bluuebunny/crossref_metadata_2025_split huggingface dataset:
Micelle formation by AB block copolymers of polystyrene and poly(dimethylsiloxane) in n‐alkanes
Authors: Dawkins John V. , Taylor Graham 
Published: April 2003

AbstractAB block copolymers of polystyrene and poly(dimethylsiloxane) have been synthesized by “living” anionic polymerisation methods. The micellar behaviour of these block copolymers in n‐alkanes has been investigated as a function of the molecular weight of the polystyrene anchor A block and of the anchor/soluble balance (ASB) calculated from the relative block lengths. Micelle sizes have been determined by electron microscopy and are shown to conform to a simple geometrical model based upon two concentric spheres, when the ASB is below 18.
Eine oligomeranaloge friessche umlagerung oligomerer 2‐acetoxy‐1,3‐phenylenmethylene
Authors: Kämmerer Hermann , Evers Heinz , Böhmer Volker 
Published: April 2003

Abstractα‐Hydro‐ω‐hydroxypoly(5‐chloro‐2‐hydroxy‐1,3‐phenylenemethylene)s (1a, b), the oligomeric condensation products from 4‐chloro‐2,6‐bis(hydroxymethyl)phenol and 4‐chlorophenol with hydrochloric acid in 1,4‐dioxane, could be completely dehalogenated at room temperature and atmospheric pressure with hydrogene/Raney‐Ni. The resulting oligomers 2a, b were esterified with acetic anhydride, and the esters 3a, b were subjected to a oligomer analogous Fries rearrangement to form the linear α‐hydro‐ω‐hydroxypoly(5‐acetyl‐2‐hydroxy‐1,3‐phenylenemethylene)s 4a and 4b. The characterization of the products was mainly done by spectroscopic methods.
Application of spin trapping technique to radical polymerization, 18. Initiation mechanism of vinyl polymerization with N,N‐dimethylaniline N‐oxide/acid anhydride systems
Authors: Sato Tsuneyuki , Kita Shinji , Otsu Takayuki 
Published: April 2003

AbstractThe mechanism of radical formation from the radical initiator systems N,N‐dimethylaniline N‐oxide (DMAO)/acid anhydride, was investigated by spin trapping technique. 2‐Methyl‐2‐nitrosopropane (BNO) was used as spin trapping reagent. In the DMAO/acetic anhydride system, both methyl and N‐methylanilinomethyl radicals were trapped by BNO as the corresponding amine N‐oxyl radicals. However, only ethyl and undecyl radicals were trapped from DMAO/propionic anhydride and from DMAO/lauric anhydride system, respectively. In the DMAO/benzoic anhydride system, the amine N‐oxyl radical derived from N‐methylanilinomethyl radical and another amine N‐oxyl radical were observed. The latter one is likely to be derived from a radical formed by hydrogen abstraction from the methyl group of DMAO by a benzoyloxyl radical. When the concentrations of DMAO and benzoic anhydride were lowered, phenyl radical was also trapped. From these findings, the initiation mechanism of vinyl polymerization with the DMAO/acid anhydride systems was proposed and discussed.
Thermodynamic studies on hemoglobin solutions
Authors: Nakajima Kuniyasu , Baba Yoshihiro , Kagemoto Akihiro , Fujishiro Ryoichi 
Published: April 2003

AbstractThe heat of solution and the osmotic pressure of bovin hemoglobin in aqueous solution have been measured at 298 K using a twin microcalorimeter and an osmometer. The heat of association, ΔH, from calorimetric measurement and the association equilibrium constant, K, from osmometric measurement have been estimated, respectively. Also the thermodynamic quantities of the hemoglobin molecule which associates from 2αβ to the original α2β2 form are calculated. In all systems of the hemoglobin solutions, the value of dissociation equilibrium constant, K', calculated as the reciprocal of K, and that of ΔH seem to be of comparable order to those determined by the other investigators.
Oxidation and chlorination of atactic polypropylene under γ‐irradiation
Authors: Omichi Hideki , Hagiwara Miyuki , Araki Kunio 
Published: April 2003

