bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polymer effect on the electron‐donating character of a polymeric donor, 3. Formation of charge‐transfer complexes between polymer containing carbazolyl groups and three kinds of common acceptors
Authors: Iwatsuki Shouji , Arai Kiyotaka 
Published: April 2003

AbstractCharge‐transfer complex formations with carbazole containing polymers are studied by using copolymer donors. Donors employed are poly(N‐vinyl carbazole) (poly[1‐(N‐carbazolyl)ethylene]), (PVK), copolymers of N‐vinyl carbazole (VK) and vinyl acetate (VAc) with various compositions, and N‐ethyl carbazole (NEK). As acceptor are used p‐chloranil (2,3,5,6‐tetrachloro‐2,5‐cyclohexadiene‐1,4‐dione) (CA), tetracyanoethylene (ethylenetetracarbonitrile) (TCNE) and 2,4,5,7‐tetranitrofluorenone (TNF). A smooth bathochromic shift in the wave length of maximum absorption λmax was observed with increasing the VK content in copolymers when CA and TCNE were used as common acceptor. In the case with TNF, since PVK and the copolymers give too broad charge transfer absorption bands, their λmax cannot clearly be read. In both cases with CA and TCNE, the association constant of charge‐transfer complex formation KCT was found to decrease with increasing the VK content in the copolymers, whereas in the case with TNF it increases. The thermodynamic parameters of complex formation were also discussed: ΔH and ΔS were found to decrease with increasing VK content in all cases with three common acceptors. Differences in their degrees of contribution to the free energy of the complex formation between enthalpy and entropy probably causes two types of variation of KCT with the VK content in the copolymers. In addition, effects of acceptors and solvents on the charge‐transfer complex formation were studied. A difference in λmax between with NEK and with PVK, corresponding to the so‐called polymer effect, was observed to be largest when CA was used as common acceptor and also to become larger as the dielectric constant of the solvent is increased.
Conformational flexibility of isotactic poly‐1‐olefins
Authors: Ajò David , Granozzi Gaetano , Zannetti Roberto 
Published: April 2003

AbstractThe conformational flexibility of isotactic polypropylene, isotactic poly‐1‐butene and isotactic poly(3‐methyl‐1‐butene) has been studied by theoretical methods, especially in relation to their polymorphism. The energy calculations show the predominant contribution of intramolecular effects and allow a valid interpretation of polymorphous behaviour. Furthermore, the conformational mobility of the side chains of the macromolecules plays a very important role in establishing the lowest‐energy structure.
Über die polymerisation von 1‐chlor‐2,3‐epoxypropan
Authors: Mateva Rosa , Kabaiwanov Wl. 
Published: April 2003

AbstractThe kinetics and the thermodynamic features of the polymerization of 1‐chloro‐1,3‐epoxypropane with the complex \documentclass{article}\pagestyle{empty}\begin{document}${\rm Cl}_{\rm 5} \mathop {{\rm Sb}}\limits^ \ominus \cdots \mathop {\rm S}\limits^ \oplus {\rm O}_2$\end{document} were studied. It was found that the process proceeds with a negative temperature coefficient, Ea=−51,29 kJ/mol ( − 12,25 kcal/mol), ΔHp=−18,8 kJ/mol (−4,5kcal/mol), ΔSp=−74,5 J mol−1 K−1 (−17,8 cal mol−1 K−1), and with the ceiling temperature of 52,6°C. The molecular masses of the polymers were determined and a possible mechanism of the polymerization process was suggested.
Molekulare und chemische uneinheitlichkeit von copolymeren aus trübungstitrationen von GPC‐eluaten
Authors: Hoffmann Martin , Urban Heinrich 
Published: April 2003

