bluuebunny/crossref_metadata_2025 huggingface dataset:
Dopant Exchange in Conducting Polypyrrole Films
Authors: Maddison David S. , Jenden Charles M.
Published: April 2007

Polypyrrole films containing a variety of dopants were synthesised. Special attention was given to ensuring that all films were morphologically similar so that differences in the electronic properties of the films were more strongly associated with the intrinsic character of the dopants, in particular their electron affinity. To achieve this, dopant exchange was performed by an electrochemical process and a strong correlation was found between dopant electron affinity (X) and film electrical conductivity.
Photo‐reversible Reaction in Polymer Langmuir‐Blodgett Films
Authors: Nakanishi Fusae
Published: April 2007

Preparation of photoreactive Langmuir‐Blodgett (LB) films was carried out using polymers/oligomers prepared from long‐chain dialkyl esters of di‐and tetra‐olefins and having cyclobutane rings in the main chain. These polymers/oligomers formed stable monolayers on a water surface when mixed with arachidic acid. These monolayers could be deposited onto a substrate successfully forming Y‐type films. The oligomer LB films were polymerized on irradiation. The polymer LB films showed a photo‐reversible process between polymers and oligomers, depending on wavelength of the irradiating light. On the basis of spectral data and molecular weight change, this behaviour was found to be caused by cleavage and formation of cyclobutane rings.
The influence of the draw ratio of melt‐spun polyethylene fibres on γ‐irradiation induced effects as observed by ESR
Authors: Albert Candiera F. , Ken Busfield W. , Pomery Peter J.
Published: April 2007

The influence of draw ratio on free radical behaviour in melt‐spun polyethylene fibres has been examined using ESR spectroscopy. The stability of free radicals produced by γ‐irradiation is greatest some where between draw ratio 1 and 10. The general trend of radical stability has been found to correlate with the trend of gel content with draw ratio. The possible link between the extent of crosslinking and the production of stable radicals has been discussed in terms of morphological aspects.
Crystallization kinetics of native (pure) and commercial gutta percha (transpolyisoprene) and the influence of metal salts, oxides, ‘thermoplast’ and colouring agents on its crystallization rate
Authors: Arvanitoyannis Ioannis , Blanshard John M. V. , Kolokuris Ioannis
Published: April 2007

The kinetics of crystallization of gutta percha (trans‐polyisoprene) were studied both in its native form and as the commercial product currently used for dental purposes. Mixtures of native gutta percha with selected low molecular weight substances (BaSO4, CdSO4, Bi2O3, ZnO), ‘Thermoplast’—a commercially formulated plasticizer, and colouring agents were also examined. It was shown that any incompatibility of the aforementioned substances caused an increase in the crystallization rate, while compatibility decreased the rate of crystallization.
Studies on polymer latex films: IV. Comparison of the permeability of latex and solvent‐cast films
Authors: Roulstone B. J. , Wilkinson M. C. , Hearn J.
Published: April 2007

Latex and solvent‐cast films have been prepared from poly(butyl methacrylate) surfactant‐free latices and their permeabilities to water vapour and an aqueous organic solute (p‐nitrophenol) have been studied. Latex films show considerable ageing effects and their performance is very dependent upon the conditions of film formation but their barrier properties are not necessarily inferior. A greater dependence on film orientation is evident for latex films.
Structural adhesive performance in marine environments
Authors: Horton Trevor , Spinks Geoffrey M. , Isles Neils A.
Published: April 2007

