bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis of poly(phenyltrifluoroethoxyphosphazene) by direct reaction of trimethylsilyl azide with bis(2,2,2‐trifluoroethyl) phenylphosphonite
Authors: Matyjaszewski Krzysztof , Montague Robert , Dauth Jochen , Nuyken Oskar 
Published: April 2003

AbstractThe reaction between bis(2,2,2‐trifluoroethyl) phenylphosphonite and trimethylsilyl azide at temperatures from 70 to 120°C provides a mixture of bis(2,2,2‐trifluoroethoxy)phenylN‐(trimethylsilyl) phosphoranimine and poly(phenyl‐2,2,2‐trifluoroethoxyphosphazene). The polymer is probably formed by phosphine azide intermediates because the phosphor‐animine is thermally stable up to 200°C. The polyphosphazene is an amorphous stereo‐random polymer with a glass transition temperature at −31°C.
Novel dialkylaminoalkyl‐ and dialkylaminoalcoxy‐benzophenones as polymerization photoinitiators. II. Photocalorimetric study on photoinitiated polymerization of butyl and lauryl acrylates
Authors: Mateo J. L. , Bosch P. , Catalina F. , Sastre R. 
Published: April 2003

AbstractA photocalorimetric study of butyl and lauryl acrylates (BA and LA) polymerization photoinitiated by several benzophenone derivatives is reported. Molecular weight measurements and end‐chain group analysis of the samples are also described and the results are compared with those obtained by dilatometric technique. The role played by the long methylene chain in lauryl acrylate is discussed
Synthesis and calorimetric curing study of amino‐terminated PEEK oligomers
Authors: Corfield G. C. , Wheatley G. W. , Parker D. G. 
Published: April 2003

AbstractAmino‐terminated polyetheretherketone (PEEK) oligomers were prepared by the condensation of 4,4′‐difluorobenzophenone and hydroquinone in the presence of a calculated excess of m‐aminophenol endblocker. The molecular weight of the oligomer was controlled by the manipulation of the ratio of difluoride to hydroquinone with the appropriate stoichiometric amount of m‐aminophenol ensuring amino termination. The thermally induced self‐crosslinking of these oligomers was studied by differential scanning calorimetry (DSC). Curing was found to be quite slow, taking up to 1 h to reach completion at 668 K. Cured materials were all completely amorphous in contrast to the semi‐crystalline starting material. The limiting Tg reached on curing was found to be proportional to the percentage of reactive terminal groups, as would be expected.
Synthesis of poly(phenylacetylene)s containing trifluoromethyl groups for gas permeable membrane
Authors: Hayakawa Yoshio , Nishida Masakazu , Aoki Toshiki , Muramatsu Hiroshige 
Published: April 2003

AbstractPoly(phenylacetylene)s containing trifluoromethyl groups on their benzene rings were synthesized, and gas permeation behaviors of their films were examined. Permeability coefficients for O2 and N2, diffusion selectivity (Do2/DN2) and solubility selectivity (SO2/SN2) were estimated. The gas permeability of polymer films were found to be enhanced remarkably with introduction of trifluoromethyl groups into the polymers: poly[2,4,5‐tris(trifluoromethyl)phenylacetylene], Po2 = 7.8 × 10−8 [cm3 (STP) cm cm−2 s−1 cm Hg−1], Po2/PN2 = 2.1. The relationship between the polymer structures and their gas permeability was discussed.
The effect of the steric hindrance on metallic cation conduction in polymer electrolytes
Authors: Liu H. , Yeh T. F. , Lee H. S. , Skotheim T. A. , Okamoto Y. 
Published: April 2003

