Thin Films Constructed by Centrifugal Deposition of Highly Deformable, Charged Microgels

Thin films composed entirely of microgel building blocks were fabricated using two kinds of self-cross-linked, oppositely charged microgels, via centrifugal deposition. Atomic force microscopy studies revealed that both microgels form very thin monolayer films due to a large degree of microgel deformation during deposition. Meanwhile, centrifugal deposition from a mixture of these two kinds of microgels resulted in the formation of microgel bilayers with a total thickness of around 20 nm. The film thickness increased linearly with the deposition time. Additionally, isotropic stretching/release by heating/cooling of the dried microgel films generated complicated buckling patterns, while anisotropic (uniaxial) stretching/release resulted in parallel buckling perpendicular to the stretching direction. The damage caused by anisotropic stretching and 100 °C treatment can be healed by addition of water, while damage caused via treatment at 150 °C cannot be healed due to the occurrence of polymer cross-linking, which inhibits the mobility of the microgel building blocks.