bluuebunny/crossref_metadata_2025_split huggingface dataset:
Exploitation of introducing of catalytic centers into layer galleries of layered silicates and related epoxy nanocomposites. I. Epoxy nanocomposites derived from montmorillonite modified with catalytic surfactant‐bearing carboxyl groups
Authors: Guo Baochun , Ouyang Xing , Cai Changgeng , Jia Demin 
Published: February 2004

AbstractMontmorillonite (MMT) was modified with the acidified cocamidopropyl betaine (CAB) and the resulting organo‐montmorillonite (O‐MMT) was dispersed in an epoxy/methyl tetrahydrophthalic anhydride system to form epoxy nanocomposites. The intercalation and exfoliation behavior of the epoxy nanocomposites were examined by X‐ray diffraction and transmission electron microscopy. The curing behavior and thermal property were investigated by in situ Fourier transform infrared spectroscopy and DSC, respectively. The results showed that MMT could be highly intercalated by acidified CAB, and O‐MMT could be easily dispersed in epoxy resin to form intercalated/exfoliated epoxy nanocomposites. When the O‐MMT loading was lower than 8 phr (relative to 100 phr resin), exfoliated nanocomposites were achieved. The glass‐transition temperatures (Tg's) of the exfoliated nanocomposite were 20 °C higher than that of the neat resin. At higher O‐MMT loading, partial exfoliation was achieved, and those samples possessed moderately higher Tg's as compared with the neat resin. O‐MMT showed an obviously catalytic nature toward the curing of epoxy resin. The curing rate of the epoxy compound increased with O‐MMT loading. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1192–1198, 2004
Reversible nonlinear conduction in high‐density polyethylene/acetylene carbon black composites at various ambient temperatures
Authors: Song Yihu , Zheng Qiang , Yi Xiao‐Su 
Published: February 2004

AbstractThe reversible nonlinear conduction (RNC) in of high‐density polyethylene/acetylene carbon black composites with different degrees of crosslinking was studied above room temperature and below the melting point of high‐density polyethylene (HDPE). The experimental current density‐electric field strength curves can be overlapped onto a master curve, suggesting that the microscopic mechanisms for the appearance of RNC exist regardless of the ambient temperature and the crosslinking degree of the HDPE matrix. The relationship between the crossover current density and the linear conductivity can be explained in the framework of the dynamic random‐resistor‐network model. According to these results, two electron‐tunneling models are suggested to interpret the microscopic conduction behavior. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1212–1217, 2004
Poisson's ratio of cellulose Iβ and cellulose II
Authors: Nakamura Ken'Ichi , Wada Masahisa , Kuga Shigenori , Okano Takeshi 
Published: February 2004

AbstractPoisson's ratios of cellulose Iβ and cellulose II were determined for purified ramie and mercerized samples by X‐ray diffractometry. Poisson's ratio was 0.38 for [200]/[004] of cellulose Iβ and 0.30 for [200]/[004] and 0.46 for [110]/[004] of cellulose II. The smaller [200]/[004] Poisson's ratio for cellulose II could be ascribed to closer intermolecular association through hydrogen bonding and van der Waals forces. Poisson's ratio for [11¯0]/[004] of cellulose II was estimated to be negative. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1206–1211, 2004
Estimation of the agglomeration structure for conductive particles and fiber‐filled high‐density polyethylene through dynamic rheological measurements
Authors: Wu Gang , Zheng Qiang 
Published: February 2004

AbstractA study on the correlation between electrical percolation and viscoelastic percolation for carbon black (CB) and carbon fiber (CF) filled high‐density polyethylene (HDPE) conductive composites was carried out through an examination of the filler concentration (ϕ) dependence of the volume resistivity (ρ) and dynamic viscoelastic functions. For CB/HDPE composites, when ϕ was higher than the modulus percolation threshold (ϕG ∼ 15 vol %), the dynamic storage modulus (G′) reached a plateau at low frequencies. The relationship between ρ and the normalized dynamic storage modulus (Gc′/Gp′, where Gc′ and Gp′ are the dynamic storage moduli of the composites and the polymer matrix, respectively) was studied. When ϕ approached a critical value (ϕr), a characteristic change in Gc′/Gp′ appeared. The critical value (Gc′/G′p)c was 9.80, and the corresponding ϕr value was 10 vol %. There also existed a ϕ dependence of the dynamic loss tangent (tan δ) and a peak in a plot of tan δ versus the frequency when ϕ approached a loss‐angle percolation (ϕδ = 9 vol %). With parameter K substituted for A, a modified Kerner–Nielson equation was obtained and used to analyze the formation of the network structure. The viscoelastic percolation for CB/HDPE composites could be verified on the basis of the modified equation, whereas no similar percolation was found for CF/HDPE composites. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1199–1205, 2004
Effect of composition on the width of the calorimetric glass transition in polymer–solvent and solvent–solvent mixtures
Authors: Savin Daniel A. , Larson Anne M. , Lodge Timothy P. 
Published: February 2004

