bluuebunny/crossref_metadata_2025 huggingface dataset:
Cover Picture: Diastereoselective Temporary Silicon‐Tethered Ring‐Closing‐Metathesis Reactions with Prochiral Alcohols: A New Approach to Long‐Range Asymmetric Induction (Angew. Chem. Int. Ed. 15/2003)
Authors: Evans P. Andrew , Cui Jian , Buffone Gerald P.
Published: April 2003

Taking control of stereochemistry should lead to an enhanced understanding of the conformational aspects that affect diastereoselectivity in medium‐sized ring systems. The temporary silicon‐tethered ring‐closing‐metathesis reactions described by P. A. Evans et al. on page 1734 ff. represent a new strategy for long‐range asymmetric induction that provides a useful approach to 1,4‐, 1,5‐, and 1,6‐stereocontrol.
Multiple‐primer DNA sequencing method
Authors: Gharizadeh Baback , Ghaderi Mehran , Donnelly Declan , Amini Bahram , Wallin Keng‐Ling , Nyrén Pål
Published: April 2003

A multiple‐primer DNA sequencing approach suitable for genotyping, detection and identification of microorganisms and viruses has been developed. In this new method two or more sequencing primers, combined in a pool, are added to a DNA sample of interest. The oligonucleotide that hybridizes to the DNA sample will function as a primer during the subsequent DNA sequencing procedure. This strategy is suited for selective detection and genotyping of relevant microorganisms and samples harboring different DNA targets such as multiple variant/infected samples as well as unspecific amplification products. This method is used here in a model system for detection and typing of high‐risk oncogenic human papilloma viruses (HPVs) in samples containing multiple infections/variants or unspecific amplification products. Type‐specific sequencing primers were designed for four of the most oncogenic (high‐risk) HPV types (HPV‐16, HPV‐18, HPV‐33, and HPV‐45). The primers were combined and added to a sample containing a mixture of one high‐risk (16, 18, 33, or 45) and one or two low‐risk types. The DNA samples were sequenced by the Pyrosequencing™ technology and the Sanger dideoxy sequencing method. Correct genotyping was achieved in all tested combinations. This multiple‐sequencing primer approach also improved the sequence data quality for samples containing unspecific amplification products. The new strategy is highly suitable for diagnostic typing of relevant species/genotypes of microorganisms.
High‐throughput capillary electrophoretic method for determination of total aminothiols in plasma and urine
Authors: Lochman Pavel , Adam Tomáš , Friedecký David , Hlídková Eva , Škopková Zuzana
Published: April 2003

Increased interest in the analysis of aminothiols in body fluids during the last years results in a request for high‐throughput analytical methods for their determination. We report here a novel, high‐throughput method for the determination of total concentrations of biogenous aminothiols – homocysteine, cysteine, glutathione, cysteinylglycine, γ‐glutamylcysteine, and of penicilamine, mercaptopropionylglycine, and cysteamine, three compounds used to treat disorders of aminothiol metabolism in plasma and urine. Samples were reduced with tris(carboxyethyl)phosphine and labeled with 5‐(bromomethyl)fluorescein. Capillary electrophoretic separations were performed in 60 mmol/L borate – 15 mmol/L sodium dodecyl sulfate – 2‐amino‐2‐methyl‐1‐propanol, pH 10.0, with laser‐induced fluorescence detection. Analysis time was less than 2 min. The assay is linear (r > 0.999) up to 500 μmol/L. Reproducibilities of migration times (coefficient of variation, CV) were < 0.5%. Interassay repeatabilities (CV, n = 10) were 5.08% and 6.09% for 5 μmol/L addition of homocysteine and 0.60% and 3.78% for 100 μmol/L addition of cysteine in plasma and urine, respectively. Recovery values were within 94–106% and sensitivity was better than 0.19 μmol/L for all analyzed compounds. Results agreed well with a standard high‐performance liquid chromatography (HPLC) method. The diagnostic usefulness of the method has been proven on 79 samples of cystinuric patients and 12 samples of homocystinuric patients. We report here a novel method for the determination of aminothiols in body fluids by capillary electrophoresis (CE). Determination is fast and sensitive enough for diagnostic purposes.
Numerical calculation of the electroosmotic flow at the cross region in microfluidic chips
Authors: Jin Ya , Luo Guo‐An
Published: April 2003

A numerical study is presented for the electroosmotic flow (EOF) at the cross region in microfluidic chips. The distributions of the electric potential due to the electric double layer (EDL) and the external electric field are discussed and the calculation of the latter can give rough speculations on the flow tendencies in the channels during various operation modes. Simplification of the two‐dimensional Navier‐Stokes (N‐S) equations is obtained by focusing on the solution of interior flows, and the numerical calculation results show good agreement with the experimental images. The sample leakage to the separation channel during the “float” sampling proved to be caused not only by the sample diffusion, but also by the weak extension of the sampling electric field. It is also verified that with suitable voltage configuration, the “pinch” sampling mode is better than the “float” mode in sample plug control.
Normal human dermal fibroblasts: Proteomic analysis of cell layer and culture medium
Authors: Boraldi Federica , Bini Luca , Liberatori Sabrina , Armini Alessandro , Pallini Vitaliano , Tiozzo Roberta , Ronchetti Ivonne Pasquali , Quaglino Daniela
Published: April 2003

