bluuebunny/crossref_metadata_2025 huggingface dataset:
Samarium(II) iodide: A diastereoselective reagent for the synthesis of aromatic 1,2‐diol structures — model reactions
Authors: Wege V. U. , Greiner A.
Published: April 2003

Variation of the reaction conditions for the C—C coupling reaction of aromatic carbonyl compounds to their 1,2‐diol structures in the presence of samaraium(II)‐iodide led to different diastereoselectivities. The molar ratio of the starting materials, substituents, and solvent variation had a significant influence on 1,2‐diol formation. An interpretation of the observed results is suggested. Sterical demands of the active complex and an intramolecular samarium‐oxygen interaction could lead to the diastereomer ratio obtained.
Anionic polymerization of fluorostyrenes
Authors: Sugiyama K. , Ishizone T. , Hirao A. , Nakahama S.
Published: April 2003

Anionic polymerizations of 2‐, 3‐, and 4‐fluorostyrenes (2‐, 3‐, and 4‐FSt) were carried out at −78°C in THF with sec‐butyl‐lithium, oligo(α‐methylstyryl)lithium, ‐dipotassium, and (1,1‐diphenyl‐3‐methyl‐pentyl)lithium as initiators to give the respective polymers in quantitative yields. The propagating carbanion derived from 2‐FSt is found to survive at least for 5 min at—78°C, affording the anionic living poly(2‐FSt) with predictable molecular weight and very narrow molecular weight distribution. The addition of styrene to the anionic living poly(2‐FSt) in THF affords poly(2‐FSt)‐block‐polystyrene in quantitative efficiency, indicating the high nucleophilicity of the propagating carbanion of 2‐FSt. During the polymerization of 3‐FSt, the benzyne intermediate is formed probably due to meta‐fluoro substitution to cause polymer coupling reaction. Poly(4‐FSt) produced has narrow molecular weight distribution and slightly higher molecular weight than the calculated one. The results of the polymerizations of 2‐FSt and 4‐FSt suggest that persistency of the propagating carbanionic species of 4‐FSt is slightly lower than that of 2‐FSt at −78°C.
A novel living coordination polymerization of alkoxyallenes by a π‐allylnickel catalyst [1]
Authors: Tomita I. , Kondo Y. , Takagi K. , Endo T.
Published: April 2003

A coordination polymerization of alkoxyallenes (2a‐2f) by the [η3‐(allyl)NiOCOCF3] (1) /PPh3 system was carried out to obtain a polymer (3) bearing exomethylenes on the main chain. The structure of the obtained polymer was confirmed by 1H‐, 13C‐NMR and IR spectra, and was revealed to consist of two units, one bearing an exomethylene side chain and the other an end ether side chain as a result of 1,2‐ and 2,3‐polymerization. In the case of methoxyallene, the ratio was estimated as 32:68. The number average molecular weight (M̄n) of the resulting polymer varied linearly with increasing ratio of monomer to initiator. The molecular weight distributions (M̄w/M̄n) of the polymers obtained here were always approximately 1.1. These results may strongly support that the present polymerization proceeds by a living mechanism. Under an inertatmosphere, the propagating end of the polymer was quite stable and could be kept without any decrease in activity for more than a week. The proportion of 1,2‐ and 2,3‐polymerization was a little affected by the substituents on the alkoxyallenes, as the steric bulkiness of the substituents increased the content of 2,3‐polymerization units.
Thermodynamics and molecular ordering of carbonate‐type dimer liquid crystals with emphasis on the geometrical characteristics of the linking group
Authors: Abe A. , Furuya H. , Nam Su Yong , Okamoto S.
Published: April 2003

Mainchain liquid crystals having a regularly alternating rigid‐flexible repeating structure often exhibit distinct odd‐even oscillation in their thermodynamic quantities with respect to the number of methylene units in the spacer. The effect has been widely observed from dimer (DLC) to polymer liquid crystals (PLC), but not in the monomer liquid crystals (MLC) which comprise a mesogenic unit carrying one or two tails. The degree of oscillation varies depending on the chemical structure of the linking group used to join the spacer with mesogenic units. In our previous work, we have suggested that such characteristics are mainly due to the geometrical arrangement of the linkage. In this work, we have prepared a series of carbonate‐type MLCs NCϕϕOCOO(CH2)n—1CH3, where ϕ is a phenyl group, as well as DLCs NCϕϕOOCO(CH2)nO‐COOϕϕCN. The thermodynamic behaviors at the nematic‐isotropic NI transition have been compared with those previously reported for the ether‐type DLCs. For the dimer series, the molecular orientation and the spacer conformation were investigated by using 2H NMR technique. The origin of the difference in the odd‐even behaviors has been traced back to the geometrical characteristics of the linking groups, which affect the relative orientation of the terminal mesogenic cores, thus leading to modification of the conformational distribution in the nematic state. The analysis has yielded the nematic conformation which satisfactorily reproduces the observed values of the dipolar and quadrupolar couplings. The bond conformation vs. bond order plots are shown for the n odd and n even systems together with the corresponding results derived previously for the ether‐type DLCs. Although the numbers of bonds of the flexible spacer are not exactly comparable with each other, the conformational ordering along the spacer tends to be pronounced in both DLC systems.
Oxidation–reduction alternating copolymerization of stannylenes with p‐benzoquinone derivatives
Authors: Kobayashi S. , Iwata S. , Shoda S.
Published: April 2003

