bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis and conformational study of poly(L‐lysyl‐L‐valyl‐L‐lysine) in the solid state and in aqueous solution
Authors: Ciaschi Roberto , D'Alagni Maria , Mignucci Gianfranco
Published: April 2003

The synthesis and some conformational properties of aqueous solutions of poly(L‐lysyl‐L‐valyl‐L‐lysine) at different ionization degrees, are reported. IR, UV, CD, and X‐ray measurements were performed on the sequential polypeptide in solution and in the solid state within the pH ranges of 6,4 to 7,2 (charged state) and of 10,4 to 11,0 (uncharged state). The presence of β‐ and probably α‐helical and random coil conformations is detected by IR spectroscopy in the solid state. X‐ray data show that the polymer in the charged form is likely packed as antiparallel β‐pleated sheets, whereas in the uncharged state there are some evidences for an α‐helical packing. The study of aqueous solutions of the polymer by UV spectroscopy seems to indicate that β‐ and a mixture of α‐ and β‐helices exist in the charged and uncharged state, respectively. However, the coexistence of random coil or other conformations cannot be excluded. The corresponding CD spectra support the interpretation supplied in the solid state. The results of this investigation further suggest that the introduction of valyl residues in a copolymer chain, containing residues which are α‐helix formers, favours the β‐conformation.
Synthesis and conformational study of poly(L‐valyl‐L‐valyl‐L‐lysine) in solution and in solid state
Authors: D'Alagni Maria
Published: April 2003

The synthesis and the conformational study of poly(L‐valyl‐L‐valyl‐L‐lysine) were carried out in aqueous and in organic solvents as well as in the solid state. X‐ray measurements indicate the presence of β‐helices. IR, UV, and CD spectra suggest the occurrence of β‐, unordered, and α‐conformations both in solution and in the solid state. The gradual transition from the charged to the uncharged state seems to increase the β‐helical structure at the expense of the random coil content. The same trend is observed passing from water solution to methanol/water, acetonitrile/water and trimethyl phosphate/water mixtures. Again, as for other sequential copolypeptides containing the valyl residue, more than one conformation is detected and the β‐structure results the most ordered in the solid state.
Polymerisation von fulvenen, 2. Spektroskopischer strukturbeweis für kationische polyfulvene
Authors: Slongo Mario , Schönholzer Stefan , Rentsch Christoph , Neuenschwander Markus
Published: April 2003

The cationic polymerisation of pentafulvenes 1a–g yields highly unsaturated macromolecules. The structure of the resulting polymers 2a–g has been proved by combination of spectroscopic methods, especially by analysis of the 13C NMR‐spectra.
Polymerisation von fulvenen, 3. Strukturbeweis für kationische polyfulvene durch vergleich mit modellverbindungen
Authors: Schönholzer Stefan , Slongo Mario , Rentsch Christoph , Neuenschwander Markus
Published: April 2003

The structure of cationic poly(6,6‐dimethylfulvene) (2a) has been confirmed by synthesis of 4 model compounds 6, 7, 8, 9 and comparison of the spectral data with those of the polyfulvene. 5‐Isoproylidenetricyclo[5.2.1.02.6]dec‐3‐ene (6) shows the same sensitivity towards oxygen as 2a. The reaction of 6 with oxygen yields a 1:1‐copolymer, for which structure 10 has been proved by means of spectroscopic methods.
ZnCl2 complexes of para‐substituted phenyl methacrylates in radical copolymerization with styrene
Authors: Szumilewicz Joanna , Połowiński Stefan
Published: April 2003

Copolymerization of phenyl methacrylate, p‐tolyl methacrylate, and p‐chlorophenyl methacrylate with styrene was carried out in the absence and in the presence of ZnCl2. It was found by 13C NMR, 1H NMR, and IR spectroscopy that complexes of zinc chloride with the corresponding methacrylates are formed. Reactivity ratios as well as Q and e values for the monomers and complexes were calculated. A correlation between e values and 13C chemical shift of the vinyl group of monomers and complexes with ZnCl2 was found.
The high pressure polymerization of pure ethylene
Authors: Buback Michael
Published: April 2003

A series of pure ethylene polymerizations performed to maximum pressures of 2,5 kbar and temperatures up to 250°C is discussed. The rate data which are obtained via quantitative infrared and near infrared spectroscopy closely fit to an overall polymerization rate law of the order 2,5 ± 0,2 in the ethylene concentration. The overall activation energy is determined to be 136,3 ± 6 kJ/mol. For the initiation reaction an activation energy of 209,8 ± 12 kJ/mol is derived. This fairly large value establishes that in dense high purity ethylene a thermally initiated (spontaneous) reaction to high molecular weight material occurs.
Théorie des chaînes de Markov et distribution moléculaire dans les copolycondensats linéaires, 2. Systèmes d'ordre II
Authors: Durand Dominique , Bruneau Claude‐Marcel
Published: April 2003

Application of a mathematical model — based jointly on Graph Theory and Markov chains theory — to the molecular distribution in monodimensional systems of order II (i.e. systems with functional groups belonging to two distinct co‐reactive species A and B) allows one to obtain very general matrix expressions for the molecular distribution functions of many linear copolycondensates.
Polymer‐solvent interactions in mixed solvents, 1. Isotactic, syndiotactic and atactic poly(methacrylic acid) in water/2‐chloroethanol mixtures
Authors: Bottiglione Vincent , Morcellet Michel , Loucheux Claude
Published: April 2003

