The last decade have witnessed an increasing interest in biobased organic-inorganic hybrid materials, where properties of each component are combined giving remarkable characteristics. However, some of the basic parameters which dominate the formation of such materials are still unclear. In this work, we develop and characterize new organic-inorganic hybrids made of micro/nano fibrillated cellulose (MFC/NFC) and inorganic nanoparticles (NP), trying to better understand the fundamentals operating behind the assembling of the different constituents.

1. Experimental
Microscopic Characterization of Nanofibrillated Cellulose-
Inorganic Nanoparticle Hybrid Systems
J. Hidalgo1,3, S. Peresin2, G. Kortaberria3 and A. Tejado1
1 Tecnalia Research & Innovation , Area Anardi 5, Azpeitia, Spain
2 VTT-Technical Research Centre, Biologinkuja 3, Espoo, Finland
3 University of the Basque Country, Plaza Europa 1, Donostia-San Sebastian, Spain
Objective The last decade have witnessed an increasing interest in biobased organic-inorganic hybrid materials, where properties of each component are
combined giving remarkable characteristics. However, some of the basic parameters which dominate the formation of such materials are still unclear. In this
work, we develop and characterize new organic-inorganic hybrids made of micro/nano fibrillated cellulose (MFC/NFC) and inorganic nanoparticles (NP),
trying to better understand the fundamentals operating behind the assembling of the different constituents.
Three cellulose types, i.e. MFC, NFC and dicarboxylated cellulose fibres
(DCC), were combined with three inorganic NP: titanium dioxide (TiO2),
sodium montmorillonite (MMT) and organically modified montmorillonite
(OMMT). Atomic Force Microscopy (AFM) and Field Emission Scanning
Electron Microscopy (FE-SEM) were employed to study the topology of
such nanocomposites prepared by either casting or spin coating.
Inorganic Nanoparticles
OMMTMMT TiO2
Organic Substrates
NFCMFC DCC
Acknowledgements Cost Action FP1105, for funding this research in the frame of a Short Time Scientiffic Mission (STSM).
VTT (High Performance Fibre Products Group) and Aalto University for helping with AFM and SEM analysis.
Cellulosepreparation
Homogenizer
3 times 400m
+
5 times 200m
MFC
Z-shaped interaction chamber.
Microfluidics Inc., USA
Mechanical treatment
Periodate oxidation
Chlorite oxidation
DCC
Di carboxylated cellulose chains
Chemical treatment
TEMPO oxidation
Homogenizer
NFC
(2,2,6,6-Tetramethyl-piperidin-1-yl)oxyl
TEMPO radical
MFC
Chemo-mechanical treatment
5 times 200m
+
5 times 100m
+
+ +
Mixing
1wt%1wt%
MFC/NFC NP
Casting on polystyrene dish
Spin coating + Pt sputtering
Ultrasonication
Hybridpreparation
Conclusions Stability of suspensions was evaluated and correlated with the quality of the films formed via casting or vacuum filtration. Remarkably,
while MMT always gives rise to stable suspensions and good quality films, TiO2 causes severe flocculation of NFC and DCC, showing identical behaviour to
OMMT. Microscopic analyses confirm those floc promoting interactions and succeed in characterizing different features of the samples, such as the well-
defined profile height differences, the disintegrating effect of sonication on DCC sample and the homogeneous nanoparticle layer of OMMT on MFC substrate.
NFC/OMMT
MFC/MMT
Preliminary assessments
Film Formation by casting
Hybrids
Suspension Stability Charge Interaction with NP Stability of suspensions Filmability
Key parameter: Anionic charge density of cellulosic substrates
DCC NFC MFC
MFC NFC DCC
MMT
MFC NFC DCC
OMMT
MFC NFC DCC
MFC NFC DCC
Settling
TiO2
MFC NFC DCC
MFC NFC DCC
Settling
bad film
AFM Images Linear height profiles extracted from AFM images
According to roughness results some appreciations can be made:
 NFC ( ≈100nm) is more fibrillated and smoother than MFC ( ≈200nm),
but DCC ( ≈50nm) is the smoothest cellulose sample.
 MMT-containing hybrids show almost identical roughness ( ≈200nm)
regardless the type of cellulose substrate.
 The MFC/OMMT hybrid has a very flat and regular surface ( ≈ 10nm).
 Strong aggregation is observed when comparing TiO2 NP (particle size≈21nm)
and MFC/TiO2 hybrids ( ≈ 400nm).
good film
CellulosicsubstratesMFCHybrids
SEM Images
1 µm
1)Bundles of fibrils.
2)Uniform surface of thin fibrils.
3)One big cellulose fibre breaking in
smaller fibrils.
4)Surface looks to be empty at lower
magnification level. Only previous
shown fibrillated fragments are observed.
5)At higher magnification, nanosized
fibrils can be clearly seen covering the
whole surface.
10 µm
Different roughness of the samples is already visible: big fibrils of MFC, MMT aggregates and softer surface on NFC and DCC.
The surface of fibrils is covered by a layer of clay.
Best hybrid films (MFC)
Cellulosic substrates
10 µm 10 µm
50 µm
1 µm
50 µm50 µm50 µm
1 µm 1 µm
Most Settled Suspensions (Study of aggregates)
Huge nanoclay aggregates, some fully and others partially covered by a layer of
nanofibrils.
5 µm
25 µm
1 µm
TiO2 particles are uniformly dispersed.
With a higher magnification level, in NFC/TiO2 hybrid all NP are fully covered by fibrils. On the
other hand, DCC/TiO2 hybrid has uncovered nanoparticles (sharp edges can be seen). That explains
the settling of NFC/TiO2 suspension totally, and the cloudy upper part of the DCC/TiO2 revealing a
weaker interaction between NP and cellulose nanofibrils.
5 µm 5 µm
100 nm 100 nm
250 nm