bluuebunny/crossref_metadata_2025_split huggingface dataset:
Functional monomers and polymers, 62. Synthesis of polypeptides from dipeptide 4‐acyl‐2‐nitrophenyl esters
Authors: Hanabusa Kenji , Kondo Koichi , Takemoto Kiichi 
Published: April 2003

AbstractA series of active glycylglycine 4‐acyl‐2‐nitrophenyl esters having different chain length of the acyl groups (that is, 4‐acetyl‐, 4‐hexanoyl‐, and 4‐dodecanoyl‐2‐nitrophenyl esters) was prepared, and their polycondensation was studied in various solvents at 30°C. In general, the yield of the polycondensates was high in nonpolar solvents, while the reaction in polar solvents was accompanied by formation of the cyclodimeric product. D,L‐Alanyl‐D,L‐alanine, glycyl‐D,L‐alanine and D,L‐alanylglycine 4‐dodecanoyl‐2‐nitrophenyl esters were also prepared and their polycondensation was tried.
Propriétés viscoélastiques de la poly(α,α‐diéthyl‐β‐propiolactone)
Authors: Noah Joseph , Prud'homme Robert E. 
Published: April 2003

AbstractThe viscoelastic properties of poly(α,α‐diethyl‐β‐propiolactone) were investigated in the linear range using stress relaxation and dynamic mechanical methods. Using Ferry's reduction method, a horizontal shift factor was determined at each temperature, that satisfactorily agreed with the WLF equation in the transition zone. No vertical shift was required to superimpose different relaxation curves. The apparent activation energy was temperature dependent and passed through a maximum near Tg whose value is (311 ± 2)K. The relaxation spectrum has been calculated according to the first method of approximation of Schwarzl and Staverman. It consists of a high intensity plateau at shorter times, a wedge type portion with a slope of −0,15 and a low intensity plateau at longer times. Dynamical mechanical measurements revealed a β relaxation peak at 333 K and yielded the evidence of a γ peak around 120 K.
Molecular size and gel formation in branched poly(methyl methacrylate) copolymers
Authors: Whitney Robert S. , Burchard Walter 
Published: April 2003

AbstractBranched copolymers of methyl methacrylate with ethylene dimethacrylate or pentaerythritol tetramethacrylate with high weight average molecular weights Mw were prepared by free radical polymerization. The double bond conversion of these polymers (β) was measured dilatometrically and the gel point (βc) was located by extrapolation of bulk viscosity measurements. The polymers were studied by light‐scattering, 1H NMR and viscometry. Hence it was possible to investigate the relationship between the molecular weight Mw and the reduced conversion quantity (1 − β/βc)−1 and also the molecular weight dependence of the z‐average mean square radius of gyration 〈S2〉z. Considerable deviations from the classical Stockmayer theory but also from percolation theory were observed. 1H NMR showed a relative small extent of ring formation (10 to 24%) and a reduced apparent reactivity of the pendant double bonds, while the delay in the gel formation appeared to be caused by a much higher ring formation (80 to 90%). This apparent inconsistency is explained by a size‐dependent ring formation, where the extent of ring formation is increased with the molecular dimensions; simultaneously, the pendant double bonds become progressively less accessible to cross‐linking by growing radicals. The molecular weight dependence of 〈S2〉z is found to be in agreement with this heterogeneous reaction model.
Haupt‐ und seitenkettenkristallinität bei isotaktischen poly(1‐alkylethylen)en, 3. Änderung der ordnungszustände bei den höheren homologen
Authors: Trafara Gundolf 
Published: April 2003