Stannylenes, bis[bis(trimethylsilyl)amido]tin(II) (1) and bis[bis(trimethylsilyl)methyl]tin(II) (2), have been copolymerized with p‐benzoquinone derivatives to afford a novel class of tin‐containing polymers (4 and 5) having a tetravalent tin unit and a p‐hydroquinone unit alternatingly in the main chain. The oxidation state of the stannylenes changes from two to four while the p‐benzoquinone moiety is reduced to the corresponding p‐hydroquinone unit, indicating that the copolymerization proceeds via a redox process (oxidation‐reduction copolymerization). Some of the resulting copolymers are stable at room temperature and soluble in common organic solvents such as chloroform and n‐hexane. The molecular weight (Mw) of the resulting copolymers was in the range of 1.1 x 105 to 4.9 x 103.
Uniform polymer beads of micrometer size
Authors: Horák D.
Published: April 2003

Various methods are reviewed that have been developed in recent years to produce uniform polymer beads with diameter larger than 1 μm. Methods such as emulsifier‐free emulsion polymerization, suspension polymerization (including non‐standard polymerization devices and a method of activated swelling), dispersion polymerization, precipitation polymerization, and other techniques are covered. The discussion focuses on the mechanism of bead formation and variables influencing the properties of the beads. Potential applications of monosized beads in both industry and research are described.
Static and dynamic light scattering from multicomponent polymer mixtures PS/PDMS/PMMA/toluene
Authors: Benmouna M. , Duval M. , Strazielle C. , Hakem F.‐I.
Published: April 2003

The static and dynamic scattering properties of multicomponent polymer mixtures are examined starting from the theoretical formalism based on the random phase approximation (RPA) for multicomponent polymer mixtures in the presence of a low molecular weight solvent. The results are compared with the light scattering data reported recently by Strazielle and coworkers [1] for polystyrene/polydimethylsiloxane/polymethylmethacrylate/toluene mixtures. The present paper is an extension of the work published recently by these authors [2] and considers data obtained from several concentrations of PMMA. It also includes a discussion of the dynamic properties which are obtained by quasi‐elastic light scattering.
X‐ray diffraction and TGA studies on annealed PPT twaron fibers and powder
Authors: Hindeleh A. M. , Obaid A. A. Abu
Published: April 2003

Twaron fiber is spun from the polymer poly(paraphenylene terephthalamide), PPT, and has a crystallinity of 82%. Wideangle X‐ray diffraction, combined with the multipeak resolution procedure, was applied to study the changes in the structure after annealing the fiber in the temperature range of 100–675°C. The structural parameters included crystallinity (crystalline order), microparacrystal (mPC) size, and netplane spacing. A thermogravimetric analysis (TGA) was made to determine the loss in mass of the fiber in the temperature range in which the annealing study was carried out.

Crystallographically‐disordered (amorphous) powder of the PPT polymer was prepared by grinding crystalline Twaron fibers, which had a crystallinity of 87%, in a vibratory ball mill for a period of 64h. A study was then made to determine the extent to which the original crystallinity or mPC size is restored after annealing the powder in the temperature range of 100–425°C.
Polymerization of acrylonitrile with magnesiumdialkyls. Reaction conditions and stereospecificity
Authors: Opitz G. , Heller A. , Scheller D. , Berger W.
Published: April 2003

The stereospecificity of acrylonitrile polymerization initiated by organometallic compounds of alkali and alkaline earth metals was investigated. The triad tacticities of the polymers obtained was analyzed by 13C NMR and the molecular weights and their distributions were measured by size exclusion chromatography. A decisive influence of temperature on acrylonitrile polymerization initiated by dialkylmagnesium (di‐n‐hexyl‐ and di‐n‐butylmagnesium) in mesitylene was found. Products polymerized at temperatures above 100°C contain high molecular weight fractions with predominantly isotactic configuration (isotactic triad content 50—55%). The stereospecificity of polymerization was observed only in a medium which is a non‐solvent for the product. All the other investigated metalorganics do not initiate a stereospecific polymerization on these conditions. In order to elucidate the stereospecific polymerization mechanism we examined NMR data by model calculations. The triad tacticity of some predominant isotactic polyacrylonitrile samples is described by the enantiomorphic sites (e.m.s.) model. This means that the propagation takes place at enantiomeric catalyst sites which determine the configuration of the incoming monomer unit. Summarizing the experimental observations and the interpretation of the polymer structure, a model of the active centers involving associated dialkylmagnesium structures is proposed.
Thermal and microwave‐activate non‐aqueous free‐radical dispersion polymerization of methyl methacrylate in n‐heptane
Authors: Albert P. , Hölderle M. , Mülhaupt R. , Janda R.
Published: April 2003

Thermal and microwave‐induced free‐radical non‐aqueous dispersion polymerization of methyl methacrylate (MMA) in the presence of poly(styrene)‐block‐poly(ethene‐alt‐propene) dispersing agent were compared. For controlled polymerization in the microwave field, a new microwave polymerization reactor was built to afford uniform heating and to control temperature via microwave power variation. At identical MMA concentration and polymerization temperature of 70°C no special effect of the microwave field on conversions, molecular weights and particle sizes of PMMA was detected with respect to conventional thermal free radical dispersion polymerization.
Microwave‐treated low‐density polyethylene films
Authors: Hindeleh A. M. , Bulos B. R.
Published: April 2003

