bluuebunny/crossref_metadata_2025_split huggingface dataset:
Turbidimetric studies of aqueous poly(vinyl alcohol) solutions
Authors: Peppas Nikolaos Ath 
Published: April 2003

AbstractA freezing‐thawing process of aqueous poly(vinyl alcohol), (PVA) solutions was undertaken to study the supermolecular PVA structures produced. Aqueous solutions of 2,5 to 15 wt.‐% PVA were frozen at −20°C for 45 to 120min and were subsequently thawed for long periods of time (up to 12h) at 23 ± 1°C. The transmittance of visible light was recorded as a function of thawing time. Determination of the parameters of the supermolecular particles in the PVA solutions was done by application of Klenin's theory. The average radii of the particles were in the order of 1,6–2,3 μm.
Infrared spectroscopic studies on polyethylene, 1. The measurement of low levels of chain branching
Authors: Baker Clive , Maddams William F. 
Published: April 2003

AbstractThe problems encountered in the infrared spectroscopic estimation of the low levels of chain branching present in high density polyethylene, using the compensation method, are discussed systematically. The precision to be expected has been determined and it is shown that, if possible, a correction should be applied for methyl groups present at the chain ends. This is feasible with some types of polymer but more difficult with others. The compensating wedge in the reference beam of the spectrometer should be made of polymethylene rather than a high molecular weight polyethylene. The ultimate sensitivity of the manual compensation method is about one methyl branch per two thousand carbon atoms. However, when this is supplemented by computer smoothing and off‐line computation of average transients (C.A.T.), a significant improvement is obtained in the signal to noise ratio, and branching levels down to 0,1 methyl groups per thousand carbon atoms are readily measured.
Infrared spectroscopic studies on polyethylene, 4. The examination of drawn specimens of varying stress crack resistance
Authors: McRae Margaret A. , Maddams William F. 
Published: April 2003

AbstractInfrared spectra, with both unpolarised and polarised radiation, have been obtained for a series of Phillips type high density polyethylenes of varying stress crack resistance. They were examined after cold drawing, by neck propagation, under standard conditions, and the presence of uniaxial orientation was confirmed by X‐ray pole figure measurements. Intensity measurements with unpolarised radiation on the bands at 1080, 1352, and 1894 cm−1 showed that with samples of bad stress crack resistance both the folds and the tie chains increase in concentration at the expense of the regularly folded chains in crystalline regions, whereas only the tie chains increase with samples having good stress crack resistance. Dichroic measurements on nine bands, the majority of them characteristic for methylene groups in gauche and trans conformations in amorphous regions, show that there is no marked degree of orientation of the chain folds or tie chains with samples of good stress crack resistance. However, there is significant orientation, particularly of the tie chains, for samples with poor stress crack resistance.
Strukturuntersuchung von polyestern durch direkten abbau im massenspektrometer, 2. Aliphatische polyester
Authors: Lüderwald Ingo , Urrutia Hernando 
Published: April 2003

AbstractDie Abbaureaktionen von Polyestern aus Adipinsäure und Äthylenglykol 1a, Tetradeuteroäthylenglykol 1b, 1,3‐Propandiol 1c und 2,2′‐Oxydiäthanol 1d sowie aus Bernsteinsäure und Äthylenglykol 2a, 1,4‐Butandiol 2b und 2,2‐Dimethyl‐1,3‐propandiol 2c wurden im Massenspektrometer untersucht. Die Polymeren wurden direkt in der Ionenquelle des Massenspektrometers pyrolysiert und die entstehenden thermischen Bruchstükke durch Elektronenstoß ionisiert und fragmentiert. Die Pyrolyse‐ und Fragmentierungsreaktionen lassen sich nebeneinander nachweisen.Die Kenntnis der Mechanismen beider Abbauschritte ermöglicht es, strukturisomere Polyester zu unterscheiden.
Feldionen‐ und Elektronenstoß‐Massenspektrometrie von Polymeren und Copolymeren, 5. Aliphatische und aromatische Polyamide und Polyimide
Authors: Düssel Heinz‐Jürgen , Rosen Heinz , Hummel Dieter O. 
Published: April 2003

