bluuebunny/crossref_metadata_2025_split huggingface dataset:
Changes in sol fraction during peroxide crosslinking of linear low‐density polyethylenes with homogeneous distribution of short chain branching
Authors: Sajkiewicz P. , Phillips P. J. 
Published: April 2003

AbstractFTIR measurements of sol fractions were carried out in order to assess side reactions during dicumyl peroxide (DCP) crosslinking of linear low density polyethylenes (LLDPEs) with homogeneous distribution of short chain branching. The changes of methyl and olefinic unsaturation concentration were measured as a function of degree of branching and DCP content. The changes of methyl and vinylidene concentration indicate that the scission probability has greater significance for the samples with initial branch content above 31 CH3/1000 C and increases with increasing DCP concentration. The analysis of trans‐vinylene concentration indicates that the probability of disproportionation also increases with increasing DCP content. The changes of methyl concentration in the sol fraction of the sample containing initially ca. 23 CH3/1000 C with increasing DCP content could be interpreted using the dependence of crosslinking efficiency on branch content found previously for some range of branch concentration. © 1995 John Wiley & Sons, Inc.
Synthesis and polymerization of coupled compounds of 1,11‐dodecadiyne
Authors: Nezu S. , Walsh S. , Meille V. , Yoshida M. , Lando J. B. 
Published: April 2003

AbstractThe dimer, trimer, and tetramer of 1,11‐dodecadiyne, HCC(CH2)8CCH, were synthesized. The solid‐state polymerization of the dimer was investigated by infrared (IR) spectroscopy. IR bands due to the diacetylene moiety were identified through the comparison of the IR spectra of the dimer, trimer, and tetramer. The dimer was found to have two polymorphs, melt‐crystallized and solution‐crystallized. Both of the polymorphs undergo solid‐state polymerization by exposure to γ‐ray or UV irradiation. The former has higher polymerizability for the diacetylene moiety than the latter. The solid‐state polymerization of the terminal acetylene group was not observed. It is shown that the previously reported dimer structure in which both the diacetylene and terminal acetylene groups are polymerized to form an inherently electrically conducting polymer is incorrect. © 1995 John Wiley & Sons, Inc.
Swelling‐assisted modification of poly(ethylene terephthalate) by methacrylic acid
Authors: Xue Jianxian , Wilkie Charles A. 
Published: April 2003

AbstractWhen a poly(ethylene terephthalate), PET, film is heated in an aqueous solution of methacrylic acid in the presence of hydrogen peroxide as an initiator, it is found that the weight of the film is increased. The amount of methacrylic acid that may be added onto the film is dependent upon the concentration of the monomer, the initiator, and the temperature at which the reaction occurs. Pretreatment of the film with 1,1,2,2,tetrachloroethane causes swelling and the amount of add‐on is increased as the swelling level increases. Methacrylic‐acid‐modified PET films hydrolyze at room temperature in aqueous sodium hydroxide; the rate of hydrolysis is dependent upon the amount of add‐on and the concentration of the base. This procedure leads to a chemically induced blend of polymethacrylic acid and poly(ethylene terephthalate), and grafting of the monomer onto the polymer film does not occur. © 1995 John Wiley & Sons, Inc.
Synthesis and characterization of new soluble aromatic polyamides from diaminotetraphenylimidazolin‐2‐one and various aromatic dicarboxylic acid chlorides
Authors: Park Ki Hong , Kakimoto Masa‐Aki , Imai Yoshio 
Published: April 2003

