Electronic Supporting Information
Comparison of Hydrogels Prepared with
Ionic-Liquid-Isolated vs Commercial Chitin and
Cellulose
Xiaoping Shen,†,‡ Julia L. Shamshina,§ Paula Berton,†,║ Jenny Bandomir,† Hui Wang,† Gabriela
Gurau§,║ Robin D. Rogers*,†,║
†
‡
Department of Chemistry, The University of Alabama, Tuscaloosa, AL 35487, USA
Key Laboratory of Bio-based Material Science and Technology (Ministry of Education),
Northeast Forestry University, 26 Hexing Road, Harbin 150040, China
§
║
525 Solutions, Inc., 720 2nd Street, Tuscaloosa, AL 35401, USA
Department of Chemistry, McGill University, 801 Sherbrooke St. West, Montreal, QC H3A
0B8, Canada
* Corresponding author. E-mail: [email protected]
Electronic Supporting Information
Comparison of Hydrogels Prepared with Ionic-Liquid-Isolated vs Commercial Chitin and Cellulose
EXPERIMENTAL
Materials. The IL, 1-ethyl-3-methylimidazolium acetate ([C2mim][OAc], >95%), was
purchased from IoLiTec (Tuscaloosa, AL, USA). Deionized (DI) water with specific resistivity
of 17.38 MΩ cm at 25 °C was obtained from a commercial deionizer (Culligan Co., Northbrook,
IL). Acidic polyoxometalate (POM) in its hydrated form (H5[PV2Mo10O40]·29H2O) was donated
by Japan New Metals Co. (Akita, Japan). Other chemical reagents, including sodium chlorite,
glacial acetic acid, sodium hydroxide (NaOH) pellets (≥ 98%), urea (99.8%), epichlorohydrin
(ECH, ≥ 99%), absolute ethanol, indigo carmine (dye content 91%), and phosphate buffer saline
(PBS) tablets (one tablet was dissolved in 200 mL of DI water producing buffer solution of pH =
7.4), were all obtained from Sigma-Aldrich (St. Louis, MO) and used as received without further
purification.
Pure chitin (from crab shells) and practical grade chitin (PG-chitin; from crab shells) were
purchased from Sigma-Aldrich (St. Louis, MO). PG-chitin was additionally purified by IL
dissolution and regeneration (see below), obtaining the polymer denoted as Rec. PG. Chitin
extracted from shrimp shells (SS, donated by the Gulf Coast Agricultural and Seafood
Cooperative (Bayou La Batre, AL)) using [C2mim][OAc] via the procedure described in our
previous papers1 (see below) was denoted as IL-chitin throughout the text. Microcrystalline
cellulose (MCC) with a degree of polymerization of 270 was purchased from Sigma-Aldrich
(Milwaukee, WI). Cellulose-rich materials (CRM-175 and CRM-POM) were reconstituted from
poplar wood powder (Populus Alba, sapwood supplied by Harbin Yongxu Company, China)
using the procedures described in our previous reports 2 , 3 (see below). All biomass and
biopolymers were ground into powder using a lab mill (Janke & Kunkel Ika Labortechnik,
Wilmington, NC), separated into different particle sizes of < 125, 125‒250, and 250‒1000 µm
using brass sieves (Ika Labortechnik, Wilmington, NC), and stored in an oven (Precision
Econotherm Laboratory Oven, Natick, MA) at 80 °C before use.
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Comparison of Hydrogels Prepared with Ionic-Liquid-Isolated vs Commercial Chitin and Cellulose
Reconstitution of PG-chitin with IL. Since the presence of insoluble traces in the solution
of PG-chitin in NaOH/urea influenced the accuracy of viscosity measurement, PG-chitin was
first reconstituted from its IL solution (Rec. PG-chitin). 0.4 g PG-chitin powder was added into
19.6 g [C2mim][OAc] in a 80 mL beaker. The mixture was heated at 100 °C for 1 h, then
centrifuged at about 2000 rpm for 10 min (Dynac Becton Dickinson Centrifuge model 42010,
Sparks, MD) to precipitate the undissolved residues. The supernatant solution was poured into
200 mL DI water to regenerate chitin from the solution. After stirring overnight, chitin was
washed with DI water over ten times through centrifugation. The yield of Rec. PG-chitin was
about 49.5%.
