bluuebunny/crossref_metadata_2025_split huggingface dataset:
On the kinetics of emulsion copolymerization of methyl methacrylate and ethyl acrylate in the presence of hydrocarbons
Authors: Capek Ignác 
Published: April 2003

AbstractThe emulsion copolymerization of methyl methacrylate with ethyl acrylate initiated by ammonium peroxodisulfate in the presence of a blend of anionic and non‐ionic emulsifiers was investigated at 60°C. The polymerization under batch conditions was conducted to both low and high conversion. The kinetics of the emulsion copolymerization was studied in both the absence and the presence of diluents such as toluene and octane. Unexpectedly both diluents strongly reduced the rate of copolymerization. This reduction increased with increasing diluent concentration. The rate of polymerization was found to increase with increasing conversion up to high conversion. The average particle size increased very slightly with increasing concentration of the diluent. The average number of radicals per particle was found to increase with increasing conversion and to decrease with increasing diluent concentration. The decrease of the radical concentration with diluent concentration was attributed to the desorption of monomer radicals from a polymer particle and to the increase of the termination rate. It is proposed that the hydrophilicity of the monomeric radicals is the driving power of the desorption process.
Locus of interaction of dibenzoyl peroxide with radical inhibitors in inverse microemulsions
Authors: Vašková Viera , Hloušková Zuzana , Juraničová Viera , Bartoň Jaroslav 
Published: April 2003

AbstractThe locus of interaction of the oil‐soluble radical initiator dibenzoyl peroxide with inhibitors of various water‐solubility in inverse microemulsion toluene/water in the presence of sodium bis(2‐ethylhexyl)sulfosuccinate (AOT) was studied. It was found that the most probable locus of interaction of dibenzoyl peroxide with water‐soluble Fremy's salt, the predominantly water‐soluble 4‐hydroxy‐2,2,6,6‐tetramethylpiperidin‐1‐N‐oxyl, and/or predominantly oil‐soluble 4‐stearoyloxy‐2,2,6,6‐tetramethylpiperidin‐1‐N‐oxyl in the system under investigation in the presence and/or absence of monomers could be the interlayer between the water micropool and the toluene macrophase.
1H and 13C nuclear magnetic relaxation and molecular motion in solid poly(L‐alanine)
Authors: Fedotov Vladimir D. , Zadihanov Rustem A. , Spěváček Jiří , Straka Jaroslav 
Published: April 2003

AbstractNuclear magnetic relaxation data both for proton and for carbon‐13 nuclei in solid‐powder poly(L‐alanine) are analyzed together, in order to obtain information on the molecular motions in polypeptides. For this analysis the “model‐free” approach is used. Three types of internal motions are determined in the α‐helix conformation of the investigated polymer. An inhomogeneous distribution of correlation times is shown to be inherent in each type of motion. The first type is the methyl group rotation around the symmetry axis with correlation times of about one hundred picoseconds at room temperature. The second type are the small‐amplitude (≈10°) individual oscillations of backbone groups as well as of the axis of the methyl group, with correlation times from ten to one hundred nanoseconds at room temperature. The last type is the α‐helix backbone motion with correlation times of a few microseconds at room temperature and with amplitudes of 20° or more, which possibly represents the cooperative motion of several neighbouring groups in the main chain.
Cationic polymerization of methoxyallene with protonic acids
Authors: Takahashi Tatsuya , Yokozawa Tsutomu , Endo Takeshi 
Published: April 2003

AbstractThe cationic polymerization of methoxyallene (1) was carried out with some protonic acids at −50°C in dichloromethane. Polymer yield and molecular weight increase with the degree of acidity of the protonic acid (CF3CO2H < CH3SO3H < CF3SO3H), whereas the remaining double bond content in the polymer decreases with the acidity of protonic acids. Consequently, to obtain a polymer with high molecular weight and high double bond content (i. e., low degree of side reactions), the polymerization of 1 with medium acidic CH3SO3H gives the best results. It gives a highly unsaturated polymer in moderate yield, which can not be obtained with Lewis acids such as BF3OEt2.
Polymides, 2 Curing characterization and thermally induced polymerization of polyimides based on reverse Diels‐Alder reaction
Authors: Su Ching‐Yie , Lee Yu‐Der 
Published: April 2003

