bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermal cis‐trans isomerization and temperature‐dependent phase behaviour of polyisoprene‐polyacetylene solutions
Authors: Dai Liming 
Published: April 2003

AbstractPolyacetylene can be solubilized by making copolymers with polyisoprene via anionic polymerization of isoprene using BuLi as the initiator, followed by Ziegler‐Natta copolymerization of acetylene onto the polyisoprenyllithium chains using either Ti(OBu)4 or CoCl2. In the present study, the effects of temperature on cis‐trans isomerization of the polyacetylene blocks and the phase behaviour of the PI‐PA copolymers in solution were investigated. We found that isomerization of the cis‐polyacetylene blocks in a solution of the PI‐PA copolymer is retarded by some intramolecular barriers, making the cis‐isomer rather stable. Reducing the temperature below about 12°C was found to cause a phase transformation from the worm‐like structure to spherical micelles in solution.
Acrylonitrile‐sodium methallylsulfonate copolymer in dimethyl sulfoxide. NMR approach to the phase diagram
Authors: Viallat Annie , Margulies Monique Marie , Addad Jean‐Pierre Cohen , Thomas Michel 
Published: April 2003

AbstractThe temperature and concentration dependences of the physical state of solutions of an acrylonitrile‐sodium methallylsulfonate copolymer in dimethyl sulfoxide (DMSO) are investigated from calorimetric and NMR measurements within the temperature range where the solvent crystallization and/or polymer ordering in solution can occur. (i) For solutions of global monomeric molar fraction higher than 0.45, ordering of a fraction (<0.15) of the polymer can occur. Temperatures of polymer melting and polymer ordering are reported. The composition of the liquid phase coexisting with ordered polymer is found to depend on the global concentration of the solution. At low temperatures, i.e., at temperatures for which DMSO crystallizes, three phases are found to coexist: ordered polymer, crystalline DMSO and disordered solution. (ii) For solutions of global monomeric molar fractions smaller than 0.45, the polymer is disordered at all temperatures. Crystallization of pure DMSO is observed and the melting/crystallization curve of DMSO is determined by NMR and described with simple thermodynamic considerations.
Rheo‐optical fourier transform infrared spectroscopy of polyurethanes and their blends with polyolefins
Authors: Fischer Wolfgang B. , Pötschke Petra , Pompe Giesela , Eichhorn Klaus‐Jochen , Siesler Heinz W. 
Published: April 2003

AbstractRheo‐optical Fourier transform infrared spectroscopy was used to analyze the orientational behavior of hard and soft segments of thermoplastic poly(ether urethane)s (TPU‐Et) and poly(ester urethane)s (TPU‐Es) and their blends with a 20 mass‐% contribution of either polyethylene (PE) or polypropylene with an amorphous rubber phase (PP). The blends show a reduced stress level, lower elongation‐to‐break and a lower degree of orientation of the segments — especially for the TPU‐Es blends — compared to those of pure TPU's when uniaxially elongated. Blends of TPU‐Et with PP show reduced stress but increased strain compared to pure films of TPU‐Et. This is caused by an improved adhesion of the rubber phase in the polypropylene and the polyether phase of TPU‐Et. Optical micrographs visualize deformed polyolefin particles in elongated films of TPU‐Et/PP blends. In the TPU‐Et/PP blend we could achieve equivalent orientation for the polyolefin phase and the segments of TPU‐Et caused by this higher phase adhesion compared to the other blends. Orientation functions (OF's) of absorption bands which specifically represent hard or soft polyurethane segments or which are characteristic of the polyolefin phase have been calculated to monitor the molecular alignment due to the mechanical treatment.
Photoreactive diimide models of benzhydroltetracarboxylic dianhydride: Synthesis, characterization and photopolymerization
Authors: Rames‐Langlade Géraldine , Monjol Pierre , Sekiguchi Hikaru , Mercier Régis , Sillion Bernard 
Published: April 2003

