bluuebunny/crossref_metadata_2025 huggingface dataset:
13C NMR study of the tacticity of poly(propylene oxide)s prepared by polymerization with α,β,γ,δ‐tetraphenylporphyrin/AlEt2Cl as initiator system: An example of first‐order markovian statistics in ring‐opening polymerization
Authors: Borgne Alain Le , Spassky Nicolas , Jun Chang Lim , Momtaz Ardéchir
Published: April 2003

Racemic and enantiomerically enriched poly(propylene oxide)s were prepared using α, β, γ, δ‐tetraphenylporphyrin/AlEt2Cl as initiator system. Triad tacticity of the polymers was analyzed by 13C NMR spectroscopy (62,89 MHz). A predominance of isotactic triads was observed in the case of the racemic polymer, corresponding to a non‐random distribution of configurational units in the polymer chain. A model correlating tacticity with enantiomeric excess of starting monomer in the case of a first‐order Markovian distribution was established. Good agreement between experimental results and calculated triad contents (according to the model previously described) was observed for enantiomerically enriched polymers. This indicates a steric control by the last unit of the growing chain end. The influence of the size of the substituent was examined for the case of poly(1,2‐epoxybutane). The origin of the chain‐end effect is discussed.
Modelization of the photocatalyzed oxidation of polyolefins, 3. Oxidation of model hydrocarbons with ZnO
Authors: Lacoste Jacques , Arnaud René , Singh Raj Pal , Lemaire Jacques
Published: April 2003

The present paper reports on analytical aspects of the ZnO photocatalyzed oxidation of linear and cyclic alkanes. Normal and branched hydrocarbons were examined as models in the photoageing of both polyethylene and polypropylene, respectively. IR, GC‐MS and chemical analyses confirm the formation of hydroxyl and carbonyl groups and ascertain the presence of γ‐lactones in the photooxidation of polyolefins. In the presence of ZnO as pigment, ketone groups accumulate and no acidic groups are observed. The formation of γ‐lactones is favoured in substituted aliphatic alkanes like 2,4‐dimethylpentane and 2,2,4‐trimethylpentane, i.e. in molecules where methyl groups are in β‐position of a tertiary carbon atom. A mechanism of the formation of γ‐lactones in photooxidation of both model alkanes and polyolefines is proposed.
2H NMR study of correlated spin‐lattice relaxation in solid polyelectrolyte complexes of poly(dimethyliminioalkylenes) (α,ω‐ionenes) and polystyrenesulfonate
Authors: Westermark Bertel , Spiess Hans Wolfgang
Published: April 2003

Spin‐lattice relaxation rates (1/T1) have been used to study the correlation between the molecular motions in the polyion components of polyelectrolyte complexes from poly(dimethyliminioalkylenes) (α,ω‐ionenes) and polystyrenesulfonate. The length of the alkyl chains in the α,ω‐ionenes has been varied studying the complexes with 3,3‐ionene, 6,6‐ionene, and 10,10‐ionene, respectively. In the latter, three different positions in the alkylene chains were deuterated selectively. The relaxation rate curves show that the more rigid polystyrenesulfonate component of the complexes is relaxed through the rapid large‐angle motions in the alkylene chains of the α,ω‐ionenes. In the complex with 10,10‐ionene coupling is stronger with the mobility of the CH2 groups adjacent to the quaternary ammonium ion.
Synthesis of polystyrene macromonomers for use in polycondensation reactions
Authors: Heitz Thomas , Höcker Hartwig
Published: April 2003

The preparation of aromatic macromonomers with hydroxyl functions was achieved by termination of living polystyrene (PSLi) upon addition of 2,5‐dimethoxybenzyl bromide (2) or 1,1‐bis(4‐methoxyphenyl)ethylene (16). Ether cleavage with boron tribromide resulted in the formation of the de‐protected macromonomers 15 and 17. Side reactions occurring in the functionalisation reaction with 2 were investigated by means of a respective model reaction. The formation of side products could be suppressed by reacting PSLi with 1,1‐diphenylethylene prior to functionalisation with 2. The macromonomers were characterized by GPC, UV, and FT‐IR spectroscopy.
Crosslinkable liquid‐crystalline combined main‐chain/side‐group polymers with low glass transition temperatures
Authors: Bualek Sauvarop , Zentel Rudolf
Published: April 2003

Crosslinkable and crosslinked liquid‐crystalline polymers with elastic properties were prepared from main‐chain and combined main‐chain/side‐group polymers. These polymers exhibit nematic, smectic A, and smectic C phases. Polymers of these types with azoxybenzene as mesogen do not crystallize upon cooling. As a consequence, the liquid‐crystalline phases are frozen in glassy around room temperature.
Characterization of cellulose nitrate with gel permeation chromatography ‐ low angle laser light scattering (GPC‐LALLS), GPC‐infrared, and membrane osmometry
Authors: Wirsén Anders
Published: April 2003

Cellulose nitrates with nitrogen contents in the range 11,2 to 13,3 mol‐% are characterized with gel permeation chromatography (GPC) using various detectors, membrane osmometry, static low angle laser light scattering (LALLS) and solution viscosity measurements. The molecular weight data from GPC‐LALLS are generally in good agreement with those obtained by static LALLS and membrane osmometry. GPC‐infrared is used to analyze the nitrogen content. These techniques are also used to characterize cellulose nitrate in propellants. A comparison between two different column packings in GPC‐LALLS analysis is integrated into this study.
Electron transfer from carbanionic salts to linear sequences of conjugated double bonds, 1. Mechanism of n doping of polyacetylene
Authors: Rudatsikira Alphonse , Mathis Claude , Francois Bernard
Published: April 2003

