bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis of silicone graft polymers and a study of their surface active properties
Authors: Kawakami Yuhsuke , Murthy Ramaswamy Aswatha Narayana , Yamashita Yuya
Published: April 2003

Silicone macromers 5, having a methacryloyl group at one end, and controiled molecular weights, were prepared by anionic polymerization of hexamethylcyclotrisiloxane (2) and subsequent termination with chlorosilane compounds containing a polymerizable vinyl groups. Graft polymers with siloxane grafts were prepared by copolymerization of these macromers with methyl methacrylate (MMA) or styrene. The surface active properties of MMA‐based graft polymers were investigated by studying the extent of surface modification of films of graft polymer‐poly(methyl methacrylate) blends.
Untersuchungen zur klärung der sensibiliserten photodegradation von polystyrol in lösungen, 1. Experimentelle befunde zum kettenabbau
Authors: Woliński Leszek , Turzyński Zbigniew , Witkowski Konrad , Zaleska Wiestawa
Published: April 2003

Polystyrene (mass average molar mass M̄ = 609700 g/mol; molecular non‐uniformity M̄/M̄ − 1 = 0,55) solutions in 8 different solvents were irradiated by light of a mercury lamp (wavelength λ ≥ 270 nm). The rate of photodegradation of the polymer (as determiened from ΔM̄w measurements by light scattering) is strongly solvent‐dependent and only slightly dependent on the O2 concentration in the irradiated solutions. An attempt to interpret this „sensibilized”︁ photodegradation will be given in the second part of this series.
Polymers containing enzymatically degradable bonds, 9. Chymotrypsm catalyzed hydrolysis of a p‐nitroanilide drug model, p bound via oligopeptides onto poly(vinylpyrrolidone‐co‐maleic anhydride)
Authors: Pató János , Azori Mária , Ulbrich Karel , Kopeček Jindřich
Published: April 2003

Copolymers of 1‐vinyl‐2‐pyrrolidone with maleic anhydride which contain oligopeptide sidechains with l‐phenylalanine p‐nitroanilide (Phe‐NAp) end groups were synthesized. The chymotrypsin catalyzed hydrolysis of these polymers was studied. The rate of p‐nitroaniline release was found to depend on the structure of the oligopeptied sequences: GlyGlyValPheNAp > GlyValPheNAp > GlyGlyPheNAp. From a comparison with similar substrates based on poly[N‐(2‐hydroxypropyl)methacrylamide] the influence of the structure of the polymeric backbone on the rate of cleavage of bonds at the ends of oligopeptide side‐chains was estimated.
The role of the termination by the polymer chain in the cationic polymerization of oxetane and 3,3‐dimethyloxetane
Authors: Bello Antonio , Pérez Ernesto , Fatou José Ma Gómez
Published: April 2003

The ring opening polymerization of oxetane and 3,3‐dimethyloxetane was carried out in dichloromethane at 25°C with triethyloxonium hexafluoroantimonate as catalyst. After polymerization, the flow times were measured for active and terminated solutions in high vacuum. In the case of oxetane, the data support the presence of branched structures in the active solutions formed by an intermolecular chain transfer reaction to the polymer chains, to give non‐strained oxonium‐ions. This intermolecular side reaction was not detected in the case of 3,3‐dimethyloxetane, if the presence of intramolecular chain transfer to a small extent is not excluded.
Phase separation by synthesis of semi‐interpenetrating network on the basis of polystyrene and poly(butyl methacrylate) from homogeneous solution
Authors: Lipatov Yury S. , Shilov Valery V. , Gomza Yury P. , Kovernik Grigory P. , Grigor'Eva Olga P. , Sergeyeva Ludmila M.
Published: April 2003

Phase separation by semi‐interpenetrating polymeric network formation based on the copolymer styrene‐divinylbenzene (PS‐DVB) and poly(butyl methacrylate) (PBMA) was investigated by light scattering. The time for phase separation was measured as a function of the rate of the copolymerization reaction and of the composition of the initial blend. The time until the outset of phase separation decreases with increasing content of PBMA in the blend. The change in concentration of DVB does not influence the process of phase separation.
Autoxidation of thiols with tetrasodium cobalt(II)phthalocyaninetetrasulfonate, bound to poly(vinylamine), 3. Dependence on molecular weight
Authors: Brouwer Wilfried M. , Piet Pieter , German Anton L.
Published: April 2003

Polymeric catalysts consisting of cobalt(II)phthalocyanine, CoPc(NaSO3)4, coordinatively bound to poly(vinylamine) of various molecular weight, were used as oxidation catalysts in the conversion of thiols to disulfides. The molecular weight of the polymeric ligand, poly(vinylamine), largely affects the reaction rate below a critical polymer concentration of about 0,01 w/v%. The activation enthalpy ΔH does not depend on the degree of polymerization (DP) of the polymeric ligand and from visible light spectra it appears that electron transfer of the thiolanion to Co(II) to yield Co(I) is favored when low instead of high molecular weight ligands are used. The observed catalytic oxidation rate of thiol is considerably higher for low molecular weight ligands (DP 20 – 40) in the low polymer concentration region. This may be attributed to a change in base strength in the micro‐environment of CoPc(NaSO3)4 due to conformational differences between low and high molecular weight ligands, manifested at low polymer concentration. When the ligand has no polymeric character, e. g. 1, 3‐propanediamine, low catalytic activity is observed.
Cinétique et mécanisme de la polymérisation de i'acrylamide initiée par le système réadox: Fe3+/complexe organique de Fe(III)/Na2S2O5
Authors: Cvetkovska Maja , Grčev Toma , Petrov Gjuro
Published: April 2003

