bluuebunny/crossref_metadata_2025 huggingface dataset:
Imidazolium‐modified clay‐based ABS nanocomposites: a comparison between melt‐blending and solution‐sonication processes
Authors: Modesti M. , Besco S. , Lorenzetti A. , Zammarano M. , Causin V. , Marega C. , Gilman J. W. , Fox D. M. , Trulove P. C. , De Long H. C. , Maupin P.H.
Published: June 2008

Acrylonitrile–butadiene–styrene (ABS) nanocomposites containing imidazolium‐modified montmorillonite have been prepared by melt‐blending (MB) and solution‐sonication in order to study the effects of processing on the morphology and properties of the polymer/clay composites. The structure‐property relationships of the prepared composites have been studied by means of X‐ray diffraction (XRD), transmission electron microscopy (TEM), mechanical testing, dynamic‐mechanical analyses (DMA), thermal gravimetrical analyses (TGA), fluorescence probe confocal microscopy, and fluorescence spectroscopy (FS). X‐Ray and TEM show that both nanocomposites have a mixed intercalated/exfoliated structure. Fluorescence probe confocal microscopy reveals that the sonicated sample has a more homogeneous dispersion: this result is confirmed by the values of elongation at break and flexural elastic modulus measured for the composites. Fluorescence spectroscopy has also been used to investigate the distribution of clay in the composites and results indicate that clay layers in ABS are preferentially located in the styrene‐acrylonitrile (SAN) phase, independent of the dispersion process used. Published in 2008 by John Wiley & Sons, Ltd.
Synthesis and characterization of hyperbranched polytriazole via an ‘A2 + B3’ approach based on click chemistry
Authors: Xie Jianda , Hu Lihua , Shi Wenfang , Deng Xiaoxu , Cao Zhuangqi , Shen Qishun
Published: June 2008

BACKGROUND: The ‘A2 + B3’ type of polymerization has been demonstrated to be an alternative route towards hyperbranched polymers. Some highly crosslinked hyperbranched polymers have been prepared via copper(I)‐catalyzed click reactions of multivalent azides and alkynes. To obtain hyperbranched polymers without gelation and develop the A2 + B3 type of polymerization based on click reactions, the specific reaction conditions need to be investigated.

RESULTS: In this work, a hyperbranched polytriazole (hb‐PTA) was synthesized through the A2 + B3 approach using a click reaction. 4‐N,N′‐bis(2‐azidoethyl)amino‐4′‐nitroazobenzene and 1,3,5‐tris(alynyloxy)benzene were synthesized for use as the A2 and B3 monomers, respectively. This was a ‘one‐pot’ polymerization carried out using a slow‐addition method. The obtained hb‐PTA was soluble in common organic solvents. The molecular structure was characterized using 1H NMR, Fourier transform infrared and gel permeation chromatography analyses. The degree of branching of hb‐PTA was determined to be around 0.50.

CONCLUSION: The hb‐PTA was successfully synthesized via the A2 + B3 approach based on a click reaction. The polymerization conducted in dilute solution adopting slow addition of A2 to B3 resulted in hb‐PTA in the absence of gelation. The obtained hb‐PTA exhibited high thermal stability. Copyright © 2008 Society of Chemical Industry
Blending polypropylene with glycidyl methacrylate‐containing polymer to improve adhesion to elastomers
Authors: Paul Shreya , Verenich Svetlana , Pourdeyhimi Behnam
Published: June 2008

BACKGROUND: Polypropylene (PP) is one of the most widely used polyolefins but gets restricted in surface applications due to its non‐polar nature. Surface properties of films made of PP were modified to improve their adhesion to elastomeric polymers such as thermoplastic polyurethanes (TPU), especially to Pebax® [poly(ether‐block‐amide)].

RESULTS: Surface modification of PP was brought about by blending it with glycidyl methacrylate (GMA)‐containing polymer to increase its surface energy. Films of modified PP were analyzed to determine the blending efficiency and characterized using contact angle measurements, differential scanning calorimetry, X‐ray photoelectron spectroscopy and scanning electron microscopy. Molecular dynamics simulations were done to determine surface and bulk properties of PP blended with GMA. The computational results correlated very well with the experimental data and revealed that the changes in the surface energy can be linked to the position of the functional group within the sample. T‐Peel tests indicated a 2.4 times increase in adhesion to Pebax® and only 1.7 times increase in adhesion to TPU compared to unmodified PP.

CONCLUSION: The surface energy and enhanced adhesion proved that PP was successfully modified and its surface made more polar. Copyright © 2008 Society of Chemical Industry
Synthesis and characterization of biodegradable lactic acid‐based polymers by chain extension
Authors: Gu ShuYing , Yang Ming , Yu Tao , Ren TianBin , Ren Jie
Published: June 2008

BACKGROUND: Poly(lactic acid) (PLA), coming from renewable resources, can be used to solve environmental problems. However, PLA has to have a relatively high molecular weight in order to have acceptable mechanical properties as required in many applications. Chain‐extension reaction is an effective method to raise the molecular weight of PLA.

