bluuebunny/crossref_metadata_2025 huggingface dataset:
Asymmetric‐selective polymerization of (R,S)‐α‐methylbenzyl acrylate initiated with Grignard reagent/(‐‐)‐sparteine and its modified systems
Authors: Okamoto Yoshio , Gamaike Hisataka , Yuki Heimei
Published: April 2003

Asymmetric‐selective (or stereoelective) polymerization of racemic α‐methylbenzyl acrylate (2a) was studied with Grignard reagent/(–)‐sparteine and its modified catalyst system in toluene. All catalyst svstems polymerized preferentially the (R)‐monomer over the (S)‐monomer. The Grignard reagent/(–)‐sparteine system showed very low activity and gave the polymer only in a few per cent yield at −78°C. The addition of secondary amines such as piperidine and diethylamine to the catalyst system improved not only the activity but also the selectivity. The optical purity of the polymer initially formed with the cyclohexylmagnesium bromide/(–)‐sparteine/diethylamine system at − 78°C was 84%, and at about 80% polymer yield almost optically pure monomer was recovered. Asymmetric selectivity decreased with an increase of temperature. The dyad tacticity of the polymer was determined by 1H NMR spectroscopy. There was no clear correlation between the selectivity and tacticity. The role of the amines in the catalyst systems was investigated by 1H NMR spectroscopy.
Limites de solubilité des polyacrylamides partiellement hydrolysés en présence d'ions divalents
Authors: Schwartz Thierry , François Jeanne
Published: April 2003

The limits of solubility of hydrolyzed polyacrylamide in aqueous solution containing divalent cations is studied by turbidimetry. The stability is very poor in the presence of Ca++ and Ba++ and is better with Mg++ and Mn++. Conductivity and density measurements show that Ca++ and Ba++ are trapped without dehydration in intra‐and intermolecular bridges between two carboxylic groups of the polymer. Light scattering and viscosity studies allowed to propose a model according to which for polymer concentrations, Cp, lower than concentration of chain overlapping Cp* these cations induce intramolecular coil‐globule transition, and for Cp > Cp*, there are aggregates of globules by intermolecular bridges.
Flow properties of ethylene/vinyl acetate copolymers
Authors: Iruín Juan J. , Guzmán Gonzalo M. , Ansorena Javier
Published: April 2003

A series of linear and branched fractions of an ethylene/vinyl acetate (EVA) copolymer is characterized by viscometry and gel permeation chromatography (GPC) exclusively. Characterization results are applied to the study of the influence of branching on flow properties of concentrated solutions of EVA fractions. Newtonian viscosity‐concentration‐molecular weight relationships are obtained for both linear and branched samples. Graessley's theory of entanglements for linear polymers is tested with a set of fractions. Experimental flow curves come out to be independent of the linear or branched nature of the samples.
Mechanism of the short chain branching in low density polyethylene
Authors: Stoiljkovich D. , Jovanovich S.
Published: April 2003

In this paper the validity of the well‐known Roedel's “back‐biting” mechanism is questioned. It is shown that number and type of branches depend on the degree of order (entropy) of compressed ethylene molecules. A new mechanism for the short chain branching in low density polyethylene is proposed, based on the effect of the supermolecular species in compressed ethylene in this reaction. An equation for calculation of the number of branches for ethylene polymerization in a wide range of temperature (−5 to + 200°C) and pressure (40 to 7000 atm) is given.
Feasibility of the light scattering method to characterize composition heterogeneities of copolymers
Authors: Tanaka Takeshi , Omoto Mitsuru , Inagaki Hiroshi
Published: April 2003

Feasibility of light scattering as a method to characterize the composition heterogeneities of copolymers is examined with special reference to those measurements which are made in an isorefractive solvent, i.e., a solvent giving zero refractive index incrementvfor the copolymer. It is established theoretically and experimentally that the concentration dependence in the Zimm plot for an isorefractive system is almost absent, irrespective of the thermodynamic properties of the solvent employed. In addition, the error to which determination of the heterogeneity parameterQis subject due to inaccuracy invis minimum whenvis zero. By virtue of these facts,Qmay be determined with higher precision in an isorefractive solvent than in any other solvents. Under optimum conditions, it seems possible to determineQwith sufficient precision, ifQ⪆ 1·103andQ/Mw⪆ 2·10−3. These values are about an order of magnitude lower than those generally believed to be the applicability limits of the light scattering method.
Polymerization of methyl methacrylate with phenylmagnesium bromide — stereoregularity, molecular weight distribution and polymerization mechanism —
Authors: Matsuzaki Kei , Tanaka Hiroo , Kanai Taiichi
Published: April 2003

The stereoregularity and molecular weight distribution of poly(methylmethacrylate)s prepared with phenylmagnesium bromide or diphenylmagnesium as catalyst in tetrahydrofuran/toluene mixed solvents were investigated in detail. Some of the polymers were fractionated according to molecular weight or by adsorption with silical gel and the stereoregularities of the fractions were determined. An eneidic mechanism of propropagation was proposed based on the experimental results.

1H NMR spectroscopy of deuterated phenylmagnesium bromide and of its reaction with methyl methacrylate indicated that an eneidic mechanism resulted from a Schlenk type equilibrium, which is shifted to the diphenylmagnesium species at low temperatures and in nonpolar solvents.
Synthèse de monoalcools et de monoacides chlorofluorés par télomérisation avec des telogènes chlorofluorés
Authors: Boutevin Bernard , Hugon Jean‐Pierre , Pietrasanta Yves
Published: April 2003

