Table 2 Characteristics of OTFT devices fabricated as photoalignment polymers coated onto SiO2 and SiO2 gate insulator
Gate Insulator
Polymer-I/SiO2
Polymer-II/SiO2
SiO2
Direction of current
Mobility/cm2 V21 s21
Ioff/A
S?S/V decade21
Ion/Ioff
m//
mH
m//
0.3
2.56 6 1028
7.8 6 10210
4.7 6 10210
9.88 6 10210
4.28 6 10211
5.9
5.8
2.8
3.8
1.2
103
104
104
104
105
0.05
0.12
0.12
0.21
mH
1
200 MHz): d (ppm) 8.22–8.18 (m, 2H, aromatic protons), 7.77
(d, 2H, aromatic protons), 7.60 (d, 1H, vinylene proton), 7.41
(t, 2H, aromatic protons), 7.32 (d, 2H, aromatic protons), 6.52
(d, 1H, vinylene proton). Mp: 227–228 uC.
yield: 95%). H NMR (DMSO-d6, 200 MHz): d (ppm) 8.23–
8.16 (m, 2H, aromatic protons), 7.94–7.87 (m, 3H, aromatic
protons), 7.47–7.30 (m, 8H, aromatic protons and vinylene
proton in cinnamate), 7.18 (s, 2H, vinylene protons in
maleimide), 6.91 (d, 1H, vinylene proton in cinnamate). 13C
NMR (DMSO-d6, 500 MHz): d (ppm) 169.91, 164.93, 163.44,
152.40, 149.57, 145.74, 134.73, 132.98, 132.85, 131.83, 130.11,
129.09, 128.04, 122.61, 122.43, 117.21, 116.35, 116.06. Anal.
Calcd for C26H16FNO6: C, 68.27% ; H, 3.53% ; N, 3.06% ;
Found: C, 67.22% ; H, 2.11% ; N, 3.06%. Mp: 250–252 uC.
Synthesis of N-hydroxyphenylmaleimide (3)21
A three-necked flask equipped with a Teflon stirrer and a
thermometer was injected with nitrogen gas through a nitrogen
purge tube and cooled with cold water to maintain its
temperature below 15 uC. 4-Aminophenol (7 g, 0.064 mol)
was added into a solution of maleic anhydride (7.55 g,
0.077 mol) in DMF (20 ml), which was stirred for about 2 h
in a water bath below 15 uC with a nitrogen purge so as to
obtain a clear amic acid solution. Then, a mixture containing
phosphorus pentaoxide (3.7 g, 0.013 mol), sulfuric acid (1.77 g,
0.018 mol), and 30 mL of DMF was added dropwise into
the amic acid solution during a period of 1 h. The resulting
mixture, after stirring at 80 uC for about 6 h, was cooled and
poured into 500 mL of ice water to obtain a precipitate, which
was washed with deionized water and recrystallized in
isopropyl alcohol and further dried in a vacuum to obtain
N-hydroxyphenylmaleimide (8.71 g, yield: 72%). 1H NMR
(DMSO-d6, 200 MHz): d (ppm) 9.66 (s, 1H, –OH), 7.09 (s, 2H,
vinylene protons in maleimide), 7.03 (d, 2H, aromatic
protons), 6.80 (d, 2H, aromatic protons). Mp: 187 uC (lit:
185–186 uC).
Synthesis of poly[N-(4-(4-fluorobenzoyloxycinnamoyl)-
oxyphenyl)maleimide] (Polymer-I)
In a 50 mL Schlenk flask were placed N-(4-(4-fluorobenzoyl-
oxycinnamoyl)oxyphenyl)maleimide (1 g, 2.2 mmol), AIBN
(0.05 g, 0.3 mmol) and 20 mL of 1,4-dioxane. The oxygen
dissolved in 1,4-dioxane was removed by a degassing process
with a nitrogen freeze–thaw cycling method. The polymeriza-
tion mixture was stirred at 90 uC for 24 h under a nitrogen
atmosphere. After the polymerization was over, solvent was
removed to about 10 mL and the polymerization mixture
was poured into 300 mL of methanol to precipitate. The
precipitated polymer was collected by filtration and washed
with methanol. Then, vacuum drying was carried out to obtain
0.9 g (yield: 90%) of poly[N-(4-(4-fluorobenzoyloxycinnamoyl)-
oxyphenyl) maleimide] (Polymer-I). 1H NMR (DMSO-d6,
200 MHz): d (ppm) 8.38–7.78 (5H, aromatic protons), 7.74–
7.10 (8H, aromatic and vinylene protons), 7.10–6.71 (1H,
vinylene proton).
Synthesis of N-(4-(4-fluorobenzoyloxycinnamoyl)oxyphenyl)-
maleimide (FBCPM)20
A
round bottomed flask containing 4-fluorobenzoyloxy-
Synthesis of poly[(N-(4-(4-fluorobenzoyloxycinnamoyl)-
oxyphenyl)maleimide)-alt-styrene] (Polymer-II)
cinnamic acid (5.44 g, 0.019 mol), methylene chloride (50 mL)
and thionyl chloride (6.8 g, 0.057 mol) was held under a
nitrogen atmosphere. The reaction was carried out at 40 uC
until a transparent solution was obtained. After the reaction,
the solvent and thionyl chloride were removed under vacuum,
and the obtained product, 4-fluorobenzoyloxycinnamoyl
chloride, was used without further purification for the next
reaction. In a round bottomed flask, N-hydroxyphenylmale-
imide (3.97 g, 0.021 mol) was dissolved in 40 mL of THF, then
triethylamine (2.3 g, 0.023 mol) was added, and agitation was
carried out for 30 minutes. Afterwards 4-fluorobenzoyloxy-
cinnamoyl chloride in methylene chloride was slowly added
dropwise with vigorous agitation at 5 uC. After the exhaustion
of 4-fluorobenzoyloxycinnamoyl chloride, the reaction was
carried out for 24 h. Then, it was poured into a mixture of
water (400 mL) and methanol (400 mL), and the precipitate
was filtered off. The product was washed using water
and methanol, and followed by vacuum drying to give N-(4-
(4-fluorobenzoyloxycinnamoyl)oxyphenyl)maleimide (8.3 g,
In a 50 mL Schlenk flask were placed N-(4-(4-fluorobenzoyl-
oxycinnamoyl)oxyphenyl)maleimide (1 g, 2.2 mmol), AIBN
(0.06 g, 0.37 mmol) and 24 mL of 1,4-dioxane. The oxygen
dissolved in 1,4-dioxane was removed by a degassing process
with a nitrogen freeze–thaw cycling method. The polymeriza-
tion mixture was heated up to 90 uC. Then, 0.23 g (2.2 mmol)
of styrene was added and the reaction was carried out for 24 h
under nitrogen atmosphere. After the polymerization was
over, solvent was removed to about 10 mL and the poly-
merization mixture was poured into 300 mL of methanol to
precipitate. The precipitated polymer was collected by filtra-
tion and washed with methanol. Then, vacuum drying was
carried out to obtain 1.1 g (yield: 89%) of poly[(N-(4-(4-
fluorobenzoyloxycinnamoyl)oxyphenyl)maleimide)-alt-styrene]
(Polymer-II). 1H NMR (DMSO-d6, 200 MHz): d (ppm)
8.38–7.78 (5H, aromatic protons), 7.74–6.71 (14H, aromatic
and vinylene protons).
This journal is ß The Royal Society of Chemistry 2005
J. Mater. Chem., 2005, 15, 5029–5036 | 5035