AbstractDie aliphatischen Polyamide Polyamid‐6 (1), Polyamid‐6,6 (2) und die aromatischen Polyamide der Terephthalsäure mit verschiedenen Diaminen [p‐Phenylendiamin, (3), 4,4′‐Biphenylylendiamin, (4), 4,4′‐Oxydianilin, (5)] sowie Polyimide der Pyromellitsäure mit aliphatischen Diaminen [Äthylendiamin, (6), Hexamethylendiamin, (7)] und aromatischen Diaminen [4,4′‐Biphenylylendiamin, (8), 4,4′‐Methylendianilin, (9), 4,4′‐Isopropylidendianilin, (10), 4,4′‐Oxydianilin, (11)] wurden bei Temperaturen zwischen 800 K und 1073 K im Vakuum des Hochtemperatureinlaßsystems eines Massenspektrometers pyrolysiert und durch Feldionenmassenspektrometrie untersucht. Amine, Amide, Imide und Nitrile sind charakteristische Fragmente des thermischen Abbaus. Die Abbaumechanismen, welche durch Struktur und Ausbeute der thermischen Zersetzungsprodukte bestimmt sind, werden beschrieben.
A comparative electric birefringence study of hydroxyethyl cellulose and other cellulose derivatives in water
Authors: Foweraker Alan R. , Jennings Barry R. 
Published: April 2003

AbstractBoth the amplitude of the electric birefringence and the rotary relaxation time have been measured for each of six samples of hydroxyethyl cellulose in water in the molecular weight range 3.104 to 6.105. Both these electrical and hydrodynamical properties have been considered in terms of a number of conformation models including the rigid rod, the weakly bending rod, the worm‐like coil, and the freely jointed chain. At sufficiently low molecular weight, rigid rod behaviour is indicated. This changes to a very flexible rod at higher molecular weights. In addition, a ratio of the electrical parameters as for an equivalent rod to the equivalent rod length indicates an important characteristic factor for these molecules which is a sensitive indicator of molecular flexibility. This is illustrated by comparing the data with similar results for other members of the cellulose family namely, amylose, methyl cellulose, and sodium carboxymethyl cellulose.
Infrared spectroscopy of semicrystalline poly(vinyl alcohol) networks
Authors: Peppas Nikolaos A. 
Published: April 2003

AbstractInfrared spectroscopy was used for the quantitative determination of the degree of crystallinity of semicrystalline crosslinked polymeric films with particular application to the characterization of poly(vinyl alcohol) (PVA) networks. The intensity of the 1141 cm−1 band of the IR spectrum of PVA is sensitive to crystalline parts of the polymeric chains. A correlation between the degree of crystallinity and the intensity of this band was established. The experimental results were in accord with crystallinities obtained by density measurements of the same samples, after swelling in water until thermodynamic equilibrium. The crystallinities depended, however, on the time‐temperature history of the samples. Using this method, it is verified that the swelling process of the network does not affect the crystalline parts of the PVA chains.
Preparation, fractionation, and structure of block copolymers polystyrene‐poly(carbobenzoxy‐L‐lysine) and polybutadiene‐poly(carbobenzoxy‐L‐lysine)
Authors: Billot Jean‐Pascal , Douy André , Gallot Bernard 
Published: April 2003