Telomerizations of chlorofluorinated telogens CF3CCl3 and
\documentclass{article}\pagestyle{empty}\begin{document}$${\rm Cl\rlap{--} (CFCl \hbox{---} CF}_{\rm 2} {\rm \rlap{--} )}_{\rm n} {\rm CCl}_{\rm 3}$$\end{document} (1 ≤ n ≤ 4) with acrylic, allylic, and vinylic monomers were studied. With allyl alcohol and 2‐hydroxyethyl acrylate the corresponding fluorinated adducts 1 and 2 were obtained directly. Vinyl and allyl acetates led to the adducts 4a, b and 5a, b, respectively, which could be transformed into the corresponding acetals and alcohols. Telomerizations of methyl acrylate and methacrylate led to the fluorinated adducts 12a and b in the presence of copper chloride as catalyst or also with iron trichloride in the case of methyl methacrylate. By intramolecular elimination the methacrylate adducts were transformed into the lactons 13 and 14 and the acrylate adducts by reduction into the alcohols 1 and 2. The same reduction of the methacrylate adduct led to the 2,4,4‐trichloro‐5,5,5‐trifluoro‐2‐methyl‐1‐pentanol (15). Independent on the applied catalyst the telomerization of vinylacetic acid led to the monoaddition product, whereas in the case of methacrylic or acrylic acid the formation of monoadducts or higher addition products was found to depend on the catalyst.
Kinetik von copolymerisationen, 3. Geschwindigkeit der copolymerisation von N‐vinyl‐2‐pyrrolidon, styrol und methylmethacrylat
Authors: Braun Dietrich , Disselhoff Gabriele , Quella Ferdinand
Published: April 2003

The rates of the binary copolymerizations of N‐vinyl‐2‐pyrrolidone, styrene, and methyl methacrylate were investigated dilatometrically. In both systems with N‐vinyl‐2‐pyrrolidone as one of the two monomers the rate of copolymerization can be described by a theory of Abkin, whereas a theory of Russo and Munari can be applied to the behavior of the system styrene/methyl methacrylate.
Hochmolekulare produkte der kondensationspolymerisation von 4,4′‐methylendibenzaldehyd mit aliphatischen diaminen und polyfunktionellen isocyanaten
Authors: Tokarzewski Ludomir , Ragan‐Kusa Zenona
Published: April 2003

Polymeric Schiff‐bases (3a–gand5a–c) were synthesized by condensation polymerization of 4,4′‐methylenedibenzaldehyde (1) with diamines2a–gor diisocyanates4a–c. In addition, a polymeric hydrazone was synthesized by reaction of the dioxime of1with the isocyanate4aand a crosslinked product was prepared from a trifunctional isocyanate and1. The products were characterized by elemental analysis and IR spectroscopy. Their physico‐chemical properties were determined and discussed as function of the number of CH2‐groups in the repeating units.
Polymer ester von sären des phosphors, 7. Polymerisation des 1‐oxo‐2,6,7‐trioxa‐1‐phosphabicyclo[2.2.1]heptans
Authors: Gehrmann Thomas , Vogt Walter
Published: April 2003

1‐Oxo‐2,6,7‐trioxa‐1‐phosphabicyclo[2.2.1]heptane is transformed in situ (prepared from trimethyl phosphite and glycerol) at −78°C in the presence of a trace of water into a crosslinked polymer containing constitutional repeating units with 5‐ and 6‐membered rings. The reaction with reagents containing hydroxyl groups (water, acetic acid, alcohol) leads to the degradation of the network with the formation of soluble fragments with Pn = 35–50. This reactivity and the possibility to obtain other derivatives from the fragments make this polymer a carrier for pharmacologically active polymers with the advantage of decomposing only into the innocuous components phosphoric acid and glycerol.
Chloro‐ionenes with ether bonds in the backbone chain. Determination of rate constants, orders of reaction and molecular weights
Authors: Bortel Edgar , Kochanowski Andrzej , Gozdecki Wiesław , Kozłowska Hanna
Published: April 2003

The subject of the investigation concerns chloro‐ionenes prepared from N,N,N′,N′‐tetramethylethylenediamine as well as N,N,N′,N′‐tetramethylhexamethylenediamine and from bis(2‐chloroethyl) ether as dihalide. The orders of reaction have been determined and were found to be n = 2 and n = 1,8, respectively. The established rate constants have a strong dependence on temperature due to the comparatively high energies of activation of ≈ 70 kJ/mol.–A reliable method has been worked out for determining the molecular weights of polyquaternaries with high charge densities in the backbone of the chain. The method is based on analytical ultracentrifugation according to the procedure of Archibald. From the investigations carried out, the conclusion can be drawn, that, in order to get proper results four extrapolations must be made. The measurements can be performed in the original solutions, in which the ionenes have been prepared, allowing the results to be obtained quickly by a computer.–The measured weight‐average molar masses of the ionenes were in the range between 1 500 and 4 000 g/mol.
Glass transition temperatures of copolymers (ethylene glycol/diethylene glycol) terephthalates
Authors: de la Campa Jose G. , Guzmán Julio , de Abajo Javier , Riande Evaristo
Published: April 2003

Copolymers of (ethylene glycol/diethylene glycol) terephthalates were prepared by melt polycondensation. The values of the glass transition temperatures of the copolyesters, determined by dilatometry are in fair agreement with those predicted by the Fox equation. It was also found that the conformational entropy can be used to correlate equilibrium flexibility and glass transition behaviour of the copolyesters.
Internal mobility of PMMA in concentrated CDCl3 solutions, 2. 13C NMR spectra
Authors: Zajíček Jaroslav , Pivcová Hana , Schneider Bohdan
Published: April 2003

The 13C NMR relaxation parameters (T1, line widths and NOE factors) were measured and analyzed for two samples of atactic poly(methyl methacrylate) (PMMA) of molecular weight Mw 4,20·104 and 1,76.106 in CDCl3 solutions in the concentration range 11 to 54% (by weight) of polymer, at 297 and 323 K. By this analysis it was found that the backbone segmental motion of PMMA is spatially isotropic in the whole measured concentration range; the motion of the α‐CH3 group may be approximated by the double reorientation model; the motion of the ester CH3 group can be approximated by the isotropic model only at concentrations lower than 12%; in more concentrated solutions, a satisfactory approximation is obtained neither by the isotropic, nor by the double reorientation models. The reasons of this behaviour are discussed.
Cationic polymerization of thietanes initiated by trityl salts: Mechanism of the initiation reaction
Authors: Florquin Stefaan M. , Goethals Eric J.
Published: April 2003

