Dynamic Materials from Microgel Multilayers

Abstract

Multilayer coatings made from hydrogel microparticles (microgels) are conceptually very simple materials: thin films composed of microgel building blocks held together by polyelectrolyte "glue". However, the apparent simplicity of their fabrication and structure belies extremely complex properties, including those of "dynamic" coatings that display rapid self-healing behavior in the presence of solvent. This contribution covers our work with these materials and highlights some of the key findings regarding damage mechanisms, healing processes, film structure/composition, and how the variation of fabrication parameters can impact self-healing behavior.

Responsive Microgels at Surfaces and Interfaces

“…Even in such multilayer architectures, the sensitivity of the individual microgel particles and the reversibility of the responsive behavior remain. Together with a remarkable mechanical stability this inspires studies on self-healing effects in microgel multilayer structures based on hydration and reswelling [58] and the use of microgel multilayers as host media for a controlled drug release.…”

Water‐Triggered Self‐Healing Coatings of Hydrogen‐Bonded Complexes for High Binding Affinity and Antioxidative Property

“…Among intrinsic self‐healing coatings, water‐enabled self‐healing coatings are especially promising because the healing is accomplished by simply soaking the coatings in water or exposing them to moisture, without using any special devices or chemicals. Lyon and co‐workers first developed hydrogel thin films/coatings on polydimethylsiloxane by layer‐by‐layer (LBL) assembly of submicrometer‐sized polyanionic gel particles and linear polycations; these films can rapidly heal micrometer‐sized defects after exposed to water. Subsequently, Sun and co‐workers have fabricated various kinds of water‐enabled self‐healing coatings by LBL assembly of polyelectrolyte multilayers .…”

“…Subsequently, Sun and co‐workers have fabricated various kinds of water‐enabled self‐healing coatings by LBL assembly of polyelectrolyte multilayers . Up to now, all water‐enabled self‐healing coatings are prepared by LBL assembly . This method is advantageous in easy preparation and fine control over the coating structures.…”

Functional Microgels for the Decoration of Biointerfaces

“…When utilizing polymer coatings based on linear polymers, the maximum thickness that can feasibly be achieved with grafting‐from processes of layer‐by‐layer deposition of multiple layers is limited . However, the fabrication of coatings using microgels allows for tunable thicknesses, from tens of nanometres to several hundred microns . This can be achieved by modulating the sizes of the microgels used for generating the coatings, or using a layer‐by‐layer approach, such as that demonstrated by South et al .…”

“…[27] However, the fabrication of coatings using microgels allows for tunable thicknesses, from tens of nanometres to several hundred microns. [28] This can be achieved by modulating the sizes of the microgels used for generating the coatings, or using a layer-by-layer approach, such as that demonstrated by South et al [29] In their work, South and coworkers utilized centrifugal (or active) deposition as a comparison to passive deposition of microgels onto a substrate. They fabricated multilayer microgel films through coulombic interactions between a pre-functionalized cationic substrate, anionic microgels and polycations, which were introduced in intermediate deposition steps for bringing about charge reversal on the surface.…”