bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis of polar vinyl monomer–olefin copolymers by α‐diimine nickel catalyst
Authors: Marques Maria M , Fernandes Susete , Correia Sandra G , Caroço Susana , Gomes Pedro T , Dias Alberto R , Mano João , Rausch Marvin D , Chien James C W 
Published: August 2002

AbstractVinyl acetate, methyl methacrylate, acrylonitrile and methyl vinyl ketone were investigated for co‐ and terpolymerization with ethylene and ethylene–propylene. Precursor [bis(N,N ′‐dimesitylimino)acenaphthene]dibromonickel, activated by methylaluminoxane was used as a catalyst system and trialkylaluminium was employed to block the polar groups for these polymerizations. Polymerization activities of the order of magnitude of 106 in the case of vinyl acetate and methyl methacrylate, and 105 in the case of acrylonitrile were achieved. Microanalysis and GPC of acrylonitrile copolymers found about 17 units of acrylonitrile per polymer chain. Copolymers with very different properties from the parent homopolymers were obtained in all cases except that of methyl vinyl ketone.© 2001 Society of Chemical Industry
Preparation of polystyrene–graphite conducting nanocomposites via intercalation polymerization
Authors: Chen Guo‐Hua , Wu Da‐Jun , Weng Wen‐Gui , He Bin , Yan Wen‐li 
Published: August 2002

AbstractIn situ polymerization of styrene was conducted in the presence of expanded graphite obtained by rapid heating of a graphite intercalation compound (GIC), to form a polystyrene–expanded graphite conducting composite. The composite showed excellent electrically conducting properties even though the graphite content was much lower than in normal composites. The transition of the composite from an electrical insulator to an electrical semiconductor occurred when the graphite content was 1.8 wt%, which is much lower than that of conventional conducting polymer composites. TEM, SEM and other studies suggest that the graphite was dispersed in the form of nanosheets in a polymer matrix with a thickness of 10–30 nm, without modification of the space between carbon layers and the structure of the graphite crystallites. The composite exhibited high electrical conductivity of 10−2 S cm−1 when the graphite content was 2.8–3.0 wt%. This great improvement of conductivity could be attributed to the high aspect ratio (width‐to‐thickness) of the graphite nanosheets. The rolling process strongly affected the conductivity and the mechanical properties of the composite.© 2001 Society of Chemical Industry
Cationic photopolymerization of polyfunctional 1‐propenyl ether systems
Authors: Sangermano Marco , Malucelli Giulio , Bongiovanni Roberta , Priola Aldo , Annby Ulf , Rehnberg Nicola 
Published: August 2002

AbstractThe cationic photopolymerization of trimethylolpropane tripropenyl ether (TPE), initiated by a diaryl iodonium salt, has been investigated. The influence of the presence of different alcoholic additives on the rates of photopolymerization and on the properties of the networks obtained has been studied. New 1‐propenyl ethers (trimethylolpropane dipropenyl ether (DPE) and its acetyl ester) were synthesized and employed as modifying agents in TPE photopolymerization. The thermal and dynamic‐mechanical properties of the films obtained have been investigated and are correlated with the structure of the networks and to the mechanism of the curing reaction; a microheterogeneous structure of the network was shown by dynamic‐mechanical thermal analysis.© 2001 Society of Chemical Industry
Shape memory effect of poly(methylene‐1,3‐cyclopentane) and its copolymer with polyethylene
Authors: Jeong Han Mo , Song Ji Hun , Chi Ki Whan , Kim Il , Kim Ki Tae 
Published: August 2002

AbstractPoly(methylene‐1,3‐cyclopentane) (PMCP) cyclopolymerized from 1,5‐hexadiene by metallocene catalyst, rac‐(ethylenebis(1‐indenyl))Zr(N(CH3)2)2 is partially crystalline and has a value of elongation at break of more than 400% in the temperature range 25–85 °C. The shape memory effect of PMCP with moderate molecular weight is enhanced by sequentially polymerized polyethylene segments, the crystalline phase of which seems to strengthen the fixed structure which memorizes the original shape. The glass transition temperature or melting temperature of PMCP can be selectively used as shape recovery temperature when an appropriate deformation temperature is chosen.© 2002 Society of Chemical Industry
Effects of shear rate, viscosity ratio and liquid crystalline polymer content on morphological and mechanical properties of polycarbonate and LCP blends
Authors: Tan L P , Yue C Y , Tam K C , Lam Y C , Hu X 
Published: August 2002