Proteins present within the cell layer and those released in the cell medium from in vitro cultured normal human dermal fibroblasts were separated and characterized in terms of their isoelectric point and molecular weight, by two‐dimensional (2‐D) gel electrophoresis. All spots in the synthetic gel were firstly analyzed by the Melanie 3 software and compared with those of breast cancer cells, colorectal epithelial cells, HL60, lymphoma cells, and platelets, already available on‐line. From the identification of 144 spots from both the cell layer and the medium, we were able to recognize 89 different proteins, since a certain number of spots represented different isoforms of the same molecule. Identifications were performed by matching with on‐line 2‐D databases, and by matrix assisted laser‐desorption/ionization‐time of flight‐mass spectrometry (MALDI‐TOF‐MS), in order to confirm the identification by matching, or to identify new proteins. The procedure we used allows (i) to design a highly reproducible reference map of the proteome of adult human normal fibroblasts in culture, (ii) to evaluate protein species produced in the cell layer as well as those released in the culture medium, and (iii) to compare data from gel matching with those obtained by MS. This work represents an essential step for a better knowledge of mesenchymal cells, given the widespread use of this cell type in both clinical and experimental investigations.
Identification of a specifically expressed modified form of novel PSP‐94 protein in the secretion of benign prostatic hyperplasia
Authors: Xu Kexin , Wang Xianghong , Ling Ming‐tat , Lee Davy T. W. , Fan Tianyong , Chan Franky L. , Xuan James J. W. , Tsao Sai‐Wah , Wong Yong‐Chuan
Published: April 2003

Using two‐dimensional gel electrophoresis, we investigated the profile of prostatic secretory proteins in human expressed prostatic secretion (EPS) from benign prostate hyperplasia (BPH) patients and compared the patterns with normal controls. We identified three specifically expressed proteins, including prostate secretory protein 61 (PSP61), in EPS from benign BPH patients but absent in normal controls. In addition, we found that PSP61 was a modified isoform of the well‐documented PSP‐94, which had a perfect matching (100% homology) to the first 61 amino acids of the PSP‐94 protein but with a deleted C‐terminus. This shortened PSP61 was not due to alternative splicing of the PSP‐94 gene at transcription level. Our results provide first evidence on the possibility of using PSP61 as a specific biological marker for diagnosis of BPH.
Also sprach Zarathustra..
Authors: Unterstell Rembert
Published: April 2003

Das Emmy Noether‐Programm eröffnet dem Religions‐wissenschaftler Michael Stausberg eine neue Perspektive
Wenn die Götter sichtbar werden
Authors: Demmer Ulrich , Heidemann Frank
Published: April 2003

Die Jenu Kurumba sind Jäger und Sammler. Die Stammesrituale vermitteln erstaunliche Einblicke in die Lebensordnung dieser indischen Gemeinschaft
New archaeo‐stratigraphic data for the TD6 level in relation to Homo antecessor (Lower Pleistocene) at the site of Atapuerca, north‐central Spain
Authors: Canals Antoni , Vallverdú Josep , Carbonell Eudald
Published: April 2003

The sediments of the TD6 level of Gran Dolina Cave at Sierra de Atapuerca, Burgos, Spain, consist of a series of mud flows with angular clasts. The TD6 deposit has two parts: an upper part, known as the Aurora stratum, which yields Homo antecessor remains, and a lower part with rather homogeneous sediment. The excavation of TD6 level did not reveal a sequence of diachronic occupations. Instead, the contextual and stratigraphic studies permitted us to describe and delimit the micro‐units forming the TD6 deposit. The study of the distribution of archaeological remains based on vertical archaeological profiles, using an archaeo‐stratigraphic method, allowed us to document the occurrence of a series of archaeological levels within the apparent homogeneous deposit. Variations in the density of archaeological remains along the archaeo‐stratigraphic levels permitted us to define two occupational cycles in TD6. These cycles seemingly show increased activities through time, culminating in the Aurora level with the presence of cannibalized Homo antecessor remains. © 2003 Wiley Periodicals, Inc.
Short contribution: A practical alternative to Kubiena boxes for the collection of samples for micromorphological analysis
Authors: Josephs Richard L. , Bettis E. Arthur
Published: April 2003

This note proposes a practical and economical alternative to using Kubiena boxes for the collection of undisturbed soil or sediment samples for micromorphological analysis. The authors promote the use of plastic electrical outlet boxes (gang boxes) that can be purchased at any hardware store for around 20 cents apiece. In addition to availability and low cost, plastic gang boxes are preferred by thin‐section laboratories over that of the aluminum Kubiena boxes because they cause less wear on the thin‐sectioning equipment. As with Kubiena boxes, the samples are impregnated directly in the gang boxes, yet they are more easily and efficiently retrieved, thus facilitating overall sample preparation and insuring a final product of equal or better quality. © 2003 Wiley Periodicals, Inc.
Origin of post‐Minoan caves and volcaniclastic cave fill, Thera (Santorini), Greece
Authors: Ramage Joan M. , Shaw George H. , Hoffman Jeff A. , Johnston Sarah A.
Published: April 2003

The Aegean island of Thera (Santorini) was covered by tephra from its cataclysmic Late Bronze Age (ca. 3600 yr B.P.) eruption. Vertical exposures of the eruptive sequence show secondary, nonvolcanic, circular (in cross section) features composed of stratified sediment. Many are inaccessible from the floors of modern quarries and appear to be caves filled with younger sediment, but show no connection to the land surface. A filled cave was found in the wall of a modern gully outside the modern quarries, and a filled cave was found in a terrace scarp, well above the modern gully. Natural (and probably rapid) incision by gullies into the thick tephra deposit left many locations with lateral access to tephra. Inhabitants from post‐Minoan to recent times excavated tephra for materials and buildings, and caves were subsequently filled by sporadic (possibly seasonal) flood events that deposited sediment. These gullies may have provided access for modern tephra removal that isolated the filled caves high on the modern quarry walls. © 2003 Wiley Periodicals, Inc.
Short contribution: Strategies and techniques in collecting micromorphology samples
Authors: Goldberg Paul , Macphail Richard I.
Published: April 2003

Micromorphology plays an important role in understanding the context and formation of archaeological deposits and soils. However, little information about the strategies and considerations for collecting samples for micromorphological analysis has been published. This is especially so for stony or crumbly deposits that are difficult to remove while preserving their undisturbed nature. We present several techniques and strategies to facilitate the collection of micromorphological samples by people with limited experience. © 2003 Wiley Periodicals, Inc.
Thin film melt polymerized single crystals of poly(p‐oxybenzoate)
Authors: Rybnikář František , Liu Jiang , Geil Phillip H.
Published: April 2003

