Formation of flower-like aggregates from assembly of single polystyrene-b-poly(acrylic acid) micelles

Abstract

Amphiphilic block copolymer polystyrene-block-polyacrylic acid (PS-b-PAA) self-assembles into spherical core-shell micelles in the block-selective solvent water with the PS block as the core and the PAA block as the shell. When adding 1-propanol to the micellar solution and then casting the micellar solution at suitable temperatures, the spherical core-shell micelles are assembled into flower-like aggregates on substrates such as glass, formvar film or silicon. The size of the flower-like aggregates ranges from 2 × 2 µm² to 15 × 15 µm². Casting temperature, substrate type and character of the block copolymers and additive can all affect the assembly of PS-b-PAA micelles. The assembly of micelles is similar to the fractal aggregation of inorganic particles and a possible reason is discussed.