bluuebunny/crossref_metadata_2025_split huggingface dataset:
Morphological study of melt‐crystallized linear low‐density polyethylene by transmission electron microscopy
Authors: Hosoda Satoru , Kojima Keitaro , Furuta Motonobu 
Published: April 2003

AbstractThe morphology of the lamellae in non‐isothermally crystallized linear low‐density polyethylene (LLDPE), conventional high‐pressure low‐density polyethylene (HP‐LDPE), and a high‐density polyethylene (HDPE) sample was investigated by transmission electron microscopy (TEM). LLDPE exhibits clearly two different types of lamellae, i.e., thick, long, and straight lamellae like those of HDPE, and thin, short, and curved lamellae which grow among the former ones. Also LLDPE shows the broadest distribution of the values for the lamella thickness among the three types of polyethylenes mentioned. The average lamella thickness decreases in the order HDPE > LLDPE > HP‐LDPE. Fractions were used to study the effects of the kind and the degree of short chain branching (SCB) and of the molecular weight in the range from 4100 to 3,1·105. SCB has a predominant influence on the lamella thickness as well as on the shape, while the molecular weight does not largely affect lamella thickness but affects the shape of the lamellae. Further it was revealed from TEM observation that the isobutyl branch decreases lamella thickness more effectively than does the ethyl branch. This is in accordance with results from small‐angle X‐ray and differential scanning calorimetry measurements.
Analyse du photoviellissement des materiaux polymères par évolution de la perméabilité aux gaz
Authors: Philippart Jean‐Louis , Gardette Jean‐Luc 
Published: April 2003

AbstractThe variations of diffusion constants and permeability for carbon dioxide, oxygen and nitrogen in poly(ether‐block‐amide)s were measured during the photooxidation of the polymer. The determination of these constants appears to be a sensitive criteria to characterize the photooxidative evolution of polymers. The decrease of the diffusion constant, observed in the course of photooxidation, is interpreted by the formation of chemical crosslinks and by the existence of physical interactions between primary hydroperoxidic photoproducts. Several treatments were developed which modify the nature of these oxidized groups; the evolution of diffusion constants is related to the modification of the interactions between these groups.
Cinétiques de télomérisation, 7. Calcul de k/kTe en polymérisation radicalaire de divers monomères
Authors: Boutevin Bernard , Piétrasanta Yves 
Published: April 2003

AbstractIn contrast to the usual method of determination of the principle ratio in radical polymerization, k/kTe, which is based on the comparison of the rate of polymerization with the concentration of initiator, a method was used consisting in the representation of loge([M]0/[M]) versus (1 − e−kdt/2). The results obtained with styrene, vinyl acetate, acrylic acid, methacrylic acid, and 3,3,4,4,5,5,6,6,7,7,8,8,8‐tridecafluorooctyl acrylate (1) were found to be in good agreement with those already obtained by the other method.
Structural analysis of alkene/maleic anhydride copolymers
Authors: Rätzsch Manfred , Zschoche Stefan , Steinert Volker , Schlothauer Klaus 
Published: April 2003

AbstractStructural investigations on maleic anhydride (MAn) copolymers with ethene, propene and styrene, their products of hydrolysis, and their methyl half‐esters by means of 13C NMR spectroscopy are presented. The spectra of 2,3‐diethylsuccinic acid and its anhydrides in the erythro‐ and threo‐configuration and of butylsuccinic acid and its anhydride were obtained and compared with the spectra of the copolymers. In each case the results show the formation of both threo(trans)‐ and erythro(cis)‐structures. At a polymerization temperature of 60°C the proportions were 88% threo to 12% erythro for ethene/MAn copolymers and 80% threo to 20% erythro for propene/MAn copolymers, a ratio which was confirmed also by the hydrolyzed forms. Copolymerization at 150°C leads, in the case of propene/MAn, to 67% threo and 33% erythro. The production of ethene/MA copolymer via the copolymerization of ethene and fumaric acid half‐ester and its saponification to ethene/fumaric acid leads to a ratio of 38% threo to 62% erythro. These results are in accordance with the thermal stabilities of the configurations. In the case of styrene/MAn copolymer it is not possible to obtain a unique interpretation of the configurations from the spectra. For the conversion of propene/MAn and styrene/MAn copolymers by means of methanol to half‐esters it can be derived from the 13C NMR spectra how many of the half‐ester moieties are obtained in the neighbourhood of the methyl and phenyl groups, respectively, of the olefin.
Solution and membrane properties of zwitterionic polymers
Authors: Itoh Yoshihiro , Abe Koji , Senoh Saburo 
Published: April 2003

