bluuebunny/crossref_metadata_2025_split huggingface dataset:
Particle formation in emulsion polymerization, 1. Oligomers in emulsion polymerization of vinyl acetate
Authors: Hergeth Wolf‐Dieter , Lebek Werner , Kakuschke Rolf , Schmutzler Klaus 
Published: April 2003

AbstractThe oligomers formed in the beginning of the emulsion polymerization of vinyl acetate were characterized by surface tension measurements, analysis of molecular weight distribution and light scattering. The results indicate that primary particle formation in the emulsion polymerization of vinyl acetate is due to an oligomeric micellization. Additionally, these oligomers are strongly adsorbed onto highly dispersed silica particles in the aqueous phase. This effect leads to a disaggregation of the filler particles during the beginning of the emulsion polymerization.
Living cationic polymerization of vinyl ethers with a bifunctional initiator
Authors: Yoshida Tatsuhiro , Sawamoto Mitsuo , Higashimura Toshinobu 
Published: April 2003

AbstractA new bifunctional initiator, CF3COOCH(CH3)OCH2CH2OC6H4C(CH3)2C6H4OCH2CH2OCH(CH3)OCOCF3 (2), was prepared from the corresponding divinyl ether and trifluoroacetic acid in carbon tetrachloride at 0°C. The 2/ethylaluminium dichloride (EtAlCl2) initiating system induced well‐defined living cationic polymerizations of isobutyl vinyl ether (IBVE; in hexane CH3(CH2)4CH3) and 2‐acetoxyethyl vinyl ether (2‐vinyloxyethyl acetate, AcOVE; in toluene) at temperatures up to +40°C in the presence of an excess amount of 1,4‐dioxane (an added base for cation stabilization). The number‐average molecular weights (M̄n) of the polymers increased in direct proportion to monomer conversion, continued to increase on addition of fresh monomer, and were close to the calculated values assuming that each molecule of 2 produces one living polymer chain. The bifunctionality of the living polymers was confirmed by comparing the polymerizations with 2 and its monofunctional analog C6H5OCH2CH2OCH (CH3)OCOCF3 (3), and further shown by quenching the living ends with the sodiomalonic ester Na⊕ ⊖CH(COOC2H5)2 to form telechelic polymers with malonate groups. The diester terminals could be transformed into the corresponding carboxylic acids by hydrolysis followed by decarboxylation. Sequential living polymerization of IBVE and AcOVE with the 2/EtAlCl2 initiating system in the presence of 1,4‐dioxane and subsequent hydrolysis of the pendant ester groups led to ABA‐type amphiphilic triblock copolymers where the hydrophilic poly(2‐hydroxyethyl vinyl ether) segment could be either center or outer blocks.
Preparation and permeability properties of chitosan membranes having hydrophobic groups
Authors: Seo Toshihiro , Ohtake Hitoshi , Kanbara Takaki , Yonetake Koichiro , Iijima Toshiro 
Published: April 2003

AbstractMembranes consisting of N‐acylated chitosan and carrying hydrophobic groups were prepared and the states of water in these membranes were examined by differential scanning calorimetry (DSC). The contents of freezable and non‐freezable water were found to be closely related with the structure and properties of the membranes. On the other hand, their permeability properties for sodium salts are found to be affected considerably by modifying the membrane structure as well as the cationically charged groups. With respect to D,L‐amino acids, the selective permeation of the L‐isomer was enhanced in the hydrophobic chitosan membrane, suggesting the possibility to separate optical isomers by membrane transport.
[1.1.1]Propellanes. From a hydrocarbon curiosity to a versatile monomer for the synthesis of structurally new polymers
Authors: Schlüter Arnulf‐Dieter , Bothe Harald , Gosau Jan‐Michael 
Published: April 2003

