bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pivalolactone, 1 interchange reactions with polypivalolactone
Authors: Tijsma Edze Jan , van der Does Leen , Bantjes Adriaan , Vulic Ivan 
Published: April 2003

AbstractEster interchange, alcoholysis, and acidolysis of polypivalolactone (PPVL) were studied by melting PPVL with bisphenol diacetates, 1, 4‐butanediol, or aromatic diacids. Interchange of PPVL with the diacetates and the diol occured readily, in particular in the presence of a titanium catalyst. Melting PPVL with 10 mol‐% of bisphenol‐Adiacetate in the presence of 0,5 wt.% tetrabutylorthotitanate resulted in an incorporation of 33% of the diacetate in the polymer chains, whereas the logarithmic viscosity number decreased by 81%. The ester interchange was suggested to proceed by an initial cleavage of ester bonds in the polymer chain of PPVL, resulting in the formation of shorter chains, followed by a reaction between the newly formed ester end‐groups and initially present hydroxyl chain ends. The acidolysis of PPVL with the diacids proved to be less effective; in the case of the acidolysis of PPVL with 10 mol‐% isophthalic acid, less than 1% of the diacid was incorporated in the polymer chains and a decrease in the logarithmic viscosity number of only 22% was found. Both the high stability of the ester bond in PPVL towards acids in general and the heterogeneity of these systems were supposed to cause the behaviour of PPVL with respect to acidolysis. The results concerning the interchange reactions with PPVL were compared with studies on other polyesters.
New polymers with coronand structure
Authors: Klemm Elisabeth , Alhakimi Gamil , Schütz Heidrun 
Published: April 2003

AbstractNew polymers with an alternating sequence of non‐polar aliphatic chains and coronands were synthesized via Diels‐Alder addition polymerization of bis(2‐pyrones) with bismaleimides; number‐average molecular weight M̄n: 18000 (vapour pressure osmometry), glass transition temperature T̄g: 250°C. The chemical structures of these polymers are supported by NMR spectra and model reactions. The reaction mechanism is discussed.
Inter‐ and intramolecular interactions in polyelectrolyte complex formation with polyampholytes
Authors: Kötz Joachim , Hahn Mathias , Philipp Burkart , Bekturov Esen A. , Kudaibergenov Sarkyt E. 
Published: April 2003

AbstractEmploying polyampholytes (inclusively polybetaines) of different chemical structure containing carboxylic groups and various basic nitrogen functions, homosymplex formation, as well as the competition between homo‐ and heterosymplex formation on addition of an appropriate polyelectrolyte, was investigated in dependence of pH and ionic strength by means of viscometry and turbidimetry. With most, but not with all, of the polyampholytes, the expected viscosity minimum at the isoelectric point, with its steepness depending on polyampholyte structure, was observed. Competition of homo‐ and heterosymplex formation at and near the isoelectric point is mainly governed by the pK values of the species involved, the level of zwitter‐ion formation of the polyampholyte and the effect of non‐Coulombic interactions, for example, via hydrogen bonds.
Synthesis of new cycloaliphatic epoxy resins and their crosslinking
Authors: Roig Antoni , Galià Marina , Cádiz Virginia , Mantecón Ana , Serra Angels 
Published: April 2003

AbstractThe reaction of cycloaliphatic and glycidylic oxiranes with primary amines was examined; no reaction was observed for the former. From unsymmetrical cycloaliphatic glycidylic imide derivatives and primary amines, it was possible to obtain well defined epoxy‐terminated biscycloaliphatic resins containing imide rings, which were identified by 13C NMR spectroscopy and elemental analysis. These epoxy resins were crosslinked by simple heating without hardeners and epoxide/amine‐networks were obtained. The action of phthalic anhydride as curing agent gave different results depending on the nature of the starting cycloaliphatic group. Thus, while tetrahydrophthalimide derivatives, N‐(2,3‐epoxypropyl)perhydro‐4,5‐epoxyphthalimide (2), underwent crosslinking, nadimide derivatives, N‐(2,3‐epoxypropyl)‐5,6‐epoxybicyclo [2.2.1] heptane‐2,3‐dicarboximide (1) did not react. Differential scanning calorimetry was used to follow the reaction; in all the cases, only the dynamic method was applied, in order to obtain kinetic parameters. The values for activation energies are comparable to those reported for the curing of epoxide systems.
A dilatometric study on antiplasticized and plasticized poly(vinyl acetate)
Authors: Knoglinger Johann , Schausberger Alois 
Published: April 2003