It is shown that the mechanism of polyacetylene (PA) reduction (or n “doping”) by alkaline carbanionic salts and butyllithium is a simple electron transfer without addition. In this reduction reaction the dicarbanionic dimer of 1,1‐diphenylethylene (DD2– Na2+) is quantitatively converted to 1,1‐diphenylethylene. The reduction by 3‐methyl‐1,1‐diphenylpentyllithium produces free radicals which deactivate in solution by coupling and disproportionation. But the strong dependence of the ratio of disproportionation to coupling of these radicals on solvent polarity is unusual: no coupling is observed in diethyl ether or pentane, while it is the most important reaction in THF. sec‐Butyllithium in pentane also reduces PA by a simple electron transfer process. The “doping” levels can be deduced accurately from the quantitive analysis of the by‐products by gas chromatography.
Composite model for the thermal expansivity of polymers
Authors: Biswas Prabir K. , Sengupta Shyamal , Basu Ashok N.
Published: April 2003

The thermal expansivity of semicrystalline polymers is interpreted within the framework of the composite model which has already been found useful in describing mechanical and optical properties as well as the thermal conductivity of a large number of polymers. The model assumes the polymers to be an aggregate of units composed of crystalline and amorphous phases. The thermal expansivities of the unit are calculated in terms of those of the constituents. In the undrawn state the units are distributed randomly, and the isotropic thermal expansivity of the bulk results. The development of strong anisotropy in thermal expansivity on drawing is explained in terms of preferred orientation of the units. The orientational changes on drawing have been directly calculated from the birefringence versus draw ratio data. The results of these investigations indicate that the present model is quite successful in interpreting thermal expansivity data for poly(oxymethylene) and poly(propylene) over the entire draw ratio and temperature range.
Polymeric bound porphyrins and their precursors, 7. Synthesis of water‐soluble, positively charged polymers with covalently bound moieties of porphyrin derivatives
Authors: Wöhrle Dieter , Krawczyk Gerhard , Paliuras Mihail
Published: April 2003

Positively charged polymers 6–13 containing covalently bound moieties of tetraphenylporphyrin (1), phthalocyanine 2 and naphthocyanine 3 were obtained by reaction of poly(chloromethylstyrene) with low‐molecular weight substituted porphyrins (1 b, 2 b, 2 d, 3 c) in the presence of triethylamine. The water‐soluble polymers contain moieties of one or of two or three different porphyrin derivatives.
Regioselectively modified stereoregular polysaccharides, 12. Synthesis of (1→6)‐α‐linked polysaccharides consisting of D‐glucose and 2,3,4‐tri‐O‐octadecyl‐D‐glucose units
Authors: Ichikawa Haruo , Kobayashi Kazukiyo , Sumitomo Hiroshi
Published: April 2003

By ring‐opening copolymerization of 1,6‐anhydro‐2,3,4‐tri‐O‐octadecyl‐β‐D‐glucopyranose (1) with 1,6‐anhydro‐2,3,4‐tri‐O‐benzyl‐β‐D‐glucopyranose (2) using phosphorus pentafluoride as initiator in dichloromethane at 0°C, stereoregular copolymers 3, with M̄n = 6 · 103 to 24 · 103 were obtained. For debenzylation of copolymers 3, either the reduction with sodium in liquid ammonia or radical bromination‐hydrolysis was applied, depending on solubility and copolymer composition. Poly[2,3,4‐tri‐O‐octadecyl‐α‐D‐glucopyranosyl‐(1→6)‐stat‐α‐D‐glucopyranosyl‐(1→6)] (4,) exhibits characteristic solution properties arising from its amphiphilic structure. Polysaccharide 4, with mole fractions of trioctadecylated unit (x) below 0,03, are water‐soluble and interact with magnesium 1‐anilino‐8‐naphthalenesulfonate (ANS) in water. The polysaccharide 4 (x = 0,29), which is soluble in chloroform, was found to solubilize an aqueous methyl orange solution in chloroform. Formation of micelles in water and reversed micelles in chloroform is suggested.
Propene polymerization with MgCl2 supported Ziegler catalysts: Activation by hydrogen and ethylene
Authors: Spitz Roger , Masson Patrick , Bobichon Charles , Guyot Alain
Published: April 2003

Complementary experiments confirm the recent findings that the rate of propene polymerization is temporary enhanced if a small amount of ethylene is introduced during the polymerization, normalizing after consumption of ethylene by copolymerization. In addition, the study of the sequence distribution of propene monomeric units in the copolymerization carried out under various conditions revealed that the activation by ethylene does not involve the propagation steps, but the re‐initiation after deactivation. A similar temporary activation effect was observed after the addition of small amounts of hydrogen. In this case, however, hydrogen is not consumed. Thus, the deactivation observed after the initial rate enhancement is due to another reason. The deactivation could be shown to be reversible after removal of the adsorbed hydrogen when either ethylene or hydrogen was added again to allow re‐initiation of the polymerization. One of the important reasons of the continuous decrease of the propene homopolymerization rate may be due to the fact, that, after a transfer step, the re‐initiation of polymerization does not take place spontaneously. Small amounts of ethylene or hydrogen allow the reinitiation to take place, at least for some kind of active sites.
New developments in star polymer synthesis. Star‐shaped polystyrenes and star‐block copolymers
Authors: Lutz Pierre , Rempp Paul
Published: April 2003

