Layer-by-Layer Directly-Assembly of Polyelectrolyte Multilayers with Foaming Structures

Download or read book Layer-by-Layer Directly-Assembly of Polyelectrolyte Multilayers with Foaming Structures written by Lihua Xu and published by . This book was released on 2015 with total page 62 pages. Available in PDF, EPUB and Kindle. Book excerpt: In recent decades, dynamic Layer-by-Layer (LbL) assembly of multilayer thin films has been widely recognized for many reasons, especially for its versatile functionality and ease of fabrication. Films can be fabricated towards huge amounts of materials, such as polyelectrolytes, organic components, polymeric microgels, etc. Through the long history of LbL assembly research, few papers proposed ideas of making porous films or foamed films directly or indirectly, as foamed material contained plenty of pores, which could be used in insulation materials and fast food-packages. In several papers, the step of acid treatment aimed for irreversible structure transformation applied into films fabricated by the LbL assembly method. This indirect method makes procedures more complex, so direct fabrication with LbL is necessary. However, time-consuming problems and challenges from external environmental factors still limits the development of this technique. In this thesis, a facile fabrication of porous films through the LbL assembly method was introduced. Strong polyelectrolyte, polycation poly(diallyldimethylammonium-chloride) (PolyDADMAC) and polyanion poly(styrene sulfonate acid) (PSSA) are utilized as the original material. And PolyDADMAC was slightly modified by sodium hydroxide (NaOH) and carbon dioxide (CO2) in order to get the bicarbonate structure at the side groups along the chain of the polyelectrolyte. In order to deeply study the films, some other particles, such as the surfactant brij-76 and RDS laponite were added into certain solutions for comparison. Films were achieved by alternately putting clean glass slides into the polycation and polyanion solutions with the rinsing step in between. 20-bilayer film can be achieved after repeating the procedures above 20 times. The principle is that the bicarbonate functional group will react with the hydrogen ions for the sake of letting the gas carbon dioxide out and then make the porous structure throughout the film. The morphology of the films measured by an atomic force microscope (AFM) and a scanning electron microscope (SEM) shows that porous structures are obvious through the whole film when no sodium bicarbonate (NaHCO3) is added into the anion solution. The results help to solve the problem of directly making the foaming films as well as simplifying the procedures.