a simple one-pot route to highly charged cationic...
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A simple one-pot route tohighly charged cationiccellulose nanocrystals
Latifah Jasmani, Samuel Eyley, RachelWallbridge, Wim Thielemans
Renewable Materials and Nanotechnology ResearchGroup, KU Leuven @ Kulak
Thursday 6th March 2014L. Jasmani, S. Eyley, R. Wallbridge, W. Thielemans, Nanoscale, 2013, 5,
10207–10211.
IntroductionCellulose nanocrystalsPrevious one-pot cationizations of CNCs
Our methodology
Results
Conclusion
Outline
IntroductionCellulose nanocrystalsPrevious one-pot cationizations of CNCs
Our methodology
Results
Conclusion
Sam Eyley Pyridinium grafted CNCs 3 / 20
Cellulose nanocrystals
I Derived from cottonI High cellulose contentI Bleached source commercially available
I Sulfuric acid (10.06 M) hydrolysis at 45 ◦CI Approximately 7nm×7nm cross section dimensionsI Purified by
I CentrifugationsI Dialysis with deionized waterI Mixed-bed ion exchange resin
I Freeze driedI What reactive groups are present on the surface of the
nanocrystals?
Introduction Methodology Results Conclusion
Sam Eyley Pyridinium grafted CNCs 4 / 20
Nanocrystal surface
I Surface hydroxyl groups -∼ 3mmolg−1
I Primary 1 mmol g−1
I Secondary 2 mmol g−1
I Reactive 1−2mmolg−1
I Also consider:I Sulfate estersI Adsorbed waste species
from hydrolysisI Ethanol extraction removes
absorbed species andimproves consistency withesterificationsM. Labet and W. Thielemans, Cellulose, 2011, 18,
607–617.
NOH =n1 + n2
ρNAL1L2c
(L1 + L2d(110)
+L1 + L2d(11̄0)
)
NOH = Total number of surface hydroxyl groupsn1 = Number of 1◦ hydroxyls facing (110) in unit celln2 = Number of 2◦ hydroxyls facing (110) in unit cellc = Unit cell c dimensiond(110) = (110) plane spacingd(11̄0) = (11̄0) plane spacingρ = Density of crystalline celluloseNA = Avogadro’s constantL1 = Width of nanocrystalL2 = Height of nanocrystal
OHOH
O
OH
OO
OHOH
OH OHOH
O
OH
O
OH
O
OH
OMe
OMe OH
OMe
OMe
xylobiose 1,6-anhydroglucose
vanillic acid 3,4,5-trimethoxyphenol
Introduction Methodology Results Conclusion
Sam Eyley Pyridinium grafted CNCs 4 / 20
Nanocrystal surface
I Surface hydroxyl groups -∼ 3mmolg−1
I Primary 1 mmol g−1
I Secondary 2 mmol g−1
I Reactive 1−2mmolg−1
I Also consider:I Sulfate estersI Adsorbed waste species
from hydrolysisI Ethanol extraction removes
absorbed species andimproves consistency withesterificationsM. Labet and W. Thielemans, Cellulose, 2011, 18,
607–617.
NOH =n1 + n2
ρNAL1L2c
(L1 + L2d(110)
+L1 + L2d(11̄0)
)
NOH = Total number of surface hydroxyl groupsn1 = Number of 1◦ hydroxyls facing (110) in unit celln2 = Number of 2◦ hydroxyls facing (110) in unit cellc = Unit cell c dimensiond(110) = (110) plane spacingd(11̄0) = (11̄0) plane spacingρ = Density of crystalline celluloseNA = Avogadro’s constantL1 = Width of nanocrystalL2 = Height of nanocrystal
OHOH
O
OH
OO
OHOH
OH OHOH
O
OH
O
OH
O
OH
OMe
OMe OH
OMe
OMe
xylobiose 1,6-anhydroglucose
vanillic acid 3,4,5-trimethoxyphenol
Introduction Methodology Results Conclusion
Sam Eyley Pyridinium grafted CNCs 5 / 20
Previous one-pot cationizations of CNCs
I Glycidyltrimethylammonium chlorideI First reported by Hasani et al. - DS 0.02 - Surface DS 0.1
M. Hasani, E. D. Cranston, G. Westman and D. Gray, Soft Matter, 2008, 4, 2238–2244.
CelO
OH
N+Cl –
a) 7% NaOH(aq) , 30 min
OHOH
O
OH
OH
O OOH
OH
OH
OH
n
Cel-OH = b) 1 eq. GTMAC, 65°C, 5 h
I Thixotropic suspensionsI BirefringenceI Low degree of substitutionI Hydrolysis of GTMAC by aqueous NaOHI 15 day purification
Introduction Methodology Results Conclusion
Sam Eyley Pyridinium grafted CNCs 5 / 20
Previous one-pot cationizations of CNCs
I Glycidyltrimethylammonium chlorideI First reported by Hasani et al. - DS 0.02 - Surface DS 0.1
