bluuebunny/crossref_metadata_2025_split huggingface dataset:
Flow properties of concentrated solutions of polyarylate in m‐cresol
Authors: Zabala M Jesus , Santamaria Anton , Peña Juan J. , Muñoz M Eugenia 
Published: April 2003

AbstractThe flow properties of concentrated solutions of polyarylate from bisphenol A/50:50 isophthalic acid: terephthalic acid in m‐cresol are studied. The results are discussed in terms of critical concentration Cc and critical molecular weight Mc for the onset of entanglements. Values of Cc = 8,2 wt.‐% and Mc ≈ 3500 are obtained. The dependence of the Newtonian viscosities with temperature allows to obtain different energies of activation of flow for each polyarylate/m‐cresol system, ranging from 9 to 13 kcal/mol (= 37,7 to 54,4 kJ/mol). The following free‐volume‐additivity equation is proposed to fit these data:

where Ea, Eap, and Ead are the activation energies of the solution, the polymer and the solvent, respectively. Vp and Vd are the polymer volume fraction and the diluent volume fraction, respectively, and αp and αd represent the differences between the volume coefficients of expansion above and below the corresponding glass transition temperatures for the polymer and the solvent.
Zum einfluß von zwischenmolekularen Wechselwirkungen auf Die Polymerisation, 12. Copolymerisation von 2‐Naphthylmethacrylat mit Styrol in verschiedenen Lösungsmitteln
Authors: Boudevska Hrissanta , Bratschkov Christo , Todorova Olga , Braun Dietrich , Czerwinski Wojciech K. 
Published: April 2003

AbstractA study of the copolymerization behaviour of 2‐naphthyl methacrylate (M1), with styrene (M2) was carried out at 60°C in solution with 2,2′‐azoisobutyronitrile as initiator and in different solvents. The following values for the monomer reactivity ratios were obtained by means of the Joshi‐Joshi method:

Chloroform: r1 = 0,16 ± 0,14, r2 = 0,81 ± 0,46
1,4‐Dioxane: r1 = 0,34 ± 0,09, r2 = 0,49 ± 0,39
Acetone: r1 = 0,54 ± 0,11, r2 = 0,63 ± 0,30
Acetonitrile: r1 = 0,24 ± 0,09, r2 = 0,39 ± 0,33

These results are in good agreement with those obtained by means of the Fineman‐Ross and Kelen‐Tüdős methods. The solvent effect is discussed in terms of charge‐transfer complexation between monomer and solvent molecules.
Copolymérisation radicalaire du méthyl‐4 styrène avec le méthacrylate de méthyle ou l'acrylonitrile. Détermination des rapports de réactivité
Authors: Lin Dar Jong , Petit Alain , Néel Jean 
Published: April 2003

Abstract4‐Methylstyrene (S) was copolymerized with methyl methacrylate (M) or acrylonitrile (A) in benzene or N,N‐dimethylformamide solution, respectively. The reactions were carried out at 50°C, using 2,2′‐azoisobutyronitrile as free‐radical initiator. The copolymer compositions were determined from oxygen (SM) or nitrogen (SA) analysis, 100 MHz 1H NMR, and 25 MHz 13C NMR spectra. These methods lead to the same results. Data plotted according to the Kelen‐Tüdős (K‐T) procedure indicate that the copolymerization of S with M can be adequately described by the terminal‐unit model. The corresponding reactivity ratios (rS = 0,46 ± 0,02 and rM = 0,35 ± 0,02) were in good agreement with literature values and conform with the Q, e‐scheme. On the other hand, the K‐T plot for copolymerization of the SA system indicates deviations from the terminal model (rS = 0,27 ± 0,02 and rA = 0,10 ± 0,01) in the S‐ and A‐rich regions. This departure was interpreted in terms of penultimate effects on the reactivity of the S‐ and A‐ended radicals. The values of the corresponding reactivity ratios were as follows: rSS = 0,18 ± 0,03, rAS = 0,34 ± 0,04, rAA = 0,06 ± 0,01, and rSA = 0,13 ± 0,01. The theoretical curve of copolymer composition versus monomer feed, calculated with these parameters, is in excellent agreement with the experimental data. This finding shows that, on the basis of the composition data alone, the penultimate model provides an appropriate description of the copolymerization of S and A.
Poly(vinylsaccharide)s, 2 Synthesis of some poly(vinylsaccharide)s of the amide type and investigation of their solution properties
Authors: Klein Joachim , Herzog Dieter 
Published: April 2003

