bluuebunny/crossref_metadata_2025_split huggingface dataset:
Formation and properties of triol‐based polyester networks
Authors: Fasina Ayoola B. , Stepto Robert F. T. 
Published: April 2003

AbstractNetworks have been prepared by reacting polyoxypropylene triols with sebacoyl chloride at equal concentrations of hydroxyl and acid chloride groups. The reactions were allowed to go to completion to form the networks studied. The gel points of the reaction mixtures were also determined and used as a basis for the correlation of the properties of the networks formed at complete reaction. Reactions were carried out at 27°C, in bulk and in diglyme as solvent, and the shear moduli of networks formed, in the dry state and at equilibrium swelling in diglyme, were measured at the same temperature using uniaxial compression. Deviations from Gaussian behaviour wer found to decrease as the dilution of the reaction mixture forming the network increased. For apparent values of the molecular mass between junction points (Mc) greater than about 104, essentially Gaussian stress‐strain behaviour was observed. For the triols used, such values of Mc may be obtained from dilute reaction systems. Values of Mc increased with pre‐gel intramolecular reaction and indicate that in the limit of a perfect gelling system, a perfect network is formed. The values of Mc found are generally larger than those expected for the perfect network (M), irrespective of whether phantom or affine behaviour is assumed, and are consistent with network imperfections being elastically ineffective loops, caused by pre‐gel intramolecular reaction, rather than entanglements.
The heats of dilution of poly(1‐vinyl‐2‐pyrrolidone)/alcohol systems
Authors: Ogawa Hideo , Baba Yoshihiro , Kagemoto Akihiro 
Published: April 2003

AbstractIn order to obtain information about the heat interaction parameter between poly(1‐vinyl‐2‐pyrrolidone) (PVP) and alcohols, a flow microcalorimeter equipped with a new type of pump was constructed, and heats of dilution of PVP in alcohol solutions were measured using this microcalorimeter at 298,15 ± 0,001 K. The heat interaction parameter depends considerably on the concentration of the polymer and the chain length of the alcohols.
Conformational transition in poly[4‐(1,1,3,3‐tetramethylbutyl)phenyl methacrylate] and poly(4‐tert‐butylphenyl methacrylate) in dilute solutions
Authors: Sarabia Carmen , Radic Deodato , Gargallo Ligia 
Published: April 2003

AbstractTemperature dependence of viscosity data and refractive index increment was investigated on two polymers: poly[4‐(1,1,3,3‐tetramethylbutyl)phenyl methacrylate] (1a) and poly(4‐tert‐butylphenyl methacrylate) (1b) in dilute solution. A discontinuity in intrinsic viscosity was observed over a narrow temperature range. From this behaviour it was possible to visualize sharp changes of unperturbed dimensions (Kθ) and thermodynamic parameters (B). This phenomenon can be accounted for by assuming conformational changes of the chain in the chosen solvent in a specific temperature range. These changes can be also observed by discontinuities in refractive index increments dn/dc. In the case of 1b the conformational change disappears on addition of a polar solvent (CHCl3).
Syntheses of thermotropic liquid crystalline polymers, 1. Azoxy and azo type polyesters
Authors: Iimura Kazuyoshi , Koide Naoyuki , Ohta Ryo , Takeda Masatami 
Published: April 2003

AbstractAzoxy and azo type polyesters were obtained by combination of an azoxybenzene or an azobenzene group as a mesogenic core with different flexible chain lengths of ethylene glycol groups. The thermal properties of these mesomorphic polymers are discussed related to their chemical structures. The mesomorphic temperature region becomes narrower with increasing flexible chain length. Further, the transition temperature from the mesomorphic phase to the isotropic liquid is higher for the azoxy type polyester than for the azo type polyester.
Polymere Phthalocyanine und ihre Vorstufen, 3. In situ Gasphasensynthese und einführende elektrochemische Charakterisierung polymerer Phthalocyanine auf metallischen Trägern
Authors: Bannehr Rüdiger , Jaeger Nils , Meyer Gunter , Wöhrle Dieter 
Published: April 2003