AbstractThe higher homologues for isotactic (it) poly(1‐alkylethylene)s (from it‐poly(1‐dodecylethylene) to it‐poly(1‐eicosylethylene)) show three polymorphic modifications. The modification of highest order crystallizes in an orthorhombic structure (modification I). This modification is formed during melt crystallization at a cooling rate ϕ < 2,5 K·s−1. The main‐chain conformation is a quaternary helix. The side‐chains are tilted 130,6° against the axes of the helices and crystallize like orthorhombic polyethylene. The DSC‐curves of these homologues in modification I show the endotherm of melting and an endotherm at a temperature, about 25 K to 30 K below the melting temperature. The endotherm at the lower temperature is caused by atactic material in the samples, by only partially ordered crystallites in isotactic material, and by the change of conformation of some CH2‐groups of the side‐chains near the main chain.
Nature et consequence des interactions se développant lors de la mise en contact de polyéthylène avec des produits mouillants et non mouillants, 1. cas des produits mouillants apolaires (alcanes) et polaires (alcools)
Authors: Escoubes Marcelle , Berticat Philippe , Chabert Bernard , Soulier Jean‐Pierre 
Published: April 2003

AbstractThe nature of interactions between polyethylene and a wetting solute was analyzed to know if the interface can be characterized by the expression of the sticking work or if other phenomena than adhesion and wetting must be taken into account. In this way, the sorption isotherms, the molar interaction heats and the cinetic characters of the sorption gave informations about the possible importance of a diffusion of the solvent. Two types of systems were investigated: polyethylene/alkanes and polyethylene/alcohols. The formation of almost homogeneous solutions or, on the contrary, of aggregates is discussed.
Polymer‐solvent interactions: Dextrans in water and DMSO
Authors: Basedow Arno Max , Ebert Klaus Heinrich , Feigenbutz Willi 
Published: April 2003

AbstractEnthalpies of solution, dilution and mixing of several dextran fractions with different molecular weights (MW) and low MW carbohydrates were determined in water and dimethyl sulfoxide at 25°C. The enthalpies of solution of dextran increase in the oligomer range up to a MW of about 1000; for higher MWs the enthalpies of solution are almost constant. The enthalpies of dilution decrease strongly with increasing MW and remain constant for MWs higher than 2 000. The interaction parameter was found to depend on the concentration of the solute in both solvents. From the experimental results it can be concluded that dimethyl sulfoxide is a better solvent for glucose and dextran than water. In dilute solutions glucose interacts considerably more strongly with the solvent than dextran. The conformational properties of dextran are similar in both solvents; for MWs above 2 000 the degree of solvation is found to be independent from the MW.
Solvent effect on the asymmetric induction copolymerization of styrene with maleic anhydride in the presence of lecithin
Authors: Doiuchi Tohru , Minoura Yuji 
Published: April 2003

AbstractThe asymmetric induction radical copolymerization of styrene (St) with maleic anhydride (MAn) was studied in various solvents with different dielectric constants in the presence of lecithin as a chiral surfactant. The observed specific rotation of the resulting alternating copolymer decreased with an increase in the dielectric constant of the solvent used. It was concluded that the asymmetric induction depends mainly upon the incorporation of MAn within the reversed lecithin micelles.
Hypochromism of polyhalogenvinylcarbazoles
Authors: Pielichowski Jan , Obrzut Jan 
Published: April 2003

AbstractSpectrophotometric studies in the UV region were carried out for a series of chlorine and bromine derivatives of N‐ethylcarbazole and poly(N‐vinylcarbazole). All the examined polymers, in the whole spectral range, exhibit considerably less absorptivity than their low molecular models, i.e. ethylcarbazoles. Absorption bands of the polymers are shifted, in comparison to the respective absorption bands of halogenethylcarbazoles, towards shorter wavelenghts. Halogen substituents in the carbazole ring reduce the transfer energy π → π*. This bathochromic effect is especially observable for low‐energy bands 1La and 1Lb, and it was noticed that the bromine substituent exerts more influence than the chlorine substituent.
Aqueous polymerization of methyl methacrylate using quinoline‐sulfur dioxide complex and tetrahydrofuran‐sulfur dioxide complex as initiators
Authors: Ghosh Premamoy , Chakraborty Soumen , Biswas Samir 
Published: April 2003