AbstractThe structure and synthesis of some poly(vinylsaccharide)s is described. Five different monomers, N‐saccharide‐substituted acryl‐and methacrylamides, were prepared and polymerized to high molecular weight products using different initiator systems. The influence of the chemical structure of the saccharide moiety on the solution properties was studied by viscosity and light scattering measurements, and a comparative discussion of the solution behaviour of poly(2‐deoxy‐2‐methacrylamido‐D‐glucose), poly(1‐deoxy‐1‐methacrylamido‐D‐glucitol), poly(1‐acrylamido‐1‐deoxy‐D‐glucitol) and polyacrylamide is made. The effects of hydrogenation on the intrinsic viscosity of poly(2‐deoxy‐2‐methacrylamido‐D‐glucose) is shown. The crosslinking of poly(1‐acrylamido‐1‐deoxy‐D‐glucitol) as a side reaction was examined by 13C NMR spectroscopy.
Preparative synthesis of guanylate‐rich fragments of the terminal sequence of macronuclear DNA from hypotrichous ciliates using the phosphotriester method in solution
Authors: Schott Herbert , Semmler Rolf , Cloß Knut , Eckstein Heiner 
Published: April 2003

AbstractGuanylate‐rich oligodeoxyribonucleotides d(G4T4), d(T4G4), d(T4G4T4), d(G4T4G4), and d(T4G4T4G4) were synthesized in amounts up to 350 mg using the triester method in solution. These oligonucleotides correspond to fragments of the terminal of macronuclear DNA from hypotrichous ciliates. The protected oligonucleotides were obtained by block‐condensation of protected 5′‐hydroxyl and 3′‐phosphate derivatives. Mixtures of 2,4,6‐triisopropylbenzenesulfonyl chloride/N‐methylimidazole or 2,4,6‐trimethylbenzenesulfonyl chloride/N‐methylimidazole were used as condensating agents. Different concepts of protecting the nucleotides were investigated and it was found that yields and purities of the resulting oligonucleotides do not depend essentially on the employed concept. The 36mer d(G4T4G4T4G4T4G4T4G4) was obtained by enzymatic phosphorylation of aliquots of the dodecamers d(G4T4G4) and d(T4G4T4), followed by ligation with T4 DNA ligase.
Synthesis and characterization of liquid‐crystalline copolymers with dichroic dyes and mesogens as side groups
Authors: Ringsdorf Helmut , Schmidt Hans‐Werner , Eilingsfeld Heinz , Etzbach Karl‐Heinz 
Published: April 2003

AbstractLiquid‐crystalline copolymers with covalently attached dichroic dyes were synthesized and characterized. Copolymers with high anthraquinone and trisazo‐dye content were obtained by copolymerization of dye monomers with 4‐cyanophenyl 4‐(6‐acryloyloxyhexyloxy)benzoate (1) and 6‐acryloyloxyhexyl 4‐(trans‐4‐propylcyclohexyl)benzoate (2). Particular attention is given to the influence of the dye content and the dye structure on the liquid‐crystalline behavior of the copolymers.
Synthesis and characterization of vinyl monomers with blocked isocyanato groups
Authors: Sadoun Tahar , Clouet Gilbert , Brossas Jean 
Published: April 2003