Extraction of IL-chitin. Shrimp shells (SS) were dried at a specialized facility by pressing
with a screw press and in a fluidized bed dryer at 160 °C until the material had a final moisture
content of less than 5 wt%. This dried material was then pulverized with a hammer mill to
particles with diameters ≤ 0.635 cm before shipping to The University of Alabama. 1.3 g of
oven-dried SS powder was mixed with 63.7 g of [C2mim][OAc] in a 125 mL Erlenmeyer flask.
The mixture was heated via microwave irradiation at 2‒3 s pulses with manual stirring between
each pulse for 5 min until a honey-like solution was formed. The warm and flowable solution
was transferred into two 50 mL centrifuge tubes and centrifuged at about 2000 rpm for 10 min to
remove undissolved residues. The solution was carefully decanted into 400 mL of deionized (DI)
water and stirred overnight. After settling for 4 h, the aqueous supernatant was carefully decanted
and the remaining suspension was transferred into centrifuge tubes for centrifugation to remove
the aqueous phase. Subsequently, fresh DI water was added to each of the centrifuge tubes and
the resultant suspension was sonicated (Branson Sonicator 5510-DTH, Danbury, CT) for 20 min.
Centrifugation, aqueous phase removal, fresh DI water addition, and sonication steps were
consecutively repeated 10 more times. The regenerated chitin was oven-dried overnight at 90 °C,
ground and sieved into particles with three different diameters of < 125, 125‒250, and > 250 µm.
Ash content was determined as the final constant mass obtained by heating the dry sample in
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Comparison of Hydrogels Prepared with Ionic-Liquid-Isolated vs Commercial Chitin and Cellulose
a crucible in a muffle furnace at 525 °C.4 Chitin content was determined according to the Black
and Schwartz methodology.5
Preparation of CRMs. The mixture of 0.5 g wood powder and 10 g [C2mim][OAc] in a 50
mL beaker was heated in an oil bath at 175 °C for 30 min with vigorous stirring. The biopolymer
was then regenerated in 100 mL of water/acetone (1:1, v/v) and filtered to obtain CRM-175. The
mixture of 0.5 g wood powder, 10 g [C2mim][OAc] and 0.05 g POM was heated at 110 °C for 2
h under stirring, and CRM-POM was obtained after regeneration in the same way.
Determination of lignin content. The lignin content of the original wood and CRMs were
determined by a scaled down TAPPI method.6 0.1 g of dried wood or CRM was placed into a 20
mL vial, and 1.5 mL (for wood) or 2.0 mL (for CRM) of 72 wt% H2SO4 aqueous solution was
added. The mixture was stirred at room temperature for 2 h and then transferred to a 200 mL
round-bottomed flask. The mixture was subsequently diluted with 56 mL (for wood) or 75 mL
(for CRM) of DI water, and refluxed for 4 h. The resulting mixture was filtered and dried. Acid
insoluble lignin (Klason lignin; LK) was determined gravimetrically. The filtrate was diluted to
200 mL with DI water, and the acid soluble lignin (LAS) was calculated from UV absorbance
using the Cary 3C UV-visible Spectrometer (Palo Alto, CA) at 205 nm in Eq. (1):
LAS  100%  [(
A
 0.2 ) / 0.1]
110
(1)
where A is the UV absorbance of the diluted filtrate, 110 is the extinction coefficient (L g-1 cm-1)
of the lignin solution, 0.2 is the volume (L) of the diluted filtrate, and 0.1 is the mass (g) of the
dried wood or CRM material used.
