Development of PS-PMMA Block Copolymers Incorporating Poly(<i>n</i>-butyl methacrylate) for Low Temperature Thermal Annealing toward Perpendicular Microdomain Alignment

Block copolymers (BCPs) have garnered significant attention due to their ability to spontaneously assemble into well-ordered, periodic nanostructures, making them promising candidates for next-generation lithography. In this study, polystyrene-block-{poly[2-hydroxy-3-(2,2,2-trifluoroethylsulfanyl)-propyl methacrylate]-random-poly(n-butyl methacrylate)-random-poly(methyl methacrylate)} (PS-b-PGFBM), a derivative of the well-established PS-b-PMMA system, was synthesized. By introducing a fluorinated poly(glycidyl methacrylate) segment, PS-b-PGFBM achieves a higher level of chemical incompatibility between styrene and methacrylate blocks compared to PS-b-PMMA. Furthermore, poly(n-butyl methacrylate) (PnBMA), which has a low glass transition temperature (Tg, ~25 °C), was incorporated to lower the overall Tg of the BCP, thereby facilitating self-assembly at reduced annealing temperatures. Notably, thin films of PS-b-PGFBM, spin-coated onto neutral layer-modified silicon substrates, formed perpendicular lamellae with a domain spacing of 15.6 nm after thermal annealing at 160 °C, 40 °C lower than the annealing temperature required for similar BCPs without PnBMA.