bluuebunny/crossref_metadata_2025 huggingface dataset:
Konstruktion eines vollautomatischen präzisionschromatographen auf der basis der phasendistributionschromatographie (PDC)
Authors: Greschner Georg S.
Published: April 2003

The design of a fully automatized chromatograph based on Phase Distribution Chromatography (PDC) is presented and some of the most important results of the measurements shown. PDC represents a dynamical phase separation as column method: the separation of the polymer components in a PDC‐column is based on thermodynamic‐kinetical interactions of the mobile phase (the polymer to be analyzed) below the theta temperature of the system by a gel of the same high polymer situated on the surface of small glass beads. The sigmoidal shape of the measured PDC calibration curves can be explained by introducing a dynamical flow‐equilibrium in the system sol/gel which highly differs from the thermodynamic equilibrium at low temperatures of the column.
Kombination und disproportionierung von modellradikalen für die wachsende polystyrolkette
Authors: Gleixner Günther , Olaj Oskar Friedrich , Breitenbach Johann Wolfgang
Published: April 2003

The mechanism of the bimolecular reaction between the model radicals for polystyryl: 1‐phenylethyl, 1‐phenylpropyl, and 1,3‐diphenylpropyl radical is investigated by means of gas chromatography. The radicals are generated either at 80°C by thermal or at 20°C by photochemical decomposition of the corresponding azoalkanes in benzene solution. At 80°C 7,5% of the 1‐phenylethyl radicals, 12,9% of the 1‐phenylpropyl radicals, and 13,5% of the 1,3‐diphenylpropyl radicals undergo disproportionation. Since the structure of these model radicals approaches that of the growing polystyrene chain in this order one may expect polystyryl radicals to disproportionate to about the same extent as 1,3‐diphenylpropyl radicals. In photolysis experiments evidence for ortho coupling of 1‐phenylalkyl radicals is found. Photoisomerisation of this ortho coupling product leads to the formation of a small amount of a thermally stable unsymmetrical dimer.
Zur definition eines nichtganzzahligen Kopplungsgrades für Gemische ein‐ und zweikettiger Polymermoleküle
Authors: Olaj Oskar Friedrich , Gleixner Günther
Published: April 2003

In free radical polymerization the polymers usually represent a mixture consisting of molecules from one (degree of coupling k = 1) and two (k = 2) independently grown chains. In case the chain lengths at the moment of stabilization obey the same most probable Schulz‐Flory distribution over the total conversion interval (as e.g. at low conversions) the molecular weight distribution (m. w. d.) is a superposition of two Schulz distributions with degrees of coupling k = 1, and k = 2, respectively. Frequently, however, this m. w. d. has been described by a Schulz distribution with a non‐integer k. It is pointed out that the deviations of such a representation of the m. w. d. from the correct one may not always be negligible. Furthermore, there is no unique way to ascribe a degree of coupling k to such an m. w. d. Thus, the use of a non‐integer k should be avoided for the characterization of these polymers, especially when the interrelations between the m. w. d. and the kinetic parameters are to be discussed.
Condensation polymerization of diphenyl 2,2′‐diiodobiphenyl‐4,4′‐dicarboxylate with some di‐ and tetraamino compounds
Authors: Banihashemi Ahmad , Kiaizadeh F.
Published: April 2003

In connection with the research for new thermostable high molecular weight materials several polybenzimidazoles were prepared by condensing diphenyl 2,2′‐diiodobiphenyl‐4,4′‐dicarboxylate (1) with 3,3′‐diaminobenzidine (2), bis(3,4‐diaminophenyl) ether, 3,3′,4,4′‐tetraaminobenzophenone, 1,2,5,6‐tetraaminoanthraquinone, and 1,2,4,5‐tetraaminobenzene. Depending on the reaction time and temperature, partial replacement of iodine atoms by phenoxy groups occurred in the polymers. Model compounds were prepared by condensation of ester 1 with o‐phenylenediamine, 2,3‐diaminopyridine, and 3,4‐diaminopyridine. IR, UV, and 1H NMR spectra of the model compounds were taken. The high thermostability of the polymers could be shown by thermogravimetry.
Darstellung und Derivatisierung von linearem Polyvinylamin zur selektiven Komplexbildung in homogener Phase
Authors: Bayer Ernst , Geckeler Kurt , Weingärtner Karl
Published: April 2003

