bluuebunny/crossref_metadata_2025_split huggingface dataset:
Preparation of 4‐tert‐butyloxocalix[n]arenes and their properties as UV‐absorbers
Authors: Ninagawa Akira , Cho Kazuhiro , Matsuda Haruo 
Published: April 2003

Abstract5,11,17,23‐Tetra‐tert‐butyl‐25,26,27,28‐tetrahydroxy‐2‐oxocalix[4]arene (4a), 5,11,17,23,29,35‐hexa‐tert‐butyl‐37,38,39,40,41,42‐hexahydroxy‐2‐oxocalix[6]arene (4b), and octa‐tert‐butyl‐octahydroxy‐trioxocalix[8]arene (4c) were synthesized via 4‐tert‐butylcalix[4]‐, [6]‐ and [8]arenes from 4‐tert‐butylphenol as a starting material. 5,5′‐Di‐tert‐butyl‐2,2′‐dihydroxybenzophenone (7) was synthesized via 5,5′‐di‐tert‐butyl‐2,2′‐dimethoxybenzophenone (6) from bis(5‐tert‐butyl‐2‐methoxyphenyl)methane (5). 1,4‐Dioxane solutions of 4a, 4b, 4c, 6, and 7 were irradiated. The photostabilities of 4b and 4c were found to be better than those of 4a, 6, and 7. A poly(vinyl chloride) film, containing 0,06 mmol/g of 4b, was found to be most stable against photoxidation.
Ion‐conducting grafted polypropylene film, 1. Controlled oxidation of a polypropylene film for volume grafting
Authors: Narȩbska Anna , Bukowski Zbigniew 
Published: April 2003

AbstractThe oxidation of a polypropylene (PP) film was studied with respect to activation for volume grafting. To attain the content of peroxides adequate for an intended graft level, the five oxidation variables: temperature, time, oxygen pressure and concentrations of initiator and surfactant were optimized. For a statistical analysis, the experiments were planned according to a hyper‐graeco‐latin square. The relation between the reaction variables and the ratio of peroxides and hydroperoxides within the polymer was determined. The distribution of the oxygencontaining products inside the peroxidized PP film was monitored by transmission and attenuated total reflection in the infrared region. The optimum variables enable an oxidation of PP to a desired degree, with peroxide groups uniformly distributed throughout the film, and at minor disturbance of the mechanical characteristics of the material.
Ion‐conducting grafted polypropylene film, 2. Volume grafting of polypropylene and gradient composition of poly(propylene‐g‐acrylic acid)
Authors: Nareska Anna , Bukowski Zbigniew 
Published: April 2003

AbstractGrafting of acrylic acid onto a pre‐activated polypropylene film was investigated, varying the concentrations of monomer and Fe2+ ‐ions, the polymerization time and temperature. Experiments were planned according to a scheme of a latin square, and statistical analyses were performed for the optimization of the grafting variables. The concentration of ferrous ions was found to be the most significant variable for the graft level. At low concentration, ferrous ions act as activator of grafting but no grafting takes place at relatively high concentrations. The distribution of grafted poly(acrylic acid) within a PP film was examined by microphotometry of the coloured slides of the film. The grafted layer of PP reaches the center only at about 30% of grafted poly(acrylic acid) and up to 70% the distribution of grafted poly(acrylic acid) is still non‐uniform with a decreasing amount of the polyacid from the surface to the center. The film samples containing 30% of grafted poly(acrylic acid) already show conductivity in alkaline media and are interesting ion conducting materials.
Cinétiques de télomérisation, 5. Détermination des degrés de polymérisation moyens cumulés dans les réactions de télomérisation et de polymérisation radicalaires
Authors: Boutevin Bernard , Piétrasanta Yves 
Published: April 2003

AbstractTwo principal methods are described for the determination of the cumulative number‐average and weight‐average degrees of polymerization in polymerization and telomerization reactions. The first method for the calculation of both quantities uses the ratio of monomer concentration and concentration of radicals created. In the second the instantaneous number‐average degrees of polymerization of short intervals of monomer conversion are added up. A comparison of the two methods is given and an application is studied for redox telomerization of ethyl acrylate with carbon tetrachloride.
Mechanism of ring‐opening polymerization of 1‐methylbicyclo[2.2.1]hept‐2‐ene using metathesis catalysts
Authors: Hamilton James G. , Ivin Kenneth J. , McCann G. Malachy , Rooney John J. 
Published: April 2003