The viscosimetric behaviour and the preferential solvation of syndiotactic, isotactic, and atactic poly(methacrylic acid), [poly(1‐carboxy‐1‐methylethylene)] are studied in water/2‐chloroethanol mixtures. The experimental results show that the preferential solvation of the polymer is strongly dependent on its local conformation. In the case of the syndiotactic sample, a close correlation has been established between the compact structure ↔ coil conformational transition and the variation of the preferential and absolute solvation of the polymer by 2‐chloroethanol, asserting the importance of hydrophobic interactions in the stabilization of the compact structure. Experimental data concerning the isotactic sample suggest the existence of an “inverse compact structure” in 2‐chloroethanol‐rich mixtures.
Polymer‐solvent interactions in mixed solvents, 2. Isotactic, syndiotactic and atactic poly(methacrylic acid‐co‐benzyl methacrylate) in water/2‐chloroethanol mixtures
Authors: Bottiglione Vincent , Morcellet Michel , Loucheux Claude
Published: April 2003

The viscosimetric behaviour and the preferential solvation of syndiotactic, isotactic and atactic copolymers of methacrylic acid and benzyl methacrylate are studied in water/2‐chloroethanol mixtures. The experimental results show that the presence of benzyl groups stabilizes the compact structure. In the case of the syndiotactic samples, the extent of the preferential hydration domain, which is related to the existence of the compact structure, is dependent on the composition of the copolymer. Experimental results also suggest that the presence of the benzyl groups destabilizes the inverse compact structure existing in 2‐chloroethanol‐rich mixtures.
Conformational change of poly(L‐lysine) by formation of complexes with poly(styrene sulfonate)
Authors: Kōmoto Tadashi , Cho Chong Su , Kawai Tohru
Published: April 2003

Circular dichroic studies were made on the conformational change of poly(L‐lysine) (PLL) by complex formation with sulfonated polystyrenes (PSS) as functions of pH, temperature and polymer compositions in comparison with the complexes of PLL with sulfated poly(vinyl alcohol) (PVS). The coil‐to‐helix transition of PLL by complex formation at neutral and acidic pHs, which took place in the PLL/PVS (with high degrees of sulfation) complexes, was prevented in the PLL/PSS complexes due to the less chain flexibility of PSS than PVS. Above pH 11, the α‐helix of PLL was partially broken into random coil by complex formation with PSS. The drastic decrease in the solution viscosity by the complex formation revealed a large contraction of PSS chain and subsequently a large strain of the α‐helical PLL chain so as to give the breakdown of the α‐helix. This is denoted a strain‐induced conformational change of PLL. It was found that the α‐helix of PLL was thermally stabilized by the complex formation with PSS as in the case of PLL/PVS complexes. A β‐to‐α transition of PLL by the complex formation with PSS was also found, while the β‐form was maintained in the PLL/PVS (with high degrees of sulfation) complexes.
Photostability of some carbenium salts
Authors: Velichkova Rumyana S. , Toncheva Veska D. , Panayotov Ivan M.
Published: April 2003

The photolysis of triphenylmethyl salts with anions such as SbCl, FeCl and AsF was investigated in inert and oxygen atmosphere. On irradiation by visible light the characteristic bands of the cation disappeared in 20 min and in 15 h at concentrations of 10−4 M and 10−3 M, respectively. The main photolytes identified were triphenylmethane, triphenylchloromethane, triphenylcarbinol, benzophenone, fluorenone, fluorene, 9‐hydroxy‐9‐phenylfluorene, 9‐phenylfluorene besides 2–3% nonidentified products. The results showed that the product composition of the photolyzed mixture depended only slightly on the atmosphere used, the differences in the amounts of the products being more significant.
Terpolymérisation acrylonitrile — styrène — acrylate de méthyle, 1. Etude cinétique de la terpolymérisation en émulsion, en réacteur fermé
Authors: Rios Leonardo , Pichot Christian , Guillot Jean
Published: April 2003

Binary and ternary copolymerizations of the acrylonitrile (A) / styrene (S) / methyl acrylate (M) system were carried out by emulsion polymerization, using sodium lauryl sulfate as emulsifier and potassium persulfate as initiator. Kinetic studies of the reaction mixture by gas chromatography and simulation calculation of the copolymer composition versus conversion show that the classical theory of copolymerization (propagation rate by Markov chain 1st order) can be applied to the emulsion polymerization of this system, even at high conversion level. It was found that, when a conversion limit is obtained, the polymerization can be started again owing to a new addition of the more rapidly consumed monomer (styrene, in this case); it appears that both polymerization process and conversion effect do not involve appreciable variations of the polymer radical reactivity.
Study on polymer solutions in solvent mixtures in the vicinity of the critical point of the solvents, 2. Systems methanol/cyclohexane/poly(tetrahydrofuran) and water/butyl cellosolve/poly(ethylene glycol)
Authors: Dondos Anastasios , Izumi Yoshinobu
Published: April 2003

Turbidimetric and viscometric results obtained with the ternary systems methanol/cyclohexane/poly(tetrahydrofuran) and water/butyl cellosolve/poly(ethylene glycol) are reported. The turbidimetric results show that a small quantity of polymer changes extensively the coexistence curve of the solvent mixture, especially near the critical point of the two solvents. The viscometric results show that both polymers, poly(tetrahydrofuran) and poly(ethylene glycol) present abnormally high dimensions near the critical point of the two liquids.
Langfristige konformationsänderung von makromolekülen in lösung, 1. Polyacrylamide
Authors: Kulicke W.‐M. , Kniewske R.
Published: April 2003

