A Robust Fabrication Method for Amphiphilic Janus Particles via Immobilization on Polycarbonate Microspheres
Immobilizing particles on beads, fibers or filaments, when only one side is exposed to the reaction medium and therefore can be selectively functionalized, is a scalable and easy to control strategy for the fabrication of amphiphilic Janus particles. Here we describe a new, robust method for the fabrication of amphiphilic Janus particles by the immobilization of Polymethylsilsesquioxane (PMSQ) particles on polycarbonate (PC), a high impact-resistance polymer with superior mechanical properties. The immobilization of the particles on the PC microspores is preformed via inverse solvent displacement method. PMSQ particles are added to a PC solution in tetrahydrofuran (THF), a good solvent for PC. The solution is then precipitated by the introduction of aqueous surfactant solution (anti solvent for PC) under an ultrasonic field. It is important to note that THF and water are miscible and do not form an emulsion.
During precipitation, PMSQ particles are assembled onto the surface of the PC spherical precipitates/microspheres. The exposed hemispheres of the PMSQ particles are then selectively silanized by (3-Aminopropyl)triethoxysilane (APTES) to introduce amine groups on their surface.
Figure 1. (a) HRSEM images of PMSQ-COOH amphiphilic Janus particles decorated with covalently immobilized amine functionalized silica nanoparticles (NPs). (b) Overlay confocal microscopy images of the PMSQ-COOH amphiphilic Janus particles labeled with 6-aminofluorescein. (c) Fluorescein signal
To increase the polarity of the functionalized hemispheres, the amine groups are further modified to introduce carboxyl groups. SEM characterization confirms the fine embedment of PMSQ particles onto the PC microspheres. Fluorescent confocal microscopy, EDX and ATR-FTIR analysis conclusively proof the successful fabrication of amphiphilic Janus particles. The immobilization of particles onto a highly rigid polymeric microspheres such as PC opens up the possibility to develop a robust fabrication procedure due to the properties that can arise from the durability of the PC including high resistance against temperature fluctuations and harsh mixing conditions during preparation. This method can be implemented toward a large variety of other synthetic commercial polymers such as polyamide, polyether sulfones, Polyether ether ketone or similar.
Polymers 2018, 10, 900; doi:10.3390/polym10080900