bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis of polydiphenylgermylene single crystals from diphenyldichlorogermane
Authors: Kong Eric Siu Wai , Wunderlich Bernhard
Published: April 2003

Polymer single crystals with a germanium backbone have been synthesized. The synthesis involves a thermally induced generation of divalent radicals, transport of these radicals and subsequent addition polymerization on a cold surface. The polymerization was carried out under vaccum. Crystallization during polymerization was found to occur resulting in extended chain macromolecular crystals. These crystals were prismatic with a number‐average molecular weight of 11300. The melting range of the \documentclass{article}\pagestyle{empty}\begin{document}$ \rlap{--} ({\rm GePh}_2 \rlap{--})_{\rm n} $\end{document} crystals is 285 to 295°C. The glass transition temperature of the same polymer in its amorphous state was found to be 96°C (20°C/min heating rate using differential thermal analysis). The crystal structure of the intermediate octaphenylcyclotetragermane is compared to that of octaphenylcyclotetrasilane and polydiphenylgermylene.
Solid state polymerization and physical properties of crystalline complexes of phenazine and diacetylene‐monocarbonic acids
Authors: Tieke Bernd , Bloor David
Published: April 2003

The polymerization behaviour and physical properties of 2:1 complexes of 2,4‐diynoic acids and phenazine have been studied by optical and Raman spectroscopy and X‐ray diffraction. Models are proposed for the molecular arrangements in the pure acids and the complexes, which explain the unique ability of the phenazine to form complexes. The polymerization of the complexes proceeds via a homogeneous solid‐solution up to a limiting value of 65% polymer. During the reaction a rearrangement of the aliphatic side‐chains occurs, which affects the optical absorption of the polymer backbone.
Kinetics of polymerization of tetrahydrofuran initiated by acetyl perchlorate
Authors: Alamo Rufina , Guzmán Julio , Fatou José G.
Published: April 2003

The kinetics of the polymerization of tetrahydrofuran by acetyl perchlorate in methylene chloride solution was studied, and the results were compared with those previously reported by using perchloric acid/acetic anhydride as catalyst. The initiation and propagation mechanisms are discussed by taking into account the influence of the counterion. The initiation reaction takes place instantaneously, but the propagation proceeds by macroesters and macroions and the contribution of macroester to propagation is much lower than the contribution of macroions.
Préparation d'adsorbants chromatographiques plurifonctionnels et asymétriques. Application à la purification de la céphalosporine C
Authors: Sacco Daniel , Dellacherie Edith
Published: April 2003

Some asymmetric and polyfunctional stationary phases were prepared by attachment of the ε‐amino group of L‐lysine copper complex to crosslinked polystyrene or agarose, substituted or not by hydrophilic spacer arms. After copper elimination, the sorbents exhibit three functions, one of a carboxylic acid and one of an α‐primary amine, and moreover one of a secondary amine located at a variable distance far from the asymmetric carbon, but near the backbone of polymer. These sorbents were tested in the chromatographic extraction of cephalosporin C (1) from an aqueous mixture containing several α‐amino acids. They exhibit an affinity higher for the antibiotic than for the amino acids and even for the dicarboxylic amino acids.
Recherche de télomères à activité pharmacologique potentielle, 2. Télomères de l'acide acrylique et greffage de composés hydroxylés
Authors: Bauduin Gérard , Bondon Daniel , Martel Jacques , Piétrasanta Yves , Pucci Bernard
Published: April 2003

Several telomers of acrylic acid with carbone tetrachloride were prepared. Their average degree of polymerization, which was between 10 and 50, was determined by several analytical methods (elemental analysis, viscosimetry, and GPC). From the kinetic equations of telomerization a relation between DPn of these telomers and the experimental conditions is established. Fixation of hydroxylic compounds through direct esterification was studied and it was found that the prepared telomers can be used as hydrosoluble carriers for drugs containing primary alcohol or phenol functions.
Polystyrene‐immobilised imidazole ligands; synthesis and complex formation with transition metal salts
Authors: Welleman J. A. , Hulsbergen F. B. , Reedijk J.
Published: April 2003

