(600g) Facile Preparation of Nano-Sized Anisotropic Spherical Polyelectrolyte Brushes and Chemical Force Microscope Imaging for Their Regioselective Assembly

Here we demonstrate a facile method based on selective surface modification to prepare anisotropic spherical polyelectrolyte brushes (ASPBs) with a tailored surface property and geometry. At the first step, a strategy of Pickering emulsion was adopted to efficiently mask precursor nanoparticles, i.e. the precursor nanoparticles composed of polystyrene (PS) core and photo-initiator shell spontaneously embedded into the surface of molten wax bead, and locked by freezing the wax bead. The following step is proceeding with further modification on the unprotected surface of those trapped nanoparticles. Poly(acrylic acid) chains were chemically grafted to form robust brushes on exposed side of precursor particles under UV irradiation, which resulted in an asymmetrical geometry and property on the surface of nanoparticle. To take advantage of the anisotropism of ASPBs, we studied their alignments and orientations on solid surfaces with a different affinity. A chemical force microscope was employed to provide a high resolution imaging for their regioselective assembly. The probe was modified with mercaptan quaternary ammonium salt so as to interact with anionic brushes but inactivate the interaction with PS surface. Our work herein not only present a solution to a facile synthesis and characterization of anisotropic particles, but a way to exploit to control the geometry, the surface property, and the supraparticular assemblies of particles at nanoscale, even open the door to manipulate single nanoparticle in three dimensions.