bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polymerisationsauslösung mit substituierten Ethanen, 1. Polymerisation von Methylmethacrylat mit 1,1,2,2‐Tetraphenyl‐1,2‐diphenoxyethan
Authors: Błedzki Andrzej , Braun Dietrich 
Published: April 2003

Abstract1,1,2,2‐Tetraphenyl‐1,2‐diphenoxyethane (TPPA) initiates at 70°C the polymerization of methyl methacrylate. In the first period oligomers of the type 1 with two phenoxydiphenylmethyl end groups (Pn ≈ 1 – 20)
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are formed by primary radical termination. These telechelics are effective initiators of the further free radical polymerization of vinyl monomers.
Adsorption of polymers at the solution/solid interface, 15. Styrene‐vinylferrocene copolymers
Authors: Barrios A. Diaz , Howard G. J. 
Published: April 2003

AbstractA series of styrene‐vinylferrocene random copolymers is synthesised and characterised. Their adsorption from carbon tetrachloride and from chloroform is measured on to pyrogenic SiO2, TiO2 and Al2O3. The level of adsorption depends on the solvent, the adsorbent and the copolymer composition. From chloroform, very few vinylferrocene units are required to increase adsorption markedly above that of polystyrene, and further compositional change has little effect on the level of adsorption. The compositional dependence of adsorption of the copolymers from carbon tetrachloride is more complex. 1H NMR studies show that a very high proportion of repeating units are held close to the silica surface. With polystyrenes, the fraction of units of restricted mobility decreases with polymer molecular weight and with surface coverage; at partial surface coverage virtually all the phenyl groups of low molecular weight polystyrene (mol. wt. = 4000) are immobilised. The copolymers also show large restricted fractions, which decrease along the adsorption isotherm, but which show no significant dependence on polymer composition. Higher restricted fractions seem to be associated with poorer solvent quality.
1H and 13C NMR studies on the interaction between N‐acetyl‐L‐alanine methylamide and trifluoroacetic acid
Authors: Asakura Tetsuo 
Published: April 2003

Abstract1H and 13C NMR chemical shifts and also spin‐lattice relaxation times of N‐acetyl‐L‐alanine methylamide were measured in the solvent system deuteriochloroform/trifluoroacetic acid, in order to discuss aspects of the interaction between peptide units and the acid. The maximum displacement in the acid proton peak and marked decreases in the 1H and 13C spin‐lattice relaxation times of the amide were observed at an acid/amide mole ratio of ≈ 2. These strongly suggests a 1:2 amide‐acid interaction. Moreover, taking into account the differences of the acid concentration dependences between the two kinds of NH proton peaks and those between the two kinds of CO carbon peaks, a solvation model was proposed in which both the alanyl NH and the alanyl CO groups adjacent to the Cα carbon in the amide are linked by intermolecular hydrogen bonding with both the carbonyl group of one acid molecule and the acid proton of another acid molecule, respectively. In addition, intermolecular hydrogen bonding occurs also between these two acid molecules.
Dilute solution properties of methyl methacrylate/acrylonitrile random copolymers, 2. Stockmayer fixman relations
Authors: Kashyap A. K. , Kalpagam V. 
Published: April 2003

AbstractThe Stockmayer‐Fixman relation was used to evaluate the short range and long range interaction parameters for methyl methacrylate/acrylonitrile copolymers of 0,566 and 0,657 mole fraction of monomeric units of acrylonitrile in the solvents acetonitrile, 2‐butanone, dimethyl formamide, and γ‐butyrolactone, at different temperatures (30, 45, and 60°C). The values of K0 were found to be lower than those of the parent homopolymers, and their values depend on both solvent and temperature. Even negative K0‐values were obtained, in cases in which the Mark Houwink exponent a is nearly unity. The values of the polymer‐solvent interaction parameter, χ1, are high and close to 0,5, indicating that these solvents are not good. The values of the excess interaction parameter, χAB, are negative and are not affected by temperature. The large extension of these copolymer chains, as exhibited by a and α‐values, can be understood in terms of unusual short range interactions only. Similar results were obtained for some cellulose derivatives.
Substituted and branched polychalcones. Syntheses and characterization by spectrometric methods
Authors: Malm Bo 
Published: April 2003