The modification of polystyrenes (1 – 8% cross‐linked) by imidazole ligands, via chloromethylation, is described. The resulting resins, having 10–40% of the phenyl groups substituted by a CH2(N)‐imidazolyl group, have been treated with first‐row transition metal salts under varying conditions. Upon reaction of the modified polymer with the transition metal salts in CHCl3, a shrinking of the polymer is observed which is explained by additional cross‐linking by the metal ions. The final products have the general formula Mt(PS‐Iz)m(NnBuIz)nX2, in which PS‐Iz stands for a polystyrene‐bound imidazole ligand, NnBuIz forN‐butylimidazole (a ligand used to solubilize the metal salts in CHCl3) and X for the anion (perchlorate, nitrate, tetrafluoroborate, chloride, bromide). Metal ions used are Co(II), Ni(II), Cu(II), and Zn(II); values of 2–6 have been found formin most cases. The value ofnusually is very small (0,2–1,0) in most cases. Spectroscopically the polymeric coordination compounds behave like the corresponding monomeric coordination compounds, Mt(N‐benzylimidazole)mX2, indicating that the imidazole ligands in the polymer are quite flexible in their coordination behaviour, except in case of very low degrees of substitution or high degrees of cross‐linking.
Subkatalytische Effekte in Systemen Isopren/Organolithium/Elektronendonator, 3. System Isopren/Oligoisoprenyllithium/1,2‐Dimethoxyethan
Authors: Davidjan Asya , Nikolaew Nikolai , Sgonnik Vladimir , Krasikow Valerii , Belenkii Boris , Erussalimsky B.
Published: April 2003

Molecular weights and structural characteristics of the polymers formed in the system isoprene/oligoisoprenyllithium (OILi)/1,2‐dimethoxyethane (DME)/hexane (mole ratio DME/OILi = 0,01) for various conversions at −30°C were determined. The results obtained corroborate the former conclusion that the complexation of an electron donor with the monomeric form of the growing chain reduces the reactivity of the latter.
Polymethacrylic acid Derivatives, 1. Preparation, Characterization, and Potentiometric study of poly(N‐methacryloyl‐L‐alanine‐co‐N‐phenylmethacrylamide)
Authors: Morcellet‐Sauvage Joëlle , Morcellet Michel , Loucheux Claude
Published: April 2003

Poly(N‐methacryloyl‐L‐alanine) and poly(N‐methacryloyl‐L‐alanine‐co‐N‐phenylmethacrylamide) containing up to 38 mole‐% of N‐phenylmethacrylamide were synthesized by radical copolymerization. These polymers were characterized by UV and IR spectroscopy and by conductimetric titrations. The samples were then studied by potentiometric titrations in pure water and in aqueous organic solvents, in the temperature range of 5 ‐ 65°C. The experimental results show that, opposite to poly(methacrylic acid), poly(N‐methacryloyl‐L‐alanine) takes no compact structure in water. The insertion of N‐phenylmethacrylamide induces the appearance of this compact structure over 15 mole‐% of this residue. Thereafter, the stability of the compact structure increases when increasing the amount of N‐phenylmethacrylamide. Experimental results suggest that it is due to increasing Van der Waals interactions between the hydrophobic side chains.
Polymerisationsauslösung mit substituierten ethanen, 3. Struktur und Taktizität der Oligomeren aus Methylmethacrylat und 1,1,2,2‐Tetraphenyl‐1,2‐diphenoxyethan
Authors: Balard Henri , Błedzki Andrzej , Braun Dietrich
Published: April 2003

The 1H NMR‐spectra of MMA oligomers with two phenoxydiphenylmethyl end groups, 1, are discussed. The syndiotactic and isotactic dimers and two heterotactic and one syndiotactic trimer could be identified, whereas no isotactic trimer was found.
Effect of solvent on 13C NMR chemical shifts of tetrad methylene carbons of poly(vinyl chloride)
Authors: Ando Isao , Asakura Tetsuo
Published: April 2003

