bluuebunny/crossref_metadata_2025_split huggingface dataset:
Coordination/organometallic polymers based on diphosphine and diisocyanide ligands
Authors: Harvey Pierre D. 
Published: July 2003

AbstractThis paper reviews various coordination/ organometallic polymers in which the metal atoms are incorporated in the backbone using diphosphine and diisocyanide ligands. Such ligands includes diphosphines of the type bis(diphenylphosphino)alkane where alkane is (CH2)m with m = 1, 3‐6, bis(diphenylphosphino)acetylene (dpa), and bis(dimethylphosphino)methane (dmpm), and diisocyanides such as 1,8‐diiso‐cyano‐p‐menthane (dmb) and p‐diisocyanotetra‐methylbenzene (ditmb). The metal fragments are monocations such as Cu+, Ag+, and Au+, dinuclear species such as Pd2(dmb)22+, Pd2(dppm)22+, M2(dmpm)32+ (M = Cu, Ag), and clusters such as M4(dmb)42+ (M = Pd, Pt).
Preparation of synthons for carborane containing macromolecules
Authors: Parrott Matthew C. , Marchington Erin B. , Valliant John F. , Adronov Alex 
Published: July 2003

AbstractThe modification of para‐carborane with appropriate functionalities for incorporation within a dendrimer framework was accomplished by functionalizing the carbon centers with protected alcohol and free acid groups. These compounds are excellent candidates for utilization as functional linkers between two generations of an aliphatic polyester dendrimer structure. Future assembly of these structures will result in dendritic macromolecules containing carboranes within their interior and will be enveloped by hydrophilic groups (hydroxyls) to maintain their water solubility and biocompatibility. These structures have potential applications in Boron Neutron Capture Therapy and Synovectomy. Additionally, carboranes were coupled to polymerizable acrylate structures, and it was shown that the resulting carborane monomers could be polymerized using living free‐radical polymerization techniques.
Conjugated metallopolymers
Authors: Leung Alfred C.W. , Chong Jonathan H. , MacLachlan Mark J. 
Published: July 2003

AbstractConjugated polymers incorporating transition metals have enormous potential for chemically‐tuneable conducting and semiconducting polymers. Unfortunately, progress in this field has been limited by the challenge of preparing suitable metal‐containing monomers, the difficulty of polymerizing them in a controlled manner, and the limited solubility of the resulting polymers. We are developing new, soluble conjugated metal‐containing polymers that contain transition metals in a conjugated organic backbone.
Cyclophosphazenes as polymer modifiers
Authors: Gleria Mario , Po Riccardo , Giannotta Giorgio , Fiocca Luisa , Bertani Roberta , Fambri Luca , La Mantia Francesco Paolo , Scaffaro Roberto 
Published: July 2003

AbstractThe utilization of Cyclophosphazenes as polymer modifiers is reviewed, with particular concern to their exploitation as versatile chain extenders, possibly for recycle problems, crosslinkers, to enhance mechanical properties of polymeric materials, branchers, to selectively introduce ramifications in linear polymers, and compatibilizers, to favor the formation of blends between originally incompatible organic macromolecules. The great versatility of the synthetic methods put forward for these substrates, together with the ease of controlling their modification, functionalization and reactivity are important parameters for the evaluation of which type of use is more feasible for these trimers. The importance of cyclophosphazenes bearing organic polymeric chains, azide groups, 2‐oxazoline derivatives and oxirane rings in connection with organic conventional macromolecules is critically highlighted.
New functional inorganic polymers containing phosphorus
Authors: Gates Derek P. , Tsang Chi‐Wing , Wright Vincent A. , Yam Mandy 
Published: July 2003

AbstractThe C=C bond plays numerous roles in polymer science. This moiety is used as a precursor to polymers by addition polymerization and has been incorporated into π‐conjugated polymers. The addition polymerization reaction has been extended to P=C bonds and the first example of a poly(methylenephosphine) has been prepared. The new macromolecule is of moderate molecular weight (ca. 104 g/mol) and the oxidized polymers are air‐stable. Poly(p‐phenylenephosphaalkene), the first π‐conjugated polymer containing P=C bonds in the backbone, has been prepared. The UV/Vis spectrum of this polymer shows a red shift in λmax when compared with molecular model systems.
Silole‐containing linear and hyperbranched polymers: synthesis, thermal stability, light emission, nano‐dimensional aggregation, and optical power limiting
Authors: Lam Jacky Wing Yip , Chen Junwu , Law Charles Chi Wang , Peng Han , Xie Zhiliang , Cheuk Kevin Ka Leung , Kwok Hoi Sing , Tang Ben Zhong 
Published: July 2003

