Novel organosoluble polyimide based on an asymmetric bis(ether amine): 3, 4′-Bis(4-aminophenoxy)-benzophenone

Article abstract of DOI:10.1016/j.cclet.2011.09.014

A new kind of asymmetrical ether diamine, 3,4′-bis(4-aminophenoxy) benzophenone (BABP), was synthesized from the nucleophilic substitution reaction of 4-chloronitrobenzene and 3,4′-dihydroxybenzophenone in the presence of potassium carbonate, followed by catalytic reduction with SnCl ₂·6H₂O and concentrated hydrochloric acid. The prepared diamine was employed in the preparation of a novel polyimide containing asymmetrical diaryl ether segments via the polycondensation of it with BTDA by a two-step method. The resulting polyimide exhibits excellent solubility, film-forming capability and high thermal resistance.

Full text of DOI:10.1016/j.cclet.2011.09.014

Available online at www.sciencedirect.com
Chinese Chemical Letters 23 (2012) 121–122
www.elsevier.com/locate/cclet
Novel organosoluble polyimide based on an asymmetric
bis(ether amine): 3, 40-Bis(4-aminophenoxy)-benzophenone
*
Qian Qian Bu, Shu Jiang Zhang, Hui Li, Yan Feng Li
State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Institute of
Biochemical Engineering & Environmental Technology, Lanzhou University, Lanzhou 730000, China
Received 5 May 2011
Available online 8 November 2011
Abstract
A new kind of asymmetrical ether diamine, 3,40-bis(4-aminophenoxy)benzophenone (BABP), was synthesized from the
nucleophilic substitution reaction of 4-chloronitrobenzene and 3,40-dihydroxybenzophenone in the presence of potassium
carbonate, followed by catalytic reduction with SnCl2ꢀ6H2O and concentrated hydrochloric acid. The prepared diamine was
employed in the preparation of a novel polyimide containing asymmetrical diaryl ether segments via the polycondensation of it with
BTDA by a two-step method. The resulting polyimide exhibits excellent solubility, film-forming capability and high thermal
resistance.
# 2011 Yan Feng Li. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.
Keywords: Asymmetrical diamine; Ether diamine; Organosoluble polyimide
It is well known that polyimides hold outstanding properties, however, most of them have high melting
temperatures or softening temperatures and limited solubility in most solvents because of their rigid backbones and
strong interactions between chains, which restrict their application in corresponding fields [1–4]. For the progress of
polyimide materials, the synthesis of new aromatic monomers and related polyimides with both good solubility and
maintained thermal stability would be a major research topic focused. In general, several approaches have been
devoted to enhancing the solubility of polyimides, including introduction of flexible linkage and geometrically or
molecularly asymmetric structures into the polymer backbone [5,6]. Introduction of aryl–ether linkage and
asymmetric structure into the aromatic polyimide chains can improve the solubility without deterioration of their own
excellent properties, but there are many difficulties in synthesis and purification of asymmetric diamine monomer.
In this paper, a new kind of asymmetric diamine with aryl–ether linkage, 3,40-bis(4-aminophenoxy)-benzophenone
4 had been designed and synthesized as a potentially convenient condensation monomer to form asymmetric ether
polyimides. The diamine monomer, 4, was prepared in a high yield of 86% by the catalytic reduction of intermediate
dinitro compound, 3, which was obtained by a nucleophilic chloro-displacement reaction of 4-chloronitrobenzene (2
equiv.) with 2 (1 equiv.) in the presence of potassium carbonate in dimethylacetamide in 72% yield. 1 was synthesized
through the Friedel–Crafts acylation of 3-methoxybenzoyl chloride (1 equiv.) with anisole (1 equiv.) in CH2Cl2 in 93%
* Corresponding author.
E-mail address: liyf@lzu.edu.cn (Y.F. Li).
1001-8417/$ – see front matter # 2011 Yan Feng Li. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.
doi:10.1016/j.cclet.2011.09.014