The initiation reaction of the cationic polymerization of 3,3‐dimethylthietane by trityl hexafluoroantimonate occurs by a fast and quantitative direct addition of the trityl cation to the sulfide function thus producing the corresponding polymer with tritylthio head‐groups. In contrast with this mechanism, the reaction of the trityl salt with the non‐polymerizable sulfides tetrahydrothiophene and diethyl sulfide, leads to a slow hydride abstraction from the sulfide. With these sulfides an equilibrium [carbenium ion + sulfide ⇌ sulfonium ion] is also observed. At 25°C the association constants were found to be 2,27 and 0,096 1 · mol−1 for tetrahydrothiophene and diethyl sulfide, respectively (in CD2Cl2). The initiation mechanism by sulfonium ion formation is explained by the high reactivity of the formed four‐membered ring trityl sulfonium ion which disturbs the carbenium ion‐sulfonium ion equilibrium and ultimately leads to quantitative initiation.
Studies on carboxymethylated cellulose: Potentiometric titrations, 1
Authors: Trivedi Harikrishna C. , Patel Chiman K. , Patel Raman D.
Published: April 2003

The effect of polymer concentration and degree of substitution of carboxymethylated cellulose (CMC) on the dissociation constant was studied by potentiometry. The dissociation was found to be suppressed progressively either by decreasing [CMC] or increasing the degree of substitution of the CMC sample.
Polymerization of 2,4‐hexadiene with neodymium catalysts and characterization of the resulting polymers
Authors: Wang Fosong , Bolognesi Alberto , Immirzi Attilio , Porri Lido
Published: April 2003

The polymerization of (E,E)‐2,4‐hexadiene with the Al(C2H5)2Cl/Nd(OCOR)3/Al(iBu)3 system was examined. High molecular weight crystalline polymers were obtained in polymerizations carried out at room temperature or below. IR and NMR examination showed the polymers to consist predominantly of trans‐1,4 units. Degradative oxidation gave the racemic form of 2,3‐dimethylsuccinic acid, thus indicating a threo structure for the polymers. X‐ray analysis indicated that the polymers contain stereoregular sequences with a trans‐1,4‐threo‐diisotactic structure.
Synthesis and copolymerization of a polyamine macromer: Molecular design of a new functional graft copolymer
Authors: Nishimura Takao , Maeda Mizuo , Nitadori Yoshiaki , Tsuruta Teiji
Published: April 2003

To develop a new method for molecular design of functional polymers, polyamine macromers 4, 10, and 16 were synthesized by lithium alkylamide catalyzed polyaddition reactions of N,N'‐diethylethylenediamine (1), 1,4,10,13‐tetraoxa‐7,16‐diazacyclooctadecane (7), and piperazine (12) to 1,4‐divinylbenzene (2), respectively. Copolymerization of these macromers with styrene gave a new type of graft copolymers 6, 11, and 19, having polyamine grafts. Copolymerization data indicated that the length and number of graft chains could be controlled by adjusting the molecular weight of the macromer and its initial concentration in the copolymerization system. The crystallinity of 16, 19, and other macromers (17, 18) having piperazine units was discussed.
Stereoregularity of polystyrene derivatives, 1. Poly(methylstyrene)s and poly(methoxystyrene)s obtained with ziegler catalyst, cationic catalyst, or radical initiators
Authors: Kawamura Tokiji , Uryu Toshiyuki , Matsuzaki Kei
Published: April 2003

The 13C NMR spectra of methylstyrenes and methoxystyrenes and their polymers prepared with radical initiators, a Ziegler catalyst, or a cationic catalyst were measured. The spectra of the polymers were assigned by the chemical shifts of the monomers and gated‐decoupling method. The absorption of the aromatic C1 carbon of each polymer, which varied by the polymerization conditions, was assigned in terms of a pentad sequence assuming that the Bernoullian statistics holds for the polymerization of ring substituted styrenes. The stereoregularities calculated from C1 carbon absorptions were compared with those of polystyrenes obtained unter the same polymerization conditions. In the radical polymerization of ortho‐derivatives, where the substituent locates near the polymer backbone, high syndiotactic polymers (Pr = 0,80 − 0,83) were prepared. The effect of the substituent in para‐derivatives did not appear. On the other hand, random polymers were generally fromed by cationic polymerization regardless of the position and the type of the substituent.
Heteroaggregation of some dye‐pairs induced by organic and inorganic chromotropes
Authors: Pal M. K. , Ash Sudhir Kumar , Ghosh Bijan Kumar
Published: April 2003

Heteroaggregations of the pair of cyanine dyes pinacyanol and thiacarbocyanine induced by the polyanions poly(potassium styrenesulfonate) and poly(potassium vinyl sulfate), and of methylene blue and acridine orange induced by mercuric chloride are described. In each case the characteristic of heteroaggregation, namely the enhancement of the metachromatic band of the partner dye having λmax at relatively shorter wavelength at the expense of the absorbance at the metachromatic band of the other dye, is reflected in the difference spectra. The dependence of the shape of the metachromatic band of pinacyanol on the nature of the polyanion inducing metachromasia is also reflected in the heteroaggregation of this dye and thiacarbocyanine induced by the two different polyanions. Mercuric chloride, though not a polyanion, also induces strong heteroaggregation of methylene blue and acridine orange.
Functional polymers, 11. Synthesis and polymerization of 2‐(2‐hydroxy‐5‐vinylphenyl)‐2H‐benzotriazole
Authors: Yoshida Shohei , Vogl Otto
Published: April 2003

