bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polymerization of 1,3‐butadiene with the catalyst system composed of a cobalt compound and methylaluminoxane
Authors: Takeuchi Masaki , Shiono Takeshi , Soga Kazuo 
Published: April 2007

AbstractPolymerization of 1,3‐butadiene was conducted with a CoBr2(PPh3)2 and methylaluminoxane catalyst. From the spectroscopic analysis of both crude and hydrogenated polymers, it was found that the polymer produced with the catalyst was composed of approximately 35% cis‐1,4‐ and 65% 1,2‐units without stereoregularity. Effects of temperature, Al/Co ratio and addition of some Lewis bases on the polymerization were also examined in some detail.
Dielectric behaviour of iron‐doped cellulose acetate films
Authors: Sharma A. K. , Ramu Ch. 
Published: April 2007

AbstractThe effect of iron doping and its concentration on the dielectric properties of cellulose acetate films was studied as a function of temperature (range 300–440 K) and frequency (range 10 kHz‐10 MHz). Undoped films exhibited a peak near 350 K in the capacitance versus temperature plots, while the dielectric loss exhibited two peaks. The dielectric capacitance decreased with increased dopant concentrations while the dielectric loss showed an increase. The peak positions, however, shifted towards higher temperatures in both cases. Presence of dopant ions and formation of charge transfer complexes/molecular aggregates are suggested as the possible reasons for this behaviour.
Phase equilibria of quasi‐binary systems consisting of multicomponent polymers 1 and 2. III—Coexistence curve
Authors: Shirataki Hironobu , Matsuda Shigenobu , Kamide Kenji 
Published: April 2007

AbstractAs an extension of the theory established previously (Brit. Polym. J., 23 (1990) 285 and 299), a method for calculating the coexistence curve (CC) was proposed for multicomponent polymer 1/multicomponent polymer 2 system. The polymer composition, molecular weight distribution existing in two liquid phases and their phase volume ratio (R) can be calculated for the systems of polymer whose molecular weight characteristics and the initial composition are known in advance. Systematic computer experiments were carried out to disclose the effect of the average degree of polymerization (DP), the DP distribution of two polymers and the initial concentration on phase diagram including CC. The polydispersity of the polymers can not be ignored in CC as in the case of the cloud point curve (CPC) and the critical solution point (CSP). In the vicinity of CPC, the two‐phase volume ratio changes dramatically corresponding to a slight change in the thermodynamical interaction parameter X12 between polymers 1 and 2. As the initial polymer concentration approaches CSP, R approaches unity and DP distributions of polymers partitioned in two phases reduce to that of the original polymers.
Aromatic polyesters (polyarylates) containing arylene sulfone ether linkages
Authors: Idage Bhaskar B. , Idage Susheela B. , Vernekar Subhash P. 
Published: April 2007

AbstractA series of soluble aromatic polyesters (polyarylates) containing arylene sulfone ether linkages and having inherent viscosities of 0.36–1.10 dl/g were prepared by the two‐phase low temperature polycondensation of 4,4′‐[sulfonyl‐bis(p‐phenyleneoxy)]dibenzoyl chloride and 3,3′‐[sulfonylbis(p‐phenyleneoxy)]‐dibenzoyl chloride with various bisphenols in an organic solvent‐aqueous alkaline solution system in the presence of a phase transfer catalyst. Bisphenols 4,4′‐[sulfonylbis(p‐phenyleneoxy)]diphenol and 3,3′‐[sulfonylbis(p‐phenyleneoxy)]‐diphenol were synthesized in quantitative yields by an improved procedure. The aromatic polyesters prepared were characterized by infrared spectroscopy, elemental analysis, solution viscosity, thermogravimetric analysis, differential scanning calorimetry and X‐ray diffraction. The polyesters prepared had glass transition temperatures in the range 150–230°C and initial decomposition temperatures of 397–491°C. They gave transparent, tough and flexible films by the solution casting technique.
Synthesis and characterization of HDPE‐g‐butyl acrylate
Authors: Raval Heta , Singh Y. P. , Mehta M. H. , Devi Surekha 
Published: April 2007

AbstractHigh density poly(ethylene) was grafted with butyl acrylate using benzoyl peroxide as free radical initiator in an inert atmosphere and toluene as solvent. Reaction time, temperature, initiator concentration and ratio of monomer to polymer were varied to study their effects on percentage grafting and grafting efficiency of butyl acrylate on to HDPE. The graft copolymers were characterized by IR spectroscopy and thermal analysis.
Synthesis and characterisation of polyamideimides from bis(4‐trimellitimidophenyl)sulfone
Authors: Venkatesan D. , Srinivasan M. 
Published: April 2007

