Supporting Information for:

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1 Supporting Information for: Cellulose Nanofiber/Nanocrystal Reinforced Capsules: A Fast and Facile Approach Toward Assembly of Liquid-Core Capsules with High Mechanical Stability. Anna J. Svagan, 1,2* Anna Musyanovych, 1 Michael Kappl, 1 Max Bernhardt, 1 Gunnar Glasser, 1 Christian Wohnhaas, 1 Lars A. Berglund, 3 Jens Risbo 2 and Katharina Landfester 1 1 Max Planck Institute for Polymer Research, Ackermannweg 10, Mainz (Germany). 2 University of Copenhagen, Dept. of Food Science, Rolighedvej 30, 1958 Fredriksberg C (Denmark) 3KTH Royal Institute of Technology, Wallenberg Wood Science Center, SE Stockholm (Sweden) Figure S1. The effect on ultra-sonication on a 0.5 wt% NFC/CNC suspension. In (BEFORE) the suspension is shown prior to ultra-sonication. In (AFTER) the suspension has been subjected to 2x120 s of ultra-sonication at 80% amplitude and under ice cooling (Branson Sonifier W-450-Digital with ½ tip). 1

2 Figure S2. (a) AFM image and (b) TEM image of nanofibrillated cellulose and cellulose nanocrystals used in capsules synthesis. The sides of the image in (a) are 5.0 µm. The scale bar in (b) is 500 nm. Figure S2 shows an AFM (a) and TEM (b) image of the blend of cellulose nanofibers and nanocrystals obtained when using the processing route described in the experimental section. The nanocrystals have a length of around 140 nm or less. Figure S3. The size of capsules obtained when doubling the amount of NFC from 0.5 wt% (a) to 1 wt% (b) in the aqueous phase during capsule synthesis. The capsule compositions are S7 in (a) and S7b (b). Figure S3 shows NFC based capsules that have been synthesized with different amounts of NFC in the aqueous phase. By increasing the solid content in the aqueous phase from 0.5 (a) to 1 wt% (b), the average diameter of the capsules decreased. 2

3 Figure S4. FT-IR Spectra of neat NFC (I), NFC grafted with IPDI(II), and capsules (III, formulation S2). In Figure S4, a close-up of the FTIR spectra presented in the manuscript (Figure 3) is given. It shows the results for a neat NFC sample (I) and NFC after chemical grafting with excess IPDI (II). The last result (III) is for capsule formulation S2 given in Table 1 of the manuscript. 3

4 Figure S5. (a) The distribution of the thickness values obtained by TEM for NFC based capsules (S9). Insert: TEM images of a cross-section of a NFC based capsule. (b) The distribution of the measured thickness values for PU capsules. The insert is a TEM image of a cross-section of a PU capsule. (b) Histogram showing distribution of the Young s modulus values obtained for PU and NFC-reinforced (S9) capsules. 4

5 Mechanical modelling Elastic modulus for a nanocomposite film A simple empirical expression 1 was employed to calculate the elastic modulus,, in the case of a shortfiber nanocomposite film. In this case, the NFC/CNC are oriented random in the plane and evenly distributed throughout the thickness of the matrix material: (1) Where E and E are derived from:, 1 (2),, (3) If the weight fraction of nanofibers is 17 wt%, then this corresponds to a volume fraction,, of vol% ( / 1.5 and 1.25 ). With, = 100 GPa,, = 15 GPa (Diddens et al.) 2 and = 0.8 GPa, gives = 6.31 GPa With, = 60 GPa,, = 15 GPa and = 0.8 GPa, gives = 4.1 GPa. References (1) Agarwal, B.D.; LJ Broutman, L.J. Analysis and Performance of Fiber Composites, 1980, John Wiley & Sons, New York. (2) Diddens, I.; Murphy, B.; Krisch, M.; Muller, M. Macromolecules 2008, 41,