bluuebunny/crossref_metadata_2025 huggingface dataset:
Mathematical properties of polydisperse systems, 3. Calculation of molecular weight distribution from light scattering on gaussian polymer coils. Inversion by means of a nonlinear fit
Authors: Greschner Georg S.
Published: April 2003

The molecular weight distribution (MWD) of a high polymer is calculated from a weakly perturbed Zimm‐plot of the classical light scattering on dilute solutions of Gaussian polymer coils (theta state). A typical Zimm‐plot is simulated corresponding to the measurements of high accuracy as would be obtained by using the laser photometer described by Hack and Meyerhoff. The accuracy as published by these authors for small dissymmetries is used. Two numerical methods for calculating the MWD are briefly described and tested, both using an empirical formula for the Laplace image of the calculated MWD.
Phasentransferkatalysen durch ein polymers mit dibenzo‐18‐krone‐6 als ankergruppe
Authors: Blasius Ewald , Janzen Klaus‐Peter , Klotz Helmut , Toussaint Adrien
Published: April 2003

Among numerous polymers with cyclic polyethers and non‐cyclic ethers as anchor groups, the condensation resin with dibenzo‐18‐crown‐6 as anchor group (℗‐DB‐18‐C‐6), which can be easily prepared, exhibits the best properties for phase‐transfer catalysis. It catalyses substitution, dichlorocarbene and polymerisation reactions which do not take place at all or only in a low yield without the catalyst. For substitution reaction the highest yields are up to 95% in the liquid phase and up to 70% in the gaseous phase. For chlorocarbene reactions yields up to 76% are reached. For the polymerisation of 2‐pyrrolidone, started by potassium 2‐pyrrolidonate, the yield is at 80%.
Chain transfer of alcohols in the polymerization of acrylic esters
Authors: Nandi U. S. , Singh M. , Raghuram P. V. T.
Published: April 2003

Transfer constants were determined from the thermal polymerization of methyl, ethyl, and butyl acrylates for methyl, ethyl, propyl, and isopropyl alcohols at 80 °C, utilising “mixedsolvent” systems wherever necessary. It was observed that the chain transfer constant for alcohols is not much affected by lengthening of the ester group in the acrylates, and the reactivity of the solvent is enhanced by an increased substitution at the α‐carbon atom in the alkyl group.
Caractérisation texturale par thermoporométrie et par adsorption‐désorption d'azote de résines à l'état gonflé
Authors: Brun Maurice , Quinson Jean‐François , Spitz Roger , Bartholin Michel
Published: April 2003

Thermoporometry is applied to determine the porous distribution of different resins in the swollen state. In some particular cases, a comparision is possible with results of the BET‐BJH methods applied to the same products dried by lyophylisation. Such a comparison enables a better understanding of the organisation and the formation of swollen systems. This determination of the porous texture of swollen resins is particularly useful for the understanding and the forecast of the general behaviour of resins.
Symmetric markov trials. Syndiotactic poly(propylene) and heterotactic polymers
Authors: Elias Hans‐Georg
Published: April 2003

Symmetric Markov first order mechanisms are defined by equal conditional probabilities for the homotriad formation and a heterotacticity independent of homotacticity. The model predicts linear relationships between homotriad and diad fractions, restricted diad ranges, and a characteristic dependence of the persistence length on the diad fraction. Data on the syndiospecific propylene polymerization are in accordance with this model which also seems to describe heterotactic polymerizations.
Synthese neuer pseudoleiterpolymere mit 7H‐benzimidazo[2,1‐a]benzo[d,e]isochinolin‐7‐on‐3,11‐diyl‐einheiten in der hauptkette
Authors: Jedliński Zbigniew , Gaik Urszula , Kowalski Bogdan , Korshak Vasilii V. , Rusanov Aleksandr L. , Berlin Alla M. , Fidler Saul Kh.
Published: April 2003

A series of novel semi‐ladder polymers containing 7H‐benzimidazo[2,1‐a]benzo[d,e]isoquinolin‐7‐on‐3,11‐diyl units in the chain was prepared by one‐step high temperature solution polycondensation of 4,4′‐oxy‐,4,4′‐carbonyl‐, and 4,4′‐sulfonyldi‐1,8‐naphthalenedicarboxylic anhydride (1a‐c) with 2,2′‐diamino‐4,4′‐oxydianiline (2) or 2,2′‐diamino‐4,4′‐hexafluoroisopropylidenedianiline (4). The similarity of the IR and UV spectra of the polymers and the model compounds 7a‐c confirms the presence of the benzimidazobenzoisoquinolinone rings in the polymer chain. All the resulting polymers have excellent thermal stability both in argon and in air. The polymers prepared from 4 are soluble in 1‐methyl‐2‐pyrrolidone and phenol/1,1,2,2‐tetrachloroethane.
Synthesis of casein‐g‐poly(vinyl acetate)
Authors: Mohan Doraiswamyraj , Radhakrishnan Ganga , Rajadurai Sambosankaran
Published: April 2003

Casein‐g‐poly(vinyl acetate) was synthesized using potassium persulfate as initiator. Changes in monomer concentration, initiator concentration, backbone concentration, and temperature were effected. The rate of total conversion of monomer, the rate of homopolymerization and graft copolymerization, the grafting efficiency and the percentage of grafting were calculated. The grafting results were discussed in the light of grafting efficiency and percentage of grafting. They were found to be lower in the case of casein‐g‐poly(vinyl acetate) when compared to those of casein‐g‐poly(butyl acrylate).
Identification of polymers by mass spectrometry, 2. Polymers containing 1‐trifluoromethylvinylene, 1,4‐phenylene, and/or 2,5‐thiophenediyl units
Authors: Holzmann Gerhard , KoßMehl Gerhard , Nuck Rolf
Published: April 2003

