bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis and characterization of new poly(aryl ether)s with isolated fluorophores
Authors: Hwang Shiao‐Wen , Chen Shinn‐Horng , Chen Yun 
Published: October 2002

AbstractFour novel poly(aryl ether)s (P1–P4) consisting of alternate isolated electron‐transporting (3,3″′‐bis‐trifluoromethyl‐p‐quaterphenyl for P1, P3 or 3,3″′‐dicyano‐p‐quaterphenyl for P2, P4) and hole‐transporting fluorophores [N‐(2‐ethylhexyl)‐3,6‐bis(styryl)carbazole for P1, P2 or 9,9‐dihexyl‐2,7‐bis(styryl)fluorene for P3, P4] were synthesized and characterized. These poly(aryl ether)s can be dissolved in organic solvents and exhibited good thermal stability with 5% weight‐loss temperature above 500 °C in nitrogen atmosphere. The photoluminescent (PL) spectra of the films of these polymers showed maximum peaks at around 442–452 nm. The PL spectral results revealed that the emission of polymers was dominated by the fluorophores with longer emissive wavelength via the energy transfer from p‐quaterphenyl to 3,6‐bis(styryl)carbazole or 2,7‐bis(styryl)fluorene segments. Therefore, the p‐quaterphenyl segments function only as the electron‐transporting/hole‐blocking units in these polymers, and the other segments are the emissive centers and hole‐transporting units. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital energy levels of these polymers were measured by cyclic voltammetry. The electron‐donating nitrogen atom on carbazole resulted in the higher HOMO energy levels of P1 and P2 than those of P3 and P4. The single‐layer light‐emitting diodes (LED) of Al/poly(aryl ether)s (P1–P4)/ITO glass were fabricated. P1, P2, and P4 revealed blue electroluminescence, but P3 emitted yellow light as a result of the excimer emission. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2215–2224, 2002
Peroxide‐mediated crosslinking of poly(ethylene oxide)
Authors: Emami Shahriar H. , Salovey Ronald , Hogen‐Esch Thieo E. 
Published: October 2002

AbstractThe crosslinking of poly(ethylene oxide) (PEO) with a difunctional peroxide such as 2,5‐bis(tert‐butylperoxy)‐2,5‐dimethylhexane (Luperox 101) may proceed through at least two different pathways. Thus, the thermally formed alkoxy radicals abstract hydrogen from PEO, and the resulting PEO radicals may combine or react with the peroxide radicals to give ether or acetal crosslinks. However, these reactions also produce noncrosslinking acetals and vinyl ethers. The acetals may react further with peroxy or other radicals and yield orthoesters and ketene acetals. These and similar groups, in the presence of dilute acids, are susceptible to acid hydrolysis, leading to the disintegration of the gels. The gels, upon swelling in dilute acids, undergo a slow degradation process that is not observed for unmodified PEO. The acid hydrolysis is confirmed by a combination of size exclusion chromatography and dynamic mechanical analysis. IR analysis shows the presence of hydroxyl end groups and the presence of carboxylates rather than aldehyde groups, this is consistent with orthoesters and ketene acetal intermediates. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3021–3026, 2002
Radical polymerization behavior of ethyl ortho‐(4‐phenyl‐1,3‐dioxolan‐2‐yl)phenyl fumarate
Authors: Seno Makiko , Sunagawa Seigo , Sato Tsuneyuki 
Published: October 2002

AbstractThe polymerization of ethyl ortho‐(4‐phenyl‐1,3‐dioxolan‐2‐yl)phenyl fumarate (EPDPF) with dimethyl 2,2′‐azobisisobutyrate (MAIB) was kinetically investigated in benzene. The polymerization rate (Rp) at 60 °C was presented by Rp = k[MAIB]1.1[EPDPF]0.8. The number‐average molecular weight of poly(EPDPF) was in the range of 2500–3500. Analysis of 1H and 13C NMR spectra of the resulting polymers suggested that the radical polymerization of EPDPF proceeds in a complicated manner involving vinyl addition, intramolecular hydrogen abstraction, and ring opening of the cyclic acetal. The polymerization system involved electron spin resonance (ESR)‐observable poly(EPDPF) radicals under the practical polymerization conditions. ESR‐determined apparent rate constants (2.0–8.5 L/mol s) of propagation increased with increasing initiator concentration and decreasing monomer concentration. The apparent rate constants (0.68–6.6 × l06 L/mol s) of termination decreased with the monomer concentration and slightly increased with the initiator concentration. The activation energies of initiation (Ei), propagation (Ep), and termination (Et) were calculated as Ei = 158, Ep = 41, and Et = 30 kJ/mol, respectively. Radical copolymerization of EPDPF with styrene was also examined at 70 °C in benzene. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2945–2955, 2002
Phthalide as an activating group for the synthesis of poly(aryl ether phthalide)s by nucleophilic aromatic substitution
Authors: Knauss Daniel M. , Bender Jack T. 
Published: October 2002

