Synthesis and properties of polyaniline derivatives with liquid crystallinity

Article abstract of DOI:10.1021/ma002122h

Polyanilines with liquid crystalline (LC) substituents, which consist of a flexible methylene spacer and phenylcyclohexyl moiety as a mesogenic core, were synthesized. Polymerizations were performed using ammonium persulfate and perchloric acid as the cat

Full text of DOI:10.1021/ma002122h

Macromolecules 2002, 35, 2545-2551
2545
Synthesis and Properties of Polyaniline Derivatives with Liquid
Crystallinity
Hir om a sa Goto a n d Ka zu o Ak a gi*
Institute of Materials Science, University of Tsukuba, Tsukuba, Ibaraki 305-8573, J apan
Received December 13, 2000; Revised Manuscript Received December 3, 2001
ABSTRACT: Polyanilines with liquid crystalline (LC) substituents, which consist of a flexible methylene
spacer and phenylcyclohexyl moiety as a mesogenic core, were synthesized. Polymerizations were
performed using ammonium persulfate and perchloric acid as the catalytic system. The polymers were
quite soluble in organic solvents such as THF and chloroform. The polymers were characterized by IR,
1
UV-vis, H NMR, and 13C NMR spectroscopies. The oxidized form of the pristine polyaniline derivative
with a liquid crystalline group and neutral form prepared by ammonia treatment were examined with
respect to the liquid crystallinity. The polymers with the longer flexible methylene spacer (n ) 10) of the
oxidized form and neutral form exhibited thermotropic liquid crystallinity. Phase transitions and the
corresponding enthalpy changes were evaluated using differential scanning calorimeter measurements.
The smectic liquid crystallinity was characterized by fan-shaped texture through polarizing optical
microscope observations. The LC domains of polyaniline derivative were growing like strings and aligned
parallel to the magnetic field.
In tr od u ction
Polyaniline is one of the most promising electrically
conducting polymers because of its chemical stability,
relatively high conductivity, and unique optical prop-
erty. The conducting form is generated from an oxida-
tion through a protonation, giving rise to remarkable
changes in electrical and optical properties.1,2 The
emeraldine base of protonated polyaniline film can be
stretched up to 20 times to exhibit a higher conductivity.
The proton doping of polyaniline using camphorsulfonic
acid in m-cresol increases the conductivity by several
orders of magnitude.3 This is the concept of secondary
doping, based on the change in the conformation of
polyaniline from a compact coil to an expanded coil.4
These results imply the importance of the morphological
effect in electrical conductivity. Introduction of a liquid
crystal to the conjugated polymer should give macro-
scopic alignment in the polymeric system, which would
allow us to control the conductivity using an external
force such as an electrical or magnetic force field.5 Here
we report the synthesis of a LC polyaniline derivative
with a mesogenic group in side chain to enhance
electrical and optical properties. The LC group consists
of a phenylcyclohexyl moiety as the mesogen core and
flexible methylene spacer. The main-chain polyaniline
derivative has various forms based on the redox and
acid-base reactions, as shown in Figure 1.
F igu r e 1. Schematic chemical structure diagrams of poly-
aniline in various oxidation states.
Tetrahydrofuran (THF), ethanol, acetone, and ether were
distilled prior to use.
Proton (1H) and carbon (13C) nuclear magnetic resonance
(NMR) spectra were measured in CDCl3 using a Bruker AM-
500. Chemical shifts are represented in parts per million
downfield from tetramethylsilane as an internal standard. Gel
permeation chromatographic (GPC) analyses were carried out
at room temperature. The GPC column was calibrated with a
polystyrene standard. Optical absorption spectra were mea-
sured at room temperature using a HITACHI U-2000 spec-
trometer with a quartz cell. Infrared spectra were measured
using a J ASCO FT-IR 550 spectrometer.
Since the polymer of the as-grown form (pristine
polyaniline) had been acidified and doped by the cata-
lyst, it was reduced with ammonia solution to give the
neutral emeraldine. The liquid crystallinity of the
pristine and neutral emeraldine forms of the polyaniline
derivatives were examined. The polyaniline derivative
with decamethylene spacer (n ) 10) in the LC side chain
indeed showed liquid crystallinity, although that with
hexamethylene spacer (n ) 6) showed no LC.
1-[p -(tr a n s-4-n -P en t ylcycloh exyl)p h en oxy]-6-b r om o-
h exa n e (1). Sodium (4.6 g, 0.2 mol) was added to 150 mL of
ethanol in a three-necked round-bottom flask equipped with
a magnetic stirrer and Ar line at room temperature. After
sodium was completely dissolved in ethanol, p-(trans-4-pen-
tylcyclohexyl)phenol (49.3 g, 0.2 mol) was added to the solution
and stirred at room temperature for 12 h. Subsequently, the
solution was transferred to a pressure equalized dropping
funnel, and it was connected to a four-necked round-bottom
flask with a mixture of 1,6-dibromohexane (195.2 g, 0.8 mol)
and 100 mL of ethanol. The solution was very slowly added to
the 1,6-dibromohexane in ethanol at 60 °C under an argon
Exp er im en ta l Section
Gen er a l Asp ects. All experiments were performed under
an argon atmosphere using Schlenk/vacuum line techniques.
