MICELLAR DYNAMICS IN AQUEOUS-SOLUTIONS OF PEO-PPO-PEO BLOCK-COPOLYMERS

The dynamics of poly(ethylene oxide)-poly(propylene oxide)-poly(ethyle ne oxide) micelle rearrangements were studied using iodine laser tempe rature jump experiments with light-scattering detection. Two relaxatio n processes were detected: the first, fast one was accompanied by an i ncrease in scattered light intensity, while the second, slow process w as accompanied by a reduction in light intensity. The Aniansson-Wall t heory was used to interpret the experimental results. The equilibrium micelle structures at the start and end points of the temperature jump experiment were used as input for the Aniansson-Wall equations. The s olution of these equations agrees qualitatively with experimental data and suggests the mechanisms associated with the two time constants. T he first time scale, in the tens of microseconds to about 10 ms range, is attributed to unimer insertion into micelles. The other time scale , in the 1-100 ms range, is associated with the rearrangement of the m icelle size distribution. It is shown that the second process is often not observed either because the unimer supply is insufficient or beca use the micelle number density is not temperature dependent.