bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polymer conformation and NMR chemical shifts, 2. Methoxyl protons NMR spectra of alternating copolymers of methyl (meth)acrylate with (α‐methyl)styrene
Authors: Tanabe Tsuneaki , Koinuma Hideomi , Hirai Hidefumi 
Published: April 2003

Abstract1H NMR spectra of alternating copolymers of methyl acrylate with styrene, methyl acrylate with α‐methylstyrene, and methyl methacrylate with α‐methylstyrene show triplet splittings at the methoxyl protons regions, which apparently reflect the cotacticity of triad sequences having a (meth)acrylate unit in the center. The two intervals between two neighboring peaks of the triplet are nearly equivalent for each alternating copolymer, whereas the absolute value of the splitting width is significantly different from one alternating copolymer to another. A theoretical interpretation is given for this observation by calculating the chemical shifts of the methoxyl protons in combination with a conformational analysis of the copolymers. The chemical shift of the protons in meso or racemic type dyad sequence is assigned by averaging the shieldings over all the preferred conformations for the dyad and is accumulated to give the shifts in triad sequences: iso = meso + meso, hetero = meso + racemic, syndio = racemic + racemic. The cotacticity‐dependent splittings thus calculated are quantitatively in accordance with the observed spectra and discussed in terms of conformational variation of the copolymers depending on the presence of α‐methyl group(s) in neither, either, or both of the monomeric unit(s).
Phase distribution chromatography (PDC) as a method for the investigation of polymers in solution 1. Thermodynamics and transport
Authors: Greschner Georg S. 
Published: April 2003

AbstractA phenomenological theory of the Phase Distribution Chromatography (PDC)‐separation effect is outlined and a theoretical equation for the measured PDC‐calibration curves is given. Assuming a reversible‐thermodynamical equilibrium in the polystyrene‐PDC‐column, only a relatively small part of the measured PDC‐calibration curves could be explained: namely those running below their tangents. In order to explain the whole sigmoidal shape of the experimental curves, a theory of steady state in the system sol/gel was developed assuming deformation of the polymer coil near the gel front due to the stress related to the velocity gradient. The resulting dynamical flow‐equilibrium differs highly from the reversible‐thermodynamic one at suitable low column temperatures. It leads to two typical calibration regions explaining the resolution power of the PDC‐column as a function of temperature. Analysis of the first one (reversible‐thermodynamical) starts with a three‐parameter partition function and leads to two contributions of the heat of transfer of a P‐mer from the gel into the sol of the column. These results are compared with those of Schulz, von Günner and Gerrens, and of Schulz and Horbach. In this way a physical interpretation of the three parameters in the partition coefficient of the P‐mer in the system gel/sol of the PDC‐column can be given.
Reactions of polyamide 6 and 6,6 with 1,5‐difluoro‐2,4‐dinitrobenzene: Photometric technique for the determination of the degree of crosslinking
Authors: Rossbach Volker , Mroszewski Klaus Dieter , Zahn Helmut 
Published: April 2003

AbstractDuring the reaction of polyamide 6 or polyamide 6,6 with the bifunctional crosslinking agent 1,5‐difluoro‐2,4‐dinitrobenzene in heterogeneous media, 5‐fluoro‐2,4‐dinitrophenylamino groups and 4,6‐dinitro‐1,3‐phenylenediamino groups are formed within the polymer. Owing to their different VIS‐spectroscopic behaviour, the concentration of both groups can be determined by means of a bicomponent analysis,

where c1 and c2 represent the concentration of 5‐fluoro‐2,4‐dinitrophenylamino and 4,6‐dinitro‐1,3‐phenylenediamino groups, respectively, and A375 as well as A425 represent the absorbances at 375 nm and 425 nm, measured in a 1 cm cell (solvent: 2,2,2‐trifluoroethanol). N‐(5‐fluoro‐2,4‐dinitrophenyl)‐ε‐aminocaproic acid and N,N'‐(4,6‐dinitro‐1,3‐phenylene)‐di‐ε‐aminocaproic acid are used as model compounds in order to calibrate the photometer. It is demonstrated that the degree of crosslinking, determined by means of the bicomponent analysis, is in accordance with the change of molecular weight, determined viscosimetrically.
Synthesis of new monomers having a primary amino group by lithium alkylamide catalyzed addition reaction of N‐alkylethylenediamines with 1,4‐divinylbenzene
Authors: Maeda Mizuo , Nitadori Yoshiaki , Tsuruta Teiji 
Published: April 2003

