bluuebunny/crossref_metadata_2025_split huggingface dataset:
Micelle formation and anomalous behaviour in the system polystyrene‐block‐poly(ethylene/propene)/poly(isobutene)/5‐methyl‐2‐hexanone
Authors: Quintana José R. , Salazar Ramiro A. , Villacampa Manuel , Katime Issa A. 
Published: April 2003

AbstractSolubilization of poly(isobutene)Systematic IUPAC name: poly(1,1‐dimethylethylene).
by micelles of polystyrene‐block‐poly(ethylene/propene) block copolymer with a copoly(ethylene/propene) core was investigated. The weight of poly(isobutene) solubilized was found to be proportional to the concentration of block copolymer in the solution. No influence of the presence of poly(isobutene) on the critical micelle temperatures has been found. However, the addition of poly(isobutene) to the micellar solution seems to favour the anomalous behaviour found in micellar solutions of the block copolymers used in this study.
Side‐Chain liquid‐crystalline polymers containing a siloxane spacer, 2. Effects of mesogenic groups on the thermal properties of side‐chain liquid‐crystalline polymers containing a disiloxane unit in the spacer
Authors: Nagase Yu , Takamura Yuriko , Abe Hirokazu , Ono Kunihiko , Saito Takanori , Akiyama Eiich 
Published: April 2003

AbstractA series of side‐chain Iiquid‐crystalline polymers was prepared containing disiloxane units in the spacer. The polymers consist of a polymethacrylate backbone and several kinds of mesogenic side groups. For the synthesis of the desired monomers, silanol compounds carrying a mesogenic groups were prepared as the intermediates. The polymers were obtained by ordinary free‐radical polymerization. As the mesogenic groups, linear‐type p‐ or p′‐substituted phenyl and biphenylyl benzoates, p‐ or m‐substituted benzoyloxybiphenyl groups and laterally attached biphenylyl benzoate‐type mesogens were chosen, and the structural effects on the thermal properties of the polymers were investigated. In the case of linear‐type mesogens, only when triple‐core mesogens were introduced a stable smectic mesophase was observed with a wide range of phase stability, while on mesophase was observed for the linear double‐core and the laterally attached mesogens. On the other hand, a highly ordered smectic phase was observed for polymers having linear‐type triple‐core mesogens with p‐alkoxy and m‐cyano end groups. Furthermore, it was revealed that the introduction of a disiloxane unit in the spacer lowered the temperature range of the mesophase, in comparison with polymers having an alkylene spacer with the same backbone component and mesogens.
Regio‐ and stereo‐selective alternating copolymerization of carbon monoxide with propene
Authors: Xu Frank Y. , Zhao Allen X. , Chien James C. W. 
Published: April 2003

AbstractCompounds of palladium with ten different chelated bisphosphine ligands were investigated for their catalysis of alternating copolymerization of propene with carbon monoxide. The bisphosphine structure and chelate ring size influence strongly the activity, regio‐ and stereo‐selectivity of the catalysts. Molecular mechanics calculations on the π‐olefin complex showed that the non‐bonded interaction between propene and the ligands on Pd is both regio‐ and stereo‐selective. Primary insertion is about seven times more probable than secondary insertion for the Pd complex of bis(diphenylphosphino)butane ligand. The enantioselective catalysts favor the meso enchainment of propene. Gas chromatography/mass spectrometry (GC‐MS) of oligomers showed that most chains are initiated by PdH species with less frequent initiation by PdOCH3 complexes; β‐hydrogen elimination is the dominant chain termination process.
Polymeric protecting groups, 5. Polymerizable urea compounds with 2‐methylpropyloxycarbonyl function as a modified tert‐butoxycarbonyl‐type amino‐protecting group
Authors: Gormanns Marcus , Ritter Helmut 
Published: April 2003

