bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polyamides X.34: A New Class of Polyamides with Long Alkane Segments
Authors: Ehrenstein Moritz , Smith Paul , Weder Christoph 
Published: September 2003

AbstractA new series of semi‐crystalline polyamides (PA), which comprise extended aliphatic segments between the amide moieties and which display an interesting amphiphilic character has been synthesized and characterized. The polymers PA‐2.34, PA‐4.34, PA‐8.34, PA‐10.34, and PA‐12.34 were prepared by melt‐polycondensation of salts of tetratriacontanedioic acid and the respective short‐chain diamine. The thermal properties of these polymers were investigated by differential scanning calorimetry, thermogravimetric analysis, and dynamic mechanical thermal analysis. The new polyamides exhibit melting temperatures that depend on the length of the diamine and range between 166 (PA‐12.34) and 190 °C (PA‐2.34). Solid transitions were observed between 38 and 57 °C. The materials displayed a rather limited solubility in common polyamide solvents, but readily dissolved in alkylsulfonic acids. All members of the series formed thermo‐reversible gels in the highly polar sulfuric acid and 1,2,3,4‐tetrahydronaphthalene, reflecting their interesting amphiphilic character. Young's moduli and tensile strengths of melt‐processed, isotropic films of the polyamides investigated were in the range of 0.5–0.7 GPa and 20.30 MPa, respectively, independent of the length of the diamine used.Melting temperatures of polyamides PA‐X.34 (x) and 1,2,3,4‐tetrahydronaphthalene/PA‐X.34 gels (37.5 wt.‐% polyamide, determined from the second DSC heating scans) (+).magnified imageMelting temperatures of polyamides PA‐X.34 (x) and 1,2,3,4‐tetrahydronaphthalene/PA‐X.34 gels (37.5 wt.‐% polyamide, determined from the second DSC heating scans) (+).
Hydrolytic Polycondensation of Bisphenol‐A‐Bischloroformate Catalyzed by Phase‐Transfer Catalysts
Authors: Kricheldorf Hans R. , Böhme Sigrid , Schwarz Gert , Schultz Claus‐Ludolf 
Published: September 2003

AbstractThe hydrolytic interfacial polycondensation of bisphenol‐A‐bischloroformate was performed with four different phase‐transfer (PT) catalysts: N‐butylpyridinium bromide, triethylbenzylammonium (TEBA) chloride, tetrabutylammonium hydrogen sulfate, and tetraphenylphosphonium bromide. These polycondensations were conducted at 5 or 35 °C initial reaction temperature. The resulting polycarbonates were characterized by viscosity and SEC measurements and by MALDI‐TOF mass spectrometry. The four PT catalysts gave quite different results with respect to molecular weight and formation of cyclic polycarbonates. The highest molecular weights (number average, $\overline M _{\rm n} \approx 215\;{\rm kDa}$ and weight average, $\overline M _{\rm w} \approx 600\;{\rm kDa}$) were obtained with TEBA‐Cl. Lower temperatures and high feed ratios of TEBA‐Cl proved to be favorable for both high molecular weights and high fractions of cycles. Cyclic polycarbonates were detectable in the mass spectra up to 14 kDa (technical limit of the measurements). Low molecular weights in combination with unreacted chloroformate groups proved that the other PT‐catalysts were less efficient under the given reaction conditions.MALDI‐TOF mass spectrum of the polycarbonate No. 3b.magnified imageMALDI‐TOF mass spectrum of the polycarbonate No. 3b.
New Organo‐Soluble Conjugated Polyquinolines
Authors: Krüger Hartmut , Janietz Silvia , Sainova Dessislava , Wedel Armin 
Published: September 2003

AbstractPolyquinolines are under discussion as n‐type materials for organic field effect transistors, organic light‐emitting diodes and organic solar cells together with other N‐heterocycle‐containing conjugated polymers. But most of these conjugated polyquinolines are not soluble in common organic solvents. Therefore, a new synthetic pathway is presented in this work leading to organo‐soluble polyquinolines. The results of the synthesis and characterization of the obtained new organo‐soluble polyquinolines are shown. The electrochemical reduction and oxidation behavior of these polymers is studied by cyclovoltammetric measurements. All studied polymers can be reversibly oxidized and reduced. The absorption and luminescence properties are investigated. Organic light‐emitting diodes (OLEDs) are prepared from the new polyquinolines as an active single layer. The electroluminescence behavior and the characteristics of the OLEDs are discussed.Electroluminescence spectra of the LEDs with polymers 8a–c as emissive layers.magnified imageElectroluminescence spectra of the LEDs with polymers 8a–c as emissive layers.
New Aromatic tert‐Amines for Application as Photoinitiator Components in Photocurable Dental Materials
Authors: Ahn Kwang‐Duk , Han Dong Keun , Lee Suck‐Hyun , Lee Chan‐Woo 
Published: September 2003

