Rapid and reversible morphology control in thin films of poly(ethylene oxide)-block-POSS-containing poly(methacrylate)

Here we report rapid control of the morphology of a polyhedral oligomeric silsesquioxane (POSS)-containing block copolymer (PEO ₁₄₃-b- PMAPOSS ₁₂), which is composed of poly(ethylene oxide) (PEO) and POSS-containing poly(methacrylate), (PMAPOSS), between ordered arrays of dots and lines for several tens of seconds by a combination of thermal annealing and solvent annealing. The PEO ₁₄₃-b-PMAPOSS ₁₂ was synthesized by atom transfer radical polymerization of POSS methacrylate by using a macroinitiator of PEO. An ordered array of dots was obtained by thermal annealing for the as-spun cast thin film at 90°C for 60 s. The resultant ordered dots were quickly converted to lines by solvent annealing with chloroform vapor at room temperature for 120 s. The lines were converted back to dots by thermal annealing under the same conditions (90°C, 60 s) without any changes to the initial diameter, d-spacing or thickness. We also demonstrated the simple and rapid formation of a hexagonally packed array of dots by spin casting onto a trench-patterned silicon wafer under chloroform vapor. Under thermal and solvent annealing conditions, reversibility and a high degree of ordering in the phase morphology of PEO ₁₄₃-b-PMAPOSS ₁₂ are distinctive properties that can be attributed to highly mobile polymer chains.