AbstractThe gas phase reaction of 1,2,4,5‐tetracyanobenzene (3) with metal sheets like Cu, Ni, Co, Fe, and Ti exhibits the in situ formation of polymeric phthalocyanine coatings 1. The electrochemical behaviour of layers of 1 is investigated by means of cyclic voltametric measurements. Determination of layer‐thickness and electrical resistance is also performed.
Oxydation photothermique d'élastomères de polyuréthannes thermoplastiques, 1. Propriétés des hydroperoxydes formés
Authors: Gardette Jean‐Luc , Lemaire Jacques 
Published: April 2003

AbstractThe photothermal oxidation of thermoplastic polyurethane elastomers was studied, observing the behaviour of four types of model polymers based upon various hard segments (aromatic or aliphatic) and various elastomeric phases (polyether or polyester). Four types of hydroperoxy groups were observed. By chemical titrations of these hydroperoxides and spectrophotochemical measurements, the thermal and photochemical stability of these compounds was studied. An interpretation of the appearance of hydroxylated compounds during photothermal oxidation is given for the four model polymers.
Substituted and branched polychalcones, 2. Polymeric and solubility properties of the polychalcones
Authors: Malm Bo , Lindberg J. Johan 
Published: April 2003

AbstractThe polymeric and solubility properties of polychalcones 2a, b prepared by Friedel‐Crafts acetylation of vanillin (3a) and p‐hydroxybenzaldehyde (3b) were investigated. The polymers had limited solubility, and only polychalcones obtained from vanillin were completely soluble in dimethyl sulfoxide (DMSO); the others swelled in this solvent. Approximate values for the average molecular weights between cross‐links, Mc, were calculated from the swelling in DMSO using the Flory‐Rehner equation. Average molecular weights (Mw and Mn) and molecular weight distributions of the soluble fraction were determined by gel permeation chromatography on Sephadex G gels in DMSO. Mn corresponded to the molecular weights of the polymers in ethanol and of the acetylated materials in chloroform obtained with a vapour pressure osmometer.
On the photoinitiation of free radical polymerization‐laser flash photolysis investigations on thioxanthone derivatives
Authors: Amirzadeh Gholamreza , Schnabel Wolfram 
Published: April 2003

AbstractLaser flash photolysis studies and stationary polymerizations were carried out with the aim to elucidate kinetics and mechanisms of photoinitiation processes based on thioxanthone (TX)/amine interactions. During these studies prominence was given to reactions which significantly influence the initiator efficiencies. Thus, rate constants of the reactions 3TX* + monomer (kq), 3TX* + amine (kXH), and ketyl radical + monomer (k) were determined; kq decreases according to the series: styrene (St) > N‐vinyl‐2‐pyrrolidone (VP) > methyl methacrylate (MMA) > acrylonitrile (AN) > butyl vinyl ether (BVE) > vinyl acetate (VA) from 6·109 l·mol−1·s−;1 to 2·104 l·mol−1·s−1. Substitution in the 2‐position of TX by methyl (MTX), isopropyl (ITX) and Cl (CTX) generally causes a decrease of kq, except for the systems CTX/VP and CTX/BVE. The kXH values range from 6 to 8·109 l·mol−1·s−1 for typical amines, e.g. ethyl 4‐((dimethylamino)benzoate). Ketyl radicals react rather slowly with monomers; for CTX k in l·mol−1·s−1: 7·103 (St), 4·102 (VP), 4·101 (MMA), ⩽ 10 (BVE). O2 reacts rapidly with ketyl radicals: k = 2·109 l·mol−1·s−1 (TX). Rates of polymerization ν (monomer consumption) determined at [M] = 5 mol/l and [amine] = 10−1 mol/l are equal for TX, ITX, MTX, and CTX, but increase according to the series AN < MMA < VP; ν depends on the thioxanthone and the monomer concentration according to ν ∝ [TX]1/2[M].
Interaction of polystyryl radical with copper(II) complexes
Authors: Baruah Shashi Dhar , Dass Narendra Nath 
Published: April 2003

