Control of functionalities in polymer nanoparticles (PNPs) is important for their application. Thus, there is an interest for well-defined nanoparticle platforms to which desired functions could readily, and in modular fashion, be imparted. Herein, we report an amine-reactive PNP platform for the modular synthesis of functional PNPs from poly(pentafluorophenylmethacrylate) (poly(PFPMA)) through a simple substitution/nanoprecipitation/photo-crosslinking strategy. Substitution of amine containing coumarin into poly(PFPMA) allows for the achievement of structural stability of nanoprecipitated particles through photo-crosslinking after nanoprecipitation, making it possible to carry out subsequent chemical transformations in organic solvents if needed. We demonstrate that various small molecules and an amine-terminated polymer could be used to modify the crosslinked PNPs to endow them with various functions including fluorescence and responsiveness to temperature changes. The functional PNPs were characterized with variable temperature dynamic light scattering (DLS), UV-vis, and photoluminescence (PL) spectroscopy, and transmission electron microscopy (TEM). (C) 2016 Wiley Periodicals, Inc.