Abstract[1.1.1]Propellanes are introduced to polymer chemistry as a new class of highly reactive monomers which polymerize regiospecifically with breaking of the central CC σ‐bond. These rather unique hydrocarbon monomers undergo ring‐opening polymerizations with formation of both homo‐ and copolymers and, in addition, can be used as starting materials for classical poly‐condensation chemistry. A wide variety of new polymers is presented all of which contain the bicyclo[1.1.1]pentane fragment, a linearly connecting, rigid unit. This article focusses on questions related to synthesis and structure elucidation.
Interpolymer association between poly(acrylic acid) and vinyl alcohol‐vinyl acetate copolymers in dilute aqueous solutions
Authors: Staikos Georges , Bokias Georges 
Published: April 2003

AbstractInterpolymer association and complexation between poly(acrylic acid) and vinyl alcohol‐vinyl acetate copolymers (PVAL‐AC) in dilute aqueous solutions were investigated by means of reduced viscosity and pH measurements. The influence of the degree of saponification of PVAL‐AC and of the molecular weight of both polymers on complexation were examined. The viscosity measurements show the formation of gel‐like or compact complexes and that association is strongly increased by the presence of acetate units in the PVAL‐AC copolymer. The degree of complexation was calculated from the results of pH measurements. Some special aspects of the two different experimental approaches are discussed.
Modelling and kinetic study on radical polymerization of methyl methacrylate in bulk, 1. Propagation and termination rate coefficients and initiation efficiency
Authors: Shen Jiacong , Tian Yuan , Wang Guobin , Yang Meilin 
Published: April 2003

AbstractIn this work the exact data of the rate coefficients of propagation kp and termination kt, and initiator efficiency f as well as their variations with conversion during the whole processes of the polymerization of methyl methacrylate in bulk have been measured using electron paramagnetic resonance (ESR) without any assumptions and approximations. kp was calculated directly from the synchronously measured data of the concentration of radicals and polymerization rate. kt was determined under nonsteady‐state conditions by using the after‐effect technique in the ESR measurement. f for the initiation with dimethyl 2,2′‐azoisobutyrate was evaluated from the initiation and termination rates. The ESR spectra show that the polymerization system is in a micro‐heterogeneous state and there exist inactive radicals. A model of a diffusion‐controlled reaction is proposed.
Liquid‐crystalline polymer gels, 4. Photocontrol of dye orientation in a polymer gel having a cholesteric liquid‐crystalline order
Authors: Kishi Ryoichi , Sisido Masahiko 
Published: April 2003

AbstractA dichroic dye, 1,4‐diaminoanthraquinone, was covalently linked to an azobenzene derivative carrying a long alkyl group. The photochromic dye showed a trans‐to‐cis photoisomerism with somewhat reduced quantum yield, probably due to an energy transfer from the azobenzene unit to the dye unit. The cis‐to‐trans reverse photoisomerization was induced not only by irradiating the absorption band of the cis‐azobenzene unit, but also by irradiating the red‐edge of the absorption band of the dye unit. The photochromic dye was doped in a polymer gel having a cholesteric liquid‐crystalline order (CLC gel). Circular dichroism was induced at the absorption bands of both the azobenzene and the dye unit. The induced circular dichroism (ICD) of the dye absorption band was reversibly changed when the azobenzene unit was photoisomerized reversibly, indicating that the orientation of the dye group is affected by the structural change of the azobenzene unit.
Thermodynamics of copolymerization of 1,3‐dioxolane with 1,3‐dioxepane and 1,3‐dioxane
Authors: Szymanski Ryszard 
Published: April 2003

AbstractThe equilibrium copolymerization of 1,3‐dioxolane with 1,3‐dioxepane in CH2Cl2 solution and with 1,3‐dioxane without solvent is analyzed, and the equilibrium constants of homo‐ and cross‐propagations are estimated and discussed. The corresponding thermodynamic parameters are calculated. The reported thermodynamic parameters of homopolymerization of 1,3‐dioxane (ΔHss = −3,1 kJ · mol−1, ΔSss = −35,5 J · mol−1 · K−1), were determined on the basis of the copolymerization data. Predictions of comonomer concentrations and microstructure of copolymers in the equilibrium copolymerization system are presented for any initial composition, on the basis of the determined equilibrium constants.
Equilibrium between 1,3‐dioxane and its cyclooligomers
Authors: Szymanski Ryszard 
Published: April 2003