Abstract1‐[2‐(4‐chloroanilinocarbonyloxy)‐2‐methylpropyl]‐3‐methacryloylurea (4) was prepared by addition of 1‐(2‐hydroxy‐2‐methylpropyl)‐3‐methacryloylurea (3) to 4‐chlorophenyl isocyanate as a model compound. The new monomer 4 acts as a modified tert‐butoxycarbonyl (BOC)‐type amino‐protecting group which can be homopolymerized and copolymerized with methyl methacrylate (MMA) upon radical initiation. The kinetics of the deprotection of the aromatic amine under acidic conditions which leads to the formation of 2‐methacryloylamino‐5,5‐dimethyl‐Δ2‐1,3‐oxazoline (7) was followed by means of 1H NMR spectroscopy.
Copolymerization of propene and butadiene with MgCl2 supported titanium catalytic systems
Authors: Dassaud Jean‐Philippe , Guyot Alain , Spitz Roger 
Published: April 2003

AbstractUpon copolymerization of propene and butadiene, using the recent generation of high mileage stereospecific MgCl2 supported TiCl4AIR3 catalytic systems, it is possible to incorporate a small proportion of butadiene units in polypropene, keeping reasonable, although strongly reduced, activity. The isospecificity of the catalysts for the propene polymerization is not affected, and even may be improved upon butadiene incorporation. The butadiene is incorporated in blocks of trans‐1,4 units. The amount of incorporation is dependent on the temperature, on the presence and then on the nature and concentration of a silane compound as an external Lewis base, and also on the nature of the alkylaluminium cocatalyst. The silane causes a small amount of 1,2‐butadiene units to be incorporated. The molecular weights of the polymers are strongly decreased but the crystallinity is only slightly affected.
Polymeric liposomes formed from a new phosphatidylcholine with terminal diene groups
Authors: Anikin Alexei , Chupin Vladimir , Anikin Michael , Serebrennikova Galina , Tarahovsky Jury 
Published: April 2003

AbstractA novel polymerizable phospholipid with conjugated diene groups at the hydrocarbon chain ends, 1,2‐bis(11,13‐tetradecadienoyl)‐sn‐glycero‐3‐phosphocholine (7), was synthesized. This phospholipid gives liposomes which can be readily polymerized upon γ‐and UV‐irradiation. The conversion is up to 95% within 10 h at 60°C or within 3 days at room temperature. According to light scattering, 31P NMR and electron microscopy, the polymerized liposomes are detergent‐resistent and maintain their structure under ultrasonic treatment and in organic solvent media.
Liquid‐crystalline polysulfones, 3. New copolymers from 1‐alkenes with sulfur dioxide
Authors: Braun Dietrich , Arnold Norbert , Liebmann Andrea , Schmidtke Ingrid 
Published: April 2003

AbstractA large number of new liquid‐crystalline 1‐alkenes with various mesogenic groups based on substituted phenyl benzoate or biphenyl and with different spacer lengths (2‐10 methylene groups) were synthesized and copolymerized with sulfur dioxide by free‐radical initiation to produce alternating polysulfones with liquid‐crystalline side chains. The phase transition temperatures of the 1‐alkenes and polysulfones were determined; their clearing temperatures lie in the ranges 43–138°C and 89–194°C, respectively. The liquid‐crystalline phases of the polysulfones, as determined by means of X‐ray diffraction, show a great variation, i.e. cholesteric and nematic as well as various smectic phases were obtained.
Blends of alkyloxy‐substituted liquid‐crystalline aromatic polyesters and copolyesters with poly(ethylene terephthalate)
Authors: Schleeh Thomas , Salamon Leszek , Hinrichsen Georg , Koβmehl Gerhard 
Published: April 2003