AbstractThe synthesis, characterization and photopolymerization of bisimide compounds carrying a photoreactive methacryloyl group were investigated. Those photoreactive diimide models, derived from benzhydroltetracarboxylic dianhydride (1), were prepared in N‐methyl‐2‐pyrrolinone (NMP), either by a thermal or by a chemical imidization. In the thermal method, the bisimide carrying benzhydrol group was first synthesized by condensation of 1 with 4‐tert‐butylaniline at 180°C. The hydroxyl group was then chemically modified by an excess of methacryloyl isocyanate (6) in NMP. In the chemical method, a photosensitive dianhydride, derived from the reaction between 1 and 6, was prepared and then condensed with aniline at 25°C by means of propionic anhydride with triethylamine, which leads to the formation of the corresponding imide. By means of IR, the photopolymerization of the methacrylic double bond that takes place in the presence of a photoinitiator under irradiation at 365 nm was then investigated. It was found that the most effective photoinitiator for these photoreactive model compounds is the Michler's ketone/triethanolamine system. The further aim of the present investigation is to prepare novel negative‐type photosensitive polyimides.
Determination of the polydispersity of poly(tetramethylene ether) glycol by means of high‐performance liquid chromatography and curve fitting
Authors: Graf Hermann , Schulz Günter , Plitzko Klaus‐Dieter 
Published: April 2003

AbstractA modified high‐performance liquid chromatographic method for the analysis of the molecular weight distribution of poly(tetramethylene ether) glycol (PTMEG) is described. The weight percentage of the polymer homologues, up to a degree of polymerization X of 79, can be determined. This covers about 93 wt.‐% of the material with number‐average molecular weight M̄n = 1000, but only 65 wt.‐% of that with M̄n = 2000. Direct calculation of the means M̄n, M̄w, and M̄z from these percentages leads to erroneous results because of the neglect of the summands with X > 79. Therefore, a curve fit is performed and M̄n, M̄w, and M̄z are calculated from the fitting parameters. From the known molecular weight distribution functions, Wesslau's and Kubin's function yielded the best fit. The results of this method are compared with those of gel permeation chromatography, viscosimetric measurements, supercritical fluid chromatography, matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry, and evaporative light scattering detector methods. The scope and the limitations of this method are discussed.
Liquid crystalline siloxane macromolecules with steroidal mesogens
Authors: McHugh Colin M. , Tomlin David W. , Bunning Timothy J. 
Published: April 2003

AbstractSeveral new vinyl and allyloxybenzoate steroidal‐based mesogens were synthesized and attached to cyclic tetramethylhydrosiloxane rings using standard hydrosilation chemistry. The steroids examined, all derivatives of cholesterol, 3β‐hydroxy‐24α‐ethylcholest‐5,22‐diene, 3α‐hydroxyandrostan‐17‐one, 3β‐hydroxyandrostan‐17‐one, and 3β‐hydroxypreg‐5‐en‐20‐one were chosen because structural variations in the 17‐β aliphatic chain of the tetracyclic core were present. The synthesis and phase behavior of these mesogenic compounds are discussed with respect to previous systematic investigations linking structural features to mesomorphic behavior. Macromolecular cyclic siloxanes derivatized with these steroidal mesogens were characterized for liquid crystallinity using differential scanning calorimetry (DSC), polarized optical microscopy (POM), and X‐ray diffraction. Compounds with 17‐β ketone substituents possessing vinylbenzoate spacer groups do not exhibit liquid crystallinity, whereas similar compounds with allyloxybenzoate spacer units exhibit broad smectic mesophases. The ability to from partially or fully interdigitated layered mesophases with respect to the 17‐β substituent is examined using X‐ray diffraction. The results indicate the length and flexibility of the 17‐β group must be considered along with the nature of the spacer group in determining phase behavior.
Infrared spectra and compositional analysis of styrene/2‐ethylhexyl acrylate copolymers
Authors: Chatzi Eleni G. , Kammona Olga , Kentepozidou Anastasia , Kiparissides Costa 
Published: April 2003

