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Supplementary Information
Corona Liquid Crystalline Order Helps to Form Single Crystals
When Self-Assembly Takes Place in the Crystalline/Liquid
Crystalline Block Copolymers
Zaizai Tong,a,b,c
Yanming Li, a
Haian Xu,a Hua Chen,
a Weijiang Yu,
a Wangqian
Zhuo,a Runke Zhang,
a Guohua Jiang
a,b,c,*
a Department of Materials Engineering, Zhejiang Sci-Tech University, Hangzhou
310018, P. R. China
b National Engineering Laboratory for Textile Fiber Materials and Processing
Technology (Zhejiang), Hangzhou 310018, P. R. China
c Key Laboratory of Advanced Textile Materials and Manufacturing Technology
(ATMT), Ministry of Education, Hangzhou 310018, P. R. China.
2
Experimental Section
Materials. 2-(Dimethylamino)ethyl methacrylate (DM) was passed through a basic
Al2O3 column prior to use to remove the inhibitor. ε-Caprolactone was dried over
CaH2 and distilled under reduced pressure. Tetrahydrofuran (THF) and toluene for
polymerization were refluxed with sodium flakes and freshly distilled. Copper
bromide was washed with acetic acid and diethyl ether for several times and dried
under vacuum. Stanneous 2-ethylhexanoate (Sn(Oct)2) (99%) was purchased from
Acros and distilled under reduced pressure to remove the water prior to use.
Bis(2-ethylhexyl) sulfosuccinate sodium salt (AOT) and methyl orange (MO) were
purchased from Aladdin without any treatment. The other commercially available
chemicals were used without further purification. The details for synthesis of initiator
2-hydroxyethyl 2-bromo-2-methylpropanoate (2-HBMP) were described in
elsewhere.1
Sample Synthesis
Synthesis of PDM homopolymer. PDM homopolymer was synthesized via atom
transfer radical polymerization (ATRP) using 2-HBMP initiator. The detailed
synthetic process is given below. In a Schlenk flask, 2-HBMP (100 µL, 0.70 mmol),
12 mL DM monomer (71 mmol), 1,1,4,7,10,10-hexamethyltriethylenetetramine
(HMTETA) (180 μL, 0.78 mmol), fresh distilled THF (15.0 mL) were mixed and
stirred for 10 min under nitrogen protection. The mixture was immediately frozen in
liquid nitrogen, and a vacuum was applied. After 3 freeze-thaw cycles, CuBr (100 mg,
3
0.70 mmol) was added under N2. Then the flask was put into an oil bath at 65 C for 3
h. Polymerization was quenched into liquid nitrogen and the product was dissolved in
THF and passed through an alumina column to remove the metal complex. After
being concentrated, the THF solution was precipitated in n-hexane. The purification
was repeated thrice and the obtained sample was further dried in a vacuum oven
overnight at 40 C. The polymerization degree of DM is 42 estimated from 1H NMR.
Synthesis of PCL-Br ATRP Macroinitiator. PCL-Br macroinitiator was
synthesized via the ring opening polymerization (ROP) of ε-CL in anhydrous toluene
using 2-HBMP as the initiator and Sn(Oct)2 as the catalyst. In a typical example,
HBMP (121 µL, 0.85 mmol), ε-CL (10.0 mL, 85.2 mmol), and 20 mL of dry toluene
were added into a Schlenk flask equipped with a magnetic stirring bar under nitrogen
atmosphere. Then the tube was immersed in an oil bath with a temperature of 110 C.
Polymerization was initiated after 10 min by injecting a solution of the catalyst
Sn(Oct)2 in toluene corresponding to 0.1 mol% of the monomer. Polymerization was
terminated after 24 h by cooling to room temperature. The reaction mixture was
diluted with tetrahydrofuran (THF) and then precipitated into an excess of methanol
thrice. Finally, the precipitates were collected by filtration and dried in a vacuum oven
at 40 C.
Synthesis of PCL-b-PDM. Atom transfer radical polymerization (ATRP) was
chosen to prepare the diblock copolymers. The detailed synthetic process is given
below. In a Schlenk flask, 300 mg of PCL macroinitiator, 500 μL DM monomer,
1,1,4,7,10,10-hexamethyltriethylenetetramine (HMTETA) (30 μL), fresh distilled
4
THF (4.0 mL) were mixed and stirred for 10 min under nitrogen protection. The
mixture was immediately frozen in liquid nitrogen, and a vacuum was applied. After 3
freeze-thaw cycles, CuBr (5.34 mg) was added under N2. Then the flask was put into
an oil bath at 65 C for 2 h. Polymerization was quenched into liquid nitrogen and the
product was dissolved in THF and passed through an alumina column to remove the
metal complex. After being concentrated, the THF solution was precipitated in
n-hexane. The purification was repeated thrice and the obtained sample was further
dried in a vacuum oven overnight at 40 C.