2‐(2‐Hydroxy‐5‐vinylphenyl)‐2H‐benzotriazole (9) was prepared by a seven step synthesis in about a 25% overall yield starting fromo‐nitroaniline. Diazotization in aqueous HCl gave a diazonium salt which was coupled withp‐ethylphenol to an azo‐dye which was reduced with zinc powder in sodium hydroxide solution to 2‐(2‐hydroxy‐5‐ethylphenyl)‐2H‐benzotriazole (4). This compound was acetylated and then brominated withN‐bromosuccinimide to 2‐[2‐acetoxy‐5‐(1‐bromoethyl)phenyl]‐2H‐benzotriazole (6) which was dehydrobrominated with triethylamine in acetonitrile or tributylamine in dimethylacetamide to the vinyl compound which was hydrolyzed to9. This monomer was readily homopolymerized and copolymerized with styrene and methyl methacrylate using 2,2′‐azobis(2‐methylpropionitrile) as initiator.
Photoinitiators and photoinitiation, 3. Comparison of the photodecompositions of α‐methoxy‐ and α,α‐dimethoxydeoxybenzoin in 1,1‐diphenylethylene as model substrate
Authors: Groenenbook Cornelis J. , Hageman Hendrik J. , Overeem Ton , Weber Anton J. M.
Published: April 2003

The photodecomposition of α‐methoxydeoxybenzoin (1) and α,α‐dimethoxydeoxybenzoin (2) was investigated both in the absence and in the presence of 1,1‐diphenylethylene. The resulting products indicate that benzoyl radicals add to the olefinic double bond (initiation of polymerization), whereas the α‐methoxybenzyl radicals generated from 1 do not add to the olefinic double bond (no initiation), but preferentially combine with other radicals (termination of polymerization). This reaction is largely suppressed in the case of α,α‐dimethoxybenzyl radicals generated from 2 owing to sequential fragmentation into inactive methylbenzoate and highly reactive methyl radicals which add to the olefinic double bond and thus contribute to the initiation.
Interaction between polynucleotides in aqueous NaCl solution, 4. Poly(riboadenylic acid) — poly(2‐riboinosinic acid) system
Authors: Fujioka Kazuhiko , Baba Yoshihiro , Kagemoto Akihiro
Published: April 2003

Solution properties of poly(A) and poly(I) solution at a mole ratio of poly(A) to poly(I) of 1/2 were studied by means of calorimetry and a modified differential scanning calorimetry (DSC) with the help of circular dichroism (CD) and ultraviolet (UV) spectral methods. It was found that the heat of mixing, ΔHM, depends sharply on the ionic strength. At [NaCl] < 10−2 mol · dm−3 ΔHM is nearly zero. At higher ionic strength ΔHM decreases and reaches a minimum value at [NaCl] ≈︁ 2 · 10−2 mol − dm−3. Above this ionic strength ΔHM increases again. This behavior is explained on the basis of the formation of a triplex poly(A) · poly(2I) and the transition of poly(I) from a disordered to an ordered structure with increasing ionic strength. The heat of formation, ΔH, of the poly(A) · poly(21) triplex was estimated to be ca −41 kJ per mole of base triplet. Above an NaCl concentration of 2 · 10−1 mol · dm−3 the triplex formation may be represented by the following scheme:
NMR studies of chitin and chitin derivatives
Authors: Gagnaire Didier , Saint‐Germain Jean , Vincendon Marc
Published: April 2003

The 13C NMR spectra of N‐acetyl‐D‐glucosamine (1) and chitobiose (2), monomer and dimer of chitin, were assigned and used to assign the 13C NMR spectra of chitin in lithium thiocyanate and in LiCl/dimethylacetamide solutions. The dissolution of chitin in formic acid was studied. IR, 13C and 1H NMR spectra show that dissolution occurs by a reaction of formic acid with chitin with the formation of formyl chitin as a statistical derivative of chitin. 13C NMR spectra of diformyl‐ and diacetylchitin were also assigned to characterize these regular polymers.
Carriers for drugs and enzymes based on copolymers of allyl glycidyl ether with acrylamide
Authors: Pitha Josef , Zawadzki Stefan , Hughes Barbara A.
Published: April 2003

Copolymerization of acrylamide with allyl glycidyl ether yielded water soluble polymers containing an epoxy group; addition of a crosslinking agent, N,N′‐methylenebis(acrylamide), to the copolymerization mixtures resulted in the formation of similar though water insoluble polymers. Condensation of a potent beta‐adrenergic antagonist AlmH, which contains a reactive amino group, with a polymer containing an epoxy group yeilded a pharmacologically active polymer. The polymer containing the epoxy group was also converted, by reaction with sodium thiosulfate and subsequent reduction, into a mecapto groups containing polymer which was also water soluble. The latter polymer was converted by condensation with a beta‐adrenergic antagonist AlmCOCH2Br, which contains a reactive bromoacetamido group, into a pharmacologically active polymer.
Polymethacrylic acid derivatives, 3. Potentiometric and conductimetric titrations of poly‐[N‐methacryloyl‐L‐alanine‐co‐N‐phenylmethacrylamide] and poly[methacrylic acid‐co‐benzyl methacrylate]
Authors: Morcellet‐Sauvage Joëlle , Morcellet Michel , Loucheux Claude
Published: April 2003

The compact → coil conformational transition of two series of hydrophilic‐hydrophobic copolymers derived from poly(methacrylic acid) was studied by potentiometric and conductimetric titrations. The samples used were poly(N‐methacryloylalanine‐co‐N‐phenylmethacrylamide) containing up to 50 mole‐% of the hydrophobic residue (P series) and poly(methacrylic acid‐co‐benzyl methacrylate) containing up to 25 mole‐% of the hydrophobic residue (S series). The determination of the free enthalpy of the transition and of the domain of the degree of ionization in which the transition occurs, show inportant differences in the behaviour of the two series of copolymers. These differences are explained by an entropy‐enthalpy compensation for the S series due to strong hydrophobic interactions between the aromatic side chains. Conductimetric titrations allow, in some cases, the determination of the degree of ionization at the beginning and at the end of the conformational transition.
Stereocontrol in the free radical polymerization of N‐vinylcarbazole
Authors: Terrell David R. , Evers Fritjof
Published: April 2003