The initiation of acrylamide polymerisation in aqueous media with a redox system of the type Fe3+/organic complex of Fe(III)/Na2S2O2 was studied. Several carboxylated amines containing the iminodiacetate group as a basic structural unit were used as complex forming reagents. A direct relation between complex stability and initiation efficiency was found. The polymerisation kinetics were studied with the most effective intiating system. Several kinetic parameters were determined and an essential relationship between polymerisation behaviour, polymer characteristices and component ratio of the initiation and polymerisation system was found. An attempt was made to explain these results.
Oxydation photothermique d'élastomères de polyuréthannes thermoplastiques, 4. Influence d'un oxyde à caractère photocatalytique
Authors: Gardette Jean‐Luc , Lemaire Jacques
Published: April 2003

A photocatalyst like TiO2 may be introduced into a polymer to control the initiation process, to protect the photo‐instable products, and to limit the oxidation to a surface phenomenon. In the case of aromatic polyurethanes, the quantum yields of photocatalytic oxidation are low as compared with the quantum yields of direct photooxidation. Photoactive pigments behave as stabilisers for the oxidation pathway. On the other hand, the photocatalyst acts as a screen for the Fries photorearrangement products and inhibits their photooxidation. Yellowing of polyurethanes is partly due to the photoinduced oxidation and partly to the Fires photorearrangement products. It is shown that in the presence of photoactive pigments the yellowing of polyurethanes due to Fires photorearrangement is the most determental process.
Synthesis and properties of 9,10‐dialkoxyanthracenes as fluorescent probes specific of polyolefins and their application to orientation measurement in polyethylene
Authors: Young Chor Keung , Jasse Bruno
Published: April 2003

9,10‐Dialkoxyanthracenes with an even number of carbon atoms n in the aliphatic chain from n = 2 to n = 18 were prepared by reaction of the corresponding bromoalkanes with the sodium salt of dihydroanthraquinone. Ultra‐violet and fluorescence spectra as well as life‐times of the excited state of these different fluorescent probes were determined. Higher terms with n ≥ 8 proved to be valuable to measure the amorphous phase orientation in polyolefins.
Les effets thermiques associés à la transition vetreuse de films de poly(téearéphatalate d'éthylène)
Authors: Chauchard Jacques , Lachenal Gilbert
Published: April 2003

Differential scanning calorimetry and thermomechanical analysis are used for examining the thermal behaviour of amorphous poly(ethylene terephthalate) films in the glass‐transition range. By variation of the heating rate between 0,2 and 100 K. · min−1, it is possible to obtain either an exotherm associated with a shrinkage, or an endotherm, or both of these phenomena. It is found that very low heating rates not only give rise to a retardation mechanism but also to a molecular rearrangement.
Functional polymers and sequential copolymers by phase transfer catalysis, 1. Alternating block copolymers of unsaturated polyethers and aromatic poly(ether sulfone)s
Authors: Percec Virgil , Auman Brian C.
Published: April 2003

Williamson etherification in the presence of phase transfer catalysts was successfully applied to the synthesis of alternating block copolymers and regular copolymers. Unsaturated polyethers(5a and 5b) containing chloroallylic (electrophilic) end groups (prepared from cis‐or trans‐1, 4‐dichloro‐2‐butene and Bisphenol A) and aromatic poly(ether sulfone)s (3a) containing terminal phenol (nucleophilic) groups were polycondensed in the presence of tetrabutylammonium hydrogen sulfate as phase transfer catalyst to give alternating block copolymers. The same telechelic polymers were chain‐extended with dinucleophilic or dielectrophilic monomers under similar reaction conditions. Both the regular copolymers and the alternating block copolymers were characterized by gel pormeation chromatography and DSC.
Preparation of a polysulfone by polycondensation of disodium 4,4′‐oxydibenzenesulfinate with 4‐bromomethylbenzyl bromide
Authors: Sato Moriyuki , Yokoyama Masaaki
Published: April 2003

Polycondensations of 4‐bromomethylbenzyl bromide (p‐xylylene dibromid) (1) were carried out with 4,4′ ‐oxydibenzenesulfinate (3) in the presence of phase transfer catalysts, investigating the effect of reaction media, catalysts, monomer concentration, and reaction time. The polymer with the highest molecular weight was obtained at a monomer concentration of 8/15 mol/1 in nitrobenzene at 80°C for 48 h in the presence of tetrabutylammonium chloride. The characterization of the product by 1H NMR and IR spectra and by elemental analysis indicates the structure of a copolymer (5), containing both sulfinate and sulfone linkages in the main chain. Thermogravimetry of the product shows that its thermostability is lower than that of commercial poly(ether sulfone)s.
Structure of active species in the cationic polymerization of β‐propiolactone and ε‐caprolactone
Authors: Hofman Andrzej , Szymański Ryszard , Słomkowski Stanislaw , Penczek Stanislaw
Published: April 2003

The study of the structure of the end‐groups of poly(β‐propiolactone) and poly(ε‐caprolactone) by 1H, 31P{1H} NMR, and IR spectroscopy revealed that the mode of ring scission in the monomer in the first propagation step depends on the initiator used. In the initiation of the β‐propiolactone and ε‐caprolactone polymerization with halonium salts ((CH3)2Br⊕SbF6⊖ or (CH3)2I⊕SbF6F6⊖) the exocyclic oxygen atoms in the monomer molecules are attacked and oxonium ions are formed. The propagation steps proceed with alkyl‐oxygen bond scission in the active center and with attack at the exocyclic oxygen atom in the subsequent monomer molecule. Thus, the tertiary oxonium ions are the exclusive active species from the very beginning of the polymerization. Acylium cations (CH3CO⊕ SbF6⊖ or CH3CH2CO⊕SbF6⊖) as initiators attack both exo‐and endocyclic oxygen atoms in the monomers and the initiation proceeds with almost equal proportions of alkyl‐oxygen and acyl‐oxygen bond scission. Thus, in the polymerization of β‐propiolactone the concentration of the acylium growing species decreases with increasing number of propagation steps and finally the tertiary oxonium ions are becoming the exclusive growing species. In the polymerization of ε‐caprolactone the active acylium centers apart from propagation participate also in side reactions leading to the cleavage of a proton.
Polymers from renewable sources, 2. Kinetics and polyurethane formation from furan‐based diisocynates
Authors: Cawse John L. , Stanford John L. , Still Richard H.
Published: April 2003

