bluuebunny/crossref_metadata_2025_split huggingface dataset:
Intrinsic viscosity of intramolecularly crosslinked polyelectrolyte: Poly(vinyl alcohol)/borax systems
Authors: Ochiai Hiroshi , Kurita Yuji , Murakami Ichiro 
Published: April 2003

AbstractThe intrisic viscosity [η] of poly(vinyl alcohol) (PVA) was determined in aqueous solutions with various concentrations cb of borax (Na2B4O7) as functions of molecular weight M and concentration cs of NaCl as an added salt. Polyelectrolyte viscosity behaviour was observed for the systems containing both borax and NaCl, due to the complexation with negatively charged borate ions B(OH)−4 · [η] changes depending on the ionic strength I. It was found that the Stock‐mayer‐Fixman treatment for the molecular‐weight dependence of [η] is valid in the lower molecular‐weight range (M < 105), even though the present PVA chain contains some intrachain crosslinks. Theta conditions can be attained at an appropriate concentration cs Θ of NaCl. The value of cs Θ is dependent on cb, but the conformational parameter from the Stockmayer‐Fixman treatment K0 is almost independent of cb. The effect of intrachain crosslinks becomes evident only as a considerably large negative value for the excluded volume parameter B at infinite ionic strength. In addition, the electrostatic part of the expansion factor α was found to be linearly correlated to a reduced parameter (M/I)1/2 for all cb systems, from the slope of which the charge density was estimated.
Decay of radical initiators in emulsion copolymerization of unsaturated polyesters and styrene
Authors: Bauer Harald , Ortelt Martina , Joos Betina , Funke Werner 
Published: April 2003

AbstractEmulsion copolymerization of unsaturated polyesters (UP) with styrene was initiated by potassium peroxodisulfate and by azodiisobutyronitrile (AIBN). The decay rates of both initiators were compared and influences of temperature, electrolyte and concentration of the reaction components studied. Initiation radicals from the persulfate partly add to unsaturated UP units and decarboxylate terminal acid groups of the UP. Initiation by AIBN predominantly occurs in the aqueous phase, and side reactions with this initiator are neglectable.
Group transfer polymerization of methyl methacrylate in acetonitrile, 2. Initiation by trimethylsilyl cyanide
Authors: Speikamp Hans‐Dieter , Bandermann Friedhelm 
Published: April 2003

AbstractResults of group transfer polymerization of methyl methacrylate (MMA) in acetonitrile with tetraethylammonium cyanide (Et4NCN) and tris(dimethylamino)sulfonium difluorotrimethylsilicate (TASF2SiMe3) as catalysts and trimethylsilyl cyanide as initiator are presented. It is shown, that both catalysts behave similarly with respect to catalysis of the initiation and the propagation step and of the termination step of the growing chains with the solvent, TASF2SiMe3 being more active than Et4NCN.
Structural study of compounds modelling elementary polymer units, 5. Molecular and crystal structures of C, C′‐disubstituted o‐carboranes
Authors: Lindeman Sergey V. , Khotina Irina A. , Teplyakov Mikhail M. , Struchkov Yurii T. , Korshak Vasilii V. 
Published: April 2003