AbstractAqueous polymerization of MMA was kinetically studied using separately two complexes of sulfur dioxide as initiators, namely, quinoline‐sulfur dioxide (Q‐SO2) complex and tetrahydrofuran‐sulfur dioxide (THF‐SO2) complex. In each case the initiator exponent was 0,5 and the monomer exponent was 1,5. Kinetic data, inhibitory effect of hydroquinone, and incorporation of sulfoxy end groups in the polymers indicate a radical mechanism of polymerization with first order dependence on monomer for the rate of initiation while termination appears to take place bimolecularly.
Nuclear magnetic resonance studies on polymer carbanions, 1. Living polystyrene and its model compounds
Authors: Matsuzaki Kei , Shinohara Yoshinao , Kanai Taiichi 
Published: April 2003

Abstract1H and 13C NMR investigations were carried out on polystyryl carbanions and model compounds for the active chain end of living polystyrene, changing counter cation (Li, K, and Cs), solvent, and temperature. The structure of the model compounds with K and Cs as counter cation was planar with sp2‐hybridized α‐carbon, which indicates strongly hindered rotation of the phenyl ring. For the model compound with lithium as counter cation, the phenyl ring rotation was hindered at lower temperatures. The 13C1H coupling constants of the compound indicated less sp2 character of α‐carbon. The differences in the chemical shifts of the two ortho or meta carbons depended on the type of counter cation, suggesting an interaction between counter cation and phenyl ring. Quantum chemical calculations on the structure of the model compounds were carried out and the results were compared with the excess charge distributions calculated from 13C NMR chemical shifts.
15N NMR spectroscopy, 25. Terpolymerization of glycine‐NCA, leucine‐NCA, and valine‐NCA
Authors: Hull William E. , Kricheldorf Hans R. 
Published: April 2003

AbstractThe copolymerization of Leu‐NCA and Val‐NAC was achieved in solution by initiation with benzylamine, diethylamine, triethylamine, pyridine or by simple heating of the pure monomers to 120°C. Under similar conditions the terpolymerization of Gly‐NCA, Leu‐NCA and Val‐NCA was carried out. 400 MHz 1H NMR spectra and natural abundance 36,48 MHz 15N NMR spectra of the resulting copolypeptides were measured in trifluoroacetic acid. The various kinds of peptide groups of these copolypeptides show individual 15N NMR signals because of strong neighboring residue effects. The quantitative evaluation of NMR spectra allows one to calculate the average length of the homogeneous blocks and the copolymerization parameters. The terpolymerization of Gly‐NCA, Leu‐NCA and Val‐NCA was found to behave like a superposition of the corresponding binary copolymerizations. The primary amine‐initiated terpolymerization of Gly‐NCA, Val‐NCA and γ‐methyl Glu‐NCA, was also investigated.
Haloaldehyde polymers, 15. Stabilization of polychloral by posttreatment
Authors: Corley L. Steven , Vogl Otto 
Published: April 2003

AbstractPolychloral prepared by anionic polymerization has primarily alkoxide endgroups as the living terminal ends. The initial endgroups depend on the type of nucleophile used for the initiation. Alkoxide‐terminated polychloral degrades to monomer on heating to slightly above 100°C or on extraction with methanol or acetone. Programmed DTG shows a degradation rate maximum (MDT) near 150°C. Terminations of the polymer endgroups were observed when the polymer was allowed to stand for long periods of time before workup. The type and amount of stabilization depends on the cation and residual monomer. With HCI the alkoxide ends can be protonated to give hydroxyl terminated polychloral, which is stable to extraction and has an MDT of 220°C. Acylation or alkylation as posttreatments could not be shown to produce the expected acyl‐ or alkyl endcapped polychloral, but posttreatment with acetyl chloride produced partially stable polymer (one MDT higher than 300°C) without detectable acetyl endgroups. The most effective posttreatment is with PCl5/CCl4 which gives highly stabilized polychloral with an MDT near 350°C. The treatment was only effective in thin sections of polymer and appeared to have introduced a chlorine endgroup.
Thermal degradation of polyurethanes investigated by direct pyrolysis in the mass spectrometer
Authors: Ballistreri Alberto , Foti Salvatore , Maravigna Pietro , Montaudo Giorgio , Scamporrino Emilio 
Published: April 2003