AbstractStudies were conducted on the effects of shear rate, viscosity ratio and liquid crystalline polymer (LCP) content on the morphological and mechanical properties of polycarbonate (PC) and LCP blends. The LCP (LC5000) used was a thermotropic liquid crystalline polymer consisting of 80/20 of parahydroxybenzoic acid and poly(ethylene terephthalate) (PHB/PET). The viscosity ratio (viscosity of LCP: viscosity of matrix) was varied by using two processing temperatures. Due to the different sensitivity of materials to temperature, variation in the processing temperature will lead to varying viscosity of the components in the blends. Based on this principle, the processing temperature could be manipulated to provide a favourable viscosity ratio of below unity for fibre formation. To study the effect of shear rate, the flow rate of the blend and the mould thickness were varied. The shear rate has a significant effect on the fibrillation of the LCP phase. The effect was more prominent when the viscosity ratio was low and the matrix viscosity was high. At 5 wt% LCP, fibrillation did not occur even at low viscosity ratios and high shear rates. It was also observed that the LCP content must be sufficiently high to allow coalescence of the dispersed phase for subsequent fibrillation to occur.© 2002 Society of Chemical Industry
A metallic intermediate band high efficiency solar cell
Authors: Luque Antonio , Martí Antonio 
Published: August 2002

AbstractThe theory of a novel type of solar cell is presented that contains a base made of a semiconductor with a metal‐like intermediate band (IB). The behavior of the IB and of the entire cell is studied taking into account photon recycling, that is, the emission of luminescent photons that may be subsequently absorbed. The results show that, in ideal conditions, this device is more efficient than the best two‐junction series‐connected tandem cells. This advantage might be maintained for less ideal cases. Although the material needed to achieve this device is yet unknown, some hints are given in the paper concerning its synthesis. Copyright © 2001 John Wiley & Sons, Ltd.
Multiple band and impurity photovoltaic solar cells: General theory and comparison to tandem cells
Authors: Green Martin A. 
Published: August 2002

AbstractOne way to improve photovoltaic solar energy performance is to absorb photons by processes involving multiple energy thresholds, such as in tandem cells, that employ multiple solar cells of different semiconductor bandgaps. Recently, another multiple threshold approach has been analysed based on a single bandgap cell with an intermediate impurity band. In the present work, the approach is extended to the N‐band cell, shown to be capable of higher performance than an N‐cell tandem. A generic approach to obtaining the selective photon absorption required for high efficiency is also described and the resulting insights applied to a new analysis of the impurity photovoltaic effect. Copyright © 2001 John Wiley & Sons, Ltd.
Ammonia recycling and cadmium confinement in chemical bath deposition of CdS thin layers
Authors: Malinowska B. , Rakib M. , Durand G. 
Published: August 2002

AbstractCadmium sulfide thin layers in polycrystalline solar cells are produced by chemical bath deposition (CBD). This process produces wastes containing ammonia and cadmium. These two chemicals must be recovered, and if possible recycled, from an environmental and economic point of view. A process has been implemented in order to recover ammonia and to confine cadmium. A new closed reactor has been designed and fabricated in order to trap ammonia vaporized during the deposition step. Ammonia is absorbed from the exhaust gas from the CBD reactor. The wastes are treated in an ex situ process which enables recovery of the major part of the large amounts of ammonia used in the process. Concentrated solutions of pure ammonia are obtained (more than 10 mol/l). In connection with this operation, all of the cadmium, except a very small amount, is precipitated, mainly as cadmium sulfide, owing to decomposition of the thiourea introduced in excess. Microfiltration with a glass‐fiber filter of about 0.7 μm cut‐off produces a filtrate of very low cadmium concentration (< 10 μg/l). Optimization of both pH and residual ammonia concentration should make it possible to lower this residual cadmium concentration. This effluent is the only waste product of the process. The filtration cake containing cadmium compounds may be stored in specialized landfills after standard treatment or, better, treated to recover and recycle the metal without generation of any other harmful effluent. Copyright © 2001 John Wiley & Sons, Ltd.
Long‐term stability of dye‐sensitised solar cells
Authors: Hinsch A. , Kroon J. M. , Kern R. , Uhlendorf I. , Holzbock J. , Meyer A. , Ferber J. 
Published: August 2002