RESULTS: A high molecular weight biodegradable lactic acid polymer was successfully synthesized in two steps. First, the lactic acid monomer was oligomerized to low molecular weight hydroxyl‐terminated prepolymer; the molecular weight was then increased by chain extension using 1,6‐hexamethylene diisocyanate as the chain extender. The polymer was characterized using 1H NMR analysis, gel permeation chromatography, differential scanning calorimetry and Fourier transform infrared spectroscopy. The results showed that the obtained polymer had a Mn of 27 500 g mol−1 and a Mw of 116 900 g mol−1 after 40 min of chain extension at 180 °C. The glass transition temperature (Tg) of the low molecular weight prepolymer was 47.8 °C. After chain extension, Tg increased to 53.2 °C. The mechanical and rheological properties of the obtained polymer were also investigated.

CONCLUSION: The results suggest that high molecular weight PLA can be achieved by chain extension to meet conventional uses. Copyright © 2008 Society of Chemical Industry
Photophysical properties of fluorene‐based copolymers synthesized by connecting twisted biphenyl units with fluorene via para‐ and meta‐linkages
Authors: Lu Ping , Zhang Haiquan , Li Mao , Zheng Yan , Ma Yuguang , Chen Xinfang , Tamai Naoto
Published: June 2008

BACKGROUND: Wide bandgap semiconducting polymers are of great interest in the development of organic and polymeric emissive materials for display purposes since they can be used to generate light of all colors either by irradiation of luminescent dyes or by energy transfer to emissive dopants. The aim of the present work is to construct new fluorene‐based semiconducting polymers with a wide bandgap.

RESULTS: A novel polyfluorene derivative, poly[(9,9‐dihexyl‐2,7‐fluorene)‐alt‐(5,7‐dihydrodibenz[c,e]oxepin)], with a wide bandgap, was synthesized by connecting rigidly twisted biphenyl monomers with dihexylfluorene via para‐linkages and it was compared with poly[(9,9‐dihexyl‐2,7‐fluorene)‐alt‐(spirocyclohexane‐1,6′‐dibenzo[d,f][1,3]dioxepin)], which has meta‐linkages. Both polymers emit in the ultraviolet and blue regions. Electronic spectral absorption data and electrochemical measurements demonstrate that ca 40° torsion angle of the biphenyl units induces an increase in the HOMO–LUMO gap of 0.18 eV, and that meta‐linkage of the twisted segment in the polymer induces another increase of 0.24 eV compared to polydihexylfluorene.

CONCLUSION: The new twisted biphenyl compounds are efficient segments to tune the bandgaps of conjugated polymers. The two fluorene‐based copolymers have wide bandgaps and exhibit potential as host materials. Copyright © 2008 Society of Chemical Industry
Interfacial polymerization of an epoxy resin and carboxylic acids for the synthesis of microcapsules
Authors: Pascu Oana , Garcia‐Valls Ricard , Giamberini Marta
Published: June 2008

BACKGROUND: Microencapsulation technology promises new applications such as intelligent microstructures, phase change materials and self‐healing composites. Microcapsule synthesis and characterization have been researched extensively; however, the well‐known polymerization between epoxy resins and carboxylic acids has not been used to prepare microcapsules.

RESULTS: Microcapsules were prepared by interfacial polymerization of an oil‐in‐water emulsion which contained a commercial epoxy resin and multifunctional carboxylic acids. The microcapsules obtained were characterized using optical microscopy and scanning electron microscopy. Experiments performed at lower stirring rates led to larger microcapsules, in the range 100–400 µm, while higher stirring rates resulted in microcapsules in the range 10–50 µm.

CONCLUSIONS: Microcapsules can be prepared by interfacial polymerization of epoxy resins, an extensively studied and widely used class of polymers. By means of NMR characterization we gained insight into the mechanism of polymerization at the interface wherein products coming from the more hindered ring opening as well as from intermolecular transesterification are identified. The presence of a crosslinker affects the morphology of the external microcapsule surface. Copyright © 2008 Society of Chemical Industry
Demographics and professional practices of school psychologists: A comparison of NASP members and non–NASP school psychologists by telephone survey
Authors: Lewis Michael F. , Truscott Stephen D. , Volker Martin A.
Published: June 2008

A national telephone survey was conducted to examine potential differences between National Association of School Psychologists (NASP) members and non–NASP member school psychologists. Identified schools were contacted by telephone and the researchers asked to speak with the school psychologist. A sample of 124 practicing school psychologists was obtained. Overall, 57.3% (n = 71) of respondents were NASP members, and 42.7% (n = 53) were not. In most respects, current results were similar to NASP‐member‐only surveys. Current results suggest that previous studies overestimated the proportion of NASP members among school psychologists and may have underestimated the total number of school‐based practitioners. Significant differences between NASP members and nonmembers were found in ethnicity, national certification, professional organization membership, and use of Curriculum Based Measurement. Results are discussed in the context of previous national surveys. © 2008 Wiley Periodicals, Inc.
A survey investigating school psychologists' measurement of treatment integrity in school‐based interventions and their beliefs about its importance
Authors: Cochrane Wendy S. , Laux John M.
Published: June 2008

