bluuebunny/crossref_metadata_2025_split huggingface dataset:
Syntheses and condensation polymerizations of 3‐hydroxybutyric acid derivatives of pyrimidine bases
Authors: Hattori Masahira , Takai Hiroshi , Kinoshita Masayoshi 
Published: April 2003

Abstract4‐(1,2,3,4‐Tetrahydro‐5‐methyl‐2,4‐dioxo‐1‐pyrimidinyl)‐3‐hydroxybutyric acid (1a) and 4‐(1,2,3,4‐tetrahydro‐2,4‐dioxo‐1‐pyrimidinyl)‐3‐hydroxybutyric acid (1b) were synthesized via the addition reaction of thymine (3) and 4‐ethoxy‐1,2‐dihydro‐2‐oxopyrimidine (7), respectively, to 1‐chloro‐2,3‐epoxypropane and subsequent cyanization, followed by acid hydrolysis of the products. Condensation polymerizations of 1a and 1b were carried out using dicyclohexylcarbodiimide, 2,4,6‐triisopropylbenzenesulfonyl chloride or p‐toluenesulfonyl chloride as dehydrating agents. The resulting oligoesters 2a and 2b are light‐yellow powders with molecular weights of about 700, according to gel filtration measurements. Their UV spectra show a hypochromicity of 3–4% when mixed with denatured yeast RNA in 0,1 M Na2HPO4 solution.
Circular dichroism and structure of Schiff's bases of hydroxybenzaldehydes anchored to poly(L‐lysine) and poly(L‐α,γ‐diaminobutyric acid)
Authors: Dentini Mariella , De Santis Pasquale , Savino Maria , Sforza Maria Pia , Verdini Antonio Silvio 
Published: April 2003

AbstractSchiff's bases of ortho‐, meta‐ and para‐hydroxybenzaldehydes with poly(L‐α,γ‐diaminobutyric acid) and poly(L‐lysine) were investigated in solution of methanol and methanol‐water mixtures by circular dichtroism, absorption spectroscopy and equilibrium dialysis techniques. The results so far obtained allow us to propose a molecular model, which fully justifies the stereospecific binding of ortho‐hydroxybenzaldehyde with the polypeptide chain; moreover it is able to explain the dramatic change of the chemical equilibrium in the hydrolysis reaction.
Solvatation préférentielle des polymères: Effet de la masse moléculaire sur les résultats expérimentaux et comparaison avec les prévisions théoriques
Authors: Dondos Anastasios , Benoît Henri 
Published: April 2003

AbstractThe preferential solvation coefficient λ′ has been studied as a function of the molecular weight of the polymers and the composition of the mixed solvents for the following ternary systems: polystyrene/benzene/cyclohexane, poly(2‐vinylpyridine)/benzene/cyclohexane, polystyrene/benzene/methanol, polystyrene/carbon tetrachloride/methanol and poly(2‐vinylpyridine)/chloroform/ethanol.It is shown that the extrapolated value λ′∞ for infinite molecular weight better obeys the theoretical expressions established by Read and Pouchly than the value for a finite molecular weight.When interactions are weak the Read formula can be used, when they are stronger one has to use the formula on Pouchly et al., but all these theories give just a qualitative description of the phenomenon and cannot be used quantitatively in the presence of strong interactions such as hydrogen bonds.
Synthèse de poly(oxyéthylène)s rendus biospécifiques par fixation de stéroïdes en extrémités de chaînes. Utilisation d'un poly(oxyéthylène) substitué par des groupes estradiol pour extraire l'isomérase Δ5→4 oxo‐3 stéroïde, par partage d'affinité
Authors: Chaabouni Abdelaziz , Hubert Patrick , Dellacherie Edith , Neel Jean 
Published: April 2003

