Observation of a re-entrant kinetic glass transition in a micellar system with temperature-dependent attractive interaction
Department of Nuclear Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.The European Physical Journal E (Impact Factor: 1.76). 12/2002; 9(3):283-6. DOI: 10.1140/epje/i2002-10081-5
We detect in a tri-block co-polymer micellar system an ergodic-to-nonergodic-to-ergodic transition, as a function of temperature, in a range of concentrations, by photon correlation measurements. The shear viscosity is also shown to jump two order of magnitude at these transition temperatures. Surprisingly, the structure factor as measured by small angle neutron scattering shows a marked narrowing at the structural arrest state. Rationalization of these results with the existence of an attractive branch in the phase diagram of an attractive colloid system predicted by mode coupling theory is made.
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ABSTRACT: The comparison of aggregation behaviors between the branched block polyether T1107 (polyether A) and linear polyether (EO)60(PO)40(EO)60 (polyether B) in aqueous solution are investigated by the MesoDyn simulation. Polyether A forms micelles at lower concentration and has a smaller aggregation number than B. Both the polyethers show the time-dependent micellar growth behaviors. The spherical micelles appear and then change to rod-like micelles with time evolution in the 10 vol% solution of polyether A. The micellar cluster appears and changes to pseudo-spherical micelles with time evolution in the 20 vol% solution of polyether A. However, the spherical micelles appear and change to micellar cluster with time evolution in the 20 vol% polyether B solution. The shear can induce the micellar transition of both block polyethers. When the shear rate is 1 × 105 s−1, the shear can induce the sphere-to-rod transition of both polyethers at the concentration of 10 and 20 vol%. When the shear rate is lower than 1 × 105 s−1, the huge micelles and micellar clusters can be formed in the 10 and 20 vol% polyether A systems under the shear, while the huge micelles are formed and then disaggregated with the time evolution in the 20 vol% polyether B system. KeywordsBranched block polyether-Aggregation behavior-Micelle-MesoDyn simulationColloid and Polymer Science 11/2010; 288(16):1581-1592. DOI:10.1007/s00396-010-2294-7 · 1.87 Impact Factor
Article: Characterizing Complex Fluids[Show abstract] [Hide abstract]
ABSTRACT: Among the experimental techniques used to characterize complex fluids, neutron scattering has played a unique and successful role, primarily for two reasons: (1) neutrons access the proper length and time scales, especially small-angle neutron scattering and reflectometry for structural and kinetic studies and neutron spin echo for dynamic investigations; and (2) for hydrogen-containing substances, the exchange of hydrogen by deuterium facilitates labeling on a molecular scale, an extremely important method for deciphering complex structures in multicomponent materials. In this short review, we give a number of examples for successful neutron studies of dense particle suspensions, including aggregation phenomena, in situ kinetic studies on shape transformations, shear-induced surfactant self-assembly phenomena near surfaces, and dynamics of complex fluids. Finally, we give an outlook on future developments.11/2003; 28(12):907 - 912. DOI:10.1557/mrs2003.253
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ABSTRACT: We report a set of viscoelastic measurements in aqueous solutions of a copolymer micellar system with attractive interactions, a system characterized by a percolation line (PT), and a structural arrest (SA) in the particle diffusion motions of a kinetic glass transition (KGT). We observe, in both transitions, dramatic variations in both the elastic (or storage G′(ω)) and loss components (G″(ω)) of the shear moduli. At the PT, rheological data are characterized by a scaling behavior, whereas at the SA G′ and G″ develop a plateau and a marked minimum, respectively. These behaviors are described in the frame of percolation models and mode coupling theory (MCT).Physica A: Statistical Mechanics and its Applications 12/2003; 330(1):206-217. DOI:10.1016/j.physa.2003.08.026 · 1.73 Impact Factor
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