AbstractCompositional analysis of a series of free‐radical emulsion polymerized styrene/2‐ethylhexyl acrylate copolymers following close to random polymerization statistics was accomplished by elemental analysis, UV and IR. A satisfactory agreement was obtained between the three independent techniques. IR calibration curves were constructed based on sequence‐independent infrared absorption bands determined by plotting peak intensities against the number fraction of each of the possible monad, dyad and triad structures in the copolymers. The intensities of the skeletal ring breathing vibration of styrene units at 1 602 cm−1 as well as the CO stretching vibration of the saturated ester group of 2‐ethylhexyl acrylate units at 1158 cm−1 were shown to be representative of the copolymer composition, whereas the position and shape of the carbonyl stretching band at 1730 cm−1 were shown to depend on both the composition and the monomer sequence distribution. A calibration curve not requiring the use of an internal thickness band was obtained by plotting the ratio of absorbances of the 1 602 cm−1 and the 1 158 cm−1 peaks as a function of the mole ratio of the corresponding monomers in the copolymer.
Synthesis of block copolysaccharides by ring‐opening polymerization of anhydro sugar derivatives
Authors: Choi Yoon Soung , Uryu Toshiyuki , Yoshida Takashi 
Published: April 2003

AbstractRing‐opening polymerization of anhtydro sugar derivatives was carried out with Lewis acid catalysts to produce block copolysaccharides. Polymerization of 1,4‐anhydro‐2,3‐diO‐tert‐butyldimethylsilyl‐α‐D‐ribopyranose (ADSR) with boron trifluoride etherate proceeded linearly and rapidly within 1 h to give silylated 1,5‐α‐D‐ribofuranan in almost quantitative yield. Although the molecular weight distribution of the polymers was not narrow (M̄w/M̄n = 1.61 ∼ 1.73), the relationship between monomer conversion and number‐average molecular weight was linear, indicating livingness of the ring‐opening polymerization. Thus, an AB block copolysaccharide composed of two different polysaccharide chains was synthesized for the first time in the two‐stage polymerization of ADSR and 1,4‐anhydro‐2,3‐di‐O‐benzyl‐α‐D‐ribopyranose (ADBR) at −40°C. Block copolysaccharides having different stereoregular monomeric units (i.e., ribopyranosidic and ribofuranosidic units) were obtained by block copolymerization of 1,4‐anhydro‐2,3‐O‐benzylidene‐α‐D‐ribopyranose (ABRP) and ADBR. In addition, a block heteropolysaccharide consisting of (1 → 5)‐α‐D‐xylofuranan and (1 → 5)‐α‐D‐ribofuranan was prepared from 1,4‐anhydro‐2,3‐di‐O‐tert‐butyldimethylsilyl‐α‐D‐xylopyranose (ADSX) and ADBR by making use of this polymerization technique. The GPC curves of block copolymers shifted toward the higher molecular weight region, maintaining the molecular weight distributions of the corresponding homopolymers in the first stage of polymerization. The number‐average degree of polymerization of the polyADSR‐block‐polyADBR was estimated to be 113 for ADSR and 221 for ADBR unit. The 13C NMR spectra of the resulting block copolymers were different from those of the random copolymers.
Polyanhydrides 10. Aliphatic polyesters and poly(ester‐anhydride)s by polycondensation of silylated aliphatic diols
Authors: Kricheldorf Hans R. , Gomourachvili Zaza 
Published: April 2003

AbstractA new class of biodegradable copolyesters was prepared by polycondensation of sebacoyl chloride with mixtures of silylated isosorbide and silylated O,O′‐bis(2‐hydroxyethyl)hydroquinone in bulk. A class of poly(ester‐anhydride)s was synthesized from sebacoyl chloride and mixtures of silylated O,O′‐bis(2‐hydroxyethyl)hydroquinone and silylated 4‐hydroxybenzoic acid. A second class of poly(ester‐anhydride)s was obtained by polycondensation of sebacoyl chloride with mixtures of silylated isosorbide and silylated 4‐hydroxybenzoic acid. The molar ratio of anhydride and ester groups was varied via the proportion of 4‐hydroxybenzoic acid in the feed. All polyesters were characterized by inherent viscosities, elemental analyses, 1H NMR and IR spectra, WAXS and DSC measurements. All polyesters proved to be semicrystalline materials.
Molecular characterization and chain flexibility of linear polyacetals containing poly‐perfluoro(oxymethylene‐ran‐oxyethylene) macromers
Authors: Turri Stefano , Sanguineti Aldo , Levi Marinella 
Published: April 2003

