No abstract

In this paper, the formation of microscopic polystyrene/poly(methyl methacrylate) Janus particles by using environmentally benign solvents and surface active agents is presented. Janus particles are formed by the rapid polymer phase separation that occurs when an oil-in-water suspension is allowed to dry. Biodegradable or bio-inert organic solvents and surface active agents are used. These solvents affect the particle morphology, which is studied in detail. The environmentally friendly solvent ethyl acetate can replace the more commonly used toluene for the preparation of Janus particles. Confocal Raman microscopy is used to visualize and analyze the phase separated Janus particles. Results indicate that the polystyrene hemisphere as minor component within the particle is covered with a thin PMMA layer on its surface.

Phase-separated polymer droplets with micron-size diameter and nanometer-size height were prepared by casting a dilute solution of two polymers, polystyrene and poly(methylmethacrylate). Staining with an electron acceptor allowed us to distinguish between the two polymers by fluorescence microscopy.

Phase-separation of polymers in thin films produces a wide variety of patterns. Here we show that a polystyrene/poly(methylmethacrylate solution can form stable phase separated structures when an additive such as chitosan or acetic acid is used. The phase separated films were analyzed by fluorescence microscopy. Possible applications of these films are as etching masks for solar cells or for security systems.

Polymer droplets are formed by a dewetting process from dilute solution. They have diameters of 0.3–30 µm and a height approximately 5% their diameter. The dewetting is a nonequilibrium process, but can be controlled to achieve a narrow size distribution of the droplets. To date, one major limitation of the dewetting process for the formation of self-organized microstructures was that the height/diameter ratio and interdroplet distance could not be separately controlled. Here, we describe a post-dewetting treatment of the polymer droplets with a swelling agent that leads to a marked shape change, without detaching the droplet. This shape change can be applied to commodity polymers, such as polystyrene, as well as to electrically conducting polymers, such as poly(hexylthiophene). Thermal annealing then leads to a reversal of the shape change. One possible application is adaptive microlenses.