bluuebunny/crossref_metadata_2025 huggingface dataset:
Nuclear magnetic resonance in a swollen polycarbonate. Fine structure of 1H NMR line
Authors: Tekely Piotr , Turska Eligia
Published: April 2003

Several components have been found to be present in the 1H NMR absorption line in polycarbonate (poly(oxy‐1,4‐phenyleneisopropylidene‐1,4‐phenyleneoxycarbonyl)), swollen in carbon tetrachloride. The α‐component, in the form of a Gaussian function is due to polymer chains present in areas with considerable degree of order. The intermediate β‐component can be fitted with good accuracy by the calculated spectrum, by treating the magnetic dipole‐dipole interaction as a perturbation of the proton two‐spin system. The effect of second neighbours gives a finite width to components of that line. Such a type of fine structure determines with good accuracy the distance between two protons in the ortho‐position in the phenyl ring executing some specific motions. Such phenyl rings can be present in tie‐molecules of limited mobility performing a conformational reorientation motion. The γ‐component is due to the micro‐Brownian motion of polymer chains present in the system and also to lower molecular weight fractions of the polymer. This component can be generally described by an appropriate Lorentz function.
Molecular motion in solid polyethylene as studied by 2D wide line NMR spectroscopy
Authors: Hentschel Dietmar , Sillescu Hans , Spiess Hans Wolfgang
Published: April 2003

2D NMR spectra have been measured at variable temperatures between −100°C and +110°C in a sample of melt crystallized deuterated polyethylene (PE). The line shape could be decomposed into a central part originating from deuterons in the amorphous regions and outer parts from crystalline regions of PE. The “NMR crystallinity” determined from this separation was 72% in agreement with the X‐ray crystallinity of 74%. Changes of the crystalline NMR line shape were interperted in terms of oscillations around the chain axis, the r.m.s. oscillation amplitude varying from 5° at 40°C to 12° at 110°C. The central part of the NMR line shape indicates the existence of a “narrow” and a “medium” component due to different motional processes in the amorphous regions.
Composés modèles pour étudier la synthèse de polyesters insaturés
Authors: Fradet Alain , Brigodiot Maryvonne , Maréchal Ernest
Published: April 2003

In order to study the side reactions occuring during the synthesis of unsaturated polyesters, several 2‐hydroxypropyl esters were synthesized by reduction of the corresponding acetylmethyl esters 1a–i. It was found that on heating they are partly isomerized to the 1‐methyl‐2‐hydroxyethyl esters. The extent of isomerization was determined at various temperatures by NMR spectroscopy, both in solution and in bulk. An analysis of the NMR spectra is given and a mechanism of the isomerization is suggested.
15N NMR spectroscopy, 17. Stereospecificity of the polymerization of D,L‐alanine‐NCA and D,L‐valine‐NCA
Authors: Kricheldorf Hans R. , Hull William E.
Published: April 2003

D,L‐Alanine‐NCA containing 1,5% 15N and D,L‐Valine‐NCA containing 2,4% 15N, were synthesized and polymerized under various conditions. 36,48 MHz 15N NMR spectra of the resulting poly(D,L‐amino acid)s were measured in trifluoroacetic acid, and the peak for the isotactic triad in each polymer was assigned by comparison with other alanine‐ and valine containing polypeptides. In the case of D,L‐alanine‐NCA the formation of isotactic blocks was favored, when the “activated monomer mechanism” was operating. In the case of D,L‐valine‐NCA, however, syndiotactic blocks were predominantly formed under the same reaction conditions. The initiation with primary amines results in almost atactic sequences. A helical secondary structure of the growing peptide chain is found to be an unnecessary condition for the stereospecificity of a NCA polymerization. The synthesis of Boc‐D,L‐Ala‐D,L‐Ala‐OMe from tert‐butoxycarbonyl‐D,L‐alanine and D,L‐alanine methyl ester was carried out under various conditions, and the stereospecifity was investigated by means of natural abundance 15N NMR spectra. The results are discussed with respect to the polymerization of D,L‐alanine‐NCA and D,L‐valine‐NCA.
Radical polymerization of methacrylic acid in the presence of poly(4‐vinylpyridine) in methanol
Authors: Fujimori Kiyohisa
Published: April 2003

The rate of radical polymerization of methacrylic acid (MA) was found enhanced in the presence of poly(4‐vinylpyridine) (P4VP) of various molecular weights (M̄η) in methanol. The rate maximum shifted from 1 : 1 mole ratio of [P4VP]/[MA], based on the repeating units, to a larger polymer‐monomer ratio and also the rate enhancement was smaller, when P4VP of smaller M̄η was used. The overall energy of activation was 36,1 and 60,7 kJ/mol in the presence and absence of P4VP, respectively. The M̄η of poly(methacrylic acid) (PMA) prepared with P4VP was about 10 times larger than the M̄η of PMA prepared without P4VP.
Synthesis of oligopeptides by copolymerization of aminoacetonitrile and various aminonitriles with basic catalysts
Authors: Ree Keiu , Minoura Yuji
Published: April 2003

The copolymerizations of aminoacetonitrile (AAN) with α‐aminopropionitrile (α‐APN), α‐aminoisovaleronitrile (α‐AVN), α‐aminoisocapronitrile (α‐ACN), and N‐methylaminoacetonitrile (MAAN) were carried out to obtain co‐oligoamidines by using basic catalysts such as barium sec‐butoxide ((s‐BuO)2Ba) at 100°C in dioxane. The resulting co‐oligoamidines were converted into co‐oligopeptides by hydrolysis. The rate of the homopolymerization of aminonitriles decreased in the following order: AAN>α‐APN>MAAN>α‐AVN>α‐ACN. From the composition curves in the copolymerizations, the reactivity of AAN with respect to other aminonitriles was the following: AAN‐AAN>AAN‐α‐APN>AAN‐MAAN>AAN‐α‐AVN>AAN‐α‐ACN.
Copolymerization of carbon dioxide with propylene oxide in the presence of catalysts based on alkylmetal compounds and pyrogallol
Authors: Rokicki Andrzej , Kuran Witold
Published: April 2003