The 13C NMR chemical shifts of tetrad CH2 carbons of poly(vinyl chloride) are observed in solvents covering a wide range of relative dielectric constants and show extreme sensitivity to the solvent. The chemical shifts are interpreted theoretically by means of the solvaton‐CNDO/2 MO theory.
Comportement viscosimétrique des télomères acrylate d'éthyle/tétrachlorure de carbone
Authors: Piétrasanta Yves , Rigal Gérard , Schaeffner Pierre
Published: April 2003

The intrinsic viscosities of some acrylic telomers prepared by redox catalysis were measured with an Ubbelohde capillary viscosimeter. The variation of density during dilution appears to be a very important parameter. Thus, the viscosimetric results become coherent according to Huggins' theory on polymers, and a calibration curve available for the whole range of molecular weights can be established.
Functionalization of poly(ethylene glycol) and monomethoxy‐poly(ethylene glycol)
Authors: Bückmann Andreas F. , Morr Michael , Johansson Göte
Published: April 2003

Simple methods are described for the substitution of poly(ethylene glycol) and monomethoxy‐poly(ethylene glycol) substitution. Affinity ligands, coenzymes, or enzymes can be covalently attached to the substitution product or they can be used as liquid ionexchangers.
Hydrogenation of alkenes, alkynes, and other substrates catalyzed by polymeric Pd(II) complexes of 2,3,6,7‐octanetetraone tetraoxime
Authors: Yukimasa Hidefumi , Sawai Hiroaki , Takizawa Takeo
Published: April 2003

Coordination polymers prepared from 2,3,6,7‐octanetetraone tetraoxime and bis(benzonitrile)palladium dichloride catalyzed the hydrogenation of alkenes, alkynes, carbonyl compounds, azobenzene and other substrates with some selectivity. The catalytic activity and selectivity were dependent on the palladium content in the complex.
Molybdenum complexes with polymer‐bound cysteine and their catalysis in acetylene reduction
Authors: Koide Mikio , Suganuma Noriyuki , Tsuchida Eishun , Kurimura Yoshimi
Published: April 2003

Water soluble polymers with cysteine residues (Pcys) were synthesized by the copolymerization of S‐benzyl‐N‐benzyloxycarbonyl‐4'‐vinyl‐L‐cysteineanilide and acrylic acid or methacrylic acid. These copolymers were reacted with Mo(V)2O to Mo(V)‐Pcys complexes with di‐μ‐oxo bridged binuclear structure. The absorption maximum of these complexes appears at 330 nm in aqueous solution. ESR study suggests that mononuclear Mo(III)‐Pcys complexes (g = 1,997) are formed by reduction of Mo(V)‐Pcys complexes with NaBH4. These Mo(III)‐Pcys complexes are effective catalysts for the reduction of acetylene in the presence of NaBH4 and their catalytic activities are 2—3 times greater than that of the corresponding low molecular weight Mocysteine complex. The higher activity of the polymer complexes is explained by the enhancement of the proportion of monomuclear species due to the stretching of the polymer chain caused by the electrostatic repulsions between the carboxyl anions on the side chains.
Die emulsionscopolymerisation von tetrafluorethylen mit propylen bei niedrigen temperaturen
Authors: Kojima Gen , Hisasue Michio
Published: April 2003

Tetrafluoroethylene and propylene were copolymerized in emulsion at low temperatures (≈25°C) by use of a redox catalyst containing ammonium peroxodisulfate, ferrous sulfate, ethylenediaminetetraacetic acid (EDTA) and hydroxymethane sulfinate. The kinetical study suggested that the working mechanism of the catalyst conforms the following scheme:
magnified image
where the reduction of the ferric ion seems to be rate determining (i.e. k1 ≫ k2) and the hydroxyl ion plays an important role. The overall polymerization reaction is supposed to proceed according to the Case I of the Smith‐Ewart theory under the experimental conditions examined.
1H and 13C NMR spectra of poly(propyl α‐bromoacrylate) and poly(methyl α‐bromoacrylate)
Authors: Hatada Koichi , Kitayama Tatsuki , Saunders Keith , Lenz Robert W.
Published: April 2003

