bluuebunny/crossref_metadata_2025_split huggingface dataset:
Studies on chitosan‐induced metachromasy, 1. Metachromatic behaviour of sodium 2′‐hydroxy‐1,1′‐azonaphthalene‐4‐sulfonate in the presence of chitosan
Authors: Gummow Beryl D. , Roberts George A. F. 
Published: April 2003

AbstractSolutions of chitosan in dilute acetic acid are shown to induce a metachromatic effect in the visible spectrum of the anionic dye sodium 2′‐hydroxy‐1,1′‐azonaphthalene‐4‐sulfonate (3) (C.I. Acid Red 88). The presence of chitosan reduces the intensity of λmax at 505 nm, whilst a new absorption band appears at 450 nm. This change may be observed visually as a change in colour from red to orange, suggesting that it may be of use in histological staining tests. A 1:1 stoichiometry is shown to exist between protonated amine groups on the polymer chain and negatively charged dye ions, at the point where the decrease in λmax reaches a minimum. Quantitative use of the metachromatic effect enables the determination of either the concentration in solution of a chitosan sample of known structure, or the amine group content of a chitosan sample of unknown structure.
Polymerization of propene in the presence of MgCl2‐supported Ziegler‐Natta catalysts, 1. The role of ethyl benzoate as “internal” and “external” base
Authors: Busico Vincenzo , Corradini Paolo , De Martino Luigi , Proto Antonio , Savino Vito , Albizzati Enrico 
Published: April 2003

AbstractThe effect of ethyl benzoate (EB) as a component of the solid catalyst (“internal” base) and/or of the co‐catalyst (“external” base) on propene polymerization in the presence of different MgCl2‐supported Ziegler‐Natta systems was investigated systematically. From the experimental results, it is suggested that internal EB mainly prevents TiCl4 from coordination on the MgCI2 crystal faces where mostly non‐stereospecific active sites would be formed, whereas external EB inhibits selectively the non‐stereospecific centres and decreases the reaction of the alkylaluminium with the internal base. A possible model of active sites for isotactic 1‐alkenes polymerization in the presence of MgCl2‐supported catalysts is presented, which is in good agreement with a large number of known experimental facts.
Moisture‐curable rubbers, 1. Moisture‐cure of halogenated butyl rubbers
Authors: Yamashita Shinzo , Yamada Akira , Ohata Masatoshi , Kohjiya Shinzo 
Published: April 2003

AbstractChlorinated and brominated butyl rubbers (CIIR and BIIR) were each compounded with 3‐aminopropyltriethoxysilane (APS) and dibutyltin dilaurate on a two‐roll mill, and were pressed at 150°C for 20 min. The resulting sheets were cured by soaking them in water. The progress of the moisture‐cure was followed by determining the network‐chain density (νs). The rate of the moisture‐cure was found to depend on the soaking temperature. The resulting maximum vs was, however, independent of the soaking temperature. The kinetic study of the reactions of CIIR and BIIR with APS in toluene revealed that the maximum replacement of the halogen atoms with APS (m) was ≈ 40% in CIIR and ≈ 70% in BIIR. Thus, the apparent cross‐linking efficiency of the moisture‐cure was evaluated from νs and m.
Kinetics and peculiarities of phase separation in the formation of semi‐interpenetrating polymer networks
Authors: Lipatov Yury S. , Grigor'yeva Olga P. , Kovernik Grigory P. , Shilov Valery V. , Sergeyeva Ludmila M. 
Published: April 2003

AbstractThe initial stages of phase separation in the formation of semi‐interpenetrating polymer networks (semi‐IPN's) based on copolymer from styrene with divinylbenzene (DVB)/poly(butyl methacrylate) (PBMA) were studied using an optical laser diffractometer. It was found that phase separation obeys the mechanism of spinodal decomposition. The peculiarity of phase separation in the system studied is due to the existence of a two‐stage process. Each stage exhibits different interdiffusion coefficients, sizes of microheterogeneity areas and activation energies.
Cinétiques de télomérisation, 4. Nouvelle méthode de détermination des constantes de transfert en catalyse radicalaire
Authors: Bauduin Gérard , Boutevin Bernard , Mistral Jean‐Pierre , Sarraf Léna 
Published: April 2003