Quaternization of Block Copolymers. The block copolymers, PCL-b-PDM, were
quaternized according to a literature procedure.2 The preparation of PCL170-b-qPDM22
is given as an example. A clear solution of PCL170-b-PDM22 (80.7 mg, eq DM=0.078
mmol) in nitromethane (10 mL) was stirred for 10 min in a Schlenk flask under
nitrogen flow. Then iodomethane (50 equiv, 243 μL), dissolved in 4 mL of
nitromethane, was added dropwise under nitrogen. The solution became slightly
yellow after iodomethane was completely added. The reaction was continued for 2
days under reflux. The mixture was then concentrated and dissolved in DMF, dialyzed
against deionized water for 3 days to remove the organic solvent. Finally, the product
was then freeze-dried for 1 day and vacuum-dried at 50 °C for another 2 days.
Complexation Between Bis(2-ethylhexyl) Sulfosuccinate Sodium Salt (AOT)
and PCL-b-qPDM. The preparation of PCL-b-qPDM/AOT is given as an example.
PCL-b-qPDM was dissolved in DMF in a Schlenk flask, to which 1.05 equiv of AOT
dissolved in DMF was then added. The solution was stirred at room temperature for
5
30 min to ensure completely dissolved. Then the solution was poured into an excess
of deionized water and the complexed product, PCL-b-qPDM/AOT, was precipitated
from the solution. The obtained product was washed with deionized water for several
times to remove residual AOT molecules. And the purification was repeated thrice by
precipitation. Energy dispersive analysis (EDS) showed the absence of Na+ and I
−,
indicating essentially complete (stoichiometric) complexation with no excess AOT.
Characterization. The molecular weight and the polydispersity index (PDI) were
evaluated by gel permeation chromatography (GPC) using a Waters system calibrated
with standard polymethyl methacrylate. DMF with 1% lithium bromide (LiBr) was
used as an eluent at a flow rate of 1.0 mL min−1
. 1H NMR spectra were recorded on a
Bruker DMX-400 MHz. A FEI Quanta 200 FEG environmental scanning electron
microscope equipped with an energy dispersive spectrometer (EDS) was used to
verify the presence or absence of Na+ and I
− in the complexes. The UV-Vis spectra of
the samples were recorded on a Hitachi U-3010 spectrophotometer. TEM
observations were carried out using a JEOL JEM-1230 electron microscope at an
acceleration voltage of 80 kV. TEM samples were prepared by dropping 4 μL of the
micellar solution onto carbon-coated copper grids. Tapping mode atomic force
microscopy (AFM) was conducted on an XE-100E instrument (PSIA cooperation,
Korea). A drop of micellar solution was deposited on a piece of silicon wafer and
spin-coated at 3000 r min-1
for 30 s and the thickness of single crystals was measured.
Wide-angle X-ray diffraction scattering (WAXS) experiments were performed at
6
BL16B1 beamline in Shanghai Synchrotron Radiation Facility (SSRF) in China. The
wavelength of X-ray was 1.24 Å, and the sample-to-detector distance was set as 358
mm. Solution samples for WAXS measurement were sandwiched between two
polyimide membranes and transmittance mode was carried out. Dried samples for
WAXS measurement were collect by centrifugation of micellar solution at 15000 r
min-1
for 1 h and finally vacuum-dried for 1 day to remove residual solvent.
Two-dimensional (2D) WAXS patterns at room temperatures were recorded. The 2D
WAXS patterns were converted into one-dimensional (1D) WAXS profiles using
Fit2D software.
Preparation of the Micellar Solution. The complexed diblock copolymers were first
dissolved in DMF to obtain a homogeneous solution with a concentration of 1 mg/mL.
Then methanol was added very slowly (5 mL/h) to the solution while stirring until the
volume ratio of methanol and DMF in the solution was reached in a preset ratio. After
complete crystallization, the solution was dialyzed against methanol to remove the
DMF and the final solution concentration was 0.2 mg/mL.
