bluuebunny/crossref_metadata_2025_split huggingface dataset:
Studies of formation of bivalent metal ion complexes with poly‐U
Authors: Sorokin Victor A. , Levchenko Irina V. , Valeev Vladimir A. , Gladchenko Galina O. , Blagoi Yuri P. , Li Ren G. 
Published: April 2003

AbstractDifferential UV spectroscopy is employed to investigate the interaction of poly‐U with Mg2+, Ca2+, Mn2+ and Cu2+ ions in aqueous solution. Mg2+ and Mn2+ ions are observed to bind only to the polynucleotide phosphates, while Cu2+ and Ca2+ also interact with the poly‐U bases. The most probable coordination sites are O(4) and also N(3) for Cu2+ ions. N(3) is a coordination site of Cu2+ ions in UMP and uridine. The rest of the ions do not interact with the bases of the free monomers. Unlike the non‐cooperative Cu2+‐UMP binding, the ion interaction (including Ca2+) with the poly‐U bases is characterized by a positive cooperativity. The association constant of Ca2+ (45 1.mol−1) is 45 times lower than that of Cu2+.
Solid‐state 13C nuclear magnetic resonance studies of side‐group conformations in the rigid‐rod polyester poly[1,4‐phenylene 2,5‐bis(hexadecyloxy)terephthalate]
Authors: Whittaker Andrew K. , Falk Uwe , Spiess Hans Wolfgang 
Published: April 2003

AbstractThe 13C solid‐state NMR spectra of the aromatic polyester 1 with flexible hexadecyloxy side chains are measured at temperatures below and above its solid‐solid phase transition in order to study the conformation of the side chains. The signals due to the CH2 carbons reflect the ratio of trans and gauche conformations at the various positions along the chain. An increase in the gauche content was observed towards the end of the side chain in both phases, however, in the low temperature phase the spectra are dominated by all‐trans sequences. The solid‐solid transition, as detected by differential scanning calorimetry corresponds to a large increase in the gauche content at all positions on the side chain, except near to the rigid polymer backbone. Above the solid‐solid transition a small residual concentration of all‐trans sequences was detectable.
Water effects on the zwitterionic polymerization of cyanoacrylates
Authors: Eromosele Ighodalo C. , Pepper David C. , Ryan Bernard 
Published: April 2003

AbstractThis paper presents a number of qualitative and semi‐quantitative observations on the effect of small concentrations of water on the polymerizations of butyl cyanoacrylates by tertiary amines in THF. It reports also that, in the absence of other bases, large concentrations (approx. 1 mol/l) of water can cause the polymerization of ethyl cyanoacrylate, in THF, even in presence of normally inhibiting amounts (10−5 mol/l) of p‐toluenesulfonic acid. A formal kinetic scheme of a stationary‐state polymerization, initiated by hydroxyl anions, is presented and discussed.
Monoplanar small angle neutron scattering by semicrystalline polymer solids containing homogeneously distributed otherwise identical deuterated polymer molecules
Authors: Peterlin A. 
Published: April 2003

AbstractThe first “linear” range of inverse reduced scattering intensity of N stems in monodisperse clusters versus q2 with the initial slope R/2 is followed by a second nearly 20% steeper and 10 times wider quasi‐linear range. The difference slightly decreases with polydispersity of the clusters. This case will not be discussed here. One may deduce from the second range the fictive number N of stems and gyration radius Rcc which differ less than 10% from the true values obtained from the first “linear” range. But the fine structure of the equal monoplanar clusters on the scattering molecule may change enormously with interior gaps while keeping constant the scattering intensity in the interesting region, N and Rcc of the cluster. In the sensitive range of the first two quasi‐linear ranges all these 3 quantities are so little affected by the changes of fine structure that small angle neutron scattering (SANS) yielding N and Rcc does not permit any statement on these changes. The calculations of SANS results with some equidistant gaps which retain N and Rcc yield the same intensity distribution in the interesting range. This follows from the fact that N commands the intensity while Rcc rules not only the first but also the second quasi‐linear range. The perfect merging of the first with the second quasi‐linear ranges in the SANS of polyethylene demands a special arrangement of a single gap separating one single stem from the bulk of the active stems in the cluster.
Cinnamic acid as a comonomer in radical polymerizations
Authors: Barson C. Anthony , Bevington John C. , Huckerby Thomas N. 
Published: April 2003

