Supporting Information
Well-Defined Liquid Crystal Gels from Telechelic
Polymers
Yan Xia, Rafael Verduzco, Robert
H. Grubbs, Julia A. Kornfield
Division o
f Chemistry a
nd Chemical Engin
eerin
g, Californ
ia Institute of Technology,
Pasadena, Californ
ia 91
125
Experimental
General Procedures.
NMR spectra were reco
rded on a Varian Mercu
ry 30
0 M
Hz
spectrom
eter. All NMR spectra were
recorded in
CDCl
3
or DMSO-
d
6
, and referenced to
residual proteo species. For end group
analysis, a Varian Mercury 500 MHz
1
H NMR
was used. FT-IR spectra were recorded on
a P
erkin-E
lm
er Paragon 1000 spectrometer.
Gel perm
eation chrom
atography (GPC) wa
s carried out in THF on two PLgel 5μm
mixed-C colum
ns (Polym
er Labs) connected
in
series with
a DAW
N EOS m
ultiangle
laser light s
cattering (
MALLS) detecto
r and
an Optilab DSP diff
erential ref
ractometer
(both from
Wyatt Technology). No calib
ration standards were used, and d
n
/d
c
values
were obtain
ed for each injection by assum
ing 100% m
ass elution from
the colum
ns.
Materials.
Dichloroethane (DCE) was dried over CaH
2
and distilled prior to use.
trans
-5,6-dihydroxy-cyclooctene
1
, and 5-hydroxy-cyclooctene
2
were synthesized
accord
ing to
literature p
rocedures. All other m
aterials were us
ed as receiv
ed.
Synthesis of functionaliz
ed cyclooctene-based monomers.
Ethyl 6-
brom
ohexanoate (19.8 mL, 111 mmol)
was attached to 4-cyano-4
‘
-hydroxybiphenyl
S1
(15.4g, 78.9 mmol) in anhydrous D
MF (100 m
L) with anhydrous K
2
CO
3
(10.8 g, 78.1
mmol) at 90 °C for 6 h. The product was recrys
tallized in ethanol
(89% yield), and was
then deprotected by reacting with KOH (6
g, 150 mmol) in anhydrous
ethanol (200 mL)
at 90 °C for 6 h. 1 M HCl (50 m
L) was adde
d to precipitate the acid product which was
collected by
filtration, w
ashed
with water and cold acetone,
and dried in vacuo at 6
0 °C
(95% yield).
The acid (5.2 g, 16.2 m
mol) was reacted in SO
Cl
2
(60 m
L, 766 mm
ol) at 70 °C
for five hours to convert into the acid chloride. Excess SOCl
2
was
rem
oved under
reduced pressure. The acid chloride was then
dissolved in 20 m
l anhydrous THF and was
added dropwise to a solution of
tra
ns
-5,6-dihydroxy-cycloocten
e (0.77 g, 5.4 mmol) in
anhydrous pyridine (5 mL, 63.2 mmol) and
anhydrous THF (50 m
L). The m
ixture was
refluxed for 24 h and the product was purifie
d by extraction with 1 N HCl (20 mL, 3
tim
es), f
ollo
wed by extr
action
with a satu
rated s
olution
of
aqueous NaHCO
3
(50 m
L) and
with a saturated aqueous solution of KCl
(50 mL). The product was dried over MgSO4
and purified on a silica gel colu
mn (ethyl
acetate/h
exanes, 3:7 v
/v) to g
ive 1.6 g
disubstituted cyclooctene
1
as a white crys
tal (40
% yield).
1
H NMR (300 MHz, CDCl
3
)
δ
7.69-7.60 (m, 8H), 7.52-7.49 (m
, 4H), 6.97-6.94 (m
, 4H), 5.64 (t,
J
= 4.2 Hz, 2H), 5.18 (t,
J
= 3.3 Hz, 2H), 3.98 (t,
J
= 6.3 Hz, 4H), 2.52-2.00 (
m, 12H), 1.85-1.45 (m
, 12H);
13
C
NMR (75 MHz, CDCl
3
)
δ
172.6, 159.6, 145.2, 132.6, 131.4, 128.7, 128.3, 127.0, 119.5,
115.0, 109.5, 73.7, 67.7, 34.3, 29.9, 28.9, 25.7, 24.7, 23.0. HRMS (FAB)
m/z
calc.
for
C
46
H
48
O
6
N
2
: 724.3522, found 724.3512.