7
13 14 15 16
Rotention time (min)
PCL-Br
PCL170
-b-PDM22
PCL170
-b-PDM35
PCL170
-b-PDM72
(a)
13 14 15 16 17
Retention time (min)
PCL70
PCL70
-b-PDM17
PCL70
-b-PDM32
(b)
Figure S1. GPC traces of two series of PCL based block copolymers, (a) PCL170 based BCPs and
(b) PCL70 based BCPs.
Table S1. Molecular Characteristics of PCL, PDM and Various BCPs
Polymers a)
Mn b)
(g/mol) PDI b)
Complexed BCPs fPCL c)
PCL70 11600 1.07
PCL70-b-PDM17 14500 1.13 PCL70-b-qPDM17/AOT 0.44
PCL70-b-PDM32 16100 1.14 PCL70-b-qPDM32/AOT 0.30
PCL170 26600 1.08
PCL170-b-PDM22 31500 1.11 PCL170-b-qPDM22/AOT 0.60
PCL170-b-PDM35 32300 1.16 PCL170-b-qPDM35/AOT 0.48
PCL170-b-PDM72 36700 1.14 PCL170-b-qPDM72/AOT 0.31
PCL170-b-PDM85 38200 1.17 0.59 d)
PDM42 8200 1.09 qPDM42/AOT a)
Composition was estimated from 1H NMR spectra.
b) Number average molecular weights and PDI were characterized from GPC.
c) Weight fraction of PCL in complexed PCL-b-qPDM/AOT.
d) Weight fraction of PCL in common diblock copolymer, PCL170-b-PDM85.
8
Figure S2. The EDS analysis spectrum of PCL170-b-qPDM22/AOT.
0.0 0.2 0.4 0.6 0.8 1.00.4
0.5
0.6
0.7
0.8
0.9
1.0
Tra
nsm
itta
nce
Methanol content (Vmethanol
/Vsolution
)
Figure S3. The transmittance of 1 mg/mL PCL170-b-qPDM22/AOT DMF solution on
the methanol content during the methanol dropping process.
Figure S4. TEM micrographs of PCL170-b-qPDM22/AOT at different methanol/DMF
ratios. The methanol/DMF ratio is indicated in the figures.
Element Wt % mol %
C 66.60 72.64
N 3.89 3.67
O 25.12 20.35
S 7.72 3.24
Na 0.09 0.05
I 0.47 0.05
9
Figure S5. AFM height image and corresponding of the profile of
PCL170-b-qPDM72/AOT, and the thickness of the single crystals is 13 nm.
It indicates that the PCL blocks crystallize under the present condition of assembly,
and the solvent-soluble qPDM/AOT chains distribute on the top and bottom basal
surfaces of the PCL cores. Based on the method reported by Cheng et al., the formula
below is used to calculate the thickness of PCL layer.
/
/
/ ( )
/ ( ) /
PCL c c a a
n PCL PCL PCL PCLPCL overrall PCL c c a a qPDM AOT
n PCL PCL PCL PCL n qPDM AOT
M W Wd d
M W W M
Here, the physical meanings of the parameters in the formula are expounded in Table
S2. To simplify the calculation, the crystallinity of PCL is set to be 1 and the density
of the block is around 1 g/cm3 as summarized in Table S2. Therefore, based on the
above equation, the thickness of individual PCL and qPDM/AOT layers is estimated
to be 4.4 and 4.3 nm, respectively.
10
Table S2. The physical meanings of the parameters in the formula.
Parameter Physical meaning Value
dPCL The thickness of PCL lamella 4.4 nm
doverall The thickness of overall lamella 13 nm
𝑀𝑛𝑃𝐶𝐿 Mn of PCL block 19400
𝑀𝑛𝑞𝑃𝐷𝑀/𝐴𝑂𝑇
Mn of qPDM/AOT block 31200
𝑊𝑃𝐶𝐿𝑐 The crystallinity of PCL 1
𝜌𝑃𝐶𝐿𝑐 The density of crystalline PCL 1.2 g/cm
3
𝑊𝑃𝐶𝐿𝑎 The content of amorphous PCL 0
𝜌𝑃𝐶𝐿𝑎 The density of amorphous PCL 1.0 g/cm
3
𝜌𝑞PDM/AOT The density of qPDM/AOT ~1 g/cm3
1 2 3 4
Inte
ns
ity (
a.u
.)