A survey of individuals holding the Nationally Certified School Psychologist (NCSP) credential was conducted via the Internet to gather information regarding their measurement of treatment integrity in school‐based interventions and their beliefs about its importance. A sample of 806 self‐selected professionals holding the NCSP credential provided data about the extent to which they measure treatment integrity and the methods they used to measure it when developing interventions via one‐to‐one and group/team consultation. Results showed that 97.6% agreed that measurement of treatment integrity was a key factor to consider and to include when evaluating interventions and when using intervention data for special education eligibility decisions. Few, however, reported regularly documenting it in one‐to‐one (only 11.3%) or group/team consultation (only 1.9%). Recommendations for how school psychologists and other school staff can increase their measurement of treatment integrity in school‐based interventions are offered. © 2008 Wiley Periodicals, Inc.
Vocational assessment of secondary students with disabilities and the school psychologist
Authors: Fives Christopher J.
Published: June 2008

Although much progress has been made in the identification and remediation of academic learning difficulties, less attention has been given to the career development of students with disabilities. Through their psychoeducational evaluations school psychologists are in an excellent position to provide useful information about the vocational functioning of these students. Some school practitioners may be hesitant to contribute fully to the vocational assessment process because they are unfamiliar with vocational behavior literature. In an effort to encourage greater involvement, the school psychologist's role as member of a career assessment team is discussed, and vocational theory and research concerning interest, ability, and personality characteristics are reviewed. Assessment and data integration strategies are offered. © 2008 Wiley Periodicals, Inc.
Assessing giftedness in children: Comparing the accuracy of three shortened measures of Intelligence to the Stanford–Binet Intelligence Scales, Fifth Edition
Authors: Newton Jocelyn H. , McIntosh David E. , Dixon Felicia , Williams Tasha , Youman Elizabeth
Published: June 2008

This study examined the accuracy of three shortened measures of intelligence: the Woodcock–Johnson Tests of Cognitive Ability, Third Edition Brief Intellectual Ability (WJ III COG BIA) score; the Stanford–Binet Intelligence Scale, Fifth Edition Abbreviated IQ (SB5 ABIQ); and the Kaufman Brief Intelligence Test IQ Composite (K‐BIT) in predicting giftedness as assessed by the SB5 Full Scale IQ score (SB5 FSIQ). Participants were 202 third grade students who were individually administered the SB5, WJ III, and K‐BIT. Four scores (SB5 ABIQ, K‐BIT, WJ III COG BIA, and SB5 FSIQ) were extracted. Correlational analyses revealed positive, significant relationships among the four scores. Discriminant function analyses, conducted to examine the accuracy of the three shortened measures of intelligence in predicting giftedness, revealed that overall, the WJ III score was the most accurate, and the K‐BIT score was the least accurate in identifying giftedness. © 2008 Wiley Periodicals, Inc.
General education teacher judgments of their low‐performing students' short‐term reading progress
Authors: Graney Suzanne Bamonto
Published: June 2008

This study investigated the accuracy of classroom teachers' judgments of the reading progress of their low‐performing students. Participants were 36 second grade teachers and students in their lowest reading groups (n = 150). Student progress was monitored weekly using reading‐curriculum‐based measurement (R‐CBM) procedures. After 6 weeks, teachers were asked to rate their students' progress. Expert judges later reviewed the teachers' R‐CBM graphs and rated the individual and group progress based on the graphs. Teacher ratings did not correlate with expert ratings or the R‐CBM slope estimates. Expert ratings correlated highly with slope estimates. Teachers' estimates of progress were significantly higher than expert judges' ratings, indicating that teachers may overestimate student progress. Implications for practice and future research are discussed. © 2008 Wiley Periodicals, Inc.
Associations between peer‐perceived status and aggression in young adolescents
Authors: Walcott Christy M. , Upton Amber , Bolen Larry M. , Brown Michael B.
Published: June 2008

Different functions within different forms of aggression were examined in relation to peer‐perceived preference and popularity among middle school students. Two hundred and three 7th grade students were nominated by a subset of their grade mates based on indices of likeability, popularity, and aggressiveness. Both linear and curvilinear associations were examined. Lower peer preference, but higher popularity, was associated with increased levels of all types of aggression, supporting the need to differentiate the relationship between aggression and these two facets of peer status. Relational aggression was associated with both low and high levels of popularity. Overt aggression was related to low peer preference and, to a lesser degree, high peer preference. It appears that what separates low‐ and high‐status students is not the presence of aggression per se, but how effectively their displays of aggression achieve their social goals. Findings are discussed in respect to social dominance theory, and implications for practice are considered. © 2008 Wiley Periodicals, Inc.
Child race and gender as moderators of the association between teacher–child relationships and school adjustment
Authors: Murray Christopher , Waas Gregory A. , Murray Kelly M.
Published: June 2008

This investigation examines teacher and child perceptions of teacher–child relationships and early school adjustment among children (N = 157) in low‐income urban schools. Consistent with prior research, findings indicated that teacher–child relationships were associated with early school adjustment; however, the strength of this association varied depending on perspective (i.e., teacher vs. student) and by student characteristic. Associations between predictor and criterion variables were stronger for within‐rater perspectives than across raters. Children's race moderated the association between teacher–child relationships and early school adjustment when examining data from the same source (i.e., teacher) and across raters (i.e., teacher and student). Gender did not moderate these associations. The implications of these findings for future research focused on understanding teacher–child relationships are discussed. © 2008 Wiley Periodicals, Inc.
A mechanistic dichotomy in concerted versus stepwise pathways in hydride and hydrogen transfer reactions of NADH analogues
Authors: Yuasa Junpei , Fukuzumi Shunichi
Published: June 2008