AbstractCinnamic acid affects the initiation processes when methyl methacrylate is polymerized at 60°C using benzoyl peroxide as initiator. Work with peroxide doubly‐labelled with carbon‐14 and tritium has shown that the balance between benzoate and phenyl end‐groups is significantly shifted in favour of ester end‐groups. On the other hand, study involving peroxide enriched with carbon‐13 has given no evidence for the presence in the polymers of benzoate end‐groups attached to units derived from cinnamic acid. It is proposed that the acid impedes the decarboxylation of the benzoyloxy radical. Cinnamic acid copolymerizes to some extent with styrene, methyl acrylate and acrylonitrile but less readily with the related monomers having a‐methyl groups. The effect of the nature of the diluent is clearly shown for the copolymerization with styrene; the presence in the polymerizing system of N,N‐dimethylformamide at quite low concentration causes appreciably less cinnamic acid to be incorporated than when bulk monomer or solutions of monomer in toluene are used.
Etude par 1H NMR des groupements chlorométhyles du poly(chlorure de vinyle), 1. Synthèse et étude de modèles moléculaires chloro‐4 chlorométhyl‐3 heptane et trichloro‐1,2,4 pentane
Authors: Doan Huynh Dong , Pétiaud Roger , Llauro‐Darricades Marie‐France 
Published: April 2003

Abstract4‐Chloro‐3‐chloromethylheptane (2) and 1,2,4‐trichloropentane (3) were synthesized and analysed by means of 1H NMR. These compounds — with two asymmetric carbon atoms — are models for two types of structure involving chloromethyl groups present in poly(vinyl chloride): short chloromethyl branches and chain end groups resulting from reinitiation by a chlorine atom. The spectra of these compounds allow a better understanding of the corresponding resonance region observed in standard PVC.
Cationic polymerization of bis(1‐alkylvinyl)benzenes and related monomers, 2. Controlled syntheses of 1,1,3‐trimethyl substituted polyindanes
Authors: Dittmer Thomas , Gruber Freddy , Nuyken Oskar 
Published: April 2003

Abstract1,1,3‐Trimethyl substituted polyindanes were synthesized in the presence of Brønsted acids (H2SO4, CF3COOH) or Lewis acids (BCl3, AlCl3) using 1,4‐diisopropenylbenzene (1), 1,4‐bis(1‐hydroxy‐1‐methylethyl)benzene (2) or 1,4‐bis(1‐chloro‐1‐methylethyl)benzene (3) as monomers. The effects of experimental conditions on yields, molar masses and polymer structure were studied in detail with respect to monomer and initiator used, their concentrations, reaction time and experimental procedure. It was shown, that polymerization temperatures above the ceiling temperature and low monomer concentrations favour the formation of indane units. However, in particular the uniformity of the polymer structure is sensitive to the experimental conditions, mainly to the initiator and to the procedure used. DSC measurements on the polymers proved the remarkable heat‐resistance of polyindanes (Tdec. ≥ 450°C; Tg ≈ 210°C). The thermal properties were related to the polymer structure and were compared with those of some commercial polymers.
“Porcupine” polymers and double‐star polymers
Authors: Taromi Faramarz Afshar , Rempp Paul 
Published: April 2003

