bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermally initiated emulsion polymerization of 1,4‐divinylbenzene
Authors: Kast Hans , Funke Werner 
Published: April 2003

AbstractThe rate of polymerization and the size of the latex particles formed in the thermally initiated emulsion polymerization of 1,4‐divinylbenzene (DVB) was studied as a function of emulsifier concentration, monomer‐to‐water ratio and reaction temperature. Furthermore, kinetic data of the thermal polymerization in solution have been determined. Contrary to normal emulsion polymerization the thermal polymerization of DVB occurs preferentially in the monomer droplets at the rate of a bulk polymerization, whereas latex particles are formed only from the monomer solubilized in micelles at a rate similar to a polymerization in solution. This results in an apparent decrease of the polymerization rate and an increase in size of the latex particles with increasing emulsifier concentration. Crosslinking in polymerization of DVB is discussed as the ultimate reason for the observed features and a mechanism of polymerization based on these conclusions is presented.
The initiation of polymerization of unsaturated tertiary amines with carboxylic acids
Authors: Hrabák František , Hynková Vlasta 
Published: April 2003

AbstractThe polymerization rate (Rp) of N‐methyl‐N‐phenyl‐2‐aminoethyl methacrylate (MPAEMA) initiated with 2,2' ‐azodiisobutyronitrile (AIBN) at 50°C increased considerably after the addition of CCI3COOH, and distinctly after the addition of CH3COOH. Rp in a benzene solution of 2 mol. dm−3 MPAEMA and 5 · 10−2 mol. dm−3 CCl3COOH (without AIBN) was 13% · h−1. [η] of the obtained polymer corresponded to 64 cm3 · g−1. The polymerization order of MPAEMA initiated with CCl3COOH is 0,93 with respect to monomer and 0,51 with respect to CCl3COOH. The overall activation energy of polymerization of MPAEMA calculated from the temperature dependence of Rp between 20 and 50°C is 43 ± 1,2 kJ · mol−1. In a benzene solution of 2 mol.dm−3 MPAEMA, 5 · 10−2 mol · dm−3CCl3COOH and 5 · 10−3 mol · dm−3 1,4‐benzoquinone at 50°C the polymerization does not proceed for 6 h. In a benzene solution of 2 mol · dm−3 4‐dimethylaminostyrene (4‐DMAS) and 2 mol · dm−3 CH3COOH (without AIBN), 40% of monomer polymerized within one hour. [η] of the polymer was 4 cm3 · g−1. The overall activation energy of polymerization of 4‐DMAS in the presence of CH3COOH is ca · 54 kJ · mol−1. The addition of 5 · 10−3 1,4‐benzoquinone slows down the polymerization rate only slightly. The effect of acids on the elementary polymerization reactions is characterized.
Kinetics and stereocontrol of phenylalanine N‐carboxyanhydride polymerizations
Authors: Elias Hans‐Georg , El‐Sabbah Mohamed M. B. 
Published: April 2003

AbstractL‐, D‐, and various D,L‐phenylalanine N‐carboxyanhydrides (NCA's) were polymerized with benzylamine and various concentrations of N‐methylbenzylamine, respectively, in N,N‐diethylformamide at 25°C. Three kinetic stages were observed for all systems: a fast “initiation” stage (I) followed by a slower stage (II) and a faster pseudo‐first order propagation stage (III). The initiation rate is higher for N‐methylbenzylamine than for benzylamine. The propagation rate constants, kpL, of the stage II polymerization of the L‐monomer are independent of initiator type and concentration, whereas the corresponding stage III rate constants vary with the initial monomer/initiator ratio. For each propagation stage, the ratios of rate constants, kpD,L/kpL and kpD,L/kpD, respectively follow the pattern predicted by the absence of crossover reactions. Molar masses calculated from monomer conversion are higher than those determined from amine end group concentration for N‐methylbenzylamine initiated polymerizations, but lower for benzylamine initiated ones.
HIO4‐oxidized soluble polysaccharides as polyfunctional links for covalent binding of enzymes, 1. Preparation of polysaccharides and matrices for their binding
Authors: Reiner Roland H. , Batz Hans‐Georg 
Published: April 2003

