bluuebunny/crossref_metadata_2025_split huggingface dataset:
Rheological properties of native and hydrolyzed starches in dependence on composition and concentration
Authors: Vorwerg Waltraud , Radosta Sylvia 
Published: March 2011

AbstractThe structure formation of starch polysaccharides in aqueous solutions is determined by the ratio of amylose to amylopectin and the molecular properties of these components. Our research is focused on establishing defined correlations between composition, molecular structure in diluted solutions and rheological properties of concentrated aqueous starch polysaccharide solutions. Diluted solutions were investigated by size exclusion chromatography with multi angle laser light scattering detector. Measurements of concentrated aqueous solutions were carried out by a Bohlin cs‐rheometer with programmed stress using a cone‐plate geometry of 40 mm diameter and a cone angle of 4 degrees. Gels were characterized by oscillatory measurements taking into account the frequency dependence of the storage and loss moduli and the influence of a stress sweep on the moduli. The concentration dependence was investigated with starches of potato, wheat, maize and wrinkled pea. Starches with quite similar amylose content as from potato, wheat and maize, show different behavior in rheological properties.Further differences in structure formation were obtained by enzymatic hydrolysis of potato and wheat starch with bacterial α‐amylase. The hydrolyzing conditions were chosen such that the degradation led to molecular weights between 5*105 and 107 g/mol. Detailed information about molecular composition was obtained by fractionation of degraded starches. The amylopectin was found to be degraded more strongly than the contained amylose.In comparison to native starch polysaccharide fractions the amylopectin hinders the gelation process in dependence on its molecular weight distribution and the length of the outer chains.
New developments in the analysis of the substitution pattern of polysaccharide derivatives
Authors: Mischnick Petra 
Published: March 2011

AbstractThe analysis of the primary structure of polysaccharide derivatives has to consider different structural levels. In the field of the monomer analysis anion exchange chromatography enables the investigation of some anionic derivatives and methyl ethers. Two analytical strategies for the analysis of the substituent distribution along the polymer chain are outlined, and the results from model studies on methyl amyloses prepared under homogeneous and heterogeneous conditions are discussed.
Deprotonation patterns of disaccharides in coordinating cellulose solvents: A status report
Authors: Kettenbach Gerhard , Klüfers Peter , Mayer Peter 
Published: March 2011

AbstractCrystals of metal complexes of deprotonated open‐chain oligosaccharides which may serve as models for the action of coordinating cellulose solvents on the polysaccharide molecule, are generally harder to obtain in a quality suitable for X‐ray analysis than in the case of monosaccharides. Four preliminary crystal structure analyses are presented which settle the significance of intramolecular hydrogen bonds towards the metal ligating acceptors. The metal binding sites of sucrose include both 1,2‐ and 1,3‐diolato complex formation, whereas α,α‐trehalose has been found in the 1,2‐diolato coordination mode.
Temperature‐responsive hydrogels from cellulose
Authors: Nishimura Hiroshi , Donkai Nobuo , Miyamoto Takeaki 
Published: March 2011

AbstractThe aim of this work is to prepare the temperature‐responsive cellulosic hydrogels undergoing a large volume change in an aqueous solution on heating or cooling. To this end, we prepared 0‐methyl cellulose (MC) and O‐(Z‐hydroxy‐3‐butoxypropyl) cellulose (HBPC) which precipitate out of solution on heating without forming gel. MC and HBPC derivatives prepared by homogeneous reactions were proved to be promising raw materials for the cellulosic hydrogels mentioned above. The results on the phase separation of the derivatives were discussed in terms of the distribution of substituents along the cellulose chain and in the anhydroglucose units.
Colloidal properties of star polymers
Authors: Roovers Jacques 
Published: March 2011

AbstractRegular star polymers with functionality f = 64 and f = 128 have such high segment density that they resemble “hard sphere” objects in dilute solution. In semi‐dilute solution they form a macrocrystalline ordered phase with spacings of the order of 100 to 500Å. They are physical gels. Their melt properties are characterized by a long term relaxation process not found in stars with fewer arms.
Does compressibility affect the results obtained by small angle neutron scattering?
Authors: Joanny J.‐F. , Benoît H. , Stockmayer W. H. 
Published: March 2011

