Cellulose Nanocrystals E-Book

Wadood Y. Hamad

• Herausgeber: John Wiley & Sons
• Kategorie: Wissenschaft und neue Technologien
• Serie: Wiley Series in Renewable Resources
• Sprache: Englisch

Seitenzahl: 586

Veröffentlichungsjahr: 2017

Beschreibung

Research into cellulose nanocrystals is currently in an exponential growth phase, with research into potential applications now strengthened by recent advances in nanomanufacturing. The possibility of routine commercial production of these advanced materials is now becoming a reality.

Cellulose Nanocrystals: Properties, Production and Applications provides an in-depth overview of the materials science, chemistry and physics of cellulose nanocrystals, and the technical development of advanced materials based on cellulose nanocrystals for industrial and medical applications. Topics covered include:

• A comprehensive treatment of the structure, morphology and synthesis of cellulose nanocrystals.
• The science and engineering of producing cellulose nanocrystals and the challenges involved in nanomanufacturing on a large industrial scale. 
• Surface/interface modifications of cellulose nanocrystals for the development of novel biomaterials with attractive structural and functional properties.
• The scientific bases for developing cellulose-based nanomaterials with advanced functionalities for industrial/medical applications and consumer products. 
• Discussions on the (i) reinforcing potential of cellulose nanocrystals in polymer nanocomposites, (ii) utilization of these nanocrystals as efficient templates for developing tunable photonic materials, as well as (iii) applications in sustainable electronics and biomedicine.

Cellulose Nanocrystals: Properties, Production and Applications will appeal to audiences in the physical, chemical and biological sciences as well as engineering disciplines. It will be of critical interest to industrialists seeking to develop sustainable new materials for the advanced industrial economies of the 21st century, ranging from adaptive “smart” packaging materials, to new chiral, mesoporous materials for optoelectronics and photonics , to high-performance nanocomposites for structural applications.

Leseprobe

Table of Contents

Cover

Title Page

Series Preface

Foreword

Prologue

1 New Frontiers for Material Development and the Challenge of Nanotechnology

1.1 Perspectives on Nanotechnology

1.2 Societal Ramifications of Nanotechnology

1.3 Bio‐inspired Material Development: The Case for Cellulose Nanocrystals

1.4 A Glance at Bio‐inspired Hierarchical Materials

1.5 Concluding Thoughts

2 Assembly and Structure in Native Cellulosic Fibers

2.1 Physical and Chemical Characteristics of the Cellulose Molecule

2.2 Morphology and Structure of Native Cellulosic Fibers

2.3 Physical and Mechanical Properties of Native Cellulosic Fibers

3 Hydrolytic Extraction of Cellulose Nanocrystals

3.1 Introduction

3.2 The Liberation of CNCs Using Acid Hydrolysis

3.3 Reaction Kinetics of CNC Extraction

3.4 Processing Considerations for Sustainable and Economical Manufacture of CNCs

3.5 Micro/Nano Cellulosics Other Than CNCs

4 Properties of Cellulose Nanocrystals

4.1 Morphological Characteristics of CNCs

4.2 Structural Organization of CNCs

4.3 Solid‐State Characteristics of CNCs

4.4 CNCs Chiral Nematic Phase Properties

4.5 Shear Rheology of CNC Aqueous Suspensions

4.6 Thermal Stability of CNCs

5 Applications of Cellulose Nanocrystals

5.1 Prelude

5.2 The Reinforcing Potential of CNCs in Polymer Nanocomposites

5.3 CNC‐Stabilized Emulsions, Gels, and Hydrogels

5.4 Controlled Self‐Assembly of Functional Cellulosic Materials

5.5 Toward Bio‐inspired Photonic and Electronic Materials

5.6 CNCs in Biomedicine and Pharmaceuticals

5.7 Environmental, Health, and Safety Considerations of CNCs

5.8 Perspectives and Challenges

Epilogue—The Never‐Ending Evolution of Scientific Insights

Bibliography

Subject Index

End User License Agreement

List of Tables

Chapter 01

Table 1.1

Typical physical properties of different forms of cellulosic micro/nano materials and structures obtained using distinctly different processing—mechanical, chemical, and/or enzymatic—of the same raw material, softwood kraft pulp fibers

.

Chapter 03

Table 3.1

Elemental analysis data, calculated sulphate group/anhydroglucose unit, yield, and degree of polymerization (DP) of the extracted cellulose materials from hydrolysis of softwood kraft pulp at various sulfuric acid concentrations and temperatures for 25 min

.

Table 3.2

Elemental analysis data, calculated sulphate group per 100 anhydroglucose units, yield, and DP of the extracted cellulose materials from the hydrolysis of bleached softwood kraft pulp using 64 wt. % of sulfuric acid at 65°C for various times

.

Chapter 04

Table 4.1

Calculated integrals (%) for most of the peaks observed in the

13

C CPMAS spectra of CNC material in freeze‐ and air‐dried forms, as obtained from DMFIT

.

Table 4.2

Parameters derived from powder XRD spectra of CNC materials described in Table 4.1

.

Table 4.3

Typical data for the residual mass loss (as percentage) of H

2

SO

4

‐hydrolyzed CNC material of different pH at different temperatures

.

Chapter 05

Table 5.1

Physical properties for CNCs compared to other high‐performance reinforcing materials.

List of Illustrations

Chapter 01

Figure 1.1 Pollia condensata

fruit, another natural material exhibiting structural color, that is, internal color produced via the interference and diffraction of light passing through innate, ordered nanostructures (right image)

.

Figure 1.2

(a) A photograph of porous scaffolds of practical dimensions obtained by freeze‐casting of ceramic suspensions. (b) SEM image of the lamellar architecture of ice‐templated Al

2

O

3

/PMMA hybrid materials.

Figure 1.3

Schematic representation of the structure of egg‐box junction zones in TEMPO‐mediated oxidation of cellulose/alginate/calcium system: (a) coordination of Ca

2+

in a cavity created by a pair of guluronate sequences along alginate chains; (b) laterally associated egg‐box multimer in the composite sponge; (c) oxidized cellulose nanocrystals (OCNs) in the cross‐linking of alginate sponge; and (d) construction of the semi‐interpenetrating polymer network (SIPN) composed of oxidized microfibrillated cellulose (OMFC) and alginate. The black solid circles in (a) represent the oxygen atoms possibly involved in the coordination with Ca

2+

.

Chapter 02

Figure 2.1

Cellobiose, the monomer of cellulose

.

Figure 2.2

13

C NMR CP‐MAS spectra of I

α

and I

β

cellulose

.

Figure 2.3

Schemas of the micellar, continuous, fringed micellar, and fringed fibrillary structural theories describing crystalline and amorphous components in polymeric fibers

.

Figure 2.4

Conceptual schematics—first proposed by Forgacs (1963)—of the cell wall layers of a typical fiber or tracheid, showing fibrillar and/or microfibrillar directions

.

Figure 2.5

Schematic representation of a hemp stem (left), and SEM of the fractured end of kenaf bast (subjected to tensile loading) illustrating the fiber bundle morphology characteristic of nonwood plant fibers (right)

.

Figure 2.6

Models of a submicroscopic element—first proposed by Mark (1980)—in a layer of a fiber wall (left), and a basic unit cell wall (right). The unit contains a single rectangular anisotropic filament surrounded by a matrix of thickness, t

.

Chapter 03

Figure 3.1

Pictorial representation of the ultrastructure of lignocellulosic fibers

.

