bluuebunny/crossref_metadata_2025 huggingface dataset:
The effect of temperature on the behavior of poly(o‐chloroaniline) salts: conductivity and spectral studies
Authors: Palaniappan S.
Published: April 2003

Conducting poly(o‐chloroaniline) salis have been prepared by chemical polymerization of o‐chloroaniline with five different acids. Composition and the extent of dopant in poly(o‐chloroaniline) salt systems have been determined. Poly(o‐chloroaniline) samples have been heat treated at four different temperatures 150, 200, 275 and 375°C and characterized by electron paramagnetic, infrared and electronic absorption spectral measurements. Thermal stabilities of the chemically synthesized poly(o‐chloroaniline) salts have been studied by spectral methods. It was found that the polymer is apparently stable up to 200°C, and at around 275°C crosslinking takes place. It is inferred that the electron paramagnetic resonance signal observed in the conducting material does not arise from the current‐carrying species, but rather from neutral paramagnetic species. No definite correlation exists between conductivity and the extent of dopant or spin concentration.
Residual stress and deformation during rapid cooling process in an epoxy plate
Authors: Hwang Jae Young , Kim Sung Chul
Published: April 2003

Residual stress in the epoxy plate during a rapid cooling process was measured by the layer removal method and calculated by the linear thermoviscoelastic theory considering specific volume relaxation. The relaxations of the tensile modulus and specific volume were measured by an Instron thermomechanical analyzer. When the starting temperature of the cooling process was near the glass transition temperature of the cured epoxy, the residual stress in the epoxy plate was smaller than when the starting temperature was higher than the glass transition temperature. However, the transient stress in the cured epoxy plate was higher when the starting temperature was near the glass transition temperature than when the starting temperature was higher than the glass transition temperature. The quenched epoxy plate was compressed in the direction parallel to the surface and expanded in the thickness direction.
Anisotropic dispersion polymerization of N‐(4‐aminobenzoyl)–caprolactam in polymer melts
Authors: Mülhaupt Rolf , Rösch Joachim
Published: April 2003

When N‐(4‐aminobenzoyl)–caprolactam (PAC) is injected into polymer melts, dispersions of anisotropic polyaramide particles with average diameters of 100–400 nm and aspect ratios of 5–10 are formed within few minutes. At 200°C PAC dispersion polymerization yields caprolactam and predominantly poly(p‐phenylenebenzamide), whereas with increasing polymerization temperatures PAC ring‐opening polymerization accounts for the incorporation of 6‐aminocaproic acid units into the polyaramide backbone. Covalent bond formation between microparticle surfaces and functional groups of the matrix polymer provides excellent interfacial adhesion and stabilizes the anisotropic polyaramide microparticle dispersions. This in situ PAC dispersion polymerization during melt processing, producing polyaramide‐whisker reinforced thermoplastics, represents a versatile route to organic microcomposites exhibiting improved stiffness and strength.
Ordering processes in polyester thermoplastic elastomers
Authors: Fischer Christian , Economy James
Published: April 2003

Synthesis of thermoplastic elastomers derived from poly‐tetramethylene glycol (PTME glycol), dimethylterephthalate and different mixtures of ethylene and butylene glycol is described. Extended heating near the crystalline melting point of these systems leads to a measurable increase in the melting point of 15–20°C. This ordering process can be reversed by heating at 250°C or well above the melting point. These results are interpreted in terms of sequence ordering within existing crystallites via interchain transesterification on heating near the melting point. Heating at 250°C is best explained as randomization of the ordered ester units.
ABS blends with phenoxy: morphology, thermal, mechanical and rheological properties
Authors: Choi Chi Hoon , Lee Soo Min , Kim Byung Kyu
Published: April 2003

Blends of ABS (acrylonitrile–butadiene–styrene) with phenoxy(poly(hydroxyether bisphenol A)) were prepared using a Branender single screw extruder. Scanning and transmission electron micrographs (SEM, TEM) showed a typical two‐phase morphology; particle‐in‐matrix (90/10) (ABS/phenoxy by weight), 70/30, 10/90), island/sea (30/70) and co‐continuous (50/50) morphologies. The glass transition temperature (Tg) of SAN was almost unchanged in the blends, while the Tg of phenoxy increased by about 5 °C in the blends. The synergistic effect of tensile modulus and strength was noted in ABS‐rich blends, where a drastic drop of ductility was seen, and the results were interpreted in terms of rubber particle migration form SAN to phenoxy phase, which was visualized by TEM. Melt viscosity showed yield in ABS‐rich blends, and generally followed the log additivity.
Features of composites prepared by radical graft‐polymerization of styrene to a hydrophilic macromer adsorbed on ultrafine colloidal particles
Authors: Yoshinaga Kohji , Nagao Kenichi
Published: April 2003

Polymer modifications of ultrafine monodispersed colloidal metal oxide particles, smaller than 80 nm in diameter, by the graft‐polymerization of styrene to a hydrophilic macromer adsorbed on the surface were investigated. The polymerization in ethanolic silica and titania colloid solution, which had negatively larger ζ‐potentials, −30 and −42 mV in neutral aqueous solution respectively, gave poly(styrene)–silica or titania composite, being of nonspherical shape. The modifications of colloidal particles, having lower surface energy, such as Al(OH)3 and CeO2–TiO2–SiO2 complex, led to the formation of spherical composites, ranging in size from 500 to 3000 nm, of scattered metal oxide or hydroxide particles.
Polymerizable phospholipids: a novel class of biomaterials
Authors: Singh Alok , Schnur Joel M.
Published: April 2003