AbstractPolyimides were prepared by the condensation of 3‐phenyltricyclo[6.2.2.02,7]‐2,11‐dodecadienne‐5,6:9,10‐tetracarboxylic dianhydride with diamines. Thermal curing of these polyimides was studied using thermogravimetry, infrared spectroscopy, nuclear magnetic resonance spectroscopy, mass spectroscopy and elemental analyses. The results were compared with those of a model imide compound and a neat dimaleimide. It is proposed that the thermal curing mechanism is controlled by a reverse Diels‐Alder reaction, a three‐dimensional polymer network being formed following the degradation of the polymer. Based on these studies, a three‐dimensional structure is proposed if the curing temperature was over 330°C. The weight loss of isothermal thermogravimetry studies was tentatively used to determine the composition of the crosslinked structure and elemental analyses confirmed the results.
Photochemical behaviour of cinnamoyl‐containing crystalline polymers with comb‐like structure
Authors: Stumpe Joachim , Zaplo Olaf , Kreysig Dieter , Niemann Manfred , Ritter Helmut 
Published: April 2003

AbstractAmorphous and crystalline comb‐like poly(methacrylamides) containing cinnamoyl moieties in the side chain were synthesized and characterized. On UV‐irradiation these polymers and related monomeric model compounds undergo E‐Z photoisomerization, [2 + 2] photocycloaddition and photo‐Fries rearrangement. The competition between these photoreactions was investigated in solution and solid films. The quantum yield of the photocycloaddition and the maximum of conversion of chromophores are much higher in solutions and in films for the crystalline homopolymer compared to the amorphous copolymer. The disappearance of crystallinity caused by isomerization in solution and in films caused by cycloaddition was demonstrated by means of DSC measurements. In films with side‐chain crystallinity the quantum yield of cycloaddition increases with rising temperature but falls drastically above the melting point. The crystallinity of the polymer influences photoreactivity of the cinnamoyl moiety, and, on the other side, photoisomerization and cycloaddition destroy the crystalline order.
Porosity determination of poly[(trimethylolpropane trimethacrylate)‐co‐(methyl methacrylate)] gels
Authors: Schmid Andrea , Flodin Per 
Published: April 2003

AbstractIn this paper we studied the influence of the copolymerization of trimethylolpropane trimethacrylate (TRIM) with methyl methacrylate (MMA) on the pore structure of the resulting gels. TRIM and MMA were suspension‐copolymerized with toluene as pore‐forming agent. All gels have bimodal pore‐size distributions. The size distribution of large pores (r > 50 Å) of the solvent‐free poly(TRIM‐co‐MMA) broadens when the TRIM/MMA ratio decreases. The size distribution of small pores (r < 50 Å) shows sharp maxima for pores with a radius of 20 Å. In the swollen state the separation range for the poly(TRIM‐co‐MMA) particles of polystyrene standards varies with the TRIM/MMA ratio. The results of the porosity measurements of the swollen gels show good agreement with the results obtained from the dry gels. The porosity of the dry gels was studied with scanning electron microscopy, nitrogen adsorption/desroption and mercury porosimetry. The pore‐size distributions of the swollen poly(TRIM‐co‐MMA) gel particles were calculated from the size‐exclusion chromatography (SEC) results.
Multifunctional initiation of lactide polymerization by stannous octoate/pentaerythritol
Authors: Kim Soo Hyun , Han Yang‐Kyoo , Kim Young Ha , Hong Sung Ill 
Published: April 2003

AbstractL‐Lactide was polymerized with stannous 2‐ethylhexanoate (stannous octoate) in the presence of pentaerythritol to investigate multifunctional initiation. The prepared oligomers contain starshaped 4‐arm molecules when the mole ratio of [lactide]/[pentaerythritol] is above 32. The molecular weight of oligomers coincides with the [lactide]/[pentaerythritol] ratio, indicating that pentaerythritol in conjugation with stannous octoate is an initiator for the “living” polymerization of L‐lactide.
Standardized polymerizations of ethylene and propene with bridged and unbridged metallocene derivatives: A comparison
Authors: Kaminsky Walter , Engehausen Rüdiger , Zoumis Konstantin , Spaleck Walter , Rohrmann Jürgen 
Published: April 2003

AbstractEthylene and propene were homopolymerized with 11 different metallocene‐methylalumin‐oxane (MAO) catalysts 1–11 using a constant set of parameters. The catalytic activity of the two unbridged and 9 ansa‐metallocenes as well as the properties of the polymers, such as molecular weight, width of molecular weight distribution, melting point, and, with polypropene, chain microstructure, were investigated. It was found that structure variations of the catalysts cause rather different catalytic behaviour, which further diversifies the performances with the two different monomers. In some cases this comparison allows insight into the nature of the influencing factors.
Stereospecific polymerization of methylthiirane in homogeneous phase, 2. Mechanism of stereoregulation
Authors: Dumas Philippe , Sigwalt Pierre , Guérin Philippe 
Published: April 2003

