bluuebunny/crossref_metadata_2025_split huggingface dataset:
Multilayered Assembly of Cellulose Derivatives as Primer for Surface Modification by Polymerization
Authors: Woo C. K. , Schiewe B. , Wegner G. 
Published: December 2005

AbstractSummary: Rod‐like cellulose polymers, with flexible isopentyl side chains, form supramolecular constructs by the Langmuir‐Blodgett (LB) technique. These have been employed to model an ultrathin multilayered primer for surface modification by polymerization. Multilayers of this polymer were doped with a solution of a photosensitizer and then exposed to methyl methacrylate, (MMA) in either the vapor or liquid phase. Polymerization of the monomer swollen construct was induced photochemically. FT‐IR spectra reveal that photoinitiation in presence of the photosensitizer or irradiation in the far UV region induces photografting by hydrogen abstraction from the constituents of the layered assembly. Employing a combination of photoinitiators (benzophenone and 4,4′‐bis(diethylamino)‐benzophenone) and irradiation of the construct that was saturated by monomer from the gas phase in the near UV region caused the formation of a semi‐interpenetrating polymer network. Linear polymer chains of PMMA grow and entangle inside the layered assembly of the cellulose derivative. The resulting composite consists of two polymers, isopentylcellulose and poly(methyl methacrylate) demonstrating a possibility to produce a homogeneous layered composite film at nanoscopic scale as revealed by the X‐ray reflectometry. Surface photopolymerization was also achieved in the liquid phase where the monomer and photoinitiator solution was in direct contact with the layered assembly.Schematic picture of the composite films consisting of multilayered CIPC and PMMA incorporated via vapor phase photopolymerization. The scale of the CIPC hairy‐rods and periodic spacing is only schematically represented.magnified imageSchematic picture of the composite films consisting of multilayered CIPC and PMMA incorporated via vapor phase photopolymerization. The scale of the CIPC hairy‐rods and periodic spacing is only schematically represented.
Formation of Novel Layered Nanostructures from Lanthanide‐Complexes by Secondary Interactions with Ligating Monomers in Miniemulsion Droplets
Authors: Ramírez Liliana Patricia , Antonietti Markus , Landfester Katharina 
Published: December 2005

AbstractSummary: The addition of neutral, inert inner shell lanthanide complexes such as Gd(III)‐(tmhd)3, Eu(III)‐(fod)3, or Ho(III)‐thmd3, broadly available as NMR shift reagents, towards ester‐containing monomers such as butyl acrylate and subsequent polymerization in miniemulsion droplets leads to the spontaneous formation of highly organized layered nanocomposite particles, as revealed by electron microscopy and small angle X‐ray scattering. The nanocomposite comprises a lanthanide complex phase and a polymer phase with a lamellar repeat period of about 3.5 nm, rather independent of the system composition.TEM micrograph of a PGd‐3 nanocomposite and corresponding chemical structure of the complex Gd(tmhd)3.magnified imageTEM micrograph of a PGd‐3 nanocomposite and corresponding chemical structure of the complex Gd(tmhd)3.
Carbon Nanotube‐Adsorbed Electrospun Nanofibrous Membranes of Nylon 6
Authors: Kim Hyun Suk , Jin Hyoung‐Joon , Myung Seung Jun , Kang Minsung , Chin In‐Joo 
Published: December 2005

AbstractSummary: A simple and mass‐producible method was developed to densely assemble multiwalled carbon nanotubes (MWNTs) onto electrospun nylon 6 nanofibrous membranes. The process consists of dispersing the acid‐treated MWNTs in surfactant solutions or organic solvents, and dipping the nanofibrous membranes in the resulting dispersion for only 60 seconds, followed by the extraction of the surfactants in pure water and drying. The conductivity of the MWNT‐adsorbed nanofibrous membranes ranges from 2.2 × 10−2 to 1.5 × 10−1 S · cm−1, as determined by the four probe method, which implies that the MWNTs are adsorbed uniformly and densely along the nanofibrous membranes. Furthermore, the results suggest that there is a strong interaction between the acid‐treated MWNTs and nylon 6. We also investigate the amount of MWNTs present in the membranes using thermogravimetric analysis.SEM images of the non‐woven fibrous nylon 6 membranes after dip‐coating in a dispersion of the MWNTs in surfactant‐containing water.imageSEM images of the non‐woven fibrous nylon 6 membranes after dip‐coating in a dispersion of the MWNTs in surfactant‐containing water.
Microwave‐Assisted Free Radical Polymerizations and Copolymerizations of Styrene and Methyl Methacrylate
Authors: Stange Heiner , Ishaque Michael , Niessner Norbert , Pepers Michel , Greiner Andreas 
Published: December 2005