The viscosity of aqueous polyacrylamide solutions does not remain constant. During a period of many weeks it decreases by as much as 30%. Simultaneously a loss of flocculation activity occurs. This unusual behaviour — also called ageing or solution instability — is examined. Viscosity and light scattering investigations were made. The viscosity was also determined by addition of substances which influence hydrogen bonds. It could be demonstrated, that in high molecular weight polyacrylamide hydrogen bonds are effective. Light scattering measurements result in curved angular dependence of scattered light, which must be regarded as real and specific for the high molecular weight polyacrylamides in water. The Zimm plot for polyacrylamide in ethylene glycol was undistorted. The refractive index increment decreases with time during the investigations. From the Zimm plots it follows, that the radius of gyration decreases with time. The molecular weight however remains constant. Based on the experimental results a mechanism is assumed with a long‐term conformational change of the macromolecules. The orientated segments — stabilized by hydrogen bonds — are slowly destroyed by occupation of “active sites” by water molecules. Chain degradation as well as disentanglement could be excluded. A molecular interpretation is given.
Study of surface potential characteristics of corona charged ethyl cellulose layers for its relevance in electrothermography
Authors: Pillai P. K. C. , Gupta A. K. , Goel Malti
Published: April 2003

A solution cast layer of ethyl cellulose on aluminium substrate shows high charge acceptance on corona charging. Its surface potential decay characteristics are studied at room temperature and at higher temperatures. Addition of a thermosensitive dye in the polymer matrix shows enhanced contrast potential at constant IR exposure. Optimum conditions for suitability of the polymer in electrothermography is determined by studies on different weight proportions of dye. The effect of layer thickness on surface potential characteristics is also investigated.
Anionic copolymerisation of elemental sulfur with 2,2‐dimethylthiirane
Authors: Duda Andrzej , Penczek Stanislaw
Published: April 2003

The copolymerization of elemental sulfur (2) with 2,2‐dimethylthiirane (1), initiated with sodium thiophenolate in benzene solution was studied. By 1H NMR and laser Raman spectroscopy of the resulting copolymers 3 it could be shown that true copolymers with short polysulfide chains are formed and that starting with a sufficiently large ratio of 2/1 diads of 1 are absent.
Polymer modification and synthesis using sulfenyl derivatives, 11. New polymers from oxidation of adducts of benzene‐ and toluenesulfenyl chlorides with cis‐1,4‐polybutadiene
Authors: Gordon Cameron G. , Asif S. , Chishti A.
Published: April 2003

Adducts of cis‐1,4‐polybutadiene with both benzene‐ and toluenesulfenyl chlorides were conveniently oxidised in a second stage modification with m‐chloroperbenzoic acid to yield novel sulfone thermoplastic polymers. These have higher glass transition temperatures and are more thermostable than the parent adducts.
Chlorination of polyethylene single crystals
Authors: Guzmán Julio , Fatou José Gomez , Pereña José Manuel
Published: April 2003

Chlorination under mild conditions of suspensions of polyethylene single crystals demonstrated that a selective attack on the fold surface takes place. Two polyethylene molecular weight fractions (Mn = 47000 and Mn = 150 000) were used and single crystals were grown isothermally from p‐xylene at 88°C. The chlorine content was changed from 4 wt.‐% to 30 wt.‐% and to this level no evidence for crystal attack and loss of crystallinity was found. The melting temperatures of chlorinated single crystals decrease with increasing chlorination up to about 15 wt.‐% chlorine content and then stay constant for higher chlorine contents. Moreover, the heat of melting of the chlorinated single crystals is constant and is independent of the chlorine content up to 25 wt.‐%. These results are compared with those of samples of chlorinated polyethylene recrystallized from solution and from the melt.
Struktureller aufbau und physikalisches verhalten vernetzter epoxidharze
Authors: Fischer Michael , Lohse Friedrich , Schmid Rolf
Published: April 2003

Network structures and physical properties of products obtained either by crosslinking polyepoxides with polyphenols, and by dicyanodiamide or by catalytic polymerization are discussed and compared with those obtained by amine or anhydride curing. The highest crosslinking density is achieved by the polymerization of epoxy compounds. In polymerization, the glass transition temperature may rise by more than Δ Tgv = 100 K. Amine and phenol curing result in similarly structured networks with mobile aliphatic segments and comparatively low crosslinking densities. Impact resistance based on dissipation of mechanical energy increases as network density decreases, a maximum being achieved with a medium chain length of 25 – 35 atom intervals between crosslinking points. The mechanical stability of polymers is limited by the cohesive strength KF. This latter corresponds to the maximum shear strength of bonds TKFmax, which was measured within the temperature range of 77 K to 450 K, in accordance with the equation

This equation was derived from Eyring's model of viscosity, correlating B and C with activation volume, activation energy, Tg, and strain rate. B equals the cohesive strength at 0 K. It is determined by intermolecular forces but does not depend on the density of crosslinking. An increase of Tg due to crosslinks or bulky segments causes a decrease of C and therefore a reduction of the temperature dependence of KF. Hence, cohesive strength at room temperature is improved.
Thermotropic liquid crystalline polymers, 4. Study of crystalline and liquid‐crystalline comb‐like polymers with mesogenic side groups by IR spectroscopy
Authors: Shibaev Valery P. , Platé Nicolai A. , Smolyansky Alexander L. , Voloskov Alexander Ya.
Published: April 2003

The IR spectra (in the region of 400–3600 cm−1) of comb‐like polymers in crystalline, liquid‐crystalline, and fluid isotropic phases were studied, and the effect of the chemical structure of the long side chains on the crystalline and liquid‐crystalline states were examined. The spectroscopic criteria of phase transitions in comb‐like polymers were established and the fragments of the side chains involved in the formation of the liquid‐crystalline phase, were determined.
Electrochemical studies of some three component copolymers in nonaqueous media
Authors: Chatterjee S. K. , Pachauri L. S.
Published: April 2003

