PhD defense Siyu Li
DATE CHANGE: 8 March 2023
Time: 13.30 h
Place: TU Eindhoven
Summary: Coatings protect and decorate innumerous surfaces, such as buildings, furniture, and automobiles. They are composed of several ingredients, including polymer binders, pigments, solvents, and additives, that work together to form a solid layer on a surface. Based on solvent composition, coatings can be classified in two categories: solvent-borne and water-borne. Solvent-borne use organic solvents, which have high environmental and health impacts due to the emission of volatile organic compounds (VOC). Water-borne systems use water as dispersing medium, and currently attract much interest due to their low VOC emissions, lower health impact and thus also better compliance with regulations.
However, some challenges are still associated with water-borne coatings, such as poor solvent resistance and insufficient mechanical properties. These challenges can be addressed with colloidal particles of inorganic/organic hybrid nature. By precisely controlling the morphology of these colloids, the final film can be engineered to have the desired coatings properties.
We have designed hybrid supracolloidal particles with a strawberry-like morphology, of a spherical polymer core partially covered by a corona of silica nanoparticles. The optimal conditions to assemble these strawberry-like supracolloidal particles in aqueous medium were found both in diluted, and concentrated dispersions which can be directly used for paint formulations. For coatings prepared from chemically bonded supracolloidal particles, a continuous honey-comb-shaped silica skeleton was formed throughout the coating. This nanostructured network largely improves the mechanical properties and water resistance of water-borne films. They also provide intriguing properties such as structural color, green/blue reflection upon water immersion and self-recoverability from damages, scratches.
This study provides insights on how the fine-tuning of the different colloids and aqueous dispersions parameters can be used to control the stability of supracolloids on aqueous dispersions, the water-borne film formation process, and the final properties of water-borne coatings. The strawberry supracolloids developed are of interest for research in the colloids and interface chemistry fields and can be applied in a large range of applications, such as in coatings, sensors and optical devices.
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