bluuebunny/crossref_metadata_2025_split huggingface dataset:
Macromolecular Design via the Interchange of Xanthates (MADIX): Polymerization of Styrene with O‐Ethyl Xanthates as Controlling Agents
Authors: Destarac Mathias , Brochon Cyril , Catala Jean‐Marie , Wilczewska Agnieszka , Zard Samir Z. 
Published: February 2003

AbstractControl of the free‐radical polymerization of styrene was achieved using a series of eight xanthates of the general structure RS(CS)OEt as reversible addition fragmentation chain‐transfer agents. The influence of the nature of the R leaving group was explored. It was found that the transfer ability of the xanthate is markedly improved with increasing stability of R and its steric hindrance. Group R strongly influences the Mn evolution profile during polymerization, but only influences the polydispersities to a small extent. The cyanoisopropyl group was shown to be the best leaving group, leading to an increase in the molecular weight during polymerization that was close to linearity. The living character of the polymerization and the high purity of the chain structures were supported by matrix‐assisted laser desorption ionization time‐of‐flight (MALDI‐TOF) mass spectrometry and 13C NMR spectroscopy. A zero‐order dependence of the kinetics of polymerization on the xanthate concentration was observed.
Conversion versus time plots for thermal bulk polymerizations of styrene at 110 °C in the presence of various xanthates.magnified imageConversion versus time plots for thermal bulk polymerizations of styrene at 110 °C in the presence of various xanthates.
Rheological Properties of Micellar Aqueous Solution of Hydrophobically Modified Poly(ethylene glycol) (C12E25)
Authors: Yamazaki Ritsuko , Inomata Katsuhiro , Nose Takuhei 
Published: February 2003

AbstractThe rheological properties of micellar aqueous solutions of hydrophobically modified ethylene glycol oligomer, poly(ethylene glycol) monododecyl ether (C12E25), have been studied over a wide range of concentration and temperature. The micellar solution of C12E25 exhibits a sol‐gel transition accompanied by a disorder‐to‐order transition of micelle particles. The following conclusions were made: (1) The sol solution behaves like an ordinary viscous liquid of Newtonian flow, presenting no sign of any change in associations. (2) Under shear deformation, the gel exhibits a yield point around the strain of a few per cent, followed by a plastic flow with further deformation. The plastic flow exhibits a strong non‐Newtonian flow. (3) As the shear rate increases, the sol‐gel transition temperature, observed by steady‐flow viscosity, becomes lower with a reduced sharpness of transition. (4) The long‐range structural order of the lattice in the gel, destroyed by the plastic flow, is suggested to substantially recover in 10–100 s.
Concentration dependency on the steady‐flow viscosity at the shear rate of 10 s−1 for C12E25 aqueous solutions at 70 °C. The inset shows the linear–linear plots.magnified imageConcentration dependency on the steady‐flow viscosity at the shear rate of 10 s−1 for C12E25 aqueous solutions at 70 °C. The inset shows the linear–linear plots.
UV‐Curable Azobenzene Polymer Bearing Photo‐Crosslinkable Moiety for Stabilization of Photo‐Fabricated Surface Relief Structure
Authors: Kimura Tatsumi , Kim Jun.‐Young , Fukuda Takashi , Matsuda Hiro 
Published: February 2003