AbstractVinyl monomers containing blocked isocyanato groups were prepared in one step, by blocking the isocyanato group of 2‐isocyanatoethyl methacrylate with phenol, propanone oxime, butanone oxime, benzophenone oxime or ε‐caprolactam, or in two steps, by blocking one of the two isocyanato groups of 4‐methyl‐1,3‐phenylene diisocyanate with phenol or ε‐caprolactam and the second group with 2‐hydroxyethyl methacrylate. The 1H NMR and the IR spectra of these monomers are discussed.
Electrochemical and chemical syntheses and doping of [poly(2,2′‐dithienyl)‐5,5′‐diylvinylene]
Authors: Bragadin Marcantonio , Cescon Paolo , Berlin Anna , Sannicolò Franco 
Published: April 2003

AbstractThe electroconductive polymer poly[(2,2′‐dithienyl)‐5,5′‐diylvinylene] (1) was prepared by both electrochemical and chemical methods starting from trans‐di(2‐thienyl)ethylene (2). The electrochemically prepared material showed electrical conductivities of up to 40 Ω−1 · cm−1; the neutral, chemically prepared polymer was droped with iodine or arsenic pentafluoride but the conductivities were low. The experimental procedures are described and an interpretation of the results is given.
Synthesis, structure, and phase behaviour of liquid‐crystalline rigid‐rod polyesters and polyamides with disc‐like mesogens in the main chain
Authors: Ringsdorf Helmut , Tschirner Peter , Hermann‐Schönherr Otto , Wendroff Joachim H. 
Published: April 2003

AbstractAromatic polyesters and polyamides with disc‐like mesogens in the main chain were prepared from tetra‐substituted hydroquinones and derivatives of 1,4‐phenylenediamine. Depending on the atomatic acids (terephthalic acid, 2,5‐dialkoxyterephthalic acid) used in the condensation reaction, the repeating units of these polymers carried 4 or 6 lateral substitutents. All polymers are highly soluble in several organic solvents, e.g. CHCl3, toluene, acetone. The phase behaviour of the polymers was studied by means of differential scanning calorimetry and optical polarizing microscopy. Depending on the number of lateral substitutents the polyesters and polyamides show crystalline and thermotropic liquid‐crystalline phases. X‐ray investigations showed a board‐like Packing of the rigid‐rod polymers which we have termed as a “sanidic” (meaning board‐like) phase.
Thermoelastic and photoelastic properties of crosslinked liquid‐crystalline side chain polymers
Authors: Gleim Wolfgang , Finkelmann Heino 
Published: April 2003

AbstractMeasurements of stress and birefringence of crosslinked liquid‐crystalline side chain polymers are reported. The results are compared with those obtained for conventional elastomers. It is found that the thermoelastic behaviour in the nematic state completely differs from that observed for common polymer networks due to the anistropic ordering of the mesogenic side chains. The retractive force in the nematic state is found to be independent of path, indicating that the nematic phase is a homogeneous phase. Photoelastic investigations prove the propotionality of stress and birefringence above the clearing temperature Tc which is similar to common elastomers. The stress‐optical coefficient, however, strongly depends on temperature in the pretransformation region. X‐ray measurements show a uniform orientation of the mesogenic side groups in the nematic state. The diffraction patterns observed contain many more reflexes than observed for common nematics.
Structural study of compounds modelling elementary polymer units, 4. Molecular and crystal structures of three isomers of 4,4′‐bis(x‐hydroxyphenoxy)octafluorobiphenyl
Authors: Lindeman Sergey V. , Struchkov Yury T. , Malichenko Boris F. , Shklover Valerii E. , Vasnev Valerii A. , Kameneva Tatiana M. , Sheludko Evgenii V. 
Published: April 2003

AbstractThe paper presents an X‐ray study of the isomers 4,4′‐bis(2‐hydroxyphenoxy)‐, 4,4′‐bis(3‐hydroxyphenoxy)‐, and 4,4′‐bis(4‐hydroxyphenoxy)octafluorobiphenyl, which are used as monomers in the synthesis of polyarylates. The molecular packing in crystals is characterized by intermolecular H‐bonds, donor‐acceptor and stacking interactions between the benzene rings of adjacent molecules, which results in considerable distortion of the molecular geometry. Notably, bending of biphenyl fragments accompanied by distortion of benzene ring planarity was observed, along with unusual conformations of oxydiphenylene fragments and distortions of bond angles at ipso‐carbon atoms bonded to ether oxygen atoms.
Anionic block polymerization of β‐lactones initiated by potassium solutions, 1. Synthesis of poly(4‐methyl‐2‐oxetanone‐block‐2‐oxetanone)
Authors: Jedliński Zbigniew , Kowalczuk Marek , Kurcok Piotr , Brzoskowska Lilianna , Franek Jan 
Published: April 2003