Determination of hemicellulose content. The determination of hemicellulose content was
based on NaClO2 delignification and NaOH treatment.2,7 1 g dried biomass and 37.5 mL DI
water were transferred to a 100 mL round-bottom flask equipped with a 25 mL Erlenmeyer flask
inverted in the neck of the reaction flask. 0.25 mL glacial acetic acid and 0.3 g sodium chlorite
were added successively into the mixture. The flask was placed in an oil bath and heated at 75 °C
for 1 h with magnetic stirring. An additional 0.25 mL glacial acetic acid and 0.3 g sodium
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Comparison of Hydrogels Prepared with Ionic-Liquid-Isolated vs Commercial Chitin and Cellulose
chlorite were added and the reaction mixture was heated for another 1 h. The addition of
chemicals and one-hour heating were repeated 2 more times. After reaction, the flask was placed
in a refrigerator to cool the reactants below 5 °C. The product was filtered using nylon filter
paper, and washed with DI water and acetone successively. The resulting holocellulose (i.e.,
hemicellulose and cellulose) was oven-dried at 90 °C overnight and weighed.
12.5 mL NaOH aqueous solution (17.5 wt%) was added to a 100 mL beaker containing 0.5 g
holocellulose obtained as above. The mixture was stirred at room temperature for 40 min, then
12.5 mL DI water was added to it. After 5 min, the residue was filtered, followed by adding 20
mL acetic acid aqueous solution (10 wt%). The residue was filtered again, and washed with 500
mL boiling water during filtration. The resulting cellulose was oven-dried at 90 °C overnight and
weighed. The content of hemicellulose was the difference between the contents of holocellulose
and cellulose.
Selection of NaOH/urea System for each Biopolymer. Eight freshly-prepared NaOH/urea
aqueous systems (2/0, 2/2, 4/4, 6/4, 7/12, 8/4, 12/6, 20/0 wt% NaOH/wt% urea) were used to
dissolve 1 wt% of each biopolymer by freeze/thaw (F/T) treatment as follows: 0.02 g of
biopolymer powder was added to 1.98 g of NaOH/urea solvent in a vial and the mixture was
stirred at room temperature for 2 min. The mixture was then frozen by immersing the vial in a
dry ice/ethanol cold bath (ca. -72 °C) for 3 min, followed by thawing at room temperature (ca. 8
min) and subsequent vigorous stirring (5 min). The F/T cycles were repeated several times to
achieve full dissolution. If the biopolymer was not dissolved after 12 F/T cycles, it was then
designated as insoluble.
Viscosity determination of biopolymer solutions. Viscosity values of biopolymer solutions
(1 wt%) in NaOH/urea systems were determined using a Cambridge Viscosity Viscometer
(VISCOlab 3000, Medford, MA). The sample chamber of the viscometer was cooled by using
PVC tubing which was filled with coolant mixture (a 50% v/v mixture of ethylene glycol/H2O)
and chilled in a refrigerator before use. This tubing was wrapped around the stainless steel
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Comparison of Hydrogels Prepared with Ionic-Liquid-Isolated vs Commercial Chitin and Cellulose
exterior of the viscometer chamber to cool it below 10 °C. Approximately 0.7 mL of the
biopolymer solution was transferred into the cooled chamber with a 1.0 mL syringe. The correct
sized piston according to the expected viscosity range was selected and introduced into the
chamber. Then the chamber was heated by the movement and friction between the piston and the
solution during measurement. The viscosity and error values with the increase of temperature
were recorded.
Determination of Maximum Concentration Values. To determine the maximum
concentration of a biopolymer that could be dissolved in the optimized NaOH/urea system using
the F/T treatment, a 1 wt% biopolymer solution in NaOH/urea was initially prepared. Then,
biopolymer was added to increase 0.1 wt% of its concentration in the solution, followed by its
dissolution through F/T treatment. The addition of biopolymer was repeated until the solution
solidified immediately after thawing at room temperature.
Preparation of Physical Hydrogels. The maximum biopolymer concentrations that could be
dissolved in the corresponding NaOH/urea system were used to form physical hydrogels. 1 g of
the biopolymer/NaOH/urea solution was heated at temperatures of 30‒60 °C for different times,
until firm hydrogels were formed. If after 24 h heating no firm gelation was observed, it was
determined that no gel formation was possible using that biopolymer solution.
The minimum biopolymer concentration needed to get firm physical hydrogels was also
determined. 1 g of biopolymer/NaOH/urea solutions at concentrations of 1‒4 wt% were heated at
50 °C (for cellulose) or 60 °C (for chitin) for 4 h. The resulting hydrogels were transferred with a
lab spoon into 100 mL of DI water. The water was changed every 8 h until the pH value was
neutral (usually after 3 times).
