Dynamical properties in dense triblock copolymer micellar system

Abstract

We present results of analyses of an extensive set of dynamic light scattering (PCS) and viscoelastic (frequency dependent complex moduli) measurements in concentrated aqueous solutions of a triblock copolymer L64 (PEO 13PPO 30PEO 13) micellar system at different temperatures. In particular we study the system dynamical properties in a region of the phase diagram characterized by the existence of a percolation process and a kinetic glass transition. Both the processes, temperature and concentration dependent, are related with adhesive interaction between micelles. The intermediate scattering function (ISF) shows an ergodic to non-ergodic transition on crossing a temperature and concentration dependent line. Viscoelasticity data, determined by means of frequency-dependent complex moduli, satisfy the scaling relations predicted by the scalar elasticity percolation theory and well account for the glass transition process, give indication that percolation and the ergodic non-ergodic transitions take places in separate regions of the phase diagram. Detailed analysis of ISF and rheological data, conducted in terms of the mode coupling theory (MCT) gives evidence of a logarithmic decay on the density fluctuations, which could be attributed to a higher order singularity, followed by a power-law behavior.