Figure 3.2

Schematic presentation of the polymeric structure of cellulose, showing highly ordered (crystalline) to least ordered (amorphous) regions. (a) Crystallites linked by disordered or amorphous regions and (b) isolated highly ordered crystallites

.

Figure 3.3

Yield vs. DP of the extracted, H

2

O‐insoluble cellulose materials from the hydrolysis of bleached softwood kraft pulp (DP = 1178) at various sulfuric acid concentrations and temperatures for 25 min (Hamad and Hu 2010)

.

Figure 3.4

Effect of hydrolysis temperature on the degree of sulfation (DS), degree of polymerization (DP), and particle size of CNC extracted from bleached kraft hemlock pulp at a constant sulfuric acid concentration and hydrolysis time. (Note: Left

y‐

axis represents both mean size and DP, while right

y‐

axis DS.)

Figure 3.5

Time‐of‐flight secondary ion mass spectroscopy (ToF‐SIMS) spectra of CNC particles processed using 60 wt. % and 65°C (a) and 64 wt. % and 45°C (b). CNC samples were mounted on a 1 cm × 1 cm clean silicon wafer using a double‐sided tape, and analysis was performed using PHI TRIFT V nanoTOF SIMS instrument. Both positive and negative (not shown) secondary mass spectra of each CNC sample were measured using 30 keV Au

+

primary ion beam at static mode with 400 µm × 400 µm analytical area. The spectra consistently indicate that the CNC samples are similar in their fragment regions (

m/z

up to 200), but the contrast becomes evident in their intact molecular regions. This indicates that CNC particles obtained using higher acid concentration and lower temperature (~64 wt. % and 45°C) have heat‐sensitive oligomers adsorbed onto the CNC surface

.

Figure 3.6

A conceptual flow diagram depicting the principal steps for CNC manufacture—with a particular focus on the process design for CNC separation and acid recovery. The dialysis module can effectively combine more than one function (purification, homogenization, and concentration), and can be repeated as many times as necessary depending on scale‐up requirements and efficiency—that is, module surface area essentially defines efficiency and quality of the extraction process. (AP, acid preparation; BG, bioenergy generation; ET, effluent treatment; RM, raw material.)

Figure 3.7

SEM micrograph of microfibrillated cellulose, MFC

.

Figure 3.8

SEM micrographs showing MCC morphology and structure. The arrows in the image point to cellulose crystallites in MCC particles. The scale bars in the images are 100 µm (left) and 5 µm (right)—after Mathew

et al.

(2005)

.

Figure 3.9

SEM micrograph of bacterial cellulose (Nakagaito

et al.

2005)

.

Chapter 04

Figure 4.1

Experimental

13

C cross‐polarization magic angle spinning nuclear magnetic resonance (CP/MAS NMR) spectrum of lyophilized CNC (black), acquired using 4096 scans (see text for further experimental details), with an overlay of a simulated spectrum for cellulose II (gray) obtained using DMFIT and the assignments reported for cellulose II

.

Figure 4.2

Micrographs of CNCs in aqueous suspension at high (top left) and low (top right) concentrations imaged using a scanning transmission electron microscope (STEM), where the CNC spindles (or rods) are shown as discrete nano‐scaled particles. The bottom SEM micrographs show lyophilized CNC self‐assemblies, whose morphology is characterized by agglomerates of parallelepiped, rod‐like structures of nano‐scale cross sections. (CNCs were extracted from bleached softwood kraft pulp using 64% sulfuric acid concentration at 45°C for 25 min.)

Figure 4.3

Cross‐polarized transmission (left image) and reflection (right) optical images of air‐dried CNCs suspension clearly showing the fingerprint local periodic structure.

Figure 4.4

SEM of partially hydrolyzed pulp obtained using 40% H

2

SO

4

at 65°C for 25 min

.

Figure 4.5

SEM of evaporation‐induced self‐assembled (EISA) CNC films produced from suspensions at (a) 25°C, pitch

, P

 = 2.57 µm ± 0.23, (b) 55°C

, P

 = 1.32 µm ± 0.23, (c) 75°C

, P

 = 1.07 µm ± 0.19, and (d) 100°C. Note the gradual reorganization of the chiral nematic order as temperature is increased, until complete randomness as 100°C. At ~75°C, some order is still notable in certain regions of the CNC film

.

Figure 4.6

Chiral nematic organization remains exquisitely evident in lyophilized (or freeze‐dried) CNC material. (a) Macro image of the longitudinal section of freeze‐dried CNC isolated from a storage vial. (b)–(c) Reflected light microscopy of material obtained from (a). Note the fingerprint pattern. (d)–(e) SEM images clearly depicting the periodic layering and chiral organization within each layer of a segment of the freeze‐dried CNC material shown in (a).

Figure 4.7

(a) Comparison of the

13

C CPMAS spectra for, from top to bottom, Sample 2 air‐dried, Sample 2 freeze‐dried, Sample 1 air‐dried, and Sample 1 freeze‐dried CNC. The increase in intensity for the lines assigned to C

4

amorphous, C

6

amorphous (see Table 4.2), and a line which may possibly be assigned to

(β)/I

β

(Hesse and Jaeger 2005) correlate with the increase in the amorphous area (listed), as determined from powder XRD measurements. (b) T1 relaxation profile for all

13

C types in air‐dried Sample 1. The spectra clearly indicate that the regions assigned as amorphous in Table 4.1 are more mobile than the crystalline components. (c) T1 inversion recovery data points and fits for the line assigned to C

6

amorphous for Sample 1 freeze‐dried (data: +; fit: solid black line), Sample 1 air‐dried (data: ×; fit: dotted black line), Sample 2 freeze‐dried (data: *; fit: solid gray line), and Sample 2 air‐dried (data: ; fit: dotted gray line)

.

Figure 4.8

Wide‐angle X‐ray diffractograms for (freeze‐dried) CNC materials extracted from bleached kraft softwood pulp using 64 wt. % sulphuric acid for 25 min at the indicated temperatures

.

Figure 4.9

Diffraction pattern for (freeze‐dried) CNC (64 wt. %, 45°C, 25 min) resolved into crystalline peaks and amorphous background (following the Ruland–Rietveld analytical approach). The residual plot (shown in gray) represents the difference between the actual diffraction pattern and the resolved (modeled) peaks

.

Figure 4.10

Degree of polymerization (DP) vs. crystallinity (a) and crystallite size (b) of the extracted cellulose materials from the hydrolysis of the softwood kraft pulp (DP = 1178) with various sulphuric acid concentrations at various hydrolysis temperatures (for 25 min)

.

Figure 4.11

2

H/

13

C REDOR spectra (reference, dephased, and difference) for 2‐day liquid D

2

O‐soaked CNC after a dipolar evolution time of 3.2 ms.

Figure 4.12

(a–e) Model fits of

2

H/

13

C REDOR data to dephasing curves calculated with the cellulose I

β

–B structure

.

Figure 4.13

13

C/

31

P REDOR spectra, where the solid line is the

13

C reference spectrum collected with

31

P dephasing pulses. The dashed line (exchanged in the vertical axis by a factor of 50) shows the difference spectrum in the presence of the

31

P dephasing

.

Figure 4.14

The three levels of structure in CNC films: (a) Model of two cellulose I chains in crystalline domains, based on the findings of Witter et al. (2006). The cylinders represent the cellulose chains. (b) Assuming that the rods which come together to form the chiral nematic phase are 3 × 3 nm, then roughly nine of the cellulose I chains would form a rod (gray). As reported by Orts et al. (1998) and Lima and Borsali (2004), these rods are helically twisted along their length of 20–200 nm, in the presence of high salt, for example. (c) The (straight or helically twisted) rods come together in layers to form the chiral nematic phase of CNC

.