A new method for the synthesis of compact, multifunctional star‐shaped polystyrenes was designed. A plurifunctional metalorganic initiator is obtained upon reaction of potassium naphthalene with commercial divinylbenzene. The resulting polymeric “core” exhibits a number of metalorganic sites. In a subsequent step, these sites initiate the polymerization of styrene to yield a star‐shaped polymer. High numbers of branches can be obtained, thus rendering these molecules extremely compact. However, the major advantage of the “core first” method is that it allows functionalization of the branches at their outer end, thus providing the possibility of further reaction or selective adsorption. This “core first” method was also applied to the preparation of star‐block copolymers formed of a polystyrene block and a poly(ethylene oxide) block.
Configurational statistics of polymers obtained by ring‐opening polymerization of heterocyclic monomers
Authors: Sepulchre Maurice
Published: April 2003

A general reexamination of the configurational statistics of polymers obtained by ringopening polymerization of heterocyclic monomers is presented. The polymers under study involve one or two asymmetric centres in the main chain per monomeric unit. Sequence probabilities are calculated for Bernoullian, and first‐ and second‐order Markov propagation models. The analyses of two polymers [poly(styrene oxide) and poly(tert‐butyloxirane)] for which tacticity data are available in the literature are given as examples.
Polymeric phthalocyanines and their precursors, 14. Synthesis and analytical characterization of polymers from oxy‐ and arylenedioxy‐bridged diphthalonitriles
Authors: Wöhrle Dieter , Schulte Bernd
Published: April 2003

Phthalocyanine moieties containing polymers 3 a – e were prepared by the reaction of several oxy‐ and arylenedioxy‐bridged diphthalonitriles 2 a – e in the absence or the presence of metal salts or metals. The structure of the polymers was thoroughly discussed on the basis of their IR and UV/VIS spectra. According to the nitrile end groups determined by IR spectroscopy, the structurally uniform polymers consist of phthalocyanine moieties. Saponification of the nitrile end groups of 3 a – e leads to polymeric phthalocyanines with carboxylic acid end groups with a lower degree of annulation than that of the polymers before saponification. The low‐molecular‐weight phthalocyanines 5a, b were prepared as model compounds for the polymers.
Solid‐state 13C NMR studies of vulcanized elastomers, 4. Sulfur‐vulcanized polybutadiene
Authors: Zaper A. Marie , Koenig Jack L.
Published: April 2003

The sulfur vulcanization of cis‐1,4‐polybutadiene was studied by solid‐state 13C NMR spectroscopy. Polybutadiene is cured with several different formulations including sulfur and accelerators in order to determine the network structure of the resulting vulcanizates. Polysulfidic crosslinks bound to the methylene carbons of the polybutadiene repeating unit were observed in the rubber network. Cyclic sulfide structures were detected in the network structure in addition to cis‐to‐trans chain isomerization. Two different pulse sequences were used for the NMR experiments of the sulfur‐vulcanized cis‐polybutadiene. The gated high power decoupling NMR experiment reflects the mobile regions of the vulcanizate sample while the cross polarization pulse sequence reflects the regions of the sample which are inherently more rigid. The cross polarization spectra of the samples cured with high sulfur levels showed that a considerable amount of rigidity is found in the vulcanized cis‐polybutadiene network. It was also possible to obtain cross polarization spectra of the lightly crosslinked polybutadiene vulcanizates. This is in contrast to the NMR results of the vulcanized natural rubber systems which generally tended to have considerably more mobility.
Synthesis and characterization of styrene‐based polymer supports
Authors: Arshady Reza
Published: April 2003

A number of reactive styrene derivatives 3a – h was synthesized and copolymerized in suspension with styrene and divinylbenzene to produce beaded styrene‐based resins 5a – h, carrying bromo, methoxy, chloromethyl, hydroxymethyl, hydroxyethyl, or α‐hydroxy‐4‐methoxybenzyl groups. The swelling behaviour of selected samples of these resins was studied in tetrahydrofuran, toluene, dichloromethane, dioxane, ethyl acetate, dimethylformamide, and methanol. Swellability data are given for resin samples having different percentages of crosslinking and for those produced in the presence of chlorobenzene as a monomer diluent (or polymerization solvent). The significance of the swellability data are briefly discussed in terms of the nature of solvent, the degree of crosslinking and the effect of the monomer diluent on the matrix structure. Details of a series of model reactions of the resin‐bound functional groups are also given, and the results are discussed on the basis of resin swellability and polymer‐substrate compatibility.
Sulfur‐containing polymers, 4. Polymers with thiocarbonate and dithiocarbonate moieties from aliphatic dithiols. Syntheses and characterization
Authors: Berti Corrado , Marianucci Elisabetta , Pilati Francesco
Published: April 2003

Several polycarbonate analogues with sulfur atoms replacing all or part of the oxygen atoms in the carbonate units of the polymer, were prepared by interfacial synthesis from aliphatic dithiols and phosgene or bisphenol‐A bischloroformate or bisphenol‐A polycarbonate oligomers. That way, polydithiocarbonates (containing SCOS groups) (2a – c), polythiocarbonates (containing OCOS groups) (4a – c) and block copolymers 6a – c (containing OCOO groups, mainly, and OCOS groups randomly distributed along the chain) were prepared. The expected chemical structures were confirmed by 1H NMR, 13C NMR and FT‐IR spectroscopy. Their thermal transitions were investigated by DSC, and the effects of replacing oxygen atoms for sulfur atoms are discussed.
Rheological properties of moderately concentrated solutions of polystyrene‐block‐polybutadiene‐block‐polystyrene in different selective solvents and at different temperatures
Authors: Baloch Musa Kaleem , Rauf Abdur
Published: April 2003