AbstractWith the aim to determine the main structural characteristics of amorphous (branched and different‐unit) polymers of the polyphenylene type, prepared by polycyclocondensation of carborane‐containing mono‐ and diacetylaromatic compounds, an X‐ray structural study of four model compounds was carried out, viz. of 1,2‐bis[4‐(4‐acetylphenoxy)phenyl]‐1,2‐dicarba‐closo‐dodecaborane(12) (1) (triclinic crystals, a = 8,205 Å, b = 13,505 Å, c = 14,019 Å, α = 90,44°, β = 97,08°, γ = 97,24°, space group P1, Z = 2, R = 0,045 for 2663 reflections), 1,2‐bis(4‐phenoxyphenyl)‐1,2‐dicarba‐closo‐dodecaborane(12) (2) (monoclinic crystals, a = 14,813 Å, b = 17,133 Å, c = 11,211 Å, β = 112,43°, space group P21/c, Z = 4, R = 0,066 for 3 286 reflections), 1,2‐bis(4′‐acetylbiphenyl‐4‐yl)‐1,2‐dicarba‐closo‐dodecaborane(12) (3) (orthorhombic crystals, at −120°C a = 13,405 Å, b = 9,276 Å, c = 22,86 Å, space group Pnam, Z = 4 molecules on the m plane, R = 0,039 for 1 147 reflections), and 1,2‐bis(4‐acetylbenzyl)‐1,2‐dicarba‐closo‐dodecaborane(12) (4) (orthorhombic crystals, at −120°C a = 22,03 Å, b = 26,23 Å, c = 8,026 Å, space group Fdd2, Z = 8 molecules lie on the two‐fold axis, R = 0,051 for 577 reflections). The strained structure of the C,C′‐o‐diphenyl‐substituted carboranyl fragment is established, the high conformational flexibility of 4‐phenoxyphenyl linkages is confirmed and a tendency toward separate autoassociation of acetyl‐containing polar groups and carborane nuclei is shown, with the autoassociation of polar groups completely suppressing that of carborane nuclei in case of conformational rigidity and shortness of the arylene linkages. These and other structural characteristics of the investigated model compounds and their crystals, in case they turn out to be characteristic also for the corresponding polymers and their precursors, should largely determine the structure and physico‐chemical properties of their corresponding polymers.
Partitioned polymerization, 1. Transfer of initiator and/or monomer
Authors: Bartoň Jaroslav , Juraničová Viera , Hloušková Zuzana 
Published: April 2003

AbstractThe polymerization of acrylamide initiated by 2,2′‐azobisisobutyronitrile in the system water/benzene and water/ethyl acetate (vol. ratio 3 : 1), the emulsion polymerizations of methyl methacrylate, butyl methacrylate, styrene and acrylonitrile, and the emulsion copolymerization of butyl methacrylate with acrylonitrile and styrene with acrylonitrile initiated by ammonium peroxodisulfate in the presence and/or absence of the inhibitor 4‐stearoyloxy‐2,2,6,6‐tetramethylpiperidine‐1‐oxyl were studied. These systems represent a model of the partitioned polymerization. The partitioned polymerization is characterized by the deposition of a monomer and an initiator in different, mutually immiscible phases, e.g. water and oil phase, before polymerization. In order to start the polymerization the monomer (initiator) must transfer into the phase where the initiator (monomer) is situated. Application of the principle of partitioned polymerization led to the formulation of a novel approach to the initiation mechanism of emulsion polymerization of polar and non‐polar monomers initiated by water soluble or oil soluble initiators.
Studies in ring‐opening polymerization, 9. Co‐metathesis of cyclic alkenes and unsaturated esters
Authors: Amass Allan J. , Dale Audrey L. , Tighe Brian J. 
Published: April 2003

AbstractThe polymerization of cyclopentene in the presence of an unsaturated ester led to the synthesis of low‐molecular‐weight polypentenamer with a terminal functional group by ringopening metathesis polymerization using WCl6/AlEtCl2/EtOH as catalyst. Unlike most reactions of this nature the efficiency of the catalyst system is high because the ester used possesses an electron withdrawing group, the trichloromethyl group. The presence of this group ensures that the complex formed between the metal carbene complex and the ester group is reduced in stability and catalyst concentrations normally used for ring‐opening metathesis polymerizations can be used (mole ratio W : CP = 1 : 1000), the concentrations of ester being quite high (mole ratio ester : CP = 1 : 5). Under these conditions reasonably high yields of liquid polymers are obtained.
The formation of trans‐epoxides during the photochemical oxidation of cis‐polyisoprenes to liquid rubbers
Authors: Burfield David R. 
Published: April 2003