AbstractThe phthalide ring was examined as an activating group for nucleophilic aromatic substitution. The proposed mechanism by which activation occurs is through a ring opening of the phthalide ring to form a Meisenheimer‐like σ complex. 3,3‐Bis(4‐fluorophenyl)phthalide was synthesized and examined under different reaction conditions to determine its suitability for polymer formation. Semiempirical calculations at the PM3 level suggested that 3,3‐bis(4‐fluorophenyl)phthalide is only moderately activated, whereas 1H, 13C, and 19F NMR spectroscopy suggested that the monomer was not sufficiently activated for nucleophilic aromatic substitution. However, low‐molecular‐weight polymers (number‐average molecular weight < 7000 g/mol) were produced from bisphenol A, hydroquinone, and phenolphthalein. The polymers were characterized by gel permeation chromatography, matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry, NMR spectroscopy, and differential scanning calorimetry. The polymers displayed relatively high glass‐transition temperatures. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3046–3054, 2002
Synthesis and characterization of a fluorinated polyanhydride
Authors: Kaur Sarjit , Doerr Allison , Thompson Adrienne , Dalby Charlie 
Published: October 2002

AbstractA fluorinated aromatic polyanhydride (B) was synthesized from the melt condensation of mixed anhydrides of 4,4′‐(hexafluoroisopropylidene)bis benzoic acid. Although the mixed anhydride from acetic anhydride yielded only a mixture of oligomers (weight‐average molecular weight < 2000), higher weight‐average molecular weight materials in the range of 15,000–18,000 were obtained with trifluoroacetic anhydride. Polymer B was soluble in chloroform and tetrahydrofuran, had a relatively high glass‐transition temperature of 176 °C with no melting point detected to 310 °C, and showed excellent thermal stability (5% weight loss observed at 380 °C by thermogravimetric analysis). The hydrolytic degradation of the fluorinated polyanhydride in a 0.1 M phosphate buffer of pH 7.4 at 37 °C was initially zero‐order, with 35% degradation occurring in 10 days. Loss of film integrity following that led to accelerated degradation, and almost complete dissolution was observed by the 16th day. The stability of the fluorinated polyanhydride in the solid state and in the solvent tetrahydrofuran was also evaluated. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3027–3036, 2002
Poly(acrylamide) grafts on spherical bead polymers for extremely selective removal of mercuric ions from aqueous solutions
Authors: Sonmez H. Bulbul , Senkal B. F. , Bicak N. 
Published: October 2002

AbstractPoly(acrylamide) grafted from solid polymer particles provides a simple solution for extremely selective removal of mercuric ions from aqueous solutions. The grafting of polyacrylamide has been performed, in high yields (164%), by redox initiation from iminoacetic acid groups created on crosslinked spherical beads (210–420 μm) of glycidyl methacrylate/methyl methacrylate/ethylene glycol dimethacrylate terpolymer. In the grafting, homopolymer formation has been reduced greatly (22%) by the treatment of the bead polymer with ceric ammonium nitrate before the addition of acrylamide monomer. The mobility of the graft chains provides nearly homogeneous reaction conditions and rapid mercury binding ability, as for low molecular weight amides [mercury sorption by a 0.105‐g polymer sample from 105 mL of a 7.74 × 10−4 mol L−1 (∼155 ppm) Hg(II) solution shows first‐order kinetics with respect to the Hg(II) concentration, k = 1.1 × 10−3 s−1]. The mercury sorption capacity under nonbuffered conditions is around 3.6 mmol g−1 (i.e., 720 g of mercury/kg) and mostly occurs with the formation of diamido–mercury linkages, which result in the crosslinking of polyacrylamide brushes outside the spherical beads. The crosslinks can be destroyed by treatment with hot acetic acid, without hydrolysis of the amide groups. This process allows a complete elution of the mercury as mercury acetate, and the overall result is reversible crosslinking of the outer shell by mercuric ions. The material presented is efficient in the removal of mercury at concentrations measured in parts per million, and the mercury sorption is extremely selective over some foreign ions, such as Fe(III), Cd(II), Zn(II), and Pb(II). © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3068–3078, 2002
Scratching behavior of elastomeric poly(dimethylsiloxane) coatings
Authors: Zhang S. L. , Tsou A. H. , Li J. C. M. 
Published: October 2002