AbstractLinear polyacetylenes and hyperbranched polyphenylenes carrying 1,2,3,4,5‐pentaphenylsilolyl (PS) pendants are designed and synthesized. Homo‐polymerization of HC≡CPS, HC≡C(CH2)9OPS, and C6H5C≡C(CH2)9OPS and (co)polycyclotrimerization of (HC≡C)2PS with 1‐octyne are effected by NbCl5‐, WCl6‐, MoCl5‐, and TaCl5‐based catalysts. High molecular weight linear (1‐3) and hyperbranched polymers (6) are obtained in high yields (Mw up to ∼70 × 103 and yield up to 85%). All the polymers are thermally stable, losing little weight when heated to 350°C. Whereas all the polymers emit faint light when molecularly dissolved, polymers 2, 3, and 6 become emissive when aggregated in poor solvents or when cooled to low temperatures. Restricted intramolecular rotations of the phenyl rings upon the axes of the single bonds linked to the silole cores may be responsible for the aggregation‐ or cooling‐induced emission. A multilayer electroluminescent device using 3 as an active layer emits a blue light of 496 nm with maximum brightness, current efficiency, and external quantum yield of 1118 cd/m2, 1.45 cd/A, and 0.55%, respectively. Polymers 6 are non‐linear optically active and strongly attenuate the optical power of intense laser pulses, whose optical limiting performances are superior to that of C60, a best‐known optical limiter.
Lewis acidic organoboron polymers
Authors: Qin Yang , Cheng Guanglou , Parab Kshitij , Sundararaman Anand , Jäkle Frieder 
Published: July 2003

AbstractWe have developed a highly efficient new method for the introduction of Lewis acidic boron centers into the side chains of organic polymers. Our methodology involves three steps: (i) the controlled polymerization of a functional monomer, (ii) the exchange of the functional group for Lewis acidic boron centers, and (iii) the fine‐tuning of the Lewis acidity of the individual centers through substituent exchange reactions with nucleophiles. This approach gives access to a family of new well‐defined organoboron polymers including moderately Lewis acidic poly(arylboronates) and the first examples of highly Lewis acidic fluorinated triarylborane polymers.
Poly(ferrocenylsilanes) as etch barriers in nano and microlithographic applications
Authors: Hempenius Mark A. , Lammertink Rob G.H. , Péter Mária , Vancso G. Julius 
Published: July 2003

AbstractThin films of organic‐organometallic block copolymers are shown to be efficient self‐assembled templates for nanolithography. Block copolymers composed of organic blocks such as polyisoprene or polystyrene and a poly(ferrocenylsilane) block microphase separate to form a monolayer of densely packed organometallic spheres in an organic matrix. The high resistance of the organometallic phase to reactive ion etching enables the nanoscale patterns to be transferred into silicon substrates, forming nano structured surfaces. Electrostatic self‐assembly of poly(ferrocenylsilane) polyanions and polycations is discussed as a means to form laterally structured organometallic multilayer thin films by area‐selective adsorption onto chemically patterned substrates.
Polyethers and thioethers incorporating neutral and cationic organoiron complexes
Authors: Abd‐El‐Aziz Alaa S. , Todd Erin K. , Okasha Rawda M. 
Published: July 2003

AbstractThe synthesis of linear and star‐shaped oligomers containing cationic and neutral organoiron groups in their structures was achieved by reaction of cationic arene complexes of cyclopentadienyliron containing terminal hydroxyl groups with 1,1′‐ferrocenedicarbonyl chloride or ferrocene carboxylic acid. The use of chloroarene complexes allowed for the formation of triiron complexes that were subsequently polymerized via nucleophilic aromatic substitution with various oxygen‐ and sulfur‐based dinucleophiles. The corresponding polyethers and thioethers were isolated in good yields and these materials exhibited excellent solubilities in polar organic solvents. Cyclic voltammetric investigations revealed that the cationic iron centers pendent to the polymer backbones underwent reversible reduction steps, while the neutral iron centers within the polymer backbones underwent reversible oxidation steps. Photolysis of these polymers resulted in the removal of the cationic cyclopentadienyliron moieties pendent to the polymer backbones. Thermogravimetric analysis (TGA) revealed that the cationic iron complexes were cleaved from the polymers at approximately 210 °C. Differentials scanning calorimetry (DSC) revealed that the glass transition temperatures of the cationic polymers occurred at higher temperatures than their neutral analogs.
Pulsed Laser Polymerization at Low Conversions: Broadening and Chain Transfer Effects
Authors: O'Shaughnessy Ben , Vavylonis Dimitrios 
Published: July 2003

