bluuebunny/crossref_metadata_2025 huggingface dataset:
Encapsulation of Hb into unsaturated lipid vesicles and γ‐ray polymerization
Authors: Sakai Hiromi , Takeoka Shinji , Yokohama Hiroaki , Nishide Hiroyuki , Tsuchida Eishun
Published: April 2003

A carbonyl hemoglobin (HbCO) solution was stirred with a mixed powder of polymerizable 1,2‐bis(2,4‐octadecadienoyl)‐sn‐glycero‐3‐phosphocholine (DODPC), cholesterol and stearic acid (7/7/2 by mol). The mixture was extruded through polycarbonate membrane filters (final pore size = 0.2 μm Ø). The average diameter of the resulting vesicles was 203 ± 39 nm. The [Hb]/[Lipid] ratio (the weight ratio of Hb in vesicle to lipid) increased with the Hb concentration, and decreased with the NaCl concentration. A maximum [Hb]/[lipid] ratio was observed at pH 6.9, which was the same as the isoelectric point of Hb. The vesicles were stabilized by γ‐irradiation (60Co) because the bilayer lipids bound each other to yield polyphospholipids. Denaturation of Hb by γ‐irradiation was not detected. These polyphospholipid vesicles encapsulating Hb were stable even against the freeze–thaw cycles and the freeze‐drying procedure.
The effect of curing conditions on the physical and mechanical properties of styrenated polyester
Authors: Nasr Elsayed S. , Abdel‐Azim A.‐A. A.
Published: April 2003

The curing behavior of unsaturated polyester resin was investigated. In the present study, styrene, methyl ethyl keton peroxide (MEKP) and cobalt octoate (CO) have been selected as solvent (monomer), catalyst and accelerator, respectively. The effect of the concentration of both MEKP and CO on the curing exotherm, curing time, hardness and compressive strength of the prepared copolymers was investigated.
Polymerization and photoinitiation behavior in the light‐cured dental composite resins
Authors: Fujimori Yukio , Kaneko Takashi , Kaku Takahiko , Yoshioka Naoki , Nishide Hiroyuki , Tsuchida Eishun
Published: April 2003

The polymerization behavior and photoinitiation process in the visible light‐cured dental composite resins were studied using ESR and IR spectroscopies. The concentration of methacryl propagating radical corresponded to the transmittance of irradiated light. While the radical was stable and long‐lived in the cured resin, its concentration quickly decreased in the oral cavity due to the ventilation of atmospheric oxygen accompanied by respiration. Camphorquinone radical in the presence of tertiary amine easily initiated the radical polymerization. A decrease in monomer consumption was explained by the inhibition effect of oxygen in the photoinitiation process. Post‐curing by the residual radical proceeded effectively in the deeper part of the resin.
Exploitation of the current knowledge of antioxidant mechanisms for efficient polymer stabilization
Authors: Pospíšil Jan
Published: April 2003

New mechanistic knowledge of antioxidant and photoantioxidant mechanisms is interpreted to meet the requirements of processing stability and durability of commercial plastics, rubbers and coatings in hostile environments. Factors reducing stabilizer activity and some ecological concerns dealing with polymer stabilization are included.
Polymer nanocomposites with “ultralow” refractive index
Authors: Zimmermann Lorenz , Weibel Martin , Caseri Walter , Suter Ulrich W. , Walther Paul
Published: April 2003

Nanocomposites of gelatine and gold were prepared by reduction of AuCl4H in a gelatine solution, followed by a spin coating process and a brief washing. The thickness of the films thus obtained was typically 200–400 nm. The surface of the nanocomposites was investigated by scanning electron microscopy (SEM) and surface profilometry. The size of the gold particles is in the range of ca. 2–10 nm, as elucidated by transmission electron microscopy (TEM). Refractive indices were measured by ellipsometry at wavelengths of 632.8 and 1300 nm. The refractive index depends linearly on the volume fraction of gold, at least at 1300 nm. The lowest refractive indices measured are 1.008±0.060 at 1300 nm and 0.963±0.062 at 632.8 nm (limits are 95% confidence interval). These values are, to our best knowledge, the lowest reported for a polymer or polymer composite.
Computational examination of the electrophilic reaction on oxidative polymerization of phenyltrimethylsilane with sulfur chloride
Authors: Shouji E. , Yamamoto K. , Katoh J. , Nishide H. , Tsuchida E.
Published: April 2003

