bluuebunny/crossref_metadata_2025_split huggingface dataset:
A new method for the prediction of diffusion coefficients in poly(ethylene terephthalate)
Authors: Welle Frank 
Published: December 2012

AbstractPoly(ethylene terephthalate) (PET) is used in several packaging applications, especially for beverages. Due to the low concentration of potential chemical compounds like polymer additives or monomers leached out of the polymers and found in food or beverages, the compliance of a PET packaging material is shown often by use of migration modeling. Diffusion coefficients for migrants, however, are rare in the scientific literature. The aim of the study was to develop an equation for the prediction of diffusion coefficients in PET on the basis of activation energies of diffusion for possible migrants in PET. As a result, a correlation between experimentally determined activation energies of diffusion EA and the volume of the migrant V was established for PET. In addition, a correlation of the pre‐exponential factor D0 with the activation energy EA was found. Combining both correlations lead to an equation where the diffusion coefficients DP are predictable from the molecular volume V of the migrant. The equation might be useful for migration prediction and consumer exposure estimations. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Effect of organic modification on structure and properties of room‐temperature vulcanized silicone rubber/montmorillonite nanocomposites
Authors: Jincheng Wang , Wenli Hao 
Published: December 2012

AbstractThe aim of this work was to study the effect of different organomontmorillonite on the structure and properties of room‐temperature vulcanized silicone rubber (RTV) composites. Quaternary ammonium salts (QAS) and hyperbranched QAS were used as intercalation agents to treat Na+‐montmorillonite and formed two kinds of organomontmorillonite, OMMT and HOMMT. OMMT/RTV and HOMMT/RTV composites were prepared using these organomodified silicate layers. Properties such as tensile strength, elongation at break, swelling behavior, and thermal stability were researched and compared. The addition of OMMT and HOMMT improved the mechanical properties of RTV composites. The composites with 3 mass % HOMMT showed the highest tensile strength and elongation at break, 5.4 MPa and 425%, which was 29 and 97% higher than that of pure RTV. The RTV composites exhibited excellent thermal stability and swelling behavior. At loading of 3 mass % of HOMMT, Tonset, and Tmax was 452 and 640°C, respectively, 33 and 150°C higher than that of pure RTV. A combination of X‐ray diffraction (XRD) test, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) studies was used to characterize the structure and reinforcing mechanism of these clays. The diffraction peaks in XRD curves were almost absent in the scattering curve of RTV/HOMMT (3 mass %). This was due to the possibility of having exfoliated silicate layers dispersed in the polymer matrix. A careful observation of an area of platelet tactoid of 3% HOMMT filled composite in SEM and TEM revealed the uniform dispersion of the silicate layers in the composites. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Copolymerization of ethylene with unsaturated alcohols and methylmethacrylate using a silylated α‐diimine nickel catalyst: Molecular modeling and photodegradation studies
Authors: Matos Inês , Fernandes Susete N. , Liu Hua‐Rong , Tevtia Amit K. , Singh R. P. , Lemos MANDA , Lemos Francisco , Marques Maria M. 
Published: December 2012

AbstractIn this article, the experimental results obtained in the copolymerization of ethylene with polar monomers using a silylated α‐diimine nickel catalyst are described and compared with those obtained with a non‐silylate similar one. The results show that the introduction of a siliyl group in the para‐position of the imine moiety turns the catalyst less sensitive toward polar functionalities. However, the reactivity observed in copolymerization reactions was found to be reduced both the global polymerization and incorporation rates. Molecular modeling calculation allowed us to understand both the preferred insertion mode and the intermediate product structures for E/MMA copolymerization. Photodegradation studies showed that the presence of polar groups in the copolymers increases their rate of oxidation and turn them more easily degradable. The stabilization performed by Tinuvin 770 showed that for long‐exposure times, it is not very effective regardless it is only mixed or grafted to the copolymer. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Preparation and characterization of cyhalothrin‐loaded poly(2‐hydroxyethyl methacrylate)‐co‐polylactide (PHEMA‐co‐PLA) ultrafine particles
Authors: Fan Tengfei , Wu Xuemin , Wu Yan 
Published: December 2012