The free radical polymerization of N‐vinylcarbazole (VK) was investigated in hexane, nonane, toluene, HMPT, DMF, DMAC, and DMSO. Isotactic propagation was found to be energetically favoured by between 1500 and 4600 J · mol−1 for all the solvents investigated, although the entropy difference between syndiotactic and isotactic propagation strongly favoured syndiotactic propagation by between 11 and 20 J · mol−1K−1. Variation in the steric microstructure between an isotactic mole fraction of 0,25 and 0,47 was obtained by varying the polymerization temperature and solvent. The activation enthalpy differences between isotactic and syndiotactic propagation (ΔH≠s/i − ΔH≠i/s), for the free radical polymerization of methyl methacrylate (MMA) and VK were compared and the steric configurations involved in the propagation process considered. It was concluded that electronic interaction between radical and monomer appeared to determine the energetic preference of the growing chain for isotactic or syndiotactic propagation in free radical propagation. This energetic preference was correlated with the e‐factor in the Q − e scale. Data for the free radical polymerization of VK, MMA, and vinyl trifluoroacetate showed that solvent polarity has a weak influence on the energetic preference of the growing chain for isotactic or syndiotactic propagation. This energetic preference was correlated with the π* solvent polarity scale.
Studies on formaldehyde resins, 19. General base catalysis in hydroxymethylation of melamine with formaldehyde
Authors: Sato Kenji , Konakahara Takeo , Kawashima Mikio
Published: April 2003

Hydroxymethylation of melamine with formaldehyde to form N‐(hydroxymethyl)melamine (2,4‐diamino‐6‐hydroxymethylamino‐1,3,5‐triazine) was investigated kinetically by the use of hydrogen phosphate/phosphate buffers in aqueous media at pH 11 − 12. This reaction was found to follow a general base catalysis which results from the kinetic investigation, showing that the reaction takes place by a concerted mechanism involving base, melamine, and formaldehyde. This mechanism differs from that of the base catalyzed hydroxymethylation of phenol or benzamide with formaldehyde, because the acidic phenol and benzamide easily form their conjugate bases by addition of the basic catalyst in a preceding equilibrium step.
Heat capacity of poly(oxy‐2,6‐dimethoxy‐1,4‐phenylene)
Authors: Jauhiainen Tuure‐Pekka
Published: April 2003

The heat capacities of poly(oxy‐2,6‐dimethoxy‐1,4‐phenylene) were measured from 160 to 480 K using a differential scanning calorimeter (DSC) interfaced to a computer for data collection and processing. The values for the heat capacities between 160 and 420 K were tabulated. Below 280 K they depend only slightly on the molar mass, whereas above 280 K the conformational changes of the end groups have a noticeable effect. Wunderlich's addition scheme for the calculation of heat capacities from the empirical group contributions gives results that agree within ± 1% with the experimental data. The heat capacity jump ΔCp at Tg depends inversely on the molar mass. Wunderlich's “bead” model for ΔCp values is discussed for poly(oxy‐2,6‐disubstituted‐1,4‐phenylene).
Thermal expansion of poly(oxy‐2,6‐dimethoxy‐1,4‐phenylene)
Authors: Jauhiainen Tuure‐Pekka
Published: April 2003

The thermal expansion coefficient of poly(oxy‐2,6‐dimethoxy‐1,4‐phenylene), PPOO, was measured from 150 to 500 K, using a thermomechanical analyzer connected to a computer for the data handling. Poly(oxy‐2,6‐dimethyl‐1,4‐phenylene), PPO, and some brominated poly(oxy‐2,6‐disubstituted‐1,4‐phenylene)s were studied as reference materials. The apparent glass transition temperatures of the high molar mass polymers were 456 K for PPOO and 487 K for PPO, and the changes in cubic thermal expansion coefficients at Tg were 6,01 · 10−4 K−1 for PPOO and 4,23 · 10−4 K−1 for PPO. The activation of the β‐relaxation was found for PPOO at 260 K and attributed to the hindered torsional oscillations of the backbone phenylene groups. Another transition was found at 160 − 170 K and interpreted as the γ‐relaxation due to the oscillatory motion of the methoxy groups. Reasons for the differences in the thermal expansion behaviour of PPOO and PPO are discussed.
Cyclopolymerization of N‐methacryloyl‐N‐methylcrotonamide
Authors: Yamada Bunichiro , Saya Toshiaki , Ohya Takahiro , Otsu Takayuki
Published: April 2003

N‐Methacryloyl‐N‐methylcrotonamide (MMCA) was prepared by the reaction of methacryloyl chloride with N‐methylcrotonamide. While N,N‐disubstituted methacrylamide and crotonamide, which can be considered as structual moieties of MMCA, do not homopolymerize, nevertheless MMCA yielded a homopolymer consisting of 5‐membered cyclic repeating units. MMCA was found to be more reactive than N‐propyldimethacrylamide in copolymerization with styrene and methyl methacrylate. Since the polymer radical adds to the methacrylamide moiety, the steric hindrance of a β‐methyl group in the crotonamide moiety must be less significant than that of the α‐methyl group of the methacrylamide moiety in the dimethacrylamide. The 5‐membered ring formation during the polymerization of MMCA was facilitated by the favorable conformation of the three carbon atoms concerned in the ring closure to achieve coplanarity, which is required for the fast 5‐membered ring closure. The coplanarity of the three carbon atoms and reluctance to homopolymerize of the reacting double bonds seem to be the minimum requirements for forming of a polymer consisting of solely 5‐membered cyclic repeating units.
Dynamic mechanical properties of polyurethane networks containing sodium tetraphenylborate, 2. The modulus dependence on temperature, frequency, and salt concentration
Authors: Killis Andréas , Le Nest Jean‐François , Gandini Alessandro , Cheradame Hervé
Published: April 2003