Figure 4.15

Ionic strength influence on the phase separation in CNC aqueous suspensions at fixed concentration. Actual behavior is represented, for 3 wt. % CNC after 25 days of standing, at different NaCl concentrations (top images), and concomitant schematic illustrations (bottom) of these effects on CNC phase separation

.

Figure 4.16

(a) CD spectra of films produced from CNC suspensions with concentrations of 0.1 (black), 0.2 (black dashed), 0.5 (dark gray), 1.0 (dark gray dashed), and 2.0 w/w % (gray) at room temperature. (b) Plot of ln(1/

P

) of the CNC films vs. ln(c) for CNC particles. The error bars represent the error associated with determining the maximum reflection wavelength in the CD spectra. The fit yielded the following parameters:

y

 = (−0.225 ± 0.002)

x

 − (5.602 ± 0.001), R

2

 = 0.9999.

Figure 4.17

(a) Shear rate dependence of the order parameter,

S

, for CNC nanoparticles of

L

 = 180 nm () and

L

 = 280 nm (), along with the viscosity profile for

L

 = 280 nm as a function of shear rate (). A higher concentration was used for the shorter particles so that the viscosities of the two samples would be equivalent.

(b) Viscosity as a function of nanorod concentration for shear rates of 0.01 and 100 s

−1

.

Figure 4.18

Effect of ultrasound energy input (level of sonication) on the viscosity material function at (a) 5 wt. % and (b) 7 wt. % CNC suspensions

.

Figure 4.19

Polarized optical micrographs of 7 wt. % CNC suspensions at rest: (a) unsonicated sample, (b) sample sonicated at 500 J, (c) sample sonicated at 1000 J, and (d) sample sonicated at 2000 J energy applied per gram of CNC in suspension

.

Figure 4.20

Steady‐state viscosity vs. shear rate for (a) unsonicated CNC suspensions and (b) CNC suspensions sonicated at 1000 J/g CNC with concentrations varying from 1 to 7 wt. %.

Figure 4.21

Steady‐state viscosity versus shear rate of 1 wt. % (), and 7 wt. % () CNC suspensions before sonication (solid symbols) and after sonication at 1000 J/g CNC (open symbols)

.

Figure 4.22

Polarized optical micrographs of CNC suspension (5 wt. %, unsonicated) during steady shear tests, at shear rates of (a) 0.01 s

−1

, (b) 0.05 s

−1

, (c) 0.1 s

−1

, (d) 0.5 s

−1

, (e) 1 s

−1

, and (f) 10 s

−1

.

Figure 4.23

Polarized optical micrographs of CNC suspension (5 wt. %, 1000 J/g CNC sonicated) during steady shear tests, at corresponding shear rates of (a) 0.01 s

−1

, (b) 0.05 s

−1

, (c) 0.1 s

−1

, (d) 0.5 s

−1

, (e) 1 s

−1

, and (f) 10 s

−1

.

Figure 4.24

Complex viscosity │

η

*│ (), storage modulus

G

′ (), and loss modulus

G″

() vs. angular frequency of unsonicated (solid symbols) and sonicated at 1000 J/g CNC (open symbols) of (a) 3 wt. %, (b) 5 wt. %, (c) 7 wt. %, and (d) 10 wt. % of CNC suspensions

.

Figure 4.25

Cox–Merz rule comparison of (a) unsonicated and (b) sonicated at 1000 J/g CNC samples at different concentrations. The open symbols represent the steady shear viscosity, and the solid symbols represent complex viscosity. Failure of this rule indicates significant structural formation

.

Figure 4.26

Steady shear viscosity vs. shear rate at various temperatures from 10 to 50°C of CNC suspensions, sonicated at 1000 J/g CNC, with concentrations of (a) 3 wt. %, (b) 5 wt. % (c) 7 wt. %, and (d) 10 wt. %

.

Figure 4.27

Polarized optical micrographs at (a) 20°C, (b) 30°C, and (c) 40°C of 5 wt. % CNC suspension under constant shear rate of 0.1 s

−1

.

Figure 4.28

Temperature effects on shear viscosity for a 5 wt. % CNC suspension (sonicated at 1000 J/g CNC) at different shear rates

.

Figure 4.29

Effect of temperature on the complex viscosity of CNC suspensions at various concentrations and at a constant angular frequency of 1 rad/s

.

Figure 4.30

(a, b) Viscosity vs. shear rate for CNC suspensions possessing 4.39 OSO

3

H/100 glucose units. All suspensions were sonicated for 1000 J/g CNC

.

Figure 4.31

(a, b) Viscosity vs. shear rate for CNC suspensions possessing 3.55 OSO

3

H/100 glucose units. All suspensions were sonicated for 1000 J/g CNC

.

Figure 4.32

POM micrographs of CNC suspension possessing 4.39 OSO

3

H/100 glucose units at different concentrations

.

Figure 4.33

POM micrographs of CNC suspension possessing 3.55 OSO

3

H/100 glucose units at different concentrations

.

Figure 4.34

Storage moduli

, G′

(solid symbols), and loss moduli,

G″

(open symbols), vs. angular frequency

, ω

, of CNC suspensions possessing (a) 4.39 and (b) 3.55 OSO

3

H/100 glucose units at different concentrations

. All suspensions were sonicated to 1000 J/g CNC.

Figure 4.35

Shear rate‐dependent viscosity profiles for constant‐mass, isotropic CNCs suspensions at different electrolyte concentrations (up to 10 mM NaCl). At ~15 mM NaCl, the CNC suspension undergoes coagulation (not shown)

.

Figure 4.36

Shear rate‐dependent viscosity profiles for 7 wt. % (a) and 10 wt. % (b) CNC suspensions at different electrolyte concentrations

.

Figure 4.37

POM images for 9 wt. % CNC suspensions at different NaCl concentrations, taken at shear rate of 0.01 s

−1

. The scale bar is 50 µm in all images

.

Figure 4.38

Storage

, Gʹ

(filled symbols), and loss,

Gʺ

(open symbols), moduli vs. angular frequency

, ω,

at different CNC concentrations without NaCl

.

Figure 4.39

Storage

, Gʹ

(filled symbols), and loss

, Gʺ

(open symbols), moduli vs. angular frequency

, ω

, for (a) 7 wt. % and (b) 10 wt. % CNC suspensions at different NaCl concentrations

.

Figure 4.40

Storage

, Gʹ

(filled symbols), and loss

, Gʺ

(open symbols), moduli vs. angular frequency

, ω,

for (a) 12 wt. % and (b) 15 wt. % CNC suspensions at different NaCl concentrations

.

Figure 4.41

Correlation functions for a 10 wt. % CNC sample under oscillatory shear measured from 0 to 300 s at (a)

f

 = 1 Hz and (b)

f

 = 10 Hz. The evolution of the fist echo is shown for various strains. The echo amplitude drops significantly from 1 at

γ

0

 = 15% and

f

 = 1 Hz and 27% and

f

 = 10 Hz exhibiting shear‐induced irreversible rearrangement (yielding). The initial decay rate with stain at

f

 = 10 Hz. The linear dependence indicates the absence of wall slip

.

