Rapid Directed Assembly of Block Copolymer Films on chemically patterned surfaces at Elevated Temperatures

We report on the rapid directed assembly of poly(styrene-b-methyl methacrylate) (PS-b-PMMA) block copolymer thin films at elevated temperatures well above the glass transition temperature (Tg) on chemically patterned surfaces. The time needed for defect free assembly, where the chemical pattern (L$_{S})$ closely matches the natural length of the block copolymer (L$_{0})$, is strongly dependant on the annealing temperature. Annealing times range from 150 minutes at 180 \r{ }C to 3 minutes at 230 \r{ }C. This system behavior is well described as a simple thermally activated process with an apparent activation energy (\textit{$\Delta $E}$_{a})$ of 182 kJ/mol and a polymer diffusion coefficient of 7.5E-15 cm$^{2}$s$^{-1}$ at 190 \r{ }C. Modeling this behavior predicts annealing times of 13.5 seconds at 250 \r{ }C and 1.9 seconds at 280 \r{ }C. While these times are difficult to investigate experimentally, a one minute anneal at these elevated temperatures not only shows perfect assembly where L$_{S}$ = L$_{0}$, but also where L$_{S} <$ L$_{0}$.