AbstractFor the determination of transfer constants CT to the telogen in telomerization reactions started with free radicals we used three methods. The first one is the method of Mayo, the second one is based on the variation of the conversion degree of telogen to monomer and the last method requires the knowledge of the cumulated number‐average degree of polymerization DPn and monomer conversion αM of the samples during the reaction. Verifications of the proposed laws are made for methacrylic acid telomerization with CCl3Br and methyl methacrylate telomerization with benzenethiol as a telogen and 2,2′‐azoisobutyronitrile as the initiator at 70°C. The transfer constant to CCl3Br is ca. 0,03 and that to C6H5SH ca. 1,5.
Structures et propriétés diélectriques des poly(α‐acétoxystyréne)s parasubstitués
Authors: Monthéard Jean‐Pierre , Camps Marcel , Belfkira Ahmed , Chatzopoulos Michel , Granger Robert , Jorat Luc , Noyel Gérard 
Published: April 2003

AbstractThe relations between structure and isothermal, dielectric properties of poly(α‐acetoxystyrene)s substituted in para position by OCOCH3 (1a), OCOCH2CH3 (1b), OCOCH2CH2CH3 (1c), OCOC6H5 (1d), OCOCH2CH2Cl (1f) and OCOOCH3 (1g) were studied. The dielectric constants, at 105 Hz and 20 ± 2°C, were found to be: 3,79 (1a), 3,36 (1b), 3,18 (1c), 3,51 (1d), 3,36 (1e), 3,65 (1f) and 3,07 (1g). The polymers 1a–1g do not show any α‐ or β‐transition. Increasing bulkiness of the para substituent gives rise to a decreasing dielectric constant due to an increase of the degree of syndiotacticity, as determined from 1H and 13C NMR spectra.
Selective grafting of hydrogels onto multiphase block copolymers
Authors: De Feng Xin , Voong) (S. T. , Sun Yan Hui , Qiu Kun Yuan 
Published: April 2003

AbstractSelective graft copolymerizations onto different segments of a poly(ether‐urethane) (PEU) by using two different methods, i.e. ceric salt initiation and controlled oxidation, were investigated. By ceric salt initiation the grafting takes place mainly at the hard segment, while the controlled oxidation gives grafted hydrogels at the soft segment. The effects of different factors on graft copolymerization in both methods including ceric salt concentration, monomer concentration, PEU composition and oxidation time were investigated. Another kind of multiphase block copolymers, a poly(ether‐ester), also can be graft‐copolymerized by both methods.
DRIFT study of functional group interconversions on modified silica surfaces
Authors: Davies Julian A. , Sood Anup 
Published: April 2003

AbstractTreatment of surface‐activated silica gel with 4‐(chloromethyl)phenyltrimethoxysilane leads to the formation of a modified silica with pendant benzyl chloride surface functionality. Oxidation of this substrate leads to the formation of surface‐attached benzaldehyde functional groups, whereas reaction with sodium ethanethiolate generates a silica gel modified with surface thioether functionalities. Oxidation of the surface thioether groups produces substrates with pendant sulfoxide or sulfone functional groups, depending upon the reaction conditions. Silica gels with surface thioether or sulfoxide functionalities act as heterogeneous supports for transition metals and both substrates exhibit reactivity in bridge cleavage reactions of [Pt2 (μCl)2Cl2(PPh3)2]. All surface‐modified silica gels were characterized by diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, in conjunction with other techniques. The DRIFT method is shown to be a powerful tool for the characterization of low volume concentration, surface‐modified, insoluble substrates.
Electrochemical polymerization of dithienylethylene, ‐butadiene, and ‐hexatriene
Authors: Tanaka Susumu , Sato Masa‐aki , Kaeriyama Kyoji 
Published: April 2003

