Growth of porous chitin-nanofibrous structure via layer-by-layer self-assembly under existing ionic effects for antireflective and antifogging coatings

[Display omitted] •Antireflective and antifogging multifunctional coating composed of nanofibers.•Coating structures were designed under controlling existing ionic effects.•Polymer conformation changes optimized the adsorption via layer-by-layer.•The possibility of ionic effects boosts the buildup for porous coatings. Antireflection surfaces reduce reflectance and maximize 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 utilization of fiber materials. 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, this 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. This versatile procedure for producing porous materials should prove valuable for a wide variety of industrial applications.