Structure and intermicellar interactions in block polyelectrolyte assemblies

Amphiphilic diblock polyelectrolytes are becoming popular in industrial applications due to their versatility, ranging from usage in pharmaceuticals to personal care products. Many of these systems also exhibit interesting rheological and morphological behavior. Our system is based on a polystyrene-poly(ethyl acrylate) diblock. The properties can be tuned by utilizing a simple hydrolysis reaction, converting poly(ethyl acrylate) (PEA) to poly(acrylic acid) (PAA). We study the effect of this hydrolysis reaction on the interaction between micelles of polystyrene-poly(acrylic acid) in water using small-angle and ultra-small-angle neutron scattering. We see that as more PEA is converted to PAA, the aggregation number and polystyrene core size decrease. We also studied the effect of cationic (DTAB) and anionic surfactant (SDS) on the PS-PAA diblocks using small-angle neutron scattering. We see that as SDS is added, there are no significant changes in the micellar structure. However, on the addition of DTAB past the CMC, we observe changes in the spectra that may correspond to complexation between the PS-PAA micelles and DTAB aggregates.