* Corresponding author.
10.1021/ma002122h CCC: $22.00 © 2002 American Chemical Society
Published on Web 02/22/2002

2546 Goto and Akagi
Macromolecules, Vol. 35, No. 7, 2002
atmosphere. The addition was completed after 4 h, and the
reaction mixture was stirred for another 8 h. After evaporating
the solvent and excess dibromohexane under reduced pressure,
the solution was thoroughly washed with 1 N HCl and water
and then extracted with ether. The ether layer was dried over
CaCl2, and the organic solvent was removed under reduced
pressure. The crude product was recrystallized from ethanol
to give 47.5 g (0.12 mol) of white prisms (yield 58%). Anal.
Calcd for C23H37BrO: C, 67.47; H, 9.11; Br, 19.51. Found C,
67.65; H, 9.27; Br, 19.50. IR (KBr, cm-1): 3039, 2955, 2919,
2847, 1613, 1581, 1515, 1469, 1447, 1390, 1304, 1282, 1246,
(CH2)3, (CH2)3), 1.60 (m, 2H, CH2), 1.69 (m, 10H, (CH2)5), 2.01
(s, 3H, CdOCH3), 2.24 (t, 1H, bridgehead CH of c-hex), 3.49
(t, 2H, CH2OPh-c-hex), 3.86 (t, 2H, CH2OPh), 6.66 (d, 2H, Ph),
6.71 (d, 1H, Ph), 6.76 (t, 1H, Ph), 6.85 (t, 1H, Ph), 6.94 (d, 2H,
Ph), 7.86 (s, 1H, NH), 8.10 (d, 1H, Ph) ppm (TMS). 13C NMR
(CDCl3, 500 MHz): δ 13.68, 14.69, 17.64, 22.57, 24.31, 25.38,
25.93, 26.00, 26.55, 29.00, 29.22, 29.34, 32.16, 33.55, 34.48,
37.22, 37.30, 43.63, 67.78, 68.58, 111.02, 114.14, 120.23,
120.63, 123.91, 127.38, 139.74, 139.78, 147.50, 157.06, 168.70
ppm (TMS).
2-[6-(p-(tr a n s-4-P en tylcycloh exyl)p h en oxy)h exyloxy]-
a n ilin e Hyd r och lor ic Sa lt (5). To a solution of 9.5 N HCl
(10 mL) in ethanol (100 mL) which was maintained at 60 °C,
2-[6-(p-(trans-4-pentylcyclohexyl)phenoxy)]acetanilide (3) (2.8
g, 5.9 mmol) was added with vigorous stirring in a three-
necked round-bottom flask equipped with a magnetic stirrer
and linked with the Ar line. The resulting slurry was stirred
for 48 h. The voluminous precipitate was filtered off and
recrystallized from ethanol to give a white solid 2.0 g (4.2
mmol, yield 71%). Anal. Calcd for C29H43NO2Cl: C, 73.68; H,
9.18; N, 2.96, Cl; 7.40. Found: C, 73.64; H, 9.56; N, 2.71; Cl,
7.38. IR (KBr, cm-1): 2921, 2852, 2564, 1968, 1619, 1503, 1455,
1
1180, 1111, 1075, 966, 836, 812, 722, 624, 565, 541. H NMR
(500 MHz, CDCl3): δ 0.89 (t, 3H, CH3), 1.03 (q, 2H, CH2), 1.19-
1.43 (m, 15H, c-hex(CH2)3), c-hex ) cyclohexyl, 1.76 (2H, t,
CH2), 1.86 (m, 8H, (CH2)4), 2.39 (t, 1H, bridgehead CH of
c-hex), 3.42 (t, 2H, BrCH2), 3.91 (t, 2H, CH2OPh), 6.80 (d, 2H,
Ph) 7.10 (d, 2H, Ph) ppm (TMS). 13C NMR (CDCl3, 500 MHz):
δ 14.09, 22.69, 25.31, 26.64, 27.91, 29.15, 32.20, 32.69, 33.65,
33.73, 34.57, 37.31, 37.38, 43.71, 67.64, 114.22, 127.57, 140.01,
157.11 ppm (TMS).
1-[p -(tr a n s-4-P en t ylcycloh exyl)p h en oxy]-10-b r om o-
d eca n e (2). The synthetic procedure and purification of
this compound are the same method as for the preparation of
1, utilizing 1,10-dibromodecane instead of 1,6-dibromodecane.
Yield 62% (white powder). Anal. Calcd for C27H45BrO: C,
69.66; H, 9.74; Br, 17.16. Found: C, 69.60; H, 9.21; Br, 17.12.
