Layer-by-Layer Codeposition of Polyelectrolyte Complexes and Free Polyelectrolytes for the Fabrication of Polymeric Coatings

The layer-by-layer (LbL) codeposition of polyelectrolyte-polyelectrolyte complexes (PECS) and free polyelectrolytes with oppositely charged polyelectrolytes for the fabrication of polymeric films has been systematically investigated. Aqueous dispersions containing positively charged diazoresin (DAR)-poly(acrylic acid) (PAA)complexes (denoted as DAR-PAA)and free DAR were used as the dipping solutions for LbL film fabrication with PAA. Simultaneous deposition of DAR-PAA complexes and free DAR with PAA took place under a nondrying LbL deposition process that produced bilayered thick polymeric films with the hierarchical PAA/DAR-PAA coatings rooting in the underlying continuous PAA/DAR Films. The structure of the bilayered polymeric films depends largely on the ratio of DAR-PAA complexes to free DAR in the dipping solution. The more rapid deposition of PAA/DAR-PAA coatings than that of the PAA/DAR films accounts for the formation of bilayered polymeric films because DAR-PAA complexes have larger dimensions than DAR in solution. The bilayered polymeric coatings with hierarchical structures rooting ill continuous films have enhanced adhesion with the underlying substrates because of the increased contacting area. After chemical vapor deposition of a layer of fluoroalkylsilane, the bilayered polymeric coatings can be easily converted into superhydrophobic. In contrast, the LbL codeposition of DAR-PAA complexes and DAR with PAA produces thin and compact films without bilayered structures when a N-2 drying step is conducted after each layer deposition. The present study is meaningful in deeply understanding the deposition behavior and structure tailor of LbL assembled films using PECS its building blocks.