Figure 4.42

Thermogravimetric responses of H

2

SO

4

‐hydrolyzed CNCs is pH sensitive. (Solid line represents CNC films at pH = 7; dotted line, pH = 10; and dashed line, pH = 3.) Thermal stability improves at neutral and basic pH. Thermogravimetric testing was conducted using Perkin Elmer Pyris 6 instrument equipped with Pyris V6.0 software. The samples (approximate mass between 5 and 6 mg) were individually heated at a constant rate of 10°C/min in nitrogen (flow rate = 20 ml/min). Heating was continued until the sample attained constant mass

.

Figure 4.43

Thermogravimetric responses for H

2

SO

4

‐hydrolyzed CNC films (control, dashed line), and solvolytically desulfated CNC film (solid line), and BuOH‐washed solvolytically desulfated CNC film (dotted line). Sulfation was reduced from 298 mmol/kg CNC for the control film to 18 mmol/kg CNC for the desulfated CNC film.

Figure 4.44

SEM micrographs (at three magnification scales) of solvolytically desulfated CNC films, where the particles completely lose their chiral nematic organization. This occurs regardless of the hydrolysis conditions used for CNC synthesis—see SEM images for sulfated and heated CNC films shown in Figure 4.5

.

Figure 4.45

X‐ray diffractometric patterns of lyophilized (Na‐form) CNC indicating structural stability from approximately −125 to ~300°C and suitability for high‐temperature processing. Heating was carried out in capillary tubes using GADDS system operated at 50° intervals. (Typical X‐ray settings are described in Section 4.3.1.)

Chapter 05

Figure 5.1

CNCs are nanomaterials that possess the full suite of properties described in this illustration. As such, CNCs are the only functional nanomaterials derived from entirely renewable resources using selective strong mineral acid hydrolysis. It is apposite to note that other mechanical or chemi‐mechanical treatments of biomass produce cellulose nanostructures that only share some of the attributes described earlier.

Figure 5.2

Schematic illustrations of the stress–strain response and corresponding physical properties of reinforcement, matrix, and composite. Here, UTS, ultimate tensile strength;

ε

f

,

strain at failure;

E,

modulus of elasticity (or Young’s modulus); and toughness, the shadow area under stress–strain curve (includes both elastic and plastic contributions).

Figure 5.3

Examples of chemical agents that can react with ─OH on cellulose surface.

Figure 5.4

Dynamic mechanical data—top plot represents the tan

δ,

and bottom one, the storage modulus, as functions of temperature—for nanocomposites of CNCs and PVA. It is evident the reinforcing effect of CNCs increases with increasing loading—rubbery storage modulus is increased twofold at around [CNCs] = 9.1 wt. % and fourfold at [CNCs] = 20 wt. %. The

T

g

of the polymer nanocomposites are practically unaffected. (DMA testing was performed at the same relative humidity and in tensile mode with a DMA Q800 TA Instrument. Measurements were made at 1 Hz constant frequency, 0.15% strain amplitude, 30–100°C temperature range, and 5°C/min heating rate.)

Figure 5.5

Experimental data and percolation predictions for the dynamic mechanical response for CNC–PVA nanocomposites as a function of CNC volume fraction. The top figure represents the logarithm of the storage tensile modulus at 35°C (below

T

g

),

and the bottom at 80°C (above

T

g

). The experimental data present a better fit to the percolation model than to the Halpin–Kardos model—which assumes good dispersion of reinforcement, but no reinforcement–reinforcement interactions. For percolation modeling, the following assumptions were followed:

E

f

,

modulus of the CNC network = 10 GPa;

E

m

,

modulus of the polymer matrix at 35°C = 4.76 GPa, and at 80°C = 0.227 GPa. (Refer to Section 5.2.8 for details.) The experimental data show equivalent, or better, correspondence to the percolation model, indicating the “excellent” compatibility between CNCs and PVA within the nanocomposite.

Figure 5.6

X‐ray diffractograms for CNC, PVA, and CNC–PVA nanocomposites at different CNC loadings. It is evident that the structure of CNCs remains intact throughout the nanocomposites, and CNC presence becomes apparent at loadings above 4 wt. %, which is approximately the critical percolating threshold. Diffraction was carried out using a Bruker D8 Advance powder X‐ray diffractometer equipped with a CuX

α

X‐ray tube, a diffracted beam graphite monochromator and NaI scintillation detector. (More specifics regarding XRD experimentation can be found in Hamad and Hu 2010.)

Figure 5.7

Scanning electron micrograph illustrating typical morphology of spray‐dried cellulose nanocrystals (SD‐CNCs).

Figure 5.8

Scanning electron micrographs of spray‐freeze dried CNCs (SFD‐CNCs) illustrating the interior structure. When low concentrations (0.5 wt. %) of aqueous CNC suspension are used, SFD‐CNCs have morphologies that are porous, agglomerated and filament‐like (a–c). However, for higher concentrations (6 wt. %), SFD‐CNCs appear as spherical, foam‐like structures (d–f)

.

Figure 5.9

Schematic depicting solution ring‐opening polymerization reaction of CNCs and

L

‐lactide in a suitable solvent, where the former is dispersible as individual nanoparticles and the latter easily dissolved (a). Alternatively, bulk ring‐opening polymerization reaction occurs with surface‐modified CNCs suspended in molten

L

‐lactide (b).

Figure 5.10

DSC thermograms of neat PLA, CNC, and CNC–PLLA nanomaterials, I–III (prepared by

in situ

ring‐opening polymerization according to Hamad and Miao 2014) carried out in nitrogen environment at 10°C/min.

T

c

and

T

m

increase with increasing molecular weight, and the choice of catalyst used in the

in situ

polymerization process (at the same reaction conditions) affects the molecular weight—higher MW for Sn(oct)

2

.

Figure 5.11

Isochronal evolution of the storage modulus,

E′,

as a function of temperature for neat PLA films and nanocomposite films produced from extruding CNC–PLLA nanomaterials at different CNC loadings, prepared by in situ ring‐opening polymerization, and commercial PLA (Hamad and Miao 2014). (a) The graph illustrates crystallization and softening effects in highly crystallizable PLA, whereas (b) depicts the responses in poorly crystallizable PLA. In both cases, the role of CNCs as effective nucleating agents is clear.

Figure 5.12

(a) Neat PLA and CNC–PLA nanocomposite films. (b) SEM images illustrating CNC dispersion within an extruded CNC–PLA nanocomposite pellet from which the film in (a) is made. All films appear transparent; however, there appears a yellow haze with CNC–PLA nanocomposite films—due to the interaction between

L

‐lactide and Sn(oct)

2

in small laboratory‐scale settings. The transparent nature of the CNC–PLA nanocomposite film indicates that dispersion—or nonaggregation—of the cellulose nanoparticles within the biopolyester is optimal and uniform following the

in situ

ring opening polymerization approach described in Hamad and Miao (2014).

Figure 5.13

Gas barrier performance global map for typical packaging materials—for example, poly(ethylene terephthalate), PET, PLA, and high‐density poly(ethylene), HDPE, as well as CNC and CNC–PLA nanocomposite films. CNCs, through influencing the crystallization state of the polymer resin, contribute to improving both gas and water vapor barrier properties (normalized with respect to film thickness).

Figure 5.14

Reaction scheme of the free‐radical, surface‐grafting polymerization of dimethylamino propyl methacrylamide (DPMA) in the presence of CNCs. The reaction is carried out at pH ≈ 11.5 using ammonium persulfate (APS) as initiator, at 50°C for ~18 h. The resulting nanomaterial, P(DPMA)–CNCs, can then be used with the epoxy‐hardener emulsion system to cast and cure the nanocomposite material.

