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Norio Tsubokawa - One of the best experts on this subject based on the ideXlab platform.
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Photografting of polymers onto nanosized Silica Surface initiated by eosin moieties immobilized onto the Surface
Journal of Polymer Science Part A: Polymer Chemistry, 2004Co-Authors: Masayoshi Satoh, Kumi Shirai, Hiroshi Saitoh, Takeshi Yamauchi, Norio TsubokawaAbstract:The photograft polymerization of various vinyl monomers onto nanosized Silica Surfaces was investigated. It was initiated by eosin moieties introduced onto the Silica Surface. The preparation of the Silica with eosin moieties was achieved by the reaction of eosin with benzyl chloride groups on the Silica Surface.These were introduced by the reaction of Surface silanol groups with 4-(chloromethyl)phenyltrimethoxysilane in the presence of t-butyl ammonium bromide as a phase-transfer catalyst. The photopolymerization of various vinyl monomers, such as styrene, acrylamide, acrylic acid, and acrylonitrile was successfully initiated by eosin moieties on the Silica Surface in the presence of ascorbic acid as a reducing agent and by oxygen. The corresponding polymers were grafted from the Silica Surface. The grafting efficiency (percentage of grafted polymer to total polymer formed) in the photoinitiation system was much larger than that in the radical polymerization initiated by Surface radicals; these radicals were formed by the thermal decomposition of azo groups introduced onto the Silica Surface. It was found that the polymer-grafted Silica gave stable dispersions in good solvents of grafted polymer and the wettability of the Surfaces can be easily controlled by grafting of polymers.
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Grafting of ‘dendrimer-like’ highly branched polymer onto ultrafine Silica Surface
Reactive and Functional Polymers, 1998Co-Authors: Norio Tsubokawa, Hajime Ichioka, Toshiya Satoh, Shinji Hayashi, Kazuhiro FujikiAbstract:Abstract To modify ultrafine Silica Surface, the grafting of polyamidoamine dendrimer, a new class of topological macromolecules, onto the Silica Surface was investigated. Introduction of amino groups as an initiator site on the Silica Surface was achieved by the treatment of the Silica with γ-aminopropyltriethoxysilane. Polyamidoamine dendrimer was propagated from Silica Surface by repeating two processes: (1) Michael addition of methyl acrylate to Surface amino groups, and (2) amidation of the resulting esters with ethylenediamine. The amino group content of the resulting Silica increased from 0.40 mmol/g to 8.30 mmol/g after 10th generation. In addition, the percentage of grafting increased with increasing generation and reached to 575.7% after 10th generation. However, these values were considerably smaller than the theoretical values. This indicates that the propagation of dendrimer grafting from Silica Surface was not achieved theoretically and ‘dendrimer-like’ highly branched polymer was grafted onto the Surface, because of steric hindrance of grafted dendrimer. The effects of amino group content as an initiator site and reaction conditions on the grafting of the polymer onto Silica Surface were also investigated. Dendrimer-like highly branched polymer grafted ultrafine Silicas gave a stable dispersion in a good solvent for the polyamidoamine dendrimer.
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Surface grafting of polymers onto ultrafine Silica: cationic polymerization initiated by benzylium perchlorate groups introduced onto ultrafine Silica Surface
Polymer Bulletin, 1995Co-Authors: Norio Tsubokawa, Kazuhiro Saitoh, Yukio ShiraiAbstract:The cationic graft polymerization initiated by benzylium perchlorate groups introduced onto ultrafine Silica Surface was investigated. The introduction of benzylium perchlorate groups onto the Surface was achieved by the reaction of silver perchlorate with Surface benzyl chloride groups, which were introduced by the treatment of Silica with 4-(chloromethyl)phenyltrimethoxysilane. The cationic graft polymerization of styrene and cationic ring-opening polymerization of ε-caprolactone were found to be initiated by the Surface benzylium perchlorate groups and the corresponding polymers were grafted onto the Surface. The percentage of grafting onto Silica Surface decreased with increasing polymerization temperature, because chain transfer reaction of growing polymer cation is accelerated with increasing polymerization temperature.