IR (KBr, cm-1): 2924, 2913, 2847, 1610, 1580, 1512, 1466,
1445, 1394, 1279, 1244, 1178, 1114, 1040, 1018, 970, 894, 836,
809, 765, 723, 645, 624, 541. 1H NMR (CDCl3, 500 MHz): δ
0.88 (t, 3H, CH3), 1.01 (q, 2H, CH2), 1.19-1.43 (m, 21H, c-hex-
(CH2)3, (CH2)3), 1.76 (t, 2H, CH2),1.84 (m, 10H, (CH2)5), 2.38
(t, 1H, bridgehead CH of c-hex), 3.46 (t, 2H, BrCH2), 3.90 (t,
2H, CH2OPh, 6.70 (d, 2H, Ph), 7.09 (d, 2H, Ph) ppm (TMS).
13C NMR (CDCl3, 500 MHz): δ 14.11, 22.72, 25.62, 26.07,
26.68, 28.17, 28.75, 29.37, 29.45, 32.24, 32.84, 33.57, 33.70,
33.94, 34.62, 37.36, 37.43, 43.76, 67.96, 114.27, 127.57, 139.91,
157.25 ppm (TMS).
2-[6-(p-(tr a n s-4-P en tylcycloh exyl)p h en oxy)h exyloxy]-
a ceta n ilid e (3). Sodium (0.28 g, 12 mmol) was added to 50
mL of ethanol in a three-necked round-bottom flask equipped
with a magnetic stirrer. 2-Hydoxyacetanilide (1.85 g, 12 mmol)
was then added to the solution. The color of the solution turned
from pale yellow to green. After 24 h, 1-[p-(trans-4-pentylcy-
clohexyl)phenoxy]-6-bromohexane (1) (5 g, 12 mmol) and KI
(2 g, 12 mmol) were added to the solution. After refluxing 24
h at 60 °C, the reaction mixture was thoroughly washed with
1 N HCl and water and then extracted with ether. The ether
layer was dried over CaCl2, and the organic solvent was
removed under reduced pressure. The crude product was
passed through a column chromatograph (ethyl acetate/hexane
) 2/1) and recrystallized from ethanol to give 3.8 g (8 mmol)
as a white powder (yield 67%). Anal. Calcd for C31H45NO3: C,
77.62; H, 9.46; N, 2.47. Found: C, 77.32; H, 9.75; N, 2.47. IR
(KBr, cm-1): 3744, 3368, 3305, 2854, 1666, 1603, 1539, 1517,
1449, 1375, 1325, 1242, 1179, 1110, 1039, 999, 889, 833, 748,
700, 613. 1H NMR (CDCl3, 500 MHz): δ 0.88 (t, 3H, CH3), 1.03
(q, 2H, CH2), 1.19-1.54 (m, 15H, c-hex(CH2)3, c-hex ) cyclo-
hexyl), 1.82 (m, 8H, (CH2)4), 2.15 (s, 3H, CdO(CH3)), 2.37 (t,
1H, bridgehead CH of c-hex), 3.73 (t, 2H, CH2OPh-c-hey), 3.93
(t, 2H, CH2OPh), 6.81 (d, 2H, Ph), 6.85 (d, 1H, Ph), 6.92 (m,
1H, Ph), 6.99 (t, 1H, Ph), 7.09 (d, 2H, Ph), 7.74 (s, 1H, NH),
8.34 (d, 1H, Ph) ppm (TMS). 13C NMR (CDCl3, 500 MHz): δ
14.12, 16.76, 22.66, 24.90, 25.63, 25.96, 26.66, 29.14, 30.90,
32.24, 33.68, 34.62, 37.34, 43.76, 67.66, 68.56, 110.93, 114.24,
119.62, 121.00, 123.58, 127.58, 140.12, 145.16, 147.07, 157.13,
168.05 ppm (TMS).
1
1254, 1173, 1121, 1002, 823, 752, 556. H NMR (CDCl3, 500
MHz): δ 0.81 (t, 3H, CH3), 0.96 (q, 2H, CH2), 1.12-1.56 (m,
15H, c-hex(CH2)3), 1.78 (m, 8H, (CH2)4), 2.33 (t, 1H, bridgehead
CH of c-hex), 3.68 (t, 2H, CH2OPh-c-hex), 3.94 (t, 2H, PhOCH2),
6.72 (d, 2H, Ph), 6.82 (m, 2H, Ph), 6.85 (m, 2H, Ph), 7.17 (m,
1H, Ph), 7.65 (d, 1H, Ph), 10.43 (s, 1H, NH) ppm (TMS). 13C
NMR (CDCl3, 500 MHz): δ 14.11, 22.65, 25.62, 25.76, 26.86,
28.97, 29.31, 32.24, 33.69, 34.63, 37.36, 37.43, 43.74, 67.98,
68.68, 112.21, 114.22, 119.65, 120.61, 124.42, 127.54, 129.68,
139.85, 152.20, 157.22 ppm (TMS).