AbstractThe block polymerization of 4‐methyl‐2‐oxetanone (β‐butyrolactone) with 2‐oxetanone (β‐propiolactone) proceeds fast with a yield of more than 90%, in the presence of potassium solutions in THF containing 18‐crown‐6. Poly(4‐methyl‐2‐oxetanone‐block‐2‐oxetanone) polymers having the expected molecular weight and composition are formed by this way. Their glass transition and melting temperatures as well as their melting enthalpies, determined by DSC, show a strict correlation with block polymer composition.
Synthèse de composéas photoréticulables, 8. Réaction des téalomères du méthacrylate d'époxy‐2,3 propyle avec l'acide acrylique et cinnamique
Authors: Boutevin Bernard , Piétrasanta Yves , Parisi Jean Pierre 
Published: April 2003

AbstractThe addition reaction of methacrylic acid (6) to the telomer 3, resulting from 2,3‐epoxypropyl methacrylate (1) and dodecanethiol (2), (DPn = 6) was studied. The percentage of addition at 60°C was found to be 32 after 24 h. When using an epoxide/methacrylic acid mole ratio of 2:1 Products were obtained which can easily be crosslinked by UV irradiation and which stick to aluminium to give water‐resistant products.
Investigation of the polymerization mechanism of 4′‐methylenespiro[2‐benzofuran‐2,2′‐(1,3‐dioxolane)]
Authors: Pan Cai‐Yuan , Lu Shao‐Xiang , Bailey Wiliam J. 
Published: April 2003

AbstractThe propagation reaction of 4′‐methylenespiro[2‐benzofuran‐2,2′‐(1,3‐dioxolane)] (2), initiated by a free radical initiator, was studied by analysis of the polymer structure and by kinetic investigation. The results indicate that the polymer has the structure of poly [methylene‐spiro[2‐benzofuran‐2,2′‐(1,3‐dioxolane)]‐4′‐ylidene‐co‐(2‐oxotrimethylene)] (10). A reasonable propagation mechanism is proposed.
Studies on formaldehyde resins, 25. Kinetic study on the hydroxymethylation of melamine by means of HPLC
Authors: Yoshii Toshio , Konakahara Takeo , Sato Kenji 
Published: April 2003

AbstractThe kinetics of hydroxymethylation of melamine (2,4,6‐triamino‐1,3,5‐triazine) with formaldehyde to form N‐(hydroxymethyl)melamine (2,4‐diamino‐6‐hydroxymethylamino‐1,3,5‐triazine) was investigated in aqueous hydrogen phosphate/phosphate buffer solutions in the range of pH 10,51 to 12,20 at 20°C, determining unreacted melamine by means of HPLC. As a result, this reaction is subject to a general base catalysis, and the second order rate constant k is expressed by k = k′ + kA − [A−] + k[A−]2/[HA] (or k [A−][OH−]), where HA and A− denote acid and basic constituents of the buffer, and k′ is the rate constant in unbuffered media. This rate equation is compared with those reported previously.
The laser‐flash‐initiated polymerization as a tool of evaluating (individual) kinetic constants of free‐radical polymerization, 2. The direct determination of the rate of constant of chain propagation
Authors: Olaj Oskar Friedrich , Bitai Irene , Hinkelmann Franz 
Published: April 2003