Novel furan‐based diisocyanates (2a – c) were reacted with 1‐butanol and basic kinetic studies were made. The results were compared with those obtained from 4,4′‐methylenediphenylene diisocyanate (1) under similar conditions. The kinetics of these model reactions were found to be complex even in the presence of added catalysts. The isocyanates 2 studied, were shown to behave as benzylic type compounds with reactivities intermediate between those of aryl and alkyl diisocyanates. Comparative studies were made on segmented copolyurethanes prepared from 1 and from a furfuryl diisocyanate 2a having structural similarity to 1. The diol components used in these studies were 1,4‐butanediol and polytetrahydrofuran. The segmented co‐polyurethanes prepared from the furfuryl diisocyanate can thus be derived from a single naturally occurring source material, namely furfuraldehyde. These polymers were shown by differential scanning calorimetry and dynamic mechanical analysis to possess properties comparable to analogous copolyurethanes derived from oil‐based sources.
Dilute solution properties of poly(methyl methacrylate) in acetonitrile + carbon tetrachloride mixtures
Authors: Vázquez Jesús , de Blas Luis , Prolongo Margarita G. , Masegosa Rosa M. , Hernández‐Fuentes Irmina , Horta Arturo
Published: April 2003

Heterotactic poly(methyl methacrylate) (PMMA) is studied by light scattering and viscometry in the mixture acetonitrile + CCl4. Both liquids are poor solvents of PMMA, but their mixture is a very good solvent of this polymer. The total sorption potential of the coil is calculated from second virial coefficient and intrinsic viscosity results. Unperturbed dimensions, Mark‐Houwink exponent, Schulz‐Blaschke constant, and coil expansion factor are also determined. The enhanced total solvent sorption is larger in this mixture than in any other cosolvent system of PMMA thus far studied. This is due to the strong repulsive interactions between acetonitrile and CCl4. Such interactions also determine the inversion in preferential sorption that occurs close to equimolar composition. Acetonitrile can interact favourably with the ester group of PMMA and unfavourably with its methylene backbone. The role of such opposing interactions and of liquid order in acetonitrile are taken into account to discuss the results.
Molecular modelling of the anisotropy of motion in polysaccharides: an example
Authors: Gagnaire Didier , Pérez Serge , Tran Vinh
Published: April 2003

A qualitative analysis of NMR relaxation data is reported, using motional models based on the consideration of conformational states arising from the architectural specificity of the different building units of a polysaccharide. The choice of a pertinent referential axis, such as either a local helical axis or a local inertial axis is discussed.
Über polymere 4‐vinylimidazolide und deren verwendung als acylierungsreagenzien
Authors: Manecke Georg , Stärk Michael
Published: April 2003

Several copolymers of 4(5)‐vinylimidazole (1a) containing different amounts of divinyl‐benzene (DVB) as crosslinking agent and also copolymers of 1a (crosslinked, 4 mol‐%) with styrene, 4‐vinylpyridine, 1‐vinylimidazole, or 4‐vinylbenzoic acid were obtained by radical polymerisation. The pendant imidazole‐groups of all of these polymers could be acylated in their 1‐position. The swellability of the resulting polymeric N‐acylated imidazoles in suitable solvents was investigated. They were used for the acylation of amines and alcohols, variing the mole ratio reactive polymer/substrate, the reaction time, and the solvent. A gradual reacitivity was found for the reaction with low molecular mass compounds according to the nucleophilicity of the substrates. Ethanolamine could be selectively N‐acetylated and in the case of the mono‐trifluoroacetylation of hexamethylenediamine significantly high yields of mono‐acylated product were obtained. After the reaction the polymers could be regenerated without any loss of activity.
Etude de la synthèse et de la microstructure du polyallylbenzène
Authors: Boiteux‐Steffan Gisèle , Pham Quang Tho
Published: April 2003

Poly(allylbenzene)s were synthetised by Ziegler‐Natta catalysts: {VCl3 + Al[CH2CH(CH3)2]3} and {TiCl4 + Al[CH2CH(CH3)2]3}. Two different polymers were obtained. Examination of their microstructures by IR and 1H13C NMR spectroscopy suggests that one of the polymerization mechanisms proceeds via isomerization of allylbenzene.
Formation of high molecular weight polythiiranes in aqueous‐organic media
Authors: Amerik Yuri B. , Shirokova Lidia A. , Toltchinsky Isaak M. , Krentsel Boris A.
Published: April 2003

The influence of water on the polymerization of thiirane and 2‐methylthiirane with CdCO3 was studied. The polymerization process takes place only when a large interface monomer‐water is formed. This is achieved by the presence of an amount of water in the reaction mixture which is comparable with that of the monomer. The polarity of the solvent does not influence the rate of formation of poly(2‐methylthiirane). The polymerization is carried out in the mass of monomer or in the presence of an alcohol and a solvent not miscible with water.
On the kinetics and mechanism of thermal degradation of polystyrene, 2. Formation of volatile compounds
Authors: Schröder Ulrich K. O. , Ebert Klaus H. , Hamielec Archie W.
Published: April 2003