Abstract2,6‐Di‐t‐butylphenol and oligo(ethylene oxide) bound covalently to polyisocyanate were synthesized and characterized. The ionic conductivities of their Li, Na, and K phenolates were studied at various temperatures. The conductivities were in the range of 10−7−10−5 S/cm at 30°C. The conductivity of Na and K salts was approximately 102 greater than that of the Li salts. The t‐butyl groups serve to dissociate K and Na ions from the phenoxide. The cations, therefore, are more mobile as a result increasing the conductivity. The temperature dependence of ionic conductivity suggests that the migration of ions is controlled by segmental motion of the polymer, shown by linear curves obtained in Vogel–Tammann–Fulchere plots. The polyisocyanate backbone is a rather stiff structure, however, a flexible oligo(ethylene oxide) side chain forms complexes with metal ion. Since the ion transport is associated with the local movement of polymer segments, the rigidity of the polymer backbone does not have much influence on the ion mobility.
Kinetic study of light‐induced polymerization by real‐time UV and IR spectroscopy
Authors: Decker C. 
Published: April 2003

AbstractReal time ultraviolet (RTUV) spectroscopy was used to study the photolysis kinetics of a radical‐type morpholino initiator, during the polymerization of a multiacrylate monomer exposed to UV radiation in bulk, in solution, in a polyurethane‐acrylate resin, and in a poly(methyl methacrylate) matrix. The photolysis rate constant k was determined from the exponential loss profile recorded; it was found to vary between 0.1 and 3s−1, depending on the light intensity and on the monomer concentration. The quenching of the photoinitiator excited states by the acrylate monomer was shown to be an important deactivation pathway which substantially reduces the rate of initiation. The observed influence of the film thickness and photoinitiator concentration on the k value were accounted for by the internal filter effect. Conversion versus time curves were recorded by real time infrared (RTIR) spectroscopy for the various systems examined, thus allowing a direct comparison of both the actual polymerization rate and the residual unsaturation content of the cured polymer. Various factors were shown to be responsible for the early stop of the polymerization, such as depletion of the photoinitiator, O2 inhibition, or vitrification of the polymer. The photoinitiated cationic ring‐opening polymerization of a cycloaliphatic diepoxy monomer was also studied in real time by RTUV and RTIR spectroscopy. Despite a very fast photolysis of the triarylsulphonium initiator, the polymerization of the epoxy monomer developed less rapidly than for the acrylic monomer, with shorter kinetic chain lengths. A linear relationship was found to exist between the decay rate constant and the light intensity, for both the radical and the cationic photoinitiators, as expected for a direct photolysis process.
Liquid crystalline ionomers. II. Main chain liquid crystalline polymers with terminal sulfonate groups
Authors: Zhang Baoyan , Weiss R. A. 
Published: April 2003

AbstractLiquid crystalline ionomers containing sulfonate groups on the terminal unit of the chain were synthesized by an interfacial condensation reaction of 4,4′‐dihydroxy‐α,α′‐dimethyl benzalazine, the monofunctional dye fast yellow (FY), and a 50/50 mixture of sebacoyl and dodecanedioyl dichlorides. The weight‐average molecular weights were estimated from inherent viscosity measurements to be between 6000–11,000 and the sodium sulfonate concentrations ranged from 0–18.4 meq/100 g polymer. Elemental analyses, however, indicated much higher molecular weights, which suggested that there was a distribution of chains with one, two, or no FY endgroups. The polymers were semicrystalline and melted at ca. 140°C to form nematic mesophases that were stable over a temperature range of ca. 80°C. They were thermally stable to about 350°C. The ionomeric nature of the polymers was confirmed by the presence of intermolecular associations in nonpolar solvents, as demonstrated by dilute solution viscosity measurements.
Liquid crystalline polyethers based on conformational isomerism. XIX. Synthesis and characterization of flexible polyethers based on 1‐(4‐hydroxyphenyl)‐2‐(2‐r‐4‐hydroxyphenyl) ethane with H, F, CH3, Br, Cl, and CF3 as R groups
Authors: Percec V. , Zuber M. 
Published: April 2003