A mechanistic dichotomy of one‐step versus stepwise pathways in hydride and hydrogen transfer reactions of NADH analogues is discussed including the relation between two pathways: a continuous change versus a discontinuous change of the mechanism. Examples of stepwise electron–proton–electron transfer through a charge transfer (CT) complex in hydride transfer from NADH analogues to hydride acceptors are presented including the detection and the reactivity of the intermediate, that is, radical cations of NADH analogues. The relation between stepwise versus one‐step mechanisms of hydride and hydrogen transfer reaction of NADH analogues is also clarified by showing examples of the change of the mechanism including the borderline. Copyright © 2008 John Wiley & Sons, Ltd.
Nonclassical forces: Seemingly insignificant but a powerful tool to control macromolecular structures
Authors: Fujiki Michiya , Saxena Anubhav
Published: June 2008

Strong chemical forces such as covalent and ionic bonds are responsible for building discrete molecules, nature dwells on noncovalent forces weaker by three orders in magnitude, like the hydrophobic effect, hydrogen bonding, and van der Waals forces. Despite being weak, they possess the potential to drive spontaneous folding or unfolding of proteins and nucleic acids and the recognition between complimentary molecular surfaces. The power of these forces lies in the cooperativity with which they act, thereby generating a cumulative effect of many bonding interactions occurring together. Many ongoing research aims to translate the potential of these forces to the synthetic world to create desired structures with specific chemical functions. Achieving this offers unlimited opportunities for designing and synthesizing the most complex structures with specific applications. This highlight aims to reflect the critical role these noncovalent forces play in controlling macromolecular structures, which hold immense untapped potential for applications defying conventions, and briefly touches on the concept of homochirality in nature based on chiral and weak noncovalent interactions in synthetic nonpolar Si‐catenated polymers. It sheds some light on the discovery and characterization of Si/F‐C interactions in fluoroalkylated polysilanes in chemosensing of fluoride ions and nitroaromatics with a great sensitivity and selectivity. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4637–4650, 2008
Poly(glycerin 1,3‐dimethacrylate)‐based monolith with a bicontinuous structure tailored as HPLC column by photoinitiated in situ radical polymerization via viscoelastic phase separation
Authors: Aoki Hiroshi , Tanaka Nobuo , Kubo Takuya , Hosoya Ken
Published: June 2008

In this article we described our new approach to the polymer monolith with its morphology tailored for HPLC application to small solutes such as drug candidates. We prepared polymer monoliths based on glycerin 1,3‐dimethacrylate, GDMA with a bicontinuous structure by in situ photoinitiated free radical polymerization (UV irradiation at 365 nm). Our photopolymerization was carried out with a monodispese ultra high molecular weight polystyrene solution in chlorobenzene uniquely formulated as a porogen. The poly‐GDMA monoliths in bulk, rod and capillary thus prepared showed a bicontinuous network‐like structure featured by their fine skeletal thickness nearly in sub μm size. This monolithic structure was considered as a time‐evolved morphology frozen by UV‐irradiation via viscoelastic phase separation induced by the said porogenic polystyrene solution. According to our μHPLC measurement with acetophenone as a model solute, the UV prepared poly‐GDMA capillary demonstrated a much shaper elution profile affording higher column efficiency and permeability as compared with the thermally prepared capillary of the same bore size. Our investigation showed experimentally that poly‐GDMA monoliths with a well‐defined bicontinuous structure could be prepared reproducibly by photoinitiated radical polymerization via viscoelastic phase separation using the said unique porogen. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4651–4673, 2008
Synthesis and properties of triaryl diamine‐based hole‐transporting monomer and polymer
Authors: Tomkeviciene A. , Simokaitiene J. , Grazulevicius J. V. , Jankauskas V.
Published: June 2008

The synthesis and properties of hole‐transporting triaryl diamine‐based low‐molar‐mass compounds and polymer are reported. Comparative study on their thermal, optical, and photoelectrical properties is presented. All the synthesized compounds are found to form glasses with the glass transition temperatures in the range of 43–119 °C as characterized by differential scanning calorimetry. The ionization potentials of these compounds range from 5.31 to 5.40 eV as determined by electron photoemission method. Hole‐drift mobilities in the films of the synthesized compounds were estimated by the xerographic time‐of‐flight technique. They were found to reach 10−3 cm2/Vs at electric field of 6.4 × 105 V/cm. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4674–4680, 2008
Structure and activity transition of lysozyme on interacting with and releasing from polyelectrolyte with different hydrophobicity
Authors: Gao Gao , Yao Ping
Published: June 2008

The complexes of lysozyme with poly(isobutylene‐alt‐maleic acid) (PIMA) and poly(1‐tetradecene‐alt‐maleic acid) (PTMA) at pH 7.4 were characterized using static and dynamic light scattering. The electrostatic interaction of PIMA with lysozyme results in a loose complex structure, while the electrostatic and hydrophobic interactions between PTMA and lysozyme produce a compact complex structure. Lysozyme in PIMA complex particles remains a part of activity and structure analyzed by circular dichroism and substrate hydrolysis. However, lysozyme loses its tertiary structure and activity completely in PTMA complex. NaCl is more effective to dissociate PIMA–lysozyme complex by screening the electrostatic interaction, whereas GdHCl is more effective to dissociate PTMA–lysozyme complex by forming GdHCl–PTMA precipitates through extra hydrophobic interactions. In the release process, the denatured lysozyme molecules are able to avoid hydrophobic aggregation and fully regenerate their native structure and activity. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4681–4690, 2008
Preparation and microstructural analysis of poly(lactic‐alt‐glycolic acid)
Authors: Stayshich Ryan M. , Meyer Tara Y.
Published: June 2008

