bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis and thermal stability, dielectric, and conductivity characteristics of some carbazole‐bearing pendant and backbone sulfones
Authors: Mitra Pradyot , Biswas Mukul 
Published: April 2003

AbstractA group of poly(N‐vinylcarbazole) pendant polysulfones has been prepared by reacting it with benzene, toluene, p‐chlorobenzene‐ and p‐nitrobenzenesulfonyl chloride and N‐methyl carbazole, 3,6‐disulfonyl chloride by the Friedel Crafts reaction. Carbazole‐based backbone polysulfones have also been prepared by the reaction of N‐methyl carbazole, 3,6‐disulfonyl chloride and biphenyl, naphthalene, anthracene, and carbazole in presence of anhydrous aluminum chloride. The various sulfone polymers, thus prepared, have been structurally characterized by elemental analysis and IR spectroscopy. Detailed analyses of thermal stability, dielectric, and conductivity characteristics have revealed certain significant differences between these two types of sulfone polymers.
Properties and swelling characteristics of cross‐linked poly(vinyl alcohol)/chitosan blend membrane
Authors: Kim Jin Hong , Kim Ju Young , Lee Young Moo , Kim Kea Yong 
Published: April 2003

AbstractBlend membrane consisting of poly(vinyl alcohol) (PVA) and chitosan was prepared from a solvent‐casting technique and characterized for their intermolecular interactions using infrared and X‐ray diffraction methods. Cross‐linking the blend with glutaraldehyde produces a membrane with lower crystallinity and a smaller swelling degree, but having improved thermostability and mechanical properties. The present blend membrane shows a pH‐dependent swelling characteristic and will be discussed in detail. © 1992 John Wiley & Sons, Inc.
Effect of acid–base interaction on the sorption characteristics of liquids in poly(vinylidene fluoride)
Authors: Myeong Wan‐Jae , Ihm Son‐Ki 
Published: April 2003

AbstractThe sorption characteristics of various liquids in poly(vinylidene fluoride) (PVDF) were investigated in relation to the Lewis acid–base interaction between the liquids and the polymer. The sorption amount of various liquids and the sorption selectivity of binary mixtures in PVDF were measured and their characteristics were found to be significantly affected by acid–base interaction. The acid–base interaction was evaluated from the Drago constants of PVDF, which were obtained by extending the Fowkes' method observing the shift of stretching frequency of the carbonyl bond of ethylacetate sorbed in PVDF. The partial molar enthalpy change of mixing at infinite dilution was estimated using the Drago constants of PVDF and used as a parameter explaining the sorption characteristics of liquids in PVDF. © 1992 John Wiley & Sons, Inc.
Characterization of cellulose–chitosan blend films
Authors: Hasegawa Makoto , Isogai Akira , Onabe Fumihiko , Usuda Makoto , Atalla Rajai H. 
Published: April 2003

AbstractInteractions between cellulose and chitosan molecules in cellulose–chitosan blend films, prepared using trifluoroacetic acid as a cosolvent for the two polysaccharides, were studied by X‐ray diffraction and Raman analyses and by measurements of mechanical properties of the blend films. Crystallinity of cellulose in the blend films decreased with an increase in chitosan content. The blend films had tensile strengths of 45–100 MPa and Young's moduli of 2–7.5 GPa in dry states. These values had the maximum around 30% chitosan content in the blend films. These results suggested the presence of interactions between cellulose, chitosan, and water molecules in the films. However, Raman analysis suggested that cellulose and chitosan molecules in the blend films seemed to have the same secondary structures as those in 100% cellulose and 100% chitosan films, respectively. Thus, these results indicate the presence of interactions in the interfacial region between small domains of cellulose and chitosan. The presence of chitosan molecules may lead to decrease in the domain size of cellulose, and to increase in the interfacial region between cellulose and chitosan domains.
Synthesis of substituted polymethylenes from acenaphthylene by radical polymerization and copolymerization
Authors: Otsu Takayuki , Matsumoto Akikazu , Nakamura Keisuke 
Published: April 2003