AbstractA new type of aromatic tert‐amine with a bisphenol A (BPA) skeleton has been prepared and applied as a photoinitiator (PI) component for enhancing photosensitivity in formulations of visible light curable dental polymers. Two N,N‐dimethylamino (DMA) groups were incorporated into BPA diglycidyl ether to make 2,2‐bis[4‐(2‐hydroxy‐3‐(p‐N,N‐dimethylaminobenzoyloxy)propyloxy)phenyl]propane (DMABPA). One or two (meth)acryloyl groups were reacted with the hydroxyl groups of DMABPA to obtain the polymerizable, BPA‐based tert‐amines DMABPA‐1M (one methacrylate), DMABPA‐2M (two methacrylates), and DMABPA‐1A (one acrylate). The aromatic tert‐amines and ethyl p‐(N,N‐dimethylamino)benzoate (EDMAB) were combined with a camphorquinone sensitizer to form a photoinitiating system, which was applied in photopolymerizations of dental resin formulations, based on Bis‐GMA as a matrix prepolymer, by visible light exposure. The photoconversion of the formulations using the new aromatic tert‐amines as PIs was determined by the spectral changes in FTIR absorption intensities of methacrylate groups in cast films. High conversion (over 70%) resulted from photopolymerizations with (meth)acrylated DMABPA‐(1M, 2M, and 1A).magnified image
Novel Glass Fiber‐Reinforced Composites Having a UV and Peroxy Curable Fluoropolymer Matrix
Authors: Turri Stefano , Sanguineti Aldo , Lecchi Romina 
Published: September 2003

AbstractNovel glass fiber‐reinforced composites were prepared from E‐glass fibers and perfluoropolyether (PFPE), polyurethane acrylate, and methacrylate resins. The PFPE resins were synthesized by a two‐step process and formulated with reactive acrylic diluents obtaining two compositions with different viscosity and fluorine content. These formulations were photocrosslinked by UV‐A radiation and characterized by tensile and dynamic‐mechanical properties as well as by impact resistance. The two UV cured fluoropolymer compositions are high modulus (> 1 GPa), polyphasic materials characterized by a fracture toughness higher than conventional polymer matrices, like epoxies and unsaturated polyesters. Unidirectional laminate composites were also prepared by hand lay‐up and crosslinked both photochemically and thermally. Mechanical characterization of glass fiber‐reinforced composites was carried out by tensile tests and shear adhesion measurements, showing a good fluoropolymer‐glass adhesion strength (ca. 9 MPa). Surface characterization of composites by static contact angle measurements allowed the calculation of the total surface tension γs according to Wu's harmonic mean approximation. Surface tension is very low (< 20 mN/m) suggesting a preferential stratification of PFPE segments at the material‐air interface.
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Study of the Effects of Gamma Irradiation on the Structure and Physical Properties of Low Density Polyethylene Films Containing Hindered Amine Stabilizers
Authors: Kaci Mustapha , Remili Chérifa , Khima Rochedine , Sadoun Tahar 
Published: September 2003

AbstractThe effect of gamma‐irradiation on the structure, rheology, and mechanical properties of low density polyethylene (LDPE) films containing some new hindered amine stabilizers (HAS) has been investigated and the results obtained were compared to additive free samples. The HAS used involved various structures such as an alkoxyamine, a polymer bound HAS and a HAS modified with siloxane; these are commercially known as Tinuvin 123, Sanduvor PR 31 and Uvasil 299, respectively. It was found that the carbonyl index values measured by FTIR spectroscopy increased linearly with the radiation dose for all the samples studied, however this increase was less pronounced for the stabilized samples. The formation rates of carbonyls followed the order LDPE > LDPE/Uvasil 299 > LDPE/PR 31 > LDPE/Tinuvin 123. The second order derivative UV analysis showed the formation of vinyl groups in the irradiated samples at higher doses (812 kGy), while vinylidene groups were detected only in the films stabilized with PR 31 and Tinuvin 123. The curves of the melt flow rate (MFR) exhibited a fast increase for the unstabilized sample after 67 kGy, indicating the occurrence of chain scission. The stabilized samples on the other hand showed an evident increase in MFR from almost 300 kGy. The contribution of different HAS for the durability of LDPE films under γ rays was evaluated by determining the half‐value‐dose, which is related to the radiation resistance of the material. The results indicated that the presence of HAS in LDPE films improves the half‐value‐dose of those stabilized with Tinuvin 123 by 2.5 times against 2.4 and 2 for PR 31 and Uvasil 299, respectively. These data correlate well with the results obtained by FTIR and MFR measurements. Finally, the higher efficiency of Tinuvin 123 could be assigned to its appropriate oxidation state to enter the stabilization mechanism directly.An example of the new HAS.magnified imageAn example of the new HAS.
Preparation of Nanoporous Polyimide Films from Poly(urethane‐imide) by Thermal Treatment
Authors: Krishnan P. Santhana Gopala , Cheng Chia Zheng , Cheng Yeo Swee , Cheng Jimmy Wu Chi 
Published: September 2003