AbstractPolychalcones 4a, b were prepared by a Friedel‐Crafts acetylation of vanillin (3a) and p‐hydroxybenzaldehyde (3b) and by a Fries rearrangement of the acetates in nitrobenzene using AlCl3 as catalyst. The reaction was carried out in one step under a variety of reaction conditions (time and temperature). The polymers were characterized by UV, IR and 1H NMR spectroscopy. The polychalcones obtained from p‐hydroxybenzaldehyde had a limited solubility, but they swoll in DMSO and in dilute NaOH.
Syntheses of diacetylene monomers from N‐(nitrophenyl)amine substituted diacetylene alcohols
Authors: Horner Charles J. , Garito Anthony F. , Desai Kirit N. 
Published: April 2003

AbstractSeveral new classes of asymmetric diacetylene monomers of the type O2NArNHCH2CCCCCH2R have been synthesized from nitroaniline diacetylene alcohols. The solid state polymerization behavior of several members of these classes has been examined.
Micellisation de copolymères séquencés polystyrène‐polyvinylpyridinium, 3. Influence de la concentration en sel et de la température
Authors: Selb Joseph , Gallot Yves 
Published: April 2003

AbstractThe effects of the salt concentration and temperature on the micellization phenomenon of polystyrene‐poly(4‐vinyl‐N‐ethylpyridinium bromide) block copolymers in dilute solution are investigated in solvents selective for the polyelectrolytic part (water‐methanol‐LiBr mixtures). The polystyrene moiety being in non‐solvent media remains rather collapsed whatever temperature and salt concentration. On the contrary, the latter parameters modify strongly the conformation of the soluble polyelectrolytic chains and therefore determine the “quality” of the solvent essentially towards the polyvinylpyridinium blocks. Consequently an increase of the temperature or a decrease of the salt concentration have the same effect on the behaviour of the copolymers. In the case of a copolymer with a small molecular weight polystyrene block (Mw = 2 700), the unimer‐multimer (single molecules/micelles) equilibrium is easily shifted in favour of the single molecules by increasing the temperature or decreasing the ionic strength. On the contrary, if the polystyrene moiety is longer (Mw = 6 000 – 13 000) the micellar weight of the system is little or even not at all influenced by the ionic strength and the temperature. These results emphasize that, for the investigated systems, it is the “insoluble” blocks which essentially govern the micellization phenomenon.
Synthesis and tumor‐inhibiting activity of new heparin‐bound nitrogen mustard analogues
Authors: Kim Sung‐jho , Höcker Hartwig , Kern Werner 
Published: April 2003

AbstractNew nitrogen mustard analogues in which bis(2‐chloroethyl)‐amino groups are separated by oxyethylene groups, 1,14‐dichloro‐3,12‐bis(2‐chloroethyl)‐3,12‐diaza‐6,9‐dioxatetradecan (3c) and 1,17‐dichloro‐3,15‐bis(2‐chloroethyl)‐3,15‐diaza‐6,9,12‐trioxaheptadecane (3d), were synthesized by reaction of bis(2‐hydroxyethyl)amine (2) with bis(2‐chloroethyoxy)ethylene (1a) and with 1,11‐dichloro‐3,6,9‐trioxaundecane (1b), respectively, followed by treatment with thionyl chloride. The analogues were then complexed with heparin. The resulting heparin‐complexes show inhibiting activity against transplanted Sarcoma‐180 A in mice.
On the salt‐linkage formations of porous and nonporous silica particles with trimethylammonium glycol chitosan iodide
Authors: Kokufuta Etsuo , Hirai Yasumasa , Nakamura Isei 
Published: April 2003

