bluuebunny/crossref_metadata_2025_split huggingface dataset:
Interfacial tension of blends containing thermotropic liquid crystalline polymers
Authors: Kenig S. 
Published: April 2003

AbstractA method is proposed to determine the interfacial tension of immiscible blends containing a liquid crystalline polymer (LCP) and a flexible‐molecule polymer, under flow conditions.The method is based on Taylor's theorem for immiscible fluids, i.e., that a suspended drop of liquid A in liquid matrix B is deformed in shear or elongational flow in proportion to the ratio of interfacial to viscous stresses. Taylor's theorem, as originally derived, applies to low concentrations, Newtonian fluids and small deformations. Thus, the theorem was modified to account for “Power Law” fluids in elongational flow and large deformations, more applicable to the system under investigation.The elongational viscosities of the LCP and the flexible polymer (polycarbonate) as a function of elongational rate were determined using converging type flow. The two polymers exhibited a Power‐Law behavior in elongational flow and, hence, the experimental constitutive equations of state were used to quantify the viscous stresses.The interfacial stresses were modified for large deformations by taking into consideration the deformed shape and hence increased surface area of the elongated LCP particle. Using the modified expression, the interfacial tension of LCP and PC was determined to be in the range of 5–6.6 dyne/cm.
The Poole–Frenkel effect on nitrated poly(N‐vinylcarbazole)
Authors: Zamora F. , Franco A. D. , González M. C. 
Published: April 2003

AbstractIn studying electrical conduction of nitrated poly(N‐vinylcarbazole) (PNVC), several homodispersed samples of PNVC were nitrated by using two different nitration methods, resulting in mononitrated and dinitrated PNVC, respectively, with a really distinct polymer bulk structure which is responsible for the response of the charge carriers to an applied electric field. Electrical behavior in mononitrated PNVC is due to charge transfer complexes, while in dinitrated PNVC it is due to a dipole orientation effect.
Design of oxidation‐resistant coatings for high‐temperature composites
Authors: Jung Holger , Economy James 
Published: April 2003

AbstractFabrication of oxidation‐resistant carbon fiber reinforced carbon composites requires use of high‐temperature CVD deposition of coatings such as SiC. In this paper the use of low‐temperature chemical approaches for depositing oxidation‐resistant coatings was explored. Coatings of SiO2, B2O3, and SiC were examined, with the intent of distinguishing possible failure mechanisms. Factors contributing to poor oxidation resistance of these coatings include presence of microcracks in the original preparation of the coating and diffusion of oxygen through the coating at high temperatures.
Precipitation temperature of poly(ethylene glycol) in some electrolyte solutions
Authors: Oun A. M. , Daudi B. M. , Omar M. M. 
Published: April 2003

AbstractThe effect of sodium fluoride, sodium bromide, tetramethyl ammonium chloride, tetramethyl ammonium bromide and sodium formate on both precipitation and θ‐temperatures of poly(ethylene glycol) (Mw = 4000) in aqueous solution have been determined. Curves have been drawn to represent the effect of such ions on both the θ and the precipitation temperatures of the polymer. The effectiveness increases in the order (CH3)4 NBr, NaBr, (CH3)4NCl, NaF and HCOONa. The Mw‐temperatures obtained at infinite dilution are 445 K for NaBr, NaF, (CH3)4 NBr and (CH3)4NCl and 415 K for HCOONa.
Properties of glass‐fiber reinforced composites based on liquid diglycidyl ether of bisphenol‐c‐epoxy resin
Authors: Soni H. K. , Patel V. S. , Patel R. G. 
Published: April 2003

AbstractGlass‐fiber reinforced epoxy composites were fabricated from the matrix resin liquid diglycidyl ether of bisphenol‐C (DGEBC) using various amines as curing agents with and without fortifier (20 phr). The epoxy laminates were evaluated for their mechanical properties, such as flexural strength, interlaminar shear strength (ILSS), tensile strength and shore‐D hardness. Dielectric properties, such as the dielectric constant, tan δ, dielectric loss and the resistivity of the laminated samples, were measured. The effect of the chemical reagents on the mechanical properties (i.e. flexural strength, lLSS) was also studied.
Positive working resists sensitive to visible light, I: poly(tert‐butyl and 2‐phenylpropyl‐2 methacrylates) sensitized with diphenyliodonium salt — p‐aminobenzylidene dye system
Authors: Ohe Yasushi , Ichimura Kunihiro 
Published: April 2003

