The Experts below are selected from a list of 318 Experts worldwide ranked by ideXlab platform

Zhiyu Huang - One of the best experts on this subject based on the ideXlab platform.

  • Spherical to wormlike Micelle transition in a pseudogemini surfactant system with two types of effective ph responsive groups
    Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2016
    Co-Authors: Qianping Shi, Baogang Wang, Zhiyu Huang
    Abstract:

    Abstract A novel pseudogemini surfactant system, which has two types of pH-responsive groups in the connection of the alkyl chain and the spacer, has been developed and investigated by adjusting pH. These two types of pH-responsive groups both worked for the Micelle transition because they had different ionization degrees and electrostatic attraction forces with the aid of pH variation. The system could be promptly switched between low viscosity fluid and high viscoelastic solution. Besides, the pH-responsive ability was studied by the steady and dynamic rheological measurements, which is effective after several cycles of pH adjusting with the almost invariable magnitude level of viscosity. The transition between Spherical Micelle and wormlike Micelle for the surfactant system at different pH values could be further confirmed by dynamic light scattering and cryogenic transmission electron microscopy characterization.

  • ph responsive anionic wormlike Micelle based on sodium oleate induced by nacl
    Journal of Physical Chemistry B, 2014
    Co-Authors: Hongsheng Lu, Zhiyu Huang
    Abstract:

    A pH-responsive anionic surfactant wormlike micellar system induced by NaCl has been developed. In this work, the anionic surfactant, sodium oleate (NaOA) solutions, transforms from low-viscosity fluid into high-viscoelastic solution induced by NaCl of 200 mM to 350 mM concentration. According to the above, the solution reversibility has been studied via changing pH value of the solution. This pH-responsive solution can be promptly switched between gel-like solution and waterlike fluid in a narrow pH value range. Steady and dynamic rheological measurements are employed to characterize the pH-responsiveness at different pH. The transformation between wormlike Micelle and Spherical Micelle in the various pH solutions is demonstrated by dynamic light scattering tests, cryo-TEM, and NMR measurements. The pH-responsive property of the system is attributed to the carboxylate ion contained by sodium oleate. With higher pH value, the ionized carboxylate combines with NaCl closely and thus forms wormlike Micelles....

Jianxi Zhao - One of the best experts on this subject based on the ideXlab platform.

  • Spherical Micelle formation by mixed quaternary ammonium surfactants with long and short tails in ethanol water solvent and micellar freezing upon solubilising styrene polymerisation
    Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2017
    Co-Authors: Jianxi Zhao
    Abstract:

    Abstract The association of mixed docosyltrimethylammobium bromide and octadecyltrimethylammonium bromide, C 22 TABr/C 18 TABr, in ethanol (a common solvent favoured for both their alkyl tails and head-groups) induced by the addition of water (a non-solvent for the tails) has been studied using light-scattering measurements. Under the assistance of NaBr, which promoted the surfactant molecules to pack tightly in the Micelles, mono-disperse Spherical Micelles composed of mixed C 22 TABr/C 18 TABr were obtained in ethanol/water (15/85 wt%). Styrene was solubilised into the templating C 22 TABr/C 18 TABr Micelles (β surf , the molar ratio of C 18 TABr to C 22 TABr, was 2.5) and then was polymerised in situ . To achieve a good freezing effect, the amount of styrene solubilised, represented as the molar ratio of styrene monomer to total surfactants, n st / n surf , was required to be greater than 4.87 for this templating micellar system. The diluting tests demonstrated that, after polymerisation, the styrene-containing Micelles froze their microstructure well. Light-scattering measurements, and TEM observation, all indicated that these Micelles were mono-dispersed, and retained their Spherical shape. As swollen by polystyrene, the Micelle had an avarage radius of 18 nm.

