Kang Hee Ku1
UNIST1
Complex microscale colloids are material platforms for a wide range of sensing scenarios and can be tuned and configured by a variety of chemical and physical phenomena. In particular, the soft boundaries of colloids produce various synergetic effects by exploiting self-assembling polymers. First, I will present the state-of-the-art in the programmed design of anisotropically shaped polymer particles driven by phase-separation upon solvent evaporation from interface-engineered emulsions. In particular, two different topics: 1) block copolymer (BCP) particles with reversible shape-changing property activated by wavelength-selective light irradiation, and 2) full-color reflective photonic polymer particles capable of a dynamic color change will be discussed. First, the key to achieving light-responsive shape transitions of BCP particles is the design and synthesis of surfactants containing photo-cleavable groups (i.e., nitrobenzyl esters and coumarin esters) or photo-isomerizable groups (i.e., spiropyran) that modulate the amphiphilicity and interfacial activity of the surfactants in response to light of a specific wavelength. These light-induced changes in surfactant structure modify the surface and wetting properties of BCP particles, affording both shape and morphological transitions of the particles. Next, dendronized brush block copolymers are used to achieve highly ordered axially stacked lamellae with large domain size, allowing a near-perfect photonic multilayer. The photonic ellipsoids are functionalized with magnetic nanoparticles organized into bands on the particle surface to produce real-time on/off coloration by magnetic field-assisted activation.