Low‐density polyethylene films, 80 μm thick, were exposed to microwave radiation and the following parameters were characterized: (i) the monoclinic to orthorhombic phase transformation, crystallinity and crystallite size using wide‐angle X‐ray diffraction, (ii) mechanical properties, and (iii) light absorption in the wavelength range of 200—800 nm. The following effects have been detected after microwave treatment: The major orthorhombic phase component increased, the monoclinic component decreased, the orthorhombic crystallite size decreased, the crystallinity, which was taken as the ratio of the scatter from the orthorhombic phase to the total scatter under the whole diffraction scan, increased. The mechanical properties improved. No change in the absorption of light was detected.
Measurement of orientation in uniaxially drawn polyacrylonitrile
Authors: Bashir Z.
Published: April 2003

In the literature, an estimate of the degree of orientation in drawn polyacrylonitrile (PAN) fibers is often inferred from the arc‐width of the strongest equatorial peak at 2ϑ = 16.8° in the wide angle X‐ray diffraction pattern. The absence of sharp meridional peaks in the diffraction pattern of oriented PAN means that chain orientation‐factors cannot be directly calculated. In this work, Wilchinsky's method for calculating the degree of chain orientation from the azimuthal intensity distribution of a strong equatorial peak has been adopted.
Combined LC main chain/side chain polymers
Authors: Zentel R. , Brehmer M.
Published: April 2003

Combined LC‐polymers possess the structural properties of both LC main chain and LC side chain polymers. Beneath this structural speciality, their broad LC‐phases and their polymorphism (different smectic phases and one nematic phase as a function of temperature) make them interesting. Crucial to an understanding of them is the fact that main chain and side chain mesogens orient parallel to each other and interact cooperatively to form the LC‐phase. Due to this synergism the temperature range of the LC‐phase is much broader than that of the corresponding LC main chain and LC side chain polymers. This interplay of main chain and side chain mesogens allows structures to be designed with preferably nematic or smectic phases. Whenever both types of mesogens can arrange in the same height, preferably smectic phases are formed. If this is not possible, the nematic phase dominates.

The incorporation of chiral groups allows cholesteric and chiral smectic C* phases to be prepared. For the latter, ferroelectric modes have been observed dielectrically. By crosslinking of combined LC‐polymers, combined LC‐elastomers can be prepared, in which the LC‐phases are nearly unchanged. These elastomers allow a mechanical orientation of the LC‐phases and, in particular, an untwisting of the helical superstructure of cholesteric and chiral smectic C* phases. In the latter case ferroelectric monodomains are obtained. The piezoeffect — to be expected — for LC‐elastomers with chiral smectic C* phases was first demonstrated for this class of polymers.
A spectroscopic and quantitative characterization of various fractions of the heterogeneous polymer system (EPDM‐g‐maleic anhydride)‐g‐polyamide 66 using high resolution 13C solid state NMR and IR techniques
Authors: van der Velden G. , Nelissen H. , Veermans T.
Published: April 2003

The structure of EPDM grafted onto polyamide 66 has been analyzed with high resolution solid state 13C NMR and IR spectroscopy. Details about the EPDM rubber include the amount of rubber incorporated in this blend, the sequence analysis of the EPDM rubber and an estimate of the type and amount of termonomer used (in this case only trans 1.4‐hexadiene). The sample contains 20% EPDM rubber, 6% polyamide 66 grafted onto EPDM rubber and 74% neat polyamide 66. Some evidence has been obtained via IR spectroscopy for the presence of cyclic imide groups, derived from grafted maleic anhydride groupings. No evidence for the use of a coupling agent could be obtained from either the 13C SPE‐MAS spectra of the interphase enhanced polyamide 66 or from the isolated rubber phase.
Structure and properties of polyamide 6 modified by N‐trialkylsilylcaprolactam
Authors: Mateva R. , Mateev M. , Delev O.
Published: April 2003

The physical behavior ofpolyamides of type N 6 with different contents of N‐trialkylsilylcaprolactam (SL) has been investigated by mechanical spectrometry, differential scanning calorimetry and wide‐angle X‐ray scattering. The copolymers have been obtained by an anionic polymerization in bulk under isothermal conditions. The presence of a bulky substituent at the nitrogen atom of the amide group plays an essential role for the number of the hydrogen bonds as well as for the formation of physical and chemical bonds. This bonds results in significant changes of the physical behavior of the modified polyamides. These changes have been studied.
Polymerization of N‐ethylmaleimide with cyclic ketene O,N‐acetals as catalyst
Authors: Fernández S. , Letsch J. , Klemm E.
Published: April 2003

Isopropylidene‐3,4,4‐trimethyl‐oxazolidine 3 is an initiator for the radically and anionically induced polymerization of N‐ethylmaleimide (NEMI) (Scheme 2). An electron transfer from the CT‐complex of NEMI/3 leads to the radical anion/radical cation pair. In THF (ϵ=7.58) diradicals result from these processes, connected with a radical homopolymerization of NEMI (experiment A). The polymerization is inhibited by TEMPO and not by H+‐ions (experiments B and G). In NEMI as “solvent” (experiment E), which possesses a high dielectric constant, we postulate an anionic mechanism for the NEMI homopolymerization. The polymerization also takes place in the presence of TEMPO and it is inhibited by H+‐ions (experiments F, C).
Self‐diffusivity of diblock copolymers in solutions in neutral good solvents
Authors: Anastasiadis S. H. , Chrissopoulou K. , Fytas G. , Appel M. , Fleischer G. , Adachi K. , Gallot Y.
Published: April 2003

