Enhancement of Hydrophobic Properties of Cellulose Fibers via Grafting with Polymeric Epoxidized Soybean Oil

We report on an efficient method for the formation of modified cellulose-based materials with enhanced hydrophobic properties, formed by grafting with polymeric epoxidized soybean oil (ESO) as a renewable, environmentally friendly, and low cost raw material. The grafting process occurred via ring-opening polymerization, wherein the cellulose hydroxyl groups acted as initiators in the presence of a SnCl4 catalyst, linking the cellulose fibers and ESO via ether linkages, thereby forming a polymeric matrix. The surface polarity was therefore decreased by the substitution of cellulose hydroxyl groups for long-chain hydrophobic alkane moieties from ESO. The water contact angle of modified filter paper reached 145.1° with the surface free energy decreasing to 22.07 mJ m–2 and a hydration free energy of −13.09 mJ m–2. The presence of polymeric ESO nanoparticles on the modified cellulose fibers suggested that the hydrophobicity was not only dependent on the surface composition but was also closely related to the surface morphology. To reveal the effects of surface morphology on hydrophobicity, smooth cellulose films anchored to mica plates via PVAm with a surface roughness of 1.698 nm were prepared by spin coating and modified with ESO. The thus-formed modified cellulose films also contained polymeric ESO nanoparticles which increased their roughness and enhanced their hydrophobic properties.