AbstractBlends containing poly(ethylene terephthalate) (PET) and a series of alkyloxy laterally substituted liquid‐crystalline copolyesters (HTO5‐X series 1) in various ratios were prepared in the melt at 260°C by mechanical mixing. The visual and light microscopical appearance of the blends in the solid state and in the melt was found to be homogeneous for those blends which contained an aliphatic‐rich HT05‐X copolyester. The homogeneous appearance can be explained by a colloidal dispersion of the liquid‐crystalline polymer (LCP) in PET. Obvious phase separation in the melt occurs slowly after long periods of time. Phase separation is forced by annealing at about 270°C, where a change of viscosity is observed, and by shearing the sample. Characterization of theblends by DSC experiments shows that the thermal behaviour of all blends is dominated by the phase transitions of PET and that the LC‐low‐phase of the HTO5‐X copolyesters with a high degree of alkyloxy substitution is suppressed. The WAXS diffraction patterns of all blends contained an amorphous halo. For blends with low HTO5‐X concentration, inner reflexions from the nematic sanidic phase, as exhibited by the HTO5‐X copolyester, could be observed. For blends with higher HTO5‐X copolyester concentration, characteristic reflexions from HTO5‐X copolyester crystals could be observed. The number of X‐ray reflexions of the crystalline LCP in the blend is reduced compared to that of the pure LCP.
Vinyl polymerization initiated with the lanthanum versatate/p‐chlorobenzenediazonium tetrafluoroborate system
Authors: Sato Tsuneyuki , Toyosu Kentaro , Tanaka Hitoshi 
Published: April 2003

AbstractThe system of lanthanum versatate (1) and p‐chlorobenzenediazonium tetrafluoroborate (2) was found to induce effectively polymerizations of electron‐accepting monomers such as methyl methacrylate (3) and di‐2‐ethylhexyl itaconate (DEHI). The polymerization rate (Rp) was expressed by Rp = k[1/2]0,44 [3]0,65 at 50°C fixing the mole ratio of 1 and 2 at unity. The overall activation energy of the polymerization was calculated to be 37, 1 kJ · mol−1. The spin trapping result revealed that the initiator system produces p‐chloropheneyl radicals. The polymerization system of DEHI was observed to involve ESR‐observable propagating polymer radicals, indicating that the polymerization initiated with the 1/2 system proceeds through radical mechanism. During the polymerization, the ESR spectrum was changed in shape, suggesting that the propagating polymer radicals interact with some species formed by the initiation reaction. Interacting polymer radicals were also observed in the polymerizations of diethyl itaconate and N‐dodecylmaleimide with the 1/2 system. The polymerization systems of MMA, styrene and butyl acrylate were also found to involve ESR‐observable radicals, although it is vague whether they are propagating polymer radicals or not.
Intramolecular excimer formation in polyesters from terephthalic acid and six 2R,2R′‐propanediols
Authors: Mendicuti Francisco , Mattice Wayne L. 
Published: April 2003

AbstractFluorescence has been measured for six polyesters derived from terephthalate and six 2R,2R′‐propanediols, represented by HOCH2CRR′CH2OH. The solvent effects on the emission spectra permit separation of the six polymers into two groups. One group consists of the five polyesters in which R and R′ are alkyl groups, and the other group has only one member, that being the polyester with R = R′ = H. Modelling suggests that the origin of the difference between the two groups lies in the access by the polyester with R = R′ = H to a conformation (inaccessible when R and R′ are alkyl groups) that forms a very tight complex between two successive aromatic rings.
Rate coefficients for free‐radical polymerization of butyl acrylate to high conversion
Authors: Buback Michael , Degener Bettina 
Published: April 2003

AbstractThe free‐radical polymerization of butyl acrylate is studied between 25°C and 80°C at pressures up to 2500 bar. The reaction is measured by applying excimer laser techniques in conjunction with time‐resolved high‐pressure near infrared spectroscopy. Rate coefficients of propagation, kp, and termination, kt, are obtained for an extended temperature, pressure, and conversion range. The dependence of kt on conversion is analyzed by means of a kinetic model which considers segmental diffusion, translational diffusion, and reaction diffusion. It turns out that free‐radical termination is essentially determined by reaction diffusion.
Solvent effects on free‐radical polymerization, 5. Analysis of homopolymerization rate on the basis of the reactant‐solvent complex model
Authors: Czerwinski Wojciech Krzysztof 
Published: April 2003