Carbon dioxide was copolymerized with propylene oxide (PO, 2‐methyloxirane) in the presence of a catalyst system based on alkylmetal compounds (MtRn, Mt = Zn, Cd, Al) and pyrogallol (PG) at mole ratios 1:1, 2:1, and 3:1, respectively. The reaction was found to produce an alternating copolymer poly(propylene carbonate), [poly(oxycarbonyloxypropylene)], using Zn and Cd containing catalysts and non‐alternating copolymers with Al containing catalysts. For the system ZnR2/PG (mole ratio 2 : 1), the most active system, the influence of substituents R at the zinc atom, as well as effects of solvents and complexing agents on the copolymer yield and intrinsic viscosity were investigated. The results are discussed in terms of an anionic coordinative copolymerization mechanism.
Kinetic evidence for the mechanistic difference in the aqueous polymerization of acrylonitrile
Authors: Hariharan S. S. , Maruthamuthu Meenakshi
Published: April 2003

Kinetic evidence indicated two different mechanistic pathways in the polymerization of acrylonitrile initiated by peroxodiphosphate‐vanadyl ion redox system in aqueous solution depending upon the concentration of the reducing metal ion employed. The mechanistic difference lies in the termination reaction, exclusively mutual termination occurring in the concentration range [VO2+]=2,5·10−3 to 5·10−3 mol·dm−3 and exclusively linear termination taking place in the concentration range [VO2+] =10−2 to 25·10−3 mol·dm−3.
Über die lichtstreuergebnisse in polystyrol‐lösungen, 1. Gegenüberstellung von theorie und experiment
Authors: Woliński Leszek , Witkowski Konrad , Turzyński Zbigniew
Published: April 2003

From theoretically and experimentally obtained light scattering cross sections of some polystyrene solutions and the discrepancy between theory and experiment the question of correlated fluctuations of the components of the scattering tensor δεik is discussed. It is found that this discrepancy can be explained only in part by the consideration of the intermolecular interference effects and the supposed change of the scattering cross section of the solvent in the solution.
Die beschreibung von radikalischen polymerisationen durch integrale beziehungen
Authors: Stickler Manfred
Published: April 2003

Integral equations are given for the kinetic analysis of several free‐radical polymerization schemes. These relationships combine conversion and reaction time as variables directly accessible by experiment. In this way is obtained a higher accuracy than with the usual differential treatment and a deeper quantitative insight into individual reaction steps is possible. A modified Mayo equation is derived which takes into account monomer consumption and initiator decomposition and which, in the case of a polymerization with primary radical termination, also enables the estimation of the ratio disproportionation/combination solely by time‐conversion and molecular weight data.
Mechanismus der photopolymerisation des styrols, 2. Zur photochemie und photokinetik der intermediären photo‐(4π + 2π)‐addukte des styrols
Authors: Kauffmann Harald Friedrich
Published: April 2003

The unsensitized photoinitiation of styrene polymerization is accompanied by the formation of some typical oligomeric key substances, which are indicative of two 4π + 2π‐photo‐intermediates (I), viz. 1‐phenyl‐1,2,3,8a‐tetrahydronaphthalene (1) and 2‐phenyl‐1,2,3,8a‐tetrahydronaphthalene (1′). Owing to the very different absorption coefficients of monomer and I, formation and consumption and, therefore, the photo stationary concentration of I exhibits a pronounced dependence on the wavelength λe of the light used for irradiation. Under conditions, where the exciting light is not homogeneously but totally absorbed in the system (λe = 291 nm, corresponding to the 0–0 band of the lowest 1Lb←1A transition in styrene), the intermediates I can be enriched to such an extent, that they are detectable not only by UV‐absorption (310⩽/nmλ/nm ⩽ 360) but also—with the aid of a special high vacuum technique—by 1H NMR spectroscopy, which gives unambiguous proof for the molecular structure suggested for I. Moreover, the photochemistry, the photokinetics and the photophysical behaviour of I were investigated in detail. In the absence of any fluorescence (φ < 10−4) of the intermediate the overall quantum yield for consumption was found to be φ–1 = 1. It is shown, that the photo‐retro‐Diels‐Alder process is the dominating reaction (φ2M = 0,94) and the 1,3‐H‐sigmatropic rearrangement does not contribute more than φPhT⩽0,06. Together with the mean natural molar absorption coefficients φI = 18400 dm3·mol−1·cm−1 for λ = 313 nm and φI = 7300 dm3·mol−1·cm−1 for λ = 335 nm the photostationary concentration [I]∞ is calculated to range from [I]∞ = 8,7.10−6 mol. dm−3 at λe = 313 nm to [I]∞ = 1,2.10−6 mol.dm−3 at λe = 335 nm, which proved to be independent of the intensity of the incident light J0.
Novel butadiene‐isobutene copolymers obtained by means of coordination catalysts: Synthesis and physico‐chemical characterization
Authors: Priola A. , Corno C. , Ferraris G. , Cesca S.
Published: April 2003

