Shape Memory Cellulose-Based Photonic Reflectors

Biopolymer-based composites enable
to combine different functionalities using renewable materials and
cost-effective routes. Here we fabricate novel thermoresponsive photonic
films combining cellulose nanocrystals (CNCs) with a polydiolcitrate
elastomer exhibiting shape memory properties, known as hydroxyl-dominant
poly­(dodecanediol-co-citrate) (PDDC-HD). Iridescent
films of CNCs are first made by evaporation-induced self-assembly,
then embedded in the PDDC-HD prepolymer, and finally cured to obtain
a cross-linked composite with shape memory properties. The fabricated
samples are characterized by polarized optical microscopy, scanning
electron microscopy, and thermomechanical cycling. The obtained hybrid
material combines both intense structural coloration and shape memory
effect. The association of stiff cellulose nanocrystals and soft polydiolcitrate
elastomer enhances the overall mechanical properties (increased modulus
and reduced brittleness). This hybrid nanocomposite takes advantage
of two promising materials and expands their possibilities to cover
a wide range of potential applications as multiresponsive devices
and sensors. As they perform from room to body temperatures, they
could be also good candidates for biomedical applications.