AbstractPoly(2‐hydroxyethyl methacrylate)‐co‐polylactide (PHEMA‐co‐PLA) and its corresponding cyhalothrin‐loaded ultrafine particles were successfully synthesized and prepared, respectively. The chemical structures of the copolymers have been confirmed by Fourier transform infrared spectroscopy (FTIR), 1H‐nuclear magnetic resonance (1H‐NMR), 13C‐nuclear magnetic resonance (13C‐NMR), and thermogravimetric analysis (TGA). Furthermore, the particle size, the cyhalothrin loading content (LC), and the cyhalothrin release behavior were investigated. PHEMA‐co‐PLA proved to be a good material for the preparation of ultrafine particles for lipophilic pesticide delivery. The developed cyhalothrin‐loaded PHEMA‐co‐PLA ultrafine particles showed good dispersity in water and sustained release behavior. In addition, it is easy to be prepared by both nanoprecipitation method and emulsion/solvent evaporation method. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Conformational, thermal, and ionic conductivity behavior of PEO in PEO/PMMA miscible blend: Investigating the effect of lithium salt
Authors: Ghelichi Mahdi , Qazvini Nader Taheri , Jafari Seyed Hassan , Khonakdar Hossein Ali , Farajollahi Yaser , Scheffler Christina 
Published: December 2012

AbstractIn this research, influence of incorporating LiClO4 salt on the crystallization, conformation, and ionic conductivity of poly(ethylene oxide) (PEO) in its miscible blend with poly(methyl methacrylate) (PMMA) is studied. Differential scanning calorimetry showed that the incorporation of salt ions into the blend suppresses the crystallinity of PEO. The X‐ray diffraction revealed that the unit‐cell parameters of the crystals are independent of the LiClO4 concentration despite of the existence of ionic interactions between PEO and Li cations. In addition, the complexation of the Li+ ions by oxygen atoms of PEO is investigated via Fourier transform infrared spectroscopy. The conformational changes of PEO segments in the presence of salt ions are studied via Raman spectroscopy. It is found that PEO chains in the blend possess a crown‐ether like conformation because of their particular complexation with the Li+ ions. This coordination of PEO with lithium cations amorphize the PEO and is accounted for suppressed crystallinity of PEO in the presence of salt ions. Finally, electrochemical impedance spectroscopy is used to characterize the ionic conductivity of PEO in the PEO/PMMA/LiClO4 ternary mixture at various temperatures. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Enhancing particle erosion resistance of glass‐reinforced polymeric composites using carbon nanofiber‐based nanopaper coatings
Authors: Zhang Na , Yang Fan , Guerra Dante , Shen Changyu , Castro Jose , Lee James Ly 
Published: December 2012

AbstractSand erosion may cause severe damage of blades in wind turbine and helicopter blades as well as many surface components of airplanes. In this study, thin nanopapers made of carbon nanofibers (CNFs) are used to enhance the resistance of solid particle erosion of glass fiber (GF)/wind epoxy composites. Finite element computer simulations are used to elucidate the underlying mechanisms. The much higher particle erosion resistance of nanopapers compared to GF‐reinforced epoxy composites is attributed to the high strength of CNFs and their nanoscale structure. The excellent performance in particle erosion resistance makes the CNF‐based nanopaper a prospective protective coating material for the turbine blades in the wind energy industry. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Microwave assisted glycolysis of poly(ethylene terepthalate) for preparation of polyester polyols
Authors: Chaudhary Saurabh , Surekha Parthasarathy , Kumar Devendra , Rajagopal Chitra , Roy Prasun Kumar 
Published: December 2012