Poly(1‐aminoethylene) (polyvinylamine) (4) was prepared by hydrazinolysis of poly(1‐succinimidoethylene) (2) [poly(N‐vinylsuccinimide)]. The water‐soluble polymer 4, with more than 95% of primary amino groups, was used as basic material for the synthesis of macromolecular complex forming reagents. By the reaction of poly(1‐ammonioethylene chloride) (3) [poly(vinylamine hydrochloride)] with 2‐pyridinecarbaldehyde a complex forming polymer 5 was obtained, which is highly selective for iron. Poly{1‐[bis(carboxymethyl)amino]ethylene} (6) from 4 and chloroacetic acid is a reagent for copper, whereas poly[1‐(3‐methylthioureido)‐ethylene] (7) from 4 and N‐methylisothiocyanate shows a good selectivity for mercury. The ultrafiltration technique allows a continuous procedure for the separation of the polymer complexes. The formation and stability of the prepared complexes of 4and its derivatives 5, 6, and 7 in homogeneous phase are investigated and discussed.
Enantioselektive Trifluoracetylierung mit Hilfe chiraler Polyamide
Authors: Günster Engelbert J. , Schulz Rolf C.
Published: April 2003

(S)‐Poly(2‐aminobutyric acid) (1) [(S)‐poly(imino‐1‐methyl‐3‐oxotrimethylene)] was transformed into its N‐trifluoroacetyl derivative 4. The IR spectra and the circular dichroism of both substances were compared. In addition, (S)‐poly[N‐(1‐phenylethyl)acrylamide] (2) ((S)‐poly‐[1‐(1‐phenylethylaminocarbonyl)ethylene]) was trifluoroacetylated leading to polymer 5. 4 was found to react as trifluoroacetylating agent with L‐1‐phenylethylamine (L‐3) twice as fast as it reacts with D‐3. Accordingly, the reaction of 4 with D,L‐3 leads preferentially to the L‐form of N‐(1‐phenylethyl)trifluoroacetamide with optical yields up to 6%. The reaction of 5 with D,L‐3 affords the D‐form of N‐(1‐phenylethyl)trifluorcacetamide with optical yields up to 13%.
Anionic polymerization of 2,2,4,4‐tetramethyl‐6,6‐diphenylcyclotrisiloxane a model siloxane monomer of heterogeneous composition of a reactive grouping
Authors: Mazurek M. , Ziȩtera J. , Sadowska W. , Chojnowski J.
Published: April 2003

The anionic polymerization of 2,2,4,4‐tetramethyl‐6,6‐diphenylcyclotrisiloxane (1), its copolymerization with hexamethylcyclotrisiloxane (2), and the homopolymerization of 2 were studied. It was found that the polymerization of 1 initiated with potassium trimethylsilanolate proceeds with the formation of 2,2,4,4,6,6‐hexamethyl‐8,8‐diphenylcyclotetrasiloxane (3). When using lithium butyldimethylsilanolate/HMPT as initiator an inversion of the reactivity order in the homopolymerization of 2 and 1 was observed. The results indicate that both propagation and depropagation occur with a high degree of regioselectivity, which is dependent on the applied catalyst.
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

1H 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

A 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

During 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

Lithium 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

Kinetic 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

A 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

Poly(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

Photopolymerization 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

The 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

The 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

Polyamides 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

Polycyclocondensations 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

Monodispersed 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

By 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

The 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

1H 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

UV 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

The 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‐\nulldelimiterspace} 2}} } \mathord{\left/ {\vphantom {{\left[ \eta \right] = \Phi (\overline {r_{{\rm av}}^{\rm 2} } )^{{3 \mathord{\left/ {\vphantom {3 2}} \right. \kern‐\nulldelimiterspace} 2}} } {M_{{\rm av}} }}} \right. \kern‐\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

Several 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

α‐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.
Polymérisation anionique de l'acroléine, 3. Analyse des microstructures par 1H NMR et 13C NMR et mécanisme de polymérisation
Authors: Gulino Danièle , Pascault Jean Pierre , Pham Quang Tho
Published: April 2003

