bluuebunny/crossref_metadata_2025_split huggingface dataset:
TiCl4/MgH2‐supported Ziegler‐type catalyst system, 2. Effect of Ti concentration, Ti content and surface area of TiCl4/MgH2 catalyst on the concentration of active sites in ethylene polymerization
Authors: Jaber Isam A. , Hauschild Klaus , Fink Gerhard 
Published: April 2003

AbstractThe determination of active centres concentration in ethylene polymerization using various TiCl4/MgH2‐Al(C2H5)3 catalytic systems, by the 14CO radio‐tagging method, is reported. It is found that with increasing the absolute titanium amount the concentration of active centres, [C*], increases, whereas the propagation rate constant, kp, decreases. In addition, using various TiCl4/MgH2 catalysts in ethylene polymerization, it is found that the lower the Ti content, the higher is the surface area of the catalyst and the higher is the polymerization activity. Determination of [C*] shows consclusively that the decrease in the polymerization activity observed to occur with increasing the Ti content, and thus decreasing the surface area, is unequivocally due to a reduction in the concentration of active centres but not to any fundamental change in the value of the propagation rate constant.
Induced optical activity on side‐chain aromatic chromophores in copolymers of (−)‐menthyl acrylate with 1,2‐diphenyl‐1,2‐ethanedione‐2‐O‐acryloyloxime
Authors: Angiolini Luigi , Carlini Carlo , Tramontini Maurilio 
Published: April 2003

AbstractIn the present paper the synthesis of optically active copolymers from (−)‐menthyl acrylate (MtA) and 1,2‐diphenyl‐1,2‐ethanedione‐2‐O‐acryloyloxime (BMOA) by radical initiation is described. The copolymers obtained, having different contents of photosensitive O‐acyloxime moieties, were characterized by FT‐IR, 1H NMR and GPC measurements, and their chiroptical properties investigated by circular dichroism. The induced chirality on BMOA co‐units is assigned to isolated rather than to sequential BMOA units. Thus, the induced chirality is due to the molecular dissymmetry of individual O‐acyloxime chromophores flanked by opticaly active MtA units.
Synthesis and characterization of hetero‐arm star copolymers
Authors: Tsitsilianis Constantinos , Chaumont Philippe , Rempp Paul 
Published: April 2003

AbstractHetero‐arm star copolymers are constituted of a central core carrying branches of two kinds. The two‐stage synthesis of such polymer species involves an arm‐first step and a core‐first step: A linear anionic living polystyrene precursor was used to initiate the polymerization of a small amount of divinylbenzene, yielding star‐shaped polystyrene bearing living sites inside the cores; in a second stage these sites were used to initiate the polymerization of another monomer — butyl methacrylate —, more electrophilic than styrene. This second step results in the formation of a new set of branches originating from the same polydivinylbenzene cores. The star polystyrenes, and the hetero‐arm star copolymers were characterized adequately, and their molecular weights were found to be in satisfactory agreement with expectation. The presence of some remaining linear precursor in the star polymer samples is discussed thoroughly on the basis of a detailed computerized analysis of the size exclusion chromatograms of both the star polystyrene samples and the hetero‐arm star copolymers.
Copolymerization of styrene and ethylene in the presence of different syndiospecific catalysts
Authors: Longo Pasquale , Grassi Alfonso , Oliva Leone 
Published: April 2003

AbstractSome catalytic systems based on Ti or Zr compounds and methylalumoxane have been investigated with regard to their ability to promote styrene‐ethylene copolymerization. 13C NMR analysis shows that the structure and the composition of the copolymerization products are dependent on the catalytic system and on the transition metal/methylalumoxane mole ratio. Polymers containing phenylethylene units bridging polyethylene sequences are generally obtained in the presence of Ti‐based catalysts. In the presence of cyclopentadienyltitanium trichloride/methylalumoxane with high A1/Ti mole ratio one can obtain copolymers of ethylene and syndiotactic polystyrene. Zr‐based catalyst don't promote copolymerization at all.
Untersuchungen zur linearen thiol‐en‐photopolymerisation
Authors: Klemm Elisabeth , Sensfuß Steffi , Holfter Uta , Schütz Heidrun 
Published: April 2003