AbstractNovel aromatic polyamides, having inherent viscosities of 0.76‐2.31 dL/g, were synthesized by the low temperature solution polycondensation of a new highly phenylated diamine monomer having an imidazolinone group, 1,3‐bis(4‐aminophenyl)‐4,5‐diphenylimidazoline‐2‐one (TPIDA), with various aromatic diacid chlorides. All the polymers were amorphous, and most of the polyamides were readily soluble in organic solvents such as N‐methyl–2‐pyrrolidone, N,N‐dimethylacetamide (DMAc), and m‐cresol. Flexible and tough films could be prepared from the DMAc solutions of these soluble aromatic polyamides. The glass transition temperatures and 10% weight loss temperatures under nitrogen of the polyamides were in the range of 275–315°C and 430–505°C, respectively. © 1995 John Wiley & Sons, Inc.
Studies on the thermotropic liquid crystalline polymer. XII. Synthesis and properties of crosslinkable thermotropic liquid crystalline homo‐ and copoly(ether‐ester)s
Authors: Lai Wen Wei , Chang Teh Chou 
Published: April 2003

AbstractA series of crosslinkable thermotropic liquid crystalline poly(ether‐ester)s and copoly(ether‐ester)s was prepared. All of the polymers were crosslinked by thermal treatment or photo‐irradiation upon heating. The thermal stability and thermal crosslinking reaction of these polymers were investigated. These polymers also could be crosslinked by copolymerization with vinyl monomers, such as styrene or methyl methacrylate. The crosslinked polymers exhibited thermotropic liquid crystalline behavior after softening by heating. The phase behavior of linear polymers and crosslinked polymers was studied by differential scanning calorimetry (DSC) and an optical polarizing microscope equipped with a heating stage. © 1995 John Wiley & Sons, Inc.
Synthesis and properties of aromatic polyamides derived from 1,6‐bis(4‐aminophenoxy)naphthalene and aromatic dicarboxylic acids
Authors: Yang Chin‐Ping , Hsiao Sheng‐Huei , Jang Chin‐Cheng 
Published: April 2003

AbstractA new bis(phenoxy)naphthalene‐containing diamine, 1,6‐bis(4‐aminophenoxy)naphthalene, was synthesized in two steps from the condensation of 1,6‐dihydroxynaphthalene with p‐chloronitrobenzene in the presence of potassium carbonate, giving 1,6‐bis(4‐nitrophenoxv)naphthalene, followed by hydrazine hydrate/Pd—C reduction. A series of polyamides were synthesized by the direct polycondensation of the diamine with various aromatic dicarboxylic acids in the N‐methyl‐2‐pyrrolidone (NMP) solution containing dissolved metal salts such as CaCl2 or LiBr using triphenyl phosphite and pyridine as condensing agents. The polymers were obtained in quantitative yield with inherent viscosities of 0.78–3.72 dL/g. Most of the polymers were soluble in aprotic solvents such as N,N‐dimethylacetamide (DMAc), N,N‐dimethylformamide (DMF), NMP, and they could be solution‐cast into transparent, flexible and tough films. The casting films had tensile strength of 102–175 MPa, elongation at break of 8–42%, and tensile modulus of 2.4–3.8 GPa. The polymers derived from rigid dicarboxylic acids such as terephthalic acid and 4,4′‐biphenyldicarboxylic acid exhibited some crystalline characteristics. The glass transition temperatures of the polyamides were in the range of 238–337°C, and their 10% weight loss temperatures were above 487°C in nitrogen and above 438°C in air. © 1995 John Wiley & Sons, Inc.
Kinetics and molecular weights distribution study of neodymium‐catalyzed polymerization of 1,3‐butadiene
Authors: Nickaf J. B. , Burford R. P. , Chaplin R. P. 
Published: April 2003

AbstractThe homopolymerization of 1,3‐butadiene in a stirred batch reactor with the catalytic system Nd octoate/diethyl‐aluminium chloride/triisobutyl‐aluminium in n‐heptane was studied. The effect of various reaction conditions on especially high conversion and molecular weight is reported. Polymerization is shown to be first order with respect to both monomer and neodymium. Molecular weights are high and broadly distributed. Chain transfer to triisobutylaluminium is the main factor governing molecular weight development. A mechanism of polymerization is presented with the chain transfer process incorporated. © 1995 John Wiley & Sons, Inc.
Synthesis of new polyimides by Diels–Alder reaction of bis(2‐pyrone)s with bismaleimides
Authors: Alhakimi Gamil , Klemm Elisabeth , Görls Helmar 
Published: April 2003

