bluuebunny/crossref_metadata_2025_split huggingface dataset:
Highly Ordered 2D Hydrogen‐Bonded Structures of a Tetralactam Macrocycle on the Au(111) Surface
Authors: Kossev I. , Reckien W. , Kirchner B. , Felder T. , Nieger M. , Schalley C. A. , Vögtle F. , Sokolowski M. 
Published: January 2007

AbstractMonolayers of a tetralactam macrocycle, which are commonly used as building blocks in the synthesis of rotaxanes or catenanes, are deposited on a Au(111) surface by using vapor deposition. Due to self‐organization, 2D highly ordered supramolecular networks form. From scanning tunneling microscopy (STM) and concomitant density‐function theory calculations, two structurally different phases are found. In both phases, pairs of hydrogen bonds between the amide groups of next‐neighbor macrocycles are responsible for the structural arrangement of the macrocycles. The structure of both phases differs from that of bulk lattice planes, which reveals that the Au(111) surface acts as a template for the growth of the specific 2D structures. These networks of tetralactam macrocycles possibly open a route to study mechanical interlocking processes or guest/host interactions of the molecules in further detail by using STM.
Nanostructure of potato starch. II. Structure of a highly crystalline gel obtained by retrogradation using X‐ray diffraction techniques
Authors: Bayer R. K. , Baltá‐Calleja F. J. 
Published: January 2007

AbstractA highly crystalline gel (65% crystal portions) was prepared by retrogradation of injection‐molded potato starch in humid atmosphere. The different components of the nanostructure were identified by means of successive melting processes using “in situ” simultaneous wide and low angle X‐ray diffractions. At low temperatures, structural changes such as annealing phenomena or evaporation of water, giving rise to a thickening of the gel, are observed. In the range of 55–75°C, a first transition due to melting of a layered structure of concentric sphere‐like alternating crystalline and amorphous lamellar shells (amylopectine, AP, being the crystalline component) is detected. Analysis of results reveals that the AP crystallization contributes 25% to the overall crystal fraction. A spherulitic structure of alternating radial lamellae from amylose (AM) or AP melts in a higher temperature region between 75 and 86°C. This modification represents the major contribution to crystallinity of about 40%. Unexpectedly, the crystalline blocks of such a structure are abnormally anisometric; i.e., they are thicker than their width. This has been related to a contraction of the AMAP‐co‐spherulite due to an excessive growth of the AP‐shell crystals. The anisometry of the blocks of the AMAP lamellae vanishes at the beginning of the melting of the AP shell crystals, just when the total crystallinity decreases below 50% at 60°C. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 689–696, 2007
Measurement of AC conductivity and dielectric properties of flexible conductive styrene–butadiene rubber‐carbon black composites
Authors: Mohanraj G. T. , Chaki T. K. , Chakraborty A. , Khastgir D. 
Published: January 2007

AbstractFlexible conductive polymer composites were prepared using styrene–butadiene rubber (SBR) as a matrix and conductive carbon black as filler. The filler loading was varied from 10 to 60 phr. The effect of frequency, filler loading, temperature, and applied pressure on the AC conductivity, permittivity, and loss factor of the composites was studied. The AC conductivity of low and high loaded composites was found to be frequency dependent and independent respectively. The permittivity and the loss factor were continuously decreasing with increasing frequency. The increase in filler loading increased the AC conductivity, dielectric constant, and loss factor of the composites. Increase in temperature imposed increase in conductivity and permittivity of the composites. With increasing applied pressure the properties showed exponential increase. The effect of time under a constant compressive stress was studied and dielectric relaxation times were evaluated. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 986–995, 2007
Influence of extrusion, stretching and poling on the structural and piezoelectric properties of poly (vinylidene fluoride‐hexafluoropropylene) copolymer films
Authors: Huan Yan , Liu Yayan , Yang Yifei , Wu Yanan 
Published: January 2007

