Totally Organic Redox-Active pH-Sensitive Nanoparticles Stabilized by Amphiphilic Aromatic Polyketones

Amphiphilic aromatic polymers have been synthesized by grafting aliphatic polyketones with 4-(aminomethyl)benzoic acid at different molar ratios via the Paal–Knorr reaction. The resulting polymers, showing diketone conversion degree of 16%, 37%, 53%, and 69%, have been complexed with the redox-active 2,3,5-triphenyl-2H-tetrazolium chloride, a precursor molecule with which aromatic–aromatic interactions are held. Upon addition of ascorbic acid to the complexes, in situ reduction of the tetrazolium salt produced 1,3,5-triphenylformazan nanoparticles stabilized by the amphiphilic polymers. The stabilized nanoparticles display highly negative zeta potential [−(35–70) mV] and hydrodynamic diameters in the submicron range (100–400 nm). Nonaromatic polyelectrolytes or hydrophilic aromatic copolymers showing low linear aromatic density and high linear charge density such as acrylate/maleate and sulfonate/maleate−containing polymers were unable to stabilize formazan nanoparticles synthesized by the same method. Th...