Polymers containing 1‐trifluoromethylvinylene, 1,4‐phenylene, and/or 2,5‐thiophenediyl units (6a, b and 8a‐d), obtained by base‐free Wittig condensation reactions with phase transfer catalysts, were investigated combining direct evaporation in the ion source of a double focusing mass spectrometer with the “Linked‐Scan” metastable technique. This method could be shown to allow the unequivocal identification and differentiation of components in polymers up to high mass regions (m/z ≤ 3000). The degree of polycondensation up to 18 aromatic/heteroaromatic units in the chain was determined by mass chromatography, which correlated with the HPLC results. Terminal groups and sequence ions were characterized by comparison of metastable transitions of selected ions with model compounds. Detailed information on the polycondensation reaction was obtained. In addition to linear products, cyclic species with 3 to 18 arylene‐1‐trifluoromethylvinylene units were formed. The main fragmentations may be explained by sterical effects of both the α‐trifluoromethylstilbene moiety and the heteroaromatic analogues in the polymeric chains.
The effect of electron donors on the polymerization of styrene initiated with organolithium compounds
Authors: Kmínek Ivan , Kašpar Miroslav , Trekoval Jiří
Published: April 2003

The kinetics of the polymerization of styrene with oligostyryllithium and butyllithium in the presence of electron donors was investigated calorimetrically. There is no simple correlation between the accelerating effect (1,2‐dimethoxyethane > tetrahydrofuran > N,N,N′,N′‐tetramethylethylenediamine = triethylamine) of the individual electron donors upon the polymerization and their ability to form complexes with the respective organolithium compounds. This is qualitatively explained by considering preceding coordination reactions between organolithium compounds (or their complexes with electron donors) and the monomer in the reaction scheme. An irreversible degradation reaction between butyllithium and 1,2‐dimethoxyethane occurring at T > 278 K is described. The products of this reaction are lithium methoxide, decane and hexyl methyl ether.
Investigation of the influence of the interaction between anionic detergents and a copolymer of n‐vinyl‐2‐pyrrolidone with vinylamine on the biological activity of these detergents
Authors: Solovsky Mikhail V. , Anufrieva Elizaveta V. , Panarin Evgenii F. , Pautov Vladimir D. , Afinogenov Gennadii, E.
Published: April 2003

The interactions between sodium dodecyl‐ and tetradecylsulfater or sodium alkylbenzenesulfonate and a copolymer of N‐vinylpyrrolidone with vinylamine (9 : 1 by mole) in aqueous solution were investigated by polarized luminescene. Polymer complexes of these anionic detergents with the copolymer were obtained and their antimicrobial and toxic properties as well as their effect on a bacterial enzyme, penicillinase, were investigated, It was found that these polymer complexes do not disintegrate on passing from aqueous to salt solutions, are 4 to 5 times less toxic than the initial anionic detergents and are comparable to the latter in both their antimicrobial activity and the ability for inhibiting penicillinase.
Relation entre les paramètres diélectriques et la cinétique de réaction de polymérisation en phase liquide
Authors: Soualmia Achour , Huraux Claude , Depax Bernard
Published: April 2003

The aim of this study is to characterize the state of progress of a polymerization reaction by a non‐destructive electric method. For this purpose, results deduced from measurements of complex permittivity are compared with those obtained from chemical analysis of the reaction mixture at successive instants of its evolution. Chemical analysis allows the rate of disapperace of expoxy groups during the polymerization reaction in liquid phase to be evaluated. Exploitation of electric measurements of complex relative permittivity enables the evolution of the polymerization to be followed from both the product of the epoxy group concentration and the square of the mean value of their dipole moment and also from the most probable relaxation time of this dipole. As expected, the variations of relaxation time are closely correlated to those of the viscosity of the medium.
Polymere mit phosphor‐stickstoff‐bindungen, 6. Zur polymerisation von hexakis(2,2,2‐trifluorethoxy)cyclotriphosphazen bei anwesenheit von bortrichlorid
Authors: Horn Hans‐Georg , Kolkmann Friedrich
Published: April 2003

Hexakis(2,2,2‐trifluorethoxy)cyclotriphosphazene (1b) reacts with borontrichloride at elevated temperatures to give a mixture of polymeric phosphazenes containing imino dichloro and imino bis(trifluoroethoxy)phosphoranetriyle units. The reaction was investigated by 31P NMR. Separation of several fractions of polymers was achieved by hexane/benzene solvent extraction. Molecular weights have been determined by means of membrane and/or vapor pressure osmometry. A reaction mechanism is discussed.
Electron‐transfer reaction of a copper(II) complex bound to an amphiphilic block copolymer: A plastocyanin model
Authors: Nishide Hiroyuki , Tsuchida Eishun
Published: April 2003

A water‐soluble tri‐block copolymer (1) composed of hydrophilic poly(ethylene oxide) and hydrophobic poly(styrene‐co‐1‐vinylimidazole) was synthesized as a model compound of the apoenzyme of plastocyanin. Visible and electron spin resonance spectra of the Cu complex bound to the imidazole residue of 1 showed that the Cu complex is surrounded by a hydrophobic domain even in aqueous medium. The outer‐sphere electron‐transfer reaction of Cu(II) with Fe(II) (phenanthroline)3 proceeded faster (with a large activation entropy) for the polymeric Cu/1 complex than for the monomeric Cu/1‐ethylimidazole complex, while the reduction with ascorbic acid was slower for the polymeric complex.
Synthesis and free radical ring‐opening polymerization of 2‐methylene‐4‐phenyl‐1,3‐dioxolane
Authors: Bailey William J. , Wu Shang‐Ren , Ni Zhende
Published: April 2003