AbstractBy use of mercury dilatometry the volume expansion coefficients in the molten and in the glassy state, as well as the glass transition temperatures, were determined for poly(vinyl acetate) samples containing moderate quantities of soluble water‐free salts. These measurements were completed by the investigation of samples containing only plasticizer as additive or a combination of plasticizer and soluble water‐free salts. The flex energy and the hole formation energy were calculated from the theory of Gibbs and DiMarzio. One finds a correlation between the effectiveness of glass transition elevation by the salts and the effectiveness of the salts to support the thermal degradation of poly(vinyl acetate).
Zwitterionic polysoaps with reduced density of surfactant side groups
Authors: Anton Peter , Laschewsky André 
Published: April 2003

AbstractSeveral zwitterionic polymers were prepared by radical homopolymerization of surfactant monomers which bear diallyl, diene or vinylcyclopropane moieties. These polymer systems were complemented by alternating copolymers of appropriate zwitterionic vinyl compounds. Thus, polymers with reduced (as compared with simple vinylic homopolymers, or statistical copolymers) and well defined density of surfactant side groups are obtained. The solubilities found for these polymers are dominated by polymer geometry rather than by the balance of hydrophilic and hydrophobic fragments, thus corroborating a “main‐chain spacer” model proposed recently. All water‐soluble polymers exhibit characteristic features of classical polysoaps, as shown by surface tension measurements and by solubilization of hydrophobic dyes. In contrast, the water‐insoluble copolymers are capable to form stable monolayers at the air‐water interface.
Mechanisms and kinetics of the anionic polymerization of acrylates, 3. Effect of lithium chloride and lithium tert‐butoxide on the oligomerization of tert‐butyl acrylate
Authors: Janata Miroslav , Lochmann Lubomír , Müller Axel H. E. 
Published: April 2003

AbstractThe influence of lithium tert‐butoxide (tBuOLi) and of lithium chloride on the oligomerization of tert‐butyl acrylate (tBuA) initiated by tert‐butyl α‐lithioisobutyrate (tBiB‐Li) was investigated. These additives affect both the kinetics and the product distribution. Whereas the addition of LiCl leads to a narrower molecular‐weight distribution (MWD) the presence of tBuOLi induces broader MWD's, characterized by a very high fraction of the dimer. Both additives decrease the rates of propagation to different degrees. These effects are discussed on the basis of the formation of aggregates and adducts, the lithiated dimer having a higher tendency to form aggregates than the other oligomers. The stability of the growth centres in this oligomerization is increased in the presence of these additives, tBuOLi exhibiting a much stronger effect than LiCl. The interaction of the lithiated dimer with the additives could not be demonstrated in the IR spectra of these mixtures.
Living cationic polymerization of isobutyl vinyl ether by trimethylsilyl halide/zinc halide initiating systems: effects of carbonyl compounds
Authors: Kamigaito Masami , Sawamoto Mitsuo , Higashimura Toshinobu 
Published: April 2003