AbstractThe equilibrium between 1,3‐dioxane and its cyclooligomers in bulk has been studied. The equilibrium constants of cyclooligomerization at three temperatures (273, 294 and 313 K) and the corresponding thermodynamic parameters were estimated. The only relatively stable cyclooligomer is the dimer. The thermodynamic parameters of its polymerization were found to be ΔHssThe subscript “ss” indicates that as the initial state for the dimer and as the final state for the polymer solutions were chosen of the corresponding compounds in the equilibrium reaction mixture.
= 3,7 kJ · mol−1, ΔSss = 22,6 J · mol−1 · K−1.
Crystal structure of fibers from a novel rigid‐rod aromatic polyamide containing a pyrimidine moiety
Authors: Rutledge Gregory C. , Oertli Alfred G. 
Published: April 2003

AbstractFibers of a novel rigid‐rod polyamide containing a 1:1 ratio of phenylene:pyrimidine moieties have been produced and evaluated. The lyotropic liquid‐crystalline behavior of the polymer and the spinnability of the nematic dope were established. The as‐spun fibers exhibit low degrees of orientation and crystallinity. Heat treatment of the dry fibers resulted in crystallinities as high as 45% in coexistence with an amorphous phase component. Evaluation of the crystal structure by wide‐angle X‐ray diffraction suggests a pseudo‐orthorhombic crystal cell with lattice dimensions (a; b; c) of (7,3 Å; 5,1 Å; 12,8 Å) and containing two repeating units per unit cell.
2H NMR study of molecular motions in polydimethylsiloxane and its mixtures with aerosils
Authors: Litvinov Victor M. , Spiess Hans Wolfgang 
Published: April 2003

Abstract2H NMR was used to investigate the effect of fillers on the molecular motions in mixtures of polydimethylsiloxane (PDMS) with different fillers. For active fillers with hydrophilic surface OH groups the molecular mobility at the polymer‐filler interface is strongly different from that outside the adsorption layer. The influence of concentration and type of filler on molecular motions was determined. In particular an adsorption layer differing in mobility from bulk PDMS could be detected just above the glass transition temperature in systems filled with hydrophobic Aerosil. The role of molecular dynamics at the polymer‐filler interface for the reinforcement of silicon rubbers is discussed.
Stationary‐state kinetics in the polymerization of ethyl α‐cyanoacrylate by phenazines
Authors: Pepper David Charles 
Published: April 2003

AbstractAmines 1–5 of a family of phenazines have been examined as initiators for the anionic polymerization of ethyl α‐cyanoacrylate in tetrahydrofuran at 20°C. 1 and 2 are inactive; 3 initiates a polymerization of the slow‐initiation‐no‐termination (SINT) type. 4 and 5 induce different kinetic patterns of which that from 5 (Chlofazimine) has been studied in detail. Coloured polymers are produced, whose absorbance gives an (inverse) measure of the chain length. Stationary‐state kinetics are established and values of all rate constants evaluated or estimated. The mechanism is interpreted as a zwitterionic polymerization initiated at the secondary NH group, thus making the initial group of the chain a tertiary ammonium ion, whose potentially acidic proton can then act as terminator to the carbanionic propagating ends.
Polymerization of furfuryl alcohol with trifluoroacetic acid: the influence of experimental conditions
Authors: González Regino , Martínez Ricardo , Ortiz Pedro 
Published: April 2003

