bluuebunny/crossref_metadata_2025_split huggingface dataset:
Properties of membranes from polyelectrolyte complexes consisting of methyl glycol chitosan, [2‐(diethylamino)ethyl]dextran, and poly(potassium vinyl sulfate)
Authors: Kikuchi Yasuo , Kubota Naoji , Maruo Kazushi , Goto Yasuo 
Published: April 2003

AbstractWater‐insoluble polyelectrolyte complexes (PEC) were prepared by mixing methyl glycol chitosan (MGC, 1) and [2‐(diethylamino)ethyl]dextran (EA, 2) with poly(potassium vinyl sulfate) (PVSK, 3) in aqueous solution at various hydrogen ion concentrations. Elemental analyses, IR spectroscopy, and solubilities of PEC reveal that PEC differ in molecular structure and properties according to pH. It seems that the degree of dissociation and the conformation of MGC, EA, and PVSK change with pH. PEC membranes were made by casting from solutions of all kinds of PEC, and transport phenomena through the membrane of PEC prepared in 4 wt.‐% HCl solution were investigated under various conditions. The driving force of the transport depends on the membrance potential, Donnan potential, and diffusion potential, according to measurements of the transport ratio of Na+ and the electric potential difference between the left‐ and right‐hand side of the membrane. Moreover, the permeability of K+ is higher than that of Na+.
Spectroscopic characterization of chromic transition in polydiacetylenes, 3
Authors: Chang Chih , Coyne Laurence D. , Hsu Shaw Ling 
Published: April 2003

AbstractFrom optical absorption and infrared data, we have been able to establish the existence of a direct relationship between the weakening of the hydrogen‐bonding properties of the side‐chain and the chromic transition of the main chain for poly{1,2‐bis{4‐[N‐(butoxycarbonylmethyl)‐carbamoyloxy]butyl}‐1‐buten‐3‐ynediyl} (poly4BCMU), a family of soluble polydiacetylenes disubstituted with 4‐[N‐(butoxycarbonylmethyl)carbamoyloxy]butyl side chains. This observation is in contrast to the lack of correlation found for polydiacetylene film. Our data also show that this chromic transition is unaffected by the gelation process found for this family of polydiacetylenes.
Coil expansion and dimensions of poly(dimethylsiloxane) in alkane/2‐butanone mixtures
Authors: Celda Bernardo , Gómez Clara , Gavara Rafael , Tejero Roberto , Campos Agustin 
Published: April 2003

AbstractThe intrinsic viscosities, [η], for the ternary systems alkane (1)/2‐butanone (2)/poly(dimethylsiloxane) (PDMS)(3), with the alkanes decane, dodecane and hexadecane, are determined at 20,0°C. The constants a of the Mark‐Houwink equation and the constant of the unperturbed dimensions, KΘ, of the polymer are evaluated over the whole composition range of the binary solvent mixture. [η] shows a pronounced maximum at intermediate compositions as found in cosolvent mixtures. In these cosolvent mixtures, the numerical values of KΘ are higher than in the single‐component solvents, because the cosolvent mixtures correspond to a mixed solvent with an excess free energy, GE ≥ 0, the increase in KΘ being only moderate though. A new procedure taking into account ternary interactions, to evaluate the intrinsic viscosity in ternary systems from GE values is proposed. The influence of ternary interactions through a constant (1–2aχ) is also investigated. From these new expressions the constant of the apparent polymer unperturbed dimensions, K, and (1–2aχ) are calculated and compared with those directly evaluated from second virial coefficients.
Polymerization of lactams, 79. Preparation of the cyclic dimer of 2‐pyrrolidone
Authors: Brožek Jiří , Roda Jan , Králíček Jaroslav 
Published: April 2003

AbstractAn alternative method for the preparation of the cyclic dimer 3 of 2‐pyrrolidone is presented, which is based on hydrolysis of 1‐(1‐pyrrolin‐2‐yl)‐2‐pyrrolidone (4, x = y = 3), and some physicochemical properties of 4 and its hydrolytical products are discussed.
Dielectric and viscometric behaviour of poly(dibenzyl itaconate) as a function of temperature
Authors: Gargallo Ligia , Yazdani‐Pedram Mehrdad , Radić Deodato , Hernández‐Fuentes Irmina , Horta Arturo 
Published: April 2003