We have synthesized anionic polyacroleins using various initiators (naphthalene complex, tert‐butyllithium) in different solvents (tetrahydrofuran, toluene). We have studied the 1H NMR and 13C NMR spectra of the polymers and assigned monomeric units and diads by comparison with spectra of four compounds corresponding to the different microstructure arrangements. By this method, we have clearly proved the presence of 1,4‐ as well as 3,4‐ and 1,2‐units. But numerous cyclisations occur on the 1,2‐units. Using only the 1H NMR method, a first estimation of the microstructure was obtained. 13C NMR gave further information and permitted the estimation of the (1,4‐cis)/(1,4‐trans) ratio. Furthermore the presence of hydroxyl groups along the chains has also been established. A satisfactory determination of the 1,2,3,4‐ and 1,4‐structure percentages of several polyacroleins has been obtained using 1H NMR and 13C NMR simultaneously. A mechanism of acrolein polymerization, based on two different living ends is proposed. The microstructure indicates the existence of several complexation phenomena. When the living end/metal and monomer/metal complexations are weak (with Na+ e.g.), the polymer consists mainly of 1,4‐ and 3,4‐units. On the other hand, with Li+, the microstructure has a high 1,2‐content. Moreover, the living end/Li+ complexation would decrease with the chain length, because of the increasing attraction of the cation by the other complexing sites on this chain.
Conformation des polyacrylamides partiellement hydrolyses en solution aqueuse
Authors: Schwartz Thierry , François Jeanne
Published: April 2003

A series of hydrolyzed commercial polyacrylamide samples were fractionated by successive precipitation fractionation. The radius of gyrationRGand the intrinsic viscosity [η] of the fractions were measured as a function of the molecular weight and the NaCl concentrationcs. The fractions were found to present the classical behaviour of polyelectrolytes with a conformation of expanded coils atcs= 0,1 mol/l. By increasing the salt concentration, the dimensions of the coils were found to become those of the unhydrolyzed, less expanded, polyacrylamide molecules.
Asymmetric induction in the radical copolymerization of mono and di‐l‐menthyl fumarate with styrene
Authors: Kurokawa Masahiro , Yamaguchi Hidemasa , Minoura Yuji
Published: April 2003

Radical copolymerizations of mono‐ and di‐l‐menthyl fumarate (1 and 2) with styrene (St) were carried out, and the copolymers were hydrolyzed with potassium hydroxide. The products show still optical activity even after the removal of the optically active side chain, because of an introduction of asymmetry into the main chain of the copolymer. The specific rotation per one of the diad sequences of hydrolyzed poly(1‐co‐St) was the same as that of hydrolyzed poly(2‐co‐St). The mechanism of asymmetric induction and the position of the new asymmetric center are discussed based on the measurements of UV spectra, optical rotation, and circular dichroism.
Stereoregularity of polystyrene derivatives, 3. Poly(methylstyrene)s Obtained by Anionic Catalysts
Authors: Kawamura Tokiji , Uryu Toshiyuki , Matsuzaki Kei
Published: April 2003

The stereoregularity of the polymers of ortho‐, meta‐, and para‐methylstyrenes prepared with various anionic catalysts was determined by means of 13C NMR spectroscopy. The substituent effect on the stereoregularity was discussed comparing with that of polystyrenes obtained under the same polymerization conditions. Syndiotactic‐rich poly(methylstyrene)s were prepared with butyllithium in toluene and the syndiotacticity increased in the order of para‐, meta‐, and ortho‐derivatives. Although the structure of the polymers prepared with sodium‐naphthalene (Na‐naph.) in THF did not change with the position of the substituent, in toluene, however, the methyl group at ortho‐position influences the stereoregularity. The trend of the stereoregularity of the polymers produced by potassium‐naphthalene was almost the same as that of poly(methylstyrene)s prepared by Na‐naph. Nearly random polymers were obtained with the cesium ion as catalyst.
Structural characterization of unsaturated polyesters
Authors: Paci Maurizio , Crescenzi Vittorio , Supino Nicola , Campana Francesco
Published: April 2003

A few unsaturated polysters prepared by melt polycondensation of maleic anhydride, phthalic anhydride, and aliphatic glycols in different proportions have been characterized. The salient features of the 1H and 13C NMR spectra of the polyesters and of model compounds are compared. It appears that from 15 to 20% of maleic acid residues have reacted with excess glycol to yield branching points while the remaining free olefinic double bonds have undergone cis → trans isomerization almost quantitatively along the oligomeric chains.
Die kristallstruktur von cycloalkanen
Authors: Trzebiatowski Thomas , Dräger Martin , Strobl Gert R.
Published: April 2003