Phenyltrimethylsilane possesses a higher HOMO energy (–9.34 eV) than nonsubstituted benzene (>0.41 eV). The π electron of the phenyltrimethylsilane localizes on the benzene ring at the ipso position rather than at the para position. Two center energies calculated by the MNDO‐PM3 method indicate that the CSi bond is facilitated to cleave in comparison with the CH (para position) one of the benzene ring. Phenyltrimethylsilane and phenyl bis(trimethylsilane) were polymerized with sulfur chloride through the cationic oxidative polymerization. The product is isolated as oligo(p‐phenylene sulfide), with a melting point of 150–190°C. An electrophile attacks the carbon atom linked to the Si atom in phenyltrimethylsilane. The new synthetic route of PPS can be established on the basis of the computational calculation.
Oxygen dissolution and transport in cobaltporphyrin‐bound organophosphazene membranes
Authors: Nishide H. , Kawakami H. , Nishihara S. , Tsuda K. , Suzuki T. , Tsuchida E.
Published: April 2003

Rubbery poly(organophosphazene)s were synthesized, and were combined with cobaltporphyrin (CoP) which binds molecular oxygen rapidly and reversibly. The apparent oxygen‐binding equilibrium constant (Kapp) is in proportion to the physical solubility coefficient of oxygen in the polymer, although the reduced equilibrium and thermodynamic parameters are not dependent on the polymer matrix species. Diffusivity of oxygen via the fixed CoP(DC) is enhanced for poly(organophosphazene) membranes with a larger oxygen diffusion constant. Poly(organophosphazene) membranes with both a large Kapp and DC yield high oxygen permeability.
γ radiolysis of neat 2‐phenylheptamethyltrisilane as a model of polysilastyrene
Authors: Nakao Ren , Oka Kunio , Dohmaru Takaaki , Abe Yasuo , Horii Toyokazu , Kitao Teijiro
Published: April 2003

2‐Phenylheptamethyltrisilane as a model compound of polysilastyrene was irradiated at a high dose (1440 kGy) of γ‐rays without any additive. The trisilane was found to be resistant to γ‐rays, while it gave small amounts of Me6Si2, Me3SiSiMe2Ph, Me3SiH, Me3SiSiHMePh and (Me3Si)2 SiMeC6H4SiMe3. These products can be interpreted as being due to a chain contraction of the trisilane with the extrusion of methylphenylsilylene, a methyl migration with the extrusion of dimethylsilylene, a scission of an Si–Si bond due to an attack by hydrogen atoms, and a substitution of a hydrogen atom on the phenyl group by a trimethylsilyl radical. The same reactions, except the chain contraction, are observed in the cases of pentamethylphenyldisilane and 1,2‐diphenyltetramethyldisilane. On the basis of the data obtained, the chemical behavior of polysilastyrene during the irradiation is discussed.
Polyaniline: evidence of oxygen–polarons interactions to explain the high selectivity values in oxygen/nitrogen gas permeation experiments
Authors: Rebattet L. , Geniès E. , Allegraud J.‐J. , Pinéri M. , Escoubes M.
Published: April 2003

High selectivity between oxygen and nitrogen has been found by gas permeation with doped polyaniline. Because of the small difference in kinetic diameters, solubility rather than diffusion may explain the preferential oxygen permeation. Electron spin resonance (ESR) measurements have been performed to check whether interactions of oxygen with polarons in polyaniline exist. A tenfold decrease in the spin number was observed when the polymer was in the presence of oxygen rather than nitrogen. This result was interpreted as being due to interactions between oxygen triplet states and polarons of polyaniline.
Synthesis of novel polystyrene derivatives with pendant oligo(oxyethylene)cyclo‐triphosphazenes and ionic conductivities of their LiClO4 complexes
Authors: Inoue K. , Tanigaki T. , Yuan Z.
Published: April 2003

