bluuebunny/crossref_metadata_2025_split huggingface dataset:
Studies of the characteristics in the synthesis of polystyrene‐block‐poly(ethylene‐co‐propylene) through a transformation of an anionic to a Ziegler‐Natta mechanism
Authors: Zhang Xuequan , Li Weidong , Huang Baotong 
Published: April 2003

AbstractRestriction of β‐elimination in polystyrene‐lithium (PSLi) in the block copolymerization of polystyrene with poly(ethylene‐co‐propene) catalyzed with PSLi/TiCl4 (resulting in sample A‐2) by adding a spacer of a few monomeric units of isoprene (I) (PS‐InLi/TiCl4 (n ≤ 3)); resulting in sample A‐3), was evidenced by a M̄w/M̄n‐value of 2,67 lower than that of sample A‐2, and a crystallinity (χ) of 7,4% in the poly(ethylene‐co‐propene) (EPR) block in sample A‐3. These, together with shorter ethylene (E)‐sequences EEEn≥1, 27,6%) and a higher content of inverted propylene units (P) make the EPR‐block in A‐3 look like a polymer obtained with a soluble vanadium catalyst. This is due to the solubilization of the active centers by the PS chains. Higher M̄w/M̄n‐values (4,23) and crystallinity of the EPR block (18,3%) and longer EEEn≥1 sequences (55,4%) in the case of sample A‐2 make it to look like a typical polymer as obtained with a heterogeneous Ti‐catalyst. Comparison of sample A‐3 with that obtained by E‐P copolymerization with BuLi/TiCl4 (sample A‐1) corroborates the solubilization effect of PS in A‐3 and the effects of the typical heterogeneous catalyst used for the preparation of A‐1, showing up in EEEn≥1 (A‐1: 63,4% A‐3: 27,6%), M̄w/M̄n (A‐1: 35,7; A‐3: 2,67) and P̄ (A‐1: nil; A‐3: 4%).
Analysis of the linear methods of determining copolymerization reactivity ratios, 10. Estimation of errors and planning of experiments in penultimate systems
Authors: Kelen Tibor , Tüdős Ferenc , Braun Dietrich , Czerwinski Wojciech K. 
Published: April 2003

AbstractFor a recently proposed new linearization method of the two‐parameter penultimate model (monomer M2 does not homopolymerize, i.e. r2 = 0), an estimation of confidence intervals for both parameters r1 and r1′ is presented. A procedure of minimizing the experimental error in both parameters was developed according to statistical planning of experiments. In analogy to the already existing procedure of planning (classical model) an “efficiency factor” of planning, Q, was introduced, which makes it possible to estimate the quality of planning for a given series of copolymerization experiments.
New polymer syntheses, 45. Soluble and meltable poly(benzobisthiazole)s derived from substituted terephthalic acids
Authors: Kricheldorf Hans R. , Engelhardt Jürgen 
Published: April 2003

AbstractA not perfectly pure 1,4‐bis(trimethylsilylamino)‐2,5‐bis(trimethylsilylthio)benzene was prepared as starting material for all condensations. Condensations with 4‐chlorobenzoyl chloride under a variety of reaction conditions revealed formation of benzobisthiazoles at temperatures ≥250°C. Condensation with various aryloxy or bisalkoxyterephthaloyl chlorides in an one‐pot procedure yielded substituted poly(benzobisthiazole)s. All poly(benzobisthiazole)s were soluble in mixtures of dichloromethane or chloroform and trifluoroacetic acid (TFA). Inherent viscosities up to 2,0 dl/g were found in this solvent system. Neither homo‐ nor copoly(benzobisthiazole)s formed a freely flowing melt up to 450°C, where thermal degradation beings to affect the properties. Thermogravimetric analyses in air proved that aryloxy‐substituted polymers possess a significantly greater thermostability than alkoxy‐substituted ones.
Photosensitive multilayer films of tetraolefinic compounds: preparation and polymerization‐depolymerization behaviour
Authors: Nakanishi Fusae 
Published: April 2003

