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Mikio Konno - One of the best experts on this subject based on the ideXlab platform.

  • Environmentally adaptable pathway to emulsion Polymerization for Monodisperse Polymer nanoparticle synthesis
    Polymer, 2015
    Co-Authors: Haruyuki Ishii, Daisuke Nagao, Naoto Kuwasaki, Mikio Konno
    Abstract:

    Abstract An environmentally adaptable method is proposed for emulsion Polymerization to produce Monodisperse Polymer nanoparticles at surfactant concentrations much lower than conventional emulsion Polymerization. The present method is based on an idea of employing a surfactant with a low critical micelle concentration (CMC) to generate a large number of Polymer particles in the presence of micelles at low surfactant concentrations and to cease the particle generation by the micelle disappearance in early reaction stage for attainment of high monodispersity of particles. A hydrophobic monomer of styrene (St) and a less hydrophobic monomer of methyl methacrylate (MMA) were used in the present emulsion Polymerization at a total monomer concentration of 0.3 M with an initiator of ammonium persulfate (APS) and a long alkyl chain surfactant of sodium octadecyl sulfate (SOS). The Polymerization was conducted at a high APS concentration of 20 mM that gave the CMC as low as 0.085 mM for SOS. An increase in the monomer mole fraction of MMA increased the number of Polymer particles, while the high monomer mole fraction of MMA failed to stabilize the dispersion of particles. The Polymerization for a monomer ratio of St/MMA = 1/1 could produce Monodisperse Polymer particles of 33 nm at a surfactant concentration of 1 mM that was higher than its CMC (0.085 mM) but much lower than several ten mM of surfactant concentrations in conventional emulsion Polymerization.

  • advanced synthesis for Monodisperse Polymer nanoparticles in aqueous media with sub millimolar surfactants
    Polymer, 2014
    Co-Authors: Haruyuki Ishii, Daisuke Nagao, Motohiro Ishii, Mikio Konno
    Abstract:

    Abstract Highly Monodisperse polystyrene nanoparticles with mean diameters of less than 100 nm are synthesized via aqueous emulsion Polymerization using an amphoteric initiator (VA-057) in the presence of sub-millimolar concentrations of anionic surfactant. Since the net charge on the initiator is almost zero at neutral pH, the resultant latex particle size is mainly determined by surfactant adsorption. Polymerizations were performed in the presence of a range of anionic surfactants with differing critical micelle concentrations (CMC) by varying the concentrations of surfactant, initiator and monomer, and also the ionic strength. Sodium dodecyl benzene sulfonate (SDBS), sodium hexadecyl sulfate (SHS), and sodium octadecyl sulfate (SOS) have relatively low CMCs and so enable formation of highly Monodisperse nanoparticles at relatively low (sub-millimolar) surfactant concentrations, CS (i.e. below the CMC in each case). Empirically, it was found that the particle number, Np, and coefficient of variation of the particle size, CV, were strongly dependent on the CS/CMC ratio: Np increased almost in proportion with the square of this ratio, while the CV exhibited a minimum at approximately CS/CMC = 0.20. Higher ionic strength reduced the particle size, which is consistent with the above relationship because the addition of salt lowers the CMCs of ionic surfactants. Polymer latex particles produced using such formulations form highly regular, close-packed colloidal arrays.

  • Encyclopedia Of Polymer Science and Technology - Monodisperse Polymer Particles
    Encyclopedia of Polymer Science and Technology, 2014
    Co-Authors: Mikio Konno, Daisuke Nagao
    Abstract:

    This review summarizes recent advances in the synthesis of Monodisperse Polymer particles with Polymerization in solutions. After introducing the Monodisperse Polymer particles and their potential applications, we first focused on common Polymerization techniques for Monodisperse Polymer particles ranging from sub-micrometers to micrometers. Among the techniques, soap-free emulsion Polymerization, which is a surfactant-free heterogeneous Polymerization in water without any organic solvents, was reviewed in detail from an environmentally friendly viewpoint. Then, soap-free emulsion Polymerizations for obtaining Monodisperse Polymer particles with hybrids or composite structures were discussed. Synthetic methods for functional, highly Monodisperse composite particles such as fluorescent Polymer particles and magnetic Polymer particles are presented. It also includes preparations of anisotropic Polymer particles such as dumbbell-, snowman-, rod-, and raspberry-shaped particles and particles having a depression. Finally, template applications of the composite particles with Polymer-removable methods for the creation of hollow or movable part in different shell shapes are discussed. Keywords: Monodisperse particles; Polymerization; particle shape; morphology; nonspherical

  • advanced soap free emulsion Polymerization for highly pure micron sized Monodisperse Polymer particles
    Polymer, 2014
    Co-Authors: Kazuhiro Shibuya, Haruyuki Ishii, Daisuke Nagao, Mikio Konno
    Abstract:

    Abstract A previously proposed method of soap-free emulsion Polymerization employing an amphoteric initiator, 2,2′-azobis[ N -(2-carboxyethyl)-2-methylpropionamidine] (VA-057), was extended to synthesize micron-sized, Monodisperse polystyrene (PSt) particles at low impurity levels. Initial pH values of solutions in which anionic PSt particles were formed were adjusted between neutral pH and 8.9 with a tiny amount of strong base such as NaOH to constitute a low-impurity Polymerization system. Micron-sized Polymer particles with a narrow size distribution were obtained in a pH range of 8.1–8.9. Different strong bases of KOH, Ca(OH) 2 and tetramethylammonium hydroxide were also added to examine electrostatic interaction between PSt particles formed in the low-impurity system, indicating that surface charge density of PSt particles is an important factor to determine size distributions of PSt particles formed. Polymerizations at high styrene concentrations and an appropriate VA-057 concentration succeeded in preparation of highly pure, Monodisperse PSt particles with an average size of 1.86 μm.