Ionic conductivities of complexes of polystyrene derivatives having a spacer, CH2O(CH2CH2O)n (poly‐(SEDEP), n = 1; poly(SDEDEP), n = 2), between backbone and pendant penta(methoxyethoxyethoxy)cyclotriphosphazene with LiClO4 were investigated as functions of temperature and salt concentration. The glass transition of temperature of poly(SEDEP) and poly(SDEDEP) was observed at −64 and −65°C, respectively. The extent of Tg elevation of the Li+–polymer complexes was not affected by the difference of spacer in the host polymers. The conductivities of the complexes exhibit non‐Arrhenius temperature dependence. The conductivities of poly(SDEDEP)–Li+ complexes were somewhat higher than those of poly(SEDEP) systems and the maximum value close to 10−4 S/cm at 50°C has been achieved at [Li+]/O = 0.08. The results are compared with those obtained previously for the complexes based on polymers which have the similar structures but no spacer, and the correlation between the conduction mechanism and polymer characteristics is discussed.
Ion conduction in mixtures of oligo(ethylene oxide) comb–branch polymer with dipositive cation salts
Authors: Cowie John M. G. , Ferguson Roderick , Billotte Stephane
Published: April 2003

A series of polymer–salt, solid solutions have been prepared using a comb–branch polymer with oligo(ethylene oxide) side chains and salts of divalent cations. The salts used were magnesium, zinc and copper triflate, and the copper (I) and copper (II) bromides. Homogeneous, single‐phase, solid solutions were obtained, except for CuBr, which showed poor solubility in the polymer. The addition of salt caused an increase in the glass transition temperature of the system, which was taken to be a reflection of the effective coordination of the cation by the polymer. The a.c. ion conduction was measured using the complex impedance method, and conductivities were obtained as a function of temperature. The magnitude of the conductivity was generally higher in these systems than observed in comparable mixtures when conventional polyethylene oxide was the host polymer. Conductivity was also found to depend on the length of the ethylene oxide side chain in the comb–branch polymers. There is some indication from the present results that the divalent salts may only be partially ionized giving only monovalent species, but this conclusion remains circumstantial until further work is carried out on similar multivalent salt systems.
Constant‐voltage polarization of symmetric polymer electrolyte cells with non‐blocking electrodes
Authors: Vincent Colin A. , Bruce Peter G. , Hardgrave Martin T. , Shi Jie
Published: April 2003

The steady state current flowing in a polymer electrolyte when a constant potential difference, ΔV, is applied to a symmetric cell of the type

has been determined as a function of the magnitude of the d.c. potential, the salt concentration and the temperature in amorphous PEO:LiCF3SO3 and PEO:LiClO4 systems.

Such measurements may be used to determine a practical electrolyte parameter, the current fraction, F+, which is defined as the ratio of the current flowing when the cell is passing a steady state current following establishment of a stable concentration gradient, to the current flowing in the absence of a concentration gradient. Under certain circumstances it is possible to identify the limit of the current fraction for ΔV → 0, F, with the transport number of M+. More generally, measurements of F+ yield useful information about the maximum current density which may be maintained at steady state, provided that the electrolyte conductivity is known—a situation which can be rapidly attained in paractical thinfilm devices.

It was found that: (i) F fell very significantly as the salt concentration was increased for the two lithiumbased systems; (ii) for these systems, F increased significantly with temperature at concentrations below 2.0 mol dm−3; (iii) F values for the LiCF3SO3‐based electrolytes were significantly higher than those for the LiClO4‐based electrolytes of the same concentration; (iv) F values for the LiCF3SO3‐based electrolytes were independent of the molecular weight of the polymer host.
Composite polymer ionics: advanced electrolyte materials for thin‐film batteries
Authors: Scrosati Bruno , Croce Fausto
Published: April 2003

In recent years there has been a continuously growing interest in the development and characterization of polymeric materials having a fast ionic transport. If prepared in the form of thin films, these materials behave as very convenient electrolytic separators for the realization of advanced design, plastic‐like, electrochemical power sources. Various classes of these polymer ionics have been developed and today many choices are available for the realization of devices with different energy and power capabilities. In this paper we describe the properties of a class of composite polymer ionic conductors having improved mechanical and electrochemical properties and which appear particularly suitable for the realization of high‐energy, rechargeable lithium batteries.
Gel‐type solid polymer electrolytes for rechargeable film batteries
Authors: Kabata Toshiyuki , Fujii Toshishige , Kimura Okitoshi , Ohsawa Toshiyuki , Samura Tetsuya , Matsuda Yoshiharu , Watanabe Masayoshi
Published: April 2003