AbstractThe generic aim of the present work is to reduce the time required for glycolytic depolymerization of PET by employing microwave irradiation instead of the conventional heating process. Glycolysis of PET was performed in the presence of glycols of different molecular weight under microwave irradiation. Experimental conditions like PET : glycol ratio, reaction time and concentration of glycerol were optimized to maximize the product yield. In the presence of ethylene glycol, bis‐(hydroxyethyl) terephthalate (BHET) could be obtained in excellent yields in significantly lesser time (30 min) as compared to 8–9 h by conventional heating process. The BHET yield could further be increased by a second step glycolysis of the residual oligomers. This increased efficiency of the microwave assisted process has been attributed to the high microwave absorption capacity of glycols which results from their high loss factor. PET could also be glycolysed in the presence of higher glycols, however the reactivity of diols was found to decrease with increase in the molecular weight. The polyols obtained were reacted with aromatic diphenylmethane diisocyanate to prepare polyurethane foams, which were characterized by various techniques for determination of their physical, mechanical and structural properties. The compressive strength of the polyurethane foams was found to be inversely proportional to the molecular weight of the glycolysed polyol used for its preparation. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Practical Synthesis of (20S)‐10‐(3‐Aminopropyloxy)‐7‐ethylcamptothecin, a Water‐Soluble Analogue of Camptothecin
Authors: Watanabe Tatsuya , Tsuboi Yasunori , Nomura Sumihiro 
Published: December 2012

AbstractA robust, practical synthesis of (20S)‐10‐(3‐aminopropyloxy)‐7‐ethylcamptothecin (T‐2513, 5), which is a water‐soluble analogue of camptothecin, has been developed. The key step in this synthesis is a highly diastereoselective ethylation at the C20 position by using N‐arylsulfonyl‐(R)‐1,2,3,4‐tetrahydroisoquinoline‐3‐carboxylic acid ester as a chiral auxiliary, which affords the key intermediate ethyl‐(S)‐2‐acyloxy‐2‐(6‐cyano‐5‐oxo‐1,2,3,5‐tetrahydroindolizin‐7‐yl)butanoate (8 k) in 93 % yield and 87 % de. Optically pure compound 8 k was obtained by a single recrystallization from acetone and its further elaboration through Friedlander condensation afforded compound 5. This synthesis does not require any chromatographic purification steps and can provide compound 5 on a multi‐gram scale in 6.3 % overall yield (16 steps).
New bis‐ferrocenyl end‐capped peptides: synthesis and charge transfer properties
Authors: Donoli Alessandro , Marcuzzo Vanessa , Moretto Alessandro , Crisma Marco , Toniolo Claudio , Cardena Roberta , Bisello Annalisa , Santi Saverio 
Published: December 2012

AbstractIn this article, the successful preparation of a new series of 310‐helical peptides of different length containing two terminal ferrocenyl (Fc) units and based on the strongly foldameric α‐aminoisobutyric (Aib) acid is reported. The synthesis of the FcCO(Aib)nNHFc (n = 1−5) homo‐peptides was performed by solution methods. Moderate to good yields (26−85%) were obtained in each of the difficult coupling steps of FcCOOH and the corresponding H(Aib)nNHFc compounds by C‐activation with the 1‐(3‐dimethylaminopropyl)‐3‐ethylcarbodiimide/7‐aza‐1‐hydroxy‐1,2,3‐benzotriazole method. Information on the CO···HN intramolecularly hydrogen‐bonded networks was initially obtained from FT‐IR absorption measurements. The NH stretching (amide A) region allowed us to distinguish which amide protons are involved in intramolecular hydrogen bonds and indicates the formation of an incipient 310‐helix structure for peptides containing at least two Aib residues. This conclusion was confirmed by 1H NMR titrations of the NH groups of the peptides in CDCl3 with dimethylsulfoxide and by crystallographic analysis of the Nα‐acylated FcCO(Aib)5NHFc pentapeptide amide. The two redox‐active Fc groups covalently bound to the termini of the foldameric peptide architectures were used as electrochemical probes. The end‐to‐end effects of electron holes generated by single and double oxidations were analyzed by means of electrochemical and spectroelectrochemical techniques. The results of these studies indicate that charge transfer across the peptide main chain does occur in the five peptides. In particular, in the pentapeptide 5, charge is transferred through an intramolecular Fe···Fe separation of 14 Å. © 2012 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 100: 71–81, 2013.
Development of sensory neuropathy in streptozotocin‐induced diabetic mice
Authors: Murakami Tatsufumi , Iwanaga Takayuki , Ogawa Yoshinao , Fujita Yoshiaki , Sato Eiji , Yoshitomi Hironori , Sunada Yoshihide , Nakamura Akihiro 
Published: December 2012