AbstractEffects of carbonyl compounds [acetone, acetophenone, and benzaldehydes (p‐MeO, p‐NO2, and unsubstituted)] were investigated in the polymerization of isobutyl vinyl ether (IBVE) by trimethylsilyl halide/zinc halide (Me3SiX/ZnX2; X = I, Br, Cl) initiating systems in toluene at −15°C. In the presence of acetone and the three benzaldehydes, Me3Sil/Znl2 induced living cationic polymerization, where the number‐average molecular weights (M̄n) of the polymers increased proportionally to monomer conversion and agreed with the calculated values on the assumption that one living polymer per molecule of Me3SiI is formed. The molecular weight distributions (MWDs) stayed very narrow (M̄w/M̄n ≤ 1,1) throughout the reaction. With acetophenone, the M̄n values were larger than the calculated values and the MWDs were slightly broader. For less reactive silyl halides, Me3SiBr and Me3SiCl, p‐MeO‐benzaldehyde gave better results in terms of M̄n values and MWDs than unsubstituted benzaldehyde. 1H NMR analysis of the polymer end structure and the products of model reactions has shown that the initiation occurs via a silyloxycarbocation (Me3SiOC+R1R2 · X−) that is generated by a reaction of Me3SiX with carbonyl compounds.
Thermodynamics of hexanal, its bulk polymerization and polyhexanal from 0 to 340 K at standard pressure
Authors: Lebedev Boris , Vasil'yev Valery , Novosyolova Nina 
Published: April 2003

AbstractIn the present work the enthalpy, entropy and Gibbs function were obtained from calorimetric results, for the bulk polymerization of hexanal in the temperature range from 0 to 330 K at a pressure of p = 101,325 kPa. The physical transitions of hexanal between 11 and 340 K and polyhexanal from 5 to 340 K were studied in a vacuum adiabatic calorimeter, and the corresponding thermodynamic parameters of the monomer and the polymer were determined. From the results obtained the thermodynamic functions of hexanal and polyhexanal were calculated in the range from 0 to 340 K. In a differential automatic microcalorimeter the enthalpy of depolymerization of polyhexanal in acetic acid to the initial monomer was directly measured. The ceiling temperatures of the transition processes of the liquid monomer into the crystalline and highelasticity polymer were estimated.
Crystallinity of uniform triblock oxyethylene/methylene/oxyethylene (EmCnEm) oligomers studied by X‐ray diffraction, differential scanning calorimetry and Raman spectroscopy
Authors: Campbell Carl , Viras Kyriakos , Richardson Michael J. , Masters Andrew J. , Booth Colin 
Published: April 2003

AbstractUniform triblock oligomers with a central methylene block and outer oxyethylene blocks terminated by methoxy groups, CH3(OCH2CH2)mO(CH2)n(OCH2CH2)mOCH3 (EmCnEm), were prepared and studied in the solid state by X‐ray diffraction, differential scanning calorimetry and Raman spectroscopy. Both fully crystalline and partly‐crystalline structures were found, with chains in wholly trans‐planar and mixed‐trans‐planar/helical conformations. Comparison is made with previous results for triblock oligomers of type CnEmCn and diblock oligomers of type CnEm.
The anionic polymerization of acrylates, 5. Controlling the molecular weights in the polymerization of 2‐ethylhexyl acrylate initiated by the mixed initiator lithium ester‐enolate/lithium tert‐butoxide
Authors: Vlček Petr , Otoupalová Jaroslava , Kříž Jaroslav 
Published: April 2003

AbstractIn the anionic polymerization of 2‐ethylhexyl acrylate the possibility of controlling the molecular weights of the resulting polymers by varying the initial stoichiometric conditions was studied. The starting concentrations of monomer and initiator, tert‐butyl 2‐lithioisobutyrate, were varied in the range 0,24–1,20 mol/L and 0,006–0,017 mol/L, respectively, so that the mole ratio [M]0/[I]0 spanned the range from 14 to 160. The mole ratio tert‐butyl 2‐lithioisobutyrate: Li tert‐butoxide was 1 : 3 in all experiments. A Mixture toluene/tetrahydrofuran (volume ratio 9 : 1) was used as reaction medium. The molecular weights of the polymers formed (37 00–55 000) depend linearly on the ratio [M]0/[I]0. All products have narrow molecular‐weight distributions. The efficiency of the initiator is not quantitative, but in the range investigated it does not depend markedly on the concentration conditions. NMR analysis of the polymers indicates that the polymerization is initiated by Li ester‐enolate and any metal transfer from the initiator to the monomer can be neglected. The polymerization is shown to proceed by the mechanism which is close to the ideal “living” process.
Coordination polymerization of lactides, 3. Copolymerization of L,L‐lactide and ε‐caprolactone in the presence of initiators containing Zn and Al
Authors: Bero Maciej , Kasperczyk Janusz , Adamus Grazyna 
Published: April 2003

