bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of alkyl groups on the rate constants of propagation and termination in the radical polymerization of dialkyl itaconates
Authors: Sato Tsuneyuki , Takahashi Yoshiko , Seno Makiko , Nakamura Hiroyuki , Tanaka Hitoshi , Ota Tadatoshi 
Published: April 2003

AbstractPolymerization of dialkyl itaconates with dimethyl azoisobutyrate (5) was studied in benzene at 50°C by means of electron spin resonance (ESR). The monomers used are dimethyl (1), diethyl (2), dibutyl (3) and di‐2‐ethylhexyl (4) itaconates. All the polymerization systems involve ESR‐observable propagating polymer radicals under the actual polymerization conditions. The polymerization rate (Rp) and degree of polymerization of the resulting polymer increase in going from shorter to longer alkyl groups. The ESR‐determined rate constants of propagation (kp) and termination (kt) decrease as the alkyl chain becomes longer. kp of 1 is 3,3 times higher than that of 4, while kt of 1 is 590 times higher than that of 4. Thus, the steric effect due to the alkyl group suppresses much more termination than propagation, leading to the fact that Rp increases as the alkyl group becomes larger.
Association of macromolecular prodrugs consisting of adriamycin bound to poly(L‐glutamic acid)
Authors: Nukui Masahiro , Hoes Kees , van den Berg Hans , Feijen Jan 
Published: April 2003

AbstractSoluble macromolecular conjugates for the controlled delivery of the strongly hydrophobic antitumor drug adriamycin (ADR) were prepared. The association behaviour of two types of these amphiphilic conjugates consisting of ADR bound to poly(L‐glutamic acid) (PGA) in aqueous solution was investigated using absorbance and fluorescence spectroscopy as well as GPC and lowangle laser light scattering (LALLS) measurements. ADR was bound via the aminoribosyl moiety either directly with PGA side‐chain groups or via oligopeptide spacer groups. UV/VIS, GPC and LALLS data showed that in buffer solution both ADR conjugates associate intermolecularly. The data of the directly bound ADR conjugates are consistent with the presence of multimers of different degrees of association in equilibrium with single polymer chains. In contrast, spacer‐containing ADR conjugates associate to give stable uniform multimers. UV/VIS and fluorescence spectroscopy performed at very low conjugate concentration show that polymer‐bound ADR residues associate intramolecularly as well. The degree of intra‐ and intermolecular association of the conjugate‐bound ADR molecules depends on the type of conjugate, ADR load and conjugate concentration as well as on ionic strength of the solvent, the presence of organic cosolvents and temperature. The data indicate that hydrophobic domains in spacer‐containing conjugates are more stable compared with directly bound conjugates, probably due to enhanced flexibility and the presence of hydrophobic leucine residues. It is concluded that spacer‐containing conjugates of ADR may have a potential for effective drug delivery under in vivo conditions due to their solution properties in addition to the biodegradability of the drug‐polymer bond.
Side‐chain liquid‐crystalline polysalts. Synthesis and thermal properties of poly{1‐[ω‐(4′‐methoxy‐4‐biphenylyloxy)alkyl]‐4‐vinylpyridinium bromide} or poly[1‐(2‐{2‐[2‐(4′‐methoxy‐4‐biphenylyloxy)ethoxy]ethoxy}ethyl)‐4‐vinylpyridinium bromide]
Authors: Navarro‐Rodriguez Dámaso , Frère Yves , Gramain Philippe 
Published: April 2003

AbstractThe synthesis and thermal properties of a new type of side‐chain liquid‐crystalline polymers, incorporating ionic groups, are described. The polymers are obtained upon spontaneous polymerization (simultaneous quaternization and polymerization) of 4‐vinylpyridine in the presence of ω‐(4′‐methoxy‐4‐biphenylyloxy)alkyl or 2‐{2‐[2‐(4′‐methoxy‐4‐biphenylyloxy)ethoxy]ethoxy}‐ethyl bromide. Fully quaternized polymers of high molecular weight are obtained. As the analogous low‐molecular‐weight molecules previously studied these polymers form smectic mesophases, although the mesogenic groups, which include the pyridinium rings, are directly connected to the polyvinylic backbone.
Synthesis of comb‐like methacryl polymers containing condensates of 11‐aminoundecanoic‐ and 6‐aminocaproic acid in the side chains
Authors: Niemann Manfred , Ritter Helmut 
Published: April 2003

