Responsive Layer-by-Layer Films

Layer-by-layer (LbL) assembly has been extensively researched as a versatile method to produce smart coatings and capsules with a distinct multilayered structure. This specific fabrication technique provides ways to induce responsiveness not only through the chemically engineered macromolecular components, but also through the way the multilayers are built up. This chapter is dedicated to LbL fabrication-specific responsiveness, as well as to the recent developments in multilayers composed of specifically tailored polymers. This chapter further focuses on chemically- and biologically-responsive LbL systems, with main applications in the biomedical field. In the introduction, general aspects of LbL assembly as a fabrication technique are described, along with physicochemical aspects of the assemblies. The second part describes the physicochemical aspects in more detail with examples on how variation in deposition conditions, such as pH and ionic strength, can be used to induce responsiveness upon the resulting multilayers. This section also highlights several reports on the fabrication of compartmentalized multilayered coatings for tunable disassembly or release of incorporated materials. The third part describes recent examples of multilayers fabricated with chemically tailored biomaterials for various chemical and biological responsiveness. More specifically, the multilayer disassembly can be triggered through inherent responsiveness of one of the multilayer components, through chemically- or biologically-triggered degradation of one of the multilayer components, or through disruption of the interlayer interaction between two or more components of the multilayers.