bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mechanism of the molecular hysteresis
Authors: Sano Mitsuru 
Published: April 2003

AbstractThe redox behavior in acetone solution of (1,5‐dithiacyclooctane 1‐oxide)bis(pentaammineruthenium(II)) has been characterized, where the concept of “molecular hysteresis” is presented. Detailed thermodynamics for the complex are studied, in which intramolecular electron transfer rates for Ru3+OS/Ru2+→Ru2+SO/Ru3+ were determined as 0.12 sec−1 and 0.055 sec−1.The molecular hysteresis consists of two important factors: isomerizations for the sulfoxideruthenium complexes and the slow intramolecular electron transfer in the complex; both are examined. Isomerization rates for Ru3+S→O and Ru2+O→S determined range from 0.4 to 5000 sec−1 and from 0.7 to 16 sec−1, respectively, for [Ru(NH3)5(sulfoxide)]2+/3+. A mechanism for the slow electron transfer in the complex is also presented. Features of molecular hysteresis are discussed.
Electron transfer of heme proteins on the ITO electrode in polymer solvents
Authors: Ohno Hiroyuki , Kawahara Natsue Y. 
Published: April 2003

AbstractThe redox reaction of poly(ethylene oxide) (PEO)‐modified hemoglobin (PEO–Hb) was analyzed in PEO oligomers with cyclic voltammetry. The PEO–Hb was made soluble in PEO with molecular weight of 200 (PEO200) containing 0.5 M KCI. Quasi‐reversible redox signals of PEO–Hb were obtained by using an indium tin oxide (ITO) glass working electrode. PEO–Hb, cast on the ITO electrode, also showed the redox response in PEO with molecular weight of 400 (PEO400). The peak current of PEO–Hb on the ITO electrode gradually increased during potential cycling. The effect of the scan rate on the quantity of electricity (Q) was analyzed after the peak current reached a constant value. The constant Q value was observed at the scan rate ranging from 30 to 500 mV/sec. The number of reactive PEO–Hb molecules was estimated from this constant Q‐value. It was suggested that the electron transfer was carried out at the first layer of the PEO–Hb which was in direct contact with the ITO electrode. The quantity of electricity of PEO–Hb increased when the ITO electrode was first washed in an aqueous medium with ultrasonicator. This strongly suggested that the more effective surface area of the ITO electrode turned to be covered with PEO–Hb when the microporous region of the ITO particles was more hydrated.
Structural effect of redox active sites on electron hopping rate in mixed conducting copolymers
Authors: Nagasaka Hideaki , Watanabe Masayoshi 
Published: April 2003

AbstractThe copolymers consisting of a redox monomer, vinylferrocene or 10‐methyl‐3‐vinylphenothiazine, and an ion‐conducting monomer, ω‐methoxy‐nona(ethylene oxide)‐methacrylate, have been prepared. The copolymers, complexed with lithium perchlorate, exhibit reversible redox activity in the absence of low molecular solvents. The charge transport during the redox reactions is carried out by electron hopping reactions between the redox active centers, indicating that the copolymers can be regarded as intrinsic ion/electron mixed conductors. The electron hopping rates during the redox reactions have been evaluated by using an electrochemical technique under diffusion‐controlled conditions. The electron diffusion coefficients in the vinylferrocene and 10‐methyl‐3‐vinylphenothiazine copolymers are 6.8 × 10−12 cm2 sec−1 and 3.2 × 10−11 cm2 sec−1 at room temperature, respectively, and are larger in the latter copolymer. The electron hopping rate would be influenced by the slow and temperature‐dependent dynamics of the polymer segment, judging from the relatively low electron diffusivity and from its quite large and non‐Arrhenius temperature dependency.
Preparation and photochromic properties of oligomeric poly(dimethylsiloxane) with the spiropyran or spirooxazine moiety in the side chain
Authors: Nakao Ren , Ueda Norikazu , Abe Yasuo , Horii Toyokazu , Inoue Hiroo 
Published: April 2003