2-[10-(p-(tr a n s-4-P en tylcycloh exyl)p h en oxy)d ecyloxy]-
a n ilin e Hyd r och lor ic Sa lt (6). The synthetic procedure and
purification of this compound are the same method as for the
preparation of 5, utilizing 4 instead of 3. Yield 84% (white
solid). Anal. Calcd for C33H51NO2Cl: C, 74.89; H, 9.71; N, 2.65;
Cl, 6.70. Found: C, 74.41; H, 9.59; N, 2.63; Cl, 6.24. 13C NMR
(CDCl3, 500 MHz): δ 14.13, 15.26, 22.73, 25.63, 25.08, 26.12,
26.22, 26.66, 28.93, 29.30, 29.40, 32.25, 33.70, 34.62, 37.36,
37.43, 43.76, 67.96, 69.11, 112.20, 114.26, 119.67, 120.53,
124.50, 127.59, 129.64, 139.93, 152.27, 157.26 ppm (TMS).
P oly[2-(6-(p -(tr a n s-4-p en t ylcycloh exyl)p h en oxy)h ex-
yloxy)a n ilin e] (P r istin e, Oxid ized F or m ) (7). 2-[6-(p-
(trans-4-Pentylcyclohexyl)phenoxy)hexyloxy]aniline hydrochlo-
ric salt (1.5 g, 3.2 mmol) (5), 1 mL of 70% HClO4 in 20 mL of
distilled water, and 10 mL of CHCl3 were stirred in an
Erlenmeyer flask at 0 °C. 1 g of (NH4)2S2O8 in 20 mL of water
was then added dropwise to the solution. The color of the
solution was changed from gray-blue to purple as the reaction
progressed. After 24 h, the solution was filtered and washed
with a large amount of distilled water. Subsequently, the
polymer was washed with a large amount of methanol until
the liquid was clear. The polymer was dried under reduced
pressure to yield 1.2 g of the oxidized form of the polyaniline
1
derivative. H NMR: (CDCl3, 500 MHz): δ 0.89 (t, 3H, CH3),
0.95 (q, 2H, CH2), 1.03-1.56 (m, 15H, c-hex(CH2)3), 1.89 (m,
8H, (CH2)4), 2.38 (s, 3H, bridgehead CH of c-hex), 3.79 (s, 4H,
CH2OPh × 2), 6.78 (d, 2H, Ph), 7.08 (d, 2H, Ph) ppm (TMS).13C
NMR: (CDCl3, 500 MHz): δ 14.12, 22.72, 25.61, 25.93, 26.66,
29.17, 29.33, 32.24, 33.67, 34.60, 37.34, 37.42, 43.73, 67.75,
68.69, 114.24, 127.59, 139.99, 157.15 ppm (TMS).
P oly[2-(10-(p -(tr a n s-4-p en t ylcycloh exyl)p h en oxy)d e-
cyloxy)a n ilin e] (P r istin e, Oxid ized F or m ) (8). The syn-
thetic procedure and purification of this polymer are the same
method as for the preparation of polymer 7. 13C NMR (CDCl3,
500 MHz): δ 14.11, 22.65, 22.72, 25.61, 26.07, 26.67, 29.38,
29.49, 29.54, 30.90, 31.66, 32.23, 33.67, 34.81, 37.35, 37.42,
43.74, 67.97, 68.60, 114.26, 127.57, 139.91, 157.25 ppm (TMS).
P oly[2-(6-(p -(tr a n s-4-p en t ylcycloh exyl)p h en oxy)h ex-
yloxy)a n ilin e] (Neu tr a l F or m ) (9). Poly[2-(6-(p-(trans-4-
pentylcyclohexyl)phenoxy)hexyloxy)aniline]-pristine (7) (1 g)
and 50 mL of 1 N ammonia solution were prepared in a three-
necked round-bottom flask equipped with a magnetic stirrer.
The solution was stirred for 24 h at room temperature. The
2-[10-(p-(tr a n s-4-P en tylcycloh exylp h en oxy)d ecyloxy)]-
a ceta n ilid e (4). The synthetic procedure and purification of
this compound are the same method as for the preparation of
3, utilizing 2 instead of 1. Yield 70% (white powder). Anal.
Calcd for C35H53NO3: C, 78.46; H, 9.97; N, 2.61. Found: C,
78.96; H, 10.71; N, 1.80. IR (KBr, cm-1): 3422, 3368, 2923,
2852, 1687, 1604, 1519, 1448, 1384, 1242, 1117, 1112, 103.8,
830, 758, 630, 588, 545. 1H NMR (CDCl3, 500 MHz): δ 0.76 (t,
3H, CH3), 1.04 (q, 2H, CH2CH3), 1.16-1.42 (m, 21H, c-hex-

Macromolecules, Vol. 35, No. 7, 2002
Polyaniline Derivatives 2547
Sch em e 2
Sch em e 1
ammonium peroxodisulfate and 1 M HClO4, where the
bulky LC substituents on the aniline rendered the
monomer insoluble in aqueous media. The product was
washed with a large amount of methanol to give the
purple color oxidized form of the polyaniline derivative
(7 or 8). The pristine polyaniline was reduced in a 1 M
ammonia aqueous solution and washed with methanol
to yield the neutral form (9 or 10), as shown in Scheme
2.