Preparation of Chemical Hydrogels. Biopolymers were dissolved in the corresponding
NaOH/urea at different concentrations (1 and 2 wt% chitin solutions, 4 wt% MCC and
CRM-POM solutions, and 1 wt% CRM-175 solution) using the F/T technique. Then, 0.1 g ECH
(in excess relative to the ‒OH groups of the biopolymer in solution) was added as a cross-linker
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Comparison of Hydrogels Prepared with Ionic-Liquid-Isolated vs Commercial Chitin and Cellulose
to 1 g of the biopolymer solution and stirred at room temperature for 5 min. After removing the
stir-bar, the solution was heated at 60 °C for 2 h (for chitinous solutions) or at 50 °C for 1 h (for
cellulosic ones) in an oil bath. The obtained hydrogels were washed with 100 mL DI water for 24
h until neutral pH was achieved.
Drying of hydrogels. After washing, three different drying techniques were used, i.e.,
oven-drying (80 °C, overnight), freeze-drying (here kept rotating on a rotary evaporator under
vacuum when immersed into 0 °C bath), and supercritical-drying using CO2 (ScCO2-drying). No
pretreatment of the hydrogels was needed before oven drying, while for freeze-drying, the
hydrogel was frozen in liquid nitrogen before dehydrating. In the case of ScCO2-drying, the
hydrogel was immersed in absolute ethanol (ca. 20 mL), and the ethanol was renewed two more
times every 3 h, resulting in the formation of an alcogel. The alcogel was Sc-CO2 dried using a
DCP-1 critical point dryer (Denton Vacuum Inc., Moorestown, NJ).
The alcogel was Sc-CO2 dried using a DCP-1 critical point dryer (Denton Vacuum Inc.,
Moorestown, NJ). The sample chamber and its exhaust valve were immersed in a water bath (at
room temperature), and connected to a liquid CO2 tank. After sealing the chamber for 10 min,
the chamber exhaust valve was slightly opened to slowly bleed off the ethanol along with liquid
CO2 (for 5 min). The chamber pressure was maintained within 800‒900 psi all along. This
sealing/bleeding process was repeated 4 times, until ethanol was completely replaced by CO2.
Once the drying was completed, all valves were closed; the cold water in the water bath was
removed and replaced with hot water (ca. 50 °C). After the pressure in the chamber rose over
1800 psi, the exhaust valve was slightly opened to slowly vent the chamber, with pressure
dropping not faster than 100 psi/min. The obtained aerogel was stored in a sealed vial before use.
Calculation of ECH consumption. During hydrogel formation, the loss of biopolymers in
the gel was caused by the removal of the stir bar before thermal gelation. Therefore, the real
mass of ECH reacted with biopolymers in the chemical gels (mECH) was estimated under the
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Comparison of Hydrogels Prepared with Ionic-Liquid-Isolated vs Commercial Chitin and Cellulose
assumption that the mass of biopolymers in the chemical gel was equal to that in the physical gel
of the same biopolymer concentration, which was calculated in Eq. (2):
mECH  M ECH  nECH  M ECH 
mgel
mchemical  m physical
,
 M ECH 
M gel
M ECH  M Cl  M H
(2)
where MECH is the relative molecular mass of ECH (92.5 g/mol), nECH the mole number of ECH,
Δmgel the mass gain of the chemical gel due to the cross-linking compared with the physical gel,
ΔMgel the relative molecular mass gain of the biopolymer in the chemical gel due to the
cross-linking, mchemical the real mass of the chemical gel, mphysical the real mass of the physical gel.
MCl and MH are the relative molecular mass of chlorine (35.5 g/mol) and hydrogen (1 g/mol),
respectively.
Shrinkage, Density, and Porosity. The shrinkage of the alcogels (Salco) and aerogels (Saero),
in comparison with the original hydrogels, was calculated using Eqs. (3) and (4), respectively:
Salco (%)=
Saero (%)=
Valcogel -Voriginal
Voriginal
Vaerogel -Voriginal
Voriginal
 100%
(3)
 100%
(4)
where Voriginal, Valcogel, and Vaerogel are the volumes of the original hydrogel, alcogel, and aerogel,
respectively.