AbstractSeveral polyamideimides have been synthesised by the interaction of a number of aromatic diamines with an imidedicarboxylic acid. Since these polymers incorporated a preformed imide group, they did not pose the common problems encountered in imidisation of polyamic acids. They were synthesised by low temperature (<5°C) polycondensation, in 75–92% yields and had viscosities in the range 0.18–0.39 dl/g. They were characterised by IR spectra, elemental analysis, X‐ray and thermal methods, and possessed very high solubility in polar aprotic solvents.
Structure and solution properties of prepared randomly branched polystyrene as compared to linear polystyrene standards
Authors: Oun Ahmed Mohammed 
Published: April 2007

AbstractSamples of divinylbenzene (DVB)‐styrene copolymer were prepared by free radical polymerization using benzoyl peroxide as initiator. The samples were fractionated and characterized using a light‐scattering technique. The expansion and branching factors were calculated from the light‐scattering data for the branched copolymer and standard linear samples of the same total molecular weight and were found to be comparable with literature data.
Thermal transitions, microstructure and miscibility in ternary polyblends based on poly(vinylidene fluoride)
Authors: Del Río Carmen , Acosta Jose Luis 
Published: April 2007

AbstractThe morphology, microstructure and compatibility of binary and ternary polyblends based on poly(vinylidene fluoride) have been studied by means of glass transition temperature, isothermal crystallization kinetics analysis and scanning electron microscopy in order to determine the possibilities offered by poly(vinyl acetate) for compatibilizing poly(vinylidene fluoride) and polystyrene. Calorimetric and dynamic mechanical analyses demonstrate that poly(vinyl acetate) tends to ‘compatibilize’ blends of PVF2/PS, although the results of the two analyses do not agree with each other; we presume that this is due to differences in the techniques employed.
Isomerization of silyl ketene acetals: Models for the propagating chain end in group transfer polymerization
Authors: Brittain William J. , Dicker Ira B. 
Published: April 2007

AbstractThe rate of E/Z isomerization for the propagating end in group transfer polymerization (GTP) of methyl methacrylate (MMA) is comparable to the rate of propagation for bifluoride catalysis, in contrast to bibenzoate catalysis where propagation is faster. Methyl 2,2,4‐trimethyl‐5‐methoxy‐5‐(trimethylsiloxy)pent‐4‐enoate, 4 (the product of the initiation step in the GTP of MMA), was used as the model of the GTP living end. The rate of monomer addition to 4 was independent of the starting E/Z isomer ratio. The observation of random tacticity in the polymers prepared via anionically catalyzed GTP can be adequately explained by comparable rates of E/Z isomerization and propagation or in the case of bibenzoate catalysis, by the assumption that E and Z propagating ends react with similar stereochemistry. Silyl ketene acetal 2 (a model of the polyacrylate propagating end) underwent HgI2 catalyzed E/Z isomerization at a rate comparable to the polymerization of ethyl acrylate.
Molecular weight and concentration effects on gel/sol transitions in a segmented rigid‐rod polyimide solution
Authors: Lee Sung Koo , Cheng Stephen Z. D. , Wu Zongquan , Lee Chul Joo , Harris Frank W. , Kyu Thein , Yang Jen‐Chang 
Published: April 2007

AbstractGel/sol and order/disorder transitions can be observed in a segmented rigid‐rod polyimide solution at different concentrations and molecular weights. This polyimide was synthesized from 3,3′,4,4′‐biphenyltetracarboxylic dianhydride and 2,2′‐bis(trifluoromethyl)‐4,4′‐diaminobiphenyl in refluxing 3‐cresol in a one‐step process. Above about 140°C, the polymers are completely soluble in 3‐cresol in a concentration range up to 12(w/w)%. During cooling, the hot solutions undergo a mechanical sol/gel transition to form thermally reversible gels. In the gel state, an ordered structure develops. Both the gel/sol and order/disorder transitions are dependent upon concentration, temperature, and molecular weight, but the two transitions exhibit different kinetics. Possible mechanisms of these transitions are discussed.
Peer‐ and self‐rated correlates of a teacher‐rated typology of child adjustment
Authors: Lindstrom, Jr. William A. , Lease A. Michele , Kamphaus Randy W. 
Published: April 2007