AbstractIn the living polymerization of methylthiirane initiated with bis(isopropyl‐(S)‐cysteinato)‐cadmium, stereospecificity depends on temperature of propagation, on initiator concentration and also on the length of the growing polymer chain. The kinetics of stereospecific and non‐stereospecific processes are described. In both cases, the order with respect to monomer is equal to zero and that with respect to initiator is one‐half. The stereospecific propagation is proposed to involve cadmium thiolates associated as “dimeric species” and coordinated by both the monomer and by an oligomeric or polymeric chain.
Investigation on the spherulitic morphology of poly(ether‐ether‐ketone)
Authors: Zhang Zhiyi , Zeng Hanmin 
Published: April 2003

AbstractThe spherulitic morphology of poly(ether‐ether‐ketone)Systematic name: poly(oxy‐1, 4‐phenyleneoxy‐1,4‐phenylenecarbonyl‐1,4‐phenylene).
(PEEK) has been studied by using polarizing light microscopy, IR and differential scanning calorimetry. It has been found that in distinct cases the spherulites of PEEK show radiated or banded morphology, which can change from one to another upon thermal treatment. The process was found to be reversible and also affected by the film thickness.
The effect of comonomer composition on the emulsion copolymerization of N,N′‐methylenebis(acrylamide) and an unsaturated polyester
Authors: Capek Ignác 
Published: April 2003

AbstractThe aqueous emulsion copolymerization of N,N′‐methylenebis(acrylamide) (MBA) and an unsaturated polyester (UP) initiated with potassium peroxodisulfate was kinetically investigated at 50°C as a function of comonomer feed compositions. The reaction order with respect to the monomer concentration was found to be proportional to the UP monomer concentration at medium conversions and independent of the UP monomer concentration at low conversions. The high reaction order obtained from the dependence of the particle concentration on UP monomer concentration was attributed to the multifunctionality of UP monomer. At low conversions, an enrichment of the copolymer in UP structural units is observed. The polymerization was suggested to proceed in the aqueous phase, in the UP micelles and in the shell of the polymer particles.
Asymmetric induction arising from the chiral twist of 2,2′‐binaphthyl template in the cyclopolymerization of divinyl ethers
Authors: Yokota Kazuaki , Kakuchi Toyoji , Yamamoto Toshiya , Hasegawa Toshiyuki , Haba Osamu 
Published: April 2003

AbstractCationic cyclopolymerization of divinyl ethers, which were derived from (R)‐ or (S)‐1, 1′‐bi‐2‐naphthol with methyl, phenyl, and bromo groups in the 3,3′‐positions, yielded polymers with changing optical rotation according to the reaction conditions. Model compounds, therefore, corresponding to the three stereoisomeric forms of the constitutional units, i. e., two racemo (R,R‐and S,S‐) forms and one meso form, were synthesized to confirm the origin of changing optical rotation in the polymers. 1H NMR analysis showed that the polymers change their optical rotation due to the configuration, which has a tendency to be preferentially a racemo‐diisotactic structure at higher monomer concentrations and in less polar solvents. The chiral twist of the (R)‐or (S)‐binaphthyl template induces the main chain to form an asymmetric R,R‐ or S,S‐racemo sequence, respectively, in the cyclopolymerization.
The structural order of some novel ionic polymers, 2. Models of molecular packing
Authors: Tsukruk Vladimir , Mischenko Nikolay , Köberle Peter , Laschewsky André 
Published: April 2003

AbstractThe molecular packing and spatial correlations of two isomeric zwitterionic polymethacrylates and one polyacrylate analog are studied by means of X‐ray analysis and conformational calculations. The analysis of the correlation functions and density distribution profiles suggest a double‐layered molecular packing which is discussed for the three polymers investigated, with respect to their different chemical structures. Whereas the zwitterionic polymethacrylates studied exhibit liquid‐like short‐range order, the polyacrylate analog exhibits an ordered double‐layered superstructure.
Doped non‐conjugated polymers with enhanced electrical conductivity
Authors: Schopov Ivan , Sinigerski Vesselin 
Published: April 2003

