A Novel Approach Endowing Nanocalcium Carbonate with Amphiphobic Properties Through Perfluoropolyether Carboxylic Acid Surface Modification: Elucidating the Surface Modification Mechanism

Acquiring an amphiphobic nanocalcium carbonate (NCC) is a perplexing problem in the long term because of its hydrophility. This restricts its application in self-cleaning coatings and other super-low surface energy engineering fields. This study offers a novel and simple approach that endows NCC with an amphiphobic property through surface modification using perfluoropolyether carboxylic acid in the presence of sodium hydroxide. The modification process was optimized at a 5 wt% modifier concentration, 50 °C, and a duration of 40 min. Comprehensive characterization was performed using FT-IR, TG-DTA, SEM, HR-TEM, NMR and XPS techniques, in contrast with the previous literature describing hydroxyl groups. Notably, FT-IR analysis indicates that no hydroxyl groups were detected on the NCC surface. The modification mechanism involves COO− groups from the modifier forming Ca-O ionic bonds with calcium sites on the NCC surface. HR-TEM analysis revealed an exceptionally thin modifier film (2–5 nm) on the NCC surface. Despite this minimal thickness, it endows NCC with remarkable amphiphobic properties, with water and oil contact angles up to 120.4° and 139.9°, respectively. These findings expand insights into the surface modification mechanism of NCC and its potential application fields.