Gel‐type solid polymer electrolytes (SPE) which consisted of LiBF4 as the electrolyte, a mixture of propylene carbonate and 1,2‐dimethoxyethane as the solvents, and a mixture of ethoxypolyoxyethyleneacrylate and trimethylolpropanetriacrylate as the monomers, were prepared by photopolymerization. The composition range for the gelation and the SPE formation was defined. Relationships between the composition of the SPE, and the ionic conductivity and modulus were clarified. The ionic conductivity of the SPE film, the composition of which was 13 wt% monomer, 20 wt% LiBF4 and 67 wt% solvent, was 2.7 × 10‐3 S/cm, and the modulus was 103 dyn/cm2 at 25°C. When a polyaniline(PANI)/SPE interface was formed on polyaniline films by photopolymerization at the optimal composition, the redox behavior of PANI was almost equivalent to that in nonaqueous electrolyte solutions. The discharge capacity of a Li/SPE/PANI film rechargeable battery was 116 mAh/g‐PANI (based on the weight of PANI), almost the same as that of a Li/nonaqueous electrolyte solution/PANI cell.
Recent advances in photosensitive polyimides
Authors: Ahne Hellmut , Leuschner Rainer , Rubner Roland
Published: April 2003

The state of the art of photosensitive polyimides is reviewed with respect to the incorporation of photosensitivity into both polyimide precursors and soluble polyimides, for patterning in positive and negative modes. This paper emphasizes, in particular, the discussion of the performance of commercially available photosensitive polyimides with respect to their applications in electronics. The decisive properties, especially the patterning performance, and in the case of precursors the curing conditions, required to obtain full imidization, thermomechanical and electrical properties, solvent resistance and water uptake, as well as planarization of the commercially available materials, are compared with each other. An outlook presents the future demands on photosensitive polyimides.
Synthesis and mechanical properties of novel photosensitive polyimides
Authors: Khanna Dinesh N.
Published: April 2003

This paper surveys novel photoimageable polyimides (PHIMPI), with emphasis on synthesis. Details of the chemistry and synthesis techniques on PHIMPI are discussed. A number of associated issues such as swelling, storage stability, shrinkage, photospeed, solvent developability, moisture absorption, thermal expansion and mechanical properties are presented.

Most of the photoimageable polyimides that are commercially suitable to date are negative‐acting, although recent developments in positive‐acting PHIMPI are included.
A mechanism for the electron beam lithography of solvent‐soluble photosensitive polyimides
Authors: Yamashita Takashi , Kudo Takafumi , Horie Kazuyuki
Published: April 2003

Solvent‐soluble and intrinsically photosensitive polyimides were prepared, and their electron beam reaction was investigated. Negative tone patterns were formed by the electron beam irradiation of PI(BTDA/DEDPM) and PI(BEDA/DEDPM). The mechanism for the pattern formation of PI(BTDA/DEDPM) was determined from transient absorption measurements, changes in the molecular weights, and IR spectrum measurements to be crosslinking via hydrogen abstraction by the triplet excited state benzophenone moiety. For the case of PI(BEDA/DEDPM), the pattern was formed by insolubilization due to chemical change in the polymer. These reactions are found to be so inhomogeneous that insolubilization of the polymer occurs at an early stage of gelation.
Photosensitive polyimides for applications in electrical and optical interconnection technology
Authors: Chakravorty K. K.
Published: April 2003

The application of photosensitive polyimides in electrical and optical interconnection technology is discussed. Critical properties of two photosensitive polyimide formulations with significantly different structural chemistries have been compared. Polyamic ester based formulations such as Selectilux® HTR3 show significant distortions in the photopatterned features upon high‐temperature baking, which can be ascribed to anisotropic shrinkage. A BTDA‐alkylated diamine based preimidized formulation (Probimide®), on the other hand, shows a more uniform shrinkage of the photopatterned features. HTR3 films interacts strongly with metals such as copper, which adversely affect the photopatternability of these materials. Planarization behavior in multiple layer structures has also been investigated. We explored the viability of these materials for applications in optical interconnection. Probimide® materials exhibit low scattering losses and appear to be promising candidates for the development of a MCM‐compatible optical interconnection technology. We also describe here a novel technique for optical recording of refractive index patterns in Probimide® films.
Photoreactive fluorinated polyimide protected by a tetrahydropyranyl group (THP) based on photo‐induced acidolysis
Authors: Omote Toshihiko , Hayashi Syun'ichi , Ishii Kazuhisa , Naitoh Kazuhiko , Yamaoka Tsuguo
Published: April 2003