Polymerizable phospholipids are organic monomers that are able to self‐assemble into membranes. This is quite similar to the self assembly of naturally occurring lipid membranes found in biological systems. The polymerizable lipids can then be polymerized to stabilize these membranes. These stabilized structures have a number of different morphologies which offer a variety of technically attractive features. This article reviews the chemical and physical properties of these materials in terms of their technological applications.
Effect of the thermal history on the phase transition and the liquid crystalline structure of thermotropic polyesters
Authors: Lee Young Jun , Kim Sung Chul
Published: April 2003

A series of triad type thermotropic polyesters based on phenylsulfonyl hydroquinone and α,ω‐bis(4‐carboxyphenoxy)alkane was prepared, and the effect of the thermal history on the phase transition and the liquid crystalline structure of the polyesters was studied. The phase transition was significantly affected by the thermal history. When annealed at various temperatures, multiple endotherms were observed for all polyesters in DSC thermograms. A phase stability concept was employed to explain the complicated phase transitions. The time evolution of the liquid crystalline structure was investigated by optical microscopy and transmitted light intensity measurement under crossed polars during annealing. The steady decrease in the density of disclinations with accompanying increase of transmitted light intensity was observed. Depending on the surface conditions of the liquid crystal polymer film, two markedly different domain growth patterns and different textures were found on isothermal annealing; the continuous wormlike texture and the discontinuous droplet texture. The structural relaxation of the deformed texture during annealing was also studied. When shear was applied, the characteristic banded texture was formed in all polyesters.
Oxygen‐binding property of hemoglobin films
Authors: Chung Jooeun , Takeoka Shinji , Nishide Hiroyuki , Tsuchida Eishun
Published: April 2003

Oxygenated and deoxygenated hemoglobin films were obtained by drying corresponding hemoglobin solutions with maltose (≧0.3 M). The resulting hemoglobin films were homogeneous and smooth, and the methemoglobin formation in the oxyhemoglobin film was well suppressed. The dry, rigid networks of maltose molecules work to preserve the conformation of hemoglobin against the removal of water. The coordination of oxygen to the deoxygenated hemoglobin film was slow and saturated up to 50%, while nearly 100% saturation was achieved if the film contained a residual moisture of 8.7%.
Conducting composites from EPDM–EVA blends
Authors: Ghosh M. K. , Das C. K.
Published: April 2003

The effect of ethylidene norbornene (ENB) content of ethylene propylene aiene rubber (EPDM) and vinyl acetate (VA) content of ethylene vinyl acetate copolymer (EVA), as well as the blending sequence, on the conductivity of composites based on EPDM–EVA–carbon black have been studied. Black master batches show a lower extent of cure than the preblended system followed by black addition. EPDM having a high ENB content shows higher conductivity under ambient conditions. Preblended systems give rise to higher conductivity in the case of low‐ENB content EPDM. But for high‐ENB content EPDM, the blending of black master batches imparts high conductivity. Two types of conduction are observed in this case and the transition temperature depends on the VA content of EVA. It appears that there exists a correlation between activation energy of curing and that of conduction.
Mechanical and thermal properties of dragline silk from the spider Nephila clavipes
Authors: Cunniff Philip M. , Fossey Stephen A. , Auerbach Margaret A. , Song John W. , Kaplan David L. , Adams W. Wade , Eby Ronald K. , Mahoney David , Vezie Deborah L.
Published: April 2003

Dragline silk from the spider, Nephila clavipes, was characterized by thermal analysis (TGA, DSC, DMA), computational modeling, scanning electron microscopy and by quasi‐static as well as high rates of strain. Thermal stability to about 230°C was observed by TGA, two transitions by DMA, −75°C, representative of localized motion in the amorphous domain, and a main chain motion associated with partial melt at 210°C. Tensile tests indicated average initial modulus, ultimate tensile strength and ultimate tensile strain of 22 GPa, 1.1 GPa and 9%, respectively. The corresponding properties of the best fibers tested were 60 GPa, 2.9 GPa and 11%, respectively. High strain rates (>50,000%/sec) indicated similar mechanical properties to the average values indicated above. Microscopy showed compressive and tensile strains to failure of 34%. Computational modeling yielded a crystal modulus of 200 GPa.
Thermotropic behavior of aromatic copolyesters based on 3,4′‐substituted diphenyl ether
Authors: Carpaneto Luca , Costa Giovanna , Marsano Enrico , Morinelli Sergio , Piombo Vadim , Valenti Barbara
Published: April 2003

Recently, flexible rod‐like monomers based on conformational isomerism have been used to synthesize fully aromatic thermotropic polymers of reduced processing temperature and good thermal stability. 3,4′‐Dihydroxy and 3,4′‐dicarboxydiphenyl ethers HE and DE, obtained by modified Ullmann condensations between proper hydroxy and bromo derivatives, are investigated as basic components for homo‐ and copolyesters with the above‐mentioned characteristics. Homopolymers from HE and terephthaloyl chloride or DE chloride and 2‐methyl (or phenyl) hydroquinone, synthesized by low temperature solution polycondensation, melt to an isotropic fluid; the chain packing is frustrated in the latter by asymmetrical substitution on the aromatic rings, which causes a sequence randomization as well as an increased chain separation. The incorporation of linear rigid units, by partial substitution of the flexible monomers with 1,4 aromatic moieties, leads to thermotropicity, but the critical content of 1,4 units varies with the steric hindrance of the diphenol. Variation of chain rigidity, arising from the chemical structure, composition and sequence distribution, can account for the thermal behavior of the samples and, in particular, for their different abilities to give liquid crystalline behavior.
Improvement of the properties of polyarylate reinforced with liquid crystalline polymers
Authors: Zaldua Ane , Muñoz M. Eugenia , Peña Juan J. , Santamaria Anton
Published: April 2003