AbstractAtactic polypropylene was irradiated in vacuo, in O2, and in Cl2 with 60Co γ‐rays, and changes in polymer structure were investigated by means of IR and ESR measurements of the irradiated polymer and by mass spectrometry of gaseous products. The irradiation in vacuo mainly produced H2 with small amounts of lower hydrocarbons (C1 – C3). As a radical product, only an alkyl radical was observed. The increase in IR absorption at 886 cm−1 indicated the formation of vinylidene unsaturation. The irradiation in O2 produced oxygenated products such as CO, CO2, and H2O with a reduced amount of H2. In the irradiation in Cl2, HCI was a main gaseous product. The existence of CCl bonds and a small amount of polyenyl groups in the irradiated polymer indicated that the radiation‐induced chlorination of APP was partly followed by elimination of HCl through a zip mechanism.
Linear oligopeptides, 60. Synthesis by the liquid‐phase method and characterization by amino acid analyses of two complete monodispersed homologous series derived from L‐alanine (to the octapeptide) and L‐valine (to the hexapeptide)
Authors: Bonora Gain Maria , Toniolo Claudio 
Published: April 2003

AbstractThe synthesis by the liquid‐phase method of the two complete, monodispersed homo‐oligopeptide series having the general formula t‐Boc\documentclass{article}\pagestyle{empty}\begin{document}$\rlap{--}(\ {\rm L} - {\rm X}\rlap{---} )$\end{document}nGly‐OPEG (I:X=Ala, n=1‐8; II: X = Val, n = 1–6) is described. The chemical purity of the various products was assessed by thin layer chromatography and amino acid analyses. The influence of chain length and steric effects on the formation of peptide bonds and their stability to acid hydrolysis is also illustrated.
Formaldehyde polymers, 26. Syntheses and condensations of substituted triphenoxy and triphenyl derivatives of 1,3,5‐triazine
Authors: Ninagawa Akira , Kawazoe Masao , Matsuda Haruo 
Published: April 2003

Abstract2,4,6‐Tris(4‐hydroxymethyl‐2,6‐dimethylphenoxy)‐1,3,5‐triazine (4a), 2,4,6‐tris(2,6‐dimethylphenoxy)‐1,3,5‐triazine (4b), and 2,4,6‐triphenoxy‐1,3,5‐triazine (4c) were synthesized by reactions of 2,4,6‐trichloro‐1,3,5‐triazine (3) with 4‐hydroxymethyl‐2,6‐dimethylphenol (2), 2,6‐dimethylphenol (1), and phenol, respectively, in the presence of metallic sodium or sodium hydroxide. 2,4,6‐Tris(4‐hydroxyphenyl)‐1,3,5‐triazine (4d) was prepared by trimerization of p‐cyanophenol. The condensation polymerization of 4a and cocondensations of 4a, with the other 1,3,5‐triazine derivatives or with novolak resin were carried out in the presence of p‐toluenesulfonic acid at 200°C. In the cocondensations of 4a with 4b, 4c, 4d, 2,4,6‐tris(2‐hydroxyphenyl)‐1,3,5‐triazine (4e) or with novolak resin, the reactivity of the comonomers was found to decrease in the order: novolak resin ≫4e≥4c>4b>4d. The disappearance of the absorption band belonging to the hydroxymethyl group as well as the appearance of the carbonyl absorptions could be observed in the IR spectrum of the condensation resins, however, only small intensities of carbonyl absorptions in the spectrum of the cocondensation product of 4a with novolak resin. The thermal decomposition of the resins was determined by thermogravimetry.
Syntheses of polyamides containing uracil and adenine
Authors: Hattori Masahira , Kinoshita Masayoshi 
Published: April 2003