AbstractThe stoichiometry of the salt‐linkage formations of nonporous and porous silica particles with trimethylammonium glycol chitosan iodide (TGCI) was investigated by comparing the results of colloid titration and adsorption experiments with those of potentiometric titrations. The surface charge (Q) of colloidal silica as function of pH was evaluated by means of the colloid titration with TGCI. On the other hand, the density (D) of ≡ SiO⊖ groups of silica gel at different pH was also evaluated by the adsorption experiment of TGCI. These results obtained were compared with the Q vs. pH and D vs. pH curves which were obtained by the potentiometric titrations at various ionic strengths for colloidal silica and silica gel, respectively. It was concluded that the ≡ SiO⊖ groups on the surface of nonporous colloid silica form the salt‐linkages stoichiometrically with ⊕N(CH3)3‐groups in TGCI, whereas the salt‐linkage formation between ⊕N(CH3)3‐groups in TGCI and ≡ SiO⊖ groups of silica gel does not follow the stoichiometric relationship, since the salt‐linkages of the ≡ SiOominus; groups in the pores of the silica gel could be affected by the steric hindrance of the TGCI chain.
Ion‐trapping in cationic polymerization, 2. Relative rates of trapping and relative chemical shifts for structurally differing phosphines as trapping agents
Authors: Matyjaszewski Krzysztof , Penczek Stanisław 
Published: April 2003

AbstractThe reaction of ethyl trifluoromethanesulfonate with phosphines to form phosphonium salts was used as a model reaction for the “trapping” of the various propagating species by phosphines in the polymerization of THF and other cyclic ethers. In dichloromethane at 25°C, the values of the bimolecular rate constant ktr were determined for various phosphines. For (C6H5)3P:5.10−3 mol−1.l.s−1, for (C6H5)(CH3)2P:0,22 mol−1.l.s−1, for (C6H5)(n‐C3H7)‐(CH3)P:0,13 mol−1.l.s−1, and for (n‐C4H9)3P: 1,3 mol−1.l.s−1. It was found that the ratio ktr/ka (ka is the rate constant of the ethylation of THF by ethyl trifluoromethanesulfonate) changes from 40 for triphenylphosphine to 104 for tributylphosphine. Differences of chemical shifts, measured for various quaternary phosphonium cations differing in one substituent, were observed for ions with various substituents (e.g. based on parent methylpropylphenylphosphine).
Einfluß des temperns auf die negative thermische ausdehnung von polyethylen
Authors: Karl Veit‐Holger , Wolf Frank‐Peter 
Published: April 2003

AbstractThe linear thermal coefficient of expansion for high density polyethylene, extended to draw ratios λ = 8 to 16 is α = −24·10−6 K−1 at 20°C. This value results from the orientation of crystallites with an expansion coefficient αc = −12·10−6 K−1 and from stresses in the amorphous phase. Using the model of series coupling of crystalline and amorphous parts the value αam ≤ −50·10−6 K−1 is calculated for a crystallinity xv = 70%. From measurements of Young's modulus the fraction of tie‐molecules χtie = 0,4% of the sample is assessed and the expansion coefficient αtie = −90·10−6 K−1. Annealing of the samples leads to shrinkage while the density ρ increases slightly and the expansion coefficient α increases considerably. Samples annealed at temperatures closely below the melting point show a slight decrease of the density at 20°C but a value of α exceeding that of isotropic samples. This effect can be explained by preferred orientation of the crystal a‐axis in fibre direction as soon as orientation starts to break down.
13C NMR spectra of polymers made by ring‐opening polymerization of (±)‐endo‐5‐methylbicyclo[2.2.1]hept‐2‐ene using metathesis catalysts
Authors: Ivin Kenneth J. , Lam Luk‐Mui , Rooney John J. 
Published: April 2003

