All-cellulose composites based on microfibrillated cellulose and filter paper via a NaOH-urea solvent system: supporting information Benoît Duchemin a,*, Déborah Le Corre b,1, Nolwenn Leray b, Alain Dufresne c, Mark Staiger b a LOMC, UMR 6294 CNRS-Université du Havre, Normandie Université, 53 rue Prony, 76058 Le Havre, France b MacDiarmid Institute for Advanced Materials and Nanotechnology, Department of Mechanical Engineering, University of Canterbury, Private Bag 4800, Christchurch 8140, New Zealand c Laboratoire Génie des procédés papetiers, Institut National Polytechnique de Grenoble (EFPG-INPG) BP65, 38402 Saint-Martin d’Hères Cedex, France 1 Present address: Plant and food research, Canterbury Agriculture & Science Centre, Gerald St, Lincoln, 7608, New Zealand * Corresponding author. Tel : +33235217154 ; fax : +33235217198 Email address: benoit.duchemin@univ-lehavre.fr (B. Duchemin). XRD The samples were analysed in the transmission mode using a “gonio scan” (-) on a Pan’alytical X’pert powder diffractometer equipped with a CoK source at 40 kV and 40 mA with λ = 1.7902 Å. Programmable anti-scatter slits had a fixed aperture of ½° whereas the anti-diffusion slits had a fixed aperture of 1°. The detector was a linear Pix’cel 1D detector. The scan was performed in the 5-50° range in steps of 0.013° (118 s/step). The samples (1 layer) were stacked between two kapton foils. A kapton background was measured and substracted from all the curves. The curves were then area normalized. All curves were rescaled at the copper wavelength (λ = 1.5418 Å) according to Bragg’s law. FP 20 min 40 min 80 min 3h 12h 10 15 20 25 2. (°) 30 35 40 Figure S1. Diffractograms of filter paper before (top) and after various dissolution times (below). MFC 20 min 40 min 80 min 3h 12h 10 15 20 25 30 35 40 2. (°) Figure S2. Diffractograms of microfibrillated cellulose before (top) and after various dissolution times (below). A method using a successive simulation of powder diffractograms and the measurement of their relative amorphous/cellulose I/cellulose II amount in the signal thanks to a least square procedure was used (Nam et al. 2016). This method has the advantage of taking into account the signal of the severely overlapped peaks of weaker intensities. This part of the signal is often erroneously included as part of the amorphous content when simple peak fitting procedures are used. As a consequence, the crystallinity measured using this method is closer to the true crystallinity of the specimens, as measured using other more complex methods such as the Rietveld method. In comparison to the Rietveld method, this method has the benefit of being relatively operator-insensitive. The small number of parameters adjusted during the least-square fitting also means that the method is fast, simple and can be applied to poorly crystalline samples which contain a mixture of cellulose I and cellulose II. 10 20 30 40 50 10 20 30 40 50 10 20 30 40 50 10 20 30 40 50 10 20 30 40 50 10 20 30 40 50 Figure S3. Simulated diffractograms of ACC using modeled powder diffractograms and a semi-empirical background. FP (left) and MFC (right) after 0 (top; only cellulose I), 20 min (middle; mixture of cellulose I and II) and 40 min (bottom; only cellulose II) long dissolutions. It was also possible to simulate diffractograms of cellulose I using the assumptions of various FWHM for a range of crystallite sizes ranging from extremely thick crystallites to thin crystallites with only two chains stacked together in the direction perpendicular to the (200) plane. This simulation demonstrated that the maximum of the measured diffractograms was shifted to lower values solely on the effect of peak broadening and independently of the lattice parameters. The crystallite width was calculated using Scherrer equation assuming a peak centered at the diffractograms maximum, an artifact that will be dealt with in detail in a subsequent publication. 90 80 23 70 22.9 60 22.8 50 22.7 40 30 22.6 20 22.5 Crystallite width d (Å) Diffractogram maximum (°) 23.1 10 22.4 0 0 2 4 6 8 10 12 FWHM (°) Figure S4. Variation of the diffractograms maximum (blue)) and measured crystallite width (red) as a function of the FWHM parameter as set in Mercury. ATR-FTIR All measurements were performed on a Perkin-Elmer “Frontier” spectrometer equipped with an Attenuated Total Reflectance accessory. The scans were accumulated from eight passes with a resolution of 2 cm-1 in the 4000-650 cm-1 range. Each spectrum is the average of three measurements at three different locations. Calculations of the total crystallinity index (TCI) was performed from the ratio of the absorption peaks 1372/2900 cm-1 (Nelson 1964; Carillo 2004). These two peaks were chosen because of their low susceptibility to water (C-H bending at 1372 cm-1, and C-H or CH2 stretching at 2900 cm-1). Contrary to Segal’s method in XRD, this method is applicable for both cellulose I and II. The strongest band of the three bands at 2900 cm-1 was chosen. Figure S5. Transmittance data of filter paper (a) and microfibrillated cellulose (b) as obtained after dissolution times of 3 h (top) and 12 h (bottom). Table S1. TCI of the cellulose substrates after various dissolution times. Dissolution 0 80 min 3h 12 h FP 0,95 0,79 0,49 0,53 MFC 0,66 / 0,73 0,73 time Mechanical testing The toughness of the composites was also assessed by measuring the area under the stressstrain curve from the start of the tensile test until the specimens were fractured. These values are comparable to those of common synthetic materials used for packaging. FP 3 MFC Toughness (MJ.m-3) 2.5 2 1.5 1 0.5 0 0 20 40 80 Dissolution time (min) Figure S6. Toughness of the composites after various dissolution times.