Nanocellulosic Materials - Fraunhofer IAP · Nanocellulosic Materials Derek G. Gray Department of Chemistry, McGill University, Pulp and Paper Building ... The nanocellulose family

Nanocellulosic Materials

Derek G. Gray

Department of Chemistry, McGill University, Pulp and Paper Building

3420 University Street, Montreal, QC Canada H3A 2A7

www.gray-group.mcgill.ca

Fraunhofer IAP, 6th Biopolymer Colloquium, January 23, 2014, International Congress Center, Berlin.

Reviews:

Nanocelluloses: Klemm et al., Angew. Chemie Int. Ed., 2011, 50, 5438-5466.

Nanocrystalline cellulose: Habibi et al., Chem. Rev. 2010, 110, 3479–3500.

Cellulosic nanomaterials: Moon et al., Chem. Soc. Rev., 2011, 40, 3941–3994.

CHEMISTRY McGill University

“Production and Applications of Cellulose Nanomaterials”, Postek, R. J.et al., Eds., TAPPI Press, Atlanta, GA, June, 2013

Recent review lists >50 different research groups working on preparation, properties and applications of cellulose nanocrystals and cellulose nanofibrils!


The literature contains a wide range of terms for cellulose-derived nanomaterials:-

Cellulose micelles

Cellulose whiskers

Cellulose crystallites

Microcrystalline cellulose (MCC)

Cellulose nanocrystals (CNC)

Nanocrystalline cellulose (NCC)

Bacterial nanocellulose

Microfibrillar cellulose (MFC)

Nanofibrillar cellulose (NFC)

Cellulose filaments

…etc.

Note that these are not synonyms:- The names often, but not always, refer to different materials!


• Cellulose nanocrystals (nanocrystalline cellulose, NCC), made by acid hydrolysis of natural cellulose fibres.

• Cellulose nanofibrils (nanofibrillar cellulose, NFC), made by mechanical defibrillation, usually after pretreatment such as TEMPO-catalysed oxidation.

• Combinations of these and other treatments (e.g. cellulose whiskers).

• Bacterial cellulose.

Alternative classification: • Short (~200 nm) highly crystalline nanocrystals. • Long (> 1000 nm) entangled nanofibrils

The nanocellulose family


Long > 1 μm

Short ~150 nm

(or many other sources of fibrous cellulose)

Two main classes of nanocellulose (Thanks to Profs Bob Pelton and Emily Cranston,

McMaster University)


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Both short and long nanocelluloses usually contain charged groups on their surfaces: • Short Cellulose Nanocrystals (CNC) prepared by sulfuric acid hydrolysis

are stabilized in suspension by surface sulfate half-ester groups.

• The preparation of long Cellulose Nanofibrils (NFC) is facilitated by incorporation of surface carboxyl groups by TEMPO-catalysed oxidation.

• The surface anionic groups may be associated with different counter-cations that influence nanocellulose properties.

OCH2OH

H H

OHH

H

HO

H

H

O

HH

CH2OH

OH

O

OHO

H

OCH2OH

H H

OH

H

HO

H

O

The nanocellulose family


1. Start with cellullose

2. Remove cellulose*

3. Product: cellulose

Tight control of starting material history and reaction conditions are necessary!

Typical size, 150 x 8 nm

*Sulfuric acid hydrolysis: Rånby, B.G., Acta Chem. Scand., 3, 649 (1949) *Ammonium persulfate oxidation: Leung A. C. W. et al., Small 2011, 7, 302–305

Cellulose nanocrystal preparation


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A suspension of cellulose nanocrystals in pure water at low concentrations forms a clear stable isotropic fluid.

At higher concentrations, the nanocrystals self-align to form a chiral nematic liquid crystalline phase in equilibrium with isotropic phase.

Biphasic cellulose nanocrystal suspension (crossed polars)

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J.-F. Revol et al., Int. J .Biol. Macromol., 14, 170-172 (1992).

Cellulose nanocrystal preparation Liquid crystal formation


• Sulfate half-ester stabilized • Non-specific substitution • Common counter-ions: H+, Na+

• Carboxyl group stabilized • TEMPO-catalysed oxidation at

primary OH or ammonium persulfate oxidized • Common counter-ions: H+, Na+

Stabilization of cellulose nanocrystal suspensions Anionic surface substituents


EPTMAC HPTMAC-CNC

NONaOH CNC

OOH

NCl ClCNC-OH

• (2,3-Epoxypropyl)trimethylammonium chloride (EPTMAC)

• NaOH 7% w/v at 65oC for 5h

• Dilute to quench, dialyse and sonicate

• Product: cellulose nanocrystals with some (2-hydroxypropyl) trimethylammonium chloride groups on the surface.

CNC-OH Cellulose nanocrystals

M. Hasani et al., Soft Matter 4, 2238-2244 (2008)

100 µm

Stabilization of cellulose nanocrystal suspensions Cationic surface substituents


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Araki, J.; Wada, M.; Kuga, S. Langmuir 2001, 17, 21–27. Kloser, E.; Gray, D.G. Langmuir 2010, 26, 13450–13456.

Base-catalysed addition of α-epoxy,ω-methoxy-terminated poly-(ethylene oxide), MW ~2000.

Stabilized by grafting poly(ethylene oxide) chains onto CNC surfaces

Stabilization of cellulose nanocrystal suspensions Non-ionic surface substituents


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Phase separation theory, based on Onsager’s excluded volume theory for charged rods, works OK to explain ordered phase separation.

S. Beck-Candanedo et al., Macromolecules, 40(9), 3429-3436 (2007)

But explaining effects of added salts, polymers etc. is challenging! Three aqueous phases in equilibrium have been observed for a CNC/dextran system !

