Cellulose nanocrystals in smart and stimuli-responsive materials: a review

"Smart" stimuli-responsive materials have been the subject of decades of research because of their versatility and particularly their use in medical and sensing applications. While these materials are often composed exclusively of responsive polymers, there is growing interest in smart hybrid systems that contain at least two distinct components, each contributing uniquely to the final material. Cellulose nanocrystals (CNCs) have found extensive application in smart hybrid systems, as CNCs can both contribute to the mechanical and optical properties of the system and bear stimuli-responsive surface modifications. This review covers the recent body of work on CNC-containing smart hybrid systems, with attention given to the fabrication methodologies that have been employed to generate both physically and optically adaptable CNC-based smart systems. Additionally, the unique application of CNCs in self-healing composites and shape memory polymers will be discussed. (c) 2020 The Author(s). Published by Elsevier Ltd.