The morphology of poly(p‐oxybenzoate) polymerized from p‐acetoxybenzoic acid (pABA) in constrained thin films at temperatures between 130°C and 315°C for various times is described. Polymerization below the melting point of the monomer, 196°C, occurs by a sublimationrecrystallization‐melting process, with polymerization occuring in the melt. Lamellar crystals, often bilayered, are found that are ca. 100 Å thick as well as single disclination domains. Electron diffraction patterns indicate the presence of either phase I or II in a given crystal, with the unit cell for phase II being proposed; the molecular axes are normal to the lamellae. Polymerization above 200°C results in holes in the lamellae; it is suggested that polymerization also is in the form of lamellae followed by the hole formation as further reaction occurs in the crystalline state, initial “crystal” growth at all temperatures is in the liquid crystalline state.
In situ polymerization of tetraethoxysilane in poly(vinyl acetate)
Authors: Girard‐Reydet Emmanuel , Lam Thanh My , Pascault Jean Pierre
Published: April 2003

The in situ polymerization of tetraethoxysilane (TEOS) in poly(vinyl acetate) (PVAc) yields homogeneous and transparent nanocomposite materials. It was shown that covalent bonds occur between the organic chains and the inorganic clusters, preventing macroscopic phase separation. For an initial amount of TEOS higher than a critical value, gel formation is observed. Up to this critical TEOS content, improved mechanical properties, which persist at high temperatures, are obtained.
Evaluation of unperturbed polymer dimensions from intrinsic viscosity in non‐ideal solvents
Authors: Abdel‐Azim Abdel‐Azim A.
Published: April 2003

For solutions of polystyrene (PS) samples of different relative molecular mass (molecular weight) M and intrinsic viscosities [n] have been measured at 298,15 K in pure toluene (T) and toluene/methanol (MeOH) mixtures. Upon mixing toluene (good solvent (1)) and methanol (nonsolvent (2)), a systematic decrease in the solvation power was obtained. A critical examination of the Stockmayer‐Fixman method for obtaining unperturbed dimensions from intrinsic viscosity measurements has been made. It was found that the unperturbed dimensions were not constant and different from those measured in a theta solvent (T/MeOH mixture having volume fraction of methanol (ϕMeOH) = 0,23). The derived values of unperturbed dimensions were found to increase with increasing Kuhn‐Mark‐Houwink‐Sakurada exponent a. A modified form of the Stockmayer‐Fixman equation is presented. It is suggested that the volume effect be taken into account in a complementary fashion to obtain accurate estimates of unperturbed dimensions from data in active solvents where the mean‐square end‐to‐end distance 〈r2〉 increases at these conditions more rapidly than M. Different viscosity measurements of polystyrene (PS) and poly(N‐vinyl‐2‐pyrrolidone) solutions containing non‐ideal solvents were taken from the literature and found that the newly proposed, though purely empirical equation is valid.
Hydrogen activation in propene polymerization with MgCl2‐supported Ziegler‐Natta catalysts: the effect of the external donor
Authors: Chadwick John C. , Miedema Arjen , Sudmeijer Olof
Published: April 2003

13C NMR analysis of relatively low‐molecular‐weight polypropylenes prepared using the catalyst system MgCl2/TiCl4/phthalate ester‐AlEt3‐external Lewis base has revealed the presence of up to around 20% butyl (n‐Bu) chain ends, indicative of regioirregular (2,1‐) monomer insertion followed by chain transfer with hydrogen. The effect of hydrogen on catalyst activity depends on the nature of the external donor, and the results indicate that at least part of the observed increase in catalyst activity in the presence of hydrogen can be ascribed to the regeneration of active species via chain transfer at dormant (2,1‐inserted) sites.
Synthesis and 13C NMR characterization of ethylene glycol/terephthalic acid/hydroxybenzoic acid copolyesters
Authors: Abis Luigi , Po Riccardo , Schimperna Giuliana , Merlo Edoardo
Published: April 2003

Copolyesters of terephthalic acid, p‐hydroxybenzoic acid and ethylene glycol were prepared by high‐temperature melt polycondensation, starting from different hydroxybenzoic acid derivatives. Methyl p‐hydroxybenzoate monomers having the hydroxyl either free, etherified with ethylene glycol or esterified with terephthalic acid were used. The chemical structure of the copolyesters obtained was characterized by means of 13C NMR spectroscopy, and chemical shifts were assigned to the respective carbons. The investigation clearly indicates that oxybenzoate units are quantitatively present in the polymer as etherified (on the hydroxyl group) and esterified (on the carboxylic group) with ethylene glycol. Similar analyses were performed on intermediate products formed after the transesterification stage. They point out that at this stage the hydroxyl group is free when starting from methyl p‐hydroxybenzoate, while a noticeable amount of ether is already present when starting from the monomer esterified with terephthalic acid. A reaction scheme encompassing these results and based on the competition between esterification and etherification process of the phenolic hydroxyl is put forward.
Poly(methyl methacrylate)‐block‐poly(ethyl acrylate) by group transfer polymerization: synthesis and structural characterization
Authors: Masař Bohumil , Vlček Petr , Kříž Jaraslav , Kovářová Jana
Published: April 2003