The synthesis of novel butadiene (B)‐isobutene (I) copolymers, prepared with coordination catalysts, is reported and discussed. The best results were obtained by using at −40°C ternary systems, based on TiCl4, (i‐C4H9)3Al or (i‐C4H9)2AlH, and benzophenone or acetophenone, previously aged at −78 °C. The formation of the novel B–I copolymers was accompanied by polybutadiene (cis‐ and trans‐1,4‐units were prevalent) and, sometimes by cationic I–B copolymer. The new copolymers, after isolation, underwent thorough spectroscopic investigations. IR analysis yielded the microstructure of B units: trans‐1,4=55%, cis‐1,4=31%, and 1,2=14%. 1H NMR spectroscopy showed that I unit is present only in alternating triad BIB and ruled out the presence of any I homosequence. The study, by 13C NMR, of both the original and hydrogenated copolymer evidenced that only trans‐1,4‐B is linked to I units and hence the copolymer structure is described by IBI and IBnI (where n≥2) sequences. A copolymer containing 30% of I showed the following mole fractions of triads centered on B: FIBI=0,158; FBBI+IBB=0,382; and FBBB=0,462. The mechanistic implications of the copolymer structure are discussed.
Thermal analysis of oxidized poly(acrylonitrile‐co‐methyl methacrylate)
Authors: Radhakrishnan Ganga , Nagabhushanam T. , Joseph K. T. , Santappa M.
Published: April 2003

Poly(acrylonitrile‐co‐methyl methacrylate) films were oxidized in an air oven and in an oxidation chamber at temperatures of 80 to 200°C. Differential thermal analysis of these oxidized films showed that the exothermic peaks increased with increasing oxidation temperature. The change of viscosity, the insolubility in dimethylformamide and IR analyses indicate both intramolecular and intermolecular reactions.
Die thermische polymerisation von methylmethacrylat, 2. Bildung des ungesättigten dimeren
Authors: Stickler Manfred , Meyerhoff Günther
Published: April 2003

The spontaneous thermal polymerization of methyl methacrylate (MMA) is accompanied by the production of serveral oligomers among which a linear unsaturated dimerH‐1(dimethyl 1‐hexene‐2,5‐dicarboxylate) is predominant. The reaction kinetics of this dimer formation was investigated in bulk and in solution. The temperature dependence of the second order dimerization constant was determined asReaction mechanisms for the thermal dimer formation of MMA are discussed.
Characterisation of poly(acrylamide) in solution
Authors: Klein Joachim , Conrad Klaus‐Dieter
Published: April 2003

Using a set of laboratory poly(acrylamide) samples in the molecular weight region M̄w = 5.105 to M̄w = 6.106 the following relations have been established, the polymer concentration c given in g/cm3:

([η], intrinsic viscosity; s0, sedimentation constant)
Mainly based on light scattering experiments a more detailed description on molecular dimensions and solution structure of PAAm/H2O and PAAm/ethylene glycol systems is given. In both systems the relation a = 3v − 1 (a and v being the exponents of the intrinsic viscosity — and root‐means‐square end‐to‐end distance — molecular weight functions) holds.
Polymer conformation and NMR chemical shifts, 1. 1H NMR spectrum of alternating methyl methacrylate‐styrene copolymer
Authors: Koinuma Hideomi , Tanabe Tsuneaki , Hirai Hidefumi
Published: April 2003

NMR chemical shifts of the methoxyl and α‐methyl protons in the alternating methyl methacrylate‐styrene copolymer are calculated by taking into account the contributions of the diamagnetic shielding and the magnetic anisotropy effect of the benzene rings in styrene units. The conformational probabilities of the copolymer chain are calculated according to Flory's matrix method. It is deduced from the calculation that NMR should occur at higher field for the methoxyl and at lower field for the α‐methyl protons of the methyl methacrylate unit in meso configuration with an adjacent styrene unit (regarding the methoxycarbonyl and phenyl groups) than for the corresponding protons in the unit of racemic configuration. Further, the differences between the chemical shifts for these protons in meso and racemic dyads are nearly equivalent to the differences in chemical shifts between two adjacent peaks of the observed triplet spectra. This result indicates that the spectral assignment based on a theoretical calculation is quite consistent with the one made by a conventional simulation method: from the lower magnetic field, peaks of cosyndiotactic, coheterotactic, and coisotactic triads appear in this order for the methoxyl protons and in the opposite order for the α‐methyl protons. Magnetic anisotropy effect contributes to these tacticity‐dependent chemical shifts to a far greater extent than diamagnetic shielding. The variation of the chemical shifts due to measuring temperature, probability of isotactic addition, and interactions between groups more than five bonds apart is also discussed.
The solid‐state polymerization of some bis(arylsulfonate) esters of 2,4‐hexadiyne‐1,6‐diol
Authors: Ando David J. , Bloor David , Hubble Christopher L. , Williams Richard L.
Published: April 2003

Existing evidence suggests that the solid‐state polymerization of disubstituted diacetylenes is controlled by (a) the packing of the monomeric units in the crystal lattice, and (b) the elastic strain which is present in partially polymerized crystals. To investigate these ideas further, a number of closely related bis(arylsulfonate) derivatives of 2,4‐hexadiyne‐1,6‐diol, analogous materials to the extensively investigated bis(p‐toluenesulfonate) ester of this diol, have been synthesized, and their solid‐state reactivity studied. Topochemical polymerization was observed only for those compounds with benzenesulfonate and p‐methoxybenzenesulfonate substituents. In the case of the latter, structurally different reactive and unreactive crystalline modifications were obtained. Polymerization kinetics for the reactive modification differ strikingly from those of the p‐toluenesulfonate compound, despite the fact that the initial elastic strains in the two materials appear comparable.
Polymerization of propylene with γ‐Al2O3‐ or SiO2‐supported titanium tetrachloride catalyst
Authors: Soga Kazuo , Izumi Katsuyuki , Terano Minoru , Ikeda Sakuji
Published: April 2003