AbstractIn three consecutive steps involving halogenation, amination, and condensation with a convenient acyl derivative (1 or 2), α‐hydro‐ω‐hydroxypoly(oxyethylene) (3) was transformed into poly(oxyethylene)s 7 containing 0,6 to 1,3 mol of 3‐[3,17β‐dihydroxy‐1,3,5(10)‐estratrien‐7α‐yl]butyroyl end groups or 0,7 mol of 3‐oxo‐4‐androsten‐17β‐ylcarboxyl end groups per mol of polymer. Applying the method of affinity partitioning, the former poly(oxyethylene) derivative 7 was used to purify successfully Δ5→4 3‐oxosteriod isomerase contained in a crude extract from Pseudomonas Testosteroni.
13C NMR sequence analysis, 15. Copolymerization of alanine‐NCA with other α‐amino acid NCAs
Authors: Kricheldorf Hans R. , Schilling Gerhard 
Published: April 2003

AbstractAlanine‐N‐carboxylic acid anhydride (Ala‐NCA) was copolymerized with glycine‐NCA, phenylalanine‐NCA, valine‐NCA, leucine‐NCA, and sarcosine‐NCA in various solvents and with various catalysts; 22,6 MHz 13C NMR spectra and 90 MHz 1H NMR spectra of the resulting copolypeptides were measured in trifluoroacetic acid and from the signal intensities the rate of incorporation was estimated. The copolypeptides poly(Ala/Gly) and poly(Ala/Phe) contained both monomeric units in an almost equal concentration, while the low reactivity of Val‐NCA and Leu‐NCA resulted in a lower concentration of these residues compared with Ala in poly(Ala/Val) and poly(Ala/Leu). The 13C NMR spectra of poly(Ala/Gly) exhibit four CO‐signals which could be assigned by comparison with the corresponding homopolypeptides and with the sequence polypeptides (Ala‐Ala‐Gly‐Gly)n, and (Ala‐Gly‐Gly)n. From the intensities of these CO‐signals the average length of the homogeneous blocks was calculated. Both block lengths and rate of incorporation proved to be almost independent of solvent, catalyst, and reaction temperature. Poly(Ala/Phe) and poly(Ala/Sar) show also four CO‐signals, but poly(Ala/Val) only two and poly(Ala/Leu) one. The number and shape of the CO‐signals allow one to decide whether random copolypeptides were obtained or not.
Vernetzung von amylose mit Epichlorhydrin, 2. Untersuchung der Vernetzungsprodukte nach dem Gelpunkt
Authors: Pfannemüller Beate , Sperlich Marianne 
Published: April 2003

AbstractA series of amylose gels prepared by reaction of amylose solutions in 1 M aqueous NaOH with 1‐chloro‐2,3‐epoxypropane (epichlorohydrin) at different concentrations were characterized by several methods: (a) The density of cross‐links was estimated by equilibrium swelling of the gels in water at room temperature. The molecular weight of the segments between the cross‐links (Mc) derived from the Flory equation decreased exponentially with the epichlorohydrin concentration used for gelation. The results obtained for weakly cross‐linked gels are in the same order as the values determined previously by analytical methods. (b) Further differentiation of the gels and the corresponding sol fractions was achieved by enzymes specific for amylose. The size of the fragments resistent to α‐amylase was found to increase linearly with epichlorohydrin concentration. Only minor attack by the exo‐enzyme β‐amylase was found, indicating lack of longer unsubstituted pendant branches. The presence of some short branches is deduced from their priming activity in phosphorolytic synthesis. The grafted amylose chains are located solely at the surface of the gels. The weakly cross‐linked gels give characteristic colours with iodine indicating slightly longer free amylose segments in the gel than in the corresponding sol. The nature of iodine binding by cross‐linked amylose chains is discussed.
Borverbindungen, 9. Metathetische Ring‐Ring‐Gleichgewichte bei Dioxaboracycloalkanen
Authors: Gerwarth Ulrich W. 
Published: April 2003