  • Spherical Micelle formation by mixed quaternary ammonium surfactants with long, and short, tails in ethanol/water solvent and micellar freezing upon solubilising styrene polymerisation
    Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2017
    Co-Authors: Jianxi Zhao
    Abstract:

    Abstract The association of mixed docosyltrimethylammobium bromide and octadecyltrimethylammonium bromide, C 22 TABr/C 18 TABr, in ethanol (a common solvent favoured for both their alkyl tails and head-groups) induced by the addition of water (a non-solvent for the tails) has been studied using light-scattering measurements. Under the assistance of NaBr, which promoted the surfactant molecules to pack tightly in the Micelles, mono-disperse Spherical Micelles composed of mixed C 22 TABr/C 18 TABr were obtained in ethanol/water (15/85 wt%). Styrene was solubilised into the templating C 22 TABr/C 18 TABr Micelles (β surf , the molar ratio of C 18 TABr to C 22 TABr, was 2.5) and then was polymerised in situ . To achieve a good freezing effect, the amount of styrene solubilised, represented as the molar ratio of styrene monomer to total surfactants, n st / n surf , was required to be greater than 4.87 for this templating micellar system. The diluting tests demonstrated that, after polymerisation, the styrene-containing Micelles froze their microstructure well. Light-scattering measurements, and TEM observation, all indicated that these Micelles were mono-dispersed, and retained their Spherical shape. As swollen by polystyrene, the Micelle had an avarage radius of 18 nm.

Yusuke Yamauchi - One of the best experts on this subject based on the ideXlab platform.

Susumu Okazaki - One of the best experts on this subject based on the ideXlab platform.

  • all atom molecular dynamics study of a Spherical Micelle composed of n acetylated poly ethylene glycol poly gamma benzyl l glutamate block copolymers a potential carrier of drug delivery systems for cancer
    Journal of Physical Chemistry B, 2009
    Co-Authors: Hiroshi Kuramochi, Yoshimichi Andoh, Noriyuki Yoshii, Susumu Okazaki
    Abstract:

    An all-atom molecular dynamics simulation of a Spherical Micelle composed of amphiphilic N-acetylated poly(ethylene glycol)−poly(γ-benzyl l-glutamate) (PEG−PBLG-Ac) block copolymers was performed in aqueous solution at 298.15 K and 1 atm. Such copolymers have received considerable attention as carriers in drug delivery systems. In this study, we used copolymers consisting of 11 EG units and 9 BLG units as models. Starting from the copolymers arranged Spherically, the calculation predicted an equilibrium state consisting of a slightly elliptical Micelle structure with a hydrophobic PBLG inner core and a hydrophilic PEG outer shell. The Micelle structure was dynamically stable during the simulation, with the PEG blocks showing a compact helical conformation and the PBLG blocks an α-helix form. Multiple hydrogen bonds with solvent water molecules stabilized the helical conformation of the PEG blocks, leading to their hydration as shown by longer residence times of water molecules near the PEG ether oxygen at...

  • All-atom molecular dynamics study of a Spherical Micelle composed of N-acetylated poly(ethylene glycol)-poly(gamma-benzyl L-glutamate) block copolymers: a potential carrier of drug delivery systems for cancer.
    The journal of physical chemistry. B, 2009
    Co-Authors: Hiroshi Kuramochi, Yoshimichi Andoh, Noriyuki Yoshii, Susumu Okazaki
    Abstract:

    An all-atom molecular dynamics simulation of a Spherical Micelle composed of amphiphilic N-acetylated poly(ethylene glycol)-poly(gamma-benzyl L-glutamate) (PEG-PBLG-Ac) block copolymers was performed in aqueous solution at 298.15 K and 1 atm. Such copolymers have received considerable attention as carriers in drug delivery systems. In this study, we used copolymers consisting of 11 EG units and 9 BLG units as models. Starting from the copolymers arranged Spherically, the calculation predicted an equilibrium state consisting of a slightly elliptical Micelle structure with a hydrophobic PBLG inner core and a hydrophilic PEG outer shell. The Micelle structure was dynamically stable during the simulation, with the PEG blocks showing a compact helical conformation and the PBLG blocks an alpha-helix form. Multiple hydrogen bonds with solvent water molecules stabilized the helical conformation of the PEG blocks, leading to their hydration as shown by longer residence times of water molecules near the PEG ether oxygen atoms compared with that of bulk water. Some water molecules have also been found distributed within the hydrophobic core; they showed continuous exchange with bulk water during the simulation. Those molecules existed mostly as a cluster in spaces between the copolymers, forming hydrogen bonds among themselves as well as with the hydrophobic core through hydrophilic groups such as esters and amides. The water molecules forming hydrogen bonds with the Micelle may play an important role in the stabilization of the Micelle structure.