Thermal degradation of polystyrene (PS) was carried out in the absence of oxygen between 292 and 336°C. The formed volatile products were analysed qualitatively and quantitatively by means of gas charomatography. It was found that the composition of the volatile fraction is a function of conversion and independent of temperature for most of the products. A radical chain mechanism is proposed to explain these experimental results.
Kinetics of the polymerization of styrene with butoxytitanium trichloride and trialkylaluminium
Authors: Sehra Jagdish C. , Gundiah Subbaraya
Published: April 2003

The kinetics of polymerization of styrene in heptane was investigated using butoxytitanium trichloride and triethylaluminium/triisobutylaluminium as cocatalysts. A steady state polymerization after an initial period of declining rates lasting for 20 – 60 min was observed. Both the catalysts systems polymerize styrene at a slow rate ( ≈ 10−6 mol · dm−3 · s−1). The steady state rates show a maximum at an [A1] : [Ti] ratio of 1,5 and exhibit a first‐order rate law with reference to both the monomer and the catalyst. Addition of triethylamine, an electron donor, greatly influences the rates of polymerization when triethylaluminium is used, whereas in the case of triisobutylaluminium, the rates are not greatly influenced by the presence or absence of triethylamine. The effect of the electron donor on the rates of polymerization can be explained by the competitive complexation of the alkylaluminium and the electron donor at the active site. The overall activation energy of polymerization (44 – 46 kJ · mol−1) is in accord with a coordinated anionic mechanism. An alkylated alkoxytitanium halide species as the chemical entity affecting polymerization is suggested.
Etude du couplage chromatographie d'exclusion‐diffusion de la lumière, 1. Dispositif expérimental et étude de polystyrènes «références»
Authors: Beltzung Laure , Strazielle Claude
Published: April 2003

The possibilities of coupling size exclusion chromatography with light scattering (GPC‐DDL) are studied. The continuous light scattering detector is a modified (laser He‐Ne excitation) classical light scattering apparatus Fica 42000, equipped with a flow cell of low capacity (120μl). With this cell, a detection of the scattered light is obtained only at an angle of 90°. The light scattering detector is coupled with a GPC apparatus (packed with 10 μm gel particles). The precision, reproducibility and limitation to obtain molecular weight distribution curves of “standard” linear polystyrenes are studied.
Etude du couplage chromatographie d'exclusion — diffusion de la lumière, 2. Application a quelques problèmes particuliers
Authors: Beltzung Laure , Strazielle Claude
Published: April 2003

A continuous light scattering detector coupled to a gel permeation chromatography (GPC) instrument (GPC‐LS), as described in the preceding paper, is used to determine the hydrodynamic structure factor g′ of branched polystyrene samples and to establish the viscosity law for poly(methyl methacrylate), poly(vinyl chloride), and poly(vinyl acetate) by comparing the results from GPC‐LS and GPC analysis (with molar mass calibration with linear, monodisperse polystyrene samples).
Precipitation studies of polystyrene from solution
Authors: Lau Ming Yan , Poh Beng Teik
Published: April 2003

The precipitation behaviour of polystyrene from solution was studied for the ternary system of polymer/solvent/precipitant, the solvent being toluene or ethyl methyl ketone and the precipitant methanol. The relationships between the efficiency of precipitation and temperature of precipitation, concentration of the solution, molecular weight of the polymer, and the solvent system were investigated. The optimum volume ratio of the polymer solution to precipitant, in order to obtain maximum efficiency of precipitation for a particular system, was derived from graphical plots. The results indicated that the efficiency increases with increasing concentration of the solution, molecular weight of polymer, and thermodynamically “poorer” solvent, but decreases with increasing temperature between 200 K and 300 K. It was also observed that a plot of the efficiency of precipitation versus the volume ratio of polymer solution to precipitant passes through a maximum for all the systems studied. The optimum volume ratio of polymer solution to precipitant exhibits a similar behaviour just as in the case of the efficiency of precipitation. Information obtained from this study enables one to select the best combination of the parameters affecting precipitation, in order to produce a high yield of precipitate of polystyrene at a relatively low cost of solvent and precipitant for a particular temperature of precipitation.
Beitrag zur Diskussion um die Morphologie von polyacetylen
Authors: Weßling Bernhard
Published: April 2003

We analysed by raster electron microscopy Luttinger‐polyacetylene as a powder and as a film, both in pristine and (SbF6−‐electrochemically) doped form. The samples had been intensively washed with MeOH/HCl. One sample had, according to the results of transmission electron microscopy, fiber morphology. All samples show globules as primary structure arranged in clusters (in powder), mono‐layers, or chains (in film) (which previously led to “fibril theory”). The primary spherical particles have diameters from 0,02–0,05 μm. The “fibril” sample has very small spherical primary particles, which may develop using low catalyst amounts. Our results support that the conductivity characteristics is governed by phenomena antiparallel to the chain direction (change‐transfer‐complexes).
13C NMR spectroscopy of 2‐formamido‐2‐methylpropyl acrylate and poly(2‐formamido‐2‐methylpropyl acrylate)
Authors: Reddy Boreddy S. R. , Arshady Reza , George Maurice H.
Published: April 2003

The synthesis and characterization of 2‐formamido‐2‐methylpropyl acrylate (FMPA) is reported. 13C NMR spectra of FMPA in CDCl3, CD3OD, DMSO‐d6, DMF‐d7, and D2O exhibit two pairs of lines for all seven carbon atoms at room temperature; the ratio of the two conformers varies moderately with solvent (21 : 79 to 41 : 59). The conformers are believed to involve strong internal hydrogen bonding which is not completely broken even by the addition of trifluoroacetic acid to CDCl3 (1/1, v/v). However, the pairs of lines coalesce in turn as the temperature is raised to 120°C in DMSO‐d6. FMPA was polymerized at 35°C in DMF and CHCl3, using a free radical initiator and the polymer was characterized by 13C NMR spectroscopy.
Functional metal‐porphyrazine derivatives and their polymers, 12. Synthesis and properties of polyimides containing a metalphthalocyanine ring and a pyridyl group
Authors: Shirai Hirofusa , Takemae Yoshitaka , Kobayashi Kesayoshi , Kondo Yoshiyuki , Hirabaru Okikazu , Hojo Nobumasa
Published: April 2003

