Microphase-Separated Brushes on Square Platelets in PS-b-PEO Thin Films.

In polystyrene-block-poly(ethylene oxide) thin films, microphase-separated brushes on the square platelets can be obtained via fast solvent evaporation by controlling the tethering density (0.08 < σ < 0.11). The tethering density of the brushes is proportional to the thickness of the PEO crystal and increases with increasing initial solution heating temperature (T(i) ). When T(i)  < T(m) , where T(m) is the melting point of PEO, brushes with microphase-separated structures are observed. The formation of microphase-separated brushes depends on two factors: the strong incompatibility between PS and noncrystalline PEO chains (attached to the crystalline PEO) and the weak interaction between PS-PS brushes.