The composition, f, and concentration, ϕ, dependence of the self‐diffusion coefficients of diblock copolymers in solutions in a common good solvent have been investigated by pulsed‐field‐gradient nuclear magnetic resonance and photon correlation spectroscopy. The difference in the entanglement characteristics of the parent homopolymers was found to be very important in determining the diffusion coefficients. The investigation on toluene solutions for a series of poly(styrene‐b‐isoprene) diblocks, possessing almost similar molecular weights and compositions ranging from 0.18 to 0.74, showed that the dependence of the diffusivity on diblock composition f conforms with the progressive transition from the Rouse to the entanglement regime at different concentrations due to the different critical molecular weights for entanglement of the parent homopolymers. The same idea can account for the diblock composition dependence of the self‐diffusivity for poly(styrene‐b‐butadiene) diblocks. Moreover, the self‐diffusivities for three poly(styrene‐b‐methyl methacrylate) diblocks in toluene are insensitive to copolymer composition (0.35 to 0.69) in accord with the very similar entanglement characteristics of the two blocks.
Synthesis of highly stereo‐ and regio‐regular isotactic poly(phenylglycidylether) using ionic coordinative initiators
Authors: Ronda J. C. , Serra A. , Mantecón A. , Cádiz V.
Published: April 2003

Racemic and optically active 3‐phenoxy‐1,2‐epoxypropane (phenylglycidylether, PGE) were polymerized in an ethereal solvent by an initiator system formed by combination of aluminum isopropoxide with one of four different zinc salts (chloride, bromide, iodide and acetate) in several ratios. Conversions and molecular weights of the isotactic polymer fraction are clearly related to the coordinating ability as a Lewis acid of the salts. Using water as co‐initiator, the non‐stereoselective sites are inactivated and therefore conversions and molecular weights of isotactic polymer increase. Both racemic and enantiomerically pure PPGEs show similar X‐ray patterns but some differences in the DSC plots are observed. Conversions, molecular weights and degrees of crystallinity of the isotactic polymer fraction obtained were studied and related to the polymerization conditions and the reaction mechanism.
Synthesis of block copolymers by nitroxyl‐controlled radical polymerization
Authors: Steenbock M. , Klapper M. , Müllen K. , Pinhal N. , Hubrich M.
Published: April 2003

The homopolymerization of methyl methacrylate (MMA) in the presence of 2,2,6,6‐tetramethyl‐1‐piperidinyloxy (TEMPO) is described and compared to the TEMPO‐mediated polymerization of styrene. Furthermore, the formation of block copolymers between MMA and styrene from polystyrene chains with TEMPO fragments as end groups is examined. The degree of block formation is estimated by GPC analyses. ESR experiments are performed on the polystyrene chains to study the scission behavior of the TEMPO fragments.
Recrystallization of HDPE in HDPE/iPP quenched films
Authors: Yan S. , Petermann J. , Yang D.
Published: April 2003

Epitaxial crystallization behavior of HDPE/iPP double layers under quenching and annealing conditions has been studied by means of transmission electron microscopy (TEM). The results obtained from bright field TEM observations indicate that in the as‐quenched state the HDPE that is in direct contact with the surface of the oriented iPP substrate recrystallizes in the form of oriented crystallites dispersed on the iPP substrate. The electron diffraction results show that besides the two normally observed epitaxial orientations between HDPE and iPP, there is also a special orientation with [001]HDPE ‖ [001]iPP. The HDPE which is in contact with the clean surface of a glass slide crystallizes in small lamellae with random orientation. In the boundary region, the epitaxially crystallized HDPE small lamellae stop right on the boundary of the oriented iPP film. If the quenched samples are annealed at 128°C (below Tm of HDPE) for 2 h, the small HDPE crystals grow to thick lamellae in both areas. But only the epitaxial orientation of HDPE with [001]HDPE ‖ [101]iPP has been observed.
Lipase‐Catalyzed ring‐opening polymerization and copolymerization of 15‐pentadecanolide
Authors: Uyama H. , Kikuchi H. , Takeya K. , Kabayashi S.
Published: April 2003

Enzymatic ring‐opening polymerization of a 16‐membered lactone, 15‐pentadecanolide (PDL), has been carried out in bulk using various lipases of different origin as catalyst. The polymerization with Pseudomonas fluorescens lipase (lipase PF) catalyst afforded the corresponding polyester in high yields. The rate of the polymerization catalyzed by lipase PF at a temperature lower than 45°C was very small, whereas the polymerization at higher polymerization temperature (≥60°C) proceeded much faster. Lipase derived from Pseudomonas cepacia was also active for the polymerization of PDL. The polymerization catalyzed by Candida cylindracea lipase at high temperature (75°C) afforded the polymer with molecular weight up to 2.0 x 104. The polymerization behavior of PDL through lipase catalysis has been compared with that of ε‐caprolactone (ε‐CL). PDL showed an enzymatically higher polymerizability than ε‐CL, despite the smaller ring‐strain of PDL, which is due to the stronger recognition of PDL by lipase. Enzymatic copolymerization of PDL with other lactones using lipase PF catalyst produced copolymers with molecular weight of several thousands. From 13C NMR analysis, the diad sequence distributions were determined.
Self‐compacting smectic polymers. An unusual temperature dependence of interlayer distance for side chain polysiloxanes in sm a and sm b phases
Authors: Kozlovsky M. V. , Haase W.
Published: April 2003