AbstractDiabetic polyneuropathy is a major complication of diabetes and the most common cause of peripheral neuropathy. Sensory‐dominant neuropathy is the most common type. We previously used streptozotocin (STZ)‐induced diabetic ddY mice with sensory neuropathy to evaluate the therapeutic effects of vascular endothelial growth factor and placental growth factor isoforms. In this study, to characterize the development of diabetic sensory neuropathy, electrophysiological, behavioral, and histopathological studies were performed in these diabetic mice. A significant difference in sensory conduction velocity in the tail nerve was observed between healthy and diabetic mice at 1 week after STZ injection. Diabetic mice developed hypoalgesia at 5 weeks after STZ injection. Axon area and myelin thickness of the myelinated fibers were increased in 17‐week‐old healthy mice compared with those in 8‐week‐old healthy mice. However, these increases were retarded in 17‐week‐old diabetic mice. In unmyelinated fibers, axon area was significantly reduced in 17‐week‐old diabetic mice compared with 8‐ and 17‐week‐old healthy mice. These findings suggest that both impaired maturation of myelinated fibers and atrophy of unmyelinated fibers simultaneously occur in the early stage of diabetes in these mice. Our mouse model may be useful for studying the pathogenesis of and therapies for diabetic sensory neuropathy.
Bystanders' Support of Cyberbullied Schoolmates
Authors: Macháčková Hana , Dedkova Lenka , Sevcikova Anna , Cerna Alena 
Published: December 2012

ABSTRACTThis study examined factors that increase or decrease the support a bystander offered to a victim of cyberbullying. Possible determinants of supportive behaviour were analyzed using a four‐step hierarchical regression analysis on data from 156 Czech children (12–18 years old; M = 15.1; 54% females) who witnessed their schoolmates being victims of cyberbullying. Among individual characteristics, only a general tendency toward prosocial behaviour was a positive predictor of supportive behaviour. Other factors such as age, gender, self‐esteem, and problematic relationships with peers had no effect. Among contextual factors, existing relationships with the victim, upset feelings evoked by witnessing victimization, and direct requests for help from the victim triggered supportive behaviour, while strong relationships with the bully inhibited it. Fear of intervening played no role. The practical implications of the findings are discussed with regard to the roles of the emotional response of the bystander and direct requests for help from the victim in cyberbullying interventions. Copyright © 2012 John Wiley & Sons, Ltd.
A Modular Synthesis of Teraryl‐Based α‐Helix Mimetics, Part 2: Synthesis of 5‐Pyridine Boronic Acid Pinacol Ester Building Blocks with Amino Acid Side Chains in 3‐Position
Authors: Peters Martin , Trobe Melanie , Breinbauer Rolf 
Published: December 2012

AbstractOne of the most common protein–protein interactions (PPI) is the interaction of the α‐helix of one protein with the surface of the second one. Terphenylic scaffolds are bioinspired motifs in the inhibition of PPIs and have been identified as suitable α‐helix mimetics. One of the challenging aspects of this strategy is the poor solubility of terphenyls under physiological conditions. In the literature pyrrolopyrimidine‐, pyrimidine‐ or pyridazine‐based mimetics have been reported to show improved solubility. We present a new convergent strategy for the synthesis of linear pyridine‐type teraryls based on a phenylic core unit. A general approach for the synthesis of 3,5‐disubstituted pyridine‐based boronic acid pinacol esters with amino acid side chains in the 3‐position (representing Phe, Leu, Ile, Lys, Asp, Asn) is presented and exploits the functional group tolerance of the Knochel–Grignard reagents. The building blocks have been used in a convergent in situ two‐step synthesis of teraryl α‐helix mimetics.
Sulfinylnitriles: Sulfinyl–Metal Exchange–Alkylation Strategies
Authors: Nath Dinesh , Fleming Fraser F. 
Published: December 2012