The viscoelastic behaviour of polyether‐based polyurethane networks containing sodium tetraphenylborate was investigated by means of dynamic mechanical measurements. A quantitative analysis of the storage modulus dependence on temperature, frequency, and salt concentration gives rise to three superposition correlations, viz. frequency‐temperature, frequency‐concentration, and concentration‐temperature. The frequency‐temperature superposition follows a WLF behaviour, while the other two are approximately linear expressions particularly well verified in the zone of the transition state.
Crystallinity of methylene‐oxyethylene‐methylene triblock oligomers derived from nonaethylene glycol
Authors: Domszy Roman C. , Booth Colin
Published: April 2003

Block oligomers of general formula CH3(CH2)nO[CH2CH2O]9(CH2)nCH3 where n = 0 to 25 have been prepared. All blocks are monodisperse. Examination of their crystallinity (by differential scanning calorimetry, X‐ray scattering, infra‐red and Raman spectroscopy) shows that, within defined limits (n > 9, crystallisation temperature high), the block oligomers can crystallise completely. A likely structure is 7/2 helical monoclinic oxyethylene blocks and planar zigzag low density methylene blocks, with the oxyethylene helices normal to the lamella end‐planes and the methylene chains titled.
Copolymerization of methyl acrylate with isobutylene in the presence of lewis acids
Authors: Florjanczyk Zbigniew , Kuran Witold , Langwald Norbert , Sitkowska Jadwiga
Published: April 2003

The copolymerization of methyl acrylate (MA) and isobutylene (IB) in the presence of Lewis acids (EtAlCl2, Et2AlCl, Et3Al, AlCl3, and ZnCl2) at low Lewis acid/MA mole ratio was investigated. EtAlCl2 and Et2AlCl were found to initiate the spontaneous reaction. An alternating copolymer was produced in this reaction when an excess of IB in the initial monomer feed was used. The copolymerization in the presence of Et3Al, AlCl3, and ZnCl2 did not proceed spontaneously and was initiated by dibenzoyl peroxide (BPO). In this case MA‐rich copolymers are formed even in systems containing a large excess of IB in the monomer feed. The addition of BPO to systems containing ethylaluminium chlorides strongly diminishes the tendency towards alternating propagation. It was concluded that the mode of initiation has a significant influence on the copolymer composition. The alternating copolymerization by EtAlCl2 was studied in detail in order to determine the influence of the catalyst concentration, monomer feed ratio, reaction temperature and time on the monomer conversion, copolymer composition, molecular weight and tacticity.
Functional monomers and polymers, 89. Synthesis of poly(β‐alanine) in the functional reversed micelle
Authors: Hanabusa Kenji , Shirai Hirofusa , Hojo Nobumasa , Kondo Koichi , Takemoto Kiichi
Published: April 2003

Active β‐alanine 4‐acyl‐2‐nitrophenyl esters (5a—j) containing ω‐phenyl‐ or ω‐cyclohexyl acyl groups were prepared and their polycondensation was studied, which can take place in the reversed micelle to give poly(β‐alanine). Non‐polar solvents were suitable for the polycondensation, while no polymer was formed in protic and dipolar aprotic solvents. Esters having long linear acyl groups (5n—o) were also reactive enough to give the polymer. However, the esters containing phenyl and cyclohexyl groups (5a—j) were much more reactive and gave the polymer in high yield even if the linear acyl chain was only short.
On the kinetics and mechanism of thermal degradation of polystyrene
Authors: Ebert Klaus H. , Ederer Hanns J. , Schröder Ulrich K. O. , Hamielec Archie W.
Published: April 2003

The thermal degradation of polydisperse polystyrene samples with mol. wts. (M̄n) between 60000 and 22000 has been investigated at different temperatures under oxygen free conditions. Product analysis has been carried out by GPC. The experimental degradation could be simulated by a model consisting of scission and depolymerization. The dynamical behaviour of this model is expressed in a matrix from. The ratio of scission and depolymerization is constant for all polymers and different temperatures during degradation. Therefore, a master curve could be evaluated, which gives a general relation between the decrease of mol. wt. and the mass of volatiles. Finally a radical chain mechanism has been proposed in a lumped form which is consistent with the kinetic model and the experimental results.
Stoichiometric salt‐linkage formation of trimethylammonium glycol chitosan iodide with a carboxylic type ion exchanger
Authors: Kokufuta Etsuo , Fujii Susumu , Nakamura Isei
Published: April 2003

The adsorption of trimethylammonium glycol chitosan iodide (TGCI) on Dowex CCR‐2 resin was investigated at different pH values and resin weights. The concentration of Na+ or Ca2+ ions, released by the ion exchange reaction with TGCI, was measured by inductively coupled plasma spectroscopy. It was found that the amount of the released ions is comparable to that of the absorbed TGCI. This indicates that the salt‐linkage formation of carboxylate ions of the exchanger with ⊕N(CH3)3‐groups in TGCI follows a stoichiometric relationship. This result is discussed in connection with the form of the polymer layer adsorbed on the solid surface.
Mechanical properties of chitosan films: Effect of solvent acid
Authors: Kienzle‐Sterzer Carlos A. , Rodriguez‐Sanchez Dolores , Rha ChoKyun
Published: April 2003

The apparent Young's modulus shows a linear relationship with junction density of chitosan films. The linear relationship of apparent Young's modulus with chitosan concentration is also observed. The linear relationship depends of the acid used in the casting solution. Relaxation times were of the order of 104 seconds, indicating a slow physical process. Stress‐relaxation behavior of swollen chitosan films, prepared by solvent casting from dilute acetic or propionic acid solutions, can be represented by a one‐component Maxwell model.
High molecular weight derivative of trypsin‐kallikrein inhibitor for potential medical use, 1. Preparation and characterization
Authors: Saudek Vladimír , Drobník Jaroslav , Havranová Marie , Čechová Dana
Published: April 2003