AbstractThe distributions of molecular weights and of chemical compositions of a binary linear copolymer may be determined by gel permeation chromatography (GPC) followed by turbidimetric titration of the eluates. Eluate fractions of 5,0ml are automatically collected and titrated within 7 min. The intensityRof the scattered light at a wavelength λ0=940nm is measured at an angle of 19° to the primary beam and corrected for the change of solution volumeVduring titration. The solubilities of chemically different molecules of a mixture are influenced somewhat but not substantially by the components of the mixture.During the titration the turbidity of the eluates from graft copolymers often increases with time discontinuously, the points of inflection indicating the precipitation of a new species of molecules. If the dependence of solubility on chemical composition and concentration is known for the particular elution volume, the chemical composition of each species of the titrated molecules may be evaluated from these points of inflection. The elution volumeVEand the chemical composition are used for obtaining the molecular weightMfrom plots ofMvs.VEfor different chemical compositions. The concentration of a certain species of molecules in the eluate cannot be derived fromRitself as has been tried up to now because the turbidity continues to increase after complete precipitation of the polymer. However the rate of coagulation is proportional to the concentrationcof precipitated polymer. This leads to a nearly linear dependence ofR·V/V0on logVwith a slope porportional toc2. The velocity constants of this coagulation are nearly independent of molecular weight and chemical composition. Therefore the concentration of the first precipitated component of a mixture may be determined absolutely with a relative error of about ±4% at a concentration of 50 mg/l of the mixture. The molecules of a second component of the mixture precipitated at a later stage of the titration are quickly adsorbed by the particles of the first component. After this the enlarged particles coagulate with the coagulation constant of the second component. The velocity of coagulation is now proportional to the sum of the concentrations of the first and second components. The distribution of chemical compositions of the molecules in an eluate may therefore be derived from the increase of turbidity with volume at different points of the titration curve. By plotting such distribution perpendicularly over the curves representing constant elution volume in theM‐composition‐plane one obtains a three‐dimensional surface resembling a mountain range which characterises completely the molecular and compositional distribution of a binary copolymer.
1H NMR spectroscopic studies on the reaction of methoxymethyl isocyanate with alcohols and the side reactions
Authors: Sikorski Ryszard T. , Kowalczyk Mieczysław , Krzywański Jan , Mikołajczyk Marian 
Published: April 2003

AbstractAlkyl N‐methoxymethylcarbamates (3) were synthesized by treating methoxymethyl isocyanate (1) with alcohols 2 in the presence of triethylamine. By means of 1H NMR spectroscopy and using the deuterated carbamate 3b it could be demonstrated that carbamates 3 undergo decomposition, accompanied by elimination of methanol from the methoxymethylene grouping and by the formation of polycondensates 5. It was found that 1 and 3 react in the presence of basic catalysts to give polyadducts 7.
Synthese und Strukturuntersuchung des Poly(1‐hydroxytetramethylen)s
Authors: Ritter Wolfgang , Eichin Karl‐Heinz , Elgert Karl‐Friedrich 
Published: April 2003

AbstractPoly(1‐hydroxytetramethylene) was prepared via hydroboration of cis‐1,4‐poly(butadiene). The structure of the polymer chain generated by a random hydroxylation of the carbon double bonds of the butadien units was determined by 13C NMR spectroscopy.
Photochimie de la polyacrylophénone en solution, 2. Courbe d'inhibition à fortes concentrations en inhibiteur. Désactivation statique et solvatation préférentielle
Authors: Salvin Roger , Meybeck Jean 
Published: April 2003

AbstractStatic quenching performed on the type II cleavage of polyacrylophenone, poly(1‐benzoylethylene), (PAP) in 1‐methylnaphthalene, (MeN) as solvent and as quencher, has allowed us to evaluate the rate constant of electronic triplet‐triplet energy transfer Kel for the system PAP‐MeN.This value is similar with the value determinated for the system valerophenone‐MeN. indicating that Kel is independant of the carbonyl position free or bound to a polymer chain.The aspect of the quenching curve at high concentration of MeN in benzene has been associated with phenomenona of preferential solvation of benzene in the ternary system PAP‐MeN‐benzene which has been determinated by the method of dialysis equilibrium.
Polymorphie, Kristallinität und Schmelzwärme von Poly(ε‐caprolactam), 1. IR‐spektroskopische Untersuchungen
Authors: Simak Petr 
Published: April 2003