Poly(methyl methacrylate)‐block‐poly(ethyl acrylate) (PMMA‐block‐PEA) was synthesized by sequential group transfer polymerization (GTP) in tetrahydrofuran at −30°C using (1‐methoxy‐2‐methyl‐1‐propenyloxy)trimethylsilane (MTS) as an initiator and tetrabutylammonium fluoride monohydrate (TBAF · H2O) as a catalyst. First, the PMMA macroinitiator was prepared in situ in quantitative conversion and its lifetime was at least 15 min. In the second step, an equimolar amount of ethyl acrylate was polymerized with a conversion of 67–88% and PMMA‐block‐PEA with number‐average molecular weight 5000 < M̄n < 11 500 and polydispersity 1,4 < M̄w/M̄n < 2,1 was obtained. The number of chains almost does not change during the polymerization and the initiating efficiency of MTS was in both steps ca. 0,65–0,80. The diblock structure of the copolymer was confirmed by the 13C NMR spectrometric direct proof of the bond‐linking of both blocks and by comparing the DSC behaviour of the copolymer with that of the corresponding blend of the homopolymers. No contamination of the block copolymer with the homopolymers was detected by the analytical methods used for the structural characterizations.
Synthesis and functional analysis of phenyl‐end‐blocked poly(methyl methacrylate) with N,N′‐dimethyl‐N,N′‐bis(phenethyl)thiuram disulfide as a thermal iniferter
Authors: Haque Shah Abdul , Clouet Gilbert
Published: April 2003

Phenyl‐end‐blocked poly(methyl methacrylate) was synthesized by bulk polymerization of methyl methacrylate by a new functional iniferter, viz., N,N′‐dimethyl‐N,N‐bis(phenethyl)‐thiuram disulfide by thermal polymerization. The iniferter was synthesized and characterized by elemental analysis, ultraviolet, infrared, 1H and 13C nuclear magnetic resonance (1H NMR and 13C NMR). Some kinetic parameters like rate of polymerization, variation in the molecular weight and transfer constants as a function of iniferter concentration in the temperature range between 55°C and 100°C have been studied. The rate of polymerization increased with increasing temperature but passed through a maximum with respect to the iniferter concentration. The rate did not follow straight‐line behaviour with respect to iniferter concentration as usually found with alkylthiuram disulfides. The chain transfer due to iniferter exhibited the usual temperature dependence, and the activation energy was of the same order of magnitude as for the aliphatic thiuram disulfide. Spectral and thermal analyses of the resultant polymers confirmed the terminal functionalization of the polymer chains.
Polymerizability of methyl α‐substituted acrylates containing methoxycarbonyl groups
Authors: Kudoh Masaki , Akutsu Fumihiko , Odagawa Yoshiyuki , Naruchi Kiyoshi , Miura Masatoshi
Published: April 2003

Dimethyl 4‐methyl‐1‐pentene‐2,4‐dicarboxylate (3) and trimethyl 4‐methyl‐1‐octene‐2,4,7‐tricarboxylate (4) are not radically homopolymerizable. Dimethyl 1‐hexene‐2,4‐dicarboxylate (5) polymerizes slowly to yield a small amount of oligomers. Homopolymerization of dimethyl 1‐butene‐2,4‐dicarboxylate (6) affords a high‐molecular‐weight polymer. Radical copolymerization of these methyl α‐substituted acrylates (M2) with styrene (M1) was carried out at 60°C using AIBN, and the following monomer reactivity ratios were obtained; 3: r1 = 0,983, r2 = 0,000; 4: r1 = 0,938, r2 = 0,000; 5: r1 = 0,672, r2 = 0,119; 6: r1 = 0,566, r2 = 0,195. The polymerizability of these methyl acrylate derivatives is influenced by the steric effect of the α‐substituents.
Stereocontrol mechanism of an organozinc complex having chair‐type structure in the polymerization of tert‐butylethylene oxide; comparison with propylene oxide
Authors: Tsuruta Teiji , Hasebe Yoshihiro
Published: April 2003

A ring‐opening polymerization of racemic tert‐butylethylene oxide (t‐BEO) was carried out with a well‐defined organozinc complex, [CH3OCH2CH(CH3)OZnOCH(CH3)CH2OCH3]2·[C2H5ZnOCH(CH3)CH2OCH3]2 ([Zn‐MP]2,2), as initiator. The 13C NMR analysis showed that the main chain of poly(t‐BEO) is isotactic although the initiation reaction between t‐BEO and [Zn‐MP]2,2 is much less enantioselective compared with the very high selectivity in the propagation stage. In the R,S‐copolymerization reaction of t‐BEO (R/S = 64/36), no change in the optical purity of the residual monomer was observed at any extent of conversion. It was concluded from these results that the enantioselection in the propagation stage at any particular site is perfectly governed by the chirality of the first t‐BEO molecule that entered and reacted at the site of [Zn‐MP]2,2. The mechanism of the stereocontrol processes for the [Zn‐MP]2,2 initiated polymerization of t‐BEO is discussed in comparison with that for the polymerization of propylene oxide.
Assemblies of liquid crystalline polyelectrolytes and amphiphilic compounds
Authors: Ciferri Alberto
Published: April 2003

A tentative mechanism of aggregation of amphiphilic molecules to a rigid mesogenic polylelectrolyte is suggested. A basic soluble unit may grow laterally and longitudinally, eventually forming nematic phases and gels. Relevance to self‐assembly of complex biological structures is hypothesized.
Syntheses and ESR spectra of radicals produced in the thermal decomposition of tetraarylsuccinonitriles
Authors: Plaček Jan , Szőcs Ferenc , Braun Dietrich , Skrzek Thomas
Published: April 2003

Tetraarylsuccinonitriles 2a–e were synthesized via oxidative dimerization of diarylacetonitriles 1a–e in basic media. The thermal decomposition of 2 results in two identical cyanodiarylmethyl radicals 3. Both 1H and 13C NMR analyses of 1a–e and 2a–e and ESR spectra of 3a–e are presented and discussed. The results of ESR measurements provide a plausible explanation for the different reactivity of cyanodiarylmethyl radicals 3a–e in free radical polymerization.
Thermally crosslinked rigid‐rod aramids, 2. Fiber spinning and fiber properties
Authors: Glomm Bernhard , Rickert Christoph , Neuenschwander Peter , Suter Ulrich W.
Published: April 2003