AbstractSoluble hydrophillc polyaldehydes can be used as linking and crosslinking reagents for the modification and immobilization of proteins. An imine bond (or possibly an α‐hydroxyamino bond) between NH2 functions of proteins or matrices and the aldehyde functions of the soluble polymer is formed under mild conditions. The polyaldehydes used were HIO4‐oxidized soluble polysaccharides of different degrees of oxidation, and the NH2 matrices were Enzacryl AA and Enzacryl AH (for reference purposes also aminohexylcellulose), macroporous copolymer of glycidyl methacrylate reacted with ammonia, and nylon 6 and Estapor latices both with surface amino groups. Dextrans and Zulkowski starch were readily oxidized with HIO4, the degree of oxidation being determined by means of a modified photometric aldehyde determination method. As regards the reaction of the matrices with the polyoxidized polysaccharides (“glycosidation of the matrix”), it was found that 20 h incubation at 20°C and phosphate buffer pH = 6 furnished good results. In the investigations discussed in the present paper, relatively large quantities of polysaccharide were used for incubation, in order to achieve a high degree of glycosidation. For a closer analysis of matrices, several methods for the determination of the NH2 concentrations on matrices were examined; in this case the reaction with pentafluorobenzaldehyde in aqueous phase followed by fluoride‐analysis furnished well reproducible results.
Circular dichroism for the examination of an interaction between polyglutamic acid and oligoamines
Authors: Pal Medini K. , Böhmer Volker , Kern Werner , Nath Jagannath 
Published: April 2003

AbstractThe interaction of poly(L‐glutamic acid) with 3,6‐dioxaoctamethylenediamine was studied by circular dichroism spectroscopy under different conditions. In aqueous solution at pH 5,6 and in aqueous 1,4‐dioxane (30–50 vol.‐%) at pH 7,3 the conformation of poly(L‐glutamic acid) was completely changed from α‐helical to random coil in the presence of an excess of the diamine.
Diels‐Alder reaction of a trace amount of styrene with cyclopentadiene in a liquid phase
Authors: Nagai Susumu , Ueda Akira , Ikezawa Hiroshi 
Published: April 2003

AbstractWith the intention to prove the possibility of applying the Diels‐Alder reaction to trap a trace amount of residual styrene monomer in polystyrene, a model reaction between cyclopentadiene with styrene in a dilute o‐chlorobenzene solution was carried out. In the presence of an excess amount of dicyclopentadiene, the consumption of styrene was measured with time lapse by means of gaschromatography. At temperatures ranging from 140 to 220°C, the amount of styrene was observed to decrease remarkably until it reached an equilibrium concentration. The higher the temperature was, the higher the equilibrium concentration became. The equilibrium constants at each temperature and the activation energy for the reaction were calculated.
SynthèSe de copolymères triséquencés polybutyramide‐polystyrène et polybutyramide‐polyisoprène
Authors: Schmitt Michel , Franta Emile , Rempp Paul , Froelich Daniel 
Published: April 2003

AbstractThe synthesis of triblock copolymers with crystalline outer blocks of polybutyramide and a central block of polystyrene or polyisoprene was performed. First polystyrene (or polyisoprene) fitted at both ends with acyllactam functions were obtained. In a second step these endstanding functions promote the lactame polymerization to yield the polyamide blocks. A careful characterization of the resulting samples was carried out. The behaviour of these block copolymers is typically that of a thermoplastic elastomer, whereby the crystalline blocks constitute the physical crosslinks in the samples.
Interaction of sodium dodecyl sulfate with poly(L‐lysine) in aqueous solution
Authors: Inoue Yoshio , Teraoka Nobuaki , Suzuki Yasuyuki , Chûjô Riichiro 
Published: April 2003

AbstractThe interactions between a homopolypeptide, poly(L‐lysine) [(Lys)n], and an anionic surfactant, sodium dodecyl sulfate (NaDodSO4), were studied by 13C NMR spectroscopy in D2O solution. By observing the chemical shift of the ε‐amino carbon of lysine monomer in D2O solution at pH 7,3 in presence and absence of NaDodSO4, direct evidence was found for electrostatic interaction between the protonated lysine ε‐amino group and the head group of the anionic surfactant. At this pH, the (Lys)n chain in NaDodSO4 solution adopts the β‐form conformation and the solubility of NaDodSO4/(Lys)n complexes is too small to observe 13C‐spectra. At more alkaline solutions, where the (Lys)n chain forms α‐helices, the surfactant's polar group interacts with the uncharged lysyl side chain through hydrogen bonding. In the initial binding of the surfactant to (Lys)n, both the surfactant head group and alkyl chain contribute to the association with (Lys)n. With an excess of surfactant bound to α‐helical (Lys)n, NaDodSO4/(Lys)n complexes show high solubility and all carbon atoms of the surfactant molecules show micelle shifts. These results suggest that the surfactant molecules form micellelike clusters around the (Lys)n helices exposing the surfactant polar head group to the medium and enhancing the solubility of NaDodSO4/(Lys)n complexes.
Equilibrium sorption of disperse dyes in annealed high‐density polyethylene films with relation to their mosaic‐block structures
Authors: Masuko Toru , Hasegawa Shigeo , Yonetake Koichiro , Karasawa Mikio 
Published: April 2003

