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.