Some three‐component copolymers have been prepared by condensing formaldehyde with each of the following groups of monomeric species: (i) sulfanilic acid + p‐toluidine + p‐bromoaniline; (ii) p‐aminobenzoic acid + p‐toluidine + p‐bromoaniline; (iii) sulfanilic acid p‐aminobenzoic acid + p‐bromoaniline. The composition of the copolymers has been deduced from electrometric titration studies in nonaqueous media, and Br content of the copolymers. Differentiation of acidic functional groups and the degree of polymerization of the copolymers could be obtained from their titration curves.
Study on mechanochemical syntheses of some macromolecular complexes of vanadium and manganese with polyamides and polyester‐polyamides as ligands
Authors: Simionescu Cristofor , Vasiliu‐Oprea Cleopatra , Negulianu Claudia
Published: April 2003

Polymeric metal complexes were synthesized mechanochemically by ultrasonic action on mixtures of poly(ethylene terephthalate), ethylenediamine, and vanadium trichloride or by vibratory milling of a mixture of poly(ϵ‐caprolactam) and manganese dichloride (MnCl2·4H2O). The influence of duration of ultrasonic action or vibratory milling as well as the ratio of reagents on the efficiency of complexation was studied. The resulting products were characterized spectroscopically (by IR and ESR spectra), by elemental analyses, and by X‐ray diffraction. They show a relatively high thermostability and semiconductivity.
Untersuchungen zur thermodynamik und konformation von makromolekülen in polymermischungen in der nähe von entmischungspunkten durch neutronenbeugung
Authors: Schmitt Burghard J. , Kirste Rudolf G. , Jelenič Jernej
Published: April 2003

The structure and the thermodynamics of polymer blends made from two poly(styrene/acrylonitrile) copolymers with a different ratio of styrene/acrylonitrile are investigated by neutron scattering. These systems are endothermic, exhibit a positive value for the Huggins parameter χ and show phase separation at sufficiently large molecular weights. The results are in good agreement with the corresponding states theory of Prigogine and Patterson. Other polymer blends are exothermic, exhibit negative χ‐values and are compatible even for infinitely large molecular weights. In these cases one can adapt the theoretical equations to the experiments by the introduction of a suitable parameter for an exothermic contact energy. This is shown for blends from poly(methyl methacrylate) and poly(styrene/acrylonitrile).
Synthèse par voie radicalaire de polymères à extrémités hydroxylées, 7. Synthèse de polybutadiènes: Études cinétiques
Authors: Brosse Jean‐Claude , Legeay Gilbert , Bonnier Maryvonne , Pinazzi Christian
Published: April 2003

It could be shown that radical polymerizations of butadiene in methanol, initiated by hydrogen peroxide, cleaved in two hydroxyl radicals by thermal reaction, give three types of products: oligomers formed predominantly during the two first hours, polymers formed by an autoacceleration phenomenon, mainly during the two first hours, and polymers of high molecular weight, formed after two hours of reaction. The results show that the reaction order is about 1,6. In addition, thermal initiation was also observed.
Coenzyme models, 21. Oxidative trapping of carbanion intermediates by a flavin immobilized in cationic polymers
Authors: Shinkai Seiji , Kusano Yumiko , Manabe Osamu
Published: April 2003

Aromatic aldehydes 5 and α‐keto acids 8 in the presence of cyanide ion, which usually give the benzoin condensation products, were converted oxidatively to the corresponding benzoic acids 10 by the catalytic action of the title flavin. The change in the reaction route cannot be achieved completely by flavin 1. Product analyses and kinetic measurements established that the carbanion intermediate, \documentclass{article}\pagestyle{empty}\begin{document}${\rm R}\hbox{---} \mathop {\rm C}\limits^ \ominus \left( {{\rm OH}} \right)\left( {{\rm CH}} \right)$\end{document}, which is formed through rate‐limiting deprotonation or decarboxylation of the cyanide‐adducts, is oxidized immediately by the title flavin. The influence of polymer structure on the efficiency of flavin trapping is discussed.
Dielectric behavior of ethylcellulose in concentrated solutions
Authors: Araki Kazuo , Togawa Shigeru , Miyama Tamio , Imamura Yoshio
Published: April 2003

Measurements of dielectric relaxation were made for a series of solutions of ethylcellulose in benzene. The concentrations ranged from 0,5 to 20 wt.‐% and two polymers of different molecular weight were used. The dielectric dispersion was measured over the frequency range of 30 Hz – 3 MHz at 30 – 50°C. The concentration dependence of the critical frequency below and above the critical concentration is interpreted by the free volume effect. It was found that the dielectric relaxation times are constant above the critical concentration and that the activation energy increases with concentration. The observed relaxation time is analyzed by Fröhlich's theory assuming two limiting relaxation times. The lower limit in the relaxation time, τ1, is concentration‐independent above the critical concentration, in contrast to the upper relaxation time τ2, which depends on concentration. These relaxation times, τ1 and τ2, however, are interpreted by the same free volume effect. The unperturbed molecular dimension at the critical concentration is also discussed.
Stufenweise darstellung eines cycloheptamers aus p‐kresol, 4‐tert‐butylphenol und formaldehyd. Vergleich mit einem phenolischen, heptanuklearen kettenoligomer
Authors: Kämmerer Hermann , Happel Günter
Published: April 2003

A phenolic cycloheptamer (11) and an analogous chain oligomer (10) with nearly the same structure were gained by stepwise syntheses. The cycloheptamer has a higher melting point and a better solubility in chloroform. In contrast to the chain oligomer his infrared spectrum indicates a stronger association of the hydroxyl groups which is not influenced by the solvent. The mass spectra announce a preferred statistical cleavage along the chain of compound 10 and a great stability of the ring of 11 which preferentially loses his substituents. The 1H NMR spectra confirm the constitutions of the chain (10) and ring compound (11). The cycloheptamer is distinguished by a ring inversion or a pseudorotation, seen by the NMR signals of the methylene protons. The activation energy of the pseudorotation is determined.
Functional polymers, 5. Preparation and polymerization of methyl 4‐vinylsalicylate, 4‐vinylsalicylic acid and 4‐vinylacetylsalicylic acid
Authors: Tirrell David , Vogl Otto
Published: April 2003