A novel class of polyimides (6a – c) containing Mt(II)‐phthalocyanine rings was synthesized by solution condensation in N‐methyl‐2‐pyrrolidone of Mt(II)‐[2,9, or 10(or 2,16, or 17)bis(3,4‐dicarboxybenzoyl)]phthalocyanine dianhydride [Mt(II)‐dahPc: Mt(II) = Co(II), Ni(II), and Cu(II)] with 2,6‐diaminopyridine, followed by thermal imidation. The polyimides showed room temperature dc‐conductivities in the range of 10−12 − 10−9 Ω−1 · cm−1, and, after quaternization of the pyridine group, the conductivities increased by 1 to 3 orders of magnitude.
Interaction of cross‐linked polyacrylic acid with cetyltrimethylammonium bromide
Authors: Musabekov Kuanyshbek , Abilov Zharylkasyn , Beisebekov Marat
Published: April 2003

The interaction of cross‐linked copolymers of acrylic acid with divinylbenzene (PAA‐C‐L) with the micelle‐forming surface‐active cetyltrimethylammonium bromide (CTMAB) is studied. It is shown that the ion‐exchange interaction of PAA‐C‐L with CTMAB at small degrees of polyelectrolyte cross‐linking is analogous to the interaction of linear polyacrylic acid with CTMAB. The total quantity of surface‐active substances (SAS) bound to PAA‐C‐L increases with an increase of the SAS concentration in the solution, with the pH of the medium, and with the quantity of the binding agent in the ion exchange resin.
Complex formation between bovine serum albumin and poly(acrylic acid) as studied by viscometry, circular dichroism, and fluorescence spectroscopy
Authors: Kuramoto Noriyuki , Sakamoto Munenori , Komiyama Jiro , Iijima Toshiro
Published: April 2003

The complex formation between bovine serum albumin (BSA) and poly(acrylic acid) (PAA) in water was studied by viscosity measurements. It was found that at a BSA/PAA mole ratio of 233 the reduced viscosity of the solution shows a minimum, indicating that binding take place nonspecifically on the BSA surface. Circular dichroism (CD) spectra indicate that BSA does not suffer conformational alteration by the presence of PAA. Fluorescence spectroscopic studies were performed on 1‐anilinonaphthalene‐8‐sulfonate(ANS)‐BSA systems in presence of monocarboxylic acids or PAA. Again, in contrast to the hydrophobic binding of the monoacids, it was found that PAA binds to BSA nonspecifically on the surface.
Sodium metatungstate, a new medium for binary and ternary density gradient centrifugation
Authors: Plewinsky Bodo , Kamps Rainer
Published: April 2003

Sodium metatungstate, Na6[H2W12O40] is presented as a new medium for density‐gradient centrifugation. This electrolyte may be used in aqueous, aqueous sodium chloride, or in methanol solutions. The sedimentation behaviour of sodium metatungstate in binary (Na6[H2W12O40]/H2O) and in ternary (Na6[H2W12O40]/NaCl/H2O) systems is presented and discussed. Practical examples are presented from macromolecular chemistry (Sedipur), biochemistry (DNA), and mineralogy (sodium‐aluminium mica).
Quasielastic light scattering studies of the pressure‐induced denaturation of lysozyme
Authors: Nyström Bo , Roots Jaan
Published: April 2003

The pressure‐induced denaturation of lysozyme in acetic acid/acetate buffer at pH = 4,0 was studied in the pressure range 1 – 4500 atm (0,10 · 106 – 456 · 106 N/m2) by photon correlation spectroscopy. The hydrodynamic radius RH, initially independent of pressure, was at moderate pressures observed to pass through a minimum. At higher pressures, in the transition region, RH upon pressure denaturation was approximately 9%. This increase was significantly smaller than those reported from quasielastic light scattering measurements on lysozyme solutions utilizing chemical agents and temperature as denaturants. Speculative arguments for this behaviour are presented. Upon releasing the pressure the return of RH was not reversible. The influence of pressure on the mutual diffusion coefficient was studied for a low and a high concentration. The results indicate that there exist enhanced intermolecular interactions at higher concentrations.
Investigation of polyesters of adipic acid and sebacinic acid with hydroquinone by pyrolysis‐mass spectrometry
Authors: Aguilera Carlos , Lüderwald Ingo
Published: April 2003

The structure and thermal degradation behaviour of polyesters of adipic acid and sebacinic acid with hydroquinone were investigated by direct pyrolysis in the ion source of a mass spectrometer. Poly(oxyadipoyloxy‐1,4‐phenylene) (1) and poly(oxyebacoyloxy‐1,4‐phenylene) (2) undergo a cleavage of the ester bond as a very selective thermal degradation reaction (Eq. (iii)). In order to differentiate the thermal and electron impact induced degradation reactions of these polyesters the fragmentation pathways of corresponding low molecular weight esters were followed.
Syntheses and thermodynamic studies on the protonation behaviour of polymers containing acylpiperazinyl units in the backbone or in the side chain of a vinyl polymer
Authors: Barbucci Rolando , Casolaro Mario , Ferruti Paolo , Tanzi M. Cristina , Grassi Lucia , Barozzi Chiara
Published: April 2003