AbstractThree types of poly (vinylidene fluoride‐hexafluoropropylene) (PVDF–HFP) copolymer films were prepared by extrusion, stretching as well as simultaneously stretching and static electric field poling (SSSEP), respectively, and measured by the differential scanning calorimetric, wide angle X‐ray diffraction, fourier transformation infrared‐attenuated total reflection, and Dynamic mechanical analysis. The experimental results showed that the films prepared by stretching and SSSEP have higher crystallinity and β phase than by extrusion. SSSEP improved the chain orientation enormously both in crystalline and amorphous regions, resulting in the highest storage modulus. Because of the lower β phase content, the extruded films exhibited the lowest piezoelectric coefficient d33. For the stretched and SSSEP films, although the β phase content was similar, the d33 was distinct because of the different potential energy for the rotation of the dipoles. In addition, the SSSEP films gave the maximum d33 (24 pC/N), higher than the other PVDF–HFP copolymer films that have been reported. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 858–862, 2007
Effect of rubber particle cavitation on the mechanical properties and deformation behavior of high‐impact polystyrene
Authors: Serpooshan V. , Zokaei S. , Bagheri R. 
Published: January 2007

AbstractRubber particle cavitation has been the focus of many investigations because it dramatically affects the mechanical properties of polymeric blends. In this work, the effect of rubber particle cavitation on the mechanical behavior of high‐impact polystyrene was studied. The extent of cavitation in rubber particles was varied via different thermal contraction/expansion cycles in the range of −100 to 23°C. Tensile, creep, and Charpy impact tests were conducted to evaluate the effects of the degree of cavitation on the general mechanical properties. The notch‐tip damage zone and deformation micromechanisms were also investigated by a transmitted optical microscopy technique to reveal the effects of cavitation on toughness. The results of this investigation illustrate a close relationship between the degree of rubber particle cavitation and the mechanical performance of high‐impact polystyrene. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1110–1117, 2007
Synthesis and characterization of poly(allyl methacrylate) obtained by γ‐radiation
Authors: K. Vardareli Tuğba , Usanmaz Ali 
Published: January 2007

AbstractAllyl methacrylate was polymerized by γ‐radiation under vacuum in solution and atom transfer radical polymerization (ATRP) methods and also in the presence of atmospheric oxygen in bulk. The kinetic curve is S‐type with a longer induction period, because of the presence of oxygen, in bulk polymerization. The curve for the solution polymerization is almost linear with a short induction period. The rate started to decrease after about 60% conversion and reached to a limiting conversion of 100%. The polymerization by ARTP method using γ‐radiation as initiator instead of conventional heating method gave a kinetic curve of linear character up to about limiting conversion of 100%. The polymers obtained were mostly gel type with linear chain fractions at lower conversions. The polymer characterizations were carried out by FTIR, differential scanning calorimetry, NMR, TGA, and XRD methods. The polymers were shown to proceed by the opening of vinyl groups. The allyl groups caused a limiting crosslinking, but 98–99% of the allyl groups are shown by FTIR and NMR, unchanged during the polymerization. The cyclic type polymer formation was not likely taking place. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1076–1083, 2007
Formation of polymethylsiloxanes with alkyl side groups
Authors: Mukbaniani O. , Titvinidze G. , Tatrishvili Tamara , Mukbaniani Nino , Brostow Witold , Pietkiewicz Dorota 
Published: January 2007

AbstractHydrosilylation of α,ω‐bis(trimethylsiloxy)methylhydrosiloxane to alkenes in the presence of a catalyst was performed at several temperatures (30–70°C). Comb‐type methylsiloxane oligomers with various alkyl substituted groups in the side chains have been obtained. Not all active ≡SiH groups participate in the reaction. The reaction order, activation energies, and rate constants have been determined. The synthesized oligomers were characterized by 1H, 13C, 1H COSY NMR, and FTIR spectroscopy. Calculations using the quantum‐chemical semiempirical AM1 method for modeling reaction between methyldimethoxysilane [Me(MeO)2SiH] and hexene‐1 were performed to evaluate possible reaction paths. For all initial, intermediate, and final products, enthalpies of formation as a function of the distance between ≡CSi≡ bonds are calculated. The hydride addition is energetically more favorable according to the anti‐Markovnikov rule than according to the Markovnikov rule. Comb‐type oligomers were characterized by gel‐permeation chromatography, differential scanning calorimetry, thermogravimetry, and wide‐angle X‐ray diffractometry. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1176–1183, 2007
Structure–property relationships in acrylate/epoxy interpenetrating polymer networks: Effects of the reaction sequence and composition
Authors: Nowers Joseph R. , Costanzo Joseph A. , Narasimhan Balaji 
Published: January 2007