AbstractThe photoinitiated free‐radical polymerization of 3,6‐dioxa‐1,8‐octanedithiol and bis(allyl) hydroquinone ether or ethylene glycol divinyl ether leads to poly(thioethers) having anti Markovnikov structure with number‐average molar mass M̄n: 14000, 12000 g/mol, respectively. The chain propagation is limited by disulfide propagation is limited by disulfide production (nearly 3%) and cycle production (nearly 4 %). Differential scanning calorimetry (DSC) investigations showed that the rate of polymerization decreases in the series vinyl ether ≫ allyl ether > 1‐alkene. The influence of the dithiol structure (β‐mercapto ether, thioglycolate, aliphatic thiols) is not dominant.
Preparation of polyimide/polydimethylsiloxane graft copolymer and its permeabilities for gases and liquids
Authors: Nagase Yu , Mori Shigehiro , Egawa Masahiko , Matsui Kiyohide 
Published: April 2003

AbstractPolyimide/polydimethylsiloxane (PI/PDMS) graft copolymers with various PDMS contents were prepared by polycondensation of PDMS macromonomer 1 with aromatic diamines and pyromellitic dianhydride followed by heating at 220°C. The PDMS content of the grafts copolymers was controlled by changing the average degree of polymerization of the PDMS macromonomer in the range between 4 and 21. Graft copolymer membranes were prepared by casting films in the poly(amic acid) stage 2 and subsequent imidation upon heating. PI/PDMS membranes thus obtained are insoluble. The permeability coefficients towards nitrogen, oxygen, hydrogen, methane and carbon dioxide were evaluated. In the region of a PDMS content above 50 wt.‐%, the oxygen permeability coefficient of a PI/PDMS graft copolymer membrane is > 10−8 cm3(STP) · cm · cm−2 · s−1 · cmHg−1. In addition, the permeability coefficient of methane is remarkably enhanced in comparison with a PI membrane. Preferential permeation of ethanol was observed through the graft copolymer membrane in the case of pervaporation of aqueous ethanol solution. Furthermore, acetone, acetonitrile and tetrahydrofuran were efficiently separated from water at any solvent/water ratio in the mixture.
Polymerization by [3 + 2] cycloaddition, 4. Polymers from hexafluoroacetone azine and diallylic compounds
Authors: Nuyken Oskar , Maier Gerhard , Burger Klaus 
Published: April 2003

Abstract“Criss‐cross” cycloaddition polymerization between hexafluoroacetone azine and several diallylic compounds, such as diallyl ethers or diallyldimethylsilane, is described. In one case (with diallyl resorcinol ether) a polymer could be produced which is completely soluble in common organic solvents. The number‐average molar mass of this product is M̄n = 12000 g/mol. The expected structures of the polymers (or their soluble fractions) are confirmed by spectroscopic methods.
Synthesis, polymerization and copolymerization of 5‐methyl‐3‐methylene‐2‐pyrrolidone
Authors: Van Beylen Marcel , Samyn Celeste 
Published: April 2003

AbstractA new lactam monomer containing a vinylidene group was synthesized, namely, 5‐methyl‐3‐methylene‐2‐pyrrolidone (4). The homopolymerization and copolymerization with methyl methacrylate and with styrene were studied. The copolymerization parameters r1 and r2 were also evaluated. Hydrolysis of the pendent lactam groups yields a polyelectrolyte (or homopolymer) with pendent γ‐amino acid units.
Thermotropic liquid‐crystalline polymers, 28. Structural transformation “nematic‐smectic A — reentrant nematic” in a comb‐like polymer and its mixture with a low‐molar‐mass liquid‐crystal compound
Authors: Kostromin Sergey G. , Shibaev Valery P. , Diele Siegmar 
Published: April 2003

