bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermisch und UV‐photochemisch initiierte hochdruckpolymerisation des ethylens, 2. Molmassen‐verteilung
Authors: Buback Michael , Choe Chul‐Rim , Franck Ernst‐Ulrich
Published: April 2003

The molar mass distribution of polyethylenes synthesized at pressures up to 2500 bar and temperatures to 255°C with thermal and partly with photochemical initiation is determined by GPC. In the limiting situation of high pressure, low temperature, and small conversion a distribution function based on a limited set of kinetic equations provides a fair representation of the experimental data. The transfer constant with the monomer is derived as a function of pressure and temperature. The logarithmic normal distribution reasonably represents the molar mass distribution of the high pressure polyethylenes if the conversion is low and if both empirical parameters are taken as temperature dependent. The degree of long chain branching is analyzed for the ethylene polymerization as a function of pressure and temperature and to maximum conversions of 30%. It turns out that even at conversions as low as 2% long chain branching is not negligible.
Herstellung und eigenschaften von polyacenaphthylen, 3. Photoabbau von polyacenaphthylen
Authors: Stelter Thomas , Springer Jürgen
Published: April 2003

Thermally prepared polyacenaphthylene when irradiated in solution undergoes random chain scission. The photodegradation is solvent‐ and temperature‐dependent and leads to a lower limit of the degree of polymerization. Polymeranalogous reactions and crosslinking can be found to occur simultaneously. A certain fraction of „weak links”︁ was detected in the polymer.
Metalloesters, 11. “Disproportionation” of living (lithiated) oligomers of methyl methacrlylate
Authors: Lochmann Lubomír , Trekoval Jiří , Müller Axel H. E.
Published: April 2003

The decomposition reactions of the lithiated dimer, trimer, and tetramer of methyl methacrylate (MMA) in THF at 25°C were investigated. The decomposition of the lithiated dimer proceeds via depolymerization to lithiated monomer and MMA, addition of MMA to residual lithiated dimer, resulting the trimer (“disproportionation” of the dimer), and subsequent autocondensation of the products. The lithiated trimer almost exclusively undergoes cyclo‐autocondensation, whereas for the lithiated tetramer both reactions proceed simultaneously to a remarkable degree. It is shown that the relative rate of autocondensation, which is highly dependent on the degree of polymerization of the oligomer, controls the distribution of products formed. The results indicated that the depolymerization of living PMMA is an important factor even at room temperature, potentially affecting the MWD of the polymers.
Functional polymers and sequential copolymers by phase transfer catalysis, 2. Synthesis and characterization of aromatic poly(ether‐sulfone)s containing vinylbenzyl and ethynylbenzyl chain ends
Authors: Percec Virgil , Auman Brian C.
Published: April 2003

A simple method for the synthesis of α,ω‐bis(vinylbenzyl) aromatic poly(ether‐sulfone)s (2) and their transformation into α,ω‐bis(ethynylbenzyl) aromatic poly(ether‐sulfone)s (4) is presented. This method involves a fast and quantitative Williamson etherification of the α,ω‐bis(hydroxyphenyl)polysulfone with a mixture of p‐ and m‐chloromethylstyrenes in the presence of tetrabutylammonium hydrogen sulfate as phase transfer catalyst, a subsequent bromination, and then a dehydrobromination with potassium tert‐butoxide. The DSC study of the thermal curing of these α,ω‐bis(vinylbenzyl)polysulfones and α,ω‐bis(ethynylbenzyl)polysulfones demonstrates high thermal reactivity for this new class of styrene‐terminated oligomers.
Structure‐reactivity relation for polymines and derivatives in activated ester hydrolysis
Authors: Everaerts Albert , Samyn Celest , Smets Georges
Published: April 2003

Three polymeric amines, poly(1‐aminoethylene) (polyvinylamine) (PVNH2) and linear and branched poly(iminoethylene)s (polyethylene(imines)) (1‐PEI and b‐PEI) as well as their dodecyl (D) and imidazolylmethyl (Im) substituted derivatives were used for the hydrolysis of p‐nitrophenyl acetate (PNPA), 4‐acetoxy‐3‐nitrobenzoic acid (ANBA) and some of their homologues in order to elucidate the relations between their overall structures and their catalytic activities. In each series polymers of similar degree of substitution were compared, namely PVNH2‐D18 and PVNH2‐D18‐Im16; b‐PEI‐D20 and b‐PEI‐D20‐Im18; 1‐PEI‐D20 and 1‐PEI‐D20‐Im16. The degree of branching of b‐PEI was 41%. All reactions were carried out at 28,7°C in aqueous solution, and followed spectrometrically. Using a catalyst concentration in large excess with respect to the substrate concentration (10−4 mol · l−1) the reactions were found to obey pseudo‐first order kinetics. By plotting log [Substrate] against time, k2 (cat) and consequently k2 rate constantes were evaluated. For each series of polymers, k2 increases considerably by dodecyl substitution (hydrophobic‐), imidazolylmethyl substitution (catalytic‐) and by the use of a charged substrate (electrostatic effects). At similar degree of substitution the catalytic activity is always in the following order: l‐PEI < PVNH2 < b‐PEI. Using the method of Kosower‐Mikes the polarity of the microenvironment of l‐PEI and b‐PEI was found to be almost equal. Substitution of l‐PEI with ethyl or 2‐diethylaminoethyl side groups (40% substitution) modifies only slightly the catalytic effect of l‐PEI. It is, therefore, concluded that the primary amino groups of the side chains in b‐PEI are reponsible for its much higher reactivity than that of l‐PEI and PVNH2. Experiments with [Substrate] > [Catalyst] were carried out with b‐PEI, b‐PEI‐D20‐lm18 and l‐PEI‐D20‐Im16. Under these conditions the reactions follow Michaelis‐Menten kinetics and permit the comparison of the complexation constant and rate constant of hydrolysis for the three systems. In the case of b‐PEI hydrolysis, reactions towards PNPA carried out at different temperatures, indicate a low enthalpy of activation, ΔH≠ = −196 j · mol K−1 is strongly negative. On the contrary the enthalpy and entropy of complexation are low, indicating low hydrophobic effects.
Polyurethanes containing binaphthyl groups
Authors: Tanaka Mamoru , Nakaya Tadao
Published: April 2003