AbstractInterpenetrating polymer networks (IPNs) of poly(ethylene glycol) 200 diacrylate and diglycidyl ether of bisphenol A were formed over a range of compositions and with different reaction sequences. We controlled the reaction sequence by thermally initiating the cationic epoxy polymerization, photoinitiating the free‐radical acrylate polymerization, and changing the processing order. The reaction was monitored by attenuated total reflectance Fourier transform infrared spectroscopy, photo differential scanning calorimetry. and modulated differential scanning calorimetry (mDSC). The glass‐transition temperature was estimated from mDSC. Mechanical and rheological tests provided the strength and hardness of the materials. Morphology and phase separation were explored with optical and scanning electron microscopy. All of the physical properties were dependent on IPN composition. Some properties and the morphology were dependent on the reaction sequence. Significant differences in glass‐transition temperature were observed at the same composition but with different reaction sequences. Even with minimal structure, correlations existed between the morphology and material properties with partially phase‐separated samples exhibiting maximum damping. The rapid reaction allowed minimal phase separation, yet different reaction sequences resulted in significantly different properties. This systematic study indicated that the relationships between phase morphology, processing, and the physical properties of IPNs are complex and not predictable a priori. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 891–901, 2007
Synthesis and characterization of novel two‐component conjugated polythiophenes with 3‐octyl and 3‐isooctylthiophene side chains
Authors: Feng Weidong , Qi Zhengjian , Sun Yueming 
Published: January 2007

AbstractWith copolymerization functionalization, a novel solution‐processable polymer, poly{(3‐octylthiophene)‐co‐[3‐(2‐ethyl‐1‐hexyl)thiophene]} (P3OTIOT), combining the electrochemical properties of poly(3‐octylthiophene) (P3OT) and poly[3‐(2‐ethyl‐1‐hexyl)thiophene] (P3IOT) was synthesized by the FeCl3‐oxidative approach. The characterization of the polymers included Fourier transform infrared, 1H‐NMR, gel permeation chromatography, thermogravimetric analysis (TGA), ultraviolet–visible spectroscopy, and photoluminescence (PL). P3OTIOT had excellent solubility in common organic solvents. Investigations of the optical properties showed that the optical band‐gap energy of P3OTIOT was similar to that of P3OT (2.43 eV) at 2.45 eV and 6% lower than that of P3IOT in CHCl3 solutions. The bandwidth of the P3OTIOT absorption approached that of P3OT, ranging from 370 to 570 nm, and the emission maximum of P3OTIOT was only 50 nm blueshifted with respect to that of P3OT. However, the PL intensity of P3OTIOT was 7 times higher than that of P3OT. TGA studies showed that P3OTIOT had very good thermal stability, losing 5% of its weight on heating to 300°C. It is suggested that P3OTIOT has low band‐gap energy, a high PL quantum yield, and processability. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1169–1175, 2007
Evaluation of carbonization tar in making high performance polyacrylonitrile‐based carbon fibers
Authors: Wang Yan‐Xiang , Wang Qiang 
Published: January 2007

AbstractThe polyacrylonitrile carbonization tar is discussed in detail by using gas chromatographic‐mass spectrometer and electron paramagnetic resonance. It is a viscous liquid that constitutes complicated condensed components resulting from polymer decomposition. It was demonstrated that the predominant products were acrylonitrile dimer and trimer species with trifle cyclohexane and cyclopentane. Moreover, the fragmentation course occurred in temperature range of 400–600°C and decomposed in 525°C most drastically. The formation of the tar could be regarded as random fragmentation of linear chain segments among ladder structures accompanying with secondary decomposition. After adjusting the middle temperature carbonization technology, depending on the components and formation of tar, the high performance carbon fibers were obtained that had tensile strength of 4.2–4.5 Gpa, elongation at break 1.7%–1.8%, modulus 235–240 Gpa. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1255–1259, 2007
Reducing volume shrinkage by low‐temperature photopolymerization
Authors: Lu Bo , Xiao Pu , Sun Mengzhou , Nie Jun 
Published: January 2007

AbstractLow‐volume‐shrinkage poly(triethylene glycol dimethacrylate) was made by photopolymerization at a low temperature. The final double‐bond conversion and dynamic mechanical analysis indicated the optimal cure temperature to be −40°C, at which a cured sample had less volume shrinkage than samples cured at room temperature but similar mechanical properties. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1126–1130, 2007
Effect of an organoclay on the reaction‐induced phase‐separation kinetics and morphology of a poly(ether imide)/epoxy mixture
Authors: Peng Mao , Li Dasong , Chen Ying , Zheng Qiang 
Published: January 2007