Fibers of three rigid‐rod aromatic copolymers, produced by polycondensation of 2,2,6,6‐tetraoxo‐1,3,5,7‐tetrahydro‐2,6‐dithia‐s‐indacene‐4,8‐diamine (DSDA), p‐phenylenediamine and terephthaloyl dichloride, were spun from nematic solutions and characterized by wideangle X‐ray‐diffraction (WAXD) measurements and mechanical tests. A post‐spin heat treatment was employed to improve the low degrees of orientation and crystallinity exhibited generally by the untreated fibers. The dominating crystal structures of the copolymers are similar to “modification I” of the well known fibers from poly(p‐phenyleneterephthalamide) (PPTA). Thermally induced crosslinking of the fibers in the solid state was performed simultaneously with post‐spin treatment. The influence of the annealing conditions on the mechanical fiber properties and the molecular order in the fibers was also investigated. All mechanical parameters were time‐dependent, probably due to the generation of stable radicals during heat treatment. The radicals may give rise to chain scission.
Preparation and properties of new photo‐functional polymers, 1. N‐substituted maleimide/styrene copolymers containing pendant para‐nitrobenzyl groups
Authors: Chiang Wen‐Yen , Lu Jin‐Yuh
Published: April 2003

A new photo‐functional copolymer was designed by etherification or esterification of poly‐[N‐(4‐hydroxyphenyl)maleimide‐co‐styrene] or poly[N‐(4‐carboxyphenyl)maleimide‐co‐styrene] with p‐bromomethylnitrobenzene using 1,8‐diazabicyclo[5.4.0]‐undec‐7‐ene (DBU) as the base in an aprotic solvent. The chain‐stiffening effect of the N‐substituted maleimide group provided good thermal stability. It was observed that the photosensitivity of the copolymer is enhanced by the addition of a base like tributylamine.
Liquid‐Crystalline side‐chain AB block copolymers by direct anionic polymerization of a mesogenic methacrylate
Authors: Bohnert Robert , Finkelmann Heino
Published: April 2003

AB block copolymers with a liquid‐crystalline and an amorphous block are synthesized by anionic copolymerization of 4‐[4‐(4‐methoxyphenylazo)phenoxy]butyl methacrylate (1) with either styrene or methyl methacrylate (MMA). The polymerization of 1 proceeds from polystyrenelithium capped with 1,1‐diphenylethylene to produce polystyrene‐block‐poly(1), while poly(1)‐block‐PMMA is prepared by addition of MMA to the “living” poly(1) anion. A large variety of block copolymers is obtained with narrow molecular weight distribution and definite composition. The mesophase behaviour of these samples is analyzed with respect to the chain length of the liquid‐crystalline block. Electron microscopy of a high‐molecular‐weight polystyrene‐block‐poly(1) provides direct evidence for a microphase‐separated structure composed of spherical polystyrene domains embedded in a liquid‐crystalline matrix. For the corresponding poly(1)‐block‐PMMA, however, electron microscopy indicates no structure, although dynamic mechanical analysis proves microphase separation.
Chromatographic investigations of macromolecules in the critical range of liquid chromatography, 6. Analysis of the methyl methacrylate block in block copolymers of decyl and methyl methacrylate
Authors: Pasch Harald , Augenstein Michael , Trathnigg Bernd
Published: April 2003

Using liquid chromatography at the critical point of adsorption the molar mass and the polydispersity of the individual blocks in block copolymers of decyl and methyl methacrylate are determined. In addition, the total molar mass and the chemical composition of the block copolymers are calculated and compared to data from conventional size exclusion chromatography (SEC) and SEC with coupled density‐refractive index detection. The agreement of the data obtained by the different methods is found to be very good.
Synthesis, properties and biodegradability of polyesters based on 1,3‐propanediol
Authors: Witt Uwe , Müller Rolf‐Joachim , Augusta Josef , Widdecke Hartmut , Deckwer Wolf‐Dieter
Published: April 2003

Aliphatic homopolyesters and copolyesters based on 1,3‐propanediol and containing terephthalic acid as aromatic compounds and sebacic acid as aliphatic compound were synthesized by condensation in bulk. Intrinsic viscosity and weight‐average molecular weight were measured. Melting temperatures were studied by differential scanning calorimetry. For all polyesters the biodegradability was tested. Test media were inoculated with either municipal compost eluates or decanted sewage sludge. Criteria measured were visible changes, weight loss, and scanning electron microscopy indicating the visible changes of the surface. Compositions of copolyesters were characterized by 13C NMR spectroscopy. As a major result it is concluded that biodegradability depends substantially on the sequential structure of the polymer.
Kinetic and electron paramagnetic resonance studies on radical polymerization. Radical copolymerization of p‐tert‐butoxy‐styrene and dibutyl fumarate in benzene
Authors: Sato Tsuneyuki , Shimooka Sumio , Seno Makiko , Tanaka Hitoshi
Published: April 2003

The copolymerization of p‐tert‐butoxystyrene (1) (M1) and dibutyl fumarate (2) (M2) initiated with dimethyl 2,2′‐azobisisobutyrate (3) was studied in benzene at 60°C kinetically and by means of electron paramagnetic resonance (EPR) spectroscopy. The monomer reactivity ratios were determined to be r1 = 0,18 and r2 = 0,01, indicating that homopropagation of M2 is almost negligible in the copolymerization. The copolymerization system was revealed to involve EPR‐observable propagating polymer radicals under practical copolymerization conditions. The apparent rate constants of propagation (kp) and termination (kt) determined by EPR show a rapid increase in the range from 0,9 to 1,0 of feed composition (f1 = {[M1]/([M1] + [M2])}) of M1. From the relationship between kp and f1 based on Fukuda's penultimate model, the rate constants of propagation of copolymerization were evaluated; k111 = 140 L · mol−1 · s−1, k211 = 4,3 L · mol−1 · s−1, k112 = 778 L · mol−1 · s−1, k212 = 24 L · mol−1 s−1 and k121 = 19 L · mol−1 · s−1, suggesting a pronounced penultimate effect.
Synthèse et caractérisation d'un amorceur azoïque disulfonique. Application à la polymérisation de l'acide acrylique
Authors: Bessière Jean‐Marie , Boutevin Bernard , Loubet Olivier , Piétrasanta Yves
Published: April 2003