AbstractA novel photosensitive multilayer film was prepared using a solid‐state photoreactive compound having four double bonds, dihexyl 5,5′‐(1,4‐phenylene)bis(2‐cyano‐2,4‐pentadienoate) (PCPAC6). PCPAC6, which forms a stable mixed monolayer on the water surface when mixed with arachidic acid, was transferred onto a substrate, thereby forming an Y‐type multilayer film. The multilayer film has an absorption maximum at 356 nm, showing a blue shift with respect to that of crystals. This indicates that the molecular arrangement of PCPAC6 in the multilayer film is different from that in the crystals. The multilayer film is very sensitive to visible light and was converted into the oligomer or polymer film on irradiation. The polymer film shows a photoreversible transition between polymers and oligomers, depending on the wavelength of the irradiating light. This phenomenon is caused by the cleavage and formation of cyclobutane rings.
Cyclopropanation of poly[(methylphenylsilanediyl)‐(Z)‐butenylene]. Synthesis and characterization of poly[(methylphenylsilanediyl)methylenecyclopropylenemethylene]
Authors: Liao Xiugao , Lee Howard Shih‐Jen , Weber Williams P. 
Published: April 2003

AbstractPoly[(methylphenylsilanediyl)methylenecyclopropylenemethylene] (3a) was prepared by cyclopropanation of the CC double bonds of poly[(methylphenylsilanediyl)‐(Z)‐butenylene] (2a) by a Simmons‐Smith reaction. Alternatively, 3a was prepared by a Birch reduction of the dichlorocarbene adduct poly[(methylphenylsilanediyl)methylene(2,2‐dichloro‐1,3‐cyclopropanediyl)‐methylene] (4a). Both 3a and 4a show the characteristic absorptions in the 1H, 13C, and 29Si NMR, IR and UV spectra. Their molecular weight distributions, determined by GPC, are rather broad and their thermal stabilities (by TG) are relatively high.
Thermally irreversible photoresponsive polymers: Synthesis and preliminary characterization of copolymers containing side‐chain trans‐cinnamamide chromophores
Authors: Shen Sunny , Torkelson John M. , Elbert Jeffrey E. , Lewis Frederick D. 
Published: April 2003

AbstractA novel photoresponsive polymer containing organic chromophores which possess thermal stability as well as substantial and reversible responsiveness upon external photostimulus has been developed. trans‐2{4‐[2‐(Dimethylcarbamoyl)vinyl]phenoxy}ethyl methacrylate (1) was synthesized and copolymerized by free‐radical methods with methyl methacrylate giving a copolymer poly[(methyl methacrylate)‐co‐1] (poly(MMA‐co‐1)) (2) with cinnamamide moiety chromophores randomly attached as side groups. Photoisomerization and ultraviolet absorbance were used to examine the photostationary states and solubility changes upon photoirradiation. Poly[(methyl methacrylate)‐co‐1] (90,7 : 9,3 mol%) with 9,3 mol‐% cinnamamide content has better solubility in a polar solvent such as acetonitrile (theta temperature ΘPMMA = 30°C) than in a nonpolar solvent such as carbon tetrachloride (ΘPMMA = 27°C). Photoisomerization of the trans‐cinnamamide to cis‐cinnamamide units significantly shifts the cloud point of poly[(methyl methacrylate)‐co‐1] (90,7 :9,3 mol‐%) in carbon tetrachloride; this cloud point shift is reversible by photoisomerization back to the trans state. However, in a hydrogen‐bonding solvent such as tert‐butyl alcohol, while photoirradiation of poly[(methyl methacrylate)‐co‐1] (90,7 :9,3 mol%) yields a significant shift in cloud point, this is not reversible by photoirradiation as hydrogen‐bond formation between the tertiary amide and the hydroxylic solvent reduces the isomerization efficiency. Fatigue of the photoreversibility of the copolymer, which is not present in dilute solutions of the cinnamamide chromophore, is noted.
Graft copolymers, 1. Anionic grafting reactions
Authors: Jenkins Aubrey D. , Tsartolia Eugenia , Walton David R. M. , Horská‐Jenkins Jitka , Kratochvíl Pavel , Stejskal Jaroslav 
Published: April 2003