Alternating copolymers of glycolic (G) and lactic (L) acid were prepared by the condensation of the preformed dimers: LLG and LracG. By size exclusion chromatography (THF, PS standards), poly(LLG) exhibited a molecular weight (Mn) of 15.6 kg mol−1, with a weight average molecular weight (Mw) of 26.9 kg mol−1 and a PDI of 1.72. The Mn for poly(LracG) was 9.2 kg mol−1, with a Mw of 12.9 kg mol−1 and a PDI of 1.40. The NMR spectra of poly(LLG) were consistent with an isotactic microstructure. NMR spectra of the racemic poly(LracG) were consistent with an atactic structure. The methylene region of the 1H NMR spectrum showed a tetrad level of resolution of the nearby stereochemical relationships, for example, iii. Resonances for other groups in both the 1H and 13C NMR spectra gave only a triad level of resolution. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4704–4711, 2008
Self‐assembly of metallo‐supramolecular block copolymers in thin films
Authors: Fustin Charles‐André , Guillet Pierre , Misner Matthew J. , Russell Thomas P. , Schubert Ulrich S. , Gohy Jean‐François
Published: June 2008

The self‐assembly of a metallo‐supramolecular PS‐[Ru]‐PEO block copolymer, where ‐[Ru]‐ is a bis‐2,2′:6′,2″‐terpyridine‐ruthenium(II) complex, in thin films was investigated. Metallo‐supramolecular copolymers exhibit a different behavior as compared to their covalent counterparts. The presence of the charged complex at the junction of the two blocks has a strong impact on the self‐assembly, effecting the orientation of the cylinders and ordering process. Poly(ethylene oxide) cylinders oriented normal to the film surface are obtained directly regardless of the experimental conditions over a wide range of thicknesses. Exposure to polar solvent vapors can be used to improve the lateral ordering of the cylindrical microdomains. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4719–4724, 2008
Controlled cationic polymerization of cyclopentadiene with B(C6F5)3 as a coinitiator in the presence of water
Authors: Kostjuk Sergei V. , Radchenko Alexei V. , Ganachaud François
Published: June 2008

The controlled cationic polymerization of cyclopentadiene (CPD) at 20 °C using 1‐(4‐methoxyphenyl)ethanol (1)/B(C6F5)3 initiating system in the presence of fairly large amount of water is reported. The number–average molecular weights of the obtained polymers increased in direct proportion to monomer conversion in agreement with calculated values and were inversely proportional to initiator concentration, while the molecular weight distribution slightly broadened during the polymerization (Mw/Mn ∼ 1.15–1.60). 1H NMR analyses confirmed that the polymerization proceeds via reversible activation of the COH bond derived from the initiator to generate the growing cationic species, although some loss of hydroxyl functionality happened in the course of the polymerization. It was also shown that the enchainment in cationic polymerization of CPD was affected by the nature of the solvent(s): for instance, polymers with high regioselectivity ([1,4] up to 70%) were obtained in acetonitrile, whereas lower values (around 60%) were found in CH2Cl2/CH3CN mixtures. Aqueous suspension polymerization of CPD using the same initiating system was successfully performed and allowed to synthesize primarily hydroxyl‐terminated oligomers (Fn = 0.8–0.9) with Mn ≤ 1000 g mol−1 and broad MWD (Mw/Mn ∼ 2.2). © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4734–4747, 2008
Local forms of molecular mobility in copolymethacrylates containing side‐chain nonlinear optical chromophores
Authors: Nikonorova Natalia A. , Smirnov Nikolai N. , Diaz‐Calleja Ricardo , Yakimansky Alexander V.
Published: June 2008

Local forms of molecular mobility of comb‐like random copolymethacrylates, containing side‐chain nonlinear optical chromophores and amyl‐ or octafluoroamyl‐groups, are studied. In the glassy state, two relaxation processes are found, which are due to reorientation of terminal polar groups (γ2‐process) and rotation of chromophore groups about their long axes (β‐process). For octafluoroamyl‐containing copolymers, the γ2‐process is superposition of the two molecular motions due to reorientation of terminal chromophore groups and CF2H groups. The intensity and relaxation times in the range of the γ2‐process depend on the chemical structure and concentration of chromophores in a copolymer. For the β‐process, the molecular mobility weakly depends on the chromophore structure, being mainly determined by the relative lengths of the rigid chromophore and flexible side chains. On the global spectrum of depolarization current it was observed the γ1‐process due to reorientation of (CH2)n spacers between chromophore groups and copolymer backbone. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1488–1496, 2008
Structural and conformational changes during thermally‐induced crystallization of poly(trimethylene terephthalate) by infrared spectroscopy
Authors: Yamen Mustafa , Ozkaya Sabahattin , Vasanthan Nadarajah
Published: June 2008