Polyurethanes containing binaphthyl groups were synthesized by reaction of diisocyanates – 4,4'‐diphenylmethane diisocyanate (MDI), 2,4‐toluylene diisocyanate (TDI) and hexamethylene diisocyanate (HDI) – with 2,2'‐(1,1'‐binaphthyl‐4,4'‐ylenedioxy)diethanol (3). The polyurethane obtained from 3 with MDI has an intrinsic viscosity [η]90DMSO90°C of 0,14 dl · g−1 and a melting point of 244 – 260°C, that from 3 with TDI has an [η]90°CDMSO of 0,12 dl · g−1 and a melting point of 181 – 191°C, and that from 3 with HDI has an [η]90°CDMSO of 0,11 dl · g−1 and a melting point of 222 – 241°C. These polymers were found to be crystalline. Segmented polyurethanes (SPU) from 3 with prepolymers of poly(tetramethylene glycol) (PTG), (M = 1079) and MDI or HDI (mole ratio PTG:MDI (or HDI) = 1:2) were also synthesized. The SPU from MDI has an intrinsic viscosity [η]90°CDMSO of 0,56 dl · g−1 and a melting point of 260–275°C, and that from HDI has an [η]90°CDMSO of 0,50 dl · g−1 and a melting point of 231 – 253°C. These polymers show slight crystallinity.
Etude par résonance magnétique nucléaire du 1H et 13C des télomères du chlorure de vinyle et du tétrachlorure de carbone
Authors: Bessière Jean Marie , Boutevin Bernard , Taha Mohamed
Published: April 2003

The adducts and bi‐adducts of the reaction of vinyl chloride with carbon tetrachloride, CCl3(CH2CHCl)nCl and Cl(CHClCH2)CCl2(CH2CHCl)pCl respectively, have been studied by 13C and 1H NMR. The identification of the characteristic peaks of each product enables of much better control of the purity of the telomerization reactions. Moreover, it was possible to resolve complex spin systems in 1H NMR (up to 9 non‐equivalent spains). In particular the threo and erythro conformation of the tri‐adducts could be assigned without any ambiguity. Thanks to model molecules, the chemical shifts were specified in 13C NMR for all carbon atoms with similar groups.
Studies of crosslinked poly(N‐vinyl‐2‐pyrrolidone) by calorimetry and by NMR
Authors: Tenhu Heikki , Sundholm Franciska , Bjorksten Johan
Published: April 2003

Aqueous solutions of poly(N‐vinyl‐2‐pyrrolidone) are converted to gels by reaction with potassium peroxydisulfate K2S2O8. The degree of crosslinking in the gel fractions depends on the amount of persulfate used. The degree of crosslinking is related to the amount of non‐freezing bound water in the gels by means of differential scanning calorimetry in the temperature range from −50°C to + 170°C. The chemical nature of the bonds formed during gelation is studied by 1H and 13C NMR Spectroscopy and by swelling tests. NMR measurements point to the formation of aliphatic sidechains as well as crosslinks in the gelation. The swelling tests give low values for the number of crosslinks, hence the formation of branched chains strongly influences the properties of the gels. In contrast to what was expected no carboxyl groups are found in the gels.
Epitaxy of helical polyolefins: Polymer blends and polymer‐nucleating agent systems
Authors: Lotz Bernard , Wittmann Jean‐Claude
Published: April 2003

Helical polyolefins (polypropylene (PP) and poly(1‐butene)) (PB‐1) possess crystallographic faces in which the side‐groups form well aligned rows. These structural features are shown, through a number of examples, to interact with linear polymers (polyethylene (PE) and polyamides) and nucleating agents. These interactions explain, on the basis of characteristic epitaxial relationships, the mutual activity of certain pairs of crystalline polymers and the hitherto puzzling “universality” of some nucleating agents towards both linear (i.e. PE‐like) polymers and helical polyolefins.
Homogeneous Ziegler‐Natta catalysis: Efficiency improvement of vanadium catalyst systems by tributyltin hydride for the ethylene/propylene/diene terpolymerization
Authors: Giannetti Enzo , Mazzocchi Romano , Albizzati Enrico , Fiorani Tiziana , Milani Federico
Published: April 2003

The effect of tributylin hydride on different vanadium‐based homogeneous catalytic systems for the ethylene/propylene/diene (EPD) terpolymerization was studied. Productivity improvements were always observed. Studied on the composition of the polymerization residues as well as on the interaction between single components of the catalytic system were also carried out. The results are interpreted on the basis of the enhanced oxidation of the vanadium(II) species by radical intermediates resulting from the reaction between tin hydrides and the chlorinated organic activator.
Induction of metachromasia and circular dichroism in some dyes by sulfated bael gum polysaccharide and its anticoagulant property, 1
Authors: Pal Medini Kanta , Bhattacharyya Ashoke Kumar
Published: April 2003

