bluuebunny/crossref_metadata_2025_split huggingface dataset:
Preparation and study of cellulose acetate membranes modified with linear polymers covalently bonded to Starburst polyamidoamine dendrimers
Authors: Ledesma‐García J. , Orozco Germán , Antaño René , Godínez Luis A. 
Published: September 2008

AbstractNovel ion‐selective membranes were prepared by means of the noncovalent modification of a cellulose acetate (CA) polymer with either poly(ethylene‐alt‐maleic anhydride) or poly(allylamine hydrochloride) chains covalently linked to Starburst amine‐terminated polyamidoamine (PAMAM) dendrimers generations 4 and 3.5, respectively. Linear polymer incorporation within the porous CA membrane was performed with mechanical forces, which resulted in modified substrates susceptible to covalent adsorption of the relevant dendritic materials via the formation of amide bonds with a carbodiimide activation agent. The membranes thus prepared were characterized by chemical, physical, and spectroscopic measurements, and the results indicate that the dendrimer peripheral functional groups were the species that participated in the ion‐exchange events. The prepared materials were also evaluated for their ion‐exchange permeability with sampled current voltammetry experiments involving cationic and anionic species {[Ru(NH3)6]3+ and [Fe(CN6)]3−, respectively} as redox probe molecules under different pH conditions. As expected, although permeability was favored by opposite charges between the dendrimer and the electroactive probe, a clear blocking effect took place when the charge in the dendritic polymer and the electroactive complex was the same. Electrochemical impedance spectroscopy measurements, on the other hand, showed that the PAMAM‐modified membranes were characterized by good selectivity and low resistance values for multivalent ions compared to a couple of commercial ion‐exchange membranes. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Anionomeric waterborne poly(urethane semicarbazide) dispersions and their adhesive properties
Authors: Aruna Palanisamy , Kumar D. B. Rohini 
Published: September 2008

AbstractAqueous polyurethane dispersions were prepared from isocyanate‐terminated ionic polyurethane prepolymers by chain extension with dihydrazides. These water‐borne dispersions had excellent adhesive properties and were used to bond leather and canvas. The base polymers were varied with respect to (1) the ionic content with the same chain extender and (2) the nature of the chain extender with the ionic content kept constant. Studies on the particle size and viscosity revealed that the ionic content had an influence on the aforementioned properties: the particle size decreased and the viscosity increased with increasing ionic content. The polarity of the films cast from the dispersions were determined with contact‐angle measurements: hydrophilic character was exhibited by all the compositions. X‐ray studies revealed that the increase in the ionic content led to increasing intensities of the diffraction peaks due to increased secondary forces of bonding. The tensile strength measurements showed that the films were highly elastomeric and had good mechanical strength, which varied with the composition. A shear strength and peel strength analysis of specimens obtained through the bonding of leather to leather, leather to canvas, and canvas to canvas revealed that the waterborne dispersions were excellent adhesives for bonding leather surfaces. Thus, a very efficient, ecofriendly waterborne dispersion of polyurethane that could find applications in bonding leather in the footwear industry was prepared successfully. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Electrically conductive nanocomposites of polyaniline with poly(vinyl alcohol) and methylcellulose
Authors: Chattopadhyay Dipankar , Bain Mrinal Kanti 
Published: September 2008

AbstractElectrically conductive nanocomposites of HCl‐doped polyaniline (PANI–HCl) nanocolloid particles with water‐soluble and film‐forming polymers such as poly(vinyl alcohol) (PVA) and methylcellulose (MC) were prepared by the redispersion of preformed MC‐coated submicrometric PANI–HCl particles in PVA and MC solutions under sonication for 1 h and the casting of the films from the dispersions followed by drying. The submicrometric polyaniline (PANI) particles were prepared by the oxidative dispersion polymerization of aniline in an acidic (1.25M HCl) aqueous ethanol (30 : 70) medium with MC as a steric stabilizer. The particles contained 4.7 wt % MC and had a conductivity of 7.4 S/cm. They had an oblong shape of 203 nm (length) and 137 nm (breadth). Sonication broke the oblong‐shaped particles to sizes of ∼10 nm in the PVA matrix and ∼60 nm in the MC matrix. The electrical conductivity of these films was measured, and the percolation threshold was determined. The composites had the characteristics of a low percolation threshold at a volume fraction of PANI of 2.5 × 10−2 in the PVA matrix and at a volume fraction of 3.7 × 10−2 in the MC matrix. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Preparation and characterization of antibacterial zeolite–polyurethane composites
Authors: Kamışoğlu K. , Aksoy E. A. , Akata B. , Hasirci N. , Baç N. 
Published: September 2008

