Bioinspired coloration of cellulose nanocrystals (CNCs)
has advanced
a new era of wide applications for decoration, sensing, and anti-counterfeiting.
However, the solid structural color films suffer from strong angle-dependent
iridescence and a limited color range due to the spatial arrangement
caused by kinetic arrest during evaporation-induced self-assembly
of CNCs. Here, a ternary co-assembly approach is demonstrated to prepare
CNC films with weak/non-angular optical response and wide-range colors.
Structural coloration is enabled by the long-range and short-range
ordered photonic structure of CNCs. A cationic polymer, poly(dimethyl
diallyl ammonium chloride), is introduced to influence the CNC self-assembly
through electrostatic attraction, inducing the structural transition
to the long-range disordered/short-range ordered structure as well
as presenting the gradual change from iridescent structural colors
to non-iridescent colors. Additionally, a hydrophilic small compound,
glycerol, is used to adjust the helical pitch of nanostructured CNC
arrays, offering the broad-range coloration. The CNC-based composite
material is further used as an optical coating for anti-counterfeiting
and realizing color patterning and angle-dependent selective color
changes.