AbstractPhotochemical hydrogen peroxide catalyzed degradation of both natural rubber and synthetic cis‐polyisoprene is shown to result in the formation of a low‐molecular‐weight oil functionalised with hydroxyl, carbonyl and epoxide groups. Interestingly, the epoxide groups are shown to be of a trans‐configuration. A scheme is proposed to account for the formation of trans‐epoxide as well as concomitant mainchain isomerization. The preferential formation of trans‐epoxide in free radical oxidations strongly suggests that the naturally occurring cis‐epoxide, present in natural rubber, is due to a stereospecific enzymatic process, and is not the byproduct of radical oxidation.
Effects of ionenes on structure and catalytic activity of cobaltphthalocyanine, 3. Interaction of 2,4‐ionene with cobaltphthalocyanine and model compounds
Authors: van Welzen Joke , Van Herk Alex M. , German Anton L. 
Published: April 2003

AbstractIn order to obtain detailed information about the interaction between the constituents of the cobaltphthalocyanine‐tetrasodium sulfonate/ionene system, a catalyst used in thiol autoxidation, 2,4‐ionene was studied in combination with Fe(CN)4−6, Fe(CN)3−6, congo red, and several metal(II)phthalocyanines. In all cases, stoichiometric complexation was observed, at a ratio where the positive charges on the polymer were just matching those of the anionic species. The hexacyanoferrate complexes were found to be less stable than the dye complexes, due to the formation of dye aggregates in the latter systems. These aggregates appear to enhance the electrostatic interaction with the polymer to such an extent that even irreversible ionomeric “crosslinking” may occur. The results are discussed in relation to the catalytic activity of the polymeric catalyst.
Etude cinétique de la polymérisation en émulsion du styrène en présence d'éamulsifiants amphiioniques de type sulfobétaïne
Authors: Essaddam Hatem , Pichot Christian , Guyot Alain 
Published: April 2003

AbstractEmulsion polymerization of styrene was carried out at 70°C with sodium persulfate as initiator in the presence of 3 different sulfobetaïne‐type amphoteric surfactants. Their micellar properties were well‐characterized as function of temperature, ionic strength and pH. The kinetic behavior, based on the analysis of monomer consumption, particle size and molecular weight, was found to depend on the emulsifier type and concentration. The results were compared with those obtained in the presence of sodium dodecyl sulfate (1) and under emulsifierfree conditions. With dodecyldimethylammoniopropanesulfonate (2), the kinetic behavior was similar to what is observed in 1‐emulsified polymerization, whereas with dimethyloctadecylammoniopropanesulfonate (3) and 3‐N‐acetyl‐N‐(dodecyldimethylammoniomethyl)aminopropanesulfonate (4), exhibiting lower critical micell concentration, the particle formation mechanism was also controlled by homogeneous nucleation associated with a limited flocculation period. The pH was found to affect the polymerization kinetics, however, the effect was more likely attributed to the initiator decomposition.
Aminolysis of low‐molecular‐weight and polymeric 4‐nitrophenyl esters
Authors: Frechet Jean M. J. , Mikeš František , Výprachtický Drahomír , Lam Hoang , Labský Jiří 
Published: April 2003

Abstract4‐Nitrophenyl methacrylate (1a), 4‐nitrophenyl esters of some N‐methacryloyl‐ω‐amino acids (1b −d) and 4‐nitrophenyl esters of N‐acetyl‐ and N‐methacryloyltryptophane (2a and 2b) were prepared and characterized. Copolymers of 1 a −d and 2 b with N‐2‐hydroxypropylmethacrylamide (HPMA), N‐isopropylmethacrylamide (iPMA) and N‐ethylmethacrylamide (EMA) were also prepared. The 4‐nitrophenyl ester content of the copolymers was determined spectrophotometrically from their UV absorption and from the UV absorption of the 4‐nitrophenolate ion which is released upon hydrolysis of the active esters with 0,1 M sodium hydroxide. The difference between these values depends on both the type of polymerizable active ester used and the comonomer. The proportion of non‐hydrolyzable structure is especially high in the case of copolymers containing 4‐nitrophenyl esters of the methacryloylated α‐amino acids 1b and 2b. The formation of non‐hydrolyzable structures is likely due to side reactions which occur during polymerization. The polymers prepared by copolymerization of the polymerizable 4‐nitrophenyl esters were not found to be suitable for the preparation of polymeric fluorescent probes by a chemical modification route. It was found that the rate of aminolysis of low‐molecular‐weight and polymeric activated esters increases with increasing the number of methylene groups in the N‐(ω‐aminoalkyl)‐5‐dimethylamino‐1‐ naphthalenesulfonamides (dansylamines) 3a–f.
Liquid‐crystalline poly(β‐aminoester)s. Thermotropic mesomorphism and degradability in solution
Authors: Laus Michele , Angeloni Annino Sante , Galli Giancarlo , Chiellini Emo 
Published: April 2003