AbstractHigh‐molecular‐weight copolymers of L,L‐lactide with ε‐caprolactone were synthesized using initiators containing aluminium and zinc, i.e., AlEt2OEt, ZnEtOiPr, Al(acac)3 and AlEt3 + ZnEt2 + H2O. The chain microstructure was revealed to vary from random to diblock arrangement, depending on temperature and the kind of initiator used. In case of Al(acac)3 as initiator, the reactivity ratios of L,L‐lactide and ε‐caprolactone were determined to be rL = 44 and rC = 0,28, respectively.
Coordination polymerization of lactides, 4. The role of transesterification in the copolymerization of L,L‐lactide and ε‐caprolactone
Authors: Kasperczyk Janusz , Bero Maciej 
Published: April 2003

AbstractTwo modes of transesterification in copolymerization of L,L‐lactide with ε‐caprolactone in the presence of initiators containing Al and Zn were found. The quantitative analysis of the contributions of both types of transesterification reactions is revealed. The transesterification ability of initiators containing zinc is greater than that of initiators containing aluminium. Decrease of the reaction temperature tends to reduce both the first and the second mode of transesterification, leading to an elongation of blocks in the copolymer chains.
Fluorinated gels for gel permeation chromatography
Authors: Juhl Hans‐Jürgen , Heitz Walter 
Published: April 2003

AbstractThe aim of these investigations was the development of stationary phases for GPC compatible with fluorinated solvents. The properties of crosslinked copolymers of 4‐(2‐heptafluoropropoxy‐1, 2,2‐trifluoroethoxy)styrene (1) were investigated in dependence of the mode of synthesis. Divinylbenzene (DVB) was used as crosslinking agent. In the case of homogeneously crosslinked gels, 1 mol‐% of DVB results in a gel with an exclusion molecular weight of 2000. Heterogeneous crosslinking copolymerization of 1 with DVB in presence of inert diluents results in gels with exclusion limits from 5000 to 4000000 in dependence of the diluent composition. Characterization of the gels in GPC experiments was carried out with 2‐(1,2‐dibromotrifluoroethoxy)‐1,1,2,3,3,3‐hexafluoro‐1‐(perfluoropropoxy)propane (PPVE2Br2), hexafluorobenzene, 1,1,2‐trichlorotrifluoroethane (FrigenR113) and trifluoromethylbenzene as eluents.
Doping of poly(phthalidylidenearylene)s. Interaction of iodine with poly(3,3′‐phthalidylidene‐4,4′‐biphenylylene)
Authors: Novoselov Igor V. , Zolotukhin Mikhail G. , Nikiforova Galina I. , Kapina Alevtina P. , Shishlov Nikolai M. , Latchinov Aleksei N. , Sangalov Yuri A. 
Published: April 2003

AbstractInteractions of iodine with films prepared from poly(3,3′‐phthalidylidene‐4,4′‐biphenylylene) (PPB) were studied by IR, far‐IR and UV spectroscopy. The carbonyl group of the lactone cycle was found to play a main role in the complexation of iodine with PPB. Iodine incorporated into the polymer transforms into polyiodide ions ( I, n = 1 − 3). Various polyiodides, along with complexed iodine (I2comp), may exist in the polymer at a time, and can be transformed into each other, depending on ambient conditions. The process of doping is almost completely reversible. After removal of iodine from the polymer by heating, the latter restores its starting properties.
Concentration dependence in the transport of alkali metal ions against their concentration gradient across cation exchange membranes
Authors: Uragami Tadashi , Tamura Tomoko 
Published: April 2003