A prominent reduction of the layer thickness, d1, in the Sm A and Sm B phases with increasing temperature has been observed for a series of side chain polymers. The maximum decrease in d1 value for one of the copolymers is ∼7Å; i.e. 15% of its total value. The influence of the chemical structure of the main chain and side groups on the effect has been studied. Models have been proposed for packing of mesogenic side groups at different temperatures.
Fractionation of partially stereoregular poly(propylene oxide) from acetonitrile solution
Authors: Colak N. , Akgün A.
Published: April 2003

Partially stereoregular poly(propylene oxide) (PPO) samples synthesized using Pruitt‐Bagett catalysts (PBC) were fractionated at 40°C and 70°C from acetonitrile solution by adding small portions of water. The formed polymer‐rich phases were clear liquids except the first three fractions obtained at 40°C; those were solids. The fractions were characterized with their viscosity average molecular masses and melting points. Results showed that the procedure described in the present report fractionates partially stereoregular PPO on the basis of molecular weight, independent of their tacticity.
Liquid crystalline block and graft copolymers
Authors: Fischer H. , Poser S.
Published: April 2003

Since the first reports on the combination of liquid crystalline polymers in block (1985) and graft (1986) copolymers with amorphous and semi‐crystalline polymers, the scientific interest has been focused on understanding how the size and type of the mesophase displayed by the liquid crystalline part(s) affects the LC → isotropic transition and the order in the LC domains themselves with respect to the morphology displayed. An overview of the work that has been done so far will be given, as well as a closer discussion of the interaction between morphology and LC phase behavior as evaluated on a large number of very well defined LC side group block copolymers. Furthermore, applications and results of mechanical and optical investigations are discussed.
Influence of the elimination temperature on light emitting devices prepared from poly(p‐phenylene vinylene)
Authors: Herold M. , Gmeiner J. , Schwoerer M.
Published: April 2003

We report detailed measurements on the thermal conversion of the tetrahydrothiophene prepolymer to poly(p‐phenylene vinylene) (PPV) and show the influence of the elimination conditions on the properties of PPV and on light emitting devices (LEDs) prepared in the configuration ITO/PPV/Al. Electroluminescence correlates with a diode behavior in the current—voltage characteristic and can be observed for PPV heated at a minimum temperature of 130°C. Increase of the elimination temperature results in a red‐shift of both the photoluminescence and electroluminescence spectra by ≈10 nm, which enables us to control the color of our LEDs in a small range. We have observed that refered to the brightness of the devices the optimum elimination temperature is 160°C, and we show that a further increase of temperature does not improve the properties of PPV‐ LEDs.
The characteristics of polydienes obtained with lanthanide‐based catalysts
Authors: Iovu H. , Hubea G. , Hurst S. J.
Published: April 2003

Polyisoprene and polybutadiene samples, prepared from the respective monomers using lanthanide‐based catalysts, have been analyzed in terms of microstructure, glass transition temperatures and stabilities to thermo‐oxidative degradation. Quantitative determination of 1,4‐cis/trans, 1,2‐ and 3,4‐contents have been made from the IR spectra of the polymers. Attempts to use 1H and 13C NMR and Raman spectroscopy to analyze the microstructure of the materials has at best proved only partially successful. TGA and IR spectroscopy have been used to study the influence of catalyst residue on the thermo‐oxidative degradation of the polymers.
Morphology of a conducting polymer and its relation to the electronic properties
Authors: Paschen S. , Carrard M. , Senior B. , Chao F. , Costa M. , Zuppiroli L.
Published: April 2003

We have investigated the morphology of a heavily disordered conducting polymer, polypyrrole doped with large polymeric anions. An extensive microscopy study (scanning electron microscopy, atomic force microscopy and transmission electron microscopy) together with previously obtained information on the samples' electronic properties conveys to us the following image: the observed globules of diameters between 10 and 100 nm originate from the polymeric dopants forming coils with the doping centers concentrated on the coil surfaces and the polypyrrole surrounding the whole. In this way polypyrrole‐rich “sheets” run through the whole sample and guarantee the electrical continuity which prevails even in samples with polypyrrole volume fractions as low as several per cent. For the first time, the building block of the “fractal” cauliflower structure, observed also in many other electrochemically prepared conducting polymers, could be identified.
Evaluation of equation‐of‐state parameters and the description of PVT‐data
Authors: Rudolf B. , Ougizawa T. , Inoue T.
Published: April 2003

For three different equation‐of‐state theories the characteristic parameters of two polymers were calculated, and the ability of the theories to describe PVT‐data using these parameters was investigated. The comparison between the different theories shows that, concerning the description of PVT‐data, the modified cell model of Dee and Walsh is not only superior to the theory of Flory, Orvoll and Vrij and that of Sanchez and Lacombe as reported before, but also to the theory of Simha and Somecynsky and the open cell model of Zhong, Wang and Lu. Finally, simple formulae are given to calculate the characteristic parameters of the latter two theories from those of the theory of Flory, Orwoll and Vrij.
Biphasic polystyrene ionomers neutralized by bifunctional organic counterions
Authors: Dulac L. , Bazuin C. G.
Published: April 2003