Durability of adhesively bonded aluminium joints was investigated for both stressed and unstressed joints exposed to environments of air, distilled water, 0.5% sodium chloride solution and 5% sodium chloride solution. Testing involved the use of marine grade aluminium, two acrylic adhesives and two epoxy resin adhesives. Surface preparation consisted of a solvent wipe degreasing procedure. The acrylic adhesives used in this study displayed greater bond durability than cpoxy resins. Results also reaffirmed that the combination of stress and environmental exposure is more detrimental to bond durability than environmental exposure alone. The combined effects of stress and dilute salt solution were found to be more detrimental to adhesive bond durability than stress combined with distilled water, or concentrated salt solution. Two possible causes of bond deterioration considered were corrosion of the aluminium adherend and instability of the interface. Either of these explanations could account for the observed results; however, more work is required to verify these theories.
Microstructure of styrene copolymers with 2‐phenyl‐1,1‐dicyanoethene
Authors: Kharas Gregory B. , Mirau Peter A. , Watson Kenneth , James Harwood H.
Published: April 2007

Microstructure analysis of styrene copolymers with 2‐phenyl‐1,1‐dicyanoethene, as deduced from high resolution 1H and 13C NMR spectroscopy (DEPT, HETCOR, NOESY and JMODXH). demonstrated the formation of both head‐to‐head and head‐to‐tail alternating monomer structures. Conventional head‐to‐tail structures are explained as the result of cross propagation of ‘free’ monomers, whereas anomalous head‐to‐head structures are rationalized through the addition of monomer complexes of predicted geometry. The results indicated that the copolymer skeletal regioselectivity is dependent on participation of both free monomers and monomer donor‐acceptor complexes in the propagation steps of the copolymerization.
A kinetic study on MMA bulk radical polymerization
Authors: Shen Jia‐Cong , Wang Gou‐Bin , Yang Mei‐Lin , Zheng Ying‐Guang
Published: April 2007

The nonequalities of the reactivity and the micro‐environment of propagating radicals has been found in MMA bulk polymerization. This nonequal reactivity results from varying rates of diffusion in different micro‐surroundings. The decrease of radical reactivity is caused by the trapping of the segments around the propagating radical.
The synthesis and characterization of poly(ethylene oxide)‐b‐poly‐(dimethylsiloxane) diblock copolymers
Authors: Kiràly Zoltàn , Vincent Brian
Published: April 2007

Poly(ethylene oxide)‐b‐poly(dimethylsiloxane) (PEO‐b‐PDMS) diblock copolymers have been synthesized by hydrosilation coupling. Allyl‐terminated PEO and dimethylsilane‐terminated PDMS macromers have been prepared by living anionic polymerization, followed by subsequent functionalization. The diblock copolymers, as well as the preformed macromers, have been characterized by gel‐permeation chromatography, vapour pressure osmometry, FTIR spectroscopy and 1H‐, 13C‐ and 29Si‐FTNMR spectroscopy. The results obtained from these techniques are presented in detail for PEO(M̄;n = 2120), PDMS(M̄n = 2220) and the corresponding diblock copolymer.
Non‐steady‐state model for kinetics of free radical polymerization, 4. Direct thermal initiation
Authors: Yan Deyue , Lin Jianming , Yuan Cuiming
Published: April 2007

This paper deals with the non‐steady‐state kinetics of direct thermal initiated polymerization. The initiation is assumed to be a bimolecular reaction of the monomer. The relationship between the radical concentration and the monomer conversion is rigorously derived. In further treatment a few very close approximations are introduced based on the fact that the number of monomer molecules reacting in the initiation step is much less than that consumed in the propagation step for a process producing high polymer, and the value of the rate constant for propagation or chain transfer is much lower than that for chain termination. Expressions for various molecular parameters, such as molecular weight distribution, number‐average and weight‐average degrees of polymerization, and dispersity, are given. Several numerical examples are provided.
Drop stabilisation by inorganic solids in suspension polymerisation: modification by electrolytes using a wax model
Authors: Zhiping Wang , Brooks B. W.
Published: April 2007