The cyclic ketene acetal, 2‐methylene‐4‐phenyl‐1,3‐dioxolane (3), was shown to undergo free radical ring‐opening polymerization to produce the polyester, poly[γ‐(β‐phenyl)butyrolactone]. The monomer 3 was synthesized by an acetal exchange reaction of chloroacetaldehyde dimethyl acetal with styrene glycol in an 87% yield followed by dehydrochlorination of the resulting cis and trans‐2‐chloromethyl‐4‐phenyl‐1,3‐dioxolane (2) with potassium tert‐butoxide in tert‐butyl alcohol in a 70% yield. 3 was shown to undergo essentially quantitative free radical ring‐opening at all temperatures from 60–150°C and also nearly complete regioselective ring‐opening with cleavage to give the more highly stable secondary benzyl free radical. Even in free radical copolymerization with styrene, methyl methacrylate, vinyl acetate, or 4‐vinylpyridine, 3 gives essentially complete ring opening to introduce an ester groups into the backbone of the addition copolymer. The structures of the polymers were established by elemental analysis and 1H and 13C NMR spectroscopy.
Biomimetic approach to the design of a pyridoxal enzyme model, 2. Cyclocopolymerization as a new method of constructing polymers with defined arrangement of functional groups in the chain
Authors: Belokon' Yuri N. , Tararov Vitali I. , Savel'eva Tatiana F. , Lependina Olga L. , Timofeyeva Galina I. , Belikov Vasili M.
Published: April 2003

Water‐soluble polyacrylamide samples of various molecular weight, containing salicylaldehyde and lysine moieties, were prepared by copolymerization of (Nα‐5‐methacryloylamino‐salicylidene‐Nϵ‐methacryloyl‐(S)‐lysinato) (pyridine)copper (II) (1) with acrylamide, followed by destruction of the copper complex by the disodium salt of EDTA. It is shown that at pH > 6 the formation of “internal” aldimine occurs in these samples. The degree of assembly of “internal” Schiff base is considerably higher than in the model low‐molecular weight system and does not depend on: a) the molecular weight of the polyacrylamide sample; b) the polymer concentration in buffer solution; c) the presence of a cross‐linking agent. On the basis of these data a conclusion is made that in the copolymerization of 1 with acrylamide, methacryloyl moieties, bonded with the amino groups of salicylaldehyde and lysine, form macrocycles, the cyclocopolymerization rate being much higher than the rate of cross‐linked polymer formation. After the removal of copper ions from the polymer the lysine and salicylaldehyde moieties remain attached to the same polymer chain in the immediate vicinity of each other, thus favouring the formation of “internal” aldimine.
Oligomères amphiphiles obtenus par voie radicalaire, 1. Synthèse et caractérisation d'oligomères de l'acide acrylique à extrémité dodécylthio
Authors: Cellard Bernard , Pichot Christian , Revillon André
Published: April 2003

Oligomeric emulsifiers were prepared by the technique described by Roe, with special care of composition and molecular weight. Acrylic acid was polymerized in 2‐propanol with lauroyl peroxide as initiator in the presence (at various ratios) of 1‐dodecanethiol (8) as transfer agent to control the chain length. A good agreement was found between the various methods used for kinetic determination and oligomer characterization (1H NMR, sulfur analysis, vapor pressure osmometry, acidimetry, GPC). Values of kpkt‐1/2, transfer constants for thiol 8 and solvent, nature of chain ends, polydispersity, and molecular weight were determined. Polymer fractionation was successfully performed using different solvents for recovery.
Oligomères amphiphiles obtenus par voie radicalaire, 2. Propriétés stabilisantes de latex d'oligomères de l'acide acrylique à extrémité dodécylthio
Authors: Cellard Bernard , Pichot Christian , Revillon André
Published: April 2003

The efficiency of oligomeric acrylic acid with dodecylthio chain ends as emulsifier for stabilizing polymer emulsions (polystyrene as standard and vinyl acetate‐butyl acrylate copolymer latexes) against monovalent (NaCl) and divalent (CaCl2) electrolytes was tested. Oligomers which were not neutralized were found to impart effective stabilization in the presence of both electrolytes. In the case of the potassium salts, a strong stabilization was obtained against NaCl, but a poor one against CaCl2. It appeared that the polymer polarity was of minor importance for controlling the phenomenon. Stability results are interpreted in terms of differences in oligomer adsorption at the water‐polymer interface high ionic charge densities (as expected with the neutralized oligomers), and the steric effect of the hydrophilic sequence in the adsorbed oligomer layer.
Über enzymanalog gebaute polymere, 15. Über die synthese von (R)‐ und von (S)‐1‐(4‐vinylopohenyl)ethylamin und einiger anderer monomere mit funktionellen gruppen
Authors: Wulff Günter , Gimpel Jürgen , Feld Jochen , Hufnagel Ingo
Published: April 2003

The synthesis of a number of new polymerizable monomers containing functional groups is reported [(R)‐ and (S)‐1‐(4‐vinylphenyl)ethylamine (R)‐5 and (S)‐5, (R), (S)‐N,N‐dimethyl‐1‐(4‐vinylphenyl)ethylamine ((R),(S)‐6, (R), (S)‐trimethyl‐1‐(4‐vinylphenyl)ethylammonium iodide ((R),(S)‐7), dihydroxy‐6‐indenylborane (9), and (S)‐2‐(6‐indentyl)‐4‐methyl‐1,3,2‐dioxaborolane (10)]. By racemic resolution optically pure (R)‐ as well as (S)‐1(4‐vinylphenyl)ethylamine could be obtained. Furthermore dihydroxy(4,6‐dimethyl‐7‐indeyl)borane (11) was synthesized. The products were characterized by NMR spectroscopy.
Configurational characteristics of the polysulfides, 1. Dipole moments of poly(pentamethylene sulfide)
Authors: Riande E. , Guzman J. , Welsh W. J. , Mark J. E.
Published: April 2003

Poly(pentamethylene sulfide)

Structure‐based name: poly(thiopentamethylene).