AbstractConductive poly[(2,2′‐bithiophene‐5,5′‐diyl)‐(1,3‐butadienylene)] (1b) and poly[(2,2′‐bithiophene‐5,5′‐diyl)‐(1,3,5‐hexatrienylene)] (1c) films were obtained from the electrochemical polymerization of the corresponding α,ω‐dithienylpolyenes in the presence of Bu4NClO4 as a supporting electrolyte. These polymers were identified by their IR spectra. The current efficiency was 72 and 82%. Electrochemical polymerization of 1,2‐bis(2‐thienyl)ethylene did not give a film but a powder as product. In the UV spectrum of poly(1b), oxidized with ClO4 as counterion, three bands are observed at 350, 455 and 1 000 nm (shoulder). The last two bands dissappear in the neutral film. ESCA indicates that the S2p peak in symmetrical in the neutral film, but the oxidized films show a shoulder on the higher binding energy side of the peak. The neutral film shows an asymmetrical ESR signal, whereas that of the oxidized one is symmetrical. In air the conductivity decreases to about 20% of the initial value in 70 days, but the neutral film is quite stable.
The influence of molecular interaction on polymerization, 10. On the copolymerization of methacrylic acid with styrene
Authors: Boudevska Hrissanta , Todorova Olga 
Published: April 2003

AbstractFree radical copolymerization of methacrylic acid (MA) with styrene (St) at 60°C, initiated by 2,2′‐azoisobutyronitrile (AIBN) is carried out in hydrogen‐bond forming solvents and in solvents not capable of forming hydrogen bonds but exhibiting different dielectric constants. The influence of the solvent on copolymerization reactivity ratios, rate of polymerization, composition, molecular weight and polydispersity of the copolymers obtained is shown. The reactivity ratios of methacrylic acid rMA and of styrene rSt are determined by two different methods with good agreement. The values obtained by the Kelen‐Tüdös method are as follows:

in carbon tetrachloride: rMA = 0,54 ± 0,01; rSt = 0,06 ± 0,03;
in chloroform: rMA = 0,51 ± 0,01; rSt = 0,08 ± 0,03;
in acetone: rMA = 0,43 ± 0,00; rSt = 0,65 ± 0,02;
in 1,4‐dioxane: rMA = 0,41 ± 0,02; rSt = 0,59 ± 0,05;
in acetonitrile: rMA = 0,06 ± 0,02; rSt = 0,29 ± 0,00.
Changes of reactivity ratios depending on the medium are explained on the basis of the results from IR and 1H NMR spectroscopy and gel permeation chromatography (GPC).
Effect of alcohols on the thermal denaturation and aggregation of arachin at pH 3,6
Authors: Kella Navin Kumar D. , Rao M. S. Sivaraja 
Published: April 2003

AbstractThe effects of three simple aliphatic alcohols, viz., methanol, ethanol and 1‐propanol, on the thermal denaturation and protein‐protein interactions of arachin at pH 3,6 were studied by melting temperature, electrophoresis, UV difference and fluorescence spectral measurements. Alcohols increase the heat‐induced protein‐protein interactions as shown by gel melting temperature and electrophoretic measurements. UV difference and fluorescence spectral measurements revealed that the addition of alcohols to arachin, before and after heating and cooling, enhances its denaturation. The probable explanation for the promotive effect of alcohols on the thermal denaturation and aggregation of arachin is discussed.
NMR study of poly(phthalidylidenearylene)s
Authors: Zolotukhin Mikhail G. , Panasenko Anatoly A. , Sultanova Venera S. , Sedova Elvira A. , Spirikhin Leonid V. , Khalilov Leonard M. , Salazkin Sergei N. , Rafikov Sagid R. 
Published: April 2003