Blends of polyarylate of bisphenol A, PAr, with two commercial main chain liquid crystalline polymers, Vectra A950 and Vectra B950, are studied. From dynamic viscoelastic measurements it is deduced that both systems (PAr/Vectra A950 and PAr/Vectra B950) are immiscible and scanning electron microscopy (SEM) micrographs show the presence of spherical domains of the liquid crystalline polymer when PAr constitutes the matrix. Extrusion capillary measurements reveal that, under conditions of temperature and shear rate similar to those of processing, the viscosity is reduced to approximately 10% of its value when the content of liquid crystalline polymer is only 20%. This great improvement of the rheological properties is observed in both PAr/Vectra A950 and PAr/Vectra B950 blends. The effect of draw ratio on Young's modulus for different compositions is also analyzed, pointing out the reinforcing action of both liquid crystalline polymers on polyarylate: for instance, 20% of Vectra B950 in the blend gives rise to a 700% increase of the modulus of fibres prepared at a draw ratio of 50. SEM of the extrudates reveals that the spherical domains are elongated at the entrance of the capillary giving rise to a microfibrillar morphology which is related to the excellent rheological and mechanical properties of the blends.
Utility of a liquid crystalline diacrylate for bistable switching cholesteric gel displays
Authors: Behrens Ulrike , Kitzerow Heinz‐Siegfried
Published: April 2003

We investigated cholesteric liquid crystals containing an anisotropic polymer network created by in situ photo‐polymerization of a mesogenic diacrylate. In contrast to previous studies, we used a liquid crystalline diacrylate to achieve bistable switching between the reflecting Grandjean texture and the diffuse scattering focal conic texture. The switching behavior depends considerably on the orientation of the liquid crystal during the polymerization. For polymerization in the Grandjean texture, the response times for switching to the reflecting state were lowered compared to the pure liquid crystal. The chromaticity coordinates indicate that this new type of display is very promising for additive color mixing.
Carbon–epoxy composites based on fibers coated with nylon 6,6: hygrothermal ageing versus interlaminar shear strength
Authors: Duvis T. , Papaspyrides C. D.
Published: April 2003

Carbon fibers were coated in situ with a thin film of polyhexamethylene adipamide by an interfacial polycondensation technique. The modified fibers were used for the preparation of epoxy‐based unidirectional composites. Specimens of these materials were immersed in water until equilibrium conditions were attained. The weight gain at equilibrium was determined as a function of the immersion temperature, the fiber volume fraction and the polyamide content deposited on the fibers. Water penetration in specimens made with uncoated carbon fibers increases when the volume fraction decreases. Introduction of the polyamide interlayer initially increases the water absorption, but reduces it at higher immersion temperatures and/or higher polyamide contents. The treated specimens were subjected to the short beam test to determine the interlaminar shear strength (ILSS). The data show that the ILSS decreases with water penetration but increases when the immersion temperature increases from 40 to 70°C. The overall performance encountered is discussed in terms of the possible roles of the polyamide interphase while taking into account mechanisms concerned with matrix plasticization, interphase degradation and residual stress relaxation.
Cyclic polymers: past, present and future
Authors: Semlyen J. A. , Wood B. R. , Hodge P.
Published: April 2003

Methods for characterising cyclic polymers are illustrated by reference first to dilute solution methods for cyclic poly(dimethylsiloxane) (PDMS) and then to the entrapment of cyclic polymers in networks. Preparative routes to cyclic polymers are then reviewed, including ring‐chain equilibration reactions, coupling and condensation reactions and new methods using polymer‐supported reagents. Some of the properties of cyclic PDMS are discussed, including differences between ring and chain polymer properties such as their melt viscosities and glass transition temperatures. Methods for preparing the first polymeric catenanes are described, using polymer‐supported reagents. Future directions for cyclic polymer chemistry are indicated, including topological polymer chemistry.
Stabilization of vinylidene chloride barrier resins
Authors: Howell B. A. , Warner B. S. , Rajaram C. V. , Ahmed S. I. , Ahmed Z.
Published: April 2003

Vinylidene chloride copolymers have a number of superior properties, most notably a high barrier to the transport of oxygen and other small molecules. As a consequence, these materials have assumed a position of prominence in the packaging industry. At processing temperatures these copolymers tend to undergo degradative dehydrochlorination. Unsaturation generated via interaction of the polymer with a variety of agents commonly encountered during polymerization or processing introduces an allylic dichloromethylene unit which may function as a major defect (labile) site for the initiation of degradation. Three approaches to the potential stabilization of these materials have been examined. The first involved the addition of agents, e.g. metal formates, capable of converting labile dichlormethylene units into non‐reactive groups which would interrupt propagation of the degradative dehydrochlorination. The second involved the incorporation into the polymer of a commoner capable of scavenging free chlorine atoms. The third involved the preparation of copolymers which contains units capable of reaction with (consumption of) a mole of hydrogen chloride to expose a good free radical stabilizer to scavenge chlorine atoms.
Development of radiation‐grafted FEP‐g‐polystyrene membranes: Some property–structure correlations
Authors: Gupta Bhuvanesh , Büchi Felix N. , Scherer Günther G. , Chapiro Adolphe
Published: April 2003

