New perspectives for the application of cellulose nanofibers as building blocks in functional materials

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1 Final Meeting CST FP1205, KTH Stockholm New perspectives for the application of cellulose nanofibers as building blocks in functional materials Zheng et al., Empa 2014 Sehaqui et al., Empa, 2014 Siqueira et al., Empa, 2015 Tanja Zimmermann Head of Applied Wood Materials Lab Functional Cellulose Materials Empa Materials Science and Technology, Switzerland

2 Motivation for use of Cellulose Nanofibers (CNF) Lightweight material, builds network structures Renewable resource, biodegradable High strength and stiffness water storage capacity, rheology modifier High surface area and aspect ratio High reactivity, barrier properties Transparent gel (1.5 % w/w) Powder (Eyholzer, 2010) Translucent films (Nogi, 2009) Porous material (porosity ~ 99%)

3 Chemical functionalization of CNF Chemistry as a powerful «toolbox» to decorate nanocelluloses and expand their application fields - Controlled modification (esp. esterification, etherification, condensations) - Modification of starting material, single nanofibers, films, foams - Impact of the modification on the materials properties: thermal stability, crystallinity, dispersion in organic solvents, wettability, etc DS Time (min) Functionalized nanofibers Functionalized films Functionalized foams

4 Research interest in nanocelluloses in Europe Research interest increased within the last 10 to 15 years enormously number of SCI papers from about 50 in 2004 to far more than 1000 in 2016 Compared to US and Canada more research on fibrillated cellulose than on cellulose nanocrystals water Up-scaling activities at industrial scale especially in Scandinavia (e.g. Borregaard, Stora Enso, UPM, ) using grinding or homogenization technologies, new also in Switzerland (Wicor Weidmann) Various pre-treatments (TEMP-oxidation, enzymatical treatment, etc.) dodecane Main Applications in Coatings, films, functional (nano)papers, barrier papers Composites Packaging Purification / separation technologies Hydrogels and Aerogels. 1 cm

5 Research interests and application examples of CNF at Empa Health and performance, superabsorbents, sensors (CNF in hydrogels) Natural resources and pollutants (CNF membranes/ foams/ aerogels) water CNF-based functional materials dodecane 1 cm Nanostructured materials, Composites (nanopapers, CNF (composite) films) Energy, Sustainable Built Environment (CNF foams/ aerogels)

6 Health and performance, superabsorbents, sensors

7 NFC as high capacity carrier for proteins and peptides Schematic view of two-step reaction for the covalent immobilization of adsorbed biomolecules to oxidized-nfc. Collaboration PhD thesis Ramon Weishaupt, Empa St. Gallen (Lab of Katharina Maniura) Weishaupt et al Biomacromolecules 7

8 Biomedical sensor applications The sensing cyanobacterial biomolecule C-phycocyanin (CPC) was genetically engineered and integrated into NFC films as carrier material. CPC-CNF films as biosensors for the detection of free copper ions in human blood serum (heavy metal sensitive fluoreszent emission). Collaboration PhD thesis Ramon Weishaupt, Empa St. Gallen Weishaupt et al Adv. Func. Mat. 8

9 Nanostructured Materials, Composites Direct ink writing («3-D-Printing») Coating applications

10 Direct ink writing using Cellulose Nanocrystals Direct ink writing (DIW) technique as powerful extrusion based technique for fabrication of 3D microstructures. We optimised a CNC water-based highly concentrated ink (20 wt%) in terms of viscoelastic properties Yield stress 349 Pa, storage modulus G > loss modulus G Work of Dr. Gilberto Siqueira Rod-like shape CNC: average lengths of 120 nm ± 35 nm and diameters of 6.5 nm ± 2.2 nm. Empa Center for X-ray Analytics Complex Materials - ETH Zürich Lewis group Harvard University

11 3D Printing of Cellulose Crystals (CNC) ordered structures a b c d e Degree of orientation up to 84 % (calculated from 2 D-WAXS measurements 3D printed structures of all cellulose-based composites. a) Photograph of 3D printed filaments composed of 16 layers. b, c) AFM (b) phase and (c) height images of the 3D printed filaments surfaces. d) Drawings representing the CNC 3D printed filaments. Work of Dr. Gilberto Siqueira Siqueira et al Advanced Funct. Materials Empa Center for X-ray Analytics Complex Materials - ETH Zürich Lewis group Harvard University

12 Composites: Transparency by UV spectroscopy Chemical modification of CNC: more transparent composites. Modified material CNC composite: transmittance ~ 92% Unmodified CNC composite: transmittance ~ 80%. (inks contained HEMA monomer (hydroxyethyl methacrylate), PUA oligomer (polyether urethane acrylate), photoinitiator and 10 wt% non-modified or acetylated CNC)

13 Mechanical properties of polymer composites Matrices: Stiff and Brittle (M1) Soft and Rubbery (M2) Enhanced mechanical properties of composites. Differences between composites tested in the longitudinal and transverse directions.