The 13C NMR spectra measured at 25 MHz of the methyl and propyl esters of isotactic and syndiotactic poly(α‐bromoacrylate) were sufficiently resolved to be analysed for pentad tacticity sequences. The pentad tacticity of the syndiotactic polymers prepared with free radical initiators at −40°C agreed with those calculated for Bernoullian sequence distributions based on Pr values of 0,83–0,87. The tacticities of the isotactic polymers prepared with heterogeneous catalysts were determined on the basis of these assignments. Good internal consistency was obtained between the calculated and observed pentad proportions from the quaternary and carbonyl carbon peaks in the spectra of these polymers. The order of chemical shifts for the meso and racemic dyads and tetrads in these polymers were opposite to those found in the equivalent methacrylate polymers, but as with the latter, the 13C‐T1 values were longer in the isotactic than in the syndiotactic polymers.
Micellisation de copolymères séquencés polystyrène‐polyvinylpyridinium, 2. Influence des caractéristiques moléculaires des copolymères
Authors: Selb Joseph , Gallot Yves
Published: April 2003

The influence of the molecular characteristics of polystyrene‐poly(4‐vinyl‐N‐ethylpyridinium bromide) block copolymers (PS‐PVPQ) on their dilute solution properties is investigated in a solvent selective for polyelectrolytic moieties (water‐methanol‐0,1 mol/1 LiBr mixtures). It is shown that the association degree depends much more upon the length of the insoluble hydrophobic part of the macromolecule than on the length of the soluble hydrophilic part. Micelle dimensions could not be determined from light scattering measurements because of the compactness of the particles. Attempts for the calculation of micelle size were made using a star‐like micellar model.
Thermally initiated emulsion polymerization of 1,4‐divinylbenzene
Authors: Kast Hans , Funke Werner
Published: April 2003

The 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

The 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

L‐, 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

Soluble 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

The 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

With 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

The 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

The 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

A 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

The 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

A 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

The 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

A 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

Polystyrene 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

A 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

The 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

The 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

New 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

The 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

Acenaphthylene 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

Partially 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.
Etude de radicaux libres forméas par irradiation ultraviolette de l'amidon: Application aux réctions de photodégradation et de photogreffage
Authors: Merlin André , Fouassier Jean‐Pierre
Published: April 2003

General investigations of radical processes in starch were carried out. ESR experiments showed that UV irradiation of starch, both in photosensitized and unphotosensitized experiments, results in chain scission and radical generation on the glucosidic ring. It was shown that benzophenone, deoxybenzoin and derivatives (2a–d) are efficient sensitizers. The ESR spectra were interpreted by assuming superposition of three signals; they were ascribed to radicals formed by chain scission and hydrogen abstraction. In addition photodegradation processes of starch in the presence and absence of photosensitizers were investigated. The amount of chain scissions was followed under various experimental conditions and appeared as a function of the initiator. Moreover, oxygen was shown to enhance the yield of chain scissions: this was explained through the formation of peroxide functions at C1‐position. UV light induced grafting of a vinyl monomer onto starch was also investigated. It appeared that chemical grafting can easily be achieved through a radical reaction. Moreover, the percentages of grafting and degradation were strongly dependent on the photoinitiator. The whole results gave the possibility to select an efficient initiator of the grafting reaction. In the case of methyl methacrylate, α,α‐dimethoxydeoxybenzoin (2a) appears to be the most efficient initiator. However, previous works as well as the present work suggest that the grafting efficiency is strongly dependent on the three components: substrate, monomer, and initiator.
Internal mobility of PMMA in concentrated CDCl3 solutions, 1. 1H NMR spectra
Authors: Zajíaček Jaroslav , Pivcová Hana , Schneider Bohdan
Published: April 2003

Measurements of the second moment and analysis of the derivative shape of 1H NMR spectra of PMMA have shown that in CDCl3 solutions containing 60% (w/w) or more of polymer, the internal mobility of PMMA is similar to the mobility of the pure polymer. The main chain is rigid on the NMR scale, and only CH3 groups are mobile. The motion of CH2 groups, representing the segmental mobility of the backbone chain, becomes appreciable on the NMR scale at concentreations of 60–50%, depending on the temperature. Measurements of 1H MAR‐NMR spectra of solutions containing 30% or more of polymer indicate spatial anisotropy of internal motions of PMMA. This spatial anisotropy is probably due to intermolecular interactions of ester groups, similarly as in the gels of the PMMA stereocomplex.
Die molekulargewichtsverteilung bei der kontinuierlichen anionischen polymerisation
Authors: Panke Dietrich
Published: April 2003