AbstractComb‐like liquid‐crystalline polyacrylate, 1, containing 4′‐cyano‐4‐biphenylyl mesogenic groups and forming a reentrant nematic (Nr) phase, as well as its mixture with 4‐cyano‐4′‐hexyloxybiphenyl were studied by X‐ray diffraction. X‐ray diffraction patterns of magnetically‐oriented samples and the micro‐densitometer curves obtained from them allowed to observe the distortion of the layers with orthogonal packing of the mesogenic groups in the Nr phase. These results are compared with electrooptical data obtained earlier. As a result a domain formation with tilted arrangement of the mesogenic groups in the pseudolayer is proposed.
Study on epoxy network solid electrolytes
Authors: Ba Henfei , Peng Xinsheng , Qi Yuchen , Chen Donglin , Wang Fosong 
Published: April 2003

AbstractBlends of the diglycidyl ether of poly(ethylene glycol) (1)IUPAC name of1: α‐(2,3‐epoxypropyl)‐ω‐(2,3‐epoxypropoxy)poly(oxyethylene).and the triglycidyl ether of glycerol (2)IUPAC name of2: 1,2,3‐tris(2,3‐epoxypropoxy)propane.were crosslinked in the presence of LiClO4which seems to act as both a catalytic curing agent and as the source of the ionic charge carriers. The cured film showed a rather high ionic conductivity of about 10−5S/cm at 25°C. The effect of composition, salt concentration and molecular weight of1on the conductivity and on the glass transition temperatureTgof the cured1/2LiClO4system was examined. The conductivity increased whereasTgdecreased with increasing1/2ratio. An increase of the molecular weight of1favoured the lowering ofTgand thus raised the conductivity. As to the effect of LiCIO4concentration, the maximum conductivity occurred at about 5 wt.‐% of LiClO4andTgincreased with increasing LiClO4content. The temperature dependence of the conductivity followed the Vogel‐Tamman‐Fulcher equation. This indicated that the ionic conductivity is effected by the cooperative segmental motion. All of the prepared specimens were found to be amorphous. They were mechanically strong films and showed rubber‐elasticity at room temperature.
Ordered odd‐number terpolyamides, 2. Crystal structure
Authors: Prieto Arcadi , Coutin Bernard , Sekiguchi Hikaru , Subirana Juan A. , Guerra Sebastián Muñoz 
Published: April 2003

AbstractA combined X‐ray diffraction and electron microscopy study was carried out on both the solution‐grown crystals and oriented films of nylons 3/5/7 and 7/5/3. These regular odd‐odd‐odd terpolyamides have such sequence of amide groups along the chain that they have to be aligned parallel in order to form every hydrogen bond without strain. It was found that a layered α‐structure with hydrogen‐bonded sheets made up of parallel chains in fully extended conformation is adopted in both cases. These results are not necessarily generalized to odd‐numbered nylons where an antiparallel alignement of chains is compatible with the formation of hydrogen bonds. Chain‐folded lamellar crystals obtained from solution were investigated by electron diffraction and their surface topology examined by polymer decoration with polyethylene. A bimodal orientation of hydrogen‐bonded sheets within the lamella is assumed to occur in order to account for the obtained decorating patterns. Either way, chain foldings are not contained in such sheets but intersect them at an angle of about 60°.
A DSC study on miscible blends containing two crystalline components: poly(ε‐caprolactone)/poly[3,3‐bis(chloromethyl)oxetane]
Authors: Guo Qipeng 
Published: April 2003

AbstractBlends of poly(ε‐caprolactone) (PCL) with poly[3,3‐bis(chloromethyl)oxetanel] (Penton) were prepared by casting from a common solvent. All blends show a single, composition‐dependent glass transition temperature (Tg), indicating that the blends are miscible in the amorphous state and in the melt. The crystallization rate of PCL in the blend decreases with increasing Penton content, that of Penton decreases with increasing PCL content. The crystallinity index of PCL in the blend decreases with increasing Penton content owing to the enhanced Tg of the system, whereas that of Penton does not depend on composition. The interaction parameter B of the two polymers in the melt was found to be −15 J/cm3.
Preparation of sodium 5‐methyl‐3,7‐octadienoate and its polymerization under irradiation with UV light
Authors: Arai Kenichiro , Miyahara Shigeyoshi 
Published: April 2003