The evidence for biphasic morphology in lightly sulfonated polystyrene (PS‐SSA) ionomers neutralized by bifunctional organic cations (namely, 1,6‐hexanediamine or HDA) is established by comparing their dynamic mechanical behavior, as a function of ion content and degree of neutralization, with that for metal‐neutralized biphasic ionomers. The trends as a function of ion content regarding the transition temperatures and intensities of the HDA‐neutralized ionomers parallel what is observed for metal‐neutralized ionomers, in particular polystyrene‐based ones. A small‐angle X‐ray scattering peak, identified as an “ionomer peak”, is observed in the PS‐SSA‐HDA ionomer of the highest ion content studied. Furthermore, it was observed that partial neutralization affects the cluster phase more strongly than the matrix phase. This can be explained by the contribution of the acid groups to the matrix Tg, and their ability, when present in large amounts, to affect the ionic interaction strength or facilitate ion hopping, which influences primarily the cluster Tg.
Problems relating to long period determination in polyethylene shish‐kebab structures
Authors: Michler G. H. , Naumann I. , Baltá Calleja F. J. , Ania F.
Published: April 2003

The X‐ray long periods from high molecular weight injection molded polyethylene (PE) with a shish‐kebab structure have been compared with values derived from electron micrographs. It is shown that while small angle X‐ray scattering (SAXS) presents two long periods, the direct measurements from transmission electron microscopy (TEM) furnish only the lower SAXS periodicity. In an attempt to clarify this discrepancy of results, laser light diffraction and Fourier transformation of electron micrographs have been undertaken. Using this method two long periods are found in all regions investigated. Results are discussed in terms of the role played by the structured or “weakly crystalline” interlamellar parts, containing a lower electron density, which are neglected by the small angle scattering of X‐rays and which give rise in particular regions to larger scattering periodicities.
Comparison of the viscoelastic properties of syndio‐ and isotactic polypropylenes
Authors: Eckstein A. , Friedrich C. , Lobbrecht A. , Spitz R. , Mülhaupt R.
Published: April 2003

The viscoelastic properties of fourteen syndio‐ and isotactic polypropylenes (PPs) were measured in the molten state at several temperatures by means of oscillatory rheometry. Metallocene catalysis allows the control of molecular mass of both PP families and provides narrow molecular mass distributions (MMD) with a polydispersity of about 2. The validity of the Arrhenius and WLF equations for PP was checked. Syndio‐ and isotactic PP follow Arrhenius behavior but exhibit different activation energies of flow. From the dynamic shear moduli, viscoelastic parameters were determined and correlated with molecular mass. The dependence of the zero shear viscosity on the weight average molar mass exhibits the well‐known scaling relation. Stereoregularity has an important effect on the viscoelestic behavior of PP melts.
Anisotropic surface eruptions on polymerized diacetylene crystals
Authors: Shivshankar V. , Sung C. , Kumar J. , Tripathy S. K. , Sandman D. J.
Published: April 2003

Surface eruptions that are approximately 0.5 μm in diameter at the base and about 700 Å in height have been observed by atomic force microscopy on single crystals and films of polydiacetylenes of the alkylurethanes of 5,7‐dodecadiyn‐1,12‐diol when the polymerization is performed using 60Co gamma radiation in the presence of air. The eruption process is associated with monomer polymerization and is anisotropic, as the eruptions are found only on the (100) face of single crystal specimens. Crystals having surface eruptions are irreversibly converted from blue to red at room temperature on exposure to a single pulse of 532 nm laser light while crystals lacking eruptions do not undergo this change.
Phase inversion with gel/sol/gel‐treatment — a new technology for the formation of hollow‐fiber membranes at a wet spinning process
Authors: Albrecht W. , Weigel Th. , Paul D.
Published: April 2003

The preparation of hollow‐fiber membranes with high asymmetric morphology by a wet spinning process by phase inversion of polymer solutions with a nonsolvent medium is normally connected with the formation of a relatively dense unwelcome skin. One possibility to eliminate this disadvantage is a phase inversion process with gel/sol/gel‐treatment, whose physicochemical peculiarities are descibed in this paper. In the gel/sol/gel‐treatment an initially wet hollow‐fiber membrane is contacted with a solvent and subsequently with a nonsolvent again. Such a technology causes a second phase inversion at the outer surface of the hollow‐fiber membrane. Results about parameters influencing the gel/sol/gel‐process are presented as an illustration for the treatment of polyacrylonitrile hollow‐fiber membranes with a special structure. In conclusion, first ideas of the mechanism of this process are formulated.
Unique morphology of poly(azomethine ethers) sheared in the liquid crystalline state
Authors: Dean D. , Geil P. H.
Published: April 2003

The morphology and electron diffraction patterns of sheared films of a series of aliphatic‐aromatic poly(azomethine ethers) with n = 1,4 and 7–10 CH2 units in the aliphatic segment have been characterized by transmission electron microscopy. The films were prepared by shearing in the liquid crystalline (nematic) state. In all cases, lamellae ca. 400 Å thick and more or less perpendicular to the shear direction and perpendicular to the substrate were obtained. Annealing increases the lamellar thickness and overall order. Redrawing of annealed, sheared samples of n = 10 suggests they consist of chain folded lamellae. Electron diffraction (ED) yielded h0l single crystal patterns in all cases, except for n = 1, which yielded orthorhombic, fiber‐like patterns. The h0l patterns suggest a planar, single crystal orientation over the entire sample. Annealing sheared samples above the crystal‐liquid crystal transition temperature resulted in reorientation of the molecules (from parallel to perpendicular) with respect to the substrate. ED patterns changed accordingly from h0l to hk0. Sheared samples with n = 4 gave both orthorhombic and monoclinic diffraction patterns.
Syntheses and spectroscopic pH titrations of naphthol‐labeled poly(methacrylic acid)s
Authors: Itoh Y. , Ogura K. , Hirota T. , Hachimori A. , Abe K.
Published: April 2003