AbstractAnionic block copolymerization of styrene and divinylbenzene is known to lead to the formation of star‐shaped macromolecules. This “arm‐first” method has been widely used and studied. The present paper is devoted to two special aspects of this method: The first is concerned with the efficiency of the protection exerted by the arms on the crosslinked core, preventing gelation of the reaction medium. A number of “porcupine” polymers involving bulky cores, fitted with a large number of arms, were synthesized and characterized. The second deals with the possibility of using the “living” carbanionic sites present in the cores, either for purpose of functionalization, or to grow new branches from the core. The presence of remaining unsaturations in the core was evidenced. This is a drawback, since the possibility for “transverse” bonds to be formed results in couplings, inducing gelation.
Synthesis and antitumor activity of chitosan carrying 5‐fluorouracils
Authors: Ouchi Tatsuro , Banba Toshio , Fujimoto Mitsuo , Hamamoto Shigeki 
Published: April 2003

AbstractIn order to provide a polymeric drug of 5‐fluorouracil (5FU) with reduced side‐effects, having affinity for tumor cells and exhibiting high antitumor activity, four kinds of chitosan derivatives were synthesized carrying 5FUs through some kinds of spacers via ether, amide, ester, or carbamoyl bonds. The release behaviors of 5FU and 5FU residues were studied in vitro at 37°C in various aqueous media. The antitumor activity was tested against p‐388 lymphocytic leukemia in female CDF1 mice in vivo by intraperitoneal injection of the polymeric drugs followed by intraperitoneal injection of the leukemia cells (i. p./i. p.). Chitosan fixing 5FU at 2‐position through a hexamethylene spacer and carbamoyl linkages (9) exhibits a higher effect with respect to prolongation of life than free 5FU. The chitosan‐5FU conjugates obtained do not display acute toxicity in the high dose range.
Synthesis, polymerization and copolymerization of a new organotin monomer. Application of a copolymer as catalyst for reductive dehalogenation of alkyl halides
Authors: Endo Takeshi , Kawamoto Hiroshi , Takata Toshikazu 
Published: April 2003

AbstractA new organotin monomer, N‐[3‐(tributylstannyl)propyl]methacrylamide (5) was synthesized in 49% yield by hydrostannylation of acrylonitrile with tributyltin hydride and subsequent reduction of the resulting 3‐tributylstannylpropionitrile (3) with lithium aluminium hydride into 3‐tributylstannylpropylamine (4) which reacted with methacryloyl chloride to afford 5. Polymerization of 5 and copolymerization of 5 with styrene gave homopolymer 6 and copolymer 7, respectively. In a model study on the stability toward solvolysis, N‐(3‐tributylstannylpropyl)propionamide (8) showed no reactivity, whereas the corresponding ester derivative, 3‐tributylstannylpropyl propionate (9), easily reacted with ethanol to release the tin moiety. Monobromostannyl derivative 10, formed by the reaction of 7 with bromine, showed the catalytic activity in the reductive debromonation of dodecyl bromide with sodium borohydride under photoirradiation conditions at room temperature.
13C Nuclear magnetic resonance characterization of poly(propylene) prepared with homogeneous catalysts
Authors: Cheng H. N. , Ewen John A. 
Published: April 2003

AbstractThe minor resonances in the 13C NMR spectrum of poly(propylene) prepared with soluble Group 4 metallocene/methylalumoxane catalysts are fully characterized. The 13C shifts for regioirregular sequences, chain‐end structures, and 1,3‐propylene adduct are obtained for both isotactic and atactic components. In both components the dominating mechanism is 1,2‐insertion, with much lower amounts of 2,1‐insertion and 1,3‐insertion depending on the catalysts used. The isotactic component is stereoregular in all insertion modes. In the atactic components random stereosequences are observed. The regiostructures suggest that the propagation step is catalyticsite controlled even for the atactic component.
Polymerization by [3 + 2] cycloaddition, 3. Polyimides
Authors: Nuyken Oskar , Maier Gerhard , Burger Klaus , Albet Angels Serra i 
Published: April 2003