AbstractSpirobenzopyran 1, with the 3‐(diethoxymethylsilyl)‐propyl group at the N atom, was synthesized. The condensation reaction of the spiropyran 1 and diethoxydimethylsilane gave oligomeric poly(dimethylsiloxane) with the spiropyran moiety in the side chain. The oligomer was photochromic; its colour changed from colorless to purple‐red on uv irradiation and the color faded on visible irradiation or on standing in the dark. The half‐decay time of the thermal decoloration was about twice that of monomeric spiropyran dissolved in the dimethylsiloxane oligomer. Photochromic poly(dimethylsiloxane) with the spirooxazine moiety in the side chain was also prepared.
Preparation of poly(1,4‐phenylene)s by electro‐oxidative polymerization
Authors: Oyaizu Kenichi , Yamamoto Kimihisa , Asada Toshio , Nishide Hiroyuki , Tsuchida Eishun 
Published: April 2003

AbstractThe effect of substituents on the electropolymerization of benzene derivatives and the redox properrties of the corresponding polymers were determined using Brown's substituent constants (σ+). Electron‐donating groups lower the oxidation potential by which increase in the current efficiency was observed. However, stabilization of the produced cation radicals by the electron‐donating groups resulted in a decrease in the polymerization efficiency. The appropriate values of σ+ for the efficient polymerization ranged near −1.5.
Mechanical properties of films from polymer latices
Authors: Zosel Albrecht 
Published: April 2003

AbstractThe mechanical behavior of latex films is governed by their macromolecular nature as well as by their origin from particles dispersed in an aqueous medium. When monomers of different polarity are copolymerized in emulsion copolymerization, a heterogeneous distribution of the polar groups in the latex and the film can occur, owing to the different water solubilities of the comonomers. Films from these latices in many cases show a two‐phase morphology, first, consisting of the main polymer within the particles and, second, a phase which is concentrated in the interphase between the original particles and which has a strong influence on the mechanical properties of the films. Films from latices with crosslinked particles behave like homogeneous networks in the linear viscoelastic range, i.e. at small strains. Structured networks are found when latex films are interparticularly crosslinked during or after film formation, e.g. by polar bifunctional monomers or metal salts. Tensile tests of films show that the mechanical strength of latex films develops in the last stage of film formation by interdiffusion and entaglement formation across particle boundaries.
Structure–property relationships of latex films: a special emphasis on viscoelastic behavior and water vapor permeability
Authors: Richard Joël 
Published: April 2003

AbstractThe purpose of this work is to investigate the structure and related properties of polymer films obtained upon latex dehydration and coalescence of the particles. Coalesced latex films can be considered as cellular structures, in which the cell cores consist of the hydrophobic particle cores, while the array of interfacial membranes mainly contains hydrophilic species. The linear viscoelastic behavior of the films and their water vapor permeability properties are investigated using dynamic micromechanical analysis and vapor sorption, respectively. It is shown that both core and membrane have a strong effect on the film properties. The structure and viscoelastic behavior of polymer films obtained from sterically stabilized latexes are also studied and compared with that observed for films obtained from electrostatically stabilized ones.
High strain thermomechanical properties of IBMA‐functionalized poly(butyl acrylate) films
Authors: Hidalgo Manuel , Cavaillé Jean‐Yves , Guillot Jean , Perez Joseph , Zanetto Jean‐Emile 
Published: April 2003

AbstractBatch emulsion polymerization was used in order to obtain latexes from a mixture of butyl acrylate (ca. 90% mole), and a hydrophobic crosslinkable functional monomer called N‐isobutoxymethyl acrylamide (ca. 10% mole). Films were then cast from these latexes, and their thermomechanical properties were studied before and after a heat treatment intended to provoke crosslinking of the functional groups. The differential thermal analysis and the dynamic mechanical analysis of the film samples proved that the functional monomer copolymerized with butyl acrylate; the dynamic mechanical analysis revealed also that crosslinking took place after the heat treatment. Different kinds of high strain experiments (among which there were stress relaxation tests) were carried out in a tensile testing machine Important differences were thus shown to appear between the “as‐dried” and “annealed” samples. In the case of stress relaxation experiments, simple mechanical models were used in order to fit the experimental data, both during the stretching experiment and the stress relaxation following it. The analysis of the high‐strain experiments and their simulation led to the conclusion that the films contained high molecular weight polymers having a broad molecular weight distribution, and that their crosslinking enhanced the entropic elastic behavior, even though a viscoelastic, large relaxation time contribution was kept; the hypothesis of its coming from a trapped‐entanglement effect was proposed.
Glass transition and film formation of VeoVa/vinyl acetate latices; role of water and co‐solvents
Authors: Heymans Denis M. C. , Daniel Mervyn F. 
Published: April 2003

