Hydrogels with self-assembling ordered structures and their functions

Biological soft tissue and synthesized hydrogel both belong to the same 'soft and wet' class of substances, that is, they are both soft and contain water. However, whereas biological tissue such as muscles displays various forms of functionality, hydrogels generally have poor functionality, primarily due to the difference in structure biological tissue has a sophisticated structure whereas most hydrogels are amorphous. In recent years, biomacromolecules, block copolymers and liquid-crystalline molecules have been used to develop self-assembled architectures in synthetic physical or chemical hydrogels via intermolecular noncovalent interactions such as ionic bonding, hydrophobic interactions and hydrogen bonding. Ordered structures on various length scales endow the hydrogels with additional functions with promising applications in materials science, such as in tissue engineering and mechano-optical sensors. In this review, we briefly describe the recent developments in designing hydrogels with ordered structures of molecular assemblies and the resultant functionalities.