AbstractPulsed laser polymerization (PLP) is widely employed to measure propagation rate coefficients kp in free radical polymerization. Various properties of PLP have been established in previous works, mainly using numerical methods. The objective of this paper is to obtain analytical results. We obtain the most general analytical solution for the dead chain molecular weight distribution (MWD) under low conversion conditions which has been hitherto obtained. Simultaneous disproportionation and combination termination processes are treated. The hallmarks of PLP are the dead MWD discontinuities located at integer multiples of n0 = kpt0CM, where t0 is the laser period and CM is the monomer concentration. We show that chain transfer reduces their amplitude by factors $e^{ - c_{tr} Ln_0 }$, consistent with numerical results obtained by other workers. Here ctr is the chain transfer coefficient and Ln0 (L = integer) are the discontinuity locations. Additionally, transfer generates a small amplitude continuous contribution to the MWD. These results generalize earlier analytical results which were obtained for the case of disproportionation only. We also considered two classes of broadening: (i) Poisson broadening of growing living chains and (ii) intrinsic broadening by the MWD measuring equipment (typically gel permeation chromatography, GPC). Broadening smoothes the MWD discontinuities. Under typical PLP experimental conditions, the associated inflection points are very close to the discontinuities of the unbroadened MWD. Previous numerical works have indicated that the optimal procedure is to use the inflection point to infer kp. We prove that this is a correct procedure provided the GPC resolution σ is better than n. Otherwise this underestimates Ln0 by an amount of order σ2/n0.Schematic of a chain transfer reaction with monomer as the transfer agent.imageSchematic of a chain transfer reaction with monomer as the transfer agent.
Occupied and Accessible Volumes in Glassy Polymers and Their Relationship with Gas Permeation Parameters
Authors: Ronova Inga A. , Rozhkov Egor M. , Alentiev Alexander Yu. , Yampolskii Yurii P. 
Published: July 2003

AbstractIn order to relate the microstructure of polymer chains to the gas permeation properties, a novel method is proposed for the calculation of the van der Waals (Vw), occupied (Vocc), and accessible (Vacc) volumes of polymers, using polyimides as examples. In this approach,VoccandVaccvalues are obtained as characteristics of polymer–gas systems. Correlations betweenVoccand the gas permeability (P) and diffusion (D) coefficients are demonstrated. Accessible volume,Vacc, determined experimental densities, andVocccalculated using a Monte Carlo technique, as well as the fractional accessible volume (FAV) (Vacc/Vsp), whereVspis the specific volume of polymers, also correlate well with thePandDvalues. The slopes of these correlations increase with increasing molecular size of the diffusing molecules. In addition, the parameters of the equations forD(FAV) andP(FAV) strongly depend on conformation rigidity (Kuhn segment) of the polyimides. An interpretation of the results obtained is presented.Definition of occupied volume.imageDefinition of occupied volume.
Elevated basal reactive oxygen species and phospho‐Akt in murine keratinocytes resistant to ultraviolet B–induced apoptosis
Authors: Butts Brent D. , Kwei Kevin A. , Bowden G. Tim , Briehl Margaret M. 
Published: July 2003

AbstractResistance to apoptosis may be a critical phenotype that cells must acquire during skin carcinogenesis. The Akt kinase is a known upstream regulator of apoptosis in many cell types and has been shown to be activated by increased reactive oxygen species (ROS). We have previously demonstrated that two malignant variants (6M90 and 6R90) of the mouse keratinocyte 308 cell line have elevated ROS because of loss of catalase activity, and that this elevated ROS confers a growth advantage. We report here that in addition to a growth advantage, chronically increased ROS in the variants resulted in an increase in resistance to ultraviolet (UV) B–induced apoptosis. This resistance was due to basal increases of Akt phosphorylation in the malignant variants compared to the 308 cells. Modulation of ROS in 6M90 and 6R90 cells by catalase overexpression or antioxidant treatment resulted in decreased levels of Akt phosphorylation and subsequent loss of resistance to UVB‐induced apoptosis. Conversely, treatment of 308 cells with hydrogen peroxide caused increases in Akt phosphorylation and increased apoptosis resistance. These results indicate that the chronically elevated ROS often observed in tumors may contribute to a malignant phenotype by keeping Akt in a phosphorylated state, resulting in increased apoptosis resistance. © 2003 Wiley‐Liss, Inc.
Impaired motor coordination in mice lacking neural recognition molecule NB‐3 of the contactin/F3 subgroup
Authors: Takeda Yasuo , Akasaka Keiko , Lee Suni , Kobayashi Satoru , Kawano Hitoshi , Murayama Shigeo , Takahashi Naoki , Hashimoto Kouichi , Kano Masanobu , Asano Masahide , Sudo Katsuko , Iwakura Yoichiro , Watanabe Kazutada 
Published: July 2003