An X‐ray structure analysis was performed on single crystals of the cycloalkane (CH2)36. The lattice belongs to the space group Aa and is arranged in layers. The unit cell has the dimensions α = 1,033 nm, b = 0,824 nm, c = 4,22 nm, β = 107, 1° and contains four molecules. The molecules consist of two stretched stems which are linked by sharp folds at each end. The folds have the conformation …t(g g t g g) t… lying parallel to the b‐axis. Raman measurements suggest that the stems are slightly twisted. A comparison of the homologous series (CH2)n, n = 36, 48, 60, and 72 using X‐ray powder methods showed that the (CH2)36‐structure, including the fold conformation, is also representative for the longer chain cycloalkanes.
Inhibition of radical polymerization by polyconjugated polymers with anthracene repeating units
Authors: Schopov Ivan , Jossifov Christo
Published: April 2003

The thermal and the benzoyl peroxide initiated polymerizations of styrene and methyl methacrylate in presence of three polyconjugated polymers with anthracene repeating units are investigated. Participation in the inhibition reaction of the polymer methylene end groups is shown. A charge transfer complex formation between the polyconjugated polymers as donors and the propagating radicals was assumed as another factor determining inhibition activity.
Living anionic stereospecific polymerization of 2‐vinylpyridine, 3. Structure of models of active centres and mechanism of polymerization
Authors: Soum Alain , Fontanille Michel
Published: April 2003

The mechanism of the stereospecific polymerization of 2‐vinylpyridine initiated by organomagnesium compounds in non‐polar solvents, was studied. Triad and pentad data were found to be consistent with a first‐order Markov‐polymerization process. 1H and 13C NMR studies on model molecules of the active species showed an sp3 hybridization of the carbanion and a coordination of the Mg cation by the last and the penultimate pyridine rings of the living chain. The NMR characterization of the monomer coordination with the Mg cation of the active species indicates that two transition states are possible. For steric reasons, only one of them is highly probable, leading to isotactic linkages.
Synthèse et propriétés du poly(p‐triméthylsilystyrène)
Authors: Chaumont Philippe , Beinert Gérard , Herz Jean E. , Rempp Paul
Published: April 2003

p‐Trimethylsilylstyrene was found to be polymerisable anionically. When the reaction is carried out at low temperature in THF as solvent the polymer—poly(p‐trimethylsilylstyrene)—is obtained in a quantitative yield and exhibits a low polydispersity. The glass transition temperature, viscosity‐molecular weight relationships, and 1H and 13C NMR spectra were investigated in order to compare the influence of the trimethylsilyl group located at the benzene nucleus with respect to polystyrene and some other p‐subtituted polystyrenes. The presence of the trimethylsilyl group in para position of the aromatic nucleus results in an increase of the rigidity of the polymer chain and in an increase of the glass transition temperature.
2‐tert‐butyl‐6‐vinylnaphthalene polymers, 2. Steric effects of tert‐butyl group on intramolecular energy transfer from naphthalene to anthracene chromophore
Authors: Nakahira Takayuki , Sasaoka Tatsuya , Iwabuchi Susumu , Kojima Kuniharu
Published: April 2003

Poly(2‐vinylnaphthalene) and poly(2‐tert‐butyl‐6‐vinylnaphthalene) having small fractions of 2‐vinylanthracene were prepared to examine the effect of bulky tert‐butyl groups on the intramolecular singlet energy transfer from naphthalene to anthracene chromophore. The steric interactions of the tert‐butyl groups were found not only to reduce excimer formation and thereby increase the donor lifetime, but to suppress energy migration through the donor chromophores, giving a significant reduction of the overall transfer efficiency.
Anionic polymerization of oxiranes and cyclic siloxanes initiated with potassium salt‐crown ether systems
Authors: Koinuma Hideomi , Naito Katsuyuki , Hirai Hidefumi
Published: April 2003

Potassium carboxylates and 18‐crown‐6 form initiator systems for the anionic polymerization of oxiranes to afford polyethers with an acyloxy group at one of the chain ends. Because of the slow initiation as compared to the propagation step, the resulting polymers have wide molecular weight distributions (Mw/Mn ≈ 4,0). The presence of a small amount of water in the catalysts accelerates the initiation to give polymers with narrow molecular weight distributions (Mw/Mn ⩽ 1,2). The polymerization of methyloxirane is accompanied by a significant chain‐transfer reaction to the monomer, especially at high temperatures. Hexamethylcyclotrisiloxane is also polymerized by the same initiators. Furthermore, potassium salts of carboxylic acids initiate the polymerizations in the presence of a crown ether.
Die polymerisation von N‐ethylaziridin, seine copolymerisation mit N‐(2‐hydroxyethyl)aziridin und die überführung der copolymeren in die N‐(2‐chlorethyl)‐analoga
Authors: Kern W. , Mannschott Ch. , Höcker H.
Published: April 2003