AbstractSummary: Radical homopolymerizations and copolymerizations of styrene were performed in toluene and N,N‐dimethylformamide (DMF) as solvents using different initiators with and without microwave irradiation. Only the homopolymerization of styrene under microwave irradiation in DMF with DtBP showed significantly enhanced styrene conversion whereas other initiators resulted in no or only slight increase of styrene conversion under microwave irradiation. In any case, DMF was required to gain in styrene conversion under microwave irradiation. Significantly higher monomer conversions were observed under otherwise comparable conditions in the copolymerization of styrene and methyl methacrylate (MMA) in DMF. Microwave‐induced selectivity of monomers was not observed in copolymerizations.Yield of styrene polymerizations under varying reaction conditions initiated by DtBP.imageYield of styrene polymerizations under varying reaction conditions initiated by DtBP.
Polymeric Nanocomposites of Polyurethane Block Copolymers and Functionalized Multi‐Walled Carbon Nanotubes as Crosslinkers
Authors: Jung Yong Chae , Sahoo Nanda Gopal , Cho Jae Whan 
Published: December 2005

AbstractSummary: We report on a new route to synthesize polymeric carbon nanotube‐polyurethane (PU) nanocomposites. Multi‐walled carbon nanotubes (MWNTs) functionalized by chemical modification were incorporated as a crosslinker in prepolymer, which was prepared from a reaction of 4,4′‐methylene bis(phenylisocyanate) and poly(ε‐caprolactone)diol. The reinforcing effect of carbon nanotubes in crosslinked MWNT‐PU nanocomposites was more pronounced as compared to that in conventional MWNT‐PU nanocomposites. The optimum content of chemically modified MWNTs for crosslinking with polyurethane was determined to be approximately 4 wt.‐% in our samples, based on observation of a NCO peak in FT‐IR spectroscopy. MWNT‐crosslinked polyurethane containing 4 wt.‐% modified MWNTs showed the highest modulus and tensile strength among the composites and pure PU. The presence of functionalized MWNTs in the polymeric nanocomposite yielded enhancement in the thermal stability due to crosslinking of the MWNTs with PU.Possible configuration for MWNT‐PU nanocomposite molecules and FT‐IR spectra of samples obtained during reaction of prepolymer with functionalized MWNTs (second step).imagePossible configuration for MWNT‐PU nanocomposite molecules and FT‐IR spectra of samples obtained during reaction of prepolymer with functionalized MWNTs (second step).
Reversible Addition‐Fragmentation Transfer Polymerization in the Presence of MMT Immobilized Amphoteric RAFT Agent
Authors: Zhang Bao‐Qing , Pan Cai‐Yuan , Hong Chun‐Yan , Luan Bin , Shi Peng‐Jie 
Published: December 2005

AbstractSummary: A novel reversible addition‐fragmentation transfer (RAFT) agent, 10‐carboxylic acid‐10‐dithiobenzoate‐decyltrimethylammonium bromide (CDDA), was synthesized and intercalated into montmorillonite (MMT). Successively, the CDDA‐intercalated MMT was used as RAFT agent in the in situ RAFT polymerization for preparation of the polystyrene/MMT nanocomposites. After separation of MMT, the polymers obtained have predictable molecular weight and narrow polydispersity. XRD spectra and TEM images of the nanocomposites demonstrated exfoliated structure. Thermal stability of the composites has been noticeably improved.image
Force Spectroscopy of Individual Stimulus‐Responsive Poly(ferrocenyldimethylsilane) Chains: Towards a Redox‐Driven Macromolecular Motor
Authors: Zou Shan , Hempenius Mark A. , Schönherr Holger , Vancso G. Julius 
Published: December 2005