Bovine trypsin‐kallikrein inhibitor (TKI) was bound on three different water‐soluble hydrophilic carriers derived from poly[N‐(2‐hydroxyethyl)‐D,L‐aspartamide] and containing a binding group (aromatic amine) and an additional modifying group (anionic or hydrophobic). The binding was performed by coupling of diazonium salts formed on the carrier with tyrosines in TKI. The product was characterized by means of sedimentation measurement, viscometry, electrophoresis, amino acid analysis, GPC, and antiproteolytic activity. TKI was found to be attached to the carrier by one or two tyrosines, the latter case being more frequent than it would correspond to independent random reactivity of the accessible tyrosines and the carrier molecules are crosslinked by the attached TKI. This is due to a fraction of two point attached TKI, as estimated according to a tree‐like model. All three samples preserved good activity toward trypsin and chymotrypsin.
Kinetics of the formation of salts of dibasic acids with hexamethylenediamine in 1‐propanol and bifunctional catalysis by the solvent
Authors: Amirtha Nagarajan , Ganesan Ramachandran
Published: April 2003

The kinetics of the reaction between hexamethylenediamine (HMD) and dibasic acids (malonic, succinic, glutaric, and adipic acid) were studied in the temperature range 18–42°C using 1‐propanol as solvent. The total order of the reaction is two, first order in HMD and first order in the dibasic acid. The stoichiometry of the reaction is 1:1 and NMR and IR spectral analyses show that the product is an organic salt with and groups present. A mechanism was proposed in which a proton is transferred from the acid molecule to the base through a solvent molecule which acts as a bifunctional catalyst (both as a proton‐acceptor and proton donor). Values of the rate constants, Arrhenius activation energies, preexponential factors, and entropies of activation are consistent with the proposed mechanism. There is a very strong evidence to show that the “half‐anion” produced in the first ionization of the dicarboxylic acids is the real reactive species.
Sorption of water in hydrophilic polymers, 2. Thermodynamics of mixing of water with poly(2‐hydroxyethyl methacrylate) and with poly[2‐(2‐hydroxyethoxy)ethyl methacrylate]
Authors: Pouchlý Julius , Beneš Svatopluk , Máša Zdeněk , Biroš Ján
Published: April 2003

Sorption isotherms and heats of immersion of water in poly(2‐hydroxyethyl methacrylate) (PHEMA) and in poly[2‐(2‐hydroxyethoxy)ethyl methacrylate] (PHEOEMA) were determined at 25°C and the Gibbs energy, enthalpy and entropy of mixing were calculated from the data. The results confirm that the physical state of the polymer plays a decisive role in the thermodynamics of sorption. At the temperature of measurement, pure PHEMA is in the glassy state and after sorption of a certain amount of water it passes into the viscoelastic state. Similar to other cases of mixing of a glassy polymer with a low‐molecular weight liquid, the entropy and enthalpy changes are negative, with contributions due to the difference between the physical states of both pure components predominating in them. The thermodynamics of liquid mixtures can be used only for PHEOEMA which at 25°C is in the viscoelastic state. The mixing of water (especially of the first additions) with PHEOEMA is exothermal, being at the same time connected with a negative residual entropy, the effect of which predominates at 25°C. As a result, the affinity of water to the polymer, expressed through a change in the Gibbs energy, is comparatively weak. This is why in this system no strongly bound water is involved, even if the ΔH and ΔS values indicate some sort of increase in ordering during mixing.
Synthesis, characterization, and electrical conductivity of polyesterification products with tetrathiafulvalene units, and their TCNQ complexes
Authors: Koßmehl Gerhard , Rohde Michael
Published: April 2003

Polyesterification products with tetrathiafulvalene units 3a–e were prepared from tetrathiafulvalenedicarbonyl dichloride (1) and various α,ω‐diols (2a–e) containing 2 to 16 methylene groups. The red to brown products 3a–e with melting points between 235°C and 128°C are insoluble in all common organic solvents, except for 3e which is soluble in hot DMF. Molecular weights determined by vapor pressure osmometry as well as from elemental analysis data have been found to be ≥2000. The structures were proved by IR, MS, and electronic spectra. The electrical conductivities of 3a–e are between 4 . 10‐8 and 4 · 10‐13 Ω‐1· cm‐1. In TCNQ complexes the electrical conductivities are enhanced by one to five orders of magnitude.
A comment on the estimation of random branching from viscosity measurements
Authors: Mrkvičková Libuše , Quadrat Otakar
Published: April 2003

The hydrodynamic behaviour of polydisperse branched copolymers of methyl methacrylate with a small amount of ethylene dimethacrylate was investigated in several solvents possessing different “solvent power”. It was found that with increasing degree of branching the viscometric expansion coeficient α of these copolymers decreases compared with the expansion of the linear analogs α (before the gel point α/α ≈ 0,5). This phenomenon is demonstrated to be useful in the application of viscometry as a method of estimation or determination of branching.
Enthalpy of polymerisation of ethylene oxide and of copolymerisation of ethylene oxide with 7‐oxabicyclo[2.2.1]heptane
Authors: Andruzzi Fulvio , Suradi Sukiman , Pilcher Geoffrey
Published: April 2003

The enthalpies of combustion of poly(ethylene oxide), ΔH(c)=‐1178,7 ± 1,3 kJ . mol‐1, and of a random copolymer of overall molar composition 0,41 (poly(ethylene oxide)) + 0,59 (poly(oxy‐1,4‐cyclohexylene)), ΔH(c)=‐2566,4 ± 1,8 kJ . mol‐1, were measured at 298,15 K by high‐precision bomb calorimetry. The enthalpy of polymerisation of ethylene oxide was derived as ΔH (l → c) = ‐102,4 ± 1,6 kJ . mol‐1. The enthalpy of copolymerisation of ethylene oxide and 7‐oxabicyclo[2.2.1]heptane was ΔH (l → c) = ‐63,0 ± 2,1 kJ . mol‐1, compared with ‐68,1 ± 1,6 kJ . mol‐1 for producing the two homopolymers in the proportion in which the monomers were present in the copolymer. It is concluded that insertion of an ethylene oxide unit into a poly(oxy‐1,4‐cyclohexylene) chain does not affect the strain‐energy by a significant amount.
On the conformational characteristics of acrylamide polymers
Authors: Chiantore Oscar , Trossarelli Luigi , Guaita Marino
Published: April 2003