AbstractVisible‐light‐sensitive positive type resists have been developed. The chemistry to form images is based on the cleavage of side chain ester bonds of poly(methacrylates) catalyzed by an acid which is generated on sensitized photodecomposition of a diphenyliodonium (DPI) salt. Homopolymers and copolymers of tert‐butyl methacrylate (BMA) and 2‐phenylpropyl‐2 methacrylate (PPMA) were used as acid labile polymers. Exposure of thin films of the poly(methacrylates) containing DPI salt and p‐dimethylaminobenzylidene derivatives to an Ar laser beam emitting 488 nm light and subsequent heat treatment resulted in solubility alteration of the polymers, which became soluble in a protic solvent system. Considerable reduction of film thickness was observed after heating an image‐wise exposed thin film of PPMA polymers. The minimum exposure energies of 488 nm light for the positive image formation were 60 mJ/cm2 and 40 mJ/cm2 for BMA and PPMA homopolymers, respectively.
Phase transition of layer structure of poly(p‐benzenedithiol‐co‐p‐diethynylbenzene) by heat or photon mode
Authors: Kobayashi Eiichi , Ohashi Toyoshi , Furukawa Junji 
Published: April 2003

AbstractPhase transition of the layer structure of poly(p‐benzenedithiol‐co‐p‐diethylbenzene) obtained in solid state polymerization was studied by a thermal treatment or UV irradiation under a nitrogen atmosphere. The peak intensities in the X‐ray diffraction diagram of polymers gradually decreased with the thermal treatment time above 55°C. Below 50°C the layer structure of polymers hardly changed. The apparent activation energy for the phase transition was about 15 Kcal/mol [63 KJ/mol] at the initial stage and gradually decreased to a few Kcal/mol [ca. 2 KJ/mol]. UV light from a high‐pressure mercury lamp also gradually induced the phase transition from the layer structure to an amorphous one. The pristine polymer possesses phase transition points at 75, 95 and 130°C. The exothermic transition at 75°C can be understood as the thermal destruction of the semistable layer structure. The exothermic transition at 95°C may be correspond to the cis → trans thermal isomerization of the C°C bond in the polymer main chain.The diffuse reflectance spectrum of the pristine polymer differed from that of the amorphous polymer obtained by the thermal treatment of the pristine polymer. SEM photographs of the pristine polymer showed a particular surface structure, i.e. entangled fibrous material. TEM photographs of the pristine polymer exhibited a bright valley‐and‐hill structure, whereas that of the amorphous polymer obtained by thermal treatment exhibited a plain surface.
The effect of PVAc on the efficiency of thermal reactions in PS/PVAc blends in relation to the atmosphere
Authors: Kamińska A. , Kaczmarek H. 
Published: April 2003

AbstractThe thermal stability of polystyrene (PS) blends with polyvinyl acetate (PV Ac) has been investigated. It was found that PV Ac acts as a sensitizer of the thermal degradation of these blends when the process takes place in a nitrogen atmosphere. In air PV Ac acts as a stabilizer, and the temperature of the decomposition of these blends is higher than that of pure PS. This stabilization is caused by PV Ac favoring an oxidation reaction without breaking the polymer chains.
Modification of mono‐dispersed silica colloid particles with polymer silane coupling agents
Authors: Yoshinaga Kohji , Horie Ryouhei , Saigoh Futoshi , Kito Taketoshi , Enomoto Naoyuki , Nishida Hiroyasu , Komatsu Michio 
Published: April 2003

AbstractThe reaction of monodispersed silica colloid with hydrophobic and hydrophilic polymer coupling agents in the presence of ammonia afforded dispersible polymer/SiO2 composites into organic solvents without aggregation.
Acid generation and deprotecting reaction by diphenyliodonium 9,10‐dimethoxyanthracene‐2‐sulfonate in a novolak positive photoresist based on chemical amplification
Authors: Naitoh Kazuhiko , Yamaoka Tsuguo , Umehara Akira 
Published: April 2003

AbstractIn a positive photoresist composed of diphenyliodonium 9,10‐dimethoxyanthracene‐2‐sulfonate as a novel photoacid generator, bisphenol A protected with tertbutoxycarbonyl group as a dissolution inhibitor, and a novolak resist matrix, the efficiency of photo‐acid generation and deprotective reaction were investigated by means of UV‐visible and IR spectroscopies. The quantitative measurement of photogenerated acid by using the acid‐sensitive dye exhibited 0.18 as the quantum yield of acid generation in novolak resin film. The lithographic evaluation of this system as a chemically amplified resist was studied. The catalytic chain length for the acid‐catalyzed deprotection step was determined as about 100 when 10 min post‐exposure bake (PEB) at 80°C was given. The sensitivity and the resolution as a positive resist are 180 mJ/cm2 and higher than 1 μm, respectively under the PEB conditions mentioned above.
Dielectric, magnetic and mechanical properties of ferrite composites
Authors: Biernholtz H. , Kenig S. , Dodiuk H. 
Published: April 2003