Bael (Aegle marmelos) gum polysaccharide (AMA), a polyacid polysaccharide with a high equivalent weight (2091) was shown to exhibit a very weak chromotropic character and to fail to induce a metachromatic spectral shift of the dye toluidine blue. Sulfation of the polysaccharide to a carboxylate/sulfate mole ratio of 1 (AMA‐S2; equivalent weight 698) largely enhances the chromotropic character. AMA‐S2 shows a blue shifted metachromasia with toluidine blue (TB) and pinacyanol chloride (PCYN), and a red shifted J‐band with N,N′‐diethylpseudoisocyanine chloride (PIC). Mixtures of AMA‐S2 with both PCYN and PIC exhibit a strong circular dichroism in the visible range of the respective dye/polyanion system. The anticoagulant property of the Bael gum polyasaccharide also improves with its sulfation, as expected.
Synthesis of new polynaphthalimidophenylquinoxalines and their copolymers
Authors: Korshak Vasilij V. , Krongauz Jergienija S. , Belomoina Natasha M. , Jediński Zbigniew , Kowalski Bogdan , Paliwoda Adam
Published: April 2003

A series of novel polyphenylquinoxalines containing naphthalimide structures in the chain were prepared by reacting 3,3′‐diaminobenzidine, 3,3′,4,4′‐tetraaminodiphenyl ether and 3,3′,4,4′‐tetraaminodiphenyl sulfone with the two new monomers of N,N′‐bis(4‐benzoylcarbonylphenyl)‐4,4′‐(1,3‐phenylenedioxy)‐di‐1,8‐naphthalenedicarboximide (3a) and N,N′‐bis(4‐benzoylcarbonylphenyl)‐4,4′‐[isopropylidenebis(1,4‐phenyleneoxy)]‐di‐1,8‐naphthalenedicarboximide (3b). The obtained polymers exhibit high decomposition temperatures, their Tg values being, however, below 300°C. Their solubility in common solvents, e.g. chloroform, is excellent, but their molecular weight is low. Higher molecular weight products were obtained by copolymerization of 3a, b with N,N′‐bis(4‐benzoylcarbonylphenyl)‐1,8 : 4,5‐naphthalenetetracarboxdiimide (3c) yielding films and fibers with good mechanical properties.
Syntheses of macrocyclic oligoesters from 5‐hydroxymethyl‐2‐furancarboxylic acid
Authors: Hirai Hidefumi , Naito Katsuyuki , Hamasaki Taihei , Goto Minoru , Koinuma Hideomi
Published: April 2003

New macrocyclic oligoesters 3a – d, containing furan rings, were synthesized by condenzation of 5‐hydroxymethyl‐2‐furancarboxylic acid (1) using 2‐chloro‐1‐methylpyridinium iodide (2) as condensing agent. Water‐insoluble products were separated by GPC and characterized by IR, NMR, MS, and elemental analysis. The product distribution was found to depend remarkably on the reaction conditions. When the mole ratio of 2 to 1 was 1,65 in pyridine was solvent, the cyclic trimer 3a and the tetramer 3b were obtained, both in more than 30% yield. In addition higher cyclic oligoesters (3c – d), linear oligoesters (5b – e), and the polyester (6) were formed. When a large amount of tributylamine was used as a scavenger of hydrogen halides in toluene as solvent, the polyester was the main product. Condensation in hexane in place of toluene, yielded the linear oligoesters as main products. A mechanism is proposed for the formation of the cyclic oligoesters.
Recherche de télomères à activité pharmacologique potentielle, 6. Introduction de moleécules relais entre le principle actif et la chaine télomère
Authors: Bauduin Gérard , Bessière Jean‐Marie , Martel Jacques , Piétrasanta Yves
Published: April 2003

Reactions of insertion of components serving as bridges between a pharmacologically active constituent and a water‐soluble telomeric chain, were carried out. Model compounds containing hydroxyl, amine or carboxylic functions were studied. In each case a bifunctional compound could be found, which is capable of reacting with the model. The resulting products could be fixed on a telomer. The results with the model compounds were applied to the fixation of the carboxylic drug indometacin.
Propylene polymerization on titanium‐magnesium catalysts, 3. Influence of the products resulting from the interaction of trialkylaluminium with aromatic esters on the activity and stereospecificity
Authors: Sergeev Sergei A. , Bukatov Gennadii D. , Zakharov Vladimir A.
Published: April 2003

The influence of the conditions of interaction between AlR3 and aromatic esters (D) and of the products formed on the activity and stereospecificity of the actalytic system TiCl4/ethyl benzoate/MgCl2 + Al(i‐Bu)3 + D in propylene polymerization was studied. An increase of the polymerization temperature above 60°C leads to a decrease in the activity of the titaniummagnesium catalyst (TMC) and in the isotacticity of the polypropylene produced. A preliminary interaction of AlR3 with D at elevated temperatures diminishes the isotacticity of the polymer and has no influence on the activity of TMC. IR spectroscopy was employed to study the influence of the temperature and time of AlR3 interaction with the esters as well as that of the composition of AlR3 (AlEt3 or Al(i‐Bu)3) on the process of reduction of these esters. Reduction products such as aldehydes, ketones, and primary alkoxy derivatives of aluminium cannot provide of high stereopecificity of TMC. High stereospecificity is rather thought to be provided by the interaction of active sites with a free ester or tertiary alkoxy derivaties of aluminium. The contribution of each of these processes depends on the catalyst composition and on the polymerization conditions.
Thermodynamic and hydrodynamic properties of aliphatic polyesters, 3. Analysis of osmotic and light scattering data of poly(β‐propiolactone) in 2,2,2‐trifuloroethanol in terms of a universal scaling law for the osmotic pressure in the excluded volume limit
Authors: Rosenvasser Daniel , Figini Rubén V.
Published: April 2003

Osmotic and light scattering data of poly(β‐propiolactone) in 2,2,2‐trifluoroethanol, a thermodynamically very good solvent, are analyzed in terms of a universal scaling law for the osmotic pressure in the excluded volume limit. The polymolecularity correction function to calculate osmotic pressures from light scattering data is deduced and a numerical method to treat simultaneously all the measured osmotic pressures at different concentrations is developed. It is shown that, for a given concentration, provided the molecular weight of the polymer species together with its radius of gyration is known, the osmotic pressure of its dilute and semidilute solutions can be calculated.
A small angle neutron scattering study of an oligo(oxytetramethylene)
Authors: Miller John A. , Cooper Stuart L.
Published: April 2003