The density and porosity of the aerogels were calculated using Eqs. (5) and (6), respectively:
 aerogel (g / cm3 )=
Porosity (%)= (1-
M aerogel
Vaerogel
 aerogel
)  100% 8
 OD
(5)
(6)
where δaerogel, Maerogel, and Vaerogel are the density, mass, and volume of the aerogel, respectively,
and δOD is the density of the corresponding oven-dried gel (assuming no pores were present).
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Comparison of Hydrogels Prepared with Ionic-Liquid-Isolated vs Commercial Chitin and Cellulose
Rehydration Measurement. An aerogel was immersed in a sealed vial filled with 20 mL DI
water at room temperature for 24 h to fully rehydrate. Then the rehydrated hydrogel was taken
out with a lab spoon and the water on the surface was gently removed using a Whatman filter
paper. The rehydration kinetics of the hydrogel were studied by plotting the mass recovery of the
rehydrated hydrogel at each time interval during rehydration, which was calculated using Eq. (7):
Mass Recovery %  =
Mt
M original
 100%
(7)
where Mt and Moriginal are the masses of the rehydrated hydrogel at time t and the original
hydrogel, respectively. When the hydrogel reached saturation (final time), the mass recovery of
the fully rehydrated hydrogel was obtained.
The rehydration ratio was calculated using Eq. (8):
Rehydration Ratio % =
M rehydrated
M aerogel
 100%
(8)
where Mrehydrated and Maerogel are the masses of the fully rehydrated hydrogel and the aerogel,
respectively.
Dye loading and release. 0.005 g indigo carmine dye was dissolved in 5 mL phosphate
buffer saline (PBS) solution (pH 7.4) with stirring, to obtain a dye/PBS solution of 1 mg/mL.
Further dilutions (0.015, 0.01, 0.008, 0.005, 0.002, and 0.001 mg/mL) were then prepared, and a
standard calibration curve of dye concentration was acquired by measuring the absorbance of
these 6 groups of dilute dye solutions at 610 nm using a Cary 3C UV-visible Spectrophotometer
(Palo Alto, CA). The obtained calibration curve (Fig. S1) showed a good linear correlation
(R2=0.99633).
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Comparison of Hydrogels Prepared with Ionic-Liquid-Isolated vs Commercial Chitin and Cellulose
Fig. S1. Standard calibration curve of dilute dye (indigo carmine) aqueous solutions.
To load the dye, there were two methods: a) immersing an aerogel in 5 mL of 1 mg/mL dye
aqueous solution, or b) immersing an aerogel in 5 mL of 0.5 mg/mL dye/ethanol solution (due to
the lower saturation concentration) in a sealed vial at 25 °C for 24 h. After loading, the hydrogels
were taken out and wiped gently with filter paper to remove the dye solution on the surface. The
loaded hydrogels from method "a" were transferred into 50 mL fresh PBS to test the dye release,
while the ones from method "b" were ScCO2-dried again to conduct PXRD test.
For release, the beaker containing the loaded hydrogel and PBS solution was placed in a C25
incubator shaker (New Brunswick Scientific Co., Edison, NJ) at 25 °C and 100 rpm. At certain
time intervals, 2 mL of the dye/PBS solution was taken out, diluted to 4 mL with fresh PBS
solution, and analyzed by UV-Vis spectrometry. The withdrawn solutions were replaced with 2
mL fresh PBS solution to maintain constant volume of the release medium. The total loading
mass (Mloading) of the hydrogels was estimated by determining the dye mass remaining in the
loading solution (after dilution). The cumulative dye release of the hydrogel in PBS was then
quantified as mass released at time t (Mt) over Mloading.