AbstractIn order to elucidate the dependence of electrical conductivity on conjugation length, polyketones built up of short conjugated aromatic blocks and methylene chains of different length were studied. As obtained, the polymer exhibit very low electrical conductivities of about 10−15 S/cm. Upon doping with iodine the conductivity increases up to 10 orders of magnitude and samples become paramagnetic. The colour turns from yellow to black, and a new absorption maximum appears in UV spectrum at 365 nm characteristic of I3−. The monomers and a model compound do not absorb iodine. In the polymers we assume some ordering of the aromatic moieties, which enables enhanced π‐π interaction. The result could be considered as an extension of the conjugation, thus allowing partial oxidation (doping) and therefrom enhanced conductivity. We explain the doping and the conductivity of polydienes in a simillar way. The conclusion is that extended conjugation along the chain is not a prerequisite for higher conductivity.
Copolymerization of ε‐caprolactone and morpholine‐2,5‐dione derivatives
Authors: Veld Peter J. A. in't , Wei‐Ping Ye , Klap Richard , Dijkstra Pieter J. , Feijen Jan 
Published: April 2003

AbstractNovel biodegradable poly(ester‐amide)s were prepared by ring‐opening copolymerization of ε‐caprolactone and 3‐ and/or 6‐alkyl‐substituted morpholine‐2,5‐dione derivatives. The copolymerizations were carried out in the bulk using stannous octoate as an initiator. Molecular weights of the copolymers ranged from 1,0 · 104 to 8,3 · 104 and decreased with increasing mole fractions of morpholine‐2,5‐dione derivatives in the feed. 13C NMR sequence analysis indicated that the copolymers had a random distribution of ε‐oxycaproyl and depsipeptide units, which resulted from the occurrence of transesterification reactions during copolymerization. The results of the DSC measurements and 13C NMR sequence analysis showed a close relationship between the crystallinity and average length of ε‐oxycaproyl blocks. Copolymers with a mole fraction of depsipeptide units smaller than 0,20 were semi‐crystalline, whereas incorporation of larger amounts of depsipeptide units resulted in amorphous copolymers. The melting point depression as a function of the molar composition of the semi‐crystalline copolymers was in good agreement with the melting point depression predicted by the Baur equation, which indicated the rejection of depsipeptide units from crystals consisting of ε‐oxycaproyl units.
Macromonomers via 1,3,6‐trioxocane polymerization
Authors: Krüger Hartmut , Pasch Harald , Much Helmut , Gancheva Valeria , Velichkova Rumiana 
Published: April 2003

AbstractThe ring‐opening polymerization of 1,3,6‐trioxocane (TO) in the presence of 2‐hydroxyethyl methacrylate (HEMA) leading to macromonomers is described. According to the activated monomer mechanism the oligo(1,3,6‐trioxocane)s are terminated with HEMA‐groups. The obtained macromonomers are non‐uniform in end functionality. With high‐performance liquid chromatography (HPLC) at the critical point of adsorption and supercritical fluid chromatography (SFC) it is possible to characterize the molar mass and functionality distribution of the macromonomers. Using these chromatographic methods functionality uniform fractions are available.
Changes in liquid‐crystalline phase behaviour of some poly[p‐(methacryloyloxyalkyleneoxy)benzoate]s with bromination at the m‐position in the mesogens
Authors: Ferg Ernst , Kühnpast Kurt , Cackovic Hinko , Springer Jürgen , Rodekirch Gerhard , Wolff Dietmar , Rübner Joachim 
Published: April 2003

AbstractThe structural properties of side‐group liquid‐crystalline polymers with large electronegative space‐filling substituents at the mesogenic groups were investigated. The synthesis and characterization of some poly[m‐bromo‐p‐(methacryloyloxyalkyleneoxy)benzoate]s are reported. Their liquid‐crystalline properties were investigated using differential scanning calorimetry and X‐ray diffraction techniques and were compared to some unsubstituted compounds found in the literature. A general decrease in the phase transition temperatures and in the order of the liquid‐crystalline phases for the Br‐substituted compounds was observed. It can be concluded that the liquid‐crystalline properties of polymers with large side‐group substituents at the mesogens can be maintained if long flexible or large electron‐rich end groups are introduced.
Cationic copolymerization of norbornadiene with styrene by AlEtCl2/tert‐butyl chloride catalyst system, 2. Effect of polymerization conditions on “crosslinking” and “polymer linking” reactions
Authors: Sagane Toshihiro , Minami Shuuji 
Published: April 2003