AbstractThe reaction of various substituted bis(2‐pyrone)s with bismaleimides in dilute solution was carried out to produce linear soluble polymers with coronand structure. The number‐average molecular weights of the polymers ranged from 7000 to 18,000 (vapor pressure osmometry). Polymer structures were identified by NMR spectroscopy and model reactions. The stereochemistry and the mechanism are discussed. © 1995 John Wiley & Sons, Inc.
Synthesis and characterization of hydrophilic thermotropic block copolyetheresters
Authors: Hsiue Lin‐Tee , Ma Chen‐Chi M. , Tsai Hong‐Bing 
Published: April 2003

AbstractThe block copolyetheresters with a hard segment of poly (hexamethylene p,p′‐bibenzoate) and a soft segment of poly (ethylene oxide) were prepared by melt polycondensation of dimethyl‐p,p′‐bibenzoate, 1,6‐hexanediol, and polyethylene glycol (PEG) with molecular weights of 400, 1000, 2000, or 4000. These block copolyetheresters were characterized by intrinsic viscosity, GPC, FT‐IR, 1H‐NMR, and water absorption. The thermotropic liquid crystalline properties were investigated by DSC, polarized microscope, and x‐ray diffraction. The block copolyetheresters exhibit smectic liquid crystallinity due to the polyester segment. The transitions are dependent on the molar content and the molecular weight of PEG used. The block copolyetheresters show high water absorption due to the hydrophilic nature of the poly (ethylene oxide) segment. The water absorption increases with increasing PEG content. As the molecular weight of PEG increases, the water absorption increases significantly. The results indicate that the water absorption of the poly (ethylene oxide) segment in the block copolymers is affected by the presence of polyester segments. © 1995 John Wiley & Sons, Inc.
Synthesis and characterization of polyfunctional crosslinking agents for cyanate resins
Authors: Fyfe C. A. , Niu J. , Mok K. 
Published: April 2003

AbstractAn efficient crosslinking monomer for a mixed cyanate/epoxy resin system, bisphenol‐A‐monocyanate monoglycidyl ether 3, has been synthesized and characterized. The intermediate compound, the monoglycidyl ether of bisphenol‐A 2, was also isolated and purified by extraction and chromatographic separation using a silica gel column. The cyanate functional group in the crosslinking monomer 3 can be cured easily by heat to form a triazine structure 8, but the epoxy functional group in the crosslinking monomer 3 can not be cured without affecting the cyanate group because the latter is more reactive both under heat and basic conditions. A practical approach for the application of the crosslinking monomer 3 is discussed and tested. Most interestingly, under heat curing, a very tough and strong resin material was produced from this crosslinking mixed resin mixture. By using a secondary amine, diethylamine, as a curing agent, the cyanate groups in the crosslinking monomer 3 react to form the structures 11 or 12, depending on the molar ratio of monomer 3 to diethylamine. A bifunctional crosslinking agent for a mixed cyanate (thermoset) and polyolefin (thermoplastic) resin system, 2‐allylphenyl cyanate 16, has also been synthesized and characterized. Like 3, 2‐allylphenyl cyanate 16 easily forms the crosslinking triazine compound 17 upon heating. 17 is a crystalline solid with mp = 110–111°C. As a crosslinking agent, 2‐allylphenyl cyanate 16 reacts not only with itself, but also with other cyanates to form heterogeneous triazine rings, exemplified by triazines 18 and 19. Even though it does not self polymerize through the allyl double bond, it can copolymerize with an other olefinic monomer, such as methyl methacrylate, to form a crosslinked and insoluble polymer. © 1995 John Wiley & Sons, Inc.
Studies on the chemical syntheses and on the characteristics of polyaniline derivatives
Authors: Mattoso L. H. C. , Manohar S. K. , Macdiarmid A. G. , Epstein A. J. 
Published: April 2003

