Layer‐by‐Layer Self‐Assembled Multilayer Stimuli‐Responsive Polymeric Films

Abstract

IntroductionMultilayer polymeric films fabricated through the layer-by-layer (LBL) self-assembly technique are able to integrate stimuli-responsive materials into the films through various intermolecular interactions. The ease of the fabrication process and the excellent control of the film composition and morphology, combined with the capability of coating substrates conformally, offers a wide range of multilayer films that change film properties such as permeability, wettability, color, and solubility upon external stimuli. This chapter reviews the methods of building LBL multilayer films and the approaches to control the structures of the films. These smart films provide numerous applications in controlled drug release, sensing, energy generation, and flow regulation with their unique response to external stimuli including pH and temperature change, photo irradiation, application of electrical fields, and specific molecular interactions.Stimuli-responsive coatings, also known as smart coatings, are able to change their properties upon external stimuli including temperature, pH, salt concentration, light, presence of specific molecules, and other factors. The capability of changing surface behavior in an accurate and predictable manner has generated numerous applications ranging from chemical sensing, separations, and drug delivery to various bioapplications. To name a few, smart coatings with tunable hydrophilic/hydrophobic wettability have been used in the development of microand nanofluidic devices, self-cleaning and antifog surfaces, and sensor devices [1-3]. Photochemical-responsive coatings have been applied to build a surface that releases nitric oxide [4] over nanometer length scales for photochemotherapeutic applications, and a surface that can be photoactivated for spatiotemporal control of cell adhesion during cell cultivation [5,6]. The control of the properties of these smart coatings can be achieved through the stimuli-responsive materials forming self-assembled monolayers (SAMs) and polymer films. Among various approaches to fabricate responsive polymer films, multilayered polymer films, generally referred as polyelectrolyte multilayer (PEM) films, fabricated through the LBL assembly technique, have been proven to be effective smart coatings with Handbook of Stimuli-Responsive Materials. Edited by Marek W. Urban