bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ethylene oligomerization catalyzed with dichlorobis‐(β‐diketonato)zirconium/organoaluminium chloride systems
Authors: Oouchi Kunihiro , Mitani Makoto , Hayakawa Michiya , Yamada Tohru , Mukaiyama Teruaki 
Published: April 2003

AbstractThe combination of a dichlorobis(β‐diketonato)zirconium compound 1 and dimethyl‐aluminium chloride was found to be an active catalyst for the oligomerization of ethylene to produce linear C4–C22 α‐olefins. The catalytic activity and the product distribution of the resulting oligomers was influenced by the structure of the β‐diketonato ligands, which affect the electron density at the zirconium center.
Synthesis and properties of new segmented block poly(urethane‐urea)s containing phosphatidylcholine analogues and polybutadienes
Authors: Chen Tian‐Ming , Wang Yan‐Feng , Li Yu‐Jun , Kitamura Masaya , Nakaya Tadao 
Published: April 2003

AbstractNew hydrophobic‐hydrophilic microphase‐separated block segmented copoly(urethane‐urea)s were synthesized by introducing hydrophobic polybutadienes as the soft segments and 4,4′‐methylenediphenyl diisocyanate, hexamethylene diisocyanate, ethylenediamine, and a hydrophilic phosphatidylcholine analogue as the hard segments in the backbones of these polymers. The results of ATR‐IR and XPS show the coexistence of phosphatidylcholine analogues and polybutadienes on the surface of cast films of the synthesized poly(urethane‐urea)s. Furthermore, TEM cross sectional observation of the cast film PBDP‐1370 indicates that it possesses a hydrophilic‐hydrophobic microphase‐separated domain structure.
Reversible photodimerisation of ω‐anthrylpolystyrenes
Authors: Coursan Magali , Desvergne Jean Pierre , Deffieux Alain 
Published: April 2003

AbstractThe preparation of polystyrene with controlled molar masses and narrow dispersity endcapped with an anthrylmethyl ether group, as well as the study of their photophysical properties, are described. Under irradiation at 336 nm dimerisation of the polystyrene chains is observed. This process results from the formation of a symmetrical head‐to‐tail photodimer between two anthryl end groups. When irradiated at lower wavelength (λ = 228 nm), the original ω‐anthrylpolystyrene chains are quantitatively restored. These dimerisation/dissociation cycles can be conducted more than ten times without any detectable degradation of the photosensitive polymer. The fluorescence emission quantum yield and fluorescence lifetime of the ω‐anthryl moieties and the quantum yield of the dimerisation and of the reverse process have been measured.
Comparison of thermal and microwave‐activated polymerization of ε‐caprolactone with titanium tetrabutylate as catalyst
Authors: Albert Philipp , Warth Holger , Mülhaupt Rolf , Janda Ralf 
Published: April 2003

AbstractThermal and microwave‐activated ring‐opening polymerization at 180°C in the presence of titanium tetrabutylate at different ε‐caprolactone/titanium tetrabutylate molar ratios were compared. A special equipment was developed to control polymerization in the microwave field and to simultaneously monitor viscosity build‐up as well as changes in microwave powers corresponding to input, reflection and transmission. Conversion, measured by means of viscosity build‐up, and number‐average molecular weight of poly(ε‐caprolactone) were similar for both processes and did not indicate advantages relating to the use of microwave irradiation.
Hydroxytelechelic polybutadiene, 14. Gelation of a radically obtained hydroxytelechelic polybutadiene with 4,4′‐methylenedi(phenyl isocyanate)
Authors: Allard‐Breton Bétrice , Audenaert Marc , Pham Quang Tho 
Published: April 2003

