Micellar and fractal aggregates formed by two triblock terpolymers with different arrangements of one charged, one neutral hydrophilic and one hydrophobic block

Abstract

We have studied the self-assembled structures of two triblock amphiphilic polyelectrolytes of different topologies, containing a charged poly[sodium(sulfamate/carboxylate)isoprene] (SCPI) block, a polystyrene (PS) hydrophobic block and a hydrophilic neutral poly(ethylene oxide) (PEO) block in aqueous solutions, using Small Angle Neutron Scattering (SANS) and Light Scattering (LS). SANS reveals micellar and fractal aggregates in coexistence for both systems. In the case of SCPI-b-PS-b-PEO there is a higher content in fractal aggregates in comparison with PS-b-SCPI-b-PEO. In both cases the micellar aggregates are stable under different solution conditions, whereas the fractal aggregates appear to break upon addition of salt in the PS-b-SCPI-b-PEO system. The detailed picture of the micellar aggregates is consistent with the anticipated morphology of charged and neutral spherical macromolecular brushes, extended to mixed and sequential brushes. The analytical description obtained by SANS is used to interpret the LS data which is very sensitive to the presence of two species and therefore provides information on average values of the measured parameters.