AbstractThe rate of polymerization was described as a function of the monomer concentration of 36 monomer/solvent systems in terms of the reactant‐solvent complex (RSC) model. One‐, two‐and three‐parameter optimization procedures were used to fit the rate function to experimental data. Fitting increments were the complex equilibrium constant K and the relative monomer reactivity parameter r11. Irrespective of the optimization procedure, K and r11, were found to correlate with the monomer exponent n and to be K = 0 and r11, = 1 at n = 1. In these cases the RSC model reduces to the classical rate model. Despite the weak character of the monomer (radical)/solvent complexation, this interaction should not be neglected in rate modelling. The RSC model is a convenient tool to describe the chain propagation separately.
The miscibility and phase separation in binary blends of poly(vinyl chloride) with methyl methacrylate/acrylonitrile copolymers
Authors: Lath Dieter , Lathová Elena , Cowie John M. G. 
Published: April 2003

AbstractThe miscibility of poly(vinyl chloride) with poly(methyl methacrylate‐stat‐acrylonitrile) has been studied. Poly(vinyl chloride) is miscible with methyl methacrylate/acrylonitrile copolymers having acrylonitrile contents between 2,0 and 17 wt.‐%. All calculated binary segmental interaction parameters were positive, suggesting immiscibility of the corresponding binary homopolymer blends.
Photoinitiated cross‐linking of silicones, 10. Photoinitiated cross‐linking of silicone acrylates as studied by fourier transform infrared spectroscopy
Authors: Bajdala Jürgen , Müller Uwe , Wartewig Siegfried , Winkler Katrin 
Published: April 2003

AbstractThe photoinitiated cross‐linking of silicone acrylates is studied by FT‐IR spectroscopy. The influences of light intensity, exposure time and type of photoinitiator are described. The parameters of the kinetic equation are determined. It is shown that oxygen acts as an inhibitor. The asymmetric CO stretching IR band of the uncross‐linked and cross‐linked system can be separated into two bands which are attributed to different conformations and geometric arrangements of the acrylate groups, respectively.
Elementary processes of the Ziegler catalysis, 7. Ethylene, α‐olefin and norbornene copolymerization with the stereorigid catalyst systems ipr[flucp]zrcl2/mao and me2si[ind]2zrcl2/mao
Authors: Herfert Norbert , Montag Peter , Fink Gerhard 
Published: April 2003

AbstractThe stereorigid ansa‐metallocene catalysts [2,4‐cyclopentadien‐1‐ylidene(isopropylidene)‐fluoren‐9‐ylidene]zirconium dichloride/methylaluminoxane (iPr[FluCp]ZrCl2/MAO) and [(dimethylsilylene)bis(η5‐inden‐1‐ylidene)]zirconium dichloride/methylaluminoxane (Me2Si[Ind]2‐ZrCl2/MAO) are different in respect to the symmetry and, therefore, to the behaviour of the stereospecifity, in the size of the angle between the planes of the π‐ligand systems and in the homopolymerization behaviour of ethylene and propene. The present paper concerns itself with comparing the investigations of the ethylene/α‐olefin and the ethylene/cycloolefin copolymerization with both catalyst systems. The main kinetic result for both catalysts is that the α‐olefins show an accelerating effect on the ethylene polymerization rate during the copolymerization whereas norbornene shows exclusively a rate‐decreasing effect. The acceleration effect can be explained by an increase in the concentration of active centres and/or an increase of the rate constant of the ethylene insertion. The analysis of the microstructures of the formed copolymers by the use of statistical models demonstrates that in copolymers with a high content of α‐olefins, the experimental trial distributions can only be described satisfactorily with second‐order Markovian statistics. That means that in this case the last two monomers have influence on the insertion of the subsequent monomer. A further main result of all investigated copolymerizations is that the r‐parameters for the α‐olefin insertion are more favourable for the system iPr[FluCp]ZrCl2/MAO than for the system Me2Si[Ind]2ZrCl2/MAO; the reason for this is the different size in the coordination gap aperture of the π‐ligands. Furthermore, the r‐parameters show only a small dependence on the chain length of the α‐olefin. Finally, it is remarkable that the stereospecifity (syndiotactic or isotactic α‐olefin blocks) remains intact in the copolymers.
Synthesis of polyureas by polycondensation of diamines with active derivatives of carbonic acid
Authors: Katsarava Ramaz D. , Kartvelishvili Tamara M. , Japaridze Nona N. , Goguadze Tsisana A. , Khosruashvili Tamara A. , Tiger Roald P. , Berlin Pjotr A. 
Published: April 2003