AbstractAryldihydroxyboranes (2,10) condense with α,ω‐alkanediols HO(CH2)xOH (6), which leads to an equilibrium of oligomeric rings (7) of different size due to a ligand exchange at the boron atom. With low diols (6, x = 2,3) the rate of establishing the equilibrium of the exchange reaction is slow enough for isolating the five‐ and six‐membered heterocycles (7, n = 1). Diols with x≥5, however, lead to the equilibrium mixture of oligomeric heterocycles in a somewhat analogous way to olefin metathesis.
13C‐Relaxationsuntersuchungen zum Einfluß des Lösungsmittels auf die Kettenbewegung von Polystyrol
Authors: Gronski Wolfram , Murayama Nobumichi 
Published: April 2003

AbstractTemperature dependent measurements of 13C spin lattice relaxation times and of nuclear Overhauser enhancement factors were carried out for atactic and isotactic polystyrene in tetrahydrofuran and for atactic polystyrene in 1,4‐dioxane. The analysis of the relaxation data by means of a Cole‐Cole distribution of correlation times confirms the additivity of intramolecular and solvent viscosity dependent activation energies. For atactic and isotactic polystyrene the same intramolecular activation energy of 21 ± 5kJ/mol is obtained for the segmental motion. A comparison with 13C relaxation measurements of other authors shows that the intramolecular activation energies and the anisotropy of the segmental motion are increasing simultaneously by changing the solvent from toluene over pentachloroethane to tetrahydrofuran. Based on the experimental findings the chain motions in polystyrene are interpreted as diffusion controlled processes in the hindering potential of the CC bonds of the chain backbone which is modified by conformation dependent interactions between phenyl groups and solvent molecules.
Molecular weight and chain length distribution of native poly(β‐1,4‐D‐mannose) from cell walls of the alga codium
Authors: Marx‐Figini Marianne , Coun de Matus María 
Published: April 2003

AbstractPoly(β‐1,4‐D‐mannose)Commonly named mannan.
was isolated from cell walls of the alga Codium decorticatum by methods proved to preserve its native degree of polymerization. The intrinsic viscosities obtained on native mannan nitrates from algae harvested in different years possess values [η]≈440ml.g−1 with a maximum deviation of 9%, independent of the year of harvest and the age of the cell walls. Osmotic measurements on one of these samples resulted DPn = 375. Fractionation experiments on the same material revealed a nearly monodisperse chain length distribution. The notable independence of the degree of polymerization from the growth conditions and the age of the plants together with its monodispersity let assume a biopolymerization mechanism which is controlled genetically and not by the time of synthesis.
Self‐quenching interaction between ferrocene units in photooxidation‐reduction sensitized by copolymers of 1‐ferrocenylethyl methacrylate
Authors: Nakahira Takayuki , Minami Chiyo , Iwabuchi Susumu , Kojima Kuniharu 
Published: April 2003

AbstractCopolymers of 1‐ferrocenylethyl methacrylate (FEMA) with styrene (St) and methyl methacrylate (MMA) were prepared, and their photosensitizing capability with respect to oxidation‐reduction between L‐ascorbic acid and Fast Red A was examined in dimethylformamide. With both types of copolymers, the higher the FEMA content, the lower the relative quantum yield of the sensitization. The observed decrease in the relative quantum yield was interpreted in terms of Perrin's model of static quenching interaction between excited and near‐by ground‐state ferrocene units. The mean sequence length of FEMA in the polymer was found to be an appropriate parameter for the local ferrocene concentration with respect to the polymer. Both energy migration and quenching interaction were thus suggested to occur among nearest‐neighbor ferrocene units along the polymer chain; the latter prevails over the former. It was also suggested that the ester carbonyl group of MMA units interacts with near‐by excited‐state ferrocene units.
Catalytic properties of 4(5)‐imidazolylmethylated poly(vinyl alcohol) in the hydrolysis of p‐nitrophenyl acetate
Authors: Kida Masaaki , Nakano Hidehiko 
Published: April 2003

