Self-assembly of polystyrene nanoparticles induced by ice templating

Abstract

An investigation was performed to develop a facile route, named as ice templating, for large scale of three-dimensional assembling of polystyrene nanoparticles. The organic nanoparticles were assembled into a macroscopic subject with sophisticated three-dimensional microstructure, induced by growing ice crystals in freezing process of particle suspension. By controlling freezing direction, freezing rate, and particle concentration in suspension, various interesting microstructures were prepared, including three-dimensional connected porous lamellas, bundles of ribbons, and fibers with uniform diameter (~1.5μm), high aspect ratio, and same orientation. Freezing direction is the key factor to control the assembling direction of particles, while, freezing rate and particle concentration are important parameters which affect morphology and size of microstructures. On the other hand, the route of ice templating has many advantages, including environmental friendly, low cost, high output and universality. Other materials, such as metal and semiconductor nanoparticles, could also be used in our platform for preparation of smart materials and structures. It is anticipated that by this simple approach, various functional nanoparticles would be efficiently assembled into macroscopic subject with sophisticated microstructures which offer synergistic, optimized properties of individual zerodimensional elements, and hence, the derived composite materials or structures could implement desired functions with better performance.