AbstractRadical polymerization of acenaphthylene (Ace) as a 1,2‐disubstituted ethylene was investigated. It was found that the polymerization rate (Rp) was expressed as follows: Rp = k[Ace]1.0[AIBN]0.68, and that the overall activation energy was 113 kJ/mol for polymerization with 2,2'‐azobisisobutyronitrile (AIBN) in benzene at 50–70°C. Poly(Ace) obtained was characterized by NMR spectroscopy and GPC. Some substituted copolymethylenes were also prepared by radical copolymerization of Ace with other 1,2‐disubstituted ethylenes, that is, maleic anhydride, diisopropyl fumarate, and N‐cyclohexylmaleimide. The monomer reactivity ratios were determined from comonomer–copolymer composition curves.
N‐methylation of wholly aromatic polyamides for size‐exclusion chromatography
Authors: Mourey T. H. , Guistina R. A. , Bryan T. G. , Thornbury R. F. , Blevins R. , Perry R. J. , Turner S. R. 
Published: April 2003

AbstractWholly aromatic polyamides, including poly(1,4‐phenyleneisophthalamide) and poly(1,4‐phenyleneterephthalamide) are N‐methylated to render them soluble in N,N‐dimethylformamide, a common size‐exclusion chromatography eluent. The procedure N‐methylates 50–55% of the total amide linkages in these two examples, permitting reproducible measurement of their absolute molecular weight distributions using differential viscometry detection. There is no observable degradation in molecular weight resulting from the N‐methylation, provided the excess methylating reagent is destroyed shortly after completion of the derivatization by quenching with potassium acetate. The validity of the molecular weight data obtained by the method is confirmed by light‐scattering measurements on derivatized polymer and by comparison to the molecular weight of underivatized polymer that can be approximated from the intrinsic viscosity in concentrated sulfuric acid. The method is applicable to a variety of wholly aromatic polyamide structures. Examples are given.
Preparation of monodisperse carbonaceous particles with micro‐, meso‐, and macroporous structures
Authors: Daer Khaled M. , Levendis Yiannis A. 
Published: April 2003

AbstractSpherical, highly porous synthetic carbon particles have been prepared from formulations of either poly(furfuryl alcohol) or poly(vinyl acetate) mixed with a solvent and poreforming agents. Production was carried out by atomizing these mixtures inside a thermal reactor and drying the resulting aerosol. The size of the collected polymeric particles was controlled by preadjusting the parameters of the atomization process. Fine‐tuning of the process resulted in the generation of batches of monosized particles. Subsequent thermal degradation at 600°C resulted in porous chars with controlled pore‐size distributions. Several distinct pore structures were superimposed using this technique with pore widths spanning the region from a few nanometers to a few tens of micrometers. Spherical and equal‐sized macropores were also generated with a special technique described herein. All chars were produced in batches of spherical and monodisperse particles, with diameters in the range of 20–150 μm. BET surface areas were measured to vary from 1 m2/g to over 150 m2/g prior to any oxidative treatment. Porosities varied from 10 to 80%.
Thermal aging of plasticized PVC. II. Effect of plasticizer loss on electrical and mechanical properties
Authors: Audouin L. , Dalle B. , Metzger G. , Verdu J. 
Published: April 2003

AbstractThe change of mechanical properties was followed during thermal aging at 85, 95, 105, and 120°C of the 10 PVC–didecylphthalate extrudates studied in the first part of this paper, but also of four new samples differing only by the plasticizer concentration. For these latter samples, the change of dielectric properties was also studied. It appears that the dielectric properties are essentially the function of the plasticizer concentration whatever is the initial concentration or aging conditions. In contrast, the mechanical properties vary in a more complex way and cannot be predicted by a simple physical model. It is suggested that, among other factors, the depth distribution of plasticizer can play an important role.
Thermotropic liquid crystalline behaviors of ethylcellulose
Authors: Jianan Chen , Yifang Huang , Jinyue Yuan , Shaoqiong Yan , Hua Ye 
Published: April 2003

AbstractThe thermotropic liquid crystalline behaviors of ethylcellullose (EC) were investigated by DSC, polarizing microscope with hot stage, and capillary rheometer. It was found that only those EC that have the ethoxyl content over 45% can exhibit the thermotropic liquid crystalline behaviors: the DSC trace showed the transition from mesophase to isotropic phase, the texture appeared under the crossed polarizer, and the rheological flow curves exhibited two yield points.
Graft copolymerization of methacrylates onto wool fibers
Authors: Liouni Maria , Touloupis Costas , Hadjichristidis Nikos , Karvounis Sotiris , Varriano‐Marston Elizabeth 
Published: April 2003