AbstractThe aqueous solution properties of poly(4‐vinylpyridinium sulfopropylbetaine) (PVPyPS, systematic name: poly{1‐[1‐(3‐sulfonatopropyl)pyridinium‐4‐yl]ethylene} (1)) and poly(3‐methacryloylethoxycarbonylpyridinium sulfopropylbetaine) (PMAPS, systematic name: poly{1‐methyl‐1‐[2‐[1‐(3‐sulfonatopropyl)pyridinium‐3‐ylcarbonyloxy]ethoxycarbonyl]ethylene} (2)) are investigated. Polymers 1 and 2 are soluble only in salt solutions and their intrinsic viscosity increases with increasing salt concentration, this being a common property of poly(sulfobetaine)s. Hydrogel membranes containing PVPyPS are opaque in pure water but become transparent in salt solution.
Kinetics of the free radical copolymerization of diethyl maleate with styrene
Authors: Braun Dietrich , Cei Gustavo 
Published: April 2003

AbstractThe free radical copolymerization of diethyl maleate (M1) with styrene (M3) was studied in bulk at 60°C with azoisobutyronitrile as initiator. In order to compute the reactivity ratios, we determined the copolymer composition by microanalysis of the carbon content. The evaluation of the data was carried out according to two procedures; the Kelen‐Tüdös linearization method and the non‐linear least‐squares of Tidwell and Mortimer. The ratios obtained with the latter, r13 = 0,001 and r31 = 6,592, yielded a better fit. Different kinetic models were tested to describe the observed dependence of reaction rate on monomer mixture composition. The experimental results could be successfully described according to a kinetic model that assumes diffusion control of the termination reaction. The resulting kinetic equation contains two parameters whose values were determined from the experimental copolymerization rates. The value of one of these parameters could be obtained also from homopolymerization data for styrene. This proves that the parameters have physical significance and are not arbitrary quantities chosen to fit the experimental results.
Calculation of the integral chemical distribution of block copolymers
Authors: Pallaske Ulrich , Kuhn Rainer 
Published: April 2003

AbstractCalculations show for an anionic block copolymerization under ideal conditions that the integral chemical distribution of a block copolymer (with given number‐average molar mass and average chemical composition) should be independent of the number of blocks in the copolymer and thus independent of the way in which the monomers are added during polymerization. Calculations for block copolymers consisting of styrene and butadiene are given to illustrate the decrease of the width of the chemical distribution with increasing molar mass. The chemical distributions of styrene‐butadiene block copolymers determined experimentally by successive fractional demixing with demixing solvents are consistently broader than the calculated ones. This must be attributed to association equilibria of the initiator and of the living polymer chains and also to termination reactions of the polymer chains. The theoretically expected narrow chemical distributions can be obtained approximately by head and tail fractional demixing of the copolymers with demixing solvents.
Reactivity of N‐alkylated cyclic iminoether salts having vinyl groups, 2. Polymerization and copolymerization of 2‐isopropenyl‐3‐methyl‐2‐oxazolinium salts
Authors: Miyamoto Masatoshi , Sano Yoshiyuki , Kimura Yoshiharu , Saegusa Takeo 
Published: April 2003

Abstract3‐Methyl‐2‐isopropenyl‐2‐oxazolinium salts (4a, b) were prepared by alkylation of 2‐isopropenyl‐2‐oxazoline (2). Their preparation is much easier than that of their vinyl analogues, 3‐methyl‐2‐vinyl‐2‐oxazolinium salts, which cannot be isolated due to their high tendency to polymerization. 4a, however, was found, to show a low tendency toward radical and anionic polymerization, but it can be smoothly radically copolymerized with some vinyl monomers. The copolymerization parameters of 4a were determined and discussed in comparison with those of 2.
Photodimerization and photopolymerization of amphiphilic cinnamic acid derivatives in oriented monolayers, vesicles and solution
Authors: Koch Horst , Laschewsky André , Ringsdorf Helmut , Teng Kang 
Published: April 2003

AbstractCinnamic acid moieties were incorporated into amphiphilic compounds containing one and two alkyl chains. These lipid‐like compounds with photoreactive units undergo self‐organization to form monolayers at the gas‐water interface and bilayer structures (vesicles) in aqueous solutions. The photoreaction of the cinnamic acid moiety induced by 254 nm UV light was investigated in the crystalline state, in monolayers, in vesicles and in solution in organic solvents. The single‐chain amphiphiles undergo dimerization to yield photoproducts with twice the molecular weight of the corresponding monomers in organized systems. The photoreaction of amphiphiles containing two cinnamic acid groups occurs via two mechanisms: The intramolecular dimerization produces bicycles, with retention of the molecular weight of the corresponding monomer. The intermolecular reaction leads to oligomeric and polymeric photoproducts. In contrast to the single‐chain amphiphiles, photodimerization processes of lipoids containing two cinnamic acid moieties also occur in solution in organic solvents.
Some spectral and thermal contributions to the curing of new epoxy compounds with aromatic diamines
Authors: Serra Angels , Cádiz Virginia , Martínez Pedro‐Alberto , Mantecón Ana 
Published: April 2003