The shear viscosity of a moderately concentrated solution of the triblock copolymer polystyrene‐block‐polybutadiene‐block‐polystyrene is studied in a common solvent (1,4‐dioxane) and in so‐called selective solvents (mixtures of 1,4‐dioxane with different alcohols). In the latter, which dissolve only the styrene blocks and precipitate the butadiene blocks, the block copolymer molecules aggregate and form micelles with the precipitated blocks as the core and the dissolved blocks as the cilia. The micelle solutions exhibit non‐Newtonian behaviour over certain concentration ranges. The viscosity of the micellar solutions in the dilute regime is found to be lower than that of their unimer solutions (i. e., the viscosity measured in 1,4‐dioxane) at the same concentration, whereas at higher concentrations the situation is opposite. The viscosity of micellar solutions is first increasing and then decreasing with temperature for all selective solvents used. These variations with concentration and temperature are explained in terms of micelle structure, intermicellar entanglement, swelling of the inner core and coiling of the micelle cilia.
Polyurethane ionomers: Order in 4,4′‐methylenedi(phenyl isocyanate)‐ and hexamethylene diisocyanate‐based poly(ether‐urethane) cationomers
Authors: Chen Show‐An , Chan Wu‐Chung
Published: April 2003

Polyurethane cationomers from poly(oxytetramethylene) of molecular weight 2000 as soft segments, 2,2′‐methyliminodiethanol as chain extender, glycolic acid as quaternization agent, and 4,4′‐methylenedi(phenyl isocyanate) (MDI) and hexamethylene diisocyanate (HDI) as diisocyanates are synthesized and characterized by using wide‐angle X‐ray diffraction, dynamic mechanical analysis, differential scanning calorimetry and tensile‐elongation testing. It is found that, in the unionized and ionized cases, the hard segments exhibit a disorder and short‐ and long‐range order, but no crystallinity. The ordered hard segments in the hard domains aggregate so tightly as to act as crosslinks, such that crystallization of soft segments occurs during elongation. Such disorder and order are also found to exist in the solutions of ethyl methyl ketone as reflected in variations of conductivity and viscosity during addition of water at 20°C. Ionization by insertion of the acid can disrupt the order in MDI and HDI systems, but can increase the cohesion between the neighbouring hard segments, the latter being predominant over the former. Dispersion is apt to disrupt the long‐range order in HDI systems but has only an insignificant effect on the order in MDI systems.
Intrapolymeric interactions of bile pigments covalently anchored to an insoluble polystyrene‐based resin, as determined by gel‐phase 13c NMR
Authors: Feliz Miguel , Giralt Ernest , Ribó Josep M. , Trull Francesc R.
Published: April 2003

Bile pigments covalently anchored to beads of a polystyrene‐based resin show in gel‐phase 13C NMR spectroscopy hydrogen‐bond interactions between the anchored groups. Such interactions are similar to those observed in homogeneous solution: attached 5(1 H)‐pyrromethenones in aprotic solvents show dimer formation analogously to what happens in homogeneous solution.
Temperature dependence of the polymorphous phases of nylon 6
Authors: Fichera Annamaria , Malta Viscardo , Marega Carla , Zannetti Roberto
Published: April 2003

The α, γ, γ* polymorphous forms and the physical mixtures of the α and γ‐like forms of Nylon 6 were examined from room temperature up to the melting point by X‐ray diffraction techniques. The α‐ and γ*‐forms evinced a more evident structural change as a function of temperature than the γ‐form. The study carried out on the polymorphous forms of Nylon 6 at temperatures higher than room temperature furnished new insights in comparison to usual annealing. The level of structural order and the specific aspects of the structure were found to be largely determinant for the equilibrium state in the polymorphous forms of Nylon 6 from room temperature up to the melting point.
A real‐time drawing study of melt‐crystallized ultra‐high molecular weight polyethylene. Comparison with conventional X‐ray results
Authors: van Aerle Nick A. J. M. , Braam Ad W. M.
Published: April 2003

In the past morphological changes, caused by uni‐axial drawing of flexible polymers have been studied mostly under conditions, quite different from the drawing conditions. This could give rise to certain artefacts, leading to mis‐interpretations. Up to now very little was known about this possibility. Therefore, X‐ray patterns obtained by conventional drawing studies and by real‐time X‐ray drawing studies are compared in this paper. It will be shown, that although some results on melt‐crystallized polyethylene discussed here show indeed small differences, conventional X‐ray studies can be used without any problem for qualitative studies. However, studies of deformation phenomena in elastic deformable regions as well as quantitative X‐ray studies require real‐time measurements.
Influence of shear on the demixing of polymer solutions, 1 apparatus and experimental results
Authors: Krämer‐Lucas Helga , Schenck Heiko , Wolf B. A.
Published: April 2003

An apparatus for turbidimetric measurements of demixing temperatures under shear flow is presented, and the results of experiments with trans‐decahydronaphthalene/polystyrene (TD/PS) solutions, investigating molecular weights ranging from 100 kg/mol to 1770 kg/mol, are compared with viscometric data. It is found that the sign and magnitude of shear effects depend on molecular weight (Mw), polymer concentration (c2), and shear rate (). For the first time, it was possible to study a solution which exhibits shear dissolution at low shear rates but shear demixing at high shear rates.
Polyuréthannes à propriétés emulsifiantes et électrolytiques, 2. Cinétique de polycondensation en solution des alkylimino‐2,2′ diéthanols avec le diisocyanate d'isophorone. Etude par 1H et 13C NMR
Authors: Gerard Jean‐Francois , Perchec Pierre Le , Pham Quang Tho
Published: April 2003