AbstractLithium alkylamide catalyzed addition reaction of N‐alkylethylenediamines (1) with styrene was examined. It was found that N‐alkyl‐N‐(2‐phenethyl)ethylenediamine (3) was formed selectively in preference to N‐alkyl‐N′‐(2‐phenethyl)ethylenediamine (4). The identification of products was carried out by 13C NMR. On the basis of the results obtained, a new type of styrene derivative having a primary amino group (6) was synthesized by lithium alkylamide catalyzed addition reaction of 1 with 1,4‐divinylbenzene.
Eigenschaften gemischter mizellen aus perfluorierten und nicht fluorierten kohlenwasserstoff‐tensiden
Authors: Bauernschmitt Dieter , Hoffmann Heinz 
Published: April 2003

AbstractKinetic and thermodynamic measurements were carried out on mixtures of ionic hydrocarbon‐ and perfluoro detergents. As systems the two combinations C8F17SO3N(CH3)4/C14H29SO4N(CH3)4and C8F17SO3Li/C12H25SO4Li were used. The critical micelle concentrations (cmc) of the mixtures are higher than the cmc‐values of the pure components, but lower than the values which would be observed if no mixed micelles were formed. This result is a clear indication of the existence of mixed micelles. The kinetic data on the C8F17SO3N(CH3)4/C14H29SO4N(CH3)4mixtures show that the mixed micelles have considerably lower aggregation numbers than the pure micelles. The large aggregates that are responsible for the viscoelastic behaviour of solutions of C8F17SO3N(CH3)4are not detectable in the detergent mixtures. The mean residence time of a detergent ion is lower in the mixed micelles than in the pure micelles. The solubility of a perfluoro‐detergent in a hydrocarbon micelle is higher than vice versa. For the C8F17SO3Li/C12H25SO4Li combination the observed concentration of micellar nuclei is several orders of magnitude larger for the perfluoro system than for the hydrocarbon system. As a consequence, in mixtures up to a mole fraction of 0,8 of hydrocarbon detergent, the micelles are formed via nuclei of the perfluoro detergent.
Kinetics of thermooxidation and photooxidation of poly(oxy‐2,6‐dimethyl‐1,4‐phenylene), 2. A suggestion of the reaction mechanism
Authors: Petrûj Jaroslav , Sláma Zdeněk 
Published: April 2003

AbstractA basic kinetic scheme for the thermo‐ and photodegradation of poly(oxy‐2,6‐dimethyl‐1,4‐phenylene) (1) is suggested on the basis of a comparison of theoretically possible reactions and the experimental results described in a previous work. Various possibilities of initiation are discussed (direct oxidation, thermal, catalytic, or photochemical decomposition of the hydroperoxy groups). The decomposition of hydroperoxy groups is considered to be the most important initiation reaction. The kinetic chain length of thermooxidation is very close to unity; the major reaction products (containing alcohol and aldehyde groups) are probably formed through the termination process. The relationship deriving from the kinetic scheme indicates the second reaction order in [1], which was experimentally found in mixtures of 1 with polystyrene. In the case of photooxidation the dominant role is played by quinone structures as photosensitizers. The routes leading to the formation of alcohol, ester, and aldehyde groups as the most significant oxidation products are discussed.
Cationic degradation of poly(2,3‐dimethylthiirane)s: A method for microstructure determination of the polymers
Authors: Goethals E. J. , Simonds R. , Spassky N. , Momtaz A. 
Published: April 2003

AbstractPoly(cis‐2,3‐dimethylthiirane) and poly(trans‐2,3‐dimethylthiirane) — poly(cis‐DMT) and poly(trans‐DMT) — obtained by different polymerization mechanisms are degraded to cyclic compounds containing at least two structural units by treatment with a catalytic amount of a strong alkylating agent such as triethyloxonium tetrafluoroborate or methyltrifluoromethyl sulfonate (“methyl triflate”). The main degradation product is 3,4,6,7‐tetramethyl‐1,2,5‐trithiepane and an equimolar amount of 2‐butene. The trithiepane can exist as six different geometrical isomers which can be separated by GL‐chromatography. Poly(trans‐DMT) leads to the two isomers where both pairs of vicinal methyl groups are in trans position to each other. The ratios fo the two isomers can be correlated with the microstructure of the starting polymers. This was proved by degradation studies of optically active poly(cis‐DMT): the higher the optical activity the higher the ratio of two isomers in the degradation mixture. The results indicate that the polymers (also the optically active polymers) do not show Bernoullian statistics, the number of isotactic diads (or triads) always being higher than expected.
Photopolymerization of methyl methacrylate using quinoline‐chlorine charge transfer complex as the photoinitiator
Authors: Ghosh Premamoy , Chakraborty Soumen 
Published: April 2003