AbstractA range of olefin metathesis catalysts has been used to prepare ring‐opened polymers of (±)‐endo‐5‐methylbicyclo[2.2.1]hept‐2‐ene (1), having cis double bond contents of 22–100%. The 13C NMR spectra of these polymers are interpreted in terms of TH, TT, HH, HT and tt, tc, ct, ccstructures (T = tail, H = head, referring to the methyl group orientation; t = trans, c = cis, referring to the double bond configuration). The fine structure of the olefinic region at 75 MHz indicates that the cis/trans double bond distribution is blocky when the cis content is more than 50%. The chemical shifts of the ring carbons indicate puckering of the cyclopentane rings. The cis relationship of the methyl carbon and the adjacent olefinic carbons causes an upfield shift in both cases.
Preparation and characterization of a polyacrylamide resin containing thiol groups. Study of the reversible Zn(II) fixation
Authors: Deratani André , Sebille Bernard 
Published: April 2003

AbstractNew resins (6) containing thiol groups within a hydrophilic matrix are described. They contain up to 3,6 mmol thiol groups per g of dry polymer and were prepared by thiolation, via thiolester group formation, of various crosslinked polymers of N‐acryloylaminomethylchloroacetamide (1c) which was synthetized. Their ability to extract Zn(II) ions was evaluated. The effects of contact time, pH, and complexing agents on the fixation reaction were studied. It was found that the equilibrium is reached in a few minutes, the optimal capacity at pH 6 being about 2 mmol Zn(II) per g. The fixation involves three reactions: two leading to thiol group complexation, the third being the retention by the amide function of the resin saturated with Zn(II).
Competition of addition and condensation polymerization at the thermal treatment of 4‐methacryloyloxybenzoic acid and 4‐acryloyloxybenzoic acid
Authors: Golova Ludmila K. , Amerik Yuri B. 
Published: April 2003

AbstractThe nature of the processes of the formation of macromolecules during the thermal treatment of 4‐methacryloyloxybenzoic acid (1) and 4‐acryloyloxybenzoic acid (6) was studied. It was shown, that during the thermal treatment of 1 at 250°C (above the ceiling temperature of the addition polymerization) only a condensation polymerization (polycondensation) takes place. In the case of 6 both addition and condensation polymerization are possible at these temperatures. The rigid chains of the resulting poly(oxy 1,4 phenylenecarbonyl) (3) are parallelized spontaneously and the corresponding ordered melt exhibits a liquid crystalline state. The rigid chain polymer 3 is formed too as a result of polymeranalogous transformations of the corresponding polymers poly[1‐(4‐carboxyphenoxycarbonyl)‐1‐methylethylene] (2) (from 1) and poly[1‐(4‐carboxyphenoxycarbonyl)ethylene] (7) (from 6).
Darstellung von oligothymidinphosphaten durch chemische partialhydrolyse von desoxyribonucleinsäure
Authors: Schott Herbert 
Published: April 2003

AbstractThe method of preparation of oligo(thymidine phosphate)s by chemical partial hydrolysis of herring sperm DNA is described. The DNA is degraded in three steps to a mixture of oligomeric thymidine phosphates. Homologeous thymidine phosphates of the series p(dT)1–6p; p(dT)1–7, (dT)1–7p; (dT)1–7 are isolated chromatographically from the partial hydrolysate in pure form on a preparative scale. The advantages and disadvantages of this new and simple method in comparison to complicated synthetic procedures are discussed.
Radiation polymerisation of solid trioxane at low doses
Authors: Atreyi M. , Kumar Surendra 
Published: April 2003

