Nanoparticle Assembly Modulated by Biobased Polymers and Its Coating Application*

We study how nanoparticles assemble in a dried film containing biobased polymers. Different nanoparticles were dispersed with hydroxyethyl cellulose (HEC) and hydroxyethyl starch (HES). It was discovered that polymer morphology has a profound influence on the assembly structures of nanocomposite. In addition, an unexpected highly fractal network structure assembled by nanoparticles were formed in HEC matrix with different types of nanoparticles. Electron microscopy and small X-ray scattering offer the detailed analysis of the structures. Based on these results, we further developed a biobased waterborne coating system to effectively block the UV radiation while maintaining the transparency using ZnO nanoparticles. Our new coating materials can lead to coating films ~ 100 times thinner than the previously reported coating systems of similar UV-blocking performance. The same concept can be applied to other polymer nanocomposite systems. The study opens the opportunity of utilizing more sustainable biobased materials for high-value functional coating applications.