AbstractPolymers of the title monomer have been made using 24 different metathesis catalysts, based on Nb, Mo, W, Re, Ru, Os and Ir compounds. Their structure, determined by 13C NMR spectroscopy, varies from all‐cis (ReCl5) to all‐trans (RuCl3, OsCl3) and from fully biased (head‐tail) to unbiased. The bias stems partly from an inability to from head‐head dyads containing cis double bonds and partly from the dipolar interaction between the propagating metal‐carbene complex and the monomer in forming the [2 + 2] transition state. Arguments are presented to show that the formation of biased polymers proceeds largely through a metal carbene species in which the last‐added monomeric unit has its methyl group adjacent to the metal centre (PH). In high‐cis polymers the sequences of three double bonds are such as to indicate that a kinetic distinction must be made between species in which the previous double bond formed was cis or trans (PHc or PHt), consistent with the observation that high‐cis polymers of related monomers have a blocky cis/trans distribution.
Use of the DEPT pulse sequence to facilitate the 13C NMR structural analysis of lignins
Authors: Bardet Michel , Foray Marie‐Françoise , Robert Danielle 
Published: April 2003

AbstractOne of the multipulse sequences in FT 13C NMR, the DEPT pulse sequence, was used to decrease the complexity and to improve the information content of 13C NMR spectra of macromolecules such as milled wood lignins (MWL) extracted from hardwoods (Birch and Aspen MWL). This sequence gives the possibility to edit subspectra selectively for CH, CH2 and CH3 carbons, and benefits from a large intensity enhancement for the carbon atom signals, due to polarization transfer. Thus, it is possible to discriminate precisely between quaternary and tertiary aromatic carbon atoms and to show unambiguously the presence of p‐hydroxybenzoate structures in Aspen MWL and their absence in Birch MWL. In addition, the DEPT sequence has made possible the observation of signals which, with classical experiments, are overlapped by others signals, either partially, like the C‐γ signal of syringaresinol units or completely like the C‐α signal in cinnamaldehyde units. Preliminary results indicate that quantitative data might be obtained from the edited spectra.
Synthesis of an electron‐acceptor polymer and its charge transfer complex with an electron‐donor polymer
Authors: Abe Koji , Haibara Susumu , Itoh Yoshihiro , Senoh Saburo 
Published: April 2003

AbstractA polymeric charge‐transfer complex (CT complex) was prepared from poly(N‐vinylcarbazole) (PVCz) as an electron‐donor polymer and poly[2‐(methacryloyloxy)ethyl 4,5,7‐trinitro‐9‐oxo‐2‐fluorenecarboxylate] [poly(1)] as an electron‐aceptor polymer. Equilibrium constants, K, and thermodynamic parameters for the polymeric CT complex formation and for monomeric model systems were determined. The mole ratio of the components in the CT complex is 1:1 except for the system ethylcarbazole (EtCz)‐poly(1). K decreases in the following order: PVCz‐poly(1) > EtCz‐1 > PVCz‐1 ≫ EtCz‐poly(1). The difference in K is mainly due to the entropy term.
Reversible oxygen‐binding to poly(ethyleneimine)‐cobalt complexes in aqueous solution
Authors: Nishide Hiroyuki , Yoshioka Hiroshi , Wang Shen‐guo , Tsuchida Eishun 
Published: April 2003

AbstractCobalt(II) complexes of poly(ethyleneimine)s 1 in aqueous solution are able to form with oxygen a μ‐peroxo adduct as is evidenced from stoichiometry and spectral properties. The oxygen adduct of Co/1 is characterized by its higher rate constant and activation entropy of the oxygen dissociation step, in comparison with those of the low‐molecular‐weight analogue Co/tetraethylenepentamine (2). This is related with the smaller affinity of Co/1 to oxygen and the reversibility in oxygen‐binding. The dissociation of the oxygen molecule coordinated to and bridged with Co/1 is facilitated by a distortion of its μ‐peroxo structure due to electrostatic repulsion of polycationic 1.
Thermotropic polyesters, 2. Synthesis of regular polyesters from aromatic dicarboxylic acids and phenols or aliphatic diols, and study of their mesomorphic properties
Authors: Bilibin Alexander Yu. , Tenkovtsev Andrey V. , Piraner Olga N. , Pashkovsky Evgenii E. , Skorokhodov Serguei S. 
Published: April 2003