AbstractNanoporous polyimide films were prepared in two steps. The first step is the preparation of poly(urethane‐imide) films by casting blend solutions containing various weight percentages of poly(amic acid) and phenol blocked polyurethane prepolymer (from 1,6‐hexamethylene diisocyanate and poly(ethylene glycol)). Three poly(amic acid)s were obtained from biphenyltetracarboxylic dianhydride (or) 2,2‐bis(3,4‐dicarboxyphenyl)hexafluoropropane dianhydride with 1,4‐phenylenediamine (or) 2,5‐dimethyl‐1,4‐phenylenediamine. Poly(urethane‐imide) films were characterized by density and surface energy measurements, AFM, DSC, TMA, mechanical properties and TGA. In the second step, these films were thermally treated above 300 °C to give nanoporous polyimide films. During thermal treatment, less thermally stable urethane domains decomposed, leaving porous polyimide films. The presence of pores was confirmed by scanning electron microscopy (SEM). The dielectric constant of the polyimide film was found to decrease with increasing amounts of urethane content.A nanoporous polyimide film.magnified imageA nanoporous polyimide film.
Tensile Fracture and Failure Behavior of Thermoplastic Starch with Unidirectional and Cross‐Ply Flax Fiber Reinforcements
Authors: Romhány Gábor , Karger‐Kocsis József , Czigány Tibor 
Published: September 2003

AbstractThermoplastic starch (MaterBi®) based composites containing flax fibers in unidirectional and crossed‐ply arrangements were produced by hot pressing using the film stacking method. The flax content was varied in three steps, viz. 20, 40 and 60 wt.‐%. Static tensile mechanical properties (stiffness and strength) of the composites were determined on dumbbell specimens. During their loading the acoustic emission (AE) was recorded. Burst type AE signal characteristics (amplitude, width) were traced to the failure mechanisms and supported by fractographic inspection. The mechanical response and failure mode of the composites strongly depended on the flax content and the flax fiber lay‐up. It was established that the tensile strength increases until 40 wt.‐% flax fiber content but stays almost constant above this value. In the case of 40 wt.‐% unidirectional fiber reinforcement, the tensile strength of the composite was 3 times greater than that of the pure starch matrix. The flax fiber reinforcement increased the tensile modulus of the pure starch by several orders of amplitude.SEM picture of the fracture surface of a composite with UD flax reinforcement.magnified imageSEM picture of the fracture surface of a composite with UD flax reinforcement.
Research on Preparation, Structure and Properties of TiO2/Polythiourethane Hybrid Optical Films with High Refractive Index
Authors: Lü Changli , Cui Zhanchen , Guan Cheng , Guan Jingqi , Yang Bai , Shen Jiacong 
Published: September 2003