AbstractThe polymerization of styrene initiated by 2,2′‐azoisobutyronitrile (AIBN) was studied in N,N‐dimethylformamide (DMF) solution at 60°C in the presence of tetrakis(N,N‐dimethylformamide)copper(II) perchlorate, and also in the presence of its monoazido copper(II) complex [Cu(DMF)3N3]+. The monoazido complex in DMF was prepared in situ by mixing solid sodium azide with tetrakis(N,N‐dimethylformamide)copper(II) perchlorate in a mole ratio of 1:1. The nature of the complex was established by Job's method. The equilibrium constant K for the reaction [Cu(DMF)4]2+ + N ⇌ [Cu(DMF)3N3]+ + DMF determined by the limiting logarithmic method was found to be 1,25 · 104l · mol−1. The presence of [Cu(DMF)4]2+ ions in the polymerization systems caused retardation, but [Cu(DMF)3N3]+ ions produced well defined induction periods. The rate constants at 60°C for the interaction of polystyryl radical towards [Cu(DMF)4]2+ and [Cu(DMF)3N3]+ ions were calculated to be 6,6 · 102 and 5,74 · 104 l · mol−1 · s−1, respectively.
On the kinetics of hydrolytic degradation of native cellulose
Authors: Marx‐Figini Marianne , Coun‐Matus Mari 
Published: April 2003

AbstractThe kinetics of the hydrolytic degradation of celluloses the molecular properties of which still correspond largely to those of the native state are studied. The hydrolytic agent has been 0,5 mol/l aqueous solution of KHSO4. The degrees of polymerization were determined viscosimetrically in copper ethylene diamine (CuEn) as solvent under standard conditions. In order to convert viscosity‐average and weight‐average degrees of polymerization DPη and DPw in the corresponding number‐average DPn, a DPw/DPn calibration curve had been elaborated using polymer analogeous nitrates of a series of samples degraded under the same conditions. The results reveal that hydrolytic degradation of native cellulose takes place by two simultaneously occurring kinetic mechanisms, for which the following rate constants were derived: k1 = 0,12 h−1, k2 = 3,88·10−6 h−1, and k1 = 0,79 h−1; k2 = 38,35 · 10−6 h−1, corresponding to a degradation temperature of 40°C and 60°C, respectively, and related to an initial degree of polymerization DP0 = 13 000. The number of faster cleaving bonds per molecule (β1) and the number average of normally splitting bonds being between two “weak links” (β2) resulted in β1 ≈ 3,5 and β2 ≈ 3 600. The activation energies of the rapid and the slower reaction were found to be 20 kcal/mol (83,7 kJ/mol) and 24 kcal/mol (100,4 kJ/mol), respectively. Additional degradation experiments on the same, but pre‐swollen or pre‐reduced samples did not provoke any variations in the results. It can be excluded, therefore, that the simultaneous occurrence of two kinteic mechanisms is a consequence either of facts which involve diffusion control, or the existence of “stressed” bonds. The found relatively high activation energies rather permit to assume native modifications in the chemical structure of the cellulose molecule as the most probable reason for the faster bond splitting reaction.
NMR study of molecular motion in solid and molten polystyrene: Application of the deuteron dilution technique
Authors: Lindner P. , Rössler E. , Sillescu H. 
Published: April 2003

