Alkyne-rich patchy polymer colloids prepared by surfactant-free emulsion polymerization.

While free radical polymerization methods are employed frequently to prepare sub-micron polymer particles, we hypothesized that surfactant-free emulsion polymerization (SFEP) methodology may prove beneficial for obtaining functional polymer particles by solution polymerization methods that preclude the need for conventional surfactants. To test the effectiveness of SFEP for the preparation of functional colloids, solution polymerization of several monomers, including propargyl acrylate (PA), styrene (Sty) and tert-butyl acrylate (t-BA), was performed over a range of monomer ratios and reaction scales. Electron microscopy and infrared spectroscopy were employed to evaluate the outcome of SFEP for particle size, shape, surface anisotropy, and chemical composition. Combining this characterization with optimized SFEP synthesis, we found that spherical polymer particles-homopolymers of PA as well as copolymers-were obtained in the 60-300 nm diameter size range. Successful inclusion of PA enabled the use of the particles in copper-catalyzed azide-alkyne cycloaddition reactions (CuAAc). Moreover, electron microscopy characterization with backscattering revealed chemical and shape anisotropies on copolymer particles indicative of monomer phase-separation during particle formation. Overall, the SFEP methodology represents a straightforward, one-pot, bottom-up approach to yield a library of functional polymer particles, while avoiding undesirable aspects associated with conventional surfactants.