The synthesis of a water‐soluble azo initiator was performed in four steps: action of hydrazinium sulfate onto 4‐phenylbutan‐2‐one followed by an addition of hydrogen cyanide onto the azine, then oxydation with bromine and finally chlorosulfonation of the obtained aromatic azo compound. The overall yield of this azo compound was about 40%. The kinetical and thermal parameters were determined by differential scanning calorimetry. The decomposition rate constant (kd) is similar to that of 2,2′‐azoisobutyronitrile (AIBN) but the activation energy (ca. 38 kJ/mol) is lower than that of AIBN. The polymerization with this initiator in aqueous medium has advantages as compared with Fenton's reagent.
Compensating the composition drift in reactivity ratio calculations for copolymerizations carried to high conversions
Authors: Catalgil‐Giz Huceste , Giz Ahmet T.
Published: April 2003

The effect of composition drift on the accuracy of linearised methods of determining the reactivity ratios in copolymerization reactions is calculated. It is shown that, when the reactivity ratios differ widely, even at a very low conversion of 5% the drift causes large errors in the ratios found with these methods. However, by using an appropriate average of the initial and the final monomer ratios, the errors due to the composition drift can be significantly reduced, so that linearised methods with averaging can be used with confidence at moderate (30–50%) conversions.
Synthesis and characterization of new hydrophobic polyurethanes for biomedical applications
Authors: Marconi W. , Martinelli A. , Piozzi A. , Zane D.
Published: April 2003

The synthesis of new segmented polyurethanes containing as chain extender N‐hexadecyl‐2,2‐bis(hydroxymethyl)propionamide (alone or with 1,4‐butanediol at different mole ratios) is described. The degree of hydrophobicity and the glass transition temperatures Tg were found to be proportional to the alkyl chain content of the polymer. Also the amount of bonded albumin is proportional to the alkyl group content of the polymer, and platelet adhesion is remarkably lower for the 100% alkylated polymer (PEUHDA) than for the standard non‐alkylated polyurethane (PEU). This behaviour was confirmed by SEM evaluation, showing a much lower degree of activation of platelets on albuminized PEUHDA films. It was not possible to ascertain with sufficient reliability a different behaviour, with respect to platelet adhesion, of the polymers containing alkyl chains in the range 9 ÷ 50 mol‐%, due to the relatively high error of the evaluation systems.
Polyanhydrides, 5. Thermotropic poly(ester anhydrides) derived from monoalkylthioterephthalic acids, hydroquinone and 4‐hydroxybenzoic acid
Authors: Kricheldorf Hans R. , Domschke Angelika
Published: April 2003

Monoalkylthioterephthalic acids and their acyl chlorides were prepared via nucleophilic substitution of diethylbromo‐ or diethyl chloroterephthalate with thiols. Various poly(ester anhydrides) were synthesized by polycondensation of alkylthioterephthaloyl chloride with silylated 4‐hydroxybenzoic acid and silylated hydroquinone. The resulting poly(ester anhydrides) were characterized by elemental analyses, inherent viscosities, IR spectroscopy, differential scanning calorimetry (DSC) and wide‐angle X‐ray scattering (WAXS) measurements, optical microscopy and 13C NMR cross polarization/magic angle spinning (CP/MAS) spectroscopy. For the chain packing of these monosubstituted poly(ester anhydrides) a sanidic type of layer structure with a “back‐to‐back array” of the main chains is proposed. The alkyl side chains form ordered domains with predominantly all‐trans conformations. In most cases, three endotherms are observable in the DSC heating traces corresponding to the melting of the side chains and to reversible transitions into two different liquid‐crystalline phases.
Photodegradation of poly[ethylene‐co‐propene‐co‐(5‐ethylidene‐2‐norbornene)] rubbers, 2. Physical and dynamic‐mechanical behaviour under accelerated conditions
Authors: Scoponi Marco , Pradella Fiorella , Carassiti Vittorio , Tartari Davide
Published: April 2003

The physical and dynamic‐mechanical behaviour during the photo‐oxidation under accelerated conditons of three poly(ethylene‐co‐propene‐co‐5‐ethylidene‐2‐norbornene) (EPDM) rubbers with different contents of 5‐ethylidene‐2‐norbornene

System. name: 5‐ethylidenebicyclo[2.2.1]hept‐2‐ene.

(ENB) are reported. These results show the dependence of the glass transition temperature both on the ENB content and on the photo‐oxidation time in accordance with network formation in the rubber matrix under accelerated conditions. The tensile experiments also show an increase of the elastic modulus as function both of ENB content and of photo‐oxidation time. The Murayama and Mooney‐Rivlin equations are applied to estimate the average molecular weight between two crosslinking nodes occurring in the rubber matrix during photo‐oxidation with tensile and dynamic‐mechanical experiments, respectively. Some correlations of physical and dynamic‐mechanical changes with the proposed mechanism of photo‐oxidation, due to the formation and reactivity of unsaturated groups, show that the crosslinking processes prevail over chain scissions.
Synthesis and magnetic properties of mesogenic side‐chain polymers containing stable radicals
Authors: Allgaier Jürgen , Finkelmann Heino
Published: April 2003

An amorphous and a liquid‐crystalline side‐chain polymer containing stable nitroxyl radicals are synthesized, the free radical being located either in a piperidine N‐oxyl or a 1,3‐oxazolidine N‐oxyl moiety. These polymers are available by reaction of precursor polymer having a formyl group in every repeating unit with low‐molecular‐weight nitroxyl free radicals functionalized with an amino group. The conversion of the polymer‐analogous reaction is nearly quantitative. Both the amorphous and the liquid‐crystalline polymer show paramagnetic behaviour in the temperature range from 6 to 300 K.
The system poly(4‐hydroxystyrene)/poly(vinyl acetate)/acetone: An experimental and theoretical study
Authors: Luengo Gustavo , Rubio Ramon G. , Sanchez Isaac C. , Panayiotou Constantinos G.
Published: April 2003

In an effort to assess the intermolecular interactions between poly(4‐hydroxystyrene)

IUPAC name: poly(4‐vinylphenol).