Conformational changes occurring during thermally‐induced crystallization of poly(trimethylene terephthalate) (PTT) by annealing have been studied using density measurement, differential scanning calorimetry (DSC), and mid‐infrared spectroscopy (MIR). Infrared spectra of amorphous and semicrystalline PTT were obtained, and digital subtraction of the amorphous contribution from the semicrystalline PTT spectra provided characteristic MIR spectra of amorphous and crystalline PTT. The normalized absorbance of 1577, 1173, and 976 cm−1 were plotted against the crystallinity showing that these bands can be used unambiguously to represent the trans conformation while the band at 1358 cm−1 can be used to represent gauche conformation of methylene segment. The presence of a weak band at 1358 cm−1 in the amorphous spectrum suggested that a small amount of gauche conformation is present in the amorphous phase. Infrared spectroscopy has been used for the first time as a means to estimate the trans and gauche conformations of methylene segments in PTT as a function of Ta. The amount of gauche conformation was plotted against the crystalline fraction and the extrapolation of this plot to zero crystalline fraction provided a value of 0.07, suggested that the pure amorphous phase consist of ∼ 7% gauche conformation. It was found that the amorphous and crystalline gauche conformation increases at the expense of amorphous trans conformation during thermally induced crystallization of PTT. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1497–1504, 2008
The effect of interfacial viscosity on the droplet dynamics under flow field
Authors: Yu Wei , Zhou Chixing
Published: June 2008

The effects of interfacial viscosity on the droplet dynamics in simple shear flow and planar hyperbolic flow are investigated by numerical simulation with diffuse interface model. The change of interfacial viscosity results in an apparent slip of interfacial velocity. Interfacial viscosity has been found to have different influence on droplet deformation and coalescence. Smaller interfacial viscosity can stabilize droplet shape in flow field, while larger interfacial viscosity will increase droplet deformation, or even make droplet breakup faster. Different behavior is found in droplet coalescence, where smaller interfacial viscosity speeds up film drainage and droplet coalescence, but larger interfacial viscosity postpones the film drainage process. This is due to the change of film shape from flat‐like for smaller interfacial viscosity to dimple‐like for larger interfacial viscosity. The film drainage time still scales as Ca0 at smaller capillary number (Ca), and Ca1.5 at higher capillary number when the interfacial viscosity changes. The interfacial viscosity only affects the transition between these limiting scaling relationships. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1505–1514, 2008
Self‐assembly in solutions of block and random copolymers during metal nanoparticle formation
Authors: Meristoudi A. , Pispas S. , Vainos N.
Published: June 2008

The self‐assembly behavior of poly(isoprene‐b‐acrylic acid) and poly(styrene‐b‐2‐vinylpyridine) amphiphilic block copolymers, as well as a poly(styrene‐r‐2‐vinylpyridine) amphiphilic random copolymer was investigated in slightly selective organic solvents (tetrahydrofuran and toluene) in the presence of Ag and Au ions and subsequently Ag, Au metal nanoparticles, by means of dynamic light scattering. In the range of concentrations studied the copolymers exist in the form of micelles with cores composed of acrylic acid and 2‐vinylpyridine segments in equilibrium with unimers. The addition of metal ions and their subsequent transformation to metal nanoparticles shifts the equilibrium in favor of the micelles. The concentration of the inorganic components has also a considerable effect on the size of the polymeric aggregates. A similar behavior is observed for the random copolymer. Attenuated total reflectance Fourier transform infrared spectroscopy (ATR‐FTIR), UV‐visible spectroscopy, and transmission electron microscopy (TEM) give valuable additional information on the nature of the interactions between the polymeric and inorganic components, as well as on the characteristics of the metal nanoparticles and the hybrid micelles formed in each case. The presented results have a direct relation to the synthesis of metal nanoparticles under confinement by utilization of copolymer nanoreactors and appropriate solution conditions. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1515–1524, 2008
Fluorination of Polymers by Means of He/CF4‐Fed Atmospheric Pressure Glow Dielectric Barrier Discharges
Authors: Fanelli Fiorenza , Fracassi Francesco , d'Agostino Riccardo
Published: June 2008

He/CF4‐fed GDBDs were used to fluorinate PP and PET. The effect of various process parameters on the polymers surface composition and morphology, as well as on their wettability was investigated inside the GDBD existence domain. An extensive surface fluorination of treated polymers due to the grafting of F atoms and CFx radicals was observed. The increase of CF4 concentration in the feed, of treatment duration, and of excitation frequency resulted in an increase of the fluorination degree corresponding to F/C ratios as high as 1.18 and 1.22 for PP and PET, respectively. The emission spectra of GDBDs fed by helium in mixture with CF4, CHF3, C2F6 and C3F8 were compared.

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Characterization of Microwave Plasma Torch for Decontamination
Authors: Shimizu Tetsuji , Steffes Bernd , Pompl René , Jamitzky Ferdinand , Bunk Wolfram , Ramrath Katrin , Georgi Matthias , Stolz Wilhelm , Schmidt Hans‐Ulrich , Urayama Takuya , Fujii Shuitsu , Morfill Gregor Eugen
Published: June 2008

An atmospheric low‐temperature microwave plasma torch has been developed and applied to disinfection. The size of the plasma output is relatively large (35 mm in diameter). Ar gas at a flow rate of 2.2 slm and 85 W microwave power are used. Plasma discharges are produced between the tip of each electrode and the inner surface of the cylinder. When an Escherichia coli culture is placed for 2 min at 20 mm below the torch, where the gas temperature is sufficiently cool, the bacteria are almost completely killed within a 40 mm diameter circle. The UV radiation is one of the major players responsible for killing bacteria, others being the reactive species and the charged particles.