AbstractSyntheses of parent polyaniline and methyl, methoxy, and ethoxy ortho‐substituted polyanilines were performed using the conventional chemical methodology and monitored using the new open‐circuit‐potential (Voc) profile technique. The intermediate pernigraniline oxidation state was identified and isolated at the Voc maximum (A) during the conventional chemical synthesis of poly(o‐methoxyaniline) in the emeraldine oxidation state. The introduction of the substituent on the aniline ring leads to longer polymerization times and lower Voc values. Syntheses in the presence of two different monomers in solution were also investigated and showed preferential polymerization of the monomer with the lowest Voc potential. All polymers produced were characterized by elemental analysis, gel permeation chromatography, UV‐VIS spectroscopy, and cyclic voltammetry. The influence of the substituent on the Voc profile and on the polymer characteristics are rationalized in terms of steric and electronic effects. © 1995 John Wiley & Sons, Inc.
A simple assay for screening translational activity of non‐natural amino acids. Implications for polymer synthesis on messenger RNA templates
Authors: Kothakota Srinivas , Yoshikawa Eiichiro , Murphy Owen J. , Mason Thomas L. , Tirrell David A. , Fournier Maurille J. 
Published: April 2003

AbstractThe ability to incorporate unnatural amino acids into biologically synthesized proteins will greatly extend the impact of protein engineering on polymer materials science. The present report describes the use of a rapid cell‐free assay to assess the incorporation potential of unnatural amino acids in Escherichia coli. The assay features a coupled transcription‐translation system (‘Zubay system’) to screen incorporation of amino acid analogs into plasmid‐encoded proteins. Activity estimates are based on the ability of an analog to compete with a radiolabeled natural amino acid, and toxicity effects are screened by monitoring incorporation of a second, unrelated amino acid. The assay was established with analogs known to be active in vivo, using a common bacterial expression vector as template DNA. Positive results were obtained with the leucine analog 5,5,5‐trifluoroleucine, the proline analogs azetidine‐2‐carboxylic acid and thiazolidine‐4‐carboxylic acid, and three isomers of mono‐fluorophenylalanine (o,m,p). No activity was observed for the phenylalanine analogs 2‐thienylalanine and 3‐thienylalanine. The results suggest that the cell‐free assay will be a useful predictor of in vivo incorporation and a useful tool in the design and synthesis of genetically engineered materials. © 1995 John Wiley & Sons, Inc.
Rigid‐rod polymers with polysiloxane side chains. 2. Synthesis and characterization of aromatic polybenzobisoxazoles with polysiloxane side chains and composite formation with polysiloxane matrices
Authors: Sakakibara Akihito , Itoh Maki , Mita Itaru 
Published: April 2003

AbstractAromatic polybenzobisoxazoles, having polydimethylsiloxane side chains (SCPBOs), were prepared using terephthaloyl chloride‐terminated polydimethylsiloxane macromonomers and 3,3′‐bis(trimethylsiloxy)‐4,4′‐bis(trimethylsilylamino)biphenyl for the purpose of dispersing rigid‐rod molecules in silicone matrices for molecular reinforcement. The degree of polymerization of the side chain was varied from 7.8 to 45.4, and a small amount of (3‐butenyloxy)terephthaloyl chloride was copolymerized to give the polymers a functionality that can be linked to the matrices. For all the SCPBOs, the WAXD pattern showed only diffuse reflections, suggesting limited structural regularity, although the polymers were optically anisotropic. No melting transition was observed below the side chain decomposition temperature, 350°C. A polydimethylsiloxane/polybenzobisoxazole composite elastomer was obtained first curing the polysiloxane matrix containing the prepolymer of the SCPBO, followed by in situ thermal ring closure of the prepolymer. Some reinforcement was observed, but the presence of plasticizing effect by the unbound SCPBO was suggested at the same time. © 1995 John Wiley & Sons, Inc.
Propene polymerization using homogeneous MAO‐activated metallocene catalysts: Me2Si(Benz[e]Indenyl)2ZrCl2/MAO vs. Me2Si(2‐Me‐Benz[e]Indenyl)2ZrCl2/MAO
Authors: Jüngling Stephan , Mülhaupt Rolf , Stehling Udo , Brintzinger Hans‐Herbert , Fischer David , Langhauser Franz 
Published: April 2003

