bluuebunny/crossref_metadata_2025_split huggingface dataset:
Anionic polymerization of dodecamethyl‐cyclohexasiloxane (D6) with lithium cryptate as a counterion
Authors: Lestel Laurence , Boileau Sylvie 
Published: March 2011

AbstractA kinetic study of the anionic polymerization of dodecamethylcyclohexasiloxane (D6) has been carried out in toluene at 25°C with the cryptate Li+ + [211] as the counterion. The rate constants of propagation of D6 and of the formation of cyclic oligomers have been determined. The results are in good agreement with those reported previously for the anionic polymerization of D3 and D4 under the same conditions. The rate constants of propagation and of formation of D6 have been found to be equal to 1.1 l‐mol−1.h−1 and 0.05 h−1, respectively. In the case of the anionic polymerization of cyclosiloxanes with Li+ + [211] as the counterion, the order of reactivities of Dx as a function of × is as follows:
Synthesis and characterization of main‐chain thermotropic aromatic polyazomethines with siloxane spacers
Authors: Madec Pierre‐Jean , Pérès Richard , Maréchal Ernest 
Published: March 2011

AbstractNew main‐chain liquid crystal copolymers have been synthesized in the polyazomethine series from two polycondensation routes (polyhydrosilylation and polyimination). The mesogenic units are separated with siloxane spacers. The obtained copolymers have been characterized by size‐exclusion chromatography and NMR and FT‐IR spectroscopies; their mesomorphic behavior has been investigated by polarizing microscopy, differential scanning calorimetry and RX diffraction. Moreover, when the polycondensation reactions are carried out in solution or when the copolymers are kept in a solvent, we observed the formation of macrocyclic dimers, which have been isolated and characterized.
Electrocatalyzed step polymerization of 3, 6‐dibromo‐N‐alkylcarbazoles
Authors: Faïd K. , Adès D. , Chevrot C. , Siove A. 
Published: March 2011

AbstractPoly (N‐alkyl‐3, 6‐carbazolediyl)s were synthesized by step polymerization of the corresponding 3, 6‐dibromo‐monomers, electrocatalyzed from a NiBr2/2.2&‐bipyridine complex in N, N dimethylacetamide. From both gel‐permeation chromatography analyses during the course of electrosynthesis and electrochemical behavior studies of the systems, it was deduced a coupling process occuring by step polymerization. Mechanism of formation of the growing chains, in homogeneous phase, is discussed. According to the proposed mechanism and to physical features, polymer chains have a well‐defined structure.
Polymer synthesis by means of germylene and stannylene
Authors: Kobayashi Shiro 
Published: March 2011

AbstractDivalent group 14 metal species, a germylene(la) and a stannylene(lb), behaved as a comonomer(reductant monomer) in the copolymerization with p‐benzoquinone derivatives(oxidant monomer)(“oxidation‐reduction copolymerization”) and as an initiator for anionic monomers. The copolymerization took place without initiator at a lower temperature to give an alternating copolymer. N‐phenyl‐p‐quinoneimine also behaved as a reactive oxidant monomer toward la and lb. These species have been shown to induce the polymerization of anionically polymerizable monomers such as methyl methacrylate, methacrylonitrile, and 4‐vinylpyridine. Based on the mechanistic examination of the polymerization, a new alternating copolymerization between la and 2‐cyclohexene‐l‐one has been developed to produce a copolymer having a metal‐enolate structure, which involves the oxidation‐reduction process during the copolymerization.
Reactions under mixing in viscous polymeric media
Authors: Blumen A. , Sokolov I. M. 
Published: March 2011

AbstractMixing of viscous liquids is of common occurence in polymer technology. We consider the effects of mixing on the simplest bimolecular reaction A+B→O. Under mixing often lamellar arrays of striations of the A and B reactants are formed. The structure of these arrays and the thinning of the striations during mixing determine the kinetics of the reaction. We consider both a premixed situation (where the reaction is diffusion‐controlled) and also a situation where mixing and reaction take place simultaneously.
Membranes of high performance polymers
Authors: Haubs M. , Herold F. , Krieg C. , Meyer‐Blumenroth U. , Schneider J. , Wagener R. , Wildhardt J. 
Published: March 2011