Ch a r a cter iza tion . The monomers of 5 and 6 were
produced in good yields. Molecular weights of the
corresponding polymers (neutral forms, 9 and 10) are
summarized in Table 1. These values range from 9200
to 14 100 in Mn according to polystyrene standard,
which indicates that the compounds are real polymers.
The results of the elemental analyses of the polymers
are also listed in Table 1.
solution was then washed with distilled water. The polymer
was dried under reduced pressure to yield 0.8 g of the neutral
form. 1H NMR (CDCl3, 500 MHz): δ 0.81 (t, 3H, CH3), 0.93
(q, 2H, CH2), 1.13-1.45 (m, 15H, c-hex(CH2)3), 1.77 (m, 8H,
(CH2)4), 2.29 (s, 1H, bridgehead CH of c-hex), 3.66 (s, 4H, CH2-
OPh × 2), 6.71 (d, 2H, Ph), 7.12 (d, 2H, Ph) ppm (TMS). 13C
NMR (CDCl3, 500 MHz): δ 14.11, 22.72, 25.51, 25.78, 26.87,
28.93, 29.19, 32.23, 33.66, 34.61, 37.34, 37.42, 43.73, 67.96,
68.69, 112.25, 114.23, 119.52, 120.63, 124.48, 127.54, 129.94,
139.84, 152.16, 157.19 ppm (TMS).
P oly[2-(10-(p -(tr a n s-4-p en t ylcycloh exyl)p h en oxy)d e-
cyloxy)a n ilin e] (Neu tr a l F or m ) (10). The synthetic proce-
dure and purification of this polymer are the same method as
1
for the preparation of polymer 9. H-NMR (CDCl3, 500 MHz):
δ 0.89 (t, 3H, CH3), 0.93 (q, 2H, CH2), 1.12-1.46 (m, 15H,
c-hex(CH2)3), 1.77 (m, 8H, (CH2)4), 2.31 (s, 1H, bridgehead CH
of c-hex), 3.65 (s, 4H, CH2OPh × 2), 6.52 (d, 2H, Ph), 7.28 (d,
2H, pH) ppm (TMS). 13C NMR (CDCl3, 500 MHz): δ 14.12,
22.73, 25.63, 26.06, 26.86, 29.08, 29.39, 29.50, 29.54, 30.90,
31.60, 32.25, 33.69, 34.62, 37.35, 37.43, 43.75, 67.97, 68.57,
112.27, 114.28, 120.12, 121.32, 124.57, 131.96, 129.12, 131.91,
152.18, 157.28 ppm (TMS).
The small amount of chlorine in the neutral forms is
-
due to residual ClO4 ion which was not be able to be
removed by ammonia treatment. Figure 2 shows IR
absorption spectra of 6 (monomer), 8, and 10 (polymers).
The IR spectrum of the monomer 6 showed a broad
peak at 2560 cm-1, which was assigned to overlapped
-CH3 stretching and -NH3+ stretching vibrations. The
IR spectra of the polymers 8 or 10 showed no absorption
Resu lts a n d Discu ssion
Mon om er Syn th esis. Two kinds of monomers con-
sisting of a liquid crystalline group with a hexameth-
ylene spacer or decamethylene spacer (n ) 6, 10) were
synthesized in three steps, as shown in Scheme 1.
p-(trans-4-Pentylcyclohexyl)phenol was reacted with
4-fold excess of a dibromoalkane in ethanol by the
Williamson’s etherification to obtain 1 or 2. Evaporation
was carried out to remove any excess dibromoalkane,
followed by recrystallization from ethanol in ca. 60%
yield. In the next step, the LC group (1 or 2) was
introduced to the ortho position of an acetanilide by the
same etherification method in ethanol to yield 3 or 4.
Compound 3 or 4 was purified by column chromatog-
raphy (ethyl acetate/hexane ) 2/1), followed by recrys-
tallization from ethanol, to yield 67-70%. Subsequently,
this compound was treated with HCl at 60 °C to remove
the acetyl fragment. The analytically pure compound
of the hydrochloric aniline salt as a monomer 5 or 6 was
obtained through recrystallization from ethanol.