AbstractThe catalytic hydrolysis of p‐nitrophenyl acetate (PNPA) by 4(5)‐imidazolylmethylated poly(vinyl alcohol) (IMPVA) was studied. When IMPVA (\documentclass{article}\pagestyle{empty}\begin{document}$ \overline {{\rm DP}} \approx 2000 $\end{document}, imidazolyl content: 2,7 mole‐%) was used as catalyst, the rate of catalytic hydrolysis showed substrate saturation phenomena and could be described by a Michaelis‐Menten kinetics with Km = 3,3 mmol·l−1 and kcat = 9,4·10−3 min−1. Km and kcat increased with increasing imidazolyl content in the IMPVA (imidazolyl content = 13,0 mole‐%, Km = 53 mmol·l−1 and kcat = 8,7·10−2 min−1). Addition of ethanol to the reaction mixture resulted in a decrease in Km and kcat (ethanol conc. = 50 vol.‐%, Km = 1,5 mmol·l−1 and kcat = 1,7·10−3 min−1). In the presence of boric acid, Km increased, while kcat varied in a complicated manner. The catalytic properties of IMPVA were found to be also affected by the degree of polymerization, and when an IMPVA of \documentclass{article}\pagestyle{empty}\begin{document}$ \overline {{\rm DP}} \approx 500 $\end{document} with an imidazolyl content of 2,7 mole‐% was used as catalyst, substrate saturation phenomena were not observed.
Preferential solvation of poly(acrylic acid) and its sodium salt in water/dioxane mixtures: A comparison with poly(α‐L‐glutamic acid)
Authors: Morcellet Michel , Loucheux Claude 
Published: April 2003

AbstractThe preferential solvation of poly(acrylic acid) and its sodium salt in water/dioxane mixtures was studied. The comparison with results previously obtained on poly(χ‐L‐glutamic acid) indicates the preferential solvation of the latter polymer by dioxane is due to the existence of the peptide group in the polymer. The viscosimetric behavior of poly(acrylic acid) in water/dioxane mixtures is interpreted by the existence of water‐dioxane complexes with a definite stoechiometry.
Electric field effects in the polymerization of α‐methylstyrene
Authors: Akbulut Ural , Birke Ronald L. , Fernandez Jack E. 
Published: April 2003

AbstractWe here report the boron trifluoride diethyletherate initiated polymerization of χ‐methylstyrene in 1,2‐dichloroethane. With platinum foil electrodes and an applied electric field of 1–3kV/cm, the initial rate of disappearance of monomer is the same in the absence or presence of the electric field. The rate of formation of polymer at high conversions, however, decreases when the electric field is imposed. The NMR, UV absorption, and fluorescence spectra of the polymers are affected by the field, whereas the IR, ESCA spectra, and melting point of the polymer are unaffected by the field. To probe the reasons for these field effects, we obtained oxidation and reduction potentials of monomer, solvent, and initiator by polarographic or cyclic voltammetric methods. All the components of the system were easily reduced or oxidized. Also, when the anode and cathode were separated by a sintered glass disk, the amount of polymer formed in the anode compartment was greater than that in the cathode compartment. These results suggest that the observed electric field effects are due to electrochemical reactions rather than to the second Wien effect.
Kinetische und morphologische untersuchungen zur polymerisation von oxacyclischen monomeren im festen zustand, 3. Zur morphologie der bei der polymerisation von trioxan mit chemischen katalysatoren entstehenden polyoxymethylene
Authors: Muñoz‐Escalona Antonio 
Published: April 2003

AbstractThe nascent crystal structure and morphology of poly(oxymethylene) (POM) obtained from 1,3,5‐trioxane crystals, induced by gaseous chemical initiators, was studied in order to clarify the solid‐state polymerization mechanisms of this monomer. The polymerization starts at the surface of the monomer crystals and propagates towards its interior. The polymerization rate, therefore, depends on the size of the crystals and not on the initiator amount. Hexagonal fibrous crystals without a main orientation were obtained on the surface of the monomer crystal. These crystals orientated themselves along the c‐axis of the monomer, due to the polymerization propagation inside the crystals by simultaneous solid‐gas polymerization and crystallization mechanisms. The orientation depended on the reactivity of the initiator, the order being: BF3‐O(C2H5)2 > SnCl4 > H2SO4‐paraformaldehyde. The orientation was also improved by increasing the polymerization temperature, obtaining POM crystals similar to those found by radiation induced polymerization. At low polymerization temperature folded chain crystals were obtained similar to those encountered by solution polymerization according to crystallization succeeding polymerization mechanisms.
Diffusion of gases in cellulose triacetate
Authors: Patel V. M. , Patel K. C. , Patel R. D. 
Published: April 2003

