Waterborne Hybrid Acrylic/Protein Nanocomposites with Enhanced Hydrophobicity by Incorporating a Water Repelling Protein

The incorporation of natural proteins as a renewable resource in the production of hybrid latexes has high interest in academia and industry, due to the opportunity to synthesize novel eco-friendly materials with special functionalities, improved properties, and biodegradable character. This article pursues the synthesis by miniemulsion polymerization of novel waterborne nanoparticles which adequately combine 3 main components: (i) a low T-g acrylic copolymer that provides controllable mechanical properties; (ii) casein, an amphiphilic protein that allows polymer particle stabilization without employing an emulsifier, which means a challenge for producing stable polymer dispersions; and (iii) zein, a water repelling protein which balances the hydrophilic character of casein. The obtained emulsifier-free hybrid latexes present high compatibility among components, resulting in new materials with improved properties. Hybrid films formed exhibit enhanced water resistance when incorporating a very low fraction of zein (5% with respect to the total protein content) and a hydrophobic surface with a contact angle similar to the pure acrylic film (82 degrees). The main characteristics of hybrid nanoparticles and relevant properties of obtained films are discussed here.