14 CNF composite films for wood coating applications Use CNF to modify mechanical / physical properties of wood coatings Cracking Haildamage CNF for reinforcement 30 µm Photodegradation Fungal growth CNF as carrier material functionalization with nanoparticles and organic components UV-absorber/Zinc oxide, HALS; biocides 0.4 µm lsson et al 2011 Nature NT PhD thesis Franziska Grueneberger Grueneberger et al Cellulose Grueneberger et al J. Mater. Sci. Grueneberger et al Prog. rg. Coat. Grueneberger et al Colloid and Polymer Science

15 Vision Wood Module, Unmodified CNF can act as multifunctional wood coating additive, that is compatible to different tested acrylic and alkyd resins. CNF act as conventional thickener and rheological modifier, since the viscosity and flow behavior of the coating is strongly dependent on the NFC content. CNF can act as carrier and dispersing agent for various wood protecting compounds such as nanoparticles, UV-absorber or biocides. CNF influence the film formation and reduce undesired crack formation in brittle coating films. CNF have a great potential as novel multifunctional additive

16 Natural resources and pollutants CNF membranes, filters, foams, and aerogels for depollution

17 CNF in environmental remediation Work of Dr. Houssine Sehaqui Functions: C - : carboxylate N + :trimethyl ammonium C: carbon (pyrolysis) Contaminants: M + : Heavy metal ions NM: Natural organic matter (humic acid) NPs: Nanoparticles A - : anions (nitrate, phosphate, sulfate and fluoride)

18 CNF pyrolysis CNF can be pyrolysed leading to a carbon-rich material (char) for non-polar species absorption/adsorption. WCNF BCNF ACNF Intensity CI Intensity SEM Stefelova, J. et al. (2017) ACS Sustainable Chemistry & Engineering XRD TEM CI Intensity CI Wood, bacteria and algae CNF

19 Structure HD: heat drying SCD: super critical drying BuFD: tertbutanol freezedrying The structure of the char ressembles the structure of the CNF substrate.

20 il/solvents absorption a b a Uptake (g g -1 ) Uptake (g g -1 ) 90 Motor oil Mineral oil Silicone oil Acetone Chloroform Ethanol Toluene Dodecane (kg m -3 ) (kg m -3 ) (kg m -3 ) (kg m -3 ) Black, green, and red indicate WCNF, BCNF, and ACNF Uptake weight versus density of substrate Low density (high porosity) CNF prepared via freeze-drying gives chars with a good oil/solvent absorption capacity (up to 118 g/g). Char from bacterial cellulose gives best absorption performance optimum oleophilicity, mechanical properties and pores characteristics.

21 Dyes adsorption % Removal HD FD SCD BuFD % Removal WCNF char BCNF char ACNF char HDCNF 0 15 min 2 hours 1 day 10 days 0 15 min 120 min 400 min 1 day 3 days 10 days 1 month Methylene blue =410 mg L -1 Crystal violet Congo red f Ref AD FD BuFD SCD Ref BuFD Ref BuFD The drying method of CNF affects the adsorption properties of the chars. Best performance for high surface area chars from supercritical C 2 drying of CNF. For the same drying method, CNF with high crystallinity (from algae) gives chars with higher adsorption capacity.

22 Energy, Sustainable Built Environment NFC foams for gas capture and insulation

23 Aerogels/ Foams for gas capture Ambient air C 2 capture C 2 -free air Low grade heat, e.g. solar heat Pure C 2 release Use of C 2 for greenhouses, carbonisation of beverages, synfuels.. Gebert Rüf, ETH spin-off Climeworks LLC, ETH Zürich, Professorship of Renewable Energy Carriers PhD thesis Christoph Gebald Stability of C 2 capture capacity over 100 sorption/desorption cycles Gebald et al Patent application Gebald et al. 2011, 2013, 2014 Env. Science and Technology

24 Aerogels/ Foams for gas capture C 2 capacity (mmol/g) PEI-19 PEI-31 PEI-44 PEI-52 PEI-62 Evolution of the C 2 adsorption capacity over 5 consecutive DAC cycles for the CNF/PEI sorbents. Cycle number on top of each bar. xidized CNF and high molar mass polyethylenimine (PEI), foam via freeze-drying Porosity >97 %, specific surface area m 2 /g Professorship of Renewable Energy Carriers Sehaqui et al Env. Science and Technology.

25 Super insulating hybrid materials Utilization of silylated 3D nanocellulose scaffold to reinforce the mesoporous inorganic silica aerogel network Reinforced silica aerogel Polysiloxane layer, NFC substrate Multiscale assembly Possible to reinforce super-insulating silica aerogels with 3D organic nanocellulose scaffold Silylation promotes the adhesion between the organic scaffold and the mesoporous silica network Super-insulating hybrid materials (l 20 mw/m K) Me Si H Si Si H H Si Si Si Si H Me Me H Si Si Si H Me H NFC Si H Si Si 2 + silylated scaffold Si Si Me Compatibilization Zhao et al Adv. Funct. Mater. Collaboration with the groups of Dr. Matthias Koebel, Dr. Philippe Tingaut, Prof. G. Sèbe, Univ. Bordeaux Cellulose structure totally covered with silica

26 Energy technologies, Sust. Built Environment Thermal insulation in buildings C 2 capture for air purification NH 2 Health and performance Bio-composite hydrogels, superabsorbents, sensors Barrier properties packaging, Functional films, 3-D printing, Coatings Nanostructured materials Composite films CNF mh n C Water repellency in coatings and films il/water separation, removal of metal ions from water Natural Ressources and Pollutants

27 Acknowledgments Dr. Philippe Tingaut and all present and former co-workers of the Cellulose Nanocomposites (new Functional Cellulose Materials) group Research and Industry partners CTI (Swiss National Agency for Research and Innovation) Gebert Rüf Foundation Swiss National Science Foundation (NFP66) European Commission under the 7th Framework Programme

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