AbstractPoly(ε‐caprolactam), (polyamide‐6) crystallizes in different modifications, which show different characteristic IR absorption bands. The absorption coefficients of the bands were evaluated from the dependence of their intensity on temperature and specific volume of different polyamide‐6 samples. A method is described how to determine quantitatively the amounts of α‐ and γ*‐modifications and of the amorphous phase. On the basis of these data the densities of the samples were calculated and shown to agree with the values determined experimentally. The specific volume of the amorphous phase is v = 0,917 cm3/g, and is independent of any contents of α, γ*‐, or γ‐modifications the samples may contain.
Effects of trivalent phosphorus compounds on vinyl polymerizations, 4. Radical reactivities of chlorophosphines
Authors: Nigenda Socorro E. , Caballero Deyanira , Ogawa Takeshi 
Published: April 2003

AbstractIn order to study the radical reactivities of trichlorophosphine, dichloro(phenyl)phosphine, and chlorodiphenylphosphine, the polymerizations of various vinyl monomers were carried out in the presence of these chlorophosphines using 2,2′‐azodiisobutyronitrile as an initiator. The reactivities were discussed from the results obtained for the rates and the degrees of polymerization and for the phosphorus contents of the polymers obtained. It was found that the tertiary radicals (such as that derived from methacrylonitrile and methyl methacrylate) were inert to these chlorophosphines, but the secondary radicals (such as those from vinyl acetate, methylacrylate, acrylonitrile, styrene, etc.) reacted with the chlorophosphines, and their reactivities depended on the stabilities of the polymer radicals. Only styrene gave copolymers. As a general mechanism the addition of the polymer radical to the phosphine followed by elimination of one of the four substituents on the phosphorus, was suggested.
Kinetics of the heterogeneous acid hydrolysis of regenerated cellulose
Authors: Vrhovac Ljubica P. , Rašajski Slavko N. 
Published: April 2003

AbstractThe kinetics of the early stage of acid catalyzed heterogeneous hydrolysis of different samples of regenerated cellulose at low temperatures (0, 20, and 30°C) was studied. The degradation of macromolecules was followed by determining the decrease of the degree of polymerization by measuring the viscosity of cellulose solutions in cadoxen. Interpretation of the experimental results using equations for first order reactions showed that in the studied experimental range first order kinetics cannot be applied. It was found that the rate constant decreases during the course of the hydrolysis at constant temperature. However, the experimental results could be explained by kinetic equations for heterogeneous processes with a solid and a liquid phase in the heterogeneous system. Kinetic parameters calculated from these equations point out that the process could be described as a diffusion controlled process.
Effect of carbonyl compounds on long‐wave UV photooxidation of polystyrene films
Authors: Kubica Joanna 
Published: April 2003

AbstractIt was found that the rate of secondary photooxidation reactions initiated by light not absorbed by polystyrene (PS) is related to the concentration of carbonyl compounds produced initially in pure PS films. Photochemical experiments carried out with a group of twelve low‐molecular‐weight compounds as models of the most likely carbonyl products of PS photooxidation showed that mainly diketones sensibilize the long‐wave UV photooxidation of polystyrene.
Zur Taktizität von Poly(α‐methylstyrol), 5. Die Abhängigkeit der Taktizität von der Reaktionstemperatur und der Anfangsmonomerkonzentration
Authors: Wicke Reinhard , Elgert Karl‐Friedrich 
Published: April 2003