A polyimide (6F‐THP) with a tetrahydropyranyl group (THP) in its side chain has been synthesized. The THP group exhibits a high acidolysis rate in this polymer's film. This rate was faster than that of a tertbutoxycarbonyl group (t‐BOC), which has been previously reported [1]. Furthermore, the deprotected fluorinated polyimide (6FDA‐AHHFP) became soluble in an aqueous base due to the presence of a hydroxyl group attached to the phenyl group of the diamine segment. The polyimide thus provides high performance as a photopolymer when used in conjunction with a photoacid generator after the post‐exposure baking process (PEB). The photoacid generators used in this study were p‐nitrobenzyl‐9,10‐dimethoxyanthoracene‐2‐sulfonate (NBAS) and diphenyliodonium‐9,10‐dimethoxyanthoracene‐2‐sulfonate (DIAS). The quantum yields of photodissociation and photoacid generation were also measured. The photoacid‐generating quantum yields closely corresponded to the photosensitivities of the photoreactive polyimide system. It was confirmed that the THP group was easily deprotected even in the 6F‐THP film with p‐toluenesulfonic acid as a model acid catalyst. The activation energy of the THP deprotection reaction was determined to be 12.8 kcal/mol (19.5 kcal/mol in the case of t‐BOC). The relationships between the THP deprotecting rate constant (kd) and acid molecular size and between kd and polyimide structure were further investigated.
Positive photosensitive polyimides with cyclobutane structure
Authors: Abe Toyohiko , Mishina Makoto , Kohto Noriaki
Published: April 2003

A new family of positive photosensitive polyimide (PPI) systems composed of solvent soluble polyimides (Pls) with cyclobutane (CBDA) structures and diazonaphthoquinone compounds (DNQ) has been prepared. Heat and catalytic imidizations were carried out to obtain CBDA Pls; the former was better than the latter in controlling the molecular weight of the Pl. The OH groups in the Pls were easily acetylated during catalytic imidization, so COOH groups were selected as weak acidic groups in the Pls. The COOH groups were also effective in giving the Pls an alkaline solubility. Therefore, Pls having COOH groups were superior to those having OH groups for PPI systems. The photosensitive properties of various PPl systems containing COOH were found to vary with the fraction of COOH groups in the Pls, the content of DNQ in the systems, and the molecular weight of the Pls.
Photoreactive fluorinated polyimide protected by tetrahydropyranyl (THP) group based on chemical amplification: Acid generation in polyimide film and lithographic properties
Authors: Naitoh Kazuhiko , Ishii Kazuhisa , Yamaoka Tsuguo , Omote Toshihiko
Published: April 2003

The photochemistry of photoacid generator (PAG), diphenyliodonium 9,10‐dimethoxyanthracene‐2‐sulfonate (DIAS) and diphenyliodonium 8‐anilinonaphthalene‐1‐sulfonate (DIANS) was investigated in both alkalinesoluble polyimide (6FDA‐AHHFP) and novolak films. The quantum yields of photodissociation of DIAS and DIANS in both 6FDA‐AHHFP and novolak films. The quantum yields of photodissociation of DIAS and DIANS in both 6FDA‐AHHFP and novolak films were determined as 0.11, 0.21, 0.12 and 0.26, respectively. On the other hand, the quantum yields for acid generation from DIAS and DIANS in both of these films were 0.07, 0.18, 0.09 and 0.22, respectively, in the presence of an acid indicator. These results indicate that the values of the quantum yields of photodissociation and photoacid formation for DIAS and DIANS in 6FDA‐AHHFP film are lower than those in novolak film. In order to elucidate the lowering of the quantum yields in 6FDA‐AHHFP film, fluorescence quenchings of sodium 9,10‐dimethoxy‐anthracene‐2‐sulfonate and ammonium 8‐anilinonaphthalene‐1‐sulfonate by a model compound of polyimide was carried out in acetonitrile. The fluorescences of these two salts were efficiently quenched by the model compound with the diffusion‐controlled rate constant in acetonitrile, suggesting that a strong electron‐accepting capability of the imide carbonyl group may hinder the electron transfer process within PAG molecules in 6FDA‐AHHFP film. Although a polyimide (6F‐THP) protected by tetrahydropyranyl group is insoluble in aqueous base, 6F‐THP film containing PAG became soluble in a 2:1 mixture of 2.0 wt% tetramethylammonium hydroxide (TMAH) and methanol by exposure to 365 nm light and successive post‐exposure baking (PEB) at 120°C for 10 min. The sensitivity and contrast of 6F‐THP with DIANS after the PEB conditions mentioned above were 110 mJ/cm2 and 3.7, respectively. A high‐resolution pattern with a good profile was transferred into the 3 μm thickness of the 6F‐THP film.
Photosensitive polyimides consisting of simple mixtures of 4‐substituted diazonaphthoquinones and polyamic acids
Authors: Hayase Shuzi , Mikogami Yukihiro , Takano Kei , Nakano Yoshihiko , Hayase Rumiko
Published: April 2003