AbstractThe synthesis and free‐radical polymerization of four methacrylic macromonomers, methyl 6‐(6‐methacryloylaminohexanoylamino)hexanoate (5), methyl 11‐(11‐methacryloylaminoundecanoylamino)undecanoate (6), and the corresponding acids 7 and 8, are described. The polymers were characterized by DSC and TG analysis. Viscosity measurements show that the polymers tend to associate because of hydrogen bonding. Additionally, incompatibility of the polymers with polyamide‐6 was found by DSC measurements.
Cationic polymerization of bis(1‐alkylvinyl)benzenes and related monomers, 4. Synthesis of monomers with long alkyl side chains
Authors: Nuyken Oskar , Leitner Michael B. , Maier Gerhard 
Published: April 2003

AbstractHomologues of the series 1,4‐bis(2‐methyl‐2‐alkenyl)benzene (6) are potential monomers for the systematic synthesis of alkyl‐substituted polyindans. The first five homologues were prepared by Witting‐synthesis, starting from 1,4‐diacetylbenzene (5) and the corresponding n‐alkyltriphenyl‐phosphonium bromide (3). Three double‐bond isomers were qualitatively and quantitatively identified by 1H and 13C NMR spectroscopy. The reaction conditions chosen favour Z‐olefination, and the selectivity ratio of Z‐ and E‐olefin formation in each step was estimated.
Effect of catalyst isospecificity on the copolymerization of propene with 1‐hexene
Authors: Sugano Toshihiko , Gotoh Yukitaka , Fujita Takashi , Uozumi Toshiya , Soga Kazuo 
Published: April 2003

AbstractCopolymerization of propene with 1‐hexene was performed at 40°C under atmospheric pressure using both aspecific and isospecific catalysts composed of TiCl3/MgCl2 and Al(C2H5)3, and of Solvay type TiCl3 and Cp2 Ti(CH3)2 (Cp: cyclopentadienyl), respectively. The isospecific catalyst gave two kinds of copolymers with different content of 1‐hexene, whereas the aspecific catalyst gave a uniform copolymer abundant in 1‐hexene. Both copolymers produced with the isospecific catalyst were found to show isotactic stereoregulation in the propylene units. From these results, it was concluded that the catalyst composed of Solvay type TiCl3 and Cp2 Ti(CH3)2 has two kinds of isospecifically active species which differ in the monomer reactivity ratio for propene‐1‐hexene copolymerization.
Enzymatic degradation of microbial poly(3‐hydroxybutyrate) films
Authors: Kumagai Yoshiharu , Kanesawa Youko , Doi Yoshiharu 
Published: April 2003

AbstractThe effects of crystallinity and spherulite size on the enzymatic degradation of microbial poly(3‐hydroxybutyrate) (PHB) films have been studied at 37°C and pH 7,4 in aqueous solutions of an extracellular PHB depolymerase from Alcaligenes faecalis T1. The rate of enzymatic degradation of PHB films decreases with an increase in crystallinity, but it is little influenced by the size of PHB spherulites. It was suggested that the PHB depolymerase firstly hydrolyzes the PHB chains in the amorphous state on the surface of the films and subsequently erodes the PHB chains in the crystalline state.
Hydroquinone oxidation catalyzed by pyridine‐Cu(II) complexes attached to polyorganosiloxanes
Authors: Nemoto Nobukatsu , Ishii Hiroji , Ueno Yukihiko , Ikeda Koji , Takamiya Nobuo 
Published: April 2003