AbstractSodium 5‐methyl‐3,7‐octadienoate (2) was synthesized as an amphiphile which contains a double bond at the chain end. The micelle formation behaviour of 2 was examined by measuring the electric conductivity of its aqueous solutions; the pre‐critical micelle concentration (pre‐CMC) and the genuine critical micelle concentration (CMC) were estimated to be 0,09 and 0,23 mol · 1−1, respectively. Polymerization of 2 under irradiation with UV light was investigated, and it was found that practically no polymer is obtained at concentrations lower than the pre‐CMC, while the amount of polymer obtained increases rapidly with increasing concentration of 2 in the polymerization system at concentrations higher than the pre‐CMC. The number‐average degree of polymerization of poly(2) is about 6. Pre‐CMC and CMC of poly(2), which are inferred to correspond to the concentrations to start intra‐ and intermolecular aggregation, are 1,2 · 10−3 and 9,4 · 10−3 mol · 1−1, respectively. These results are compared with those of sodium 10‐undecenoate.
Elektronenmikroskopische untersuchungen zum monomer‐volumenanteil in polyvinylchlorid‐latexpartikeln im verlauf der emulsionspolymerisation
Authors: Paulke Bernd‐R. , Tauer Klaus , Büchtemann Andreas , Müller Ingo , Schulz Eckhard 
Published: April 2003

AbstractMonomer‐swollen poly(vinyl chloride) latex particles directly taken from emulsion polymerization were fixed and stained with a dilute solution of osmium tetroxide. The particle size distribution of this dispersion was compared with that of the corresponding monomer‐free latex by transmission electron microscopy. The monomer volume fractions of the particles ϕM were calculated in dependence of their diameter (d). Smaller particles contain more vinyl chloride than larger ones under the experimental conditions adjusted. The mean value of the monomer volume fraction agrees with experimental data published by Berens and Nilsson. The equation of Morton, Kaizerman and Altier was used to estimate the Flory‐Huggins interaction parameter χ. An upper and a lower limit for χ was calculated applying the experimental values of d and ϕM in the particle size range investigated. The real χ for the particles observed lies between these limits.
Kinetic and statistical derivation of the copolymerization equation
Authors: Farina Mario 
Published: April 2003

AbstractA critical analysis of the various methods of derivation of the copolymerization equation leads to the following conclusions: the steady‐state assumption is not a necessary condition for the “kinetic” derivation; all known methods of derivation are implicitly or explicitly related to the condition of chain continuity; other methods, simpler than the traditional ones, are reported in the literature and deserve more attention.
Polyarylenes and poly(arylenevinylene)s, 3. Oligomeric model compounds for poly(9,10‐anthrylenevinylene)
Authors: Weitzel Hans‐Peter , Bohen Angelika , Müllen Klaus 
Published: April 2003

AbstractSome reactions for the synthesis of poly(phenylenevinylene), PPV, are examined for their capability to form poly(9,10‐anthrylenevinylene). The reasons for the failure of these reactions are described. Soluble oligomers with up to seven anthracene units are synthesized. The properties of the oligomers are studied and conclusions for the properties of poly(9,10‐anthrylenevinylene), PAV, are drawn.
Chemical modification of polymer main chain — A new path to liquid‐crystalline polyesters with long siloxane segments. Significance of molecular mobility in the formation of the liquid‐crystalline state
Authors: Zuev Vjacheslav V. , Smirnova Galina S. , Nikonorova Natalja A. , Borisova Tamara I. , Skorokhodov Sergei S. 
Published: April 2003