AbstractPoly(β‐aminoester)s 7 – 12, containing in the repeating unit ethylenebis(carbonyloxy‐1,4‐phenylene)carbonyloxy groups interconnected by polymethylene segments of different length and coupled by diamino spacers, were synthesized from mesomorphic diacrylates and secondary diamines. The thermal behavior and the solution properties of the polymers were investigated. Depending on the structure of the repeating unit, the polymers were found to give rise to either isotropic or anisotropic melts. The incidence and extension of the mesophase are favored in poly(β‐aminoester)s based on even numbered methylene segments and 2‐methylpiperazinediyl spacers. The polymer samples were found to degrade at room temperature, when dissolved in solutions containing water, an organic base or an acid. Based on a macromolecular model compound (14) a degradation process is suggested involving a selective cleavage of the benzoate ester groups assisted by the amino groups in β‐position.
Preparation of metal‐free polyphthalocyanine thin films by an evaporation‐polymerization method
Authors: Abe Katsuya , Ohkatsu Yasukazu , Kusano Toru 
Published: April 2003

AbstractA thin film (thickness: 200 nm) of metal‐free polyphthalocyanine, which is insoluble in organic solvents, was prepared by an evaporation‐polymerization process under mild conditions developed by us. The thin film is not only though, but it also resists chemicals and heat. Its conductivity is 1,1 · 10−4 S · cm−1, and it increases to 0,15 S · cm−1 on I2‐doping.
Synthèse, polymérisation et copolymérisation d'un dérivé 2h‐benzotriazolylphényl de l'acétate de vinyle
Authors: Camps Marcel , Monthéard Jean‐Pierre 
Published: April 2003

Abstract1‐(4‐Acetoxy)‐3‐(2H‐benzotriazolylphenyl)vinyl acetate (4) was synthesized. The polymerization of 4 afforded polymer 5 with a relatively low molecular weight (= 2000). Copolymerizations of 4 (3,7 wt.‐%) were carried out with styrene and methyl methacrylate to copolymers 6 and 7, respectively. Polymer 5 and copolymers 6 and 7 were characterized by 1 H and 13 C NMR and by IR and UV spectroscopy. Their UV spectra show a strong absorption in the near UV spectrum. 4 may thus be considered as a potential comonomer for UV protection.
Physical behaviour of stereoblock‐isotactic polypropylene
Authors: de Candia Francesco , Russo Roberto , Vittoria Vittoria 
Published: April 2003

AbstractPreliminary results regarding the physical behaviour of a stereoblock‐isotactic polypropylene are reported. The polymer was obtained using a soluble Ziegler‐Natta catalyst and films were prepared by pressure molding. The particular steric configuration is responsible of low crystallinity and small crystal size; the bulk structure can be represented by a fringed micellar model in which small crystallites act as physical crosslinks. The observed behaviour being typical of a thermoplastic elastomer well agrees with the suggested model.
13C NMR characterization of copolymers of ethylene and perdeuteroethylene
Authors: Cheng H. N. , Dziemianowicz Theodore S. 
Published: April 2003

AbstractCopolymers of ethylene and ethylene‐d4 were prepared, and their composition and comonomer sequence distribution determined from high‐field 13C NMR spectra. For a conventional Ziegler‐Natta catalyst, deuterium was shown to decrease the reactivity of ethylene.
Thermal and rheological properties of poly(vinyl alcohol) hydrogels prepared by repeated cycles of freezing and thawing
Authors: Watase Mineo , Nishinari Katsuyoshi 
Published: April 2003