Figure 5.15

Stress vs. strain behavior of the P(DPMA)–CNC–epoxy nanocomposite system indicating synergetic improvements in the mechanical performance. (Concentration of the P(DPMA)–CNC nanomaterial is 4 wt. % in the system, and of CNC is 3 wt. %.) Relative to the neat epoxy system (a pure gilycidyl ether of bisphenol A with an epoxide equivalent weight of 171–175 and a polyetheramine primary diamine curing agent with an average molecular weight of about 230), there is ~20, 30, and 80% improvement in ultimate tensile strength, Young’s modulus and strain‐to‐failure of the novel P(DPMA)–CNC–epoxy nanocomposite system (Hamad and Su 2012)

.

Figure 5.16

Dynamic mechanical response—storage (a) and loss (b) moduli—of the P(DPMA)–CNC–epoxy nanocomposite system described earlier. There is an order‐of‐magnitude change in storage modulus for the nanocomposite system relative to neat epoxy extending over the full range of the rubbery state (Hamad and Su 2012).

Figure 5.17

Schematic diagram of the series‐parallel model.

R

and

S

represent the rigid (reinforcement) and the soft (polymer matrix) phases, respectively, and

ψ

the volume fraction of the percolating rigid phase.

Figure 5.18

Theoretical plots, based on percolation theory, of the relationship between storage modulus and CNC volume, or weight, fractions illustrating the role aspect ratio (in the range 10–100) plays in predicting the mechanical properties of “ideal” CNC‐reinforced nanocomposites. Two variables are examined: CNC network strength, 10 GPa (a and c) and 5 GPa (b and d); the polymer matrix density is taken to be 0.9 g/cm

3

(a and b) or 1.23 g/cm

3

(c and d).

Figure 5.19

Examples of Pickering emulsions stabilized by CNCs at different concentrations. (a) Water : oil = 2 : 8 wt. %, [CNCs] in water = 1 wt. %, and (b) water : oil = 5 : 5 wt. %, [CNCs] in water = 5.5 wt. %. (Scale bars: (a) 1 mm, and (b) 10 microns.)

Figure 5.20

(a–c) Confocal laser scanning microscopy (CLSM) images of hexadecane‐in‐water emulsion stabilized by CNCs, indicating that above closed packing conditions the spherical droplets are transformed to a polygonal shape.

Figure 5.21

(a) Tensile stress–strain behavior for GMA‐g‐CNC/PAM nanocomposite hydrogel (20 wt. %) relative to typical chemically cross‐linked hydrogels (BIS/PAM). The response regions for GMA‐g‐CNC polymer nanocomposite hydrogels can be categorized as: linear elastic (region I), viscoelastic (region II), visco‐plastic response (region III), and yielding/relaxation (region IV). (b) The graph represents the tensile stress–strain curves for this polymer nanocomposite hydrogel at different functionalized CNC concentrations (10, 20, and 50 wt. % relative to acrylamide weight).

Figure 5.22

SEM (a, b) and polarized light (c, d) micrographs depicting the chiral nematic organization of EISA films prepared from CNC–DMAPS nanocomplexes (CNCs : DMAPS = 1 : 0.41)—cf. Figure 4.5 illustrating the same for neat EISA CNC films.

Figure 5.23

The stress–strain behavior of EISA CNC–DMAPS films depends on DMAPS dosage and pH. If the pH is changed from neutral (main plot) to ~2.5 (inset), the maximum stress of the film is dramatically reduced (comparison is made for CNC : DMAPS = 1 : 0.41). The stretch in both cases is only slightly affected. The photograph in the sub‐insert illustrates the flexibility of the film. Legend: CNC : DMAPS = 1 : 1 (solid black line) and 1 : 0.41 (dashed black line).

Figure 5.24

Synthetic route to photonic nanopaper or mesoporous photonic cellulose (MPC) films. Initially, an aqueous suspension of cellulose nanocrystals (CNCs) is combined with a urea‐formaldehyde (UF) precursor. Following evaporation‐induced self‐assembly (EISA), a CNC–UF composite with chiral nematic order is obtained. Thermal curing of the composite is followed by treatment with aqueous KOH to yield MPC films.

Figure 5.25

Structural characterization of MPC films. (a) Solid‐state

13

C CP/MAS NMR spectra of the CNC–UF composite and MPC; (b) PXRD pattern of pristine CNCs (cellulose I), CNC–UF composite, and MPC; and (c) Isothermal N

2

adsorption of MPC dried from EtOH with supercritical CO

2

(BET surface area), as well as the corresponding BJH pore‐size distribution calculated from the adsorption branch of the isotherm (inset).

Figure 5.26

Optical characterization of the CNC–UF composite and resulting MPC film. (a) Photograph of composite film after curing with its SEM image on the bottom. (b) Photograph of MPC air dried from H

2

O with its SEM image on the bottom. (c) Photograph of MPC dried from EtOH with supercritical CO

2

with its SEM image on the bottom.

Figure 5.27

Sensing performance of the functional MPC films. (a) Photographs of MPC soaked in different EtOH : H

2

O ratios as indicated, and (b) UV‐Vis (solid lines) and CD spectra (dashed lines). (c) Swelling kinetics of MPC: Curve shows the dependence of the wavelengths on time when a dry sample is immersed in water. (d) Pressure response of MPC at 0, 0.4, 0.8, 1.6, 2.7, 5.9, and 7.8 × 10

6

 N/m

2

(first and final value given in graphic) showing a clear blue‐shift of the peak reflectance wavelengths. (e) Peak reflection wavelengths vs. pressure plotted, the data were fit with an exponential curve.

Figure 5.28

Self‐assembly of CNCs with silica sol‐gel precursors indicates the fingerprint‐like texture characteristic of the formation of a chiral nematic phase as illustrated by polarized optical microscopy, POM (a). Evaporation of the mixture to dryness yields an iridescent composite (b, c) whose structural color depends on the silica loading. After calcination of the composite to remove the CNC template, mesoporous sol‐gel derived films are obtained that retain their intense structural color (d). The use of organosilica precursors yields flexible films after acid hydrolysis to remove the CNC template from the composite (e). Cracking observed during evaporation can be eliminated in the mesoporous silica films by the addition of polyols such as glucose, leading to large, crack‐free films (f).

Figure 5.29

Helium ion microscopy of chiral nematic mesoporous (a–d) ethylene‐bridged organosilica and (e, f) silica at varying magnification.

Figure 5.30

Effect of refractive index changes on the photonic properties of CNMS films. (a) Series of photographs showing the reversible color change that occurs upon wetting and drying a CNMS film. (b) Circular dichroism (CD) spectra of a CNMS film at different sucrose concentrations ranging from 0 to 50 wt. %. (c) Plots of peak intensity and position vs. refractive index for the series of CD spectra shown in (b).

Figure 5.31

Chiral nematic mesoporous titania thin films prepared by nanocasting appear iridescent through a left‐handed circularly polarized filter and opaque white through a right‐handed filter (a), illustrating the selective reflection in these materials. SEM images of the thin films (b, c) confirm mimicking CNCs’ helical, twisting structure, with globules likely introduced by titania crystallization.

Figure 5.32

Photographs and characterization of new hybrid materials templated by CNCs. (a) Silica films doped with Au and Ag NPs depicting characteristic colors arising from the plasmon resonance of the NPs.

CD spectra (b) clearly demonstrate the induction of chirality to the plasmon resonance by the chiral nematic surrounding.

(c) Photographs showing chiral nematic organosilica films before (I) and after doping with PPV (II) as well as fluorescence from PPV composites under UV illumination (III).

