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    Investigation of the formation, structure and release characteristics of self-assembled composite films of cellulose nanofibrils and temperature responsive microgels

    Year: 2011

    Journal: Soft Matter, 2011, 7, 1369-1377, 20120104

    Authors: Acciaro R 1, Aulin C 2 3 4, Wågberg L 3, Lindström T 4, Claesson PM 5 6, Varga I * 1 5

    Last authors: Imre Varga

    Organizations: 1 Institute of Chemistry, Eötvös University, 1117 Budapest, Pázmány s. 1/A, Hungary. E-mail: imo@chem.elte.hu 2 BIM Kemi AB, Box 3102, SE-443 03, Stenkullen, Sweden 3 Department of Fibre and Polymer Technology, School of Chemical Science and Engineering, Royal Institute of Technology, SE-100 44, Stockholm, Sweden 4 Innventia AB, Box 5604, SE-114 86, Stockholm, Sweden 5 Department of Chemistry, Surface and Corrosion Science, Royal Institute of Technology, Drottning Kristinas väg 51, SE-100 44, Stockholm, Sweden 6 YKI, Institute for Surface Chemistry, P.O. Box 5607, SE-114 86, Stockholm, Sweden

    Country: Sverige, Sweden, Hungary

    The possibility of forming self-organized films using charge-stabilized dispersions of cellulose I nanofibrils and microgel beads of poly-(N-isopropylacrylamide-co-acrylic acid) copolymer is presented. The build-up behavior and the properties of the layer-by-layer (LbL)-constructed films were studied using quartz crystal microbalance with dissipation (QCM-D) and ellipsometry. The morphology of the formed films was also characterized using atomic force microscopy (AFM) imaging. The applied methods clearly demonstrated the successful LbL-assembly of the monodisperse microgels and nanofibrils. The in situ QCM-D measurements also revealed that contrary to the polyelectrolyte bound microgel particles, the nanofibrils-bound gel beads preserve their highly swollen state and do not suffer a partial collapse due to the lack of interdigitation of the oppositely charged components. To probe the accessibility of the gel beads in the formed films, the room temperature ( 25 °C) loading and release of a fluorescent dye (FITC) was also investigated. The incorporation of the cellulose nanofibrils into the multilayer resulted in an open structure that was found easily penetrable for the dye molecules even at constant room temperature, which is in sharp contrast with previously reported systems based on synthetic polyelectrolytes. The amount of dye released from the multilayer films could be fine-tuned with the number of bilayers. Finally, the thermoresponsivity of the films was also shown by triggering the burst release of the loaded dye when the film was collapsed.