(P5MS) [S(CH2)5]x was prepared by the condensation polymerization of nearly equimolar amounts of pentamethylene dibromide and the sodium salt of 1,5‐pentanedithiol. Selective precipitations were used to obtain a fraction of the polymer, and dielectric constant measurements on solutions of it in benzene were used to obtain dipole moments over the range 20–60°C. Rotational isomeric state calculations based on conformational energies obtained from semiempirical potential energy functions gave results in fair agreement with experiment. Since extensive previous studies on a number of polyoxides have demonstrated the difficulty in calculating the energy of the O…CH2 interactions, the energy of the corresponding S…CH2 interactions in P5MS was adjusted to obtain better agreement between theory and experiment.
Selective step‐growth phenol‐aldehyde polymerization, 1. Synthesis, characterization and X‐ray analysis of linear all‐ortho oligonuclear phenolic compounds
Authors: Casiraghi Giovanni , Cornia Mara , Sartori Giovanni , Casnati Giuseppe , Bocchi Vittorio , Andreetti Giovanni Dario
Published: April 2003

The series of dinuclear to nonanuclear all‐ortho methylene‐bridged oligophenols 2–9 has been synthesized according to a repetitive reaction sequence involving the C‐ortho regiospecific condensation of appropriate phenoxymagnesium precursors with salicyl alcohol or paraformaldehyde. IR, UV, mass, 1H and 13C NMR characteristics of these oligomers are discussed. X‐ray crystal structures of 2, 3, and 4 are also reported.
Synthesis of block copolymers containing a carbon chain and a polypeptide block
Authors: Vlasov Gennadij P. , Rudkovskaya Galina D. , Ovsyannikova Lujdmila A.
Published: April 2003

The bifunctional initiators, bis(2‐glycylaminophenyl) disulfide (1) and 2, 2′‐azo‐2,2′‐dimethyl‐dipropionohydrazide (2), were used to obtain polymeric initiators of two types: carbon chain initiators with amino end groups initiating the polymerization of amino acid N‐carboxyanhydrides (NCAs) and symmetric polypeptide initiators containing SS or NN groups, which decompose on exposure to UV light or elevated temperature forming free radicals. These polymeric initiators were used to synthesize block copolymers (BC) containing carbon chain and polypeptide blocks of ABA and AB structures. It is shown that AB block copolymers are capable of aggregation to a much higher extent than those of ABA type. These BC can form liquid‐crystalline polymer structures and undergo controlled biodegradation by enzymes.
Active centre determination in Ziegler‐Natta polymerization. A direct catalyst characterisation method
Authors: Burfield David R.
Published: April 2003

In contrast to conventional approaches to active centre determination in Ziegler‐Natta polymerization, a method is proposed whereby the active catalyst rather than the polymerization system as a whole is studied. The method is based on the observation that addition of non‐polymerizable olefins such as α‐methylstyrene to catalyst systems promoted with Al(iBu)3 leads to displacement of isobutene from the active sites. Active site concentration are derived from quantitative determination of liberated isobutene or labelled cumene derived by quenching the treated catalyst with [O‐3‐H]‐methanol. Values of active site concentration were found to be of the order of 0,3 mmol per mol of V and 2,6 mmol per mol of Ti for VCl3 and TiCl3. AA catalysts, respectively.
Über polyarylenalkenylene und polyheteroarylenalkenylene, 13. Synthesen und charakterisierung von poly (dithieno[3,2‐b: 2′, 2′,3′‐d]thiophen‐2, 6‐diylvinylenarylenvinylen)en und einigen modellverbindungen
Authors: Koßmehl Gerhard , Beimling Peter , Manecke George
Published: April 2003

From Witting‐reactions of dithieno[3,2‐b: 2′, 3′‐d]thiophene‐2, 6‐dicarboxaldephyde (1) with “mono‐and bis‐Wittig‐salts” of the benzene and thiophene series poly(dithieno[3,2‐b: 2′,3′‐d]‐thiophene‐2,6‐diylvinylenearylenevinylene)s 3a—c and some model compounds 5a—c were obtained. Wittig‐reactions of dithieno[3,2‐b: 2′,3‐d]thiophene‐2‐carboxaldehyde (6) with “mono‐and bis‐Wittig‐salts” gave model compounds 7a—c and 8a, c. The structures of all compounds were confirmed by elements analyses, IR‐and electronic spectra, those of the model compounds additionally by mass spectra, and in case of sufficient solubility by 1 H NMR spectra. The electrical conductivities of all compounds and the thermooxidactive degradation of the polymers 3a, c were investigated.
Electric field‐induced instabilities in nematic and cholesteric polyesters
Authors: Corazza Paola , Sartirana Maria Luisa , Valenti Barbara
Published: April 2003

Electric field‐induced instabilities are investigated in the thermotropic mesophases of polyesters synthesized from 4,4′‐isopropenylenediphenol and adipic acid (polyester 1) or adipic acid and (+)‐3‐methyladipic acid (50:50) (copolyester 2). D. C. and low frequency A. C. voltages are applied. Polyester 1 behaves like a conductive nematogen with negative dielectric anisotropy. The Williams domain pattern and the dynamic scattering mode are observed; at about 5 kHz the existence of a cut‐off frequency is foreseen. According to the behavior of low molecular weight cholesterics, copolyester 2 goes from a predominantly planar texture to a focal conic one when the electric field is applied parallel to the helical axis of the planar texture. Periodic perturbations arise in polyester 1 doped with cholesteric copolyester 2 when the field is applied perpendicular to a cholesteric planar texture with oily streaks. The frequency dependence of the threshold voltage Vt for square grid is reported. As in nematic polyester 1 at about 5–10 kHz Vt appears to diverge. The behavior above Vt is in line with the results reported for low molecular weight nematic‐cholesteric mixtures with εa < 0. The square grid pattern is replaced by the tilted polygonal texture which relaxes when the field is turned‐off. Due to the higher viscosity of the polymer the recovery of the planar texture is slower than in the case of conventional mesogens.
Dependence of the long period of nylon 6 on annealing time
Authors: Hirami Matsuo
Published: April 2003