AbstractWhen a polymerizable system is subjected to periodic light flashes, which induce the formation of primary radicals, a pseudostationary state is established which is characterized by a periodic profile of the (polymer) radical concentration. Within such a period of length t0 the radical concentration will decay according to a second‐order rate law. At the end of this period the radicals, which have escaped termination up to this moment, have propagated up to a chain length L0 = t0·kp·cM, kp representing the propagation rate constant and cM the monomer amount concentration. When the next flash arrives these radicals are opposed to a strongly increased overall concentration of radicals which leads to an enhanced probability for their termination. As a consequence the formation of dead polymer molecules with a chain length close to L0 is favoured. The chain‐length distribution of polystyrene prepared under such pseudostationary conditions, which was evaluated by gel permeation chromatography, in fact exhibits such a peak. The analysis of the theoretical distribution curves, derived in this communication, reveals that it is easily possible to correlate this peak to L0, independently of the mode of termination (disproportionation or combination). Thus, a method of evaluating kp is derived without any reference to the termination rate constant kt and largely independent of all features which usually cause problems in the evaluation of kp and kt (such as primary radical termination etc.). The experimental results agree fairly well with the data reported in literature, especially with those obtained from the number of particles and the rate of polymerization in emulsion systems.
Emulsion copolymerization of methyl methacrylate and ethyl acrylate, 2. Effect of emulsifier concentration and emulsifier blend composition on the polymerization behaviour
Authors: Capek Ignác , Bartoň Jaroslav , Tuan Le Quang , Svoboda Václav , Novotnýa Vlastimil 
Published: April 2003

AbstractThe free radical emulsion copolymerization of methyl methacrylate and ethyl acrylate initiated by ammonium persulfate at 60°C in the presence of a blend of anionic and non‐ionic emulsifiers was investigated. In the interval 2 the rate of copolymerization is approximately proportional to the 0,6th power of the total emulsifier concentration. The number of final polymer particles is proportional to the 0,5th power of the total emulsifier concentration. The dependence of the rate of copolymerization on the composition of the emulsifier system is described by a curve with a maximum at a mole fraction of non‐ionic emulsifier of about 0,5. The mean particle size keeps a constant value until the maximum of the polymerization rate is reached. Beyond this maximum the particle size abruptly increases (mole fraction of non‐ionic emulsifier ≈0,5). The rate of copolymerization, the conductivity and stability of the polymer latex increase, whereas the particle size and interfacial tension of latex and the number‐average molecular weight of copolymer decrease with increasing total concentration of the emulsifier blend.
Spectrophotometric and dichroic studies of poly(vinyl alcohol)‐iodine blue induced by boric acid and tartaric acid
Authors: Pal Medini Kanta , Pal Prasun Kumar 
Published: April 2003

AbstractBoric acid induces blue colour with λmax at 670 nm in the poly(vinyl alcohol) (PVA)‐iodineiodide system. Tartaric acid (other hydroxy acids, H3PO4, NaH2PO4, NH4Cl, etc.) also induces blue colour with λmax at 590 nm. Unlike starch‐iodine blue, PVA‐iodine blue does not exhibit dichroism in the visible range; the latter system does neither induce chiral aggregation of dyes as done by starch‐iodine. The observed CD in the short UV range, the shape, sign, and [θ]‐values of which depend on the nature of the colour inducing agent as well as on the presence of dye, is interpreted to be induced from the asymmetric carbon atoms of PVA to which I is associated at random, as well as from the asymmetric carbon atoms binding an unhydrolysed acetoxy group present in commercial PVA.
Equilibrium polymerization initiated by polymer chains with active sites
Authors: Cai Gang‐feng , Yan De‐yue 
Published: April 2003

AbstractAccording to the theory of multifunctional equilibrium polymerization, the two‐dimensional molecular weight distribution function for the equilibrated copolymers generated from polymer chains with active sites is derived. On this basis the average molecular weights, grafting ratio, grafting efficiency, grafting success, branching distribution, and frequency of grafts, etc. can be predicted from polymerization conditions.
Sequence and branching distribution of ethylene/1‐butene copolymers prepared with a heterogeneous Ziegler catalyst
Authors: Kuroda Nobuyuki , Nishikitani Yoshinori , Matsuura Kazuo , Miyoshi Mitsuji 
Published: April 2003