AbstractThe dielectric and viscometric behaviour of poly(dibenzyl itaconate) (1) in 1,4‐dioxane is studied as a function of temperature. The dipole moments at 25°C and at 33°C are determined by measuring the dielectric constant as a function of polymer concentration at fixed temperature. Also, the variation of the dielectric constant for a fixed concentration is determined at several temperatures in the temperature range between 15 and 39°C. The dipole moment is by 10% higher at 33°C than at 25°C, and the variation of the dielectric constant with temperature shows a stepwise increase between 25°C and 30°C. Viscosity measurements demonstrate an anomalous behaviour of 1 in 1, 4‐dioxane at approximately the same range of temperatures. At ca. 25°C the value of the Huggins constant drops to practically zero. By measuring samples with different molecular weights the unperturbed dimensions, interaction parameter, and Mark‐Houwink‐Kuhn‐Sakurada exponent are obtained. All of these parameters exhibit a discontinuity at ca. 25°C. The variations in the dielectric and viscometric behaviour with temperature are attributed to a conformational change of the macromolecules of 1 in 1, 4‐dioxane.
Polymerization of bicyclic acetals, 14. Synthesis of an amphiphilic block copolymer via ring‐opening polymerization of 6,8‐dioxabicyclo[3.2.1]octane with a polysaccharide macroinitiator
Authors: Okada Masahiko , Sumitomo Hiroshi , Ito Takahiro 
Published: April 2003

AbstractA polysaccharide macroinitiator (M̄n = 5000 to 28000) (1), having a reactive chlorine atom at the reducing end, was prepared by ring‐opening polymerization of 1,6‐anhydro‐2,3,4‐tri‐O‐benzyl‐β‐D‐glucose (TBLG) with antimony pentachloride as initiator in presence of acetyl chloride in dichloromethane at −60°C. Macroinitiator 1 in combination with silver hexafluoroantimonate was found to induce the polymerization of 6,8‐dioxabicyclo[3.2.1]octane (DBO) in tetrahydrofuran, 2‐methyltetrahydrofuran, or tetrahydropyran at −78 to 0°C. Fractionation of the reaction products gave a block copolymer (2) composed of poly(TBLG) and poly(DBO) segments. Debenzylation of 2 provided an amphiphilic block copolymer (3) consisting of hydrophilic (1→6)‐α‐D‐glucopyranan (dextran) and hydrophobic poly(DBO) [(1→6)‐linked polysaccharide skeleton] segments. Block copolymer 3 is soluble in dimethyl sulfoxide and swells in water and chloroform.
Solution properties and chain dimensions of poly(trimethylene sulfide)
Authors: Sánchez Angeles , Bello Antonio , Marco Carlos , Fatou José G. 
Published: April 2003

AbstractPoly(trimethylene sulfide) (PTS) synthesized by means of anionic polymerization was studied with regard to its solubility behaviour and unperturbed chain dimensions. The Flory‐Huggins interaction parameter was used to determine the solubility parameter of PTS, δ = 10,0 cal1/2 · cm−3/2, which agrees with the calculated one. PTS fractions were isolated by means of fractional precipitation from chloroform/hexane at 50°C. Their number‐average molecular weight, M̄n, and the intrinsic viscosity, [η], were measured in chloroform at 25°C. From these data the relation [η] = 3,10 · 10−4 M̄ was estimated. A value of the characteristic ratio, 〈r2〉0/(n l2) = 4,0, was determined from the Burchard‐Stockmayer‐Fixman plot, which shows that this chain molecule has high flexibility.
Longitudinal volume viscosity of isotactic polypropylene
Authors: Alonso‐Abengozar Ana , Aleman Jose V. 
Published: April 2003