AbstractA new commercial radically obtained hydroxytelechelic polybutadiene (HTPB‐A) was examined by 1H NMR at 500 MHz, and a corrected interpretation of the complex proton methylene resonance of the vinyl‐type primary alcohol was done. The weight‐average hydroxyl functionality F̄w (OH) was determined by using critical conversions at gel points of the (HTPB‐A + diisocyanate) systems, on the one hand, and swelling at equilibrium on the other. The functionality polydispersity index of HTPB‐A is close to unity.
Raman spectroscopic study on water in aqueous gelatin gels and sols
Authors: Tsukida Noriaki , Maeda Yasushi , Kitano Hiromi 
Published: April 2003

AbstractA Raman spectroscopic study on property changes of water in aqueous gelatin media was carried out. The state of water in gelatin gels and sols at various temperatures and concentrations was studied in connection with the conformation of polymer chains. When gelatin with a low molecular weight was used, there was no gel‐sol transition, and the structure of water observed by Raman spectroscopy was not significantly affected by the presence of gelatin. When gelatin with a high molecular weight was used, on the other hand, the structure of water strongly depended on the concentration of gelatin both in the gel and the sol state. A contribution of small spaces surrounded by entangled gelatin chains (which exist both in high concentration gels and sols) to the perturbation of the structure of incorporated water was suggested. It was also found that, at 60°C, gelatin chains in the low concentration region induced an enhancement of structured water. This is the first finding that water soluble polymers at high temperature induce the network structure of water.
Temperature‐responsive polymer microspheres prepared with a macroinitiator
Authors: Kitano Hiromi , Kawabata Junko 
Published: April 2003

AbstractA macroinitiator was prepared by coupling of the disuccinimidyl ester of 4,4′‐azobis(cyanovaleric acid) with poly(N‐isopropylacrylamide) (PIPA) with terminal amino group. Styrene and divinylbenzene were copolymerized with the initiator in the presence of sodium dodecylsulfate. The polymer microspheres obtained have PIPA chains on their surfaces, and the stability of a suspension of the microspheres in the presence of electrolyte is largely influenced by the temperature, whereas that of microspheres without PIPA chains is not. The usefulness of macroinitiators to prepare various polymer materials which are responsive to external stimuli was strongly emphasized.
Chromatographic investigations of polyacetals in the critical range of liquid chromatography, 1. Analysis of 9‐anthrylmethyl‐terminated poly(1,3,6‐trioxacyclooctane)s
Authors: Gancheva Valeria B. , Vladimirov Nikolai G. , Velichkova Rumiana S. 
Published: April 2003

AbstractBifunctional poly(1,3,6‐trioxacyclooctane)s were obtained with (CF3SO2)2O as initiator in cationic ring‐opening polymerization via active chain‐end mechanism. To achieve a precise characterization of poly(1,3,6‐trioxacyclooctane) fractions with respect to molecular weight and end functionality, induced termination with ultraviolet (UV)‐active 9‐anthrylmethyl derivatives (ACH2—) was performed. This group improves the detection of the end‐functions and the separation into functionality fractions as it changes the hydrophilic‐hydrophobic balance of the macromolecules. With high‐performance liquid chromatography (HPLC) at the critical point of adsorption combined with photo‐diodearray detection and gel‐permeation chromatography (GPC) characterization of the molecular weight and the functionality distributions of the products was realized. Semipreparative separation followed by GPC and 1H nuclear‐magnetic resonance (NMR) analysis of the fractions was used to determine their molecular weight distribution, average structure and type of the end groups. These analyses confirmed the correctness of the results from HPLC, based on elution at “critical conditions” of oligomers fitted with UV‐active groups. This method is suitable for the separation of poly(1,3,6‐trioxacyclooctane)s with molecular weights less than 20000.
Protection and polymerization of functional monomers, 26. Synthesis of well‐defined poly[4‐(3′‐butynyl)styrene] by means of anionic polymerization of 4‐(4′‐trimethylsilyl‐3′‐butynyl)styrene
Authors: Ishizone Takashi , Hirao Akira , Nakahama Seiichi , Tsuda Katsuyuki 
Published: April 2003