AbstractA phenomenological theory of disperse dye sorption is presented in view of the mosaic‐block structure model of a crystalline polymer. The sorption model is essentially based on the idea that disperse dyes are dissolved into two kinds of amorphous regions within the polymer: one consists of chains with relatively random conformation (the end region); the other is mainly composed of chains whose molecular arrangement is predominant in parallel alignment (the side region). Experimental findings derived from the equilibrium uptakes at 80°C of four disperse dyes by variously‐annealed high‐density polyethylene (PE) films are fully examined in terms of this theory. The dye sorption into the end region in every dyeing case decreases monotonically with increasing the crystallinity of PE; whilst that into the side region increases definitely, particularly in the case of rod‐like dye molecules. The latter is probably reflected on the increase in the fraction of the amorphous chains with trans‐type conformation, the development of which may be accompanied by thickening of lamellae, since straight‐type chains of this molecular shape are preferentially effective in binding tightly to the rod‐like dye molecules.
Eine neue methode zur ermittlung kinetischer und kalorischer daten einer radikalischen copolymerisation durch differentialthermoanalyse
Authors: Fink Johannes Karl 
Published: April 2003

AbstractThe heats of copolymerization of styrene and methyl methacrylate were measured by means of differential thermal analysis (DTA). Extrapolating the DTA curves to time zero, monomer reactivities and the ratio of the rate constants of termination can be obtained by a new method of evaluation. Calibration is not necessary for this procedure. With calibration, however, the rates and the heats of polymerization can also be measured. The data agree well with those reported in the literature.
Direct polymerization of N‐carboxy anhydride of L‐glutamic acid
Authors: Kawai Tohru , Kōmoto Tadashi , Honda Nobuyoshi 
Published: April 2003

AbstractA new method of polymerization of the N‐carboxy anhydride (NCA) of glutamic acid is presented by which poly(glutamic acid) is obtained directly from the NCA without protecting its carboxyl group. The principle underlying is that by adjusting the mole ratio of the initiator butylamine, [I], to the monomer, [A], butylamine can be used as protecting agent for the carboxyl group of the NCA so that the rest of butylamine acts as initiator in the heterogeneous polymerization in acetonitrile. Quantitative conversion was obtained for an [A]/[I] ratio of 1. In analogy to other heterogeneous polymerizations of NCAs in acetonitrile, this is due to the formation of the helix during polymerization, which was confirmed by IR absorption and X‐ray diffraction measurements. As the [A]/[I] ratio increases, the conversion, the helix content of the resultant polymer, and the amount of butylamine combined with it decrease drastically. It is suggested that “copolymerization” of the amine‐protected and unprotected NCAs occurs, giving rise to a partially helical chain, whose contents of the amine‐protected side chains and accordingly of the helix are the higher the smaller the [A]/[I] ratio.
Conformations and crystallization of poly(amino acid)s in collapsed monolayers
Authors: Kawai Tohru , Kōmoto Tadashi , Kato Shigemichi 
Published: April 2003

AbstractThe relationships were studied between the conformation of various poly(amino acid)s, as revealed by optical rotatory dispersion and viscosity of the solutions and polarized IR spectra of the collapsed film of their monolayers developed from the solutions, as well as the state of the aggregation of the molecules and the crystalline texture in the film, as revealed by electron microscopy. In the cases of poly(L‐alanine) and poly(L‐leucine), the α‐helical conformation in the mixed solvent of trifluoroacetic acid (TFA) and chloroform, used for the development into their monolayers, was maintained in their monolayers and collapsed films, and the rigid helical molecules were aligned perpendicularly to the direction of the applied pressure. In the case of poly(S‐methyl‐L‐cysteine), it was found that two types of β‐structure coexist, i.e., a cross‐β type (due to intramolecular hydrogen bonding) and an intermolecular β‐structure (due to intermolecular hydrogen bonding) in the solution state, whose amounts depend on the composition of the mixed solvent and polymer concentration, reflecting in the mixed structure of lamellar and fibrous crystals in the collapsed film. The aggregation of poly(S‐methyl‐L‐cysteine) molecules with the above two types of conformations seems to occur on the development of their solution onto the water surface. The same seems to apply to the case of poly(L‐valine).
A novel synthetic route to all‐ortho novolac resins
Authors: Casiraghi Giovanni , Sartori Giovanni , Bigi Franca , Cornia Mara , Dradi Emanuele , Casnati Giuseppe 
Published: April 2003