Abstract2‐(2,4‐Dioxo‐1,2,3,4‐tetrahydropyrimidin‐1‐yl)methylsuccinic acid (2a) and 2‐(6‐aminopurin‐9‐yl)methylsuccinic acid (2b) were synthesized through the addition reaction of uracil and adenine, respectively, to dimethyl methylenesuccinate, followed by hydrolysis of the resulting dimethyl esters. Dicarboxylic acid 2a was further converted to the corresponding di‐p‐nitrophenyl ester 3a and dicarboxylic acid 2b was converted to the di(cyanomethyl) ester 3b. The active esters 3a and 3b were polycondensed with diamines such as 1,2‐diaminoethane, 1,6‐diaminohexane, 4‐aminomethylbenzylamine, and piperazine in solution, giving polyamides containing uracil and adenine as the side group. The polyamides were found to have molecular weights in the range of about 1000–5000. The polyamides derived from 1,2‐diaminoethane and piperazine were soluble in water.
Synthetic polymers containing sugar residues, 2. Synthesis and properties of poly(urea‐urethane)s derived from D‐glucosamine and diisocyanates
Authors: Kurita Keisuke , Hirakawa Nobuhiko , Iwakura Yoshio 
Published: April 2003

AbstractPoly(urea‐urethane)s containing D‐glucosamine residues in the main chain were prepared by direct addition polymerization of D‐glucosamine and diisocyanates. The polymerization reaction proceeded smoothly in N,N‐dimethylacetamide or hexamethylphosphoric triamide under certain conditions without blocking the excess hydroxy groups. The resulting poly(urea‐urethane)s were all soluble in polar solvents and had inherent viscosities of up to 1,27 dl·g−1. These polymers had D‐glucosamine residues with three pendant hydroxy groups in each unit, and they exhibited good reactivity toward acetylation and also very high water absorption.
Acrylonitrile copolymerization. Sequence distribution in acrylonitrile‐styrene copolymers by 13C NMR: Conversion and solvent effects
Authors: Pichot Christian , Pham Quang‐tho 
Published: April 2003

AbstractCopolymers of acrylonitrile (A) and styrene (S) were synthetized in either N,N‐dimethylformamide (DMF) or toluene by free radical polymerization. Their sequence distribution was studied by 13C NMR at 25, 2 MHz. The observed sequence distributions follow first order Markov statistics and may be calculated using the set of reactivity ratios rA = 0,13 and rs = 0,36 (DMF) or 0,40 (toluene) provided the copolymers remain soluble during polymerization. The reactivity ratios were calculated graphically from the experimental triad distributions observed by 13C NMR using the method of Chiang et al. Deviations from first order Markov statistics were observed for heterogeneous polymerizations or for acrylonitrile rich initial monomer mixtures in DMF. No influence of steric hindrance on the cotacticity of the copolymer chain was noticed within the resolving power of our instrument.
Regiospecificity of titanium‐based catalyst system for propene polymerization
Authors: Doi Yoshiharu 
Published: April 2003

AbstractThe sequence distribution of inverted monomeric units in the stereoirregular polypropylenes, prepared with the TiCl4/Al(C2H5)3 catalyst system, has been examined by 13C NMR. Observed dyad and triad sequence distributions were in good agreement with those calculated from first‐order Markov statistics. The regioselectivity of an inserting propene seems to depend not only on the polarity of the active carbon‐titanium bond but also on the steric effects of the last propylene unit of a growing chain.
Synthesis of polyaminoquinones by vinylogous nucleophilic substitution polymerization of 2,5‐disubstituted p‐benzoquinones with diamines
Authors: Ueda Mitsuru , Sakai Naoyuki , Imai Yoshio 
Published: April 2003

AbstractVinylogous nucleophilic substitution polymerization of 2,5‐dihydroxy‐p‐benzoquinone and 2,5‐dimethoxy‐p‐benzoquinone with various diamines in m‐cresol afforded polyaminoquinones with inherent viscosities as high as 0,5 dl.g−1 in quantitative yields. The polyaminoquinones, except for the polymer derived from 1,3‐bis(aminomethyl)benzene, were partially soluble or practically insoluble in organic solvents, but were solubilized by alkaline hydrosulfite reduction. Thermal analyses showed an initial weight loss at around 200°C in both air and nitrogen atmospheres, followed by gradual decomposition.
Thermal decomposition of flame retardant acrylonitrile copolymers investigated by direct pyrolysis in the mass spectrometer
Authors: Ballistreri A. , Foti S. , Montaudo G. , Pappalardo S. , Scamporrino E. , Arnesano A. , Calgari S. 
Published: April 2003