Small angle neutron scattering experiments were performed on a blend of deuterated and protonated hydroxyl terminated oligo(oxytetramethylene)s. The oligomer had a number‐average molecular weight of 1000. The experimental data were fitted to a Debye function in order to obtain the radius of gyration of the chains. The measured radius of gyration, which was corrected for molecular weight distribution, was found to compare well with the values reported in the literature for poly(oxytetramethylene) in a theta solvent, as measured by viscosity methods and extrapolated to a molecular weight of 1000. Thus, this short oligomeric species has a random coil configuration. The weight‐average molecular weight determined from the SANS data was 1540, compared with a value of 1450 determined from high performance liquid chromatography. This implies that no isotopic segregation of the deuterated and protonated species occurs.
Structural studies on molecular complexes of polyethers, 3. Urea‐polyether complexes
Authors: Suehiro Kazuaki , Urabe Akira , Yoshitake Yoshiharu , Nagano Yoshiaki
Published: April 2003

Complexes of urea with polyethers, \documentclass{article}\pagestyle{empty}\begin{document}$\rlap{‐‐} [\left( {{\rm CH}_2 } \right)_m {\rm O\rlap{‐‐} ]}_n$\end{document} (m = 2–4, 6, 8–10), were prepared, and their crystal structures and decomposition temperatures were studied. The crystal structures of the complexes with polyethers (m ≥ 3) are similar to those of n‐alkanes, so‐called urea adducts. Only poly(oxyethylene), (m = 2), presents a complex of a different type of crystal structure. The decomposition temperatures of the complexes are in the range of 134 to 144°C and change in parallel with the melting points of polyethers themselves against the number of CH2 groups in the monomeric units.
Functional polymers, 32. 5‐Methoxy‐ and 5‐hydroxy‐2H‐benzotriazol‐2‐yl mono‐ or disubstituted resorcinols or phloroglucinols
Authors: Xi Fu , Basset Walter , Vogl Otto
Published: April 2003

Four new 5‐methoxy‐2H‐benzotriazol‐2‐yl mono‐ or di‐substituted resorcinols and phloroglucinols 5a, b and 6a, b were synthesized by reaction of resorcinol or phloroglucinol with 4‐methoxy‐2‐nitrobenzenediazonium chloride in a 1:1 or 1:2 mole ratio and subsequent reductive cyclization with zinc and sodium hydroxide. The methoxy groups of all four compounds were cleaved with dry hydrogen bromide gas in dimethylformamide leading to the corresponding hydroxyl derivatives 7a, b and 8a, b in nearly quantitative yields. Unlike the reaction of phloroglucinol with a large excess of 2‐nitrobenzenediazonium chloride, which gave the trisubstituted product, with 4‐methoxy‐2‐nitrobenzenediazonium chloride no phloroglucinol derivative with three 5‐methoxy‐2H‐benzotriazol‐2‐yl groups could be obtained. All the resulting products were characterized by their IR, 1H, and 13C NMR, and UV spectra. The resorcinol derivatives (both methoxy‐ and hydroxy‐) Showed λmax of 345 nm and an absorption coefficients as high as 4 · 104 l · mol–1 · cm−1, and the phloroglucinol derivatives a λmax of 350 nm and an absorption coefficient as high as 4,5 · 104 l · mol−1 · cm−1.
Dynamic and static light scattering from critically branched polymer solutions
Authors: Kajiwara Kanji , Burchard Walther , Kowalski Michael , Nerger Dittmar , Dušek Karel , Matějka Libor , Tuzar Zdeněk
Published: April 2003

Critically branched polyurethanes of varying molecular weight were prepared from poly(oxypropylene)triol and methylenedi‐p‐phenylene diisocyanate with and without solvent. The static/dynamic light scattering from DMF solutions of these samples was measured. The results were discussed in terms of the classical (Flory‐Stockmayer, FS) and percolation theory of gelation; the bulk‐polymerized sample obeyed the FS process, whereas the solution‐polymerized samples were better described by the percolation process.
Polyphenylene als Ausgangssubstanz für leitfähige Materialien
Authors: Simitzis Johannis , Dimopoulou Chrysoula
Published: April 2003

p‐Polyphenylens were synthesized from benzene with the catalytic systems AlCl3/CuCl2/H2O and FeCl3/H2O under various conditions; also o,m,p‐polyphenylenes were synthesized from biphenyl with the catalytic system AlCl3/CuCl2. A method was described for estimating the amounts of polyphenylenes and oligophenylenes, formed during the polymerization of benzene. The synthesized polyphenylenes were characterized by their melting points, elemental analysis, IR‐analysis and X‐ray studies. The polyphenylenes, except for the material synthesized with FeCl3/H2O, are crystalline. The materials synthesized with FeCl3/H2O were amorphous and contained a greater amount of chlorine. The polyphenylenes exhibit electrical conductivities, according to which they can be classified as semiconductors. The importance of three factors, which also influence the value of the electrical conductivity of the polyphenylenes, namely the crystallinity, the presence of chlorine and the structure (p‐ or o,m,p) of the polyphenylenes is stressed.
Halbleiter‐Materialien aus der Pyrolyse von Polyphenylenen
Authors: Simitzis Johannis , Dimopoulou Chrysoula
Published: April 2003