Changes in the thickness L of lamellar crystals with annealing time on heat treatment at 200–215°C for an unoriented film (I) and a drawn yarn (II) of nylon 6 are studied by small angle X‐ray diffraction (SAXD). For sample I, both the spacing (i.e. the thickness L) and the intensity of the diffraction peak in a SAXD diagram increase abruptly within ca. 1 min, and then remain constant, while for sample II, they continue to increase slowly over a wide range of annealing time (≈ 100 h). The features found for sample I are discussed in terms of chain translational mechanisms in comparison with other polymers such as polyethylene and poly(ethylene terephthalate). From the features found for sample II, the effect of the initial orientation of the polymer on the thickening behavior of lamellar crystals is estimated. It is concluded that the restriction of molecular chain movement results in the retarded thickening behavior during the annealing process.
The molecular structure of diphenylmethyl methacrylate
Authors: Kageyama Hiroyuki , Miki Kunio , Tanaka Nobuo , Kasai Nobutami , Okamoto Yoshio , Hatada Koichi , Yuki Heimei
Published: April 2003

The molecular structure of diphenylmethyl methacrylate has been determined by means of X‐ray diffraction. Crystals are monoclinic, space group C2/c, a = 29, 177 (2), b = 6,017(1), c = 16,110(1) Å, β = 96,840(5)°, and Z = 8. The structure was solved by the direct method and refined by the block‐diagonal least‐squares procedure to R = 0,071 (Rw = 0,091) for 1768 measured reflections. The molecule has an antiperiplanar conformation as to the CC and CO double bonds about the C(1)C(2) bond and a synperiplanar conformation as to the CO and CO bonds about C(1)O(1).
Télomères monofonctionnels du chlorure de vinyle, 3. Cinétique par catalyse rédox
Authors: Boutevin Bernard , Piétrasanta Yves , Taha Mohamed
Published: April 2003

A kinetic study of the redox telomerization of vinyl chloride with carbon tetrachloride was carried out. Transfer constants of PVC to the metallic ion (CFen), initiation rate (ki), and functionnality of the resulting telomers were measured. Instantaneous and cumulated polymerization degrees, (DPn)i and (DPn)cum were determined with the help of a theoretical study. These constants provide a rigorous control of the telomerization of vinyl chloride with RCCl3, (R containing an alcohol or ester group).
Correlation of data on preferential sorption using the modified flory‐huggins equation
Authors: Pouchlý Julius , Živný Antonín
Published: April 2003

An equation derived from the Flory‐Huggins relation with the concentration‐dependent interaction parameters gij and the ternary parameter gT was used in the correlation of reported data on the preferential sorption in macromolecular coils. A linear plot was suggested, assuming that the dependence of gT on the composition of the mixed solvent resembles that of g12, i.e. gT(u1) = ag g12(u1). Linear correlation could be carried out in 19 ternary systems out of 22, and the correlation constants were used to calculate the difference of interaction parameters g13 − (V1/V2)g23 and the proportionality constant ag. For most systems, ag is positive and smaller than unity; for systems containing chloroform it approaches zero. The difference between the interaction parameters gij and the interaction parameters χij is discussed. A comparison between the difference g13−(V1/V2)g23 obtained by a linear correlation of data on preferential sorption with the values calculated using data on the respective binary systems was possible only for the system benzene/cyclohexane/polystyrene; the fit was very good. It is shown how the individual parameters of the Flory‐Huggins equation affect the occurrence, position and type of inversion in preferential sorption.
On the principle of equal reactivity in solution polycondensation
Authors: Kuchanov S. I. , Keshtov M. L. , Halatur P. G. , Vasnev V. A. , Vinogradova S. V. , Korshak V. V.
Published: April 2003

The influence of the degree of polymerization of oligomers (1 ≤ l ≤ 50) on the reactivity of the OH endgroups is exemplified by the reaction of oligoterephthalates of phenolphthalein with benzoyl chloride under ϑ‐conditions. It is found that with increasing chain length l the hydroxyl group activity increases according to an S‐form law. It is suggested that the ester groups of the macromolecule influence the activity of the OH endgroups due to solvation effects. This suggestion is confirmed theoretically and experimentally.
Zur polymerisation von methylmethacrylat bis zu hohen umsätzen: Experimentelle untersuchungen zur theorie des trommsdorff‐effektes nach cardenas und o'driscoll
Authors: Panke Dietrich , Stickler Manfred , Wunderlich Winfried
Published: April 2003

The kinetic model given by Cardenas and O'Driscoll, which describes the bulk polymerization of methyl methacrylate (MMA) in the region of the gel effect by the concept of chain entanglements, is extended to the region of the glass effect in accordance with a proposition made by Marten and Hamielec based on the free volume theory. Equations for the calculation of the instantaneous and cumulative molecular weight distributions are derived, too. Dilatometric measurements over the entire conversion range were performed at various temperatures and with three different initiators. For each series of measurements the three adjustable parameters of the extended model were fitted to the time‐conversion data. Contrary to the assumptions, it was then found that at least one of the parameters of the model of Cardenas and O'Driscoll (α0) depends both on the concentration and the type of the initiator. The calculated molecular weight distributions are much broader than the experimental ones. Thus the model of Cardenas and O'Driscoll at its present state does not seem to describe adequately the real polymerization behavior of MMA.
Synthèse de polysiloxanes organofonctionnels, 1. Chloration des poly(diméthylsiloxane)s par le chlorure de sulfuryle
Authors: Reyx Danièle , Guillaume Pierre
Published: April 2003