AbstractRecently a few papers have been devoted to the scattering by polymer solutions and blends(1,2) assuming that the systems under investigation are compressible, contrarily to what is usually done. This is motivated by the fact that if one uses the theory of incompressible mixtures in scattering experiments, one obtains values of the Flory(3) χ parameter which are inconsistent with the values obtained by other techniques. In this paper we would like to show that, contrarily to what has been said, the effect of compressibility can be easily evaluated; it is very small and already corrected in the classical treatment of the data used in light or neutron scattering experiments.
Correlation hole effect in comblike copolymer systems obtained by hydrogen bonding between homopolymers and end‐functionalized oligomers
Authors: Huh J. , Ikkala O. , Ten Brinke G. 
Published: March 2011

AbstractMonodisperse block copolymer systems in the homogeneous melt exhibit small angle X‐ray scattering peaks at finite nonzero angle due to characteristic correlation hole concentration fluctuations. Here we will address these fluctuations for comblike copolymer systems obtained by strong association between polymers and end‐functionalized oligomers. Experimentally, the dominant fluctuations have been found by us to vary between conventional long wave length fluctuations (for weak hydrogen bonding) as for simple mixtures, and finite wave length fluctuations (strong hydrogen bonding), characteristic for block copolymer systems. Monte Carlo computer simulations show that both regimes will occur in one and the same system depending on the temperature. The transition between both regimes is directly related to the fraction of free oligomers, which depends on the temperature and the interactions. The structure factors are analysed in terms of the Random Phase Approximation applied to a mixture of free oligomers and comb copolymers, using a uniform distribution of teeth along the polymer chains and a binomial distribution in the number of polymers with a given number of teeth, confirmed numerically, as input. The agreement is excellent both at high and low temperatures.
Mesophase structure and alignment under different fields of liquid crystalline main‐chain/side‐group block copolymers
Authors: Galli Giancarlo , Chiellini Emo , Francescangeli Oriano , Ferri Dino , Wolff Dietmar , Springer Jürgen , Laus Michele , Angeloni Annino S. 
Published: March 2011

AbstractLiquid crystalline block copolymers are new materials in which multiple molecular interactions can provide the driving force for complex phase behaviors and states of order. Block copolymers containing both liquid crystalline main‐chain polyester and side‐group polymethacrylate blocks were investigated. They phase separated in the liquid crystalline state and their individual mesophases coexisted. The copolymers responded very differently when either a mechanical or a magnetic field was used for alignment. In the fibers the orientations of the side‐group and main‐chain smectic planes with respect to the fiber axis depended critically on the block lengths and on their distinct tendencies to align, whereas under a magnetic field the mesogens aligned collectively with their long molecular axis parallel to the field, independent of the copolymer structure.
Synthesis of poly(p‐phenyleneterephthalamide) in presence of polymer matrices
Authors: Russo Saverio , Mariani Alberto , Mazzanti Sabina L. E. , Ruggeri Giacomo , Conio Giuseppina 
Published: March 2011

AbstractThe direct syntheses of poly(p‐phenyleneterephthalamide) in presence of poly(vinylpyrrolidone) and poly(4‐vinylpyridine) as matrices have been carried out following the so‐called Yamazaki's and Higashi's methods. The intrinsic viscosity data of the resulting polyamide were found to be strongly dependent on the matrix used as well as on its molecular weight.
Star‐shaped and hyperbranched polyesters
Authors: Kricheldorf Hans R. 
Published: March 2011

AbstractIn contrast to a‐a/b‐b type monomers, the a‐b monomers(e.g. hydroxy‐ or amino carboxylic acids) possess a much greater synthetic potential. Using 3‐ or 4‐hydroxy‐benzoic acid and 4‐hydroxyphenylpropionic acid (phloretic acid) starshaped polyesters with controlled molecular weight were prepared. Analogously, starshaped liquid‐crystalline copolyesters were synthesized, and the influence of star‐centers on the stability of the nematic phase was studied. Three polycondensation methods were elaborated and compared for the synthesis of hyperbranched homo‐ and copolyesters. Both the degree of branching and the nature of the endgroups were varied and their influence on the solubility, crystallinity and melt rheology was investigated. Furthermore, A‐B‐A triblock co‐polymers with hyperbranched A‐blocks, and hyperbranched poly(ester‐amide)s were synthesized and characterized.
Block Copolymers by high temperature oligomer‐coupling reactions: Bis(5‐oxazolinone)/OH reaction
Authors: Lefébvre Hervé , Fradet Alain 
Published: March 2011