AbstractPropene was polymerized at 40°C and 2‐bar propene in toluene using methylalumoxane (MAO) activated rac‐Me2Si(Benz[e]Indenyl)2ZrCl2 (BI) and rac‐Me2Si(2‐Me‐Benz[e]Indenyl)2ZrCl2 (MBI). Catalyst BI/MAO polymerizes propene with high activity to afford low molecular weight polypropylene, whereas MBI/MAO is less active and produces high molecular weight polypropylene. Variation of reaction conditions such as propene concentration, temperature, concentration of catalyst components, and addition of hydrogen reveals that the lower molecular weight polypropylene produced with BI/MAO results from chain transfer to propene monomer following a 2,1‐insertion. A large fraction of both metallocene catalyst systems is deactivated upon 2,1‐insertion. Such dormant sites can be reactivated by H2‐addition, which affords active metallocene hydrides. This effect of H2‐addition is reflected by a decreasing content of head‐to‐head enchainment and the formation of polypropylene with n‐butyl end groups. Both catalysts show a strong dependence of activity on propene concentration that indicates a formal reaction order of 1.7 with respect to propene. MBI/MAO shows a much higher dependence of the activity on temperature than BI/MAO. At elevated temperatures, MBI/MAO polymerizes propene faster than BI/MAO. © 1995 John Wiley & Sons, Inc.
Preparation and photocrosslinking behaviors of polyesters derived from trans‐2,2′‐dihydroxystilbene
Authors: Chen Yun , Tsay Cherng‐Jing 
Published: April 2003

AbstractThe monomer, trans‐2,2′‐dihydroxystilbene (DHS), has been prepared by asymmetric photocleavage (254 nm) of coumarin dimer acid derived from coumarin dimer. Four new polyesters are successfully synthesized by interfacial polycondensation of the DHS with adipoyl chloride, azelaoyl chloride, sebacoyl chloride, and dodecanedioyl dichloride, respectively. The reduced viscosities of the polyesters decrease from 0.32 to 0.11 dL/g as the number of methylene unit in diacid chlorides increases from 4 to 10. From DSC investigation, it is found that the polyesters are semi‐crystalline polymers with Tm = 39–192°C. Under 350 nm light, photocrosslinking behavior in solution and film‐state is investigated by UV spectral change with irradiation time (350 nm). The photoreactive stilbene chromophores in the main chain dimerize to form cyclobutane derivatives, and lead to crosslinking of the polyesters. Photosensitivity in the film state has also been evaluated by their characteristic curves. Polyester from dodecanedioyl dichloride (5d) exhibits the highest initial reaction rate and ultimate crosslinking ratio. © 1995 John Wiley & Sons, Inc.
Liquid crystalline block copolymers containing rigid units and flexible ethylene terephthalate segments
Authors: Ignatious Francis , Lu Caixia , Kim Jiheung , Kantor Simon W. , Lenz Robert W. 
Published: April 2003