AbstractTwo different units have been incorporated into polymer backbones to provide sites for potential anionic grafting reactions. In the first case, the sites were provided by p‐vinylacetophenone residues, and the technique attempted involved the addition of polystyryl anions. In the second case, the functional sites were p‐isopropenylstyrene residues, and these were used as initiating centres, from which grafts of poly(methyl methacrylate) were grown by means of anionic polymerisation initiated by butyllithium. Only the second method was met with success.
Influence of coagulation process on solid‐phase structure of poly(1,3,4‐oxadiazole‐2,5‐diyl‐1,4‐phenylene): non‐solvent induced crystallization
Authors: Calandrelli Luigi , Immirzi Barbara , Malinconico Mario , Martuscelli Ezio , Riva Fernando 
Published: April 2003

AbstractA preliminary investigation on the influence of the coagulation process on the solid‐phase structure of poly(1,3,4‐oxadiazole‐2,5‐diyl‐1,4‐phenylene) (1) is reported. Interesting correlations between the method of coagulation of the polymer from sulfuric acid solution and the structure which develops, as observed by thermal analysis, X‐ray diffraction, infrared spectroscopy, and optical microscopy are found. A new method for the preparation of highly crystalline spherulites of 1 is described. This method allows to grow a relatively large number of “single spherulites”, because coagulation and crystallization induced by a non‐solvent may be stopped before impingements occur.
Emulsion polymerization of butadiene, 2. Polymerizations with sodium dodecyl sulfate
Authors: Weerts Pierre A. , van der Loos J. L. M. , German Anton L. 
Published: April 2003

AbstractThe emulsion polymerization of butadiene was investigated with sodium dodecyl sulfate as emulsifier, and the results were compared with those obtained with the industrial‐grade emulsifier Dresinate 214. Limited coagulation was observed in both cases, caused by the high ionic strength of the aqueous phase. Sodium dodecyl sulfate was found to be a better stabilizer than Dresinate 214. The average rate per particle in interval II (corresponding to the linear portion of the conversion vs. time curve) depends strongly on particle size, but not on recipe parameters used to vary the final particle diameter, such as the type and amount of emulsifier and ionic strength. The dependence of particle number per volume of water N on initiator ([I]) and emulsifier concentration ([E]) is usually expressed as the exponent in the empirical relationship N ∼ [I]x · [E]y. Promoting coagulation by increasing the ionic strength decreases x towards zero, while y increases sharply. Increasing [I] at constant [E] and constant ionic strength induces limited coagulation, presumably because the rate of emulsifier adsorption becomes insufficient.
Doping effects on electrical conductivity and infrared spectra of thianthrenic polymers
Authors: Bertinelli Franco , Bizzarri Paolo Costa , Casa Carlo Della , Fiorini Maurizio 
Published: April 2003

AbstractThe electrical conductivity, σ, of different samples of SbCl5‐doped thianthrenic polymers is found to vary from 10−6 to 10−3 S · cm−1. The relationship between conductivity and dopant concentration is examined for one representative sample and a transition from an insulator to a semiconductive regime is observed near a dopant/repeating unit mole ratio of 0.06, above which σ tends to saturate. A detailed infrared analysis of the doped polymers, essentially based on a comparison with the pristine (undoped) polymers and the thianthrene‐SbCl5 (1:1) complex as a model compound, is reported. A first tentative assignment of the IR spectrum of this complex is made. Additional absorptions are observed near 1120 and 1080 cm−1 and are common features of all the doped thianthrenic polymers. The new peaks, which increase with dopant concentration, seem to be intrinsic vibrations of the polymer chains in the doped material and are referred to stretching modes of CSC groups enhanced by complexation. Another characteristic absorption around 340–325 cm−1, due to SbCl stretching modes of the dopant species, is discussed.
Kinetics of 1,3‐cyclohexadiene polymerization initiated by organolithium compounds in a non‐polar medium, 2. Secondary reactions in the propagation step
Authors: François Bernard , Zhong Xing Fu 
Published: April 2003