AbstractThe dielectric and magnetic properties of carbonyl—iron (CI) and nickel zinc ferrite polymer composites were studied with respect to the ferrite particulate content and microwave frequency. From the experimental data and using empirical models that relate the composite dielectric and magnetic properties, the respective dielectric and magnetic properties of the neat fillers were estimated. The tensile properties of the particulate composites comprising CI were shown to follow qualitatively Mooney's equation for the elastic modulus. The tensile strength of an elastomeric polyurethane and PVC composites containing CI increased with particulate content, while the elongation to break decreased with filler content. SEM micrographs of tensile fracture surfaces indicated that somewhat better adhesion is obtained in the case of the polyurethane‐based composites compared to the PVC ones.
Temperature‐dependences of cationic mobility and carrier generation in solid polyether media
Authors: Xu Kang , Wan Guoxiang , Tsuchida Eishun 
Published: April 2003

AbstractThe temperature‐dependences of cationic conductivity and mobility in a macromolecular lithium salt/copolyether blend were investigated by means of complex impedance analysis and a time‐of‐flight technique, respectively. The transient ionic current after reversing the d.c. bias polarity exhibits two peaks, corresponding to cationic and anionic movement respectively, and verifying a cationic transfer number of 0.99 at 50°C. The comparison between conductivity and mobility makes it possible to reveal the temperature‐dependence of the cation carrier number. As a result, the population of free ions was found to decrease exponentially with increasing temperature. However, this “anomalous” behavior of salt dissociation has little effect on the temperature‐dependence of conductivity, since it is cation carrier mobility rather than its number which is the main factor influencing the ion transport process.
A new method of growing crystalline networks in polymer matrices by simultaneous CT complex formation and in situ crystallization
Authors: Jeszka Jeremiasz. K. , Tracz Adam 
Published: April 2003

AbstractA new method of preparing conductive polymer composites by growing crystalline networks of conductive additives in polymer matrices (reticulate doping) is described. The method consists of treating the polymer containing molecularly dispersed donor additive with acceptor/solvent vapors. In the swollen polymer layer simultaneously CT complex formation and crystallization takes place which for proper conditions leads to the formation of a network of the CT complex crystallites, making the film surface‐conducting.The preparation and properties of surface conductive films using several electron donors and an iodine acceptor are described. The films obtained show surface resistivities of 104–106 ohm and are generally stable under ambient conditions.
Synthesis of polymers having photocrosslinkable moieties for second‐order nonlinear optics
Authors: Hashidate Sadahito , Nagasaki Yukio , Kato Masao , Okada Shuji , Matsuda Hiro , Minami Nobutsugu , Nakanisi Hachiro 
Published: April 2003

AbstractSecond‐order non‐linear optical polymers having photocrosslinkable moieties were synthesized by cationic polymerization of monomer (I) and monomer (II). The polymerization proceeded rapidly to give linear polymers in high yields. Monomer reactivity ratios were calculated to be r1 = 0.90 and r2 = 0.96 (r1r2 = 0.86), indicating that these monomers copolymerized through the almost ideal copolymerization mechanism. The photocrosslinking reaction of an equimolar copolymer film underwent the conversion of up to ca. 70% upon irradiation with a 500 W high‐presure mercury lamp for 5 min. The electric field induced polar orientation of the chromophores (pendant 4‐nitrophenyloxy groups) in a photocrosslinked polymer was stable for more than 10 days. This polymer exhibits a nonlinear coefficient d33 of 5.6 × 10‐10 esu measured at a pumping wavelength of 1064 nm.
Thermal properties of solvolysis lignin‐derived polyurethanes
Authors: Nakamura K. , Hatakeyama T. , Hatakeyama H. 
Published: April 2003