The preparation of γ‐Al2O3‐ and SiO2‐supported titanium tetrachloride catalysts for the polymerization of propylene is described. The ESR spectra of these products, measured at −196°C, display broad signals with g‐values of 1,942 and 1,952 in the cases of γ‐Al2O3 and SiO2, respectively, which are assignable to Ti(III) species. The concentration of the Ti(III) species depends strongly upon the conditions of treatment. With these products as catalysts the polymerization of propylene takes place at 40 −75°C in the absence of any activator. The polymerization activity significantly depends upon the conditions of catalyst treatment, but it is approximately proportional to the concentration of the Ti(III) species. The molecular weight and the isotacticity of the resulting polymer remain almost unchanged. These results lead to the conclusion that Ti(III) is the active species in these catalysts.
The initiation of polymerisations by aluminium halides
Authors: Grattan David W. , Plesch Peter H.
Published: April 2003

The polymerisation of isobutylene by aluminium chloride and bromide in corresponding alkyl halide solution was studied by conductivity measurements and radio‐tracer techniques in high‐vacuum apparatus. Some of the reaction mixtures were killed with tritiated water. The conductivity changes during and after polymerisation and the unexchangeable tritium in the polymers support the theory that initiation is by addition of AlX to the double bond of the monomer with consequent formation of a carbenium ion which then propagates. Subsidiary experiments with styrene and 2,5‐norbornadiene and with a saturated hydrocarbon confirmed our conclusions. Contrary to accepted views, we found tertiary carbenium tetrahaloaluminates to be stable electrolytes in our very pure alkyl halide solvents. The very slow addition of isobutylene to solutions of aluminium halide in alkyl halide reduced their conductivity markedly and produced non‐reacting mixtures from which the monomer but no polymer could be recovered. This is shown to prove the long suspected complexing of isobutylene with aluminium halide and rules out all theories of initiation based on interaction of initiator molecules with monomer. It is shown that our theories can explain most features of the polymerisations; our results are compared with those of others.
Amorceurs radicalaires fonctionnels, 1. Acides tert‐butyldioxycarbonylbenzoïques
Authors: Ladousse Alain , Blavin Florence , Ducasse Yves , Filliatre Claude , Maillard Bernard , Villenave Jean‐Jacques
Published: April 2003

Among the methods to introduce functional groups in macromolecular compounds, the initiation of free radical polymerization by functional peroxyesters was investigated. m‐ and p‐tert‐butyldioxycarbonylbenzoic acids (3 and 8) were synthetized and their properties were studied. Differential scanning enthalpimetric study of the thermolysis kinetics of 3 and 8 led to the conclusion that these compounds are a little more stable than O,O‐tert‐butyl hydrogen monoperoxyphthalate (1). Thus, they could be applied under similar conditions. Solution and bulk polymerizations of styrene initiated by 3 or 8 were found to be efficient methods to obtain polystyrene substituted by carboxylic functions.
Synthesis and mesomorphic structures of new amphipathic liposaccharides
Authors: Douy André , Gervais Monique , Gallot Bernard
Published: April 2003

Amphipathic liposaccharides were synthesized by condensation of glyco‐amino acid Oβ of Ovomucoid with fatty acids containing 8 to 24 carbon atoms. Condensation was achieved by reaction of the carboxyl group of the acid (via acid chloride or O‐acylisourea as active ester) with the amino group of the asparagine residue in the glyco‐amino acid. X‐ray diffraction showed that liposaccharides exhibit in the dry state and in concentrated water solution a hexagonal structure. In this structure, long and parallel cylinders formed by the hydrophobic paraffinic chains of liposaccharides are arranged in a two dimensional hexagonal array while hydrophilic carbohydrate chains and water fill the space between the cylinders. Freeze fracture electron microscopy allowed the visualization of the hexagonal structure. The influence of the water content and of the length of the paraffinic chains on the periodic structure of the amphipathic liposaccharides was analyzed.
Kinetically controlled formation of macrocyclic oligomers in the ring‐opening polymerization
Authors: Matyjaszewski Krzysztof , Zieliński Marek , Kubisa Przemysław , Słomkowski Stanisław , Chojnowski Julian , Penczek Stanisław
Published: April 2003

Kinetic schemes are solved for polymerization systems involving competition between linear growth and cyclisation by back‐biting to an optional chain unit and/or to the last unit (end‐to‐end ring closure). A fast reaction of a growing centre with an end group may lead to a situation, called here “kinetic enhancement in macrorings”, in which the transient concentration of cyclics formed in polymerization system exceeds their equilibrium concentration. Sometimes, a peculiar kinetics may be observed in which propagation proceeds on linear active macromolecules, but the polymerization leads almost exclusively to the cyclic products. On the other hand, fast propagation due to a high reactivity of monomer may lead to kinetic reduction of macrorings. Several situations are considered with examples taken from cationic polymerization of cyclic acetals and siloxanes (kinetic enhancement) or anionic polymerization of ϵ‐caprolactone (kinetic reduction). Kinetic schemes are numerically solved by computer for some arbitrarily assumed rate constants. This is the first paper of a series aiming to relate the kinetically controlled concentration of macrorings to the polymerization mechanism and the numerical values of the rate constants.
Microneck formation in polymer single crystals
Authors: Jones Janice Breedon , Geil Phillip H.
Published: April 2003

Electron microscopy has been used to investigate the deformation by micronecking in single crystals of polyoxymethylene (POM), poly(4‐methyl‐1‐pentene) (P4M1P), and poly[3,3‐bis‐(chloromethyl)oxacyclobutane] (BCMO). When drawn on Mylar, all three polymers form micronecks bridged by microfibrils pulled from the crystal. The results of this study indicate that there is a region approximately 200 Å wide along the microneck edge that has properties different from those of the rest of the crystal. This difference appears as a change in the character of the gold particles along the microneck edges in crystals of all three polymers decorated with gold after stretch and as a gold‐free area along the edges in crystals decorated before stretch. In P4M1P and BCMO vertically shadowed with platinum after stretch, a lighter region was often seen at the edge that seemed to be due to a local lack of platinum. POM crystals subjected to any of the shadowing techniques used often had definite darkening along the edges of the micronecks which seemed to be due to decoration by residual poly(acrylic acid) used in preparation.
Orientierung und Bewegungsverhalten von Fluoreszenzsonden in nichtkristallinen Bereichen verstreckter Polyethylenfolien
Authors: Fuhrmann Jürgen , Hennecke Manfred
Published: April 2003

