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

Abstract

AbstractVertically 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, CHCl3) 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.