AbstractExternal correlates of a teacher‐rated typology of child adjustment developed using the Behavior Assessment System for Children were examined. Participants included 377 elementary school children recruited from 26 classrooms in the southeastern United States. Multivariate analyses of variance and planned comparisons were used to determine whether the teacher‐rated behavior subtypes could be differentiated and, if so, to create more complete descriptions of each cluster. Self‐perceptions of academic, social, and emotional adjustment as well as peer perceptions of behavioral attributes and social status were found to provide convergent evidence for the typology. Divergent evidence emerged related to internalizing difficulties. Parallels between the teacher‐rated typology and peer‐relations research were drawn. Most notably, peers rated Mildly Disruptive (MD) children as bullying and disruptive, consistent with teacher report. However, peers also rated MD children as “cool” and with high levels of social dominance and social control, consistent with recent reports of popular bullies. © 2007 Wiley Periodicals, Inc.
Diversity research literature on the rise? A review of school psychology journals from 2000 to 2003
Authors: Brown Stephanie L. , Shriberg David , Wang Aimin 
Published: April 2007

AbstractSchool psychologists in the United States are not nearly as diverse demographically as the students they serve (T.K. Fagan & P.S. Wise, 2000). A.H. Miranda and P.B. Gutter (2002) investigated the number of diversity‐related articles in four leading school psychology journals from 1990 to 1999 and found that there was an increase in the percentage of articles in these journals that were diversity related as compared to a study done by R.M. Wiese Rogers (1992) that examined school psychology journals from 1975 to 1990. There was a particular increase in diversity‐related articles appearing from 1995 to 1999. The present study examined school psychology journals from 2000 to 2003 to determine whether this increase was an aberration or an indication of a longer term change. Results indicate a continued trend toward more diversity‐related articles in the school psychology literature, but several gaps remain. Implications for the field are discussed. © 2007 Wiley Periodicals, Inc.
Living anionic polymerization of 2‐vinyldibenzothiophene: Homopolymer and block copolymers with styrene
Authors: Avila‐Ortega A. , Vázquez‐Torres H. 
Published: April 2007

Abstract2‐Vinyldibenzothiophene (2VDBT) was synthesized from the 2‐bromodibenzothiophene previously prepared. Then, anionic polymerization of 2‐vinyldibenzothiophene and its copolymerization with styrene were carried out under nitrogen atmosphere in benzene at 30 °C using n‐butyllithium as initiator. The anionic polymerization of 2VDBT showed a living character, since it fulfilled the criterion for the linearity of the plot of ln([M]0[M]) with time, together with the requirement that Mn must vary linearly with conversion. Narrow molecular weight distribution (MwMn < 1.1) and predictable molecular weight were obtained for homopolymerization of poly(2VDBT), taking into account the overestimation of experimental Mn(GPC) due to the possible higher hydrodynamic volume arising from the bulky dibenzothiophenyl group of poly(2VDBT) in comparison to the phenyl group of polystyrene. Also, sequential copolymerization by addition of 2VDBT and styrene yielded block copolymers showing narrow polydispersity (MwMn <1.08). The anionic polymerization of mixtures of 2VDBT and styrene was carried out and their relative reactivity ratios were estimated by applying both the Kélen–Tüdös and the Joshi–Joshi methods. The former yielded values of r2VDBT = 1.11 ± 0.77 and rSt = 0.49 ± 0.10, whereas the latter gave the values r2VDBT = 1.05 ± 0.05 and rSt = 0.50 ± 0.10 for the reactivity ratios. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1993–2003, 2007
A bidirectional ATRP‐NMRP initiator: The effect of nitroxide size on the rate of nitroxide‐mediated polymerization
Authors: Ruehl Jean , Braslau Rebecca 
Published: April 2007