AbstractThermal properties of polyurethane (PU) films prepared from solvolysis lignin (SL), polyethylene glycol (PEG) and diphenylmethane diisocyanate (MDI) were examined by differential scanning calorimetry and thermogravimetry. In the SL—PEG—MDI system, the SL content, the molecular weight (Mn) of PEG and the NCO/OH ratio were changed in order to control the thermal properties. Glass transition temperatures (Tg's) of the prepared PU's were dependent on the SL content, the Mn of PEG and the NCO/OH ratio. However, the Tg of PU was significantly influenced by the SL content: the increment of Tg was ca. 150 K when the SL content in PEG increased from 0 to ca. 50%. The decomposition of the PU's was markedly dependent on the content of SL. Other factors, such as the NCO/OH ratio and the Mn of PEG, are less dominant compared with the SL content. This fact suggests that the dissociation between the isocyanate groups and the phenolic OH groups in SL may be the major factor in the whole process of the thermal decomposition of the PU containing SL
Helical unwinding in polymer‐dispersed ferroelectric liquid crystals
Authors: Kitzerow Heinz‐ S. , Molsen Henning , Heppke Gerd 
Published: April 2003

AbstractWe demonstrate that ferroelectric liquid crystals dispersed in a polymer matrix can form uniaxially aligned elliptical droplets. The alignment is controlled by mechanical shear during the polymerization of a UV‐curable adhesive. The possibility of prealignment makes polymer‐dispersed ferroelectric liquid crystals suitable for application in flexible electro‐optical displays. In contrast to surface stabilized ferroelectric liquid crystal displays, the electro‐optical effect in our system is due to the deformed‐helix ferroelectric (DHF) effect.
Probing the surface chemical structure of some novel poly(ortho esters) prepared with N‐methyl and N‐phenyl ethanolamine by time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS)
Authors: Davies M. C. , Leadley S. R. , Paul A. J. , Vickerman J. C. , Heller J. , Franson N. M. 
Published: April 2003

AbstractThe surface chemical structures of a series of novel poly(ortho ester) homopolymer and copolymer films prepared using N‐methyl‐ and N‐phenyl‐ethanolamine (MDE and PDE) have been investigated using time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS). Systematic fragmentation patterns were observed within the ToF‐SIMS spectra up to m/z = 1600, which were readily interpreted in terms of the polymer structures. Cations were detected which could be assigned to structures arising from the diols, the ortho ester species and diads, triads etc. of the monomer, from both the homopolymer and the random portion of the copolymer chains. The analysis of the proposed ion structures suggested two major mechanisms of fragmentation based on the cleavage of the ortho ester bonds involving either the exocyclic or the endocyclic alkoxy group. The Tof‐SIMS peak area ratios for ions diagnostic of the diols and the ortho ester species reflected the bulk copolymer composition in a semi‐quantitative fashion. The observation of such relationships for high mass cations (up to m/z = 500) is particularly noteworthy and has not been reported previously. These studies allow a dramatic insight into the surface chemical structure of these poly(ortho esters), information which has formed the foundation of current investigations on the mechanisms of the acid‐catalysed surface degradation of these polymers.
Polymeric biodegradable lipospheres™ as vaccine delivery systems
Authors: Amselem Shimon , Alving Carl R. , Domb Abraham J. 
Published: April 2003

AbstractThis study describes the preparation and use of polymeric lipospheresTM as a potential vehicle for the controlled‐release of vaccines. Lipospheres are a new encapsulation technology for parenteral drug delivery that have been also used successfully as carriers of vaccines. A recombinant malaria antigen, R32NS1, derived from the circumsporozoite protein of Plasmodium falciparum, was incorporated in biodegradable polymeric lipospheres in the absence or presence of lipid A as an adjuvant. The immunogenicity of polymeric lipospheres composed of polylactide (PLD) or polycaprolactone (PCL) was tested in rabbits after intramuscular injection of the formulations. High levels of specific IgG antibodies were observed in the sera of the immunized rabbits up to 12 weeks after primary immunization, using a solid phase ELISA assay. PCL lipospheres containing the malaria antigen were able to induce sustained antibody activity after one single injection in the absence of immunomodulators. PCL lipospheres showed superior immunogenicity compared to PLD lipospheres, the difference being attributed to the different biodegradation rates of the polymers. Biodegradable polymeric lipospheres represent a pharmaceutically acceptable vaccine delivery system with immunopotentiating activity for humoral antibody responses. The high permeability to many therapeutic drugs, and a lack of toxicity, has made PCL and its derivatives well suited for controlled drug delivery. The results obtained in this study are very promising, with the expectation that the use of biodegradable polymeric lipospheres might be very useful in the conversion of multiple‐dose vaccines to single‐dose vaccination, avoiding the need for repeated immunizations.
Osteoblast culture on bioerodible polymers: studies of initial cell adhesion and spread
Authors: Laurencin Cato T. , Morris Carol D. , Pierre‐Jacques Henri , Schwartz Edith R. , Keaton Altorous R. , Zou Ligan 
Published: April 2003