AbstractHigh temperature chain‐coupling reactions in the bulk between amino‐, hydroxy‐ or carboxy‐terminated polymers and various coupling agents have been studied and applied to the synthesis of copolymers with aliphatic polyester, polyether or polyamide blocks. Thus, carboxy‐terminated oligomers can be coupled by bisoxazolines or bisimidazolines, while 4‐substituted and 4, 4‐disubstituted bis(5‐oxazolinones) are efficient coupling agents for amino‐ or hydroxy‐terminated oligomers. In the latter case, the use of a catalyst is necessary. The reaction has been optimized using a series of bisoxazolinones deriving from α‐amino‐acids and 1‐dodecanol and α, ω‐dihydroxy‐poly(ϵ‐caprolactone) as model compounds. High molar mass poly‐ϵ‐caprolactone containing α‐aminoacid moieties has been obtained in the presence of tetrabutoxytitanium as a catalyst.
Enzymatic condensation and polycondensation reactions in organic solvents
Authors: Gutman Arie L. , Knaani Dafna , Bravdo Tamar 
Published: March 2011

AbstractLipases in organic solvents catalyse lactonisation or polymerisation of ω‐hydroxyesters. Under these conditions the enzymes exhibit both enantioselectivity and prochiral selectivity. This approach was used to develop the synthesis of chiral γ‐lactones and A‐B type polyesters from racemic or prochiral hydroxyester substrate.
Effects of transformation phenomena on polymer synthesis
Authors: Pascault Jean‐Pierre 
Published: March 2011

AbstractThe chemistry and the reaction rates have been related to the phase transitions and transformations occuring during different polymer syntheses. Early cristallization of chain segments disturbs the synthesis of linear segmented polyureas or polyurethanes. The gelation process occuring during the epoxy‐amine network formation does not affect the reaction rate, but after vitrification, this reaction becomes diffusion‐controlled. In the case of modified thermoset a liquid‐liquid transition may induce a fractionation phenomenon which modifies the average functionality of the molecules and the appearance of the gel point.
Synthesis of thermotropic liquid crystalline all‐Trans‐p‐Phenylenevinylene oligomers via two‐step metathesis
Authors: Thorn‐Csányi Emma , Kraxner Peter 
Published: March 2011

AbstractLiquid crystalline products of oligomeric p‐phenylenevinylene derivates were prepared metathetically using a stable molybdenum carbene complex (Mo(NArMe2)(CHCMe2Ph)[OCMe(CF3)2]2). The synthesis was conducted via two steps: 1. Metathesis polycondensation of 2, 5‐dialkyl‐1, 4‐divinylbenzenes to oligo‐(2, 5‐dialkyl‐1, 4‐phenylenevinylene)s, 2. Endcapping of the vinyl groups via cross‐metathesis using 3‐hexene. The products were characterized by1H‐NMR and UV/Vis spectroscopy, as well as by DSC.
New functionalized polycondensates
Authors: Ritter Helmut 
Published: March 2011

AbstractPolyketones, polysulfones and polyamides are presented that contain different types of functional groups located in the main chain or in the side chain of the polycondensates. Functional groups are distyrylpyridine, cinnamic acids, and ester groups. One example is presented dealing with enzymatically catalyzed polycondensation of aniline derivative bearing a chalcon‐function. Some interest is focused on photochemical crosslinking of the materials that are suitable to prepare semipermeable membranes. The successful synthesis of polymerizable dendrimers based on aspartic acid is also described. Finally, the potential synthesis of polyamides with large ring‐components in the main chain is discussed.
Polyarylates based on 3, 4'‐disubstituted benzophenones
Authors: Stagnaro Paola , Valenti Barbara , Cavazza Barbara , Costa Giovanna , Trefiletti Vincenzo 
Published: March 2011

AbstractNew thermotropic aromatic poly(ketoesters) have been obtained by copolymerization of 3‐hydroxy‐4'‐carboxybenzophenone (3, 4'‐HCBP) or of the isomeric 4‐hydroxy‐3'‐carboxybenzophenone (4, 3'‐HCBP) with some commercial aromatic hydroxyacids. The polymers have been prepared both by direct polycondensation in solution and in bulk. Homopolymers of 3, 4'‐HCBP and 4, 3'‐HCBP melt to an isotropic liquid, while a nematogenic behaviour is shown by samples with a comonomer content higher than 30%. A preliminary investigation has been carried out to determine the influence of the liquid‐crystalline phase on their transport properties.
Transimination: An efficacious reaction for the synthesis of macrocycles
Authors: Madec Pierre‐Jean , Pérès Richard , Borgès‐Lopès Elizabeth , Jeanne‐Rose Valérie , Lafontaine Eric , Maréchal Ernest 
Published: March 2011

