Effect of Polyelectrolyte Structure and Salt Concentration on the Porous Architecture of Self-assembled DNA/Polycations Macroporous Multilayer Thin Films

Two different polycations,one is the strong polyelectrolyte of poly(diallyldimethylammonium chloride)( PDDA) and the other is the weak one of polyallylamine hydrochloride( PAH),were utilized to form multilayer thin films with deoxyribonucleic acid(DNA). Atomic force microscopy(AFM) and ultravioletvisible spectroscopy( UV-Vis) were used to investigate the effects of polycation structure and salt concentration on the macroporous architecture and growing behaviors. The results demonstrate that in the case of DNA /PDDA multilayer thin films,salt concentration effect plays an important role on the formation of macroporous structure; however,in the case of DNA / PAH multilayer thin films,there is no porous structure even at higher salt concentration in the DNA or PAH solution. This is mainly due to the inherent weak electrolyte characteristics of PAH. Therefore,in addition to the effects of molecular weight mismatch and persistent length mismatch as-mentioned,the effects of salt concentration and polyelectrolyte structure are the key factors for controlling the formation of the macroporous architectures.