Poly(methacrylic acid) (PMA) and poly(acrylamide) (PAAm) with a small mole fraction of naphthol (NpOH) residues were prepared by polymerization of methacrylic acid or acrylamide with three position isomers, methacryloylaminonaphthol. The substituent effect on the apparent pK values (pKobsd), determined by spectroscopic pH titrations in aqueous solution, was observed for the NpOH‐labeled PAAm. The electrostatic surface potential (ψ) for PMA was calculated from the difference in the pKobsd values for the labeled PMA and PAAm. The obtained ψ value decreased as the spacing between the OH moiety and the polymer main chain increased. This clearly indicates that the ψ value is a sensitive function of the distance from the polyion surface.
Properties of ultra‐high‐molecular polyethylene and related polymerization‐filled composites produced by solid‐state extrusion
Authors: Beloshenko V. A. , Kozlov G. V. , Varyukhin V. N. , Slobodina V. G.
Published: April 2003

The structural, shrinkage and mechanical characteristics were studied of specimens of ultra‐high‐molecular polyethylene (UHMPE) and polymerization‐filled composites UHMPE‐Al and UHMPE‐bauxite produced by plunger extrusion of powder material. It is shown that the dependence of the strain–stress characteristics of UHMPE and its composites on the extrusion ratio varies considerably in the presence of a filler. Mechanisms explaining the behavior of the polymer material under study are proposed.
Electroluminescent stilbenoids – electrochemically generated luminescence in solution and organic light emitting devices on a polymer blend basis
Authors: Kelnhofer K. , Knorr A. , Tak Y.‐H. , Bässler H. , Daub J.
Published: April 2003

Organic light‐emitting diodes based on molecularly doped polymer blends have been fabricated and characterized using donor–acceptor substituted stilbenoids as active dye components for hole transport, electron transport and emission. A Comparison of the electrochemically generated luminescence (ECL), the photoluminescence (PL) and the electroluminescence (EL) of the organic light‐emitting devices (OLEDs) is given.
Rheology of diblock copolymer micellar systems
Authors: Watanabe H.
Published: April 2003

This article summarizes rheological features of moderately concentrated, diblock copolymer micellar solutions in selective solvents. In solvents of monomeric sizes, spherical micelles (with glassy cores) are arranged on cubic lattices to exhibit elasto‐plastic responses. These lattices are formed due to an osmotic constraint for the conformation of solvated corona blocks of the micelles. In polymeric solvents (homopolymers) chemically identical to the corona blocks, this constraint is screened and the micelles are randomly dispersed in the systems. In this type of blends (micellar dispersions) in short, nonentangling matrices the micelles have no plasticity but exhibit two‐step viscoelastic relaxation: The fast relaxation process corresponds to relaxation of individual corona blocks while the slow process is attributable to diffusion of the micelles. Corresponding to these molecular mechanisms, the fast process exhibits modest damping of the nonlinear relaxation modulus against large step strains while the slow process exhibits much stronger damping. Under steady flow, the micellar dispersion exhibits two‐step shear‐thinning with the molecular origin identical to that for the nonlinear damping. All these rheological features of the micellar lattices and dispersions are strikingly similar, in many aspects, to the features of colloidal crystals and hard‐sphere suspensions of solid particles.
Clear evidence of the sensitivity of the solvatochromic effect to side chain functionalization in 3‐hexyl‐substituted polythiophenes
Authors: Della‐Casa C. , Costa‐Bizzarri P. , Lanzi M. , Bertinelli F.
Published: April 2003

The solvatochromic properties of 3‐hexyl‐substituted polythiophenes functionalized with an ester, ether or hydroxy group at the end of the alkyl side chain are reported. An extraordinarily large shift, Δmax = 99 nm, and a dramatic change of the UV/ vis spectral profile are found when the carboxylate is replaced with the hydroxy group by functionalization exchange. The solvatochromic behavior of each polymer is believed to be strictly related to the type of functional group owing to different physical interactions (solvation) between groups different in polarity and solvent molecules. A unique and common chromophoric unit for the final conformation of the 3‐hexyl‐substituted polythiophenes, induced by the solvatochromic effect, is also suggested.
Two‐dimensional computer simulation of spherulite formation by branching lamellae
Authors: Kalinka G. , Hinrichsen G.
Published: April 2003

The structure formation of growing spherulites by branching lamellae is simulated by a computer model. In addition to the process of linear growth of lamellae, three different mechanisms are implemented in the simulation program: the fork‐like branching of lamellae at their growth front (“front branching”), the generation of secondary lamellae at the sides of already existing lamellae (“side branching”) and the crystallization of lamellae parallel to existing lamellae (“clustering”). The simulation is performed stepwise and the branching takes place in dependence on branching probability and angle, leading to a multiplication of the lamellae and to disc‐like superstructures. Moreover, the side branching as well as the clustering mechanisms result in a gradient of “density” (crystallized entities per area unit) inside the spherulites.
Diffusion of polystyrene micronetwork spheres in melts of polyvinylmethylether
Authors: Pies C. , Sillescu H.
Published: April 2003

We have determined by forced Rayleigh scattering the diffusion coefficients of photo‐labeled polystyrene micronetwork spheres (radii ≤ 10 nm) in melts of linear polyvinylmethylether (Mw ≤ 40 000 g/mol) at temperatures of 20−80°C. An expected slippage of the spheres through the meshes of the entanglement network appears possible but is still within the experimental uncertainty of our results.
Regioselective polycondensation of benzyl 2‐amino‐2‐deoxy‐α‐D‐glucopyranoside hydrochloride with carbon dioxide
Authors: Kadokawa J. , Horiguchi T. , Sunaga E. , Karasu M. , Tagaya H. , Chiba K.
Published: April 2003

