Insights into the role of counterions on polyelectrolyte-modified nanopore accessibility

GONZALEZ SOLVEYRA, ESTEFANIA; SILES, LAURA; ANDRIEU-BRUNSEN, ANNETTE; SZLEIFER, IGAL

Orlando

Congreso; ACS Spring meeting 2019; 2019

American Chemistry Society

In recent years, abilities to functionalize nanopores have advanced significantly, allowing to engineer nanoconstructs with polyelectrolytes or responsivepolymers showing fascinating transport properties, such as gated or gradually controlled ionic permselectivity. In those systems, it is crucial to understandthe influence of external parameters such as ion type or concentration on nanopore performance. In this work, the effect of different counterions on thewetting and ionic transport in poly(2-(methacryloyloxy)ethyltrimethylammonium chloride) (PMETAC) functionalized silica mesopores was experimentally andtheoretically investigated. Static contact angles covered a range from 45 ° to almost 90° by exclusively changing the counterion. Ionic pore accessibility wasalso strongly dependent on the counterion present and was found to gradually change from accessible pores up to complete, pH-independent ionexclusion. The PMETAC- functionalized mesopores were found inaccessible for positively charged probe molecules due to the pH-independent electrostaticrepulsion. On the other hand, the pore accessibility of negatively charged probe molecules was strongly affected by the nature of the counterion: insolutions containing ClO , the accessibility is reduced as compared to the solutions of Cl and PO . In the presence of CF SO , no mesoporeaccessibility for the negative probe is observed (see Fig. 1). Based on molecular theory calculations, these experimental observations were rationalizedbased on ion binding between the METAC monomers and the counterions. In addition, the theoretical framework provided a nanoscopic view into themolecular organization inside the pores, showing a strong dependence of ion concentration and ion distribution profiles along the pore radius independence of the present ions.