(P4HS) and poly(vinyl acetate) (PVAc), two types of experimental measurements were conducted: volumetric properties and vapor pressures of solutions in a common solvent (probe). The PVT measurements for a 50:50 (w/w) binary polymer mixtures were conducted over a pressure range from 0 to 100 MPa and a temperature range from 350 to 470 K. The vapor pressures of acetone over a series of ternary systems acetone/P4HS/PVAc, and for four intermediate weight ratios PVAc/P4HS, were measured at 298,15 K, 308,15 K and 318,15 K. PVAc and P4HS interact primarily through hydrogen bonding. The probe molecule (acetone) on the other hand interacts also through hydrogen bonding with P4HS. A recent equation‐of‐state theory of hydrogen bonding has been used to correlate these measurements. Application of the theory was requiring the knowledge of the volumetric behavior of pure P4HS. Extensive PVT measurements for this polymer have also been conducted. The PVT measurements for the polymer mixture were used in order to estimate the hydrogen bonding parameters for the hydroxyl‐ester pair. The vapor pressures of the system acetone/P4HS were used in order to estimate the hydrogen bonding parameters of the hydroxyl‐carbonyl pair. On the basis of this information the theory was used to predict the vapour pressures of the ternary system. The theoretical predictions are in quantitative agreement with the experiments.
Copolyesteramides, 8. A comparison of substantially alternating 12‐oxydodecanoyl/ω‐iminoalkanoyl polyesteramides with equivalent random copolymers
Authors: Goodman Isaac , Rodríguez Maria Teresa
Published: April 2003

The polycondensation of methyl N‐(12‐hydroxydodecanoyl)‐ω‐aminoalkanoates (HO(CH2)11CONH(CH2)xCOOCH3) has been studied as a source of the alternating polyesteramides [O(CH2)11CONH(CH2)xCO]n, and the properties of the products compared with those of equivalent random copolymers of similar co‐unit ratio. Polymerization of the esters with x = 10 and 11 occurred straight‐forwardly, giving crystalline products with were distinguishable from the random counterparts by DSC but not by 67 MHz 13C NMR. For x = 5 the reaction was complicated by progressive partial elimination of the amide moiety as 6‐hexanolactam and by transamidation leading, for the polymer of highest amide content obtained, to an imperfect structure with ca. 76% of the sub‐units in alternating arrangement, the remainder being composed of oligoester and diamide units. This deviation from ideality has been elucidated by a study of the 13C NMR spectra of a wide range of model compounds which has yielded criteria for the recognition of oligomeric iminohexanoyl units, and by the NMR and MS examination of the products of aminolytic degradation. The results explain the multiple signals found in the 13C NMR spectra of the imperfectly alternating polymer (x = 5) and of its random analogues.
Anthracene derivatives as novel initiators for anionic and cationic polymerizations
Authors: Bartz Thomas , Klapper Markus , Müllen Klaus
Published: April 2003

Anionic polymerizations with an anthracene‐derived initiator are described as giving rise to polymers containing only one chromophore on each chain. The approach taken herein involves the deprotonation of dihydroanthracene (1) and the initiation of methyl methacrylate, vinylpyridine and styrene polymerization by the corresponding monohydromonoanion 2. Polymer‐analogous aromatization of the initiator generates a polymer end‐capped with an anthracene chromophore. Anthracene‐containing initiators are used also in the ring‐opening cationic polymerization of 2‐phenyl‐2‐oxazoline (3). The anthracene‐labelled polymers poly(methyl methacrylate) (4a), polyvinylpyridine (5a), polystyrene (6a) and polyphenyloxazoline (7) are examined by gelpermeation chromatography (GPC), ultraviolet (UV) and NMR measurements. The coupling of two anthracene‐labelled polymers via the [4π + 4π] cycloaddition between the terminal anthracene moieties is described.
Studies on helix‐sense‐selective copolymerization based on triphenylmethyl methacrylate
Authors: Chen Chuanfu , Ren Changyu , Zhang Janjiang , Xi Fu
Published: April 2003

Helix‐sense‐selective copolymerizations based on triphenylmethyl methacrylate (TrMA) with methyl methacrylate (MMA), benzyl methacrylate (BzMA) and diphenylmethyl methacrylate (DPMMA) in the presence of the chiral anionic complex initiator (−)‐sparteine/9‐fluorenyl‐lithium (1) were investigated. The studies concentrated on the stereoregularity of the copolymers, the relative reactivity of the monomers, the specific rotation of the copolymers and the influence of the solvent on the copolymerization. The results show that the match of TrMA with MMA of smaller size would favour the form of the copolymer with isotactic one‐handed helix having higher specific rotation as compared with BzMA ad DPMMA in toluene, but the TrMA/MMA copolymer obtained in tetrahydrofuran possessed a very low specific rotation because of the action of the polar tetrahydrofuran on the anion complex.
Double‐tailed perfluoroalkyl telomeric surfactants derived from tris(hydroxymethyl)acrylamidomethane for medical applications
Authors: Myrtil Evelyne , Zarif Leila , Greiner Jacques , Riess Jean G. , Pucci Bernard , Pavia André A.
Published: April 2003