AbstractThe structure of poly(phthalidylidenearylene)s, synthesized by electrophilic substitution reactions, was studied using 1H and 13C NMR spectroscopy. Homopolycondensation of 3‐aryl‐3‐chlorophthalides 1a – d in nitrobenzene leads to para‐substituted linear polymers 2a – d, whereas polycondensation of phthaloyl dichloride and bis[4‐(3‐chloro‐3‐phthalidyl)phenyl] ether (6) with diphenyl ether results in polymers 5 containing irregular units.
On the reactivity of phosphonyl radicals towards olefinic compounds
Authors: Sumiyoshi Takashi , Schnabel Wolfram 
Published: April 2003

AbstractPhosphonyl radicals of the structure OṖR1 (R2) with R1 and R2: C6H5(1); C6H5, OCH(CH3)2(2); CH3, OCH3(4) and OC2H5(5) were generated by UV‐photolysis of appropriate acylphosphine oxides or acylphosphonates which are effective initiators of the free radical polymerization of olefinic compounds. All five radicals are very reactive towards monomers such as methacrylonitrile, styrene and methyl methacrylate (k = 5 · 107 to 2 · 108 1 · mol−1 · s−1), as was found by employing laser flash photolysis techniques. In the cases of acrylonitrile, methyl acrylate, butyl vinyl ether, and vinyl acetate k ranged from 106–107 1 · mol−1 · s−1. The high reactivity of the radicals 1 – 5 is due to their tetrahedral structure. The Q‐e scheme of Alfrey and Price proved useful to recognize trends in the dependence of k on the chemical nature of both phosphonyl radicals and monomers.
Mechanism of chain propagation in “living” polypropylene synthesis. 1H and 13C NMR analyses of chain‐end structures
Authors: Doi Yoshiharu , Nozawa Fumie , Murata Masahide , Suzuki Sigeo , Soga Kazuo 
Published: April 2003

AbstractThe mechanism of chain propagation in the living coordination polymerization of propene initiated by the soluble V(acac)3/Al(C2H5)2Cl catalyst was studied by 1H and 13C NMR analyses of iodine‐terminated polypropylenes of low molecular weights (Mn = 630 to 3200). A vanadium‐carbon bond in the living polypropylene end reacts quantitatively with the iodine molecule to yield a new iodine‐polymer bond. The 1H and 13C NMR analyses of iodine‐bonded polypropylene provide direct evidence on the stereochemistry of the first and last inserted propylene units and the structure of the living polypropylene end.
Preparation and characterization of poly[oxy(2,6‐dimethyl‐1,4‐phenylene)] with functional end groups
Authors: Risse Wilhelm , Heitz Walter , Freitag Dieter , Bottenbruch Ludwig 
Published: April 2003

AbstractThe oxidative polymerization of 2,6‐dimethylphenol (1) and the halogen displacement polymerization of 4‐halo‐2,6‐dimethylphenols (4) yielded poly[oxy(2,6‐dimethyl‐1,4‐phenylene)] (2) with one phenolic end group. 2,2′,6,6′‐Tetramethyl‐4,4′‐isopropylidenediphenol (9a) was used as comonomer in both polymerization reactions to obtain polymer 10a, containing two phenolic end groups. Polymers of different molecular weight were synthesized by variation of the mole ratio of the comonomers. The polymers were characterized by GPC, NMR spectroscopy and end group analysis.
Copolymerization of styrene with α‐chloromaleic anhydride, 2. Spontaneous copolymerization in 1,4‐dioxane
Authors: Nagai Katsutoshi , Akiyama Kazuhiko , Kuramoto Noriyuki 
Published: April 2003