AbstractIn order to find a new class of photo‐processable liquid crystalline (LC) aligning material, five kinds of new maleimide‐based copolymers bearing both azobenzene and cinnamate moieties with different functionalization ratio have been synthesized. The properties of these five copolymers were compared regarding physical and chemical properties that are required for our aim. The photo‐induced surface relief (PSR) gratings could be fabricated on the films of these copolymers using an Ar+ laser (λ = 488 nm), and were successfully immobilized and bleached by UV‐light irradiation that causes photo‐crosslinking of the cinnamate moiety and photo‐degradation of the azobenzene moiety, respectively. The PSR inscription rate and the thermal stability have been investigated regarding the functionalization ratio between cinnamate and azobenzene side chain. The residual ratio of the PSR structure after UV‐curing was increased with increasing photo‐crosslinkable moiety. It was confirmed that the UV‐cured PSR grating structure becomes transparent at visible wavelength and was able to align LC molecules parallel to the grating direction.
Polarized optical microscope image of LC cell aligned by the PMPDC 21‐18 film with UV‐cured PSR structure (0°).magnified imagePolarized optical microscope image of LC cell aligned by the PMPDC 21‐18 film with UV‐cured PSR structure (0°).
Temperature‐Induced Polymorphic Crystals of Poly(butylene adipate)
Authors: Gan Zhihua , Abe Hideki , Doi Yoshiharu 
Published: February 2003

AbstractThe melting behavior, crystal structure, and spherulitic morphology of melt‐crystallized poly(butylene adipate) (PBA) at a temperature range from 25 to 35 °C have been investigated by differential scanning calorimetry (DSC), wide‐angle X‐ray diffraction (WAXD) and optical microscopy. Two distinct melting behaviors with double peaks have been observed after melt‐crystallizing at different temperatures. X‐ray analysis proves that these two behaviors arise from two forms of PBA crystal structures. The β‐form crystals are formed at temperatures below 31 °C, while the α‐form crystals are formed above 29 °C. When the crystallization temperature is 30 ± 1 °C, a mixture of α‐form and β‐form crystals has been formed. The influences of annealing treatment and sample preparation method on the two forms of PBA crystal structures have been discussed. The results indicate that the low temperature‐formed β‐form crystals are very sensitive to the preparation conditions.
The melting curves at different heating rates for poly(butylene adipate) after melt‐crystallized at 25 °C and 33 °C, respectively.magnified imageThe melting curves at different heating rates for poly(butylene adipate) after melt‐crystallized at 25 °C and 33 °C, respectively.
Stereoblock Copolymerization of Propylene and Methyl Methacrylate with Single‐Site Metallocene Catalysts
Authors: Jin Jizhu , Chen Eugene Y.‐X. 
Published: February 2003

AbstractSequential stereoblock copolymerization of propylene (P) and methyl methacrylate (MMA) using Group IV single‐site metallocene catalysts efficiently produces PP‐b‐PMMA stereodiblock copolymers. When activated with B(C6F5)3, C2‐symmetric rac‐Et(Ind)2ZrMe2 yields isotactic‐PP‐b‐isotactic‐PMMA diblock copolymer, whereas Cs‐symmetric Me2Si(C5Me4)(tBuN)TiMe2 affords atactic‐PP‐b‐syndiotactic‐PMMA diblock copolymer. In the copolymerization catalyzed by the C2‐symmetric catalyst, a very small amount of PMMA homopolymer formed can be removed from the copolymer by extracting the bulk polymer product with boiling methylene chloride. However, separation of isotactic PP formed if any from the copolymer product approves very difficult, due to very similar solubility between the diblock copolymer and isotactic PP homopolymer in various high‐boiling chlorinated solvents. On the other hand, in the copolymerization catalyzed by the Cs‐symmetric catalyst, both PMMA and atactic PP homopolymers formed in small weight fractions during the copolymerization can be successfully removed from the predominant copolymer product by solvent extraction using boiling heptane. After successful removal of both homopolymers, for example, an atactic‐PP‐b‐syndiotactic‐PMMA diblock copolymer has high molecular weight (Mn = 21 100), narrow molecular weight distribution (PDI = 1.08), high PMMA incorporation (33.8 mol‐% of PMMA), and moderate syndiotacticity for the PMMA block ([rr] ≈ 80%). Furthermore, the comonomer composition in the copolymer can be controlled by the time for propylene polymerization and the conversion of MMA. A pronounced activator effect is observed; when the same Cs‐symmetric catalyst is activated with Ph3CB(C6F5)4, formation of homopolymers is predominated.
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Electrochemical Polymerization of Thianaphthene in Mixed Electrolytes of Boron Trifluoride Diethyl Etherate and Trifluoroacetic Acid
Authors: Xu Jingkun , Shi Gaoquan , Zhang Jiaxin , Hong Xiaoyin 
Published: February 2003