AbstractProper samples of polyacetals containing poly‐perfluoro(oxymethylene‐ran‐oxye‐thylene) macromers were synthesized by polycondensation of a fluorinated macrodiol (Fomblin ®ZDOL) and formaldehyde and fractionated by solvent/non‐solvent separation. Of eight selected fractions, whose compositional homogeneity was checked by 19F and 13C NMR spectroscopy, the following measurements were performed: Mw by static light scattering; retention volume Vr at GPC; [η] by conventional capillary viscometry; glass transition temperature by DSC. 1,1,2‐Trichlorotrifluoroethane was used for solution measurements, from which the second virial coefficient A2, the linear Mw−Vr equation of GPC calibration, and the [η]‐Mw Mark‐Houwink‐Sakurada constants K and a were determined. From [η] and Mw data, the Kθ value (unperturbed state) was estimated by the Stock‐mayer‐Fixman‐Burchard extrapolation procedure, and the characteristic ratio C∞ of polyacetals containing poly‐perfluoro(oxyethylene‐ran‐oxymethylene) macromers was calculated through the Fox‐Flory equation. Factors related to chain flexibility were finally discussed and compared with those of corresponding fully perfluorinated copolyethers.
Etude de la dégradation thermique de deux copolymères réalisés entre l'acrylonitrile ou le méthacrylonitrile et l'α‐acétoxyacrylate de méthyle. Analyse thermogravimétrique et chromatographique en phase gazeuse couplée à la spectrométrie de masse
Authors: Ouillon Isabelle , Raihane Mustapha , Zerroukhi Amar , Bionon Bernard 
Published: April 2003

AbstractThe thermal degradation behaviour of two copolymers poly(acrylonitrile‐co‐methyl α‐acetoxyacrylate) and poly(methacrylonitrile‐co‐methyl α‐acetoxyacrylate) was studied by means of dynamic and isothermal thermogravimetry in the range 246–302°C and gas chromatography/mass spectrometry analysis. The main volatil products are acetic acid and methyl acetate and methanol in minor amounts. There is no monomer from the first copolymer. The global reaction order is zero over a wide range of conversion (α = 0,1 – 0,6), then it is one for α > 0,7, with activation energies of 160,5 and 142,9 kJ ˙ mol−1, respectively. Some amount of comonomers was found in addition in the case of the second copolymer. The kinetic law may be written as:

where A and C are constants for every temperature. The global activation energy was found to be 127,0 kJ ˙ mol−1. A kinetic model of a one order reaction with a partial auto catalytic character allows a very good fit of the experimental data with the theoretical curves over a wide range of conversion (α = 0,1–0,8).
Liquid crystal properties of poly(2‐vinylpyridine) fully quaternized with a mesogenic group
Authors: Bravo‐Grimaldo Elda , Navarro‐Rodriguez Dámaso , Guillon Daniel 
Published: April 2003

AbstractTwo poly(2‐vinylpyridine)s fully quaternized with a ω‐(4′‐methoxy‐4‐biphenylyloxy)‐alkyl group (alkyl chain of 9 and 11 carbon atoms) have been synthesized by the well known spontaneous polymerization of vinylpyridinium salts. When heated, these polymers (P2VPC9 and P2VPC11) show thermotropic liquid crystal properties. According to the X‐ray diffraction data, the observed smectic mesophase in both polymers is of the type A (SA). Results are discussed in comparison with other molecular and polymeric pyridinium salts previously described. A molecular arrangement model for the P2VP derivatives is proposed.
Methylaluminoxane: NMR analysis, cryoscopic measurements and cocatalytic ability in ethylene polymerization
Authors: Tritto Incoronata , Méalares Christel , Sacchi Maria Carmela , Locatelli Paolo 
Published: April 2003