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Plasma Process. Polym. 4/2008
Authors: Nozaki Tomohiro , Okazaki Ken
Published: June 2008

Cover: High‐purity, vertically‐aligned, single‐walled carbon nanotubes (SWCNTs) are synthesized preferentially in the atmospheric pressure non‐thermal discharge at 4 µm · min−1. The SWCNTs transform into multi‐walled carbon nanotubes (MWCNTs) and carbon nanofibers (CNFs) as the total pressure decreases in the plasma‐enhanced chemical vapor deposition regime. Further details can be found in the article by T. Nozaki* and K. Okazaki on page 300. Figures reprinted from: Ch. Taschner et al., Surf. Coat. Technol. 2003, 174, 81 with permission from Elsevier.
Early stages of β2‐microglobulin aggregation and the inhibiting action of αB‐crystallin
Authors: Pullara Filippo , Emanuele Antonio
Published: June 2008

Static and dynamic light scattering experiments on extremely clean (nanofiltered) samples of the well‐known amyloidogenic protein β2‐microglobulin (R3Aβ2m and WTβ2m) evidence the self‐assembly of early aggregates showing unexpected features. Further, we find that αB‐crystallin effectively inhibits aggregation of β2m in a far less than stoichiometric proportion, from 1:60 αB‐crystallin monomer to β2m monomer ratio, down to at least a 1:2 × 103 αB‐crystallin oligomerto β2m monomer ratio. Therefore, inhibition of the early stage of β2m aggregation by αB‐crystallin does not necessarily require a mechanicistic chaperon‐like action implying one‐to‐one binding. This highlights the role of the free energy landscape of the system and of related modifications of solute–solvent thermodynamics caused by co‐solutes, in agreement with recent work from our and other laboratories. Proteins 2008. © 2008 Wiley‐Liss, Inc.
Characterization of a sHsp of Schizosaccharomyces pombe, SpHsp15.8, and the implication of its functional mechanism by comparison with another sHsp, SpHsp16.0
Authors: Sugino Chika , Hirose Maya , Tohda Hideki , Yoshinari Yukiko , Abe Tetsuya , Giga‐Hama Yuko , Iizuka Ryo , Shimizu Masafumi , Kidokoro Shun‐ichi , Ishii Noriyuki , Yohda Masafumi
Published: June 2008

There exist two small heat shock proteins (sHsps) in the fission yeast, Schizosaccharomyces pombe (S. pombe), whose expressions are highly induced by heat stress. We have previously expressed, purified, and characterized one of the sHsps, SpHsp16.0. In this study, we examined the other sHsp, SpHsp15.8. It suppressed the thermal aggregation of citrate synthase (CS) from porcine heart and dithiothreitol‐induced aggregation of insulin from bovine pancreas with very high efficiency. Almost one SpHsp15.8 subunit was sufficient to protect one protein molecule from aggregation. Like SpHsp16.0, SpHsp15.8 dissociated into small oligomers and then interacted with denatured substrate proteins. SpHsp16.0 exhibited a clear enthalpy change for denaturation occurring over 60°C in differential scanning calorimetry (DSC). However, we could not observe any significant enthalpy change in the DSC of SpHsp15.8. The difference is likely to be caused by the adhesive characteristics of SpHsp15.8. The oligomer dissociation of SpHsp15.8 and SpHsp16.0 and their interactions with denatured substrate proteins were studied by fluorescence polarization analysis (FPA). Both sHsps exhibited a temperature‐dependent decrease of fluorescence polarization, which correlates with the dissociation of large oligomers to small oligomers. The dissociation of the SpHsp15.8 oligomer began at about 35°C and proceeded gradually. On the contrary, the SpHsp16.0 oligomer was stable up to ∼45°C, but then dissociated into small oligomers abruptly at this temperature. Interestingly, SpHsp16.0 is likely to interact with denatured CS in the dissociated state, while SpHsp15.8 is likely to interact with CS in a large complex. These results suggest that S. pombe utilizes two sHsps that function in different manners, probably to cope with a wide range of temperatures and various denatured proteins. Proteins 2009. © 2008 Wiley‐Liss, Inc.
The unintended effects of interactive objects and labels in the science museum
Authors: Atkins Leslie J. , Velez Lisanne , Goudy David , Dunbar Kevin N.
Published: June 2008

What effects do different setups of museum exhibits have on visitors' conversations and interactions? The study reported here is an investigation of the role that labels and associated materials play in visitors' conversations and interactions at a heat camera exhibit. After we introduced a label to help visitors explore the insulating properties of clothing, we found a dramatic shift in the kinds of activities and participation structures of visitors. Not only were visitors, as expected, discussing why clothing was warm, but they were doing so in a fashion more consistent with formal education than the typically more collaborative conversations seen in informal learning environments. Overall, our analyses reveal that labels and activities presented serve to frame both the activities that visitors engage in and the types of conversations that ensue and that this has deep influences on visitors' experiences at the exhibit. © 2008 Wiley Periodicals, Inc.Sci Ed93:161–184, 2009
Impact of a multiyear professional development intervention on science achievement of culturally and linguistically diverse elementary students
Authors: Lee Okhee , Deaktor Rachael , Enders Craig , Lambert Julie
Published: June 2008