AbstractThe neural recognition molecule NB‐3, which belongs to the contactin subgroup of the immunoglobulin superfamily, is expressed exclusively in the nervous system and mainly upregulated at the early postnatal stage during mouse brain development. The expression of NB‐3 in the cerebellum increases until adulthood. In contrast, the expression in the cerebrum declines to a low level after postnatal day 7. To characterize the functional roles of NB‐3 in vivo, we generated NB‐3‐deficient mice by substituting a part of the NB‐3 gene with the β‐galactosidase (Lac Z) gene. Complete overlap of the Lac Z expression in the heterozygous mouse brain with the NB‐3 immunostaining pattern in the rat cerebellum and with the previously reported pattern of in situ hybridization of NB‐3 transcripts indicated that Lac Z expression reflects the expression of NB‐3 in the mouse brain. NB‐3‐deficient mice were viable and fertile. The formation and organization of all nuclei and layers throughout the brains of mutant mice appeared normal. Behavioral tests to examine motor function showed that the mice deficient for NB‐3 were slow to learn to stay on the rotating rod in the rotorod test during repeated trials, and that they displayed dysfunction of equilibrium and vestibular senses in the wire hang and horizontal rod‐walking tests. In contrast, the mutant mice showed no difference of grasp force from the wild‐type mice. Thus, NB‐3‐deficient mice are impaired in motor coordination. © 2003 Wiley Periodicals, Inc. J Neurobiol 56: 252–265, 2003
Creating avenues for relative empowerment (CARE): A pilot test of an intervention to improve outcomes of hospitalized elders and family caregivers
Authors: Li Hong , Melnyk Bernadette Mazurek , McCann Robert , Chatcheydang Jariya , Koulouglioti Christina , Nichols Lynn W. , Lee Ming‐Der , Ghassemi Akhtar 
Published: July 2003

AbstractThe purpose of this pilot study was to evaluate the effectiveness of a family caregiver–focused intervention program (CARE) on the outcomes of hospitalized elders and their family caregivers. A randomized clinical trial was conducted with 49 family caregivers of hospitalized elders in a university medical center in upstate New York. Driven by self‐regulation and role theories, the two‐phase CARE program consisted of: (a) a mutual agreement consisting of family caregiving activities during hospitalization; and (b) audiotaped information regarding emotional responses and possible complications associated with an elderly patient's hospitalization as well as instructions for effectively participating in the elder's hospital care. The comparison program consisted of information about hospital services and policies. CARE elders had fewer incidents of acute confusion reported by family caregivers during hospitalization and fewer depressive symptoms at 2 weeks and 2 months posthospitalization than did the comparison group. CARE family caregivers participated more in the care of their hospitalized elders and had higher scores on role rewards prior to hospital discharge. Findings from this study support the need for further testing of the CARE intervention with family caregivers to determine its effectiveness on outcomes of hospitalized elders and their family caregivers. © 2003 Wiley Periodicals, Inc. Res Nurs Health 26:284–299, 2003
Using methodological triangulation for cultural verification of commitment to a plan for exercise scale among Korean adults with chronic diseases
Authors: Shin YunHee , Pender Nola J. , Yun SangKyun 
Published: July 2003

AbstractThe purpose of this study was twofold: to use methodological triangulation to increase the cultural appropriateness of the Planning for Exercise Scale (Pender, 1996), which measures commitment to a plan of action, and to psychometrically evaluate the revised scale in a selected population of 230 Korean adults experiencing chronic diseases. First, through a qualitative approach, the cultural properties of the concept were identified in order to revise Pender's Planning for Exercise Scale. The revised scale consisted of 20 items: 13 items emerged from the qualitative procedure and seven items were retained from the original scale. Through a quantitative approach, the revised scale was analyzed psychometrically. Results showed the scale had sufficient reliability and validity to warrant its use by researchers or practitioners evaluating the level of commitment to a plan for exercise among Korean adults. The revised instrument is appropriate for use in future intervention studies designed to improve the performance of exercise among Koreans who are chronically ill. © 2003 Wiley Periodicals, Inc. Res Nurs Health 26:312–321, 2003
Mother–infant interactions of medically fragile infants and non‐chronically ill premature infants
Authors: Holditch‐Davis Diane , Cox Mary Foster , Miles Margaret Shandor , Belyea Michael 
Published: July 2003