Abstractα‐Chloromaleic anhydride (CMA) copolymerizes spontaneously with styrene (ST) at a higher rate than maleic anhydride (MA), and α,α′ ‐dichloromaleic anhydride (DCMA) does not copolymerize, even in the presence of a radical initiator. The results obtained from the copolymerization of ST with CMA in 1,4‐dioxane in the absence of a radical initiator are as follows: the copolymerization is strongly accelerated by UV‐irradiation; the monomer reactivity ratios of ST and CMA at 60°C are 0,06 and 0,00, respectively; the over‐all activation energy of the copolymerization is 77,4 kJ · mol−1 (18,5 kcal · mol−1); the maximum rate of copolymerization at a constant total monomer concentration is observed at a mole fraction of ST of 0,4 to 0,5. The rate of copolymerization at equimolar feed composition is of second order with respect to the total monomer concentration. From the results obtained here and shown in the preceding paper, it was inferred that initiating radicals for the spontaneous copolymerization are formed through a charge transfer (CT) complex between the comonomers.
Use of organophosphorus(V) sulfides for the modification of propene polymerization catalysts
Authors: Karayannis Nicholas M. , Lee Sam S. 
Published: April 2003

AbstractStudies of various organophosphorus(V) sulfides, including esters of thiophosphoric acid and triorganophosphine sulfides, were evaluated as propene polymerization catalyst modifiers. Among these, triethyl thiophosphate (1a) leads to the best activity‐stereospecificity combinations. Higher alkyl or aryl esters of thiophosphoric acid lead to higher catalyst activities but significantly poorer stereospecificities, relative to 1a, while the latter modifier is advantageous over triaryl‐ or tris(diakylamino)phosphorus sulfides, as far as both activity and stereospecificity are concerned. Organophosphorus(V) sulfides appear to be better modifiers in general than the corresponding oxides. No straightforward correlations of the modifying effects of the preceding compounds to the inductive and steric effects of the substituents on phosphorus were possible, as some of these compounds (namely the thiophosphoryl or phosphoryl alkyl esters) may undergo dealkylation reactions with the components of the catalyst system, yielding alkyl chloride, traces of HCl and alkene, and polymeric metal (Ti3+ or Al3+) complexes with anionic R2POS− ligands. A number of binary modifier (1a plus an additional modifier) packages with attractive performance characteristics were developed. Evaluations of these systems in 2 h bulk propylene polymerizations showed that use of triphenylantimony oxide (8) as additional modifier leads to the best overall catalyst performance (yield: 2636 g/g AA TiCl3; hexane extractables: 0,80%). With the 1a‐collidine (9) modifier package, comparable stereospecificity but substantially lower catalyst activity were realized, while use of bis(tributylin) sulfide (6), tributyl phosphite (7) or 2,5‐dimethyltetrahydrofuran (10) as additional modifiers led to good yields (2650–3000 g/g AA TiCl3) but more than double (1,70–2,00%) the hexane extractables, relative to the 1a–8 modifier system.
Phase separations in binary mixtures of nematic liquid crystal side chain polymers and low‐molar‐mass nematic liquid crystals, 1. Influence of the chemical constitution of the low‐molar‐mass component
Authors: Benthack‐Thoms Heidi , Finkelmann Heino 
Published: April 2003

AbstractPhase diagrams of binary mixtures consisting of a liquid crystal (LC) side chain polymer and low‐molar‐mass liquid crystal compounds are investigated. The pure components are very similar in their chemical constitution and contain the same mesogenic moiety. Both components exhibit a nematic phase. Their miscibility behaviour is drastically influenced by varying the alkyl chain length of the substituent of the low‐molar‐mass LC. With increasing length of the substituent the miscibility becomes smaller in the nematic and also in the isotropic phase and a phase separation takes place with two nematic or two isotropic phases of different composition coexisting.
Aqueous polymerization of vinyl monomers in the presence of surfactants, 2. Methacrylamide
Authors: Bartoň Jaroslav , Juraničová Viera , Vašková Viera 
Published: April 2003