Sulfuryl chloride was used as chlorination agent of poly(dimethylsiloxane)s (1) in order to obtain poly(dimethylsiloxane‐co‐chloromethylmethylsiloxane) and it was found to be more specific than molecular chlorine. Identification of chlorinated and chlorosulfonated units was shown to be possible by comparison of the results of 1H NMR spectroscopy with those obtained by GLC analysis of the mixtures obtained from octamethylcyclotetrasiloxane (2). After having shown that the distribution of the various types of methyl groups in 1 and 2, modified in this way, fits correctly a binomial law and that chlorosulfonated units can be hydrolysed, copolymers containing 20 to 25% of chloromethylated units and less than 2% of unwanted dichloromethylated units are accessible by use of this chlorination agent.
Fixation sur cellulose de médicaments libérables par voie enzymatique
Authors: Lapicque Françoise , Dellacherie Edith
Published: April 2003

As an approach to the programmed release of drugs a polymeric carrier (1) from which the drug would be liberated by the degradation of definite covalent chemical bonds by means of specific enzymes, was synthesized by coupling pholcodine (2), an antitussive drug, with an insoluble, physiologically inert polymer, cellulose, using L‐phenylalanine as a spacer arm. As chemical bond between drug and amino acid an ester function was chosen linking the hydroxyl group of 2 and the carboxylic end of L‐phenylalanine. This linkage is not hydrolyzed in simulated digestive fluids containing pepsin or trypsin; it is only broken in the presence of α‐chymotrypsin to release slowly the parent drug.
New polymer syntheses, 7. Synthesis and characterization of oligomeric and high molecular weight poly(4‐hydroxybenzoate)
Authors: Kricheldorf Hans R. , Schwarz Gert
Published: April 2003

Poly(4‐hydroxybenzoate) was prepared under a variety of reaction conditions. In addition to using the well‐known monomers 4‐acetoxybenzoic acid and phenyl 4‐hydroxybenzoate, p‐tolyl 4‐hydroxybenzoate, 4‐pivaloyloxybenzoic acid, and 4‐trimethylsiloxybenzoyl chloride were also condensed. A new routine method for the determination of number average molecular weights (M̄n) was developed, namely 1H NMR spectroscopic end‐groups analysis of hydrolyzed poly‐(4‐hydroxybenzoate). By means of this technique, the relationships between monomer structure or reaction conditions, on the one hand, and the polymerization mechanism and polymer properties (e.g. M̄n), on the other hand, were investigated. Whereas bulk condensations yield molecular weights of less than 10 000, polycondensations in solution may lead to values in the range of 20000 – 50000. The best results with respect to both yield and M̄n were obtained with 4‐acetoxybenzoic acid and 4‐trimethylsiloxybenzoyl chloride. Regardless of the nature of the monomer, condensations in solution lead at first to precipitation of oligomer crystals with D̄P̄'s in the range of 6–8. Due to intra‐ and intercrystalline transesterifications, chain growth continues in these oligomer crystals even in the absence of monomer or solvent. New reaction mechanisms are discussed. Depending on the nature of the monomer and the reaction conditions, poly(4‐hydroxybenzoate) can adopt various crystal modifications. The thermal stability depends on both the degree of polymerization and crystal modifications.
Synthèse de cotélomères photoréticulables, 6. Utilisation de cotélomères biséquencés
Authors: Boutevin Bernard , Maliszewicz Marc
Published: April 2003

Photocrosslinkable block cotelomers were synthesized in three steps. In the first step a monomer M1 was telomerized with carbon tetrachloride or chloroform, in the second step a monomer M2 with the resulting macrotelogen, and in the third step the hydroxyl groups were esterified by cinnamic acid or acrylic acid. These reactions were carried out with ethyl acrylate (M1)/CCl4 by redox catalysis and subsequently with vinyl acetate (M2) by free radical initiation, or with vinyl acetate (M1)/CHCl3 by free radical initiation and subsequently with isoprene (M2) by redox catalysis, or with 2‐hydroxyethyl acrylate (M1)/CCl4 by redox catalysis, and subsequently with isoprene (M2) by redox catalysis.
Determination of absolute rate constants for radical polymerization and copolymerization of ethyl α‐cyanoacrylate in the presence of effective inhibitors against anionic polymerization
Authors: Yamada Bunichiro , Yoshioka Minoru , Otsu Takayuki
Published: April 2003

The absolute rate constants of propagation kp and of termination kt of ethyl α‐cyanoacrylate (ECNA) were determined in bulk at 30°C by means of the rotating sector method under conditions to suppress anionic polymerization; kp = 1 622 1 · mol−1 · s−1 and kt = 4,11 · 108 1 · mol−1 · s−1 for the polymerization in the presence of acetic acid, and kp = 1610 1 · mol−1 · s−1 and kt = 4,04 · 108 l · mol−1 · s−1 for the polymerization in the presence of 1,3‐propanesultone. The magnitude of k/kt determined was 6,39 · 10−3 l · mol−1 · s−1. The absolute rate constants for cross‐propagation in ECNA copolymerizations were also evaluated. Quantitative comparison of the rate constants with those of common monomers and polymer radicals shows that the strong electron‐withdrawing power of the ethoxycarbonyl and cyano groups enable the poly(ECNA) radical to add to monomers as fast as the other polymer radicals. The relatively high reactivity of ECNA, regardless of the type of attacking polymer radical, is interpreted by a transition state greatly stabilized by both the ethoxycarbonyl and the cyano groups.
On the trifluoracetylation reaction of polyamides and polyurethanes
Authors: Biagini Emilio , Gattiglia Ercole , Pedemonte Enrico , Russo Saverio
Published: April 2003