Linear poly(1,4‐piperazinediyl‐1‐oxotrimethylene) (1), in which amido and tertiary amino groups regularly alternate along the macromolecular chain, the isomeric poly[1‐(1‐piperazinyl‐carbonyl)ethylene] (8) for polyvinylic structure and its N‐methylated derivative, poly{1‐[(4‐methyl‐1‐piperazinyl)carbonyl]ethylene} (3), were prepared and characterized. Their protonation behaviour was investigated in aqueous solution by potentiometric and calorimetric techniques. In all cases the basicity constants were found to decrease linearly with α (the degree of protonation), whereas the enthalpy changes show a different behaviour toward protonation. The thermodynamic values indicate the important role of hydrophobic interactions.
New divinylidene compounds and their reaction with electron transfer reagents
Authors: Bastelberger Thomas , Thu Cuc Tran , Höcker Hartwig
Published: April 2003

Some new divinylidene compounds, 1,3‐bis[4‐(β‐styryl)phenyl]propane (2b), 1,6‐bis[4‐(β‐styryl)phenyl]hexane (2d), 2,6‐bis(β‐styryl)pyridine (1b), and 1,5‐bis(β‐styryl)naphthalene (1c), were prepared. Their reaction with electron transfer agents was investigated and compared with that of homologous divinylidene compounds. The cyclic oligomers formed after protonation were separated and characterized spectroscopically. In general, no preferential formation of isomers is observed. The cyclic dimer, however, is the main product of the electron transfer reaction of 1b and 1c.
Etude des propriétés électro‐optiques de i' ADN par biréfringence électrique à faible champ, 1. Théorie, appareillage et exploitation des résultats
Authors: Marion Christian , Roux Bernard , Bernengo Jean‐Claude
Published: April 2003

Electric birefringence (or Kerr effect) measurements can give, in principle, important informations on the optical, electrical and hydrodynamical properties of macromolecules. The theoretical basis of the Kerr effect is reviewed here so as to be applied to the determination of some molecular parameters of DNA such as optical and electrical polarizability anisotropies, permanent dipole moment, and rotatory diffusion constant. It is necessary to conduct the measurements at very low electric fields. The original device used and the methods for the analysis of the experimental data are described.
Photoinitiated degradation of poly(diacetylene)s in solution by random chain scission
Authors: Müller Michael A. , Wegner Gerhard
Published: April 2003

Poly(diacetylene)s dissolved in common organic solvents undergo random chain scission, if irradiated by UV‐light. The pure polymers and their solutions are, however, stable, if they are photoirradiated within the main‐absorption band of the polymer backbone. The usual triplet sensitizers, especially in the presence of oxygen, and radical donors such as 2,2′‐azoisobutyronitrile (AIBN) enhance the rate of photodegradation. Suitable dyes are able to sensitize the chain‐scission in the visible regions as well. Random chain scission occurs also in the dark, but only at temperatures above room temperature and is enhanced by the addition of radical‐donors, e.g. AIBN. A mechanism of chain scission, induced by the attack of a radical to a multiple bond of the polyconjugated backbone of the polymer is proposed.
The rubber elastic behaviour of crosslinked polymers and a critical consideration of theoretical concepts
Authors: Gebhard Georg , Gleim Wolfgang , Rehage Günther , Schwarz Jürgen
Published: April 2003

The elastic properties in simple elongation have been investigated under various aspects for a series of elastomers, which were crosslinked randomly in the bulk state. The results are compared with different theoretical concepts for explaining the deviations from predictions of the simple statistical theory of rubber elasticity. The results do not favour clearly any one of the theoretical concepts under discussion.
Equation of state for linear polymer melts: the chemical structure parameter and its relationship to the characteristic volume, packing densities, characteristic bulk modulus and glass transition temperature
Authors: Roszkowski Zbigniew
Published: April 2003

It is shown that the three‐parameter equation of state for linear polymer melts, although consistent with the theorem of corresponding states, contains no information about the chemical structure of the polymer chain. This information is now included in the equation via a fourth parameter representing the structure. The relations between the chemical structure parameter and the characteristic volume of the polymer, its dense packing, characteristic bulk modulus, and glass transition temperature are deduced. It is demonstrated that the properties of the polymer are influenced by the compressibility of the polymer chain, which was not taken into account in the mechanical‐statistical approaches to the equation of state for liquid polymers. It is also shown that the dense packing of a polymer is almost equal to the close packing of spheres. The determination of the parameters of the four‐parameter equation requires the knowledge of the van der Waals volume of the constitutional repeating unit and p V T data for the liquid polymer, including the glassy transition region. This region should be investigated under cooling conditions considered as isochronal, the time of viscoelastic relaxations assumed to be zero.
Linear and star‐shaped hybrid polymers, 3. An improved purification procedure for coupling products of oligosaccharides by amide linkage
Authors: Ziegast Gerd , Pfannemüller Beate
Published: April 2003

A convenient method for binding saccharides to natural and synthetic substances, polymers and low molecular weight compounds, consists in coupling via an amide linkage. For this purpose aldonolactone or amino groups are introduced at the reducting end of the saccharides which allows coupling to a great variety of amino and carboxyl groups containing compounds. Purification with the usual ion‐exchange resins based on polystyrene proved unsatisfactory for oligosaccharides due to adsorption effects and reduced ion‐exchange capacity. Excellent results on each step of conversion are obtained by chromatography on a cross‐linked poly(acrylamide) gel (Bio‐Gel P‐4 and P‐10) containing a small amount of carboxylic groups introduced by moderate saponification. The new procedure combining the effect of molecular size fractionation and ion‐exchange chromatography offers a wide field of application.
Tailor made partially substituted poly(iminoethylene) and derivatives in activated ester hydrolysis
Authors: Everaerts Albert , Samyn Celest , Smets Georges
Published: April 2003