AbstractAnionic polymerization of 4‐(4′‐trimethylsilyl‐3′‐butynyl)styrene (2) was carried out in THF at −78°C for 0.5 h with oligo(α‐methylstyryl)lithium, ‐dilithium, and ‐dipotassium. Poly(2)s possessing predicted molecular weights and narrow molecular weight distributions (M̄w/M̄n < 1.11) were quantitatively obtained in all cases. By sequential anionic copolymerization of 2 and styrene, novel block copolymers, polystyrene‐block‐poly(2) starting either from living polystyrene or living poly(2), were synthesized. After completion of the polymerization, there occurred some gradual deactivation of the propagating carbanion of poly(2) at −78°C. This deactivation reaction could be almost completely suppressed at −95°C. The deprotection of poly(2) was performed by treating with Bu4NF in THF at 0°C for 1 h. The trimethylsilyl protecting group of poly(2) was completely removed to afford a poly[4‐(3′‐butynyl)styrene] of a controlled molecular structure.
Sequence change of poly(N‐acylurethane)s based on transesterification
Authors: Kanamaru Masami , Takata Toshikazu , Endo Takeshi 
Published: April 2003

AbstractModification of poly(N‐acylurethane)s (3a–c) by transesterification with hexyl alcohol and 2‐dodecyl‐1,3‐propanediol (2a) under mild conditions was studied. 3 were prepared by polyaddition of corresponding bis(N‐acylisocyanate)s and diols under mild conditions in good yields. Reaction of poly(N‐acylurethane) (3a) (Mn = 22700) with two equivalents of hexyl alcohol started around 100°C to give the corresponding degradation products (Mn = 7 300, 120°C, 90 min). A mixture of poly(N‐acylurethane) (3b, Mn = 17500) with an equimolar amount of 2a was heated at 150°C under reduced pressure to remove 1,2‐propanediol. The polymer obtained was 3a of which yield and Mn were 57% and 6900, respectively. Transesterification of N‐acylurethane derived from phenol proceeded easier than that derived from alkanol. Aromatic poly(N‐acylurethane) (3c) derived from 4,4′‐dihydroxydiphenyl ether (2c) underwent a similar transesterification with 2a at lower temperature (80°C) without removal of 2c to give 3a in 43% yield. Thus, the modification of poly(N‐acylurethane)s (3) could be readily achieved by the transesterification with mono alcohols and diols under mild conditions without any catalyst.
Synthesis and enzymatic hydrolysis of polydepsipeptides with functionalized pendant groups
Authors: Ouchi Tasuro , Nozaki Tatsuya , Okamoto Yoshifumi , Shiratani Masahiro , Ohya Yuichi 
Published: April 2003

AbstractWater‐soluble polydepsipeptides with functionalized side‐chain groups, i.e., alternating copolymers, consisting of glycolic acid (Glc) and L‐lysine (L‐Lys), L‐aspartic acid (L‐Asp) or L‐glutamic acid (L‐Glu) residues as α‐hydroxy acid and α‐amino acid residues, respectively, were synthesized, and their biodegradation behavior was investigated. Three kinds of polydepsipeptides, poly(Glc‐alt‐Lys), poly(Glc‐alt‐Asp) and poly(Glc‐alt‐Glu), were synthesized by means of ring‐opening polymerization of the corresponding cyclodepsipeptides and subsequent deprotection of benzyl and benzyloxycarbonyl groups. In order to estimate the main‐chain cleavage behavior of polydepsipeptides with functionalized side‐chain groups, the hydrolysis behavior of the obtained water‐soluble polydepsipeptides was first investigated in phosphate buffer solution with or without an enzyme in vitro.
Determination of transfer constants of non‐ionic thiolended surfactants (transurfs) in styrene free‐radical polymerizations
Authors: Vidal Frédéric , Gilbert Robert G. 
Published: April 2003