N‐Ethylaziridine (1) was polymerized in water with HCl as initiator and copolymerized with N‐(2‐hydroxyethyl)aziridine (2). Rapid propagation and termination reactions were observed. The maximum yield increases with the initiator concentration, whereas the molecular weight decreases. This is due to the difference in basicity between the tertiary N‐atoms of the two monomers and the tertiary and the terminal secondary N‐atoms of the polymers, which causes tranfer and termination reactions. Macrocycles with a side chain on a quaternary N‐atom are formed. During the copolymerization, the more basic 1 is preferentially incorporated into the copolymer chain. The copolymerization parameters can be estimated roughly on the basis of basicity considerations: r1 > 1; r2 < 1. The ratio of the rate constants (propagation to termination) is lower for 1 than for 2. This is due to the fact that the basicity difference between the monomer and the tertiary N‐atoms of the polymer is higher for 1 than for 2. By reaction of thionyl chloride with the copolymers the desired hydrochlorides of the N‐(2‐chloroethyl) derivatives are obtained. The neutralisation with alkali did not result the free bases, since the products formed are rather due to side reactions.
Kinetics of free radical oligomerization, 2. Cooligomerization of styrene and methyl methacrylate in carbon tetrachloride
Authors: Chen Show‐An , Hwang Cheng‐Chuan
Published: April 2003

A mechanism for the cooligomerization of styrene and methyl methacrylate in CCl4 is proposed that includes: (a) the primary radicals decomposed from the initiator (benzoyl peroxide) first react with carbon tetrachloride (TX) to form the radical T*; (b) T* then reacts with styrene and successively propagates with styrene or methyl methacrylate; (c) only the cooligomer radicals ended with styrene units undergo chain transfer reaction with TX; (d) the T* radicals can also combine with each other to form the termination product T – T. From the proposed mechanism a simple scheme for predicting monomer conversion, number average molecular weight, and cooligomer composition is obtained. Values of the kinetic constants can be determined easily from the conversion data. The coolligomer composition equation developed is the same as that of Tsuchida, even though the detailed mechanism is different. Agreement of the simplified theory with the experimental data is reasonable.
Polymer conformation and NMR chemical shifts, 6. Alternating copolymer of α‐methylene‐γ‐butyrolactone with styrene
Authors: Koinuma Hideomi , Sato Kota , Tanabe Tsuneaki , Hirai Hidefumi
Published: April 2003

In view of the structural resemblance of α‐methylene‐γ‐butyrolactone to methyl methacrylate, conformation and NMR chemical shifts of poly(α‐methylene‐γ‐butyrolactone‐alt‐styrene). are calculated and compared with those of poly(methyl methacrylate‐alt‐styrene). The conformational energy surfaces for the dyad sequence models of the both copolymers are analogous to each other, as is expected from the similarity in the constituting monomeric units. Agreement of calculation with observation is satisfactory with respect to the cotacticity‐dependent splittings in the 13C NMR spectra and is improved by the fixation of a substituent in poly(α‐methylene‐γ‐butyrolactone‐alt‐styrene). Calculation of 1H chemical shifts gives an alignment of NMR signals which is in accordance with the observation.
Comparative DSC technique — application to studies of melting of branched polyethylene
Authors: Pakula T.
Published: April 2003

A version of DSC technique is proposed which ensures good accuracy in comparing the melting behaviour of two apparently similar samples. The information is obtained in the form of comparative thermograms recorded during simulataneous melting of both samples. The method is applied to observe the influence of cooling conditions and annealing on melting behaviour of low‐density polyethylene.
Dynamic NMR studies of equilibria involving active species in the polymerization of cyclic acetals. Reaction of the methoxymethyl cation with 5‐, 6‐, and 7‐membered cyclic acetals
Authors: Szymański Ryszard , Penczek Stanislaw
Published: April 2003

The cyclic acetals 1,3‐dioxolane (4a), 1,3‐dioxane (4b), and 1,3‐dioxepane (4c) give in their reactions with the methoxymethyl cation (1) a mixture of two isomeric tertiary oxonium ions: the simple products of cationation 5a‐c and the cationated rings 6, 7, 9, enlarged by two atoms. The equilibria for the studied monomers are shifted to the side of the oxonium ions as shown in the reaction schemes 2, 4, 5, and 6 (SbF‐6 or SbCIF‐5 being the corresponding anions). In the case of 4a the equilibrium is displaced almost completely to the enlarged ring 6, whereas for the other two cyclic acetals 4b and 4c the first cationated products 5b and 5c dominate. Application of the dynamic 1H NMR method allows the determination of the equilibrium constants of the reaction of 4a with 1.
Polymere charge‐transfer‐komplexe auf der basis von polyvinylalkoholacetalen, 4
Authors: GeißLer Ulrich , Schulz Rolf C.
Published: April 2003