Finely divided inorganic solids can be used for drop stabilisation in suspension polymerisation. Usually solids are dispersed in water in the presence of electrolytes formed during their preparation. Experiments, using a wax model as described previously,1 have been carried out by using two inorganic solids, magnesium phosphate and calcium phosphate, in either the presence or absence of electrolytes. The experiments showed that the effect of electrolytes depends on both the inorganic solid which is used and on the nature of the electrolyte which is present. Magnesium phosphate was a destabiliser in the absence of electrolytes but could act as a stabiliser in the presence of sodium sulphate. Calcium phosphate acted as a stabiliser both in the presence and in the absence of electrolytes.
Chain‐folding in polyethylene lamellar structure
Authors: Al‐Raheil I. A. M. , Okaz Ali M.
Published: April 2007

The nature of the chain‐folding in polyethylene lamellar structure from the melt has been studied. Permanganic etching was used to reveal the morphology by selective removal of material from the surface of the specimen. This was done to prepare the sample for transmission electron microscopy. The micrographs indicate the presence of lines (traces) parallel to the chain molecular axis. The chain inclination to the basal plane of the lamellar normal was assumed to be around 35°. With simple geometrical calculations the fold surfaces were found to be {20} planes, for which the exact angle is 34.4°.
Gamma‐radiation stabilization of polypropylene
Authors: Hassan Rezk A. M. , Senna M. M. , Abdel‐Bary E. M.
Published: April 2007

Especially synthesized compounds, together with conventional antioxi‐dants, were evaluated as radiation stabilizers of isotactic polypropylene. Electron spin resonance (ESR) determinations of free radical populations in stabilized and unstabilized samples were carried out after irradiation and at periods of up to 460 h. The same samples were mechanically tested and a correlation was found to exist between the concentration of trapped peroxy radicals and the radiation deterioration in the polymer. Post‐irradiation effects were evaluated using accelerated aging at 70°C and carbonyl index determinations at periods of up to 110 days indicated that some of the stabilizers examined are efficient inhibitors of post‐irradiation oxidation. The results are discussed in the light of the free radical mechanism of the radiation‐induced auto‐oxidative degradation of polymers.
PEO‐based polymer electrolytes
Authors: Magistris Aldo , Singh Kamal
Published: April 2007

Like a liquid solvent, poly(ethylene oxide) dissolves a wide variety of inorganic salts. Ionic conductivity occurs in the amorphous region of the polymer and typically both anions and cations are mobile to some extent. This paper discusses the preparation, thermal behaviour and ionic transport of thin cast films of PEO‐based electrolytes containing monovalent and divalent cations. The techniques that shed light on the structure‐conductivity relationship are emphasized. The temperature and composition dependence of conductivity is also considered. Finally, attention has been paid to the possible uses of these polymeric electrolytes in solid‐state electrochemical devices such as primary and secondary batteries, electrochromic displays and sensors.
Metathesis ring opening polymerization of 5,6‐dimethylenebicyclo[2.2.1]hept‐2‐ene
Authors: Shahada Lamies A. , James Feast W.
Published: April 2007

5,6‐Dimethylenebicyclo[2.2.1]hept‐2‐ene (I) polymerizes in the presence of the two‐component ring opening metathesis polymerization (ROMP) initiators WCl6/(CH3)4Sn and MoCl5/(CH3)4Sn. The product polymers were insoluble in all of many solvents investigated and are presumably cross‐linked. The product polymers were investigated by IR and solid state 13C NMR spectroscopy, which established that the material consisted predominantly of poly(1,4‐(2,3‐dimethylene‐cyclopentylene)vinylene) (II). A possible alternative route to II via thermal dehydrochlorination of poly(1,4‐(2,3‐bis(chloromethyl)cyclopentylene) vinylene) (IV) was also examined.
Chemically induced graft copolymerization of acrylonitrile on to hydrolysed wood pulp
Authors: Sabaa Magdy W. , Safy El‐Din Nabil M.
Published: April 2007