AbstractScratch testing has been performed on elastomeric poly(dimethylsiloxane) (PDMS) coatings on stainless steel with a spherical indenter. The friction coefficient (horizontal‐to‐normal force ratio) during scratching decreases with increasing normal load. This result can be explained by assuming that during scratching the contact area is determined by elastic deformation and the horizontal force is proportional to the contact area. With increasing driving speed, the friction coefficient increases, but the rate of increase decreases; this suggests that the scratching of the PDMS coating is a rate process and that the viscoelastic property of the coating influences its frictional behavior. Below a critical normal load, which increases with the coating thickness, the PDMS coating recovers elastically after being scratched so that there are no scratch marks left behind. Above the critical normal load, the coating is damaged by a combination of delamination at the coating/substrate interface and through‐thickness cracking. When the coating is damaged, there is an increase in the friction coefficient, and the friction force displays significant fluctuations. Furthermore, the critical normal load increases with the driving speed; this implies that time is needed to nucleate damage. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1530–1537, 2002
Luminescence of monolayer thin films of the fully conjugated rigid‐rod polymer poly(p‐phenylenebenzobisthiazole)
Authors: Bai S. J. , Wu C. C. , Tu L. W. , Lee K. H. 
Published: October 2002

AbstractPoly(p‐phenylenebenzobisthiazole) (PBT) is a heterocyclic, aromatic rigid‐rod polymer with a fully conjugated backbone and excellent dimensional, thermo‐oxidative, and solvent stabilities. A PBT polymer with an intrinsic viscosity of 18.0 dL/g was dissolved in methanesulfonic acid or Lewis acid. The PBT solution was spin‐coated and doctor‐bladed for freestanding films or onto an indium tin oxide (ITO) substrate. The acid was removed via coagulation. Scanning electron microscopy determined that the resultant film thicknesses were about 340 and 60 nm for PBT freestanding films and films on the ITO substrate, respectively. X‐ray scattering demonstrated that the freestanding films were in‐plane isotropic without long‐range order. The freestanding films were excited with a He‐Cd laser at 325 nm for photoluminescence (PL) response. PL spectra showed a distinct intensity maximum at 580 nm, regardless of the film‐forming conditions. After the films cooled to 67 K, the PL maximum shifted to 566 nm with enhanced intensity. Aluminum was evaporated onto the monolayer PBT thin film on the ITO substrate as an electron injector for electroluminescence (EL) response. Diodic electric behavior was observed for all monolayer PBT EL devices for the first time. A threshold voltage as low as 4 V was achieved for the monolayer EL devices. In addition, PBT EL spectra were tunable, with a maximum intensity at 570 nm at a bias voltage of 4.5 V changing to 496 nm at 7.5 V (i.e., a blueshift) with greatly increased intensity. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1760–1767, 2002
Miscibility and hydrogen‐bonding interactions in blends of carbon dioxide/epoxy propane copolymer with poly(p‐vinylphenol)
Authors: Zhang Zhihao , Mo Zhishen , Zhang Hongfang , Zhang Ying , Na Tianhai , An Yuxian , Wang Xianhong , Zhao Xiaojiang 
Published: October 2002

AbstractThe miscibility and hydrogen‐bonding interactions of carbon dioxide and epoxy propane copolymer to poly(propylene carbonate) (PPC)/poly(p‐vinylphenol) (PVPh) blends were investigated with differential scanning calorimetry (DSC), Fourier transform infrared (FTIR) spectroscopy and X‐ray photoelectron spectroscopy (XPS). The single glass‐transition temperature for each composition showed miscibility over the entire composition range. FTIR indicates the presence of strong hydrogen‐bonding interassociation between the hydroxyl groups of PVPh and the oxygen functional groups of PPC as a function of composition and temperature. XPS results testify to intermolecular hydrogen‐bonding interactions between the oxygen atoms of carbon–oxygen single bonds and carbon–oxygen double bonds in carbonate groups of PPC and the hydroxyl groups of PVPh by the shift of C1s peaks and the evolution of three novel O1s peaks in the blends, which supports the suggestion from FTIR analyses. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1957–1964, 2002
Toughening of a propylene‐b‐(ethylene‐co‐propylene) copolymer by a plastomer
Authors: Arranz‐Andrés Javier , Benavente Rosario , Peña Begoña , Pérez Ernesto , Cerrada María L. 
Published: October 2002