Monosubstituted cyclooctene
2
was synthesized in analogy to
1
by coupling the
acid chloride with 5-hydroxy-
cyclooctene (65% yield).
1
H NMR (300 MHz, CDCl
3
)
δ
S2
7.71-7.62 (m, 4H), 7.55-7.50 (m
, 2H), 7.00-6.
95 (m
, 2H), 5.73-5.57 (m, 2H), 4.88-4.80
(m
, 1H), 4.00 (t,
J
= 8.1 Hz, 2H), 2.38-2.07 (m
, 6H), 1.92-1.50 (m
, 12H);
13
C NMR (75
MHz, CDCl
3
)
δ
172.9, 159.7, 145.3, 132.6, 131.3, 129.8, 129.6, 128.3, 127.1, 119.1,
115.0, 110.0, 75.5, 67.8, 34.6, 33.8, 33.7, 28.9, 25.6, 25.5, 24.8, 24.7, 22.3. HRMS (FAB)
m/z
calc. for C
27
H
31
O
3
N:
417.2304, found 417.2294.
Synthesis of 1,8-dibromo-4-octen
e.
5-Brom
o-1-pentene (1.0 g, 6.7 mmol) was
added to a solution of Grubbs 1
st
generation catalyst (30
mg, 0.036 mm
ol) in 5 m
l
degassed CH
2
Cl
2
, and the reaction stirred at room te
mperatu
re overn
ight.
The solvent was
evaporated and the rem
aining residual was
purif
ied on
a silica g
el colum
n (ethy
l
ether/hexanes, 1:20 v/v) to give 0.80
g 1,8-dibromo-4-octe
ne (89% yield).
1
H NMR (300
MHz, CDCl
3
)
δ
5.45-5.37 (m
, 2H), 3.43-3.38 (m
, 4H), 2.24-2.12 (m
, 4H), 1.96-1.86 (m,
4H);
13
C NMR (75 MHz, CDCl
3
)
δ
129.8, 129.3, 33.3, 32.5, 32.2, 30.8, 25.7. HRM
S
(FAB)
m/z
calc. for C
8
H
14
Br
2
: 269.9442, found 269.9455.
General procedure for polymeriz
ation and end group functionaliz
ation.
In a
typical experim
ent, an oven-dried sm
all vi
al was charged with
0.725 g (1.0 mmol) of
monom
er
1
and a stir bar. Under an argon atmosphere, 1.0 m
l of de
gassed DCE was
added via syringe. The vial was then de
gassed through th
ree freeze-pu
mp-thaw cycles.
Next, the desired am
ount of CTA was injected
from
its stock solution in degassed DCE.
84 μl of a 10.0 m
g/ml Grubbs 2
nd
generation catalyst solu
tion in degassed DCE was
injected to initiate the polym
erization. The r
eaction vial was stirre
d at 55 °C under argon
for 24 h. The reaction m
ixture was quenched w
ith 0.1 m
l of ethyl vi
nyl ether and then
dissolved
in
2 m
l CH
2
Cl
2
and precipitated into 200 m
l stirring MeOH. The pale yellow
S3
precip
itate was washed
with
fresh MeOH and dried
in vacuo overnight to yield 0.70 g of
white polym
er (97% yield).
0.7 g (0.1 mmol -Br) dibrom
o-term
inated
polym
er and 13 m
g (0.2 mmol) NaN
3
were dissolved in 15 m
l DMF. The resulting
solution was stirred at
25 °C overnight and
then concentrated and precipitated into
200 m
l MeOH three tim
es and dried in vacuo
overnight to yield 0.65 g light
yellow polym
er (93% yield).
1
H NMR (5
00 MHz, C
DCl
3
)
δ
7.7-7.6 (m, 8H), 7.6-7.5 (m
, 4H), 7.0-6.9 (m,
4H), 5.4-5.3 (br, 2H), 5.1-5.0 (br, 2H),
4.05-3.9 (br, 4H), 3.3-3.2 (m
, end gr
oup -C
H
2
-N
3
), 2.4-2.3 (m, 4H), 2.2-1.45 (br m
, 20H).