AbstractResults obtained from experiments on the radiation polymerisations of solid trioxane done at dose rates one order higher but at a total dose much less than those used by earlier workers are presented. The irradiation of crystalline trioxane samples in air was done using 60Co γ‐rays at room temperature (20–30°C) followed by ‘post polymerisation’ at 55 ± 0,1°C for 24h. The polymer yield was found to increase with dose linearly initially at all dose rates and then passed through a maximum. The molecular weight versus dose curve also exhibited a maximum. Irradiation and ‘post polymerisation’ in nitrogen atmosphere did not affect the yield and molecular weight of the poly(oxymethylene) (POM) obtained, suggesting complete absence of free radical precursors in the initiation step. A comparison of the variation of the number of monomer molecules consumed per 100eV with dose obtained from the present data on ‘post polymerisation’ with that for Okamura's data on ‘insource polymerisation’ suggests that the mechanism of the two types of polymerisation is not the same.
Gel chromatographic fractionation of styrene oligomers
Authors: Sato Hisaya , Saito Kazuhisa , Miyashita Kiyoshi , Tanaka Yasuyuki 
Published: April 2003

AbstractA series of styrene oligomers having propyl end groups was prepared by oligomerization of styrene with ethyllithium followed by termination with l‐bromopropane. The fractionation of the oligomers by molecular weight and into diastereomers was investigated by gel chromatography using a high resolution styrene‐divinylbenzene gel. The most suitable eluents for the fractionation were chosen by the study of the elution behavior of the oligomers using various eluents having different polarity. The fractionation by molecular weight was done with chloroform as eluent and the 2‐ to 11‐mers of styrene were collected with purities higher than 95%. The isolated 2‐ to 5‐mers were further separated into diastereomers using diisopropyl ether as an eluent. The dimer and the trimer were fractionated into pure diastereomers. The tetramer was separated into 6 diastereomers and the fractionation of the pentamer was also relatively successful.
Stereochemistry of a model reaction for the propagation reaction in the cationic polymerization of alkyl propenyl ethers
Authors: Matsuzaki Kei , Morii Hisayuki , Inoue Naoki , Kanai Taiichi , Higashimura Toshinobu 
Published: April 2003

AbstractThe stereochemistry of the acetal addition to alkyl propenyl ethers was investigated as a model reaction for the cationic polymerization of propenyl ethers. The diastereomers of the acetal adducts were identified by model compounds with similar structure. The modes of both double bond opening and monomer addition were determined. It was demonstrated that the mode of double bond opening is independent of the geometrical structure of the ethyl propenyl ether and mainly threo‐opening takes place, whereas the mode of monomer addition is dependent on the geometrical structure of the monomer.
Functional metal‐porphyrazine derivatives and their polymers, 6. Free radical polymerization initiated by Fe(III)‐phthalocyanine‐2,9,16,23‐tetracarboxylic acid
Authors: Shirai Hirofusa , Ishimoto Akio , Kamiya Nootaka , Hanabusa Kenji , Ohki Kosuke , Hojo Nobumasa 
Published: April 2003

AbstractThe polymerization of various vinyl compounds initiated by the Mt‐phthalocyanine‐2,9,16,23‐tetracarboxylic acid (Mt‐taPc, Mt = Fe(III), Co(II), Ni(II), and Cu(II)) was studied in aprotic polar solvents in the presence and absence of molecular oxygen. Fe(III)‐taPc only was found to initiate smoothly the polymerization of methyl methacrylate (MMA) in the presence of air in aprotic polar solvents by a free radical mechanism. The kinetics of the polymerization of MMA initiated by Fe(III)‐taPc were studied under air in dimethylformamide at 60°C. The rate of polymerization, Rp, can be expressed as Rp = k[Fe(III)‐taPc]0,5[MMA]1,5. From the data of electronic and ESR spectra of this polymerization system, the polymerization mechanism is discussed.
Polyimides derived from bismethylolimides, 3. Synthesis and properties of poly(imide‐urethane)s
Authors: Kurita Keisuke , Imajo Hidetomo , Nakada Tohru , Iwakura Yoshio 
Published: April 2003