AbstractAB block copolymers with a polyvinyl block (polystyrene or polybutadiene) and a polypeptide block (poly(carbobenzoxy‐L‐lysine)) were prepared by the following method: at first the polyvinyl block was synthesized by anionic polymerization, then its living end was transformed into a primary amine function and it was used as a macromolecular initiator for the polymerization of the N‐carboxy anhydride (NCA) of an α‐amino acid. After fractionation, studies of the copolymers by IR spectroscopy and X‐ray diffraction showed, that they exhibit a lamellar structure in dioxane solution and in the dry state. In this lamellar structure the polypeptide chains, present in an α‐helix conformation, are arranged in an hexagonal array and are folded.
Mechanism of the polymerization of acrylamide initiated by the glycerol/Ce(IV) redox system
Authors: Rout Swoyam P. , Rout Anuradha , Mallick N. , Singh Baishnab C. , Santappa M. 
Published: April 2003

AbstractThe mechanism of the polymerization of acrylamide in aqueous medium initiated by the glycerol (R)/Ce(IV) redox system was studied. The rate of monomer disappearance was found to be directly proportional to [M]3/2, and R1/2 at lower concentrations of Ce(IV). The rate of the disappearance of ceric ions was found to be inversely proportional to [M] and directly proportional to [Ce(IV)] and [R]. Consistent with the findings of earlier investigations, a complex formation between monomer, acrylamide, and ceric ion is indicated. The experimental results show the termination to be mutual. On the basis of these and other kinetic results, an appropriate mechanism is proposed. At higher concentration of Ce(IV), a different mechanism seems to operate. The rates of disappearance of both the monomer and ceric ions are retarded on addition of anions like HSO4−, SO4− −, or CIO4−, but they are accelerated on the addition of Mn(II) ions. Interpretations of the above observations are furnished.
Enthalpy of polymerisation of 7‐oxabicyclo[2.2.1]heptane, and exo‐ and endo‐2‐methyl‐7‐oxabicyclo[2.2.1]heptane
Authors: Andruzzi Fulvio , Pilcher Geoffrey , Virmani Yogesh , Plesch Peter H. 
Published: April 2003

AbstractThe enthalpies of combustion of poly(oxy‐1,4‐cyclohexylene) formed from 7‐oxabicyclo[2.2.1]heptane (1) and of its derivatives formed from exo‐ and endo‐3‐methyl‐7‐oxabicyclo[2.2.1]heptane (2a and 2b) have been measured. From literature values for the enthalpies of combustion of the liquid monomers, the enthalpies of polymerisation have been derived: −ΔH(1→c)=44,3±1,9, 49,7±2,6, and 45.4±3,1 kJ mol−1, respectively. The results indicate a minimum strain energy in these polymers of ca. 15 kJ mol−1. The estimated entropies of polymerisation yield ceiling temperatures of 320, 240, 200°C respectively for the three bicyclic ethers.—The reasons for the discrepancy between our present −ΔH(1→c) for the endo compound and that previously reported2, are explained.
The cyclo‐copolymerization of diallyl compounds and sulfur dioxide, 6. 1,6‐Heptadiene and sulfur dioxide
Authors: Amemiya Yasuhiro , Katayama Masamichi , Harada Susumu 
Published: April 2003

AbstractCopolymers from 1,6‐heptadiene (1) and SO2 with various mole ratios of their units were prepared. Their structures were studied by elemental analyses, IR and 1H NMR spectroscopy. Structures containing a cyclopentane ring (2) and such containing a thiane ring (3) in the main chain are proposed.
Interferenzmikroskopische charakterisierung von faserstrukturen, 1. Die ermittlung ortsabhängiger strukturparameter von fasern
Authors: Kühnle Gerhard , Schollmeyer Eckhard , Herlinger Heinz 
Published: April 2003

AbstractThe interferometric determination of refractive indices of fibers as a function of the radius of the fiber allows statements about order and orientation along the fiber radius and therefore gives an important contribution to the analysis of the structure of fibers.An analytical model for the interpretation of interferograms of fibers is developed; its application is demonstrated in comparison with a shell model for the example of a poly(ethylene terephthalate) fiber.
Enzyme‐analogue built polymers, 4. On the synthesis of polymers containing chiral cavities and their use for the resolution of racemates
Authors: Wulff G. , Vesper W. , Grobe‐Einsler R. , Sarhan A. 
Published: April 2003

