0 100 200 300 400 500 600

-1

-0.8

-0.6

-0.4

-0.2

0

Der

ivat

ive

wei

ght l

oss

(%/℃)

T (℃)

GroundMxGpowder

Bleached MxG powder

CNFA

CNFT

CNC

OHO

OH

OH

O OOH

HOOH

O

Crystalline domainAmorphous domain

Crystalline domain

Wood cell wallsWood

Macrofibrils

Microfibrils

Nanofibers

Cellulose nanocrystal (CNC)

Cellulosenanofiber (CNF)

Preparation of Cellulose Nanofibers and Hydrophobic Nanocrystals from Miscanthus x. GiganteusRyo Kato and Stuart J. Rowan

This work was funded in part using support from the NSF Center for Sustainable Polymers CHE-1413862 and by the Institute for Molecular Engineering at the University of Chicago. We thank Aloterra Energy LLC for the donation of MxG stalks for this study.

3. Preparation of Cellulose Nanofibers from MxG 4. Preparation of Hydrophobic Cellulose Nanocrystals(Collaboration with Coates Group)

2. Background

Two major classes of nanocellulose, cellulose nanofibers (CNF) and cellulosenanocrystals (CNC), nano- or micro-sized fibers have attracted much interest asimportant green nanofillers on account of their sustainability, nontoxicity andbiodegradability. They have been prepared from a wide variety of biosources byvarious chemical and mechanical treatments.

1. Introduction

ü Oxidized cellulose nanofibers (CNFA) were prepared via an ammonium persulfate oxidation protocol from the sustainable Miscanthus x. Giganteus

ü CNFA has a relatively high aspect ratio (ca. 230) and shows a significantly higher reinforcement effect than CNC

ü Alkyl chain modified CNC was prepared via surface acylationü Stable dispersions of these alkyl chain modified CNCs in THF was achievedü Water adsorption was inhibited by the modification

Conclusions Acknowledgements

Sustainable polymers and compositesRenewable source

Polymer (matrix)

ü PLAü Bio-PETü Bio-PE…

Filler (reinforcement)

ü Lignocellulosic plant fibers

ü Industrial co-products or waste

ü Biocarbon …

Fully biobasedcomposite

Ø Thermal resistanceØ Mechanical strengthØ Compatibility

Cellulose nanomaterials

Inherent advantagesü Excellent mechanical properties ü Easy surface modification ü High crystallinity and low density

General isolation and oxidation processSignificant energy input, high cost for chemicals, multiple treatment steps …

Aspect ratios of various CNCs based on sourceSource Aspect RatioWood ca. 20Cotton ca.40

Tunicate ca.80

Chem. Rev. 2010, 110, 3479Polymers 2018, 10, 517

Miscanthus x. Giganteus Cellulose nanofibers

2. Ammonium persulfate oxidation

1. Bleach

(a) (b)

(c) (d)

(a) (b)

(c) (d)

Process CNFA

cf.) Standard CNF Procedure (Three-step)ü Perennial, non-invasive grass

hybrid (cellulose: 50%)ü Grows up to 12 ft. tall in a two

year periodü Dedicated to biomass cropping

Miscanthus x. Giganteus (MxG)

Bleaching APS oxidation

Yield: 25%

(1) (2)

NaClO270℃

(NH4)2S2O890℃

MxG stalk

Two-step chemical treatment

CNFT

(Yield: 23%)(2) Bleaching

(3) TEMPO oxidation

(1) Base treatment

NaClO

NaCl NaBrO

NaBr

NOH

NO

OHO

OH

OH

O OOH

HOOH

O

OHO

OH

O

O OOH

HOOH

O

OHO

R-CH2OH

R-COOH

11.2 nm

-2.5 nm500 nm

Material Length (nm)

Aspect ratio

Carboxylic acid density(mmol/kg)

CNFA ca. 870 230 1200

CNFT ca. 660 210 1100

CNC ca. 300 100 1000

CNFA/polyvinyl acetate (PVAc) composite film

Filler concentrations: 1 wt% (dotted line),5 wt% (dashed line), and 10 wt% (solid line)

AFM (CNFA) TGA

Composite Mechanical properties

Thermal stabilityCNFA > CNC

1000

104

105

106

107

108

109

1010

0

2

4

6

8

10

30 40 50 60 70 80 90

E' (P

a) tan d

T (℃)

103

PVAc

PVAc:CNC-CO2H

PVAc:CNFA-CO2H

PVAc:CNFT-CO2H

PVAcPVAc:CNCPVAc:CNFA

PVAc:CNFT

0

20

40

60

80

100

120

0 1 5 10

E' (M

Pa) a

t 80℃

Filler content (wt%)

PVAc:CNC-CO2H

PVAc:CNFA-CO2H

PVAc:CNFT-CO2H

PVAcPVAcPVAc:CNCPVAc:CNFA

PVAc:CNFT

CNFA shows a significantly better reinforcement capability→ High aspect ratio allows to form a stronger (more crosslinking points) percolating fiber network

Group goal: Synthesis of sustainable polyester/carbonates grafted CNCs to access one-component composites and prevent phase separation in two component systems

ü Moisture adsorption of CNCü Low dispersibility of CNC in (e.g.) THF

CNFA/PVAc(5 wt%)

Sustainable polyesters/carbonates

Chain transfer agents

ü Prevent phase separation during melt press process

ü Improve bulk mechanical properties with CNC nanofiller

Geoffrey Coates Group (Cornell Univ.)

O

R1

OO O

R2 R3

O

R1 O

R2

R3

O

O

+n

catalyst

e.g. THF

Surface acylation of CNC

OHO

OH

OSO3-

O OOH

HOOH

OHO

OH

OH

O OOH

HOOH

OOO

HOOH

OSO3-

O OOH

HOOH

OHO

OHO O

OH

HOOH

OO

O

8

OH

O

O

OO O

8

500100015002000250030003500

Tran

smitt

ance

(a.u

.)

Wavenumbers (cm-1)

CNC-SO3-

CNC-SO3- after DSA treatment without solvent

CNC-SO3- after DSA treatment in anhydride DMF

C=O (ester bonds)

(2-Dodecen-1-yl)succinic anhydride (DSA)

TGA

Issues

Motivation

100 200 300 400 500 600 7000

20

40

60

80

100

Wei

ght l

oss

(%)

T (℃)

20 40 60 80 10095

96

97

98

99

100W

eigh

t los

s (%

)

T (℃)

0.2 wt%

1.2 wt%

3.1 wt%

MoistureTHF (CNC:0.1 wt%)

Before AfterSettle Suspension

Moisture removed after heating to 60℃

We have prepared carboxylic acid functionalizedcellulose nanofibers from a sustainable grasshybrid Miscanthus x. Giganteus (MxG) by usingnew two-step ammonium persulfate (APS)oxidation. This treatment is cleaner, cheaper, anduses less toxic reagents relative to standardmethods.We have also prepared hydrophobic CNCs viareaction with a bio-based succinic anhydridederivative for studies with the Coates groupaimed at growing polyesters from the CNC surface.

H. Yang, Y. Zhang, R. Kato, S. Rowan, Carbohydrate Polymers 2019, 212, 30

Fig. Two-step APS oxidation

mxg-CNC-SO3- mxg-CNC-DSA

CNC-SO3- CNC-DSA