AbstractSubstrate‐supported polythianaphthene (PTN) films have been electrochemically synthesized by direct oxidation of thianaphthene on platinum or stainless steel electrode in mixed electrolytes of boron trifluoride diethyl etherate (BFEE) and trifluoroacetic acid (TFA). The oxidation potentials of the monomer in these media are considerably lower than those in neutral solvents. Increasing the content of TFA in the mixed electrolytes can effectively decrease the oxidation potential and increase the coupling rate of the monomer. On the other hand, a high TFA concentration can result in a negative effect on the properties of the as‐formed polymer. The mixed electrolyte of BFEE + 16.7% TFA was found to be the most suitable medium for the electrosyntheses of PTN. PTN in dedoped state is soluble in usual strong polar organic solvent such as dimethyl sulfoxide (DMSO). Fluorescent spectral studies indicate that the polymer is a blue light emitter.
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Synthesis of High‐Molecular Weight Polymers Based on N,N‐Diallyl‐N‐Methylamine
Authors: Timofeeva Larisa M. , Vasilieva Yuliya A. , Klescheva Natalia A. , Gromova Galina L. , Timofeeva Galina I. , Rebrov Alexandr I. , Topchiev Dmitry A. 
Published: February 2003

AbstractHigh‐molecular weight polymers, namely poly(N,N‐diallyl‐N‐methylammonium trifluoroacetate) and poly(N,N‐diallyl‐N‐methylamine), were prepared by radical polymerization of N,N‐diallyl‐N‐methylamine in aqueous solution in the presence of an equimolar amount of trifluoroacetic acid and by polymerization of the newly synthesized equimolecular salt N,N‐diallyl‐N‐methylammonium trifluoroacetate in gentle conditions. We have established that chain termination is controlled by the bimolecular mechanism and that degradative chain transfer to monomer transforms into effective chain transfer (see Scheme). The possibility of controlling the polymerization rate and molecular weight of polymers is demonstrated. The mechanisms of the observed phenomena are discussed.
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Synthesis and Characterization of New Acrylate and Methacrylate Monomers with Pendant Pyridine Groups
Authors: Cui Li , Lattermann Günter 
Published: February 2003

AbstractTo overcome some drawbacks of polyvinylpyridines, new monomers of acrylate and methacrylate type with pendant pyridine groups i.e., 4‐(3‐methacryloylpropyl)pyridine 1a and 4‐(3‐acryloylpropyl)pyridine 1b were successfully prepared, although it turned out to be challenging work to synthesize the acrylate monomer 1b. First polymerization studies showed that the new monomers could be polymerized easily by atom transfer radical polymerization (ATRP). The new polymers show excellent characteristics, such as very good solubility, low glass‐transition temperature, and easy quaternization.
Design and structure of new monomers 1a and 1b.magnified imageDesign and structure of new monomers 1a and 1b.
Chemical Modification of a Poly(ethylene terephthalate) Surface by the Selective Alkylation of Acid Salts
Authors: Li Jun , Maekawa Yasunari , Yamaki Tetsuya , Yoshida Masaru 
Published: February 2003

AbstractChemical modification of the hydrophilic surface of poly(ethylene terephthalate) (PET) was examined by the selective alkylation of the acid salt on the surface using acyl bromides as an electrophile with catalytic potassium fluoride. The hydrophobicity of the PET surface increased as the alkylation reaction of the hydrolyzed surface proceeded. The chemical incorporation of the alkylation reagents was confirmed by the presence of fluorine peaks in X‐ray photoelectron spectroscopy (XPS) from the fluorinated reagents. Exponential increases were observed in the emission and excitation intensities of fluorescence spectra during the reaction of the surface with a fluorescent reagent. This indicated that the esterification of carboxylic acids on the surface proceeded without deterioration of the reaction even at the later stages. The relation between changes in contact angles and the fluorescence spectra revealed that the hydrophobicity of a surface was quickly restored at the beginning of a reaction.
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Well‐Defined Ruthenium‐Coordinated Block Copolymers of 2‐Vinylpyridine with 2‐(N‐Carbazolyl)ethyl Methacrylate and Their Optical Properties
Authors: Cho Young‐Sun , Lee Hye‐Kyung , Lee Jae‐Suk 
Published: February 2003