AbstractThe transfer constants of 1‐dodecanethiol and non‐ionic thiol‐ended surfactants (transurfs) have been determined for the bulk polymerization of styrene at 70°C; these values are 19 for l‐dodecanethiol and 19 and 14 for the transurfs with 17 and 90 ethylene oxide units, respectively. Transfer constants are obtained from the high‐molecular‐weight portion of the full number molecular weight distribution.
“Liquid crystalline” thermosets from 4,4′‐bis(2,3‐epoxypropoxy)biphenyl and aromatic diamines
Authors: Mormann Werner , Bröcher Markus 
Published: April 2003

AbstractPure 4,4′‐bis(2,3‐epoxypropoxy)biphenyl (1) has been synthesized and its mesophase behaviour has been investigated. 1 forms a monotropic nematic mesophase with a virtual clearing temperature of 109°C. 1 has been cured with 2,4‐diaminotoluene (3), 4,4′‐diaminobiphenyl (4), and 4‐aminophenyl 4‐aminobenzoate (5) to investigate the possibility of formation of anisotropic networks. Virtual clearing temperatures of the diamines indicate that liquid crystalline thermosets (LCT's) might be obtained with 4 and 5. Crystallization of oligomeric products from the isotropic melt of 1 with 3 or 4, respectively, occurred on isothermal curing without formation of a mesophase, while a nematic LCT was obtained with 5.
Molecular orientation of paramagnetic metal complexes in melt‐drawn fibers of thermotropic liquid crystalline polymers
Authors: Hanabusa Kenji , Hashimoto Masami , Kimura Mutsumi , Koyama Toshiki , Shirai Hirofusa 
Published: April 2003

AbstractLiquid crystalline polyesters as host polymers and paramagnetic metal complexes as guest molecules were prepared, and melt‐drawn fibers were made from their blend at mesophase temperature. The wide‐angle X‐ray diffraction patterns of the fibers indicated that the nematic or smectic phase is frozen during melt‐drawing. The molecular orientation of the metal complexes in the fibers was investigated by means of ESR. The order parameter obtained from the ESR spectra of the fibers suggests that the base of the square planar Cu(II) and pyramidal V(IV)O complex is almost completely oriented parallel to the fiber axis.
Synthesis and characterization of second‐order nonlinear optical main‐chain polyurethanes containing acceptor‐substituted carbazole units
Authors: Zhang Yadong , Wang Liming , Wada Tatsuo , Sasabe Hiroyuki 
Published: April 2003

AbstractA diol monomer bearing carbazole units substituted with one acceptor group was prepred starting from 3‐formyl‐9‐(4‐hydroxybutyl)carbazole and hexamethylene bis(cyanoacetate) via Knoevenagel condensation. Main‐chain polyurethanes with acceptor‐substituted carbazole as nonlinear optical chromophores were obtained by addition polymerization of the carbazole diol monomer with various diisocyanates in tetrahydrofuran at room temperature using dibutyltin diacetate as a catalyst. These carbazole main‐chain polyurethanes were found to have glass transition temperatures in the range of 113–122°C and weight‐average molecular weights in the range of 6300–11000 g/mol. The chloroformsoluble polyurethanes could be spin‐coated into thin films with good optical quality. After poling, these films displayed reasonable second harmonic generation efficiencies. Preliminary results indicated that the polyurethanes have good thermal stability compared to analogous polymers without hydrogen bonds.
Infrared spectroscopic study of the structural change of polymethacrylonitrile following heat‐treatment and subsequent treatment with water
Authors: Nagata Akira , Ohta Koji , Iwamoto Reikichi 
Published: April 2003