Polyimide resists that can be developed with a basic aqueous solution were produced by simple mixtures of conventional polyamic acids and naphthoquinone diazides in which sulfonate groups are substituted at the 4‐position. The diazonaphthoquinones bearing electron‐withdrawing groups gave negative tone resists. On the other hand, those bearing electron‐donating groups gave positive tone resists. The difference in the resist behaviors depending on the photoactive structure was explained by crosslinking caused by photogenerated sulfonic acids. The thermal stability of polyimides prepared from the resists was almost the same as that of conventional polyimides.
New polyurethanes able to bind high amounts of heparin, suitable as biomedical compositions
Authors: Marconi W. , Magnone G. , Martinelli A. , Piozzi A.
Published: April 2003

The synthesis of new segmented polyurethanes containing different amounts of N,N‐diethylaminoethyl‐N′‐2,2 hydroxymethylpropionamide, and able to bind, after suitable quaternization, high amounts of heparin, is described. The quaternization is carried out on organic solutions of the polymers. Polymers have been characterized by spectroscopic techniques (transmission and reflectance IR and 1H and 13C NMR), molecular weight measurements and differential scanning calorimetry. The heparin content of the polymer films was determined by a colorimetric system, and its biological activity was evaluated in vitro by activated partial thromboplastin time (APTT) measurements. The distribution of heparin on the surface and in bulk of the heparinized films was evaluated by scanning electron microscopy (SEM) combined with X‐ray energy dispersive spectroscopy.
Antifoam effect of highly fluorinated polysiloxanes
Authors: Kobayashi Hideki , Owen Michael J.
Published: April 2003

Aqueous foaming solutions of permethylsiloxane surfactants and fluorocarbon surfactants are very resistant to antifoaming. Newly developed polysiloxane fluids having highly fluorinated chains showed very low surface tensions and were examined as antifoaming compounds to test against these two classes of surfactant systems. The fluorinated polysiloxanes evaluated were poly‐[(3,3,4,4,5,5,6,6,6 ‐ nonafluorohexyl)methylsiloxane] (PNFHMS), and 1H,1H,2H,2H‐perfluorodecyl‐terminated polydimethylsiloxane (Def‐DMS). Poly(dimethylsiloxane) (PDMS) was also studied as a standard siloxane polymer fluid for comparison. The antifoams composed of PNFHMS and Def‐DMS polymer fluids incorporated with silica showed effective antifoaming against the low surface tension aqueous solutions of representative permethylsiloxane and fluorocarbon surfactants.
Thermotropicity of fully aromatic polyesters based on 3,4′‐dicarboxydiphenyl ether
Authors: Carpaneto Luca , Marsano Enrico , Valenti Barbara , Costa Giovanna , Guenza Marina
Published: April 2003

3,4′‐Substituted aromatic monomers, consisting of two phenylene units joined together by linking groups such as ketone or methylene, have recently been used for the preparation of quasi‐rigid fully aromatic thermotropic polymers, based on conformational isomerism, with accessible transition temperatures.