AbstractThe curing reaction of the new bis(2,3‐epoxypropyl) 4,4′‐carbonyldi‐ω‐phthalimidoalkanoates 1a–c was studied with several aromatic diamines 2a–c as curing agents. The process was followed by means of spectrophotometric techniques. The influence of the nature of the curing agent on the reaction rate was examined. The adduct formation yielding first chain extension, is the first step of the reaction, followed by crosslinking, once the gel point has been reached. The products obtained were found to be rather thermostable.
Composition‐properties relationships in propene‐ethene random copolymers obtained with high‐yield Ziegler‐Natta supported catalysts
Authors: Avella Maurizio , Martuscelli Ezio , Volpe Gaetano Della , Segre Annalaura , Rossi Enrico , Simonazzi Tonino 
Published: April 2003

AbstractThe crystallization and thermal behaviour of crystallizable random propene/ethene copolymers (P‐co‐E) was systematically investigated. Index of crystallinity and, index of γ‐form, enthalpy and entropy of fusion, equilibrium melting temperature, spherulite growth rate, and overall kinetic rate constant were determined and correlated with the overall ethene content and with the concentration of specific chemical defects as determined by 13C NMR analysis (PEP, EPP, EPE triads). The samples of the copolymers, obtained with very‐high‐yield Ziegler‐Natta catalysts, were characterized by IR, 13C NMR, wide angle X‐ray scattering, and differential scanning calorimetry.
Synthesis and thermodynamic studies of two new polymers carrying amido and amino groups in the side chains
Authors: Barbucci Rolando , Casolaro Mario , Nocentini Mila , Reginato Gianna , Ferruti Paolo 
Published: April 2003

AbstractTwo linear vinyl polymers carrying amido and primary amino groups in the side chains were synthesized and characterized. Their behaviour in aqueous solution was investigated by potentiometric, viscometric and calorimetric techniques. In both cases, the basicity constants show a linear dependence on the degree of protonation α, while the enthalpy values of protonation do not. The thermodynamic results demonstrate the important role of hydrophobic interactions on the protonation process.
Hydroxytelechelic polybutadiene, 9. Kinetics of reactions in solution and in bulk between radically obtained hydroxytelechelic polybutadiene and propyl and phenyl isocyanate studied by 1H NMR
Authors: Descheres Isabelle , Pham Quang Tho 
Published: April 2003

AbstractThe kinetics of the reactions of radically obtained hydroxytelechelic polybutadiene (Arco R45M) with propyl isocyanate and phenyl isocyanate were studied by 1H NMR at high field. The reactivities of the three alcohol functions of Arco R45M were found to be different. The three individual reactions follow a 3rd order law and are accelerated by autocatalysis. There is competition between (OH, OH) auto‐association and (free OH + isocyanate) reactions. As a consequence, rate constants are strongly affected by (OH, OH) association phenomena.
Structure of 2,2,5,5,6,6,9,9‐octamethyl‐2,5,6,9‐tetrasiladecane, a structural precursor of poly[(tetramethyldisilanediyl)ethylene]
Authors: Ovchinnikov Yuri E. , Shklover Valeri E. , Struchkov Yuri T. , Polyakov Yuri P. , Gusel'nikov Leonid E. 
Published: April 2003

AbstractIn order to obtain information for suggesting the most likely molecular and crystal structure of poly[(tetramethyldisilanediyl)ethylene] (PTMDSE) an X‐ray study of the structural precursor 2,2,5,5,6,6,9,9‐octamethyl‐2,5,6,9‐tetrasiladecane (TSD) is carried out. The TDS molecule is centrosymmetric, the CSiCCSiSiCCSiC chain having an almost planar all‐trans conformation. In the crystal of TSD one can distinguish molecular layers parallel to the a b plane; the long axes of the TSD molecules form an angle of 24,4° with the layer plane; intermolecular contacts in layers are shorter, on the average, than interlayer contacts.
Polymeric prodrugs, 5. Dextran‐bound antirheumatic agent naproxen
Authors: Azori Mária , Pató János , Csákvári Éva , Tüdős Ferenc 
Published: April 2003

