bluuebunny/crossref_metadata_2025_split huggingface dataset:
Chloro‐ionenes from dichlorides and tertiary diamines
Authors: Bortel Edgar , Kochanowski Andrzej 
Published: April 2003

AbstractFive new ionenes were synthesized from tertiary diamines and dihalides. For comparison, four bromo‐ionenes were also prepared. Due to a lower C‐Br bond energy the bromo‐ionenes can be prepared from alkylene dibromides and tertiary diamines, whereas in case of chloroionenes the presence of electronegative atoms or groups of atoms in the dichlorides proved to be the condition to ensure reaction under moderate conditions. The highest initial reaction rates and lowest energies of activation (27,2–35,5 kJ/mol) were observed in runs with 1,3‐dichloro‐2‐propanon (1). Similarly, bis(2‐chloroethyl) ether (2a) proved to be a convenient dihalide for the formation of chloro‐ionenes, displaying reactivities comparable with those of 1,6‐dibromohexane. All reaction orders referring to the preparation of bromo‐ionenes investigated, were found to be about 2, whereas the formation of chloro‐ionenes is first order. In case of bromoionenes the energies of activation were higher (66,7–79,8 kJ/mol) than in the case of chloroiones (27,2–51,8 kJ/mol). The structure of tertiary diamines plays an important role as far as their basicity is concerned, influenced by resonance conjugation, which is the case with Michler's ketone (5) as well as with tetramethylurea (6). The ionenes resulting from the dihalides and tertiary amines proved to be oligomers.
Structure of active centers and mechanism of anionic and cationic polymerization of δ‐valerolactone
Authors: Hofman Andrzej , Slomkowski Stanislaw , Penczek Stanislaw 
Published: April 2003

AbstractThe determination of the structure of the end groups in poly(δ‐valerolactone) (poly(δVL)) by using 1H, 31P NMR, and IR spectroscopy showed that in the cationic polymerization of δVL, propagation proceeds via cyclic dialkoxycarbenium ions as active species and the monomer molecules are incorporated into the polyester chains by an alkyl‐oxygen bond scission. In the anionic polymerization of δVL, propagation proceeds via alcoholate anions and monomer molecules are added with breaking the acyl‐oxygen bond. A similar cationic mechanism operates with alkylating ((CH3)2I⊕SbF6⊖) and acylating (CH3CO⊕SbF6⊖) initiators. However, with the latter, the cyclic dialkoxycarbenium active centers coexist with the acylium cations during the initial period of polymerization. Finally, however, the cyclic dialkoxycarbenium ions become the only active species. The mechanisms of ionic propagation in the polymerization of β‐propiolactone, δ‐valerolactone, and ε‐caprolactone are compared.
Polymerisationsauslösung mit substituierten Ethanen, 10. Kinetik der Polymerisation von Styrol
Authors: Bledzki Andrzej , Braun Dietrich , Titzschkau Klaus 
Published: April 2003

AbstractThe rate of the free radical polymerization of styrene with substituted ethanes as initiators is characterized by a competition of “normal” and primary radical termination. With decreasing initiator concentration the reaction order with respect to monomer and initiator changes in favour of a normal termination. The kinetics of this polymerization process is derived and compared with experimental results.
Untersuchungen über Poly(arylenvinylene), 30. Synthese, Photoleitfähigkeit und Redox‐Verhalten von Poly(9‐methylcarbazol‐3,6‐diyl‐1,2‐diphenylvinylen)
Authors: Hörhold Hans‐Heinrich , Räthe Harald , Helbig Manfred , Opfermann Johannes 
Published: April 2003

