Controlled surface modification and medium-guided assembly of bacterial cellulose-based nanofibrils for the...

In this study, localized hydrophobization of bacterial cellulose-based nanofibrils (BCNFs) at the oil/water interface was investigated to obtain efficient surface esterification, medium-guided assembly, and tunable water repellency in BCNF-based films. Amphiphilic BCNFs were fabricated via in situ lauroylation within a Pickering emulsion system. BCNFs prepared by aqueous counter collision effectively stabilized toluene droplets and achieved a maximum degree of surface substitution of 0.7, which was higher than that obtained in a homogeneous dispersion system. Films cast from water dispersions of lauroylated BCNFs exhibited higher water contact angles (up to 81.1°) than unmodified BCNFs and showed minimal substrate dependence. Furthermore, lauroylated BCNF films cast from n-hexane dispersions exhibited enhanced water repellency (contact angle: 116°) compared with films cast from water dispersions. This difference was attributed to medium-dependent self-assembly and the resulting surface roughness. These findings highlight the strong influence of the dispersion medium polarity on lauroylated BCNF assembly behavior and film wettability and illustrate a sustainable approach for designing bio-inspired water-repellent thin films without fluorinated coatings.