Linear poly(iminoethylene) (polyethyleneimine) (l‐PEI) was transformed into three types of branched polymers, which differ by the length and nature of the side groups, and their degree of substitution. By reaction with (1‐benzyloxycarbonyl‐2‐methylaziridine) (N‐benzyloxycarbonyl‐propyleneimine) (Z‐PI) followed by HBr‐acidolysis, N‐2‐aminopropyl derivatives of PEI with different degrees of substitution were obtained (1‐S‐y‐PEI). The synthesis of polymers with 2‐(2‐aminopropylamino)propyl groups was carried out by first partial acetylation of 1‐PEI, subsequent treatment twice with Z‐PI followed by HBr‐acidolysis, and finally deacetylation with 6 N HCl at 100°C (2‐S‐y‐PEI). Finally, reaction of I‐PEI with Z‐5‐aminopentyl tosylate gave polymers containing 5‐aminopentyl side groups (C5‐S‐y‐PEI). The catalytic activities of these three types of polymers were compared in the hydrolysis of p‐nitrophenyl acetate and 4‐acetoxy‐3‐nitrobenzoic acid. The reactions were followed under the conditions of pseudo‐first order kinetics, for which [Catalyst] ≫ [Substrate], and also under the conditions of Michaelis‐Menten complex formation kinetics, for which [Substrate] > [Catalyst]. The results indicate that the optimum catalytic activity is determined by the length of the spacer by which the primary amino groups is linked to the main chain, resulting in the following order of activity: (2‐S‐y‐PEI) ≈ (C5‐S‐y‐PEI) > (1‐S‐y‐PEI).
Die kristallstruktur von oligo[(2‐hydroxy‐1,3‐phenylen)methylen]en
Authors: Paulus Erich , Böhmer Volker
Published: April 2003

The crystal structure of three tetranuclear phenolic compounds – 6,6′‐bis (2‐hydroxy‐5‐methylbenzyl)‐4,4′‐dimethyl‐2,2′‐methylenediphenol (1), 6‐(2‐hydroxy‐3,5‐dimethylbenzyl)‐6′‐(2‐hydroxy‐5‐methylbenzyl)‐4,4′‐dimethyl‐2,2′‐methylendiphenol (2), and 6‐(3‐tert‐butyl‐2‐hydroxy‐5‐methylbenzyl)‐6′‐(2‐hydroxy‐5‐methylbenzyl)‐4,4′‐dimethyl‐2,2′‐methylene‐diphenol (3) –, was determined by single crystal X‐ray analysis. Intramolecular hydrogen bonds between all hydroxyl groups of adjacent phenolic units are found for all molecules. They are directed to the opposite end of the molecule by the ortho‐methyl or ortho‐tert‐butyl group in compounds 2 and 3, while no special orientation is found in 1. The conformation of the phenolic units is trans/trans (anti/anti) in 1 and cis/trans (syn/anti) in 2 and 3. Consequently, in the crystal lattice, 2 and 3 form cyclic dimers via intermolecular head‐to‐tail hydrogen bonds, while the molecules of 1 are arranged to chains of indefinite length by head‐to‐head and tail‐to‐tail hydrogen bonds.
Characterization of graft copolymeres of methyl cellulose and polyacrylamide by thermogravimetry
Authors: Kohli Krishna , Mukhopadhyay Sailes , Chatterjee Satya R.
Published: April 2003

Thermal stability and degradation kinetics of methyl cellulose, polyacrylamide and methyl cellulose grafted with different amounts of polyacrylamide were investigated by thermogravimetry. Polyacrylamide was found to be more stable than methyl cellulose. The thermal stabilities of the graft copolymeres lie in between these two extremes. The order of reaction, n, and energy of activation, E, of the thermal degradation were determined for all polymer samples. It was found that E for the degradation of polyacrylamide (41,4 kcal/mol = 173,2 kJ/mol) is higher than that of methyl cellulose (31,3 kcal/mol = 131,0 kJ/mol) and that E for the graft copolymers lies in between those of the two homopolymers. The over‐all reaction order of the degradation reactions was found to be unity for all polymer samples investigated.
Speckle patterns in small angle light scattering: A random phase screen approach
Authors: Holoubek Jaroslave , Sedláček Blahoslav
Published: April 2003

The basic features of scattering are shared by a number of closely related scatterer systems. The most elementary model for these systems in the random phase screen (RPS). In this article, predictions of the RPS theory are compared with the experimental data obtained by analysing scattered light speackle patterns from a film made of a semicrystalline polymer. On the basis of results obtained, it is possible (a) to classify speckle types depending on the illuminating conditions, (b) to measure speckle “smoothing” by determining the contrast of speckle intensity fluctuations, (c) to illustrate the relation between object and speckle movements in different geometries for simple types of sample movement (rotation, linear continuous translation and step‐wise translation). The experimental data tend to confirm the validity of RPS theory in the case of polymer films. It is indicated that under certain conditions the statistical, temporal and spatial coherence properties of the scattered light are sensitive to the detailed internal structure of the scattering medium.
Liquid phase peptide synthesis by fragment condensation on a soluble polymer support, 6. The influence of peptide‐chain lengths of Boc‐oligopeptides on the coupling efficiencies of their C‐terminal amino acids in coupling reactions with polymer‐bound amino acids
Authors: Isokawa Shizuko , Kobayashi Naoyuki , Nagano Ro‐ichi , Narita Mitsuaki
Published: April 2003

