Static and dynamic light scattering have been measured on D20 solutions of nonionic surfactant C12E5 in the concentration range 3-300 g dm"3 at different temperatures. The results for the semidilute solutions at higher temperatures can be explained by the scaling theory for entangled solutions of flexible polymers which exhibit phase separations. Temperature dependences of the light scattering data suggest that the "0 temperature" exists at 27-30 °C (the lower critical consolution point is 30.5 °C), which is in approximate agreement with results of our previous studies for dilute solutions. Relation to the existence of liquid crystal phases is also discussed. Measurements of dynamic light scattering have been made on D20 solutions of C,2Ej also. The data do not follow the scaling law even at higher temperatures, which may come from the fact that C12E8 micelles are much smaller than C12E5 micelles.(44) The concept of the 9 temperature has been introduced into micellar solutions already by Fujimatsu et al.. However, the method employed in the present study is completely different from theirs. See:

can, at best, be considered an empirical means of interpreting the data. This result also suggests the onset, at increasing temperatures, of another mechanism for methoxy radical removal by 02. Both collision-induced isomerization by the reaction

Mutual diffusion coefficients (D) and self-diffusion coefficients (D') in D,Osolutions of n-dodecylpolyoxyethylene surfactants [C,,H,,(OC,H,),OH, m = 5 and 81 have been measured by dynamic light scattering and pulsedgradient F.t.n.m.r., respectively. On the basis of the ratio DID', micelle size distribution and intermicellar interactions have been discussed. The results have been compared with those for the C12E, system reported previously. Below ca. T,-30 "C (T, is the lower critical solution temperature) size distribution is narrow and intermicellar interactions are weak; this is consistent with the existence of spherical micelles. In the temperature range T, -30-T, -15 "C, the excluded volume effects are dominant and increase in magnitude with increasing temperature. At the same time, the size distribution becomes broad. These results originate from elongation of micelles. Above ca. T,-15 "C, the results can be explained by the decrease in the excluded volume effects and/or rapid increase in attractive interactions with increasing temperature. At still higher temperatures (T, -4 "C-T,), attractive interactions become dominant. Proton n.m.r. linewidths and viscosities have also been measured.