AbstractIn this study, antibacterial properties were induced in polyurethane (PU) films by the incorporation of Ag+‐loaded zeolites as fillers. The mechanical and thermal properties of the prepared composites were also investigated. For this purpose, two different types of zeolite microparticles, high‐silica zeolite beta crystals and low‐silica zeolite A crystals, were synthesized. Ag+ was added by ion exchange, and these particles were incorporated into the PU prepolymer, which was prepared from its main components of toluene diisocyanate and polypropylene ethylene glycol (medical purity). Microbiological tests revealed that both types of composites, prepared by the addition of Ag+‐containing zeolite beta or zeolite A to the PU matrix, had antibacterial properties. It was demonstrated for the first time that a high‐silica zeolite (zeolite beta) and its composite film could be effectively employed as antibacterial materials. Furthermore, mechanical and thermal characterization of the composites showed that the zeolites enhanced the mechanical properties of the polymer and did not cause any deterioration in its thermal properties. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Lower critical solution temperature determination of smart, thermosensitive N‐isopropylacrylamide‐alt‐2‐hydroxyethyl methacrylate copolymers: Kinetics and physical properties
Authors: Fares Mohammad M. , Othman Ali A. 
Published: September 2008

AbstractThe lower critical solution temperatures (LCSTs) were verified and determined for different molar feed ratios of N‐isopropylacrylamide (NIPAAm) and 2‐hydroxyethyl methacrylate (HEMA) monomers with ultraviolet spectroscopy and differential scanning calorimetry techniques. Increases in the NIPAAm monomer content played a crucial role in the LCST, which increased up to 36.7°C at 50 mol %. However, a further increase in the NIPAAm monomer content steadily reduced the LCST, which decreased to 33°C at 100 mol % NIPAAm [i.e., pure poly(N‐isopropylacrylamide)]. The rate of copolymerization, assessed by the conventional conversion (%)–time method, and the apparent activation energies were determined. The reactivity ratios of the monomers, determined by the Kelen–Tudos and Fineman–Ross techniques, together with the results of an equation, showed that the copolymer which formed was an alternating copolymer. The Q–e values for the NIPAAm monomer were determined. The equation showed the linear Arrhenius behavior of ln(r1r2) versus the reciprocal of the temperature (where r1 and r2 are the reactivity ratios of NIPAAm and HEMA, respectively): the activation energy difference [i.e., (E12 + E21) − (E11 + E22), where E12, E21, E11, and E22 are various activation energies] was found to be −109 kJ/mol. The copolymers were characterized with 1H‐NMR, 13C‐NMR, Fourier transform infrared, ultraviolet–visible, thermogravimetric analysis, differential scanning calorimetry, X‐ray diffraction, and scanning electron microscopy techniques. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Fly ash particles and precipitated silica as fillers in rubbers. III. Cure characteristics and mechanical and oil‐resistance properties of acrylonitrile‐butadiene rubber
Authors: Sombatsompop N. , Wimolmala E. , Sirisinha C. 
Published: September 2008

AbstractThis study investigated the cure characteristics, mechanical properties, and oil resistance of acrylonitrile–butadiene rubber (NBR) filled with 60 phr carbon black (CB) and different amounts of silica from fly ash [fly ash silica (FASi)] and precipitated silica (PSi). Loadings of CB and PSi silica in NBR vulcanizates reduced the scorch and cure times. An increase in the cure time of FASi–CB–NBR vulcanizates was probably caused by an interaction between the polarity of NBR and the metal oxide activators in FASi, which could retard the curing. The tensile modulus of NBR vulcanizates increased with the addition of CB and silica fillers and with immersion in hydraulic oil at 125°C. CB exhibited a more pronounced effect on the NBR reinforcement versus the PSi and FASi fillers. The tensile and tear strengths and elongation at break decreased under thermal aging in hydraulic oil. The PSi system showed better reinforcement of CB–NBR vulcanizates than the FASi system. The hardness of NBR vulcanizates increased with CB and silica. The results in this work suggest that silica from fly ash particles could be used as an extender for cost savings in NBR compounds. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Thermal conductivity models for single and multiple filler carbon/liquid crystal polymer composites
Authors: Hauser Rebecca A. , Keith Jason M. , King Julia A. , Holdren Jennifer L. 
Published: September 2008