AbstractAdding organolithiums, Grignard reagents, or zincates to sulfinylnitriles triggers a facile sulfinyl–metal exchange to afford N‐ or C‐metalated nitriles. Sulfinyl–magnesium exchange–alkylations efficiently install quaternary and tertiary centers, even in the case of tertiary sulfinylnitriles that contain a highly acidic methine proton. α‐Sulfinylalkenenitriles afford moderately nucleophilic magnesiated nitriles, and the reactivity can be dramatically increased by conversion to the corresponding magnesiates. The sulfinyl‐metal exchange is extremely fast, proceeds efficiently with quaternary, tertiary, and vinylic α‐sulfinylnitriles, and exhibits an exceptional functional group tolerance in nitrile alkylations.
Efficient Synthesis of a Regioregular Oligothiophene Photovoltaic Dye Molecule, MK‐2, and Related Compounds: A Cooperative Hypervalent Iodine and Metal‐Catalyzed Synthetic Route
Authors: Dohi Toshifumi , Yamaoka Nobutaka , Nakamura Shota , Sumida Kohei , Morimoto Koji , Kita Yasuyuki 
Published: December 2012

AbstractWe have successfully established an efficient route to the core structure of donor–acceptor head‐to‐tail (H–T)‐linked regioregular oligothiophenes, which includes the following key synthetic steps, that is, hypervalent iodine induced direct and regioselective coupling of thiophenes and the use of the obtained bithiophenes as excellent coupling substrates for the Suzuki and Stille couplings. The versatility of this new approach is highlighted in the dramatic improvement of the yield (ca. 59 % overall yield) of MK‐2, a high‐performance organic dye, for photovoltaic applications.
Computational Design, Synthesis, and Mechanochromic Properties of New Thiophene‐Based π‐Conjugated Chromophores
Authors: Prampolini Giacomo , Bellina Fabio , Biczysko Malgorzata , Cappelli Chiara , Carta Luciano , Lessi Marco , Pucci Andrea , Ruggeri Giacomo , Barone Vincenzo 
Published: December 2012

AbstractThe possibility of exploiting supramolecular architectures for the preparation of innovative mechanochromic devices has been extended by designing novel thienyl‐substituted 1,4‐bis(ethynyl)benzene dyes, which are characterized by a conjugated, rigid, rodlike core structure. This new family of chromophores was synthesized according to a simple two‐step sequential cross‐coupling reaction, and the optical properties were investigated in solution and in a polymeric matrix. To tune the mechanochromic performances in smart polymer materials, a virtual screening was set up that was able to select a derivative with optimal spectral features. The effective combination of experimental and computational investigations allowed us to spot those homologues with already potential anisotropic and aggregachromic features and characterized by the best spectral properties and luminescent response. The best candidate was synthesized and dispersed into a polyethylene matrix, indeed achieving an “in silico designed” mechanochromic material. Besides the specific applications of this novel material, the integration of computational and experimental techniques reported here defines an efficient protocol that can be applied to make a selection among similar dye candidates, which constitute the essential responsive part of such supramolecular devices.
Fully Synthetic Self‐Adjuvanting Thioether‐Conjugated GlycopeptideLipopeptide Antitumor Vaccines for the Induction of Complement‐Dependent Cytotoxicity against Tumor Cells
Authors: Cai Hui , Sun Zhan‐Yi , Huang Zhi‐Hua , Shi Lei , Zhao Yu‐Fen , Kunz Horst , Li Yan‐Mei 
Published: December 2012

AbstractGlycopeptides of tumor‐associated mucin MUC1 are promising target structures for the development of antitumor vaccines. Because these endogenous structures were weakly immunogenic, they were coupled to immune‐response‐stimulating T‐cell epitopes and the Pam3Cys lipopeptide to induce strong immune responses in mice. A new thioether‐ligation method for the synthesis of two‐ and three‐component vaccines that contain MUC1 glycopeptides as the B‐cell epitopes, a T‐cell epitope peptide, and the Pam3CSK4 lipopeptide is described. The resulting fully synthetic vaccines were used for the vaccination of mice, either in a liposome with Freund′s adjuvant or in aqueous PBS buffer. The three‐component vaccines that contained the Tetanus Toxoid P2 T‐cell epitope peptide induced strong immune responses, even when administered just in PBS. By activation of the complement‐dependent cytotoxicity (CDC) complex, the antisera induced the killing of tumor cells.