AbstractSeveral series of thermotropic liquid‐crystalline polyesters, based on 4‐chlorocarbonyl phenyl esters of aromatic dicarboxylic acids (1–4) and phenols or aliphatic diols, were synthesized and studied by polarizing microscopy and differential scanning calorimetry (DSC). A relationship between geometry of mesogenic moiety and stability of mesophase formed by the polymers was established. The effect of both the length and chemical structure of the flexible fragments on the mesomorphic properties was revealed for polyesters obtained from aliphatic diols. Several polymers were obtained whose temperatures of transition into the liquid crystalline state were found to be below 100°C. Two series of low‐molecular‐weight liquid‐crystalline compounds were synthesized to compare their properties with those of the polymers of similar structure. Most of the low‐molecular‐weight analogs have not been described so far. They predominantly form a smectic type mesophase.
Zur Bestimmung der Porenstruktur wassergequollener Cellulosefasern
Authors: Bredereck Karl , Schick Willi Adolf , Bader Evelyn 
Published: April 2003

AbstractThe pore structure of various water‐swollen fibers of cotton and regenerated cellulose was investigated by means of fiber penetration studies with saccharides and dextrans. From the data the volumes of the pores were obtained and average pore diameters and surface areas calculated assuming a slit pore geometry. There are difficulties in interpreting the results with respect to pore‐size distribution. It is shown that the surface areas are suitable parameters of the fiber structure for describing equilibrium dye adsorption of direct dyes in cellulose fibers. From this a simple dying method results for characterizing the pore structure of cellulose materials.
Infrared spectroscopic studies on polyethylene, 6. Linear low density polymers
Authors: Maddams William F. , Woolmington Jacqueline 
Published: April 2003

AbstractThe infrared spectra of five linear low density polyethylenes, containing methyl, ethyl, butyl, isobutyl and hexyl branches, respectively, were measured. Particular interest attaches to the region 800–1200 cm−1 where the spectra, although weak, show significant differences. The findings of an earlier study on the methyl rocking mode, in the vicinity of 900 cm−1, are confirmed and extended. In particular, no band was detected for the ethyl branched polymer and it must be an order of magnitude weaker than for methyl, butyl and hexyl branches. Conversely, it is displaced in frequency and is markedly stronger for isobutyl branches. The methyl wagging mode band is at about 1 150 cm−1 with the methyl branched polymer. It is relatively broad and probably consists of two overlapping components, specific for methyl branches in crystalline and amorphous regions. This mode is not of detectable intensity for ethyl, butyl and hexyl branches but, as with the rocking mode, it is anomalously strong for isobutyl branches.
Evaluation of infrared spectroscopic techniques for analysing chitosan
Authors: Domszy Julian G. , Roberts George A. F. 
Published: April 2003

AbstractThe use of the 3450 cm−1 absorption band as an internal standard in the determination of the extent of N‐acetylation of chitosan from the absorbance of the amide I band at 1655 cm−1 was studied. The results show that the technique gives consistent results that are relatively unaffected by whether the sample is air‐dried or oven‐dried. A number of chitosan samples, covering the range of N‐acetyl values from 14% to 72% were analysed by three techniques: infrared spectroscopy using the ratio A1655/A3450, hydrobromide salt titration and residual salicylaldehyde determination. There is a very good correlation between the results from infrared spectroscopy and those from the other two analytical techniques, confirming the validity of the former technique.
Small angle neutron scattering (SANS) of cyclic and linear polystyrene in toluene
Authors: Ragnetti Maurizio , Geiser Doris , Höcker Hartwig , Oberthür Radulf C. 
Published: April 2003

AbstractSamples of ring and open chain polystyrene in dilute perdeuterated toluene solution were measured by small angle neutron scattering up to a value of the scattering vector Q = 2 nm−1. The molar masses 12000 ≤ M/(g/mol) ≤ 22000, the mean square radii of gyration 〈R2〉 and the second virial coefficients A2 of the samples were determined. The results are compared to theories which describe the dependencies 〈R2〉 = f(M) and A2 = f(M) for both cyclic and linear chain molecules. A qualitative agreement between theory and experiment is obtained.
Polymorphism in poly(3,3‐dimethyloxetane)
Authors: Pérez Ernesto , Fatou José G. , Bello Antonio , Merino Juan Carlos , Pastor José M , De Saja José A. 
Published: April 2003

AbstractA detailed study of the polymorphism of poly(3,3‐dimethyloxetane) was carried out by differential scanning calorimetry and X‐ray diffraction. From the relaxed melt state, two modifications, Form II (monoclinic) and Form III (orthorhombic), are separately obtained depending on crystallization temperature. When the crystallization is accomplished for a given modification, this one is stable at any temperature below its melting temperature. However, if the crystallization of a given modification is not complete, the other modification can be crystallized from the amorphous phase. Thus, a possibility of obtaining both forms exists. The kinetic and thermodynamic factors which govern this process are analyzed. The free energies were calculated and the conclusion is that modification II is thermodynamically the most stable one at all temperatures below its melting point.
Enzymatic splitting of side chains in soluble polymers. The effect of length and structure of the side chain
Authors: Labský Jiří , Mikeš František , Blahník Aleš , Vyprachtický Drahomír 
Published: April 2003