AbstractThe calorimetric glass‐transition temperature (Tg) and transition width were measured over the full composition range for solvent–solvent mixtures of o‐terphenyl with tricresyl phosphate and with dibutyl phthalate and for polymer–solvent mixtures of polystyrene with three dialkyl phthalates. Tg shifted smoothly to higher temperatures with the addition of the component with the higher Tg for both sets of solvent–solvent mixtures. The superposition of the differential scanning calorimetry traces showed almost no composition dependence for the width of the transition region. In contrast, the composition dependence of Tg in polymer–solvent mixtures was different at high and low polymer concentrations, and two distinct Tg's were observed at intermediate compositions. These results were interpreted in terms of the local length scale and associated local composition variations affecting Tg. The possible implications of these results for the dynamics of miscible polymer blends were examined. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1155–1163, 2004
Crystallization regime behavior of poly(pentamethylene terephthalate)
Authors: Wu Pi‐Ling , Woo E. M. 
Published: February 2004

AbstractPoly(pentamethylene terephthalate) (PPT), a less studied aryl polyester, was synthesized by polycondensation and characterized by 1H NMR and gel permeation chromatography. The crystallization kinetics were investigated by means of differential scanning calorimetry and polarized light microscopy. The average value of the Avrami exponent was calculated to be 2.9, which indicated an athermal nucleation process followed by three‐dimensional crystal growth. The kinetics of spherulitic growth of PPT were analyzed with the Lauritzen–Hoffman (L–H) secondary nucleation theory, and the nucleation constants (Kg) for regimes II and III were thus determined from the slope of the L–H plot with an activation energy (U*) of 3500 cal/mol. The validity of the U* value was examined. Meanwhile, the existence of a transition from regime II to regime III at 95 °C was determined, and the value of Kg(III)/Kg(II) was 2.04. The equilibrium melting temperature of PPT was estimated to be 149.4 °C with the linear Hoffman–Weeks extrapolation method. The lateral surface free energy, fold surface free energy, and work of chain folding were estimated. These thermodynamic properties of PPT were then compared to those of other terephthalic polyesters. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1265–1274, 2004
Evidence for coupling and decoupling of parts of macromolecules by temperature‐modulated calorimetry
Authors: Wunderlich Bernhard 
Published: February 2004

AbstractEquilibrium crystals of linear macromolecules have an extended‐chain macroconformation. They can melt at the equilibrium melting temperature, whereas crystallization needs considerable supercooling, even in the presence of crystal nuclei, making the overall phase transition irreversible. The same molecules with a metastable, chain‐folded macroconformation may have a large amount of specific reversibility, that is, a fraction of the same polymer molecule that melts irreversibly may also show decoupled, reversible melting. The overall metastable, nanophase structure of such semicrystalline polymers may thus support local equilibria. The tool for the quantitative analysis is quasi‐isothermal temperature‐modulated calorimetry that can separate reversible from irreversible processes. A major review of the study of crystals of more than 20 polymers has been published. On the basis of this extensive body of information, a first discussion of decoupling of parts of macromolecules is attempted and linked to previous studies of phase equilibria. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1275–1288, 2004
Inclusion complex formation between α,γ‐cyclodextrins and organic–inorganic star‐shaped poly(ethylene glycol) from an octafunctional silsesquioxane core
Authors: Huang Junchao , Li Xu , Lin Tintin , He Chaobin , Yi Mya Khine , Xiao Yang , Li Jun 
Published: February 2004