AbstractThe physical forces causing deformation of latex particles during the film formation process have been witley studied. However, the forces resisting particle deformation are still poorly characterized. It is clear that the extent of particle deformation is dependent on the viscoelastic nature of the polymer. In an emulsion, the latex particles will normally contain water, surfactants and “free” monomers which lead to plasticization of the polymer. Although this effect has been recognized, so far it has been studied only on films that had been dried and then partially or completely swollen by water.In this work, plasticization of the emulsion polymers by water and co‐solvent has been quantified via differential scanning calorimetry investigation directly on the aqueous latex dispersions. More specifically, the plasticizing effect of water on VeoVa/vinyl acetate copolymer latices and its influence on minimum film‐forming temperature (MFFT) has been studied. A linear correlation has been found between Tg and MFFT for the wet latices. This new direct method should help to improve our understanding of the forces resisting latex film formation.Additionally, the homogeneous distribution of the hydrophobic and hydrophilic monomers (VeoVa and vinyl acetate respectively) in the latex particles was verified via a 13C‐NMR (nuclear magnetic resonance) study performed directly on the latices. This study confirmed that no significant core/shell type of morphology had influenced latex film formation.
Reactive blends of thermoplastics and latex particles
Authors: Vázquez Flavio , Cartier Hervé , Landfester Katharina , Hu Guo‐Hua , Pith Tha , Lambla Morand 
Published: April 2003

AbstractMonodisperse homogeneous and core–shell latex particles of various sized between 200 and 600 nm were synthesized by emulsion copolymerization. Some of the core–shell particles were functionalized with epoxy groups at their peripheries upon introduction of glycidyl methacrylate (GMA) during the synthesis. The core consisted of crosslinked polybutylacrylate and the shell polymethylmethacrylate. Synthesis conditions at high and low temperatures were optimized to obtain coreshell particles with a well‐defined morphology. The particles were characterized by quasi‐elastic light scattering, scanning electron microscopy and transmission electron microscopy.The latex particles functionalized with GMA were then dispersed into a reactive matrix (styrene and maleic anhydride copolymer) using a batch mixer to obtain blends with well‐defined and stabilized morphology. 4 Dimethylaminopyridine was used as a catalyst. The reaction between the epoxy groups at the particle surface and the maleic anhydride or diacid groups of the matrix was evaluated by torque and extraction techniques. A small amount of conversion generates sufficient amounts of grafted species at the matrix and particle interfaces to ensure a good interfacial adhesion.
Impact modification of thermoplastics by methyl methacrylate and styrene‐grafted natural rubber latexes
Authors: Schneider Michael , Pith Tha , Lambla Morand 
Published: April 2003

AbstractThe preparation and characterization of polymer blends with structured natural rubber (NR)‐based latex particles are presented. By a semicontinuous emulsion polymerization process, a natural rubber latex (prevulcanized or not) was coated with a shell of crosslinked polymethylmethacrylate (PMMA) or polystyrene (PS). Furthermore, core–shell latexes based on a natural rubber/crosslinked PS latex semi‐interpenetrating network were synthesized in a batch process. These structured particles were incorporated as impact modifiers into a brittle polymer matrix using a Werner & Pfleiderer twin screw extruder. The mechanical properties of PS and PMMA blends with a series of the prepared latexes were investigated. In the case of PMMA blends, relatively simple core (NR)–shell (crosslinked PMMA) particles improved the mechanical properties of PMMA most effectively. An intermediate PS layer between the core and the shell or a natural rubber core with PS subinclusions allowed the E‐modulus to be adjusted. The situation was different with the PS blends. Only core–shell particles based on NR‐crosslinked PS latex semi‐interpenetrating networks could effectively toughen PS. It appears that microdomains in the rubber phase allowed a modification of the crazing behavior. These inclusions were observed inside the NR particles by transmission electron microscopy. Transmission electron photomicrographs of PS and PMMA blends also revealed intact and well‐dispersed particles. Scanning electron microscopy of fracture surfaces allowed us to distinguish PS blends reinforced with latex semi‐interpenetrating network‐based particles from blends with all other types of particles.
Sterically stabilized silica colloids: Radical grafting of poly(methyl methacrylate) and hydrosilylative grafting of silicones to functionalized silica
Authors: Ketelson Howard A. , Brook Michael A. , Pelton Robert H. 
Published: April 2003