13C NMR analysis of carbamates and substituted ureas as model compounds, derived from 5‐isocyanato‐1,3,3‐trimethylcyclohexylmethyl isocyanate (isophorone diisocyanate) (3), allowed the quantitative determination of global conversions of hydroxyl and NCO groups. The individual conversions of the two NCO groups, as observed in the polycondensations of 2,2′‐methylimino‐ and 2,2′‐dodecyliminodiethanol (1a and 1b) with 3 in toluene, were examined. The primary NCO group of 3 was found to be two times more reactive than the secondary one. The global kinetics of the polycondensations followed the 2nd and 3rd order for conversions lower than 50%. Beyond 50% of conversion, zero order kinetics were observed because of the decrease of the rate due to the steric hindrance of both cyclohexyl and alkyl residues. Alkyl radical length in 1 and hydroxyl auto‐association equilibria were found to have the same effect on polycondensation as on condensation.
The effect of active site composition and support structure in supported catalysts on the nascent morphology of polyethylene
Authors: Semikolenova Nina V. , Nesterov Gennadii A. , Zakharov Vladimir A. , Krjukova Galina N. , Ivanov Vyacheslav P. , Gol'denberg Grigorii I.
Published: April 2003

The formation process and morphology of polyethylene (PE) produced by the non‐porous catalyst species tufa‐ and kaoline‐supported Cr(C5H5)2, Zr(BH4)4 and TiCl4 were studied by scanning electron microscopy (SEM) and X‐ray photoelectron spectroscopy (XPS). The PE morphology was found to depend upon the catalyst active component composition, the polymer yield and the morphology of the support. A quantitative estimation of the PE coverage of the catalyst particles was made.
Polymerization of 2‐methoxy‐2‐oxo‐1,3,2‐dioxaphospholane. Kinetics and polymer microstructure
Authors: Penczek Stanislaw , Libiszowski Jan
Published: April 2003

The polymerization of 2‐methoxy‐2‐oxo‐1,3,2‐dioxaphospholane (1), initiated with aluminium triisopropanolate in CH2Cl2 as solvent, was studied. Under the chosen conditions one molecule of initiator produces one polymeric chain. At low conversion exclusively linear chains of poly[oxy(methoxyphosphoryl)oxyethylene] [poly(1)] are formed. Later, chain transfer to polymer leads to extensive branching. Kinetic studies strongly indicate propagation on covalent active species. Rate constants of initiation and propagation, found from non‐stationary kinetics at 25°C, are equal to 6,5 · 10−3 mol−1 · 1 · s−1 and 4,5 · 10−1 mol−1 · 1 · s−1, respectively.
Synthesis and characterization of a polyoxyethylene derivative for the affinity labeling of human hemoglobin
Authors: Leonard Michèle , Dellacherie Edith
Published: April 2003

The possibility of preparing a polyoxyethylene derivative containing only one active group per chain, and with a narrow distribution of molecular size, was investigated. The aim of this investigation was to obtain a polymeric derivative of benzenehexacarboxylate (BHC) capable of interacting specifically inside the polyphosphate binding site of human hemoglobin (Hb) and which, after covalent coupling with this protein, could lead to conjugates with well‐defined oxygen‐binding properties. Such conjugates could be of interest in the field of blood substitutes. To minimize the percentage of high‐molecular‐weight products resulting from the fact that, on one hand, commercial monomethoxypolyoxyethylene (MPOE 5000) contained a considerable amount of difunctional and high‐molecular‐weight species, and on the other hand that several reactions were likely to lead to cross‐linked products, fractionation steps and/or chromatographic steps were carried out. The final compound obtained under these conditions (83,5% of BHC‐mono substituted polyoxyethylene, 8,5% of BHC disubstituted and 8% MPOE) was found to interact with the polyphosphate binding site of Hb, as it was capable of lowering its affinity for oxygen. After covalent coupling with deoxy‐Hb under defined conditions, this effect was strengthened, which means that the binding was probably formed with an amine of the Hb polyphosphate binding site.
Study of miscibility of the system polystyrene/poly(methylvinyl ether) by inverse gas chromatography
Authors: Elorza José María , Fdez‐Berridi María José , Iruin Juan José , Uriarte Cristina
Published: April 2003

Inverse gas chromatography technique was applied to the study of the miscibility of the system polystyrene/poly(methyl vinyl ether) (PS/PMVE) over a temperature range (75 – 155°C) including the phase separation temperature. This temperature was measured taking into account the retention diagrams of the PS/PMVE system with several probes, the comparison of the probe retention volumes in the blend with the algebraic average retention volumes of the pure homopolymers, and the variation of interaction parameter χ′23 with temperature within the temperature range investigated. According to these criteria, the phase separation temperature of the PS/PMVE (50/50 by wt.) system is within the temperature range of 115 – 120°C.
The Gordon‐Taylor equation. Additivity and interaction in compatible polymer blends
Authors: Schneider Hans Adam
Published: April 2003

An analysis of the Gordon‐Taylor equation shows that its background is based on additivity. The corresponding parameter K = ρ1 Δα2 / (ρ2 Δα1), however, may include also an interaction contribution if the quadratic concentration term is neglected in a virial‐like extension of the glass transition temperature vs. composition expression. Then K becomes a real fitting parameter. It is shown that a distinction of the two cases is possible by using the corresponding linearized form of the respective equations. The discussion of data of polystyrene/poly(2,6‐dimethyl‐1,4‐phenylene oxide), styrene copolymers/poly(2,6‐dimethyl‐1,4‐phenylene oxide) and poly(methyl vinyl ether)/polystyrene blends gives evidence for the decisive influence of the stiffer component on the glass transition behaviour of compatible polymer blends.
Synthesis and properties of para‐linked aromatic polyesters containing 2,2′‐dimethylbiphenylylene units
Authors: Schmidt Hans‐Werner , Guo Dajian
Published: April 2003