AbstractA series of organic–inorganic star‐shaped poly(ethylene glycol)s from octafunctional silsesquioxane (POSS) cores were synthesized by allylation and hydrosilylation, and they were found to form crystalline inclusion complexes with α,γ‐cyclodextrins. The results from X‐ray diffraction, cross‐polarity/magic‐angle‐spinning 13C NMR, differential scanning calorimetry, and Fourier transform infrared suggested that a channel‐type structure was established in the inclusion complexes. The characterization results also revealed that the segments of poly(ethylene glycol) arms near the POSS cores were uncovered by the cyclodextrins, whereas the cyclodextrins were closely packed along the remaining portion of the poly(ethylene glycol) arms. Molecular dynamic simulation in a Dreiding force field with Cerius2 software gave comparable results. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1173–1180, 2004
Novel urethane/epoxy resin hybrid materials using a moisture‐curing system
Authors: Okuhira Hiroyuki , Iwamoto Nobuaki , Ochi Mitsukazu , Takeyama Hidekazu 
Published: February 2004

AbstractNovel curing systems of a urethane/epoxy resin [diglycidyl ether of bisphenol A (DGEBA)] alloy using the moisture‐latent hardener ketimine (K‐systems) were investigated on the DGEBA‐rich side and were compared with aromatic diamine curing systems (A‐systems). Almost all the added DGEBA was separated from the polyurethane matrix and dispersed as 2–10‐μm‐diameter particles after curing in the A‐systems. Therefore, DGEBA did not act as a reinforcing agent for the polyurethane matrix. However, 50% of the added DGEBA was dispersed as particles with a diameter of 1–4 μm, and the other 50% was incorporated into the polyurethane matrix in the novel K‐systems. Therefore, the polyurethane matrix in the K‐systems should be reinforced effectively by both incorporated and finely dispersed DGEBA and should result in significant improvements in the stress–strain properties. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1137–1144, 2004
Controlled melting of individual, nano‐meter‐sized, polymer crystals confined in a block copolymer mesostructure
Authors: Vasilev Cvetelin , Heinzelmann Harry , Reiter Günter 
Published: February 2004

AbstractWe demonstrate a possibility to create custom‐made surface patterns on multiple length scales by melting selected nano‐meter‐sized polymer crystals confined in a highly ordered, spherical mesostructure of a hydrogenated poly(butadiene‐block‐ethylene oxide) (PBh‐b‐PEO) block copolymer. With heatable probes of an atomic force microscope as a heat source, we succeeded to provide highly locally the thermal energy necessary to individually melt such crystals. Besides this possibility for modification of surface properties, we performed detailedin situstudies of thermally induced reorganization processes and subsequent melting of polymer crystals in confined volumes of a block copolymer mesostructure. Close to the melting point, the stability of the confined crystals could be improved by annealing. In addition, the crystal size increased at the expense of already‐molten crystals, indicating diffusion of PEO blocks across the highly incompatible PBhmatrix. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1312–1320, 2004
Applicability of the transient plane source method to measure the thermal conductivity of low‐density polyethylene foams
Authors: Almanza O. , Rodríguez‐Pérez M. A. , De Saja J. A. 
Published: February 2004

AbstractThe thermal conductivity at constant pressure of a collection of crosslinked, closed‐cell polyethylene foams were measured at room temperature with the transient plane source (TPS) method. The experimental results were compared with those determined by a standard steady‐state technique. The results showed that the values measured by the TPS method follow the same trends as those measured by a heat‐flow meter. Therefore, with the TPS technique it is possible to observe the influence of structural characteristics such as cell size, black carbon content in foams, density, and so forth on thermal conductivity. However, the values obtained by the transient method were approximately 20% higher than those given by the standard method. Possible reasons for these variations are discussed. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1226–1234, 2004
Large enhancement of the ionic conductivity in an electron‐beam‐irradiated [poly(ethylene glycol)]xLiClO4 solid polymer electrolyte
Authors: Singh Th. Joykumar , Ganeshsanjeev  , Siddappa K. , Bhat S. V. 
Published: February 2004