AbstractSoluble poly(9‐methylcarbazole‐3,6‐diyl‐1,2‐diphenylvinylene) (1) Mn = 10000, was prepared by dehalogenating polycondensation of 3,6‐bis(α,α‐dichlorobenzyl)‐9‐methylcarbazole with chromium(II) acetate. The monomer was obtained from 3,6‐dibenzoyl‐9‐methylcarbazole by reaction with PCl5. The chemical structure of 1 was verified by elemental analysis, UV, IR, and NMR spectroscopy, GPC, and VPO. 1 was found to be highly photoconducting, exhibiting a dark conductivity of 10−14 S/cm, which increases on doping with AsF5 to 10−4 S/cm. Its thermal stability under nitrogen is as high as with other phenylsubstituted poly(arylenevinylene)s (dec. temp.: 540°C; residue: 72 weight‐%). The spectral distribution of sensitized (TNF, dyes) photoconductivity was studied and the redox behaviour was investigated by cyclovoltammetry. The redox potentials were found to be E = 0,90 V and E = −2,07 V (vs. Ag/AgCl). The electrochemical oxidation is reversible, associated with the formation of polydications derived from chain segments which consist of two carbazolediylvinylene units. Thus, 1,2‐dicarbazole‐3‐yl‐1,2‐diphenylethylene as model compound well reflects the redox properties of the polymer. The electrochemical band gap energy was found to be 2,97 eV, which agrees closely with the energy of the optical absorption edge of 3,04 eV.
Macromonomer synthesis. New functionalization methods
Authors: Gnanou Yves , Rempp Paul 
Published: April 2003

AbstractSo far, the syntheses of macromonomers by end‐capping of “living” anionic polymers with unsaturated electrophiles, were not always quantitative. Now, we found that macromonomers with unsaturated end groups can be smoothly prepared with quantitative yields from ω‐hydroxy‐poly(ethyleneoxide)s (PEO) applying methods of peptide synthesis. The intermediate PEO with carboxylic, p‐toluenesulfonate or chlorocarbonyl end groups were prepared with quantitative yields. They were transformed into the 4‐vinylphenyl substituted PEO macromonomers by reaction with 2‐(4‐vinylphenyl)ethanol or 4‐vinyl‐aniline, in quantitative yields, in the presence of dicyclohexylcarbodiimide and 1‐hydroxybenzotriazole or triethylamine, respectively. PEO with methacryloyl end groups were prepared from ω‐hydroxy‐PEO and 2‐isocyanato ethyl methacrylate. The resulting macromonomers were characterized by determination of the double bond content and by 1H NMR spectroscopy.
Ein Modell zur Beschreibung reversibler Copolymerisationen
Authors: Krüger Hartmut , Bauer Jörg , Rübner Joachim 
Published: April 2003

AbstractThe reversible copolymerization is described by a model derived from simple kinetic assumptions. The copolymerization behaviour of a system can be calculated from 3 experimental parameters: composition of the monomer mixture, composition and diade distribution of the copolymer. Four additional model constants represent the connection with the thermodynamics of reversible copolymerization. The model leads to the same results as the Monte‐Carlo method described in the literature. The temperature dependence of reversible copolymerizations can be simulated by the model with the thermodynamic values of the four elementary reactions.
Application of the penultimate model in the copolymerization of styrene with maleic anhydride in ethyl methyl ketone at 50°C
Authors: Brown Anthony Stuart , Fujimori Kiyohisa 
Published: April 2003

AbstractComposition data for the copolymerization of styrene with maleic anhyride in ethyl methyl ketone at 50°C were obtained using a non‐aqueous potentiometric direct titration method, and were analysed using a non‐linear least squares optimization routine. Three variants of the penultimate model were fitted to the data: the four variable model (completely general), the three variable model (rmm = 0,0) and the more usual two variable model (rmm = rsm = 0,0). Of these, the two variable model was adequate to describe the data. Best estimates of the reactivity ratios for data previously reported in the literature were calculated, and in one case the best values were markedly different to those originally given.
Crystallization, morphology, and thermal behaviour of ethylene/propylene copolymers
Authors: Greco Roberto , Mancarella Carlo , Martuscelli Ezio , Ragosta Giuseppe , Yin Jinghua 
Published: April 2003