Equations are given for the continuous anionic polymerization in a tubular reactor which describe the resulting molecular weight distribution as a function of the size of the mixing zone and of the concentration of chain terminating impurities in the solution of the monomer. Polymerization of styrene and of butyl methacrylate was conducted with different initiator concentrations, and the size of that part of the reactor where backmixing occurs was estimated from the molecular non‐uniformity of the polymers, whereas the degree of polymerization allows the determination of the concentration of the impurity. This latter quantity apparently increases with initiator concentration in the case of methacrylate polymerization and therefore suggests a reaction of the initiator with the ester group to occur. The shape of the molecular weight distribution indicates termination of the growing methacrylate chains, possibly by reaction of living chain ends with ester groups.
Decay studies of poly(vinyl chloride) electrets
Authors: Talwar Inder Mohan , Behari Shyam
Published: April 2003

Thermoelectrets of poly(vinyl chloride) were prepared at 4, 14, 20 kV/cm and 105, 115, 125 and 135°C. The final charge is always homocharge, though the initial one depends upon the polarizing parameters. With 4 and 14 kV/cm, up to 125°C, the initial charge is homo, increasing with the polarizing temperature Tp. At 135°C, it is heterocharge tending to increase with the polarizing field Ep. From the thermally stimulated depolarization glow curves, the number of dipoles per monomeric unit of the material is calculated; it is seen that this number cannot account for the heterocharge. A mica spacer placed between the dielectric and one electrode suppresses the peak current. A model is proposed to explain the electret behaviour.
Synthesen und charakterisierung polymerer cyaninfarbstoffe
Authors: Koßmehl Gerhard , Bocionek Peter
Published: April 2003

From 2,3,5,6‐tetramethylthiazolo[4,5‐f]benzothiazoldiium diperchlorate (9) and the ortho esters 2a–d or 1,1,3,3‐tetramethoxypropane (4) polymeric cyanines with trimethine (10a), substituted trimethine (10b–d), respectively pentamethine units (11) were synthesized. Model compounds (3a–e, 5, 7a–d, 8) were prepared from 1a, 1b and 6, analogously. The structures were confirmed by elemental analyses, IR, and electronic spectra. In addition, the model compounds were characterized by their 1H NMR and mass spectra.
Oxydation photothermique et photocatalysée des polyundécanamides
Authors: Tang Ly , Lemaire Jacques , Sallet D. , Mery J.‐M.
Published: April 2003

Photothermal and TiO2‐ or ZnO‐photocatalyzed oxidations of type B‐ and type K‐polyundecanamides (RILSAN) were studied analytically and kinetically. IR spectrophotometry and chemical titration showed that hydroperoxy groups in the polymer reach a fairly high photostationary concentration. Then the primary photoproducts A decompose into products with imido groups (C), the concentration of which are increasing until a photostationary value. Under irradiation, the imides C are converted into acids and amides; in thermooxidation acids are the main products. The intermediate products in photocatalysed oxidation were found to be the same as in photochemical oxidation; a photochemical protection of hydroperoxides and imides was observed, due to the inner filter effect of the absorbing pigments. It could be shown that in polychromatic light the photocatalytic activity of TiO2 (rutile) is more important than its inner filter effect; this antagonism does not depend on the concentration of the photoactive pigment.
Conformational analysis of poly(oxymethylene)
Authors: Miyasaka Taira , Kinai Yoshiyuki , Imamura Yoshio
Published: April 2003