AbstractHybrid optical films of TiO2‐triethoxysilane‐capped polythiourethane (TCPTU) with high refractive indices have been prepared via an in situ sol‐gel method. The high refractive index triethoxysilane‐capped polythiourethane (TCPTU) was synthesized by polyaddition of the triethoxysilane‐modified trimercaptothioethylamine (TMTEA) and 2,2′‐dimercaptoethylsulfide (MES) with 2,4‐tolylene diisocyanate (TDI). The titania content in the hybrid films can be adjusted from 0 to 80 wt.‐% by the feed ratio of titania precursor [Ti(OBu)4] to polymer (TCPTU). Both FTIR and DSC analyses indicate that there is chemical bonding between the titania domain and the polymer chain. TGA results suggest that the titania of high content was successfully incorporated into polymer matrices and this series of hybrid films have good thermal properties. AFM measurements indicate that in the hybrid films the titania domains are of nanosize scale and the domain size averagely decreases from 60–80 nm to 5–20 nm with increasing content of titania, and the variation of surface roughness for the hybrid films has the same trend. These may be relative to the content of TCPTU and the interaction between titania and polymer (TCPTU). The refractive indices of the hybrid films at 632.8 nm increased from 1 632 to 1 879 as the titania content varied from 0 to 80 wt.‐%.AFM image of the hybrid film.magnified imageAFM image of the hybrid film.
Synthesis of Reactive Polymeric Dyes as Textile Auxiliaries
Authors: Altomare Angelina , Ciardelli Francesco , Faralli Giada , Solaro Roberto 
Published: September 2003

AbstractNew polymeric materials containing amino‐substituted azobenzene chromophores and reactive functional groups and characterized by some hydrophilicity were prepared with the aim of investigating alternative textile dyeing routes. The indicated materials were obtained either by copolymerization of suitable monomers or by modification of preformed polymers. In both cases commercial 4‐amino‐2′,3‐dimethylazobenzene (FG) was used as chromogenic compound. According to the first synthetic strategy, the methacrylamido derivative of FG was copolymerized by free radical initiation with different monomers, such as methyl methacrylate, glycidyl methacrylate, N‐tert‐butylacrylamide, methacrylic acid, N‐vinyl‐2‐pyrrolidinone, and vinyl acetate. Reaction of FG with preformed polymers containing epoxy groups generally afforded crosslinked materials. On the other hand, low FG loading extents were recorded by amidation of polymers containing carboxylic groups. Indeed, almost quantitative conversions were obtained only in the reaction of FG with anhydride containing polymers. The chemical structure, molecular weight properties, and the physical‐chemical characteristics of all synthesized polymeric dyes were thoroughly investigated. Some very preliminary dyeing tests of different cloth types with the prepared polymeric dyes were also performed.UV absorption spectrum of poly(FGMAA) and poly(FGMAA‐co‐MMA) in chloroform at 25 °C (FGMAA = 4‐methacrylamido‐2′,3‐dimethylazobenzene).magnified imageUV absorption spectrum of poly(FGMAA) and poly(FGMAA‐co‐MMA) in chloroform at 25 °C (FGMAA = 4‐methacrylamido‐2′,3‐dimethylazobenzene).
Impact Strength and Crystallization Behavior of Nano‐SiOx/Poly(phenylene sulfide) (PPS) Composites with Heat‐Treated PPS
Authors: Lu Dan , Mai Yiu‐Wing , Li Robert K. Y. , Ye Lin 
Published: September 2003

AbstractThe effects of heat treatment on the crystal structure and impact strength of poly(phenylene sulfide) (PPS) and nano‐SiOx/ PPS nanocomposites were studied. The molecular weight of heat‐treated neat PPS was increased by 28% due to the crosslinking reaction that changed its crystal morphology. Also, the crystallinity was reduced by 18%, leading to an improvement of the Izod impact strength by 66%. Nano‐SiOx/PPS composites were manufactured by intensive compounding with 3 wt.‐% nano‐SiOx particles treated by an epoxy functional group. Test results showed that the Izod impact strength of nano‐SiOx/heat‐treated PPS composites was 91% better and the crystallinity 27% less compared to the same properties of “as received” neat PPS. Nano‐SiOx has a high specific surface area and a high surface energy; its grafted epoxy group promotes interfacial adhesion with the PPS matrix, hence increasing the Izod impact strength of the nanocomposites.TEM micrograph of NHTM‐PPS with 3 wt.‐% nano‐SiOx.magnified imageTEM micrograph of NHTM‐PPS with 3 wt.‐% nano‐SiOx.
Promoting sustainable consumption: Determinants of green purchases by Swiss consumers
Authors: Tanner Carmen , Wölfing Kast Sybille 
Published: September 2003

