• amino groups;
  • bipolar interface;
  • carboxyl;
  • charged surfaces;
  • plasma polymerization


Thumbnail image of graphical abstract

An intentional and defined grafting of the material surface with multiple positive/negative charges produced by functional groups is desired for biomedical applications. In this work, multistacked organic bipolar films containing alternating nano-layers of plasma polymerized acrylic acid (PPAac) and plasma polymerized allylamine (PPAam) are investigated in order to prepare highly polarized surfaces with positive/negative charges. Two kinds of composite films fabricated according to different depositing sequences and with –COOH or –NH2 functional groups onto their outermost surfaces are prepared. The results of ATR-FTIR and XPS demonstrate that a significant number of [BOND]COO and –NHmath image polar entities, generated from the interaction of PPAac and PPAam films, are present in these multistacked organic bipolar films. Furthermore, the remarkably increased polar surface energy of these composite films, compared with pure PPAac and PPAam films, reveals that the presence of the [BOND]COO and [BOND]NHmath image polar entities induces strong dipole orientation polarizability, and results in the redistribution of charges. The results suggest that the surface with highly polarized –COOH and –NH2 groups have high surface charges and chemical reactivity. These surfaces show promising applications for biomolecules binding and cell growth.