p‐Polyphenylenes and o,m,p‐polyphenylenes are pyrolyzed at various temperatures up to 1500°C in a nitrogen atmosphere. The weight loss during the pyrolysis and the residues of pyrolysis are studied by gravimetric measurements, elemental analysis, X‐ray analysis and electrical conductivity. The results of the measurements are interpreted by correlating the mechanism of pyrolysis with the structure and the numerical values of the electrical conductivity of the corresponding residues of pyrolysis. The maximum temperature of pyrolysis has a very important meaning for the electrical conductivity of the residues of pyrolysis, where has the polymerization conditions of the various polyphenylenes play only a secondary role. Three ranges of the temperature are distinguished (up to 600°C, 600 – 800°C, above 800°C), in which the corresponding residues of the pyrolysis are novel semiconductor materials with different structures and properties. Also the significance of chlorine as dehydrogenation agent is explained; chlorine contributes to the connection of neighbouring macromolecules; thus the presence of small amounts of Cl in polyphenylenes in the first temperature range of the pyrolysis seems to be suitable.
Etude de la polycondensation linéaire de polymères précurseurs α,ω‐bifonctionnels avec des agents de couplage bifonctionnels de faible masse molaire
Authors: Gnanou Yves , Chaumont Philippe , Lutz Pierre , Hild Gérard , Rempp Paul
Published: April 2003

Chain extension reactions involving α,β‐bifunctional precursor polymers and bifunctional coupling agents of low molecular weight were investigated both theoretically and experimentally. The number and weight molecular weight distributions were calculated, and computer simulations were performed, neglecting the weight of the coupling agent with respect to that of the precursor polymer. Examples of such chain extension reactions include the polycondensation of “living” α,β‐dicarbanionic polystyrene with 1,4‐bis(bromomethyl)benzene, and the reaction of poly(oxyethylene)glycol with a low‐molecular‐weight diisocyanate. The characterization of the resulting polymers yields results that are in satisfactory agreement with the theoretical expectation.
Water‐insoluble dextrans by grafting, 2. Reaction of dextrans with n‐alkyl chloroformates. Chemical and enzymatic hydrolysis
Authors: Chaves Manuel Sánchez , Arranz Félix
Published: April 2003

This work deals with the modification reaction of dextran with ethyl and butyl chloroformate using tertiary amines as catalyst/acceptor systems and the DMF/LiCl system as solvent. The structure of the resulting polymers was determined by means of IR, 1H and 13C NMR spectroscopy as well as by chemical analyses. The reaction rate was found to increase in the following order: N,N′‐dimethylaniline < pyridine < triethylamine. The presence of cyclic carbonates was observed when triethylamine was used as catalyst. A linear dependence of the reaction rate on polymer and pyridine concentrations and a more complex dependence on the n‐alkyl chloroformate concentration were found. Reaction rate and yield decrease with increasing amount of LiCl in the solvent medium and increase with increasing chain length of the n‐alkyl chloroformate. The activation energy was found to be 64 kJ/mol (15,3 kcal/mol). The equilibrium water content (EWC) values decreases progressively when either the content of carbonate groups or the side chain length increases. The hydrolysis in the heterogeneous phase showed that the time required for the polymer solubilization is dependent upon the nature of the carbonate groups, the temperature as well as the pH value of the medium. Dextranase was found to be inactive in the hydrolysis of water‐insoluble modified dextrans. However, the hydrolysis takes place when water‐soluble modified dextrans were used.
Copolymerization of monomethyl maleate and ‐fumarate with styrene
Authors: Rätzsch Manfred , Büttner Birgit , Steinert Volker
Published: April 2003

The copolymerization of monomethyl maleate (MMM) or monomethyl fumarate (MMF) with styrene is investigated. The dependence of the copolymerization rates on the composition of the monomer mixture and the monomer reactivity ratios r are determined. An identical structure of the MMM and MMF polymer radicals was found, that is the k21‐values of both copolymerization systems are equal (monomer 1 ≡ styrene; monomer 2 ≡ MMM or MMF). From this knowledge the difference of the copolymerization rates between MMM and MMF can be attributed to the k12‐values.
The effect of specific interactions on the sorption equilibrium in the polymer/mixed solvent system
Authors: Pouchlý Julius , Z̆ivný Antonín
Published: April 2003

Using the theory of association equilibria, equations are derived for preferential and total sorption into the coil for a ternary system containing inert liquid A, self‐associating liquid B and polymer C, capable of specific interactions with component B. Due to strong interactions, the assumption of random mixing is not valid for this system. In preceding work differences between experiment and prediction based on the classical Flory‐Huggins equation were formally described by the introduction of a ternary interaction term. For this particular system the ternary term may be interpreted as a consequence of the decrease in the entropy of mixing, caused by strong association of component B. On the contrary, if this component is bound to the polymer at the same time, the ternary term decreases. The equations derived in the paper lead to a reasonable fit with experimental data of the system benzene (A)/alcohol(B)/poly(methyl methacrylate)(C).
13C NMR study of O‐(2‐hydroxypropyl)cellulose
Authors: Kimura Keiichiro , Shigemura Takeo , Kubo Masao , Maru Yasumitsu
Published: April 2003

The proton‐decoupled signal of methyl carbons of O‐(2‐hydroxypropyl)cellulose (HPC) (1b, m ≥ 1) was found to be split into two peaks. The results of experiments on lanthanide shift and the dependence of the relative intensities of both peaks on the molecular weight of poly(oxypropylene) [poly(propylene oxide)] (PPO) indicated that the low‐field peak results from the terminal hydroxypropyl groups and the high‐field peak from the inside oxypropylene units. From the ratio between the intensities of the two peaks and the molar substitution (MS) (average number of oxypropylene units per anhydroglucose (AHG) unit), the degree of substitution (DS) (average number of hydroxyl groups substituted per AHG unit) was calculated. This new method could be applied to samples of low‐MS to which the conventional method based on the 1H NMR technique alone was inapplicable. From the analysis of 13C NMR spectra of HPC samples differing in MS, an authentic structural picuture of the HPC molecule could be proposed.
Etude des proprietés électro‐optiques des l'ADN par biréfringence électrique à faible champ, 3. Anisotropie optique et polarisabilité électrique
Authors: Marion Christian , Roux Bernard , Perrot Brigitte , Bernengo Jean‐Claude
Published: April 2003

