Reaction efficiency and retention of poly(styrene-co-maleimide) nanoparticles deposited on fibrillated cellulose surfaces

• Surface modification of micro- and nanofibrillated (MFC/NFC) cellulose by polymer nanoparticle deposits.
• Nanoparticle formation by imidization reaction.
• Nanoparticle deposition dependency on fiber fibrillation, geometrical constraints and wax.
• Modified cellulose surface demonstrates dramatic increases in hydrophobicity.
• Potential future use as paper coatings or additive in biopolymer composites.

Surface modification of micro- and nanofibrillated cellulose (MFC and NFC) under aqueous environment was performed by deposition of poly(styrene-co-maleimide) nanoparticles synthesized by imidization of poly(styrene-co-maleic anhydride) in presence of wax and ammonium hydroxide in variable amounts. Specifically, the influences of fiber fibrillation on nanoparticle formation (i.e., reaction efficiency) and permanent nanoparticle deposition on the fiber surface (i.e., retention) were investigated. The surface modification was mainly governed by the fiber diameter, surface charges and amount of wax. As such, the MFC affected the imidization reaction to a smaller extent (i.e., high reaction efficiency) and was more densely deposited by nanoparticles than NFC (i.e., high retention). Moreover, wax protected the fibers against fibrillation and peeling-off at high temperature and favored nanoparticle deposition. As a result, water contact angles of 142° were obtained for modified MFC in parallel with a surface coverage of 92%.

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