Diazido-term
inated polym
er
4
was synthesized from
monom
er
2
using a sim
ilar
procedure.
1
H NMR (50
0 MHz, CDCl
3
)
δ
7.7-7.6 (m
, 4H), 7.6-7.5 (m
, 2H), 7.0-6.9 (m
,
2H), 5.4-5.3 (br, 2H), 4.95-
4.8 (br, 1H), 4.05-3.95 (br,
2H), 3.3-3.2 (m
, end group -C
H
2
-
N
3
), 2.4-2.3 (m
, 2H), 2.2-1.2 (br m
, 16H).
General procedure fo
r cross
lin
king.
The des
ired d
iazido
-term
inated
polym
er
and CuBr (2 eq. to alkyne) were added to a
small vial with
a Tef
lon-lined cap. The vial
was evacuated and backfilled with argon three tim
es. The desired am
ount of degassed,
anhydrous DMF (resulting in a 25 wt % polymer
solution) and pentamethyl diethylene
triam
ine (PMDETA) (1 eq to CuBr) were injec
ted and the vial was stirred for 5 m
in. The
correct am
ount of tripropargylam
ine (1/3
eq to polym
er azide end group) was then
injected from its stock solution. The m
ixtur
e was stirred at room
te
mperature for 20
seconds. The vial was then placed in an oven preset to 50 °C and allow
ed to react for 2
days. The resulting gels were repeatedly extr
acted with DMF and then THF (2 h for each
extraction and for 1-2 days until th
e solution was visually
colorles
s) to rem
ove
copper
catalyst and soluble polym
er fraction. Upon dryi
ng in vacuo, the m
ateri
al returns to the
S4
light yellow
color of the prepolym
er. The elas
tom
er fil
ms for elec
tro-o
ptic stud
ies were
prepared by injecting the reacti
on m
ixture into rectangular gl
ass cells with predeterm
ined
gaps. This was required for preparing sam
ples of a unifor
m thickness. A cell was sealed
in a degassed vial with a Teflon-lined cap.
Af
ter in
jecting the re
action m
ixture into
the
rectangular cell, the vial was
placed in a heating oven at 50
o
C. After 2 days at 50 °C, the
glass cell was soaked in DMF
for several hours and opened caref
ully to rem
ove the gel.
The catalyst and soluble polym
er fraction was
extrac
ted as
described
abo
ve. The gel was
then dr
ied in
vacuo and
the resu
lting f
ilm
wa
s reswelled with 5CB for 24 h to give the LC
gel f
ilm
.
Electro
-optic measurements o
f th
e gels.
The electro-op
tic pr
operties of the gels
were m
easured under oscillating applied volta
ge using a polarized He-Ne laser, a beam
splitter, and a CCD detector
as previously described.
3
Constrained sam
ples were prepared
by pressing a LC gel sam
ple between indi
um
-tin-oxide (ITO)-c
oated quartz plates
separated by
10-μm
spacers. Unconstrained sam
ples were prepared by placing a thin (~40
μm
, m
easured using an outside m
icrom
eter
by g
ently placin
g the gel be
tween the a
nvil
and the spindle) piece of the LC ge
l in
a 100 μm
-thick gap between ITO and lecithin
coated
glas
s pla
tes f
illed
with 5CB, and the
sam
ples wer
e allowed to
sta
nd overn
igh
t to
allow f
ull a
lignm
ent of
5CB bef
ore m
easurem
ents.
S5
Spectra and Electro-o
ptic Measu
rements
-C
H
2
Br
A
-C
H
2
N
3
B
Figure 1S.
1
H NMR spectra (zoom
of region 3.1-4.2 ppm
) of polym
er
3
isolated from
polym
erization (A) and after NaN
3
treatm
ent (B).
-N
3
-CO
-CN
LCE
LCP-N
3
LCP-Br
Figure 2S.
IR spectra of polym
er
3
isolated from
polym
erization (top), after NaN
3
treatm
ent (m
iddle), and after cro
ssli
nking at acetylene:azide=1:1 (bottom
).
