MICROPHASE SEPARATION IN SQUARE PLATELETS OF BIBLOCK COPOLYMER POLYSTYRENE-BLOCK POLY(ETHYLENE OXIDE)

摘要

@@Crystalline-amorphous block copolymers have received much attention due to the complicated structural pattern and phase transformation process driven by the combined effect of crystallization and microphase separation. Herein we studied solventinduced crystallization, and microphase separation in square platelets of the semicrystalline diblock copolymer, polystyrene-b-poly(ethylene oxide) thin films. During PEO poor solvent (cyclohexane) or good solvent (water) vapor treatment, different morphological transitions were observed. In cyclohexane vapor (Figure 1), square-shaped crystals formed firstly, and then were broken out by microphase separation locally, and finally were broken out completely by crystallization around the square platelets. In water vapor (Figure 2), the imperfect crystals formed which were imperfect structures like dendrite on the inner side of the square-shaped crystals. For long time, from the edge of the square-shaped lamella to the interior exhibited gradually depressed height and microphase separation induced PEO nanopores formed in the square-shaped lamella. Eventually, the interior of the square platelets caved in and preserved square rims and PS blocks aggregated to surface clusters and embedded in PEO layer finally.