AbstractThe thermal behaviour of copolymers of acrylonitrile containing vinylidene chloride (VC2), 1‐bromo‐1‐chloroethylene (VCB), vinyl bromide (VB) units and Sb2O3, was investigated by gradually increasing the temperature of a polymer sample placed in the ion source of a mass spectrometer (MS). The resulting pyrolytic processes (time‐temperature resolved) were analyzed by detecting the volatile decomposition products formed. Sb‐halogenated species were detected in the mass spectra of the thermal decomposition products of the copolymers, and their presence is interpreted as the result of antimony‐halogen hydracids interactions during the pyrolysis.
Photochemical reactions in commercial poly(oxy(2,6‐dimethyl)‐1,4‐phenylene)
Authors: Allen Norman S. , McKellar John F. 
Published: April 2003

AbstractThe photooxidation of commercial poly(oxy(2,6‐dimethyl)‐1,4‐phenylene) (PPO) has been examined using absorption, luminescence (fluorescence and phosphorescence) and flash photolysis techniques. A comparison of the luminescence spectra of the polymer with that of the monomer 2,6‐dimethylphenol (DMP) shows that the chromophoric species responsible for light absorption in the near ultraviolet region 290–350 nm is the unit structure of the polymer itself. The fluorescence results also show the presence of an impurity chromophore in the polymer that absorbs in the visible region 400–550 nm. The flash photolysis experiments on both PPO and DMP give direct evidence for the formation of a phenoxyl radical indicating that main chain scission at the ether linkage is a major primary process in the photodeterioration of the polymer.
Polyelectrolyte complexes, 1. The effect of pH and ionic strength on the stoichiometry of model polycation—polyanion complexes
Authors: Cundall R. B. , Lawton J. B. , Murray D. , Phillips G. O. 
Published: April 2003

AbstractThe interactions between model polycations and polyanions have been studied using the fluorescent dye acridine orange as a probe. The dye emission at 540 nm is quenched by the addition of polyanions, a process which is reversed by the addition of certain polycations. Techniques have been developed which enable a determination of the stoichiometry of polyelectrolyte complexes so formed between three polyanions {carboxymethylcellulose, κ‐carrageenan and poly(styrenesulfonate)} and two polycations {poly(L‐lysine hydrobromide) and poly(p‐xylylviologen dibromide)}. A one to one pairing of acidic sites with basic groups was observed over a wide range of temperature, pH and ionic strength. Deviations from unit stoichiometry in the presence of multi‐charged metal ions have been interpreted as due to conformational changes in the polyanion. Results from viscosity measurements are included which suggest the neutralisation of charged groups in the polyelectrolyte complex.
Mechanical stabilization of molecular conformation by entrapping in a polymer matrix
Authors: Belokon' Yuri N. , Tararov Vitali I. , Savel'eva Tatiana F. , Vitt Sergei V. , Bakhmutov Vladimir I. , Belikov Vasili M. 
Published: April 2003