Methyl 4‐vinylsalicylate, 4‐vinylsalicylic acid, and 4‐vinylacetylsalicylic acid were prepared in overall yields of 28%, 21% and 16%, respectively, starting with 3‐ethylphenol. Radical polymerization of all three monomers was investigated. Methyl 4‐vinylsalicylate and 4‐vinylsalicylic acid polymerized normally via radical initiation, giving soluble polymers of high molecular weight. 4‐Vinylacetylsalicylic acid gave gelled polymerization mixtures in tert‐butanol and in dimethyl sulfoxide, using the same experimental procedure; this was shown to be a result of intermolecular transesterification during polymerization. A water‐insoluble copper complex of poly(4‐vinylsalicylic acid) was prepared. Methyl 4‐vinylacetylsalicylate was also synthesized, in 35% yield, but no polymerization experiments were performed with this monomer. These new polymeric salicylic acid derivatives are of interest as ultraviolet stabilizers, as protective agents for the skin, as metal‐complexing agents, and as potential medicinal agents.
Isotactic poly(allyl vinyl ether), 1. A study of the polymerization and a proposal of a mechanism of stereocontrol
Authors: Sikkema D. J. , Angad‐Gaur H.
Published: April 2003

Allyl vinyl ether can be polymerized to highly isotactic polymer with SbCl5 in toluene at ca. −10°C. The stereospecificity is not significantly lower than that of polymer made at ca. −75°C; The reproducibility of the process is greatly improved at the higher temperature. BF3.O(C2H5)2 proved to be an ineffective initiator, in contrast with literature data. NMR analysis, previously published for diads only from NMR data, was performed (1H and 13C) for triads as well, and partly for hexads. No evidence for stereocontrol other than the relationship between active chain end HC⊕OAllyl and incoming monomer can be inferred1

cf. Part 2 of this series10.

. A simple mechanism, featuring association between incoming monomer and counterion, invoking only steric hindrance is proposed as an explanation of these findings.
An electron spin resonance study of radical transfer reactions in γ‐irradiated vinylthiol/styrene‐copolymers
Authors: Mönig Hans , Ringsdorf Helmut , Spirk Eugen
Published: April 2003

Formation and behaviour of radiation induced free radicals in statistical copolymers from vinyl hydrosulfide and styrene (1:1, 1:4, and 1:10) were investigated by means of ESR spectroscopy. The corresponding homopolymers were also included in these studies. After γ‐irradiation of the copolymers at 77 K and subsequent annealing to 293 K it was possible to detect thio radicals. Their relative yields were found to increase with increasing styrene content. Investigations regarding the thermal behaviour of the radiation induced radicals in the copolymers allowed the assumption of two mechanisms responsible for the formation of the thio radicals: First, the formation takes place via ion radicals located at the mercapto groups at 77K. In the copolymers the stability of the thio radicals is favoured by steric hindrance through the benzene rings thus reducing the formation of disulfide bridges as termination reaction. Secondly, the formation of the thio radicals is caused by a hydrogen transfer from the mercapto groups to the benzyl radicals and/or cyclohexadienyl radicals of styrene units.
Template polycondensation of active esters containing nucleic acid bases with diamines
Authors: Hattori Masahira , Nakagawa Hiroshi , Kinoshita Masayoshi
Published: April 2003

Template polycondensations of di‐p‐nitrophenyl methylsuccinate derivatives of thymine (1) and theophylline (2) with piperazine and 4‐aminomethylbenzylamine (4‐ABA) were carried out in pyridine/methylene chloride and in DMF solutions. Polystyrenes containing adenine as a side group in various contents were used as template in this polycondensation. The polycondensation reactions of active ester 1 with diamines were effectively accelerated by the presence of the template in both solvents. On the other hand, the polycondensation reactions of active ester 2 with diamines were scarcely affected by the template under the same conditions. The maximum acceleration effect was observed in the presence of templates in which the adenine content is about 54% for the polycondensation of 1 with piperazine and about 25% for that with 4‐ABA, respectively.
Isotactic poly(allyl vinyl ether), 2. An NMR‐study of stereoregularity and relaxation times
Authors: Angad‐Gaur H. , Sikkema D. J.
Published: April 2003

The stereoregularity of poly(allyl vinyl ether), (poly[1‐(allyloxy)ethylene], 1) was studied by both 1H‐ and 13C NMR‐spectroscopy at 6,34 tesla. Even at this field the 1H NMR‐resonances severely overlap, thus hampering a reliable analysis. The situation is far better for the 13C NMR‐resonances; here even hexad splittings could be observed. Relaxation time ratios of the backbone carbon atoms are consistent with a dipolar relaxation mechanism. The relaxation time for the racemic peak is longer than that for the meso peaks, which is in contrast with literature data for other polymers7,8. This deviating behaviour could be accounted for by the higher magnetic field used in our measurements.
On the molecular weight determination by vapor pressure osmometry (VPO), 2. Molecular weight average obtained by VPO
Authors: Figini Ruben Víctor
Published: April 2003

Provided that in molecular weight determinations by vapor pressure osmometry (VPO) the relationship between M and the measured quantity (δV/c)c=0 obeys a calibration function of the type (δV/c)c=0 = KM−a, the kind of molecular weight average M̄VPO delivered by this method is derived. The deviation of M̄VPO from the true number average molecular weight M̄n is estimated from its dependence on the polydispersity and the exponent a of the calibration function.
Coordination polymers of β‐hydroxy‐γ‐amino schiff bases
Authors: Jagur‐Grodzinski Joseph
Published: April 2003