AbstractMethylaluminoxane (MAO) solutions containing known amounts of AlMe3 and solutions of different MAO samples were characterized by several methods: (a) low temperature 13C NMR analysis; (b) determination of the molecular weight of the MAO samples by cryoscopy in benzene; (c) titration of AlMe3 using 31P NMR analysis of the AlMe3 · PPh3 complex (PPh3 = triphenylphosphine) formed after addition of defined amounts of PPh3 to the MAO solutions. The results confirm the disproportionation reaction caused by AlMe3 addition. The MAO molecular weights are shown to decrease after the AlMe3 addition according to a linear relationship.The cocatalytic ability of these characterized MAOs was tested in ethylene polymerization catalyzed by rac‐Et(ind)2ZrCl2 (ind = indenyl) and the influence of the AlMe3 content, the “type” and the “aging” of MAO is correlated to the cocatalytic performance.
Synthesis and characterization of poly(arylene ether sulfone amide)s
Authors: Hsiao Sheng‐Huei , Huang Perng‐Chih 
Published: April 2003

AbstractMethyl‐substituted or unsubstituted aromatic dicarboxylic acids and diamines containing ether and sulfone linkages between phenylene units were used alone or in combination with p‐phenylenediamine, m‐phenylenediamine, terephthalic acid, and isophthalic acid to prepare flexible or semirigid aromatic polyamides by direct polycondensation activated by triphenyl phosphite and pyridine. The inherent viscosities of the obtained polymers ranged from 0.40 to 1.01 dL/g. The wholly flexible polyamides are amorphous, are readily soluble in N,N‐dimethylacetamide, dimethyl sulfoxide, and m‐cresol, and can afford transparent, flexible, and tough films by solution‐casting. The polyamides prepared from p‐phenylenediamine or terephthalic acid are partially crystalline and melt around 410°C. Differential scanning calorimetry shows glass transition temperature in the 202–255°C range for the wholly flexible polyamides. All the polyamides are thermally stable in excess of 400°C. The methyl‐substituted polyamides had higher glass transition temperatures, but lower initial decomposition temperatures, than the corresponding unsubstituted polyamides.
Preparation of hydrolyzed pH responsive ion track membrane
Authors: Tamada Masao , Asano Masaharu , Spohr Reimar , Vetter Johann , Trautmann Christine , Yoshida Masaru , Katakai Ryouichi , Omichi Hideki 
Published: April 2003

AbstractThe porous copolymer films of N‐methacryloyl‐L‐alanine methyl ester and diethyleneglycol‐bis‐allylcarbonate (diallyl oxydiethylene dicarbonate) were hydrolyzed with 1 M NaOH solution for 40 min at 25°C. The pores of the films showed pH response in diameter. The pore diameter of 3,7 μm in the buffer solution of pH 3 was closed completely at pH 5.
Transcrystallinity of thin films of isotactic poly(propylene)
Authors: Setz Stefan , Schnell Rupert , Thomann Ralf , Kressler Jörg , Mülhaupt Rolf 
Published: April 2003

AbstractThe isothermal crystallization behavior of thin films of isotactic poly(propylene) between plates coated with chromium, Teflon® or gold is studied by polarized light microscopy. At all contact surfaces between poly(propylene) and the other materials, transcrystallinity can be observed and competes with the growth of entities which originate in the bulk phase. The shape of these entities can be described by two intersecting paraboloids.
Synthesis of soluble, all‐trans poly(2,5‐diheptyl‐p‐phenylenevinylene) via metathesis polycondensation
Authors: Thorn‐Csányi Emma , Kraxner Peter 
Published: April 2003