AbstractDiffusion data of helium, nitrogen, oxygen, and carbon dioxide through glassy cellulose triacetate were obtained and analyzed by the modified time‐lag technique of DiBenedetto and Paul. Thermodynamic data were evaluated and a probable mechanism for gaseous diffusion is discussed.
15N NMR spectroscopy, 10 Investigation on structure/shift relationships of nylon‐6,6 polyamides
Authors: Kricheldorf Hans R. 
Published: April 2003

AbstractSeries of polyamides were prepared from p‐phenylenediamine, and aliphatic α,ω‐diamines on the one hand, and fumaric acid, isophthalic acid, terephthalic acid, and aliphatic α,ω‐diacids on the other hand. The natural abundance 15N NMR spectra of these polyamides were measured in trifluoroacetic acid, and relationships between the chemical shifts and the structure of the monomer units are discussed. Increasing chain length of the aliphatic diamines results in increasing downfield shift of the diamines themselves and of the polyamides derived from them. No “γ‐effect” or similar deviations from the monotonic shift function are observed; however, the influence of the diacid residues on the chemical shift is less regular. The shifts of the homopolyamides are useful for assigning or predicting the shifts of copolyamides. The 15N NMR spectrum of the copolyamide “Trogamide T” is discussed.
Determination of initiation rate in the copolymerization of acrylonitrile with methyl methacrylate carried out in N,N‐dimethylformamide
Authors: Szafko Jerzy , Mańczyk Krystyna 
Published: April 2003

AbstractResults of studies on the determination of the initiation rate of the copolymerization reaction of acrylonitrile with methyl methacrylate, initiated by 2,2′‐azoisobutyronitrile in N,N‐dimethylformamide at 60°C are reported. The inhibition method used was that involving the stable Banfield's radical (N‐[1,1‐dimethyl‐3‐(N‐oxidophenyliminio)butyl]‐N‐phenylaminyl oxide).In the case of acrylonitrile an effect of a side reaction of initiation with the stable radical was observed along with a retarding effect due to inhibition reaction products.In the homopolymerization of methyl methacrylate there takes place a slight effect from a side initiation reaction due to the Banfield's radical, the inhibition reaction products not influencing the further course of the polymerization reaction.The overall contribution of the side initiation reaction changes in the copolymerization of acrylonitrile with methyl methacrylate for different comonomer mixtures with their composition, the actual changes being non‐additive. The initiation rate depends on the composition of the monomer mixtures and may be described by the following relation:

where Ri, AN=(8,20±0,15).10−7 mol.dm−3.s−1 and Ri, MM=(7,75±0,25).10−7 mol.dm−3.s−1.
Polycondensation d'acides α‐aminés par des systèmes iode‐phosphites en présence de pyridine ou d'imidazole
Authors: Le Guilly Lionel , Brack André , Spach Gérard 
Published: April 2003

AbstractPolymerization of free α‐amino acids with a pair of reagents–an oxidizing agent (iodine) and a reducing agent (phosphonic acid esters)–was achieved in organic medium in the presence of pyridine or imidazole. A standard procedure leading to optically pure polypeptides with degrees of polymerization up to 50 could be established. Polymeric material was also obtained with a dipeptide as monomer. Some preliminary polymerizations with polyfunctional reagents such as poly(4‐vinylpyridine), cyclodiphosphites, or polyphosphites were performed.
Protected polyvinylamine fragments capable of liberation under mild conditions
Authors: Carpino Louis A. , Hettrich Gernot M. , Ringsdorf Helmut 
Published: April 2003