M. Hasani, E. D. Cranston, G. Westman and D. Gray, Soft Matter, 2008, 4, 2238–2244.
CelO
OH
N+Cl –
a) 7% NaOH(aq) , 30 min
OHOH
O
OH
OH
O OOH
OH
OH
OH
n
Cel-OH = b) 1 eq. GTMAC, 65°C, 5 h
I Thixotropic suspensionsI BirefringenceI Low degree of substitutionI Hydrolysis of GTMAC by aqueous NaOHI 15 day purification
Introduction Methodology Results Conclusion
Sam Eyley Pyridinium grafted CNCs 6 / 20
Previous one-pot cationizations of CNCs
I Glycidyltrimethylammonium chlorideI Zaman et al. suggest use of “semi-dry” method
M. Zaman, H. Xiao, F. Chibante and Y. Ni, Carbohydr. Polym., 2012, 89, 163–170.
I Limit hydrolysis of GTMACCel
O
OH
N+Cl –
a) NaOH(s) , 5 min
OHOH
O
OH
OH
O OOH
OH
OH
OH
n
Cel-OH = b) DMSO/H2O 3 eq. GTMAC, 65°C, 4 h
I DS 0.35 - Surface DS 0.78 for 5nm widthI No crystallinity informationI 3:1 GTMAC:AGU (DS 0.35)
Introduction Methodology Results Conclusion
Sam Eyley Pyridinium grafted CNCs 6 / 20
Previous one-pot cationizations of CNCs
I Glycidyltrimethylammonium chlorideI Zaman et al. suggest use of “semi-dry” method
M. Zaman, H. Xiao, F. Chibante and Y. Ni, Carbohydr. Polym., 2012, 89, 163–170.
I Limit hydrolysis of GTMACCel
O
OH
N+Cl –
a) NaOH(s) , 5 min
OHOH
O
OH
OH
O OOH
OH
OH
OH
n
Cel-OH = b) DMSO/H2O 3 eq. GTMAC, 65°C, 4 h
I DS 0.35 - Surface DS 0.78 for 5nm widthI No crystallinity informationI 3:1 GTMAC:AGU (DS 0.35)
Introduction Methodology Results Conclusion
Outline
IntroductionCellulose nanocrystalsPrevious one-pot cationizations of CNCs
Our methodology
Results
Conclusion
Sam Eyley Pyridinium grafted CNCs 7 / 20
Our methodology - esterification
I In-situ acid anhydride formation using tosyl chlorideI Reported for acetylation of cellulose fibres by Shimizu and
Hayashi in 1988Y. Shimizu and J. Hayashi, Sen’i Gakkaishi, 1988, 44, 451–456
I 6:6:1 TsCl:AcOH:AGU leads to DS 2−3I Our system: 0.9:0.9:1 TsCl:Acid:AGU
I Two acids containing alkyl bromides
Br
O OH
Br
O OH
Introduction Methodology Results Conclusion
Sam Eyley Pyridinium grafted CNCs 7 / 20
Our methodology - esterification
I In-situ acid anhydride formation using tosyl chlorideI Reported for acetylation of cellulose fibres by Shimizu and
Hayashi in 1988Y. Shimizu and J. Hayashi, Sen’i Gakkaishi, 1988, 44, 451–456
I 6:6:1 TsCl:AcOH:AGU leads to DS 2−3I Our system: 0.9:0.9:1 TsCl:Acid:AGU
I Two acids containing alkyl bromides
Br
O OH
Br
O OH
Introduction Methodology Results Conclusion
Sam Eyley Pyridinium grafted CNCs 8 / 20
Our methodologyI Simultaneous esterification and nucleophilic substitutionI Suspend 0.9:0.9:1 TsCl:Acid:AGU in pyridine
I 80 ◦C for 16 hI Argon atmosphere
SO
O Cl
R Br
OOH
N
N
R N+
O O –
N+
R
O OTs
Br /Cl–
OH Cel
R N+
O–
O+
OTs
H
Cel
Br /Cl–
N
N+
R
O O
Cel
Br /Cl/TsO–
R=H, Me
[PyH]Br
[PyH][Br /Cl]
[PyH][Br /Cl]2[PyH][Br/Cl/TsO]
Introduction Methodology Results Conclusion
Sam Eyley Pyridinium grafted CNCs 9 / 20
Our methodology - purification
I Soxhlet extractionI Dichloromethane -
24 hI Ethanol - 72 hI Dried under vacuum
Introduction Methodology Results Conclusion
Outline
IntroductionCellulose nanocrystalsPrevious one-pot cationizations of CNCs
Our methodology
Results
Conclusion
Sam Eyley Pyridinium grafted CNCs 10 / 20
FTIR - confirmation of esterification
4000 3500 3000 2500 2000 1500 1000 500
Wavenumbers /cm-1
v(C=O) v(C=C)
CNCs [Br/Cl/TsO][BnPy]-g-CNCs [Br/Cl/TsO][MeBnPy]-g-CNCs
v(C-Br)?ω(C-H arom.)?