AbstractThe synthesis of 1‐(4‐hydroxyphenyl)‐2‐(2‐fluoro‐4‐hydroxyphenyl)ethane (FBPE), 1‐(4‐hydroxyphenyl)‐2‐(2‐chloro‐4‐hydroxyphenyl)ethane (CIBPE), 1‐(4‐hydroxyphenyl)‐2‐(2‐bromo‐4‐hydroxyphenyl)ethane (BrBPE), and 1‐(4‐hydroxyphenyl)‐2‐(2‐trifluoromethyl‐4‐hydroxyphenyl)ethane (CF3BPE), of the corresponding polymers based on 1,5‐dibromopentane (RBPE‐5), 1,8‐dibromooctane (RBPE‐8), and of the copolymers based on various ratios of 1,5‐dibromopentane and 1,8‐dibromooctane [RBPE‐5/8(A/B)] is described. The phase transition temperatures and thermodynamic parameters of RBPE‐5 and RBPE‐8 polymers were compared to those of the corresponding polyethers based on 1,2‐bis(4‐hydroxyphenyl)ethane (BPE) and 1‐(4‐hydroxyphenyl)‐2‐(2‐methyl‐4‐hydroxyphenyl)ethane (MBPE) which were reported previously. Both isotropic‐nematic transition temperatures and corresponding thermodynamic parameters (i.e., enthalpy and entropy changes) decrease in the following order of the substituent R: H > F > CH3 > Cl > Br > CF3. This order corresponds to the increase of the breadth of the RBPE molecules, and agrees with the similar trends observed in low molar mass liquid crystals.
Synthesis and properties of polyamides of 3,3′‐dimethylnaphthidine and its model compounds
Authors: Cimecioglu A. L. , Weiss R. A. 
Published: April 2003

AbstractA number of polyamides and model amides based on 3,3′‐dimethylnaphthidine and various dicarboxylic acids were synthesized in N‐methylpyrrolidone containing lithium chloride either by low temperature solution or by direct polycondensation using triphenyl phosphite and pyridine. The polyamides had inherent viscosities of 0.36−5.42 dL g−1 and were, in general, readily soluble in N‐methylpyrrolidone. Amorphous members exhibited relatively high glass transition temperatures in the range of 340–380 and 200–230°C for aromatic and aliphatic polymers, respectively. All polyamides showed good thermal stability in nitrogen and in air.
Polyacrylamide gels formed with Cr+3 ion and Cr(acetate)3: Thermodynamically and kinetically controlled crosslinking reactions
Authors: Albonico Paola , Burrafato Giovanni , Lockhart Thomas P. 
Published: April 2003

AbstractThe gelation of buffered aqueous Cr+3/polyacrylamide (PAAm) solutions has been studied over the pH range 2‐11. With Cr+3 supplied as Cr(NO3)3 and a 7.5% hydrolyzed PAAm the upper limit for gelation was about pH 7, but Cr(acetate)3/PAAm solutions gelled as high as pH 9. Evidence is presented that the formation of unreactive colloidal Cr(OH)3(H2O)3, rather than polymer crosslinking, is favored thermodynamically for Cr+3/PAAm solutions at pH > 7. The crosslinks formed in Cr(acetate)3/PAAm solutions at pH 7–9 are deduced to be kinetically controlled products. Independent evidence for the kinetic stability of Cr+3/PAAm gels above pH 7 has also been obtained. Other observations relevant to the mechanism of crosslinking of PAAm with Cr(acetate)3 are described.
Radiation induced terpolymerization of tetrafluoroethylene with propylene and n‐butyl vinyl ether in bulk
Authors: Kostov G. K. , Matsuda O. , Tabata Y. , Machi S. 
Published: April 2003

