Complexation of tannic acid with polyoxypropylene diamine in water and application for the preparation of hierarchically structured functional surfaces

Abstract

We rationalize that a water-soluble low molecular weight polyoxypropylene diamine (i.e., Jeffamine® D400 polyetheramine), capable of various types of noncovalent molecular interactions through its amine and propylene oxide groups, presents a simple yet versatile opportunity to form complexes with natural polyphenol of tannic acid (TA) and be exploited to engineer functional materials and surfaces. By investigating TA-D400 complexation behaviors in water, we demonstrate that mixing weakly acidic TA and neutral D400 solutions of stock concentrations above 1.0 mg/mL allowed easy formation of colloidally stable TA-D400 complexes. Such complexes were characterized as cationic nanoparticles of typical hydrodynamic diameters less than 300 nm. Mixing ratios were found to be less of an influencer on complexation. The TA-D400 intermolecular complexation was shown to be driven primarily by hydrophobic interaction in conjunction with ionic association. A simple immersion process can induce the formation of substrate-independent, hierarchically structured, and highly hydrophilic surfaces because of adsorption of TA-D400 complexes. Such functional surfaces not only can potentially modulate cell-material interactions shown by our brief in vitro fibroblast cell culture study, but also are feasible for in situ facile reduction of HAuCl4 to achieve integration of gold nanoparticles for function enrichment. This TA-D400 system adds a new option to the toolbox of polyphenol-mediated green technologies for surface engineering.