Supporting Information
Mesogen Controlled Ion Channel of Star-shaped Hard-soft Block Copolymers
for Solid State Lithium-ion Battery
Yongfen Tong1,2, Lie Chen1, Xiaohui He1, Yiwang Chen*1
1
Institute of Polymers/Department of Chemistry, Nanchang University, 999 Xuefu
Avenue, Nanchang 330031, China; 2School of Environmental and Chemical
Engineering, Nanchang Hangkong University, 696 Fenghe South Avenue, Nanchang
330063, China
Materials
Pentaerythritol (Acros Organics, 99%) was vacuum-dried at 50 oC. Styrene (Aldrich,
99 %) was stirred with CaH2 overnight and distilled under reduced pressure before
use. Lithium perchlorate (LiClO4) and copper(I) bromide (CuBr, 98%) are purchased
from Aldrich and used as received. Poly (ethylene glycol) methyl ether methacrylate
(PEGMA, Mn=300, Aldrich) and 1,1,4,7,10,10-hexamethyl triethylene tetramine
(HMTETA, Elf Atochem) were used as received. Triethylamine (Aldrich, 99%) and
CH2Cl2 are distilled from CaH2 under a dry nitrogen purge just before used. Toluene
and tetrahydrofuran (THF) is distilled from sodium prior to use. Other chemicals are
obtained from Shanghai Reagent Co., Ltd., and used as received.
Synthesis
Synthesis of 4-cyano-4′-[(x-hydroxyalkyl)oxy]biphenyl (x=3, 10)
4-Cyano-4′-[(3-hydroxyhexyl)oxy]biphenyl. 4-Cyano-4′-hydroxybiphenyl (1.09 g,
0.0056 mol) and potassium carbonate (2.65 g, 0.017 mol) are added to acetone (50
*
Corresponding author. Tel.: +86 791 83969562; fax: +86 791 83969561. E-mail address: ywchen@ncu.edu.cn (Y.
Chen).
ml), and reflux for 2~3 h, followed by addition of 3-bromo-1-propanol (1.39 g, 0.01
mol). After refluxing for 24 h, the reaction mixture is poured into diluted HCl solution,
and the precipitated product is extracted with chloroform. The combined chloroform
extracts are washed with water and dried over anhydrous MgSO4. After filtration and
concentration, the crude product is recrystallized from methanol to yield 1.05 g (76%)
of white crystals, Mp. 113.5 ºC; 1H NMR (δppm, CDCl3): 1.03–1.51 (m, 2H, –CH2–),
3.68 (t, 2H, –OCH2OH), 4.1 (m, PhOCH2, 2H), 6.87–7.69(m, 8H, aromatic). IR (KBr):
2 224 (CN), 3 298cm-1(OH).
4-cyano-4′-[(10-hydroxyalkyl)oxy]biphenyl, which is obtained similarly with
4-cyano-4′-[(3-hydroxyalkyl)oxy]biphenyl. Mp. 78.5 ºC; 1H NMR (δppm, CDCl3):
1.01–1.99 (m, 16H, –(CH2)8–), 3.42 (t, 2H, –OCH2OH) 3.96 (m, PhOCH2, 2H),
6.89–7.65(m, 8H, aromatic). IR (KBr): 2 225 (CN), 3 288cm-1(OH).
Synthesis of Monomers x-[(4-Cyano-4′-biphenyl)oxy]alkyl methacrylate MAxLC
(x=3, 10)
3-[(4-Cyano-4′-biphenyl)oxy]propyl
methacrylate
(MA3LC).
4-Cyano-4′-[(3-hydroxyhexyl)oxy]biphenyl (7.59 g, 0.03 mol) is dissolved in a
mixture of dry tetrahydrofuran (210 mL) and triethylamine (3.33 g, 0.033 mol). To
this mixture a solution of methacryloyl chloride (3.13 g, 0.03 mol) in 50 mL of dry
THF is added dropwise. The reaction mixture is stirred at room temperature overnight.
The white solid which precipitated is removed through filtration and the solution
evaporated at reduced pressure. The residue obtained is recrystallized from 96%
ethanol to yield 7.15 g (74%) of white crystals. 1H NMR (δppm, CDCl3) :7.69 (d, 2H),
7.65 (d, 2H), 7.53 (d,2H), 6.99 (d, 2H), 6.10 (s, 1H), 5.56 (s, 1H), 4.16 (t, 2H), 4.02(t,
2H), 1.95 (s, 3H), 1.84 (q, 2H), Mp. 67 °C.