+
peak due to the -NH3 moiety. These results indicate
that the oxidative polymerization gives a polyaniline
structure. In the spectra of the polymers, the absorption
at 2800-3000 cm-1 is assigned to C-H stretching
vibrations of the alkyl moiety in the liquid crystalline
substituent. The ring stretching vibrations of the quinoid
and benzenoid forms in the polymer were observed at
1590 and 1500 cm-1, respectively. The C-N stretching
vibration6 was observed at 1380 cm-1. The absorption
at 1240 cm-1 is due to the C-O-C stretching vibration.
-
The stretching vibration of the counterion (ClO4
)
appeared at 624 cm-1 in the pristine polymers (7 or 8).
The absorption intensity is decreased during the am-
monia treatment. The absorption around 1030 cm-1 is
attributed to the CH in-plane vibration of the 1,4
position on the phenylene ring in the main chain, and
742 cm-1 is due to the CH out-of-plane vibration at the
1,2 position of the phenylene ring in the main chain. A
presence of the 827 cm-1 is characteristic of the C-H
out-of-plane bending vibrations of the para-substituted
P olym er iza tion . Interfacial polymerization was per-
formed between organic layer (CHCl3) and water using

2548 Goto and Akagi
Macromolecules, Vol. 35, No. 7, 2002
Ta ble 1. Molecu la r Weigh ts a n d Elem en ta l An a lyses for th e P olym er s of Neu tr a l F or m s
polymer
Mw
Mn
MWD
DP
C (%)
H (%)
N (%)
Cl (%)
composition (found)
composition (calcd)
9
10
22 600
16 560
14 100
9 200
1.6
1.8
32
19
77.18
78.40
9.30
9.88
3.12
2.77
1.44
1.55
C6H8.68N0.20Cl0.07
C6H9.08N0.18Cl0.04
C6H8.48N0.21
C6H8.91N0.18
Ta ble 2. Assign m en ts of th e IR Sp ectr a of th e P olym er s
Q )
NH+-B or
C-H in-plane
on benzene
ring
CH
aromatic
ring
deformation
out-of-plane on
benzene ring
polymer
νNH
νCH
N)Qa)N N-Bb-N
νCN
νCOC N)Q+)N B-NH+-B
2
7
3382 3033
2921
3260 2921
2852
3450 2917
2847
1604
1590
1576
1590
1504
1517
1503
1513
1361 1241
1390 1243
1381 1242
1396 1245
1168
1187
1157
1187
1135
1108
1138
1130
1047
1054
1024
1039
823
734
825
757
827
736
827
750
636
628
640
630
8
9
10
3350 2921
2852
a
b
Q ) quinoid unit. B ) benzenoid unit.
F igu r e 4. 1H NMR spectrum of 6.
F igu r e 2. IR absorption spectra of the monomer and the
polymers.
By the reduction with ammonia, the color of the polymer
changed from purple to dark red, and the peak at 552
nm shifted to the shorter wavelength of 468 nm. This
result implies that the absorption of 552 nm of the
pristine polyaniline may be due to the doping band of
-
the ClO4 ions.
1H a n d 13C NMR Sp ectr a . Additional information
about the monomer and polymer structures were ob-
tained from NMR spectra. The 500 MHz 1H NMR
spectrum of 6 as a monomer is shown in Figure 4.
Protons of the ammonium ion (-NH3+) give a broad
peak at 10.50 ppm. Aromatic protons of aniline unit
appear as sharp peaks at 7.71, 7.27, and 7.10 ppm. The
aromatic protons on the liquid crystalline substituent
of the phenylene moiety appear at 6.92 and 6.81 ppm.
The protons of the other methylene groups appear at
1.04-4.01 ppm, and the terminal methyl group appears
1
at 0.89 ppm. The H NMR spectrum of the polymer 8 is
shown in Figure 5.
F igu r e 3. UV-vis absorption spectra of the polymers in THF
solution: 8 (solid line); 10 (dashed line).
The peaks related to the protons on the aniline units
are difficult to be assigned. This is due to the delocalized
electron or charged species. A signal at 10.50 ppm
phenylene ring of the polymers. The results are sum-
marized in Table 2.
+
originating from the -NH3 of the monomer is disap-
The UV-vis absorption spectra of the polymers in
THF are shown in Figure 3. The absorption band of 8
(pristine, oxidized form) or 10 (neutral form) at 277 nm
is assignable to the phenylene unit in LC group. A
purple pristine polymer of 8 showed three absorption
peaks at 277, 316, and 552 nm and shoulder at 692 nm.
1
peared in the H NMR after the polymerization.
Liqu id Cr ysta llin ity. The liquid crystalline proper-
ties of 8 and 10 were examined with a differential
scanning calorimeter (DSC) and polarizing optical mi-
croscopy. The phase transition temperatures and their

Macromolecules, Vol. 35, No. 7, 2002
Polyaniline Derivatives 2549
F igu r e 5. 1H NMR spectrum of 8.