AbstractSummary: Progress in the development of a redox‐driven macromolecular motor and the characterization of its redox‐mechanical cycle using electrochemical AFM‐based single‐molecule force spectroscopy (SMFS) is described. The elasticities of individual neutral and oxidized poly(ferrocenyldimethylsilane) (PFS) macromolecules were reversibly controlled in situ by adjusting the potential in electrochemical SMFS experiments. For the operating cycle of one individual PFS‐based molecular motor, an output of 3.4 × 10−19 J and an efficiency of 5% have been estimated.Force‐extension curves of a single‐molecule motor.imageForce‐extension curves of a single‐molecule motor.
Enforcing Effect of Double‐Fullerene End‐Capped Poly(ethylene oxide) on Mechanical Properties of Poly(L‐lactic acid)
Authors: Kai Weihua , Zhao Li , Zhu Bo , Inoue Yoshio 
Published: December 2005

AbstractSummary: The fracture strain for the composite of poly(L‐lactic acid) (PLLA) and double‐fullerene end‐capped poly(ethylene oxide) (FPEOF) was observed about 100 times of PLLA with a high modulus for room‐temperature aged samples. The aggregates of fullerene of FPEOF ends give rise to the formation of physical network of poly(ethylene oxide), which forms a pseudo‐semi‐interpenetrating network with PLLA and renders the astonishing enforcing effect on the PLLA.Strain‐stress curves of PLLA and PLLA/FPEO20F6 composite.imageStrain‐stress curves of PLLA and PLLA/FPEO20F6 composite.
Dispersion Polymerization of Methyl Methacrylate in Supercritical Carbon Dioxide in the Presence of Random Copolymers
Authors: Hwang Ha Soo , Gal Yeong‐Soon , Johnston Keith P. , Lim Kwon Taek 
Published: December 2005

AbstractSummary: Statistical random copolymers of 1H,1H‐perfluorooctyl methacrylate and 2‐dimethylaminoethyl methacrylate, poly(FOMA‐co‐DMAEMA), effectively stabilized the dispersion polymerization of methyl methacrylate in supercritical carbon dioxide. Free‐flowing, micron‐sized spherical PMMA particles could be produced with poly(FOMA‐co‐DMAEMA) containing 34 w/w% FOMA.SEM image of PMMA particles prepared with poly(FOMA‐co‐DMAEMA) (34:66).imageSEM image of PMMA particles prepared with poly(FOMA‐co‐DMAEMA) (34:66).
Dynamics of Hollow Nanofiber Formation During Solidification Subjected to Solvent Evaporation
Authors: Guenthner Andrew J. , Khombhongse Sureeporn , Liu Wenxia , Dayal Pratyush , Reneker Darrell H. , Kyu Thein 
Published: December 2005

AbstractSummary: To mimic the emergence of gradient morphology in polymer nanofibers, a new theoretical approach has been developed in the context of Cahn‐Hilliard time evolution equation, alternatively known as time‐dependent Ginzburg‐Landau equation (Model B) involving concentration order parameter. The effects of solvent evaporation on the morphology evolution of the nanofibers have been demonstrated. The numerical simulation showed that the formation of skin layers is governed by the competition between solvent evaporation rate and mutual diffusion rate. That is to say the skin layers are formed in the nanotube whenever the rate of evaporation exceeds a critical value; otherwise, a solid fiber is formed. In hollow nanofibers, the layer can grow to a substantial fraction of the fiber diameter, allowing it to remain intact, albeit often in a collapsed form.The cross‐sectional concentration profile of the emerging fiber.magnified imageThe cross‐sectional concentration profile of the emerging fiber.
Rate Optimization in Controlled Radical Emulsion Polymerization Using RAFT
Authors: Prescott Stuart W. , Ballard Mathew J. , Rizzardo Ezio , Gilbert Robert G. 
Published: December 2005