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Grafting of polymers with controlled molecular weight onto ultrafine Silica Surface
Journal of Polymer Science Part A: Polymer Chemistry, 1995Co-Authors: Norio Tsubokawa, Sachio YoshikawaAbstract:To graft polymers with controlled molecular weight and narrow molecular weight distribution, the grafting of polymers onto ultrafine Silica Surface by the termination of living polymer cation with amino groups introduced onto the Surface was investigated. The introduction of amino or N-phenylamino groups onto the Silica Surface was achieved by the treatment of Silica with γ-aminopropyltriethxysilane or N-phenyl-γ-aminopropyltrimethoxysilane. It was found that these amino groups on Silica are readily reacted with living poly(isobutyl vinyl ether) (polyIBVE), which was generated with CF3COOH/ZnCl2 initiating system, and polyIBVE with controlled molecular weight and narrow molecular weight distribution is grafted onto the Surface. By the termination of living poly(2-methyl-2-oxazoline), which was generated with methyl p-toluenesulfonate initiator, with amino groups on Silica, polyMeOZO was also grafted onto the Surface. The percentage of grafting of polymer onto the Silica Surface decreased with increasing molecular weight of the living polymer, because the steric hindrance of Silica Surface increases with increasing molecular weight of living polymer. Polymer-grafted Silica gave a stable dispersion in a good solvent for grafted chains. © 1995 John Wiley & Sons, Inc.
Patrice Malfreyt - One of the best experts on this subject based on the ideXlab platform.
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Multiscale Modeling of the Polymer–Silica Surface Interaction: From Atomistic to Mesoscopic Simulations
The Journal of Physical Chemistry C, 2015Co-Authors: Gaëtan Maurel, Florent Goujon, Benoit Schnell, Patrice MalfreytAbstract:We propose here to investigate the interaction between cis-1,4 polybutadiene polymer chains and a Silica Surface. We opt for mesoscopic simulations in order to simulate the polymer chains onto significant length and time scales. We develop realistic coarse-grained (CG) models for this kind of interaction by using a bottom-up approach consisting of developing these effective CG models from atomistic simulations. We investigate then the structural and dynamical properties of polymer chains adsorbing onto a Silica Surface at different separation distances. We complete this work by studying the adsorption of free polymer chains onto the grafted Silica Surface as a function of the grafting density. The conformational and the dynamical properties of the free and grafted chains are then determined with respect to the Surface coverage.
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Multiscale modeling of the polymer-Silica Surface interaction: from atomistic to mesoscopic simulations.
Journal of Physical Chemistry C, 2015Co-Authors: Gaëtan Maurel, Florent Goujon, Benoit Schnell, Patrice MalfreytAbstract:We propose here to investigate the interaction between cis-1,4 polybutadiene polymer chains and a Silica Surface. We opt for mesoscopic simulations in order to simulate the polymer chains onto significant length and time scales. We develop realistic coarse-grained (CG) models for this kind of interaction by using a bottom-up approach consisting of developing these effective CG models from atomistic simulations. We investigate then the structural and dynamical properties of polymer chains adsorbing onto a Silica Surface at different separation distances. We complete this work by studying the adsorption of free polymer chains onto the grafted Silica Surface as a function of the grafting density. The conformational and the dynamical properties of the free and grafted chains are then determined with respect to the Surface coverage.
Kazuhiro Fujiki - One of the best experts on this subject based on the ideXlab platform.
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Grafting of ‘dendrimer-like’ highly branched polymer onto ultrafine Silica Surface
Reactive and Functional Polymers, 1998Co-Authors: Norio Tsubokawa, Hajime Ichioka, Toshiya Satoh, Shinji Hayashi, Kazuhiro FujikiAbstract:Abstract To modify ultrafine Silica Surface, the grafting of polyamidoamine dendrimer, a new class of topological macromolecules, onto the Silica Surface was investigated. Introduction of amino groups as an initiator site on the Silica Surface was achieved by the treatment of the Silica with γ-aminopropyltriethoxysilane. Polyamidoamine dendrimer was propagated from Silica Surface by repeating two processes: (1) Michael addition of methyl acrylate to Surface amino groups, and (2) amidation of the resulting esters with ethylenediamine. The amino group content of the resulting Silica increased from 0.40 mmol/g to 8.30 mmol/g after 10th generation. In addition, the percentage of grafting increased with increasing generation and reached to 575.7% after 10th generation. However, these values were considerably smaller than the theoretical values. This indicates that the propagation of dendrimer grafting from Silica Surface was not achieved theoretically and ‘dendrimer-like’ highly branched polymer was grafted onto the Surface, because of steric hindrance of grafted dendrimer. The effects of amino group content as an initiator site and reaction conditions on the grafting of the polymer onto Silica Surface were also investigated. Dendrimer-like highly branched polymer grafted ultrafine Silicas gave a stable dispersion in a good solvent for the polyamidoamine dendrimer.