AbstractAn N‐alkoxyamine macroinitiator bearing a polymeric nitroxide cap was synthesized and used to investigate the effect of nitroxide size on the rate of nitroxide‐mediated radical polymerization (NMRP). This macroinitiator was prepared from asymmetric double‐headed initiator 9, which contains both an α‐bromoester and an N‐alkoxyamine functionality. Poly(methyl methacrylate) was grown by atom transfer radical polymerization from the α‐bromoester end of this initiator, resulting in a macroinitiator (Mn = 31,000; PDI = 1.34) bearing a nitroxide cap permanently attached to a polymer chain. The polymerization kinetics of this macroinitiator in NMRP were compared with known N‐alkoxyamine initiator 1. It was found that the rate of polymerization was unaffected by the size of the macromolecular nitroxide cap. It was confirmed that NMRP using this macroinitiator is a “living” process. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2015–2025, 2007
Polymerization of conjugated 5‐[(5‐ethynyl‐1‐naphthyl)ethynyl]‐N,N‐dimethylnaphthalen‐1‐amine with rhodium and palladium complexes
Authors: Rodríguez J. Gonzalo , Tejedor Jose Luis 
Published: April 2007

AbstractThe monomer 5‐[(5‐ethynyl‐1‐naphthyl)ethynyl]‐N,N‐dimethylnaphthalen‐1‐amine was satisfactory obtained through the heterocoupling reaction of 5‐ethynyl‐N,N‐dimethylnaphthalen‐1‐amine and 4‐(5‐iodo‐1‐naphthyl)‐2‐methyl‐3‐butyn‐2‐ol catalyzed by a palladium–copper system, followed by acetone elimination. Poly{5‐[(5‐ethynyl‐1‐naphthyl)ethynyl]‐N,N‐dimethylnaphthalen‐1‐amine} was obtained through the reaction of the acetylene monomer with homogeneous rhodium and palladium catalyst complexes. The structure of the polymers always showed a trans–cisoidal chain configuration on the basis of IR and NMR spectra. Moreover, only for the rhodium catalyst complex in methanol was a dimeric product isolated in a very low yield, having a conjugated terminal ene–yne structure, which permitted the consideration of a metallated chain‐transfer intermediate in the polymer propagation. The mass determination of the polymers, by osmometry and gel permeation chromatography techniques, showed low average molecular weights. The kinetics of the catalyzed polymerization were analyzed. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2038–2047, 2007
Polyfluorene presenting dipolar pendent groups and its application to electroluminescent devices
Authors: Chien Chen‐Han , Shih Ping‐I , Wu Fang‐Iy , Shu Ching‐Fong , Chi Yun 
Published: April 2007

AbstractWe have synthesized a blue‐light‐emitting polyfluorene derivative (PF‐TPAOXD) that presents sterically hindered, dipolar pendent groups functionalized at the C‐9 positions of alternating fluorene units. The incorporation of the dipolar side chains, each comprising an electron‐rich triphenylamine group and an electron‐deficient oxadiazole group connected through a π‐conjugated bridge, endows the resultant polymer with higher highest occupied molecular orbital and lower lowest unoccupied molecular orbital energy levels, which, consequently, lead to an increase in both hole and electron affinities. An electroluminescent device incorporating this polymer as the emitting layer exhibited a stable blue emission with a maximum brightness of 2080 cd/m2 at 12 V and a maximum external quantum efficiency of 1.4% at a brightness of 137 cd/m2. Furthermore, atomic force microscopy measurements indicated that the dipolar nature of PF‐TPAOXD, in contrast to the general nonpolarity of polydialkylfluorenes, provided a stabilizing environment allowing the polar organometallic triplet dopant to be dispersed homogeneously. We also fabricated an electrophosphorescent device incorporating PF‐TPAOXD as the host material doped with a red‐emitting osmium complex to realize red electroluminescence with Commission Internationale de l'Eclairage color coordinates of (0.66, 0.34). The resulting device exhibited a maximum external quantum efficiency of 7.3% at a brightness of 1747 cd/m2 and a maximum brightness of 7244 cd/m2. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2073–2084, 2007
Influence of preparation methods on structure and properties of PA6/PA66 blends: A comparison of melt‐mixing and in situ blending
Authors: Wang X. C. , Zheng Q. , Yang G. S. 
Published: April 2007