AbstractSummary: Means of improving rates in RAFT‐mediated radical emulsion polymerizations are developed, by setting out strategies to minimize the inhibition and retardation that always are present in these systems. These effects arise from the RAFT‐induced exit of radicals, the desorption of the RAFT‐reinitiating radical from the particles, and the specificity of the reinitiating radical to the RAFT agent. Methods for reducing the inhibition period such as using a more hydrophobic reinitiating radical are predicted to show a significant improvement in the inhibition periods. The time‐dependent behavior of the RAFT adduct to the entering radical and the RAFT‐induced exit (loss) of radicals from particles are studied using a previously described Monte Carlo model of RAFT/emulsion particles. It is shown that an effective way of reducing the rate coefficient for the exit of radicals from the particles is to use a less active RAFT agent. Techniques for improving the rate of polymerization of RAFT/emulsion systems are suggested based upon the coherent understanding contained in these models: the use of an oligomeric adduct to the RAFT agent, a less water‐soluble RAFT re‐initiating group, and a less active RAFT agent.Populations of the different types of particles (left axis) along with the concentration of the initial RAFT agent, DR (right axis), as a function of time.magnified imagePopulations of the different types of particles (left axis) along with the concentration of the initial RAFT agent, DR (right axis), as a function of time.
A Definition of Dynamically Accessible Volume for Thermal Systems
Authors: Molina‐Mateo José , Meseguer‐Dueñas José M. , Gómez‐Ribelles José L. 
Published: December 2005

AbstractSummary:The glass transition and physical aging processes of a polymeric material have been simulated using the bond fluctuation model. Two potentials that represent intra‐ and inter‐molecular interactions have been employed. Simulations of different thermal histories that include cooling from equilibrium have been performed. The evolution of the system and the structure attained at low temperature are analyzed as a function of the assumed weight of inter‐ and intra‐molecular potentials in the total energy of the system. A new way of characterizing the free volume of the system and its evolution with the temperature or time is proposed. It is based on the concept of dynamically accessible volume but modified in the sense of considering the probability of an empty site to be accessed according to a Metropolis criterion. The results obtained show that the thermal redefinition of the dynamically accessible volume, TDAV, offers a better representation of the real mobility of the polymeric systems. The use of information on the structure of the system coming from the pair‐correlation function and the molecular mobility in the glassy state characterized by the time evolution of TDAV allows to reach the conclusion that a combination of inter‐ and intra‐molecular potentials produces the vitrification of the polymer system on cooling.magnified image
Molecular Weight Distribution of Living Radical Polymers
Authors: Tobita Hidetaka 
Published: December 2005

AbstractSummary: The molecular weight distribution formed in an ideal living radical polymerization is considered theoretically. It was found that the hypergeometric function that combines the most probable and the Poisson distribution represents a fundamental distribution of the living radical polymers. The number‐ and weight‐average molecular weights are derived for this fundamental distribution, together with those for polymerizations in a batch and in a continuous stirred tank reactor. These average molecular weight functions are obtained based on the arithmetic calculations without deriving the distribution functions. The effect of the monomer transfer reactions on the formed MWD is also considered. The present study clarifies the relationship between the reaction mechanism and the formed molecular weight distribution as well as the fundamental characteristics of living radical polymers.Calculated number fraction distribution N(r) development with (dashed) and without (solid) the monomer transfer reactions.magnified imageCalculated number fraction distribution N(r) development with (dashed) and without (solid) the monomer transfer reactions.
Molecular Weight Distribution of Living Radical Polymers
Authors: Tobita Hidetaka 
Published: December 2005

AbstractSummary: A new Monte Carlo simulation method is proposed for the living radical polymerization on the basis of the random sampling technique. The stable free‐radical polymerization is used as a specific reaction mechanism. The illustrative calculations are conducted to investigate the effects of simultaneous use of two different types of radical initiators, with a large and a small decomposition rate constant. The addition of second initiator that decomposes slowly leads to a significant increase in the polymerization rate. The increased frequency of forming the dead and new growing polymer chains makes the molecular weight distribution (MWD) broader. On the other hand, however, there exists a weak but definite factor to reduce the polydispersity, which may compensate the broadening. On the basis of the simulation studies, one may find an excellent reaction condition to produce polymer with a higher productivity, having a larger MW, and with a narrow distribution. The effect of the monomer transfer reactions on the formed MWD is investigated to find that the transfer reactions must be accounted for when the designed number‐average chain length is larger than about 10% of 1/Cm, where Cm is the monomer transfer constant.Calculated weight fraction distribution W(log r) with (C11) and without (C10) the second initiator.magnified imageCalculated weight fraction distribution W(log r) with (C11) and without (C10) the second initiator.
Progress in the pursuit of therapeutic adenosine receptor antagonists
Authors: Moro Stefano , Gao Zhan‐Guo , Jacobson Kenneth A. , Spalluto Giampiero 
Published: December 2005