Ta ble 3. P h a se Tr a n sition Tem p er a tu r esa (°C) a n d
Cor r esp on d in g En th a lp y Ch a n ges (J /g)b
first cooling
second heating
polymer
g-s
s-i
g-s
s-i
8
10
c
c
97 (-2.1)
64 (-1.2)
75 (1.2)
54 (0.2)
102 (7.8)
65 (1.1)
a
b
Determined by DSC. g ) glassy state, s ) smectic, i )
isotropic. Scanning rate: 10 °C/min. c No distinct DSC peak.
corresponding enthalpy changes are summarized in
Table 3.
F igu r e 6. Polarizing optical micrographs of 8: (a) without
external force; (b) intermediate state in growing of aligned LC
domains under the magnetic field; (c) macroscopic alignment
of the polyaniline derivative.
The DSC exothermic peak showed one thermal tran-
sition during the first cooling of 8; no distinct peak was
observed on the phase transition from the mesophase
to the glassy state. In the heating scan, two peaks due
to the phase transition from the glassy state to the
mesophase and from the mesophase to the isotropic
phase were observed. Moreover, polarizing optical mi-
croscopy confirmed the two phase transitions. Beyond
75 °C, the polymer becomes fluid and remains birefrin-
gent. Above 102 °C, the polymer changed into an
isotropic phase. In the mesophase between 75 and 102
°C, the polymer exhibited a purple birefringence under
polarizing light. The polymer of 10 exhibited thermal
behavior similar to polymer 8, although the phase
transition temperatures were shifted to the lower tem-
perature region. This may be due to the decrease in
rigidity of the polymer main chain accompanied by a
decrease of effective conjugation length.
Note that the polymers of 7 and 9 showed no liquid
crystallinity. This may be due to the shorter methylene
spacer of the LC substituent; the length of hexameth-
ylene spacer is not enough to enable a spontaneous
orientation.7 The polarizing optical micrograph of 8
without external force is shown in Figure 6a. Randomly
oriented optical texture of LC is observed. Although
ordinary LCs have no color, the present polymer exhibits
a red-purple color due to the existence of conjugated
absorption band in the visible region. We examined
macroscopic alignment of the polymer of 8 under a
magnetic force field. The polymer was first melted by
heating on the quartz substrate, and it was gradually
cooled to LC temperature by applying an external
magnetic field of 10 T. Figure 6c indicates the macro-
scopic alignment of the LC polyaniline derivative.
The direction of magnetic field is parallel to a hori-
zontal line of the photograph. It is seen that the LC
domains are growing like strings and aligned parallel
to the magnetic field. We also performed polarized UV-
vis measurement for the aligned polymer to comprehend
the orientational behavior of the polymer (Figure 7).
In the linear dichroism measurements, the absorption
was recorded with a polarizer placed parallel and
perpendicular to the applied magnetic field direction on
the sample. The absorption intensity in the perpendicu-
lar direction (A ) to the magnetic field was larger than
that in the parallel one (A|). Note that A| stands for
absorbance perpendicular to the polyaniline main chain
and A parallel to the main chain. This result indicates
that the transition dipole moment of the conjugated
segment was perpendicular to the direction of the
macroscopic alignment. Namely, the polymer main
chain was oriented perpendicular to the magnetic field.5
The dichloic ratio (R) and order parameter (S) of 8 were
estimated to be 5.3 and 0.68, respectively.
R ) A /A|
S ) (R - 1)/(R + 1)
where A| and A were defined as absorbances at 580
nm assignable to the π f π* transition of conjugated
polyaniline main chain that are parallel and perpen-
dicular to the magnetic field, respectively. It is clear that
the aligned polymer exhibits a linear dichroism in
absorption.

2550 Goto and Akagi
Macromolecules, Vol. 35, No. 7, 2002
F igu r e 7. Polarized absorption spectra of 8. A| and A stand
for the absorbances that are parallel and perpendicular to the
magnetic field, respectively.
F igu r e 9. Stacking structure of bilayer smectic A phase of
polymer 10.
Ta ble 4. Electr ica l Con d u ctivities of P olym er 8
σa
σ(random)
σ
σ|b,d
b
b,c
polymer
8
3.5 × 10-9
6.2 × 10-8
8.4 × 10-6
2.3 × 10-8
a
b
Cast film. In LC order. c Parallel to polymer main chain.
d
Perpendicular to polymer main chain. σ ) unit of S/cm.
and 2.3 × 10-8 S/cm, respectively. The anisotropy
between the conductivity (σ /σ|) was ∼3 × 102. The
increase of parallel conductivity (σ ) after magnetically
forced alignment is due to an increase of effective
conjugation length and partly due to an enhancement
of coplanarity of the polyaniline main chain accompa-
nied by the alignment. This suggests that, in analyzing
the change of conductivity upon the molecular orienta-
tion, an in-plane alignment of the polyaniline chain
must be considered at the same time as well as the
parallel alignment of the polymer main chain.
F igu r e 8. XRD result of 10 oriented by external magnetic
force field of 10 T: H| and H stand for parallel and perpen-
dicular directions to the magnetic field, respectively.