AbstractThe volume flow of isotactic polypropylene (i‐PP) with number‐average molecular weight M̄n = 103 200, melting temperature Tm = 426 K and glass transition temperature Tg = 238 K, has been measured. The elastic modulus of the longitudinal wave, longitudinal volume viscosity, initial longitudinal volume viscosity, and retardation times, are described for compression rates between ca. 1,0·10−5 and 200,0·10−5 s−1, and at temperatures between 443 K and 473 K as well as pressures up to 150 MPa at which no sign of crystallization was detected. The longitudinal volume viscosity decreases with increasing compression rate and with decreasing volume deformation, the behaviour being in all cases a typical non‐equilibrium one. The longitudinal volume viscosity increases with increasing temperature, the volume flow activation energy being about 78,08 kJ/mol.
Reactivity mediated by the conformation of polysaccharide hosts: Hydrolysis of 2‐chloro‐N‐dodecylpyridinium iodide in the presence of amylose derivatives
Authors: Hui Yongzheng , Gai Yonghua 
Published: April 2003

AbstractThe effects of three kinds of helix‐forming derivatives of amylose, namely, carboxymethylamylose (CMA), methylamylose (MA) and aminoethylamylose (AEA), on the hydrolysis of 2‐chloro‐N‐dodecylpyridinium iodide (CDPI) in aqueous alkaline media were studied. Based on the fact whether it is an intermolecular or intramolecular process, different results, i. e., retardation or acceleration caused by adding the host, are interpreted in terms of helical inclusion complex between the derivative of amylose and the substrate. As a polyelectrolyte, CMA forms inclusion complex only at higher ionic strength when the strong repulsion between charged groups is shielded. This conclusion was proved by the fact that all values of Kd*, which represents the stability of complex, as well as of ηsp/c and absorbance of the polyiodide complex, indicate that for MA the helix‐forming ability is independent of ionic strength, because it is a neutral polymer, but for CMA it changes drastically in the same region of ionic strength. Compared with MA, the higher retarding efficiency offered by CMA as well as by the anion micelle, SDS, can be attributed to the negatively charged groups surrounding the helix which hinder an approach of OH− to the reaction site.
Polymerization of β‐propiolactones by nickel carboxylate/tributylphosphine complexes
Authors: Carrière François J. , Blottiau Rolande , Sekiguchi Hikaru 
Published: April 2003

AbstractThe kinetics of polymerization of β‐lactones — β‐propiolactone, α‐ethyl‐α‐phenyl‐ and α‐benzyl‐α‐ethyl‐β‐propiolactone — was investigated using nickel carboxylate/phosphine complexes as initiators. The apparent rate constants of initiation and propagation, ki and kp, were calculated assuming first order kinetics. The variations of ki values with monomer concentration suggest that the mechanism is more complex, with a reaction order which is not as admitted for calculation. The infrared study has shown that the polymerization initiated by the complex is of zwitterionic type, and the kinetic curves indicate that the nickel carboxylate participates in the reaction.
Liquid‐crystalline polyurethanes, 4. Polyurethanes containing an azobenzene group in the side chain
Authors: Tanaka Mamoru , Nakaya Tadao 
Published: April 2003

AbstractPolyurethanes with azobenzene side groups attached via an alkyl spacer of different length were synthesized from N‐[4‐phenylazophenyl]‐ω‐[bis(2‐hydroxyethyl)amino]alkanamides (5) and equimolar amounts of diisocyanates such as hexamethylene diisocyanate (HDI), 4,4′‐methylenedicyclohexyl diisocyanate, 1,3‐cyclohexylenedimethyl diisocyanate, 2,4‐toluylene diisocyanate, and 4,4′‐methylenediphenyl diisocyanate. Polyurethanes obtained from diols 5 with HDI have a mesomorphic phase as determined by DSC and polarizing microscopy and are crystalline at room temperature as evidenced by X‐ray studies.
Mathematical modelling of polymers, 3. Enumeration and generation of repeating irreducible sequences in linear bi‐, ter‐, quater‐ and quinquenary copolymers and in stereoregular homopolymers
Authors: Balaban Alexandru T. , Artemi Cristian 
Published: April 2003