AbstractThe tacticity of poly(α‐methylstyrene) was measured by 1H NMR spectroscopy. The polymerisation initiated in tetrahydrofuran by butyllithium gives a dependence on the initial monomer concentration and a S‐shaped plot of log(m/r) vs. 1/T, which is not influenced by a stronger reaction medium like 1,2‐dimethoxyethane or hexamethylphosphoric triamid or by addition of LiB(C6H5)4. The activation parameters of the two straight lines A and B limiting the experimental curve are according to the equation

The temperature dependence of the propagation rate constant kw measured dilatometricly between −11°C and −75°C gives a linear Arrhenius plot. The rate constant of depolymerisation kd was calculated using the equilibrium monomer concentration. The activation parameters are

The influence of ionic dissociation on the tacticity is discussed. The results lead to the conclusion, that the contact ion pair, the solvent separated ion pair, and the free anion generate tacticities, which are undistinguishable by the applied experimental methods.
Molecular weight distribution of polysarcosine obtained by NCA polymerization
Authors: Sisido Masahiko , Imanishi Yukio , Higashimura Toshinobu 
Published: April 2003

AbstractPolymerization of sarcosine N‐carboxyanhydride was carried out in N,N‐dimethylformamide solution with some primary and secondary amines as initiators. The polymerization obeyed the first‐order kinetics. Polysarcosines obtained were fractionated by gel‐chromatography. For lower oligomers, individual oligomer components were isolated and the distribution of the degree of polymerization was calculated directly from the area of each peak. The elution diagram for higher polymers showed a single broad envelope which was analyzed by the method of Fourier analysis. In either case, the Poisson‐type distribution was observed.
Polymerization of methyl methacrylate in the presence of the system ethylaluminium dichloride—p‐chloranil
Authors: Florjańczyk Zbigniew , Kuran Witold , Lusztyk Ewa 
Published: April 2003

AbstractThe polymerization of methyl methacrylate (5) in the presence of the system ethylaluminium dichloride (2)—p‐chloranil (1) was found to proceed much easier than in the presence of only 2. The polymerization is initiated by ethyl radicals resulting from the reaction of 2 with 1. The effects of mole ratio of reactants, temperature, and reaction time on the polymerization yield and intrinsic viscosity of the polymer was studied and the results are discussed.
Studies on aqueous polymerization of acrylamide, 4. Potassium persulfate/thioglycolic acid redox system
Authors: Husain M. M. , Misra S. N. , Singh R. D. 
Published: April 2003

AbstractAqueous polymerization of acrylamide, initiated by the potassium persulfate‐thioglycolic acid redox pair, was studied at 30°C under introgen. The initial rate of polymerization R was found to be approximately proportional to the 0,5th power of potassium persulfate concentration within the range of 0,6 to 1,0 mmol−1. R was also found to vary linearly with the monomer concentration between 0,8 · 10−1 and 1,0·10−1 mol l−1 and to increase with the thioglycolic acid concentration in the interval of 3,0 to 4,0 mmol l−1. The activation energy was estimated to be 126 kJ mol−1. Addition ot NaCl, NaF, and (CH3)4NI lowered the initial rate R while MnSO4 increased it. Some aliphatic alcohols were observed to be polymerization retarders.
Polymérisation et copolymérisation d'acétoxy‐2 alcadiène‐1,3: L'acétate de (cyclohexène‐1 yle)‐1 vinyle. Synthèse d'une δ‐polycétone
Authors: Plaisance Chantal Bonnans , Levesque Guy 
Published: April 2003

Abstract1‐(1‐Cyclohexenyl)vinyl acetate (1c) was polymerized in bulk under radical conditions. The homopolymers consist only of 1,4‐units (4) which can be hydrolysed into δ‐polyketone. Reactivity ratios in radical copolymerization with styrene and acrylic comonomers were determined. The photochemical degradation of the copolymer with styrene was studied in solution.
Limiting viscosity number—molecular weight relationships for phenol‐formaldehyde resin in solution
Authors: Kamide Kenji , Miyakawa Yoshiye 
Published: April 2003