AbstractMembranes, as part of technical processes, are gaining more importance in areas such as chemicals, biotechnology or waste‐water treatment. The use of high performance polymers as membrane materials offers unique combinations of properties and allows new applications. Three different approaches towards membrane fabrication from high performance polymers such as polyaryls or polyaramides are discussed, i. e. maintenance of the polymer structure during processing and synthesis of better soluble structures via either polymer‐analogous reactions or tailor‐made copolymers. Examples of chemistry, property profiles and potential applications are given.
Gas permeability of cardo‐poly(ether‐ether‐ketone) and poly(phenylene sulfide)
Authors: Engelmann I. , Schultze J. D. , Böhning M. , Springer J. 
Published: March 2011

AbstractThe gas permeability and sorption of CO2 and N2O was measured on cardo‐poly(ether‐ether‐ketone) (C‐PEEK) and poly(phenylene sulfide) (PPS) at 298 K. The results are discussed on the basis of the dual‐mode model. Results obtained from measurements at 308 K are compared with literature data of poly(phenylene oxide) (PPO), poly(sulfone) (PSU) and poly(carbonate) (PC). While C‐PEEK shows similar transport properties as PC and PSU, the values of PPS are distinctly lower. The solubility of CO2 in the various polymers as well as the correlation of the permeability coefficients of the same polymers for He, Ar, CO2, N2, and CH4 with the kinetic molecular diameter of the gases indicate a simple relation of the transport properties with the polymer density.
Dye doped polymer films: From supramolecular photochemistry to the molecular computer
Authors: Wild Urs P. , Renn Alois 
Published: March 2011

AbstractA new concept of “molecular computing” based on spectral hole‐burning, the interaction of molecular energy levels with an externally applied electric field and the interferometric properties of holography is presented. The molecular processor introduced here relies on the spectroscopic properties of a dye doped polymer film, which simultaneously can be used for image recording and for parallel processing of the stored information.
Nanostructured materials
Authors: Gleiter H. 
Published: March 2011

AbstractIn the cores of lattice defects (e.g. dislocations, grain boundaries, phase boundaries etc.) a special state of solid matter exists due to the forces (constraints) between the atoms (molecules) in the core region of the defects and the atoms (molecules) in the surrounding strained crystal lattices. These constraints result in the formation of a solid state structure characterized by a low density (typically 60 ‐ 80 % of the crystal density) and a very broad distribution of nearest neighbour spacings. It is the basic idea of Nanostructured Materials to utilize the atomic structures formed in the cores of defects to generate a new class of materials. This goal is achieved by incorporating so many defects into a (formerly perfect) crystal that about 50 vol % of the material consists of defect cores. The results of studies by means of electron microscopy, neutron and x‐ray diffraction, various types of spectroscopy and property measurements agree with these ideas. Nanostructured Materials exhibit properties that deviate (sometimes by many orders of magnitude) from the properties of crystals and glasses with the same chemical composition.
Reactive polymer blends with thermoplastic polyurethan
Authors: Rätzsch Manfred , Pionteck Jürgen , Rische Thomas 
Published: March 2011

AbstractThe paper presents the concept of reactive coupling of thermoplastics and describes the technological preconditions and the present state of development. The examples of developments of blends of thermoplastic polyurethan (TPU), and polyethylene terephthalate (PET) serve to show that different mechanisms of reactive coupling of the blend components permit to produce high‐quality blends.
Blockcopolymers with electrically conductive microphases morphology, conductivity and crystal structure
Authors: Kempf S. , Gronski W. 
Published: March 2011

AbstractBy synthesis of TCNQ radical anion salts of poly(1,4‐butadiene‐b‐4‐vinylpyridine)(B4VP) blockcopolymers and subsequent doping with neutral TCNQ filmforming electrically conductive materials of good mechanical stability were obtained. The improved properties are achieved either by incorporation of butadiene microparticles in a coherent conductive P4VP phase or by generation of a percolating electrically conductive crystalline micronetwork embedded in a continous butadiene phase. In comparison to the homopolymers the resistance to oxidation is enhanced.
Molding plateable micropatterns of electrically insulating and electrically conducting poly(methyl methacrylate)s by the LIGA technique
Authors: Harmening M. , Bacher W. , Menz W. 
Published: March 2011