AbstractIrreducible sequences in n‐ary copolymers are defined. An exhaustive and non‐redundant lexicographically ordered list of irreducible sequences of comonomers in binary (n = 2), ternary (n = 3), quaternary (n = 4) and quinquenary (n = 5) copolymers is presented. The numbers of irreducible sequences may be found either by an explicit formula in terms of the number n of comonomers and of the length m of the sequences, or by applying the Polya‐de Bruijn theorem, as shown in detail in the first two parts of this series. For stereoregular vinyl homopolymers, or for the geometrical (E/Z) isomerism in polyalkenes, irreducible sequences are the same as in binary copolymers. A nomenclature is proposed for m‐ads in stereoregular homopolymers with m > 2, i. e. beyond isotactic for m = 1, and syndiotactic for m = 2.
Melting, crystallization, and solution behavior of chain molecules with hydrocarbon and fluorocarbon segments
Authors: Höpken Jens , Pugh Coleen , Richtering Walter , Möller Martin 
Published: April 2003

AbstractMelting, crystallization, and solution behavior of n‐alkanes with fluorocarbon segments of twelve carbon atoms on one end, F(CF2)12(CH2)nH, or on both ends, F(CF2)12(CH2)n(CF2)12F were investigated by DSC, MAS 13C NMR, light scattering, and birefringence studies. Both triblock F(CF2)m(CH2)n(CF2)mF and diblock F(CF2)12(CH2)nH compounds with 4 ≦ n ≦ 14 melt by a two‐step process. In the first step, the alkyl segment conformations gain nearly liquid like trans/ gauche ratios, while the perfluorinated segments remain ordered. “Gels” which incorporate the entire solvent are formed by crystallization from even dilute solutions of hydrocarbon and fluorocarbon solvents. The gels are built up of extremely long, interdigitated needles of the pure solute. Due to the bilayer structures and different degrees of ordering of the hydrocarbon and the fluorocarbon segments, the crystals grow preferentially in the direction parallel to the lamellar surface. Light scattering experiments in octane demonstrated the formation of micelle type associates.
The effect of crosslinking on the aggregation of syndiotactic poly(methyl methacrylate) — an investigation using nmr and infrared spectroscopy
Authors: Spěváček Jiří , Schneider Bohdan , Štokr Jan , Vlček Petr 
Published: April 2003

AbstractUsing NMR and infrared (IR) spectroscopy, the effect of crosslinking on the aggregation of syndiotactic (s) poly(methyl methacrylate) (PMMA) in toluene or o‐dichlorobenzene gels was investigated. A conclusion was drawn from the integrated band intensities in the 1 H NMR high resolution spectra that the values of fractions of aggregated units decrease with increasing crosslinking, and that the corresponding aggregates of crosslinked s‐PMMA decompose (melt), compared with uncrosslinked s‐PMMA, at somewhat lower temperatures. Already loose crosslinking markedly slows down the aggregation process. The IR spectra showed that fractions of long s‐sequences, which form helices having a high number of units per turn (conformation close to the all‐trans one), are greatly reduced due to crosslinking, and the structure of aggregated sequences is less defined. Unlike the uncrosslinked s‐PMMA, the structures arising by aggregation in gels of crosslinked s‐PMMA do not persist in the solid state.
Synthesis of polysiloxane/polyamine block copolymer using uniform size poly(dimethylsiloxane) with reactive end‐groups
Authors: Kazama Hideki , Tezuka Yasuyuki , Imai Kiyokazu , Goethals Eric J. 
Published: April 2003

AbstractPoly(dimethylsiloxane) (poly(DMS))/poly(N‐tert‐butylaziridine) (poly(TBA)) block copolymer was synthesized by two different techniques; (1) the coupling reaction of poly(DMS) having a dimethylaminopropyl end‐group (1) with living poly(TBA) (2) which was prepared with methyl trifluoromethanesulfonate as an initiator, and (2) the polymerization of N‐tert‐butylaziridine (5) using poly(DMS) having a p‐toluenesulfonyl ester end‐group (4) as macromolecular initiator, respectively.
13C NMR study of monomer composition and sequence distribution in ethylene/propylene/1‐octene terpolymers
Authors: Ye Hongwei , Xu Zhikang , Zhu Qinqin , Yan Shilin , Chen Hongzhang 
Published: April 2003