Xiaoning Yang - One of the best experts on this subject based on the ideXlab platform.
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Molecular dynamics simulation of wetting on modified amorphous Silica Surface
Applied Surface Science, 2009Co-Authors: Jingchun Chai, Shuyan Liu, Xiaoning YangAbstract:Abstract The microscopic wetting of water on amorphous Silica Surfaces has been investigated by molecular dynamics simulation. Different degrees of Surface hydroxylation/silanization were considered. It was observed that the hydrophobicity becomes enhanced with an increase in the degree of Surface silanization. A continuous transformation from hydrophilicity to hydrophobicity can be attained for the amorphous Silica Surfaces through Surface modification. From the simulation result, the contact angle can exceed 90° when Surface silanization percentage is above 50%, showing a hydrophobic character. It is also found that when the percentage of Surface silanization is above 70% on the amorphous Silica Surface, the water contact angle almost remains unchanged (110–120°). This phenomenon is a little different from the wetting behavior on smooth quartz plates in previous experimental report. This change in the wettability on modified amorphous Silica Surfaces can be interpreted in terms of the interaction between water molecules and the Silica Surfaces.
Thanh H Nguyen - One of the best experts on this subject based on the ideXlab platform.
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Deposition kinetics of bacteriophage MS2 on a Silica Surface coated with natural organic matter in a radial stagnation point flow cell.
Environmental Science & Technology, 2008Co-Authors: Baoling Yuan, Mai Pham, Thanh H NguyenAbstract:A quartz crystal microbalance (QCM) coupled with a radial stagnation point flow (RSPF) cell was used to study deposition kinetics of bacteriophage MS2 on Silica Surface coated with Suwannee River natural organic matter (SRNOM). Three stocks of MS2 stored in 1 mM NaHCO3, deionized (DI) water or phosphate buffer saline (PBS) solution were studied. MS2 stored in PBS solution were found to aggregate at all studied ionic strengths from 3 mM to 200 mM, while MS2 stored in DI water and bicarbonate solutions remained monodispersed. Isoelectric points of MS2 storedin PBS solution were lower than for those stored in DI water and 1 mM NaHCO3 solution. Nonrepulsive deposition rates of MS2 on Silica Surface coated with poly-L-lysine (PLL) were independent of ionic strength. In contrast MS2 deposition rates on bare Silica Surface or Silica Surface coated with SRNOM increased gradually and stabilized at an ionic strength of 60 mM. MS2 deposition rates on bare Silica Surface were higher than those on Silica Surface coated with SRNOM at low ionic strengths. Deposition rates on these two Surfaces were similar at high ionic strengths. Experimental data suggest that electrostatic and steric interactions were the two main deposition mechanisms of MS2 on either bare Silica or Silica Surface coated with SRNOM.
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deposition kinetics of bacteriophage ms2 on a Silica Surface coated with natural organic matter in a radial stagnation point flow cell
Environmental Science & Technology, 2008Co-Authors: Baoling Yuan, Mai Pham, Thanh H NguyenAbstract:A quartz crystal microbalance (QCM) coupled with a radial stagnation point flow (RSPF) cell was used to study deposition kinetics of bacteriophage MS2 on Silica Surface coated with Suwannee River natural organic matter (SRNOM). Three stocks of MS2 stored in 1 mM NaHCO3, deionized (DI) water or phosphate buffer saline (PBS) solution were studied. MS2 stored in PBS solution were found to aggregate at all studied ionic strengths from 3 mM to 200 mM, while MS2 stored in DI water and bicarbonate solutions remained monodispersed. Isoelectric points of MS2 stored in PBS solution were lower than for those stored in DI water and 1 mM NaHCO3 solution. Nonrepulsive deposition rates of MS2 on Silica Surface coated with poly-l-lysine (PLL) were independent of ionic strength. In contrast, MS2 deposition rates on bare Silica Surface or Silica Surface coated with SRNOM increased gradually and stabilized at an ionic strength of 60 mM. MS2 deposition rates on bare Silica Surface were higher than those on Silica Surface coa...