The field dependence of the birefringence fraction corresponding to the well‐defined long relaxation mechanism was studied for DNA. A typical saturation curve was obtained and when analysed this phenomenon gave the parameter Δn3,s from which it was possible to calculate the electrical and optical polarizability anisotropies. The results were analyzed along the lines of recent theories and experimental data.
The influence of the penultimate chain element on monomer transfer in living polymerization
Authors: Pu Zhou , Yan Deyue , Tang Weifung
Published: April 2003

The influence of the penultimate chain element on the monomer transfer in living polymerization was treated according to Elias' kinetic scheme. The Laplace transformation and a graphic method are used to obtain the exact solution of the molecular weight distribution functions. The numerical results are discussed and compared with the molecular weight distribution curve for which a penultimate effect was not considered.
Studies on the water induced plasticization behavior of nylon 4. The influence of crystallinity and radiation crosslinking
Authors: Jin Xigao , Ellis Thomas S. , Karasz Frank E.
Published: April 2003

The influence of crystallinity and radiation crosslinking on the water induced depression of the glass transition temperature in Nylon 4 [poly(2‐pyrrolidone)] has been investigated by differential scanning calorimetry. Radiation crosslinking was effective in preventing exothermic events associated with crystallization during the measurement of the incremental change in heat capacity (ΔCp); a parameter necessary for the theoretical evaluation of the depressed glass transition temperature. ΔCp, when normalized to account for fractional crystallinity, was found to deviate substantially from a linear two phase relation. A simple three phase representation of morphology is proposed to account for this deviation, and assumptions have been made regarding the distribution of plasticizer, leading to good agreement between the theoretical and experimentally observed depressions of the glass transition temperature.
Aldehydes and acetals based on acryl‐ and methacrylamides as potential monomers
Authors: Zábranský Jiří , Houska Milan , Kálal Jaroslav
Published: April 2003

Hydrophilic monomers containing aldehyde or acetal groups based on N‐substituted amides of methacrylic and acrylic acid were prepared. The structure of these monomers prevents undesirable spontaneous intramolecular cyclization reactions of pendant aldehyde groups of the corresponding polymers. The following monomers were prepared: N‐(2‐formyl‐2‐methylpropyl)‐N‐methylmethacrylamide (3), N‐(2,2‐dimethoxyethyl)‐N‐methylmethacrylamide (5a), N‐(2,2‐dimethoxyethyl) methacrylamide (5b) and N‐(2,2‐dimethoxyethyl)‐N‐methylacrylamide (12).
Polymers with aldehyde and acetal groups based on esters of methacrylic acid
Authors: Zábranský Jiří , Houska Milan , Plichta Zdeněk , Kálal Jaroslav
Published: April 2003

Soluble poly(2,2‐diethoxyethyl methacrylate) (1a) was prepared by radical polymerization in solution. Copolymers from 2,2‐diethoxyethyl methacrylate (3a), 2‐hydroxyethyl methacrylate (4) and ethylene dimethacrylate (5) were prepared by suspension polymerization in the form of crosslinked beads (50–220 μm in diameter, specific surface area up to 38 m2/g). Acetal groups of these polymers resist direct hydrolysis, but can be transacetalized. Soluble poly(3,3‐diethoxypropyl methacrylate) (1b) was prepared by radical polymerization in solution. Copolymers with 4 and 5 were prepared by suspension polymerization in the form of crosslinked beads (30 – 140 μm in diameter; specific surface area up to 46 m2). The polymers readily under go quantitative transcacetalization. Soluble poly(2‐formylethyl methacrylate) (8) was prepared by radical polymerization in solution. Copolymers of 2‐formylethyl methacrylate (7) with 4 and 5 were prepared by suspension polymerization in the bead form (diameter 75 – 350 μm; specific surface area up to 128 m2/g). The aldehyde group of these polymers is sensitive to oxidation in air. The content of aldehyde groups was measured spectrometrically and by reaction with 1,2‐ethanedithiol.
Polymers with aldehyde and acetal groups based on acryl‐ and methacrylamides
Authors: Zábranský Jiří , Houska Milan , Kálal Jaroslav
Published: April 2003

A soluble hydrophilic polymer, poly[N‐(2,2‐dimethoxyethyl)methacrylamide] (4), and a crosslinked copolymer from N‐(2,2‐dimethoxyethyl)methacrylamide (3) and N,N′‐methylenediacrylamide (5) were prepared by radical polymerization in solution. Soluble hydrophilic poly[N‐(2,2‐dimethoxyethyl)‐N‐methacrylamide] (8) and the copolymer from N‐(2,2‐dimethoxyethyl)‐N‐methylacrylamide (7) and (5) were prepared by the same procedure. Acetal groups of these polymers can be hydrolyzed with HCl. N,N‐disubstituted methacrylamides, N(2‐formyl‐2‐methylpropyl)‐N‐methylmethacrylamide (2) and N‐(2,2‐dimethoxyethyl)‐N‐methylmethacrylamide (1) do not undergo radical homopolymerization.
Synthesis and characterization of bisacrylamide microgels containing sulfo groups
Authors: Huang Ying , Seitz Ulrich , Funke Werner
Published: April 2003

Reactive microgels containing sulfo groups were prepared by copolymerization of N,N′‐methylenediacrylamide (1) and 2‐acrylamido‐2‐methylpropanesulfonic acid (2) in water. The composition of the microgels, their structure, density, molecular weight and viscosity in solution were examined depending on the composition of the monomer mixture and the reaction conditions.
Oligoamide aus Dodecandisäure und 4,4′‐Methylendicyclohexylamin. (Oligoamide des „Qiana”︁‐Typs)
Authors: Hahn Günther Erhard , Kusch Peter , Rossbach Volker , Zahn Helmut
Published: April 2003