The kinetics and yields of N‐trifluoracetylation of polyamides, polyesteramides, polyurethanes were studied by direct titration of trifluoracetic acid formed during the conversion. For polycaprolactam a limiting yield, corresponding to a complete substitution, was always achieved, independently of polymer molecular mass. The functionalization was equally effective on ultra high molecular masses or “gels”, as well as on low molecular mass compounds (monomer and higher oligomers), making possible their fast detection in any polycaprolactam sample. As the reaction starts and proceeds for most of its time in the heterogeneous phase, the substitution rate was found to be strongly dependent on the size of polymer particles. Extension of the above reaction to polyurethanes revealed that they react much slower than aliphatic polyamides, showing relevant differences in the behaviour of aromatic and aliphatic moieties.
On the thermal mobility of the amino end groups of polyamides 6 and 6,6
Authors: Schmitz Franz P. , Mroszewski Klaus‐Dieter , Rossbach Volker
Published: April 2003

Samples of polyamides 6 and 6,6 were reacted with the bifunctional reagent 1,5‐difluoro2,4‐dinitrobenzene at different temperatures in heterogeneous phase (swelling agents: 1,4‐dioxane/water and acetone/water). From the yields determined experimentally for the mono‐and bifunctional reaction of the reagent with the amino end groups of the polyamides the activation energies for the motion of the amino end groups were determined. The values are 30 to 67 kj/mol for the system acetone/water and 15 to 22 kj/mol for the system 1,4‐dioxane/water. Additionally, for both reaction media calculations were made to determine relative values of the temperatures at which the amino end groups are beginning to move.
Conformational analysis of polyoxyethylene using empirical force field methods
Authors: Miyasaka Taira , Yoshida Takaichi , Imamura Yoshio
Published: April 2003

Conformanational energies of various oligo (oxyethylene) isomers were calculated by the empirical force field method, and statistical mechanics calculations of the chain dimensions and the dipole moments were carried out. The results are seriously different from those obtained for poly (oxymethylene). Although the first‐order steric interactions in POE are of the same order of magnitude as those in n‐alkane chains, the second‐order interactions are significantly different. The second‐order interactions arising from rotations around two consecutive bonds of OCH2CH2OCH2 in g± g∓ conformation have greatly reduced steric repulsions. It was found that the reduced second‐order interaction plays an important role in the configurationdependent properties of POE. The agreement of the calculated values for the unperturbed dimensions and the temperature coefficients obtained from the force field method with experimentally observed ones is fairly good.
Interpenetration of spherulites in polymer blends
Authors: Gałȩski Andrzej , Grȩbowicz Janusz , Kryszewski Marian
Published: April 2003

When poly(oxymethylene) is doped with increasing amounts of low molecular weight poly(oxyethylene), a stepwise disappearance of the boundaries between the spherulites is observed. At a poly(oxyethylene) content of 5 wt.‐%, the replica of a bulk sample viewed in an electron microscope seems to have only centers of spherulites and slightly marked boundaries between them. A more careful examination of the replica shows that this effect is due to strong interpenetration of the lamellae of the adjacent spherulities of poly(oxymethylene). It is well known that the mechanical properties of many two‐component systems are improved by adding small amounts of a second component. On the basis of our observations it is possible to correlate the interpenetration of spherulites with the improvement of some mechanical properties of bulk samples. Interpenetration is possible when two “hollow” dendritic spherulites are brought into contact. Such a change of the spherulite structure by an additive is due to a rejection of the additive into interlamellar regions.
Structure and hydrodynamic properties of poly[styrene‐b‐(ethene‐co‐butene)‐b‐styrene] micelles in 1,4‐dioxane
Authors: Tuzar Zdeněk , Pleštil Josef , Koňák Čestmír , Hlavatá Drahomíra , Sikora A.
Published: April 2003

Three‐block copolymers poly[styrene‐b‐(ethene‐co‐butene)‐b‐styrene], where the middle aliphatic block amounts to about 70 wt.‐%, form micelles in 1,4‐dioxane with an aliphatic core and a polystyrene shell. The basic characteristics concerning the ratio unimer/micelles, the micellar molar mass, the radius of gyration, and the hydrodynamic radius were determined by combining the results of light scattering, small‐angle X‐ray scattering, photon correlation spectroscopy, osmometry, and viscometry. The characteristics of the micelles, approximated by the model of concentric spheres, were calculated from the data of light scattering and small‐angle X‐ray scattering. From a comparison of the geometric and hydrodynamic dimensions of the micelles it follows that in dilute solutions they behave like rigid spheres.
Kinetics of ϵ‐caprolactone polymerization and formation of cyclic oligomers
Authors: Sosnowski Stanisław , Słomkowski Stanisław , Penczek Stanisław , Reibel Leonard
Published: April 2003

The kinetics of the anionic polymerization of ϵ‐caprolactone, including the kinetics of macrocyclization and the kinetics of macrocycles propagation in THF solution, initiated with (CH3)3SiONa, were investigated. Rate constants of propagation (kp(n)) and of back‐biting (kd(n)) involving monomer and cyclic oligomers (macrocycles) with n = 2, 3, … monomeric units were determined for n ≤ 7. It was found that starting from the tetramer kd(n) ∼ n−1,4±0,1 and kp(n) ∼ n0,7±0,15 (in Jacobson‐Stockmayer's theory kp(n) ∼ n). This discrepancy is explained in terms of “conformational hindrance”, increasing for small cycles with the increase of the ring size until a certain ring size is reached. This hindrance decreases the availability of some of the ester groups in the macrocyclics for attack of the growing species, lowering in this way the exponent in the dependence of kp(n) on n from one to a lower value.
Elementary reactions in the cationic polymerization of oxepane. Comparison with the polymerization of tetrahydromfuran
Authors: Baran Teresa , Brzezińska Krystyna , Matyjaszewski Krzysztof , Penczek Stanisław
Published: April 2003