AbstractA new process of molding directly plateable molded plastic pieces has been developed for the mass fabrication of metal micropatterns of any shape by the LIGA‐technique. In this process, electrically insulating micropatterns of poly(methyl methacrylate) are molded on the surface of an electrically conducting poly(methyl methacrylate) composite. The composite is made of a methyl methacrylate casting resin. In the development process, the polymerization of casting resins was studied for various fillers and initiators. In addition, poly(methyl methacrylate)s filled with silver were subjected to studies of the electrical, thermal, and mechanical behavior of the composites as a function of the filler content.
Macromolecular engineering on the basis of the polymerization of 2‐oxazolines
Authors: Saegusa T. , Chujo Y. 
Published: March 2011

AbstractRing‐opening polymerization of 2‐methyl‐2‐oxazoline produces poly(N‐acetylethylenimine). This polymerization reaction proceeds in living mechanism under appropriate reaction conditions. The resulting polymer has high hydrophilicity and good compatibility with other organic polymers. On the basis of these characteristic properties, i.e., high hydrophilicity and the cleanness of polymerization reaction, the following three functional polymers have been explored.1. Non‐ionic hydrogels,2. Non‐ionic surfactants,3. Molecular hybrid with silica gel.
Transesterification in polymer blends including polycarbonate at high temperatures
Authors: Nishi Toshio , Suzuki Takashi , Tanaka Hajime , Hayashi Takafumi 
Published: March 2011

AbstractMiscibility of polycarbonate (PC)/poly (arylate) (PAr) was studied by differential scanning calorimetry (DSC), phase contrast microscopy with digital image analysis (DIA) system, FT‐IR spectroscopy, and cloud points for the PC/PAr/methylene chloride ternary systems. PC and PAr were immiscible over the whole composition range from the thermodynamical viewpoint. However, PC/PAr is homogenized by transesterification between PC and PAr at high temperatures. There is observed a competition between phase separation due to thermodynamical factor and phase dissolution due to transesterification. The pattern of the phase separation was spinodal decomposition type and the structure was successfully analysed by DIA.
Polyurethane IPN membranes
Authors: Kim Sung Chul 
Published: March 2011

AbstractHydrophilic/hydrophobic, cationic/anionic polyurethane membranes were prepared and the effect of the synthesis pressure and temperature on the morphology were evaluated. The pervaporation characteristics of the membranes for the separation of ethanol/water mixture as well as the gas separation performances in the separation of nitrogen/oxygen mixture were measured and the effect of the IPN synthesis parameters were analyzed.
Structure of valinomycin/fatty acid langmuir‐blodgett films
Authors: Howarth V. A. , Petty M. C. , Lvov Y. 
Published: March 2011

AbstractWe report on the structure of monolayer and multilayer Langmuir‐Blodgett films of mixtures of arachidic acid and the ionophore valinomycin. Compressibility measurements on the floating layers and low angle x‐ray diffraction experiments with multilayers indicate the possible miscibility of the two components at low concentrations of the ionophore. However, it would appear that the arachidic acid and valinomycin are insoluble in one another over most of the composition range.
Mechanisms of polymerization of methacrylate copolymers of biological interest
Authors: Carswell Trudy G. , Hill David J.T. , Kellman Raymond , Londero Daniel I. , O'Donnell James H. , Pomery Peter J. , Winzor Catherine L. 
Published: March 2011

AbstractThe kinetics of the free radical copolymerization of HEMA, EGDMA and TEGDA with MMA have been studied using NIR spectroscopy to follow the reduction in the total C=C concentration with time and 1H NMR to distinguish between the monofunctional and difunctional monomers. ESR measurements of the concentrations of propagating radicals during polymerization have been combined with the conversion results to derive values for the rate constants kp (propagation) and kt (termination). HEMA decreases the gel time of MMA, but the initial rate is unchanged, whereas EGDMA and TEGDA decrease the gel‐time and increase the initial rate of polymerization.
ESR applications to photochemical polymer reactions
Authors: Rånby Bengt 
Published: March 2011

AbstractESR spectroscopy combined with spin‐trapping technique is a selective and powerful method for studies of reaction mechanisms and intermediates in free radical reactions of polymer systems. The method has been applied to several problems in our research program of which three are presented in this paper. ‐ The mechanism of photo‐initiation with aromatic ketone/tert. amine and subsequent photocuring of acrylic coatings has been largely resolved. ‐ The mechanism of photocrosslinking of ethylene‐propylenediene copolymers (EPDM elastomers) studied by model compounds has been shown to involve formation of allyl radicals in the diene groups and crosslinking by allyl radical combination. ‐ The photoinitiated crosslinking of polyethylenes (LD, LLD and HD) has been studied using model compounds. It involves formation of primary alkyl and allyl radicals which crosslink the polymer by radical combination. ‐ The mechanism of photocrosslinking indicates a second order reaction, i.e. rate of crosslinking depends of the square of irradiation intensity which has been verified experimentally. This result is the basis for development of rapid crosslinking processes of technical and industrial interest.
Vibrational characterization of langmuir‐blodgett monolayers of tetra(p‐methoxyphenyl) porphine
Authors: Guhathakurta‐Ghosh U. , Aroca R. 
Published: March 2011