AbstractThe proton spin‐lattice relaxation time T1 was determined at 13,8, 55,2, and 90 MHz in polystyrene (PS‐d0) and polystyrene deuterated at the chain (PS‐d3) and the phenyl groups (PS‐d5), respectively, at temperatures between −130 and +230°C. Furthermore, T1 was measured in isotopic mixtures of PS‐d3 and fully deuterated PS‐d8 where a separation into intramolecular and intermolecular contributions was possible through the deuteron dilution technique. Above 130°C, various distributions of correlation times provide a semiquantitative understanding of the different motins seen by the protons of the partially deuterated systems. Rotating frame relaxation times in PS‐d3 and PS‐d5 reveal librational motions in the solid glass (below 100°) where the amplitudes of the phenyl group librations are much larger than those of the chain oscillations, but the correlation times are of the same order of magnitude.
Styrene polymerization induced by anilino radicals
Authors: Sugiyama Kazuo , Oda Tetsuo , Maeshima Toshihisa 
Published: April 2003

AbstractThe polymerization of styrene (St) initiated by 1,4‐dimethyl‐1,4‐diphenyl‐2‐tetrazene (1c) is studied kinetically in benzene. The polymerization proceeds through a radical mechanism. The rate equation is as follows: Rp = k [1c]0,5[St]1,0. The overall activation energy for the polymerization of St is found to be 105,9 kJ · mol−1. The efficiency of the initiator is also calculated to be 0,67. On the basis of the results, the initiating ability of N‐methylanilino radicals is discussed.
Preparation of amide and amine groups containing copolymers of methyl methacrylate and their performance in solid polymer composites
Authors: Orbay Murat , Laible Richard , Dulog Lothar 
Published: April 2003

AbstractMethyl methacrylate (MMA) was copolymerized with acrylamide, N‐methylacrylamide, N,N‐dimethylacrylamide, 1‐vinyl‐2‐pyrrolidone, 4‐vinylpyridine, and 2‐dimethylaminomethyl methacrylate in 1,4‐dioxane solution at 65°C, using AIBN as initiator, to yield copolymers with comonomer contents between about 5 and 50 mole‐%. The monomer reactivity ratios were evaluated. The copolymerizations are in general non‐azeotropic and non‐ideal. The amine group containing comonomers are preferentially incorporated in relation to MMA, but MMA is preferentially incorporated in relation to the amide group containing comonomers. The average molecular weights of the copolymers, with the exception of the N,N‐dimethylacrylamide copolymer, decrease with increasing comonomer concentration, especially in the case of the amine group containing comonomers. The increasing content of amide and amine group containing monomeric units in the copolymers influences the adsorption of the polymers on an iron oxide red pigment, the dispersion stability, as well as the adhesion of the polymer coatings on steel plates and their corrosion protection.
Branching in terminally functional polymers of low molecular weight caused by chain transfer with initiator radicals
Authors: Ivantchev Sergey S. , Barantsevich Eugene N. , Kartavykh Valentin P. , Dratch Valery A. 
Published: April 2003

AbstractEquations to calculate the density of branching arising from chain transfer to polymer with initiator radicals in terminally functional polymers of low molecular weight were derived for various polymerization conditions. The branching density was shown to be affected by the feed procedure. The relative amount of branching was found to be lower with a single addition of monomer and initiator than with continuous feed of initiator during the reaction. These conclusions were confirmed experimentally.
Enzyme‐analogue built polymers, 13. On the introduction of amino‐ and boronic acid groups into chiral polymer cavities
Authors: Sarhan Ali , Wulff Günter 
Published: April 2003

AbstractWith the aid of D‐glyceric acid as a template, an amino‐ and a boronic acid group, respectively, were introduced in a defined steric arrangement into polymers. For this, the monomer D‐N‐(4‐vinylphenyl)carbamoylethylenedioxy(4‐vinylphenyl)borane (1) was copolymerized into macroporous polymers under various conditions. The template D‐glyceric acid was split off from the polymer with 20% HCl in methanol. The specificity of the polymers obtained with one amino‐ and one boronic acid group, respectively, per cavity was derived from their ability to resolve racemic glyceric acid. Racemic resolution was also observed on equilibration of the polymers with D,L‐methyl glycerate and D,L‐glyceraldehyde.
Conformational analysis of poly(methyl acrylate) by 1H nuclear magnetic resonance spectroscopy
Authors: Matsuzaki Kei , Kawazu Fumio , Kanai Taiichi 
Published: April 2003