AbstractSeveral blends, covering the entire range of compositions, of a metallocenic ethylene‐1‐octene copolymer (CEO) with a multiphasic block copolymer, propylene‐b‐(ethylene‐co‐propylene) (CPE) [composed of semicrystalline isotactic polypropylene (iPP) and amorphous ethylene‐co‐propylene segments], have been prepared and analyzed by differential scanning calorimetry, X‐ray diffraction, optical microscopy, stress‐strain and microhardness measurements, and dynamic mechanical thermal analysis. The results show that for high CEO contents, the crystallization of the iPP component is inhibited and slowed down in such a way that it crystallizes at much lower temperatures, simultaneously with the crystallization of the CEO crystals. The mechanical results suggest very clearly the toughening effect of CEO as its content increases in the blends, although it is accompanied by a decrease in stiffness. The analysis of the viscoelastic relaxations displays, first, the glass transition of the amorphous blocks of CPE appearing at around 223 K, which is responsible for the initial toughening of the plain CPE copolymer in relation to iPP homopolymer. Moreover, the additional toughening due to the addition of CEO in the blends is explained by the presence of the β relaxation of CEO that appears at about 223 K. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1869–1880, 2002
Dornase alfa in early cystic fibrosis lung disease
Authors: Robinson Philip J. 
Published: October 2002

AbstractLeukocytes that infiltrate cystic fibrosis (CF) sputum as a result of infection have long been known to liberate large amounts of DNA, which increases sputum viscosity and promotes the cycle of chronic lung infection and inflammation that ultimately leads to respiratory failure and death. It was only recently recognized that this vicious cycle begins in infancy, and that archi‐tectural damage to CF lungs is detectable even in children with normal pulmonary function tests.Dornase alfa cleaves DNA and improves sputum viscosity in CF. Although its efficacy in reducing the risk of acute infectious exacerbations and improving pulmonary function has been recognized for a decade, there is growing interest in its potential for long‐term benefit in young patients with mild lung function abnormalities.The Pulmozyme Early Intervention Trial (PEIT) study demonstrated that dornase alfa reduces the risk of pulmonary exacerbations requiring i.v. antibiotic treatment by 34% and improves forced expiratory flow at 25–75% of forced vital capacity (FEF25–75), mid‐expiratory flow at 50% of forced vital capacity (MEF), and forced expired volume in 1 sec (FEV1) over a 2‐year period in CF patients with almost normal lung function. A post hoc subgroup analysis suggests that the magnitude of pulmonary function test (PFT) changes may vary, depending on the initial degree of lung function impairment, but that the reduction in exacerbations appears to be a consistent benefit.These results support the current view that CF patients benefit from intervention early in the course of their lung disease. Pediatr Pulmonol. 2002; 34:237–241. © 2002 Wiley‐Liss, Inc.
Evidence‐based medicine in cystic fibrosis: How should practice change?
Authors: Conway Steven P. 
Published: October 2002

AbstractThis critical review of current practice and research in some aspects of cystic fibrosis (CF) concludes that, despite recent success in prolonging life expectancy, there is still room for improvement in terms of earlier diagnosis and earlier intervention in some of its complications. Specifically, the body of evidence implies that neonatal diagnosis; early attention to nutrition, staphylococcal and pseudomonal infection, and diabetes mellitus; and early treatment with dornase alfa can all be expected to improve patients' quality and quantity of life. Pediatr Pulmonol. 2002; 34:242–247. © 2002 Wiley‐Liss, Inc.
Prevalence of asthma and asthma‐like symptoms in inner‐city elementary schoolchildren
Authors: Webber Mayris P. , Carpiniello Kelly E. , Oruwariye Tosan , Appel David K. 
Published: October 2002