AbstractCu(II) complexes of polyorganosiloxanes with pyridyl group in the side chains (1–6) were investigated as catalysts for hydroquinone oxidation. The catalytic oxidations followed Michaelis‐Menten‐like kinetics. The kinetic parameters were evaluated, and the greatest value of k2/Km is 119 dm3 · mol−1 · s−1 due to the large value of k2 (0,262 s−1) in methanol/water (vol. ratio 2/1) at 25°C. It has been shown that the main factors which influence the substrate‐binding process are hydrophobicity, hydrogen bonding between functional groups in the side chains, conjugation and basicity of pyridine, and adsorption of substrate by amido groups. Large k2 values were obtained in the present system due to flexibility and hydrophobicity of the siloxane backbone. Additionally, in the activation process, hydrogen bonding between amido groups, which is easily formed due to the flexibility of the polymer chains, should contribute to decrease both activation enthalpy and activation entropy.
Mechanisms and kinetics of the anionic polymerization of acrylates, 2. Polymerization of tert‐butyl acrylate in a flow tube reactor and effect of lithium chloride and lithium tert‐butoxide
Authors: Janata Miroslav , Lochmann Lubomír , Vlček Petr , Dybal Jiři , Müller Axel H. E. 
Published: April 2003

AbstractThe kinetics and the molecular weight distributions (MWD) in the anionic polymerization of tert‐butyl acrylate (tBuA) in tetrahydrofuran at 23 ± 3°C were investigated. Tert‐butyl α‐lithioisobutyrate (tBiB‐Li) was used as the initiator in the absence and presence of the additives lithium chloride and lithium tert‐butoxide (tBuOLi). A flow tube reactor was used which allowed very rapid mixing of reagents, within milliseconds. The polymerization is extremely fast, half‐lives being 0,01 s for the system without additive, 0,05 s for LiCl and 3 s for tBuOLi as an additive. The rate of termination was estimated from the strong UV absorption of the enolized β‐oxoester end group formed. The number‐average degree of polymerization is a linear function of conversion, the absolute values, however, demonstrate initiator efficiencies of only ca. 30%. The MWD's of the polymers formed are narrow (Mw/Mn = 1,35 without additive, M/Mn = 1,08 in the presence of LiCl and Mw/Mn = 1,77 in the presence of tBuOLi). After precipitation these values are reduced to 1,17; 1,06 and 1,32, respectively. Experiments in a stirred tank reactor and in ampoules lead to much broader MWD's. This shows that the rate of mixing has a strong effect on the MWD and is of substantial importance in these rapid polymerizations.
Flory polymer‐polymer interaction parameter between hemicellulose and lignin from hardwood
Authors: Shigematsu Mikiji , Morita Mitsuhiro , Sakata Isao 
Published: April 2003

AbstractThe interaction parameter between hemicellulose and lignin from beech wood was evaluated from vapor pressure osmometric measurements on solvent‐polymer and solvent‐polymer‐polymer solutions. Dimethyl sulfoxide (DMSO) was used as a solvent. The interaction parameters between hemicellulose and DMSO (χ01) and between lignin and DMSO (χ02) increase with increasing temperature, and the change with temperature is proportional to inverse temperature. It was found for both polymers that DMSO becomes a “poor solvent” at higher temperature. This result was also derived from the free energy of dilution. The interaction parameter between hemicellulose and lignin (χ12) was evaluated as a function of temperature from the activity of solvent in a solution of the three components. At 60°C, χ12 is positive; it decreases with increasing temperature and becomes negative at 70–80°C where a minimum is found. Above 80°C, χ12 increases again to become positive at 90°C. Thus, hemicellulose and lignin attract each other at 70–80°C, but there is repulsion between the polymers at higher and lower temperatures.
Influence du vieillissement d'une solution renfermant un polystyrène silicié et un sel de triarylsulfonium sur le pourcentage de coupure des liaisons OSi sous irradiation ultraviolette et en couche mince
Authors: Bonfils Frédéric , Giral Louis , Montginoul Claude , Sagnes René , Schué Franc̨ois 
Published: April 2003

AbstractUpon treatment with ultraviolet irradiation (wavelength λ = 254 nm) the resist containing both poly(p‐trialkylsiloxystyrene) and a triarylsulfonium salt undergoes photoinduced structural modifications which convert the silylated polymer into either poly(p‐hydroxystyrene) or poly[(p‐trialkylsioxystyrene)‐co‐(p‐hydroxystyrene)]. Aging with the use of antimonate salts rather than arsenate salts, and bulky alkyl groups favour OSi bond cleavage.
Radical‐intiated copolymers of styrene and p‐formaylstyrene, 2. Preparation and characterization of emulsifier‐free copolymer latices
Authors: Charleux Bernadette , Fanget Philippe , Pichot Christian 
Published: April 2003