Ligands 3a–d (N,N‐disubstituted 2,2′‐dihydroxy‐3,3′‐[1,4‐phenylenebis(methylenenitrilo)]‐dipropaneamines) for the preparation of the coordination polymers of Ag(I), Cu(II), Zn(II), and Ti(IV) were synthesized by condensation of terephthalaldehyde (2) with the N,N‐substituted 2‐hydroxy‐1,3‐propanediamines (1a–d). The copper and zinc coordination polymers were found to be compatible with polyethylene. Their blends could be processed by injection molding or extrusion. The thermal stability of the polymers was found to increase in the order Cu‐ <Ag‐ <Ti‐ <Zn‐derivatives. The electronic, IR, and ESR spectra of the copper coordination compounds were measured and the mechanism of formation of the coordination polymers is discussed. The polymers were found to be semi‐conductive, their electric resistivity being in the range of 103 − Ω·cm. The temperature dependence of the conductivity yielded activation energies in the range of 26 −106 kJ·mol−1. Both electronic and ionic conductance may contribute to the semiconductive properties of these coordination polymers.
Kinetics of thermooxidation and photooxidation of poly(oxy‐2,6‐dimethyl‐1,4‐phenylene), 1. Analysis of products
Authors: Sláma Zdeněk , Švejdová Emílie , Majer Josef
Published: April 2003

The time dependence of the thermooxidative degradation was measured within the temperature range of 100–150°C. The extent of degradation was characterized by monitoring the content of hydroperoxy, hydroxyl, carbonyl, and quinone groups. Moreover, oxygen absorption, weight changes, and carbon dioxide formation were followed. Calculations of material balance were carried out on the basis of weight changes, oxygen absorption, and analytically determined concentration of oxidation products. The photooxidation was also characterized by the content of hydroperoxy groups and the formation of hydroxyl, ester, and carbonyl groups. A semiquantitative method was employed to determine the concentration of carboxyl groups. In both cases the presence of xanthone moieties was observed. In samples subjected to photooxidation also a small amount of peracids and peresters was found. The mechanism of the degradation processes is discussed in some details.
New polymer syntheses, 3. Binding of nucleosides to basic polypeptides via isocyanato‐isothiocyanates
Authors: Kricheldorf Hans R. , Fehrle Martin J.
Published: April 2003

New aliphatic α‐isocyanato‐ω‐isothiocyanates of various chain lengths were synthesized from ω‐isothiocyanatocarboxylic acid chlorides and trimethylsilyl azide. The 5′‐OH group of 2′‐O,3′‐O‐isopropylideneuridine and of N6‐benzoyl‐2′‐O,3′‐O‐isopropylideneadenosine was added selectively onto the isocyanate group of aromatic and aliphatic α‐isocyanato‐ω‐isothiocyanates. The isothiocyanate group of the resulting nucleoside derivatives was then reacted with the free amino groups of polylysine, isopolylysine, polyornithine and isopolyornithine. The resulting polypeptides with pending nucleosides were characterized by elemental analyses and 360 MHz 1H NMR spectra. A new “one‐pot‐procedure” was developed to protect the primary amino group (N6) of 2′‐O,3′‐O‐isopropylideneadenosine.
Molecular weights and molecular weight distributions of poly(trimethylhexamethyleneterephthalamide) (trogamid T®)
Authors: Herold Julius , Meyerhoff Günther
Published: April 2003

Molecular weights of Trogamid T® were determined by ultracentrifugation, light‐scattering, osmometry and viscometry, molecular weight distributions by gel permeation chromatography (GPC) and five different fractionation methods. The separation efficiency of GPC with N,N‐dimethylformamide as solvent was tested with three different types of gels, crosslinked polystyrene, porous glass and crosslinked poly(vinyl acetate), the last one yielding the best results. Solution fractionations show better results than precipitation methods. All fractionations gave far too small apparent non‐uniformities. After correction according to the non‐uniformities of the fractions the results corresponded to those of the other methods. All methods resulted in U = M̄w/M̄n − 1 = 0,7 for the technical product Trogamid T®. The discrepancy to U = 1 of a Schulz‐Flory distribution can be explained by the influence of the path of reaction.
Association and crystallization of poly(ethylene oxide)
Authors: Shimada Toshio , Okui Norimasa , Kawai Thoru
Published: April 2003

The discontinuous change of the lamellar thickness with crystallization temperature was studied for low molecular weight fractions of OH‐terminated poly(ethylene oxide) (PEO). IR analyses demonstrated that almost all of the molecular chain ends were associated in the molten state, whereas a large part of their ends were free in dilute solution. Discontinuous changes were observed for low molecular weight PEO fractions crystallized from the melt, whereas continuous changes were found both for PEO's crystallized from dilute solution and those with phenylated end groups crystallized from the melt. Accordingly, it was pointed out that the association of the end groups could play an important role in the crystallization mechanism and the conformation of the resultant PEO crystals.
Kinetics of alkaline hydrolysis of polyacrylamide in solution by viscosimetric technique
Authors: Gunari Arun A. , Gundiah Subbaraya
Published: April 2003

The alkaline hydrolysis of polyacrylamide in solution is studied viscosimetrically. The viscosity of the solution increases continuously during the course of hydrolysis. The relationship between intrinsic viscosity and the extent of reaction is established, using a series of polyacrylamides with known extents of hydrolysis. The extent of reaction is determined from the observed flowtime, using the relationship between [η] and extent of reaction. The second‐order rate constant and the activation energy are in good agreement with those reported in the literature. A four‐fold increased reactivity of the amide groups towards hydrolysis is observed at very low extents of hydrolysis.
Synthesis and characterization of new polynuclear manganese‐thiolato complexes
Authors: Kaneko Masao , Ishihara Nobuhide , Yamada Akira
Published: April 2003