AbstractA facile synthesis of ortho‐linked novolacs was achieved by reaction of selected metal phenolates with paraformaldehyde. Both solvent and phenolate counter‐ion play a leading role in the ortho‐specific methylene‐bridging of the phenolic nuclei. The combined use of highperformance liquid chromatography and 13C NMR spectroscopy proved to be successful in the characterization of these resins.
Stabile polyphenoxyle, 5. Sterisch gehinderte vinylphenole zur spinmarkierung von polymeren
Authors: Braun Dietrich , Törmälä Pertti , Wittig Wolfgang 
Published: April 2003

AbstractPolystyrene chains containing different amounts of 2,6‐di‐tert‐butyl‐4‐vinylphenylacetat repeating units were deacetylated and dehydrated by means of lead dioxide or potassium hexacyanoferrate(III) to obtain polystyrene molecules containing different amounts of phenoxyl spin‐label radicals. The inter‐ and intramolecular interactions between radical moieties were studied by varying the concentrations of polymer molecules in benzene and toluene solutions and the amounts of radical units in polymer chains. The source of information of these interactions was linewidth analysis of electron spin resonance (ESR) spectra which was carried out by spectral simulations. It was shown that the linewidths of ESR spectra of spin‐labelled polystyrenes in benzene and toluene solutions practically did not change when T > 40°C. It was found that intermolecular interactions are excluded if the polymer concentration is below 250 mg/l. The intramolecular interactions were first observed when the radical concentration in polymer chains was 0,7 mole‐%. This corresponds to a mean distance of 125 repeating units between the radical moieties or a nominal distance of radical units along the polymer chains of about 400 Å. However, the spin‐spin interaction shows that the distance between radicals is at the most about 100 Å under the studied conditions. This is a consequence of random coil conformation of polymer chains in solution.
A 13C NMR study of four lignins in the solid and solution states
Authors: Maciel G. E. , O'Donnell D. J. , Ackerman J. J. H. , Hawkins B. H. , Bartuska V. J. 
Published: April 2003

AbstractA series of four solvent‐extracted lignins were subjected to solid‐state 13C NMR analysis using the cross polarization‐magic angle (CP/MAS) technique. Comparisons are made between the solid‐sample spectra and high‐field spectra obtained on solutions of these lignins. Specific signals in both the solid‐state and solution spectra can be assigned to structural features present in the lignins. Most of the spectral information present in the solution‐state spectra are seen by CP/MAS, a technique that shows great promise for the study of lignin in solid samples.
The effect of monomer crystal structure on the solid‐state polymerization of N‐vinylcarbazole
Authors: Usanmaz Ali 
Published: April 2003

AbstractThe solid‐state polymerization of N‐vinylcarbazole initiated by γ‐rays was studied by X‐rays, IR and GPC techniques to understand the role of the monomer crystal structure on the polymerization mechanism. From the X‐ray diffraction results it was possible to explain the chain growth mechanism and limiting conversion. The molecular weight distribution and the role of oxygen was explained from the GPC results. Liquid chromatography and IR results were used to explain the nature of unpolymerized monomer after reaching the limiting conversion. It was proved that the unpolymerized monomer retains its crystal structure and does not react to any other compounds.
Polymers from carbohydrate‐based monomers, 1. Poly(acylhydrazone)s from D‐glucarodihydrazide and related compounds
Authors: Roberts George A. F. , Thomas Iwan M. 
Published: April 2003