AbstractA series of soluble polymers was prepared by copolymerization of the 4‐nitrophenol ester of N‐methacryloylated ω‐amino acids (1a – i), of N‐methacryloyldiglycine (2b), of 6‐(N‐methacryloylglycylamino)‐ and of 6‐(N‐methacryloylglycylglycylamino)hexanoic acid (3a and 3b) with N‐(2‐hydroxypropyl)methacrylamide (HPMA). The resulting polymers contained roughly 3 mol‐% of nitrophenol groups. Polymeranalogous reaction with 4′‐nitro L‐phenylalanineanilide (4a) or with its N‐glycyl and N‐glycylglycyl derivates (4b and 4c), yielded polymers which at the end of their side chain of various length and structure had a bond degradable with chymotrypsin. The rate of enzymatic hydrolysis was investigated as a function of the length and structure of side chain. It was found that in copolymers possessing side chains formed by ω‐amino acid residues, the rate of hydrolysis increases with increasing length of the side chain. The rate of cleavage of the peptide bond has a maximum value for a spacer that possesses six methylene groups. With increasing length of the side chain the rate of hydrolysis again decreases. A similar dependence was observed for side chains formed by dipeptides of ω‐amino acids and glycine. In copolymers with oligoglycine side chains, the rate of enzymatic hydrolysis also increases with increasing length of side chain. In other types of side chains formed by combination of hydrophobic and hydrophilic segments, a number of factors become operative which affect the rate of enzymatic hydrolysis and are very difficult to specify.
Functional monomers and polymers, 129. Asymmetric robinson cyclization reaction catalyzed by polymer‐bound L‐proline
Authors: Kondo Koichi , Yamano Toru , Takemoto Kiichi 
Published: April 2003

AbstractThe asymmetric Robinson cyclization reaction was studied by using polymer‐bound L‐prolines as catalysts, in which the degree of crosslinking, the content of proline and the spacers of binding L‐proline to the polymers were varied. Incorporation of a spacer for binding the L‐proline moiety onto a polymer support was found to improve the catalytic efficiency considerably, which is reflected by the value of enantiomeric excess.
Peptide synthesis by using polymer‐supported N‐acylphosphoramidites
Authors: Kawanobe Wataru , Yamaguchi Kazuo , Nakahama Seiichi , Yamazaki Noboru 
Published: April 2003

AbstractDiethoxyphosphino‐substituted acetamides (1 and 2) and the polymer gel bearing dialkoxy‐phosphino groups (3,4, and 5) were prepared by reaction of chlorophosphites with acetamide and crosslinked polyacrylamides, respectively, in the presence of triethylamine. By using 1,2 and the polymer as condensing reagents, various peptides were synthesized directly from N‐protected amino acids and amino acid esters in high yields with little racemization. The highly crosslinked polymeric reagents simplified the procedure and were recycled by treatment with chlorophosphites.
Copolymerization of styrene with α‐chloromaleic anhydride, 1. Mechanism of the radical‐initiated copolymerization in 1,4‐dioxane
Authors: Nagai Katsutoshi , Akiyama Kazuhiko , Kuramoto Noriyuki 
Published: April 2003

AbstractThe radical‐initiated copolymerization of styrene (ST) with α‐chloromaleic anhydride (CMA) in 1,4‐dioxane was investigated. The formation of a 1:1 charge transfer (CT) complex between the comonomers in 1,4‐dioxane at 25°C was confirmed by UV‐spectroscopic studies, and the formation constant was found to be near zero, indicating that the complex is of contact type. An alternating copolymer was obtained by copolymerization over a relatively wide range of feed composition, and the monomer reactivity ratios, rST and rCMA, were found to be 0,07 and 0,00, respectively, at 60°C. The copolymerization at a constant total monomer concentration showed a maximum rate at a styrene mole fraction of 0,4 in the feed. The copolymerization was interpreted by a consecutive monomer addition mechanism without taking into account a participation of the CT complex in the propagation.
Caractérisation et étude physicochimique du polydiméthylsiloxane en bon solvant
Authors: Lapp Alain , Herz Jean , Strazielle Claude 
Published: April 2003

