The layer-by-layer (LbL) assembly has been demonstrated to be a convenient and versatile method to fabricate composite film materials with precise control of film composition and structure.Polymeric complexes represent a large variety of supramolecular assemblies hold together by multiple weak interactions

which include polyelectrolyte-polyelectrolyte complexes

polyelectrolyte-surfactant complexes

non-charged polymer-polymer complexes

polymeric-inorganic hybrid complexes and so forth.We demonstrate herein that the LbL assembly is unique to fabricate functional films by using polymeric complexes as building blocks:(1) It enables rapid fabrication of micrometer-thick films because of the large dimension of the polymeric complexes.(2) It facilitates the flexible control of film structures because the structure of polymeric complexes can be easily tailored in solution or in LbL assembled films.(3) The LbL assembly of polymeric complexes can build up novel functional films which are difficult or impossible to fabricate by LbL assembly of uncomplexed polymers.