AbstractThe dextran‐bound antirheumatic agent, Naproxen [(+)‐2‐(6‐methoxy‐2‐naphtyl)propionic acid] (3) was synthesized by linking the 2‐aminoethyl ester of Naproxen to the oxydized dextran via an alkylamine bond. The hydrolytic stabilities of modified dextrans were examined viscometrically. The drug release from polymeric prodrug samples containing 68–172 mg of Naproxen per g product was followed at 37°C by automatic titration at pH 8,4. The first order kinetic constant of hydrolysis, k1, was determined to be 2,46(±0,4) · 10−6 s−1. Acute toxicity tests showed no toxic effect on CFLP mice administered intraperitoneally 300 mg/kg of dextran‐bound Naproxen.
Polymeric schiff's base chelates and their precursors, 9. Synthesis of covalently and coordinatively bound polymeric chelates and their dioxygen binding in the solid state
Authors: Wöhrle Dieter , Bohlen Heike , Blum Johannes K. 
Published: April 2003

AbstractCovalently bound polymeric cobalt chelates 5 of Co(salen) type were synthesized by copolymerization of 2‐hydroxy‐5‐vinylbenzaldehyde (2) with 4‐vinylpyridine and subsequent polymeranalogous reactions. Coordinatively bound polymeric chelates 6 were obtained from Co(salen) and poly(4‐vinylpyridine) or its copolymer with styrene. Dioxygen binding studies (volumetric measurements and ESR spectroscopy) revealed that mononuclear superoxo complexes are formed reversibly.
On the rate and activation parameters for the primary decomposition of a quaternary ammonium persulfate in moderately polar organic solvents
Authors: Ghosh N. N. , Gupta G. N. , Mandal B. M. 
Published: April 2003

AbstractThe activation energy for the primary decomposition of ionpaired trioctylmethylammonium persulfate in moderately polar organic solvents was found to be about one half the value for the persulfate ion decomposition in aqueous alkaline media. However, its effect on the primary decompostion rate of the former is largely offset by the lowered entropy of activation, which adopts a negative value. The results indicate that the activated state is more ionic than the ground state. A tentative structure of the activated state which involves an intra‐ionic triple ion is proposed to account for the observed results.
Thermally stable sulfonic acid resins
Authors: Brouwer Dirk M. , van de Vondervoort Elizabeth M. 
Published: April 2003

AbstractPolystyrene‐divinylbenzene resins 2 and 3 containing carboxysulfoalkyl groups were prepared by Michael addition of phenyl ethylenesulfonate to the reaction products of the chloromethylated resins with cyanide and diethyl malonate, respectively. They display an unusually high thermal stability in water: less than 5–10% loss of SO3H after 100 hat 200°C. Their catalytic activities (hydrolysis of sucrose), expressed per equivalent of SO3H, are twice as high as those of corresponding ring‐sulfonated resins.
Different chromotropic behaviour of DNA and RNA and of poly(adenylic acid) and poly(uridylic acid) with the dye pinacyanol chloride
Authors: Pal Medini Kanta , Ghosh Bijan Kumar 
Published: April 2003

AbstractThe cyanine dye pinacyanol chloride (PCYN) distinguishes various polyanions by exhibiting two distinct types of absorption spectra of the dye‐polyanion system. This dye can also differentiate between the biopolymers DNA and RNA, as well as between poly(adenylic acid) (poly‐A) and poly(uridylic acid) (poly‐U). The dye‐RNA spectra are independent of polymer/dye (P / D) ratio and show a sharp peak at 490 nm and a very broad band around 560 nm indicating not well organized aggregation of dye cations bound to the polymer. The spectra of the dye‐DNA system are similar only at low P / D, but with increase in DNA concentration a sharp band appears at 560 nm with disappearance of the peak at 490 nm. The poly‐U/PCYN system resembles the RNA‐PCYN system and the poly‐A/PCYN system resembles the DNA‐PCYN system. These differences are interpreted to arise from the preferential binding of the dye to purine bases rather than to pyrimidine bases, and from the partial intercalation of the dye within the DNA helix at high P / D. The sharp band at 560 nm of DNA‐PCYN at high P / D is due to dimerization of PCYN — the major, if not the only, state of aggregation of the dye induced by DNA at high P / D.
Divalent cation‐induced permeability regulation of polymer membrane with permeating pathway of a synthetic polypeptide
Authors: Maeda Mizuo , Aoyama Masato , Inoue Shohei 
Published: April 2003