AbstractThe effect of electron‐beam (4–8 MeV) irradiation on the ionic conductivity of a solid polymer electrolyte, poly(ethylene glycol) complexed with LiClO4, was studied. A large enhancement of the conductivity of nearly two orders of magnitude was observed for the highest dose of irradiation (15 kGy) used. The samples were characterized with differential scanning calorimetry, matrix‐assisted laser desorption/ionization, and electron spin resonance spectroscopy. Although no free radicals were present in the irradiated samples, a decrease in the glass‐transition temperature and an increase in the amorphous fraction were observed. Even though pure poly(ethylene glycol) underwent considerable fragmentation, unexpectedly, no significant fragmentation was observed in the polymer–salt complexes. The enhancement of the conductivity was attributed to an increase in the amorphous fraction of the systems and also to an increase in the flexibility of the polymer chains due to the irradiation. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1299–1311, 2004
Miscibility and surface properties of fluorinated copolymer blends involving hydrogen‐bonding interactions
Authors: Huang H. L. , Goh S. H. , Lai Doreen M. Y. , Wee A. T. S. , Huan C. H. A. 
Published: February 2004

AbstractThe miscibility and underlying hydrogen‐bonding interactions of blends of a fluorinated copolymer containing pyridine and a nonfluorinated copolymer containing methacrylic acid were studied with differential scanning calorimetry (DSC), transmission Fourier transform infrared (TX‐FTIR) spectroscopy, and X‐ray photoelectron spectroscopy (XPS), whereas the surface properties of the blends were investigated with contact‐angle measurements, time‐of‐flight secondary‐ion mass spectroscopy, XPS, and attenuated total reflectance Fourier transform infrared spectroscopy. DSC studies showed that the presence of a sufficient amount of 4‐vinylpyridine units in the fluorinated copolymer produced miscible blends with the nonfluorinated copolymer containing methacrylic acid. TX‐FTIR and XPS showed the existence of pyridine–acid interpolymer hydrogen‐bonding interactions. Even though the anchoring effect of hydrogen bonding hindered the migration of the fluorinated component to the blend surface, it could not completely eliminate the surface enrichment of the fluorinated component and the surface rearrangement of the fluorinated pendant chain. The air–blend interface was mainly occupied by the fluorinated pendant chain, and the surface energies of the blends were extremely low, even with only 1.5 wt % of the fluorinated component in the blends. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1145–1154, 2004
Structure and mechanical properties of talc‐filled blends of polypropylene and styrenic block copolymers
Authors: Denac Matjaž , Musil Vojko , Šmit Ivan 
Published: February 2004

AbstractThe structure–property relationships of isotactic polypropylene (iPP)/styrenic block copolymer blends filled with talc were examined by optical and scanning electron microscopy, wide‐angle X‐ray diffraction, and tensile‐ and impact strength measurements. The composites were analyzed as a function of the poly(styrene‐b‐ethylene‐co‐propylene) diblock copolymer (SEP) and the poly(styrene‐b‐butadiene‐b‐styrene) triblock copolymer (SBS) content in the range from 0 to 20 vol % as elastomeric components and with 12 vol % of aminosilane surface‐treated talc as a filler. Talc crystals incorporated in the iPP matrix accommodated mostly plane‐parallel to the surface of the samples and strongly affected the crystallization process of the iPP matrix. The SBS block copolymer disoriented plane‐parallel talc crystals more significantly than the SEP block copolymer. The mechanical properties depended on the final phase morphology of the investigated iPP blends and composites and supermolecular structure of the iPP matrix because of the interactivity between their components. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1255–1264, 2004
Modeling the polymerization behavior of vegetable‐oil‐derived macromonomers in solution by computer simulation
Authors: Diamond Keri L. , Pandey Ras B. , Thames Shelby F. 
Published: February 2004

AbstractA computer simulation model was used to study the polymerization behavior of multifunctional, vegetable‐oil‐derived macromonomers. Mixtures of olefins (A) and acrylates (B) were initially randomly dispersed on a cubic lattice of size L3. Interactions between A, B, and the solvent sites were considered with respect to their relative proximity, mobility and some kinetics. The Metropolis algorithm was used to move each functional group (A and B). Stirred and equilibrated samples were prepared before reaction initiation. Reactions between the functional groups were implemented with a bonding probability kαβ, which was subject to the availability of unsaturated bonds. The conversion factor, that is, the growth of A–B bonds, was analyzed for a range of polymer concentrations (p = 0.2–0.8) with different reaction probabilities (i.e., kαβ). A stirred (nonequilibrium) sample did not allow sufficient time for the functional groups to arrange according to the interaction parameters. Therefore, the simulations were rerun with equilibrated samples and were found to be consistent with experimental observations. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1164–1172, 2004
Electric‐field‐induced molecular alignment of side‐chain liquid‐crystalline polyacetylenes containing biphenyl mesogens
Authors: Geng Jianxin , Zhou Enle , Li Gao , Lam Jacky Wing Yip , Tang Ben Zhong 
Published: February 2004