Introduction Methodology Results Conclusion
Sam Eyley Pyridinium grafted CNCs 11 / 20
XPS - confirmation of esterification
2000
1500
1000
500
CP
S
296 292 288 284Binding Energy /eV
1800
1600
1400
1200
1000
800
600
400
200
296 292 288 284
Raw data C-C/C=C C-O O-C-O O-C=O Shake-up Background Calculated profile
[Br][BnPy]-g-CNCs [Br][MeBnPy]-g-CNCs
Introduction Methodology Results Conclusion
Sam Eyley Pyridinium grafted CNCs 12 / 20
XPS - confirmation of nucleophilic substitution
I One N 1senvironment
I Binding energyconsistent withpositivelychargednitrogen
500
450
400
350
300
CP
S
406 404 402 400Binding Energy /eV
450
400
350
300
406 404 402 400
402.08 eV402.01 eV
[Br][BnPy]-g-CNCs [Br][MeBnPy]-g-CNCs
Introduction Methodology Results Conclusion
Sam Eyley Pyridinium grafted CNCs 13 / 20
XPS - confirmation of nucleophilic substitution
I One Br 3denvironment
I Binding energyfor 5/2 bandconsistent withbromide
200
150
100
50
CP
S
72 70 68 66Binding Energy /eV
120
100
80
60
40
72 70 68 66
67.38 eV 67.39 eV
5/2 3/2
[Br][BnPy]-g-CNCs [Br][MeBnPy]-g-CNCs
Introduction Methodology Results Conclusion
Sam Eyley Pyridinium grafted CNCs 14 / 20
Elemental Analysis - DS
I DS calculated from elemental analysisI Halogen analysis not specificI Surface DS based on crystallite size from XRD
Product C /% H /% N /% Hal. /% DS DSsurf
[Br][BnPy]-g-CNCs - Found 45.4 5.69 0.71 4.80 – –C7.24H10.96O5.10N0.1Br0.1 - Calc. 46.1 5.86 0.71 4.05 0.10 0.31[Br][MeBnPy]-g-CNCs - Found 48.3 5.46 1.59 8.60 – –C9.84H13.29O5.27N0.27Br0.27 - Calc. 48.9 5.46 1.59 9.07 0.27 0.85
I Difference in DS - solubility of pyridinium intermediateI High substitution - crystallinity affected?
Introduction Methodology Results Conclusion
Sam Eyley Pyridinium grafted CNCs 15 / 20
Structural integrity - XRD
I Crystallinity determined bypattern fitting
I Subtract instrumentalbackground
I Background =Amorphous content
Product % Cryst. % Mod. Total
CNCs 88 0 88[Br][BnPy]-g-CNCs 69 16 85[Br][MeBnPy]-g-CNCs 58 32 90
I Amorphous graftsI No loss of cellulose
crystallinity
Offs
et N
orm
aliz
ed In
tens
ity
403530252015102θ
Raw data Purified [Br][BnPy]-g-CNCs [Br][MeBnPy]-g-CNCs
Introduction Methodology Results Conclusion
Sam Eyley Pyridinium grafted CNCs 16 / 20
Surface charge
I Surface charge determined by Orange IIdye adsorption
I Mixed with excess Orange II solutionfor 1 minute
I CNCs removed by filtrationI Difference in concentration measured
by UV-Vis
Product Amount of Dye Surface +ve Charge Density
CNCs 0 mmol g−1 –[Br][BnPy]-g-CNCs 0.49 mmol g−1 1.08 e nm−2
[Br][MeBnPy]-g-CNCs 0.82 mmol g−1 1.81 e nm−2
O
S
O O
N
N
HO
Introduction Methodology Results Conclusion
Sam Eyley Pyridinium grafted CNCs 17 / 20
High surface charge density
I Products form stablesuspension in water aftercomplete drying in vacuo
I 7 % dispersion showsbirefringence when viewedthrough crossed polarizers
Introduction Methodology Results Conclusion
Outline
IntroductionCellulose nanocrystalsPrevious one-pot cationizations of CNCs
Our methodology
Results
Conclusion
Sam Eyley Pyridinium grafted CNCs 18 / 20
Conclusion
I Successfully cationized CNCs using esterificationI DS 0.27 almost as high as Zaman et al. (DS 0.35)
I Over 3 times lower reagent excessI Crystallinity still intact
I Lower grafting for [Br][BnPy]-g-CNCs due to solubility ofintermediate
I Highly charged products able to be re-dispersed in waterfully after complete drying in vacuo
Introduction Methodology Results Conclusion
Sam Eyley Pyridinium grafted CNCs 19 / 20
Future Work
I Absolute identification of anionic composition of productI Study binding affinities for different anionsI Test hydrolytic stability of productsI Optimize reaction conditions - reduce excessI Optimize reaction conditions - cost [Br][MeBn]-g-CNCs
Introduction Methodology Results Conclusion