AbstractA new method for the synthesis of polymers incorporating dimethylsiloxane fragments of different length based on chemical modification of liquid‐crystalline poly[oxy(dimethylsilylene)‐methyleneoxycarbonyl‐1,4‐phenyleneoxyterephthaloyloxy‐1,4‐phenylenecarbonyloxymethylene‐(dimethylsilylene)] (polymer 1) is described. A series of thermotropic LC polymers 2 with extended dimethylsiloxane segments (up to 10 Si atoms per siloxane spacer) was synthesized by means of the reaction of prepolymer 1 with octamethylcyclotetrasiloxane in the presence of a sulfocation exchanger. Investigation of the dielectric properties of the polyesters 2 revealed that there exists a relationship between the ability of the polymers to form a mesophase and their molecular mobility parameters.
Synthesis of polysiloxanes with pendant viologen groups and their characteristic behavior of aggregation and deposition observed on electron transfer
Authors: Yamada Kazunobu , Ueno Yukihiko , Ikeda Koji , Takamiya Nobuo , Kaneko Masao 
Published: April 2003

AbstractIn order to prepare polysiloxanes with the ability of electron transport, pendant viologen groups were introduced. Chloromethylated poly(methyl‐β‐phenethylsiloxane) (2) was reacted with monoalkylbipyridinium chlorides (3a, 3b) to give polysiloxanes (4a, 4b) containing pendant viologen groups. These polymers show reversible redox behavior. They are deposited on ITO electrodes when the pendant viologen dication groups are electrochemically reduced to cation radicals. The polymer deposited shows an absorption maximum (λmax) at 500 nm, which is due to a highly aggregated structure of cation radicals. On the contrary, when the electrode was coated by the polymer before the measurement (pre‐cast membrane), the cation radicals formed electrochemically show λmax at 530 nm, indicating that the degree of aggregation is lower than that in the membrane formed reductively from solution.
N‐substituted aldonamides, 4. Phase behaviour in aqueous solution of monomers and polymers with alkylaldonamide side chains — comparison with model compounds
Authors: Loos Manon , Baeyens‐Volant Danielle , Szalaï Eva , David Christiane 
Published: April 2003

AbstractN‐substituted polymethacrylamides with mesogenic side chains of formula (CH2)n NHCOR′ where R′ is derived from ribose, have been synthetized. Thermotropic and lyotropic properties of the monomers, polymers, and copolymers with butyl acrylate have been investigated.
Lösungsmittelabhängigkeit der Bruttopolymerisationsgeschwindigkeit bei der radikalischen Copolymerisation von donator‐ und Acceptormonomeren
Authors: Schmidt Hermann , Schmidt‐Naake Gudrun , Berger Werner 
Published: April 2003

AbstractThe influence of the solvent on the reactivity ratios in free‐radical copolymerization of donor monomers with acceptor monomers is very strong. The copolymerization reactivity ratios decrease with increasing donor number and dielectric constant of the solvent. This can be rationalized on the basis of the complex stability constant of the two monomers as compared with those of the monomers and the solvent.
Modellselektion bei der Copolymerisation ternärer Donator‐Acceptor systeme
Authors: Schmidt‐Naake Gudrun , Schmidt Hermann , Litauszki Beata , Berger Werner 
Published: April 2003

AbstractThe free‐radical copolymerization of donor, acceptor and neutral monomers to ternary copolymers is studied. It is shown that the composition of the ternary copolymers can be calculated from their monomer feed, in case the reactivity ratio (r) values of the three binary subsystems are known. The calculation based on the copolymer equation only considers really existing propagation steps.
Polyether‐1,2‐ and ‐1,3‐diols as macromonomers for the synthesis of graft copolymers, 1. Synthesis and characterization of the macromonomers
Authors: Fock Jürgen , Möhring Volker 
Published: April 2003

AbstractThis article describes the synthesis and characterization of a new type of macromonomers, which can be used in condensation and addition reactions affording graft copolymers. The polyether‐based macromonomers having two hydroxyl groups at one chain end were synthesized by anionic alkoxylation of hydroxy‐functional cyclic ketals, blocking by Williamson reaction and cleavage of the ketal. Moreover, the synthesis and characterization of such macromonomers having sulfonate and perfluoroalkyl end groups, respectively, were performed. Yields were influenced by side reactions depending on the type of epoxide used and the final molecular weight of the macromonomer.
Compatibility of poly(N‐vinyl‐2‐pyrrolidone) with ethyl methacrylate/2‐hydroxyethyl methacrylate copolymers
Authors: Goh Suat Hong , Lee Swee Yong 
Published: April 2003