AbstractAmerican inner‐city children are disproportionately affected by asthma. During the 1999–2000 school year, we conducted a survey of 6 Bronx, New York City elementary schools to assess the prevalence of asthma and asthma‐like symptoms as reported by parents. Children with probable asthma had symptoms within the last 12 months and parents who indicated that their child had asthma. Children with possible asthma had symptoms within the last 12 months but lacked a diagnosis.Overall, 74% (4,775/6,433) of parents returned completed surveys, identifying 20% (949/4,775) of children as probable asthmatics, and 12% (589/4,775) as possible asthmatics. In multivariate analyses, probable asthma was associated with: Puerto Rican, Black, and white race/ethnicity, male gender, having health insurance, and registration at the poorest school. Possible asthma was associated with lack of health insurance and female gender, but was not associated with any specific race/ethnicity.Our findings support the effectiveness of school‐based surveys to identify children at high risk for asthma. The challenge remains to engage children and families in appropriate follow‐up care and to manage their illness, either through the use of school‐based health centers or stronger links to community services.Pediatr Pulmonol. 2002; 34:105–111. © 2002 Wiley‐Liss, Inc.
Mechanisms of constitutive NF‐κB activation in human prostate cancer cells
Authors: Suh Junghan , Payvandi Faribourz , Edelstein Leonard C. , Amenta Peter S. , Zong Wei‐Xing , Gélinas Céline , Rabson Arnold B. 
Published: October 2002

AbstractBACKGROUNDActivation of the NF‐κB transcription factor has been previously demonstrated in two androgen receptor negative prostate cancer cell lines. We wished to extend this work to additional prostate cancer cells and to characterize the mechanisms responsible for constitutive NF‐κB activation.METHODSElectrophoretic mobility shift assays were performed to measure NF‐κB DNA‐binding activity in prostate cancer cell lines, and immunohistochemistry was performed to detect nuclear localization of NF‐κB in prostate cancer tissues. Western blot analysis was used to study the status of IκBα. Transient transfection assays were employed to characterize the contributions of IκB kinase (IKK), MAPK kinase kinases (MAPKKKs), androgen receptor (AR), and tyrosine phosphorylation to the constitutive activation of NF‐κB in the prostate cancer cell lines.RESULTSConstitutive NF‐κB activity was observed in AR‐negative cell lines as well as in the prostate cancer patient samples, but was not present in AR positive cells. A “super‐repressor” IκBα, as well as dominant negative forms of IKKβ and NF‐κB‐inducing kinase (NIK), and tyrosine kinase inhibition were able to suppress NF‐κB activity in the cells with constitutive activation.CONCLUSIONSThe constitutive activation of NF‐κB observed in prostate cancer cells is likely due to a signal transduction pathway involving tyrosine kinases, NIK, and IKK activation. Prostate 52:183–200, 2002. © 2002 Wiley‐Liss, Inc.
Folding and stretching in a Go‐like model of titin
Authors: Cieplak Marek , Hoang Trinh Xuan , Robbins Mark O. 
Published: October 2002

AbstractMechanical stretching of the I27 domain of titin and of its double and triple repeats are studied through molecular dynamics simulations of a Go‐like model with Lennard‐Jones contact interactions. We provide a thorough characterization of the system and correlate the sequencing of the folding and unraveling events with each other and with the contact order. The roles of cantilever stiffness and pulling rate are studied. Unraveling of tandem titin structures has a serial nature. The force‐displacement curves in this coarse‐grained model are similar to those obtained through all atom calculations. Proteins 2002;49:114–124. © 2002 Wiley‐Liss, Inc.
Prediction of protein secondary structures from conformational biases
Authors: Hoang Trinh Xuan , Cieplak Marek , Banavar Jayanth R. , Maritan Amos 
Published: October 2002

AbstractWe use LINUS (the “Local Independently Nucleated Units of Structure”), a procedure developed by Srinivasan and Rose, to provide a physical interpretation of and predict the secondary structures of proteins. The secondary structure type at a given site is identified by the largest conformational bias during short simulations. We examine the rate of successful prediction as a function of temperature and the interaction window. At high temperatures, there is a large propensity for the establishment of β‐strands whereas α‐helices appear only when the temperature is lower than a certain threshold value. It is found that there exists an optimal temperature at which the correct secondary structures are predicted most accurately. We find that this temperature is close to the peak temperature of the specific heat. Changing the interaction window or carrying out longer simulations approaching equilibrium lead to little change in the optimal success rate. Our findings are in accord with the observation by Srinivasan and Rose that the secondary structures are mainly determined by local interactions and appear in the early stage of folding. Proteins 2002;48:558–565. © 2002 Wiley‐Liss, Inc.