AbstractIt is confirmed that during the polymerization of 1,3‐cyclohexadiene initiated by polystyryllithium in cyclohexane a tranfer to the monomer takes place, as previously reported. It is shown that a part of the metallated monomer reinitiates the polymerization and another part decomposes to inert lithium hydride. The formation of 1,4‐cyclohexadiene is observed and interpreted. The transfer constant is deduced from measured molecular weights. The propagation constants were reported in a previous paper of this series. Knowing these values, the ratio between reinitiation and decomposition constants is deduced from a comparison between experimental kinetics and a numerical resolution of kinetic equations. This study allows a prediction of the best conditions for the synthesis of block copolymers including poly(1,3‐cyclohexadiene) sequences in 1–4 addition.
Complexation of poly(monobenzyl itaconate) and poly(N‐vinyl‐2‐pyrrolidone) in dilute solution, 2. Influence of variables involved in sample preparation
Authors: Pérez‐Dorado Angel , Piérola Inés F. , Baselga Juan , Gargallo Ligia , Radic Deodato 
Published: April 2003

AbstractUpon mixing dilute solutions of poly(monobenzyl itaconate)(c) (PMBI) and poly(N‐vinyl‐2‐pyrrolidone) (PVP) in methanol, a soluble interpolymer complex is formed whose properties depend on the method employed to prepare the sample. It was found that the local concentration of the polyacid is the controlling factor. Depending on that concentration, a metastable polymer complex is formed which turns to equilibrium upon sonication. Cooling or heating and aging time have a minor effect. The turbidity of the polymer complex depends on the polyacid concentration to the power ν (at constant polybase/polyacid ratio). For the metastable complex, ν ≈ 2, typical of week polymer complexes. Changes in turbidity are accompanied by a decrease in ν. In the equilibrium state, ν ≈ 1,5, a value being more typical of strong complexes.
The synthesis of symmetrical α,ω‐difunctional polymers
Authors: Al‐Takrity Emad Taha Bakir , Jenkins Aubrey D. , Walton David R. M. 
Published: April 2003

AbstractAnionic polymerisation of methyl methacrylate initiated by allyllithium and terminated by allyl iodide affords polymer molecules with allyl units at both ends. The method is shown to be efficient for the introduction of such other terminal moieties as hydroxyl and certain fluorescent (or fluorescence‐quenching) groups, such as 1‐pyrenyl.
Preparation of polystyrene particles with poly[(acylimino)ethylene] chains on the surface
Authors: Kobayashi Shiro , Uyama Hiroshi , Yamamoto Ikuo 
Published: April 2003

AbstractPolymer particles with poly[(acylimino)ethylene] chains on the surface were prepared by soap‐free emulsion copolymerization of styrene with a styryl‐type poly[(acylimino)ethylene] macromonomer. The macromonomer used was highly hydrophilic and soluble in water. The contour of the particles was examined by scanning electron microscopy. The copolymer particles were spherical and monodisperse. The average diameter of the particles was in the sub‐micron range and smaller than that of pure polystyrene particles prepared in a similar way. The surface composition of the particles was analyzed by ESCA (electron spectroscopy for chemical application). It was found that poly[(acylimino)ethylene] chains are enriched on the particle surface.
Studies of structure and properties of photocrosslinked polyurethane acrylates
Authors: Dai Jie , Gao Xuemin , Jiang Guoji 
Published: April 2003

