Cellulose Chemistry Course

Transcription

1 Cellulose Chemistry Course Nanofibrillated Cellulose Tekla Tammelin VTT Technical Research Centre of Finland Docent in Bioproduct Technology at Aalto University Aalto University, June 20-24, Content of the lecture I II III IV V VI Plant based nanomaterials Cellulose nanofibrils Films from cellulose nanofibrils (CNF) Barrier performance of CNF films CNF films as membrane materials Nanoscaled interfaces with CNF Conclusions 1

2 27/06/ Plant based nanomaterial - Nanofibrillated cellulose Wood fibres SEM and AFM images of nanofibrillated cellulose 27/06/ Masuko Super Masscolloider Nanofibrillated cellulose Natural cellulosic fiber Microfluidics Fluidizer Processor M- 700 M. Pääkkö, M. Ankerfors, H. Kosonen, A. Nykänen, S. Ahola, M. Österberg, J. Ruokolainen, J. Laine, P. T. Larsson, O. Ikkala and T. Lindström, Enzymatic hydrolysis combined with mechanical shearing and high-pressure homogenization for nanoscale cellulose fibril and strong gels, Biomacromolecules 8 (6) (2007), Nano- Microfibrillated cellulose 2

3 27/06/ CNF structure-function relationships Bacterial cellulose Size/Dimensions/Branching Chain or rodlike structure All dimensions in nanoscale Nanocrystals Nanofibres 6 5 Nanofibrillated Scale bar: 20 μm Microfibrillated Ribbon-like structure Overall dimensions in macroscale, fine structure in nanoscale 4 Image area 1x1 μm Image area 2x2 μm Branched structure Overall dimensions in macroscale, fine structure in nanoscale 0 Charge/Chemistry Image area 2x2 μm Image area 2x2 μm Colloidal dispersion Polyelectrolyte-like Woodfibre like Decreasing surface charge 27/06/ Understanding the nature of CNF surface by XPS How to maximize the available surface for derivatizations Determination of different carbon bonds Relative abundance of C-C bonds Johansson, L.-S., Tammelin, T., Campbell, J. M., Setälä, H., Österberg, M.Soft Matter 2011, 7, CNF surface is extremely reactive!! Free accessible OH groups generate high surface free energy Minimizing the surface free energy when exposed to hydrophobic media by accumulating air-borne contaminants passivated surfaces 3

4 27/06/ Nanofibrillar structure retained in cellulose compatible solvent Nanocellulose reactivity XPS indicates Increase in silica content Increase in the relative abundance of C-C and C- Si bonds Degree of surface substitution can be calculated AFM results confirm the successful surface modification the maintained nanofibrillar structure The same derivatisation procedure: DMA-exchanged CNF DS=1.0 ± 0.2 Toluene-exchanged CNF DS = 0.02 ± 0.01 Surface chemistry of fibers and CNF: Relative abundance of C-C bonds indicates that CNF surface is extremely reactive and is easily passivated in hydrophobic media. In CNF compatible solvent the reaction efficiency is higher and the nanoscale structure is retained 27/06/ From properties to applications CNF Properties Abundant, natural nanomaterials Renewable, biodegradable & biocompatible Film formation High strength & modulus High thermal stability Lightweight Optical transparency High water binding capability High aspect ratios & high surface area Hydrophilic Opportunities for chemical modification (surface OH) CNF Potential applications Composites Electronics Sensors Construction Paper & Pulp Filtration Coatings & surfaces Health care Rheology modifiers Aerogels Etc D. Klemm, F. Kramer, s. Moritz, T. Lindström, M. Ankerfors, D. Gray and A. Dorris, Nanocelluloses: a new family of nature-based materials, Angew. Chem. Int. Ed. 50 (24) (2011), A. Dufresne, Nanocellulose From Nature to High Performance Tailored Materials (Walter De Gruyter, Berlin/Boston, I. Siró and D. Plackett, Microfibrillated cellulose and new nanocomposite materials: A review, Cellulose 17 (3) (2010),

5 27/06/ Films from cellulose nanofibrils (CNF) 27/06/ Preparation of CNF films Traditional method Pressurized filtering Several hours of dewatering time Filter and membrane marking Thick films ( µm) Cast coating of CNF CNF coated evenly on plastic film Controlled spreading (layer thickness) adhesion and relatively fast drying No shrinkage (adhered to plastic while dried) > Smooth base surface is replicated to CNF film Thin films (5-30 µm) Drying time 5

6 27/06/ Mechanical performance of CNF film Stress-strain behaviour typical for brittle plastic-like material High variation in published data: tensile strength MPa, modulus of elasticity 5-10 GPa, strain at break <10% Henriksson et al., Biomacromolecules, 2008, 9, /06/ Semi-pilot scale preparation of CNF films Surface treatment concept (SutCo) SUBSTRATE PRE- TREATMENT COATING of CNF on SUBSTRATE DETACHING from SUBSTRATE PRESSING of CNF FILM (PRE- TREATMENT of CNF) CONTROLLED DRYING 6

