Size control of polydopamine nodules formed on polystyrene particles during dopamine polymerization with carboxylic acid-containing compounds for the fabrication of raspberry-like particles

The facile preparation of nonspherical raspberry-like particles composed of a polystyrene (PSt) core and polydopamine (PDA) nodules was described. Various polymerization parameters influencing the PDA nodules were investigated in detail. It was found that raspberry-like particles were obtained in a 1:1 water/methanol solution in the presence of compounds with carboxylic acid groups, e.g., caffeic acid (CF). The raspberry-like particles obtained were characterized in terms of their size, morphology, and chemical composition using scanning electron microscopy (SEM), transmission electron microscopy (TEM), infrared (IR) spectroscopy, elemental analysis, and solid-state nuclear magnetic resonance (NMR) measurements. Finally, the formation mechanism was discussed. Because PDA may be used to cover a variety of particle surfaces, the present method has great potential for fabricating many types of raspberry-like particles.