In this work the polyester of 3,4′‐dicarboxydiphenyl ether and hydroquinone is considered: an Ullmann condensation has been carried out for the preparation of the asymmetric monomer, and low‐temperature solution polycondensation has been used to synthesize the polymer. Although a liquid crystalline behavior could be expected, the polyester melts to an isotropic phase. Several copolymers have been prepared, by partially substituting either the asymmetric monomer with terephthalic acid or hydroquinone with different diphenols. The attempt to decrease the stability of the crystalline phase did not lead to significant results. The appearance of the nematic phase in some samples has been attributed to an increased chain stiffness, expressed in terms of persistence length as derived from molecular dynamics (MD) simulations.
Polymeric photoinitiators based on side‐chain benzoin methyl ether and tertiary amine moieties for fast UV curable coatings
Authors: Angiolini Luigi , Caretti Daniele , Carlini Carlo , Lelli Nicola
Published: April 2003

The synthesis is reported of a new series of polymeric photoinitiators obtained by copolymerization of a‐methylolbenzoin methyl ether acrylate (MBA) with different N,N‐dialkylamino alkyl acrylates.

The copolymers have been fully characterized and employed in the photoinitiated polymerization and crosslinking reactions of a standard acrylic formulation for clear curable coatings.

The photoinitiation activity of the above systems has been measured by using microwave dielectrometry and differential photocalorimetry, and compared with that found for the corresponding low‐molecular‐weight models.

The results clearly indicate that the copolymeric systems display a remarkable decrease of the induction period and an improved overall activity in the UV curing of the acrylic coatings.

An interpretation of the experimental findings is also reported.
Synthesis of poly(1.4.‐benzamide) in solutions of randomly coiled polymers
Authors: Berger Werner , Kummerlöwe Claudia , Henze Andree
Published: April 2003

The polycondensation of p‐aminobenzoic acid by the use of triphenylphospine and hexachloroethane is described. One way to obtain a mixed solution of rigid rod and flexible coil polymers is the polycondensation of the rigid chains in a solution of a flexible polymer matrix. Results on matrix polycondensation of poly(p‐benzamide) in solutions of poly(methyl methacrylate), poly(methyl methacrylate‐co‐styrene), polystyrene and polyacrylonitrile are reported. It is shown that there exists an interrelation between the phase behavior of the mixed polymer solutions and the influence of the matrix polymer on the synthesis of poly(1.4.‐benzamide). The ternary phase diagrams of the rigid rod/flexible coil polymer solutions were determined.
Photochemical reactivities of photosensitive polymers containing chalcone derivatives
Authors: Akelah Ahmed , Selim A. , El‐Deen N. Salah
Published: April 2003

Monomeric vinyl chalcone derivatives were prepared by the condensation reaction of p‐hydroxybenzaldehyde with acetophenone derivatives in the presence of sodium ethoxide as a base, followed by esterification of their hydroxy groups with methacryloyl chloride. The monomers, 4‐(methacryloyloxy)chalcone derivatives, have been polymerized by a free radical technique. Copolymers containing the chalcone groups with different ratios of p‐nitrophenylmethacrylate as photosensitizer group have also been prepared.

The photosensitivities of the polymeric chalcone derivatives were investigated through their photochemical reaction on exposure to UV light, and by measuring the changes in their UV spectra before and after irradiation. The results obtained from the disappearance rates of the CC bonds indicate that the photoreactivities of the polymers are largely affected by the position of the substituent in the phenyl ring of the chalcone, the photosensitizer group ratio, and the irradiation time.
Polymerization of olefins in the presence of metal powders with homogeneous catalysts
Authors: Kaminsky Walter , Zielonka Holger
Published: April 2003

Homogeneous catalysts based on metallocenes/methylaluminoxane are totally absorbed on surfaces of different metals. Because the methylaluminoxane is relatively stable against small molecules such as water covering metal surfaces, the aluminoxane can be fixed on powders without losing its activity. After treatment with the metallocene, active sites are only formed on the surface of the fillers. Upon injection of the olefins they are polymerized in the presence of the metals. Olefins such as ethene and propene, and cycloolefins or dienes, are used.
Chemical modification of neodymium high cis‐1,4 polybutadiene with styreneoxide
Authors: Hattori Iwakazu , Yasuda Kyouyuu , Sakakibara Mitsuhiko , Makino Kenya
Published: April 2003

