Multifunctional Nanosystems from Stimuli Responsive Nanoparticles Coated with a Reversibly Switchable Shell

摘要

We report on a method of fabricating stimuli-responsive core-shell nanoparticles using block- copolymers covalently bound to silica nanoparticles’ surface. We used the “grafting to” approach to graft amphiphilic block copolymer brushes of poly(styrene-b-2-vinylpyridine- b-ethylene oxide) and poly(styrene-b-4-vinylpyridine) onto silica nanoparticles with two different diameters: colloidal silica 200 nm in diameter and fumed silica 15 nm in diameter. We used the grafted brush’s pH-responsive properties to regulate the interactions between the particles, and between the particles and their environment. We show that this behavior can be applied for a reversible formation of particle aggregates; stabilization and switching between o/w and w/o emulsions; can be used to tune and stabilize the secondary aggregates of particles of the appropriate size and morphology in aqueous environment. The suspensions of the particles form a textured hydrophilic coating on various substrates upon casting and the evaporation of water. Heating above polystyrene’s glass transition temperature or treatment in acidic water results in back and forth switching between superhydrophobic and hydrophilic surfaces, respectively.