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Comparison of Hydrogels Prepared with Ionic-Liquid-Isolated vs Commercial Chitin and Cellulose
Characterization Methods. Powder X-ray diffraction (PXRD) analyses of biopolymers and
aerogels were performed at room temperature using a Rigaku D/MAX-2BX horizontal X-ray
diffractometer (Rigaku Co., Spring, TX) equipped with Cu-Kα radiation (λ= 1.5418 Å). The
samples were scanned within 5–35o (2θ) in continuous mode with a step size of 0.02° and step
time of 3 degrees/s. For scanning electron microscopy (SEM), the surface and cross-section of
ScCO2-dried aerogels were mounted onto an aluminum sample stub with carbon tape. Cellulosic
aerogels were sputter-coated with a gold–palladium alloy to get clearer images (due to the higher
magnification used) using an Anatech Hummer 6.6 sputter coater (Union City, CA). Samples
were placed into the sample chamber of the Hitachi S-2500 Scanning Electron Microscope
(Hitachi Ltd., Tokyo, Japan). SEM was operated at 10 kV accelerating voltage and under high
vacuum in the chamber.
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Comparison of Hydrogels Prepared with Ionic-Liquid-Isolated vs Commercial Chitin and Cellulose
RESULTS AND DISCUSSION
Composition of biopolymers
Table S1. Chemical Composition of Chitin and Cellulosic Materials.
Ash contentb
Chitin
(%)
contentb (%)
N/A
34.5(7)
27.2(9)
C, N, O, Si, Ca, Mg
Pure chitin
N/A
0.3(1)
81.8(4)
C, N, O
PG-chitin
N/A
2.2(4)
78.9(7)
C, N, O, Si, Cl, Ca
IL-chitin
20.8(8)
89.1(5)
C, N, O ,Si
Chitin
Yielda (%)
Shrimp shell
Cellulosea
a
CRM yield
0.5(2)
a
Lignin yield
d
Lignin
b
Containing elementsc
Hemicellulose
b
Cellulose
(%W)
(%L)
content (%)
content (%)
contentb (%)
Poplar wood
N/A
N/A
22.3(6)
30.3(7)
47.4(1)
CRM-175
57.6(4)
35.9(5)
12.2(3)
27.0(6)
60.8(3)
CRM-POM
60.7(8)
1.0(1)
13.7(4)
6.2(6)
80.1(2)
Yield: mass percentage of the recovered biopolymer to the raw material;
b
Component content: mass
c
percentage of the component in chitin or CRM; Data were obtained from Ref. 9; d Lignin yield: with regard
to lignin in the original wood.
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Viscosity of biopolymer solutions in NaOH/urea
Viscosity curves of PG-, IL-chitin, and CRM-175 solutions of 1 wt% concentration showed a
slope change point as temperature increased (Fig. S2), which may result from the entanglement
of biopolymer chains in the solution. This "junction temperature" varied with different
biopolymers, e.g., 28.3 °C for PG-chitin, 27.8 °C for IL- chitin, and 25.5 °C for CRM-175. On
the other hand, pure chitin, CRM-POM, and MCC solutions seemed not to entangle at this
concentration during viscosity determination, probably due to their lower MWs.
Fig. S2. Viscosity of (a) chitin and (b) cellulose solutions (1 wt%) in NaOH/urea as a function of temperature.
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Preparation of physical hydrogels
Table S2. Effect of Temperature on Curing Time in Formation of Physical Hydrogels of Chitin and Cellulose at
Maximum Concentrations.a
Cellulose
Chitin
Biopolymer
a
30 °C
Pure chitin
Pseudo
PG-chitin
c
40 °C
50 °C
60 °C
Pseudo
Pseudo
Pseudo
10 h
5h
3h
2h
b
Rec. PG
Pseudo
Pseudo
Pseudo
Pseudo
IL-chitin
> 12 h
7h
5h
4h
MCC
Pseudo
Pseudo
Pseudo
Pseudo
CRM-POM
Pseudo
Pseudo
Pseudo
Pseudo
CRM-175
> 12 h
7h
4h
3h
Maximum concentrations and their preparation are noted in Table 1;
PG-chitin from [C2mim][OAc] to remove impurities;
c
b
Rec. PG: Reconstituted
Pseudo-hydrogel: The resulting gel was not
strong enough to maintain integrity during transfer independent of heating time.
Structural confirmation of chemical cross-linking - FTIR spectroscopy
Fig. S3. FTIR spectra of physical and chemical chitin gels.