AbstractFurfuryl alcohol was polymerized by trifluoroacetic acid in methylene chloride to give a colored polymer. This polymer possesses two main sequences in which the furan rings are connected by methylene groups (sequence 1) or by dimethylene ether groups (sequence 2). The polymer is not linear but highly branched, as detected by 1H and 13C NMR spectroscopy. Variations of the experimental conditions, such as the presence of air, the trifluoroacetic acid concentration, the reaction temperature and the solvent, do not allow a significant increase in the linear structure of the polymer. However, an increase in the acid concentration or an increase in temperature produce a decrease in the ether‐bridged structure (sequences 2).
Viscosity‐temperature relationships of a polycarbonate melt: Williams‐Landel‐Ferry versus Arrhenius behaviour
Authors: Lomellini Paolo 
Published: April 2003

AbstractThe melt viscosity of polycarbonate from bisphenol‐ASystem name: 4,4′‐isopropylidenediphenol.
was measured in a wide range of temperatures, from Tg + 55°C up to about Tg + 185°C. The experimental results are discussed in terms of the classical WLF (Williams‐Landel‐Ferry) and Arrhenius models. There are clear indications that the WLF approach holds over the entire temperature range investigated. This is rather unusual as the Arrhenius behaviour is reported to be the correct one for temperatures above approximately Tg + 100°C. The most critical factor in our case seems to be the restricted number of bonds with rotational degree of freedom in the polycarbonate unit. The reduced number of virtual bonds with respect to real ones is discussed to be a possible reason for the large temperature range in which the free volume is the rate‐limiting factor for the flow process.
Energy spectra of poly(arylenevinylene)s containing different aromatic units
Authors: Ohlemacher Angela , Schenk Rainer , Weitzel Hans Peter , Tyutyulkov Nikolai , Tasseva Maria , Müllen Klaus 
Published: April 2003

AbstractThe energy gaps of poly(p‐arylenevinylene)s with phenylene, naphthylene and anthrylene subunits are determined by extrapolating the UV/VIS spectroscopic data of the oligomers. The band structure of the three polymers was theoretically investigated. The topology‐, geometry‐ and correlation‐factors were determined upon which the energy spectra of this class of one‐dimensional π‐electron systems depend.
Partitioned polymerization, 4. Seeded emulsion polymerization of methyl methacrylate
Authors: Barton̆ Jaroslav , Hloušková Zuzana , Juraničová Viera 
Published: April 2003

AbstractThe shape of the conversion curves and the rates of the emulsion polymerization in batch of methyl methacrylate (MMA) in the presence of seed particles of poly(butyl acrylate) (PBA) depend on the mass ratio of methyl methacrylate/poly(butyl acrylate) MMA/PBA and on the presence or absence of 2,2,6,6‐tetramethyl‐4‐octadecanoyloxypiperidinyl‐1‐oxyl (STMPO). Irrespective of the presence and/or absence of STMPO in the reaction system, the diameter of a polumer particle experimentally found and calculated on the assumption that no new crop of polymer particles is formed, agrees well for systems with “low” (0,632) mass ratio of MMA/PBA. For systems with “high” (3,160) mass ratio of MMA/PBA, the calculated diameter is higher than that experimentally measured. This indicates that for “low” values of MMA/PBA, all poly(methyl methacrylate) formed was only used for building up shells of poly(butyl acrylate) particles. For “high” values of MMA/PBA, about 37 mass‐% (in the absence of STMPO) or 57 mass‐% (in the presence of STMPO) of poly(methyl methacrylate) formed was used for generating a crop of poly(methyl methacrylate) particles. Retardation of the polymerization rate in the presence of STMPO is more pronounced for systems characterized by a “low” value of the mass ratio MMA/PBA. Only short inhibition periods (up to five minutes) were observed for both “low” and “high” MMA/PBA ratios. It is shown that for the “low” mass ratio of MMA/PBA the “inner” monomer transport (from PBA particles swollen with MMA) to the locus of propagation is decisive. For systems with a “hugh” mass ratio MMA/PBA, the “outer” monomer transport from monomer droplets and micelles swollen by monomer to the locus of propagation is of primary importance. To explain the experimental results a reaction mechanism for the seeded emulsion polymerization is proposed.
Radical bulk functionalization of polyethylenes with ester groups
Authors: Aglietto Mauro , Bertani Roberto , Ruggeri Giacomo , Ciardelli Francesco 
Published: April 2003