Valérie Héroguez - One of the best experts on this subject based on the ideXlab platform.

  • Separation study of organic bases on new Polymeric stationary phases under basic conditions
    European Polymer Journal, 2012
    Co-Authors: Aurélien Voisin, Annie Thienpont, Valérie Héroguez
    Abstract:

    Crosslinked Monodisperse Polymer microparticles have been synthesized and evaluated as stationary phases for the separation of basic drug molecules in reversed-phase high performance liquid chromatography. The Polymer beads were prepared by free-radical coPolymerization of divinylbenzene and styrene or vinylbenzyl chloride in acetonitrile with toluene as porogen agent using the precipitation method. Their efficiency as stationary phase was investigated at both acid (5.6) and basic (12) pH, and the results compared with those of a commercial Polymeric reversed-phase column. Separation of the organic bases was achieved with the chlorobenzyl particles at pH 12. (C) 2011 Elsevier Ltd. All rights reserved.

Tamarapu Sridhar - One of the best experts on this subject based on the ideXlab platform.

  • Effects of the polydispersity on rheological properties of entangled polystyrene solutions
    Macromolecules, 2005
    Co-Authors: Tamarapu Sridhar
    Abstract:

    Previous studies on extensional properties of entangled solutions have mainly dealt with Monodisperse Polymers. To investigate the effect of polydispersity on rheological properties of entangled polystyrene solutions, a polydisperse blend with an average molecular weight of 2.65 × 106 was made by mixing 18 components of nearly Monodisperse polystyrene. The effect of polydispersity is illustrated by comparing the rheological behavior of this blend with that of a solution of Monodisperse Polymer with the same average molecular weight and at the same concentration. Shear, small-amplitude sinusoidal flow, step strain in shear, and uniaxial extension are used in this study. The multicomponent system has a much broader relaxation spectrum and a slightly smaller zero-shear-rate viscosity than the solution of Monodisperse Polymer. The shear thinning behavior of the two solutions are very similar except that the polydisperse system shows an earlier onset of shear thinning. In step strain experiments, the polydispe...

Daisuke Nagao - One of the best experts on this subject based on the ideXlab platform.

  • Environmentally adaptable pathway to emulsion Polymerization for Monodisperse Polymer nanoparticle synthesis
    Polymer, 2015
    Co-Authors: Haruyuki Ishii, Daisuke Nagao, Naoto Kuwasaki, Mikio Konno
    Abstract:

    Abstract An environmentally adaptable method is proposed for emulsion Polymerization to produce Monodisperse Polymer nanoparticles at surfactant concentrations much lower than conventional emulsion Polymerization. The present method is based on an idea of employing a surfactant with a low critical micelle concentration (CMC) to generate a large number of Polymer particles in the presence of micelles at low surfactant concentrations and to cease the particle generation by the micelle disappearance in early reaction stage for attainment of high monodispersity of particles. A hydrophobic monomer of styrene (St) and a less hydrophobic monomer of methyl methacrylate (MMA) were used in the present emulsion Polymerization at a total monomer concentration of 0.3 M with an initiator of ammonium persulfate (APS) and a long alkyl chain surfactant of sodium octadecyl sulfate (SOS). The Polymerization was conducted at a high APS concentration of 20 mM that gave the CMC as low as 0.085 mM for SOS. An increase in the monomer mole fraction of MMA increased the number of Polymer particles, while the high monomer mole fraction of MMA failed to stabilize the dispersion of particles. The Polymerization for a monomer ratio of St/MMA = 1/1 could produce Monodisperse Polymer particles of 33 nm at a surfactant concentration of 1 mM that was higher than its CMC (0.085 mM) but much lower than several ten mM of surfactant concentrations in conventional emulsion Polymerization.