AbstractThe effect of molecular structure of phenol‐formaldehyde resin on the Mark‐Houwink‐Sakurada equation for solutions in acetone is systematically studied. Random and high‐orthophenol‐formaldehyde resins are prepared by conventional, acid‐catalyzed and Zn++‐catalyzed condensations, respectively. The relative contents of 2,2′‐, 2,4′‐ and 4,4′‐methylene linkages are determined by 13C NMR spectroscopy. From these the detailed distribution of structural isomers is calculated. Several fractions having number‐average molecular weights (by vapor pressure osmometry) M̄n≥104 are isolated by a successive solutional fractionation run from whole random polymers. For solutions of random polymer in acetone at 30°C, [η]=0,631 · M̄ (where [η] is limiting viscosity number) and for high‐ortho polymer [η]=0,0813 · M̄ are established. The former equation can be interpreted in terms of the Zimm‐Stockmayer theory of branched polymer solutions.
Untersuchungen zum oxidativen abbau nativer cellulose, 4. Stöchiometrische verhältnisse zwischen der anzahl der entstehenden spaltstellen, dem sauerstoff‐verbrauch, der CO2‐entwicklung und den materialverlusten während des abbaus
Authors: Palma A. , Jovanović S. , Schulz G. V. 
Published: April 2003

AbstractAn investigation of the kinetics of cellulose degradation confirms the scheme proposed by G. V. Schulz and Mertes with the following modifications: the fast pre‐stage of the degradation is missing, because there are no faster cleaving bonds in the native cellulose; the first step of the degradation (pre‐oxidation) in agreement with the above mentioned authors consists in the uptake of an oxygen atom: in the second step, the scisson proper, the scheme of Staudinger and Roos is replaced by the newer and better founded scheme of Haskins and Hogsed, assuming an alkoxy‐elimination; the third step (post‐oxidation) finally consists in a limited number of substeps leading to a splitting off of about three glucose units which becomes evident in the losses of material. The values of the rate constants of the three characteristic reactions determined from the steady‐state and the non steady‐state period of the reaction practically coincide.
Strukturuntersuchung von polyestern durch direkten abbau im massenspektrometer, 4. Polyester und copolyester der milchsäure und glykolsäure
Authors: Jacobi Erhard , Lüderwald Ingo , Schulz Rolf C. 
Published: April 2003

AbstractPolyesters and copolyesters of 2‐hydroxyacetic acid (glycolic acid) and 2‐hydroxypropionic acid (lactic acid) were investigated by direct pyrolysis in the ion source of a mass spectrometer. Thermal degradation of these polyesters and copolyesters at 10−6 mbar yields cyclic oligomers which are further degraded by an electron impact induced mechanism by elimination of formaldehyde or acetaldehyde and CO2 to give characteristic series of linear ions. In the pyrolysis mass spectrum of a copolyester (mole ratio of monomeric units ≈1:1) intact sequences up to 8 monomeric units can be observed.
The crystal structure of polycapryllactam (nylon 8) and of polycapriclactam (nylon 10)
Authors: Cojazzi Gianna , Fichera Annamaria , Malta Viscardo , Zannetti Roberto 
Published: April 2003

AbstractFrom X‐ray diffraction patterns of uniaxially oriented fibers, the structures of Nylon 8 and Nylon 10 were determined. They crystallize in the monoclinic system (pseudohexagonal), space group P21/b, with four monomeric units in the unit cell. The crystallographic parameters of Nylon 8 are: a=4,77; b=9,54; c=21,9 Å; γ=120°, and those of Nylon 10: a=4,78; b=9,56; c=26,9 Å; γ=120° (c fiber axis). Both structures show a γ‐type molecular packing, characterized by a shortening of the fiber repeat distances and by a twisting of the amide groups. Therefore, pleated sheets of parallel chains joined by hydrogen bonds are formed and the direction of the chains in adjacent sheets is alternately “up and down”. These structures result very similar to those of Nylon 6 and Nylon 12 in γ‐form, demonstrating once more that, in this series, by increasing the number of methylene groups, the usual crystal structure becomes the γ‐form.
Die Fraktionierung von Styrol‐Acrylnitril‐Copolymeren nach dem Acrylnitrilgehalt in zweiphasigen Lösungsmittelgemischen
Authors: v. Tavel Peter , Schaller Johann 
Published: April 2003

