Inverse Gas Chromatography Characterization of Cellulose Nanofibers: Impact of Chemical Composition on Surface Properties

ABSTRACT Inverse gas chromatography (IGC) was employed to investigate how the presence of hemicellulose influences surface properties and adsorption behavior of cellulose nanofibers. Two samples prepared under equivalent processing conditions were compared: cellulose rich nanofibers (CNFs) and nanofibers containing approximately 20 wt% hemicellulose (CNFp). Adsorption measurements were performed at infinite dilution using nonpolar and polar molecular probes at 40°C, 50°C, and 60°C. Dispersive and specific adsorption interactions were evaluated using the Hamieh approach, whereas the conventional Schultz method was applied as a complementary analysis. Although London dispersive interactions dominated the total adsorption free energy of all polar probes, the specific contribution revealed a temperature dependent contrast between the materials: CNFp exhibited higher magnitudes of specific adsorption free energy than CNFs for four of the seven polar probes at 40°C and for all seven at 50°C and 60°C, despite its less exothermic specific adsorption enthalpies. Both surfaces exhibited amphoteric behavior, with a greater affinity for the Lewis basic THF probe. The sensitivity analysis indicated that the absolute dispersive surface energy estimates were more dependent on the adopted molecular descriptors than the calculated specific adsorption free energies. Together with FTIR, zeta potential, and water contact angle measurements, the IGC results support the proposed hypothesis that the presence of hemicellulose modifies the surface adsorption environment of cellulose nanofibers, favoring the persistence of specific polar interactions, including possible contributions from hydrogen bonds, at elevated temperatures. These findings highlight the potential of tailoring nanofiber composition to control interfacial interactions in materials containing cellulose.