AbstractPhotopolymerization of MMA was carried out at 40°C in bulk and in diluted systems using quinoline‐chlorine (Q‐Cl2) C.T. complex as the photoinitiator. Bulk polymerization followed normal free radical kinetics (initiator exponent = 0,5) for [Q‐Cl2] <0,0015 mol.1−1. In diluted systems, variable monomer exponents were observed, ranging from slightly above 1 to 2,7, depending on the nature of the solvent (benzene, carbon tetrachloride, chloroform, chlorobenzene, acetone, dioxane, THF and DMF). Initiator exponent was ≤0,5 in diluted systems and it even became practically equal to zero depending on the nature of solvent and the level of dilution. The kinetic non‐ideality in diluted systems was explained on the basis of solvent‐retardation and initiator‐termination via degradative chain transfer involving solvent‐modified initiating complexes and chain radicals. The actual initiating complex appeared to be the (Q‐Cl2)‐monomer complex formed instantaneously in situ on addition of Q‐Cl2 complex to the monomer.
Functional monomers and polymers, 69. Synthesis of poly(β‐alanine) in the functional reversed micelle
Authors: Hanabusa Kenji , Kondo Koichi , Takemoto Kiichi 
Published: April 2003

AbstractThe effects of temperature and solvents on the polycondensation of active β‐alanine 4‐acyl‐2‐nitrophenyl esters1a–g, having alkyl groups with different chain lengths, were studied. Nonpolar solvents were found to be well suited for the polycondensation, which was inhibited by the presence of a small amount of methanol. The reaction was found to be affected also by the temperature, the optimum temperature being 25°C. The results can be explained by assuming an aggregation of the active esters. This was checked with the model compounds3, 4aand4b, which correspond to the (dehydrobrominated) active ester1e. The apparent mean aggregation numbers of the model compounds were determined in cyclohexane and in methanol by an osmotic method. The results led to the suggestion that the aggregation plays an important role in the polycondensation.
Investigation of the electrical conductivity of the iodine‐polyphenylacetylene charge‐transfer complex
Authors: Cukor Peter , Krugler Joel I. , Rubner Michael F. 
Published: April 2003

AbstractThe electrical conductivity of the charge transfer complex between iodine and polyphenylacetylene (PPA) has been studied. The room temperature d‐c conductivity (σ) increased by seven orders of magnitude with iodine addition, reaching a maximum of 10−5 Ω−1 · cm−1 for a 1:1 ratio of iodine to repeating unit, and its concentration dependence could be described by: σ = σ0 exp [γc(1–c) – γ/4], where c is the mole fraction of iodine. Both crystalline and amorphous cis‐PPA followed this form, the crystalline polymer having a lower conductivity at low iodine levels, but attaining the same maximum value. The trans‐polymer iodinated much less readily than cis‐PPA. Molecular weight variations did not influence iodine uptake or conductivity in the range studied. It was possible to remove virtually all iodine from the charge‐transfer complex in dynamic vacuum, and an iodine diffusion coefficient of D ≈ 10−11 cm2.s−1 was determined from the rate of weight loss. Passage of current resulted in the evolution of iodine and iodine compounds at the anode. The experiment is consistent with a predominantly ionic conduction mechanism, in which the strong concentration dependence of σ is associated with a concentration‐dependent activation energy for ionic charge‐carrier formation.
Preparation of regularly Sequenced polyamides, containing definite numbers of oxyethylene units
Authors: Sato Hisaya , Iwabuchi Susumu , Böhmer Volker , Kern Werner 
Published: April 2003

AbstractPolyamides 3 containing constant and definite numbers of oxyethylene units were prepared by condensation polymerization of suitable diamines and diesters, both of which containing oxyethylene units. The polymer structure was determined by IR and 1H NMR spectroscopy. Almost all polymers are crystals melting at ≈ 40°C and show a complexation ability towards alkalimetal cations. It was also found that diesters containing oxyethylene units show a higher condensation rate than alkylene diesters, which is explained by an inductive effect of the ether oxygene. However, no remarkable difference in the condensation rate was found between diamines containing oxyethylene units and the corresponding aliphatic diamines.
Synthesis and properties of aromatic polypyrazoles from bis(β‐substituted vinyl ketones) and aromatic dihydrazines
Authors: Ueda Mitsuru , Funayama Michio , Kawaharasaki Naomi , Imai Yoshio 
Published: April 2003

