The critical aggregation concentration(cac) and another critical micelle concentration(cmc*) were investigated by laser light scattering method in the neutral polymer/surfactant aqueous solution system. Especially, in this study poly(vinyl pyrrolidone)[PVP] and poly(2-ethyl 2-oxazoline)[PEOx] were chosen for neutral polymer due to the same chemical structure moiety of -NR-CO- but the relatively different position in chain. Sodium dodecanoate [C_12Na] was used for anionic surfactant. It is obvious that the cac is decreasing as increasing polymer concentration because the polymer chain contributes to the formation of micelle through providing the screening effect between water and hydrophobic micelle. This observation can be discussed by either Nagarajan model or Andelman model. But for the high molecular weight polymer sample, unexpectedly it shows a strong up-turn trend after some specific concentration. It can be explained under the assumption that it needs at least some minimum adsorption fraction of surfactant molecules on a polymer chain. Thus in order to satisfy this condition, as increasing polymer concentration, the cac should be increasing with the linear proportionality of c. It has been fully proved through the empirical relation of cac~c^1.3.
When cac data were plotted with the reduced concentration parameter of c[η], all cac data were put on one master curve if they are obtained from only different but high molecular weight samples in the same structure polymer. However, this reduced concentration parameter is no more effective for the cac data from two different structure polymers, for example PVP and PEOx. Based on theoretical idea, the degree of chain flexibility of (M^1/2/R_0)^3 is introduced to the former parameter and then the universality is again recovered when all cac data have been plotted against the corrected reduced concentration parameter of C[η](M^1/2/R_0)^3.
The cmc* for 39K PVP samples has shown no polymer concentration dependence at the range of c=0.1∼0.4wt%. But the same temperature dependence of cmc*, for both 39K PVP and 1270K PVP, was observed with a negative linear slope of -0.28 mM/oC. However, The 1270K PVP(0.1wt%) samples have relatively higher cmc* values by 13mM than the 39K PVP(0.1wt%) ones.