AbstractNew polycondensation reactions of active diphenyl carbonates and diphenyl carbamate with diamines were developed for the synthesis of high‐molecular‐weight polyureas. The kinetics and mechanism of carbonic acid active esters aminolysis model reactions were studied. Possible side reactions including nucleophilic substitution reaction were investigated as well. It is shown that novel methods advantageously distinguish from traditional methods of polyureas synthesis by low tendency to side reactions and facilitate the synthesis of linear polyureas and copolyureas. It is found that N,N′‐bis(trimethylsilylated) diamines and salts of diamines as monomers can be successfully used in these reactions. Bioanalogous polymers promising for biomedical application — polyureas based on L‐lysine — were synthesized using novel polycondensation reactions.
Molecular design of biodegradable functional polymers, 3. Biodegradability and functionality of poly[(sodium acrylate)‐co‐(vinyl alcohol)]
Authors: Matsumura Shuichi , Ii Sawako , Shigeno Haruo , Tanaka Toshiyuki , Okuda Fumiko , Shimura Yukimasa , Toshima Kazunobu 
Published: April 2003

AbstractAs a design for a biodegradable functional polymer, compositionally homogeneous poly[(sodium acrylate)‐co‐(vinyl alcohol)] [P(SA‐co‐VA)], containing varying amounts of vinyl alcohol groups as biodegradable segments were prepared and their biodegradability and builder performance in detergent formulations were analyzed with respect to the successive vinyl alcohol length. It was found that the acrylate copolymers having more than 80 mol‐% vinyl alcohol content showed biodegradability. That is, P(SA‐co‐VA) having a vinyl alcohol chain length of more than about 5–6 is cleaved by PVA‐degrading microbes. This indicates that the vinyl alcohol blocks, which act as biodegradable segments, should be incorporated into the polymer chain in such a manner that they are accepted as substrates by the PVA‐degrading enzymes.
Sequence‐specific conformer of peptide sequence Asn‐Pro‐Asn‐X in dimethyl sulfoxide: Synthetic and 1H NMR studies on peptides having Asn‐Pro‐Asn‐Ala sequence and their gly‐substituted analogs
Authors: Isokawa Shizuko , Narita Mitsuaki , Umemoto Kimiko 
Published: April 2003

AbstractA series of small peptides consisting of the repeating sequence Asn‐Pro‐Asn‐Ala, and their Gly‐substituted analogs, having one of the Asn residues replaced by Gly, have been synthesized to investigate the role of Asn side‐chain amido groups in stabilizing the secondary structure of the Asn‐Pro‐Asn‐Ala tetrapeptide unit. Analyses of the 1H NMR data obtained in dimethyl sulfoxide (Me2SO) revealed that the secondary structure of the tetrapeptide sequence is stabilized by virtue of the two Asn residues preceding and following Pro. The sequence‐specific turn structure, which is proposed here as the most probable conformer for the tetrapeptide unit, contains at most three intra‐molecular hydrogen bonds: between backbone CO of Asn preceding Pro and backbone NH of Asn following Pro (inverse γ turn), between side‐chain NHE and backbone CO of the same Asn following Pro, and between side chain CO of Asn preceding Pro and backbone NH of X(Ala).
Liquid‐crystalline side group polyesters with definite lengths of flexible spacers in the main chain
Authors: Böhme Axel , Novotna Eva , Kresse Horst , Kuschel Frank , Lindau Jürgen 
Published: April 2003