AbstractThe 1H NMR spectra of poly(methyl acrylate‐d1) +CHDCH(COOCH3)+n were measured in o‐dichlorobenzene and CDCl3 in the temperature range between − 20 and 145°C. Trans and gauche coupling constant were determined from the temperature dependence of the geminal coupling constants, neglecting g' conformers. It was estimated that the proportion of trans conformer is 1,5 to 1,9 times that of the gauche conformer in this temperature range.
Polymer conformation and NMR chemical shifts, 4. Contrast of 13C NMR spectra between poly(methyl acrylate‐alt‐styrene) and poly(methyl methacrylate‐alt‐styrene)
Authors: Koinuma Hideomi , Tanabe Tsuneaki , Hirai Hidefumi , Hirano Tsuneo 
Published: April 2003

AbstractThe presence of the α‐methyl group in the alternating methyl methacrylate‐styrene copolymer produces a remarkable difference in its 13C NMR spectra as compared with the spectra of the alternating methyl acrylate‐styrene copolymer; cotacticity‐dependent splittings occur only in the former spectrum. A theoretical interpretation was attempted for this characteristic spectral variation in terms of the calculated time‐averaged chemical shifts for carbons in the dyads constituting the alternating copolymers. Each (meso or racemic) dyad sequence is considered to exist in several conformational states which are mutually exchanging rapidly and the probabilities of which are determined by a statistical mechanical procedure. The calculation of cotacticity‐dependent chemical shifts is conducted for the side chain carbonyl, aromatic C1 and methoxyl carbons as well as for some main chain carbons to give good agreement with the observed peak splittings, especially with respect to the side chain carbons. In accordance with the reported assignment, the calculated differences in shielding factors between meso and racemic dyads for the side chain carbons of poly(methyl methacrylate‐alt‐styrene) are positive, i.e. the meso or isotactic peak appears at higher field than the racemic or syndiotactic peak. Furthermore, the resulting values are relatively large (≈0,63 ppm) in conformity with the experiment. The calculation for the carbons in poly(methyl acrylate‐alt‐styrene) gives a very small shielding difference (−0,04 to 0,06 ppm) by the dyad cotacticity, being consistent with the observation, i. e. absence of peak splittings.
X‐ray diffraction study of oriented diamides
Authors: Ania Fernando , Rueda Daniel R. , Calleja Francisco J. Baltá 
Published: April 2003

AbstractThe crystal unit cell of a series of normal diamides, RNHCO(CH2)2nCONHR (1) with RCH3(CH2)5 and n varying from 0 up to 4, has been determined from X‐ray diffraction patterns of oriented films. This work forms part of the study to investigate the relation between microstructure and physical properties, in particular diamagnetism. The unit cell is tricline for all members of the series having one chain molecule per unit cell. The structure of normal diamides consists of extended chains tilted 75° from the sheet edge allowing hydrogen‐bond formation within the sheet. The long spacings obtained have been associated to oblique structures of hydrogen‐bonded sheets, except for the diamide with n = 1. A. shear between adjacent hydrogen‐bonded sheets of 3 repeating chain units offers the most probable explanation for the structure of 1 with n = 0,2,3 and 4.
Aromatic poly[(amino)amide]s and poly(imidazo[4,5‐f]benzimidazole)s derived from poly[(tosylamino)amide]s, 1
Authors: Kehayoglou Aristides , Karayannidis Georgious , Sideridou‐Karayannidou Irini 
Published: April 2003

