Pore Size Control using Cooperative Assembly with Block Copolymers and Low Volatility Solvents*

Block copolymers (BCPs) provide a facile avenue to the generation of nanoporous materials with well-defined pore geometries. Cooperative assembly of BCPs with functional precursors enables families of materials to be fabricated from a single BCP template. However, the pore size is generally controlled by the BCP, which can be limiting for applications. Here, we demonstrate the ability to effectively tune the pore size (both up and down) through the addition of low volatility solvents during triconstituent co-assembly of carbonizable and silica precursors with a commercial block copolymer (Pluronic F127) that are fabricated by film casting on roll-to-roll equipment. Four different low volatility solvents with varying selectivity were examined. The pore size obtained depends on the hydrophobicity, volatility, and relative amount of solvent added. This enables mesoporous carbon-silica materials with pore sizes ranging from 5 nm to 12.8 nm. The morphology of these materials was elucidated with transmission electron microscopy (TEM) and small angle x-ray scattering (SAXS) to understand how these solvent additives impact the ordered structure.