AbstractThe radical functionalization of different types of polyethylene, such as high‐density (HDPE) and linear low‐density (LLDPE) polyethylene, with diethyl maleate (DEM) as a polar functional monomer and dicumyl peroxide (DCP) as radical initiator was investigated, and conditions for obtaining a controlled degree of functionalization and a low amount of degradation products without crosslinking were determined. Attention was paid to achieve a moderate functionalization of the polymer, in order to limit the modification of the mechanical and physical properties of the polyolefins. The molecular weight distribution of some of these polyethylenes was only moderately affected by the functionalization reaction. A critical discussion of the results outlines the fundamental role of process parameters such as stirring rate and heat exchange.
Radical‐initiated copolymers of styrene and p‐formylstyrene, 1. Solution copolymerization and characterization
Authors: Charleux Bernadette , Pichot Christian , Llauro Marie‐France 
Published: April 2003

AbstractKinetics of solution homopolymerization of p‐formylstyreneSystem name: 4‐vinylbenzaldehyde.
(A) and copolymerization with styrene (S) have been examined at 60°C in N,N‐dimethylformamide with 2,2′‐azoisobutyronitrile as initiator. For p‐formylstyrene, kp/k = 0,135 L1/2 · mol−1/2 · s−1/2 was estimated from the plot of monomer consumption versus time, i.e. a value greater than that for styrene (Kp and Kt are the rate constants of propagation and termination and termination, respectively). Reactivity ratios have been determined to be rA = 3,0 and rS = 0.2, indicating the reactivity of p‐formylstyrene to be higher than that of styrene. Moreover, from initial copolymerization rates, the cross termination factor was calculated and found to depend upon the copolymer composition. Some solution properties of the homo‐ and copolymers have been analysed: solubility of (co)polymers, their molecular weight and its distribution (by gel permeation chromatography), and their composition and monomer sequence distribution (using 1H and 13C NMR spectroscopy).
Gel permeation chromatography using porous glass beads modified with temperature‐responsive polymers
Authors: Gewehr Markus , Nakamura Katsunori , Ise Norio , Kitano Hiromi 
Published: April 2003

AbstractPoly(N‐isopropylacrylamide) (PIPA) with a carboxyl group at its end was coupled with amino group‐carrying porous glass beads by the active‐ester method. Gel permeation chromatography of dextran was carried out by using a column packed with the PIPA‐carrying glass beads. The chromatograms of dextrans with various molecular weights are strongly affected by temperature: the elution time of dextran is largely changed between 25 and 32°C due to a change in the effective pore size by the transition of the PIPA chains from coils to globules on the surface of the pores of the glass beads. These results suggest the usability of PIPA‐carrying glass beads as devices for thermo‐controllable chromatography.
Modification au deuxième degrá de polymères époxydés, 4. Fixation de i'acide naphtylacétique sur polyisoprène‐1,4 de synthèse et caoutchouc naturel liquide époxydés
Authors: Brosse Jean‐Claude , Klinpituksa Pairote , Soutif Jean‐Claude 
Published: April 2003

AbstractThe reaction of naphthylacetic acid (a plant growth stimulator) on epoxidized 1,4‐polyisoprene has been studied. The increase of the rate of addition of the acid on the oxirane rings, catalyzed by the tetramethylammonium salt of the acid, with temperature, time and concentration of the reagents, is fairly well represented by a second‐order kinetic law.
Enzymes in polymer chemistry, 6. Lipase‐catalyzed acylation of comb‐like methacrylic polymers containing OH groups in the side chains
Authors: Pavel Konstantin , Ritter Helmut 
Published: April 2003