AbstractLiquid crystalline block copolymers containing different compositions of terephthaloyl bis(4‐oxybenzoyl) (triad) mesogen and flexible ethylene terephthalate (ET) units, were synthesized in tetrachloroethane/pyridine (TCE/Py) at 150°C and in 1‐chloronaphthalene (1‐CN) at elevated temperatures. Inherent viscosities of the PET block copolymers were always lower than 0.25 dL/g. By replacing the ET blocks with butylene terephthalate (BT) blocks, a copolymer of higher inherent viscosity (> 0.8 dL/g) was synthesized in 1‐CN at 220°C. Formation of low molecular weight PET copolymers was attributed to: (1) insolubility of the block copolymer in TCE/Py and (2) formation of side products which alter the stoichiometry of the reactants when the reaction was carried out in 1‐CN. The block copolymers were characterized by 1H and 13C‐NMR spectroscopy. Copolymer compositions were calculated from 1H and 13C‐NMR data. Thermal behavior of these copolymers was analyzed by DSC and polarizing optical microscopy. All copolymers exhibited a nematic liquid crystalline texture. © 1995 John Wiley & Sons, Inc.
Synthesis and characterization of amino‐terminated telechelic polybutadiene
Authors: Xu Jiangtian , Dimonie Victoria L. , Sudol E. David , El‐Aasser Mohamed S. 
Published: April 2003

AbstractButadiene was polymerized with water‐soluble 4,4′‐azobis(amidinopropane)dihydrochloride initiator in an ethanol‐water medium at 60°C. Important variables, such as the initiator concentration, monomer concentration, solvency, and polymerization time and temperature were studied. 13C‐NMR studies showed that no observable chain transfer to ethanol occurred during the polymerization. The conversion of monomer to polymer was significantly increased while maintaining a relatively narrow molecular weight distribution by intermittent feed of the initiator. The amidino end‐groups of the polymer were transformed into amino groups by reduction using lithium aluminum hydride in THF, so that amine‐terminated polybutadiene was obtained. The amino functionality of the polybutadiene was determined by titration to be 2.0. © 1995 John Wiley & Sons, Inc.
Electrical conductivity of poly(vinyl chloride) obtained by photodehydrochlorination from laminated poly(vinyl chloride)/polypyrrole films
Authors: Ogura K. , Kisaka K. , Furukawa H. 
Published: April 2003

AbstractPoly(vinyl chloride) (PVC) has been converted to an electrically conductive structure by combined electrochemical and photochemical methods. PVC was cast on a polypyrrole (PPy) film electrode which had been electrochemically prepared. The PVC layer in the laminated PVC/PPy films was first dehydrochlorinated under the illumination of UV light, and the generated polyenes were subsequently doped with I2 and FeCl3. The maximum electrical conductivity achieved for such PVC film was 2.51 X 10−2 and 8.63 10−2 S cm−1 after I2 and FeCl3 doping, respectively. The temperature dependence of the electrical conductivity showed different behavior in higher and lower temperature ranges. In the former (T > 243 K), the T−1 law held, and the activation energy and bandgap were estimated as 0.25 and 0.49 eV, respectively. In the latter (T < 243 K), the conductivity mechanism followed the variable range hopping model (T−1/4 law) in which the radius of the localized state wave function and the density of the localized states at the Fermi level were 1.25 × 103 Å and 1.03 X 1015 eV−1 cm−3, respectively. © 1995 John Wiley & Sons, Inc.
Synthesis and cationic photopolymerization of 1‐butenyl ether monomers
Authors: Crivello J. V. , Yang B. 
Published: April 2003

AbstractA new series of cationically polymerizable mono‐, di‐ and multifunctional 1‐butenyl ether monomers have been prepared in high yields by the ruthenium catalyzed isomerization of the corresponding crotyl (2‐butenyl) ethers. Their straightforward synthesis and high reactivity in photoinitiated cationic polymerization make these monomers highly attractive for a variety of applications. Cationic polymerization rate studies showed that these monomers exhibited comparable reactivity to their related vinyl and 1‐propenyl ether analogues. © 1995 John Wiley & Sons, Inc.