AbstractColloidal silica sols having a narrow dispersity, prepared by the ammonia‐catalyzed hydrolysis of Si(OEt)4, were functionalized by reaction with vinyltrimethoxysilane (H2CCHSi(OMe)3) or methacryloxypropyltri‐methoxysilane (H2CCMeCO2(CH2)3Si(OMe)3. The electrostatically stabilized colloids were stable in acetone and dimethylformamide. Radical polymerization of methyl methacrylate in the presence of either type of functionalized particle led to particles with surfacegrafted poly(methyl methacrylate) (PMMA). The efficiency of polymer grafting was shown to be related to the nature of the functional groups. The PMMA‐modified, sterically stabilized particles were colloidally stable in solvents ranging from acetone to toluene but unstable in water or hexane. The vinyl functionalized silica was alternatively reacted with HSiMe2‐terminated silicones in a platinum‐catalyzed hydrosilylation. The resultant sterically stabilized particles were stable in hexane. It was thus possible to convert the unmodified silica to organo‐functionalized silica and finally to polymer‐grafted silica while maintaining colloidal stability. During the course of these modifications, the mechanism for colloidal stability changed from electrostatic to steric stabilization.
Polymerization of acrylamide and methylmethacrylate at the surface of submicron polypyrrole particles
Authors: Degobert Patrick , Henry François 
Published: April 2003

AbstractThis paper presents two methods of encapsulation of polypyrrole latex particles of different sizes by an insulating polymer. The first method concerns the encapsulation by inverse emulsion polymerization of acrylamide with crosslinking agent. That method is effective for the smallest particles (about 100 nm). The second method concerns encapsulation by direct emulsion polymerization of methylmethacrylate. Inhibition of polymerization occurs if potassium persulfate is used as the initiator, whereas no inhibition is observed with 4,4′ azobis 4‐cyanopentanoic acid as the initiator. These results are explained in terms of the ion‐exchange capacity of conducting polymers. This second method seems to be effective for all the sizes of polypyrrole particles. These encapsulated particles have been characterized by transmission electron microscopy, scanning electron microscopy, quasi elastic light scattering, cyclic voltametry and electrophoresis. Cyclic voltammetry recently developed on aqueous suspensions of polypyrrole particles was revealed to be the best technique because of its simplicity and speed.
Rigid aromatic fractal polyamides
Authors: Aharoni Shaul M. 
Published: April 2003

AbstractThe preparation of rigid aromatic, highly branched polyamides is described. Owing to the method of preparation and the chosen ratio of difunctional to trifunctional monomers, these entities are highly porous and not dendrimeric in nature. They better conform with the fractal model and are therefore called fractal polyamides (FPs). The effects of variations in the polymerization procedure, in total monomer concentration, in the ratio of amine to carboxyl groups and in the duration of the polycondensation reaction are investigated. Some characterization was performed and the results are presented and briefly discussed.
Prepation of poly(N‐isopropylacrylamide)‐grafted silica gel and its temperature‐dependent interaction with proteins
Authors: Yoshioka Hiroshi , Mikami Masato , Nakai Tomoko , Mori Yuichi 
Published: April 2003

AbstractPoly(N‐isopropylacrylamide) oligomer was immobilized onto a silica gel surface. The gel adsorbed a hydrophobic protein γ‐globulin (IgG) at 37°C, however, did not adsorb IgG at 24°C. The adsorbed IgG at 37°C was adsorbed by lowering the temperatue, No adsorption of a hydrophilic protein bovin serum albumin (BSA) onto this matrix was observed at 37°C nor 24°C.
Application of poly(N‐isopropylacrylamide) with pendent β‐cyclodextrin to separation of a guest substance in an aqueous solution
Authors: Yoshioka Hiroshi , Nakai Tomoko , Mori Yuichi 
Published: April 2003

AbstractPoly(N‐isopropylacrylamide) with pendent β‐cyclodextrin (PNI‐PAAm‐CD) was prepared by copolymerization of acryloyl‐β‐CD and NIPAAm. During the temperature‐induced phase separation of an aqueous solution of PNIPAAm‐CD, Toluidine Blue dye in the solution was separated into the precipitate of PNIPAAm‐CD by way of inclusion complex formation.
Mechanism of copolymerization of acrylamide with a polymerizable surfactant
Authors: Vašková Viera , Renoux Delphine , Bernard Maxime , Selb Joseph , Candau Françoise 
Published: April 2003