(d) Fluorescence quenching of the PPV composites by diluted solutions of TNT demonstrating their potential use in sensing.

Figure 5.33

Infiltration of chiral nematic organosilica films with the thermos‐responsive liquid crystals (LCs) reversibly changes the color from green (a) to transparent (b) upon heating from the liquid crystalline phase to the isotropic phase. The change in color and its reversibility can be quantified by UV‐Vis studies showing the decrease of the photonic signal upon heating the LC‐infiltrated composite material to 50°C (c) and the return of the photonic signal upon cooling to room temperature (d).

Figure 5.34

Demonstration of the potential application of mesoporous photonic plastics in security features or optical sensors. (a) The mesoporous films appears brightly red‐colored under a left‐handed circular polarizer (a, left), while its color disappears under a right‐handed polarizer (a, right). (b) The swelling behavior of the mesoporous plastics in mixtures of water and ethanol is shown by the photographs (bottom) and schematic illustration (top). Swelling of the material leads to a change in the helical pitch that affects the color of the chiral nematic polymer films. (c) The swelling kinetics of the samples in water reveals a fast response of the material to solvent changes. (d) UV‐Vis spectra show a systematic shift of the reflection signal of the chiral nematic resin during swelling in different mixtures of water and ethanol.

Figure 5.35

(a) Images from static CA measurements of CNC‐templated phenol‐formaldehyde resin films treated with HCl (left), pristine (middle), and treated with CH

2

O (right); (b) photographs of a strip of the resin films illustrating changes in color in water/ethanol binary solvent mixtures of different proportions. The left and right ends of the strip were treated with HCl and CH

2

O, respectively, while the middle part remained untreated; (c) CD spectra of the untreated (green), HCl‐treated (blue), and CH

2

O‐treated (red) resin films in dry state (solid lines) and after swelling in water (dashed lines). As the CD spectrometer that was used could not measure beyond 900 nm, the reflection peak of the CH

2

O‐treated film in the swollen state was confirmed with complementary UV‐Vis spectroscopy (red dotted line). Inkjet printing of photonic patterns on mesoporous‐resin films: (d) pattern printed as letters “UBC” on the mesoporous resin film, (e) “UBC” patterned as an image, (f) and (g) more complicated images patterned on another resin film. The pattern in (f) was revealed by swelling in water while the pattern in (g) was revealed in 20/80 (v/v) water/ethanol mixture. The appearance and disappearance of the patterns upon swelling and drying, respectively, are completely reversible.

Figure 5.36

Synthesis of the mesoporous chiral nematic bilayer phenol‐formaldehyde (PF) resin films. A suspension of CNCs is mixed with an aqueous solution of the PF polymer precursor. Layer‐by‐layer film fabrication resulted in bilayer composite films with chiral nematic organization upon evaporation‐induced self‐assembly (EISA) of the CNC–PF mixture followed by thermal curing. Treatment with alkaline solution removes (most of) the CNC template, yielding highly iridescent, bilayer mesoporous photonic resins after supercritical drying.

Figure 5.37

(a) Schematic (left) and corresponding photographs (right) of bilayer film showing selective swelling of one layer causing actuation to the direction of the opposite layer. (b) Site‐selective actuation of the bilayer resin film cut in a hand shape. All fingers are straight when the film is swollen in water (left). Alternate fingers bend when drops of acetone are put on the respective fingers and allowed to dry (panels in the middle). All fingers curl when the film is completely dry (right). The light yellow color of the bilayer films originates from the resin, and is apparent when the films are viewed on a white background.

Figure 5.38

Formation of the chiral nematic structure in nanocomposite hydrogels at varying composition. (a) POM image of a CNC/acrylamide dispersion during evaporation showing the formation of fingerprint texture characteristic of chiral nematic ordering. (b) POM of a PAAm composite prepared with high acrylamide loading soaked in water, showing fingerprint texture locked in place by photopolymerization (inset: a photograph of the swollen transparent hydrogel). (c) Photographs of iridescent PAAm composite hydrogels prepared with high CNC loading and different amounts of NaCl—increasing the ionic strength blue‐shifts the reflectance across the visible region. (d) Photograph of an iridescent photo‐patterned PAAm composite as the film swells in water. The masked region swells at a much faster rate, producing a latent image.

Figure 5.39

Swelling of the composite hydrogels: Photographs of a 6 cm diameter PAAm hydrogel as it swells in water (a) and contracts in ethanol (b). Transmission spectra of a PAAm composite in varying concentrations of aqueous ethanol are shown in (c), and the change in maximum reflected wavelength measured by circular dichroism of a PAAm hydrogel soaked in water and ethanol iteratively is depicted in (d). Finally, the maximum reflected wavelength as a function of hydrogel monomer in dry, aqueous, and ethanolic states is illustrated in (e).

Figure 5.40

Responsive behavior from CNC‐based nanocomposite hydrogels. (a) Transmission spectra of a PAAc composite in different basic solutions showing a red‐shift with increasing pH. (b) Time‐dependence of the reflected color from a PAAc nanocomposite immersed in pH 7 and pH 9.5 (lines drawn to guide the eye). (c) The maximum reflected wavelength of a cation‐exchanged PAAm/CNC nanocomposite as a function of cation in dry, aqueous, ethanol‐, and acetone‐swollen states.

Figure 5.41

SEM micrographs of air‐dried CNC–PANI–DBSA nanocomposite films depicting preservation of the chiral nematic organization after emulsion polymerization (a, b). However, further doping with, for instance, HCl disrupts the chiral nematic order (c), but maintains good conductive and mechanical properties. These semiconducting nanocomposite films are flexible, and their viscoelastic stress vs. strain responses, at constant mass ratio (CNCs : Aniline = 2) but different molar ratios of DBSA:Aniline, are shown in (d).

Figure 5.42

Chiral nematic mesoporous carbon films prepared by pyrolysis of CNC–silica composites exhibit similar helical twisting morphologies by SEM (a, b). The freestanding films can be used directly without any binders as electrodes in electrical double‐layer supercapacitors (c), and display near‐ideal capacitor behavior (d), with specific capacitances comparable to other state‐of‐the‐art carbon‐based supercapacitors.

Figure 5.43

Confocal laser scanning imaging of KU‐7 bladder cancer cells incubated for 2 h with 0.25 mg/ml of CNC–CTAB–fluorescein nanocomplexes. Micrographs illustrate (a) white light image of the KU‐7 cells, (b) stained nuclei of the cells with 4′,6‐diamidino‐2‐phenylindole (DAPI), (c) fluorescein in the cytoplasm, and (d) overlay of images b and c.