AbstractPolycyclocondensations of aromatic dihydrazines 2a and 2b with 1,6‐diethoxy‐1,5‐hexadiene‐3,4‐dione (1a) in m‐cresol and those with bis(3‐chloroacryloyl)benzenes 1b and 1c in 1‐methyl‐2‐pyrrolidone (NMP) lead to aromatic polypyrazoles 3a – f having inherent viscosities up to 0,35 dl.g−1. The polymers are soluble in polar aprotic solvents like NMP and some acidic media including m‐cresol. Thermogravimetry shows a loss of 10 wt.‐% at ≈ 500°C both in air and nitrogen.
Vacuum‐Ultraviolet circular dichroism of Protected homo‐oligopeptides derived from S‐methyl‐L‐cysteine
Authors: Coffey R. T. , Stevens E. S. , Toniolo C. , Bonora G. M. 
Published: April 2003

AbstractMonodispersed N‐and C‐protected linear homo‐oligomers of S‐methyl‐L‐cysteine (n = 2 − 7) are studied by measurements of circular dichroism in the vacuum‐ultraviolet region. In the solid state higher members of the series take up a β‐conformation. The results are compared with earlier circular dichroism and infrared absorption measurements on the same series, and also with the related norvaline and methionine series.
Oxydation photocatalytique des polypropylènes isotactique et atactique
Authors: Ginhac Jean‐Marie , Arnaud René , Lemaire Jacques 
Published: April 2003

AbstractBy photooxidation of isotactic and atactic polypropylene (PP), irradiated at wavelengths >300 nm in air, alcoholic, acidic, ester, lactonic, and unsaturated functions are formed as shown by IR spectrophotometry. The primarily formed hydroperoxy and ketone groups are rapidly photolyzed and their concentrations are kept low. In presence of UV absorbing pigments like TiO2 or ZnO, the same photoproducts are formed with lower rates than in the transparent polymers. In atactic PP, ZnO and TiO2 (rutile or anatase) show different photoactivities. When the light is absorbed in ZnO, accumulation of ketone and lactonic groups is observed. When TiO2 is the absorbing species, oxidation is going further and acidic, ester, and lactonic functions may be observed; TiO2 appears to be able to photocatalyze the disappearance of ketone groups. In isotactic PP of high cristallinity, direct photooxidation and photocatalyzed oxidation are superimposed and differences between ZnO and TiO2 cannot be observed.
Polybutadiènes hydroxytéléchéliques, 5. Addition des thiols sur les double liaisons des polybutadiènes hydroxytéléchéliques radicalaire et anionique. Etude des mécanismes d'addition par 1H et 13C NMR
Authors: de La Campa José Gonzalez , Pham Quang‐Tho 
Published: April 2003

AbstractThe products of radical addition of butanethiol (2), 2,2‐dimethylpropanethiol (3), and 4‐methylthiophenol (4) to commercial hydroxytelechelic polybutadienes Arco R45M® and Nisso G 2000® were examined by 1H and 13C NMR spectroscopy. The rates of addition were calculated by 1H NMR and the molecular weights were measured by vapour pressure osmometry. The double bonds were found to react completely with 2, whereas 3 does not react easily. Thiol 4 mainly isomerizes (cis‐1,4 into trans‐1,4). The butylthio radicals were found to be able to add to both carbon atoms of the 1,4 double bonds, whatever the addition modes of the adjacent 1,4 units might be. As far as the 1,2 double bonds are concerned the butylthio radical adds mainly to the terminal methylene carbons.
Nuclear magnetic resonance studies on polymer carbanions, 2. Model compounds for α‐methylstyrene and α‐methylstyrene tetramer dianions
Authors: Matsuzaki Kei , Shinohara Yoshinao , Kanai Taiichi 
Published: April 2003

Abstract1H and 13C NMR spectra of model compounds for the poly‐α‐methylstyryl anion, 2‐lithio, 2‐potassio, and 2‐cesio‐2‐phenylbutane, were determined. The lithium compound had a higher charge density at the α‐carbon and a lower charge on the phenyl ring than the other compounds and exhibited phenyl ring rotation at higher temperatures. The activation energy was calculated to be 61, 0 kJ/mol. The potassium and cesium compounds did not show phenyl ring rotation at 80°C. Quantum chemical calculations indicated that the larger cations interact with the phenyl ring especially with the ortho carbons. 13C NMR spectra of α‐methylstyrene tetramer dianion with sodium and potassium as counter cation were also measured and compared with those of the model compounds.
Study of conformational transitions of graft copolymers by UV spectrophotometry
Authors: Goşa Kristiana , Donescu Dan , Carp Nicoleta 
Published: April 2003