2
25 wt%
33 wt%
50 wt%
weak peak
LC3.0 nm
(a)
1 2 3 4
Inte
ns
ity (
a.u
.)
2
33 wt%
50 wt%
(b)
Figure S6. WAXS profiles of (a) qPDM42/AOT at various weight fractions in the
methanol/DMF (ratio=2) solution, (b) qPDM42/AOT0.5/MO0.5.
11
10 12 14 16 18 20 221.5 2.0 2.5 3.0 3.5 4.0
Inte
nsit
y (
a.u
.)
weak peak
2
BCP=50 mg, DMF=0.5 mL, methanol=0.5 mL
BCP=50 mg, DMF=0.5 mL, methanol=1.0 mL
BCP=50 mg, DMF=0.5 mL, methanol=2.5 mL
(110)PCL
Figure S7. Selected WAXS profiles of PCL170-b-qPDM22/AOT at indicated volume of
dropping methanol. The initial BCP concentration is indicated in the figure.
Figure S8. Morphologies of PCL170-b-qPDM22/AOT at various organic solvents. a)
methanol, b) ethanol, c) corresponding AMF height images in ethanol, size 1.5×1.5
μm, inset is the height information of the single crystal, d) n-butanol and e) n-hexanol.
a)-e) the cosolvent is DMF and f) THF.
The effect of different alcohols on the final morphology of PCL170-b-qPDM22/AOT
was probed. One can see that, in methanol, single crystals with large axial ratio are
12
shown in Figure S8a. For ethanol, the self-assembled morphology shows single
crystals with smaller size (Figure S8b). The height information of this platelet is
further examined by the AFM measurement, and the thickness of the crystals is about
10 nm (Figure S8c inset). In n-butanol and n-hexanol, ribbon-like micelles (Figure
S8d) and irregular aggregates (Figure S8e) are existed, respectively, indicating
crystallization driving force becomes weak as solvent from methanol to n-hexanol.
Figure S8 indicate that solvent quality is a key factor to determine the final micellar
morphologies. The effect of solvents on the morphologies may result from the
solubility of the organic solvents toward the PCL block. The solubility parameters for
PCL and different organic solvents are listed in Table S3. As one can see that
methanol has a lowest solubility for PCL because the solubility parameters of
methanol and PCL are quite different. By contrast, the solubility parameter of
n-hexanol is very close to that of PCL, therefore PCL is difficult to crystallize in the
presence of selective solvent, n-hexanol. As a result, irregular aggregations in small
size are assembled. This phenomenon can be further reproduced by changing the good
solvent, DMF, to THF. Because PCL block is more soluble in THF than in DMF
(Table S3), thus crystallization of PCL will be retarded in the presence of THF. One
can see that spherical micelles of PCL170-b-qPDM22/AOT are formed at
methanol/THF=2:1 (Figure S8f), indicating crystallization of PCL is severely
retarded.
13
Table S3. Solubility Parameters of Different Solvents and PCL
Solvent PCLa)
methanolb)
ethanolb)
n-butanolb)
n-hexanolb)
DMFb)
THFb)
δ (cal/cm3)
1/2 9.9 14.5 12.7 11.4 10.7 12.1 9.9
a) Calculated according to reference 3
b) Refer to 4
References:
(1) Tong, Z. Z.; Wang, R. Y.; Huang, J.; Xu, J. T.; Fan, Z. Q. Regulation of the
Self-Assembly Morphology of Azobenzene-Bearing Double Hydrophobic Block
Copolymers in Aqueous Solution by Shifting the Dynamic Host-Guest Complexation.
Polym. Chem. 2015, 6, 2214-2225.
(2) Wang, X.; Vapaavuori, J.; Zhao, Y.; Bazuin, C. G. A Supramolecular Approach to
Photoresponsive Thermo/Solvoplastic Block Copolymer Elastomers. Macromolecules
2014, 47, 7099-7108.
(3) Bordes, C.; Fréville, V.; Ruffin, E.; Marote, P.; Gauvrit, J. Y.; Briançon, S.; Lantéri,
P. Determination of Poly(ε-caprolactone) Solubility Parameters: Application to
Solvent Substitution in a Microencapsulation Process. Int. J. Pharm. 2010, 383,
236-243.
(4) Barton, A. F. M., Crc Handbook of Solubility Parameters and Other Cohesion
Parameters. CRC Press: New York, 1983.