AbstractA series of ultraviolet‐induced photocrosslinkable polyurethane acrylates was synthesized. They are composed of a polyether [poly(propylene oxide) or poly(tetramethylene oxide)] soft segment and two terminal hard segments derived from 2‐hydroxyethyl methacrylate and a diisocyanate. Based on stress‐strain and DSC measurements of their UV‐cured materials, relations between their structure and physical properties were investigated systematically. The results show that parameters which increase the content of hard segments and the crosslinking density of UV‐cured materials lead to an increase in Young's modulus and stress at break accompanied by a decrease in elongation at break. The glass transition temperature of the polyether soft segment is determined mainly by the type and molecular weight of the polyether, due to a two‐phase morphology.
Dispersion of trans‐polyoctenylene in isotactic poly(propylene), 2. Crystallization behaviour
Authors: Wenig Werner , Fiedel Heinz‐Werner 
Published: April 2003

AbstractThe crystallization kinetics of thin films of isotactic poly(propylene) (iPP) and transpolyoctenylene rubber (TOR) was investigated by optical microscopy. Nucleation densities, Avrami exponents and spherulitic growth rates show specific dependencies on the concentration of TOR in the blend. From the results it is concluded, that at a mass fraction of TOR wTOR = 0,10 the TOR is more finely dispersed in the blend than for other compositions. Due to the subsequent formation of interfaces, the nucleation is found to be predominantly heterogeneous at wTOR = 0,10, while it is preferentially homogeneous at all other compositions.
Novel synthesis of poly(benzoin) and poly(benzil). Characterization and application as photosensitizer materials
Authors: Abd‐Alla Mohamed A. 
Published: April 2003

AbstractNew photoactive polymers containing benzoin or benzil groups have been prepared by condensation of terephthalaldehyde. The influence of the alkali metal ions and solvents used upon the progress of polycondensation and yield of poly(benzoin)Systematic name: Poly(1,4‐phenylene‐1‐hydroxy‐2‐oxoethylene).
were studied. Oxidation of this polymer by nitric acid or ammonium nitrate in acetic acid afforded the corresponding poly(benzil)Systematic name: Poly(1,4‐phenylene‐1,2‐dioxoethylene).
in quantitative yield. The resulting polymers were confirmed by elemental analysis, IR, 1H NMR and UV/visible spectral data, and characterized using viscometry, DTA measurements, thermogravimetric and X‐ray analysis. The photosensitizing property of the prepared polymers was detected by fluorescence. It was found that irradiation of poly(benzoin) in DMSO solution at 285 nm causes yellow fluorescence whereas poly(benzil) does not display fluorescence at the same excitation wavelength. Moreover, the use of poly(benzil) as photosensitizer material in the photochemical cleavage of thiourea and its derivatives was also studied.
Computerized theoretical study of local structural properties of polyene and polymethylene chains in solutions. The continuum model
Authors: Rabinovich Alexander L. 
Published: April 2003

AbstractIn different solutions, the chains of cis‐1,4‐ and trans‐1,4‐polybutadiene, poly(cis‐ and trans‐propenylene), and poly(methylene) of 60 CC bonds were studied by Monte Carlo calculations. The developed computer simulation model takes into account the continuous spectrum of conformations of the chain molecule, the interdependence (in pairs) of internal rotations, hindrances to rotation and the excluded volume. The coordinate system is fixed to the molecule with the origin in the centre of mass and the axes along the principal axes of the inertia tensor. The tensors of the order parameter of each CC bond were calculated. The totality of the bond order parameters and the sequences of the bond directors were studied in this system. In “good” solvents the order parameters of bonds of the same type increase with a change of the position from the terminals towards the centre of the chain differently for single, cis‐ and trans‐double bonds.
Solution properties of poly(octadecyl methacrylate) in butyl acetate, 2. Semidilute solution
Authors: Ricker Mathias , Schmidt Manfred 
Published: April 2003