AbstractIn order to study the energy‐transfer phenomenon in ruthenium‐coordinated polymers, novel block copolymers from carbazolylethyl methacrylate and 2‐vinylpyridine were prepared by living anionic polymerization; the copolymers possessed varying repeating units and had the desired molecular weight and a narrow‐molecular‐weight distribution. The ruthenium‐coordinated block copolymers were formed by reacting [RuII(tpy)(dmbpy)Cl] with the polymers, in which the pyridine units acted as ligands. Photoluminescence and optical absorption measurements of the coordinated block copolymers were carried out to observe the energy transfer in the complexes. The energy transfer from the carbazole blocks to the ruthenium‐coordinated blocks might take place either by an intra‐ and/or an intermolecular energy‐transfer mechanism. From the optical absorption, photoluminescence, and electroluminescence studies, it was observed that the ease of the energy transfer increased with an increasing number of metal‐complex units.
Normalized electroluminescence spectra of the device (ITO/PEDOT/RuIIL2bpolym/TAZ/Alq3/Ag).magnified imageNormalized electroluminescence spectra of the device (ITO/PEDOT/RuIIL2bpolym/TAZ/Alq3/Ag).
Synthesis of Magnetic Nanocomposite Based on Amphiphilic Polyurethane Network Films
Authors: Kim Ju‐Young , Shin Dong‐Hyun , Ihn Kyo‐Jin , Nam Chang‐Woo 
Published: February 2003

AbstractMagnetic nanocomposites, showing extremely small coercivity and hysteresis loop, were synthesized using amphiphilic polyurethane networks based on amphiphilic urethane acrylate nonionomer (UAN) precursor chains. Three kinds of UAN gel films were synthesized through UV‐curing of UAN chains in the absence of a solvent, or crosslinking polymerization of UAN/water and UAN/DMAc mixtures. Even though these gel films were synthesized with the same UAN, these UAN gel films had very different microstructures depending on the preparation conditions; as a consequence, magnetic composites prepared with these crosslinked films exhibited very different size and morphology of magnetic nanoparticles. Atomic force microscopy and mechanical property measurements showed that UAN gel film (UANH) synthesized with UAN/water mixture had the highly microphase‐separated structures whereas the gel films synthesized via UV‐curing (UANV) or polymerization of UAN/DMAc mixture (UAND) had relatively homogeneous structures. The largest ellipsoidal particles were formed in UANH gel films and the smallest ellipsoidal particles and rod‐shaped particles were made up in UANV gel and UAND gel film, which was confirmed by transmission electron microscopy.Transmission electron micrograph of magnetic composite film prepared with UANV.magnified imageTransmission electron micrograph of magnetic composite film prepared with UANV.
Glass‐Transition Temperature (Tg) of Free‐Radically Prepared Polyacrylonitrile by Inverse Gas Chromatography, 2. Molecular‐Weight Dependence of Tg of Two Different Types of Aqueous Polymers
Authors: Minagawa Masatomo , Kanoh Hiroyasu , Tanno Satoshi , Satoh Masaru 
Published: February 2003