AbstractThe morphology and the texture of thin films of ethylene/propylene copolymers with crystallizable polypropylene blocks was investigated by optical and electron microscopy as a function of both molecular composition and crystallization conditions. The thermal and melting behaviour was also studied. It was found that variables such as the observed melting point as well as the enthalpy and the entropy of fusion are composition dependent. Contrary, the equilibrium melting temperature seems to be invariant with composition in agreement with the block type of the investigated copolymers.
Immobilisierung von geschützten nucleosiden und mononucleotiden an funktionalisierte perlcopolymerisationsprodukte aus methylacrylat und 1,4‐bis(vinyloxy)butan
Authors: Schott Herbert , Bretzger Waltraud 
Published: April 2003

AbstractProtected nucleic acid components were coupled to eight differently functionalized bead copolymers, prepared from methyl acrylate and 1,4‐bis(vinyloxy)butane, via amid‐, urea‐, phosphotriester‐ or carboxylic acid ester linkages. The immobilization was performed by methods used in nucleic acid chemistry. The obtained gels carry 1 to 300 μmol per gram of nucleoside or nucleotide derivatives. The yield of derivatization was found to be first of all determined by steric effects of the gel matrix, the size of the nucleic acid component and the route of synthesis selected. Anchor groups, arranged via long spacers, were not effective for the immobilization of nucleic acid components. A “carboxylate‐gel” which can immobilize 300 μmol per gram of a nucleoside derivative may serve as support in the solid phase synthesis of oligonucleotides in large scale.
Spectroscopic characterization of the chromic transition observed for polydiacetylenes
Authors: Coyne Laurence D. , Chang Chih , Hsu Shaw Ling 
Published: April 2003

AbstractThe chromic transition observed for polydiacetylene CHCl3/CCl4 solutions was found to be concentration dependent suggesting a need to reconsider the hypothesis that this transition is a single chain phenomenon. We also found that for some polydiacetylene solutions this chromic transition exhibits a significant amount of hysteresis for the cooling and heating cycles.
Cinétiques de télomérisation, 8. Détermination de la constante de transfert du phosphonate de diéthyle — effets de solvants
Authors: Bauduin Gérard , Boutevin Bernard , Pucci Bernard , Rigaud Jean‐Pierre 
Published: April 2003

AbstractThe transfer constant of diethyl phosphonate to vinyl acetate for free‐radical polymerization at 60°C in non‐aromatic solvents was found to be CT = 0,035. For aromatic solvents CT varies with the concentration of the solvent.
Translational diffusion of small molecules in polymers. Laser flash experiments with polydimethylsiloxanes
Authors: Tilley Mark , Pappas S. Peter , Schnabel Wolfram 
Published: April 2003

AbstractThe quenching of triplet‐excited acetophenone by naphthalene served as a probe reaction for studying the mobility of small molecules in polymeric matrices. The rate constants of the quenching process in polydimethylsiloxanes having weight‐average molecular weights between 3600 and 86000 were found to depend only slightly on the macroscopic viscosity η at constant temperature: kq ∝η −0,1. In the temperature range from 190 to 298 K (Tg = 152 K), the activation energy of the quenching reaction was determined as Eq = 15,1 kJ/mol, i.e. it is practically equal to the value of the activation energy of viscous flow. The high translational mobility of small molecules in very viscous polymeric matrices is explained on the basis of the concept of microviscosity according to which the trnaslational motion of small molecules in polydimethylsiloxanes at T > Tg is determined by the mobility of free volume elements due to segmental motions rather than by motions of the centers of mass of the macromolecules.
Chemical‐composition distribution of a diblock copolymer
Authors: Stejskal Jaroslav , Kratochvíl Pavel 
Published: April 2003