10-[(4-Cyano-4′-biphenyl)oxy]decatyl
methacrylate (MA10LC), similarly obtained.
Yield =73%. 1H NMR (δppm, CDCl3) :7.69 (d, 2H), 7.65 (d, 2H), 7.52 (d,2H), 6.99 (d,
2H), 6.13 (s, 1H), 5.56 (s, 1H), 4.15 (t, 2H), 4.02(t, 2H), 1.94 (s, 3H), 1.81 (q, 2H),
1.69 (q, 2H), 1.21-1.56 (m, 12H) Mp. 64°C.
Synthesis of ATRP Initiator Pentaerythritol Tetrakis(2-bromoisobutyrate)
(PERBr4)
Under N2 atmosphere, to a dried, two-neck, 100-mL flask equipped with a magnetic
bar, 2-Bromoisobutyryl bromide (36.8 g, 0.16 mol) was slowly added to a solution of
pentaerythritol (2.72 g, 0.020mol) and triethylamine (16 g, 0.16 mol) in dry THF at 0
o
C. The solution was stirred for 24 h and allowed to reach room temperature slowly.
The mixture was then transferred to a separation funnel with 350 mL of
dichloromethane and rinsed successively with 10% HCl, 5% NaHCO3, and then
deionized water. The organic phases were dried over MgSO4, and the solvent was
removed by rotary evaporation. The raw product was dissolved in a small amount of
dichloromethane and recrystallized in methanol. Yield: 79%. 1H NMR (δppm, CDCl3):
4.32 (s, 8H); 1.92 (s, 24H).
Synthesis of the Star Macroinitiator 4PS-Br4 (4PS) via ATRP
0.18 g of PERBr4 (0.24 mmol), 0.021 g of CuBr (0.144 mmol), 0.033 g of HMTETA
(0.144 mmol) and 16.0 g of styrene (154 mmol) were added to an ampoules bottle.
The bottle containing reactants was fully degassed with three freeze–pump–thaw
cycles and sealed under vacuum. It was subsequently immersed in a thermostated oil
bath at 100 oC under stirring to allow polymerization of styrene. After reaction for 6 h,
the system was cooled down to room temperature. Finally, the mixture was washed by
a large excess of methanol repeatedly. The white copolymer product was then dried in
vacuum. 1H NMR (δppm, CDCl3): 7.4–6.5 (m, 5H, aromatic), 3.7 (s, CHBr), 1.2–2.1
(m, CH2 and CH of PS).
Synthesis of the Star Macroinitiator 4PS-PEGMA-Br4 (4PS-PEGMA) by ATRP
In a typical polymerization, a Schlenk flask is charged with macroinitiator, 4PS-Br4 (1
g, 0.09 mmequiv. Br), PEGMA (3g, 10 mmol), distilled toluene (10 mL), and ligand
HMTETA (23mg, 0.1mmol) and degassed before CuBr (14.3 mg, 0.1 mmol) under
nitrogen. The solution is degassed three times with freeze-pump-thaw cycles. For a
given reaction time the flask is immersed in an oil bath preheated at 85 °C. After 4 h
of polymerization, the Schlenk flask is dipped into liquid nitrogen to stop the
polymerization. The solution is diluted with THF and passed through a column of
neutral alumina to remove the copper salts. The product is precipitated from an excess
of ether twice, filtered, and vacuum dried to give a colloidal product of
4PS-PEGMA-Br4 3.36 g. 1H NMR (δppm, CDCl3): 7.4–6.5 (m, 5H, aromatic),
4.1-3.42 (m, -OCH2CH2O-), 3.38 (s, -OCH3), 0.81–2.1 (m, CH2 and CH of PS, CH2
and CH3 of methacrylate main chain).