AbstractTerpolymerization of tetrafluoroethylene (TFE) with propylene (P) and n‐butyl vinyl ether (NBVE) induced by γ‐rays at room temperature at dose rate 5 × 105 rad/h and P/NBVE molar ratio from 49/1 to 10/40 was carried out. An alternating copolymerization between TFE and two α‐olefins was found to take place in this system, so that 50 mole % of TFE containing terpolymer is always formed at various monomer compositions. The terpolymer composition can be explained successfully by the treatment by a complex mechanism. The complex reactivity ratios of rI (TFE–complex) and rII (TFE‐NBVE complex) were calculated to be 0.5 and 0.6, respectively, assuming a complex mechanism. The polymerization rate and molecular weight increase with NBVE concentration in the monomer mixture. Colorless transparent rubber‐like polymers were obtained at each monomer composition. The glass transition temperature sharply decreases with NBVE concentration in the terpolymer but the thermal and chemical resistances of the terpolymer slightly decrease. Considering these results together with the mechanical properties it has been concluded that the 45/48/7 terpolymer of TFE/P/NBVE molar ratio is good as a practical elastomer useful at relatively low temperatures.
Study of synthesis and properties of tetrafluoroethylene–propylene copolymers
Authors: Kostov G. K. , Chr. Petrov P. 
Published: April 2003

AbstractBulk copolymerization of tetrafluoroethylene (TFE) with propylene (P) initiated by tert‐butyl peroxybenzoate (TBPB) in the temperature interval 323–363 K, monomer pressure from 2 to 9 MPa, and TFE and P molar ratio from 20/80 to 90/10 was carried out. The effect of these reaction conditions on the yield, molecular weight, and polymer composition of the copolymer synthesized was studied. Rubber‐like alternating copolymers in a wide range of monomer compositions of TFE and P (from 40 to 80 mol %) were obtained. The reaction proceeds in a stationary state without an induction period. Monomolecular chain transfer reaction (Cp = 5 × 10−4) to propylene takes place. The relative reactivity ratio of P and TFE (0.15 and 0.01, respectively) and apparent activation energy Eα = 75.8 kJ/mol of the reaction were determined.
The molecular weight limiting step in the ring‐opening polymerization of 1,1‐disubstituted epoxides catalyzed by bis(diisobutylaluminum)oxide
Authors: Nicholas Paul P. 
Published: April 2003

AbstractThe ring‐opening polymerization of 1,2‐epoxy‐4,4,4‐trifluoro‐2‐methylbutane (2) and its unfluorinated analogue, 1,2‐epoxy‐2‐methylbutane (3), gives the expected polyethers when catalyzed by bis(diisobutylaluminum)oxide. However, the molecular weights are low because of a competing deprotonation/ring‐opening of the epoxide that produces all three possible alkene end groups and their stereoisomers. With 2, deprotonation occurs mainly at the methyl group to give the terminal double bond and only minor amounts of the internal double bond. However, 3 gives the opposite regiochemistry. A model is proposed where this reaction occurs within an aluminum(polyether oxide) bound to the least hindered face of the epoxide ring. In this model, the different regiochemistries originate from a concerted and highly directed deprotonation/ring‐opening of 2 versus a step‐wise deprotonation of 3 through its ring‐opened, tertiary‐cation.
Polymer drying. V. Intramolecular‐rotor fluorescence studies of evaporation from liquid‐saturated poly(styrene‐co‐divinylbenzene)
Authors: Errede L. A. , Tiers G. V. D. , Trend J. E. , Wright B. B. 
Published: April 2003

AbstractThe fluorescence intensity and residual weight of poly(styrene‐co‐divinylbenzene) saturated with a < 0.003M solution of a intramolecular‐rotor‐fluorescent probe‐molecule in a volatile liquid were monitored simultaneously as the system evaporated at 23°C to virtual dryness. The “breakpoints” in the pattern for fluorescence increase coincided with the “breakpoints” in the kinetics of desorption with respect to the number, αt of residual sorbed volatile molecules per phenyl group in the polymer, showing that both time‐studies reflect the same physical changes in the system that occur reproducibly as αt decreases monotonically through α′s and α′g the compositions that signal respectively incipient elimination of volatile molecules immobilized by adsorption to polymer, and incipient transition of the system from the rubbery state to the glassy state. The fluorescence intensity attained its asymptotic limit before αt became equal to αg the composition identified earlier to be that which marks completion of the transition to the glassy state.
Polymer drying. VI. EPR spin‐probe studies on swelled poly(styrene‐co‐divinylbenzene)
Authors: Errede L. A. , Aus E. B. , Duerst R. W. 
Published: April 2003