AbstractLangmuir–Blodgett (LB) monolayers of tetra(p–methoxyphenyl)porphine (H2TMPP) have been prepared, transferred to glass slides and metal surfaces, and characterized using surface–enhanced Raman scattering (SERS). The technique of mixed monolayers (H2TMPP in a lipid matrix of arachidic acid) was used to obtain maximum enhancement in the SERS experiments.
Pyrolysis‐gas chromatography/fourier‐transform infrared spectrometry of poly(ester urethane) elastomers
Authors: Weber Daniela , Fülöp Gábor , Hummel Dieter O. 
Published: March 2011

AbstractThree types of industrial poly (ester urethane) elastomers were studied by Curie–point pyrolysis–gas chromatography/Fourier–Transform infrared spectrometry (Py–GC/FTIR) with a maximum pyrolysis temperature of 973 K. The samples chosen were the Urepans 600 and 641 from Bayer and Elastollan C 78 A from BASF/Elastogran. The poly(ester urethane) elastomers are composed of three units: a polyesterdiol, a short chain diol and a diisocyanate. Py–GC/FTIR allows a rapid and unambiguous identification of the polymer chains by key fragments.
A route to quantitative 13C NMR analysis of multicomponent polyesters
Authors: Hvilsted Søren 
Published: March 2011

AbstractA protocol for quantitative sequential 13C NMR analysis is developed for polyesters composed of trimethylol propane (TMP), neopentyl glycol (NPG), and adipic and isophthalic acids. TMP centred, structural models with methyl adipate and isophthalate branches in all possible combinations are synthesized and purified. A detailed 13C NMR investigation of the models unequivocally allows the identification of the TMP polyester structural sequences through the quaternary TMP carbon multiplicity. Spin‐lattice relaxation times, T1, of model quaternary TMP carbons are in the 2.3–5.2 s range, depending on the size of the specific model. This relaxation behaviour defines the experimental conditions for obtaining the quantitative assessment of all polyester polyol structural sequences based on quaternary TMP and NPG carbons. The special case dealt with here additionally centers all acid moieties between poyols in triads and thus makes quantitative determinations of all polyester constituents possible.
Segment orientation in topologically constrained networks
Authors: Sommer Jens‐Uwe , Straube Ekkehard 
Published: March 2011

AbstractUsing the continous Edwards–chain model the simultaneous influence of harmonic–like constraints and of a stochastic order parameter field on the segment orientation in polymer networks is investigated. The harmonic potential reduces the orientation order parameter in comparison to the value for an unconstrained freely jointed chain. This reference value is approached from below in the case of strong topological constraints. The introduction of a stochastic order parameter field enlarges the orientation but the reference value remains the upper boundary.
MC‐determination in elastomers by 1H‐NMR relaxation and 2H‐NMR spectroscopy
Authors: Simon G. , Schneider H. 
Published: March 2011

AbstractWe show how 1H–NMR transversal relaxation and 2H–NMR spectroscopy can be used for the determination of the number average molecular mass MC in typical elastomers at temperatures well above the glass transition temperature. MC‐results of the different NMR methods are compared among one another and with MC‐results of other common independent methods. Moreover, the NMR measurements provide a number of additional useful parameters: correlation times, portions of dangling chain ends and of sol molecules, molecular order.
Melting of isotactic polypropene in blends with atactic polypropene and isotactic poly(1‐ethylethylene)
Authors: Tampier Monika , Trafara Gundolf 
Published: March 2011

AbstractThe melting behaviour of isotactic polypropene (it–PP) in blends with atactic polypropene (at–PP) and isotactic poly(1–ethylethylene) (it–PB) was examined by thermal analysis. It is shown that the double melting endotherm obtained under certain experimental conditions is caused by new crystallization. In the examined blends the tendency of new crystallization depends on the composition.
The interactions of macrocyclic ethers by 13C dipole‐dipole relaxation time measurements
Authors: Erk Cakil 
Published: March 2011