Grafting of acrylonitrile on to hydrocellulose derived from the hydrolysis of wood pulp has been studied using cerie ammonium nitrate as initiator. The graft yield, the grafting efficiency and the total conversion were found to be highly affected by the various parameters studied including the initiator and monomer concentrations, the polymerization time and temperature. Moreover, the effect of the extent of grafting on the moisture regain property of the hydrolysed wood pulp has been also investigated.
Dielectric relaxation in poly(ethylene glycols) at 9.83 GHz
Authors: Sengwa Ram J. , Purohit Hari D.
Published: April 2007

Dielectric relaxation studies of poly(ethylene glycols), average molecular weight 200–9000, have been carried out in carbon tetrachloride solutions at microwave frequency, i.e. 9.83 GHz. Average relaxation times τ0 and relaxation times corresponding to segmental motion τ1, and group rotations τ2 have been calculated. The variations of relaxation times with increase in degree of polymerization and temperature have been determined. With the increase in the degree of polymerization the flexibility increases and hence the coiling of the chain increases. At a certain temperature there is a decrease in the relaxation time corresponding to segmental motion, suggestive of some switch‐over mechanism in higher polymers. The relaxation time corresponding to group rotations is independent of temperature and degree of polymerization.
Synthesis and characterisation of N‐toluyl methacrylatoethyl carbamates, homopolymers and copolymers with methyl methacrylate
Authors: Santhana Krishnan P. Gopala , Choudhary Veena , Varma I. K.
Published: April 2007

The paper describes the synthesis of N‐2/4‐toluyl methacrylatoethyl carbamates using 2/4‐toluyl isocyanate and 2‐hydroxyethyl methacrylate. Homopolymerisation and copolymerisation of these novel monomers with methyl methacrylate was carried out using benzoyl peroxide as an initiator and tetrahydrofuran as solvent. Photopolymerisation of N‐4‐toluyl methacrylatoethyl carbamate could be carried out without the use of photosensitiser. Structural characterisation of copolymers was done using 1H‐NMR. Thermal stability of copolymers was evaluated in a nitrogen atmosphere by dynamic thermogravimetry.
Synthesis and properties of poly(phenylene sulfide)s containing carbonyl and sulfonyl groups
Authors: Joseph K. Abraham , Srinivasan M.
Published: April 2007

With a view to study and compare the properties of poly(phenyienc sulfide)s containing carbonyl and sulfonyl backbone units, 1,4‐bis(phenylthio)‐benzene, and bis(4‐phenylthio)diphenyl sulfone, were prepared and subjected to Fricdel‐Crafts type polycondensation with various aromatic diacid chlorides. The resulting polymers had inherent viscosities in the range 0.101—0.141 dl/g. These polymers were not soluble in common organic solvents and exhibited good thermal stabilities.
Effect of initiator structure on physical and thermal properties of nylon‐6
Authors: Desai Manish R. , Pandya Madhav V. , Shah Chaitanya S.
Published: April 2007

Nylon‐6 is synthesised from ε‐caprolactam by an anionic polymerisation method, through a two‐step process using sodium metal as a catalyst and diisocyanate‐caprolactam block initiator. Two different aliphatic diisocyanates are used. The effects of diisocyanate structure and concentration on percentage cryslallinity, molecular weight, density and thermal properties of nylon are discussed.
Silica‐supported polymer‐palladium complexes as catalysts for the reduction of nitro and azo groups
Authors: Mathew Joice P. , Srinivasan M.
Published: April 2007

Palladium complexes of cross‐linked polyvinylpyridine and poly(acryl‐amide‐methacrylic acid) copolymer coated on silica gel have been used as catalysts for the hydrogenation of azo and nitro groups under 101 kPa hydrogen pressure at 30°C. Nitro aromatics were selectively and almost completely reduced to the corresponding amines. A rate equation of the type, rate = k[cat][H2] has been derived for the hydrogenation of nitrobenzene on the basis of the experimental results and kinetic data. Also the selective hydrogenation of azobenzene to hydrazobenzene could be achieved with these catalysts.
A new difunctional anionic initiator soluble in non‐polar solvents
Authors: Nugay Turgut , Küçükyavuz Savaş
Published: April 2007