AbstractIn this study, two different carbon fillers (Thermocarb TC‐300 synthetic graphite and Fortafil 243 carbon fiber) were added to Vectra A950RX liquid crystal polymer to produce single filler composites with filler concentrations of up to 80 wt % (71.4 vol %) and multiple filler composites that contained varying concentrations of both synthetic graphite and carbon fiber. The through‐plane and in‐plane thermal conductivity for each formulation was measured. For the single filler synthetic graphite and carbon fiber composites, the Nielsen model was applied to the experimental through‐plane thermal conductivity data. The parameters obtained from the single filler models were then used along with a variation of the original Nielsen model to predict the through‐plane thermal conductivities of the multiple filler composites. In‐plane thermal conductivity models were also developed using a correlation involving the square root of the product of the composite in‐plane and through‐plane thermal conductivities. This model was applied to the single filler synthetic graphite and carbon fiber composites. A variation of this model was then used to predict the in‐plane thermal conductivity for composites containing both fillers. All the models presented in this work showed good agreement with experimental data. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Synthesis, characterization, and properties of polypyrrole/expanded vermiculite intercalated nanocomposite
Authors: Lin Jianming , Tang Qunwei , Wu Jihuai , Sun Hui 
Published: September 2008

AbstractThe conductive polypyrrole (PPy) is intercalated into the interlayers of expanded vermiculite (EVMT) to produce the nanocomposite with high conductivity by a synchronous polymerization of pyrrole and intercalation of PPy reaction in aqueous solution. The structures and properties are characterized by the nanocomposite using powder X‐ray diffraction, Fourier transform infrared spectroscopy, conductivity measurements, and stability measurements. The nanocomposite exhibited a typical percolation phenomena and the percolation threshold is around mass ratio for pyrrole to EVMT 0.22. Under optimized conditions, a PPy/EVMT intercalated nanocomposite with conductivity of 67 S cm−1 is obtained. The intercalated nanocomposite has a good environmental stability. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Compatibility study in poly(tetramethyleneadipate‐co‐terephthalate)/polystyrene bioblends
Authors: Biresaw Girma , Mohamed Abdellatif , Gordon Sherald H. , Harry‐O'kuru Rogers E. , Carriere Craig C. 
Published: September 2008

AbstractBioblends of the biodegradable copolyester poly(tetramethyleneadipate‐co‐terephthalate) (EBU) and polystyrene (PS) were prepared in different weight compositions on a twin‐screw extruder at 160–200°C. The various bioblend compositions were then investigated using thermogravimetric analysis (TGA), modulated differential scanning calorimetry (MDSC), and Fourier transform infrared photoacoustic spectroscopy (FTIR‐PAS). TGA studies showed that 25/75 and 50/50 EBU/PS blends had higher thermal stability than the more thermally stable blend component, PS. The MDSC studies showed a single Tg and single Tm for the blends, that were concentration independent. The FTIR‐PAS studies indicated a small shift (4–8 cm−1) in the carbonyl absorption peaks of EBU to lower wavenumbers in 50/50 EBU/PS blend relative to that of neat EBU. It is concluded that, while the MDSC results were inconclusive, the TGA and FTIR‐PAS results support the existence of some degree of intermolecular interaction between EBU and PS components and, hence, partial compatibility in EBU/PS blends. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Synthesis and characterization of new optically active polyesters by step‐growth polymerization of novel aromatic (2S)‐4‐[(4‐methyl‐2‐phthalimidyl‐pentanoylamino)benzoylamino]isophthalic acid with aromatic diols
Authors: Mallakpour Shadpour , Sepehri Saghi 
Published: September 2008