AbstractThe kinetics of the polymerization of methacrylamide initiated by potassium peroxodisulfate in water and 2,2′‐azoisobutyronitrile (AIBN) in a water/ethanol mixture (mass ratio 9/1) were studied in the presence of the emulsifier sodium dodecylphenoxybenzenedisulfonate. The emulsifier was found to affect the relative molecular mass of polymethacrylamide, but it showed no effect on the polymerization rate. The transfer constant to the emulsifier determined amounts to 1,8 · 10−2. The polymerization rate is proportional to the square root of the potassium peroxodisulfate concentration and to the first power of the methacrylamide concentration. During initiation by AIBN, the exponent of the concentration of AIBN in an equation expressing the dependence of the polymerization rate on AIBN concentration amounts to 0,82; the exponent of methacrylamide concentration is equal to 1. The activation energy for the polymerization initiated by K2S2O8 is 67 kJ · mol−1, whereas for the polymerization initiated by AIBN it is 44,0 kJ · mol−1.
Thermotropic liquid‐crystalline polymers, 17. Liquid‐crystalline ordering in the melts of comb‐like macromolecules with mesogenic groups in the side chain. A theoretical model
Authors: Vasilenko Sergei V. , Shibaev Valery P. , Khokhlov Alexei R. 
Published: April 2003

AbstractA theory of orientational ordering in the melts of comb‐like polymers containing mesogenic groups in the side chains is proposed. A variant of the lattice method is used, which was developed in our previous publication for the analysis of the liquid‐crystalline transition in thermotropic polymers with mesogenic groups in the main chain. A full phase diagram for the system under consideration is constructed and the properties of the corresponding phase transition are determined. It is shown that for polymers with mesogenic groups in the side chain the dependence of the behaviour of the macromolecular main chain on the ordering of the mesogenic groups is much weaker than in the case of linear polymers with mesogenic groups in the main chain.
Polymerizable monolayers derived from crown ether surfactants
Authors: Winter Hans‐Jörg , Manecke Georg 
Published: April 2003

AbstractStarting from dibenzo‐18‐crown‐6, 1,10‐diaza‐18‐crown‐6 and 1,7‐diaza‐15‐crown‐5, several crown ether surfactants were synthesized. They all form stable monolayers on water. The methacryloyloxy derivative of 1,10‐bis(3‐dodecyloxy‐2‐hydroxypropyl)‐1,10‐diaza‐18‐crown‐6, 2c, could be polymerized in the monolayer by UV irradiation. This polymerizable crown ether surfactant also forms synthetic vesicles by sonication in water.
Nachweis von teilverträglichkeit in den phasengrenzflächen von polymergemischen mittels IR‐spektroskopie
Authors: Könnecke Klaus 
Published: April 2003

AbstractAmong the various methods for determining compatibility in polymer blends infrared spectroscopy, especially the FT IR method, because of its sensitivity, is a rather simple tool to detect specific interactions as a necessary condition for compatibility in polymer blends. As a special advantage, in addition to hints for compatibility, from FT IR spectroscopy informations about the functional groups involved are obtained. By means of FT IR spectroscopy in blends of poly(oxymethylene) (POM) and polymers with ester groups like poly(methyl methacrylate) (PMMA) or poly(tetramethylene terephthalate) (PBTP) the existence of intermolecular interactions between carbonyl groups and the oxygen atoms of POM can be shown. This gives a possibility to detect very weak interactions which cannot be seen with the usual compatibility methods. Nevertheless, such weak interactions may enhance properties like processing behavior or toughness by an increased adhesion between the brittle matrix polymer and the dispersed elastomer phase in impact modified polymer systems.
Adsorption of poly(4‐tert‐butylphenyl methacrylate) on silica from THF/water
Authors: Gargallo Ligia , Radić Deodato , Sarasúa Manuel 
Published: April 2003

AbstractAdsorption studies of poly(4‐tert‐butylphenyl methacrylate) (PBPh) on silica from a binary solvent (THF/water) are reported. In order to investigate the influence of the composition of the binary solvent on the adsorption of the polymer on a special silica with hydrophobic surface, measurements of the adsorption isotherms were carried out using Aerosil R‐972. The adsorption isotherm of PBPh for the hydrophobic silica/THF solution interface exhibits higher values than the isotherms for hydrophobic silica/aqueous THF solution interfaces. The amount of adsorbed polymer decreases when the water content of the binary mixture increases. The results are discussed in relation to the effects of preferential adsorption of one of the solvents by the polymer.