The conformational energies of the lower members of poly(oxymethylene), 2,4‐dioxapentane and 2,4,6‐trioxaheptane were estimated by the empirical force field method. The gauche states of the internal rotation around the skeletal CO bonds were successfully predicted to be of lower energies in both molecules. In order to calculate the unperturbed dimension and dipole moment of poly(oxymethylene), rotational isomeric state approximations were made by using the results obtained from the force field calculations on 2,4,6‐trioxaheptane. The first‐order interaction energy was estimated to be a large negative value, and the second‐order interaction energies for g±g± had non‐zero values. Although these parameters were significantly different from those estimated earlier, they reproduced the observed results fairly well. Thus the “gauche effect” of poly(oxymethylene) was explained by taking account of the effects contributed by the lone pairs of electrons on the oxygen atoms. As adopted in this study, the procedure joining the empirical force field method to the statistical mechanical one was shown to be effective for the investigation of many sorts of configuration‐dependent properties of chain molecules.
Mechanical shear degradation of polymers in solution by turbulent flow, 3. The influence of chemical constitution and thermodynamic quality of the solvent on shear degradation
Authors: Müller Hans Georg , Klein Joachim
Published: April 2003

Mechanical shear degradation of polyisobutylene, polystyrene, poly(vinyl chloride), poly(methyl methacrylate), poly(decyl methacrylate), poly(methyl acrylate), and 1,4‐polybutadiene in dilute solutions of tetrahydrofuran (THF) are studied under turbulent flow conditions through a capillary, in order to study the effect of the chemical constitution on shear degradation. In addition the influence of solvent quality on shear degradation is investigated. The changes of the molecular weight distribution curves were followed by gel permeation chromatography (GPC), in order to determine the degradation constants ki for the corresponding molecular weight distribution fractions M̄i. GPC calibration via the concept of universal calibration, Mark‐Houwink relations for polyisobutylene, poly(methyl methacrylate), poly(methyl acrylate), 1,4‐polybutadiene, and poly(dimethylsiloxane) in THF as solvent had to be established for this purpose. Substantial differences in the rate constants ki were observed as a function of M̄i, whereas a master curve resulted for all polymers except 1,4‐polybutadiene when ki was plotted against the number of main chain carbon atoms n̄i for each molecular weight M̄i. From this the shear degradation of CC single bond polymers can be represented by ki = C · n̄, C being independent of the chemical nature of the CC single bond polymer, and a varying from 1,7 to 2,6. This means that in addition to the shape of the deformed macromolecule to be degraded not only its hydrodynamic volume (in rest) but also its chain length plays an important role. As to the influence of solvent quality, the degradation constants were found to increase with decreasing solvating power of the solvent. Mechanical shear degradation of the type discussed here takes place in drag reduction by polymers.
Polymer conformation and NMR chemical shifts, 51H and 13C NMR spectra of poly(methyl methacrylate)
Authors: Koinuma Hideomi , Sato Kota , Hirai Hidefumi
Published: April 2003

Tacticity‐dependent splittings observed in 1H and 13C NMR spectra of poly(methyl methacrylate) are elucidated by a theoretical procedure which consists of conformational analysis of the polymer chain and shielding calculation. The conformation is analyzed by the statistical mechanical method combined with the force field energy calculation on the dyad sequence models. As significant shielding factors, diamagnetic, anisotropic, and electrostatic terms are taken into account for the chemical shifts of 1H NMR, while paramagnetic, diamagnetic, and anistropic terms are considered for 13C NMR. The calculation is used to assing the α‐methyl proton, methoxyl proton, methylene proton, quaternary carbon, methylene carbon, α‐methyl carbon, carbonyl carbon, and methoxyl carbon peaks split due to dyad and triad cotacticities. The results are generally consistent with the observed spectra. Especially, the calculated splitting widths are in quantitative agreement with the observed splittings of the methoxyl and α‐methyl protons resonances as well as of the carbonyl and α‐methyl carbons resonances. Effects of temperature and stereoregularity on the spectra are also discussed.
Kinetic dialysis as a method for determining mixed micelle composition
Authors: Lake Mathew
Published: April 2003

A new method for the determination of the cmc using a dialysis technique which allows monomeric species to diffuse through but not micelles has been applied for determining the mixed micelle composition. The method is based on determining the amount of surfactant that diffuses through at two different times which allows for the calculation of the cmc by use of the appropriate equation. This method requires the preparation of only one concentration of solution and lends itself particularly well to the determination of the composition of mixed micelles.