The unique drying behavior of aqueous droplets that contain soft hydrogel microspheres (microgels) upon evaporation was systematically investigated. Compared to the ring-shaped deposits that are obtained from drying solid microsphere dispersions, we have previously reported that uniformly ordered thin films are obtained from drying ∼1.2 μm-sized poly( N-isopropyl acrylamide) microgel dispersions. In the present study, we thoroughly investigated several hitherto unexplored aspects of this self-organization, such as the effect of the size, chemical structure, and "softness" of the microgels (or rigid microspheres). For the macro- and microscopic observation of the drying behavior of various microsphere dispersions, an optical microscope and a digital camera were employed. The results suggested that the convection in the aqueous droplets plays an important role for the transportation of the microgels to the air/water interface, where the softness and surface activity of the microgels strongly affects the adsorption of the microgels. On the basis of these discoveries, a design concept for the rapid formation of uniform thin films of soft microgels was proposed.

The deformation of soft hydrogel microspheres (microgels) adsorbed at the air/water interface was investigated for the first time using large poly(N-isopropyl acrylamide)-based microgels synthesized by a modified aqueous precipitation polymerization method. The deformation of the micron-sized soft microspheres could be visualized clearly and analyzed quantitatively at the air/water interface.

The three‐dimensional structure of nanocomposite microgels was precisely determined by cryo‐electron micrography. Several nanocomposite microgels that differ with respect to their nanocomposite structure, which were obtained from seeded emulsion polymerization in the presence of microgels, were used as model nanocomposite materials for cryo‐electron micrography. The obtained three‐dimensional segmentation images of these nanocomposite microgels provide important insights into the interactions between the hydrophobic monomers and the microgels, that is, hydrophobic styrene monomers recognize molecular‐scale differences in polarity within the microgels during the emulsion polymerization. This result led to the formation of unprecedented multi‐layered nanocomposite microgels, which promise substantial potential in colloidal applications.