Guide

Cover

Table of Contents

Begin Reading

Pages

ii

iii

iii

iv

v

xiii

xiv

xv

xvi

xvii

xviii

xix

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

39

40

41

42

43

44

45

46

47

48

49

50

51

52

53

54

55

56

57

58

59

60

61

62

63

64

65

66

67

68

69

70

71

72

73

74

75

76

77

78

79

80

81

82

83

84

85

86

87

88

89

90

91

92

93

94

95

96

97

98

99

100

101

102

103

104

105

106

107

108

109

110

111

112

113

114

115

116

117

118

119

120

121

122

123

124

125

126

127

128

129

130

131

132

133

134

135

136

137

138

139

140

141

142

143

144

145

146

147

148

149

150

151

152

153

154

155

156

157

158

159

160

161

162

163

164

165

166

167

168

169

170

171

172

173

174

175

176

177

178

179

180

181

182

183

184

185

186

187

188

189

190

191

192

193

194

195

196

197

198

199

200

201

202

203

204

205

206

207

208

209

210

211

212

213

214

215

216

217

218

219

220

221

222

223

224

225

226

227

228

229

230

231

232

233

234

235

236

237

238

239

240

241

242

243

244

245

246

247

248

249

250

251

252

253

254

255

256

257

258

259

260

261

262

263

264

265

266

267

268

269

270

271

272

273

274

275

276

277

278

279

280

281

282

283

284

285

286

287

288

289

Wiley SeriesinRenewable Resources

Series Editor

Christian V. Stevens—Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium

Titles in the Series

Wood Modification—Chemical, Thermal and Other ProcessesCallum A. S. Hill

Renewables—Based Technology—Sustainability AssessmentJo Dewulf and Herman Van Langenhove

Introduction to Chemicals from BiomassJames H. Clark and Fabien E. I. Deswarte

BiofuelsWim Soetaert and Erick Vandamme

Handbook of Natural ColorantsThomas Bechtold and Rita Mussak

Surfactants from Renewable ResourcesMikael Kjellin and Ingegard Johansson

Industrial Application of Natural Fibres—Structure, Properties and Technical ApplicationsJorg Mussig

Thermochemical Processing of Biomass—Conversion into Fuels, Chemicals and PowerRobert C. Brown

Biorefinery Co‐Products: Phytochemicals, Primary Metabolites and Value‐Added Biomass ProcessingChantal Bergeron, Danielle Julie Carrier, and Shri Ramaswamy

Aqueous Pretreatment of Plant Biomass for Biological and Chemical Conversion to Fuels and ChemicalsCharles E. Wyman

Bio‐Based Plastics: Materials and ApplicationsStephan Kabasci

Introduction to Wood and Natural Fiber CompositesDouglas Stokke, Qinglin Wu, and Guangping Han

Cellulosic Energy Cropping SystemsDouglas L. Karlen

Introduction to Chemicals from Biomass, Second EditionJames Clark and Fabien Deswarte

Lignin and Lignans as Renewable Raw Materials: Chemistry, Technology and ApplicationsFrancisco G. Calvo‐Flores, Jose A. Dobado, Joaquin Isac‐Garcia, and Francisco J. Martin‐Martinez

Sustainability Assessment of Renewables‐Based Products: Methods and Case StudiesJo Dewulf, Steven De Meester, and Rodrigo Alvarenga

Forthcoming Titles

Biorefinery of Inorganics: Recovering Mineral Nutrients from Biomass and Organic WasteErik Meers and Gerard Velthof

Bio‐Based SolventsFrancois Jerome and Rafael Luque

Fuels, Chemicals and Materials from the Oceans and Aquatic SourcesFrancesca M. Kerton and Ning Yan

Nanoporous Catalysts for Biomass ConversionFeng‐Shou Xiao

Cellulose Nanocrystals

Properties, Production, and Applications

WADOOD Y. HAMAD

Cellulosic Biomaterials, FPInnovations, Vancouver, CanadaDepartment of Chemistry, University of British Columbia, Vancouver, Canada

This edition first published 2017© 2017 John Wiley & Sons Ltd

Registered OfficeJohn Wiley & Sons Ltd, The Atrium, Southern Gate, Chichester, West Sussex, PO19 8SQ, United Kingdom

For details of our global editorial offices, for customer services and for information about how to apply for permission to reuse the copyright material in this book please see our website at www.wiley.com.

The right of the author to be identified as the author of this work has been asserted in accordance with the Copyright, Designs and Patents Act 1988.

All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, except as permitted by the UK Copyright, Designs and Patents Act 1988, without the prior permission of the publisher.

Wiley also publishes its books in a variety of electronic formats. Some content that appears in print may not be available in electronic books.

Designations used by companies to distinguish their products are often claimed as trademarks. All brand names and product names used in this book are trade names, service marks, trademarks or registered trademarks of their respective owners. The publisher is not associated with any product or vendor mentioned in this book.

Limit of Liability/Disclaimer of Warranty: While the publisher and author have used their best efforts in preparing this book, they make no representations or warranties with respect to the accuracy or completeness of the contents of this book and specifically disclaim any implied warranties of merchantability or fitness for a particular purpose. It is sold on the understanding that the publisher is not engaged in rendering professional services and neither the publisher nor the author shall be liable for damages arising herefrom. If professional advice or other expert assistance is required, the services of a competent professional should be sought.

The advice and strategies contained herein may not be suitable for every situation. In view of ongoing research, equipment modifications, changes in governmental regulations, and the constant flow of information relating to the use of experimental reagents, equipment, and devices, the reader is urged to review and evaluate the information provided in the package insert or instructions for each chemical, piece of equipment, reagent, or device for, among other things, any changes in the instructions or indication of usage and for added warnings and precautions. The fact that an organization or Website is referred to in this work as a citation and/or a potential source of further information does not mean that the author or the publisher endorses the information the organization or Website may provide or recommendations it may make. Further, readers should be aware that Internet Websites listed in this work may have changed or disappeared between when this work was written and when it is read. No warranty may be created or extended by any promotional statements for this work. Neither the publisher nor the author shall be liable for any damages arising herefrom.

Library of Congress Cataloging‐in‐Publication Data

Names: Hamad, Wadood.Title: Cellulose nanocrystals : properties, production, and applications / Wadood Y. Hamad.Description: Chichester, West Sussex : John Wiley & Sons, Inc., 2017. | Includes bibliographical references and index.Identifiers: LCCN 2016036141| ISBN 9781119968160 (cloth) | ISBN 9781118675700 (epub)Subjects: LCSH: Cellulose–Chemistry. | Cellulose nanocrystals. | Nanocrystals.Classification: LCC TP248.65.C45 H36 2017 | DDC 661/.802–dc23LC record available at https://lccn.loc.gov/2016036141

A catalogue record for this book is available from the British Library.

For Dima, Reemo, and Seby—lovingly inspiring, par excellence

Series Preface

Renewable resources, their use, and modification are involved in a multitude of important processes with a major influence on our everyday lives. Applications can be found in the energy sector, paints and coatings, and the chemical, pharmaceutical, and textile industry, to name but a few.

The area interconnects several scientific disciplines (agriculture, biochemistry, chemistry, technology, environmental sciences, forestry, etc.), which makes it very difficult to have an expert view on the complicated interaction. Therefore, the idea to create a series of scientific books that will focus on specific topics concerning renewable resources has been very opportune and can help to clarify some of the underlying connections in this area.

In a very fast‐changing world, trends are not only characteristic for fashion and political standpoints; science is also not free from hypes and buzzwords. The use of renewable resources is again more important nowadays; however, it is not part of a hype or a fashion. As the lively discussions among scientists continue about how many years we will still be able to use fossil fuels—opinions ranging from 50 to 500 years—they do agree that the reserve is limited and that it is essential not only to search for new energy carriers but also for new material sources.

In this respect, renewable resources are a crucial area in the search for alternatives for fossil‐based raw materials and energy. In the field of energy supply, biomass and renewable‐based resources will be part of the solution alongside other alternatives such as solar energy, wind energy, hydraulic power, hydrogen technology, and nuclear energy.

In the field of material sciences, the impact of renewable resources will probably be even bigger. Integral utilization of crops and the use of waste streams in certain industries will grow in importance, leading to a more sustainable way of producing materials.