AbstractWith the aid of a chiral template molecule functional groups could be placed in a highly crosslinked polymer in such a way that they are present in a chiral cavity in a given stereochemistry. By this method methyl, resp. 4‐nitrophenyl α‐D‐mannopyranoside‐2,3; 4,6‐di‐O‐(4‐vinylphenylboronate) (1a, resp. 1b) were copolymerized to macroporous polymers from which the templates methyl, resp. 4‐nitrophenyl α‐D‐mannopyranoside (2a, resp. 2b) could be split off in return. It could be shown that such polymers with two boronic acid groupings within the chiral cavity possess a good ability for the resolution of racemates of the template used. In the case of the separation of the enantiomers of 2b separation factors up to 2,27 could be obtained. The overall optical enrichment in a chromatographic separation amounted to 87%.
Polymerizations of 1‐(9‐anthryl)ethyl methacrylate and charge‐transfer complex formations with its polymers
Authors: Iwatsuki Shouji , Inukai Kenji 
Published: April 2003

Abstract1‐(9‐Anthryl)ethyl methacrylate (9AEMA) was prepared by condensation of 1‐(9‐anthryl)ethanol with methacryloyl chloride. The rate of AIBN initiated polymerization of 9AEMA in benzene at 60°C was intermediate between the polymerization rates of styrene and methyl methacrylate. 9AEMA/styrene copolymerization studies at 60°C resulted in the copolymerization parameters r9AEMA = 0,42±0,07 and rst = 0,37 ± 0,08. Charge transfer complexes are formed between p‐ chloranil and the 9AEMA homo‐ and copolymers. The absorption maxima of the CT‐complexes shifted to higher wavelengths with increasing 9AEMA content of the copolymers, whereas the equilibrium constant of the CT‐complex formation was independent of copolymer composition. Both the complex formation enthalpies and entropies decreased with increasing 9AEMA content of the copolymers.
Influence of nucleating agents on the crystallization of 6‐polyamide
Authors: Gurato Giorgio , Gaidano Dino , Zannetti Roberto 
Published: April 2003

AbstractThe influence of two nucleating agents on the crystallization parameters of 6‐Polyamide was investigated by differential scanning calorimetry and some substantial differences for the crystallization rate of the examined polymers were determined. The induction times ti, the semicrystallization times t1/2, the crystallization rate constants k, and the Avrami n coefficients were measured and related to the different characteristics and morphology of the specimens. The experimental data are represented in form of various plots and the microscopic examination of thin sections of the polymers allows to extend the study, showing remarkable differences in specimens morphology in correspondence of the nucleation effect.
Polymerization of lactams, 22. Effect of the reaction conditions on the anionic polymerization of 2‐pyrrolidone (part 2)
Authors: Kušková Marie , Roda Jan , Králíček Jaroslav 
Published: April 2003

AbstractThe effects of temperature, initiator and activator concentrations, and their mole ratios on the yield of the anionic polymerization of 2‐pyrrolidone and on the molecular weight of the resulting polymer were investigated. Potassium tert‐butoxide was used as the polymerization initiator, and N‐benzoylpyrrolidone as the activator. Optimum polymerization conditions were determined with the help of statistical planning of the experiments with the orthogonal composite design method.
Electrical properties of polyacetylene with various cis‐trans compositions
Authors: Shirakawa Hideki , Ito Takeo , Ikeda Sakuji 
Published: April 2003

AbstractThe electrical conductivity of crystalline polyacetylene films having various cis‐trans compositions was measured. The resistivity and the energy gap of a 92,5% trans polymer were 1,01·104Ω·cm and 0,56 eV, respectively, whereas the values of a 20,0% trans polymer were 2,35·108Ω·cm and 0,93 eV, respectively. These differences are discussed in terms of the effective conjugation length estimated from visible spectra and ESR measurements, and the spacing between molecular planes obtained by x‐ray diffraction measurements.
Preparation and characterization of poly(acrylamide‐co‐acrylic acid)
Authors: Klein Joachim , Heitzmann Rudolf 
Published: April 2003

