Nanocomposites of sodium smectite with polyether- and polystyrene-containing pendant cyclic carbonates offer a novel approach to improving hydraulic barrier properties of Na-smectite liners to saline leachates. The cyclic carbonate polyethers were prepared by cationic ring opening polymerization of a cyclic carbonate-containing epoxide, whilst polystyrene polymers having pendant cyclic carbonate groups were obtained from radical photopolymerization of styrene. Na-smectite nanocomposites of these polymers were formed via clay in situ polymerization and solution intercalation methods. X-ray diffraction (XRD) and FT-IR analysis confirmed that the polyether can be intercalated within the layers of smectite via in situ as well as solution intercalation of the pre-formed polymer. The cyclic carbonate polyether nanocomposite was more resistant to leaching in 3M aqueous sodium chloride than its respective cyclic carbonate. (C) 2016 Wiley Periodicals, Inc.