Investigations of molecular orientation and mobility within non‐crystalline regions of semicrystalline polymers yield different results depending on the experimental method used. Starting from criteria classifying the measured specific polymer property, the polarized fluorescence method is applied to investigate low density polyethylene during drawing. The measured orientation factors coincide with results acquired by other methods if the geometry of the fluorescent probe and the type of indication within the non‐crystalline regions are considered. Fluorescent probes, the quantum yield of which is enhanced in deformed, rheologically effective microregions within the non‐crystalline regions during drawing, allow to separate between the orientation and cooperative mechanism of displacement in these microregions and the behaviour of the unaffected part of the non‐crystalline phase. The volume fraction of the rheologically effective microregions is estimated. Fluorescent probes yield polymer informations, which can be understood as a result of averaging the orientation and mobility behaviour of the adjacent polymer chains.
Molecular weight distributions, 3. Gamma‐ray induced polymerization of methyl methacrylate in the solid state
Authors: Mayer Gunter , Huang Robert Y. M.
Published: April 2003

The kinetics and molecular weight distributions of the gamma‐ray induced polymerization of methyl methacrylate were investigated in the solid state in the temperature range of −50°C to −65°C. The polymerization reaction rate was found to be proportional to the amount of polymer formed. The polymerization at the freezing point did not show any special features. With increasing dose rate the radiation efficiency was found to drop faster in the solid than in the liquid state. The molecular weights showed the same features as in the liquid state polymerization previously reported and increased with percent conversion. A kinetic model for the solid state polymerization is proposed. The molecular weight distribution function could be expressed by a log‐normal distribution.
Influence of composition on the melt crystallization of isotactic random propylene/1‐butene copolymers
Authors: Crispino Luigi , Martuscelli Ezio , Pracella Mariano
Published: April 2003

The influence of composition on the overall rate of isothermal crystallization of isotactic random propylene/1‐butene copolymers is investigated. At a constant crystallization temperature a small fraction of 1‐butene co‐units inserted along a polypropylene chain causes a drastic reduction in the overall rate of crystallization. Further it is found that for a given rate of crystallization it is possible to crystallize the isotactic polypropylene at lower crystallization temperature by adding along the chain a small amount of 1‐butene as comonomer. The equilibrium melting temperature, the surface free energy of folding, the enthalpy and the entropy of fusion decrease with increasing the contents of 1‐butene in the copolymer samples.
Transcrystallization of isotactic polypropylene
Authors: Goldfarb Louis
Published: April 2003

Transcrystallization of isotactic polypropylene — on polymer, metal, and metal‐oxide substrates — has been investigated by hot‐stage polarizing microscopy. A measure of the extent of transcrystallization was obtained from a count of spherulites per unit length of substrate, the linear nucleation density. Classical free‐energy models were used to interpret variations in linear nucleation densities, in which the degree of supercooling and surface‐energy expressions were emphasized.
Einige Modelluntersuchungen zur Chemie und Struktur von Polyvinylpyrrolidon‐Halogenophoren
Authors: Schenck Hans‐Uwe , Simak Peter , Hädicke Erich
Published: April 2003

Polyvinylpyrrolidone forms complexes with hydrogen halides (HX; X = Cl, Br, I) and halogen molecules (Y2; Y = Br, I). For these compounds a structure is proposed in which the proton is coordinated to the carbonyl groups of two pyrrolidone rings by strong hydrogen bonds. The \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm XY}_{\rm 2}^ \ominus $\end{document}‐anion is attached ionically to this complex cation. The structure of these complexes could be elucidated by comparative examination of the Lig2 · HX · Y2‐complexes of model compounds such as N,N‐dimethylacetamide, N‐alkyl‐2‐pyrrolidones (2a – d), and 1,3‐bis(2‐oxo‐1‐pyrrolidinyl)butane (3) and the analogous polyvinylpyrrolidone complexes. The structure of the (N‐methyl‐pyrrolidone)2 · HI3‐complex was examined by X‐ray structure analysis. In a similar way the potassium salts (Lig2 · KX · Y2) of the complex acids could be prepared from the ligands, potassium halides, and halogen molecules. Unlike the proton, the potassium cation appears to be only weakly attached to the carbonyl groups of the ligands.
Die Messung der Dichte zur Umsatzbestimmung bei Polymerisationsreaktionen, 1. Untersuchungen an dem System Styrol‐Polystyrol in Tetrahydrofuran
Authors: Trathnigg Bernd
Published: April 2003

It is shown, that the density of a dilute solution of styrene and polystyrene of known total concentration represents the composition with high accuracy. An equation relating the density of a solution to the extent of polymerization is derived. A density measuring device according to the mechanical oscillator method proves to be a sufficiently sensitive instrument for determining the conversion in polymerization solutions even of very low concentrations.
Cinétique de cristallisation de la gélatine en solution aqueuse. Influence des différents composés moléculaires
Authors: Godard Pierre , Biebuyck Jean‐Jacques , Barriat Paul‐André , Naveau Henry , Mercier Jean‐Pierre
Published: April 2003

The gelation kinetics of gelatin of various molecular structures and also of different molecular components is studied by polarimetry. The gelation phenomenon can be analyzed as a conventional crystallization process assuming predetermined primary nucleation and unidirectional growth. The study of gelation kinetics of the different fractions displayed important alterations induced by the manufacturing process on the molecular structure and on the number of nucleation sites.
A convenient synthesis of poly[sulfonylmethylene‐1,4‐phenylenemethylene] directly from sulfur dioxide
Authors: Soga Kazuo , Nagata Ko‐ichi , Hattori Iwakazu , Ikeda Sakuji
Published: April 2003