Property–structure correlation in proton exchange membranes, prepared by simultaneous radiation grafting of styrene into FEP films and their subsequent sulfonation, was evaluated. The distribution of ionic sites across the membrane matrix was determined by microprobe measurements. The properties of these membranes, such as ion exchange capacity, swelling and ionic resistivity as a function of the degree of grafting, were studied. The thermal stability of membranes was studied using thermogravimetric analysis and ion exchange capacity measurements. Membranes undergo considerable structural changes in terms of the increase in the ionic content, enhanced hydrophilicity and decrease in crystallinity with the increasing degree of grafting. A correlation between some physical properties and stuctural changes occurring during the membrane preparation was established.
Synthesis of poly(sulfonium cation) as an alkylating reagent
Authors: Shouji E. , Nishimura S. , Yamamoto K. , Tsuchida E.
Published: April 2003

Methyl 4‐phenylthiophenyl sulfoxide is polymerized to poly(methyl‐4‐phenylthiophenylsulfonium) in poly(phosphoric acid) with a yield higher than 90%. The demethylation of poly(sufonium cation) is examined to control the composition ratio of the thiophenylene unit in the polycation. The polycation is soluble in common solvents due to the alternative structure of phenylene sufide and phenylenesulfonium cation and is easily converted to poly(phenylene sulfide) through the demethylation with a nucleophile. The poly(sulfonium cation) can be applicable as an alkylating agent for phenol, aniline and benzoic acid to the corresponding to anisole, N‐methyl aniline, N,N‐dimethyl aniline and benzoic methyl ester, respectively, with high conversion through the demethylation. These products can be isolated without a complicated purification because poly(phenylene sulfide) is precipitated in the mixture as the side product due to the poor solvent solubility.
Development of natural product (1 → 3)‐β‐D‐glucan polymers as immune‐stimulating pharmaceuticals
Authors: Williams David L. , Browder I. William
Published: April 2003

Glucan phosphate is a water‐soluble, yeast‐derived, (1 → 3)‐β‐D‐glucopyranose polymer that has been demonstrated to be a potent immune stimulant. Glucan phosphate administration is associated with stimulation of immunity and a concomitant increase in resistance to a variety of experimentally induced disease states. Preclinical safety evaluation indicates that glucan phosphate does not induce mortality or significant toxicity over a wide dose range. Phase I clinical data indicate that glucan phosphate will ameliorate immunosuppression, stimulate immunity, decrease susceptibility to infection and alter ultimate outcome in trauma patients following laparotomy or thoracotomy. This work reviews the development, characterization, preclinal and clinical evaluation of glucan phosphate.
The α‐halogeno ether function: formation and use in the design of tailor‐made polymers
Authors: Cramail Henri , Schappacher Michel , Deffieux Alain
Published: April 2003

α‐Halogeno ether species, in appropriate conditions, can induce the “living” cationic polymerization of vinyl ethers. They can also be used as initiators for the “living” polymerization of styrene derivatives. Therefore, their use as intermediates in the preparation of tailor‐made polymers and copolymers offers interesting opportunities in macromolecular synthesis. The main parameters which determine and control their reactivity are reviewed and discussed. The possibility to generate quantitatively these derivatives by various routes and from different organic functions such as aldehyde, ketone, acetal and hydroxyl is examined. Some of these routes have been used to generate the α‐halogeno ether function directly at the end of acetal and hydroxy‐terminated polymers. The latter have then been used as macroinitiators to prepare new block copolymers. The synthesis of poly(isobutyl vinyl ether‐β‐ethyl vinyl ether), poly(styrene‐β‐chloroethyl vinyl ether) and poly(chloroethyl vinyl ether‐β‐butadiene‐β‐chloroethyl vinyl ether) by this technique is described.
Methotrexate polymer implant for the treatment of head and neck cancer
Authors: Domb Abraham J. , Wartenfeld Rita
Published: April 2003

A biodegradable polymeric device releasing methotrexate (MTX) for the treatment of cancer of the head and neck was evaluated in vitro and in vivo. The polymer used for the preparation of the device was a copolyanhydride based on dimer erucic acid and sebacic acid loaded with 2–20% MTX. The drug was released constantly for about two weeks from small discs (1 × 3 mm) with complete degradation of the polymer when placed in phosphate buffer pH 7.4 at 37°C. The release and degradation rate was similar for all drug loading. MTX‐loaded discs implanted subcutaneously in mice released the drug for about ten days with about 50% elimination of the device from the implantation site. The drug concentration was the highest in the tissue in contact with the device and decreased at distance from the device following a first order kinetics. The LD50 of MTX in polymer when implanted in mice was between 20 and 40 mg per kg. (1994)
Miscible blends through hydrogen bonding: effects on polymer properties
Authors: Pearce Eli M. , Kwei T. K. , Lu Shaoxiang
Published: April 2003

Miscible blends through hydrogen bonding have been intensively studied. The effects of a variety of miscible hydrogen bonded polymer blends on properties such as thermal and thermal oxidative stability, moisture sensitivity, modulus and glass transition temperature are discussed. In addition, the preparation of semi‐interpenetrating polymer networks (IPNs) and studies of the effect of crosslinking on the miscibility in hydrogen bonded polymer blends are reviewed.
The preparation, compatibility and structure of PEEK–PES blends
Authors: Ni Zhuo
Published: April 2003