Synthesis of the Star Copolymers 4PS-PPEGMA-PMAxLC
The synthesized 4PS-PPEGMA-Br4 macroinitiator (2 g, 0.016 mmol), CuBr (0.01 g,
0.064 mmol), distilled toluene (10 mL) and MA10LC (1.5g, 0.003 mol) were added
into a dried round-bottom flask. HMTETA (0.014 g, 0.064 mmol) was then poured
into the flask. The polymerization reaction was then allowed to proceed at 85°C. At
24 h from the initiation of the polymerization, heating was stopped. The obtained
polymer was then isolated and purified by reprecipitation using a similar method as
that used for the 4PS-PPEGMA-Br4 macroinitiator.
4PS-PPEGMA-PMA3LC, similarly obtained.
Preparation of Star Copolymer /LiClO4 Electrolytes
In a typical procedure for preparing the electrolyte, copolymers and LiClO4 salt are
dissolved in acetonitrile and stirred for 24h, varying amounts of copolymers and
LiClO4 salt to achieve the desired [O]/[Li] ratios (Z). After the solution was stirred, it
was cast onto an aluminum foil; and the solvent is slowly evaporated at room
temperature for 24 h. Then, the material is heated to 60 °C under vacuum for 24 h.
The film is about 100μm thick and had a smooth surface without pinholes.
Characterization Methods
The nuclear magnetic resonance (NMR) spectra are collected on a Bruker ARX 400
NMR and Bruker AV 600 NMR spectrometer with deuterated chloroformor as the
solvent and with tetramethylsilane (δ=0) as the internal standard. The infrared (IR)
spectra are recorded on a Shimadzu IR Prestige-21 Fourier transform infrared (FTIR)
spectrophotometer by drop-casting sample solution on KBr substrates. The gel
permeation chromatography (GPC), so-called size-exclusion chromatography (SEC)
analysis, is conducted with a Breeze Waters system equipped with a Rheodyne
injector, a 1515 Isocratic pump and a Waters 2414 differential refractometer using
polystyrenes as the standard and tetrahydrofuran as the eluent at a flow rate of
1.0mL/min and 40 oC through a Styragel column set, Styragel HT3 and HT4
(19mm×300mm, 103 +104 Å) to separate molecular weight (MW) ranging from 102 to
106. Thermogravimetric analysis (TGA) is performed on a TA Mettler TG 851 for
thermogravimetry at a heating rate of 10 oC /min under nitrogen with a sample size of
8–10mg.
Differential
scanning
calorimetry
(DSC)
is
used
to
determine
phase-transition temperatures on a Shimadzu DSC-60 differential scanning
calorimeter with a constant heating/cooling rate of 10 ºC /min. Texture observations
by polarizing optical microscopy (POM) are made with a Nikon E600POL polarizing
optical microscope equipped with an Instec HS 400 heating and cooling stage. The
X-ray diffraction (XRD) study of the samples is carried out on a Bruker D8 Focus
X-ray diffractometer operating at 30 kV and 20mA with a copper target (λ= 1.54 Å)
and at a scanning rate of 1o/min. The surface image of the membranes were
investigated by scanning electron microscope (SEM), using an Environmental
Scanning Electron Microscope (ESEM, FEI Quanta 200). Transmission electron
microscopy (TEM) images were recorded using a JEOL-2100F transmission electron
microscope and an internal charge-coupled device (CCD) camera. The samples for
TEM investigation were prepared as follows: the liquid crystalline copolymers were
prepared by dropping a 2 g/L tetrahydrofuran (THF) solution on copper grids, then
heated and annealed at the desired temperatures for 2 h. Electrochemical
measurements are made in a standard three-electrode cell by an electrochemical
analyzer. Alternating current (AC) impedance measurements of the polymer
electrolytes are performed using CHI660 electrochemical workstation (CH
Instruments) over a frequency range of 10 Hz-1MHz with an amplitude of 10 mV. All
the specimens are sandwiched by two polished stainless steel blocking electrodes for
conductivity tests. These measurements are performed in the temperature range of
10-100 ºC, and the system was thermally equilibrated at each selected temperature for
at least 1 h. Complex impedance plots are computed from the raw experimental data.
