Surface-Grafted Polymeric Ionic Liquids with Tunable Morphology via / Cross-linking Methods.

Surface-grafted poly(ionic liquid) (PIL) films were prepared by both and cross-linking methods with reversible addition-fragmentation chain transfer (RAFT) polymerization. Cross-linked brushes are more stable than linear brushes without sacrificing the surface functionality and, therefore, have increased potential for applications in biomedicine and materials chemistry. The two methods, via a bifunctional cross-linker and via thermal cross-linking, were systematically compared on silicon-wafer substrates. Films obtained through cross-linking were superior to films derived from our cross-linking technique with respect to responsive behavior and controlling the formation of polymer brushes on the surface. Alternatively, more stable layers were obtained by the cross-linking method using a cross-linker based on Meldrum's acid, where the film structure could be changed from a brush to collapsed film morphologies with an increasing cross-linker ratio.