AbstractSemidilute solutions of a fraction of poly(octadecyl methacrylate) (PODMA) obtained by radical‐initiated polymerization were investigated in the theta‐solvent butyl acetate (BuAc) with static and dynamic light scattering (SLS, DLS, resp.) at four different temperatures between 13°C (near theta‐temperature Θ) and 70°C. The molar mass of the investigated sample (PODMA 4) was 3,2 · 106 g · mol−1. A concentration region from dilute to 8 c* was covered, where c* = 1/[η] was taken as the coil overlap concentration, [η] denoting intrinsic viscosity. Above c = 3c* the DLS correlation function exhibited bimodal behaviour at all temperatures. At these concentrations one finds two “apparent” molar masses, radii of gyration and diffusion coefficients for each concentration. The smaller apparent molar masses, smaller radii of gyration and larger diffusion coefficients correspond to characteristics of the transient network. The larger apparent molar masses, larger radii of gyration and smaller diffusion coefficients may be attributed to the formation of inhomogeneities in the semidilute solution.
Carbonyl‐olefin exchange reaction. A new route to conjugated polymers, 5. Effect of different catalytic systems
Authors: Jossifov Christo , Schopov Ivan 
Published: April 2003

AbstractThe influence of experimental conditions and the nature of the catalytic system on the yield of products insoluble in methanol from the carbonyl‐olefin exchange reaction (COER) was investigated. It was established that the COER of some α, β‐unsaturated carbonyl compounds can be catalyzed by transition metal halides (WCl6, MoCl5), by oxo compounds (WOCl4), and by binary systems (WCl6 + AlCl3, MoCl5 + AlCl3). Under the influence of these catalysts, some α,β‐unsaturated ketones can be transformed into conjugated polymers via different pathways. That is why the yield of the polymer product can be higher than calculated on the basis of the simple COER.
Chain‐sphere models for complexes of biological interest. Monte Carlo simulation and hydrodynamic properties
Authors: Bernal J. M. García , García M. M. Tirado , de La Torre José García 
Published: April 2003

AbstractMany complexes of biological interest, like nucleosomes or v bodies and DNA‐protein complexes, can be modelled like a structure composed by a sphere joined to a rigid rod or to a flexible chain of identical beads. In this work we present a theoretical study using these models for the evaluation of some reduced conformational and hydrodynamic properties: end‐to‐end distance, radius of gyration and translational friction coefficient. Two kinds of models were employed: a sphere joined to one of the two ends of a rod or chain and a sphere joined to the halfpoint of a rod or chain, i. e. the models show one or two arms, respectively. Several cases were studied, varying the number of chain beads N = 10, 20, 30, … 60 (with radius σ ⩽ 1/2 and bond length b = 1) and the radius of the sphere R = 1, 2, 4, 8 (in units of b). For the flexible models the position of the chain beads have been obtained randomly from Monte Carlo simulations. For these models we have made also a statistical treatment in order to obtain averaged values of the conformational and hydrodynamic properties. Finally, we conducted a comparison of our theoretical results with the experimental data for nucleosomes. The overall agreement is good and gives confidence in the applicability of our results to similar macromolecular complexes.
The environmentally controlled photoisomerization of probe molecules containing azobenzene moieties in solid poly(methyl methacrylate)
Authors: Shen Yu‐Quan , Rau Hermann 
Published: April 2003

AbstractUpon n → π* (436 nm) excitation of azobenzene probes 1, 2 and 3 in a solid film of poly(methyl methacrylate) we observe cis‐trans isomerization and a monoexponential approach towards the photostationary state; upon π → π* (313 nm) irradiation this approach is bi‐exponential. The latter is not due to the loss of concentration homogeneity during the reaction. By transferring the concept of dual isomerization mechanisms (rotation and inversion) from former work we reinterpret the “fast” component of isomerization at 313 nm excitation as being due to rigidly held molecules unable to isomerize via the rotation mechanism, but undergoing internal conversion and subsequent inversion, and the “slow” component as being due to molecules isomerizing by rotation. On 436 nm irradiation only one isomerization mechanism is active, viz. inversion.