AbstractA new diacid monomer 9 was synthesized in five steps. Starting from the reaction of L‐leucine with phthalic anhydride in acetic acid provided (2S)‐4‐methyl‐2‐phthalimidylpentanoic acid (3) in good yield. The compound 3 was converted to (2S)‐4‐methyl‐2‐phthalimidylpentanoyl chloride (4) by reaction with thionyl chloride. The resulting acid chloride 4 was reacted with p‐aminobenzoic acid (5) in dry tetrahydrofuran and (2S)‐4‐(4‐methyl‐2‐phthalimidylpentanoyl‐amino)benzoic acid (6) was obtained. Then, it was converted to (2S)‐4‐(4‐methyl‐2‐phthalimidylpentanoylamino)benzoyl chloride (7) by treatment with thionyl chloride. The reaction of acid chloride 7 with 5‐aminoisophthalic acid in dry N,N‐dimethylacetamide (DMAc) gave (2S)‐4‐[(4‐methyl‐2‐phthalimidylpentanoylamino)‐benzoylamino]isophthalic acid (9) in high yield. The step‐growth polymerization of this diacid with several aromatic diols, such as bisphenol‐A (10a), phenolphthalein (10b), 1,5‐naphthalenediol (10c), hydroquinone (10d), bisphenyl‐2,2′‐diol (10e), 4,4′‐dihydroxydiphenyl sulfone (10f), 4,4′‐dihydroxydiphenyl sulfide (10g), and 1,8‐dihydroxyanthraquinone (10h), was carried out in a system of tosyl chloride, pyridine, and N,N‐dimethylformamide (DMF) to give a series of new optically active polyesters (PE)s with good yield and moderate inherent viscosity ranging from 0.29 to 0.43 dL/g. All of the aforementioned polymers were fully characterized by FTIR and specific rotation. Some structural characterization was performed by 1H NMR and elemental analysis. These polymers are readily soluble in amide‐type solvents such as DMF, DMAc, dimethyl sulfoxide, and protic solvents such as sulfuric acid. Thermal gravimetry analysis showed that the 10% weight loss temperature in a nitrogen atmosphere was more than 360°C, which indicates that the resulting PEs have a good thermal stability as well as excellent solubility. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Investigation of the thermal decomposition behavior and kinetic analysis of PTT/phenoxy blends
Authors: Farmahini‐Farahani M. , Jafari S. H. , Khonakdar H. A. , Böhme F. , Yavari A. , Tarameshlou M. 
Published: September 2008

AbstractThermal decomposition of binary blends composed of poly(trimethylene terephthalate) (PTT) and a phenoxy resin, namely poly(hydroxy ether) of bisphenol A, and prepared by melt blending was studied using thermogravimetric analysis. The thermal decomposition behavior of the blends could be explained in terms of formation and loss of hydrogen bonds and appearance of both low and high molecular weight species due to transesterification reaction between hydroxyl groups of phenoxy with ester bonds of PTT. The kinetics of decomposition reaction was analyzed by Freeman–Carroll, Friedman, Chang, and Vachuska–Voboril methods. It was found that all of the methods well described the decomposition reaction of the blends. The correlation between the calculated values and the chemical nature of the blends was acceptable. Among all the investigated methods the Chang method showed the best correlation with the experimental data. FTIR spectroscopy was employed to study the chemical structure of the blends. The results revealed strong interaction between the blend components in the form of hydrogen bonding. Progress of these interactions was followed with time and temperature. The effects of blending and loss of hydrogen bonding on degradation behavior in this kind of reactive blends were emphasized. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Effects of ultraviolet irradiation on the static and dynamic properties of neoprene rubbers
Authors: Chou Hsoung‐Wei , Huang Jong‐Shin 
Published: September 2008

AbstractRubbers deteriorate when they are exposed to ultraviolet irradiation for long periods of time. By conducting a series of hardness measurements and simple tension tests, the static properties of neoprene rubbers before and after exposure to various durations of ultraviolet irradiation were first measured. It is found that the Shore A hardness and tensile modulus of neoprene rubbers after exposure to ultraviolet irradiation are increased but their elongation at break, tensile strength, and energy to break are significantly decreased. On the basis of a complex spring model of a vibration system, the dynamic shear properties of neoprene rubbers before and after exposure to different durations of ultraviolet irradiation were then determined from the experimental results of dynamic transmissibility tests. It is also found that the storage modulus, loss modulus, and loss factor of neoprene rubbers are drastically affected by the duration of ultraviolet irradiation they experienced. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
[Ru(bpy)2(dcbpy)NHS] Labeling/Aptamer‐Based Biosensor for the Detection of Lysozyme by Increasing Sensitivity with Gold Nanoparticle Amplification
Authors: Bai Jianguo , Wei Hui , Li Bingling , Song Lihua , Fang Lanyun , Lv Zhaozi , Zhou Weihong , Wang Erkang 
Published: September 2008