AbstractOrganically modified layered silicates with a hydroxyl‐substituted quaternary ammonium surfactant as the modifier were incorporated into a mixture of poly (ether imide) and epoxy with 4,4′‐diaminodiphenyl sulfone as the hardener. The influence of the organically modified layered silicates on the reaction‐induced phase‐separation kinetics and morphology of the poly(ether imide)/epoxy mixture was investigated with time‐resolved small‐angle light scattering, phase‐contrast microscopy, and scanning electron microscopy. The phase‐separation kinetics were analyzed by means of the temporal evolution of scattering vector qm and scattering intensity Im at the scattering peak. The organically modified layered silicates obviously facilitated an earlier onset of phase separation but reduce the phase‐separation rate and greatly retarded the domain‐coarsening process in the late stage of spinodal decomposition. The temporal evolution of both qm and Im followed the power law qm ∼ (t − tos)−α and Im ∼(t − tos)−β, where t is the reaction time, tos is the onset time of phase separation, and α and β are growth exponents. For the samples filled with organically modified layered silicates, α crossed over from 0 to about 1/3, following Binder–Stauffer cluster dynamics, and an interconnected phase structure was observed for cure temperatures ranging from 120 to 230°C. For the unfilled samples, the interconnected phase structure was observed only at cure temperatures below 140°C. At temperatures above 150°C, α crossed over from 0 to 1/3 < α ≤ 1 under the interfacial tension effect, following Siggia's theory, and the domain‐coarsening rate was very fast; this resulted in macroscopic epoxy‐rich domains. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1205–1214, 2007
Crosslinking of poly(silyl ester)s containing fumaryloxyl units in the main chain and characteristics of the crosslinked products
Authors: Han Nianfeng , Liu Zonglin , Zhou Dejie , Jin Liqiang , Shi Congwen 
Published: January 2007

AbstractTwo unsaturated poly(silyl ester)s that contained innoxious fumaryloxyl units in the main chain were prepared by the polycondensation reaction of 1,5‐dichloro‐1,1,5,5‐tetramethyl‐3,3‐diphenyltrisiloxane or 1,3‐dichlorotetramethyldisiloxane with di‐tert‐butyl fumarate under nitrogen at 100°C for 1–3 days. To investigate the crosslinking reaction of the unsaturated poly(silyl ester)s, the two unsaturated poly(silyl ester)s were crosslinked in the presence of 2,2′‐azobisisobutyronitrile as a radical initiator. After the crosslinking, the unsaturated poly(silyl ester)s, which were viscous liquids, turned into solid products. The characterization of the two poly(silyl ester)s and the crosslinked products included infrared spectroscopy, 1H‐NMR spectroscopy, differential scanning calorimetry, and thermogravimetric analysis. Comparisons were made between the linear poly(silyl ester)s and the crosslinked poly(silyl ester)s. After the crosslinking, the important resonance signal for ethenylene (CC) disappeared, and this showed that the crosslinking reaction was carried out progressively. The glass‐transition temperatures of the crosslinked poly(silyl ester)s were higher than those of the uncross‐ linked poly(silyl ester)s, and the thermal stability of the crosslinked poly(silyl ester)s was better than that of uncrosslinked poly(silyl ester)s. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1221–1225, 2007
Synthesis and characterization of polyimide–silica nanocomposites using novel fluorine‐modified silica nanoparticles
Authors: Mo Te‐Cheng , Wang Hong‐Wen , Chen San‐Yan , Dong Rui‐Xuan , Kuo Chien‐Hung , Yeh Yun‐Chieh 
Published: January 2007