AbstractThe kinetics of the transport of alkali metal ions such as Li+, K+, Na+ against their concentration gradient across cation exchange membranes such as poly[isobutylene‐alt‐(maleic anhydride)] (ISBN) and poly(styrenesulfonic acid) (PSA) membranes was studied. The transport for these ions through these membranes obeyed the Michaelis‐Menten equation at the initial stage. The affinity of alkali metal ions to a carboxy group which is a carrier in the ISBN membrane and to a sulfo group which is a carrier in the PSA membrane is in the order K+ > Na+ > Li+. This order agrees with a selective transportability of alkali metal ions through these membranes.
Ziegler‐Natta oligomerization of 1‐alkenes: a catalyst's “fingerprint”, 1. Hydrooligomerization of propene in the presence of a highly isospecific MgCl2‐supported catalyst
Authors: Busico Vincenzo , Cipullo Roberta , Corradini Paolo 
Published: April 2003

AbstractThe stereochemistry of propene polyinsertion catalyzed by a highly isospecific MgCl2‐supported Ziegler‐Natta system was investigated by means of the gas chromatographic/mass spectrometric (GC‐MS) characterization of the saturated oligomers (hydrooligomers) formed in the presence of H2 at high pressure (as a chain transfer agent). It was shown that the hydrooligomer distribution is a true catalyst “fingerprint”, from which, in case of systems with (prevailingly) a single type of active centres, both the regio‐ and the stereospecificity of polyinsertion can be quantitatively evaluated.
Copolymer‐monomer miscibility during copolymerization
Authors: El‐Begawy Salah E. M. , Huglin Malcolm B. 
Published: April 2003

AbstractSignificant drift in the compositions of copolymer and of unreacted monomer mixture is predicted to occur during the bulk copolymerization of N‐vinyl‐2‐pyrrolidone (VP) with butyl acrylate (BA), when the inital feed mixture contains 75 wt.‐% VP. The drift in copolymer composition has been confirmed by 1 the optical appearance and glass transition (Tg) behaviour of the products of the γ‐ray initiated copolymerization at various fractional conversions (C) and 2 the Tg behaviour of low‐conversion samples of poly(VP‐co‐BA) blended in propertions so as to simulate the overall composition of material that would be present cumulatively at selected values of C during an actual copolymerization. The compositions of unreacted monomer mixtures co‐existing with copolymer at selected conversions have been calculated and intrinsic viscosities [η] of blends dissolved in these VP/BA mixtures have been measured. Theta conditions for the blends have been established turbidimetrically in chloroform/heptane and the corresponding values of [η]Θ measured. The chain expansion factors thereby derived from [η] and [η]Θ show a decreasing affinity of copolymer for residual monomer during the course of copolymerization.
New side‐group liquid‐crystalline polymethacrylates
Authors: Rodekirch Gerhard , Rübner Joachim , Zschuppe Veit , Wolff Dietmar , Springer Jürgen 
Published: April 2003

AbstractA new route of synthesis of liquid‐crystalline polymethacrylates was investigated. The synthetic route involved side‐group liquid‐crystalline polymethacrylates (LCPMA) with a turned ester group between the aromatic rings in the central unit of mesogens (2) as compared with the usual LCPMA (1). For a series of compounds of this type the liquid‐crystalline properties were investigated using differential scanning calorimetry, polarizing microscopy and X‐ray diffraction techniques. Generally stable smectic phases were found for these isomeric LCPMA. The described synthetic route opens possibilities to form new polymers from a wide field of educts.
The β‐relaxation in low‐molecular‐weight and in polymeric side group ferroelectric liquid crystals
Authors: Schönfeld Axel , Kremer Friedrich , Hofmann Achim , Kühnpast Kurt , Springer Jürgen , Scherowsky Günther 
Published: April 2003