The pure isomers of cyclic monomers were synthesized besides the linear polymers by cyclocondensation reactions of dodecanedioyl dichloride and the pure isomers of 4,4′‐methylenedicyclohexylamine. The resulting cyclic amides were characterized by 1H NMR, IR and mass spectroscopy, as well as by HPLC and X‐ray diffraction. The content of these cyclic amides in “Qiana”‐Polyamide was determined by fractionated extraction and sublimation. Synthesis and properties of monomeric linear condensation product (dicarboxylic acid‐type with blocked and free end groups) are also described.
Dimethylsiloxane‐ethylene oxide block copolymers, 2. Preliminary results on dilute solution properties
Authors: Haesslin Hans‐W.
Published: April 2003

The dilute solution properties of poly(ethylene oxide)‐polydimethylsiloxane‐poly(ethylene oxide) (POE‐PDMS‐POE) triblock copolymers, of a POE‐PDMS segmented block copolymer and of a grafted PDMS‐g‐(POE‐co‐POP) copolymer are investigated by means of viscosity, light scattering and small angle neutron scattering. The experiments indicate that the copolymers are molecularly dispersed or aggregated, depending on the properties of the solvents. A rather compact conformation is deduced from the viscosity measurements. Negative A2‐values are observed in preferential solvents for one of the segments, a positiv A2‐value in a common solvent for both segments forming the block copolymer.
Polymerization of 1‐alkynes initiated by μ‐alkylidene complexes of tungsten, 2. Kinetics and mechanism of the initiation reaction
Authors: Meziane Driss , Soum Alain , Fontanille Michel , Rudler Henri
Published: April 2003

The existence of two successive and quite different stages in the polymerization of monosubstituted 1‐alkynes (1‐heptyne), initiated by a homo dinuclear μ‐alkylidene derivative of tungsten, is demonstrated. The first step leads to a mixture of species, the stability of which increases with the number of inserted monomeric units until inactivation. In order to explain the reactivation of these species in the second step, the loss of one carbonyl ligand is postulated, although no experimental evidence of that exists. The second step leads to high molecular weight polymer.
Polymerization of propene initiated with solubilized Ziegler‐Natta Li/Ti(III) based systems
Authors: Cansell François , Siove Alain , Fontanille Michel
Published: April 2003

Polymer [ TiCl2, TiCl3, 3LiCl] complexes were used as solubilized Li/Ti(III) based initiators for Ziegler‐Natta polymerization of propene, leading to block copolymers. From measurements of the amount of diblock copolymers produced, a direct determination of the efficiency of the catalytic system was made. This efficiency was found to be equal to about 80% with respect to the number of potentially active centers. The activity of such systems was studied as a function of both initiator concentration and [monomer]0. From the measured values of activity and efficiency of the system, the rate constants of propagation were deduced. The kinetic behaviour of such a system is fully consistent with that of a living one. A first order kinetics towards both propene and active center concentration was found. Therefore, the rate constant of propagation is an absolute rate constant, measuring the intrinsic reactivity of active sites. GPC, 13C NMR and DSC analyses of the block copolymers permitted the establishment of their well‐defined linear diblock structure and disclosed a partial stereoregularity of the polypropene block (≈ 50% isotactic triads).
Free radical crosslinking copolymerization in the post‐gel state, 3. Swelling and mechanical properties of polystyrene networks
Authors: Hild Gérard , Okasha Rouzi , Rempp Paul
Published: April 2003

The free radical crosslinking copolymerization of styrene with a bi‐unsaturated comonomer (divinylbenzene, ethylene dimethacrylate), present in small proportions, yields three‐dimensional polymer networks. The gelation time tc is generally longer than expected if all double bonds originating from the bi‐unsaturated monomer (including the pendent double bonds) were isoreactive. This delay in gelation has been attributed to the formation of intramolecular cyclizations, or to the lower reactivity of the pendent double bonds with respect to growing radicals. This paper, devoted to an investigation of the network forming reaction after gelation, presents some additional evidences in favor of the latter assumption, resulting from the variation of the fraction of extractable polymer, of the swelling degree and of the modulus of the swollen networks as a function of the overall degree of conversion. Furthermore, a direct proof of the role of the pendent double bonds is given by the “two‐step” crosslinking experiments carried out.
Dielectric relaxation in solid dextran and pullulan
Authors: Katsuyoshi‐Nishinari  , Shibuya Naoto , Kainuma Keiji
Published: April 2003

The temperature dependences of the dielectric constants of solid dextran and pullulan were observed at 10 Hz for various moisture levels of the polysaccharides. Because the dielectric loss peak at about −50°C, observed both in dextran and pullulan, shifted to higher temperatures and decreased its intensity with decreasing the moisture level, this peak was considered to be caused by water molecules. The peak at about −90°C for pullulan was attributed to the rotational motion of hydroxymethyl groups, while the peak at about −120°C for dextran was attributed to the libration of glucose residues around the α‐1,6 linkage. In order to examine this lower temperature process, the frequency dependence was observed in the temperature range from −110°C to −60°C.
Soluble cyclopentadienylated polymers
Authors: Miura Masatoshi , Akutsu Fumihiko , Usui Toshio , Ikebukuro Yasuhiro , Nagakubo Kuniharu
Published: April 2003