AbstractThe reaction between hexafluoroacetone azine and bis(bicyclo[2.2.1]hept‐5‐en‐2,3‐dicarboximide)s (5 and 6) (dinadimides) (mole ratio 1:1) yields polymers with number‐average molar masses between M̄n = 1700 and M̄n = 5700 depending on the reactants. The possible isomeric structures of the polymers are discussed in detail. From steric considerations which are supported by 13C and 19F NMR spectral data the number of realized isomers is reduced from sixteen to only three (12, 13 and 14). In contrast to these results, hexafluoroacetone azine and dimaleimides do not react to form polymers. This is explained on the basis of a spontaneous rearrangement of the primarily formed 1:1 adduct to 1 H‐pyrazolines.
Supported propene polymerization catalysts, 1. Supports derived from magnesium dialkyl‐sterically hindered aromatic ester complexes
Authors: Johnson Bryce V. , Karayannis Nicholas M. , Hoppin Charles R. , Ornellas Linda , Khelghatian Habet M. 
Published: April 2003

AbstractNew, highly active supported propene polymerization catalysts are prepared by activating supports derived from Mg dialkyl complexes with sterically hindered aromatic esters, such as ethyl 2,6‐dimethylbenzoate (6a), ethyl 2,4‐6‐trimethylbenzoate (7), or isopropyl benzoate (2b). The support is precipitated by reacting a hexane solution of the Mg dialkyl complex with SiCl4 and then activated by treatment with TiCl4 and diisobutylphthalate in chlorobenzene. Optimized catalysts of this type prepared from Mg dialkyl complex with 7 realize yields of 16–17 kg polypropylene/g catalyst in 2 h hexane slurry polymerizations at 70°C, 10,2 atm, with less than 1% boiling hexane extractables and 0,41–0,43 g/ml polymer powder bulk density. The cocatalyst‐external modifier package used consists of Al(C2H5)3‐dimethoxydiphenylsilane. The polymer produced is characterized by a narrow particle size distribution, which renders the title catalysts suitable for use in both slurry and solventless propene polymerization processes.
Molecular design for missile drug: Synthesis of adriamycin conjugated with immunoglobulin G using poly(ethylene glycol)‐block‐poly(aspartic acid) as intermediate carrier
Authors: Yokoyama Masayuki , Inoue Shohei , Kataoka Kazunori , Yui Nobuhiko , Okano Teruo , Sakurai Yasuhisa 
Published: April 2003

AbstractSynthesis of a novel conjugate of anticancer drug adriamycin, poly(ethylene glycol)‐block‐poly(aspartic acid), and immunoglobulin G is reported. Poly(ethylene glycol)‐block‐poly(aspartic acid), binding adriamycin on the poly(aspartic acid) chain, showed an excellent water‐solubility despite the introduction of a large amount of strongly hydrophobic adriamycin, and was found to form a micellar structure in aqueous solution. Efficient coupling between poly(ethylene glycol)‐block‐poly(aspartic acid) binding adriamycin and immunoglobulin G was achieved via disulfide linkages.
Reductive transformations, 12. Poly(9,10‐anthrylenetrimethylene) as an efficient electron acceptor
Authors: Bender Dietmar , Przybylski Michael , Müllen Klaus 
Published: April 2003

AbstractPoly(9,10‐dihydroanthrylenetrimethylene) (2) comprises a novel chain‐type structure in which 9,10‐dihydroanthracene units are linked by flexible spacer groups. Upon dehydrogenation with sulfur at elevated temperature, polymer 2 is converted into the corresponding polyanthrylene system 3. NMR‐ and UV‐spectroscopic data provide firm evidence for the dehydrogenation process. The polymer 3 was subjected to reduction with active lithium, and the resulting polyanions were characterized by NMR spectroscopy and by quenching experiments. It appears that each anthracene unit of the chain can be charged with two electrons.
Photosensitive polymers bearing iminooxysulfonyl groups. A water soluble positive‐type photoresist
Authors: Shirai Masamitsu , Katsuta Nobuyuki , Tsunooka Masahiro , Tanaka Makoto , Nishijima Kanji 
Published: April 2003