AbstractThe synthesis of poly(acylhydrazone)s from aldarodihydrazides, principally D‐glucarodihydrazide, was studied. Polymers were produced on reaction of the dihydrazides with dialdehydes and with aliphatic ketoaldehydes and diketones, but not with aromatic ketoaldehydes or aromatic diketones. The polymers, which have only limited solubilities that are not appreciably improved by copolymerization, undergo a tautomeric change on treatment with acid or alkali to give yellow‐coloured polymers. Of the poly(acylhydrazone)s prepared, that from D‐glucarodihydrazide and 2,3‐butanedione had the best overall properties, giving strong, flexible, colourless films on casting from DMSO solution.
Degradation of bulk polyethylene by nitric acid, 1. IR study of oxidized groups
Authors: Rueda Daniel R. , Cagiao Esperanza , Calleja Francisco J. Baltá 
Published: April 2003

AbstractNew IR data on the selective oxidation of polyethylene treated with nitric acid are reported. The oxidized groups introduced by the nitric acid are examined with reference to the bands at 1 710 (COOH), 1 650 (ONO2), and 1 550 cm−1 (NO2) as a function of treatment time. The influence of the reaction conditions on the amount and nature of the groups introduced is further investigated. Thus, the ratio of nitro to carboxyl groups after prolonged treatment times is approximately equal to 1/4 if the reaction is performed in open tubes. It is, however, considerably smaller (< 1/8), lowering with time, for t > 40 h, if the treatment is confined into sealed tubes. Furthermore, in addition to the established view of the polymer residues as consisting of paraffinic chains terminated by carboxyl groups the presence of covalent nitrate groups was verified. These groups are probably attached at chain folds, as an intermediary of the reaction during the first treatment hours. Finally, it is further suggested that the nitro groups introduced are preferentially localized at the periphery of the crystallites.
Uncatalysed phenol‐formaldehyde reactions. A convenient synthesis of all‐ortho novolac resins
Authors: Casiraghi Giovanni , Casnati Giuseppe , Cornia Mara , Sartori Giovanni , Bigi Franca 
Published: April 2003

AbstractThe uncatalysed reaction between phenol and paraformaldehyde in aprotic nonpolar media at 170–220°C provides an efficient inexpensive route to novolac resins with almost all of the methylene‐linkages in ortho‐ortho′ sequence. The role played by the solvent is shown to be determinant in the ortho‐specific insertion of methylene‐bridges between the phenolic units.
The polymerization of acenaphthylene by carbocation salts in nitrobenzene
Authors: Pask Stephen D. , Plesch Peter H. , Kingston Samuel B. 
Published: April 2003

AbstractAcenaphthylene was polymerized in nitrobenzene at 25°C by NO2SbF6, C2H5COSbF6, C6H5COPF6, and (C6H5)2CHSbF6. With monomer so rigorously purified that it contained only ca. 0,01 mol‐% of inhibiting impurities the reaction pattern indicated propagation by unpaired cations, and a k = 23,3 ± 2 dm3·mol−1·s−1 (the first for this monomer) was obtained. There are at least two chain‐breaking reactions of which one is the proton transfer to monomer which has K = 2,3 dm3·mol−1·s−1. The kinetic irregularities and colours which develop at high conversions are probably due to the formation of non‐propagating allylic cations from unsaturated end‐groups.
Untersuchung der grignard‐wurtz‐reaktion von partiell hydrobromiertem 1,4‐polybutadien und partiell α‐bromiertem polyoctenylen durch metathese‐abbau der polymere und identifizierung der niedermolekularen produkte
Authors: Hummel Klaus , Wedam Othmar A. 
Published: April 2003

AbstractPartially hydrobrominated 1,4‐polybutadiene and α‐brominated polyoctenylene were treated with pentyl, isopropyl, cyclohexyl, benzyl, 4‐methylbenzyl, phenyl, 4‐methylphenyl, 4‐ethylphenyl, 3,4‐dimethylphenyl, 2,4,6‐trimethylphenyl, 4‐chlorophenyl, 4‐fluorophenyl, 4‐methoxyphenyl, 3,4‐dimethoxyphenyl, and 2‐thienyl magnesium bromide. In addition partially hydrobrominated 1,4‐polybutadiene was treated with 2‐methylbenzyl, 3‐methylbenzyl and 4‐isopropylphenyl magnesium bromide. Polymers were degraded by metathesis with 4‐octene using WCl6/(CH3)4Sn as a catalyst. The low molecular products were separated by gas chromatography and identified by mass spectrometry. Mass spectra of products with 4‐alkyl(aryl)octanediylidene units (from modified polybutadiene) and 2‐alkyl(aryl)octanediylidene units (from polyoctenylene) were compared.