Charged micelles interact strongly with oppositely charged polymers to form soluable complexes. The surface charge density of micelles are able to be varied to a great extent which makes them a great model for the interactions of polyelectrolytes and oppositely charged colloids. Two systems were considered in this study, firstly, the cationic micelle composed of dimethyldodecylamine oxide (DMDAO) associated with the oppositely charged polyelectrolyte poly(2-acrylamido-2-methylpropanesulfonic acid) (PAMPS). The other system consists of mixed micelles containing the anionic surfactant sodium dodecyl sulfate (SDS) and non-ionic surfactant Triton X-100 (TX-100). Type-1 titrations were conducted for these two systems to observe the abruptness in scattering when the surface charge density is near the critical point. The formation of soluable complexes is thought to be a first order phase transition represented by a discontinuity in the derivitive of transmission with respect to surface charge density. This condition is true for micelles constituting of DMDAO, for which the degree of micelle protonation of incipient binding (β<sub>c</sub>) is indicated by a sharp increase in scattering. However, in cases with mixed micelles such as SDS/TX-100 the abruptness of the phase transition is spread over a wide range of Y, or mole fraction of SDS. It appears that this phenomenon is due to micelle polydispersity with respect to surface charge density.

Effect of micelle polydispersity on first order phase transitions in polyelectrolyte-colloid systems

253rd National Meeting (2017)

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