Molecular aggregation structure and water repellency of Poly(perfluorohexyl acrylate) with a carbamate linkage

Liquid repellency of comb-shaped polyacrylates with perfluoroalkyl side-chains associates with the ordered structure of the side-chains at the surface. The molecular aggregation structure and surface properties of poly{2-[(perfluorohexylethyl)carbamate]ethyl}acrylate (PFAUr-C₆) were studied using differential scanning calorimetry (DSC), polarized optical microscopy (POM), powder wide-angle X-ray diffraction (WAXD), grazing incidence wide-angle X-ray diffraction (GI-WAXD), temperature-controlled Fourier transform infrared spectroscopy (FTIR), contact angle measurements, and X-ray photoelectron spectroscopy (XPS). Poly[2-(perfluorohexyl)ethyl]acrylate (PFA-C₆) was compared with PFAUr-C₆ to verify the effect of carbamate linkage on the aggregation structure and surface properties. The perfluorohexyl groups in PFAUr-C₆ produced a double-layered smectic structure, whereas the perfluorohexyl groups in PFA-C₆ showed no ordered structure. The double-layered smectic structure in PFAUr-C₆ was induced by the hydrogen bonding interaction in the carbamate linkers. PFAUr-C₆ showed poor water repellency similar to PFA-C₆ because of the rapid surface rearrangement. Although the perfluorohexyl groups produced smectic order structure at the film surface, the lack of positional order in the smectic layers and the low ordered structure content allowed the surface rearrangement.