Abstract13C dipole–dipole relaxation time measurement studies of free and cation complexed cyclic polyethers in solution are reviewed briefly. The 13C dipole–dipole relaxation time of the macrocyclic ether backbone has been recognized to be a function of a motion of the molecular segment acting as a macrocyclic ligand site. This has been particularly investigated by NMR under extreme narrowing conditions.
Conformational ordering of chain molecules in liquid crystals
Authors: Abe Akihiro 
Published: March 2011

AbstractDeuterium NMR studies have been performed to elucidate orientational characteristics of some ether‐type main‐chain liquid crystals. Spacers used are of the type ‐O(CH2)nO‐ with n = 9 and 10. Dimers, homopolymers as well as copolymers in which spacers n = 9 and 10 are arranged in an alternative fashion were investigated. The quadrupolar splitting data obtained from the deuterium‐labeled mesogenic core and spacer have been studied within the rotational isomeric state (RIS) approximation. The ordering characteristics thus estimated were found to be consistent with the magnetic susceptibility data obtained by using superconducting quantum interference device (SQUID) for the same polymers.
Modelling copolymerization kinetics
Authors: O'Driscoll Kenneth 
Published: March 2011

AbstractThe composition and rate behavior of free radical copolymerizations is usually described by the Mayo‐Lewis (ML) model and the associated reactivity ratios, r1 and r2. Particularly with respect to rate, a number of systems have been found to be poorly described by the simple ML model and the penultimate unit effect (PUE) model has been suggested as an explanation. A small but significant amount of work has been done with small model analogues of polymer chains and with ESR which has established the chemical feasibility of a PUE. This paper reviews recent work with pulsed laser polymerization kinetic measurements which are successfully described in terms of a modified PUE. It is concluded that the strength of the PUE correlates inversely with the monomer reactivity ratio product, r1r2. The effect is important for rate, but not for composition.
Competition between dopants on redox reaction of polypyrrole
Authors: Ko J. M. , Rhee H. W. , Kim C. Y. 
Published: March 2011

AbstractThe surface of PPy prepared in a multiple electrolyte solution such as NaDS‐NaClO4 in H2O shows a coarser structure than that of the polymer prepared in a single electrolyte system. DS− with a large aliphatic chain is used as a dopant in preparation of PPy. The dopant is trapped in PPy when the polymer is reduced in an aqueous system. A cation Na+ or K+ is inserted into the polymer to balance the free DS− liberated form and remained in it on reduction. PPy doped with DS− shows a high degree of redox reactivity in the system of TBADS‐AN but a poor stability in repeated redox process. The degree and rate of redox reactivity enhance when an aqueous solution of NaClO4 is used as an electrolyte system. Both Na+ and ClO4−take part in the redox reaction and the reduction process is intense at only one current potential.
Room‐temperature curing epoxies and their elevated‐temperature properties
Authors: Dodiuk H. , Kenig S. 
Published: March 2011

AbstractLow‐temperature curing epoxy formulations for elevated‐temperature service were developed and characterized for adhesive repair and composite matrix. Balanced lap‐shear and peel strengths for adhesive applications and flexural and interlaminar shear strengths for composites were obtained when a blend of tetra‐functional and tri‐functional epoxies was used. For low‐temperature curing triethylenetetraamine (TETA) was proven to be effective combined with an amine terminated elastomer. The latter component served also as a toughener. Lower‐functional epoxies and curing agents resulted in a peel strength increase and a simultaneous decrease in shear strength. Furthermore, the incorporation of the lower‐functional constituents or silanes, resulted in development of a three‐phase morphology compared to a conventional two‐phase elastomer‐epoxy morphology. Thermal analysis carried out by Differential Scanning Calorimetry (DSC) and Dielectric Loss Factor (DLF) indicated that the reduced temperature‐curing formulations have relatively low activation energy and that the main cross‐linking reaction takes place close to 50°C and is completed at 120°C with a maximum glass transition temperature at 180°C. Mechanical properties of the adhesive formulation were comparable or better than existing commercial products. Flexural and interlaminar shear strengths, for glass‐epoxy composites incorporating a selected low‐curing‐temperature formulation, exhibited enhanced properties compared to commercially 120°C epoxy‐glass prepreg composites.