Although our society was much more (almost exclusively) based on renewable resources centuries ago, this disappeared in the Western world in the nineteenth century. Now it is time to focus again on this field of research. However, it should not mean a “retour à la nature,” but it should be a multidisciplinary effort on a highly technological level to perform research toward new opportunities, to develop new crops and products from renewable resources. This will be essential to guarantee a level of comfort for a growing number of people living on our planet. It is “the” challenge for the coming generations of scientists to develop more sustainable ways to create prosperity and to fight poverty and hunger in the world. A global approach is certainly favored.

This challenge can only be dealt with if scientists are attracted to this area and are recognized for their efforts in this interdisciplinary field. It is, therefore, also essential that consumers recognize the fate of renewable resources in a number of products.

Furthermore, scientists do need to communicate and discuss the relevance of their work. The use and modification of renewable resources may not follow the path of the genetic engineering concept in view of consumer acceptance in Europe. Related to this aspect, the series will certainly help to increase the visibility of the importance of renewable resources. Being convinced of the value of the renewables approach for the industrial world, as well as for developing countries, I was myself delighted to collaborate on this series of books focusing on different aspects of renewable resources. I hope that readers become aware of the complexity, the interaction and interconnections, and the challenges of this field and that they will help to communicate on the importance of renewable resources.

I certainly want to thank the people of Wiley’s Chichester office, especially David Hughes, Jenny Cossham, and Lyn Roberts, in seeing the need for such a series of books on renewable resources, for initiating and supporting it, and for helping to carry the project to the end.

Last, but not least, I want to thank my family, especially my wife Hilde and children Paulien and Pieter‐Jan, for their patience and for giving me the time to work on the series when other activities seemed to be more inviting.

Christian V. StevensFaculty of Bioscience EngineeringGhent University, BelgiumSeries Editor “Renewable Resources”June 2005

Foreword

This monograph tells the compelling story of the importance of cellulose nanocrystals as a material with many and diverse industrial applications, and hence a very significant potential market value. It lays out in profound depth the unique physical and chemical characteristics that underlie this importance and provides the understanding to assess the potential of specific, new opportunities.

The monograph is an important and timely publication. It presents the state of technical knowledge and understanding about cellulose, the production process to extract cellulose nanocrystals from natural sources of cellulose, the characterization of the nanocrystals, and the assessment of their potential application in industrial products and processes. It is a timely publication because cellulose nanocrystals are a key member of the family of cellulosic nanomaterials which are rapidly moving from a focus of scientific research toward commercial production and their introduction into commercial applications.

It is timely because world interest in cellulosic nanomaterials has grown significantly over the past few years, and we are now able to confidently predict the size range of the global economic value of their production and application, which is vast. Because of this potential economic value, industrial enterprises in a number of countries are focusing on developing their capacity to participate in this activity both in terms of the production and use of these nanomaterials. In moving forward, these firms need access to the best information available on these materials and international trade will depend on a consistent ability to specify and certify the materials produced for the full spectrum of application areas. In addition, this trade and other factors will lead to the need for coherent international science‐based standards and regulations related to the production and use of these materials: a requirement that is already recognized at both the national and international levels within, for example, the ISO Technical Committees.

The world of nanotechnology has been a focus of interest for both governments and private sector organizations for well over a decade now. In its early days, the world perspective focused on the potential importance of nanoparticles, such as nano‐silver and nano‐gold, and on areas related to carbon nanomaterials, most importantly single‐walled carbon nanotubes, which were seen to have immense potential as structural materials as well as important elements of other so‐called high technology domains such as nano‐electronics. The contribution of nanomaterials to the global economy has grown considerably over the intervening decade and is now estimated to have an annual value of many hundreds of millions of dollars. However, the future potential of these early materials seems to have been overestimated, and we are now beginning to see new areas coming into play as future major contributors. Among these nanomaterials which offer important new potential are graphene and other two‐dimensional materials as well as those derived from supramolecular assembly.

Surprising to many, the availability of cellulosic nanomaterials is seen as part of this major family of potentially important new materials with applications in a very broad range of industries. Apart from their physical and chemical characteristics, this family of materials has two other important attributes. First, they are based on natural, renewable materials and can be derived from many cellulose sources including trees and other fibrous cellulose plants such as flax and cotton that already have a substantial industrial base for their collection and processing. Second, their base material, cellulose, is also a product that has widely dispersed applications from paper and rayon through to cellulose additives in food, cosmetics, and so on. It is widely used and is recognized to have very little or no inherent human toxicity.

The monograph is also important because it presents a new approach in providing the base of technical information required for assessing the potential value of new products or processes based on cellulose nanocrystals. Innovation in nanotechnology offers a vast spectrum of potential applications which each need to be assessed for their potential as well as their market value. The challenge faced by innovators is the assessment of possible new innovations in a world market, a process that needs the base of technical information in a form that facilitates such assessment. The monograph, focused on cellulose nanocrystals, provides such an in‐depth and detailed information base and can be seen as a model for the characterisation of nanomaterials with a broad spectrum of potential applications.

The monograph takes us through the full spectrum of technical information that is the base upon which the potential of cellulose nanocrystals is built. It goes from perspectives on the importance and value of nanotechnology, the nanostructure and self‐assembly in cellulosics, the hydrolytic extraction of cellulose nanocrystals, and the morphological characteristics of cellulose nanocrystals to finally the applications of this material. In bringing this information forward, Dr. Hamad takes us systematically into a much greater detailed depth than other treatments of cellulosic nanomaterials. This is critical since, in doing so, he provides the basic information for others to assess the potential of cellulose nanocrystals in applications of interest.

This approach sets the monograph apart from other work and, as already suggested, in many ways establishes it as a model for presenting the characterization of nanomaterials and, more generally, nanotechnology. Nanotechnology is an enabling technology. It is showing progressively more and more potential across the application of enhanced technological knowledge through most, if not all, industrial sectors and into areas of sociological potential. Much of what is written about nanotechnology and its potentially unique contributions provides examples to bolster that perspective. This approach raises the interest in nanotechnology across all of the key communities in innovation from the scientific community, the industrialists, government policy, and public awareness. This positioning of nanotechnology is critical.

However, from the perspective of innovators who are focused on specific potential applications, it is significantly lacking in that it does not provide the core, detailed information that would allow them to assess the potential value of individual applications. The monograph sets out to do precisely that for cellulose nanocrystals, and it will be an essential handbook as we go from early potential applications through the subsequent generations of greater technology‐added value. Chapter 5 of the monograph presents a focused approach to this. It not only draws out the key characteristics that underlie potential applications in a very broad spectrum of domains and are provided in the earlier chapters, but it also builds on this base knowledge and explains how the assessment of the potential of the characteristics can be broken down for specific cases.

Clive Willis, PhDVice President—Research (1993–1997),National Research Council of Canada (NRC)Director General (2003–2005),NanoQuébecConvenor for Group 1,Terminology and Nomenclature,ISO Technical Committee 229 on Nanotechnology

Prologue

Cellulose, the most abundant biopolymer on Earth, has had decades of rigorous research leading to successful and remarkable developments. Paper, exceptionally important for humankind, for well over a millennium, both in the development of tangible goods and in intangible realms such as communication and knowledge, is a well‐known example. Another widely used cellulosic material has been microcrystalline cellulose—discovered by the Canadian‐American chemist Orlando A. Battista more than six decades ago—with applications in food, paints and pharmaceuticals. All cellulosic materials to date have, however, merely served as a passive substrate or filler for the functional component(s) in a variety of applications. Considering the bioavailability and societal relevance of cellulose, turning this renewable resource into an active material is a vital step towards sustainability.