In
this study, we developed azobenzene polymer particles showing
several light-induced shape changes. Conventional azobenzene particles
require exposure to polarized white or blue light on a substrate for
shape elongation. First, the dispersion polymerization of 6-[4-(4′-methoxyphenylazo)phenoxy]hexyl
methacrylate afforded unique oval or short cylindrical shapes with
controlled sizes and narrow size distributions. Then, polarized optical
microscopic observations and wide-angle X-ray diffraction measurements
suggest that the azobenzene moiety formed a uniaxially orientated
smectic-layered structure in the particles. Differential scanning
calorimetric measurements indicated that the packing structures and
particle shapes were closely related to each other. Finally, the particle
shape was altered by the trans–cis photoisomerization of azobenzene
accompanied by the deformation of the azobenzene packing structure.
Interestingly, their shape anisotropy was increased by ultraviolet
and white-light irradiation. The particle shape was changed in a dispersed
medium and on a substrate by unpolarized light. Consequently, the
combination of a light source and site varied the light-induced shape
changes of the azobenzene particles.