AbstractThe experimentally determined distribution of the chemical composition of styrene/butadiene block copolymers reported by Kuhn is compared with the results of a model calculation assuming that the constituent blocks have a gamma (Schulz‐Zimm) distribution of molecular weights and the ratios of weight‐ to number‐average molecular weights are M̄w/M̄n = 1,025 or M̄w/M̄n = 1,05. A good agreement is found between experimental and calculated distributions.
The effect of polymolecularity on the radius of gyration of stiff polymer chains
Authors: Petrus Vladimír , Bohdanecký Miloslav , Bareiss Rolf E. 
Published: April 2003

AbstractThe z‐average of the unperturbed mean‐square radius of gyration, 〈S2〉o,z, is calculated for polymolecular Kratky‐Porod worm‐like chains, commonly used to represent stiff polymer chains. Polymolecularity correction factors for the Schulz‐Zimm and logarithmic normal distribution functions are tabulated. By contrast with those for unperturbed random coils, they depend significantly on the chain length.
Monte‐Carlo‐simulation for the structure of copolymer molecules of chemical inhomogeneity of second type
Authors: Wittmer Paul , Schmitt Burghard J. 
Published: April 2003

AbstractA method is discussed for Monte‐Carlo‐simulation of copolymer molecules with chemical inhomogeneity of the second type. The copolymer molecules are formed by a polyreaction with monomer addition without chain termination, e.g. in case of an anionic “living” polymerization. The reliability of the method was statistically tested with examples. The method allows a clear presentation of the copolymer molecules mentioned in the paper.
Polymerization of sodium 10‐undecenoate under irradiation of UV light
Authors: Arai Kenichiro , Sugita Junichi , Ogiwara Yoshitaka 
Published: April 2003

AbstractThe polymerization of sodium 10‐undecenoate (UA‐Na) under irradiation of UV light was found to proceed effectively in a certain concentration range of UA‐Na. Based on the viscosity behavior of UA‐Na aqueous solutions, the effective polymerization is related to the formation of a specific type of micelle, which enhances the rate of chain propagation by localization of the double bonds of UA‐Na molecules within the micelle core. Weight‐average (M̄w) and number‐average (M̄n) molecular weights of the polymer are in the ranges of 3400–1900 and 2350–1300, respectively, depending on the concentration of UA‐Na in the polymerization system. Distribution of the molecular weight of poly(UA‐Na) is rather narrow for a radical polymerization (M̄w/M̄n ≈ 1,4). It was found that the maximum amount of benzene soluble in the aqueous solution of poly(UA‐Na) is smaller than in the aqueous solution of UA‐Na, and that poly(UA‐Na) can solubilize benzene already at very low concentration.
New synthesis of polysulfide polymers: Kinetic study
Authors: Catala Jean‐Marie , Pujol Jean‐Marc , Brossas Jean 
Published: April 2003

AbstractNew polysulfide polymers were prepared by a new process from vinyl monomers, elemental sulfur, and sodium metal in THF. The kinetic study of the reactions at −40°C has shown that the overall process can be described by the competition between a slow reaction (initiation of the monomer by the alkali metal) and a fast reaction (deactivation of the carbanion formed by elemental sulfur). These reactions lead to the establishment of a carbanion stationary state. From this data, the orders of magnitude of the apparent deactivation rates of the different carbanions were obtained: ca. 105 1·mol−1·s−1 for the styrene carbanion and 103–104 1·mol−1·s−1 for the butadiene carbanion.
Synthesis and characterization of photoconductive polymers, 1. Synthesis of poly[2‐(9‐carbazolyl)ethyl vinyl ether], poly[2‐(9‐carbazolyl)ethyl 1‐propenyl ether], and their various copolymers with ethyl vinyl ether
Authors: Haque Shah A. , Uryu Toshiyuki , Ohkawa Haruki 
Published: April 2003