AbstractGrafting of butyl (BuMA), decyl (DeMA), and octadecyl methacrylate (ODeMA) onto reduced wool was carried out by using K2S2O8 or K2S2O8–LiBr redox system as initiator. The influence of the monomer and monomer concentration, temperature, and duration of the reaction on the percentage of grafting was studied. Evidence of grafting was provided by scanning electron microscopy, size exclusion chromatography, and infrared spectroscopy.
Some aspects of stabilization and degradation of nigerian natural rubber (II): The environmental degradation of DBHBT‐modified unprocessed, unvulcanized nigerian natural rubber
Authors: Ebi G. C. , Kolawole E. G. 
Published: April 2003

Abstract3,5‐Di‐tert‐butyl‐4‐hydroxybenzyl thioglycollate (DBHBT) was bound to the natural rubber (Hevea Brasilenisis) latex using 4,4'‐azobiscyanovaleric (AZBN) acid‐ferrous sulfate redox system. The degradation of various dilutions of the master batch as cast films under environmental influence has been investigated using spectroscopic method. Latex‐bound DBHBT protects natural rubber latex against environmental degradation with an optimum concentration around 50%. The formation of C0 groups by some pathways independent of OH groups and allylic hydrogen atoms has been suggested in the natural weathering of DBHBT‐modified and unprocessed natural rubber.
Synthesis and photoelectrical properties of poly[2,6‐(p‐phenoxy)‐4‐phenylquinoline]
Authors: Kim Kyeong‐Ah , Park Soo Young , Kim Yoo Joong , Kim Nakjoong , Hong Sung Il , Sasabe Hiroyuki 
Published: April 2003

AbstractNew heteroaromatic polymer containing quinoline unit in the main chain, poly[2,6‐(p‐phenoxy)‐4‐phenyl quinoline] (PQ), was synthesized by the acid‐catalyzed self‐condensation reaction [Friedländer quinoline synthesis] of 4‐amino‐4′‐acetyl‐3‐benzoyldiphenyl ether, and its chemical structure was characterized by IR and NMR spectra and also by elemental analysis. The PQ was soluble in common organic solvents such as chloroform or tetrahydrofuran; thus a strong coherent film of this polymer could be easily prepared from the solution by the casting or spin‐coating technique. Attributing to the wholly aromatic chemical structure, PQ appeared an extremely high thermal stability as to show no weight loss up to 550°C both in air and nitrogen atmosphere. From the UV–VIS absorption spectra, we found that PQ had a strong tendency to form the charge transfer (CT) complex with electron acceptors such as 2,4,7‐trinitrofluorenone (TNF). The CT complex film of PQ–TNF showed a good photoconductivity even under the ambient room illumination and was utilized for the fabrication of photovoltaic device whose conversion efficiency was around 10−2%.
Plasma polymerization of octafluorocyclobutane and hydrophobic microporous composite membranes for membrane distillation
Authors: Kong Ying , Lin Xiao , Wu Yonglie , Chen Jie , Xu Jiping 
Published: April 2003

AbstractIn this paper, hydrophilic microporous cellulose nitrate membranes have been surface‐modified by plasma polymerization of octafluorocyclobutane (OFCB). The microporous composite membranes with a hydrophilic layer sandwiched between two hydrophobic layers have been obtained. The obtained composite membranes have been used in a membrane distillation (MD) process and have exhibited good performance. The effects of polymerization conditions, such as glow‐discharge power and deposition time, on the structures and MD performances of the obtained composite membranes have been investigated by SEM, X‐ray microscopical analysis, and XPS. The polymerization conditions should be as mild as possible in order to prepare the hydrophobic composite membrane with good MD performance. The typical MD behaviors of the obtained hydrophobic composite membranes are in agreement with that of hydrophobic membranes directly prepared from hydrophobic polymeric materials, like PVDF, PTFE, or PP.
Polyimides derived from a methylene‐bridged dianhydride
Authors: Boston Harold G. , St. Clair Anne K. , Pratt J. Richard 
Published: April 2003

AbstractA series of linear aromatic polyimide films that are based on a novel methylene‐bridged dianhydride, 3,3′‐bis(3,4‐dicarboxyphenoxy) diphenylmethane dianhydride, have been synthesized and characterized. High molecular weight polyamic acids were prepared by combining this dianhydride with numerous aromatic diamines. The effects of thermal and chemical imidization of the polyamic acids are discussed as they relate to the dielectric constant, optical transparency, and solubility of the resulting polyimide films. The objective of this work was to obtain low dielectric, optically transparent, and soluble polyimides that can be easily processed as coatings or composite matrices for advanced aerospace and electronics applications.
Modeling the effects of micromixing and start‐up procedures on bulk copolymerization and copolymer in a tubular reactor
Authors: Atiqullah M. , Hassan M. M. , Beg S. A. 
Published: April 2003

