Supporting Information

Transition of cellulose supramolecular structure during concentrated acid treatment and

its implication for cellulose nanocrystal yield

Lida Xing, Chuanshuang Hu*, Weiwei Zhang, Litao Guan, Jin Gu*

College of Materials and Energy, South China Agricultural University, Guangzhou,

510642, PR China

*Corresponding authors: Email: cshu@scau.edu.cn, gujin@scau.edu.cn; Tel.: +86 2085282568;

Fax: +86 2085281885.

4000 3500 3000 1500 1000 500

Tra

nsm

ittan

ce (a

.u.)

Wavenumber (cm-1)

a

b

c

d 2900

1737

1590

1500

1241 89

5 831

3340

1040

Fig. S1 FTIR spectra of a. eucalyptus fibers, b. de-extractive, c. de-lignification, and d.

eucalyptus cellulose fibers. The spectra clearly verify the sequential and complete

removal of lignin (831 cm-1, aromatic C H out-of-plane bending, and 1590 cm-1, aromatic

skeletal vibrations), protein (1500 cm-1) and hemicelluloses (1737 cm-1 and 1241 cm-1,

C=O stretching and C–O stretching in hemicelluloses). The characteristic peaks of

cellulose appear at 3340 cm-1, 2900 cm-1, 1040 cm-1 (stretching vibration of O-H, C-H and

C-O bonds).

10 20 30 40 50

Inte

nsity

(a.u

.)

2 (degree)

200

110110

004

Eucalyptus Cellulose

Eucalyptus fibers

Fig. S2 XRD patterns of eucalyptus fibers and cellulose. Eucalyptus fibers and cellulose

both exhibited typical cellulose Iβ XRD patterns. Cellulose purified from eucalyptus

wood (CrI: 51.1 %) owned a significantly increased CrI (70.8 %), resulting from the

removal of the lignin and hemicelluloses. These data were taken from Xing, Gu, Zhang,

Tu & Hu (2018).

10 15 20 25 30 35

004

CI and CII

CI and CII

}

CI

CI and CII

(60, 10, 45)

2 (degree)

(56, 60, 45)(58, 30, 45)

(60, 20, 45)

(62, 10, 45)

(62, 15, 45)(62, 20, 45)

(64, 10, 45)

(A, t, T)

(64, 20, 45)

(64, 15, 45)

CII

CI}

}110 110

200

004110

110 200

a

Fig. S3 XRD profiles of CSRs prepared at 45 ℃ (a) and 60 ℃ (b) for various acid

concentrations and hydrolysis times. The XRD profiles of CSR (A64, t15, T45) and

(A64, t20, T45) were taken from Xing, Gu, Zhang, Tu & Hu (2018). At 45 °C hydrolysis

temperature, CSRs obtained from 56 and 58 % acid hydrolysis exhibited typical cellulose

I XRD diffraction pattern, with the characteristic diffraction peak at 2θ angles of about

15, 16.5 and 22.5°corresponding to the cellulose I (110), (110) and (200) crystal planes,

respectively. CSR (A60, t10, T45) had typical cellulose II diffraction profile, identified

by the cellulose II diffraction peaks at 2θ=12 and 20° relating to the (110) and (110)

lattice planes. While CSR (A60, t20, T45) was pure cellulose I. All CSRs derived in 62 %

acid hydrolysis contained both cellulose I and II diffraction peaks. The intensity of

cellulose II became lower with extension of hydrolysis time. CSR (A64, t10, T45) was

completely cellulose II. But CSR (A64, t15, T45) and (A64, t20, T45) both contained a

small amount of cellulose I components, as two small diffraction peaks at 2θ=15 and

16.5°. Meanwhile, all CSRs produced at 60 °C were pure cellulose I. The changing

pattern of crystal structure for CSRs shows a similar trend as CNCs.

10 15 20 25 30 35

CI

2 (degree)

(A, t, T)

(62, 10, 60)

(60, 10, 60)

(58, 15, 60)

(56, 15, 60)

110 110

200

004

b

Fig. S4 The length and width distributions of cellulose I and II nanocrystals: CNC-I (A58, t30, T45) (a, b), CNC-I (A64, t10, T60) (c, d) and CNC-II (A64, t10, T45) (e, f).

Fig. S5 XRD profiles of EtC, WC and SHC produced with 62 wt% sulfuric acid at 45 °C for 2,

10 and 30 min. Et-2, WC-2 and SHC-2 were all mixed cellulose I and II with the characteristic

peaks at 12.0, 20.1, 22.0° representing (110), (110) and (200) cellulose II crystal planes, and

14.8, 16.5° relating to (1 10) and (110) cellulose I crystal planes. These results indicate that

cellulose was partially dissolved or swollen with a cellulose I core left, and the swollen part

formed a shell. EtC-10 and WC-10 showed mixed cellulose I and II XRD diffraction patterns,

while SHC-10 exhibited typical cellulose I XRD profile. With extended acid reaction time to 10

min, the surface disordered or swollen cellulose molecules were depolymerized to low molecular

weight products, regenerating to be cellulose II allomorph in ethanol and deionized water

coagulation bath due to lower solubility of glucans in these two solvents. In sodium hydroxide

solution bath, the low molecular weight glucans were dissolved and cellulose I core remained.

Similarly, EtC-30 was cellulose I and II mixture, while WC-30 and SHC-30 showed typical

cellulose I XRD diffraction patterns.

References

Xing, L., Gu, J., Zhang, W., Tu, D., & Hu, C. (2018). Cellulose I and II nanocrystals

produced by sulfuric acid hydrolysis of Tetra pak cellulose I. Carbohydrate Polymers,

192, 184–192.