A new family of perfluoroalkyl double‐tailed amphiphiles was synthesized in order to develop a new drug carrying and delivery system. They were obtained by telomerization of tris(hydroxymethyl)acrylamidomethane (THAM) in the presence of various double‐tailed primary and secondary thiols as chain‐transfer agents, and with AIBN as the initiator. With secondary thiols, telomerization occurred in low yields (25–35% with respect to the thiol), because of the competitive formation of a disulfide by‐product, but proceeded in higher yields (45–90%, depending on the stoichiometry of the reagents) with primary thiols, thus allowing the preparation of a new family of perfluoroalkyl telomeric THAM double‐tailed amphiphiles. Preliminary biological tests showed no detectable hemolytic activity on human red blood cells at concentrations up to 20 mmol/L (50–65 g/L), whereas the hydrocarbon analogs proved to be hemolytic at 0,002 mmol/L. The LD50 was found to be higher than 2500 mg/kg of animal.
Direct visualization of synthetic cellulose formation via enzymatic polymerization using transmission electron microscopy
Authors: Kobayashi Shiro , Shoda Shin‐ichiro , Lee Jong , Okuda Kazuo , Brown R. Malcolm , Kuga Shigenori
Published: April 2003

The process of synthetic cellulose formation in an acetonitrile‐buffer solvent system by enzymatic polymerization of β‐cellobiosyl fluoride monomer using cellulase as a catalyst was visualized by transmission electron microscopy. Synthetic cellulose could be observed as soon as 30 s after initiation of the polymerization. A micellar phase separation occurred at the initial stage of the reaction. Irregular aggregates of cellulose were formed at the boundary of the micellar particles, suggesting that the interface is the site of polymerization. The cellulose product after treatment with hot surfactant solution was strongly labeled with cellobiohydrolase I‐gold complexes, indicating that the produced polymer is cellulose. The electron diffraction pattern of the product showed the typical pattern of crystal structure of cellulose II.
Polymerization of 1,3‐dienes with methylaluminoxanetriacetylacetonatovanadium
Authors: Ricci Giovanni , Italia Salvatore , Porri Lido
Published: April 2003

Various 1,3‐dienes (1,3‐butadiene, isoprene, 2‐ethyl‐1,3‐butadiene, (E)‐ and (Z)‐1,3‐pentadiene, (E)‐2‐methyl‐1,3‐pentadiene) were polymerized with the soluble catalyst system methylaluminoxane/V (acac)3 (acac: acetylacetonato). Butadiene and (Z)‐1,3‐pentadiene gave trans‐1,4 polymers, at low and room temperature. Isoprene, 2‐ethyl‐1,3‐butadiene and (E)‐2‐methyl‐1,3‐pentadiene gave trans‐1,4‐polymers at low temperature (< −20°C), but polymers of mixed cis/trans structure at room temperature. (E)‐1,3‐pentadiene gave polymers of mixed 1,2/trans‐1,4 structure either at low or room temperature. An interpretation of the results is reported.
Polyimides by Diels‐Alder polyaddition of α‐pyrones
Authors: Alhakimi Gamil , Görls Helmar , Klemm Elisabeth
Published: April 2003

New linear polyimides 11 were synthesized via Diels‐Alder addition polymerization of α‐pyrones 9 with bismaleimides 10. The number‐average molecular weights Mn range from 10 000 to 34 000 g. mol (gel‐permeation chromatography). The chemical structure of these polymers is supported by X‐ray crystallography, NMR spectra and model reactions. The Diels‐Alder addition occurred with high endo selectivity.
Pivalolactone, 3. Reactive blending of polypivalolactone with polycarbonate
Authors: Tijsma Edze Jan , van der Does Leen , Bantjes Adriaan , Vulić Ivan , Buning Gerard Hidde Werumeus
Published: April 2003

The occurrence of interchange reactions during heating of polypivalolactone (PPVL) with three polymers and their influence on the blend properties were studied. Physical blends of PPVL and bisphenol‐A polycarbonate (PC) were found to be immiscible. By heating of PPVL/PC blends in the melt at 280°C, in diphenyl ether at 260°C and in a twin‐screw extruder (TSE) at 280°C partial formation of copolymers was observed, provided that tetrabutyl orthotitanate (TnBT) was added. After heating of equimolar PPVL/PC blends in a TSE for 15 min, a PPVL‐PC block copolymer could be isolated containing 25 mol‐% pivalolactone (PVL) units. The results from thermal analyses indicated that PPVL/PC blends had become more miscible, due to the presence of copolymers formed by interchange reactions. After heating of equimolar mixtures of PPVL and a polyarylate (PAr) in a TSE for 15 min, PPVL‐PAr copolymers with 5 mol‐% PVL units could be isolated. Probably due to this low degree of interchange, no effect on the miscibility of the initially immiscible PPVL/PAr blends could be observed. PPVL/poly(butylene terephthalate) (PBT) blends, obtained after heating in a TSE, decomposed at a temperature between the melting temperatures of PPVL and PBT, indicating that interchange reactions may have occurred.
Thermotropic liquid‐crystalline aromatic‐aliphatic polyimides, 3. Poly(imide‐carbonate)s composed of 3,4:3′,4′‐biphenyldicarboximide
Authors: Hirata Tomohiro , Sato Moriyuki , Mukaida Ken‐ichi
Published: April 2003

N,N′‐Bis(ω‐hydroxyalkyl)‐3,4:3′,4′‐biphenyldicarboximide (l = 3, 6) were prepared by a two‐step reaction (via intermediates) of 3,4:3′,4′‐biphenyltetracarboxylic dianhydride and ω‐amino‐alcohols. Polycondensation of dihydroxyalkyl derivatives of the 3,4:3′,4′‐biphenyldicarboximide (l = 3, 6) and/or biphenyl with alkylene bis(phenylcarbonate)s (m = 3, 6) afforded poly(imidecarbonate)s with high molecular weights in high yields, which were characterized by FT‐IR and NMR measurements and elemental analyses and showed good solubilities in organic solvents. The mesogenic properties of the polymers were evaluated by means of differential scanning calorimetry (DSC), observation in the polarizing microscope equipped with a hot stage and by means of powder X‐ray diffraction. The DSC curves of the imide unit rich polymers without annealing only display glass transition steps. The curves after annealing, however, show some endotherms. The polarizing microscope observation and X‐ray analyses indicated that the homo‐and copolymers from the 3,4:3′,4′‐biphenyldicarboximide derivative with longer methylene chains (l = 6) form nematic liquid‐crystalline mesophases.