AbstractA series of samples of the acrylamide/acrylic acid system with various compositions was prepared by copolymerization as well as saponification, and some new results on the kinetics of both processes are given. The products were characterized by osmometry, viscometry, GPC, DTA, and elemental analysis. The results led to the conclusion that copolymerisation and saponification lead to copolymers of identical sequential distribution of the monomeric units. It was found that the intrinsic viscosity as well as the slope factor kH · [η]2 —measured in 0,5 m NaBr solution—show a maximum at intermediate comonomer composition. This finding can be interpreted by chain stiffening due to intramolecular segmental interaction.
Enzyme‐analogue built polymers, 6. Synthesis of 5‐vinylsalicylaldehyde and a simplified synthesis of some divinyl derivatives
Authors: Wulff Günter , Akelah Ahmed 
Published: April 2003

Abstract5‐Vinylsalicylaldehyde, o‐, m‐, p‐divinylbenzenes, and 1,5‐divinylnaphthalene were prepared in high yields by using the Wittig reaction of the corresponding phosphoranes with aqueous formaldehyde.
Interferenzmikroskopische charakterisierung von faserstrukturen, 3. Die änderung des radialen verlaufes der physikalischen struktur von polyethylenterephthalat‐fasern beim färben mit dispersionsfarbstoffen
Authors: Kühnle Gerhard , Schollmeyer Eckhard , Herlinger Heinz 
Published: April 2003

AbstractThe change of the radial structure during the diffusion of dyestuffs in fibers of poly(ethylene terephthalate), [poly(oxyethyleneoxyterephthaloyl)], is studied with regard to the relationship between the dyestuff diffusion and the structure of high polymers. The fiber structure is described by interferometric measurements, which allow statements about order and orientation as a function of the diffusion path. The experimental results show that C. I. Disperse Red 60 raises the parameters which describe the order and orientation and that C. I. Disperse Blue 139 lowers these structure parameters.
Application of spin trapping technique to radical polymerization, 17.N‐hydroxysuccinimide as a radical initiator
Authors: Sato Tsuneyuki , Metsugi Makoto , Otsu Takayuki 
Published: April 2003

AbstractN‐hydroxysuccinimide (NHS) and N‐hydroxyphthalimide were found to initiate effectively vinyl polymerizations of acrylate monomers. The polymerization of methyl methacrylate (MMA) with NHS was investigated in detail. The polymerization rate (Rp) was found to depend highly on the solvents. The over‐all activation energy of the polymerization in ethyl acetate was calculated to be 76,2 kJ/mol (18,2 kcal/mol). In the low monomer concentration, Rp can be expressed as Rp = k [NHS]1/2 [MMA]3/2. The copolymerization of MMA with styrene, initiated by NHS, could be shown to proceed via radical mechanism. In order to elucidate the initiation mechanism, spin trapping technique was applied to this polymerization system. In the reaction of MMA with NHS in acetone, the 2‐carbomethoxypropyl radical was trapped by 2‐methyl‐2‐nitrosopropane, a spin trapping reagent, to give the corresponding aminyl oxide radical 2. From the results, the initiation mechanism of this polymerization is proposed and discussed.
Enthalpy of polymerisation of 2‐oxabicyclo[2.2.2]octan‐3‐one
Authors: Andruzzi Fulvio , Pilcher Geoffrey , Hacking John M. , Cavell Sue 
Published: April 2003