New polynuclear manganese‐thiolato complexes were prepared by reaction of Mn ions with chelating mercapto compounds, such as 1,2‐dimercaptoethane (DME), 3,4‐dimercaptotoluene (DMT), cystein (Cys), β‐mercaptoethyl alcohol (ME), β‐mercaptoethylamine (MEA), and mercaptoacetic acid (MAA). Potassium permanganate formed stable complexes with DME, DMT and Cys. The complexes of ME, MEA and MAA were prepared by the reaction with manganous chloride. The temperature dependencies of the magnetic susceptibility of the complexes, except Cys, obeyed the Curie‐Weiss law, indicating strong antiferromagnetic interaction between the spins on the Mn ions. The valence of the DME and DMT complexes was calculated to be IV to V, and that of the Cys, ME, MEA and MAA complexes to be II to IV. ESR spectra of the DME and DMT complexes showed broad singlet absorptions, while those of ME, MEA and MAA complexes exhibited narrow Lorentzian singlets, both types indicating strong interaction between the spins. These results and the composition indicated polynuclear complexes containing μ‐oxo (DME and DMT), μ‐chloro or μ‐thiolato (ME, MEA and MAA) structure, while Cys gave mononuclear complex.
Influence of hydroperoxides on the photothermal oxidation of polyethylene
Authors: Ginhac Jean‐Marie , Gardette Jean‐Luc , Arnaud René , Lemaire Jacques
Published: April 2003

Accumulation of secondary hydroperoxy groups linked to saturated carbon atoms of polyethylene could be observed by IR spectrophotometry after thermal or photocatalytic oxidation. It was shown that these hydroperoxides have no photoinductive effect on the overall oxidation of polyethylene. Under the same experimental conditions, the situation was found to be opposite in isotactic or atactic polypropylene; the tertiary hydroperoxides formed in thermal oxidation initiate new oxidative reactions.
Stereoregularity of poly(methyl vinyl ketone) and poly(isopropenyl methyl ketone) determined by 13C NMR spectroscopy
Authors: Matsuzaki Kei , Kanai Taiichi , Aoki Yuichi
Published: April 2003

13C NMR spectra of poly(methyl vinyl ketone)s (PMVK) and poly(isopropenyl methyl ketone)s (PIPMK) obtained by radical and anionic catalysts were measured. The 13C resonances of the CH2 carbon of PMVK were tentatively assigned to diad tacticities. The spectra of carbonyl carbon and methyl carbon of the CH3CO group of PIPMK were assigned to pentad and triad tacticities, respectively. It is shown that radically obtained PMVK and PIPMK have atactic and syndiotactic‐rich structure, respectively. The stereoregularity of radically obtained PIPMK obeys Bernoullian statistics, while that of anionically obtained PIPMK conforms to first‐order Markov statistics.
Polymerisationsauslösung mit substituierten Ethanen, 1. Polymerisation von Methylmethacrylat mit 1,1,2,2‐Tetraphenyl‐1,2‐diphenoxyethan
Authors: Błedzki Andrzej , Braun Dietrich
Published: April 2003

1,1,2,2‐Tetraphenyl‐1,2‐diphenoxyethane (TPPA) initiates at 70°C the polymerization of methyl methacrylate. In the first period oligomers of the type 1 with two phenoxydiphenylmethyl end groups (Pn ≈ 1 – 20)
magnified image
are formed by primary radical termination. These telechelics are effective initiators of the further free radical polymerization of vinyl monomers.
Adsorption of polymers at the solution/solid interface, 15. Styrene‐vinylferrocene copolymers
Authors: Barrios A. Diaz , Howard G. J.
Published: April 2003

A series of styrene‐vinylferrocene random copolymers is synthesised and characterised. Their adsorption from carbon tetrachloride and from chloroform is measured on to pyrogenic SiO2, TiO2 and Al2O3. The level of adsorption depends on the solvent, the adsorbent and the copolymer composition. From chloroform, very few vinylferrocene units are required to increase adsorption markedly above that of polystyrene, and further compositional change has little effect on the level of adsorption. The compositional dependence of adsorption of the copolymers from carbon tetrachloride is more complex. 1H NMR studies show that a very high proportion of repeating units are held close to the silica surface. With polystyrenes, the fraction of units of restricted mobility decreases with polymer molecular weight and with surface coverage; at partial surface coverage virtually all the phenyl groups of low molecular weight polystyrene (mol. wt. = 4000) are immobilised. The copolymers also show large restricted fractions, which decrease along the adsorption isotherm, but which show no significant dependence on polymer composition. Higher restricted fractions seem to be associated with poorer solvent quality.
1H and 13C NMR studies on the interaction between N‐acetyl‐L‐alanine methylamide and trifluoroacetic acid
Authors: Asakura Tetsuo
Published: April 2003

1H and 13C NMR chemical shifts and also spin‐lattice relaxation times of N‐acetyl‐L‐alanine methylamide were measured in the solvent system deuteriochloroform/trifluoroacetic acid, in order to discuss aspects of the interaction between peptide units and the acid. The maximum displacement in the acid proton peak and marked decreases in the 1H and 13C spin‐lattice relaxation times of the amide were observed at an acid/amide mole ratio of ≈ 2. These strongly suggests a 1:2 amide‐acid interaction. Moreover, taking into account the differences of the acid concentration dependences between the two kinds of NH proton peaks and those between the two kinds of CO carbon peaks, a solvation model was proposed in which both the alanyl NH and the alanyl CO groups adjacent to the Cα carbon in the amide are linked by intermolecular hydrogen bonding with both the carbonyl group of one acid molecule and the acid proton of another acid molecule, respectively. In addition, intermolecular hydrogen bonding occurs also between these two acid molecules.
Dilute solution properties of methyl methacrylate/acrylonitrile random copolymers, 2. Stockmayer fixman relations
Authors: Kashyap A. K. , Kalpagam V.
Published: April 2003

