The pulp and paper industry has modified cellulose by polyelectrolyte adsorption for centuries, in order to improve properties such as wet-strength and de-watering. This approach is especially advantageous for the modification of nanocelluloses, such as cellulose nanofibrils (CNF), as these are produced in dilute water suspension and can easily be anionically charged through TEMPO-oxidation. By utilizing controlled polymerization techniques, more advanced polyelectrolytes can be obtained, allowing the possibility to fine-tune the properties of the surfaces of cellulose fibers and fibrils.1 Herein, cationic polymer latexes have been prepared and physically adsorbed to cellulose model surfaces and cellulose nanofibrils (NFC). Charged polymer nanoparticles composed of amphiphilic block copolymers based on poly(dimethylaminoethyl methacrylate) (PDMAEMA) and a hydrophobic block composed either of a high Tg polymer, poly(methyl methacrylate) (PMMA), or a low Tg polymer, poly(butyl acrylate) (PMA), were synthesized by RAFT-mediated2 surfactant-free emulsion polymerization. During the synthesis, the amphiphilic block copolymers self-assembled into spherical cationic latex nanoparticles by polymerization-induced self-assembly (PISA).3 The lenght of the hydrophilic block. i.e. the macro-RAFT, was kept constant and latexes with varying lenght of the hydrophobic block were prepared. These cationic latexes were subsequently physically adsorbed onto cellulose model surfaces and CNF. From adsorption measurements in the QCM-D, it was shown that large amounts of latex-particles were adsorbed to the cellulose model surfaces, something which was also confirmed by AFM measurements. The surfaces were fairly hydrophobic after the adsorption and upon heat treatment of the surfaces, which collapsed the latex particles and exposed the hydrophobic core, the hydrophobicity increased. Furthermore, the latex particles were adsorbed onto NFC in solution and the modified NFC were incorporated into a PCL matrix. Results showed that the adsorption of latex particle-modified NFC improved the mechanical properties of the composites. 1A. Carlmark, Macromol. Chem. Phys., 2013, 214(14), 1539-1544 2C. Barner-Kowollik, Handbook of RAFT-polymerization. 2008, Wiley-VCH 3B. Charleux, G. Delaittre, J. Rieger, and F. D'Agosto, Macromolecules, 2012, 45, 6753-6765

Cellulose surfaces modified by latex particles prepared via RAFT-mediated emulsion polymerization

249th National Meeting (2015)

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