AbstractThe synthesis of substituted poly(p‐phenylenenvinylene) (PPV) was carried out via metathesis polycondensation of 2,5‐diheptyl‐1,4‐divinylbenzene (DHepDVB). A stable molybdenumcarbene complex served as catalyst. The preparation of the educt employed (DHepDPV, 3a) is described. The obtained poly(2,5‐diheptyl‐1,4‐phenylenevinylene) (DHepPPV, 5), an intensely yellow product, has an all‐trans‐configuration and, with a degree of polymerization of ≈ 10 is soluble in conventional organic solvents.
Spectroscopic investigation of diacetylene cross‐linking in polyamide matrices of different configurations
Authors: Gerasimov Genrikh N. , Popova Elena L. , Phomin Sergey M. , Kiryanova Tatyana V. , Teleshov Eduard N. 
Published: April 2003

AbstractWe compared the cross‐polymerization of diacetylene units, incorporated in different ways into polyamide (PA) matrices: as fragments of the PA main chains (PA1) and as pendant groups of the PA main chains (PA2). At room temperature the reaction proceeds only in PA1 via 1,4‐addition (cross‐links I). However at high temperature besides of cross‐links I another type of cross‐links (cross‐links II) is formed, presumably via 1,2‐addition reaction. In PA2 only cross‐links of type II are formed at high temperatures.
A phase polymorphism NSAdI in liquid‐crystalline polymethacrylates with 4′‐trifluoromethoxyazobenzene mesogenic side groups
Authors: Ruhmann Ralf , Thiele Thomas , Prescher Dietrich , Wolff Dietmar 
Published: April 2003

AbstractThe mesophase behaviour of liquid‐crystalline polymethacrylates with 4′‐trifluoromethoxyazobenzene mesogens and alkylene spacers \documentclass{article}\pagestyle{empty}\begin{document}$ \left( {\rlap{--} ({\rm CH}_{\rm 2} \rlap{--} )_n ,n = 2 - 6} \right) $\end{document} in the side chains was investigated and compared with that of the corresponding non‐fluorinated polymers. The fluorinated polymers with spacer lengths n = 5 and 6 are the first side‐group liquid‐crystalline polymethacrylates showing a nematic phase below a smectic A phase.
Self‐oscillating swelling and deswelling of polymer gels
Authors: Yoshida Ryo , Ichijo Hisao , Hakuta Toshikatsu , Yamaguchi Tomohiko 
Published: April 2003

AbstractNovel gel systems demonstrating rhythmically pulsatile mechanical motion similar to that of a heartbeat were developed. Self‐oscillations of swelling and deswelling for the polymer hydrogels were realized by coupling pH and temperature sensitive hydrogels with a non‐linear chemical reaction in the external solution media. The novel gel dynamics exhibiting cyclic and rhythmical oscillations may establish a new concept for functional materials that work under dynamic oscillating states.
Amphiphilic liquid‐crystalline networks — phase behavior and alignment by mechanical fields
Authors: Fischer Peter , Schmidt Claudia , Finkelmann Heino 
Published: April 2003

AbstractA cross‐linked polysiloxane carrying non‐ionic amphiphilic side‐groups attached with their hydrophobic end to the polymer backbone is synthesized. The amphiphilic groups are selectively deuterated at the α‐position of the hydrophobic alkyl chains. The phase behavior with water is studied by deuterium nuclear magnetic resonance spectroscopy. A lamellar phase (La) is observed on the low‐water‐concentration side of the liquid‐crystalline regime. The domains of the La‐phase can be aligned macroscopically by uniaxial compression of the sample.
Transition metal catalyzed ring‐opening polymerization of silicon‐bridged [1]ferrocenophanes at ambient temperature
Authors: Ni Yizeng , Rulkens Ron , Pudelski John K. , Manners Ian 
Published: April 2003

AbstractA new route to poly(ferrocenylsilanes) under mild conditions via the ring‐opening polymerization of silicon‐bridged [1]ferrocenophanes is presented. Catalytic amounts of the transition metal complexes [Rh(cyclooctene)2(μ‐Cl)]2, Pd(1,5‐cyclooctadiene)Cl2, PdCl2 and PtCl2 in C6D6 at room temperature afforded high molecular weight poly(ferrocenylsilanes) (2). In some cases a symmetrical dimer (3) was obtained as a byproduct.