The polymerization of 1,3‐butadiene (BD) was carried out in the presence of a catalyst composed of neodymium 2‐ethylhexanoate, triisobutyl aluminum, diisobutyl aluminum hydride (DIBAH), ethylaluminum sesquichloride and acetylacetone. The molecular weight of the BR could be controlled with DIBAH. The reactive polymer was then chemically modified with styreneoxide (STO). The STO content of BR increased with the decrease in the molecular weight of the BR. This polymer was modified by the STO at the chain terminal end. The physical properties of the vulcanizates with the modified BR were measured. The abrasion resistance and the tensile strength were found to be improved.
Synthesis and properties of super high molecular weight polyhexene‐1
Authors: Sukhova T. A. , Dyachkovskii F. S.
Published: April 2003

TiCl4–alkylaluminium systems have been fixed on graphite and other inorganic supports and used in hexene‐1 polymerization. Kinetic studies show a decreasing polymerization rate from high initial values. High conversions (up to 99%) are reached, although retardation by a diffusion process is observed above 60%. The polymers have high molecular weights (up to 107) and high isotacticity (up to 98.5% from 13C NMR analysis). The effects of the nature of the components (carrier, alkylaluminium), and their concentration on the polymerization kinetics and the molecular structure of the polymer are discussed. The linear chain has one alkyl group (the alkylaluminium) and one unsaturation as the chain ends. Despite the high tacticity, the polymers are amorphous and rubber‐like.
Metal ion doped polymers as media for optical memories
Authors: Manivannan Gurusamy , Changkakoti Rupak , Lessard Roger A.
Published: April 2003

Polymer materials are making an impact on optical storage technology to develop high information density and fast access type memories with a high read‐out efficiency. The principle and advantages of three‐dimensional (3‐D) data storage in the form of interference patterns (holograms) have been outlined. Three different information storage materials have been developed by doping metal ions such as Cr(VI) and Fe(III) in water‐soluble polymers, namely poly(vinyl alcohol) (PVA) and poly(acrylic acid) (PAA), which need no further thermal or chemical treatment. Volume transmission holograms have been recorded in dichromated poly(vinyl alcohol) (DCPVA), ferric chloride doped poly(vinyl alcohol) (FePVA) and dichromated poly(acrylic acid) (DCPAA), with and without an electron donor (dimethyl formamide), and xanthene dyes (fluorescein, eosin Y and Rose Bengal). Different parameters influencing the holographic performance have been optimized to achieve a high real‐time diffraction efficiency (∼70%). An electron transfer process from the polymer matrix to Cr(VI)/Fe(III), leading to the photocrosslinking of the polymer in the form of an interference pattern, has been suggested as the mechanism of information storage (hologram recording) in these materials.
The effect of the bridge group on the thermal stability of nitro‐substituted aromatic polyamides
Authors: Oh Sang Yeol , Pearce Eli M.
Published: April 2003

The effect of introducing a bridge group into the diamine moiety on the thermal stability of aromatic polyamides substituted with nitro group in the diamine ring at the ortho position to the amide group was studied. Our present work showed that the bridge group, whether it was electron withdrawing or releasing, did not have a significant effect on the activity of the nitro group for the intramolecular cyclization reaction to poly(benzoxazole)s.
Calculation of heat transfer and uniformity of chemical amplification during post‐exposure bake
Authors: Ban Hiroshi , Sakai Tomoaki , Saito Kenichi
Published: April 2003

Heat transfer in a resist‐coated silicon wafer using a bake process is theoretically evaluated by modeling the three‐dimensional diffusion process, focusing on the controllability of the lithographic performance of chemically amplified resists. Six models of various ambient conditions are used. The proximity gap between the hotplate and the wafer is found to have a dominant influence on the heat transfer process for the whole system. Because the atmosphere near the wafer acts as a thermal diffusion buffer layer, no temperature gradient occurs in the resist, even when it is subjected to convective heat transfer from the resist surface. Experimental results obtained by X‐ray lithography confirm the calculation results.
Holographic recording using visible‐light sensitive polymers based on cationic polycondensation
Authors: Hotta Tsuyoshi , Yamaoka Tsuguo
Published: April 2003

Negative‐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

The 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

The 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

The 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

The 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

Racemic 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

Poly(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

Five 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

Transparent 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

Processable 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

Facilitated 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.