Copolymers from styrene and a mixture of p‐ and m‐chloromethylstyrene were reacted with sodium cyclopentadienide in THF and precipitated in methanol at temperatures lower than −20°C to obtain soluble cyclopentadienylated polymers. Due to extensive gelation, the content of cyclopentadienyl groups could not be increased to more than 4 mol‐% except with extremely low molecular weight polymers. An improved method, in which the copolymer was cyclopentadienylated in the presence of metallic sodium, gave soluble polymers with up to 29 mol‐% cyclopentadienyl groups. Pendant cyclopentadienyl groups undergo Diels‐Alder/retro‐Diels‐Alder addition to give thermoreversible cross‐linked polymers. The amount of gel fraction of a 4 mol‐% cyclopentadienylated polymer as a function of the heating time was examined in the temperature range of 40–80°C. The DSC curve of a 29 mol‐% cyclopentadienylated polymer showed an exothermic peak due to the Diels‐Alder reaction and an endothermic peak starting around 390°C, a temperature higher than that found for the degradation of polystyrene.
Iodine‐poly(vinyl alcohol) interactions, 2. Anomalous slow quenching of the chromophore after extraction of free iodine with carbon tetrachloride
Authors: Yokota Toshio , Kimura Yoshiharu
Published: April 2003

An equilibrium blue colored solution containing poly(vinyl alcohol) (PVA)‐iodine‐boric acid was prepared at 5°C. With increasing PVA concentration, at the same concentration of iodine, the absorption band of the chromophore I (λmax = 650 nm, band D) linearly increased and the intensities of the bands for both I− (λmax = 226 nm, band A) and I (λmax = 290 nm, band B) decreased. The band due to another iodide species (λmax = 355 nm, band C), tentatively assigned to I · I2, remained unchanged. Three solutions with different PVA concentration were then extracted with the same volume of carbon tetrachloride to remove I2 present in the system. It was found that the chomophore due to I gradually decays with repeated extractions. After one extraction the change of the absorbance of I with time was measured at 5°C. In the system with a high PVA concentration the chromophore recovers the equilibrium within three days without losing much intensity, while in the systems with lower PVA concentration recovering of equilibrium takes more than four days with a considerable loss of chromophore. In the latter case, free I2 extracted is supplied by the decomposition of polyiodide ions to I−. Analysis of the rate of re‐equilibration of iodine species revealed two reaction processes: one is a reaction involving free iodine species in an aqueous environment and the other is a slow reaction involving the polyiodide ions bound in a PVA cage.
Phase transitions in polyphosphazene films: Poly[bis(trifluoroethoxy)phosphazene]
Authors: Kojima Morio , Magill Joseph H.
Published: April 2003

The morphology of cast and annealed films from poly[bis(trifluoroethoxy)phosphazene] \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm \{ PBFP,\rlap{--} [(CF}_{\rm 3} {\rm CH}_{\rm 2} {\rm O)}_{\rm 2} {\rm P = N\rlap{--} ]}_{\rm n} {\rm \} } $\end{document} has been studied by electron, scanning electron and optical microscopy. Several polymorphic forms and one mesophase (hexatic) have been established. From THF solution, PBFP has a chain folded morphology (α‐orthorhombic) which transforms into a chain extended 2D hexagonal mesophase at T(1). It remains in this state until final melting occurs at Tm = 245°C approximately. Upon cooling the melt, it quickly reverts to the hexagonal mesophase again, but then passes into a chain extended (3D) γ‐orthorhombic modification. This material is much more stable thermodynamically than the α‐form, which is friable or brittle. PBFP cannot be quenched to a glassy form from the molten state, but it can be disordered as assessed by its reduced T(1) enthalpy and less well defined morphology assessed by electron microscopy. Another crystal modification (β‐monoclinic) has been found in solution cast low molecular weight PBFP films.
Spin probe study of relaxation in poly(oxytetramethylene)
Authors: Lembicz Franciszek
Published: April 2003

Using the spin probe method, the rotational mobility of two probes in poly(oxytetramethylene) (POT) in the region of rapid and slow rotation was investigated. Based on the relaxation diagram the obtained ESR results are compared and discussed in connection with other literature data. It was found that the behaviour of the probes corresponds to the α + β relaxation in the range of high frequencies. Differences in mobility of the probes as well as anisotropy effects of rotations are also discussed.
The chemical dehydrochlorination of poly(vinyl chloride), 2. Studies on N,N‐dimethylformamide solutions
Authors: Bowley Heather J. , Gerrard Donald L. , Maddams William F.
Published: April 2003

The chemical dehydrochlorination of poly(vinyl chloride) was studied in solution in N,N‐dimethylformamide. By comparison with solutions in tetrahydrofuran, examined previously, the reaction was found to occur at a significantly enhanced rate for the four systems studied, a mass polymer of 55% syndiotacticity and a low temperature polymer of 63% syndiotacticity, dehydrochlorinated with potassium hydroxide or with potassium tert‐butoxide. Furthermore, at dehydrochlorination levels up to about 60%, markedly longer polyene sequences are formed, the more so in the case of potassium tert‐butoxide., where they reach values of at least 65, as assessed by Raman spectroscopy. For levels of 80%, and greater, there is a significant decrease in the sequence lengths, the result of cross‐linking, which is facilitated by the substantial loss of the \documentclass{article}\pagestyle{empty}\begin{document}$\rlap{--} ({\rm CHCl \hbox{---} CH}_{\rm 2} \rlap{--} )_n$\end{document} sequences that sterically protect the long polyenes in the les heavily dehydrochlorinated materials. Limited results are also presented for chemically dehydrochlorinated PVC prepared by the urea clathrate method; the insolubility of this polymer probably leads to degradation on the surface of the particles only.
A polymeric prodrug of quinidine for controlled and programmed release
Authors: Astinotti Daniel , Lapicque Françoise , Dellacherie Edith
Published: April 2003

A macromolecular prodrug of quinidine was synthesized by linking the amino ester of L‐phenylalanine with quinidine to carboxymethylcellulose via an amide bond. The release of the drug results from the hydrolysis of the ester linkage which occurs only in the presence of α‐chymotrypsin at pH 8. This specificity is relative to the nature of the ester derivative whose carboxylic moiety is an aromatic amino acid residue with L‐configuration. This prodrug contains 160 mg of quinidine per g of dry powder and allows a prolonged release (5–7 h) of the drug in an intestinal medium.