Macroscopically oriented polymeric soft materials: synthesis and functions

Owing to the similarity to biological tissues, soft materials have attracted increasing attention as components of biological tissues. However, there is a large difference between synthetic soft materials and biological tissues. Most synthetic soft materials are structurally isotropic, whereas some biological tissues have anisotropic structures that continue over a macroscopic size scale. As seen in muscle, blood vessels, articular cartilage, and iridophores, such anisotropic structures often play critical roles in producing their superb functions. Thus, the control of "structural anisotropy" is a key concept for the further exploration of functional soft materials science. Using the magnetic orientation of nanoobjects in a colloidal dispersion and subsequent in situ polymerization, we recently succeeded in developing anisotropic soft materials, in which highly oriented structures (order parameter = > 0.95) extend over a macroscopic size scale (similar to 10 cm). In addition, we demonstrated unprecedented unique functions of the resultant materials, including ultralarge mechanical anisotropy similar to articular cartilage, quick and large deformation similar to muscular tissues, and dynamic structural color modulation similar to the skin of tropical fish. Integration of the related studies on soft materials with anisotropically oriented structures would bring the concepts of artificial organs and soft robotics into reality.