AbstractPoly(imide‐urethane)s having a methylene group between the imido and the oxycarbamoyl groups were synthesized by addition polymerization of bis(N‐hydroxymethyl)imides and diisocyanates in hexamethylphosphoric triamide. Properties of the resulting poly(imide‐urethane)s were studied in comparison with those of the corresponding poly(imide‐urethane)s having no methylene group. The resulting carbamic ester linkage was found to be much more stable against nucleophiles compared with the carbamic ester linkage without the methylene group. However, there appeared to be not much difference in thermal stability between these two kinds of linkages.
Macromers as intermediates for the synthesis of graft copolymers
Authors: Sierra‐Vargas Julio , Franta Emile , Rempp Paul 
Published: April 2003

AbstractFree radical copolymerization of a macromer and a vinylic or acrylic monomer is a novel method of synthesis of graft copolymers. Each macromer unit gives yield to a graft. Accurate characterization of the samples obtained, especially by means of proton NMR, is possible. The distribution of the grafts along the chain is random. The overall molecular weights of the copolymers formed are low, however.
Reactive polymers containing pendant azetidine or azetidinium functions, 1. Synthesis of poly(acrylic ester)s and poly(methacrylic ester)s of 1‐alkyl‐3‐hydroxyazetidines and related azetidinium salts
Authors: Bogaert Yvan , Goethals Eric , Schacht Etienne 
Published: April 2003

AbstractTrans‐esterification of methyl acrylate or methyl methacrylate with 1‐alkyl‐3‐azetidinols leads to the corresponding azetidinyl acrylates or methacrylates. These new monomers are polymerized by a free radical mechanism to polymers containing pendant azetidine functions. When these polymers are treated with a mineral acid or with a strong alkylating agent, such as dimethyl sulfate, water‐soluble polymers are obtained. An alternative route is to transform the monomer into the azetidinium salt form and to polymerize this salt in aqueous solution. Azetidinium ion containing polymers are stable at room temperature but cross‐link to insoluble materials above 120°C.
Initiation of 1,1‐diphenylethylene dimerization and isobutylene polymerization by TiCl4, AlBr3 and their mixtures in hydrocarbon solvents
Authors: Masure Michèle , Nguyen‐Anh‐Hung  , Sauvet Georges , Sigwalt Pierre 
Published: April 2003

AbstractThe initiation of the dimerization of 1,1‐diphenylethylene (DPE) by AlBr3 and TiCl4 in heptane at −30°C was studied spectrophotometrically. The yields of carbocations with respect to the concentration of metal halides were low and their absolute concentrations too small to exclude the possibility of cocatalysis by residual impurities. When TiCl4 was added to DPE/AlBr3/heptane (or AlBr3 to DPE/TiCl4), the second halide did not cause an increase of the carbocation concentration greater than when it was added first. TiCl4 alone was found to be no initiator for the polymerization of isobutylene and AlBr3 is only weakly active (lower rates than those observed by Marek et al. and very low conversions were obtained). HCl is an efficient cocatalyst with AlBr3. Mixtures of TiCl4 and AlBr3 gave rates several times higher than either compound separately, and complete conversions. The enhancement of isobutylene polymerization is probably not due to an activation of the initiation step since the same effect is not observed during the cationation of DPE. An alternative explanation, based on a stabilization of the active species and/or an increase of their reactivity, is proposed.
Gel permeation chromatography of polymer mixtures
Authors: Kok Chong Meng , Rudin Alfred 
Published: April 2003

AbstractWhen mixtures of polymers are analyzed in a common gel permeation chromatographic solvent the peak elution volumes of both components are shifted with respect to their values at their nominal concentrations in the same solvent and column set. In this article a theory which has been applied previously to account for concentration effects of a single polymer in a GPC solvent is modified to predict peak elution volumes in polymer mixtures. The model invokes solvent‐solute interactions only and provides quantitative predictions of the behavior of mixtures of anionic polystyrene samples with other polystyrenes and with polybutadienes. There is no indication of polymer‐polymer repulsive effects except for polystyrene‐poly(methylmethacrylate) mixtures at relatively high concentrations.