Partially acetalisized poly(vinyl alcohol)s with degrees of acetalization between 39 and 60% were prepared by reaction of poly(vinyl alcohol) with 9‐isobutyl‐3‐carbazolealdehyde (5a) or 3‐formyl‐9‐((S)‐2‐methylbutyl)carbazole (5b). Complex formation constants and ε‐values of the charge‐transfer complexes with ethylenetetracarbonitrile, 2,5‐cyclohexadien‐1, 4‐diylidenedimalonodinitrile, 2,4,5,7‐tetranitro‐9‐fluorenone, and 2,4,7‐trinitro‐9‐fluorenone were determined. Circular dicroism measurements of the optically active CT‐complexes indicate two distinct CT‐transitions.
Oxidative polymerization of 2‐(2‐butenyl)‐ and 2‐(3‐methyl‐2‐butenyl)‐6‐methylphenol
Authors: Nishide Hiroyuki , Minakata Takashi , Tsuchida Eishun , Yamada Shigetoshi
Published: April 2003

2‐(2‐Butenyl)‐6‐methylphenol (1a) and 2‐(3‐methyl‐2‐butenyl)‐6‐methylphenol (1b) were oxidatively polymerized in the presence of a copper‐pyridine catalyst to yield poly[oxy‐2‐(2‐butenyl)‐6‐methyl‐1, 4‐phenylene] (2a) and poly[oxy‐2‐(3‐methyl‐2‐butenyl)‐6‐methyl‐1,4‐phenylene] (2b) with molecular weights >104. The polymerization rates were in the order 1b > 1a > 1a > 2,6‐dimethylphenol (3), and this order agreed with those of the rate constant of the electron‐transfer step and of the redox potential. The 2‐butenyl and 3‐methyl‐2‐butenyl group in 2 showed enough chemical reactivity for addition of bromine and epoxidation.
Cellulosic microcapsules for drug delivery, 1. Hydrocortisone release
Authors: Singh Maninder , Bala Kiran , Vasudevan Padma
Published: April 2003

Cellulose acetate was used as an encapsulating material for preparing microcapsules by the technique of coacervation for sustained drug delivery. The condition of formation of such capsules containing hydrocortisone as drug, and its subsequent release from such depots, are described. The scanning electron micrographs show the formation of good, nearly spherical capsules in the range 10–20 μm. The release of hydrocortisone from the microcapsules sustains up to 7 days.
Contribution à l'étude de la métallation de structures polyisoprène, 1. Mèthode de dosage
Authors: Brosse Jean‐Claude , Maidunny Zainul Abdin Bin , Soutif Jean‐Claude
Published: April 2003

Squalene, as a model compound, and polyisoprene were metalated by the complex of sec‐butyllithium (sec‐BuLi) with N,N,N′,N′‐tetramethylenediamine. The rate of metalation was determined indirectly by further reaction with a deactivating reagent. Amongst the various agents tested, a solution of chlorotrimethylsilane (Me3SiCl) in diethyl ether was preferred, as deactivation by this reagent does not lead to secondary reactions. The rate of silylation of sec‐BuLi by Me3SiCl was found to be influenced by the solvent and the temperature. The presence of diethyl ether, as solvent of silylation, and a reaction temperature of 0°C are suitable conditions for the reaction between lithiated polymers and Me3SiCl.
Functionalization of polymeric organolithium compounds. Carbonation
Authors: Quirk Roderic P. , Chen Wei‐Chih
Published: April 2003

The carbonation reactions of polymeric organolithium compounds with high purity, gaseous carbon dioxide have been investigated in benzene and benzene/tetrahydrofuran (75/25) solutions. The polymers investigated were poly(styryl)lithium, poly(isoprenyl)lithium, and poly(styrene‐b‐isoprenyl)lithium. In Benzene solution the products are a mixture of the carboxylic acid and the ketone (dimer). No tertiary alcohol product (trimer) was observed. In benzene/tetrahydrofuran solution, the quantitative carboxylation of chain ends was observed.