In the polymerization of oxepane (OXP), initiated with derivatives of trifluoromethanesulfonic acid, covalent and ionic active centers were simultaneously observed by 1H and 19F NMR spectroscopy. A higher proportion of secondary oxonium ions (these species detected by 19F NMR were independently observed by proton trapping with R3P in the 31P NMR spectrum). The proportion of ionic species decreases with monomer conversion, indicating a substantial contribution of bimolecular ionization of the monomer. The effective molarity in oxepane polymerization [OXP]eff ⋍ 1 mol ·I‐1 was found to be lower by a factor of 102 than [THF]eff in the polymerization of THF. The rate constant of the covalent propagation in the polymerization of OXP is similar to that measured for THF, however, due to the reduced reactivity of the oxepanium cation, the relative reactivity of the covalent active centers becomes higher than that of the ions. Thus, for OXP, in CH3NO2 at 25°C, Kpc = 3 · 10−4 mol−1 · 1 · s−1, kpi = 2 · 10−4 mol−1 · 1 · s−1 whereas for THF kpc = 5 · 10−4 mol−1 · 1 · s−1 and kpi = 2 · 10−2 mol−1 · 1 · s−1 under similar conditions. The rates of ionization and temporary termination, measured by the “temperature jump” technique, allow to determine the contributions of inter‐and intramolecular ionizations. These rates becomes equal at [OXP] = 1 mol · 1‐1 (= [OXP]eff).
Robust matrix 𝒟U‐stability analysis
Authors: Bachelier O. , Mehdi D.
Published: April 2003

In this paper, the problem of robust matrix root‐clustering is addressed. The studied matrices are subject to both polytopic and unstructured uncertainties. An original point is the large choice of clustering regions enabled by the proposed approach since these regions can be unions of possibly disjoint and non‐symmetric subregions of the complex plane. The precise purpose is, considering a specified polytope, to determine the greatest robustness bound on the unstructured uncertainty such that robust matrix root‐clustering is ensured. To reduce conservatism in the derivation of the bound, the reasoning relies on a framework based upon parameter‐dependent Lyapunov functions. The bound value is computed by solving an ℒ︁ ℳ︁ ℐ problem. Copyright © 2003 John Wiley & Sons, Ltd.
Is vaginal dermoid cyst a rare occurrence or a misnomer? A case report and review of the literature
Authors: Siu S.‐S. N. , Tam W.‐H. , To K.‐F. , Yuen P.‐M.
Published: April 2003

Vaginal dermoid cyst is a rare finding. Preoperative diagnosis of this lesion is difficult as the sonographic features are similar to those of an epidermal inclusion cyst. We report a case of vaginal dermoid cyst and present its sonographic characteristics. Copyright © 2003 ISUOG. Published by John Wiley & Sons, Ltd.
Allgemeines und spezifisches Mogeln in der Schule
Authors: Rost Detlef H. , Sparfeldt Jörn R.
Published: April 2003

Zusammenfassung. Beziehungen zwischen allgemeinem (schulfachübergreifendem) Mogeln und Subfacetten schulischen Mogelns sind von besonderem pädagogisch-psychologischem Interesse. Dimensionsanalysen bei Gymnasiasten der 8. bis 10. Jahrgangsstufen (N = 524, aus 25 Gymnasialklassen) belegen, dass sich schulische Mogelfacetten teilweise schulfachgruppenspezifisch (Mathematik/Physik vs. Deutsch/Geschichte) und teilweise schulfachübergreifend gruppieren. Die Beziehungen zu Zensuren, akademischem Selbstkonzept und Interessen deuten für das allgemeine schulfachübergreifende Mogeln in die - erwartete - negative Richtung und weisen für die Subfacetten auf konvergente/divergente Validität hin. Allgemeines schulfachübergreifendes Mogeln ist regressionsanalytisch gut aus vier Subfacetten vorhersagbar (R2 = .64).
Romanian Psychology on the International Psychological Scene: A Preliminary Critical and Empirical Appraisal
Authors: David Daniel , Moore Mark , Domuta Anca
Published: April 2003

This study directly evaluates the visibility and the impact of Romanian academic psychology on the international scene using bibliometric indicators from the PsychoINFO, the MEDLINE, and the Institute for Scientific Information (ISI). It is also intended to use this evaluation of its international impact as an indirect estimate of the quality of Romanian academic psychology and to allow a consideration of future possible directions in its development. Such information would be useful for Romanian psychology programs in making future developmental policy and would further also be informative for our international colleagues in choosing Romanian partners for various projects and for the international institutions for a better allocation of the international psychological resources. The preliminary conclusion is that although Romanian psychology is visible—an important point, considering the obstacles during the communist period—its products (i.e., publications) are still less competitive and play a minor role in international psychology. A supplementary analysis identifies the major players in Romanian academic psychology and in clinical psychology.
Domain-selective small-molecule inhibitor of histone deacetylase 6 (HDAC6)-mediated tubulin deacetylation
Authors: Haggarty Stephen J. , Koeller Kathryn M. , Wong Jason C. , Grozinger Christina M. , Schreiber Stuart L.
Published: April 2003

Protein acetylation, especially histone acetylation, is the subject of both research and clinical investigation. At least four small-molecule histone deacetylase inhibitors are currently in clinical trials for the treatment of cancer. These and other inhibitors also affect microtubule acetylation. A multidimensional, chemical genetic screen of 7,392 small molecules was used to discover “tubacin,” which inhibits α-tubulin deacetylation in mammalian cells. Tubacin does not affect the level of histone acetylation, gene-expression patterns, or cell-cycle progression. We provide evidence that class II histone deacetylase 6 (HDAC6) is the intracellular target of tubacin. Only one of the two catalytic domains of HDAC6 possesses tubulin deacetylase activity, and only this domain is bound by tubacin. Tubacin treatment did not affect the stability of microtubules but did decrease cell motility. HDAC6 overexpression disrupted the localization of p58, a protein that mediates binding of Golgi elements to microtubules. Our results highlight the role of α-tubulin acetylation in mediating the localization of microtubule-associated proteins. They also suggest that small molecules that selectively inhibit HDAC6-mediated α-tubulin deacetylation, a first example of which is tubacin, might have therapeutic applications as antimetastatic and antiangiogenic agents.