AbstractDifferential scanning calorimetry and scanning electron microscopy were carried out in order to study the relation between the structure and properties of poly(vinyl alcohol) hydrogels prepared by repeated cycles of freezing‐thawing. The effect of the number N of repeated cycles of freezing‐thawing, of the degree of saponification (DS), and of the degree of polymerization (DP) on structure and properties was examined. The elastic modulus and the endothermic enthalpy, estimated from the area surrounded by the endothermic peak, increase with increasing N, DS, and DP. The melting temperature Tm shifts to higher temperatures with increasing DS and DP, but it is almost independent of N for gels with high DS or DP. In PVA gels with lower DP or DS, Tm shifts to higher temperatures with increasing N. The temperature dependence of the elastic modulus is discussed on the basis of a theory on thermoreversible gels.
The structure of neutral polythiophene. An application of the rietveld method
Authors: Brückner Sergio , Porzio William 
Published: April 2003

AbstractThe crystal structure of polythiophene is analyzed by the Rietveld whole‐fitting method on the X‐ray diffraction powder profile. Experimental data allow only a bidimensional characterization of the structure in the plane orthogonal to the chain axis with a pgg symmetry (a = 7,79; b = 5,53 Å). Best fitting is obtained by assuming rigorous coplanarity of thiophene rings along the chain. The presence of few and weak layer‐peaks is interpreted in terms of only partial ordering of chains along their axes. The final disagreement factor, in terms of ∑|I0 − Ic|/∑ Inet, is 0,125.
Polymeric bound porphyrins and their precursors, 6. Syntheses of water‐soluble, negatively or un‐charged polymers with covalently bound moieties of porphyrin derivatives
Authors: Wöhrle Dieter , Krawczyk Gerhard , Paliuras Mihail 
Published: April 2003

AbstractWater‐soluble polymers 6–17 containing covalently bound moieties of porphyrin derivatives were prepared by reaction of poly(methacrylic acid) (4) and poly(N‐vinylpyrrolidone‐co‐methacrylic acid) (5) with the low‐molecular‐weight substituted tetraphenylporphyrin 1 b, phthalocyanines 2 b and 2 d and naphthocyanine 3 c. Besides binding of one porphyrin derivative, also combined binding of two or three different porphyrin derivatives to the polymers could be achieved. The resulting polymers are negatively charged (polymers 6–11) or uncharged (polymers 12–17).
Immobilisierte tris(2,2′‐bipyridin)ruthenium(II)‐komplexe als photosensibilisatoren für die wasserphotolyse
Authors: Nußbaumer Walter , Gruber Heinrich , Greber Gerd 
Published: April 2003

AbstractCrosslinked polymers containing pendant tris(bipyridyl)ruthenium(II) complexes [Ru(bipy)] were synthesized and examined as sensitizers for the light‐induced formation of hydrogen in the heterogeneous system H2O/immobilized Ru(bipy)/ethylenediamine‐tetraacetic acid/platinum. Hydrogen generation rates of 0,037 ml/h were obtained with Ru(bipy) ‐complexes immobilized with spacer groups onto hydrophilic carriers based on sucrose‐methacrylates as well as hydrophobic carriers based on crosslinked poly(4‐aminostyrene), whereas carrier bound complexes without spacer gave lower efficiencies in hydrogen production. The hydrogen generation rates were linear for more than 8 days.
Polymérisation induite par un plasma froid. Etude des mécanismes de polymérisation en fonction de l'épaisseur du film
Authors: Epaillard Fabienne , Brosse Jean‐Claude , Legeay Gilbert 
Published: April 2003