Abstract5‐Methacryloyl‐ and 5‐isobutyrylaminosalicylaldehydes (5a and 5b, respectively) and diastereomeric complexes of their Schiff bases with amino acids and Co(III): potassium Λ‐ and Δ‐bis‐[N‐5‐methacryloylaminosalicylidene‐(S)‐valinato]cobaltate(III) (6a, b), potassium Λ‐ and Δ‐bis[N‐5‐isobutyrylaminosalicylidene‐(S)‐norvalinato]cobaltate(III) (7a, b), potassium Λ‐ and Δ‐bis[N‐5‐methacryloylaminosalicylidene‐(S)‐norvalinato]cobaltate(III) (8a, b), have been synthesized. Copolymerization of 6–7a, b with acrylamide and N,N′‐methylenebis(acrylamide) leads to the formation of transparent hydrophilic gels in which the amino acid fragments preserve their ability of exchanging α‐hydrogen for deuterium in an alkaline medium. Comparison of the behaviour of polymer complexes ℗‐7a and ℗‐7b in the process of base‐catalyzed epimerization with their monomer analogues 8a and 8b shows that their stereoselectivity substantially changes when one goes from 8a to ℗‐7a. Such an effect may be explained by stabilization of the initial conformation of the complex molecule by the polymer matrix formed around the complex acting as a template.
Photoinitiation, 6. Copolymerization of styrene with maleic anhydride photoinitiated by the excited charge‐transfer complex styrene‐maleic anhydride
Authors: Bartoň Jaroslav , Capek Ignác , Arnold Manfred , Rätzsch Manfred 
Published: April 2003

AbstractThe kinetics of styrene (St) copolymerization with maleic anhydride (MA) initiated by light (at λ = 365 nm) was studied in acetone, acetonitrile, chloroform, and N,N‐dimethyl formamide at 30°C. With the exception of the chloroform containing system, the copolymerizations took place in homogeneous reaction media. The copolymerization rate Rp = −d([St] + [MA])/dt was found to be a function of the mole ratio of the comonomers in the reaction mixture. For a given ratio of comonomers Rp and the molecular weight of the resulting copolymer were found to be a function of the donor number of the solvent used for a given rate of initiation. Due to the dependence of Rp on the concentration of an equimolar mixture of both comonomers in acetone on [St] (at constant [MA]), and on [MA] (at constant [St]) the participation of the exciplex {St…acetone}* in the initiation reaction can be expected. The ratio of the overall rate constants for the propagation (k̄p) and termination (k̄t) reactions, k̄p/2k̄t, determined by a rotating sector technique, was found to depend on the composition of the comonomer mixture. The copolymerization rate is proportional to the square root of the intensity of incident light, which, together with the observed inhibition effect of oxygen points to a radical mechanism of the photoinitiated copolymerization of St with MA. In the presence of the photosensitizer benzophenone in the system St/MA/acetone an increase in Rp was observed, accompanied by a decrease in molecular weight of the copolymer in comparison with the system without benzophenone.
Pharmakologisch‐aktive polymere, 21. Orientierende Untersuchungen zur körperverteilung und Ausscheidung von poly[2‐(methylsulfinyl)ethylacrylat]en bei der Ratte
Authors: Hofmann Volker , Ringsdorf Helmut , Schaumlöffel Erich 
Published: April 2003

AbstractPoly[2‐(methylsulfinyl)ethyl acrylate] (1) was synthesized as well as derivatives 14C‐labelled in side groups (6) or 14C‐labelled in the main chain (11). Polymer 11 with the 14C‐labelled main chain was fractionated by precipitation. The η‐M‐relation determined by measurements of unlabelled polymers in the ultracentrifuge for comparison was used to establish the viscosimetrically determined molecular weights of the labelled fractions. After intravenous application of aqueous solutions of the polymer in rats the excretion rate up to 72 h after treatment was ascertained to ca. 50%; the concentration in the blood serum was found to be strikingly high. A tendency to reinforced storage in organs of high phagocytose activity by growing molecular weight was observed. The tumor affinity was — if at all — low.
Polymere 2,2,6,6,‐Tetraalkylpiperidin‐Derivate, 1. Tetra‐ und Pentaalkylpiperidin‐Derivate von Polyacryl‐ und Polymethacrylestern, Polyacryl‐ und Polymethacrylamiden
Authors: Karrer Friedrich E. 
Published: April 2003

AbstractA number of tetra‐ and pentaalkylpiperidine derivatives of acrylic and methacrylic acid was synthesized, polymerized, and copolymerized with several comonomers as potential UV stabilizers. In addition, by oxidation of some of these polymers and of a copolymer with peroxy compounds, polymers were obtained containing pendant nitroxyl groups. The properties of these polymers with free radical groups are discussed in relation to their spectral data.
Optically active vinyl polymers, 22. Relationship between intrinsic viscosity and molecular weight for poly‐(S)‐4‐methyl‐1‐hexene and related polymers
Authors: Neuenschwander P. , Pino P. 
Published: April 2003