AbstractAccelerated ageing tests on large numbers of nanocrystalline dye‐sensitised solar cells (nc‐DSC) show that, to first order, separation between the effects of the stresses of visible light soaking, UV illumination and thermal treatment on long‐term stability is possible. The corresponding mechanisms are electrochemical, photochemical and purely chemical in nature. It was found that visible light soaking alone is not a dominant stress factor. A dramatic improvement in UV stability has been achieved by using MgI2 as additive to the electrolyte. Thermal stress appears to be one of the most critical factors determining the long‐term stability of nc‐DSC and is strongly related to the chemical composition of electrolyte solvents and additives. Encouraging stability results have been obtained for cells based on pure nitrile‐based solvents: (1) A minor decrease in performance of initially 5.5% solar efficient cells has been found after 2000 h at 60°C without light soaking; (2) After 900 h ageing at 85°C, a decrease of 30% in maximum power has been observed; (3) After 3400 h of combined thermal stress and continuous light soaking (45°C, 1 sun equivalent) good stability with 15% decrease in maximum power can be demonstrated. It should be noted that such good thermal stability has not been reported previously for dye‐sensitised solar cells so far. Copyright © 2001 John Wiley & Sons, Ltd.
Experimental evidence of parasitic shunting in silicon nitride rear surface passivated solar cells
Authors: Dauwe Stefan , Mittelstädt Lutz , Metz Axel , Hezel Rudolf 
Published: August 2002

AbstractMany solar cells incorporating SiNxfilms as a rear surface passivation scheme have not reached the same high level of cell performance as solar cells incorporating high‐temperature‐grown silicon dioxide films as a rear surface passivation. In this paper, it is shown by direct comparison of solar cells incorporating the two rear surface passivation schemes, that the performance loss is mainly due to a lower short‐circuit current while the open‐circuit voltage is equally high. With a solar cell test structure that features a separation of the rear metal contacts from the passivating SiNxfilms, the loss in short‐circuit current can be reduced drastically. Besides a lower short‐ circuit current, dark I–V curves of SiNxrear surface passivated solar cells exhibit distinct shoulders. The results are explained by parasitic shunting of the induced floating junction (FJ) underneath the SiNxfilms with the rear metal contacts. The floating junction is caused by the high density of fixed positive charges in the SiNxfilms. Other two‐dimensional effects arising from the injection level dependent SRV of the Si/SiNxinterfaces are discussed as well, but, are found to be of minor importance. Pinholes in the SiNxfilms and optical effects due to a different internal rear surface reflectance can be excluded as a major cause for the performance loss of the SiNxrear surface passivated cells. Copyright © 2002 John Wiley & Sons, Ltd.
Linear solvation energy (LSE) correlations of the solvatochromic response and x‐ray structure analysis of hydrophilically N‐substituted Michler's ketone derivatives
Authors: El‐Sayed Mohamed , Müller Hardy , Rheinwald Gerd , Lang Heinrich , Spange Stefan 
Published: August 2002

AbstractBathochromic UV–Vis spectral shifts of two hydrophilically N‐substituted Michler's ketone derivatives, 4,4′‐bis[di(2‐hydroxyethyl)amino]benzophenone [MK(OH)4] (1) and 4‐(dimethylamino)‐4′‐[di(2‐hydroxyethyl)‐amino]benzophenone [MK(OH)2] (3), were measured in 28 solvents of different polarity. For MK(OH)4 and MK(OH)2 in non‐polar, dipolar aprotic and hydrogen‐bonding solvents, the solvatochromic responses of the two solutes conform exactly to the requirements of the Kamlet‐Taft linear solvation free energy model of solvent–solute interactions. The contribution of the hydrogen‐bond accepting property of the solvent on the bathochromic band shift of MK(OH)4 and MK(OH)2 increases with increasing number of their OH groups at the N‐substituent. The x‐ray crystallographic analysis for MK(OH)2 reveals the presence of strong intermolecular hydrogen bonds between the carbonyl oxygen atom and the 2‐hydroxyethyl group, which plays a significant role in the colour of the crystals. Copyright © 2001 John Wiley & Sons, Ltd.
Complexation of dicarboxylates and phosphates by a semisynthetic alkaloid‐based cyclophane in water
Authors: Lara Karen Ochoa , Godoy‐Alcántar Carolina , Rivera Ismael León , Eliseev Alexey V. , Yatsimirsky Anatoly K. 
Published: August 2002