Poly[sulfonylmethylene‐1,4‐phenylenemethylene] (2) was obtained from 4‐chloromethylbenzyl chloride (1), potassium and sulfur dioxide by using 1,4,7,10,13,16‐hexaoxacyclooctadecane (18‐crown‐6‐ether) as catalyst. On the other hand, the reaction of 1, potassium and sulfur dioxide in the absence of 18‐crown‐6‐ether gave preferentially poly[1,4‐phenyleneethylene] (3) by the Wurtz reaction between 1 and potassium. A detailed study was carried out on these reactions.
Alternating copolymerization of cyclohexene oxide and sulfur dioxide
Authors: Soga Kazuo , Kiyohara Kazuto , Hattori Iwakazu , Ikeda Sakuji
Published: April 2003

Copolymerization of cyclohexene oxide (CHO) and sulfur dioxide (SO2) was conducted at 80°C by using a variety of catalysts both in the presence and absence of solvent. Aromatic tertiary amines such as pyridine gave an alternating copolymer of CHO and SO2 in the presence of solvents such as 1,2‐dimethoxyethane. The alternating copolymer obtained was a white thermoplastic which could readily be thermoformed. It was soluble in acetone and chloroform but insoluble in water and hexane. From the reaction of the equimolar mixture of CHO, SO2 and pyridine at 20°C, an 1 : 1 : 1 adduct of CHO, SO2 and pyridine (see formula 2) could be isolated. This adduct was confirmed to be the active species for the present copolymerization.
Thermodynamic studies on DNA‐dye complexes
Authors: Tanaka Shigeyuki , Baba Yoshihiro , Kagemoto Akihiro , Fujishiro Ryoichi
Published: April 2003

The interaction between DNA and dyes such as acridine orange (1), proflavine (2), and 3,8‐diamino‐5‐ethyl‐6‐phenylphenanthridinium bromide (3) were studied by means of the heat of mixing and UV spectra. From the results obtained, the thermodynamic quantities of DNA‐dye complexes were estimated. It is concluded that the intercalation process forms a more stable binding than the stacking process does. Further, in each process, ΔG of DNA‐2 and DNA‐3 systems is nearly equal to that of the DNA‐1 system, but their — ΔH and — ΔS values are higher than those of the DNA‐1 system. The stability of binding in DNA‐2 and DNA‐3 systems may be governed largely by ΔH, while in the DNA‐1 system ΔS may contribute largely to the stability of binding.
Donor acceptor interactions in polymeric systems, 5. A polyurethane with pendant carbazolyl groups
Authors: Tazuke Shigeo , Nagahara Hajime , Matsuyama Yujiro
Published: April 2003

A polyurethane having pendant carbazolyl groups separated by four methylene groups was prepared and the EDA complex formation with 2,4,7‐trinitrofluorenone (TNF) was studied in chloroform. EDA complexes of the polymer and the monomer model compound are spectroscopically indistinguishable. The formation constant (K) of the polymer complex is about equal to that of the monomer model compound in the oligomeric range whereas K increases with increasing molecular weight of the polymer. This trend of polymer effect is the same for the complex formation with other acceptors such as tetracyanoethylene (TCNE) and 1,3,5‐trinitrobenzene (TNB). The formation of the polymer complex is entropically favoured although the negative enthalpy change is larger for the monomer model compound. The reasons are discussed.
Polymerization of bicyclic acetals, 8. Cationic polymerization of 6,8‐dioxabicyclo[3.2.1]oct‐2‐ene
Authors: Okada Masahiko , Sumitomo Hiroshi , Kanie Masakazu , Komada Hajime
Published: April 2003

Poly(5,6‐dihydro‐2H‐pyran‐2,6‐diyloxymethylene) (6), a new polyacetal having a dihydropyran ring in its repeating unit was prepared by selective ring‐opening polymerization of 6,8‐dioxabicyclo[3.2.1]oct‐2‐ene (5) at temperatures between −60 and −90°C in dilute methylene chloride or toluene solutions using boron trifluoride etherate as initiator. The resulting polymers, having a number average molecular weight up to 1,5 · 104, melted at 110 – 130°C and decomposed at ≈ 170°C in air. The isotactic dyad content of the polymers, estimated by 13C NMR spectroscopy, was found to be in the range of 70 to 77 mole‐%, somewhat lower than that of its saturated analogue, poly(tetrahydropyran‐2,6‐diyloxymethylene), (2). The preferred formation of the isotactic sequence along the polymer chain is rationalized in terms of the enantiomer selection by the growing chain end control mechanism as previously proposed for the polymerization of 6,8‐dioxabicyclo[3.2.1]octane, (1).
On the molecular weight determination by vapour pressure osmometry, 1. Consideration of the calibration function
Authors: Marx‐Figini Marianne , Figini Rubén Victor
Published: April 2003

A detailed study on the calibration of vapour pressure osmometry (VPO) using thirteen different samples (eight of them polystyrenes) in a range of molecular weights up to 50 000 as solutes and chloroform, dichloromethane, ethyl methyl ketone, cyclohexane, and acetone as solvents is carried out. The results show that contrary to the commonly used calibration equation M = K · (ΔV/c), the relationship between the measuring result (ΔV/C)c=0 and molecular weight M obeys a function of the type M = K · (ΔV/c) in which the exponent a differs from 1. For each of the above mentioned solvents the values of K and a are determined. The limits of applicability of VPO with respect to polymers are discussed in view of these terms and recent theoretical considerations.
Long‐lived polymer radicals, 2. An ESR study on the reactions of the propagating polymer radicals of N‐methylacrylamide and N‐methylmethacrylamide with vinyl monomers at room temperature
Authors: Tanaka Hitoshi , Sato Tsuneyuki , Otsu Takayuki
Published: April 2003

