Porous chitin-nanofibrous structure via layer-by-layer self-assembly

Scientists have studied the growth of porous chitin-nanofibrous structure under existing ionic effects for antireflective and antifogging coatings.

Antireflection surfaces reduce reflectance and maximise light transmission. Therefore, these types of surfaces play an important role in optical technologies. The precise control of coating thickness and refractive index via self-assembly from nano- to microscales has accelerated the development of antireflection surfaces. One promising technique for the production of antireflection coatings is the layer-by-layer (LbL) method, which has recently received significant improvements, particularly in the utilisation of fiber materials.

Antireflective nanofibril coatings
However, given that the ionic effect hinders self-assembly and degrades the porous nanofiber structure, nanofiber LbL films remain difficult to fabricate. To address this issue, a new study fabricates antireflective nanofibril coatings by controlling the porosity under various ionic conditions in an LbL approach. The addition of NaCl modifies the ionic condition and transforms the polymer conformations, thus increasing the porosity inside the membrane, which consists of cationic chitin nanofibers and anionic poly(acrylic acid).

The resulting structure has a transmittance of 93.7 % at 550 nm and a refractive index of 1.30. The coating reduces fogging because of the hydrophilic surface and the strong hydrogen bonding of the chitin nanofibers.