AbstractThe enthalpies of combustion of crystalline 2‐oxabicyclo[2.2.2]octan‐3‐one (1), and five different crystalline poly(oxycarbonyl‐1,4‐cyclohexylene) samples formed from 1 were measured at 298, 15 K by high‐precision bomb calorimetry. For 1, the enthalpies of combustion and of formation were, −ΔH(c) = 3717,5 ± 1,3 kJ·mol−1 and −ΔH(c) = − 466,2 ± 1,6 kJ·mol−1. After correction for the presence of n‐butyl‐ or tert‐butoxy‐end groups in the polyester samples, a consistent enthalpy of polymerisation of 1 was obtained, ΔH(c → c) = − 20,9 ± 2,3 kJ·mol−1. The enthalpy of sublimation of 1 was measured, ΔH (1) = 69,6 ± 2,1 kJ·mol−1; the value for the polyester unit was derived as 49 kJ·mol−1.
Not all polyanions induce a J‐band in the dye pseudoisocyanine
Authors: Pal M. K. , Ghosh Bijan Kumar 
Published: April 2003

AbstractN,N′‐diethylpseudoisocyanine chloride (PIC) forms compounds with various vinyl poly+ and DNA, but the shapes of the spectra of the dye‐polyanion compounds depend on the nature of the polyanions. PIC forms compounds with 1:1 polyanion/dye stoichiometries with DNA (native and denatured), polymethacrylate and poly(styrenesulfonate); and the spectra of these compounds do not show any pronounced metachromasia or red‐shifted J‐band. Polyacrylate and poly(vinyl sulfate) form compounds with polyanion/dye stoichiometry of 2:1, and give spectra with extremely sharp and red‐shifted J‐band. This is the first report on the relation between the polyanion/PIC stoichiometry and the depiction of the J‐band of the resulting compound.
Mechanical behaviour of aortic tissue as a function of collagen orientation
Authors: Roveri Norberto , Ripamonti Alberto , Pulga Carla , Jeronimidis Giorgio , Purslow Peter P. , Volpin Dino , Gotte Lorenzo 
Published: April 2003

AbstractX‐ray diffraction techniques have been used to investigate the orientation under stress of collagen fibres in pig's descending aortic wall. The variation of the limit value of the incremental modulus as a function of the collagen content seems to suggest that the extra amount of collagen going from the aortic arch downwards is deposited in a preferred orientation corresponding to the circumferential direction. The results have been used to describe the uniaxial mechanical behaviour of this tissue taking into account its composite structure.
Phenolic resins for peptide synthesis, 2. Reactivities of phenolic and amino functional groups in styrene based resins
Authors: Arshady R. , Ledwith A. , Kenner G. W. 
Published: April 2003

AbstractCopolymerisation of styrene, p‐acetoxystyrene, and divinylbenzene is a convenient way of obtaining resins for application in solid phase peptide synthesis. Phenolic group attachment sites are readily obtained by hydrolysis under mild conditions of the acetoxyl resin. In order to investigate possible effects of lyophilic (e.g. amino acid) units attached to the resin on subsequent reactivity in peptide synthesis, the coupling efficiencies of initially prepared phenolic resins and equivalent resins already functionalised with the tripeptide, H‐Leu‐Ala‐Gly, have been compared in reactions with Boc‐Gly‐ONSu and Boc‐Ile‐OTcp. The two resin types afford phenolic and primary amino‐functionalities respectively and exhibit marked solvent effects on reactivities, although swelling characteristics are rather similar. It is concluded that solvent effects on the particular coupling reactions are more important than solvent effects on swelling of the resins.
Caractérisation texturale de résines en milieu réactionnel
Authors: Brun Maurice , Quinson Jean‐François , Blanc Raymond , Negre Michèle , Spitz Roger , Bartholin Michel 
Published: April 2003

AbstractThermoporometry, a method based on the microcalorimetric analysis of liquid‐solid state transformation inside porous substances, gives access to porous volume versus pore size distribution. For the first time, this method is applied to the analysis of flexible products swellable in the reference medium. Conditions for applying transposition thermoporometry to this new class of porous substances are discussed. An example is given, which leads to suggest a model for the swelling process of a macroporous resin. Generalization of this method would induce a major progress in the study of swollen systems and enable better understanding of their structures.