The reaction between 1,5‐diethenylnaphthalene and sec‐butyllithium produces a new difunctional organolithium initiator which is soluble in non‐polar solvents and effective in the synthesis of styrene‐isoprene‐styrene triblock copolymer. Monomodal molecular weight distributions are observed for block copolymers and styrene homopolymers. The microstructure of polyisoprene blocks is similar to those polymers initiated by butyllithium in the same solvent.
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

Polymerization 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

The 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

As 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

A 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

High 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

Several 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

Samples 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

The 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

The 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

Gel/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

External 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

School 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

2‐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

An 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

The 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

We 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

The 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

In 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

A 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

An 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
Nanoparticulate delivery of suicide DNA to murine prostate and prostate tumors
Authors: Peng Weidan , Anderson Daniel G. , Bao Yunhua , Padera Robert F. , Langer Robert , Sawicki Janet A.
Published: April 2007

BACKGROUND

Currently available treatments for benign prostatic hyperplasia (BPH) and localized prostate cancer are generally effective but are often attended by serious side effects that impact on the quality of life. In particular, most current therapies are non‐specific, with surgery, radiation, and chemical ablation having the potential to cause damage to surrounding tissue. Here, we demonstrate the effectiveness of a prostate‐specific, locally delivered gene therapy for the targeted killing of prostate cells.

METHODS

Using a degradable, poly(β‐amino ester) polymer, poly(butane diol diacrylate co amino pentanol) (C32), we developed a nanoparticulate system to deliver a diphtheria toxin suicide gene (DT‐A) driven by a prostate specific promoter to cells. These C32/DT‐A nanoparticles were directly injected to the normal prostate and to prostate tumors in mice.

RESULTS

Nearly 50% of normal prostates showed a significant reduction in size, attributable to cellular apoptosis, whereas injection with naked DT‐A‐encoding DNA had little effect. Significant apoptosis was also observed in C32/DT‐A injected prostate tumors. Importantly, no damage to surrounding tissue was observed.

CONCLUSIONS

These results suggest that local delivery of poly(β‐amino ester) polymer/ DT‐A nanoparticles may have application in the treatment of BPH and prostate cancer. Prostate 67: 855–862, 2007. © 2007 Wiley‐Liss, Inc.
Detection of gene duplication signals of Ig folds from their amino acid sequences
Authors: Huang Yanzhao , Xiao Yi
Published: April 2007

Protein folds may evolve from short peptide ancestors via gene duplication and fusion. For proteins with internal structural symmetry, this means that their sequences should be made up of identical repeats. However, many of these repeat signals can only be seen at the structural level yet. Motivated by the fact that proteins may have similar structures if their sequences have more than 25% identical amino acids, we suggest a method to detect the sequence repeats of proteins directly from their sequences. Using this method, we show that the internal repetitions of the immunoglobulin folds could be identified directly at the sequence level. Proteins 2007. © 2007 Wiley‐Liss, Inc.
Molecular modeling of prohibitin domains
Authors: Winter Anja , Kämäräinen Outi , Hofmann Andreas
Published: April 2007

Prohibitins comprise a family of highly conserved ubiquitous eukaryotic proteins that mainly localize to the mitochondria. They have been implicated in important cellular processes such as cellular signaling and transcriptional control, apoptosis, cellular senescence, and mitochondrial biogenesis. Using molecular modeling techniques, we have generated structural models of human prohibitins BAP32 and BAP37, which have previously been shown to exist as large ringlike oligomers in the membrane‐bound state. The middle domain of prohibitins is evolutionary conserved in the family of SPFH (PHB) domain proteins. On the basis of the known structure of flotillin‐2, another member of the SPFH‐domain family, we have generated homology models for BAP32 and BAP37, and elucidated the implications for formation of high molecular weight oligomers. A model for the dimeric‐building block of BAP32: BAP37 for such assemblies was generated and its stability scrutinized by molecular dynamics simulations. The model of BAP32 was also analyzed as to potential ligand‐binding sites and the previously identified ligand melanogenin was docked into a membrane‐proximal cavity. The results are discussed in the context of prohibitin interactions with mitochondrial AAA‐proteases and we suggest two possible interaction interfaces between the BAP32:BAP37 building block and the protease. Proteins 2007. © 2007 Wiley‐Liss, Inc.
Impact of mirid (Creontiades spp.) (Hemiptera: Miridae) pest management on Helicoverpa spp. (Lepidoptera: Noctuidae) outbreaks: the case for conserving natural enemies
Authors: Knight Kristen MM , Brier Hugh B , Lucy Michael J , Kopittke Rosemary A
Published: April 2007