The syntheses and properties of a series of para‐linked aromatic homopolyesters with 2,2′‐dimethylbiphenylylene units are described. In the 2,2′‐dimethyl‐substituted biphenylylene unit the phenyl rings are forced into a non‐coplanar conformation, which decreases the interchain interactions. The combination of such a biphenylylene unit with a monosubstituted unit further reduces the regularity of the substituents along the polyester backbone. As a result, soluble and completely amorphous liquid‐crystalline (LC) aromatic polyesters with low phase transition temperatures are obtainable. Ternary solutions, consisting of a soluble aromatic LC polyester, a conventional randomly coiled thermoplastic and chloroform as solvent, can be used for the preparation of films and fibers.
Mobility and 29Si NMR relaxation in some cyclic siloxanes
Authors: Kosfeld Robert , Kreuzburg Christa , Krause Rosemarie
Published: April 2003

29Si NMR spin‐lattice relaxation time (T1) measurements were performed with asymmetrically substituted oligomeric cyclosiloxanes (MeRSiO2/2)n (with R = phenyl, n = 3 and R = H, n = 4 – 6). Temperature‐ and field‐dependend measurements allow separation into different relaxation mechanisms. Based on these results, molecular correlation times τc were calculated. The methyl‐H cycles were found to be more mobile than the methyl‐phenyl ones.
Approach to the composition dependence of the glass transition temperature of compatible polymer blends, 2 The effect of local chain orientation
Authors: Brekner Michael‐Joachim , Schneider Hans Adam , Cantow Hans‐Joachim
Published: April 2003

In a previous publication a new concept has been presented for the composition dependence of the glass transition in compatible polymer blends. The concept starts with the idea that besides conformational energy barriers, contacts due to interaction are responsible for both conformation and “free” volume distribution. In accordance with the Flory‐Huggins lattice theory, the contact probability has been related to the volume fraction of the components, corrected for the different volume expansion coefficients. The concept accounts for both chainspecific and interaction‐specific contributions. It is concluded that local chain orientation due to the increased hetero‐contact interaction may explain the observed molecular weight influences on the composition dependence of Tg of polymer blends. Using experimental data for poly(vinyl methyl ether)‐polystyrene (PVME‐PS) blends it is shown that this local chain orientation due to hetero‐interaction is extremely strong in blends of the low molecular weight PS with high MW PVME. Thus, apparently, the stiffer component is dominating the Tg behaviour of compatible polymer blends.
Chain mobility in solid polyelectrolyte complexes
Authors: Westermark Bertel , Spiess Hans Wolfgang
Published: April 2003

2H NMR is used to study the mobility of the alkylene chain in solid poly[(dimethyliminio)‐alkylene]s (α,ω‐ionenes) complexed with poly(styrenesulfonate). In 10, 10‐ionene the alkylene chain motion was probed on samples selectively deuterated at the 1‐, 2‐, and 4‐position as well as in the methyl part of the quaternary ammonium groups. 2H NMR spectra show that all positions in the polymethylene chains are involved in conformational jumps between trans and gauche states. The mobility of the methylene units adjacent to charged centres was found to be significantly reduced compared with that of units in the inner part of the chain. The charged quaternary ammonium groups themselves, however, do not take part in trans‐gauche isomerization. An increase in mobility resulting from increasing the length of the alkylene chains between the charge centres was observed in 3,3‐, 6,6‐ and 10,10‐ionene complexes labelled in the 2‐position. The differences in chain dynamics were also detected via EPR line shapes of small spin probe molecules incorporated into the complexes.
Rheological properties of two‐dimensional model networks
Authors: Rehage Heinz , Schnabel Edith , Veyssié Madeleine
Published: April 2003

We measured the tensio‐active properties of octamethylene dimethacrylate (1), octamethylene diisobutyrate (2) and octamethylene isobutyrate methacrylate (3) at the oil‐water interface. The results indicate that these molecules are strongly adsorbed at the boundary between oil and water. The amphiphatic compounds in the monolayer can be polymerized and cross‐linked by UV irradiation. The kinetics of surface gelation was studied by measuring the two‐dimensional shear modulus as a function of the time of irradiation. A two‐dimensional sol‐gel transition was observed which is in fairly good agreement with percolation theories. The kinetics of the two‐dimensional polymerization can be completely interpreted in terms of a simple reaction scheme. The elasticity of the two‐dimensional films depends strongly on the surface concentration of the cross‐linking agent. The rheological properties of the polymerized films exhibit typical features of rubber‐elastic systems and there exists an interesting analogy to corresponding structures of three‐dimensional networks.
Rheologic properties of semi‐rigid polymers for the example of cellulose nitrate, 2. Influence of molecular weight distribution on the flow curves of semi‐dilute solutions
Authors: González Francisco Rex , Marx‐Figini Marianne , Figini Rubén V.
Published: April 2003

The apparent viscosity η of semi‐dilute solutions of cellulose nitrate in ethyl acetate was measured as a function of shear rate at 20°C by rotational viscometry. The mass concentration c of the solutions was chosen such that the product between c and the intrinsic viscosity was 8 < c · [η] < 22, lying in the range of viscosity‐average degrees of polymerization covered by the employed samples 550 < DPη < 7600. The experimental flow curves were interpreted in terms of Graessley's theory for non‐Newtonian flow of polydisperse polymers. The polydispersities derived for five individual samples according to the theory of Graessley were used for calculating the resulting theoretical curves belonging to four binary mixtures each between two of them. The reasonable good agreement between calculated and experimental reduced flow curves of blends indicates consistency of the theory when applied to the present system of a semi‐rigid polymer. This and other results point to a flow behaviour of semi‐rigid cellulose nitrate being similar to that of linear flexible polymers.
Small angle X‐ray studies on diffusion processes at the boundary between poly(methyl methacrylate) and poly(vinylidene difluoride)
Authors: Garbella Rüdiger Wilhelm , Wendorff Joachim Heinz
Published: April 2003