AbstractThe combined effects of micromixing and start‐up procedures on free radical, bulk copolymerization of styrene and acrylonitrile in an isothermal, premixed‐feed tubular reactor have been theoretically analyzed. An axial dispersion model, which takes into account the entire range of backmixing, froms the basis of this analysis. Model predictions show that the overall conversion decreases with the increase of initial styrene content in the reactor, and is not affected by the degree of micromixing. However, for the nonazeotropic feed, the copolymer composition distribution becomes wider with the increase of initial acrylonitrile content in the reactor. For the azeotropic feed, broadening occurs with the decrease of initial acrylonitrile content in the reactor. Average copolymer composition is not affected either by micromixing or start‐up procedure.
X‐ray investigations on annealed fibers of poly(p‐phenylene‐1,3,4‐oxadiazole)
Authors: Hofmann D. , Leonhardt R. , Weigel P. 
Published: April 2003

AbstractThe influence of annealing on the supermolecular structure of commercial, thermostable fibers, spun from solutions of poly(p‐phenylene‐1,3,4‐oxadiazole) (POD) in H2SO4, is examined. The crystalline α‐modification of thermally treated POD fibers has an orthorhombic unit–cell probably of space group P212121. The symmetry of the single POD chain in these crystallites is 21. The unit–cell dimensions are a = 1.235 nm, b = 0.655 nm, c = 1.40···1.47 nm, where c depends on the annealing temperature Ta. The unit cell contains 4 chains of two monomers each. Annealing up to Ta of about 755 K causes increases in crystallite size, crystalline orientation, and linear degree of order, combined with an improved axial Young's modulus E. Thermal degradation at higher temperatures leads to the breaking of tie molecules in general, while UV‐radiation selectively damages tie molecules that are not taut.
Influence of an electric field on polar‐group orientation and adhesion at poly(ethylene terephthalate) surfaces
Authors: Lavielle L. , Nakajima K. , Schultz J. 
Published: April 2003

AbstractApplication of a high continuous electrical field accelerates the orientation kinetics of polar groups at a polymer–water interface and so improves the surface polarity. This is preliminary to adhesion establishment on a polar substrate. Adhesion of PET and gelatin performed under an electric field leads to an increase of the interfacial adhesion properties, due to simultaneous effects of the electric field at the interface. Polar‐group orientation at a polymer surface and electrical aspects of adhesion are therefore self‐consistent.
Graft copolymerization of polyfurfuryl alcohol and cellulose
Authors: Nguyen Charles , Zavarin Eugene 
Published: April 2003

AbstractViscosity of polyfurfuryl alcohol (PFA) and addition of hydroquinone exert a strong positive effect on grafting polyfurfuryl alcohol to cellulose fiber with H2O2/Fe2+ oxidant in an aqueous slurry at pH 2. Composition of the atmosphere and the nature of acids used to adjust pH does not influence the reaction, with the exception of phosphoric acid, which negatively influences polymer loading. Conducting the reaction in nonaqueous media inhibits grafting. K2S2O8, Ce(SO4)2, and K2Cr2O7 perform as well as H2O2/Fe2+, whereas H2O2/thiourea dioxide, H2O2/thiourea, NH4VO3, KMnO4, and KNO3 give inferior polymer loads; Mn3+/acetylacetonate and azobisisobutyronitrile are ineffective. A small improvement in polymer loading is obtained by gradual addition of the oxidant to the reaction slurry.
Glucose‐responsive insulin release from poly(vinyl alcohol)‐blended polyacrylamide membranes containing glucose oxidase
Authors: Chandy Thomas , Sharma Chandra P. 
Published: April 2003

AbstractGlucose‐sensitive membranes that can increase their permeability in the presence of glucose have been developed. Membranes are fabricated by free‐radical polymerization of acrylamide and poly(vinyl alcohol) blends, containing glucose oxidase (GOD). The polymers are hydrogels, with water content in the range of 85–95%, depending on the pH or glucose concentration. The gluconic acid produced by an enzymatic reaction between glucose oxidase and glucose induces a decrease in pH value of the medium. This may causes the protonation of the amino groups in the membrane, resulting in an increase in water content of the polyamine membrane or which changes the solubility of insulin and the diffusional driving force. The in vitro retention of the enzyme activity by the membrane is also reported. It appears that the problem of membrane rupture may be alleviated by the blending of polyacrylamide (AA) with poly(vinyl alcohol) (PVA), since they have demonstrated an improved wet strength, without altering their insulin‐transport properties. This preliminary report proposes the possibility of developing glucose‐sensitive membranes for controlled delivery of insulin and also benefits from ongoing research on biosensors.
Crystal orientation distributions in injection‐molded polypropylene compounds
Authors: Chen Z. , Finet M. C. , Liddell K. , Thompson D. P. , White J. R. 
Published: April 2003