AbstractThe development of systems for the growth of osteoblasts on bioerodible polymeric matrices was explored. Three classes of bioerodible polymers were studied as possible matrix supports for osteoblast growth: the poly(anhydrides), poly(phosphazenes) and poly(lactic acid/glycolic acid) copolymers. Neonatal calvarial cells from Sprague–Dawley rats were seeded onto polymer disks at a density of 1 × 104 cells/cm2. Initial attachment and spreading, rate of growth and morphology were determined, and retention of osteoblast‐like phenotype was assessed through measurements of alkaline phosphatase activity in the presence and absence of 1,25(OH)2 vitamin D3. All results were considered relative to tissue culture polystyrene.Cells were found to attach to all polymers at 8 hr post‐seeding. By 24 hr, cell numbers on all polymers were found to be decreased, except for poly(lactic acid/glycolic acid). Rat calvarial osteoblasts seeded on poly‐(lactic acid/glycolic acid) reached confluency and retained their phenotype.Successful construction of viable osteoblast–bioerodible polymer composite materials, as presented in our study, may find their usefulness as grafts for atrophic non‐unions of bone, for healing craniofacial and other defects and for use as prosthetic implants or coatings. Composite systems of osteoblast cultures may also find their usefulness in furthering our understanding of bone differentiation, maturation and metabolism in a matrix environment.
Miscibility and crystallization kinetics in blends of poly(ethylene terephtalate) and thermotropic liquid crystal polyesters
Authors: Mélot Denis , MacKnight William J. 
Published: April 2003

AbstractBinary blends of poly(ethylene terephtalate) (PET) and thermotropic liquid crystal polyester (TLCP) have been prepared by both solution and melt blending methods. The TLCPs utilized were Vectra (Hoechst Celanese), TR‐4, a TLCP synthesized in our laboratory, and a block copolymer consisting of three TR‐4 units followed by three PET units. The phase behavior of the blends was studied by differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA) and optical microscopy. The results show that none of the blends is miscible, but significant interactions exist between the PET phase and the TLCP phase in the case of TR‐4 and TR‐4 block copolymer blends. These interactions lead to a different nucleation mechanism in these blends compared to that in PET/Vectra.
Formation of PPy/Ta2O5/Ta structure by electropolymerization
Authors: Park Young‐Seo , Takeoka Shinji , Yamamoto Kimihisa , Tsuchida Eishun 
Published: April 2003

AbstractElectropolymerization of pyrrole on tantalum (Ta) electrodes was carried out in buffer solutions (0.04 M phosphoric acid, 0.04 M acetic acid, 0.04 M boric acid and 0.2 M sodium hydroxide) containing 0.1 M sodium ptoluenesulfonate (TsONa) under galvanostatic conditions and it was found that a polypyrrole (PPy) and a tantalum oxide (Ta2O5) layer are formed on a Ta electrode by an electrochemical oxidation process. The conditions of this simultaneous formation were studied in respect to current density (id), pyrrole concentration ([Py]), pH and the amount of electricity. Under certain conditions ([Py] = 0.25 M, pH = 1.8, id = 10–20 mA cm−2, the amount of electricity = 1 C), 6–8 μm thick PPy films were efficiently formed on homogeneous 30–50 nm thick Ta2O5 layers. The PPy film showed a high electrical conductivity (110 s cm−1), adhered well and covered the Ta2O5 layer. The resulting PPy/Ta2O5/Ta system is therefore proved to have excellent properties as a capacitor.
Sulfur‐containing polymers by the reaction of diphenyl sulfide with sulfur chlorides
Authors: Miyatake Kenji , Jikei Mitsutoshi , Yamamoto Kimihisa , Nishide Hiroyuki , Tsuchida Eishun 
Published: April 2003

AbstractThe electrophilic reaction of sulfur dichloride with diphenyl sulfide proceeds efficiently at room temperature to yield oligo(phenylene sulfide) in the presence of a catalytic amount of Fe powder. Sulfur dichloride shows higher reactivity than sulfur monochloride. The reaction is promoted through the activation of sulfur dichloride by Fe powder. The polymeric product contains a linear structure linked by disulfide and sulfide bonds.