Supramolecular assemblies of amphiphilic PMMA-block-PAA stars in aqueous solutions

Self-assembling properties of an amphiphilic star block copolymer, 4-arm (PMMA-b-PAA)4 with poly(Me methacrylate) core and poly(acrylic acid) shell, have been investigated in aq. solns. The stars have been obsd. to aggregate in a complex manner in aq. solns., depending on the presence or absence of salt. Screening of the electrostatic repulsion between the polyelectrolyte blocks by adding salt triggers the formation of worm-like micelles. The presence of worm-like micelles in saline solns. was revealed by Kratky anal. of the light scattering data. The coexistence of different micellar morphologies was visualized by direct imaging by cryoTEM. Due to the balance between the electrostatic and hydrophobic interactions semidilute solns. show interesting rheol. properties. Shear thinning behavior of salt-free solns. and their time-dependent gelation have been obsd., thus indicating the strong tendency of the polymers to aggregate. [on SciFinder(R)]