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Drying methods
Fig. S4. Dry chitin and cellulose gels after oven-drying (left), freeze-drying (middle), and ScCO2-drying (right).
Chitin gel code XX-m-n, where XX represents the chitin type, m is the chitin concentration, and n is the mass ratio
of ECH to chitin.
PXRD of aerogels
Fig. S5. PXRD patterns of (a) chitin and (b) cellulose particles and corresponding gels after different drying
methods.
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PXRD of loaded aerogels
Fig. S6. PXRD patterns of chitin (IL-chitin) and cellulose (CRM-175) aerogels loaded with dye molecules.
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Comparison of Hydrogels Prepared with Ionic-Liquid-Isolated vs Commercial Chitin and Cellulose
Table S3. Volumes and Masses of Chitin and Cellulose Gels (Original, Alco-, and Aerogels) during Preparation Processes.
Items
Dimensions
(D/h,
mm/mm)
Volume
3
(cm )
Mass (g)
Gel type
Physical chitin gels
Physical
Chemical cellulose gels
cellulose gels
PG-1-10
IL-1-10
PG-2-5
IL-2-5
PG-2-0
IL-2-0
MCC
CRM-POM
CRM-175
Ph-CRM-175
Original
13.0/7.0
13.0/7.0
13.0/7.0
13.5/7.5
12.0/6.0
13.0/6.0
13.0/19.0/10.0
19.0/10.0
14.5/8.0
7.0/4.0
Alcogel
11.5/6.0
11.0/6.0
12.5/7.0
12.0/7.0
12.0/6.0
13.0/6.0
8.0/15.0/4.5
13.0/6.0
10.0/7.0
7.0/4.0
Aerogel
9.5/5.5
9.0/5.0
11.0/6.0
10.5/6.5
12.0/6.0
12.0/5.5
7/12.0/3.5
11.0/5.5
7.0/4.0
7.0/4.0
Rehydrated
10/4.5
12.0/5.5
12.0/6.5
13.0/7.5
12.0/6.0
12.5/7.0
12.0/17.0/7.0
12.5/7.5
12.0/6.0
6.5/4.0
Original
0.93(2)
0.93(3)
0.93(1)
1.1(2)
0.68(1)
0.80(1)
2.0(1)
2.8(2)
1.3(1)
0.15(1)
Alcogel
0.61(2)
0.58(2)
0.85(3)
0.80(3)
0.67(2)
0.78(3)
0.48(1)
0.81(2)
0.56(2)
0.15(1)
Aerogel
0.40(2)
0.33(1)
0.57(1)
0.56(1)
0.67(1)
0.63(1)
0.25(2)
0.52(2)
0.17(1)
0.15(1)
Rehydrated
0.36(2)
0.63(2)
0.75(3)
0.99(3)
0.68(1)
0.75(2)
1.2(1)
0.92(3)
0.69(4)
0.13(1)
Original
0.96(4)
0.94(3)
1.0(1)
1.0(1)
0.75(3)
0.79(3)
2.3(3)
3.5(1)
1.7(1)
0.17(1)
Alcogel
0.39(2)
0.40(3)
0.66(2)
0.65(2)
0.58(2)
0.60(2)
0.39(2)
0.55(3)
0.33(3)
0.13(1)
a
a
0.043(1)
0.041(2)
0.0099(1)
0.0090(1)
0.061
0.0566
0.0132
0.01
0.92(2)
0.14(1)
Aerogel
0.0096(3)
0.00097(3)
0.019(1)
0.019(1)
0.017
Theoretical
0.0128
0.0128
0.0255
0.0255
0.02
Rehydrated
a
Chemical chitin gels
0.37(2)
0.62(2)
0.76(3)
0.92(3)
0.62(2)
0.017
0.02
0.74(3)
1.2
a
1.3
a
The error was too small; Chitin gel code: XX-m-n: XX represents the chitin type, m is the chitin concentration, and n is the mass ratio of ECH to chitin.
S17
Electronic Supporting Information
Comparison of Hydrogels Prepared with Ionic-Liquid-Isolated vs Commercial Chitin and Cellulose
References
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