The influence of both the peptide‐chain lengths of Boc‐oligopeptides and the degree of crosslinking of polymer supports on the coupling efficiencies of the C‐terminal amino acids of Bocoligopeptides in the coupling reactions with terminal free amino groups of amino acids linked to polymer supports was investigated. The coupling efficiencies of Boc‐oligopeptides (consisting of 3 to 10 amino acid residues) relative to those of Boc‐Val‐OH or Boc‐Met‐OH were determined by competitive coupling reactions with amino acids anchored to soluble and crosslinked polystyrene supports, using four systems of coupling reagents dicyclohexylcarbodiimide (DCC) + 1‐hydroxy‐1 H‐benzotriazole, DCC + N‐hydroxysuccinimide, DCC + N‐hydroxy‐5‐norbornene‐2,3‐dicarboximide, and N‐ethoxycarbonyl‐2‐ethoxy‐1,2‐dihydroquinoline. In the coupling reactions on soluble polystyrene supports, containing 1 mol‐% of an amino acid (per styrene monomeric unit), and on poly(styrene‐co‐divinylbenzene (1%)), containing 1 or 10 mol‐% of an amino acid, little influence of peptide‐chain lengths was observed. In reactions with amino acids anchored to poly(styrene‐co‐divinylbenzene (2%)) (containing 2 or 20 mol‐% of terminal amino groups), an increase in peptide‐chain length of Boc‐oligopeptides was found to reduce remarkably the coupling efficiencies of their C‐terminal amino acids. With poly(styrene‐co‐divinylbenzene (2%))s as supports, it was detected that amino groups are present which are sterically inaccessible for peptide fragments such as Boc‐Ala‐Ala‐Leu‐Leu‐Leu‐OH and Boc‐Ala‐Ala‐Leu‐Leu‐Leu‐Pro‐Pro‐Leu‐Leu‐Leu‐OH.
Functional monomers and polymers, 118. Asymmetric syntheses of 2‐alkylcyclohexanones using chiral polymers containing aminobornanol moieties
Authors: Liu Jui Hsiang , Kondo Koichi , Takemoto Kiichi
Published: April 2003

Cis‐endo‐3‐amino‐endo‐2‐bornanol (5) and exo‐5‐amino‐endo‐2‐bornanol (2) (prepared from endo‐2‐hydroxy‐5‐bornanone (1)) were reacted with chloromethylated polystyrene. With the resulting chiral polymers 4 and 6 asymmetric syntheses of 2‐alkyl‐cyclohexanones were carried out. These reactions showed a high enantioselectivity particularly with the chiral polymer 6, which suggests a specific restricted transition state to be important for the asymmetric alkylation reaction.
Block copolymers with broad interphase. Determination of morphological parameters and interphase width by electron microscopy and small angle X‐ray scattering
Authors: Annighöfer Frank , Gronski Wolfram
Published: April 2003

Poly(isoprene‐b‐(isoprene‐co‐styrene)‐b‐styrene) three‐block copolymers with a random copolymer centerblock and an over‐all 50 wt.‐% styrene content were analysed by electron microscopy (EM) and small angle X‐ray scattering (SAXS) in the range of 0 to 33 wt.‐% random copolymer content, where these systems possess a two‐phase lamellar morphology with enhanced broadening of the transition region between the pure isoprene and styrene phases. By evaluation of EM micrographs of ultra‐thin sections stained with osmium tetroxide and by analysis of the total meridional SAXS intensity distribution by means of a one‐dimensional paracrystalline model, the variation of the mean long period, fluctuation of lamellar thicknesses, and of the interphase width were obtained in dependence of the copolymer content. The analysis shows that the volume fraction of the interphase in variable in the range between 8,5 wt.‐% and 65 wt.‐%. In addition the SAXS analysis provides information about the functional form of the density profile in the interphase.
Polyether‐segmented polyamides as a new designed antithrombogenic material: Microstructure of poly(propylene oxide)‐segmented nylon 610
Authors: Yui Nobuhiko , Tanaka Junko , Sanui Kohei , Ogata Naoya
Published: April 2003

A series of segmented polymers based on poly(propylene oxide) (PPO) and nylon 610 was characterized. Transmission electron microscopic observations revealed spherulitic structures similar to those of semicrystalline homopolymers. Dynamic mechanical measurement and thermal analysis suggested distinct phase separation between the PPO and polyamide segments, which is generally observed for amorphous block copolymers systems. Moreover, density and X‐ray diffraction measurements indicated that the crystallization of the polyamide segments is promoted by the introduction of PPO segments in the copolymer. This is probably correlated with unique growth of crystalline lamellae in the PPO‐segmented polyamides.
Carboxyl‐terminated poly(vinyl alcohol). Chain transfer of methyl propionate to vinyl acetate
Authors: Meinander Gunilla , Charlton James L.
Published: April 2003

Poly(vinyl acetate) was prepared at 60°C with benzoyl peroxide by using methyl[carbonyl‐14C] propionate as chain transfer agent and solvent. The resulting polymer was hydrolysed to poly(vinyl alcohol) (PVAL) having carboxyl end groups and the average number of carboxyl groups per chain was unambiguously determined by comparing the activity of the polymer to that of the methyl propionate. An average density of 1,5 carboxyl groups per chain was found for poly(vinyl alcohol) prepared from poly(vinyl acetate) of DP 80 – 90. Other methods of end group analysis for carboxyl groups in PVAL are discussed.
Study of the functionalization of new acrylic polymers with ethylenediamine
Authors: Balieux Françoise , Clavelin Véronique , Daunis Jacques , Jacquier Robert , Calas Bernard , Parello Joseph
Published: April 2003

New cross‐linked polyacrylic supports, functionalized with methoxycarbonyl groups (from 0,2 to 6,0 mmol · g−1), were prepared. The reaction with ethylenediamine was realized in two ways: action of neat ethylenediamine or use of coupling agents. The yield depends on the initial loading with methoxycarbonyl groups and on the length of the spacer group. The percentage leading to the formation of side reactions of bridges, and that of unreactive methoxycarbonyl residues depends on steric factors. These results are of importance for the preparation of supports adapted to the solid phase peptide synthesis.