This paper reports the polycondensation of benzyl 2‐amino‐2‐deoxy‐α‐D‐glucopyranoside hydrochloride (1) with carbon dioxide using the triphenylphosphine/carbon tetrachloride/DBU system as a condensing agent to give poly(urethane) (2). The polycondensation of 1 with CO2 was carried out in DMF solvent in the presence of the condensing agent under CO2 atmosphere. From the NMR and IR analyses of the product, the polymerization proceeded regioselectively to form 2. The molecular weight was estimated as 2000–3000 by GPC measurement after acetylation of 2, corresponding to DP = 5–8.
Measuring chain diffusion coefficients and activation energy during coalescence of fluorescence‐labeled hard latex particles
Authors: Canpolat M. , Pekcan Ö.
Published: April 2003

The steady‐state fluorescence (SSF) technique was used to study interdiffusion of polymer chains across the particle–particle junction during film formation from hard latex particles. The latex films were prepared from pyrene (P) and naphthalene (N) labeled poly(methyl methacrylate) (PMMA) particles and annealed for long time intervals above the glass transition temperature (Tg) between 170 and 220°C. A novel correction method was suggested and employed to eliminate changing of the optical density of latex films after such annealing processes. P and N fluorescence intensities solely from the energy‐transfer processes were monitored versus annealing time and were used to measure the polymer chain diffusion coefficients Dp and DN, which were found to be between 4.34 × 10–14 and 7.68 × 10–13 cm2/s for an annealing temperature between 170 and 220°C. Using these diffusion coefficients with the Arrhenius relation, the diffusion activation energy for the polymer backbone was found to be 28 kcal/mol.
Morphology of banded spherulites in poly(ε‐caprolactone)/poly(styrene‐ran‐acrylonitrile) blends
Authors: Wang Chun , Thomann R. , Kressler J. , Thomann Y. , Crämer K. , Stühn B. , Svoboda P. , Inoue T.
Published: April 2003

The occurrence of banded spherulites in blends of poly(ε‐caprolactone) with poly(styrene‐ran‐acrylonitrile) is studied by means of optical‐, scanning electron‐, environmental scanning electron‐, and atomic force‐microscopy as well as smallangle X‐ray scattering. The measurements reveal that lamellae are confined in fibrils that bend periodically from the center of spherulites in a radial direction. The fibrils show also a regular spacing in the lateral direction. Single bent lamellae can be observed by atomic force microscopy after permanganic etching. The enrichment of amorphous material near to the growth front of the spherulites can be directly observed by polarized light microscopy after temperature jump experiments. The excluded amorphous material on the surface of the growing spherulites has the shape of droplets. This might be the main reason for the initiation of the bending process because the result is a non‐uniform stress distribution acting on the growing lamellae at the interface between spherulites and the surrounding melt. The amorphous material of the blends can be found in three areas as observed by small‐angle X‐ray scattering experiments and microscopical methods: (i) between the lamellae, (ii) excluded from the interlamellar region but within the spherulite, and (iii) for high contents of non‐crystallizable material, it can be excluded from the spherulite. The banding periodicity of spherulites as a function of the crystallization temperature can be described in terms of two models, based either (i) on the inherent twisting of lamellae perpendicular to the axis of a screw dislocation or (ii) on the dependence of the diffusion of amorphous material away from the growth front of lamellae and the temperature dependence of the rate of crystallization. Both models fail at very low supercoolings near to temperatures where the banding disappears completely.
Combining oxidative addition and polymerization: A study towards the synthesis of macromonomers
Authors: Massa W. , Faza N. , Kang Hak‐Chul , Focke C. , Heitz W.
Published: April 2003

Oxidative addition to a metal in a low valent state produces catalysts that allow reporter or functional groups to be introduced to a polymer chain end. Substituted allyltrifluoroacetates were added to Ni(0)(COD)2. The resulting π‐allyl‐Ni trifluoroacetates are dimeric in the solid state as well as in solution. The crystal structure of bis[(η3‐2‐phenylallyl)(trifluoroacetato)‐nickel(II)], bis[(η3‐2‐trimethylsilylallyl)(trifluoroacetato)nickel(II)], are given and correlated with the reactivity as polymerization catalysts. Butadiene, styrene, and norbornene are used as monomers. The substituent of the allyl group is found quantitatively to be the end group of each macromolecule. Thus it is demonstrated that no chain transfer occurs.
Chirality induction in cyclopolymerization
Authors: Yokota K. , Kakuchi T. , Uesaka T. , Obata M.
Published: April 2003

An overview of the synthesis of optically active polymers due to main‐chain chirality based on the configurational arrangement in cyclopolymerization and cyclocopolymerization is presented. The template having chiral twist transmitted its chirality to the main chain in the intramolecular cyclization of divinyl monomers to form the enantiomeric racemo cyclic units. The asymmetric cyclocopolymerization produced the polymers which were optically active even after cleaving the template. The synthesis of optically active polymers from achiral monomers using a slight amount of chiral initiator was achieved by the enantioselective cyclopolymerization. The cyclopolymerization capable of controlling stereochemistry of the cyclic constitutional units was one of useful means for asymmetric polymerization.