis of healing and fracture at polymer interfaces
Authors: Sperling Leslie H. , Klein Andrew , Sambasivam Mahesh , Kim Kyung Don 
Published: April 2003

AbstractThe interdiffusion of polymer chains across a polymer–polymer interface, and subsequent fracture to re‐create the interface is reviewed. In particular, films formed via latex coalescence provide a very large surface area. Of course, latex film formation is a very important practical problem. Healing of the interface by interdiffusion is treated using the de Gennes reptation theory and the Wool minor chain reptation model. The self‐diffusion coefficients of polystyrene and the polymethacrylates obtained by small‐angle neutron scattering, SANS, direct non‐radiative energy transfer, DET, and other techniques are compared. Reduced to 150,000 g/mol and 135°C, both polystyrene and poly(methyl methacrylate) have diffusion coefficients of the order of 10−16−10−17 cm2/sec. Variations in the diffusion coefficient values are attributed to the experimental approaches, theoretical treatments and molecular weight distribution differences. An activation energy of 55 kcal/mol was calculated from an Arrhenius plot of all polystyrene data reduced to a number‐average molecular weight of 150,000 g/mol, using an inverse square molecular weight conversion method. Interestingly, this is in between the activation energies for the α and β relaxation processes in polystyrene, 84 and 35 kcal/mol, respectively. Fracture of polystyrene was considered in terms of chain scission and chain pull‐out. A dental burr apparatus was used to fracture the films. For low molecular weights, chain pull‐out dominates, but for high molecular weights, chain scission dominates. At 150,000 g/mol, the energy to fracture is divided approximately equally between the two mechanisms. Above a certain number average molecular weight (about 400,000 g/mol), the number of chain scissions remains constant at about 1024 scissions/m3. Energy balance calculations for film formation and film fracture processes indicate that the two processes are partly reversible, but have important components of irreversibility. From the interdiffusion SANS data, the diffusion rate is calculated to be about 1 Å/min, which is nine orders of magnitude slower than the dental burr pull‐out velocity of about 0.8 cm/sec.
Three‐component photopolymer based on a novel mechanism: acid‐catalyzed polymerization and decoupling of crosslinks
Authors: Kamenosono Koji , Naitoh Kazuhiko , Kondo Syun‐ichi , Umehara Akira , Yamaoka Tsuguo 
Published: April 2003

AbstractThree‐component photopolymers comprising a photoacid generator, a bifunctional vinyl ether monomer and an aqueous base‐soluble polymer as matrix were developed. These photopolymers exhibit either positive‐ or negative‐working character, depending on the prebake temperature and the concentration of the photoacid generator. When the prebake temperature is high, the photo‐polymer film is made insoluble in aqueous base and organic solvents by the formation of crosslinks. However, on exposure to light, the crosslinks are decoupled by the photogenerated acid and the photopolymer layer becomes again soluble in aqueous base, resulting in a positive‐working character. When the concentration of the photoacid generator is low enough, the photopolymer has a negative‐working character due to the cationic polymerization of vinyl ethers. The mechanism of the photochemical reaction of the photopolymers was investigated to elucidate the complicated behavior.
Thermal behavior of bismaleimide resin
Authors: Regnier N. , Mortaigne B. 
Published: April 2003

AbstractThe cure of a bismaleimide (BMI) neat resin modified with an aromatic diamine and a siloxane elastomer, has been studied by 13C solid state nuclear magnetic resonance. Two chemical reactions occur during the cure cycle; at a low temperature, Michael's reaction predominates, while at a high temperature the polymerization of the double bond maleimide creates the network.The degradation of this BMI material was characterized with isothermal and dynamic thermogravimetric analyses in air and in nitrogen. The BMI thermal stability is lower in nitrogen than in air. This behavior is an indication of oxygen participating in reactions at high temperatures.The activation energy (Ea) of thermal degradation was determined from isothermal data using an Arrhenius equation (In V vs. 1/T). The global Ea for the weight loss in air was found to be 91 kJ/mol.The nature and the evolution of the thermal degradation products were the combined analyzed by techniques of pyrolysis, gas chromatography and mass spectrometry. The major thermal decomposition products obtained in the temperature range of 300–700°C are identified as benzene, methyl formamide, aniline, toluene and isocyanate‐derived products.
The synthesis and properties of adducts between poly(4‐vinyl pyridine) and metal alkyls
Authors: Li Xiaochang , Foster Douglas F. , Cole‐Hamilton David J. 
Published: April 2003

AbstractPoly(4‐vinyl pyridine) is used as a polymeric ligand to react with metal alkyls, MenM (n = 3, M = Al, Ga or In; n = 2, M = Cd or Zn) to form adducts. The adducts are characterized by solid state 13C NMR, infrared spectroscopy, microanalyses and differential scanning calorimetry (DSC). All the adducts are nonpyrophoric and thermally dissociable, so they may have potential both for use in adduct purification processes or for use as safer metal alkyl sources for Metal–Organic Chemical Vapor Deposition.