AbstractThe synthesis and polymerization of 2‐cyanoethyl N‐vinylcarbamate (3b) and of the corresponding 2‐trimethylsilylethyl isomer 3c are reported. The homopolymers 4b and 4c, derived from 3b and 3c, could be deblocked under mild conditions (ethanolamine for 4b and trifluoroacetic acid or tetraethylammonium fluoride for 4c) with essentially 100% unmasking of the amino function. Treatment of such unmasked amino groups in a copolymer derived from N‐vinyl‐2‐pyrrolidone and 3b with 4‐{4‐[bis(2‐chloroethyl)amino]phenyl}butyryl chloride (13) (chlorambucil chloride) gave the corresponding amide, a potential antitumor agent. Kinetic studies showed that fluoride ion cleavage of poly(2‐trimethylsilylethyl N‐vinylcarbamate) occurred at rates comparable to those observed for the low molecular weight analog 2‐trimethylsilylethyl N‐isopropylcarbamate (10).
The behaviour of poly(methacrylic acid) and poly(2‐hydroxyethyl methacrylate) in water/2‐chloroethanol mixtures
Authors: Carton Brigitte , Bottiglione Vincent , Morcellet Michel , Loucheux Claude 
Published: April 2003

AbstractThe viscosimetric behaviour and the preferential solvation of poly(methacrylic acid), (PMA, poly(1‐carboxy‐1‐methylethylene)) and poly(2‐hydroxyethyl methacrylate), (PHEMA, poly[1‐(2‐hydroxyethoxycarbonyl)‐1‐methylethylene]) in water/2‐chloroethanol mixtures were studied. The system PHEMA/water/2‐chloroethanol is a typical polymer/solvent/precipitant system in which 2‐chloroethanol is preferentially solvated in the whole range of solubility. On the contrary, the system PMA/water/2‐chloroethanol is a typical cosolvent system which exhibits the so‐called inverse adsorption. This difference is attributed to the more hydrophilic character of the carbonyl group in PMA.
Polymerization of 1‐vinylindole and its methyl derivatives. Structure of the polymers
Authors: Priola Aldo , Gatti Giuseppe , Cesca Sebastiano 
Published: April 2003

AbstractThe polymerization of 1‐vinylindole (1a) induced by free radical and cationic initiators is studied and the structure of the resulting polymers is elucidated by 13C NMR spectroscopy. Also 2‐methyl‐1‐vinylindole (1b), 3‐methyl‐1‐vinylindole (1c), and 2,3‐dimethyl‐1‐vinylindole (1d) are polymerized in order to understand the polymerization mechanism of this class of monomers. Radical polymerization affords a linear polyvinylic structure in the case of 1b and 1d, and cyclic indoline type structures in the case of 1a and 1c. Cationic polymerization gives linear structures for poly(1c) and poly(1d), but cyclic structures for 1a. Evidence is given that cyclization involves position 2 of the indole ring in the radical polymerization, and position 3 in the cationic polymerization. Five and six membered rings are formed, respectively. The indole ring was found to be unreactive, under the adopted conditions, in the linear radical propagation reaction.
Synthesis of polyamide‐sulfonamides by ring‐opening polyaddition of N,N′‐sebacoylbis(ethanesultam) with aliphatic diamines
Authors: Imai Yoshio , Hirukawa Horishi , Okuyama Kazuo , Ueda Mitsuru 
Published: April 2003

AbstractThe aminolysis of N‐benzoylethanesultam (1) was conducted as a model compound study and was found to give almost exclusively ring‐opened adduct. The ring‐opening polyaddition of N,N′‐sebacoylbis(ethanesultam) (5), synthesized from a sebacoyl chloride and ethanesultam (3), with aliphatic diamines in HMPT afforded a new class of polyamide‐sulfonamides having inherent viscosities of 0,1–0,8dl.g−1 in excellent yields. All of the polymers were soluble in polar aprotic solvents and some acidic solvents. These polymers began to decompose at around 300°C in air, as determined by TG.