The X-ray diffraction (XRD) pattern and profile of the
aligned polymer of 10 are shown in Figure 8. Two
diffraction peaks were observed at small angle in the
meridian direction of 1.9° (50.7 Å) and at large angle of
19.2° (4.5 Å) in the equator direction. These correspond
to the interlayer and inter-side-chain distances, respec-
tively. The result suggests that polymer 10 has bilayer
smectic A phase where the side chains are located on
the both sides of main chain (see Figure 9). This is also
supported by molecular mechanics (MM) calculations.
The electrical conductivity of the polymer was mea-
sured with the four-probe method. The results are
summarized in Table 4.
The conductivity of dedoped (neutral) polymer of 10
was 2.3 × 10-11 S/cm. On the other hand, the doped
(oxidized) polymer of 8 was 3.5 × 10-9 S/cm. Through
the magnetically forced alignment, the conductivity in
parallel direction to the polymer main chain (σ ) (where
the polymer main chain was oriented perpendicular to
the magnetic field) and that in perpendicular direction
to the polymer main chain (σ|) were 8.4 × 10-6 S/cm
Con clu sion
We synthesized polyaniline derivatives with LC side
chains through the interfacial polymerization. The
soluble and fusible polyaniline derivatives were char-
acterized by the IR, UV-vis, NMR, and GPC. The
polyaniline derivatives with the longer decamethylene
spacer in the LC side chain (n ) 10) exhibit a thermo-
tropic LC. This was confirmed by DSC and polarizing
optical microscope measurements. The ammonia treat-
ment for the oxidized form of the polymer caused a
lowering of the phase transition temperatures. The
alignment of the polymer main chain accompanied by
the side-chain orientation using the external magnetic
force of 10 T enhanced the electrical conductivity, giving
rise to a notable electrical anisotropy.
Ack n ow led gm en t. This research was supported by
a Grant-in-Aid from the Ministry of Education, the

Macromolecules, Vol. 35, No. 7, 2002
Polyaniline Derivatives 2551
383. (f) Trchova´, M.; Prokesˇ, J .; Stejskai, J . Synth. Met. 1999,
101, 840.
(2) Suville, R.; J ozefowicz, J .; Yu, T. L.; Perichon, J .; Buvet, R.
Tsukuba Advanced Research Alliance (TARA), and the
Kurata Foundation. The authors thank Dr. D. Ichinohe
(University of Tsukuba) for valuable discussions and
Messrs. M. Okuda, A. Hayashi, and T. Oohazama for
their kind assistance. We also thank Dr. K. Ito (Tsukuba
Magnet Laboratory, National Research Institute for
Metals) for the experiment of magnetically forced align-
ment.
Electrochim. Acta 1968, 13, 1451.
(3) Cao, Y.; Smith, P. Synth. Met. 1995, 69, 191.
(4) MacDiarmid, A. G.; Epstein, J . A. Synth. Met. 1994, 65, 103.
(5) (a) Akagi, K.; Shirakawa, H. Macromol. Symp. 1996, 104, 137.
(b) Goto, H.; Akagi, K.; Itoh, K. Synth. Met. 2001 117, 91. (c)
Goto, H.; Itoh, K.; Akagi, K. Synth. Met. 2001, 119, 351. (d)
Oguma, J .; Kawamoto, R.; Goto, H.; Akagi, K.; Shirakawa,
H.; Ito, K. Synth. Met. 2001, 119, 537. (e) Osaka, I.; Goto,
H.; Akagi, K.; Shirakawa, H.; Ito, K. Synth. Met. 2001, 119,
541. (f) Akagi, K.; Goto, H.; Kadokura, Y.; Shirakawa, H.;
Oh, S.-Y.; Araya, K. Synth. Met. 1995, 69, 13.
Refer en ces a n d Notes
(1) (a) Menardo, C.; Mechtschein, M.; Rousseau, A.; Travers, J .
P. Synth. Met. 1988, 25, 311. (b) Kuramoto, N.; Su, S.-J .
Macromolecules 2001, 34, 7249. (c) MacDiarmid, A. G.; J ones,
J r., W. E.; Norris, I. D.; Gao, J .; J ohnson, J r., A. T.; Pinto, N.
J .; Hone, J .; Han, B.; Ko, F. K.; Okuzaki, H.; Llaguno, M.
Synth. Met. 2001, 119, 27. (d) Shimano, J . Y.; MacDiarmid,
A. G. Synth. Met. 2001, 119, 365. (e) Andreatta, A.; Cao, Y.;
Chiang, J . C.; Heeger, A. J .; Smith, P. Synth. Met. 1988, 26,
(6) Tang, J .; J ing, X.; Wang, B.; Wang, F. Synth. Met. 1988, 24,
231.
(7) Finkelmann. H.; Happ, M.; Portugal, M.; Ringsdorf, H.
Macromol. Chem. Phys. 1978, 179, 2541.
MA002122H