AbstractUV absorption spectra of solutions of vinyl acetate polymers grafted on ethylene oxidepropylene oxide blockcopolymers in (90:10, v/v) ethanol/water mixture are investigated. The spectra of graft copolymers are clearly different from those of blends of the same composition. Conformational transitions of these copolymers occur in dilute solution at 35 and 60°C; the transitions are evidenced by UV differential spectra either compensated with solvent at the same temperature or with solution at 20°C. The absorbance measured at fixed wavelength as a function of temperature shows a change of slope at the transition points. However, the difference between the energies of solution and solvent as measured from differential spectra does not vary monotonously with temperature. It exhibits two minima corresponding to the transition temperatures. The plot of either this energy difference or the ratio of solvent maximum absorbance over solution maximum absorbance (from differential spectra) versus concentration allows to establish a critical concentration. Below this concentration a solution of grafted copolymers may be looked upon as dilute.
Determination of the number‐, weight‐, and z‐average dimensions of macromolecules by viscosity and GPC measurements
Authors: Bareiss Rolf E. 
Published: April 2003

AbstractThe molecular weight averages are calculated which have to be inserted into the Fox‐Flory relationship \documentclass{article}\pagestyle{empty}\begin{document}$ {{\left[ \eta \right] = \Phi (\overline {r_{{\rm av}}^{\rm 2} } )^{{3 \mathord{\left/ {\vphantom {3 2}} \right. \kern&#x02010;\nulldelimiterspace} 2}} } \mathord{\left/ {\vphantom {{\left[ \eta \right] = \Phi (\overline {r_{{\rm av}}^{\rm 2} } )^{{3 \mathord{\left/ {\vphantom {3 2}} \right. \kern&#x02010;\nulldelimiterspace} 2}} } {M_{{\rm av}} }}} \right. \kern&#x02010;\nulldelimiterspace} {M_{{\rm av}} }} $\end{document} if the number‐, weight‐, or z‐average dimensions are to be determined for polymolecular polymer samples. The resulting complex molecular weight averages \documentclass{article}\pagestyle{empty}\begin{document}$ M_{r_{\rm n} } \eta _{\rm w},{\rm }M_{r_{\rm w} } \eta _{\rm w} $\end{document}, and \documentclass{article}\pagestyle{empty}\begin{document}$ M_{r_{\rm z} } \eta _{\rm w} $\en{document} are compared with simple molecular weight averages and for Schulz‐Zimm and logarithmic normal distributions of the molecular weight their numerical relations to the viscosity‐(Mη), number‐ (Mn), and weight‐average molecular weight (Mw) calculated. A simple straight‐forward method is outlined for the determination of the number‐, weight‐, and z‐average dimensions of polymolecular polymers from viscosity and gel permeation chromatography measurements.
Preparation and properties of polyamides containing dibenzothiphenediyl and 5,5‐dioxodibenzothiophenediyl units
Authors: Srinivasan Poondi R. , Mahadevan Venkatanarayana , Srinivasan Mahalingam 
Published: April 2003

AbstractSeveral new polyamides (3a–d, 6a–d, 7a and 7b) containing dibenzothiophenediyl units were prepared by low temperature solution polycondensation of dibenzothiophenediamines (1a, b) with aromatic diacyl dichlorides (2a, b) or of aromatic diamines (5a, b) with dibenzothiophenediacyl dichlorides (4a, b). Some of the polymers were soluble in polar amide solvents or DMSO. All the polymers possess inherent viscosities in the range of 0,6 to 1 dl/g. Thermal stability and crystallinity were determined. The resulting polyamides were found to be much more stable than the corresponding polymers having open‐chain linkages.
Succinic half‐esters of poly(ethylene glycol)s and their benzotriazole and imidazole derivatives as oligomeric drug‐binding matrices
Authors: Ferruti Paolo , Tanzi Maria Cristina , Rusconi Luisa , Cecchi Roberto 
Published: April 2003

Abstractα‐Hydroxysuccinyl‐ω‐hydroxysuccinyloxypoly(oxyethylene)s (succinic half‐esters of poly‐(ethylene glycol)s) (2) of different molecular weights were prepared, and transformed into the corresponding benzotriazole and imidazole derivatives 3 and 4. The benzotriazolyl or the imidazolyl residues in these polymers can easily be exchanged. This was proved with model compounds bearing hydroxyl or amino groups. Polymers of this type may be considered as potential oligomeric drug‐binding matrices.