AbstractThe cationic copolymerization of norbornadiene (NBD) and styrene (St) was carried out with the AlEtCl2/tert‐butyl chloride catalyst system under various conditions. Detailed analyses were focused on the effect of reaction conditions on the two types of intermolecular reactions, that is, the “crosslinking” reaction to form an insoluble polymer and the “polymer linking” reaction to form a soluble polymer with a molecular weight higher than that of the non‐crosslinked polymer. The two types of crosslinking processes can explain the unique dependency of the polymer solubility on the NBD/St feed ratio. The “polymer linking” reaction is initiated after complete consumption of the monomers and is strongly affected by the polymerization conditions. For example, longer polymerization time, lower temperature, an initial monomer concentration [M]0 around 1,0–1,5 mol/L, a [t‐BuCl]0/[AlEtCl2]0 ratio around 0,75–1,0 and increasing [AlEtCl2]0 are the factors that facilitate the “polymer linking”.
Synthesis and rheological study of some maleic acid and fumaric acid stereoregular polyesters, 7. Rheological study of copolymerization reaction of configurationally pure unsaturated copolyesters and styrene
Authors: Jaćović Mihailo S. , Djonlagić Jasna , Sepulchre Maurice , Sepulchre Marie‐Odile , Spassky Nicolas 
Published: April 2003

AbstractThe crosslinking copolymerization of styrene and configurationally pure unsaturated copolyesters, containing phthalic acid and maleic or fumaric acid residues, was carried out in a dynamic shear field at a frequency of 6,28 rad · s−1 and ambient temperature. It was found that a clear distinction can be made between gelation and postgelation crosslinking. The former takes place between the onset at G′ ≈︁ G″ (G′, G″: storage and loss shear moduli) and the practical end point at (δG′/δt)max = k0, while the latter represents a first‐order process which is characterized by its rate constant, k1, and the corresponding crosslinking half‐time. The relationship between k0 and k1 was established. It appears that the reaction of the fumarate residues with styrene is much faster than that of the maleate residues. At the same degree of unsaturation of 50 mol‐%, k0 was about seven times higher for the reaction of fumarate copolyester than for the reaction of the maleates.
Viscoelastic properties of poly(dibutyl itaconate) melts
Authors: Hrabar Jova P. , Jaćović Mihailo S. , Velic̆ković Jovan S. 
Published: April 2003

AbstractComplex dynamic viscosities η* of poly(dibutyl itaconate) melts were determined for nonuniform polymers with viscosity‐average molecular weights varying from 8000 to 327000 in the temperature range from 323 to 463 K and the frequency range from 0,1 to 100 rad/s. By applying the time and temperature superposition principle, master curves for the selected reference temperature T0 = 383 K were obtained, permitting the estimation of the Newtonian viscosity in terms of molecular weights. The temperature dependence of viscous flow was analysed by verification of the linearity of the aT shift factor, interpreted via the Williams‐Landel‐Ferry equation. Deviations from linearity were observed only for very low molecular weights M and at the highest temperatures. The activation energy of viscous flow was calculated by applying the concept of absolute reaction rates and the concept of free volume. Good agreement was observed. The linearized η* vs. M dependence changes slope at a critical molar mass Mc = 69000 with exponents of M α = 1,05 below and β = 2,92 above the Mc value in the function η* = f(M). The rheological properties of poly(dibutyl itaconate) are discussed in terms of substituent size and compared to those of other related vinyl polymers.
Synthesis and properties of liquid‐crystalline side‐chain polymers containing β‐diketonato transition metal complexes
Authors: Hanabusa Kenji , Suzuki Takashi , Koyama Toshiki , Shirai Hirofusa 
Published: April 2003

AbstractPolymers (5‐7) containing β‐diketonato metal complexes of Cu2+, Ni2+ and Co3+ were synthesized from new thermotropic liquid‐crystalline poly(acrylate ester)s (4) with a mesogenic bidentate β‐diketone in the side chain, and the liquid‐crystalline properties were examined by differential scanning calorimetry (DSC), X‐ray diffraction and polarizing microscopy. The mesophase of 4 is an enantiotropic smectic A phase showing a batônnet and focal conic fan texture in polarizing microscopy. Polymers 5a‐c containing a bis(β‐diketonato) copper(II) complex also exhibit an enantiotropic smectic A phase, and polymer 5d prepared from the vinyl monomer 8 shows a nematic phase. Concerning the complexes of polymers 6 and 7 with nickel(II) and cobalt(III), only 6a and 7a containing a small amount of metal‐chelating β‐diketonate units exhibit liquid‐crystalline behavior like the parent polymer 4. It was found that the fourcoordinated square planar bis(β‐diketonate)copper(II) acts as the mesogen; both nickel(II) and cobalt(III) complexes do not work as mesogens and rather hinder the liquid crystallinity of 4. The electron spin resonance (ESR) spectra of 5a and 5b change markedly along with the transition from the smectic A phase to the isotropic one. The broadening and simplification of the spectra for the isotropic phase indicates increased interaction between neighboring bis(β‐diketonato)copper(II) complexes and substantial electron spin‐spin interaction. The ESR spectra of 5c and 5d also imply this increased interaction between neighbouring complexes and spin‐spin interaction regardless of the phase transition.