AbstractA novel [Ru(bpy)2(dcbpy)NHS] labeling/aptamer‐based biosensor combined with gold nanoparticle amplification for the determination of lysozyme with an electrochemiluminescence (ECL) method is presented. In this work, an aptamer, an ECL probe, gold nanoparticle amplification, and competition assay are the main protocols employed in ECL detection. With all the protocols used, an original biosensor coupled with an aptamer and [Ru(bpy)2(dcbpy)NHS] has been prepared. Its high selectivity and sensitivity are the main advantages over other traditional [Ru(bpy)3]2+ biosensors. The electrochemical impedance spectroscopy (EIS) and atomic force microscopy (AFM) characterization illustrate that this biosensor is fabricated successfully. Finally, the biosensor was applied to a displacement assay in different concentrations of lysozyme solution, and an ultrasensitive ECL signal was obtained. The ECL intensity decreased proportionally to the lysozyme concentration over the range 1.0×10−13–1.0×10−8 mol L−1 with a detection limit of 1.0×10−13 mol L−1. This strategy for the aptasensor opens a rapid, selective, and sensitive route for the detection of lysozyme and potentially other proteins.
Controlled Self‐Assembly of Functional Metal Octaethylporphyrin 1 D Nanowires by Solution‐Phase Precipitative Method
Authors: So Man‐Ho , Roy V. A. L. , Xu Zong‐Xiang , Chui Stephen Sin‐Yin , Yuen Mai‐Yan , Ho Chi‐Ming , Che Chi‐Ming 
Published: September 2008

AbstractMetal octaethylporphyrin M(OEP) (M=Ni, Cu, Zn, Pd, Ag, and Pt) nanowires are fabricated by a simple solution‐phase precipitative method. By controlling the composition of solvent mixtures, the diameters and lengths of the nanowires can be varied from 20 to 70 nm and 0.4 to 10 μm, respectively. The Ag(OEP) nanowires have lengths up to 10 μm and diameters of 20–70 nm. For the M(OEP) nanowires, the growth orientation and packing of M(OEP) molecules are examined by powder XRD and SAED measurements, revealing that these M(OEP) nanowires are formed by the self‐assembly of M(OEP) molecules through intermolecular π⋅⋅⋅π interactions along the π⋅⋅⋅π stacking axis, and the M2+ ion plays a key role in the nanowire formation. Using the bottom contact field effect transistor structure and a simple drop‐cast method, a single‐crystal M(OEP) nanowires‐based field effect transistor can be readily prepared with prominent hole transporting behaviour and charge‐carrier mobility up to 10−3–10−2 cm2 V−1 s−1 for holes, which are 10 times higher than that of vacuum‐deposited M(OEP) organic thin‐film transistors (OTFTs).
Trinuclear Rhodium Complexes and Their Relevance for Asymmetric Hydrogenation
Authors: Preetz Angelika , Baumann Wolfgang , Drexler Hans‐Joachim , Fischer Christian , Sun Jiangtao , Spannenberg Anke , Zimmer Oswald , Hell Wolfgang , Heller Detlef 
Published: September 2008

AbstractVarious trinuclear rhodium complexes of the type [Rh3(PP)3(μ3‐OH)x(μ3‐OMe)2−x]BF4 (where PP=Me‐DuPhos, dipamp, dppp, dppe; different ligands and μ‐bridging anions) are presented, which are formed upon addition of bases such as NEt3 to solvate complexes [Rh(PP)(solvent)2]BF4. They were extensively characterized by X‐ray diffraction and NMR spectroscopy (103Rh, 31P, 13C, 1H). Their in situ formation resulting from basic additives (NEt3) or basic prochiral olefins (without addition of another base) can cause deactivation of the asymmetric hydrogenation. This effect can be reversed by means of acidic additives.
A Novel Supramolecular System: Combination of Two Switchable Processes in a [2]Rotaxane
Authors: Li Junbo , Li Yongjun , Guo Yanbing , Xu Jialiang , Lv Jing , Li Yuliang , Liu Huibiao , Wang Shu , Zhu Daoben 
Published: September 2008

AbstractA novel supramolecular system, which is made up of a dibenzo[24]crown‐8 (DB24C8) ring component linked with a calix[4]arene derivative, a dumbbell component, containing a secondary ammonium center (‐NR2H2+‐) and a 4,4′‐bipyridinium (BIPY2+) unit, and stoppered with two 3,5‐di‐tert‐butylphenyl groups on the two termini of the dumbbell component, has been synthesized. The system displays a combination of two processes: the pH‐induced shuttling of a DB24C8 ring and the complexation/decomplexation of K+ ions. The switching process of this supramolecular system was investigated in detail by 1H NMR spectroscopy. The results showed that the supramolecular system can only switch smoothly in CD3CN. The two separated switchable processes can run together smoothly in this supramolecular system.