We made small-angle neutron scattering (SANS) study of a Pluronic $L64\mathrm{}$ micellar system in aqueous solution at high polymer concentrations (wt %), $35\%<c<\mathrm{}53\%,$ in a temperature range where a kinetic glass transition has been observed by photon correlation spectroscopy and zero shear viscosity measurements. We analyze SANS intensity distributions assuming that the micelles are spherical and interact among themselves by an effective pair potential, consisting of a hard core plus a narrow attractive square well, the depth of which is temperature dependent. The theory is able to account for the intensity distribution quantitatively when the micellar system is in the liquid phase (but qualitatively when the micellar system is in the glass state), giving values of four parameters: the aggregation number of the micelle $N,$ the volume fraction occupied by the micelles $\phi ,$ the fractional width of the square well $\varepsilon ,$ and the effective temperature $T^{*}{=k}_{B}T/u,$ where $-u$ is the depth of the square well. Thus, we are able to assign a point in the phase diagram (the $T^{*}-\phi$ plane) for each measured micellar liquid and glass state. Comparison with a phase diagram predicted recently by mode coupling theory calculation allows us to identify the existence of the so-called liquid-to-attractive-glass transition line. We also found the evidence of glass-to-glass transition at volume fraction of $0.54$ predicted by the mode coupling theory.

• Received 16 April 2002

DOI:https://doi.org/10.1103/PhysRevE.66.021403