AbstractA new family of main‐chain liquid crystal polymers containing azomethine units have been synthesized and characterized. Our attention has been focused on their strong tendency to generate macrocyclic dimers (AB)2 constituted with two mesogenic rods and siloxane spacers. In favourable conditions (diluted solution, acid catalysis) macrocycles may be rapidly formed and purely obtained by fractionation. Synthetic aspects and main thermotropic properties are discussed. In spite of their large size some macrocycles have been obtained as single crystals and then characterized by X‐ray diffraction.
Synthesis of a thermotropic polyester and the thermal behavior of its blends with poly(ethylene terephthalate)
Authors: Novack Kátia M. , Martins Jülia C. A. , Gomes Ailton S. 
Published: March 2011

AbstractA thermotropic liquid crystalline polyester (LCP) with a flexible spacer group in the main chain has been synthesized by polycondensation and mixed with poly(ethylene terephthalate) (PET). The influence of the LCP's contents on thermal properties of the blends has been determined by Differential Scanning Calorimetry (DSC). LCP and blends were also characterized by Carbon 13 Nuclear Magnetic Resonance (NMR), Fourier Transform Infrared Spectroscopy (FTIR) and Thermogravimetric Analysis (TGA).
Anisotropic polymeric networks with a controlled nanostructure
Authors: St Pourcain C. B. , Edwards S. F. , Griffin A. C. 
Published: March 2011

AbstractThe synthesis and properties of anisotropically ordered polymer networks with a controlled (molecular) nanostructure are reported. Polymer networks with only a single rigid segment (based on 1, 4‐distyrylbenzene or hydroquinone) between crosslink points were prepared by a simple polyesterification procedure. Unswollen polymer networks containing only one of these rigid segments or a combination of the two were birefringent and exhibited a reversible thermotropic phase transition. The ordering within these networks is attributed to a microphase separation of rigid aromatic and flexible aliphatic segments rather than strictly to a shape‐anisotropy driven liquid crystalline phase. The nature of ordering within these networks when swollen in 1, 2‐dichlorobenzene is also discussed.
Modification of polycyanurate networks with protic additives based on polydimethylsiloxane
Authors: Barthélémy Laurent , Boch Annie , Lafitte Jean , Mirco Valérie , Méchin Françoise , Pascault Jean‐Pierre 
Published: March 2011

AbstractHydroxy telechelic polycaprolactone / polydimethylsiloxane / polycaprolactone triblock copolymers were used to modify aromatic polycyanurate networks through a polycondensation‐induced phase separation. Model studies revealed that the cyclotrimerization mechanism in the presence of alcohol functions was complex. The additives, which activate the reaction, are finally chemically linked to the matrix. Both thermodynamic and kinetic features result in very finely divided morphologies, with highly interpenetrated phases which contribute to a great improve of the static mechanical properties.
Evolution of the dynamic mechanical relaxations during the gel formation
Authors: Durand Dominique , Nicolai Taco , Lefevre Patrice , Prochazka Frederic , Randrianantoandro Hery 
Published: March 2011

AbstractStatic and dynamic properties of a polyurethane system at different stages of the gelation process have been investigated. Shear modulus data were collected over a wide frequency range covering both the α‐relaxation and the internal modes relaxations. The evolution of the relaxation spectra in relation with the structural transformation occurring during the growth process is analysed within the percolation model.
Radiofrequency (27.12 MHz) activation of the curing reaction of epoxy resins of DGEBA type
Authors: Alazard Patrick , Gourdenne Albert 
Published: March 2011

AbstractRadiofrequency (27.12 MHz) heating is used for the activation of the curing reaction of an epoxy resin of DGEBAa) type in presence of diaminodiphenylmethane as crosslinking agent. The principle of the activation process is based on the partial conversion as heat of the dielectric loss in the organic medium due to the forced dipolar relaxation at 27.12 MHz. The samples of thermosetting matter are positioned between two parallel steel plates or electrodes, and an electrical voltage is applied. When the temperature is sufficiently high, the step‐growth reactions starts working.
Hydrodispersible copolyesters: Relationship between chemical structure and physico‐chemical properties
Authors: Fleury E. , Vidil C. , Larcheres G. 
Published: March 2011