Diffusion processes taking place across the boundary between the two compatible polymers poly(methyl methacrylate) (PMMA) and poly(vinylidene difluoride) (PVDF) were studied by means of small angle X‐ray scattering. The excess scattering resulting from thermal concentration fluctuations was used to monitor the diffusion process as a function of the molecular weight of the PMMA component and the diffusion geometry. The results obtained were analyzed on the basis of simplified versions of the interdiffusion theories proposed by Brochard (slow‐mode model) and by Kramer (fast‐mode model). This, however, required, the introduction of approximations with respect to the concentration dependences of monomer mobilities and interaction parameter and with respect to the role of molecular weight distribution. Using these approximations it is possible to account quantitatively for all experimental findings on the basis of the slow‐mode approach. Discrepancies between experimental results and theoretical predictions were found for the model based on the fast‐mode approach.
Kinetics of the conformational transition of poly(methacrylic acid) after a pH jump, 2. Studies of nonradiative energy transfer
Authors: Horský Jiří , Morawetz Herbert
Published: April 2003

Doubly labeled poly(methacrylic acid) (PMA) samples with two different concentrations of carbazole and anthracene labels were prepared, and one sample was divided into two fractions of different molecular weight. Emission spectra were recorded in solutions without added salt, at ionic strengths 0,05 and 0,40 and in a 2 : 1 water‐methanol mixture, as a function of pH. The nonradiative energy transfer (NET) from carbazole donor to anthracene acceptor decayed as the PMA coils expanded. On mixing solutions of the labeled PMA with buffer solutions of varying ionic strength in water or aqueous methanol in a stopped‐flow apparatus, the expansion of the PMA was monitored by the decrease in anthracene emission intensity when the solution was irradiated in the carbazole absorption band. Only part of the process could be followed, since the initial expansion occurred in a sub‐millisecond time. Some studies were also carried out on the kinetics of chain contraction when partially neutralized PMA solutions were acidified. The changing NET with the conformational transition of PMA was correlated with the change in the intrinsic viscosity of the polymer. The kinetic data obtained were generally in excellent agreement with those of an earlier study in which conformational changes of PMA were monitored by the changing emission of a dansyl label. In particular, the surprising slowness of the final approach to equilibrium was substantiated.
Quantum yields of the photochromic reactions of heterocyclic fulgides and fulgimides
Authors: Deblauwe Veerle , Smets Georges
Published: April 2003

Quantum yields of photocyclization of a fulgide 1a and its corresponding fulgimide 1b upon irradiation with ultraviolet light, and of the back decoloration reaction of the cyclic product 3 on irradiation with visible light, were determined in different solvents and in polymer matrices. The isomerization of the (Z)‐isomers to the (E)‐isomers is very sensitive to the glass transition temperature Tg of the matrix, especially in the case of copolymers of N‐styrylfulgimides 1c with styrene where the photochrome is linked to the polymer chain.
A study of the reduction of polyacetylene by organopotassium compounds and the structure of the resulting conducting polymer
Authors: Mathis Claude , Weizenhöfer Robert , Lieser Günter , Enkelmann Volker , Wegner Gerhard
Published: April 2003

Highly oriented trans‐polyacetylene prepared by the method of Edwards and Feast was reduced by exposure to various potassiumorganic compounds. The degree of reduction y could be adjusted to values between y = 0,01 and y = 0,15. X‐ray investigations performed with samples held under in situ conditions revealed 3 different structures. Long‐range order could not be observed up to y = 0,10. For 0,11 ≤ y ≤ 0,15 the chains pack in a square lattice. Here and for y ≤ 0,10 the chains are not in register. The distance between K+ ions which are arranged in chains of various lengths is controlled by the trans‐polyacetylene (0,48nm). Threedimensional order is only observed for y = 0,15, the chains, however, are then tilted with respect to a square basal plane, and K+ ions are only 0,40 nm apart.
The sequence length‐distribution in eutectoid copolymers as obtained from an analysis of the melting process
Authors: Rosenberger Bernd , Asbach Gerd Ingo , Kilian Hanns‐Georg , Wilke Wolfgang , Rodriguéz Mario
Published: April 2003

Thermodynamics of eutectoid copolymers is based on the assumption that the co‐units are eutectic units. At low concentration of one of these units (non‐crystallizable units, nc‐units), crystallizable sequences (c‐sequences) are formed. Segregation of the eutectic units leads to lamella‐shaped extended c‐sequence crystals, the thickness distribution of which is controlled by the c‐sequence length‐distribution (“structure‐c‐sequence length relationship”). According to thermodynamics the lamellar crystals have to melt selectively and consecutively with respect to their mean thickness. For eutectoid copolymers it is, therefore, possible to deduce the c‐sequence length‐distribution from a thermodynamic analysis of the whole melting process. A computer‐aided method of analyzing differential scanning calorimetry measurements is applied to various semicrystalline copolymers (low‐density polyethylene (LDPE), vicinal‐chlorinated polyethylene, copolymers with OCH2 units). Theoretical structure parameters (crystallinity, mean crystal thickness) and small‐angle X‐ray scattering (SAXS) ‐pattern computed from the c‐sequence length‐distribution are shown to be in good accord with the experimental data. The universal features of the crystallization behaviour of eutectoid copolymers are emphasized. The influence of topochemical reactions onto the distribution of the eutectic co‐units of copolymers containing oxymethylene units is discussed.
X‐ray investigation on highly oriented polyacetylene, 1. Crystal structure of cis‐ and trans‐polyacetylene
Authors: Perego Giovanni , Lugli Gabriele , Pedretti Ugo , Cesari Marco
Published: April 2003