AbstractA series of ethylene/propylene/1‐octene terpolymers with different composition is examined by 13C NMR. Assignments of the various carbon resonances are accomplished by comparison with spectra of ethylene/propylene, ethylene/1‐octene, and propylene/1‐octene copolymers and by INEPT multi‐pulse technique. The polymers obtained with a high‐mileage titanium‐magnesium catalyst contain no inverted propylene sequences. The intensities of all the lines are used in the calculation, and this approach allows the terpolymer composition and the sequence distribution to be determined.
X‐ray and optical investigations on polymers with mesogenic side groups
Authors: Hans Karin , Zugenmaier Peter 
Published: April 2003

AbstractBased on polarisation microscopic observation of polymers with mesogenic side groups at the phase transition isotropic‐smectic, a domain‐like structure has to be assumed for smectic phases. Two different regular‐shaped nuclei are formed at the phase transition on slightly different conditions which grow after twinning into bǎtonnets. The Avrami equation can be applied for a quantitative description of the growth of the anisotropic areas as shown for one form of the nuclei. Unoriented and sheared samples maintain their morphology when cooled from the liquid‐crystalline to the partially crystalline phase. The crystalline phase of polymers with mesogenic side groups was investigated by X‐ray diffraction on differently oriented samples. It was found that the crystallites have the same internal structure despite the fact that they exhibit different uniaxial fibre axes. Optical investigations provide helpful supplementary information for deciding what kind of layered structure is present in the crystalline and smectic phase.
Dynamic mechanical relaxations in a copolyterephthalate based on ethylene glycol and 1,4‐cyclohexanedimethanol
Authors: Benavente Rosario , Pereña José M. 
Published: April 2003

AbstractThe dynamic mechanical relaxations of poly(ethylene terephthalate) (PET), poly(1,4‐cyclo‐hexylenedimethylene terephthalate) (PCHDMT), and a copolymer of them (COP) were measured in the temperature range from −150 to 150°C by use of a dynamic viscoelastometer. The viscoelastic relaxations of COP are studied and compared with those of PET and PCHDMT. The anisotropy of the viscoelastic properties of stretched COP samples was also studied in order to distinguish between main and secondary relaxations.
Polymerization of methyl acrylate photoinitiated by 4‐dimethylamino‐4′‐isopropylbenzophenone
Authors: Mateo José L. , Bosch Paula , Vázquez Esperanza , Sastre Roberto 
Published: April 2003

AbstractThe initial rate of the polymerization of methyl acrylate photoinitiated by 4‐dimethylamino‐4′‐isopropylbenzophenone (2) varies linearly with monomer concentration and the square‐root of light intensity. For small absorbances, the initial polymerization rate, Rp, varies linearly with the square‐root of the photoinitiator concentration. For high absorbance values, Rp is independent of the photoinitiator concentration in a well‐stirred system and decreases as the photoinitiator concentration increases in an unstirred system. This marked differences between the polymerization kinetics in well‐stirred and unstirred systems is discussed. The ratio of the propagation rate constant and the square‐root of the termination rate constant, kp/k, and the quantum yield of photoinitiation were determined and related to the results previously obtained in a study on the photoreactivity of 2.
New polymer syntheses, 29. Thermotropic (co)polyesters of 2‐phenylthioterephthalic acid and various diphenols
Authors: Kricheldorf Hans R. , Döring Volker , Eckhardt Volker 
Published: April 2003