AbstractThe physicochemical properties of a series of polydimethylsiloxane were investigated in dilute solution of toluene by viscosity, light scattering and on‐line light scattering/gel permeation chromatography (LS‐GPC). The viscosity law is determined, in order to compare GPC data and LS‐GPC. The disagreement between these data is explained in terms of cohesion energy. The light scattering data are corrected for polymolecularity effects, in order to determine the excluded volume exponent v and the value of the interpenetration function ψ in the asymptotic domain. These values are in good agreement with the critical exponents obtained using the argument relying on renormalization theory.
Aqueous polymerization of vinyl monomers in the presence of surfactants, 1. Acrylamide
Authors: Bartoň Jaroslav , Juraničová Viera , Vašková Viera 
Published: April 2003

AbstractThe kinetics of the polymerization of acrylamide initiated by potassium peroxodisulfate in water were studied in the presence of the anion‐active emulsifier sodium dodecylphenoxybenzenedisulfonate. The emulsifier was found to affect the relative molecular mass of polyacrylamide, but it showed no effect on the rate of polymerization. The transfer constants to the emulsifier and the initiator were determined and amounted to of 3,6 · 10−3 and 5 · 10−3. The ratio of rate constants of termination and propagation kt / kp2 = 6,9 · 10−2 mol · dm−3 · s, determined for the polymerization of acrylamide in the presence of the emulsifier, is almost identical with the value for the polymerization without emulsifier. Thus, propagation and termination reactions of the potassium peroxodisulfate initiated polymerization of acrylamide in water are not influenced by the emulsifier.
4‐(α,α‐dimethylbenzyl)phenyl methacrylate, 1. Synthesis and crystal structure
Authors: Viersen Frits Jan , Tan Y. Yong , van Bolhuis Fré , Zwiers Renso J. M. 
Published: April 2003

Abstract4‐(α,α‐dimethylbenzyl)phenyl methacrylate (1) was prepared by reaction of 4‐(α,α‐dimethylbenzyl)phenol and methacryloyl chloride in ether. By careful crystallization from ether large monoclinic crystals could be obtained with the following crystal data: a = 6,622 (2) Å, b = 12,578 (2) Å, c = 9,892 (3) Å, β = 99,86° (3), Dc = 1,147 g · cm−3, V = 811,1 Å3, M = 280,4, λ = 0,7107 Å, μ = (Mo Kα) = 0,7 cm−1, F(000) = 300, space group P21, Z = 2. Attempts to polymerize the monomer (m.p. 46–48°C) by γ‐irradiation at ambient temperature gave only a small amount of a crosslinked product.
Assoziationsgleichgewicht und kettenstatistik bei der H‐brücken‐assoziation von N‐methylacetamid in tetrachlorkohlenstoff
Authors: Hummel Helmut , Bonart Richard 
Published: April 2003

AbstractWe have shown by a band separation technique that the IR spectrum of N‐methylacetamide in CCl4 contains four absorption bands in the amide I region. Three of them are assigned to CO groups of trans and cis monomers and free end‐groups of associates, respectively. The fourth band stems from associated CO groups. In the NH‐region only two bands, due to free and associated NH groups, are detectable. The findings can be explained in terms of intra‐ and intermolecular interactions. The equilibrium association constants are discussed, and it is shown that the length distribution of the associates does not follow the Schulz‐Flory law.
A study on the mechanism of polymorphic transition β→α in isotactic polypropylene
Authors: Garbarczyk Józef 
Published: April 2003

AbstractThe analysis of the potential energy of the crystal lattice of isotactic polypropylene during the β→α phase transition was carried out. This transformation was realized by rotations and translations within a collection of 10 iPP helices. The lattice energy was calculated by means of the atom‐atom potential method. Results and analysis of the data allow to propose a two‐stage mechanism polymorphic transformation rotation of helices being the first stage. This mechanism is discussed in relation to physico‐chemical conditions of the formation of the β‐modification and also with regard to changes of certain physical properties observed in iPP during the β→α phase transition.
Polymeric phthalocyanines and their precursors, 6. Synthesis and analytical characterization of some octasubstituted phthalocyanines
Authors: Wöhrle Dieter , Hündorf Uwe 
Published: April 2003

AbstractStarting with 2,3,9,10,16,17,23,24‐phthalocyanineoctacarbonitrile (3a) different octa‐substituted phthalocyanines 4a–7a and 3b–7b with carboxylic acid, anhydride, imido and amido groups were prepared. IR and UV/VIS spectra are discussed in detail and compared with unsubstituted phthalocyanine (1). 3–7 may be considered as low molecular weight analogues of polymeric phthalocyanines 2 with different end groups.