Acrylamide (AAm), methacrylamide (MAm), N‐methylacrylamide (NMAAm) and N‐methylmethacrylamide (NMMAm) were found to yield long‐lived propagating polymer radicals in the photo‐sensitized polymerizations in 1,4‐dioxane or benzene. The concentration of poly(NMAAm) radicals reached 1.10−3 mol/l. Some post‐effect was observed at room temperature in the photo‐sensitized polymerization of AAm with di‐tert‐butyl peroxide in 1,4‐dioxane, while no post‐polymerization proceeded at room temperature in the polymerization of NMMAm in benzene. The reactions of poly(NMAAm) and poly(NMMAm) radicals with various vinyl monomers were found to produce long‐lived propagating polymer radicals of the second monomers at room temperature. Polymer radicals of non‐homopolymerizable monomers such as α‐methylstyrene and 1,1‐diphenylethylene were easily formed in such a block‐copolymerization matrix. The formation of the propagating polymer radicals of the vinyl monomers was investigated by means of ESR spectroscopy.
Polymerization of ethylene catalyzed by titanocene systems, 1. Catalytic systems Cp2TiEtCl/AlEtCl2 and Cp2TiEtCl/(AlEtCl2 + H2O)
Authors: Cihlář Jaroslav , Mejzlík Jiří , Hamřík Oldřich , Hudec Pavel , Majer Josef
Published: April 2003

The kinetics of the ethylene polymerization catalyzed by the Cp2TiEtCl/AlEtCl2 system in toluene were investigated. Hydrolysis of AlEtCl2 in benzene was studied and the resulting oxyaluminium compounds were used as cocatalysts together with Cp2TiEtCl as catalyst for ethylene polymerization. A strong enhancement of the cocatalytic activity for the formation of oxyaluminium compounds was observed, accompanied by an increase of molecular weight. The catalyst efficiencies were found to be rather high in both the Cp2TiEtCl/AlEtCl2 and the Cp2TiEtCl/(AlEtCl2 + H2O) system. Transfer reactions are suppressed under the applied experimental conditions, but termination reactions, leading to non‐stationary kinetic patterns, may be assumed for both systems.
Preparations and asymmetric, reducing abilities of chiral polymeric amine‐boranes
Authors: Yamashita Tetsushi , Mitsui Hitoshi , Watanabe Hiroyuki , Nakamura Nobuo
Published: April 2003

Polymeric amine‐boranes 2b, 4b, and 8c and their corresponding low‐molecular‐weight model compounds 3b, 5b, and 6b were obtained by reaction of chiral amines with diborane; these amines were poly(pyrrolidine‐1,2‐diylmethylene) (2a), poly(imino‐1‐isobutylethylene) (4a), poly{[1,2‐bis(4‐vinylphenyl)ethyl]amine} (8b), 1‐methylpyrrolidin‐2‐yl‐1‐pyrrolidinyl‐methane (3a), N1‐isopentyl‐N2‐methyl‐4‐methyl‐1,2‐pentanediamine (5a), and α‐phenylphenethylamine (6a). The polymeric amine‐boranes are white powders, stable to be kept for several weeks at room temperature, whereas the low‐molecular‐weight model compounds are less stable syrup‐like materials. The reduction of acetophenone to optically active 1‐phenylethanol was carried out with the chiral amine‐boranes in the presence of boron trifluoride etherate at various reaction temperatures. The product resulting from the reduction with 8c can easily be separated from the reaction mixture by filtration. The optical yield of the product obtained with 8c was 8,9% at −40°C. The highest optical yield (25,3%) was obtained with α‐phenylphenethylamineborane 6b at 0°C.
A study of the origins of colour in alkali degraded polyacrylonitrile and polymethacrylonitrile, 3. Computer predicted structures for the degradation products
Authors: Batty Norman S. , Guthrie James T.
Published: April 2003

Possible structures for the products obtained on alkali treatment of polyacrylonitrile are considered. The Pariser‐Parr‐Pople (PPP) self‐consistent field method was applied to give λmax values for the proposed structures. The colouration of PAN by alkali was found to occur in two stages. There is a temporary colour which is destroyed by acids and a permanent colour which is not. The colour of alkali treated PMAN is entirely destroyed by acids. This temporary colouration may arise from n → π* transitions. We believe that the permanent colour of degraded PAN arises from π→π* transitions via a free radical activition mechanism and use of molecular oxygen.
Catalytic activity of polynuclear manganese‐thiolato complexes for oxidative polymerization of 2,6‐dimethylphenol
Authors: Kaneko Masao , Yamada Akira
Published: April 2003

Chelating thiolato‐manganese complexes of 1,2‐dimercaptoethane (DME), 3,4‐dimercaptotoluene (DMT), cystein (Cys), β‐mercaptoethyl alcohol (ME), β‐mercaptoethylamine (MEA), and mercaptoacetic acid (MAA) showed high activity for the oxidative polymerization of 2,6‐dimethylphenol (DMP) as heterogeneous catalysts. The complexes caused only CO coupling to give poly[oxy(2,6‐dimethyl‐1,4‐phenylene)] selectively. From the reaction in the absence of oxygen it was concluded that oxygen acts as electron‐accepting ligand. The much higher activity of DMT complex, compared with that of DME complex, was considered to be due to the π‐accepting character of the ligand. The MEA complex which showed especially strong spin‐spin interaction in the ESR spectrum exhibited also high activity.
The partial specific volume of lysozyme chloride in water under pressure
Authors: Chiri Rose‐Marie , Abétino François , Baret Jean‐François , Catella Robert , François Jeanne , Dayantis Jean
Published: April 2003

