One-Pot Fabrication of Hydrophobic Cellulose-Based Foams via Organocatalytic Modification in Aqueous Media

Abstract

Biobased lightweight foams are increasingly investigated as sustainable alternatives to fossil-derived materials; however, many existing approaches rely on organic solvents, multistep processing, or post-functionalization to impart hydrophobicity and water resistance. Here, we introduce a one-pot foam-forming strategy in which foam assembly and hydrophobization occur in a single aqueous processing step using a preformed organocatalytic aqueous formulation (OAF). This strategy simplifies processing, eliminates a separate post-functionalization step, and improves material efficiency compared with conventional routes. The OAF, which contains polysiloxane particles (PSiP), is combined directly with bleached chemithermomechanical pulp (BCTMP), chitosan, and a bioderived surfactant to generate stable wet foams. The resulting foams, referred to as OAF20-foam and OAF3-foam, exhibit formulation-dependent hydrophobic behavior. OAF20-foam displays uniformly high apparent water contact angles (>150°) on the top, bottom, and cross-sectional surfaces, whereas OAF3-foam is non-hydrophobic on the top surface but highly hydrophobic on the cross-sectional and bottom surfaces. Mechanical performance also improves markedly, with the elastic modulus increasing from approximately 2 kPa for the reference foam to 27 kPa for OAF3-foam. SEM-EDS mapping confirms a homogeneous distribution of PSiP and chitosan on the fiber surfaces of OAF20-foam. The lightweight foams exhibit high dimensional stability and shape retention under wet conditions, enable efficient oil-water separation, and recover their surface hydrophobicity after wetting and subsequent drying. This organic solvent-free, scalable process provides a practical route to advanced, renewable, and environmentally responsible lightweight materials.