Square arrays of vertically aligned nanoporous cylinders from a linear ABC triblock terpolymer

Abstract Vertically oriented nanoporous cylinders, demonstrating an unprecedented alignment persistence, were produced within freestanding poly(1,1‐dimethyl silacyclobutane)‐ block ‐polystyrene‐ block ‐poly(2‐vinyl pyridine) (PDMSB‐ b ‐PS‐ b ‐P2VP) layers (~15 μm thick) blended with short PS‐ b ‐P2VP chains by combining the non‐solvent induced phase separation (NIPS) process with a solvent vapor annealing (SVA) treatment. Here, the NIPS step allowed for the formation of an asymmetric and porous PDMSB‐ b ‐PS‐ b ‐P2VP film having a top surface exhibiting poorly‐defined nanopores while the subsequent SVA treatment enabled to produce a symmetric layer that possesses highly‐ordered cylindrical nanodomains arranged into a 27 nm period square array. As the unblended NIPS/SVA‐made PDMSB‐ b ‐PS‐ b ‐P2VP monoliths exhibited a mixed orientation of parallel and perpendicular cylinders, a blending strategy was used to achieve tetragonally‐packed PDMSB and P2VP nanodomains having an exceptional vertical alignment persistence. Such solvent‐annealed (3 h, CHCl 3 ) PDMSB‐ b ‐PS‐ b ‐P2VP monoliths blended with 20 wt% of PS‐ b ‐P2VP chains showed a water permeance close to the value measured through their parent NIPS‐made terpolymer films having poorly‐ordered nanopores.