Electronic Supplementary Material (ESI) for Polymer Chemistry.
This journal is © The Royal Society of Chemistry 2014
Electronic Supporting Information
Photoswitchable Nanocomposites made from CoumarinFunctionalized Cellulose Nanocrystals
Mahesh V. Biyani, Christoph Weder, and E. Johan Foster*
Adolphe Merkle Institute, University of Fribourg, Rte de l'Ancienne Papeterie, CH-1723 Marly 1,
Switzerland
*Corresponding Author: [email protected]
SI-Table 1. Swelling Data of EO-EPI/Cou-CNC nanocomposites before and after UV exposure
after the equilibrium swelling in deionized water for 48 h at 25 °C.
Sample
Before UV irradiation
swelling % (w/w)
After UV irradiation a
swelling % (w/w)
EO-EPI/Cou-CNC 10% w/w
22 ± 2
10 ± 2
EO-EPI/Cou-CNC 20% w/w
24 ± 2
11 ± 1
a
These experiments were performed after 240 min of UV exposure (8W, 365 nm) at room
temperature. Data represent averages N = 4 experiments ± s.d.
SI-Table 2. Summarizes weight and volume fraction of the CNCs present in nanocomposites.
a
Sample
Weight fraction
of coumarin a
Weight fraction
of CNC
Volume fraction of
CNC
EO-EPI/Cou-CNC 10% w/w
0.007
0.093
0.091
EO-EPI/Cou-CNC 20% w/w
0.014
0.186
0.183
Weight fraction of coumarin present in nanocomposites was determined by data obtained from
SI-Fig. 4.
a
O
b
c
O
i
d
O
O
N
H
e
g
f
f
f
f
h
h
a
ic
d
b
7.70
8.04
N
C
O
6.42
2.50
3.33
7.21
7.14
e
1.33
3.07
1.54
7.94
1.02 0.92 0.99 1.02 1.02
8.0
7.5
7.0
1.02
6.5
2.26 1.97
6.0
5.5
4.0
4.5
5.0
Chemical Shift (ppm)
3.5
3.0
f
f
g
0.00
2.5
4.244.36
2.0
1.5
SI-Fig. 1. 1H-NMR spectrum of 7-coumaryl-(6-isocyanatohexyl) carbamate (Cou-NCO) in
DMSO-d6.
Wavenumber (cm-1)
4000
100
3500
3000
2500
2000
1500
1000
% Transmittance
80
60
40
20
CNC
Cou-CNC
Cou-NCO
1700 cm-1
SI-Fig. 2. ATR FT-IR spectra of neat CNCs, Cou-NCO, and Cou-CNCs. A comparison shows
that the Cou-CNC spectrum feature a characteristic peak associated with the carbonyl group at
1700 cm-1, which is absent in the spectrum of the neat CNCs, and also an increase of the bands
between 2800-2950 cm-1 corresponding to alkyl chain vibrations.
3.12 µg/mL Cou-NCO
6.25 µg/mL Cou-NCO
12.5 µg/mL Cou-NCO
25.0 µg/mL Cou-NCO
250 µg/mL Cou-CNC
2.0
Absorbance (a.u.)
1.5
1.0
0.5
0.0
275
300
325
Wavelength (nm)
350
375
SI-Fig. 3. (a) UV-Vis absorption spectra of a DMF dispersion of Cou-CNCs (concentration = 250
µg/mL) and solutions of Cou-NCO in DMF (concentration = 3.12-25.0 µg/mL). As can be seen
from the spectra, both the Cou-CNCs and Cou-NCO show an absorbance with maximum around
318 nm, which is characteristic of the coumarin moiety.
SI-Fig. S4. Plot showing the absorbance of Cou-NCO solutions at 318 nm as a function of CouNCO content (black, filled squares) date extracted from the SI-Fig. S3 and of a 250 µg/mL CouCNC dispersion (black, open circle). The data were used to determine the level of
functionalization of Cou-CNCs.
Sample calculation for determining the coumarin content on Cou-CNC surface:
From the UV calibration curve of Cou-NCO, we determine 18 µg of coumarin present in 250
µg/mL of Cou-CNC dispersion.
Therefore the amount of coumarin present in 1 g/L of Cou-CNC = 18 × 106 × 4 = 72 g
Concentration of coumarin in mmol/kg = 76/molecular weight of Cou-NCO×1000
= 76/330.34 × 1000
= 217 mmol/kg
Therefore 217 mmol/kg of coumarin is estimated for the Cou-CNC.
(a)
Casting
+
70 ºC, 24 h
Cou-CNC dispersed in EO-EPI in DMF
DMF via sonication
(b)
Neat EO-EPI
EO-EPI/Cou-CNC
10% w/w
EO-EPI/CNC +Coumarin
10% w/w
SI-Fig. 5. (a) Schematic representation of the preparation of EO-EPI/Cou-CNC nanocomposite
films. (b) Photographs of films of the neat EO-EPI (600 µm) and nanocomposites of EO-EPI with
10% w/w Cou-CNCs (65 µm) or neat CNCs and unbound coumarin (50 µm).
Absorbance at 318 nm
1.6
Two side irradiaton
One side irradiaton
1.4
1.2
1.0
0.8
EO-EPI/CNC 10% w/w
0.6
0
50
100
150
200
250
Time (min) for UV irradiation at 302 nm
SI-Fig. 6. Plot showing the optical absorption of a 65 µm thick, 10% w/w EO-EPI/Cou-CNC
nanocomposite film at 318 nm as function of exposure time to the light of one or two 365 nm UV
lamps (8 W, RT). Black, filled squares represent data obtained upon irradiation with two lamps
from both sides of the sample, whereas red, filled circles represent data acquired upon irradiation
from one side only. Black, filled star represents the corresponding absorbance of a reference film
made from a 10% w/w EO-EPI/CNC nanocomposite (i.e. with unmodified CNCs).
SI-Fig. 7. Dynamic mechanical analysis (DMA) traces of a neat EO-EPI reference film as a
function of temperature before (black curve) and after exposure to UV light (8 W, 240 min, RT)
at 365 nm (red curve), at 254 nm (blue curve).
E' (MPa)
103
102
EO-EPI/Cou-CNC+Free Coumarin 10% w/w before UV
EO-EPI/Cou-CNC+Free Coumarin 10% w/w after UV
-60
-40
-20
0
20
40
60
80
100
Temperature (°C)
SI-Fig. 8. Dynamic mechanical analysis (DMA) traces of films of a nanocomposite comprising
EO-EPI, 10% w/w Cou-CNCs, and free coumarin 3.4% w/w (10 moles relative to the amount of
coumarin on the Cou-CNC) in the as-prepared state (black, filled squares) and after irradiation
(red, open squares) with light of a 365 nm UV lamp (8 W, 240 min, RT). Shown are plots of the
storage modulus E′ against temperature.
E' (MPa)
103
102
EO-EPI/CNC+Free Coumarin 10% w/w before UV
EO-EPI/CNC+Free Coumarin 10% w/w after UV
-60
-40
-20
0
20
40
60
80
100
Temperatute (°C)
SI-Fig. 9. Dynamic mechanical analysis (DMA) traces of films of a nanocomposite comprising
EO-EPI, 10% w/w unmodified CNCs, and free coumarin 3.4% w/w (10 moles relative to the
amount of coumarin on the Cou-CNC) in the as-prepared state (black, filled squares) and after
irradiation (red, open squares) with light of a 365 nm UV lamp (8 W, 240 min, RT). Shown are
plots of the storage modulus E′ against temperature.