AbstractNew poly[(amino)amide]s (4) deriving from 1,2,4,5‐benzenetetraamine and terephthalic, isophathalic, or 2,5‐furandicarboxylic acid (2a–c) were indirectly prepared by detosylation of the corresponding new poly[(tosylamino)amide]s 3, which were obtained by low‐temperature solution polymerization of 4,6‐ditosylamino‐1, 3‐phenylenediamine (1) with the dicarboxylic acid dichlorides 2a–c. In a subsequent step the poly[(amino)amide]s were converted by polydehydrocyclocondensation into the heat‐resistant aromatic poly(imidazo[4,5‐f]benzimidazole)s (5) by heating in a high vacuum. The results of elemental analysis, IR and UV spectroscopy, inherent viscosity measurements, molecular weight determination (osmometry), and thermal analysis (DSC, TG) of the prepared polymers are compared and discussed.
Terpolymérisation acrylonitrile‐styène‐acrylate de méthyle, 2. Synthèse de terpolymères homogènes en composition par polymérisation en émulsion
Authors: Rios Lèonardo , Guillot Jean 
Published: April 2003

AbstractPrevious Kinetic studies of the emulsion polymerisation of the three component system acrylonitrile (A) — styrene (S) — methyl acrylate (M) have shown that S is much more reactive than A and M, which have practically the same reactivities. As a consequence, in batch process a large copolymer composition drift is observed versus conversion. To avoid this damageable drift, two techniques were investigated, to get homogeneous macromolecules. (1) Application of the well known “semi‐continuous technique” which appeared not to be totally satisfactory, since the initial batch polymer fraction generally has a composition different from the further polymer when the monomer feed is added under starving conditions; a mixture of various macromolecules is the result. (2) The use of the composition controlled reactor, developed in this laboratory, which consists in a continuous monitored readjustment of monomer feed composition. However, due to the heterogeneous medium of an emulsion copolymerization, the copolymer exerts a small chemical heterogeneity which may be practically negligible at high monomer/water ratio. It is finally proposed that a thermodynamic approach might overcome such a behaviour and insure an actual control of the copolymer composition.
Asymmetric cyanohydrin synthesis catalyzed by synthetic dipeptides, 2
Authors: Oku Jun‐ichi , Ito Naofumi , Inoue Shohei 
Published: April 2003

AbstractIn the asymmetric addition of hydrogen cyanide to benzaldehyde to give mandelonitrile, a cyanohydrin, the highest enantiomeric excess (e.e.) ever reported (90%) was obtained with (2d) whereas the corresponding linear dipeptide gave a very low e. e. This high e. e. decreased with the reaction time, because of the racemization of the product. All cyclic dipeptides used containing an (S)‐histidine residue preferred the (R)‐product. A scheme for the interaction between the catalyst and the reactants to give the (R)‐product is proposed.
The anionic polymerization of styrene oxide. Polymer structure and direction of ring opening
Authors: Jedliński Zbigniew , Kasperczyk Janusz , Dworak Andrzej , Matuszewska Barbara 
Published: April 2003

AbstractThe direction of the oxirane ring opening in the polymerization of styrene oxide by sodium methoxide was determined on the basis of the structure of the products obtained. The oxirane ring opening was found to occur almost exclusively in β‐position. This result was compared with a model reaction, i.e. the methanol addition to styrene oxide in the presence of sodium methoxide. In the model reaction the oxirane ring opening occurred to ca. 35% in α‐position and to ca. 65% in β‐position.
Polymethacrylic acid derivatives, 4. Solubilization of azobenzene, a water insoluble nonpolar compound
Authors: Morcellet‐Sauvage Joëlle , Morcellet Michel , Loucheux Claude 
Published: April 2003

AbstractMeasurements of the solubilization of a water insoluble compound, azobenzene, inside the hydrophobic domains of compact conformations, were carried out using different polymers and copolymers. The influence of the tacticity of the polymer and the hydrophobic character of the copolymers was investigated, as well as specific intramolecular interactions between the hydrophobic residues. The influence of the solubilization on the spectral properties (λmax and εmax) of azobenzene and the copolymers was also studied. Experimental results show that no close correlation exists between the solubilizing power and the stability of the compact conformation, especially since some copolymers which take a compact conformation have no solubilizing power.