AbstractDicationic N,N′‐dibenzylated cyclophane‐type derivative 1 of a bisisoquinoline macrocyclic alkaloid, S,S‐(+)‐tetrandrine, was prepared and characterized. In aqueous solution 1 undergoes dimerization, which was studied by the concentration dependence of its 1H NMR signals. The salt effect on the dimerization constant was analyzed by using different versions of Debye–Hückel‐type equations. 1H NMR titration of 1 by 10 dicarboxylate anions of different structures revealed strong peak binding selectivity for succinate in the series of α,ω‐dicarboxylates. Aromatic carboxylates have larger binding constants and for o‐phthalate the formation of both 1:1 and 1:2 host–guest complexes is observed. Binding of nucleotides (AMP, ADP and ATP) to 1 is surprisingly insensitive to the guest charge, indicating a major contribution of stacking interactions of the nucleobase with 1. Copyright © 2001 John Wiley & Sons, Ltd.
CO2 fixation and activation by metal complexes of small polyazacyclophanes
Authors: Andrés Sergio , Escuder Beatriu , Doménech Antonio , García‐España Enrique , Luis Santiago V. , Marcelino Victor , Llinares José M. , Ramírez José A. , Soriano Conxa 
Published: August 2002

AbstractThe interaction of the cyclophanes 2,6,9,13‐tetraaza[14]paracyclophane (L1) and 2,6,9,13‐tetraaza[14]metacyclophane (L2) and of their Zn2+ and Cu2+ complexes with CO32− and its protonated forms is described. The actuation of the Cu2+–L2 system as an electrocatalyst for the reduction of CO2 to CO in water is advanced. Copyright © 2001 John Wiley & Sons, Ltd.
Kinetic models for solution imidization of polyamic acid containing naphthalene‐pendant group
Authors: Leu Tsu‐Shang , Wang Chun‐Shan 
Published: August 2002

AbstractThe kinetics and mechanisms of the solution imidization of polyamic acid resulting from a diamine, bis(4‐aminophenoxy‐3,5‐dimethylphenyl)naphthylmethane, and a dianhydride, 3,3′4,4′‐diphenylsulfonetetracarboxylic dianhydride, were studied at three various temperatures (145, 165, and 180 °C). The results were confirmed by means of 1H NMR and gel permeation chromatography (GPC). Kinetic parameters were obtained by an isothermal study, and the results were quite close to second‐order kinetics for the homogeneous solution imidization. In addition, Carother's equation, Mark–Houwink theory, and GPC were used to explain the molecular weight of the imidization processes. The apparent activation energy (Ea) was 104 KJ/mol, and the pre‐exponential factor (k0) was 3.48 × 1014. The proposed kinetic mechanism is in good agreement with the kinetic models. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 4139–4151, 2001
Synthesis and self‐assembly of fluorinated block copolymers
Authors: Hillmyer Marc A. , Lodge Timothy P. 
Published: August 2002

AbstractFluorinated block copolymers combine the unique properties of fluoropolymers and the intriguing self‐assembly of hybrid macromolecules. The preparation of the title molecules by selective fluorination procedures and the effect of fluorine incorporation on the material thermodynamics are presented. We highlight two fluorination schemes developed in our laboratory, difluorocarbene and perfluoroalkyliodide additions to polydienes, that allow for the selective and tunable incorporation of different fluorinated groups into model block copolymers. The fluorination changes the physical properties of the parent materials and leads to interesting changes in the component incompatibilities. The role of fluorination in determining block copolymer thermodynamics in both the solid state and in solution and in ultimately exploiting fluorination to produce novel, higher order structures is central to our research efforts. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 1–8, 2002
Polymerization of acrylamide photoinitiated by tris(2,2′‐bipyridine)ruthenium(II)–amine in aqueous solution: Effect of the amine structure
Authors: Rivarola Claudia R. , Bertolotti Sonia G. , Previtali Carlos M. 
Published: August 2002

AbstractThe photopolymerization of acrylamide (AA) initiated by the metallic complex tris(2,2′‐bipyridine)ruthenium(II) [Ru(bpy)3+2] in the presence of aliphatic and aromatic amines as co‐initiators was investigated in aqueous solution. Aromatic amines, which are good quenchers of the emission of the metal‐to‐ligand‐charge‐transfer excited state of the complex, are more effective co‐initiators than those that do not quench the luminescence of Ru(bpy)3+2, such as aliphatic amines and aniline. Laser‐flash photolysis experiments show the presence of the reduced form of the complex, Ru(bpy)3+1, for all the amines investigated. For aliphatic amines, the yield of Ru(bpy)3+1 increases with temperature, and on the basis of these experiments, a metal‐centered excited state is proposed as the reactive intermediate in the reaction with these amines. The decay of the transient Ru(bpy)3+1 is faster in the presence of AA. This may be understood by an electron‐transfer process from Ru(bpy)3+1 to AA, regenerating Ru(bpy)3+2 and producing the radical anion of AA. It is proposed that this radical anion protonates in a fast process to give the neutral AA radical, initiating in this way the polymerization chain. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 4265–4273, 2001
Preparation of functionalized block copolymers based on a polysiloxane backbone by anionic ring‐opening polymerization
Authors: Bauer Josef , Hüsing Nicola , Kickelbick Guido 
Published: August 2002