  • advanced synthesis for Monodisperse Polymer nanoparticles in aqueous media with sub millimolar surfactants
    Polymer, 2014
    Co-Authors: Haruyuki Ishii, Daisuke Nagao, Motohiro Ishii, Mikio Konno
    Abstract:

    Abstract Highly Monodisperse polystyrene nanoparticles with mean diameters of less than 100 nm are synthesized via aqueous emulsion Polymerization using an amphoteric initiator (VA-057) in the presence of sub-millimolar concentrations of anionic surfactant. Since the net charge on the initiator is almost zero at neutral pH, the resultant latex particle size is mainly determined by surfactant adsorption. Polymerizations were performed in the presence of a range of anionic surfactants with differing critical micelle concentrations (CMC) by varying the concentrations of surfactant, initiator and monomer, and also the ionic strength. Sodium dodecyl benzene sulfonate (SDBS), sodium hexadecyl sulfate (SHS), and sodium octadecyl sulfate (SOS) have relatively low CMCs and so enable formation of highly Monodisperse nanoparticles at relatively low (sub-millimolar) surfactant concentrations, CS (i.e. below the CMC in each case). Empirically, it was found that the particle number, Np, and coefficient of variation of the particle size, CV, were strongly dependent on the CS/CMC ratio: Np increased almost in proportion with the square of this ratio, while the CV exhibited a minimum at approximately CS/CMC = 0.20. Higher ionic strength reduced the particle size, which is consistent with the above relationship because the addition of salt lowers the CMCs of ionic surfactants. Polymer latex particles produced using such formulations form highly regular, close-packed colloidal arrays.

  • Encyclopedia Of Polymer Science and Technology - Monodisperse Polymer Particles
    Encyclopedia of Polymer Science and Technology, 2014
    Co-Authors: Mikio Konno, Daisuke Nagao
    Abstract:

    This review summarizes recent advances in the synthesis of Monodisperse Polymer particles with Polymerization in solutions. After introducing the Monodisperse Polymer particles and their potential applications, we first focused on common Polymerization techniques for Monodisperse Polymer particles ranging from sub-micrometers to micrometers. Among the techniques, soap-free emulsion Polymerization, which is a surfactant-free heterogeneous Polymerization in water without any organic solvents, was reviewed in detail from an environmentally friendly viewpoint. Then, soap-free emulsion Polymerizations for obtaining Monodisperse Polymer particles with hybrids or composite structures were discussed. Synthetic methods for functional, highly Monodisperse composite particles such as fluorescent Polymer particles and magnetic Polymer particles are presented. It also includes preparations of anisotropic Polymer particles such as dumbbell-, snowman-, rod-, and raspberry-shaped particles and particles having a depression. Finally, template applications of the composite particles with Polymer-removable methods for the creation of hollow or movable part in different shell shapes are discussed. Keywords: Monodisperse particles; Polymerization; particle shape; morphology; nonspherical

  • advanced soap free emulsion Polymerization for highly pure micron sized Monodisperse Polymer particles
    Polymer, 2014
    Co-Authors: Kazuhiro Shibuya, Haruyuki Ishii, Daisuke Nagao, Mikio Konno
    Abstract:

    Abstract A previously proposed method of soap-free emulsion Polymerization employing an amphoteric initiator, 2,2′-azobis[ N -(2-carboxyethyl)-2-methylpropionamidine] (VA-057), was extended to synthesize micron-sized, Monodisperse polystyrene (PSt) particles at low impurity levels. Initial pH values of solutions in which anionic PSt particles were formed were adjusted between neutral pH and 8.9 with a tiny amount of strong base such as NaOH to constitute a low-impurity Polymerization system. Micron-sized Polymer particles with a narrow size distribution were obtained in a pH range of 8.1–8.9. Different strong bases of KOH, Ca(OH) 2 and tetramethylammonium hydroxide were also added to examine electrostatic interaction between PSt particles formed in the low-impurity system, indicating that surface charge density of PSt particles is an important factor to determine size distributions of PSt particles formed. Polymerizations at high styrene concentrations and an appropriate VA-057 concentration succeeded in preparation of highly pure, Monodisperse PSt particles with an average size of 1.86 μm.

Andrea Pelissetto - One of the best experts on this subject based on the ideXlab platform.

  • Polymer size in dilute solutions in the good-solvent regime
    The Journal of chemical physics, 2006
    Co-Authors: Sergio Caracciolo, Bortolo Matteo Mognetti, Andrea Pelissetto
    Abstract:

    We determine the density expansion of the radius of gyration, of the hydrodynamic radius, and of the end-to-end distance for a Monodisperse Polymer solution in good-solvent conditions. We consider the scaling limit (large degree of Polymerization), including the leading scaling corrections. Using the expected large-concentration behavior, we extrapolate these low-density expansions outside the dilute regime, obtaining a prediction for the radii for any concentration in the semidilute region. For the radius of gyration, comparison with field-theoretical predictions shows that the relative error should be at most 5% in the limit of very large Polymer concentrations.

  • Virial coefficients and osmotic pressure in Polymer solutions in good-solvent conditions
    The Journal of chemical physics, 2006
    Co-Authors: Sergio Caracciolo, Bortolo Matteo Mognetti, Andrea Pelissetto
    Abstract:

    We determine the second, third, and fourth virial coefficients appearing in the density expansion of the osmotic pressure of a Monodisperse Polymer solution in good-solvent conditions. Using the expected large-concentration behavior, we extrapolate the low-density expansion outside the dilute regime, obtaining the osmotic pressure for any concentration in the semidilute region. Comparison with field-theoretical predictions and experimental data shows that the obtained expression is quite accurate. The error is approximately 1-2% below the overlap concentration and rises at most to 5-10% in the limit of very large Polymer concentrations.