The crystal structure of cis‐ and trans‐polyacetylene (PA) is investigated by X‐ray analysis on highly oriented polymers. cis‐ and trans‐PA are characterized by the same crystalline packing (Pnam space group) with a setting angle of 51°. A random distribution of short‐range in‐phase and out‐of‐phase bond alternation within the lattice is proposed for trans‐PA. For cis‐PA, the “cis‐transoid” model gives a better agreement between experimental and calculated intensities than the “trans‐cisoid” model. The results of the present work are compared with those reported in the literature which were obtained by investigating unoriented or partially oriented PA.
X‐ray investigation on highly oriented polyacetylene, 2. Crystal structure of cis‐ and trans‐polyacetylene
Authors: Perego Giovanni , Lugli Gabriele , Pedretti Ugo , Cesari Marco
Published: April 2003

The crystal structure of cis,trans‐polyacetylene (c, t‐PA) is investigated by X‐ray analysis on highly oriented samples with different contents of the two configurations. The structure is built up of mosaic‐like cis‐trans mixed crystals with the unit cell parameters perpendicular to the chain axis varying continuously between those of all‐cis‐PA and those of all‐trans‐PA. The mixed crystals contain three‐dimensionally ordered blocks of cis‐configuration and three‐dimensionally ordered blocks of trans‐configuration, arranged to each other in a nematic‐like lattice. Distorted short trans‐sequences, characterized by an appropriate slight variation of bond angles, are proposed as junctions between regular cis‐ and regular trans‐segments. The mixed crystals model gives calculated intensities for hk0 reflections in good agreement with experimental observation. Information concerning the average sequence length of cis‐ and trans‐segments in c,t‐PA are given and discussed. The formation of block‐type mixed crystals suggests that cis‐to‐trans isomerization proceeds without lattice disruption but with a mechanism not purely random.
X‐ray investigation on highly oriented polyacetylene, 3 Crystal structure of the iodine/trans‐polyacetylene complex
Authors: Perego Giovanni , Lugli Gabriele , Pedretti Ugo , Allegra Giuseppe
Published: April 2003

The crystal structure of iodine/trans‐polyacetylene complexes (CHIy)x (y = 0,009, 0,035, 0,17 and 0,30) was investigated by X‐ray diffraction analysis of highly oriented samples. An iodine‐containing phase (PAI) was observed in all cases, accompanied by residual crystallinity due to pristine polyacetylene (PA) for y < 0,17. A structural model is proposed for PAI, consisting of blocks of iodine‐saturated PA (PAIs) and blocks of PA, arranged in a mosaic‐like lattice, paracrystalline in character. PAIs, corresponding to (CHI0,40)x, is formed by layers of (CH)x chains alternating with layers containing polyiodide chains, the latter being characterized by ordered stacking of sequentially disordered (I3−‐I5−‐I3−) groups. I… C non‐bonded interactions are identified in the lattice, which may be responsible for the electron transfer from the polymer to the polyiodide anions. Short‐range transverse correlation occurs within the polyiodide layers with a resulting quasi‐regular two‐dimensional lattice of iodines. The iodine and the polymer lattices are incommensurate along c. The model fits the experimental data from an X‐ray fibre diagram. A mathematical expression is derived, which allows to evaluate the intensity scattered by the iodine lattice. An approximate expression of the non‐equatorial intensity along the ξ reciprocal direction was obtained, which accounts for the modulation of the streaks observed in the fibre pattern.
Copolymers of acrylates with sulfur dioxide: Synthesis and structural studies by 13C NMR spectroscopy
Authors: Florjańczyk Zbigniew , Floriańczyk Tadeusz , Zygadło Ewa
Published: April 2003

The copolymerization of sulfur dioxide with methyl, ethyl, butyl or 2‐ethylhexyl acrylate was studied. The influence of the composition of monomer feed and reaction temperature on the composition of the copolymers was investigated. The maximum content of sulfonyl units in the copolymers, obtained at −78°C, was found to be ca. 30 mol‐% and to decrease with increasing temperature. The sequence distribution in the copolymers was determined by 13C NMR spectroscopy. It was proved that acrylates do not undergo alternating propagation with SO2, and the minimum number of acrylate monomeric units in a homosequence is 2. The results obtained were compared with those obtained from studies on the copolymerization of SO2, with other monomers, and are discussed in terms of the alternating copolymerization theory and the penultimate model.
Preparation of block copolymers by ring‐opening polymerization of cycloalkenes initiated by a tungstencyclopentylidene complex
Authors: Greene Ruth M. E. , Ivin Kenneth J. , Rooney John J. , Kress Jacky , Osborn John A.
Published: April 2003

The possibility of making block copolymers at room temperature from the monomer pairs 2a,b/1, 4/1, 5/1 and 5/3 (1 = norbornene = bicyclo[2.2.1]hept‐2‐ene; 2a,b = anti‐ and syn‐7‐methylbicyclo[2.2.1]hept‐2‐ene; 4 = methyl endo‐bicyclo[2.2.1]hept‐5‐ene‐2‐carboxylate; 5 = endo‐bicyclo[2.2.1]hept‐5‐ene‐2‐carbonitrile; 3 = 1,5‐cyclooctadiene) was explored using

as initiator of metathesis polymerization in CD2Cl2. The reactions of successive small amounts of the monomers with the catalyst were first followed by 1H NMR to determine the rate of the reaction and the stability of the metal‐carbene propagating species. AB and ABA type block copolymers were prepared on this basis and analysed by GPC. An increase in molecular weight after each addition was observed in most cases. Secondary metathesis reactions of double bonds in the polymer chains appear to be significant only for blocks formed from 3.