AbstractDielectric spectroscopy in the microwave regime (106–1010 Hz) is employed to study the molecular dynamics of a set of ferroelectric liquid‐crystalline side group polymers with variable spacer length and different molecular weight, and on their low‐molecular‐weight counter‐part. One relaxation process is observed, the β‐relaxation, which is assigned to the hindered rotation of the mesogens around their long molecular axis. This librational process is nearly uninfluenced by the molecular weight and depends only slightly on the spacer length. At the smectic‐smectic phase transition SA/SC* the β‐relaxation does not decrease in its relaxation strength and shows no slowing down of its relaxation rate. This is in pronounced contrast to the common explanation of the origin of ferroelectricity in liquid crystals and requires a new interpretation.
Synthèse de diamines aromatiques macromoléculaires à basicité controlée à partir de poly(tétraméthylène glycol)
Authors: Bougherara Chaabane , Boutevin Bernard , Robin Jean‐Jaques 
Published: April 2003

AbstractThis study describes the synthesis of poly(tetramethylene glycol) with amino end‐groups on both sides by chemical end modification. For this purpose, α‐hydro‐ω‐hydroxypoly(oxytetramethylene) and α‐propyl‐ω‐(3‐aminopropoxy)poly(oxytetramethylene) are converted into aromatic diamines with controlled basicity. For this, different chemical reactions are performed in order to obtain different links between aromatic amines and poly(oxytetramethylene). This method leads to products which present pKavalues between 2,8 and 5,26 in accordance with theoretical values.
Trägerkatalysatoren aus C12‐allylnickel(II)‐komplexen [Ni(C12H19)]X (X = SbF6, O3SCF3) und amorphem aluminiumfluorid in toluol als modell‐katalysatoren für das technische katalysatorsystem Ni(octanoat)2/BF3·OEt2/AlEt3 zur 1,4‐cis‐polymerisation des butadiens
Authors: Taube Rudolf , Langlotz Jochen , Müller Gert , Müller Jörn 
Published: April 2003

AbstractThe η3, η2, η2‐dodeca‐2(E), 6(E), 10(Z)‐trien‐1‐yl‐nickel(II) complexes [Ni(C12H19)]X (X = SbF6, O3SCF3) were treated in toluene with amorphous aluminium trifluoride (which was prepared from AlEt3 and BF3 · OEt2) in a mole ratio 1 : 10 to 20, forming a highly active catalyst for the 1,4‐cis polymerization of butadiene. This catalyst is comparable in its activity and selectivity, and in the molar mass distribution of the polybutadiene, with the technical nickel catalyst Ni(O2CR)2/BF3ċOEt2/AlE3 developed by Bridgestone Tire Company thirty years ago. The existence of the C12‐allynickel(II) cation [Ni(C12H19)]+ on the AlF3 support could be proved by FAB mass spectroscopic measurements. In agreement with our reaction model for the allyl nickel complex catalyzed butadiene polymerization, it is concluded that the technical nickel catalyst in its effective structure can be described as a polybutadienylnickel(II) complex co‐ordinated to a polymeric fluoroaluminate anion via a fluoride bridge.
Bright field image of banded texture in lyotropic liquid crystals of a polydiacetylene
Authors: Wang Wei , Lieser Günter , Wegner Gerhard 
Published: April 2003

AbstractFormation of a banded texture was observed in thin films of a polydiacetylene prepared from the lyotropic nematic phase subject to flow. The banded texture was experimentally investigated by polarizing light microscopy and transmission electron microscopy. The banded structure is initially formed in a nematic phase of the polymer and could be imaged by TEM after its transformation to a lamellar phase which is the polymer analogon to a smectic phase in low‐molecular‐weight compounds. A mathematical description of the texture is given. During further relaxation of the system in the lyotropic state the initial orientation is lost by the formation of disclinations.