AbstractThe reactive species (radicals, ions, etc.) or the UV‐visible radiation emitted by the excitated species initiate the cold plasma induced polymerization of a monomer in the liquid or solid state. The residual CC double bond concentration of an acrylic monomer depends on the plasma characteristics (gas nature, pressure, discharge power, etc.), but also on the polymerization conditions. The UV‐visible radiation emitted in a cold plasma has more influence on the thickness of the film than the reactive species bombardment. Two simple mathematic laws describe these phenomena.
Influence of the interphase on mechanical properties in block copolymers
Authors: Bühler Fritz , Gronski Wolfram 
Published: April 2003

AbstractPolystyrene‐block‐poly(styrene‐ran‐isoprene)‐block‐polyisoprene characterized by a morphology of spherical rubbery microdomains in a continuous polystyrene matrix is considered as a model for rubber‐toughened thermoplastics in which the volume fraction of the interfacial layer can be varied by varying the volume fraction of the interblock. Stress‐strain measurements of these systems are presented in relation to their morphology, interblock volume fraction and molecular weight of the polystyrene block. The results indicate that the energy of fracture is increased with increasing width of the interfacial layer without change of Young's modulus.
Relative reaction probabilities in polymer‐polymer reactions, 1. Investigations with Monte‐Carlo model chains
Authors: Olaj Oskar Friedrich , Zifferer Gerhard 
Published: April 2003

AbstractPairs of chains taken from ensembles of five‐way cubic lattice chains (athermal or theta) were analysed for the (relative) probability of contact formation between specified segments belonging to different chains within this pair. This probability may be taken as a measure of the rate constant which characterizes bimolecular polymer‐polymer reactions which occur between active sites attached to or localized at these segments, relative to the reaction between the same active sites, if these were not bound to the polymer chains. It turns out that the (expected) effect which results from the interaction between the chains as a whole (external shielding) is of comparatively small extent and is fairly independent of chain length. The much more important contribution, however, is made by a novel phenomenon which — exhibiting a strong dependence on chain length n — is responsible for an “internal” shielding: the compatible pair configurations (i. e. those which are free of intermolecular intersections) are characterized by largely increased segment‐segment distances. As a consequence, the probability of contact formation is much lower than it would be expected from a convolution of the (mutually independent) radial distributions of the segments participating in contact formation. The overall shielding factor K can be represented as a product of the fairly independent contributions of external (KG) and internal (Kw) shielding. The overall chain length dependence is described by a power law K = Dnd, where the exponent d depends on whether two (Type I contacts), one (Type II) or no endsegment at all (Type III) is involved in contact formation. For athermal chains the exponents are d = −0,16 (Type I), d = −0,30 (Type II), and d = −0,50 (Type III), the pre‐factor being of the order of unity throughout. Θ‐systems roughly show the same general characteristics as the athermal ones, however, to a lesser extent. Thus, neither shielding nor its chain length dependence vanish, the exponents being about −0,06 (Type I), −0,1 (Type II), and −0,2 (Type III), respectively.
Liquid‐crystalline polymers containing heterocycloalkanediyl groups as mesogens, 6. Liquid‐crystalline poly[trans‐11‐{4‐[5‐(4‐methoxyphenyl)‐1,3‐dioxan‐2‐yl]‐2,6‐dimethylphenoxy}undecyl methacrylate] and poly[trans‐11‐{4‐[5‐(4‐methoxyphenyl)‐1,3‐dioxan‐2‐yl]‐2,6‐dimethylphenoxy}undecyl acrylate]
Authors: Hsu Chain Shu , Percec Virgil 
Published: April 2003

AbstractThe synthesis and characterization of poly[trans‐11‐{4‐[5‐(4‐methoxyphenyl)‐1,3‐dioxan‐2‐yl]‐2,6‐dimethylphenoxy}undecyl methacrylate] and poly[trans‐11‐{4‐[5‐(4‐methoxyphenyl)‐1,3‐dioxan‐2‐yl]‐2,6‐dimethylphenoxy}undecyl acrylate] is presented. Both polymers exhibit nematic mesophases and do not present side‐chain crystallization. At temperatures higher than 160°C the 1,3‐dioxane‐2,5‐diyl groups undergo a thermally induced trans‐cis isomerization. A radical mechanism is proposed for this isomerization.