A novel soluble polyamide containing xanthene structure and trifluoromethylphenoxy pendent

Article abstract of DOI:10.1016/j.cclet.2009.10.011

A novel polyamide containing xanthene structure and trifluoromethylphenoxy pendent was prepared from 9,9-bis[4-(4-aminophenoxy)phenyl]xanthene, a novel diamine with 2-(4-trifluoromethylphenoxy)terephthaloyl chloride, by the low temperature polycondensation. This new polyamide with the inherent viscosity of 0.95 dL/g was amorphous and readily soluble in polar solvents such as DMAc, m-cresol, etc. This polyamide showed the glass transition temperature (T_g) of 236 °C, decomposition temperature (T_d) at 5% weight loss of 455 °C and char yield of 56% at 800 °C in N₂. Transparent, flexible, and tough film of the polymer cast from DMAc solution exhibited tensile strength of 93 MPa, elongation at break of 14%, initial moduli of 2.2 GPa. The electric properties such as the dielectric constant of 3.03 (1 MHz) and surface resistance (2.78 × 10¹⁴ Ω), and the moisture uptake of 1.36% were also described.

Full text of DOI:10.1016/j.cclet.2009.10.011

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Chinese Chemical Letters 21 (2010) 242–244
www.elsevier.com/locate/cclet
A novel soluble polyamide containing xanthene structure and
trifluoromethylphenoxy pendent
*
Zhen Zhong Huang, Xue Mei Wan, Hai Bo Xiao, Shou Ri Sheng , Cai Sheng Song
College of Chemistry and Chemical Engineering, Jiangxi Normal University, Nanchang 330022, China
Received 3 July 2009
Abstract
A novel polyamide containing xanthene structure and trifluoromethylphenoxy pendent was prepared from 9,9-bis[4-(4-
aminophenoxy)phenyl]xanthene, a novel diamine with 2-(4-trifluoromethylphenoxy)terephthaloyl chloride, by the low temperature
polycondensation. This new polyamide with the inherent viscosity of 0.95 dL/g was amorphous and readily soluble in polar solvents
such as DMAc, m-cresol, etc. This polyamide showed the glass transition temperature (Tg) of 236 8C, decomposition temperature
(Td) at 5% weight loss of 455 8C and char yield of 56% at 800 8C in N2. Transparent, flexible, and tough film of the polymer cast
from DMAc solution exhibited tensile strength of 93 MPa, elongation at break of 14%, initial moduli of 2.2 GPa. The electric
properties such as the dielectric constant of 3.03 (1 MHz) and surface resistance (2.78 Â 1014 V), and the moisture uptake of 1.36%
were also described.
# 2009 Shou Ri Sheng. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.
Keywords: Polyamide; Xanthene cardo group; Trifluoromethylphenoxy pendent; Soluble
Aromatic polyamides are well known as high-performance polymers because of their combination of excellent
thermal, mechanical, and chemical properties [1]. Despite their outstanding properties, the infusibility and limited
solubility of aromatic polyamides restrict their areas of application. Therefore, numerous attempts have been made to
improve their processability. Introducing cardo groups such as fluorene [2] and tert-butylcyclohexylidene [3] is a
successful approach for improving the processability of aromatic polyamides without an extreme loss of their
outstanding properties. Additionally, it was found that the incorporation of flexible fluorinated groups into polyamide
backbones resulted in great benefits for improving polymer solubility as well as electrical and dielectric properties
[4,5]. To our knowledge, the incorporation of trifluoromethylphenoxy pendent and xanthene cardo group into the
polyamide backbone has not been reported. In this paper, a new monomer diamine, 9,9-bis[4-(4-aminophenox-
y)phenyl]xanthene (BAPX), as shown in Scheme 1, and a novel soluble polyamide containing xanthene cardo group
and trifluoromethylphenoxy pendent (Scheme 2) was prepared and characterized, and its thermal and mechanical
properties as well as electrical and dielectric behavior were also investigated.
9,9-Bis(4-hydroxyphenyl)xanthene 1 [6] and 2-(4-trifluoromethylphenoxy)terephthaloyl chloride (TFFPC) [7]
were synthesized according to our reported method. The intermediate 9,9-bis[4-(4-nitrophenoxy)phenyl]xanthene 2
* Corresponding author.
E-mail address: shengsr@jxnu.edu.cn (S.R. Sheng).
1001-8417/$ – see front matter # 2009 Shou Ri Sheng. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.
doi:10.1016/j.cclet.2009.10.011

Z.Z. Huang et al. / Chinese Chemical Letters 21 (2010) 242–244
243
Scheme 1. Synthetic route to BAPX: (a) 4-ClC6H4NO2, K2CO3, DMF, 160 8C, 8 h; (b) NH2NH2ÁH2O, Pd/C, reflux, 12 h.
Scheme 2. The structure of novel fluorinated polyamide with xanthene cardo group.
[8] was obtained from the nucleophilic chloro displacement of 4-chloronitrobenzene with the potassium phenolate of 1
in DMF. BAPX 3 [9] was prepared by catalytic hydrogenation of the dinitro compound 2 using hydrazine hydrate and
Pd/C catalyst in refluxing ethanol. The intermediate and monomer structures were confirmed by FTIR, NMR and
elemental analyses. The polyamide 4 was obtained in a one-step pathway by the low-temperature solution
polycondensation reaction of TFFPC with BAPX in DMAc solution containing a trace of pyridine cooled by an
external ice–acetone bath. The reaction temperature was maintained at –10 to 0 8C in the initial 5 h. In order to obtain
maximum molecular weight, the reaction was then allowed to proceed overnight at room temperature. The new
polyamide 4 with inherent viscosity of 0.95 dL/g, exhibited characteristic IR absorption bands (Fig. 1) of the amide
group around 3370 cmÀ1 (N–H stretching), 1633 cmÀ1 (C O stretching), and 1120 cmÀ1 (C–F stretching), along with
the characteristic absorption bands of aryl ether stretching near 1219 cmÀ1, demonstrating the formation of amide
linkages. The polymerization results and the thermal properties of polymers are summarized in Table 1. No
endothermic peak above its Tg was observed in DSC scan, which may be attributed to the amorphous structure, further
confirmed by WAXD analysis.
Fig. 1. IR spectrum of polyamide 4.