7 27/06/ Surface roughness of the CNF film Average roughness (nm) Plastic substrate NFC bottom side NFC top side Surface roughness dependent on the fibril size distribution and on the preparation method Smooth texture of the plastic surface can be replicated on the nanocellulose film (solvent cast NFC on substrates by R2R-method) G. Chinga-Carrasco, D. Tobjörk and R. Österbacka, J. Nanopart. Res. 14 (10) (2012), ; Tammelin, Tekla, Hippi, Ulla, Salminen Arto. Method for the preparation of NFC films on supports. PCT Int. Appl. (2013), WO A ; M.S. Peresin, J. Vartiainen, V. Kunnari, T. Kaljunen, T. Tammelin and P. Qvintus, in the 4th International Conference on Pulping, Papermaking and Biotechnology (ICPPB'12) (Nanjing, China, 2012), pp /06/ Clean and reactive CNF film surfaces UV/O 3 treatment XPS indicates Decrease in the relative abundance of C-C after UV/O 3 treatment (11% -> 4%) Removal of non-cellulosic carbonaeous contamination layer Contact angle results show Increased hydrophilicity Expected to facilitate more efficient CNF film surface functionalization Österberg, M., Peresin, M. S., Johansson, L.-S. and Tammelin, T., Clean and reactive nanostructured cellulose surface. Cellulose, 2013,20,

8 27/06/ The effect of UV/O 3 treatment on CNF film surface activation Direct chemical modification via surface silylation XPS indicates Clear increase in silica content Increase in the relative abundance of C-C and C-Si bonds Degree of surface substitution can be calculated C-C C-C + C-Si C-C + C-Si The same derivatisation procedure: unactivated CNF film: DSs = 0.07 UV/O 3 activated CNF film: DSs = 0.26 UV/O 3 activated + silylated unactivated + silylated unactivated CNF film 27/06/ Barrier performance of CNF films Routes to control the water sensitivity 8

9 27/06/ Nanocellulose films as packaging materials Oxygen barrier films Hydrophilic natural polymers: good barriers against nonpolar substances such as oxygen and grease in dry conditions High amount of hydrogen bonds in structure and good film formation ability Water strongly interacts with the bonds that holds chains together (swelling): the loss of barrier at high humidity conditions Hydrophilic polymeric films are extremely poor water vapor barriers. Inert, inorganic, plate-like materials with high aspect ratio retards permeation Close packing and/or high crystallinity results in better barrier. Orientation results in better barrier by creating a more tortuous diffusion path. 27/06/ CNF films with improved barrier performance with surface functionalisation Nanocellulosic materials have an inherent tendency to form films upon drying Good oxygen barrier materials especially in dry conditions Sensitive towards moisture and water Reference RH80% PP: 93 ml mm m -2 day -1 PET: 1.5 ml mm m -2 day -1 M.S. Peresin, J. Vartiainen, V. Kunnari, T. Kaljunen, T. Tammelin and P. Qvintus, in the 4th International Conference on Pulping, Papermaking and Biotechnology (ICPPB'12) (Nanjing, China, 2012), pp

10 27/06/ CNF inorganic hybrid films: ALD deposited Al 2 O 3 on CNF film Method is based on self-terminating gas-solid reactions and surface controlled layer-by-layer process. T. Hirvikorpi, M. Vähä-Nissi, J. Nikkola, A. Harlin and M. Karppinen, Surf. Coat. Technol.2012, 205, /06/ CNF films as membrane materials 10

11 Membranes from cellulose nanofibrils Membranes Selective semi-permeable barriers Biological systems and industrial processes, eg. water purification Cellulose nanofibrils (CNF) Intriguing characteristics for membrane materials, eg. large surface area, high hydrophilicity, film forming tendency Nanoenhanced membrane materials 27/06/ /06/ Nanocellulose films as templates for functional membranes CNF film with enhanced water stability Strategies to surface functionalize CNF film stimuli-responsive polymers LCST = low critical solution temperature PNIPAM undergoing a reversible transition from hydrophilic to more hydrophobic state at its LCST around 32 C on film surface. 11

12 27/06/ HEMIACETAL FORMATION ESTER FORMATION CNF film water stability achieved by bridging TEMPO CNF + PVA Water stability is assumed to be result of two mechanisms Hemiacetal formation (aldehyde and hydroxyl) Ester bond formation (carboxyl and hydroxyl) From a chemical point of view reactions should occur between TCNF fibrils Low number of fibril-fibril contact points Primary hydroxyls have already reacted in TEMPO oxidation H + Cellulose fibrils 27/06/ Crosslinking to improve wet strength 10% PVA high DH 10% PVA low DH 25% PVA high DH Crosslinking with PVA significantly improved the wet strength of films 25% PVA low DH HEMIACETAL FORMATION Wet strength of the films measured by tensile testing after soaking in water for 24 hours. ESTER FORMATION Hakalahti, M., Salminen, A., Seppälä, J., Tammelin, T., Hänninen, T. (2015) Carbohydrate Polymers, 126,