Creontiades spp. (Hemiptera: Miridae) are sucking pests that attack buds, flowers and young pods in mungbeans, Vigna radiata (L.), causing these structures subsequently to abort. If left uncontrolled, mirids can cause 25‐50% yield loss. Traditional industry practice has involved prophylactic applications of dimethoate to control mirids at budding and again a week later. The present trial was initiated to highlight the dangers of such a practice, in particular the risk of a subsequent Helicoverpa spp. lepidopteran pest outbreak. A single application of dimethoate halved the population of important natural enemies of Helicoverpa spp., and caused an above‐threshold outbreak of Helicoverpa spp. within 11 days. This shows that even a moderate (e.g. 50%) reduction in natural enemies may be sufficient to increase Helicoverpa spp. populations in mungbeans. As a result, prophylactic sprays should not be used for the control of mirids in mungbeans, and dimethoate should be applied only when mirids are above the economic threshold. Indoxacarb was also tested to establish its effect on Helicoverpa spp., mirids and natural enemies. Indoxacarb showed potential for Helicoverpa spp. control and suppression of mirids and had little impact on natural enemies. Copyright © 2007 Society of Chemical Industry
Investigation of ZnTe thin films grown by Pulsed Laser Deposition method
Authors: Kotlyarchuk B. , Savchuk V.
Published: April 2007

This paper is devoted to optimization of the Pulsed Laser Deposition (PLD) growth condition of ZnTe films on various substrates and subsequent investigation of relevant parameters of growth process, structural, optical and electrical properties of grown films. Studies of the effect of growth parameters on the structural quality and properties of grown films were carried out. X‐ray diffraction measurements showed that the ZnTe films, which have been deposited at optimal substrate temperatures, were characterized by a (111) preferred orientation with large average grain size. The optical transmission and reflectance in the energy range 1.5–5.5 eV for films grown at various substrate temperatures were measured. We calculated the variation in the absorption coefficient with the photon energy from the transmittance spectrum for samples grown at various substrate temperatures. Obtained data were analyzed and the value of the absorption coefficient, for allowed direct transitions, has been determined as a function of photon energy. We found that the undoped ZnTe films, which were grown by the PLD method, are typically p‐type and possess resistivity in the range of 103 Ω cm at room temperature. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Bio‐guided isolation of antioxidants from the stems of Dendrobium aurantiacum var. denneanum
Authors: Yang Li , Han Haofeng , Nakamura Norio , Hattori Masao , Wang Zhengtao , Xu Luoshan
Published: April 2007

Bio‐guided fractionation of the stems of Dendrobium aurantiacum var. denneanum using a 1,1‐diphenyl‐2‐picryl‐hydrazyl (DPPH) radical scavenging assay, led to the isolation of three 2‐glucosyloxycinnamic acid derivates, namely, cis‐melilotoside, trans‐melilotoside and dihydromelilotoside, respectively. Their structures were elucidated through the analysis of uni‐ and bi‐dimensional NMR, UV, IR and MS data. All these three compounds were first reported from the genus Dendrobium and exhibited potent antioxidant activities. Copyright © 2007 John Wiley & Sons, Ltd.