AbstractDirect pyrolysis in the mass spectrometer yielded evidence on the mechanisms of thermal decomposition of N‐monosubstituted and N‐disubstituted polyurethanes. Our results indicate that N‐monosubstituted polyurethanes undergo quantitatively a depolycondensation process, producing diisocyanate and diol. In contrast, disubstituted polyurethanes decompose to give selectively secondary amine, olefine and CO2.
Biomimetic approach to the design of a pyridoxal enzyme model, 1. Hydrophilic polyacrylamide gel with stereochemically defined arrangement of salicylaldehyde and lysine fragments
Authors: Belokon' Yuri N. , Tararov Vitali I. , Savel'eva Tatiana F. , Belikov Vasili M. 
Published: April 2003

AbstractA polymeric gel in which salicylaldehyde and lysine moieties are capable of forming an “internal” aldimine at pH > 6,0 has been prepared by copolymerization of Nα‐5‐methacryloylaminosalicylidene‐Nε‐methacryloyl‐(S)‐lysinatocopper (II) (1a) with acrylamide and N,N'‐methylenebisacrylamide in water with subsequent removal of the copper ions by 0,1 M HCl or the disodium salt of EDTA. The equilibrium formation constants of the “internal” aldimine are ca. 30 times (at pH 7,1) and ca. 100 times (at pH 9,2) higher than the equilibrium constants of the model reaction of Schiff base formation from 5‐isobutyrylaminosalicylaldehyde (2) and Nt‐isobutyryl‐(S)‐lysine (3). The α‐amino group of the lysine residue in the gel acts as a nucleophilic catalyst in the reaction of the salicylaldehyde moiety of the gel with semicarbazide. The reaction proceeds 5,3 times faster in the gel than in a model polymeric system which does not contain lysine moieties.
Synthesis and physico‐chemical properties of poly[4‐(1,1,3,3‐tetramethylbutyl)phenyl methacrylate]
Authors: Ojeda Tomas , Radic Deodato , Gargallo Ligia , Boys Daphne 
Published: April 2003

AbstractPoly[4‐(1,1,3,3‐tetramethylbutyl)phenyl methacrylate] (1a) was synthesized and its physicochemical properties were determined in the condensed phase and in dilute solution. The polymerization of 4‐(1,1,3,3‐tetramethylbutyl)phenyl methacrylate was carried out by radical mechanism in solution with 2,2′‐azoisobutyronitrile as initiator. Several samples were characterized by their intrinsic viscosity, by osmometric measurements, differential scanning calorimetry, and X‐ray diffraction. The viscometric behaviour of fractions of 1a was studied in good solvents and theta solvents, and the conformational parameters were calculated. Polymer 1a presents an unusual high rigidity in the chain. X‐Ray diffraction of this polymer indicates a one‐dimensional ordering of a mesomorphic type.
Haloaldehyde polymers, 18. Rate of copolymerization of chloral with isocyanates
Authors: Kubisa P. , Teshirogi T. , Hatada K. , Corley L. S. , Vogl O. 
Published: April 2003

AbstractCryotachensic copolymerization of chloral with various aliphatic and aromatic isocyanates, initiated by lithium tert‐butoxide and triphenylphosphine at 0°C, was followed by 1H NMR spectroscopy. Information on the mobility of comonomers and solvent molecules in the polymerization mixture was obtained by measuring the line width of the signals. Relative rates of incorporation of chloral and isocyanates into the copolymer were determined, indicating that the copolymer was not uniform in structure and that the content of isocyanate units increased significantly in the final stages of copolymerization.
Redox polymerisation, 6. Kinetics of the polymerisation of acrylonitrile initiated by the systems glycerol‐Mn(III) and allyl alcohol‐Mn(III) in aqueous sulfuric acid
Authors: Jayakrishnan Athipettah , Mahadevan Venkatanarayana 
Published: April 2003