AbstractGiven that overconsumption in industrial countries is a main cause of environmental degradation, a shift toward more sustainable consumption patterns is required. This study attempts to uncover personal and contextual barriers to consumers' purchases of green food and to strengthen knowledge about fostering green purchases. Survey data are used to examine the influence of distinct categories of personal factors (such as attitudes, personal norms, perceived behavior barriers, knowledge) and contextual factors (such as socioeconomic characteristics, living conditions, and store characteristics) on green purchases of Swiss consumers. Results from regression analysis suggest that green food purchases are facilitated by positive attitudes of consumers toward (a) environmental protection, (b) fair trade, (c) local products, and (d) availability of action‐related knowledge. In turn, green behavior is negatively associated with (e) perceived time barriers and (f) frequency of shopping in supermarkets. Surprisingly, green purchases are not significantly related to moral thinking, monetary barriers, or the socioeconomic characteristics of the consumers. Implications for policy makers and for companies and marketers engaged in the promotion and commercialization of green products are discussed. © 2003 Wiley Periodicals, Inc.
Relationship between product groups' price perceptions, shopper's basket size, and grocery store's overall store price image
Authors: Desai Kalpesh Kaushik , Talukdar Debabrata 
Published: September 2003

AbstractThis research investigates how consumers form an overall store price image (OSPI) of grocery stores. Whereas prior research on this topic has explored the influence of the number of products offered at lower prices and of the magnitude of such price reduction, this study addresses the following two questions: How do the (lower) prices offered on different types of products influence OSPI? Does such influence vary across consumers, and, if so, how? A general framework of product‐price saliency on consumers' OSPI is developed and tested. Specifically, based on two product‐related factors—consumption span (length of time required to finish the consumption of a standard unit of the product) and unit price, grocery‐store products are classified into four exhaustive and mutually exclusive product groups, and the relationship between OSPI and group‐level price perceptions across the four product groups is examined. The framework also examines to what extent this relationship is moderated by consumers' shopping‐basket size. Consistent with the proposed framework, this research finds strong empirical evidence of a systematic but differential relationship between OSPI and product group‐level price perceptions and also a systematic interaction effect with consumers' basket size. The findings help to identify focal product categories across distinct consumer segments and thus hold important strategic implications for category management and target marketing that are likely to increase the overall effectiveness of retail promotional strategies. © 2003 Wiley Periodicals, Inc.
Abelson tyrosine kinase is required to transduce midline repulsive cues
Authors: Hsouna Anita , Kim You‐Seung , VanBerkum Mark F.A. 
Published: September 2003

AbstractTyrosine phosphorylation‐dependent signaling cascades play key roles in determining the formation of an axon pathway. The cytoplasmic Abelson tyrosine kinase participate in several signaling pathways that orchestrate both growth cone advance and steering in response to guidance cues. Here, a genetic approach is used to evaluate the role for Abelson in growth cones during a decision to cross or not to cross the Drosophila embryonic midline. Our data indicate that both loss‐ and gain‐of‐function conditions for Abl cause neurons within the pCC/MP2 pathway to project across the midline incorrectly. The frequency of abnormal crossovers is enhanced by mutations in the genes encoding the midline repellent, Slit, or its receptor, Roundabout. In comm mutants, where repulsive signals remain elevated, increasing or decreasing Abl activity partially rescues commissure formation. Thus, both too much and too little Abl activity causes axons to cross the midline inappropriately, indicating that Abl plays a critical role in transducing midline repulsive cues. How Abl functions in this role is not yet clear, but we suggest that Abl may help regulate cytoskeletal dynamics underlying a growth cone's response to midline cues. © 2003 Wiley Periodicals, Inc. J Neurobiol 57: 15–30, 2003
Localization of ganglioside 9‐O‐acetyl GD3 in point contacts of neuronal growth cones
Authors: Negreiros Erika M. A. , Leão Ana C. M. , Santiago Marcelo F. , Mendez‐Otero Rosalia 
Published: September 2003

AbstractGangliosides are a large group of sialylated glycosphingolipids widely expressed in mammalian tissues. We have shown previously that the expression of 9‐O‐acetyl GD3 is highly correlated with periods of neurite outgrowth in the developing nervous system, and that the advance of dorsal root ganglia growth cones on laminin was halted in presence of an antibody specific for 9‐O‐acetyl GD3. In this work, we examined by immunocytochemistry and confocal microscopy whether this ganglioside is localized in point contacts in neuronal growth cones. We identified point contacts by immunoreactions with proteins, such as vinculin and β1 integrin, known to be associated with these structures in growth cones. Our observations indicate that 9‐O‐acetyl GD3 is specifically associated with vinculin and β1 integrin in point contacts of growth cones, suggesting a possible role for this particular ganglioside in the modulation of these contacts during neurite outgrowth. © 2003 Wiley Periodicals, Inc. J Neurobiol 57: 31–37, 2003