Blends of polyetheretherketone and polyethersulfone (PEEK–PES blends) were prepared either by mechanically mixing fine PEEK and PES powders or by mixing PEEK and PES solutions in H2SO4 (98%). Partially compatible blends were obtained in the latter method. The sulfurization of PEEK or PES in concentrated sulphuric acid did not occur provided that the experiment was performed within 30 min. The Tg of the PEEK component increased and that of PES component decreased with the increase of PES weight fraction; the melting exothermic peak of the PEEK component did not appear in the DSC curves of the quenched blends, suggesting that PES can effectively reduce the crystallization of PEEK component. The major absorbances of the bands were characterized by IR spectroscopy; the frequency difference between PEEK or PES and their blends were observed. A linear correlation of absorbance ratios with PEEK weight fraction was found.
Morphology and physical properties of a liquid–crystalline main‐chain polymer with flexible side chains
Authors: Damman S. B. , Buijs J. A. H. M. , Mercx F. P. M.
Published: April 2003

A molecular laminate model is used to explain the properties of unoriented and oriented films of poly(p‐phenylene‐2,5‐didodecyloxyterephthalate) cast from solution. In oriented films the two different crystal modifications, A and B, give rise to room temperature tensile moduli of 15 and 30 GPa respectively. The packing (in clusters) of the side chains in modification A, leading to a glass–like transition in the side‐chain regions around −40°C, is largely responsible for this difference. Oriented films of modification A and B have coefficients of thermal expansion of +0.3×10−5 and −1× 10−5 K−1 respectively. It is concluded that the properties of this class of polymers can be adjusted in a systematic way.
Recent advances in the formation of ultrathin polymeric membranes for gas separations
Authors: Pinnau Ingo
Published: April 2003

During the past 20 years membrane systems have been applied to a limited number of commercial gas separations. To further advance membrane‐based gas separations, current research efforts focus on optimization of (i) membrane materials, (ii) membrane structures and (iii) membrane system design. In this overview, recent developments in the formation of high‐performance gas separation membranes are discussed. The gas separation properties of state‐of‐the‐art integrally skinned asymmetric membranes and thin‐film composite membranes are summarized. Future directions for the preparation of advanced gas separation membranes are highlighted.
The melt hollow fiber spinning process: steady‐state behavior, sensitivity and stability
Authors: Lipscomb G. Glenn
Published: April 2003

The rheology of the melt hollow fiber spinning process is examined in the thin filament limit. The resulting thin filament equations are also applicable to single‐phase and two‐phase extensional flows. Using a novel numerical solution procedure, the sensitivity of the fiber spinning equations to material property and process variations is investigated. Fiber geometry is directly controlled by the mass flowrates of the core and clad fluids while the spinline tension is most strongly influenced by clad viscosity. A maximum can occur in the clad stress profile if a core liquid is used and the ratio of core to clad viscosity increases greatly with temperature. Isothermal spinning of high viscosity clad liquids with either a core gas or liquid is unstable for draw ratios greater than 20.2 as found for solid fibers.
Thermodynamic functions of thermotropic polyethers based on the semiflexible mesogen 1‐(4‐hydroxyphenyl)‐2‐(2‐methyl‐4‐hydroxyphenyl)ethane
Authors: Jin Yimin , Cheng Jinlong , Wunderlich Bernhard , Cheng Stephen Z. D. , Yandrasits Michael A.
Published: April 2003

Heat capacities of a series of thermotropic polyethers consisting of a semiflexible mesogen [1‐(4‐hydroxyphenyl) ‐ 2 ‐ (2 ‐ methyl ‐ 4 ‐ hydroxyphenyl)ethane], with n methylene flexible spacers (n = 4–12) (MBPE‐n) have been measured by DSC and fitted at low temperature to an approximate frequency spectrum, as well as at high temperature to a general equation for the liquid MBPE‐n. The latter equation is:
Cp = n(17.33 + 0.04551T) + (280.9 + 0.3839T)
where n is the number of methylenes in the polyether spacer. The calculated vibration‐only heat capacities start to show deviations from the measured heat capacities below the melting temperature, reflecting contributions from conformational disorder and motion in methylene spacers. It is suggested that part of this increase in heat capacity can be looked upon as a glass transition of the partially conformationally disordered crystals. Solid state 13C–NMR studies showed similarly that over the range of temperature some of the CC bonds in the spacer are in a rotational state similar to that in the melt. The equilibrium heats of fusion (ΔH) and the changes of heat capacity (ΔCp) for the amorphous polymer at the glass transition temperature, Tg, were determined by WAXD and DSC. Based on the discrepancy of ΔCp it is concluded that these phenylene containing polyethers have a certain amount of rigid amorphous polymer. Thermodynamic functions H, S and G for all of the polyethers have been established.
“Surface‐photografting”: new applications to synthetic fibers
Authors: Rånby Bengt , Guo Feng Zhen
Published: April 2003