AbstractPolymerisation of acrylonitrile initiated by the redox systems glycerol‐Mn(III) and allyl alcohol‐Mn(III) is investigated in the temperature range 25–45°C in aqueous sulfuric acid/acetic acid and aqueous sulfuric acid, respectively. Oxidation of both glycerol and allyl alcohol proceeds through an intermediate complex. Decomposition of the complex is reversible with glycerol, whereas with allyl alcohol it is irreversible. Addition of Mn(II) retards both oxidation and polymerisation in the former system, while with the latter oxidation in the absence of monomer is unaffected, although polymerisation rates are retarded. Mutual termination predominates with the system glycerol‐Mn(III), whereas primary radical termination accounts for the kinetics of polymerisation with the system Mn(III)‐allyl alcohol. Rate and equilibrium parameters are evaluated and their significance is discussed.
Lineare polybenzyle, 6. Polymerisation von α‐methylbenzylchlorid
Authors: Skura Josef , Lenz Robert W. 
Published: April 2003

Abstractα‐Methylbenzylchloride (1) was polymerized in ethyl chloride and in 1‐nitropropane at various temperatures with AlCl3 as catalyst, mainly at −115 and at 0°C. The polymers obtained were crystalline or amorphous, depending on the reaction conditions. The reactions were complete within seconds. The tacticity of the polymers was determined by 1H and 13C NMR‐spectroscopy. Polymers prepared at low temperatures in ethyl chloride showed isotactic sequences; in 1‐nitropropane at 0°C atactic configuration. A reaction mechanism for the formation of the isotactic polymer is proposed on the basis of GPC‐data. DSC‐data are reported and discussed.
Aromatic spiro polymers
Authors: Niume Kazuma , Kurosawa Shigeru , Toda Fujio , Uno Keikichi , Iwakura Yoshio 
Published: April 2003

AbstractAromatic spiro polymers, polyoxoindoline‐spiro‐benzimidazolines 9a–c, were prepared by the solution polycondensation reaction of biisatyls with aromatic tetramines in polar organic solvents. The spiro polymers were found to exhibit good solubility in polar organic solvents, such as N,N‐dimethylacetamide and hexamethylphosphoramide, in contrast to the insolubility of the corresponding polyindoloquinoxalines in these solvents. The improvement of the solubility was discussed mainly in terms of the hydrogen bonding and packing in polymer molecules. The spiro polymers slowly rearranged at high temperatures to give polyindoloquinoxalines with high thermal stability.
Synthesis and photochemical behavior of polynuclear dithiolato‐metal‐dye complexes
Authors: Kaneko Masao , Yamada Akira 
Published: April 2003

AbstractPolynuclear dithiolato‐metal‐dye complexes were prepared and their photochemical behaviors were studied. The dimercapto ligands used were maleonitriledithiol (MNT) and toluene‐3,4‐dithiol (TDT); metal ions were copper, manganese and nickel; and dyes were thionine (TH), tolusafranine (SAF) and methylene blue (MB). From IR spectra, elemental analyses and magnetic measurements they were found to be polynuclear complexes having bis(dithiolato)‐metal structure incorporating the dyes as cations. The complexes showed almost the same visible spectra as the free dyes. The molar absorption coefficients of the maximum absorption were in most cases larger than in the free dye. The dithiolato‐metal complex affected remarkably the photochemical reactivity of the dye incorporated in it. The rates of the photochemical reduction of the TH complexes (Cu‐MNT‐TH, Mn‐MNT‐TH and Cu‐TDT‐TH) in hexamethylphosphortriamide were higher than the free TH, while those of the SAF complexes (Cu‐MNT‐SAF and Mn‐MNT‐SAF) and MB complexes (Cu‐MNT‐MB and Ni‐MNT‐MB) were much lower than the free SAF and MB, respectively.
Immobilisierung von polymergebundenen oligodesoxyribocytidylsäuren an DEAE‐cellulose
Authors: Schott Herbert , Watzlawick Hildegard 
Published: April 2003