Abstract2‐(9‐Carbazolyl)ethyl vinyl ether (1), a known vinyl monomer, was synthesized using a phasetransfer catalyst, and homopolymerized with BF3OEt2 or EtAlCl2.2‐(9‐Carbazolyl)ethyl 1‐propenyl ether (2) was synthesized by transetherification of ethyl 1‐propenyl ether with 9‐(2‐hydroxyethyl)carbazole in a yield of 34% as a mixture of 49% cis and 51% trans isomer. It was homopolymerized in 90% yield with EtAlCl2 in toluene at −25°C. Copolymerization of 1 or 2 with ethyl vinyl ether (3) were initiated with BF3OEt2 or EtAlCl2. The yields of copolymers were 78–93%, depending on the polymerization conditions. The solubility of both homo‐ and copolymers was found to be poor. The glass transition temperatures of poly(1‐co‐3) and poly(2‐co‐3) are much lower, than those of poly(1) and poly(2).
Studies in electroactive polymers, 3. Synthesis of cyclopentene/acetylene copolymers using metathesis catalysts
Authors: Farren Trevor R. , Amass Allan J. , Beevers Martin S. , Stowell Jonathan A. 
Published: April 2003

AbstractCopolymers containing acetylene and pentenamer units were synthesized by sequential addition of cyclopentene and then acetylene to an active metathesis catalyst system. The formation of block copolymers was indicated by UV‐vis spectroscopy, gel permeation chromatography and infra‐red spectroscopy.
Moisture‐curable rubbers, 4. Moisture‐cure of chloroprene rubber
Authors: Yamashita Shinzo , Nakawaki Yuichi , Kidera Akinori 
Published: April 2003

AbstractChloroprene rubber (CR) was allowed to react with 3‐aminopropyltriethoxysilane (APS) and then cured by soaking in hot water. The moisture‐cured rubber showed a network‐chain density of 3,6·10−4 mol·cm−3 and a tensile strength at break of 10 MPa. The reaction of CR with APS was found to be a Menshutkin reaction. The activation energy and the frequency factor were 59 kJ·mol−1 and 4,3·104 l·mol−1·s−1, respectively.
Solution properties of poly(methyl methacrylate) in methyl methacrylate, 1. Viscosities from the dilute to the concentrated solution regime
Authors: Stickler Manfred , Panke Dietrich , Wunderlich Winfried 
Published: April 2003

AbstractThe viscosities of samples of poly(methyl methacrylate), PMMA, with narrow molecular weight distributions and with molecular weights in the range 1,75·104 < M̄w < 1,60.106 were measured in methyl methacrylate, MMA, as solvent at 20, 40, and 60°C in the dilute and in the semi‐dilute concentration regime. By extrapolation to zero polymer concentration the limiting viscosity numbers and therefrom the Mark‐Houwink‐Kuhn‐Sakurada parameters for PMMA in MMA were obtained. In addition, unperturbed dimensions were determined from dilute solution viscosity data. Together with some published results for more concentrated solutions of PMMA in MMA the viscosities of the semi‐dilute systems were analysed in terms of scaling theories. It was found that irrespective of temperature, polymer concentration, and molecular weight all data could be quite well fitted by a single master curve when the relative viscosity η/η0 was plotted as a function of the product of the intrinsic viscosity and mass concentration [η]·c. No sharp transitions between different concentration regimes were observed, however, and the scaling law exponents for the entangled solution are significantly higher than predicted by theory.
Fourier transform infrared spectroscopic study of polyacetylene, 2. Thermal isomerization kinetics and mechanism
Authors: Chen Zhongxin , Shen Zhiquan , Liu Min , Shi Mingxiao , Hummel Dietrich O. 
Published: April 2003

AbstractThermal isomerization kinetics of high Z (>90%) rare‐earth polyacetyleneIUPAC name: poly(vinylene).
was studied by Fourier transform infrared spectrophotometry in the temperature range of 354 to 443 K. The isomerization kinetics do not follow any simple kinetic reaction order; the apparent activation energy was determined to be 48,1 kJ·mol−1. The Z to E isomerization in polyacetylene is discussed in terms of a diradical two‐step mechanism.
Infrared spectra and crystallinity of isotactic poly(methyl methacrylate) and of its deuterated analogues
Authors: Schneider Bohdan , Štokr Jan , Spěváček Jiří , Baldrian Josef 
Published: April 2003