The apparent specific volume ν of lysozyme chloride dissolved in pure water has been measured from 1 to 4000 bar using the Adams‐Gibson‐Anderson method of trapped mercury. A parametric expression for ν as a function of solute weight fraction X2 is given for the various pressures at which the experiments have been performed. This parametric expression is valid when the densities of the solutions at atmospheric pressure and their compression at pressure P can be considered to be linear functions of the solute weight fraction X2. The relation between ν and the partial specific ν2 is discussed and it is shown that within the range of concentrations considered and given the precision of the experiments under pressure, the two quantities are indistinguishable.
Polymerization of tetrahydrofuran by bifunctional cationic initiators: Terephthaloyl perchlorate
Authors: Alamo Rufina , Guzmán Julio , Fatou José G.
Published: April 2003

The kinetics and mechanism of the polymerization of tetrahydrofuran with terephthaloyl perchlorate in methylene chloride or cyclohexane were analyzed. This polymerization produces dicationically active polymers and takes place without induction period. Propagation in both solvents proceeds as a reaction being first order in monomer, and it changes with the polarity of the solvent because ionic and covalent species take part with different growing rates. The macroester mole fractions in cyclohexane and methylene chloride are 0,99 and 0,86, respectively.
Reduction of nitrogen coordinated to polymer bound chlorobis(η‐cyclopentadienyl)titanium
Authors: Koide Mikio , Tsuchida Eishun , Kurimura Yoshimi
Published: April 2003

Dinitrogen complexes of poly{1‐[4‐(chlorodicyclopentadienyltitanio)phenyl]ethylene‐co‐1‐(4‐bromophenyl)ethylene‐co‐1‐phenylethylene} (2a – e) were synthesized. It was found that there is an equilibrium between the mononuclear and binuclear complex. Ammonia was formed after hydrolysis of the reaction mixtures resulting from 2a – e and lithium naphthalide in a nitrogen atmosphere. The yield of ammonia increased extremely with decreasing content of titanocene in the polymer. In the system with 2a 41,7 mol ammonia were formed per 1 mol of titanium.
Über den thermischen Abbau des Polypivalolactons in cyclische Oligomere
Authors: Lüderwald Ingo , Sauer Werner
Published: April 2003

Pyrolysis‐mass spectra have indicated that polypivalolactone degrades thermally into cyclic oligomers. To confirm this degradation behaviour polypivalolactone was pyrolyzed in a glass apparatus and the degradation products trapped at 0°C. After separation by preparative gel chromatography the isolated fractions could be identified as cyclic trimers to undecamers of pivalolactone and characterized by independent analytical methods. With the exception of the cyclic heptamer all odd oligomers have a lower melting point and enthalpy than the next bigger and smaller even cyclics.
Lamellar crystalline structure of block copolymers with an amorphous and a crystallizable block: Effect of the nature of the crystallizable block
Authors: Gervais Monique , Gallot Bernard , Jérome Robert , Teyssié Philippe
Published: April 2003

Block copolymers of styrene and ethylene oxide (SEO) and of styrene and ε‐caprolactone (SCL), in the dry state and in the presence of a preferential solvent of the amorphous block, exhibit a lamellar crystalline structure at temperatures below ≈50°C. In this structure the crystallized chains are folded in two superposed layers. To investigate the effect of the nature of the crystallizable block, two copolymers SEO and SCL of the same relative molecular mass and composition were studied by X‐ray diffraction and differential scanning calorimetry. It is established that the nature of the crystallizable block influences the crystallinity and the number of folds of the crystallized chains and the swelling of the amorphous polystyrene block.
Solid phase photoreduction of methylviologen on cellulose
Authors: Kaneko Masao , Yamada Akira
Published: April 2003

Methylviologen (1,1′‐dimethyl‐4,4′‐bipyridinium dichloride, MV2+) absorbed on cellulose paper can be reduced photochemically in solid phase. The ESR spectrum (singlet; g = 1,967, ΔHmsl = 13,5 gauss) shows the photochemical formation of its cation radical (MV•+). The MV•+ formed on cellulose is unusually stable against oxidation by oxygen. Photochemical formation and slow oxidation of MV•+ under air occur fairly reversibly. The concentration of MV•+ and the optical density (O.D.) at 620 nm show a linear relationship. The concentration of MV•+ at 1 O.D. corresponds to 1,07.10−8 spins/cm2 cellulose paper. The formation of carbonyl groups in MV2+/cellulose after irradiation indicates that cellulose acts as electron donor. The mechanism of the solid phase photoreduction is discussed in relation to the effect of other carbohydrates or inorganic materials as adsorbents.
Polymérisation anionique de l'acroléine, 2. Influence de la nature du contre‐ion et de la température sur la cinétique de la réaction
Authors: Gulino Danièle , Golé Jean , Pascault Jean Pierre
Published: April 2003

In tetrahydrofuran, with Na+ and Li+ as counter‐ions, the kinetic order of the anionic polymerization of acrolein is unity for monomer and for initiator. These results indicate that the living ends are not associated at the studied concentrations of initiator. The polymerization rate depends on the nature of the counter‐ion. Transfer reactions to monomer do not affect the polymerization rate but greatly change the molecular weights Mn of polyacroleins. The experimental M are much lower than the theoretical M. The propagation constants kpr and the transfer constant hm are determined using these experimental values of M. From these results, we can conclude that with Li+ as counter ion, transfer reactions are much more numerous than with Na+. Furthermore, the polymerization rate increases with temperature. The activation energies of the propagation (Ea,pr) and transfer reactions (Ea,t) can be determined separately. When the temperature increases the propagation reaction is promoted in comparison to the transfer reaction to monomer, and simultaneously transfer reactions to polymer take place. This last phenomenon restricts the upper value of the polymerization temperature.