AbstractPhotosensitive polymers were synthesized by the copolymerization of 4‐(9‐fluorenylideneiminooxysulfonyl)styrene (1) with 2‐dimethylaminoethyl methacrylate (2), 2‐diethylaminoethyl methacrylate (3), or methacrylic acid (4). On irradiation with UV light the decomposition of monomeric units of 1 (A) in the polymers led to the formation of sulfo groups in their side chain. Although the quantum yield of photodecomposition of units A was found to be independent of the fraction of units A in the copolymers, it is dependent on the polymer structure in the film. Effects of the fraction of units A in the copolymers and of the polymer structure on the photoinduced dissolution of the polymers in water were studied.
Polymerization initiated by the redox system hydrogensulfite/oxygen, 1. Polymerization of acrylic acid
Authors: Igarashi Tadashi , Kondo Akihiro , Tsushima Rikio , Aoki Shuzo 
Published: April 2003

AbstractThe polymerization of acrylic acid in water by the redox initiation system hydrogensulfite/oxygen was found to proceed fast to give oligomers in high yield, in spite of introducing a large amount of oxygen known as a strong radical inhibitor. In the polymerization system, the concentration of oxygen was kept at a very low level on account of the rapid reaction of hydrogensulfite with oxygen. At high concentration of hydrogensulfite, both hydrogensulfite oxidation rate (Rox) and polymerization rate (Rp) vary with the flow rate of air. Rp is proportional to the square root of Rox, suggesting that the termination is a bimolecular reaction, a radical intermediate formed from hydrogensulfite oxidation being the initiator of this polymerization system. Hydrogen was found to behave as a chain transfer agent, and its chain transfer constant is 0,15 at pH 6,9 and 25°C.
Synthesis an characterization of polyanhydrides containing amido groups
Authors: Hartmann Manfred , Schulz Volker 
Published: April 2003

Abstract4,4′‐Alkane‐ and oxaalkanedioyldiiminodibenzoic acids (3a–e) were prepared from 4‐aminobenzoic acid and various alkanedioyl and oxaalkanedioyl chlorides (2a–e). A series of polyanhydrides having both hydrolytically labile anhydride linkages and anilide units (4a–k) was prepared by polycondensation of the diacids 3a–k at 150–170°C via acetic mixed anhydrides, using different methods. Molecular weights, glass transition temperatures, and solubilities of the polyanhydrides were found to be dependent upon the reaction conditions and the structure of the monomers used. The highest molecular weight (Mn = 12400) was obtained by thermal polycondensation of isolated acetic mixed anhydride prepolymers formed on the reaction of the diacids 3b, 3c, and 3i with acetic anhydride.
Macromonomers of acrylates by group transfer polymerization
Authors: Witkowski Reiner , Bandermann Friedhelm 
Published: April 2003

AbstractBifunctional initiators for group transfer polymerization (GTP) were prepared, substituted by a vinyl, 2‐propyl, isoprenyl (2‐methylene‐3‐butenyl) or 4‐vinylphenyl group at the ketene acetal CC double bond. All initiators initiated GTP of methyl methacrylate in tetrahydrofuran with tris(piperdino)sulfonium bifluoride or tetrabutylammonium cyanide as catalysts to yield macromonomers with low polydispersities. It is recommended to perform GTP as the first step, since the silyl groups of the initiators give side reactions with active species of other polymerization systems. Macromonomers from isoprenyl ‐ or 4‐vinylphenyl‐substituted initiators could be radically copolymerized with styrene to yield graft copolymers. The copolymerization of acrylic macromonomers derived from the other two initiators has yet to be established.
Bifunctional initiators for group transfer polymerization
Authors: Steinbrecht Karin , Bandermann Friedhelm 
Published: April 2003