“Surface‐photografting” with UV‐irradiation of polypropylene (PP) fiber and film and high‐strength polyethylene (HSPE) yarn has been made with acrylic acid (AA) and acrylamide (AM) as monomers and benzophenone (BP), 4‐chlorobenzophenone (4‐BCP) and hydroxylcyclohexylacetophenone (HHA) as photoinitiators using a new continuous method. The grafting reaction occurs in a thin liquid layer on the fiber or film substrate, which is presoaked in a solution containing initiator and monomer. After irradiation with a highpressure mercury lamp, HPM 15 (2 kW) from Philips, for 5–20 sec at about 50°C the fiber and film surface is completely covered with a 2–8 nm thick layer of grafted polymer, analyzed by electron spectroscopy for chemical analysis. The grafting efficiency is 70–80%, i.e. only 20–30% of the polymer is homopolymer which can be removed by extraction. The grafted layers are so thin that they cannot be analyzed as weight increase (<0.1% of fiber weight). Absolute values for the amount of grafted AA polymer is analyzed by microtitration of the COOH groups at the fiber surface. The results agree well with the relative ESCA values. Grafting of commercial PP yarn with AA increases the adsorption of Crystal Violet dye with a factor of about 6. Grafting the same yarn with AM increases the adhesion to epoxy resin by a factor of 3–4 without affecting the mechanical properties of the fiber more than a few percent. For comparison, strips of blown PP film (5 mm wide) are modified by “surface‐photografting” with AM. With increasing grafting, the contact angle for drops of distilled water decreases from 90° to 20°, indicating extensive wetting. The adhesion to epoxy resin increases from about 0.35 to 1.7 N/mm2, i.e. with a factor of about 5 when the film surface is completely covered. Other comparisons are made with grafting of commercial HSPE yarn. Grafting with AA increases the adsorption of Crystal Violet dye by a factor of about 6. Grafting with AM increases the adhesion to epoxy resin from 0.25 to 1.3 N/nm2, i.e. with a factor of 5. The bulk mechanical properties of the HSPE filaments are not affected by the grafting measured as tensile strength 2.7±0.1 GPa, elongation at break 4.8±0.3%, and Young's modulus 55±3 GPa, both before and after “surface‐photografting”.
Plastic deformation and performance of engineering polymer materials
Authors: Oleinik Eduard F. , Salamatina Olga B. , Rudnev Serge N. , Shenogin Serge V.
Published: April 2003

The plastic deformation mechanism operating in polymer glasses is analyzed. The whole process consists of two main stages: nucleation of special shear defects, called PSTs (plastic shear transformations), and their disappearance. The important feature of plastic deformation of glasses is the storage of a large amount of internal energy ΔUdef upon straining. Such energy storage is the critical issue for mechanical performance of polymeric material: if the amount of stored energy is high, the appearance of macroscopic failure is very probable while glassy materials collecting a small amount of stored deformation energy are quite ductile. It is proposed that the rate of disappearance of PSTs is a key factor in dissipation of stored deformation energy. A parameter describing the dissipation ability of material upon deformation is introduced.
Photochromic polymers: effects of structure and environment on photoresponsiveness
Authors: Ciardelli Francesco , Pieroni Osvaldo , Fissi Adriano , Altomare Angelina , Solaro Roberto , Tirelli Nicola
Published: April 2003

In this review paper the photoresponsiveness of photochromic macromolecules under different structural and environmental conditions is discussed with reference to results from the authors' laboratories. Polypeptides, in particular poly(L‐glutamic acid) and poly(L‐lysine), with spirobenzopyrane side chains show photoinduced conformational variations which are amplified by addition of organic acids or bases to hexafluoro‐2‐propanol (HFP) solutions. Thus combination of light and environment effects allows modulation of order–disorder conformational transitions.

Such photoindiced conformational changes are not observed in the case of macromolecules with a hydrocarbon main chain and azobenzene or stilbene side chains, obtained by polymerization of acrylic monomers. However, even in these systems structural variations affect the dependence of optical properties on irradiation. Moreover, the combination of organic solvents and water shows that polymer solubility can be modulated by light.
Morphologies and electro‐optic properties of phenoxy/liquid crystal composite films
Authors: Kim Byung Kyu , Kim Seon Hee , Choi Chi Hoon
Published: April 2003

Morphology and electro‐optic properties of composite films composed of phenoxy and nematic liquid crystal (LC) have been studied at a film composition of 40/60 (polymer/LC by weight). Effects of temperature, frequency and voltage of applied a. c. electric field on the transmittance and response time of the films were measured.
High temperature polymer blends: an overview of the literature
Authors: DeMeuse Mark T.
Published: April 2003

A review of work which has been performed on high temperature polymer blends is presented. The discussion is divided into miscible and immiscible blends. It is pointed out that one problem with miscible polymer blends is that of processing in the miscible state. In the case of immiscible blends, particularly ones containing liquid crystal polymers, the issue of adhesion of the two phases is discussed. Finally, the need for better theoretical models for predicting miscibility in polymer blends is highlighted.
Thermal behavior of new polymer electrolytes
Authors: Fauteux D. , McCabe P.
Published: April 2003

Solid polymer electrolytes (SPE) have been identified as a class of materials which could enable the fabrication of high energy density solid state lithium rechargeable batteries which could meet the performance requirements for advanced portable electronic and automotive applications. In order to achieve this goal, novel SPE systems having high ionic conductivity and good mechanical properties at or near ambient temperature must be developed. Novel lithium salts believed to be useful in realizing this objective have recently been proposed. The thermal behavior of SPE systems based on high molecular weight poly(ethylene oxide) (PEO) and on two novel salts, the lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and the lithium tris(trifluoromethylsulfonyl)‐methanide (LiTSFM) is reported and compared with the thermal behavior of the high molecular weight PEO–lithium trifluoromethane sulfonate (LiTFLT) SPE system. Phase diagrams for the PEO–LiTFSI and PEO–LiTFSM SPE systems have been established and are discussed in terms of their impact on SPE‐based rechargeable lithium battery technologies. The use of a novel plasticizer in conjunction with the PEO–LiTFSI‐based SPE system is reported and it is shown how this modifies the thermal behavior of the PEO–LiTFSI SPE system.
Corrosion inhibition of zinc‐plated steel in 0.5, 1 and 1.5 M sulphuric acid by poly(ethylene glycol)
Authors: Oun Ahmed Mohammed
Published: April 2003

The effect of poly(ethylene glycol) (PEG) 4000 on the corrosion of zinc‐plated steel in H2SO4 has been investigated over a wide range of conditions. It was found that the corrosion rate depends upon exposure time. The rate of corrosion goes down rapidly to reach a low value, which is an almost constant value within 5 hr under most conditions. This trend was also found by Growock and Lopp for the inhibition of steel corrosion in HCl with 3‐phenyl‐2‐propyl‐1‐ol. Other workers have linked this slow fall‐off in the corrosion rate to film formation. The corrosion rate was found to decrease slowly with increasing PEG concentration, and to increase slowly with acid concentration for all conditions.