S6
01
2
0
20
40
60
80
100
0.94
0.96
0.98
0
20
40
60
80
100
Time (s)
T
r
a
n
s
m
i
t
t
a
nc
e
(
%
)
0.00
0.02
0.04
0
20
40
60
80
100
T
r
an
s
m
i
t
ta
nc
e (
%
)
Time (s)
Transm
i
ttance (%)
Tim
e
(
s
)
A
01
2
0
20
40
60
80
100
0.94
0.96
0.98
1.00
0
20
40
60
80
100
Ti
me (s)
T
r
a
n
s
m
itta
n
c
e
(
%
)
0.00
0.02
0.04
0.06
0
20
40
60
80
100
Tr
a
n
s
m
i
t
t
a
n
c
e
(
%
)
Time (s)
Tra
n
s
m
ittanc
e (%)
Time (s
)
B
Figure 3S.
Transient electro-optic response of an
unconstrained LC gel (LCG2) under an
AC electric field of 2.0 V/μm
at A) 1000 Hz
, B) 100 Hz. The insets show the electro-
optic response around the tim
e the signal is applied (top
inset) and rem
oved (bottom
inset).
S7
01
23
0
20
40
60
80
100
1.51
1.52
1.53
1.54
1.55
0
10
20
30
40
50
60
Tr
an
sm
i
t
t
a
nc
e (
%
)
Ti
me (s)
0.00
0.01
0.02
0
10
20
30
40
50
60
T
r
ans
m
i
t
t
a
nc
e (
%
)
Time (
s)
T
r
an
sm
i
tta
n
c
e (%)
Time (s)
Figure 4S.
Transient electro-optic
response of an unconstrained LC gel (LCG1) under an
AC electric field of 2.0 V/μm
at 1000 Hz. Th
e insets show the electro-optic response
near the tim
e the signal is applied (top
inset) and rem
oved (bottom
inset).
0
50
100
150
200
0
20
40
60
80
100
Voltage I
ncreasin
g
Voltage Decreasing
T
r
a
n
smi
t
t
a
n
c
e (
%
)
Voltag
e (
V
rm
s
)
Figure 5S.
Transm
ittan
ce as a f
unction of
volta
ge applied f
or an unconstra
ined LC gel
(LCG1) in a 100 μm
-thick gap. The applied AC
voltage (rm
s) sweeps from 0 to 200V at
0.5V interval and 1000 Hz.
S8
0.0
0.5
1.0
0
20
40
60
80
10
0
0.90
0.95
1.00
1.0
5
0
20
40
60
80
100
Tr
a
n
s
m
it
t
a
n
c
e
(
%
)
Tim
e (s)
0.00
0.05
0.10
0
20
40
60
80
100
T
r
ansm
i
t
t
anc
e
(
%
)
Time (s)
T
r
an
sm
it
t
a
n
c
e (
%
)
Tim
e (s)
Figure 6S.
Transient electro-optic
response of an unconstrained LC gel (monosubstituted
LCG3) under an AC electric field of 2.0 V/μm
at 1000 Hz. The insets show the electro-
optic respon
se near the tim
e the signal is ap
plied (top inset) and re
moved (bottom
inset).
0
50
100
150
200
0
20
40
60
80
100
Volta
ge
Increas
ing
Volta
ge
Dec
reasing
Transmitt
a
n
ce (%
)
Volta
ge (
V
rm
s
)
Figure 7S.
Transm
ittan
ce as a f
unction of
voltag
e applied f
or an unconstr
ained LC ge
l
(LCG3) in a 100 μm
-thick gap. The applied AC
voltage (rm
s) sweeps from 0 to 200V at
0.5V interval and 1000 Hz.
References
(1)
Jernow, J. L.; Gray, D.; Closson, W
. D.
J. Org. Chem.
1971
,
36
, 3511-
3515.
(2)
Hillm
yer, M. A.; Laredo,
W
. R.; Grubbs, R. H.
Macromolecules
1995
,
28
,
6311-6316.
S9
(3)
Ke
mpe, M. D.; Scruggs, N. R.; Verduzco, R.; Lal, J.; Kornfield, J. A.
Nature Materials
2004
,
3
, 177-182.
S10