AbstractThe crystal orientation distribution in injection‐molded bars made from several polypropylene compounds has been investigated using pole figure analysis. The fillers used were glass fibers, chalk, and talc, and some compounds contained one filler and others contained glass fibers plus one or both of the others. All compounds showed strong orientation in the skin with the b‐axis of the monoclinic crystals lying preferentially normal to the flow direction and in many cases parallel to the normal to the bar face. This normal direction orientation was very strong in compounds containing talc and is probably caused by crystals forming with their (010) planes on the talc platelet faces, which align themselves parallel to the mold face. Strong orientation persists into the interior of the moldings containing talc, whereas in the other compounds, the orientation at intermediate depths is much less pronounced than in the skin. © 1992 John Wiley & Sons, Inc.
Structural characteristics of wool fiber modified with itaconic anhydride
Authors: Tsukada Masuhiro , Goto Yohko , Romanó; Maria , Ishikawa Hiroshi , Shiozaki Hideki 
Published: April 2003

AbstractThe physicochemical properties of wool fibers chemically modified with itaconic anhydride in dimethylformamide were analyzed by DSC, TMA, and TGA and on the basis of measurements of the tensile characteristics. The acyl content in wool fiber increased even at the comparatively low reaction temperature (65°C) compared with that in silk fiber; this fact was due to the larger number of reactive sites in the wool than in silk such as basic amino acid residues. On the basis of DSC, TMA, and TGA analyses, the high thermostability of the modified wool fiber was evident. The molecular orientation, evaluated from the birefringence measurement, decreased slightly after the modification; however, tensile properties and surface characteristics of the wool fiber were not damaged. © 1992 John Wiley & Sons, Inc.
Plasticizing polyesters of dimer acid and butane diol
Authors: Bajpai U. D. N. , Singh Kavita , Nivedita  
Published: April 2003

AbstractThe polyesterification reaction between dimer acid and 1,4‐Butane diol under different experimental conditions has been studied to obtain the optimum conditions for synthesizing poly(1,4‐butanediol)dimerate plasticizers. The effect of varying molar ratio and catalyst concentration on acid number, intrinsic viscosity, and molecular weight have been investigated. It has been found that p‐toluene sulfonic acid is an effective catalyst for the polyesterification reaction. © 1992 John Wiley & Sons, Inc.
Pore formation, permeability, and permselectivity in porogen derived membranes
Authors: Eyal A. M. , Hajdu K. , Hazan B. , Edelstein D. 
Published: April 2003

AbstractPorogen derived membranes, formed on decomposition of porogen molecules homogeneously dispersed in premembranes, were divided into two groups according to permeability and permeation mechanism. The more open membranes were formed when premembranes were cast on nonwoven polyester cloth support, or when decomposition products were extracted by solvent. The molecular cut off found for these membranes was at about 1000 Daltons and permeability was mainly determined by permeants' diffusivity and concentration. Permeability through the denser membrane was mainly determined by the permeants' partial vapor pressure, leading to high permselectivities. These denser membranes allowed relatively high osmotic water permeation while practically blocking permeation of solutes, such as salt, in the opposite direction. These membranes were thus also suitable for concentration of aqueous solutions by water removal into concentrated electrolyte solutions. © John Wiley & Sons, Inc.
Synthesis of block copolymers by the combination of chain transfer polymerization and initer process
Authors: Demircioglu Perihan , Acar Metin H. , Yagci Yusuf 
Published: April 2003

AbstractRadical polymerizations of styrene (St) and methyl methacrylate (MMA) were carried out in the presence of tri phenylmethyl mercaptan (TPMM) as a chain transfer agent to give trityl (triphenylmethyl) terminated polymers. Transfer constants were found to be 17.8 and 0.71 for St and MMA, respectively. Trityl terminated polymers served as thermal “INITERS” for polymerization of vinyl monomers which proceeded via a quasi‐living radical mechanism. This procedure makes it possible to prepare block copolymers. © John Wiley & Sons, Inc.