  • a molecular dynamics study of structure and dynamics of surfactant molecules in sds Spherical Micelle
    Condensed Matter Physics, 2007
    Co-Authors: Noriyuki Yoshii, Susumu Okazaki
    Abstract:

    An analysis of structure and dynamics of surfactant molecules in SDS Micelle is presented based on molecular dynamics calculations. Two-dimentional surface correlation function for the hydrophilic sulfur atoms as well as the bond analysis between the hydrophobic alkyl chains shows that the surfactant molecules are packed sparsely in the Micelle such that they form a soccer ball-like structure characterized by the coordination number of three. The hydrophobic bond between the surfactant molecules is produced and annihilated repeatedly in a time scale of about 100 ps but disappears by their diffusion in a time scale of about 1 ns.

  • a molecular dynamics study of free energy of Micelle formation for sodium dodecyl sulfate in water and its size distribution
    Journal of Chemical Physics, 2006
    Co-Authors: Noriyuki Yoshii, Kensuke Iwahashi, Susumu Okazaki
    Abstract:

    Free energy of Micelle formation has been evaluated for Spherical sodium dodecyl sulfate (SDS) in water by a thermodynamic integration method combined with a series of large-scale molecular dynamics calculations following the chemical species model. In particular, free energy change Δμn+10 with respect to the addition of one surfactant molecule to the Spherical Micelle of size n was obtained as a function of n. The free energy profile showed a minimum followed by a maximum, which corresponds to a peak in the size distribution. The calculated peak size n=57 near its critical Micelle concentration is in good agreement with the experimental averaged aggregation number n=55–75 of the SDS Micelle. The distribution showed a rather sharp peak, indicating that the size is almost a monodisperse one. The size is likely to be insensitive to the total concentration of the surfactant.

Shin-ichi Yusa - One of the best experts on this subject based on the ideXlab platform.

  • Reversible Vesicle–Spherical Micelle Transition in a Polyion Complex Micellar System Induced by Changing the Mixing Ratio of Copolymer Components
    Macromolecules, 2016
    Co-Authors: Rintaro Takahashi, Takahiro Sato, Ken Terao, Shin-ichi Yusa
    Abstract:

    The mixing ratio dependence of the morphology of a polyion complex Micelle formed of an anionic–neutral double-hydrophilic block copolymer (AP) and a cationic–neutral double-hydrophilic block copolymer (MP) in 0.1 M aqueous NaCl solution was investigated by using small-angle X-ray scattering (SAXS), electrophoretic light scattering (ELS), and isothermal titration calorimetry (ITC), under the condition that the anionic and cationic block chains are much longer than the neutral block chains. When the anionic and cationic monomer units in the solution are nearly equimolar, the net charge of the polyion complex Micelle is close to zero, and the bilayer vesicle is formed. However, when the anionic or cationic monomer units in the solution are richer than the other, the polyion complex Micelle is charged by including the excess block copolymer component to form the smaller Spherical Micelle. The morphology transition between the vesicle and Spherical Micelle can take place reversibly by simply adding AP or MP i...

  • reversible vesicle Spherical Micelle transition in a polyion complex micellar system induced by changing the mixing ratio of copolymer components
    Macromolecules, 2016
    Co-Authors: Rintaro Takahashi, Takahiro Sato, Ken Terao, Shin-ichi Yusa
    Abstract:

    The mixing ratio dependence of the morphology of a polyion complex Micelle formed of an anionic–neutral double-hydrophilic block copolymer (AP) and a cationic–neutral double-hydrophilic block copolymer (MP) in 0.1 M aqueous NaCl solution was investigated by using small-angle X-ray scattering (SAXS), electrophoretic light scattering (ELS), and isothermal titration calorimetry (ITC), under the condition that the anionic and cationic block chains are much longer than the neutral block chains. When the anionic and cationic monomer units in the solution are nearly equimolar, the net charge of the polyion complex Micelle is close to zero, and the bilayer vesicle is formed. However, when the anionic or cationic monomer units in the solution are richer than the other, the polyion complex Micelle is charged by including the excess block copolymer component to form the smaller Spherical Micelle. The morphology transition between the vesicle and Spherical Micelle can take place reversibly by simply adding AP or MP i...