AbstractThe electron paramagnetic resonance (EPR) signal and the residual number (αt) of volatile molecules per phenyl group of poly(styrene‐co‐divinylbenzene) in samples that had been swelled to saturation in a dilute solution of a nitroxide spin‐probe (TEMPO or 4‐oxo‐TEMPO), dissolved in a volatile liquid, were monitored simultaneously as the system containing excess liquid was allowed to evaporate to dryness. The results showed that the characteristic motionally narrowed three‐line EPR spectrum began to change when αt became equal to αg (the number of sorbed molecules per phenyl group of polymer at liquid‐saturation). The ratio of the intensity of the low‐field and high‐field hyperfine peaks relative to the middle peak decreased monotonically to an asymptotic limit that was attained when αt became equal to αg (the number of residual adsorbed molecules per phenyl group of polymer at completion of the transition from the rubbery state to the glassy state). The EPR hyperfine pattern, from which the rotational correlation times were estimated, changed most significantly as αt decreased from αG to αg while exhibiting inflections at about α′s and α′g the compositions that mark, respectively, incipient desorption of adsorbed molecules and incipient transition from the rubbery state to the glassy state. The pattern between these inflections points, however, varied with the affinity of the solvent for the polymer.
Polymer drying. VII. 1H‐NMR studies of evaporation from liquid saturated poly(styrene‐co‐divinylbenzene)
Authors: Errede L. A. , Newmark Richard A. 
Published: April 2003

AbstractComposition‐studies were carried out in which samples of films composed of poly(styrene‐co‐divinylbenzene) particles enmeshed by poly(tetrafluoroethylene) fibers were saturated with dichloromethane and then allowed to evaporate at 23°C to virtual dryness as the 1H‐NMR signals and residual weight of sorbed liquid were monitored. The correlations, of 1H‐NMR line‐widths with the corresponding log of the number, αt of residual sorbed molecules per monomer unit show that sharp changes occur as αt passes through αG the composition that exists when all the liquid not sorbed (i.e., not present within the liquid‐saturated particles), has been eliminated, and again as αt passes through αg the composition that exists when the particles attain the rigidity characteristic of the glassy state. Correlation of the corresponding T1 relaxation times with log αt show that sharp changes occur when αt becomes equal first to α′s and then to α′g the compositions that exist respectively when, firstly, all the sorbed liquid not immobilized by adsorption to the polymer chains within the particles has been eliminated, and then when the desorption of immobilized liquid from the chains causes the composition to begin to undergo transition from its rubbery state to its glassy state.
Preparation of hindered piperidine and its copolymerization with propylene over a supported high activity ziegler–natta catalyst
Authors: Wilén Carl‐Eric , Auer Markku , Näsman Jan H. 
Published: April 2003

AbstractA new polymerizable stabilizer 4‐(hex‐5‐enyl)‐2,2,6,6‐tetramethylpiperidine is prepared. This sterically hindered piperidine was copolymerized with propylene over a fourth generation TiCl4/MgCl2 Ziegler–Natta catalyst, using Al(C2H5)3 as cocatalyst and diphenyldimethoxysilane, DMS, as external electron donor. The copolymer exhibited high thermo‐oxidative stability even after exhaustive extraction with n‐heptane.
Synthesis and characterization of new thermotropic liquid crystalline polymers with paired mesogens containing azobenzene unit: Poly(malonic ester)s
Authors: Han Yang‐Kyoo , Kim Dong‐Yu , Kim Young Ha 
Published: April 2003

AbstractNew thermotropic liquid crystalline poly(malonic ester)s with two symmetrical mesogenic units (paired mesogens) were prepared by the polycondensation of 1,6‐dibromohexane and novel malonic ester compounds with different flexible ethyleneoxy spacer lengths linked to azobenzene group. All the prepared malonic esters and the resulting polymers exhibited monotropic liquid crystallinity with a nematic texture. The length of the spacer had influence on the temperature of phase transition of them. A possibility of application of the prepared polymers to reversible optical information storage media was also identified through a trans–cis isomerization of azobenzene by UV irradiation.
Radical copolymerization of an electron‐accepting monomer, methyl cis‐β‐cyanoacrylate, with styrene or acrylonitrile
Authors: Nagai Katsutoshi , Okada Koichi , Kido Junji 
Published: April 2003

