Reversible swelling transitions in stimuli-responsive layer-by-layer films containing block copolymer micelles

We present a new nanoporous multilayer system with a reversible pH-triggered swelling transition. Using the layer-by-layer approach, pH-responsive block copolymer micelles with a hydrophobic core, a weak polyanion shell and a strong polycation corona formed from an ABC triblock terpolymer are included within multilayer films. The approach of complexing the strong polycationic corona with a strong polyanion leads to the creation of novel double-end-tethered polyelectrolyte brush structures confined between the hydrophobic micellar cores and the interpolyelectrolyte complexes. The swelling degree, morphology as well as the mechanical properties of the coatings are reversibly tunable by the solution pH due to the ionization-induced swelling of the pH-sensitive polyelectrolyte-brush-like shell of the incorporated micelles resulting in large-scale volumetric changes of the film. Moreover, controlling the internal film architecture by the number of deposition steps allows tuning the properties of the porous multilayers such as the density of incorporated micelles, the porosity, and the equilibrium swelling degree to more than 1200%.