The intersection in the imaginary impedance at low frequency with the real
impedance axis corresponds to the ionic conductance of the samples and hence the
conductivity values (σ) are obtained from the equation σ= (1/Rb) (t/A), where Rb
represents the bulk resistance, t is the thickness and A is the area of the sample. The
lithium transference number (t+) was determined by using a combination method of dc
polarization and ac impedance measurements. The sample was sandwiched between
two 0.5 mm-thick lithium foils (Alfa) as non-blocking electrodes and assembled in a
standard 2032 coin-cell holder in an argon gas-filled glove box. The dc voltage pulse
applied to the cell was 10 mV. The electrochemical stability of the hybrid electrolytes
was determined by linear sweep voltammetry (LSV) using stainless steel (SS) as a
working electrode and lithium as counter and reference electrodes for a
Li/electrolyte/SS cell at a scan rate of 2 mVs-1 from 1 to 8 V vs. Li/Li+.
FT-IR Analysis of Polymers
The FT-IR spectra of macroinitiator 4PS, 4PS-PPEGMA and copolymer
4PS-PPEGMA-PMA10LC are shown in Figure S1. The component absorption bands
can be easily observed in the FI-IR spectra of the star liquid crystalline copolymer,
which shows the absorbance peak of a –Ph groups at 1597 cm−1 derived from 4PS and
a –C-O-C- groups at 1107 cm−1 derived from PEGMA, a weak band at 1737 cm−1
associated with the –COO- stretch, and an obvious band of cyano functionality at
2223 cm-1 implying the presence of cyano biphenyl mesogens.
4PS-PPEGMA-PMA10LC 2223
1107
4PS-PPEGMA
4PS
1597
PER-Br4
1737
4000
3500
3000
2500
2000
Wavenumbers (cm
1500
1000
500
-1
)
Figure S1. FT-IR spectra of the macroinitiator PER-Br4, 4PS, 4PS-PPEGMA and
copolymer 4PS-PPEGMA-PMA10LC.
H2
C CH a
COO CH2CH2 O CH3
m
CH3
CH2 C cBr
CH2 C
b
CH3
COO CH2
10
O
CN
H2
C CH
a
CH 3
CH 2 C Br
b
CO O
CH 2 CH 2 O
CH 3
m
H2
C CH a Br
8.0
Figure S2.
7.0
1
6.0
5.0
4.0
3.0
2.0
1.0
0.0 ppm
H NMR spectra of the polymers 4PS, 4PS-PPEGMA and
4PS-PPEGMA-PMA10LC.
4PS-PPEGMA-PMA3LC
4PS-PPEGMA-PMA3LC
o
intensity (a.u.)
annealing at 150 C
4PS-PPEGMA-PMA10LC
4PS-PPEGMA-PMA10LC
o
annealing at 150 C
200
Figure
S3.
UV
250
spectra
300
350
Wavelength (nm)
of
the
polymers
400
450
4PS-PEGMA-MA3LC
and
4PS-PEGMA-MA10LC as-cast films and annealing from their liquid crystalline states
on a quartz plate.
100
80
60
40
4PS-PPEGMA (a)
4PS-PPEGMA-PMA3LC (b)
4PS-PPEGMA-PMA10LC (c)
20
(b)
(c)
(a)
0
0
100
200
300
400
500
600
Figure S4. TGA thermogram of copolymers recorded under nitrogen at a heating rate
of 10 oC/min
(c)
Heating Flow Endo
(a)
(b)
-58.8
-53.4
Cooling
Heating
(b)
(c)
-49.5
(a)
-50
0
50
o
Temperature ( C)
100
Figure S5. DSC thermograms of 4PS-PPEGMA-PMA10LC with various [O]/[Li]
ratios [Z = (a) 30, (b) 20, (c) 10] recorded under nitrogen during the second heating
scans at a scan rate of 10 oC /min.
Table S1. VTF parameters and Tg for electrolytes studied.
Copolymer electrolytes
4PS-PPEGMA /LiClO4
4PS-PPEGMA-PMA3LC/LiClO4
4PS-PPEGMA-PMA10LC/LiClO4
Z,[O]/[Li]
Tg(K)
T0
(K)
A
(Scm-1K0.5)
Ea
(kJ/mol)
30
20
10
30
20
10
30
20
10
217.2
222.3
226.1
215.6
228.5
235.4
214.2
219.6
223.5
167.2
172.3
176.1
165.6
178.5
185.4
164.2
169.6
173.5
2.17
1.94
1.78
0.87
2.13
1.06
0.37
1.01
0.77
7.81
6.34
6.13
4.12
5.31
4.25
5.39
4.67
4.31