AbstractPolysiloxane diblock copolymers containing a pure polysiloxane backbone were prepared by the functionalization of poly(dimethylsiloxane)‐b‐poly(methylvinylsiloxane) copolymers. The copolymers were obtained by the sequential anionic copolymerization of either 1,3,5,7‐tetramethyl‐1,3,5,7‐tetravinylcyclotetrasiloxane or 1,3,5‐trimethyl‐1,3,5‐trivinylcyclotrisiloxane with hexamethylcyclotrisiloxane. The two vinyl monomers showed large differences in the propagation rates, but both could be used for the formation of polysiloxane block copolymers. Differences in the polymerization sequences were investigated and revealed that better control was obtained if the slower propagating monomer was polymerized first. The method permitted the synthesis of block copolymers with molecular weight distributions around 1.4 and lower and high block purities. The vinyl groups of the block copolymers were quantitatively and selectively functionalized by hydrosilation or epoxidation reactions. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1539–1551, 2002
Synthesis and burst strength of water‐swollen immunoisolatory tubules
Authors: Isayeva Irada S. , Gent Alan N. , Kennedy Joseph P. 
Published: August 2002

AbstractA series of amphiphilic hydrogel tubules have been prepared by copolymerizing/crosslinking hydrophilic poly(dimethylacrylamide) segments with hydrophobic di‐, tri‐, and octamethacrylate‐telechelic polyisobutylene crosslinkers, and their elastic modulus and burst strength in the water‐swollen state were investigated. Because the burst characteristics of hydrogels have not yet been quantitatively investigated, equipment was designed and built to generate fundamental insight into the burst properties of thin‐walled (200–250 μm) narrow lumen (2–3 mm i.d.) water‐swollen tubules. The theory developed to describe quantitatively the inflation behavior of thin‐walled rubber tubules was adapted to treat our experimental observations. Changes in the burst strength, elastic modulus, and expansion during the inflation of hydrogel tubules were interpreted in terms of the molecular weight of the hydrophilic segments between crosslinking sites (Mc,hydrophilic), which in turn was calculated according to the rubber elasticity theory. According to these investigations, the burst strength of our water‐swollen amphiphilic tubules is in the 0.2–0.5 MPa range, which is sufficient for implantation and immunoisolatory applications. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2075–2084, 2002
Novel synthesis of polyimide–polyhybridsiloxane block copolymers via polyhydrosilylation: Characterization and physical properties
Authors: Andre S. , Guida‐Pietrasanta F. , Rousseau A. , Boutevin B. 
Published: August 2002

AbstractThe insertion of soft polysiloxane segments into a polyimide backbone introduces changes in its properties (processability, low surface tension, gas permeability, and lower dielectric constant). Generally, these polyimide–polysiloxane copolymers are synthesized by the condensation of a dianhydride with an aromatic diamine and an amine telechelic polysiloxane, or by transimidization between an aminopyridine‐terminated oligoimide and an amine end‐capped oligosiloxane. This study investigated another route to obtain perfectly alternating polyimide–polyhybridsiloxane (PI–PHSX) block copolymers. The hydrosilylation, widely studied previously, was performed to elaborate copolymers from an allyl telechelic polyimide and a hydrosilane telechelic polyhybridsiloxane. The use of a telechelic polyhybridsiloxane as a soft segment brought better thermostability and better chemical resistance in comparison with an oligosiloxane based on Si(CH3)2O units. Using the same allyl telechelic polyimide moiety but varying the size of the hybrid siloxane part, we obtained different PI–PHSX block copolymers, leading to thermoplastic elastomers (TPE). We investigated the effect of the soft‐segment length on the thermal resistance, activation energy of thermal degradation, mechanical behavior, and surface properties of a series three PI–PHSX block copolymers containing 36, 54, and 75 wt % polyimide. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2414–2425, 2001