AbstractAt 6 months corrected for prematurity, 41 medically fragile prematures, 20 medically fragile full‐terms, and 28 prematures without chronic illnesses were observed interacting with their mothers for 1 hr. Mothers of non–chronically ill prematures gestured to and touched their infants less, were uninvolved with them for a longer time, and spent less time interacting and looking at their infants than did mothers of medically fragile infants. Medically fragile full‐terms slept more than the non–chronically ill prematures. The non–chronically ill premature group played with objects more and exhibited more locomotion. Thus, the non–chronically ill prematures had more mature behaviors but less frequent interactions than did the medically fragile infants. These disparities reflect differences both in the infants' functional maturity and in maternal compensation for infant vulnerability. © 2003 Wiley Periodicals, Inc. Res Nurs Health 26:300–311, 2003
Dynamic properties of carbon black filled chlorinated polyethylene/hindered phenol blends
Authors: Wu Chifei , Akiyama Suburo 
Published: July 2003

AbstractAggregates of carbon black (CB) in a polymer matrix have a tendency to form a CB network. The dynamic mechanical properties of binary systems of chlorinated polyethylene (CPE) and CB or 3,9‐bis{1,1‐dimethyl‐2[β‐(3‐tert‐butyl‐4‐hydroxy‐5‐methylphenyl)propionyloxy]ethyl}‐2,4,8,10‐tetraoxaspiro[5,5]‐undecane (AO‐80) and their ternary systems were investigated. It was found that the dynamic mechanical properties of those systems depend on the colloidal properties, surface oxides, and surface modification of CB. For binary systems of CPE and CB, oxidized CB gives a high modulus at low strain amplitude and a large Payne effect compared with untreated CB. In contrast, the reverse effect was observed for their ternary systems. Consequently, a good micro‐dispersion is obtainable by surface modification due to physical adsorption of AO‐80 on oxidized CB particles via hydrogen bonds.© 2003 Society of Chemical Industry
Phosphorus‐containing polyaryloxydiphenylsilanes with high flame retardance arising from a phosphorus–silicon synergistic effect
Authors: Liu Ying‐Ling , Chiu Yie‐Chan , Chen Tsung‐Yu 
Published: July 2003

AbstractPolyaryloxydiphenylsilanes were prepared from phosphorus‐containing diols and diphenydichlorolsilane through solution polymerization. With a stoichiometric imbalance in feed monomers, the resulting polymers exhibited moderate melting points and good processing properties. The polymers prepared showed initial decomposition temperatures above 340 °C, excellent thermal stability, high char yields at 850 °C and very high limited oxygen index values of 56–59. The polymers' char yields and their (P + Si) contents showed linear relationships.© 2003 Society of Chemical Industry
Surface chemical analysis of poly(ε‐caprolactone)–perfluoropolyether–poly(ε‐caprolactone) triblock copolymers by X‐ray photoelectron spectroscopy
Authors: Toselli Maurizio , Gardella Joseph A , Messori Massimo , Hawkridge Adam M , Pilati Francesco , Tonelli Claudio 
Published: July 2003

AbstractThe air‐side surface composition of a series of poly(ε‐caprolactone)–perfluoropolyether–poly(ε‐caprolactone) triblock copolymers with different compositions and block lengths have been studied by angle‐dependent X‐ray photoelectron spectroscopy (XPS). The weight percentage of the perfluoropolyether (PFPE) and polycaprolactone (PCL) blocks, and ethylene oxide linker (RH) has been calculated in different ways: from C1s, O1s and F1s photoemission peaks and by line fitting of the C1s and O1s envelopes. The atomic sensitivity factors and the parameters used to fit the peak envelopes have been experimentally determined using some reference materials. A critical discussion of the different methods used in the surface characterization and the degradation of PFPE segments, induced by irradiation beam, have been also reported. A large excess of PFPE with respect to the bulk composition was observed in all samples, and the angular dependence of the XPS signal demonstrated that the content of the fluorinated block segment increased by decreasing the sampling depth. The PFPE surface concentration was also decreased by increasing the PCL/PFPE ratio, but the surfaces of the samples were still dominated by PFPE segments for copolymers with a bulk PFPE composition lower than 10%. Moreover, copolymers with similar PCL/PFPE bulk ratios but with different PFPE block lengths, showed similar PFPE surface composition when the number‐average molecular weight (Mn) was 2000 and 3200 g mol−1, while that observed for copolymers containing PFPE block with Mn 900 g mol−1 was lower. Copyright © 2003 Society of Chemical Industry