AbstractThe enzymatically catalyzed acylation of poly[N‐(2‐hydroxypropyl)‐11‐methacryloylaminoundecanamide‐co‐styrene] and the corresponding monomer was performed in the presence of a lipase, with vinyl acetate, phenyl acetate, 4‐fluorophenyl acetate and phenyl stearate as acylating agents. The kinetics of the enzymatically catalyzed reaction was followed by 1H NMR spectroscopy and correlated with sterical and chemical effects. The reactivity of monomer towards acylation is higher than that of the copolymer, and that of the copolymer depends on copolymer composition, pointing at steric and hydrophobic effects.
Morphological and structural properties of poly[bis(p‐phenylphenoxy)phosphazene]
Authors: Kojima Morio , Magill Joseph H. 
Published: April 2003

AbstractPoly[bis(p‐phenylphenoxy)phosphazene] (PB(4‐Ph)PP) has been investigated employing X‐ray diffraction technique and electron microscopy. Its unit cell dimensions were determined to be a = 4,18 nm, b = 1,83 nm and c = 0,957 nm with space group Pca21. At 21 5–220°C , PB(4‐Ph)PP transforms into an anisotropic liquid‐like phase corresponding to a new molecular ordering array. The thicker films are composed of the linked globules approximately 100 nm in diameter. Upon drawing, the globules transform into a rod‐like morphology 15–40 nm in width and exhibit a highly oriented X‐ray diffraction pattern. These unusual morphological features have been compared with features found in poly[bis(phenoxy)phosphazene] and poly[bis(halophenoxy)phosphazene] polymers. X‐ray diffraction and crystallization results support a smectic‐like side chain morphology.
Dielectric properties of poly(dibenzyloxyphosphazene)s
Authors: Moriya Keiichi , Tomii Koji , Yano Shinichi , Kajiwara Meisetsu 
Published: April 2003

AbstractPoly(dibenzyloxyphosphazene) (PBP), poly[bis(4‐methylbenzyloxy)phosphazene] (PMBP) and poly[bis(4‐chlorobenzyloxy)phosphazene] (PCIBP) were synthesized by reaction of poly(dichlorophosphazene) (PDCIP) and the corresponding sodium benzyl alkoxide. PDCIP was prepared by a ring‐cleavage polymerization from hexachlorocyclotriphosphazene. The dielectric properties of the polymers were studied in the temperature range of 80 to 390 K at several frequencies between 0,1 and 100 kHz. Two relaxations, a relaxation above the glass transition temperature Tg and β relaxation below Tg, were observed in PBP and PMBP. The β relaxation was only observed in PCIBP. The a relaxations are related to a glass‐rubber transition and the β relaxations to the local molecular motion of the short segments.
Analysis of the linear methods of determining copolymerization reactivity ratios, 11. Copolymerization of styrene with methyl α‐cyanocinnamate and fumaroyldipyrrolidone
Authors: Braun Dietrich , Czerwinski Wojciech K. , Bednarski Ralf , Kelen Tibor , Tüdős Ferenc 
Published: April 2003

AbstractThe composition of copolymers was determined as a function of the monomer feed for two systems: styrene/methyl a‐cyanocinnamate in toluene and styrene/fumaroyldipyrrolidone in dimethyl sulfoxide both at 60°C with 2,2′‐azoisobutyronitrile (AIBN) as initiator. To ascertain the accuracy of reaction modelling in terms of the classical and the penultimate model, the extended linearized forms of both models were applied. The styrene/methyl a‐cyanocinnamate system was found to copolymerize non‐classically; the two‐parameter penultimate model described properly the experimental data yielding r'1/r1 ≈ 3–6. The styrene/fumaroyldipyrrolidone system showed only a slight penultimate effect. However, in this case, the terminal model gave a better fit of experimental data.