122
Q.Q. Bu et al. / Chinese Chemical Letters 23 (2012) 121–122
O
O
O
OCH3
OCH3
OH
OCH
3AlCl3 / CH2Cl2
0-5 o
HBr
+
Cl
CH3COOH
C
CH3O
OH
1
2
O
O
NO2
O
NH2
O
K2CO3 / DMAc
NO2
.
SnCl2 6H2O
HCl
O
NO2
O
NH2
Cl
2
3
4
Scheme 1. Synthesis of 3,40-bis(4-aminophenoxy)-benzophenone (BABP).
yield, which was converted to 2 by demethylation reaction in the present of HBr and CH3COOH in 92% yields, as
shown in Scheme 1. In the FT-IR of 4, peaks at 3442 cmꢁ1 and 3408 cmꢁ1 belonged to –NH2 groups. The absorptions
at 1234 cmꢁ1 were assigned to the C–O–C stretching vibration, confirming the presence of the aromatic ether linkage.
In its 1H NMR (400 MHz, DMSO-d6) spectrum following signals were observed: d 7.67 (d, 2H, J = 8.8 Hz, H-7), 7.42
(dd, 1H, J = 8.0 Hz, 8.0 Hz, H-4), 7.24 (d, 1H, J = 8.0 Hz, H-5), 7.11 (dd, 1H, J = 8.0 Hz, 2.8 Hz, H-3), 7.04 (s, 1H, H-
6), 6.90 (d, 2H, J = 8.8 Hz, H-8), 6.79 (d, 2H, J = 7.8 Hz, H-9), 6.76 (d, 2H, J = 7.6 Hz, H-2), 6.58 (d, 2H, J = 7.6 Hz,
H-10), 6.55 (d, 2H, J = 7.6 Hz, H-1), 5.05 (s, 2H, Ha), 4.97 (s, 2H, Hb), and 13C NMR absorption peaks appeared at d
194.23, 163.43, 159.53, 146.75, 146.35, 145.28, 144.54, 139.45, 132.71, 130.52, 130.35, 123.35, 121.88, 121.59,
120.69, 116.63, 115.36, respectively. Elem. Anal. Calcd. for C25H20N2O3 (396.44): C 75.74%, H 5.08%, N 7.07%.
Found: C 75.90%, H 4.97%, N 7.18%. The data agree with the structure of 4.
The related polyimide was synthesized by polycondensation of BABP and aromatic dianhydride BTDA via
previous method [7]. The inherent viscosity of the resulting polyimide in the N,N-dimethylformamide solution with a
0.5 g/dL concentration at 30 8C was 0.48 dL/g. FT-IR spectra of the resulting polyimide revealed strong bands at
1782 cmꢁ1 (asymmetrical C O stretch), 1721 cmꢁ1 (symmetrical C O stretch), 1375 cmꢁ1 (C–N stretch) and
1111 cmꢁ1 and 754 cmꢁ1 (imide ring deformation), which indicated that imide ring was fully formed. The values of
5% weight loss and 10% weight loss in nitrogen of the resulting polyimide is 504 8C and 536 8C, and its Tg is 248 8C,
which showed the polyimide has excellent thermal stability. It also exhibited good solubility in common organic
solvents such as N,N-dimethylformamide, dimethylacetamide, dimethyl sulfoxid and tetrahydrofuran. Compared with
the analogous polyimide, which were prepared from a symmeric diamine, 4,40-bis(4-aminophenoxy)-benzophenone
[8], the polyimide BABP–BTDA can improve the solubility without sacrificing the thermal properties a lot.
Meanwhile, a strong and flexible film could be obtained, indicting the resulting polyimide has excellent lm-forming
capability. According to the above experimental results, the new ether-containing asymmetric diamine BABP holds
good polymerizability.
Acknowledgments
The authors acknowledge the financial support from the Natural Science Foundation of Gansu Province (No.
096RJZA047) and the Fundamental Research Funds for the Central Universities (No. lzujbky-2011-24).
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