AbstractElectric‐field‐induced molecular alignments of side‐chain liquid‐crystalline polyacetylenes [{HCC[(CH2)mOCO‐biph‐OC7H15]}, where biph is 4,4′‐biphenylyl and m is 3 (PA3EO7) or 9 (PA9EO7)] were studied with X‐ray diffraction and polarized optical microscopy. An orientation as high as 0.84 was obtained for PA9EO7. Furthermore, the molecular orientation of PA9EO7 was achieved within a temperature range between the isotropic‐to‐smectic A transition temperature and 115 °C, and this suggested that the orientational packing was affected by the thermal fluctuation of the isotropic liquid and the mobility of the mesogenic moieties. The maximum achievable orientation for PA9EO7 was much greater than that for PA3EO7. This was the first time that the electric‐field‐induced molecular orientation of a side‐chain liquid‐crystalline polymer with a stiff backbone was studied. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1333–1341, 2004
Phase behavior of modified montmorillonite– poly(ϵ‐caprolactone) nanocomposites
Authors: Pucciariello Rachele , Villani Vincenzo , Belviso Sandra , Gorrasi Giuliana , Tortora Mariarosaria , Vittoria Vittoria 
Published: February 2004

AbstractThe thermal behavior and overall isothermal crystallization kinetics of a series of organophilic modified montmorillonite–poly(ϵ‐caprolactone) nanocomposites were investigated. In general, the thermal behavior was influenced more by the type of dispersion than by the clay content. For nanocomposites in which silicate platelets were predominantly dispersed in the polymer matrix to give exfoliated structures, the thermal properties were improved with respect to those of neat poly(ϵ‐caprolactone), whereas in those cases in which simply intercalated structures were attained, the thermal properties regularly decayed as the clay content increased. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1321–1332, 2004
Technology‐Driven Alternatives for Smart Sensor Interfaces
Authors: Baschirotto A. , Malcovati P. 
Published: February 2004

AbstractThe importance of integrated microsystems is continuously growing because of the combination of two trends: the progress of silicon sensor technology and the introduction of new techniques for interface circuits. In this chapter we show how different approaches to the implementation of smart sensor systems, basically driven by the available fabrication technologies, can lead to successful designs. Three examples are presented: a fully integrated current monitor, a biaxial accelerometer, and a rotational accelerometer. The current monitor is an example of single chip implementation. It supports two different operating ranges (20 A and 200 A full scale), provides digitally programmable gain and offset with an on‐chip PROM, and achieves 9 bits of resolution and ± 0.6 LSB of linearity. The biaxial accelerometer and the rotational accelerometer are examples of implementations based on two chips in the same package. They achieve 80 dB of dynamic range with ± 1 g full‐scale signal over a 30 Hz bandwidth and 38 dB of dynamic range with 200 rad/s2full‐scale signal over an 800 Hz bandwidth.
Microelectronic Chips for Molecular and Cell Biology
Authors: Tartagni Marco , Altomare Luigi , Guerrieri Roberto , Fuchs Alexandra , Manaresi Nicolò , Medoro Gianni , Thewes Roland 
Published: February 2004

AbstractThe development of microfabricated devices manufactured in silicon, glass, or plastic materials is a well‐known trend in the research of novel biological techniques and tools over the last two decades, resulting in a multitude of start‐up companies serving the pharmaceutical, biotechnology, and diagnostics markets. However, the idea of implementing such devices on microelectronic substrates has been introduced only recently. This chapter aims to describe the state‐of‐the‐art of microsystems for molecular and cell biology produced in general purpose CMOS (complementary metal oxide semiconductor) technology, emphasizing the advantages of this approach along with their challenges and limitations. This chapter discusses significant examples of fully tested devices in comparison with existing state‐of‐the‐art techniques.