AbstractThe compatibility of poly(N‐vinyl‐2‐pyrrolidone) (PVP) with ethyl methacrylate/2‐hydroxyethyl methacrylate (EMA/HEMA) copolymers of varying HEMA contents was studied by differential scanning calorimetry. PVP is incompatible with EMA/HEMA copolymers with HEMA contents of 2,1 and 5,7 mol‐%, but is compatible with copolymers with HEMA contents of 7,5, 10,0 and 18,2 mol‐%. TheTg‐composition curves of three compatible systems can be fitted by the Gordon‐Taylor equation.
Liquid‐crystalline polysiloxanes with fluorene units, and related monomeric compounds
Authors: Koßmehl Gerhard , Schulz Michael , Vieth Hans‐Martin 
Published: April 2003

AbstractThe synthesis of the liquid‐crystalline polysiloxanes, 4a, 4b, 5a, 5b with 2,7‐disubstituted fluorene units and of the related liquid‐crystalline model compounds 2 and 3 is reported. Polymers 4a, 4b, 5a, 5b were prepared from monomers 2 and 3, respectively, and poly(hydrogenmethyl‐siloxane) (PHMS) in a polymer‐analogous reaction. The liquid‐crystalline properties of the polymers and the corresponding low‐molecular‐weight compounds 2 and 3 were characterized by differential scanning calorimetry (DSC) and polarizing microscopy. Both compounds 2 and 3 show a smectic A and a smectic E mesophase, and the resulting polysiloxanes also exhibit smectic A‐ and smectic E‐like textures but no nematic phase. The clearing point of the polymers is on the average by 100°C higher than that found for the low‐molecular‐weight compounds.
Study of heterocyclic polymers, 2. Model reactions of 2‐pyridinecarboxylic acid with glycidyl phenyl ether
Authors: Hsu Ying Gev , Hsu Miau Jing , Chen Keng Ming 
Published: April 2003

AbstractThe reaction of 2‐pyridinecarboxylic acid (picolinic acid, PA) with 2,3‐epoxypropyl phenyl ether (glycidyl phenyl ether, GPE) was studied by means of high performance liquid chromatography (HPLC). It was found that the reaction between PA and GPE is quite different from that between nicotinic acid (NA) or isonicotinic acid (ISNA) and GPE, and does not obey the kinetics of second or other order; hence the rate constant of the reaction cannot be obtained. The reaction may be described by a three‐step mechanism. PA reacts first with GPE to yield N‐(2‐hydroxy‐3‐phenoxypropyl)pyridinium‐2‐carboxylate (PA‐1). PA‐1 is then decarboxylated to form an ylide. The ylide reacts immediately with PA to yield N‐(2‐hydroxy‐3‐phenoxypropyl)pyridinium picolinate (NPP). NPP subsequently catalyzes the reaction between PA and GPE, with 2‐hydroxy‐3‐phenoxypropyl picolinate (PA‐2) as a product. Because the concentration of NPP increases with time, the rate of reaction between PA and GPE is increasing with time. The mechanism of the reaction is discussed in detail.
Pyrolysis gas chromatographic studies on polyphosphate esters of bisphenol A
Authors: Annakutty Kunnappallil S. , Kishore Kaushal 
Published: April 2003

AbstractPyrolysis gas chromatographic studies were carried out on two polyphosphate esters of bisphenol ASystematic name: 2,2′‐isopropylidendiphenol.
. The gaseous pyrolysis products were found to be mainly phenols and a few phosphate compounds. The identification of phosphorus compounds in the gas phase proves a gas phase mechanism of flame retardant action for polyphosphates. The presence of phosphoric acid in the char residue supports the existence of the conventional condensed‐phase mechanism. Thus, the study demonstrates that both condensed‐phase and gas‐phase mechanisms are operative in the flame‐retardant action of polyphosphates.