AbstractRegulation of solute permeability induced by divalent cations was performed in a polymer membrane with transmembrane permeating pathway (“channel”) of a synthetic polypeptide. The membrane material was a poly(butyl methacrylate) (backbone)/poly(L‐glutamic acid) (branch) graft copolymer. Permeability of phenyl‐1,2‐ethanediol was remarkably reduced in the presence of divalent cations such as Ca2+ and recovered by addition of ethylenediaminetetraacetic acid (EDTA). Infrared spectra of the membrane demonstrated a reversible change of the structure of pathway‐composing polypeptide chains induced alternationgly by Ca2+ and EDTA.
Ziegler‐Natta polymerization of propene: Cooperative effects of titanium ligands on the steric control of the first addition of monomer
Authors: Tritto Incoronata , Sacchi Maria Carmela , Locatelli Paolo 
Published: April 2003

AbstractA 13C NMR analysis of the methyl and ethyl end‐groups in isotactic polypropylene, prepared in the presence of TiCl3‐ and Til3‐based catalysts, was performed and the isotactic regularity of the first propylene unit added to the Ti—alkyl bond was measured. In the presence of the catalyst Til3/Al(13CH2CH3)3 the stereoregulating effects derived from the ethyl and iodine ligands are cooperative, so that the addition of the first monomeric unit is as isotactic as the following propagation steps. A comparison of the chain end‐groups of polypropylene obtained in the presence of different catalysts shows that the extent of steric control upon insertion of the first monomer molecule results not only from the presence of alkyl titanium ligands larger than methyl and of titanium halide ligands larger than chlorine, but also from mutual ligand interactions.
Influence of termination and transfer on molecular weight distribution of polymers, 2. Radical‐radical termination and monomer chain transfer
Authors: Yan De‐yue , Cai Gang‐feng , Lan Zhi‐da 
Published: April 2003

AbstractA non‐steady state kinetic treatment is rigorously performed for the free radical polymerization with instantaneous initiation, monomer chain transfer and radical‐radical termination. An explicit derivation of the molecular weight distribution function is given, and the expressions for other molecular parameters are provided. By means of the formulae given in this paper, the values of the molecular parameters of the polymer generated can be calculated from the initial conditions of polymerization and monomer conversion or reaction time.
Revival and modification of an ancient osmotic pressure equation
Authors: Schulz G. V. , Stockmayer Walter H. 
Published: April 2003

AbstractAn osmotic pressure equation proposed over 50 years ago is found to be consistent with the des Cloizeaux scaling relation for semi‐dilute polymer solutions in good solvents. With a physically plausible modification, the equation can also give a satisfactory representation of dilute solutions and of the cross‐over to the semi‐dilute regime.
The crystal and molecular structure of an asymmetric diacetylene monomer, 6‐(4‐dimethylaminobenzoyloxy)‐2,4‐hexadiynyl 3,5‐dinitrobenzoate
Authors: Vlasse Marcus , Koetzle Thomas F. 
Published: April 2003

AbstractThe crystal and molecular structure of an asymmetric diacetylene derivative, 6‐(4‐dimethylaminobenzoyloxy)‐2,4‐hexadiynyl 3,5‐dinitrobenzoate (1), was determined from x‐ray diffraction data. The crystals are monoclinic, P21/c with Z = 4 in a unit cell having dimensions, a = 11,116 (1) Å, b = 13,429 (2) Å, c = 14,672 (3) Å, β = 106,84 (6)°. The structure was solved by direct methods and refined by least‐squares techniques to an RF of 6,2% for 1 991 independent reflections. The diacetylene backbone chains are almost perfectly parallel to the ac‐plane; however, they are displaced from each other in the [010] direction. The solid‐state polymerization mechanism is discussed with respect to the geometric disposition of the diacetylene chains, which in this crystal are too far apart to permit polymerization by means of 1,4‐addition, consistent with the Baughman mechanistic model.
Liquid crystalline polymers, 1. Synthesis and structure‐properties relationship in some liquid crystalline polyetheresters
Authors: Jedliński Zbigniew , Franek Jan , Kuziw Piotr 
Published: April 2003

AbstractLiquid crystalline aromatic‐aliphatic polyetheresters with mesogenic groups of different isomeric structures and flexible oligo(oxyethylene) spacers in the backbone were synthesized and their properties were studied. The influence of the mesogenic group structure, spacer length and nature of bonds linking the mesogenic groups and the spacers, on the phase transition temperatures was elucidated. On the basis of optical textures, observed in the polarizing microscope, smectic or nematic melts were found to be present in the polymers studied, depending on the mesogenic group structure.