AbstractMonodisperse copolymer latex particles with aldehyde groups at the surface have been prepared by a two‐step process, comprising first a soap‐free emulsion polymerization of styrene using potassium peroxodisulfate as an initiator and secondly a surface functionalization of the seed particles by copolymerizing p‐formylstyrene (system. name: 4‐vinylbenzaldehyde) using various addition methods. The final latices were characterized with respect to monomer conversion, copolymer composition, particle size and distribution. Particular attention was paid to the characterization of surface aldehyde groups using two different analytical methods such as X‐ray photoelectron spectroscopy (XPS) and radioactive labelling by coupling with (1‐3H1)‐2‐aminoethanol.
Asymmetric radical‐initiated copolymerization of (−)‐menthyl sorbate with styrene
Authors: Doiuchi Tohru , Dodoh Takeshi , Yamaguchi Hidemasa 
Published: April 2003

AbstractThe radical‐initiated copolymerization of (−)‐menthyl sorbate ((−)‐3‐p‐menthyl 2,4‐hexadienoate) with styrene was carried out in benzene with 2,2′‐azoisobutyronitrile as an initiator at 50°C to give an optically active copolymer 1. While the chiral menthyl group of the copolymer was removed by hydrolysis with aqueous alkali, the hydrolyed copolymer was still optically active. Therefore, asymmetric induction must have occurred during copolymerization.
Influence of molecular weight and concentration of poly(2‐vinylnaphthalene) on the bulk polymerization of styrene under UV‐irradiation in the presence of a magnetic field
Authors: Huang Junlian , Zhu Ping , Ji Caigui , Ruan Weixiang 
Published: April 2003

AbstractThe effect of molecular weight and concentration of poly(2‐vinylnaphthalene) (PVN) on the bulk polymerization of styrene initiated by 2,2′‐azoisobutyronitrile (AIBN) was studied under UV‐irradiation in the presence of a magnetic field. It was found that in the suitable range of molecular weights (<1,7 · 103) and concentrations (1,62 to 9, 12 · 10−3 mol/L) of PVN, the molecular weight and molecular weight distribution of polystyrene significantly varied with the change of the external magnetic field. A triplet energy transfer mechanism between PVN and AIBN in the PVN cages was suggested on the basis of the experimental results.
Polymethacrylate graft copolymers with a liquid‐crystalline component
Authors: Hefft Marita , Springer Jürgen 
Published: April 2003

AbstractThis paper reports on the synthesis and characterization of graft copolymers built up by amorphous poly(methyl methacrylate) grafts and a side‐chain liquid‐crystalline backbone. The interest was focussed on the copolymerization behaviour of the liquid‐crystalline monomers and styryl‐terminated methyl methacrylate macromonomers. The radical polymerization of the liquid‐crystalline monomers depends on the liquid‐crystalline monomer concentration and on the amount and length of the grafts (macromonomers). The liquid‐crystalline backbone is the longer the higher the concentration of the mesogenic monomers itself and the smaller the molecular weight of the macromonomers. Variation of the amounts of grafts yielded a maximum length of the liquid‐crystalline backbone at approximately 4 mol‐% (for a molecular weight of 7800 of the graft).
Electrochemical polymerization of 1H,7H‐pyrrolo[2′,3′:4,5]‐thieno[3,2‐b]pyrrole and 4H‐dithieno[3,2‐b;2′,3′‐d]pyrrole
Authors: Berlin Anna , Pagani Giorgio , Zotti Gainni , Schiavon Gilberto 
Published: April 2003