The effect of temperature on corrosion rate was found to be similar to that of acid concentration. The corrosion rate decreased exponentially with poly(ethylene glycol) concentration. The percentage inhibition reached a value of 48.93 for a PEG concentration of 4 ppm: to double this, the concentration had to be increased to 40,000 ppm.

Sulphuric acid titration against sodium hydroxide showed no change in acid concentration during the corrosion protection process, thus supporting the film protection theory
Multi‐electron oxidation of formaldehyde on a platinum electrode
Authors: Nakabayashi S. , Tamura K. , Uosaki K.
Published: April 2003

The time evolution of a self‐sustained potential oscillation under constant current oxidation of formaldehyde was observed on the rotating ring disk electrode assemble. Under the condition when the potential was controlled, the laser deflection voltammogram as well as the conventional cyclic voltammogram were measured. The mechanism of the multi‐electron oxidationof formaldhyde on a platinum electode is discussed.
One‐step multi‐electron transfer mechanism of polynuclear copper complexes for molecular conversions
Authors: Viersen Frits Jan , Wilson Jennifer C. , Challa Ger , Reedijk Jan
Published: April 2003

The oxidative coupling reaction of 2,6‐dimethylphenol may result in either a desired polymeric substance (i.e. the polyphenylene ether, PPE) or the undesired “dimeric” species diphenoquinone, DPQ. The relative amounts of each product depend on the experimental conditions and the used catalytic system.

Usually copper amine compounds are used as a catalyst for the oxidative coupling reactions. They have the advantage of easy access and produce high yields of high molecular PPE; however, other metal coordination compounds, like those of Mn, may also be used as catalysts.

The present paper focuses on mechanistic studies with various copper (aliphatic and aromatic) amine compounds as catalysts. Owing to the steric constraints of the amine ligands, dinuclear Cu(II) compounds, with small bridging anionic ligands, are easily formed. Such species are believed to be the catalyst precursors. Upon addition of a base (1:1 on copper) and excess phenol, phenolate ligands coordinate as bridging ligands to copper. After a two‐electron transfer reaction, the resulting phenoxonium ligand, which is a rather poor ligand, remains attached to the Cu(I), probably coordinating via its aromatic ring. Nucleophilic attack by a phenol to the phenoxonium ion at the 4‐position is likey to be most important to the coupling reaction. In the beginning of the reaction the undesired side product DPQ is also formed via a C–C coupling reaction. With copper(II) compounds containing imidazole‐type chelating ligands, good activity was obtained; in the case of pyrazole‐based and bridging S‐donor chelating ligands, that no or very weak activity was found.

In a study of the mechanism of the propagation reaction the rate‐determining reaction was thought to be probably a one‐step, two‐electron transfer, during which the two Cu(II) ions in the dinuclear complex oxidize the phenolate to phenoxonium. After the phenoxium ion is formed the bonding with the (then) Cu(I) species is weakened and the reactions with phenolic end groups can take place. The effect of the amine ligands appears to be both steric and electronic. With certain ligands the reoxidationof the reduced catalyst is not possible.
Multi‐electron transfer reactions and exciton interactions in fibrous porphyrin and metalloporphyrin assemblies
Authors: Fuhrhop Jürgen‐Hinrich , Bindig Uwe , Rosengarten Bianca , Siggel Ulrich
Published: April 2003

Non‐covalent porphyrin and metalloporphyrin fibers of bimolecular thinness in bulk aqueous media are compared with the well‐known H‐ and J‐aggregates of cyanines. The J‐aggregates of cyanines fluoresce and are useful as photographic sensitizers. The J‐aggregates of porphyrins show light‐induced charge separation and the corresponding metal complexes produce stable radical dimers. The distance between the metalloporphyrin centers is calculated from circular dichroism spectra to be 8 Å in the J‐aggregates and about 4 Å in the H‐aggregates. Multi‐electron reactions of the fibers in the ground and excited states can therefore occur in the fibrous porphyrin assemblies. In amphiphilic tetraphenylporphyrins (“octopus porphyrin”), on the other hand, the porphyrin–porphyrin distance is much larger and the fiber dissolves electron‐accepting compounds, e.g. quinones, which also allow for multiple charge separation within such a fiber.
Multi‐electron transfer in composite phthalocyanine thin films: structure and electrochromic properties
Authors: Tominaga Tsuyoshi , Toshima Naoki
Published: April 2003