AbstractIsotactic poly‐(S)‐4‐methyl‐1‐hexene (PS4MH), poly‐(R,S)‐4‐methyl‐1‐hexene (PRS4MH) and poly‐4‐methyl‐1‐pentene (P4MP) were fractionated according to stereoregularity and molecular weight. The fractions obtained were characterized and the constants aη and K of the Mark‐Houwink equation calculated for thermodynamically good solvents at low temperatures and for theta solvents at high temperatures.
Properties of polyethylene‐polypropylene blends: Crystallization behavior
Authors: Martuscelli Ezio , Pracella Mariano , Avella Maurizio , Greco Roberto , Ragosta Giuseppe 
Published: April 2003

AbstractThe crystallization behavior of high density polyethylene/isotactic polypropylene blends (HDPE/PP) was investigated. The overall kinetics of crystallization of HDPE may be strongly influenced by the addition of a small fraction of PP. At 398 K the half crystallization time of the blend containing 10% by weight of PP is around three times larger than for pure polyethylene. This effect may be accounted for by an increase in the melt viscosity of liquid HDPE caused by PP molecules. For crystallization temperatures high enough to prevent HDPE crystallization (Tc > 400 K), the presence in the melted blends of liquid HDPE influences the crystallization of PP. In fact, the half time of crystallization of PP increases with increasing the fraction of HDPE in the blend. The kinetics show a minimum at a well defined composition (around 60% in PP) before phase inversion. The same trend is observed when the surface free energy of folding and the lamellar thickness of crystals are reported as function of composition.
Two‐Stage nature of crystallization in stretched cis‐1,4‐polybutadiene networks
Authors: Cesari Marco , Perego Giovanni , Zazzetta Alessandro , Gargani Luciano 
Published: April 2003

AbstractThe crystallization of cross‐linked cis‐1,4‐polybutadiene, stretched at room temperature, is investigated by wide and small angle X‐ray diffraction techniques, at temperatures ranging from −40°C to the melting point, Tm, and for extension ratios, λ, from 1 to 7,7. The experimental conditions adopted should approximate thermodynamic equilibrium. All the experimental findings, namely, crystallinity, preferred orientation of the crystalline and amorphous fractions, unit‐cell dimensions and others, are consistent with the formation of two types of crystals: one depending mainly on stretching, the other on temperature. The former is characterized by extended chain crystals with Tm higher than the isotropic melting point (T = −3°C); the latter by a lamellar (bulk‐like) morphology which is stable only below T. A slight increase of Tm occurs for λ < 3, when the axes of the crystallized chains are tilted with respect to the strain direction; only when untilted crystals are formed (λ > 3) a remarkable increase of Tm is observed as a function of λ. As a qualitative interpretation, the two‐fold crystallization mechanism is based on non‐uniform extensibility of the segments included between adjacent junctions of the network.
Solvent effect on the complex formation of poly(methacrylic acid) with proton‐accepting polymers
Authors: Ohno Hiroyuki , Nii Atsushi , Tsuchida Eishun 
Published: April 2003

AbstractA pair of polymers may interact with each other through hydrogen bond and form a polymer complex. Such polymer complex formation is affected by several chemical and physical factors, especially by solvent properties. This solvent effect was studied in the complex formation of poly(methacrylic acid) with a series of proton‐accepting polymers in aprotic solvents. The extraordinary behaviour of polymer complexes in dimethyl sulfoxide was well explained in terms of the strong interaction between proton‐donating polymer and dimethyl sulfoxide. In addition, a stronger proton‐accepting polymer, viz. poly(N,N‐dimethyl‐N′,N′,N″,N″‐tetramethylenephosphoramide), was synthesized. This polymer could form a polymer complex with poly(methacrylic acid) through hydrogen bond even in dimethyl sulfoxide. Selective polymer complex formation was achieved by controlling such solvent properties.