AbstractPolyimide–silica nanocomposites were synthesized with 4,4′‐oxydianiline, 4,4′‐(4,4′‐isopropylidenediphenoxy)bis(phthalic anhydride), and fluorine‐modified silica nanoparticles. Fluorinated precursors such as 4″,4‴‐(hexafluoroisopropylidene)bis(4‐phenoxyaniline) (6FBPA) and 4,4′‐(hexafluoroisopropylindene)diphenol (BISAF) were employed to modify the surface of the silica nanoparticles. The microstructures and thermal, mechanical, and dielectric properties of the polyimide–silica nanocomposites were investigated. An improvement in the thermal stability and storage modulus of the polyimide nanocomposites due to the addition of the modified silica nanoparticles was observed. The microstructures of the polyimide–silica nanocomposites containing 6FBPA‐modified silica exhibited more uniformity than those of the nanocomposites containing BISAF‐modified silica. The dielectric constants of the polyimide were considerably reduced by the incorporation of pristine silica or 6FBPA‐modified silica but not BISAF‐modified silica. The addition of a modifier with higher fluorine contents did not ensure a lower dielectric constant. The uniformity of the silica distribution, manipulated by the reactivity of the modifier, played an important role in the reduction of the dielectric constant. Using 6FBPA‐modified silica nanoparticles demonstrated an effective way of synthesizing low‐dielectric‐constant polyimide–silica nanocomposites. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 882–890, 2007
Entropy–enthalpy compensation in solution properties of solutes at infinite dilution in nonpolar polymers
Authors: Huang Jan‐Chan 
Published: January 2007

AbstractThe knowledge of the Flory–Huggins interaction parameter, χ, between organic liquids and polymers is very important in the study of their miscibility. From the temperature dependency of χ the enthalpy and residual entropy of solution can be determined. In this study literature data of thirty‐two solutes, ranging from alkanes to alcohols, at infinite dilution in isotatic polypropylene, poly(ethyl ethylene), and poly(dimethylsiloxane), were tested and linear entropy–enthalpy compensation was observed. The plot of residual free energy versus enthalpy of solution was also linear, with a lower correlation coefficient than the entropy–enthalpy plot. The range of enthalpy of solution was wider than those of the size corrected free energy of solution. In nonpolar solvents the enthalpy of solution reflected largely the interaction within the solute liquid state, and showed a linear trend with respect to solute cohesive energy density for n‐alcohols. The wide range of enthalpy of solution suggests the use of a two‐dimensional solubility parameter model to correlate the enthalpy of solution. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1241–1247, 2007
Formation of poly(vinyl alcohol)‐titanium lactate hybrid nanofibers and properties of TiO2 nanofibers obtained by calcination of the hybrids
Authors: Nakane Koji , Yasuda Kaori , Ogihara Takashi , Ogata Nobuo , Yamaguchi Shinji 
Published: January 2007

AbstractNew organic‐inorganic hybrid nanofibers, poly(vinyl alcohol) (PVA)‐titanium lactate (TL) hybrid nanofibers, were formed by electrospinning employing water as a solvent. Anatase‐type TiO2 nanofibers were obtained by calcination of the hybrid nanofibers in air. The fiber diameters of the PVA‐TL hybrid nanofibers was 200–350 nm, and the fiber diameter of the TiO2 nanofibers was 70–80% of that of the PVA‐TL hybrid nanofibers. The specific surface area and average pore diameter of the TiO2 nanofiber calcined at 500°C for 5 h were 21.0 m2/g and 7.4 nm, respectively. The photocatalytic decomposition of methylene blue using the TiO2 nanofibers was also investigated. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1232–1235, 2007
Temperature and pH sensitive star‐shaped material for the controlled release of coenzyme A
Authors: Guo Bao‐Lin , Yuan Jin‐Fang , Gao Qing‐Yu 
Published: January 2007

AbstractA novel star‐shaped copolymer was prepared by tolulene diisocyanate (TDI) trimer, poly(ethylene oxide) (PEO), P(2‐(dimethylamino)ethyl methacrylate) (PDMAEMA), and 2‐hydroxyethylacrylate (HEA) with TDI trimer as core and PEO, PDMAEMA as arm chains by addition of functional groups and copolymerization. The structure of the star‐shaped copolymer was characterized by FTIR, 1H NMR, and UV, and the molecular weight and polydispersity were determined by gel permeation chromatography (GPC). Their aqueous solution properties and controlled coenzyme A (Co A) delivery were also studied. The results showed that the copolymer had better temperature sensitivity and pH sensitivity. The release of Co A from the copolymer was dependent on the release medium such as concentration of the polymer, pH, and temperature in the aqueous solution. The higher concentration of the copolymer absorbed more Co A than the lower one. The increasing temperature accelerated Co A release from the copolymer. The pH of the solution had significant impact on the release of Co A from the copolymer. The results suggested that the novel copolymer could be used as a drug delivery carrier. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1279–1284, 2007