AbstractThe blends composed of polyamide 6 (PA6) and polyamide 66 (PA66) were obtained using two different preparation methods, one of which was the melt‐mixing through a twin‐screw extruder and the subsequent injection molding; and the other, the in situ blending through anionic polymerization of ε‐caprolactam in the presence of PA66. For the former, there existed a remarkable improvement in toughness but a drastic drop in strength and modulus; however, for the latter, a reverse but less significant trend of mechanical properties change appeared. Various characterizations were conducted, including the analyses of crystalline morphology, crystallographic form, and crystallization and melting behaviors using polarized optical microscopy (POM), wide‐angle X‐ray diffraction (WAXD), and differential scanning calorimetry (DSC), respectively; observation of morphology of fractured surface with scanning electron microscope (SEM); measurement of glass transition through dynamic mechanical analysis (DMA); and the intermolecular interaction as well as the interchange reaction between the two components by Fourier transform infrared spectrometry (FT‐IR) and 13C solution NMR. The presence and absence of interchange reaction was verified for the in situ and melt‐mixed blends, respectively. It is believed that the transreaction resulted in a drop in glass transition temperature (Tg) for the in situ blends, contrary to an increase of Tg with increasing PA66 content for the melt‐mixed ones. And the two kinds of fabrication methods led to significant differences in the crystallographic form, spherulite size and crystalline content and perfection as well. Accordingly, it is attempted to explain the reasons for the opposite trends of changes in the mechanical properties for these two blends. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1176–1186, 2007
Double yielding in PA6: Effect of mold temperature and moisture content
Authors: Shan Gui‐Fang , Yang Wei , Tang Xue‐Gang , Yang Ming‐Bo , Xie Bang‐Hu , Fu Qiang 
Published: April 2007

AbstractIn this study we have investigated the effect of mold temperature and moisture content on double yielding of virgin polyamide 6 (PA6) uniaxially deformed at room temperature. The experimental results have revealed that, to a certain extent, a limited increment in both mold temperature and moisture content will make the second yield process become more apparent. However, the double yielding behavior will disappear totally in the case of much higher mold temperature and moisture content. Instead, a typical single sharp yield or brittle fracture will be present in the former case, while in the latter case the samples only display a very broad yield, similar to a rubber‐like deformation. Maybe two critical states will be in existence in PA6 exhibiting double yielding behavior, and the critical states are probably relevant with the concentration of the interlinks and intralinks, the lamellae perfection and the crystallite size. Particular emphasis should be placed on the role of interlinks and intralinks when considering the origin of double yielding of virgin PA6 since these links affect the stress transfer significantly. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1217–1225, 2007
Electrically induced linear locomotion of polymer gel in air
Authors: Liang Songmiao , Xu Jian , Weng Lihui , Zhang Lina , Guo Xinglin , Zhang Xiaoli 
Published: April 2007

AbstractA electromechanical gel, which could be driven in air by a DC electric field, was developed using poly(vinyl alcohol)/dimethylsulfoxide gel. When the applied electric field exceeds a certain threshold, the gel exhibited a continuous and linear crawling motion. The result indicated that, under the applied electric field of 275 V/mm, the maximum crawling velocity of the gel could reach v = 1.63 mm/s, which is about 80 times larger than that reported in earlier works. At a proper range of the driving time, the average crawling speed and crawling direction could be well controlled by the external electric field. Furthermore, some factors, which have influence on the critical driving electric field of the gel, such as the swelling degree of the gel and the apparent contact area between the gel and substrate, were studied. For the first time, a mechanism based on the strong electrostatic interaction between the external electric field and the charges accumulated in the gel–air and substrate–gel interfacial regions was put forward to explain the novel motion. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1187–1197, 2007
Relationship between fine structure of polyoxymethylene copolymer plates and methanol transport properties
Authors: Fujii Yasuhisa , Shen Hui 
Published: April 2007

AbstractAn experimental study was made of diffusion behavior of methanol through three kinds of injection‐molded plates of a polyoxymethylene (POM) copolymer with different molecular weights M at 60 °C. Fine structure of the three sample plates was also examined by wide‐angle X‐ray diffraction and small‐angle X‐ray scattering, and moreover, their dynamic properties were investigated by the dynamic mechanical analysis (DMA). It is shown that the diffusion behavior may be well explained by the one‐dimensional Fick diffusion equation with a constant diffusion coefficient, and that the steady‐state transport rate increases with increasing M. As for fine structure, the crystallinity decreases slightly, and the preferential orientation and the long period increase, with increasing M. The long period of the lamellar stacking structure increases with increasing M, and it also increases with methanol transport. In DMA, the loss tangent tan δ becomes higher after the methanol transport in the wide range of temperature around the glass transition one. These results indicate that amorphous regions serve as channels for methanol molecules in the lamellar stacking structure, leading to the conclusion that the dependence of the steady‐state transport rate on M arises from the factors of crystallinity and long period. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1234–1242, 2007