The Stockmayer‐Fixman relation was used to evaluate the short range and long range interaction parameters for methyl methacrylate/acrylonitrile copolymers of 0,566 and 0,657 mole fraction of monomeric units of acrylonitrile in the solvents acetonitrile, 2‐butanone, dimethyl formamide, and γ‐butyrolactone, at different temperatures (30, 45, and 60°C). The values of K0 were found to be lower than those of the parent homopolymers, and their values depend on both solvent and temperature. Even negative K0‐values were obtained, in cases in which the Mark Houwink exponent a is nearly unity. The values of the polymer‐solvent interaction parameter, χ1, are high and close to 0,5, indicating that these solvents are not good. The values of the excess interaction parameter, χAB, are negative and are not affected by temperature. The large extension of these copolymer chains, as exhibited by a and α‐values, can be understood in terms of unusual short range interactions only. Similar results were obtained for some cellulose derivatives.
Substituted and branched polychalcones. Syntheses and characterization by spectrometric methods
Authors: Malm Bo
Published: April 2003

Polychalcones 4a, b were prepared by a Friedel‐Crafts acetylation of vanillin (3a) and p‐hydroxybenzaldehyde (3b) and by a Fries rearrangement of the acetates in nitrobenzene using AlCl3 as catalyst. The reaction was carried out in one step under a variety of reaction conditions (time and temperature). The polymers were characterized by UV, IR and 1H NMR spectroscopy. The polychalcones obtained from p‐hydroxybenzaldehyde had a limited solubility, but they swoll in DMSO and in dilute NaOH.
Syntheses of diacetylene monomers from N‐(nitrophenyl)amine substituted diacetylene alcohols
Authors: Horner Charles J. , Garito Anthony F. , Desai Kirit N.
Published: April 2003

Several new classes of asymmetric diacetylene monomers of the type O2NArNHCH2CCCCCH2R have been synthesized from nitroaniline diacetylene alcohols. The solid state polymerization behavior of several members of these classes has been examined.
Micellisation de copolymères séquencés polystyrène‐polyvinylpyridinium, 3. Influence de la concentration en sel et de la température
Authors: Selb Joseph , Gallot Yves
Published: April 2003

The effects of the salt concentration and temperature on the micellization phenomenon of polystyrene‐poly(4‐vinyl‐N‐ethylpyridinium bromide) block copolymers in dilute solution are investigated in solvents selective for the polyelectrolytic part (water‐methanol‐LiBr mixtures). The polystyrene moiety being in non‐solvent media remains rather collapsed whatever temperature and salt concentration. On the contrary, the latter parameters modify strongly the conformation of the soluble polyelectrolytic chains and therefore determine the “quality” of the solvent essentially towards the polyvinylpyridinium blocks. Consequently an increase of the temperature or a decrease of the salt concentration have the same effect on the behaviour of the copolymers. In the case of a copolymer with a small molecular weight polystyrene block (Mw = 2 700), the unimer‐multimer (single molecules/micelles) equilibrium is easily shifted in favour of the single molecules by increasing the temperature or decreasing the ionic strength. On the contrary, if the polystyrene moiety is longer (Mw = 6 000 – 13 000) the micellar weight of the system is little or even not at all influenced by the ionic strength and the temperature. These results emphasize that, for the investigated systems, it is the “insoluble” blocks which essentially govern the micellization phenomenon.
Synthesis and tumor‐inhibiting activity of new heparin‐bound nitrogen mustard analogues
Authors: Kim Sung‐jho , Höcker Hartwig , Kern Werner
Published: April 2003

New nitrogen mustard analogues in which bis(2‐chloroethyl)‐amino groups are separated by oxyethylene groups, 1,14‐dichloro‐3,12‐bis(2‐chloroethyl)‐3,12‐diaza‐6,9‐dioxatetradecan (3c) and 1,17‐dichloro‐3,15‐bis(2‐chloroethyl)‐3,15‐diaza‐6,9,12‐trioxaheptadecane (3d), were synthesized by reaction of bis(2‐hydroxyethyl)amine (2) with bis(2‐chloroethyoxy)ethylene (1a) and with 1,11‐dichloro‐3,6,9‐trioxaundecane (1b), respectively, followed by treatment with thionyl chloride. The analogues were then complexed with heparin. The resulting heparin‐complexes show inhibiting activity against transplanted Sarcoma‐180 A in mice.
On the salt‐linkage formations of porous and nonporous silica particles with trimethylammonium glycol chitosan iodide
Authors: Kokufuta Etsuo , Hirai Yasumasa , Nakamura Isei
Published: April 2003

The stoichiometry of the salt‐linkage formations of nonporous and porous silica particles with trimethylammonium glycol chitosan iodide (TGCI) was investigated by comparing the results of colloid titration and adsorption experiments with those of potentiometric titrations. The surface charge (Q) of colloidal silica as function of pH was evaluated by means of the colloid titration with TGCI. On the other hand, the density (D) of ≡ SiO⊖ groups of silica gel at different pH was also evaluated by the adsorption experiment of TGCI. These results obtained were compared with the Q vs. pH and D vs. pH curves which were obtained by the potentiometric titrations at various ionic strengths for colloidal silica and silica gel, respectively. It was concluded that the ≡ SiO⊖ groups on the surface of nonporous colloid silica form the salt‐linkages stoichiometrically with ⊕N(CH3)3‐groups in TGCI, whereas the salt‐linkage formation between ⊕N(CH3)3‐groups in TGCI and ≡ SiO⊖ groups of silica gel does not follow the stoichiometric relationship, since the salt‐linkages of the ≡ SiOominus; groups in the pores of the silica gel could be affected by the steric hindrance of the TGCI chain.