Insertion free energy of PAP[5] water channels into block copolymer membranes

Abstract

Biomimetic water channels embedded in copolymer membranes are promising candidates for next-generation desalination materials. Peptide appended pillar[5]arene (PAP[5]) is one such synthetic channel, which transports water at a rate comparable to aquaporins. In this work, we perform a design driven thermodynamic stability analysis for PAP[5] embedded in polybutadiene–polyethylene oxide (PB–PEO) membranes. We quantify thermodynamic stability in terms of insertion Gibbs free energy ΔG_ins, using thermodynamic integration methods. We investigate how ΔG_ins varies with block copolymer design. We find that stability depends importantly on hydrophobic block length, and correlates with the degree of hydration and number of counterions neutralizing the channel. Our analysis provides insight into pore-membrane interactions on a molecular scale, and guidance for the design of improved PAP[5] embedded PB–PEO membranes for desalination.