AbstractEver since the discovery of the hypotensive and bradycardiac effects of adenosine, adenosine receptors continue to represent promising drug targets. First, this is due to the fact that the receptors are expressed in a large variety of tissues. In particular, the actions of adenosine (or methylxanthine antagonists) in the central nervous system, in the circulation, on immune cells, and on other tissues can be beneficial in certain disorders. Second, there exists a large number of ligands, which have been generated by introducing several modifications in the structure of the lead compounds (adenosine and methylxanthine), some of them highly specific. Four adenosine receptor subtypes (A1, A2A, A2B, and A3) have been cloned and pharmacologically characterized, all of which are G protein‐coupled receptors. Adenosine receptors can be distinguished according to their preferred mechanism of signal transduction: A1 and A3 receptors interact with pertussis toxin‐sensitive G proteins of the Gi and Go family; the canonical signaling mechanism of the A2A and of the A2B receptors is stimulation of adenylyl cyclase via Gs proteins. In addition to the coupling to adenylyl cyclase, all four subtypes may positively couple to phospholipase C via different G protein subunits. The development of new ligands, in particular, potent and selective antagonists, for all subtypes of adenosine receptors has so far been directed by traditional medicinal chemistry. The availability of genetic information promises to facilitate understanding of the drug–receptor interaction leading to the rational design of a potentially therapeutically important class of drugs. Moreover, molecular modeling may further rationalize observed interactions between the receptors and their ligands. In this review, we will summarize the most relevant progress in developing new therapeutic adenosine receptor antagonists. © 2005 Wiley Periodicals, Inc.
Single‐mode yield in DFB laser diodes with reflecting facets
Authors: Ferreira Fernandes Carlos Alberto 
Published: December 2005

AbstractConventional DFB laser diodes present symmetric emission patterns, thus making these structures inadequate as single‐mode lasers. The simplest way of achieving single longitudinal‐mode operation is to make one or more facets as cleaved, rather than using AR coating. Single‐mode yield in asymmetric structures is calculated using matrix techniques. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 205–209, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21306
Broadband coplanar waveguide‐fed printed monopole antenna with strip‐sleeves
Authors: Coulibaly Yacouba , Denidni Tayeb A. , Talbi Larbi 
Published: December 2005

AbstractIn this paper, the design of a new broadband printed antenna for wireless applications is presented. The proposed antenna structure consists of a planar monopole fed by a coplanar waveguide (CPW) and four strip sleeves. With the integration of these parasitic elements, a wide bandwidth response is achieved. The antenna is designed at the operating frequency of 2.8 GHz, and a parametric study is also performed in order to optimize its operating bandwidth. To validate the design, an antenna prototype is fabricated and tested, and good agreement between the simulated and measured results is obtained. The experimental results show a bandwidth of 49.3%. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 209–212, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21307
A novel separable backward–central FDTD method
Authors: Yu Wenhua , Su Tao , Mittra Raj 
Published: December 2005

AbstractIn this paper, we present a novel separable backward–central FDTD (SBC‐FDTD) method in which the backward and central differences are used to discretize both time and spatial directive of the Maxwell's equations. For the type of problem in which the FDTD cell size in one direction is much smaller than those in the other directions, the time step in the proposed separable backward‐central FDTD technique can be chosen based on the largest cell size instead of the smallest one used in the conventional Yee's FDTD. Compared to the alternating‐direction implicit FDTD (ADI‐FDTD), although the proposed approach is not unconditionally stable, it allows us to explicitly solve electric and magnetic fields in one direction. Both the numerical experiments and the stability property demonstrate that the proposed scheme is stable and accurate. A TE mode wave is used to validate the proposed technique. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 212–215, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21308
Wideband MIMO measurements of outdoor NLOS channels
Authors: Yang Yaoqing , Xu Guanghan , Ling Hao 
Published: December 2005

AbstractThe measurement results of the wideband wireless multiple‐input multiple‐output (MIMO) channels in outdoor environments are presented. Our wideband wireless MIMO channel sounder consists of four transmitters and eight receivers, and operates at a carrier frequency of 1.8 GHz with a bandwidth of 2.5 MHz. After obtaining the multipath delay profiles from the data collected in non‐line‐of‐sight (NLOS) environments, realistic wideband MIMO channel capacities are computed and compared with the ideal channel simulation. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 216–218, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21309