AbstractThe molecular‐weight dependence of the glass‐transition temperature (Tg) of a series of atactic polyacrylonitriles (PAN)s was studied by inverse gas chromatographic (IGC) analysis. PANs having different molecular weights were prepared by either; (i) the addition of isopropyl alcohol as a chain‐transfer agent, or (ii) a scission reaction induced by the addition of alkali (NaOH) to a solution (N,N‐dimethylformamide solution, at 25 °C) of the resulting polymer. The intrinsic viscosity [η] was in the range of 10.9–0.1 (dl · g−1), which corresponds to a viscosity‐averaged molecular weight (Mv) of 1 590 000–3 000. As part of the results, a side reaction, which saw the conversion of the nitrile (CN) groups of PAN into amide (CONH2) and/or carboxylic acids (COOH) groups by alkali, was found to occur. The typical molecular‐weight dependence of the Tg in free‐radically prepared PAN was discussed in connection with a chain‐transfer mechanism in an aqueous medium.Molecular‐weight dependence of the Tg for PAN (WA). An error bar is given by a short vertical arrow.magnified imageMolecular‐weight dependence of the Tg for PAN (WA). An error bar is given by a short vertical arrow.
Oxidative Coupling Copolymerization of 4‐Methyltriphenylamine with Arenes
Authors: Strzelec Krzysztof , Fugino Nobutoshi , Ha Jaekook , Ogino Kenji , Sato Hisaya 
Published: February 2003

AbstractA novel synthetic method for the preparation of high‐molecular‐weight conjugated polymers is presented. It consists of the oxidation copolymerization of different arenes with triphenylamine. The structure of the copolymers was characterized by 1H and 13C NMR spectra. The copolymers have good solubility in common organic solvents and are thermally stable. Photoluminescence (PL) spectra (see Figure) showed that the color of emission depends on the type of arene units in the copolymer chain. Cyclic voltammetry (CV) measurements revealed electrochemical activity of the copolymers.PL spectra of the copolymers.magnified imagePL spectra of the copolymers.
Synthesis, Characterization, and Intramolecular End‐to‐End Ring Closure of α‐Isopropylidene‐1,1‐dihydroxymethyl‐ω‐diethylacetal Polystyrene‐block‐polyisoprene Block Copolymers
Authors: Schappacher Michel , Deffieux Alain 
Published: February 2003

AbstractCyclic polystyrene‐block‐polyisoprenes of controlled dimensions have been synthesized for the first time by the direct coupling of α‐isopropylidene‐1,1‐dihydroxymethyl‐ω‐diethylacetal‐heterodifunctional linear polystyrene‐block‐polyisoprene precursors previously prepared by living anionic polymerization. Cyclization is achieved under high dilution by intramolecular coupling of the polymer ends under acid catalyst conditions. Using this strategy polystyrene‐block‐polyisoprene macrocycles of controlled chain dimensions are prepared in high yield (> 90%). Pure cycles were finally recovered by flash chromatography. The synthesis and characterization of both the linear α,ω‐heterodifunctional polystyrene‐block‐polyisoprenes block copolymers precursors and of the corresponding cyclized chain architectures are reported.200 MHz 1H NMR spectrum (CDCl3) of cyclized polystyrene‐block‐polyisoprene copolymer (Mn = 12 000).magnified image200 MHz 1H NMR spectrum (CDCl3) of cyclized polystyrene‐block‐polyisoprene copolymer (Mn = 12 000).
Propylene Polymerization with Bis(phenoxy‐imine) Group‐4 Catalysts Using iBu3Al/Ph3CB(C6F5)4 as a Cocatalyst
Authors: Saito Junji , Onda Mitsuhiko , Matsui Shigekazu , Mitani Makoto , Furuyama Rieko , Tanaka Hidetsugu , Fujita Terunori 
Published: February 2003

AbstractThe catalytic behavior of three bis(phenoxy‐imine) group‐4 transition‐metal complexes (M = Ti, Zr, Hf), with iBu3Al/Ph3CB(C6F5)4 cocatalyst systems towards propylene polymerization was investigated under atmospheric pressure at 25 °C. The Ti complex produced ultrahigh‐molecular‐weight atactic poly(propylene), whereas Zr and Hf complexes formed high‐molecular‐weight isotactic poly(propylene)s via a site‐control mechanism. The isotactic poly(propylene) obtained with the Hf complex displayed a high melting temperature of 123.8 °C.
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Coils, Rods and Rings in Hydrogen‐Bonded Supramolecular Polymers
Authors: Tessa ten Cate A. , Sijbesma Rint P. 
Published: February 2003

