Hydrophilic to hydrophobic: Ultrafast conversion of cellulose nanofibrils by cold plasma fluorination

Abstract

The cellulose-based products are gaining increased interest, especially as a top-choice material for replacing plastics in packaging-related fields. Nevertheless, the high inherent wettability often hinders its advancement in becoming an efficient substitute in packaging industry. To bridge this challenge,the fluorocarbon plasma processing was implemented for improvement of cellulose surface hydrophobicity. This was done on the example of nanofibrils films exposed to CF4 plasma, in order to achieve hydrophilic to hydrophobic conversion in less than 10s. The saturation of water contact angle (approximately 130± 5°) was obtained after only 30s of plasma processing. The surface fluorination was the result of the presence of newly formed C–F3, C–F2 and C–F bonds confirmed by high-resolution C 1s XPS spectra. A prolonged continuous plasma functionalization resulted in structural vibrational alterations associated mostly with intense IR and Raman active stretching C–F2 mode. Simultaneously, ATR-FTIR revealed a formation of the surface-linked IR active H–F functional group. Our findings successfully demonstrate that the CF4 plasma processing can be an effective way for ultrafast cellulose conversion from hydrophilic to hydrophobic surface.