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Z.Z. Huang et al. / Chinese Chemical Letters 21 (2010) 242–244
Table 1
The polymerization and thermal properties of polyamide 4.
a
hinh (dL/g)
b
c
d
e
Rw (%)
Yield (%)
Tg (8C)
Td5 (8C)
Td10 (8C)
97
0.95
236
455
480
56
a
Detected in DMAc with a concentration of 0.5 g/dL at 30 8C.
Detected by DSC at a heating rate of 10 8C/min in N2.
5% weight loss temperature. (Determined by TGA at a scan rate of 20 8C/min in N2)
10% weight loss temperature. (Determined by TGA at a scan rate of 20 8C/min in N2)
Residual weight (%) when heated to 800 8C (Determined by TGA at a scan rate of 20 8C/min in N2).
b
c
d
e
The polyamide was readily soluble (3.0%, w/v) in DMAc, NMP, DMF, DMSO, m-cressol, and even in pyridine at
room temperature, attributable to the presence of xanthene cardo group, trifluoromethylphenoxy pendent and flexible
ether linkages, but insoluble in THF and CHCl3. Thin film (120 Â 5 mm) cast from its DMAc solution was tested for
mechanical properties in Instron instrument at 25 8C. The film had tensile strength of 93 MPa, elongation at break of
14%, and tensile modulus of 2.2 GPa. The electric properties of the polyamide film were also measured. The electric
properties such as the volume resistance, surface resistance and dielectric strength were 2.35 Â 1015 V cm,
2.78 Â 1014 V and 94 kV/mm, respectively. Moreover, the dielectric constant at 1 MHz was 3.03 and the moisture
uptake of the polyamide was 1.36%.
The thermal and mechanical properties of the new resulting polyamide were compared with those of the fluorinated
fluorene-containing polyamides [4]. In addition, this new fluorinated polyamide exhibited lower dielectric constant
than those of the fluorinated polyamides without cardo groups in the main [7], which may be speculated that this
polyamide containing xanthene cardo structures have higher bulk density resulting in larger free volume.
In conclusion, a novel diamine was synthesized, characterized, and polymerized with TFFPC to afford a novel
fluorinated polyamide with xanthene structure. The introduction of xanthene cardo group, trifluoromethylphenoxy
pendent and flexible ether linkages into the polyamide backbone resulted in dramatic changes in its properties,
especially in the improvement of solubility and lowering of the moisture uptake. This new fluorinated polyamide
exhibited good thermal stability, as well as good mechanical, electrical and dielectric properties.
Acknowledgments
We thank the National Natural Science Foundation of China (No. 20664001) and the Research Program of Jiangxi
Province Department of Education (No. 2007–-123, GJJ08166 and GJJ09138) for the financial support.
References
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[8] Mp 263–264 8C; IR (KBr): 1515, 1344 cmÀ1 (N O stretch), 1248 cmÀ1 (C—O—C stretch); 1H NMR (400 MHz, CDCl3): d 8.19 (d, 4H,
J = 8.6 Hz), 7.31 (t, 2H, J = 8.0 Hz), 7.20 (d, 2H, J = 8.0 Hz), 7.09 (t, 2H, J = 7.6 Hz), 7.07–7.03 (m, 8H), 6.99–6.94 (m, 6H); 13C NMR
(75 MHz, CDCl3): d 162.38, 152.67, 151.48, 148.50, 142.25, 141.92, 129.74, 129.45, 128.31, 125.94, 123.12, 119.97, 117.25, 116.70, 53.51.
Anal. Calcd. for C37H24N2O7: C, 73.02; H, 3.97; N, 4.60. Found: C, 73.12; H, 3.90; N, 4.70.
[9] Mp 209–211 8C; IR (KBr): 3370, 3042 cmÀ1 (N—H stretch), 1236 cmÀ1 (C—O—C stretch); 1H NMR (400 MHz, CDCl3): d 7.25 (t, 2H,
J = 7.6 Hz), 7.13 (d, 2H, J = 8.0 Hz), 7.02 (t, 2H, J = 8.8 Hz), 6.92 (d, 2H, J = 8.0 Hz), 6.87–6.81 (m, 8H), 6.77 (d, 4H, J = 8.0 Hz), 6.65 (d, 4H,
J = 8.0 Hz), 3.53 (br s, 4H); 13C NMR (75 MHz, CDCl3): d 157.47, 152.62, 148.26, 142.78, 139.38, 131.07, 130.54, 130.03, 127.80, 122.82,
121.32, 116.41, 116.20, 116.14, 53.20; Anal. Calcd. for C37H28N2O3: C, 81.00; H, 5.14; N, 5.11. Found: C, 81.14; H, 5.23; N, 5.20.