AbstractEthylene/1‐butene copolymers prepared with a heterogeneous titanium‐based catalyst were separated into five fractions by successive solvent extraction, and the triad distributions of each fraction were determined by 13C NMR measurements. Conditional probabilities (PEE, PEB, PBE, PBB), reactivity ratios (r1, r2), and persistence ratio (p) of each fraction were calculated from the triad distributions observed. The analysis of these values suggests that the heterogeneous Ziegler catalyst has multiple active sites, and the copolymer has nearly a Bernoullian sequence distribution.
Hydroxytelechelic polybutadiene, 11. Kinetics of dibutyltin dilaurate‐catalyzed addition reaction between a hydroxytelechelic polybutadiene and propyl isocyanate
Authors: Deschères Isabelle , Pham Quang‐Tho 
Published: April 2003

AbstractComplexations of 1‐octanol (O) and propyl isocyanate (PI) by dibutyltin dilaurate (DBSnDL) were examined by 350 MHz 1H NMR. Whereas the 1:1 O/DBSnDL complex was easily evidenced, the behaviour of the mixture (1 PI + 1 DBSnDL) suggested slow formation of (a) relatively stable coordination compounds(s). The three alcohol functions of the hydroxytelechelic polybutadiene Arco‐R45M® were found to be equally catalyzed by DBSnDL in the addition with PI in toluene and in the bulk. Linear relationships between initial reaction rates and catalyst concentrations were found only for mole ratios [DBSnDL]/[Arco‐R45M]® < 0,06 and 0,1 in dilute solution and in bulk, respectively. (Acro‐R45M® + PI) additions catalyzed by DBSnDL follow 3rd‐order kinetics. The activation enthalpies and entropies calculated from kinetic data show that, compared to spontaneous addition, catalyzed reaction rates are less sensitive to temperature. Negative activation entropies suggest the existence of relatively stable transition states.
Synthesis of membranes for the dehydration of water‐acetic acid mixtures by pervaporation, 1. Polymer material selection
Authors: Nguyen Trong Q. , Essamri Azzouz , Clément Robert , Néel Jean 
Published: April 2003

AbstractPoly(vinyl alcohol) (PVA) was studied for use as a basic material for membrane preparation with the aim of dehydrating water‐acetic acid mixtures. Membranes of different nature were made by blending a PVA sample of 96% hydroxyl content with a polyacid or a polybase counterpolymer in water, followed by complete evaporation. The PVA‐polybase blends gave membranes of low selectivity, unsuitable for dehydration. The membrane M5, made of a 1 : 1 (by wt.) blend of PVA with a special grade of polyhydroxycarboxylic acid (PHC1), presents a good combination of selectivity and permeability. It was studied in a water‐acetic acid mixture containing up to 10 wt.‐% of water. The Arrhenius‐type activation energy for the permeation was found to be 9,0 kcal/mol (38 kJ/mol).
Quenching of the excited state of membranes having polymerpendant tris(2,2′‐bypyridine)ruthenium(II) groups by methylviologen and dioxygen
Authors: Kaneko Masao , Nakamura Hideki 
Published: April 2003

AbstractQuenching of the excited state of copolymer‐pendant Ru(bpy) membranes by methylviologen (MV2+) and dioxygen was studied and its application proposed. The copolymers used were the copolymer of styrene (St) and 4‐methyl‐4′‐vinyl‐2,2′‐bipyridine (Vbpy) and that of methyl methacrylate (MMA) and Vbpy. The copolymer‐pendant complexes were prepared by reaction of the St‐ and MMA‐copolymers with cis‐Ru(bpy)2Cl2. The excited state of the St‐copolymer complex membrane was not quenched by MV2+ solution in aqueous medium, but quenched in methanol. The excited state of the MMA‐copolymer complex membrane was not quenched by MV2+ neither in water nor in water/methanol mixture. The excited state of St‐copolymer complex membrane was not quenched by dioxygen in water, but in methanol. The excited state of MMA‐copolymer complex membrane was quenched by dioxygen both in water and water/methanol mixture. The quenching by dioxygen can be used to measure the oxygen concentration in solutions.