AbstractThe infrared spectrum of polymethacrylonitrile (PMAN) exhibits noticeable change on heat‐treatment up to 240°C, the color of the sample changed from yellowish at 120°C, through yellow and red, to deep red at 210°C or above. A new structure
magnified image
was proposed as a plausible structure for the chromophore of the heat‐treated PMAN film, on the basis of comprehensive consideration of details of the spectral change in reference to the corresponding spectral change of polyacrylonitrile (PAN) and the spectra of compounds having similar structures. Subsequent treatment of the deep‐red PMAN with hot water further drastically changed the infrared spectrum, and in turn the color changed from deep red to yellowish. The spectrum of the hydrolyzed product was in complete agreement with that of the copolymer of methacrylonitrile and methacrylic acid. Thus the structure was found to be
magnified image
from infrared spectral comparison.
Thermoshrinking behavior of poly(vinylcaprolactam) gels in aqueous solution
Authors: Makhaeva Elena E. , Thanh Le Thi Minh , Starodoubtsev Sergei G. , Khokhlov Alexei R. 
Published: April 2003

AbstractThe swelling of newly synthesized slightly crosslinked gels of polyvinylcaprolactam (PVCa) was studied as a function of temperature. In water, PVCa gels undergo a sharp volume transition from a swollen to a collapsed state on heating. In water/alcohol mixtures, the gel first shrinks and then expands as the temperature is raised. The swelling behavior of the thermosensitive PVCa gel in surfactant solution depends on kind and concentration of the surfactant. Normally, an additional swelling of the gel is observed in the presence of ionic surfactants. Addition of the surfactant raises the collapse transition temperature of the gel. Absorption of the surfactant by the PVCa gel as a function of temperature and surfactant concentration is analysed in detail.
Thermotropic polyamides containing the benzophenone unit
Authors: Hajek Andreas , Heitz Walter , Wendling Jürgen , Wendorff Joachim H. 
Published: April 2003

AbstractThe synthesis and structure‐property relationship of fully aromatic homo‐ and copolyamides are described. They all contain the 3,4′‐substituted benzophenone and diphenyl ether moiety in the main chain. The synthesis of the polyamides was performed at low temperatures with silylated aromatic diamines and aromatic acid chlorides. The polymers possess good solubility in dipolar aprotic solvents. They display thermotropic liquid crystalline properties. Based on results obtained by means of polarization microscopy, X‐ray scattering, and molecular dynamics simulation a rather unusual structure is proposed. It consists of a superlattice composed alternatingly of smectic B layers and amorphous layers. The formation of smectic B layers is untypical for main‐chain LC polymers without aliphatic spacers.
Synthesis of water‐soluble biologically active phenol (or catechol) containing copolymers of N‐vinyl‐2‐pyrrolidone
Authors: Solovskij Michael V. , Denisov Victor M. , Panarin Eugenij F. , Petukhova Natalija A. , Purkina Alla V. 
Published: April 2003

AbstractWater‐soluble N‐vinyl‐2‐pyrrolidone (VP) copolymers containing phenol (or catechol) groups in the side chains were synthesized by reactions of copolymers of VP and crotonic acid (CA) with p‐aminophenol and by reaction of p‐nitrophenyl ester groups containing VP‐CA copolymers with dopamine. It was established that phenol (or catechol) containing multiunit VP copolymers (which were characterized by GPC, viscometry, UV, IR and 1H NMR spectroscopy) exhibit immunostimulating activity. In addition, the phenol‐containing copolymers exhibit antitumor activity. The VP‐CA‐p‐crotonoylaminophenol terpolymer can be used as a macromolecular carrier in the synthesis of a carcinogen‐polymer antigen: a polymeric azo derivative of ß‐naphthylamine.
Acyclic diene metathesis (ADMET) polymerization using a well‐defined ruthenium based metathesis catalyst
Authors: Brzezinska Krystyna , Wolfe Patrick S. , Watson Mark D. , Wagener Kenneth B. 
Published: April 2003