AbstractBifunctional initiators of group transfer polymerization (GTP) were prepared in which two silyl ketene acetal groups are linked by an oligomethylene bridge, either at their CC double bond or at their alkoxy groups. Their bifunctionality was proven for polymers of methyl methacrylate (MMA) prepared with initiators of the latter type in tetrahydrofuran (THF) with tetrabutylammonium cyanide, (C4H9)4NCN, as catalyst. Hydrolysis after complete conversion of monomer yielded chains exhibiting only half of the molecular weight of the original polymer. GTP of MMA with the new initiators in THF with (C4H9)4NCN is “living”, as could be established by the increase of number‐average molecular weights after repeated monomer addition, providing the opportunity of production of ABA block copolymers of MMA and acrylates.
Group transfer polymerization of methyl methacrylate and methyl acrylate in tetrahydrofuran with tris(piperidino)sulfonium bifluoride as catalyst
Authors: Schubert Walter , Sitz Hans‐Dieter , Bandermann Friedhelm 
Published: April 2003

AbstractGroup transfer polymerization of methyl methacrylate and methyl acrylate with (1‐methoxy‐2‐methyl‐1‐propenyloxy)trimethylsilane and (1‐methoxy‐1‐propenyloxy)trimethylsilane as initiators, respectively, and tris(piperidino)sulfonium bifluoride as catalyst in tetrahydrofuran as solvent was investigated. While the former system nearly behaves like a living system, in the latter system side reactions between the active centres and the catalyst are of greater importance and limit monomer conversion in some cases. The character of the side reactions could be revealed by NMR and GC/MS measurements. Number‐average molecular weights and polydispersities, as determined by gel permeation chromatography, show that tailoring of polymers with definite chain lengths and relatively narrow molecular weight distributions is only possible in the methyl methacrylate system. Reaction rates were proven to be very high, even at very low catalyst concentrations. Therefore, with respect to isothermicity in an industrial reactor, tris(piperidino)‐sulfonium bifluoride seems to be too active as catalyst in group transfer polymerization.
Haloaldehyde polymers, 34. 1H and 13C NMR spectra of chloral oligomers prepared by lithium tert‐butoxide initiation and the assignment of the meso/racemo addition products of the dimers
Authors: Hatada Koichi , Ute Koichi , Nakano Tamaki , Vass Frantisek , Vogl Otto 
Published: April 2003

Abstract1H and 13C NMR spectra of the mixture of chloral oligomers prepared by initiation with lithium tert‐butoxide were examined in detail. 1H and 13C NMR signals due to meso and racemo diastereomers of the dimer fraction were unequivocally assigned through the 13C‐1H COSY spectrum and the 13C NMR spectra with low‐power selective 1H‐decoupling. The two‐dimensional NOESY spectrum showed correlation peaks between the signals due to the methine (acetal) protons of the neighbouring chloral monomeric units of the most abundant isomers in the trimer and tetramer fractions. The 1H NOE enhancements and 3JCH coupling constants were measured for the dimers; the results confirmed the meso/racemo assignments based on earlier conformational analysis.
Investigation of the aminolysis of p‐nitrophenyl esters of (meth)acryloylaminophenoxyacetic acids and their copolymers with N‐(2‐hydroxypropyl)methacrylamide by 6‐aminopenicillanic acid
Authors: Solovskij M. V. , Ulbrich K. , Nazarova O. V. , Zubko N. V. , Panarin E. F. , Kopeček J. 
Published: April 2003

AbstractCopolymers of N‐(2‐hydroxypropyl)methacrylamide with p‐nitrophenyl esters of (meth)acryloylaminophenoxyacetic acids were prepared and characterized. The aminolysis of monomeric and polymeric p‐nitrophenyl esters by 6‐aminopenicillanic acid was studied. The aminolysis rate was structure‐dependent. Acryloyl derivatives were more reactive than methacryloyl derivatives. In both cases, the ortho‐derivatives were more reactive than the para‐derivatives. This phenomenon can be explained by the formation of an intramolecular hydrogen bond in the ortho‐derivatives. The synthetic methods studied are suitable for the binding of biologically active compounds containing an aliphatic amino group to polymeric carriers.