AbstractThe article discusses the development and properties of supramolecular polymers based on quadruple hydrogen bonds between self‐complementary ureidotriazine (UTr) and ureidopyrimidinone (UPy) functional groups. The high association constant with which these groups dimerize leads to polymers with a high degree of polymerization in isotropic solution. Application of these units for the functionalization of telechelic polymers results in new materials with mechanical properties approaching those of covalent polymers, but with a much stronger temperature‐dependent behavior. Solvophobic interactions between the hydrogen bonding moieties may be used to obtain supramolecular polymers with a well defined helical columnar architecture. Another consequence of the high dimerization constant of the UPy group is the phenomenon of a critical concentration in solutions of many bifunctional monomers. Below this concentration, only cycles are present, while above the critical concentration, the amount of cycles remains constant, and a polymer is formed. Conformational properties of the linker units are used to control the equilibrium between polymers and cycles, and are proposed to form a promising strategy toward tunable materials.Supramolecular polymer material with elastomeric properties resulting from functionalization with UPy groups. (Reproduced with permission. © John Wiley & Sons, Inc.)magnified imageSupramolecular polymer material with elastomeric properties resulting from functionalization with UPy groups. (Reproduced with permission. © John Wiley & Sons, Inc.)
Atom‐Transfer Radical Polymerization of 2‐(N,N‐Dimethylamino)ethyl Acrylate
Authors: Zeng Faquan , Shen Youqing , Zhu Shiping 
Published: February 2003

AbstractATRP of 2‐(N,N‐dimethylamino)ethyl acrylate (DMAEA) was investigated using CuBr or CuCl with different multidentate ligands. The catalyst was found active for DMAEA polymerization when ligated with tris[2‐(N,N‐dimethylamino)ethyl]amine. Good control over molecular weight was achieved, but quaternization of the terminal monomeric/polymeric tertiary amine by the CBr group of polyDMAEA caused chain termination. Using a chloride‐based system helped to suppress chain termination. Amphiphilic poly(methyl acrylate)‐block‐polyDMAEA was synthesized using polyMA as a macroinitiator.
Molecular weights and polydispersities of polyDMAEA versus DMAEA conversion for different catalyst systems.magnified imageMolecular weights and polydispersities of polyDMAEA versus DMAEA conversion for different catalyst systems.
Kinetic Study and New Applications of UV Radiation Curing
Authors: Decker Christian 
Published: February 2003

AbstractHighly crosslinked polymers can be readily synthesized by photoinitiated polymerization of multifunctional monomers or functionalized polymers. The reaction can be followed in situ by real‐time infrared (RT‐IR) spectroscopy, a technique that records conversion versus time curves in photosensitive resins undergoing ultrafast polymerization upon UV exposure. For acrylate‐based resins, UV‐curing proceeds with long kinetic chains (7700 mol/radical) in spite of the high initiation rate. RT‐IR spectroscopy proved very valuable in assessing the influence of various parameters, such as initiation efficiency, chemical structure of the telechelic oligomer, light intensity, inhibitory effect of oxygen, on polymerization kinetics. Interpenetrating polymer networks can be rapidly synthesized by means of UV irradiation of a mixture of difunctional acrylate and epoxy monomers in the presence of both radical and cationic‐type photoinitiators. The same UV technology can be applied to crosslink solid polymers at ambient temperature, which bear different types of reactive groups (acrylate and vinyl double bonds, epoxy ring). UV radiation curing has been successfully used to produce within seconds weathering resistant protective coatings, high‐resolution relief images, glass laminates and nanocomposites materials.Photoinitiated crosslinking polymerization.magnified imagePhotoinitiated crosslinking polymerization.