Functionality- and Size-Dependent Target-Differentiation of Nanoporous Carboxylated Polystyrenes in Polar Protic Solvents.

In this study, we investigated the functionality- and size-dependent differentiation capability of bulk nanoporous polystyrene (PS) materials in aqueous environments. A three-arm star block copolymer (consisting of dibranched PS and linear polylactide (PLA) blocks) was employed to prepare PS nanochannels with the average pore diameter of 14.2 nm. Due to the ester group at the junction of the PS and PLA blocks, a negatively charged carboxylate group could be placed as the wall functional group automatically after the PLA etching. Based on specific electrostatic interactions, the bulk PS channels with the carboxylated wall could selectively capture a water-soluble cationic dye (rhodamine 6G) in the aqueous and methanolic solutions. Furthermore, the well-defined porous PS displayed excellent size-dependent selectivity, which was proved by a fluorescence quenching experiment using differently sized gold nanoparticles (AuNPs). Rhodamine 6G dyes on the pore wall were effectively quenched by 2 nm AuNPs. In contrast, the 16 nm AuNPs (larger than the pore diameter) did not affect the brightness of the rhodamine 6G-loaded PS.