AbstractA series of α,ω‐dienes have been exposed to Ru(Cl2)(CHPh)(PCy3)2, [Ru] 3, metathesis catalyst under acyclic diene metathesis (ADMET) conditions, and the products were compared with those obtained previously using Schrock's well defined Mo and W alkylidenes. High molecular weight polymers can be synthesized using [Ru] 3 if lower monomer to catalyst ratios with respect to [Mo] 1 and [W] 2 are used. Monomer structure plays a role since 1,9‐decadiene produces molecular weights typical of ADMET chemistry, whereas 1,5‐hexadiene produces only oligomers. This decrease in reactivity is attributed to a manifestation of intramolecular π‐complexation of the tethered olefin in 1,5‐hexadiene polymerizations. Substituents at the 2‐position of α,ω‐dienes also affects polymerization in that only dimers can be produced from 2‐methyl‐1,5‐hexadiene, a result similar to the same reaction performed with [W] 2. Diallyl ether oligomerizes effectively in the presence of [Ru] 3 with a ratio of cyclics to oligomers comparable to results obtained with [Mo] 1 and [W] 2.
Synthesis and characterization of polyoxetanes containing 4‐cyanobiphenyl‐based side groups for nonlinear optical applications, 1. Chemical modification of poly[3,3‐bis(chloromethyl)oxetane]with sodium 4‐cyano‐4′‐biphenyl oxide
Authors: Guichard Bertrand , Noël Claudine , Reyx Danièle , Kajzar François 
Published: April 2003

AbstractTwo copolyethers were prepared by chemical modification of poly[3,3‐bis(chloromethyl)oxetane] with sodium 4‐cyano‐4′‐biphenyl oxide, employing the concept of having the cyanobiphenyl species serve concomitantly as both the nonlinear optical chromophore and the mesogenic moiety in the polymer. Their thermal behavior was established by means of DSC and optical microscopy. Some preliminary Corona poling experiments were performed, and the second harmonic generation coefficients d31 and d33 were measured by Maker fringe analysis. The results showed that liquid crystallinity enhances field‐induced polar ordering. The ratio d33/d31 was found to be much larger than 3, in agreement with the theoretical models for electric field poling of liquid crystalline polymers where hyperpolarizable chromophores are attached as side groups to a polymer backbone.
Conformational transitions in poly(methacrylic acid) gel/poly(ethylene glycol) complexes. Effect of the gel cross‐linking density
Authors: Karybiants Natalia S. , Philippova Olga E. , Starodoubtsev Sergei G. , Khokhlov Alexei R. 
Published: April 2003

AbstractWe present results on the effect of the cross‐linking density on the collapse of poly‐(methacrylic acid) gels induced by the interaction with linear poly(ethylene glycol) and on their subsequent reswelling (reentrant transition). The abruptness and the amplitude of both transitions increase with decreasing cross‐linking density of the gel. A special feature of the reswelling transition for the PMAA gel/PEG system is the existence of a wide range of PEG concentrations where both collapsed and swollen states of the gel are stable. The conditions for the existence of such a region are easier realized for slightly cross‐linked gels. The corresponding theoretical explanation is given. The swelling degree of the collapsed gels increases with increasing cross‐linking density, which is explained by the presence of a certain amount of hydrophilic PEG loops in highly cross‐linked gels.
Anionic ring‐opening polymerization of cyclodisilazanes, 1. General aspects
Authors: Bruzaud Stéphane , Soum Alain 
Published: April 2003

AbstractThe anionic ring‐opening polymerization of a model monomer of cyclodisilazanes 1, initiated with both organosodium and organolithium initiators, was investigated. Under specific conditions, this polymerization exhibits all the characteristics of a living process. Indeed, whatever the experimental conditions chosen, there is no evidence of back‐biting and/or transfer reactions competing with the propagation reaction. Kinetic measurements showed that this polymerization is first order with respect to the concentrations of both monmer and active centers. The absolute rate constant of propagation (kp) and the thermodynamic parameters (enthalpy and entropy) of the propagation step where calculated. On the basis of these results, a mechanism of the anionic ring‐opening polymerization of 1 is proposed.