Abstract2‐Phenylthioterephthalic acid (1a) was prepared from thiophenol and dimethyl‐2‐nitroterephthalate. Homopolyesters of this diacid were prepared by transesterification with the diacetates of hydroquinone, methylhydroquinone, or 2,5‐biphenyldiol. Copolyesters were prepared from equimolar amounts of hydroquinone and 4,4′‐biphenyldiol or from hydroquinone and 4‐hydroxybenzoic acid in various mole ratios. Inherent viscosities in the range of 0,4–2,0 dl/g were found. DSC‐measurements indicate that in the case of (co)polyesters from hydroquinone the homopolyester has the highest glass‐transition temperature (Tg = 181°C) and the highest melting point (Tm = 332°C). Also the homopolyesters from 1a and methyl‐ or phenylhydroquinone are crystalline. Furthermore, the homopolyesters from hydroquinone and 2‐(p‐tolylthio)terephthalic acid or 2‐(4‐chlorophenylthio)terephthalic acid were prepared. Microscopic observation under polarized light and WAXS‐measurements confirmed that all polyesters form a nematic melt above Tg or Tm. In most cases the mesophase extents up to ca. 460°C where thermal decomposition prevents further observation. The homo‐ and copolyesters from 1 a and hydroquinone were also subjected to thermomechanical analyses by means of the penetration method.
Tactic copolymers derived from poly(methacrylohydrazide) and functional α‐amino acids
Authors: Thevissen Josef , Klesper Ernst 
Published: April 2003

AbstractLactic acid and N‐tert‐butoxycarbonyl protected L‐alanine, L‐histidine and L‐serine were condensed with syndiotactic poly(methacrylohydrazide) (1) in aqueous solution in the presence of N‐ethyl‐N′‐(3‐dimethylaminopropyl) carbodiimide. By incomplete conversion of (1) copolymers 4a – d were obtained containing methacrylohydrazide monomeric units. By complete conversion with L‐histidine and L‐serine simultaneously, copolymers 5 containing both amino acid moieties were obtained. The N‐tert‐butoxycarbonyl protecting group was removed from the polymers by acidolysis. This reaction was followed by CD spectroscopy. All polymers were characterized by 1H and 13C NMR spectroscopy.
Thermotropic liquid‐crystalline main‐chain polyesters containing cyclooctylene units, 6. Cholesteric copolymers
Authors: Cowie John M. G. , Wu Hak H. 
Published: April 2003

AbstractA series of chiral nematic copolymers were prepared based on the new mesogenic unit cis‐1,5‐cyclooctylene bis(p‐hydroxybenzoate) (COHB). The copolymers were prepared by linking COHB coupled with (+)‐3‐methyladipic acid to COHB units combined with terephthalic acid and its bromo and nitro derivatives. A biphasic region was observed in most of the samples which made phase diagrams more difficult to establish. Mesophase stability could normally be sustained up to 50 mol‐% content of the methyladipic acid group in the copolymer. They were also sensitive to both temperature changes and shearing forces.
Some features of a novel organozinc complex, [{MeOCH2CH(Me)OZnOCH(Me)CH2OMe}2 · {EtZnOCH(Me)CH2OMe}2], as an enantiomorphic catalyst for stereoselective polymerization of propylene oxide
Authors: Yoshino Norio , Suzuki Chiaki , Kobayashi Hiroshi , Tsuruta Teiji 
Published: April 2003

AbstractSome significant features of a novel organometallic complex, [{MeOCH2CH(Me)OZnOCH(Me)CH2OMe}2 · {EtZnOCH(Me)CH2OMe}2] (3), as an enantiomorphic catalyst for stereoselective polymerization of propylene oxide (PO) are reported. Populations of triad tacticities of poly(PO) obtained with complex 3 as catalyst fit nicely with the theoretical curves of the one‐parameter equations for the enantiomorphic catalyst sites model. The observed σ2 value was much higher than that observed with other organozinc complexes (1 and 2) reported previously. Every molecule of complex 3 was proved to exist as a monomeric form in benzene and its structural feature was retained in solution even after the initiation stage of polymerization. The number of active sites of complex 3 for the oxirane polymerization was determined to be one by determining the 1‐methoxy‐2‐propanol liberated from the unreacted methoxypropoxy groups. The initiation and propagation mechanisms are discussed.