Supporting Information
Reliable dn/dc values of cellulose, chitin, and cellulose triacetate
dissolved in LiCl/N,N-dimethylacetamide for molecular mass
analysis
Yuko Ono, Takashi Ishida, Hiroto Soeta, Tsuguyuki Saito, and Akira Isogai*
Department of Biomaterials Science, Graduate School of Agricultural and Life Sciences, The
University of Tokyo, Tokyo 113-8657, Japan
Figure S1. Formation of gel-like precipitate by dilution of the original A-chitin solution in 1.0%
w/v LiCl/DMAc to 0.5% w/v LiCl/DMAc.
1
107
(a)
(b)
106
4x10-5
105
2x10-5
104
103
Differental refractive index
0.5x10 g/mL
0.25x10-4
Concentration (g/mL)
Molecular mass (g/mol)
2x10-4
6x10-5
-4
7
8
9
10
1X10-4
5x10-5
dn/dc=0.0084
R2=0.9989
0
0
6
2x10-4
5x10 -4
0
11
1X10 -3
2x10-3
2x10-3
Concentration (g/mL)
Elution volume (mL)
Figure S2. SEC elution patterns and corresponding molecular mass plots for F-MFC dissolved in
0.5% w/v LiCl/DMAc (a), and relationship between F-MFC concentration and differential
refractive index of solutions in 0.5% w/v LiCl/DMAc, determined by the off-line RI method (b).
Molecular mass (g/mol)
(a)
10 6
10 5
(b)
6x10 -5
4x10 -5
10 4
2x10 -5
10 3
0
6
7
8
9
Elution volume(mL)
10
5x10 -4
8x10 -5
11
Differental refractive index
1.1x10-3 g/mL
0.7x10-3
0.5x10-3
0.24x10-3
-3
0.13x10
Concentration (g/mL)
10 7
4x10 -4
3x10 -4
2x10 -4
1X10 -4
dn/dc=0.0911
R2=0.9997
0
0
1X10 -3
2x10 -3 3x10 -3 4x10 -3 5x10 -3
Concentration (g/mL)
Figure S3. SEC elution patterns and corresponding molecular mass plots for A-chitin dissolved
in 1.0% w/v LiCl/DMAc (a), and relationship between A-chitin concentration and differential
refractive index of A-chitin in 1.0% w/v LiCl/DMAc, determined by the off-line RI method (b).
2
Differental refractive index
1.5x10 -3
in 1.0% LiCl/DMAc
in water
1.0X10 -3
dn/dc=0.1461
R2=0.9999
5.0x10 -4
dn/dc=0.0666
R2=0.9998
0
0
2x10 -3 4x10 -3 6x10 -3 8x10 -3
10 -2
Concentration (g/mL)
Figure S4. Relationship between cellobiose concentration and differential refractive index for
cellobiose solutions in 1.0% w/v LiCl/DMAc and water, determined by the off-line RI method.
Differental refractive index
8x10 -3
6x10 -3
4x10 -3
2x10 -3
dn/dc=0.390
R2=0.9996
0
0
4.0x10 -3 8.0x10 -3 1.2x10 -2 1.6x10 -2
Concentration (g/mL)
Figure S5. Relationship between LiCl concentration and differential refractive index of
LiCl/DMAc solution, determined by the off-line RI method.
3
Calculation of the Amount of LiCl Apparently Bound to One Repeating Unit of
Cellulose and Chitin in 0.5% and 1.0% w/v LiCl/DMAc. It was assumed that 1g of cellulose
or chitin apparently bind with a g LiCl in a LiCl/DMAc solution. Then, the solute concentration
should be corrected to (1+a) g. Because a g LiCl is apparently bound to 1 g cellulose or chitin,
the differential refractive index of the surrounding LiCl/DMAc decreases from the original dn/dc
value for the 0.5% or 1.0% w/v LiCl/DMAc by [the dn/dc value of LiCl (0.390 mL/g) × a]
(mL/g) during off-line RI analysis. This decrease in the LiCl concentration of the surrounding
solvent, caused by consumption of LiCl through the formation of covalent bond-like celluloseLiCl or chitin-LiCl structures in the LiCl/DMAc solution, cannot be ignored in the off-line RI
method, because of the high cellulose or chitin concentrations used in the analysis. Nnamely, the
large amounts of hydroxyl groups of cellulose or chitin consume a large amount of LiCl through
the formation of covalent bond-like structures. In contrast, this correction can be ignored for the
dn/dc values determined by the SEC/MALLS/RI method, because of sufficiently dilute cellulose
or chitin concentrations in each SEC elution volume.
Thus, the reference dn/dc values of the 0.5% and 1.0% w/v LiCl/DMAc without cellulose or
chitin molecules in the off-line RI method is overestimated. Correspondingly, the dn/dc values of
cellulose and chitin in, for instance, 1.0% w/v LiCl/DMAc is underestimated from 0.131 and
0.138 mL/g to 0.065 and 0.091 mL/g, respectively (Table 2 in the main text). Thus, the reference
dn/dc value of 1.0% w/v LiCl/DMAc should be corrected by subtracting the [dn/dc value of LiCl
(0.390 mL/g) × a] (or dLiCl × a), from the measured dn/dc value of the reference 1.0%
LiCl/DMAc, The dn/dc value of 1 g cellulose or chitin determined by the SEC/MALLS/RI
method, corrected to be (1+a) g as solute [or dMALLS/(1+a)], should be the same as the corrected
dn/dc value determined by the off-line RI method as below,
+ × =
1+
1+
4
Figure S6. Schematic models of LiCl concentration gradient in cellulose/LiCl/DMAc solutions,
depending on the cellulose concentration, assuming the formation of covalent bond-like
structures of cellulose-LiCl in the solution.
5