AbstractAssociating polymers have been prepared by radical copolymerization in water of acrylamide with a micelleforming cationic polymerizable surfactant. To estimate the locus of initiation, the polymerizations were carried out in the presence of initiators and radical inhibitors of various solubilities (water‐soluble or oil‐soluble), and the decay of inhibitor concentration has been monitored by electron spin resonance spectroscopy. Conversion–time curves simultaneously determined. The experimental data have been interpreted by taking into account the concentration and lifetime of the different radical species (primary radicals, oligoradicals, inhibitors), their partitioning between the micelles and the aqueous continuous phase, and the dynamics of the micellar system. Analysis of the data provided some insight into the copolymerization mechanism of these micellar systems.
Surface functionalization of polystyrene latex particles with a liposaccharide monomer
Authors: Revilla J. , Elaïssari A. , Pichot C. , Gallot B. 
Published: April 2003

AbstractEmulsifier‐free latexes with immobilized carbohydrate residues have been prepared by batch or seed (co)polymerization of styrene in the presence of 11‐(N‐p‐vinylbenzyl)amido undecanoyl maltobionamide (LIMA). The critical micelle concentration and the molecular surface area of LIMA were determined by surface tension and fluorescence measurements. Batch polymerization of LIMA with styrene was first performed using potassium persulfate, proving the efficiency of LIMA as emulsifier. Seed copolymerization was then investigated using polystyrene seed particles with varying experimental conditions (especially the LIMA surface coverage). Material balance of LIMA between aqueous phase and particles was obtained by separating both phases by ultracentrifugation and it was found that the surfaceactive monomer is preferentially on or in the particle (nearly 100% in batch and at most 70% in seed copolymerization). The presence of the carbohydrate residues at the particle surface was directly evidenced by 1H‐nuclear magnetic resonance, electron spectroscopy for chemical analysis and electrophoretic mobility.
Steric stabilization of polystyrene colloids using thiol‐ended polyethylene oxide
Authors: Vidal Frederic , Guillot J. , Guyot A. 
Published: April 2003

AbstractThiol‐ended polyethylene oxide (I) has been prepared from the esterification of thioglycolic acid with monomethylether of polyoxyethylene glycol. Emulsion polymerization of styrene (and, in a few cases, methylmethacrylate as comonomer) was carried out in the presence of I using either water‐soluble azo initiator or t‐butylhydroperoxide. In the former case, bimodal particle size distribution was obtained while monodisperse latexes could be prepared in the latter case. Then a redox system was formed from I and t‐BuOOH so that I was both an initiator and a transfer agent. Good steric stabilization of the latexes was observed. The polyethylene oxide sequence of I was partly incorporated at the surface of the latex particles, but the incorporation yield remained limited (between 7 and 18%). Most of the resdue of I remained in the serum.
Preparation and characterization of cationic polystyrene latex particles of different aminated surface charges
Authors: Ganachaud F. , Mouterde G. , Delair Th. , Elaïssari A. , Pichot C. 
Published: April 2003

AbstractFunctionalized polystyrene latex particles were obtained either by seed particle functionalization or by the shot‐growth procedure using 2,2′‐azobis (2‐amidino‐propane) dihydrochloride as an initiator and vinylbenzylamine hydrochloride as a cationic monomer. The capabilities of both processes to produce functionalized particles in terms of functionalization yields coming from surface amino group titrations were compared. Different titration methods were performed and a new technique was introduced using fluorescamine.
Use of block copolymer surfactants in the inverse‐suspension polymerization of acrylamide
Authors: Hernández‐Barajas José , Hunkeler David J. 
Published: April 2003

AbstractA comprehensive experimental investigation of the inverse microsuspension polymerization of acrylamide using an oil‐soluble initiator and a block copolymeric surfactant whose hydrophobic miety is poly(12‐hydroxystearic acid) and whose hydrophilic moeity is polyethylene oxide was carried out. It was found that the initial polymerization rate was first order with respect to molar monomer concentration, first order with respect to molar initiator concentration and zeroth order with respect to molar emulsifier concentration. Based on these experimental findings, a mechanism was proposed which includes initiation, propagation transfer to monomer and termination. It also includes transfer to impurities which are believed to be found in the surfactant. The kinetic model developed from the proposed mechanism is found to be in good agreement with the experimental conversion and weight‐average molecular weight data. Comparing with sorbitan esters of fatty acids, the copolymeric surfactant provides higher polymerization rate and very high and linear molecular weight comparable to those obtained by solution polymerization.