This study examined the impact of the 3‐year implementation of a professional development intervention on science achievement of culturally and linguistically diverse elementary students. Teachers were provided with instructional units and workshops that were designed to improve teaching practices and foster positive beliefs about science and literacy with diverse student groups. The study involved third, fourth, and fifth grade students at six elementary schools in a large urban school district during the 2001 through 2004 school years. Significance tests of mean scores between pre‐ and posttests indicated statistically significant increases each year on all measures of science at all three grade levels. Achievement gaps among demographic subgroups sometimes narrowed among fourth grade students and remained consistent among third and fifth grade students. Item‐by‐item comparisons with NAEP and TIMSS samples indicated overall positive performance by students at the end of each school year. The consistent patterns of positive outcomes indicate the effectiveness of our intervention in producing achievement gains at all three grade levels while also reducing achievement gaps among demographic subgroups at the fourth grade. © 2008 Wiley Periodicals, Inc. J Res Sci Teach 45: 726–747, 2008
A novel QoS‐aware MAC protocol for voice services over IEEE 802.11‐based WLANs
Authors: Qaimkhani Irshad A. , Hossain Ekram
Published: June 2008

With the pervasive growth in the popularity of IEEE 802.11‐based wireless local area networks (WLANs) worldwide, the demand to support delay‐sensitive services such as voice has increased very rapidly. This paper provides a comprehensive survey on the medium access control (MAC) architectures and quality of service (QoS) provisioning issues for WLANs. The major challenges in providing QoS to voice services through WLAN MAC protocols are outlined and the solution approaches proposed in the literature are reviewed. To this end, a novel QoS‐aware wireless MAC protocol, called hybrid contention‐free access (H‐CFA) protocol and a call admission control technique, called traffic stream admission control (TS‐AC) algorithm, are presented. The H‐CFA protocol is based on a novel idea that combines two contention‐free wireless medium access approaches, that is, round‐robin polling and time‐division multiple access (TDMA)‐like time slot assignment, and it increases the capacity of WLANs through efficient silence suppression. The TS‐AC algorithm ensures efficient admission control for consistent delay‐bound guarantees and further maximizes the capacity through exploiting the voice characteristic that it can tolerate some level of inconsecutive packet loss. The benefits of the proposed schemes are demonstrated in the simulations results. Copyright © 2008 John Wiley & Sons, Ltd.
On the characteristics and compatibility equations for the UCM model fluid
Authors: Gerritsma M.I. , Phillips T.N.
Published: June 2008

The quasilinear system of partial differential equations governing the flow of a UCM fluid is known to be of mixed elliptic‐hyperbolic type. The compatibility equations associated with the hyperbolic part of the system are derived in this paper. There are two characteristic variables that are transported along the characteristics. These are both associated with the conditional well‐posedness of the system. The compatibility equations in this case are derived from the constitutive equation alone. There are two additional characteristics that are always present for unsteady inertial flow and which may be present for steady inertial flow. The compatibility equations associated with these characteristics involve a coupling between the momentum and constitutive equations. At an inflow boundary, it is shown that all stress components can be prescribed, despite the fact that there are only two characteristic variables that enter the domain along the streamlines. The remaining stress component is provided by fixing the incoming elastic shear waves.
Where do fractional derivatives in stress strain relations come from? A structural approach
Authors: Pfitzenreiter T.
Published: June 2008

Experiments have shown that the material behaviour of plastics, especially the viscous damping, can be described in an excellent way by the introduction of fractional derivatives in stress strain relations. From the coincidence between model and experiment the question of a deeper physical explanation arises. In this paper we will construct a structural model of polymers which explains why fractional derivatives in damping terms of stress strain relations arise.
Quasistatic inflation processes within rigid tubes
Authors: Steigenberger J. , Abeszer H.
Published: June 2008

In this paper the authors consider mechanical devices of rotational symmetry that can be seen as segments of an artificial worm or as a balloon for angioplasty. Continuing former work [7] the segment is now placed within a cylindrical or constricted rigid tube that will be touched or pressed during inflation of the segment. Both the segment's shape and the forces of contact are investigated. The main mathematical tool is the Principle of Minimal Potential Energy – handled as an optimal control problem with state constraint. The necessary optimality conditions are carefully analyzed and simulation results for characteristic examples are presented. The treatment of the problem is primarily mathematical but aiming at application.
Essentially nonlinear vibration absorber in a parametrically excited system
Authors: Shiroky I.B. , Gendelman O.V.
Published: June 2008

Dynamics and performance of a strongly nonlinear attachment in a parametrically excited system are examined. Dynamic behavior of the system is analyzed and the conditions for the various regimes of oscillation are revealed. Addition of the essentially nonlinear attachment to linear parametrically excited system brings about a family of responses with bounded amplitude and thus prevents the exponential divergence typical for the parametric resonance. Regimes and conditions, optimal for the vibration absorption, are described.