13 27/06/ Attachment of polymeric group on CNF film surface Direct chemical modification: pnipam on TEMPO CNF Element (at%) Sample C 1s O 1s N 1s S 2p TCNF-PVA TCNF-PVA esterified TCNF-PVA pnipam XPS indicates successful pnipam attachment on CNF film surface Nanoscaled surface structure retained 27/06/ Thermoresponsive membrane template Water permeability as a function of temperature Hakalahti, M.; Mautner, A.; Johansson, L.-S.; Hänninen, T.; Setälä, H.; Kontturi, E.; Bismarck, A.; Tammelin, T.; (2016) ACS Applied Materials & Interfaces, 8,

14 27/06/ Nanoscaled interfaces with CNF Electronics 27/06/ Smooth and dense CNF films as printing substrates Thin, inexpensive, flexible and biodegradable material as a substrate for e.g. printable conductive structures and organic transistors CNF film applications Flexible and OLED displays Flexible circuits and printable electronics Flexible solar panels Smart packaging Bio-applications Paper is not a viable option due to its porous structure and plastics are not biodegradable Smooth and dense film surface Silver nanoparticle ink can be used to print conductive structures on the surface Conductive structures sintered at 150ºC for 1 hour Thinnest conductive line 4 pixels, 1270dpi, 5µl droplets G. Chinga-Carrasco, D. Tobjörk and R. Österbacka, J. Nanopart. Res. 14 (10) (2012), Tobjörk, D.; Österbacka, R. Adv. Mater. 2011, 23,

15 Superlattice thin films of inorganic oxides and nanocellulosic materials Superlattice thin-film structures of alternating thermoelectric oxide layers & thin organic layers in a scale of 1 ~ 10 nm to block phonons without affecting electrons Cellulose layer: Inorganic oxide layer: Superlattice structure: Low thermal conductivity, high thermal stability, low density, flexibility High electrical conductivity High amount of interfaces reduce phonon transport and high orientation improves electrical conductivity PHONON ELECTRON nm Cellulose Acetate ORGANIC OXIDE Example of CNF potential: Thermoelectric Materials L4 Flexible film NANOLAMINATES L3 L2 L1 SEEBECK COEFFICIENT THERMAL STABILITY ELECTRICAL CONDUCTIVITY Alternative to conventional thermoelectric materials are nano-organised hybrids (nanolaminates) - Thin, electrically conductive inorganic layers from Earth-abundant elements e.g. ZnO - Single layer/sheet of cellulose material e.g. crystalline nanocellulose or nanofibrils blocks heat conduction and improves thermal stability Advantages: cheap, enhanced mechanical properties, fabrication of flexible devices <Forest Meets Chemistry>

16 Thermoelectric properties Sample Resistivity (kω) Seebeck (µv/k) ZnO CNF - freestanding film 2000 n/a ZnO TEMPO ZnO ZnO CA ZnO ~ ZnO CNF ZnO n/a Seebeck coefficient = thermoelectric power ZnO+Al CNF ZnO+Al ZnO+Al CNC ZnO+Al References Solid substrate Freestanding film Blue bar =1 µm B. Wilson, M. Putkonen, T. Tiittanen, H. Jin, M. Gestranius, T.-M. Tenhunen, M. Karppinen, T. Tammelin and E. Kontturi. Towards Cellulose-Inorganic Hybrid Films with Thermoelectric Properties. COST Action FP1105 Workshop, (May 2015) San Sebastian, Spain. Performance of Thermoelectric Materials Seebeck coefficient Sb 2 Te 3 Our samples Bi 2 Te 3 ACS Appl. Mater. Interfaces 2015, 7, J. Mater. Chem. C, 2015, 3, Proc. SPIE 5836, Smart Sensors, Actuators, and MEMS II, 711 (July 1, 2005); doi: / B. Wilson, M. Putkonen, T. Tiittanen, H. Jin, M. Gestranius, T.-M. Tenhunen, M. Karppinen, T. Tammelin and E. Kontturi. Towards Cellulose-Inorganic Hybrid Films with Thermoelectric Properties. COST Action FP1105 Workshop, (May 2015) San Sebastian, Spain. 16

17 State-of-art Clear organic-inorganic multilayer nanolaminate structures have been achieved by alternating ALD deposition and EPD, spin or dip coating of (nano)cellulose Bottom up approach allows easy construction of CNF/CNC network on solid substrates and on flexible CNF film ZnO-cellulose hybrids show promise as new state of the art thermoelectric materials Resistivity decreased from MΩ kω Seebeck values at the same level compared to conventional TE materials Thermal conductivity pending CNC films W m -1 K -1 and Bi 2 Te W m -1 K -1 (literature values) Potential for novel flexible TE generators Diaz et al. Biomacromolecules2014, 15, Conclusions Nanoscaled cellulosic materials have an inherent tendency to form films upon drying. Films prepared from cellulose nanofibrils are strong but brittle. They possess good thermal stability, smoothness, density and chemical reactivity which make them as attractive templates for bioinspired functional materials. Biobased films can act as oxygen barriers in dry conditions but they are poor moisture barriers Hydrophilic CNF films can be considered as potential tunable biobased membrane templates for nanofiltration of micropollutants and multivalent ions Natural features of nanocellulosic ultrathin films (e.g. crystallinity and thermal stability) may be exploited in electronics applications 27/06/