Thin Biobased Transparent UV-Blocking Coating Enabled by Nanoparticle Self-Assembly

Abstract

A waterborne, UV-blocking, and visually transparent nanocomposite coating was formulated with ZnO nanoparticles and 2-hydroxyethyl cellulose (HEC). The coating is highly effective (< 5% UV and ~ 65% visible transmittance) and the film thickness (0.2-2.5 μm) is ~100 times thinner than the conventional coatings of similar UV-blocking performance. The superior properties are due to the fractal structures of ZnO nanoparticles assembled within the HEC matrix, revealed by scanning electron microscopy (SEM) and smallangle x-ray scattering (SAXS). Changing the binder to 2-hydroxyethyl starch (HES) diminishes the UVblocking performance, as ZnO nanoparticles form dense globular aggregates, with an aggregation number measured by SAXS three orders of magnitude larger than the HEC coating. Since HEC and HES share the same same chemical compositionrepeating glucose unit in the polymer backbone, it suggests that the conformational characteristics of the binder polymer have a strong influence on the nanoparticle aggregation, which plays a key role in determining the optical performance. Similar structures were achieved with TiO2 nanoparticles. This study not only offers a cost-effective and readily scalable method to fabricate transparent UV-blocking coating, but also demonstrates that the unique fractal aggregation structures in a nanocomposite material can provide high performance and functionality without fully dispersing the nanoparticles.

Biobased superhydrophobic coating enabled by nanoparticle assembly

“…Nanoparticles in polymer matrices can assemble into a number of structures ranging from clusters to networks and lms. [19][20][21][22][23] Their assembly is dictated by intermolecular forces, such as hydrogen bonding, electrostatic and van der Waals forces. [24][25][26] The aforementioned forces vary in magnitude and depend on interparticle distance.…”

Superhydrophobic cotton fabrics based on ZnO nanoparticles functionalization

“…Among these additives, zinc oxide nanoparticles (ZnO NPs) are of particular interest, due to their low cost, biocompatibility and biodegradability for environmental applications and to their hexagonal prism shape, which allows an increase in the surface roughness [16,17]. Therefore, this nanomaterial can be beneficial to obtained multifunctional materials due to its numerous properties, such as water resistance, antibacterial effect, UV blocking, flame retardancy, corrosion inhibitor and electrical conductivity [18][19][20][21][22]. Gao et al [23] described the preparation of a superhydrophobic coating based on SiO 2 -coated ZnO nanorod and obtained a WCA greater than 150° (as high as 157°).…”

Self-stratification of amphiphilic Janus particles at coating surfaces

“…23,53,54 The selfassembled clusters are known to change the kinetics and coating behaviours. 55 The clusters will slow down the diffusion and change the surface adsorption behaviours of Janus particles, which will eventually prevent the stratification from happening. Fig.…”