AbstractElectrochemical polymerization of 1H,7H‐pyrrolo[2′,3′:4,5]thieno[3,2‐b]pyrrole and 4H‐dithieno[3,2‐b;2′,3′‐d]pyrrole in CH3CN + 0,1 M p‐toluenesulfonate and tetraethylammonium perchlorate, respectively, yields polymers with a conductivity of ca. 5 S/cm. Electrochemistry and elemental analysis indicate the presence of 0,6‐0,7 anions per monomeric unit, while spectroelectrochemistry agrees with a polypyrrole structure for polypyrrolothienopyrrole and a polythiophene structure for polydithienopyrrole. The redox cycle for polypyrrolothienopyrrole (at −0,53 V vs. Ag/Ag+) is close to that of polypyrrole, while that of polydithienopyrrole (at 0,0 V) is intermediate between those of polythiophene and polypyrrole. N‐Alkylsubstituted dithienopyrroles produce soluble polymers with higher conductivity (40 S/cm) and the lowest band‐gap (1,7 eV) ever reported for a polythiophene‐like polymer.
New poly(amide‐imide) syntheses, 3. Preparation and properties of cardo poly(amide‐imide)s derived from 9,9‐bis(4‐aminophenyl)fluorene, trimellitic anhydride, and various aromatic diamines
Authors: Yang Chin‐Ping , Cheng Ju‐Ming , Hsiao Sheng‐Huei 
Published: April 2003

AbstractAn imide‐ring‐containing dicarboxylic acid, N,N′‐(9‐fluorenylidenedi‐1,4‐phenylene)diphthal‐imide‐4‐carboxylic acid (1), was prepared by condensation of trimellitic anhydride and 9,9‐bis(4‐aminophenyl)fluorene. A series of new aromatic cardo poly(amide‐imide)s having inherent viscosities of 0,59‐1,13 dL/g were prepared by the direct polycondensation of this diimide‐diacid with various aromatic diamines using triphenyl phosphite and pyridine as condensing agents in 1‐methyl‐2‐pyrrolidone (NMP) in the presence of calcium chloride. The polymers are amorphous and readily soluble in highly polar solvents such as N,N‐dimethylformamide, N,N‐dimethylacetamide, dimethyl sulfoxide, NMP, and m‐cresol. Transparent and tough films can be easily cast from the polymer solutions. The glass transition temperatures of these poly(amide‐imide)s are above 320°C. Thermal analyses indicated that these polymers are fairly stable, and the 10% weight loss temperatures were recorded in the range of 532–622°C in nitrogen atmosphere.
Electrochemical synthesis of poly(p‐phenylene) in an ionic liquid
Authors: Kobryanskii Valery M. , Arnautov Sergei A. 
Published: April 2003

AbstractFlexible transparent high‐molecular‐weight (degree of polymerization higher than 90) films of poly(p‐phenylene) were obtained by electrochemical polymerization of benzene in an aluminium chloride and N‐butylpyridinium chloride based ionic liquid. Effects of the process parameters on the structure and relative molecular mass of the samples were studied. A hypothesis which considers the role of doping of macromolecules generated in the process of the polymer synthesis, is proposed.
Polyesters containing both rod‐like and disc‐like mesogens
Authors: Karthaus Olaf , Ringsdorf Helmut , Ebert Martina , Wendorff Joachim H. 
Published: April 2003

AbstractThe synthesis of a new type of combined polymers containing both disc‐ and rod‐like mesogens is reported. The polyesters, having a triphenylene derivative as a discotic mesogen in the side group and azobenzene or biphenyl derivatives as rod‐like mesogens in the main chain were characterized by polarizing microscopy, differential scanning calorimetry, and X‐ray scattering studies. The homopolymer 7 is highly crystalline, while the copolymer 8 is amorphous, both, however, do not form liquid‐crystalline phases.
New aspects in the anionic polymerization of phenyl glycidyl ether
Authors: Stolarzewicz Andrzej , Grobelny Zbigniew 
Published: April 2003

AbstractA kinetic equation describing the anionic polymerization of phenyl glycidyl ether initiated by potassium anions in the presence of 18‐crown‐6 was derived. Rate constants of growth and chain transfer reactions were calculated. The equilibrium constant of complex formation by the active centre with alcohol being a product of chain transfer reactions was also evaluated.
A KrF excimer laser induced dehydrochlorination of a chlorinated poly(vinyl chloride): Preparation of conjugated polyene and polyyne
Authors: Shimoyama Masashi , Niino Hiroyuki , Yabe Akira 
Published: April 2003