AbstractLiquid phase pairs were found in which polystyrene (PS) and styrene‐acrylonitrile (SAN)‐copolymers with an AN‐content up to 13 wt.‐% can be partitioned. They could be used for the fractionation of the copolymers according to chemical composition. The phase pairs are composed of 4 solvents, cyclohexane and nitromethane to form the phases and two solvents for the polymers. The partition ratio was measured as a function of the composition of the phase pairs, the molecular weight of PS, and of the AN‐content of the copolymers. The phase composition at which a polymer is equally distributed into both phases depends on the chemical composition of the polymer but not on its molecular weight. With other phase compositions the partition equilibrium is shifted to one phase or the other the more the degree of polymerisation increases. Based on the partition equilibrium, fractionation methods are proposed to separate the SAN‐copolymers according to their chemical composition if their molecular weight is high enough (>about 105). The conditions which determine fractionation more by molecular weight or more by chemical composition are discussed.
Photochemical reactions and stabilizing properties of 2,6‐Di‐tert‐butyl‐4‐methylphenol, 2. Photochemical processes of 2,6‐Di‐tert‐butyl‐4‐methylphenol in polystyrene films
Authors: Kowal Joanna , Waligóra Bolesław 
Published: April 2003

AbstractPhotochemical reactions of 2,6‐di‐tert‐butyl‐4‐methylphenol (BHT) were investigated in polystyrene films. It was found that the stabilizing effect of BHT on polystyrene photooxidation process consists in lowering the rate of the formation of low molecular weight carbonyl products and the yield of polymer chain scissions.
Micellar solubilization of apolar molecules
Authors: Sepulveda L. , Soto R. 
Published: April 2003

AbstractThe solubilization of anthracene, naphthalene and Orange OT by micelles of cetyltrimethylammonium bromide (hexadecyltrimethylammonium bromide), sodium laurylsulfate (sodium dodecylsulfate) and dode‐cylamine hydrochloride has been measured at 30°C. These data and others obtained from the literature are interpreted in terms of the solubilization number n and the aggregation number N by using a very simple equation relating n, N, the critical micelle concentration (CMC) and the molar solubility of the solutes. The interpretation of the solubilization leads to a new, simpler and less empirical method of finding the CMC from solubilization data. Values of n less than 1, close to 1 and much greater than 1 were found.
Studies on formaldehyde resins, 15. Base‐catalyzed hydrolysis of bis(hydroxymethyl)melamine
Authors: Sato Kenji , Yamasaki Kazumi 
Published: April 2003

AbstractThe hydrolysis of N,N′‐bis(hydroxymethyl)melamine [6‐amino‐2,4‐bis(hydroxymethylamino)‐1,3,5‐triazine] to N‐(hydroxymethyl)melamine [2,4‐diamino‐6‐(hydroxymethylamino)‐1,3,5‐triazine] was studied in dimethyl sulfoxide/water (volume ratio 1:9) using sodium hydroxide as a basic catalyst, in the region [Sodium hydroxide]0=0 to 2 mol·1−1. The study of the dependence of logk on the pH revealed that logk is nearly constant in the range of pH≈8–10 and increases with the slope of d(logk)/d(pH)≈1 in the region of pH≈11–13,5, followed by a gradual saturation at a stronger basic region where k is a first order rate constant. A rate equation for the hydrolysis is proposed, and the hydrolysis mechanism was elucidated by comparison of the theoretical curves resulting from this rate equation with the corresponding experimental curves.