AbstractN‐Anisoyl‐deoxyribocytidine‐5′‐phosphate is chemically polycondensed. From the polycondensate, oligomers containing four or more monomeric units are isolated chromatographically and subsequently linked to a soluble polyvinylalcohol. After cleavage of the nucleobaseprotecting groups, the unreacted oligodesoxyribocytidylic acids are separated from polyvinylalcohol bound oligomers through ultrafiltration. DEAE‐Cellulose is subsequently coated with this polymer‐bound oligodeoxyribocytidylic acids. The now obtained PVAL‐p(dC)n‐DEAE‐Cellulose acts as a specific sorbent in template‐chromatography.
Kuhn‐Mark‐Houwink‐Sakurada‐Beziehung für poly(ϵ‐caprolactam)
Authors: Müller Herbert , Neuray Dieter , Horbach Alfred 
Published: April 2003

AbstractThe Kuhn‐Mark‐Houwink‐Sakurada relationship for poly(ϵ‐caprolactam), (polyamide 6), is established, based on the absolute determination of the weight‐average molecular weight by light scattering. It is obtained ([η] in cm3.g−1):

The unperturbed dimensions of this polymer in both solvents are also determined by using the Stockmayer‐Fixman method.
The use of graft copolymers as enzyme supports, 3. The Immobilization of proteins and enzymes on poly(fluorostyrene) and poly(nitrofluorostyrene) — nylon graft copolymers
Authors: Abdel‐Hay Fouad , Beddows Clifford G. , Guthrie James T. 
Published: April 2003

AbstractThe radiation induced, graft copolymerization of m‐ and p‐fluorostyrene onto nylon was successfully achieved. Grafting was followed by nitration of the fluorostyrene groups in the copolymer to provide substrates which were active to the coupling of various enzymes and proteins. Bovine serum albumin, ovalbumin, pepsin, β‐galactosidase, and alkaline phosphatase proteins all coupled very efficiently but the activities of the coupled enzymes were relatively low.
Structural Study on styrene/ε‐caprolactone block copolymers in absence and in presence of a solvent of the polystyrene block
Authors: Herman Jean‐Jacques , Jérome Robert , Teyssié Philippe , Gervais Monique , Gallot Bernard 
Published: April 2003

AbstractThe lamellar crystalline structure of styrene/ε‐caprolactone block copolymers (SCL) of different compositions and molecular weights is studied by X‐ray diffraction and differential scanning calorimetry. The studies were performed in the absence and in the presence of diethyl phthalate, a preferential solvent of the amorphous polystyrene block. The influence of the molecular characteristics of the copolymer and of the solvent concentration on the parameters of the lamellar structure and especially on the number of folds and on the crystallinity of the crystallizable poly(ε‐caprolactone), (PCL), chains is established. It is shown that copolymers SCL can be divided in three categories depending upon their composition.
Copolymères du chlorure de vinylidène avec l'acrylonitrile, le chlorure de vinyle et le méthacrylate de méthyle, 2. Fusion — utilisation d'un modèle de simulation
Authors: Dumont Bernard , Berticat Philippe , Guillot Jean 
Published: April 2003

AbstractThe melting point depression in vinylidene chloride copolymers, when introducing an increasing number of units B = vinyl chloride, acrylonitrile or methyl methacrylate is studied in this paper. A Monte‐Carlo simulation model of chains growing and crystallization is applied and allows to know the proportion Xc of defects in the crystalline phase. An equation given by Sanchez is then applied, and the excess energy ε of the defect created by the incorporation of a B unit in the crystalline vinylidene chloride lattice is calculated.