AbstractInfrared spectra of partially crystalline and amorphous samples of isotactic poly(methyl methacrylate) (i‐PMMA), poly[methyl (α,α,α‐2H3)methacrylate] (i‐PMMA‐α‐CD3), poly‐[(2H3)methyl methacrylate] (i‐PMMA‐OCD3), and poly[(2H3)methyl (α,α,α,2,2‐2H5)methacrylate] (i‐PMMA‐D8) were measured. Infrared spectra of the pure crystalline forms of these substances were obtained by digital separation. It was found that in acetonitrile, CDCl3, and toluene solutions, i‐PMMA has the same conformational structure as in the amorphous state; conformational structures of crystalline i‐PMMA are not present in the solutions in measurable amounts.
Purity of liquid‐crystal polysiloxanes, 1. Isolation procedures
Authors: Nestor Gary , White Michael S. , Gray George W. , Lacey David , Toyne Kenneth J. 
Published: April 2003

AbstractThe removal of the alkene side‐chain precursor from liquid‐crystal (1.c.) polysiloxanes during their isolation by precipitation has been monitored by thin‐layer chromatography. The commonly used procedure involving only three precipitations has been shown to be frequently insufficient to remove the alkene completely from the 1.c. polymer. Using 8 to 10 precipitations and monitoring the removal of alkene to <0,1 wt.‐%, the resultant polymers have been found to have both higher glass transition temperatures and higher clearing temperatures; more consistent phase transition temperatures are also obtained from batch to batch.
The effect of contamination by side‐chain precursor on the molecular dynamics of a smectogenic siloxane copolymer as studied by dielectric relaxation spectroscopy
Authors: Attard George Simon , Moura‐Ramos Joaquim J. , Williams Graham , Nestor Gary , White Michael S. , Gray George W. , Lacey David , Toyne Kenneth J. 
Published: April 2003

AbstractTwo samples of a statistical siloxane copolymer 1 having two different pendant side‐chains have been investigated in the liquid‐crystalline state using dielectric relaxation spectroscopy. Samples 1a and 1b differed only in the number of precipitations (3 and 12, respectively) used in the purification procedure. Sample 1a, contained side‐chain precursor, whereas this contaminant was not detectable in sample 1b. It was found that the dielectric absorption curves for homeotropically‐aligned and unaligned specimens of sample 1a, were far broader than those observed for corresponding specimens of sample 1b, and there was evidence of an extra highfrequency shoulder. In addition, the frequency‐temperature locations of the overall loss peak differed between the two samples, being consistent with a plasticization effect caused by residual side‐chain precursor in sample 1a. It is shown that dielectric relaxation spectroscopy provides a convenient method for monitoring local phase separation and overall plasticization in liquid‐crystalline polymers caused by side‐chain precursor contamination.
A study of the thermal decomposition of poly(vinyl chloride) prepared at low conversion
Authors: Cuthbertson M. J. , Bowley H. J. , Gerrard D. L. , Maddams W. F. , Shapiro J. S. 
Published: April 2003

AbstractAiming to prove that commercial, 50°CPVC consists of a dual population of chains, has led us to the investigation of the thermal stability of low conversion (0,1–2%) PVC. Bulk polymers prepared at very low conversion levels were shown to be different to high conversion material. The former are more syndiotactic, and have a greater tendency to be less thermally stable, unzippering to long polyene sequences (with n > 15). These findings are consistent with the idea that initially‐produced PVC is formed by homogeneous polymerisation and that such material is intrinsically different to PVC which is formed at subsequently higher conversions by a heterogeneous route.