I2

N 250 μm

I1

C

e.g., ionic strength effects: X.M. Dong et al., Langmuir,12, 2076-2082 (1996).

Stabilization of cellulose nanocrystal suspensions Phase separation theory


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Individual cellulose nanocrystals have a negative diamagnetic anisotropy which aligns their long axes orthogonal relative to an applied magnetic field. So chiral nematic axis orients along field.

Orientation of cellulose nanocrystal suspensions in a magnetic field


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Mixture of planchettes cut from cellulose nanocrystal films prepared with different NaCl concentrations, thus giving different reflection wavelengths.

J.-F. Revol et al., US Patent 5,629,055

Another unexpected discovery…the chiral nematic order was preserved even on drying the nanocrystal suspension!

Optical properties Films cast from CNC suspensions


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Film kindly provided by Xuequan Tan, FPInnovations

The colour of the iridescent film depends on illumination, viewing angle and on background

…against a white and a black background.

10 cm

…under diffuse illumination. The same piece of film, photographed…

Optical properties Films cast from CNC suspensions


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Optical properties Biomimetic structural colours


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Viewed through 3-D Glasses (passive, circularly polarized) The left lens allows only left circularly polarized light to pass The right lens allows only right circularly polarized light to pass, and blocks left circularly polarized light

Butterfly image, made from blue cellulose nanocrystal film

The chiral nematic nature of the film can be demonstrated by simple optical observations with 3-D glasses

Optical properties CNC films reflect circularly polarized light


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Structural properties CNC suspensions and films have a left-handed helicoidal structure

This is the source of the circular polarization of reflected light

P/2


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Film structure FE-SEM of CNC film cross-section fracture surface


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This pattern is an oblique cross-section of a chiral nematic assembly of cellulose nanocrystals.


Majoinen, Kontturi, Ikkala and Gray, Cellulose (2012) 19:1599–1605

400 nm


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40 µm

Model of parabolic focal conic near centre plane showing layer orientation (left), and polarizing light microscope image of film assembled from cellulose nanocrystals in

same orientation (right)

Roman and Gray, Langmuir, 21(12), 5555-5561 (2005)

Film structure Films cast from aqueous suspensions of CNC may show spontaneous

order at longer length scales


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Possible uses for Chiral Cellulose Films: • Anti-counterfeiting components in security papers.

• As iridescent components in decorative laminates. • Optically variable non-toxic pigments.

Paperboard containing CNC planchettes Scale bar, 10 mm.


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Paperboard containing CNC planchettes Planchettes appear when viewed obliquely


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Possible uses for Cellulose Nanocrystals (NCC): • As reinforcing agent in composite materials. • As rheology modifier in cosmetics and foods. • As carrier in biomedical applications.





CNC-H+ CNC-Na+

CNC thixotropic gels in aqueous glycerol

A. Dorris and D.G. Gray, Cellulose, 19(3), 687-694 (2012). CHEMISTRY McGill University

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Possible uses for Cellulose Nanofibrils: • As reinforcing agent in paper, wet-laid products and aerogels. • As rheology modifier in coatings, construction materials and

recovery fluids. • As scaffold in biomedical applications.


Scale-up processes for short (rice-like) nanocelluloses: • FPInnovations/Domtar, Windsor, Québec. • AITF, Edmonton, Alberta. • University of Maine, Orono/ U.S. Forest Products Laboratory,

Madison, Wisconsin.

Scale-up processes for long (spagetti-like) nanocelluloses: • Innventia/KTH Stockholm • VTT/UPM Finland • Stora-Enso • University of Maine, Orono/ U.S. Forest Products Laboratory,

Madison, Wisconsin • FPInnovations/Kruger, Trois-Rivières, Québec.

Some examples of scale-up activities


NANOCELLULOSES A somewhat overlooked family of nanoparticles

Why is this? Perceptions…. • Of no interest to chemists • Boring chemistry; a long string of glucose units • Worse, chemists have failed to be able to synthesis

cellulose in any reasonable quantity • Covalent modification of cellulose seems trivial • Photonically and electronically uninteresting (spin

correlation length <1 nm)


Reality: • Cellulose is a critical component of the biosphere • Every second of daylight, megatons of cellulose are being

synthesised by green plants. • Obviously, this is the ultimate green process… • One can make a family of nanocrystals from the cellulose

provided by green plants • The products are renewable, non-toxic, almost carbon-

neutral, with interesting mechanical properties • Cellulose nanocrystals do self-assemble to give interesting

optical and magnetic properties.

NANOCELLULOSES A somewhat overlooked family of nanoparticles


Acknowledgements

Paprican staff The late Jean-François Revol, Louis Godbout McGill Chemistry Graduate Students, 3420 University St. Historically, working on CNC preparation and properties:- Julie Giasson, (Ph.D. 1995, TEM and microscopy) Xue Min Dong (Ph.D. 1998, phase separation, chirality) Catherine Edgar (Ph.D. 2002, phase separation, surface properties) Maren Roman (PDF, 2004, film structure) Stephanie Beck (Ph.D. 2006, phase separation of mixtures) Emily Cranston (Ph.D. 2008, multilayers) Elisabeth Kloser (PDF, 2009, modification) Tiffany Abitbol (Ph.D. 2011, cellulosic nanostructures) Annie Dorris (PDF 2011, gelation)

We thank NSERC (Natural Science and Engineering Research Council Canada) and Paprican (now FPInnovations) for support


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Nanocellulosic Materials - Fraunhofer IAP · Nanocellulosic Materials Derek G. Gray Department of Chemistry, McGill University, Pulp and Paper Building ... The nanocellulose family