Tannic Acid-Inspired Star-Like Macromolecules via Temporally Controlled Multi-Step Potential Electrolysis

Inspired by tea stains, a plant polyphenolic-based macroinitiator is prepared for the first time by partial modification of tannic acid (TA) with 2-bromoisobutyryl bromide. In accordance with the “grafting from” methodology, a naturally occurring star-like polymer with a polar gallotannin core and a hydrophobic poly(n-butyl acrylate) side arms is synthesized via a simplified electrochemically mediated ATRP (seATRP), utilizing multiple-step potential electrolysis. To investigate the kinetics of the electrochemical catalytic process triggered by reduction of Cu(II) or Fe(III) catalytic complex in the presence of the multifunctional initiator, cyclic voltammetry measurements are conducted. The naturally derived tannin macromolecule shows narrow MWDs (Đ = 1.57). Moreover, solvolysis of the star polymer to cleave the side arms and characterize them indicates that all chains grow to the same length (homopolymers with Mw/Mn <1.17), which confirms the well-controlled seATRP. The structure of the obtained TA-based systems is characterized microscopically (AFM) and spectroscopically (1H NMR, FT-IR). Atomic force microscopy measurements precisely determine the diameters of the obtained star polymers (19.7 ± 3.3 nm). These new star polymers may find biomedical applications as drug delivery systems and antifouling or antimicrobial coatings.