The effect of lateral substituents on the structure of the solutions and on the chain conformations of N‐substituted and N,N‐disubstituted poly(acrylamide)s is discussed. The water‐soluble polymers show solution properties influenced by the development of strong specific interactions between the chain molecules and the solvent, and by the hydrophobicity of the substituents. In non‐aqueous solvents the interactions between the polar groups of the structural units force the polymer chains to assume unusually large unperturbed dimensions, causing the chain flexibility to depend more on the overall polarity of the molecule than on the bulkiness of the substituent.
Polymere mit phosphor‐stickstoff‐bindungen, 7. Die polymerisation gemischt chlor‐ und trifluorethoxysubstituierter cyclotriphosphazene bei anwesenheit von bortrichlorid
Authors: Horn Hans‐Georg , Kolkmann Friedrich
Published: April 2003

Mixed chloro‐ and trifluoroethoxy substituted cyclotriphosphazenes 1a–d react with boron trichloride at elevated temperature to give mixed substituted polyphosphazenes of low molecular weight. The reaction was investigated by 31P NMR. Fractionation of the polymers was achieved by extraction with hexane/benzene. The low molecular weights are explained by a large amount of cyclophosphazenyl cations generated nearly simultaneously.
Synthèse par voie radicalaire de polymères à extrémités hydroxylées, 10. Synthèse de poly(méthacrylate de méthyle)s par le rayonnement UV: étude de l'influence de la nature du solvant mutuel sur la polymolécularité
Authors: Brosse Jean‐Claude , Lenain Jean‐Claude , Gauthier Jean‐Marie
Published: April 2003

Methyl methacrylate was polymerized under UV irradiation (254 nm) at room temperature by hydrogen peroxide in order to give hydroxytelechelic polymers. The polymerization was carried out in the presence of ethanol. An alcohol may be used as a diluent, as a mutual solvent of hydrogen peroxide and the monomer, and as a solvent or nonsolvent of the polymer. The influence of the alcohol is pointed out on the various characteristics of the polymerization; the results are compared with those obtained in methanol.
Effects of DNA and other polyanions on the EDTA induced photoreduction of thionine
Authors: Pal Medini Kanta , Manna Pravash Ch.
Published: April 2003

Thionine (7‐amino‐3‐imino‐3‐H‐phenothiazine) undergoes reversible photobleaching when exposed to visible light in the presence of ethylenediaminetetraacetic acid (EDTA) with the associated development of an electromotive force (emf). This photocreation between EDTA and thionine is inhibited in the presence of excess Mg+ +. Polyanions like DNA, RNA and polystyrenesulfonate also protect the dye from the EDTA induced photoreduction; this protective power of the polyanions depends on their nature and increases with their concentration. DNA, thought a weak chromotrope to form a metachromatic compound with thionine, protects the dye from photobleaching efficiently, presumbly due to the intercalation of the dye cations between base pairs of DNA; denatured DNA is relatively poorer in its ability to protect the dye and resembles RNA and polystyrenesulfonate in this respect. The results indicate that EDTA and thionine form a transient complex or are at least associated before electron transfer from EDTA to thionine in the excited‐triplet state takes place.
Metalloester, 9. Untersuchung des anfangsstadiums der anionischen polymerisation von methylmethacrylat. Reaktion von methyl‐2‐sodioisobutyrat mit methylmethacrylat
Authors: Adler H.‐J. , Lochmann L. , Pokorný S. , Berger W. , Trekoval J.
Published: April 2003

In the reaction of methyl methacrylate (2) with methyl 2‐sodioisobutrate (1) (a model of the active center in the anionic polymerization of 2) in a mole ratio of 2:1, the concentrations of all known initial compounds and reaction products were estimated. This reaction was studied in a flow reactor with reaction times between 0,02 and 1,4 s using GLC, LC and GPC as analytical methods. At the same time, a rise in temperature of the reaction mixture by 6°C was observed (for [2] = 0,2 mol/1); at a higher concentration of 2 (0,6 mol/1), this rise was 27°C and hence not negligible in the interpretation of the results. The concentration changes of the individual products were in accordance with the concept of a stepwise addition of 2, to the metalloesters. At the end of the reaction the mean molecular weight of the addition products corresponded roughly to the ratio 2/effective 1. The cyclization of Na‐trimer 4a to a cyclic trimer 9 was shown to be an important side reaction. The Na‐tetramer 5a and the higher Na‐oligomers 6a probably undergo a similar cyclization. 2 added 1 very quickly; the following approximate order of reaction rates (Scheme 1) is proposed: R1 > R2, R3, R4, … > Rc.
Synthesis and properties of block copolymers of polystyrene and poly(2‐acrylamido‐2‐methylpropanesulfonic acid)
Authors: Konishi Hisatoshi , Shinagawa Yoshinobu , Azuma Atsushi , Okano Tamon , Kiji Jitsuo
Published: April 2003

A series of A‐B‐A triblock copolymers consisting of poly(2‐acrylamido‐2‐methylpropanesulfonic acid) as outer blocks and polystyrene as the middle block was synthesized by polymerizing 2‐acrylamido‐2‐methylpropanesulfonic acid at the ends of a diethyldithiocarbamate‐terminated polystyrene, in which the terminal diethyldithiocarbamate groups act as the radical initiator under photo‐irradiation. The heterogeneous character of the block copolymers in solutions is discussed on the basis of the solubility behavior and the 1H NMR spectra.