AbstractAnionic copolyesters with sodium sulfonate functions and short polyethylene oxyde blocks are used for polyester filament sizing. These polymers were prepared using a three stages melting process at high temperature combining ester interchange, direct esterification, polycondensation and etherification reactions. A study on the relationship between chemical structure and physico‐chemical properties (glass transition temperature, solubility behaviour, hydrolytical and thermal stability) shows that the control of the ether bridges content is important.
Detailed kinetics of liquid crystalline copolyester synthesis: Copolyesterification between poly(ethylene terephthalate), terephthalic acid and hydroquinone diacetate
Authors: Ghadage Ramesh S. , Lodha Anjali , Mathew Johnson , Ponrathnam Surendra , Prasad Sudarshan D. 
Published: March 2011

AbstractThe kinetics of liquid crystalline copolyester synthesis via melt transesterification between poly(ethylene terephthalate)[PET], terephthalic acid [TA] and hydroquinone diacetate [HQDA] is examined. A number of assumptions are proposed and validated to simplify the kinetics and to make the analysis tractable. A key postulation is that the reaction originates between terephthalic acid [TA] and hydroquinone diacetate [HQDA] to form a dimer which slices PET chain. The subsequent coupling of PET segments reforms PET chain with random incorporation of TA‐HQDA units. Steady state approximation is invoked for the rate of generation of dimer. The kinetic analysis reveals the implicit simplicity of complex systems.
The mechanism of chain growth in oxidative polycondensation of phenols
Authors: Ionescu Mihail , Mihis Ana Bianca 
Published: March 2011

AbstractA new mechanism of chain extension in oxidative polycondensation of phenols has been proposed. Between the two accepted mechanisms: quinol ether redistribution and quinol ether rearrangement, the second mechanism seems to be the most important for the chain growth. The first mechanism, quinol ether redistribution, preserves the system average degree of polymerization and assures a permanent equilibration of the polymeric chains, but has only a minor contribution to the molecular weight increase. The second mechanism, quinol ether rearrangement, proved to be the most important for chain extension and was interpreted as a repeated Claisen rearrangement (a particular case of a sigmatropic rearrangement), characteristic to allyl ethers of phenols. Experimental data proved that the above mentioned mechanisms probably take place simultaneously and the real growth of the molecular weight is a result of the cumulative contributions of both mechanisms.
The acid‐catalyzed polycondensation of furfuryl alcohol: Old puzzles unravelled
Authors: Choura Mekki , Belgacem Naceur M. , Gandini Alessandro 
Published: March 2011

AbstractThis paper describes mechanistic studies aimed at understanding the origin of two important side events accompanying the linear polycondensation of furfuryl alcohol in acidic media. The first process concerns the formation of conjugated sequences along the polymeric chains. The use of model monomers and compounds simulating the structure of the linear polymer provided for the first time a full understanding of the reactions leading to multiple unsaturations. The main culprits for this process are the labile hydrogen atoms on the methylene moiteties bridging the furan rings. The second anomaly in these systems concerns the formation of networks following a complex branching mechanism. Again, model structures helped to pinpoint the origin of this process and to propose plausible reactions to describe it.
Syntheses of poly(ester‐amide)s derived from optically active amino alcohols
Authors: Koyama Emiko , Sanda Fumio , Endo Takeshi 
Published: March 2011

AbstractSyntheses of poly(ester‐amide)s derived from optically active amino alcohols are described. Poly(ester‐amide)s with M̄n 8,700–27,200 were obtained by the polycondensations of hydroxycarboxylic acids derived from maleic or succinic acid, and by those of dicarboxylic acids and diols derived from dicarboxylic acids and optically active amino alcohols using EDC·HCl in satisfactory yields. The radical additions of ethanethiol or mercaptoethanol to the polymers derived from maleic anhydride proceeded smoothly in satisfactory incorporation ratios (43∼98%). The polymer obtained from succinic anhydride and 2‐aminoethanol showed hydrolytic degradability. The Tg of the polymer derived from leucinol showed even‐odd effect with increase of methylene chain length of dicarboxylic acids.