AbstractLiquid‐crystalline polymalonates with a definite distance between the contact points of two neighbouring side groups were synthesized. The mesogenic group is azobenzene with a terminal nitro‐substituent acting as an indicator for dielectric measurements. The influence of the number of methylene groups in the main chain on the polymorphism and the dielectric behaviour has been investigated. Generally, the thermal stability of the mesophases decreases when the main chain spacer becomes longer. The relaxation frequency for the reorientation of the mesogenic side group around the short axis increases with increasing number of methylene groups in the main chain in both, the isotropic and liquid‐crystalline phases.
Enzymes in polymer chemistry, 7. Lipase‐catalyzed esterification of carboxyl‐terminated methacrylic oligomers and copolymers with isopropyl alcohol and 9‐fluorenylmethanol
Authors: Pavel Konstantin , Ritter Helmut 
Published: April 2003

AbstractThe carboxylic group of the oligoester α‐(11‐methacryloylaminoundecanoyl)‐ω‐hydroxy‐oligo(oxyundecamethylenecarbonyl) (1) was enzymatically esterified with isopropyl alcohol and 9‐fluorenylmethanol, respectively, in the presence of the lipase from Candida cylindracea. Moreover, the oligoester 1 was copolymerized with styrene and subsequently esterified with isopropyl alcohol by the same lipase. The degree of esterification and transesterification was determined by 1H NMR spectroscopy. Esterification occurred almost quantitatively, together with some transesterification, in the case of isopropyl alcohol, whereas with 9‐fluorenylmethanol only a degree of esterification as low as 30% was achieved. The formation of the enzymatically esterified oligoester units was proved by FAB mass spectrometry.
Synthesis and molecular weights of metal poly(vinyl acetate)s, 5.
Authors: Cárdenas Galo T. , Muñoz César D. 
Published: April 2003

AbstractMetal vinyl acetate (MVAc) colloids were obtained by cocondensation at 77 K of the monomer with several metals such as: Pd, Ag, Au, Zn, Cd, Ga, In, Ge, Sn, Sb and Bi. Some of these colloids are stable for months at room temperature (Au, Ag, Pd). The colloids were polymerized with different amounts of initiator (2,2′‐azoisobutyronitrile) at 65°C, and a wide range of viscosity‐average molecular weights (104 < M̄v < 106) were obtained depending upon the metal used. The particle size of these clusters dispersed in the polymer matrix is around 1400 Å. The polymers are stable even at 320°C, and the metal content is ranging from 0,01 to 0,96 wt.‐%. The color of the polymers depends upon the metal used.
Photochemical decomposition of triazenes. (Electron paramagnetic resonance study)
Authors: Staško Andrej , Adamčík Vladimír , Lippert Thomas , Wokaun Alexander , Dauth Jochen , Nuyken Oskar 
Published: April 2003

AbstractIn the photochemical decomposition of triazene RNNNR1R2 in CH3CN solutions, where R was (3‐HOOC, di‐HOOC, 4‐HOOC, 4‐CN)phenyl and R1, R2 were CH3, CH2H5, CH(CH3)2, CH2CH2OH, the corresponding phenyl‐substituted radicals were identified as 5,5‐dimethyl‐1‐pyrroline N‐oxide (DMPO) or (CH3)3CNO adducts. The reaction is described by a first‐order kinetics with a half lifetime of 7 s. If R was di‐3,5‐CON3‐C6H3, a nitrogen‐centred radical was found on radiation in the solid state as well as in CH3CN solution with DMPO as spin trap.