AbstractThe electron‐accepting property and the radical copolymerizability of methyl cis‐β‐cyanoacrylate (MCA) were studied. The monomer was found to form a contact charge‐transfer complex with styrene (ST) in chloroform at 25°C and behaved as a weak electron acceptor. The copolymerization parameters were determined in dioxane at 50°C for systems involving ST or acrylonitrile (AN) as comonomer. The reactivity ratio of ST or AN was estimated by the Kelen–Tudös method considering both the penultimate unit effect and no homopropagation of MCA. The penultimate effect for the system ST–MCA was large compared with that for the system ST–dimethyl maleate (DMM), indicating that a polar effect is mainly responsible for the penultimate effect. The terpolymerization of ST, MCA, and maleic anhydride (MA) was also studied to compare the reactivity of MCA with that of MA.
Thermal behavior of copolyimides containing bisbenzoylamine groups
Authors: Litauszki L. , Karasz F. E. , Grünberg K. , Berger W. 
Published: April 2003

AbstractIn an effort to improve the processibility of full aromatic polyimides, copolybisbenzoylamine imides were synthesized. As this study is a continuation of our work on flexibilization of the polyimide main chain, the bisbenzoylamine group was introduced stepwise into the polyimide main chain. Mixtures of pyromellitic anhydride, the rigid component, and a bisbenzoylamine‐3,3′, 4,4′‐tetracarboxylic acid dianhydride, the flexible component, were polymerized with aromatic diamines in a two‐step procedure. The thermal stability of the four series of resulting copolyimides shows parallel changes that depend on the dianhydride ratio. The functional dependence of glass transition temperature (Tg) on copolymer composition differs for hydrogen or alkyl group substitution on the nitrogen in the bisbenzoylamine group. The solubility of the copolyimides in dimethylformamide changes from 0 to 33 wt %; there is a nonlinear dependence between solubility and the dianhydride ratio.
Photodegradation of polyimides. III. The effect of chemical composition, radiation source, atmosphere, and processing
Authors: Hoyle Charles E. , Anzures Edgardo T. 
Published: April 2003

AbstractPolymide films made from diarylanhydrides with oxygen, carbonyl, and hexafluoroisopropylidene 6F bridging groups are photolabile when irradiated with unfiltered light from a medium‐pressure mercury lamp. The presence of oxygen is necessary to the photolytic degradation process, which results in the ultimate oxidative ablation of thin polyimide films. Films based on the 6F dianhydride containing a hexafluoroisopropylidene hinge group are the most unstable. However, photolysis of 6F dianhydride based polyimides in an inert atmosphere with either the unfiltered medium pressure mercury lamp or an electron beam results in no detectable changes even after long exposure times.
New polymer syntheses. LXI. Synthesis and alkylation of aromatic poly(pyrazine‐ether)s
Authors: Kricheldorf Hans R. , Jahnke Petra 
Published: April 2003

AbstractThree poly(pyrazine‐ether)s were prepared from 2,6‐dichloropyrazine, silylated bisphenol‐A and, in two cases, 4,4′‐dichlorodiphenylsulfone. The alkylation of these poly(pyrazine‐ether) with methyl triflate, dimethyl sulfate, methyl 4‐nitrobenzenesulfonate, or γ‐propanesultone was studied by 1H‐NMR spectroscopy in nitrobenzene. Several N‐methylated poly(pyrazine‐ether)s were also isolated and characterized by elemental analyses, inherent viscosities, 1H‐NMR spectra, 15N‐NMR spectra, and DSC measurements. Furthermore, their solubilities in six different solvents were determined. Complete methylation raises the glass transition temperatures, reduces the solubility in aprotic solvents, and favors dissolution in methanol or ethanol.