AbstractThe photochemical dehydrochlorination of a chlorinated poly(vinyl chloride) film was investigated with respect to the preparation of a π‐electron‐conjugated polymer. The dehydrocholorination proceeds more effectively upon irradiation with a KrF excimer laser than with a low‐pressure mercury lamp, showing the formation of new absorption bands in the range 300–800 nm. The most effective condition provided KrF excimer laser irradiation of 25− 30 mJ/cm2 at 1 Hz in a vacuum chamber of 10−6 Torr at 90°C. The surface of the irradiated film was analyzed by IR (attenuated total reflection method), X‐ray photoelectron and Raman spectroscopy. The characteristic peaks (1 112, 1 488 and 2 188 cm−1) in the Raman spectrum were ascribed to a structure having eight conjugated CC bonds and twenty conjugated CC bonds.
A new radical cation salt: Electrocrystallization of trans‐1,2‐bis(2‐naphthyl)ethene and model character of the resulting salt for conducting arylenevinylene polymers
Authors: Stenger‐Smith John D. , Lenz Robert W. , Enkelmann Volker , Wegner Gerhard 
Published: April 2003

AbstractA single‐crystal radical cation salt was obtained by anodic oxidation of trans‐1,2‐bis‐(2‐naphthyl)ethene (1,2‐DNE) with SbF−6 as the counter‐ion. The crystal structure of (1,2‐DNE)SbF6 was solved and found to be similar to the radical cation salts of unsubstituted naphthalene. The crystal structure is disordered, i.e. two orientations of the 1,2‐DNE molecules are statistically occupied. The molecular overlap, resulting from these two orientations, models the structure of the salt of poly(2,6‐naphthylenevinylene). In contrast to most other radical cation salts which are one‐dimensional conductors, a conduction mechanism of higher dimensionality is predicted on the basis of the crystal structure of (1,2‐DNE)SbF6. The identical type of disorder is also present in the crystal structure of trans‐1,2‐bis(1‐naphthyl)ethene.
Synthesis, dilute solution properties and chain flexibility of poly(diesters) of itaconic acid, 2, poly(methyl decyl itaconate)
Authors: León Arturo , Gargallo Ligia , Radić Deodato , Bravo Julio , Horta Arturo 
Published: April 2003

AbstractThe diester of itaconic acid with decyl and methyl groups was prepared and polymerized. The dilute solution behaviour of poly(methyl decyl itaconate) poly{1‐(decyloxycarbonylmethyl)‐1‐(methoxycarbonyl)ethylene} (PMeDI) was studied in tetrahydrofuran and 1‐butanol at 298 K, by light scattering, size‐exclusion chromatography, and viscometric measurements. The empirical Kuhn‐Mark‐Houwink‐Sakurada relationships were established. The molecular parameters were calculated using one theory of the excluded volume.
Comparison of zirconocene and hafnocene catalysts for the polymerization of ethylene and 1‐butene
Authors: Heiland Kirstin , Kaminsky Walter 
Published: April 2003

AbstractIn polymerizations with ethylene and copolymerizations with ethylene and 1‐butene the catalyst system rac‐ethylene(bisindenyl)zirconium dichloride (rac‐Et(Ind)2ZrCl2)/methylaluminoxane (MAO) shows lower activities than the analogous Hafnium catalyst. The polymers obtained with the hafnium‐catalyst have average molar masses up to ten times higher than those synthesized with the zirconium compound. It is remarkable that rac‐Et(Ind)2HfCl2 is much more able to incorporate the comonomer. This is expressed by the copolymerization parameters. At a polymerization temperature of +30°C, e.g., the r1‐parameter of the hafnium‐catalyst is 5,4, the corresponding parameter of the zirconium catalyst is 19,4. Polymerizations with a catalyst mixture rac‐Et(Ind)2(Hf, Zr)Cl2 (containing 95% rac‐Et(Ind)2HfCl2 and 5% rac‐Et(Ind)2ZrCl2) show that each catalyst compound produces its own polymer independently.