Both sequentially deposited double‐layered and codeposited composite thin films were prepared by using two kinds of phthalocyanines. The structure and the electrochromic property of these thin films were compared with those of simple phthalocyanine films. The structures of the films were analyzed by scanning electron microscopy (SEM), X‐ray diffrction (XRD) and electron spin resonance (ESR) spectra. From the viewpoint of morphology and crystallinity, codeposited thin films have the same structure as the simple one, having sharp peaks at ca. 2θ=7.0° in the XRD pattern and narrow crystal grains in SEM photographs. ESR measurements have revealed that phthalocyanine molecules disperse very well in the codeposited thin films in a molecular level in comparison with the physical mixture of phthalocyanine powders. This high dispersibility of the molecules in the codeposited thin films can play a role to improve the reversibility in the electrochromism. Thus, the reversibility of the phthalocyanine, which shows irreversible electrochromism in the simple film form, can be improved by the codeposition with another phthalocyanine with reversible electrochromism. In contrast, sequentially deposted double‐layered thin film gives completely different results. The electrochromism of the double‐layered film depends on the property of the simple phthalocyanine thin film which is in contact with the substrate.
Electron transfer reaction of electrochemically polymerized tris‐(amino‐phenanthroline)‐iron(II/III) complex films
Authors: Kitagawa Mako , Iwaku Masahiro , Oyama Noboru
Published: April 2003

New films of iron complex with 4,7‐bis(2‐aminophenyl)‐methylaminosulfonylphenyl)‐1,10‐phenanthroline (APP) and 5‐amino‐1,10‐phenanthroline (AP) are prepared on the electrode surface of In–Sn oxide conducting glass (ITO) by electrochemical oxidation. The thickness (Φ) of the films prepared on the ITO can be controlled by the number of cycles of the potential scan. The resulting film‐coated electrodes show well‐defined reversible vol‐tammograms corresponding to the redox reaction of the Fe(II/III) complexes in 0.1 M NaClO4 acetonitrile (AN), a mixture of butylene carbonate (BC) and propylene carbonate (PC) and poly2‐hydroxyethylmethacrylate gel containing BC and PC. The electron transfer processes within the films can be treated apparently as diffusional processes characterized by the rate constants of the apparent diffusion coefficient (Dapp). The value of Dapp increase from 1.0 × 10−9 to 1.6 × 10−8 cm2 sec−1 as the Fe complex concentration (CFe) increases from 0.06 to 1.04 M for the [Fe(AP)3] complex film (Φ=0.80 μm) in 0.2 M NaClO4/AN solution. The Dapp value for the [Fe(APP)3) complex film (CFe = 0.19 M, Φ= 0.78 μm) is 3.5 × 10−9 cm2 sec−1 in 0.2 M NaClO4/AN solution. The Dapp values of the [Fe(AP)3] complex film in the PC + BC mixture and gel containing 1.0 M NaClO4 were smaller than those obtained in AN solution by an order of magnitude. The dependence of the apparent formal potential of the Fe(II/III) redox reaction for the [Fe(AP)3] complex film on the activity of NaClO4 supporting electrolyte in AN shows that Na+ moves preferentially across the polymer/solution interfaces during the redox reaction. The Fe(II/III) redox reaction of the Fe complex films shows reversible electrochromic response between red and colorless.
Approach to improving the toughness of TGMDA/DDS epoxy resin by blending with thermoplastic polymer powders
Authors: Pascal T. , Bonneau J. L. , Biolley N. , Mercier R. , Sillion B.
Published: April 2003

A series of hot‐melt processable thermosetting compositions was prepared by blending N,N,N′,N′‐tetraglycidyl‐4,4′ ‐diaminodiphenyl‐methane/4,4′‐diaminodiphenylsulfone (TGMDA/DDS) epoxy resin and thermoplastic polymer powders with average particle size below 30 μm. The basic thermoplastic polymers were either a high Tg amorphous cardo polyimide (Tg=350°C) or commercial semicrystalline PA6 and PA12 polyamides. The resulting heterogeneous mixtures showed viscosity values below 5000 cps suitable for prepregging process. After cure, phase‐separated morphologies were maintained with a rather limited interphase miscibility as demonstrated by thermomechanical analysis. Scanning electron microscope examination of fracture surfaces pointed out a strong adhesion between the powder particles and the surrounding polyepoxy network, particularly for the potentially reactive polyamide structures. Moreover, as shown by differential scanning calorimeter analysis, the crystallinity ratio of the PA6 and PA12 powders was lowered due to melting during thermal polymerization. The fracture toughness properties of the powder‐containing materials were compared with those of a fully miscible cardo polyimide–TGMDA/DDS blend coming from an homogeneous resin composition. The best improvement in fracture energy was obtained for the powder‐modified resins. The most effective composition filled with 16 wt% of powdered polyimide exhibited a fourfold increase in GIC (388 J/m2 versus 100 J/m2) without compromising the epoxy thermomechanical stability (Tg=227°C versus 223°C).
Second‐order nonlinear optical properties of side‐chain liquid crystalline polymers studied by second harmonic generation from thin films
Authors: Alastair D. , Smith McL. , Coles Harry J.
Published: April 2003

The two independent elements of the second‐order nonlinear optical susceptibility tensor of a range of contact poled, donor–acceptor substitued side‐chain polymers are reported. The susceptibilities were measured by second harmonic generation from thin films, typically less than 0.5 μm thick, at a fundamental wavelength of 1064 nm. The largest value was χ = 2.64 pm/V which is three times greater than the χ value of KDP and was measured in a nitrobenzylidene side chain, polyhydroxystyrene polymer with an eleven unit alkyl chain spacer attaching the side group to the backbone. Typical susceptibility values obtained were χ∼0.3 pm/V and X(2)33∼1 pm/V. The coherence lengths of the materials, which lay in the range 4–12 μm, were measured at 1064 nm by the maker fringe technique using thick, wedge‐shaped samples.