Synthesis, characterization, effect of triaryl ring substituents groups on thermal and spectral properties of new soluble triphenylamine-based aromatic polyamides

Article abstract of DOI:10.14233/ajchem.2014.15331

Three new triphenylamine-containing aromatic diacid monomers, 4,4'-dicarboxy-4''-isopropyl-triphenylamine (Ma), 4,4'-dicarboxy-2'4''- dimethyl-triphenylamine (Mb, 4,4'-dicarboxy-4''-ethyltriphenylamine (Mc) were successfully synthesized via the aromatic nucleophilic fluoro-displacement reaction of 4-fluorobenzonitrile with aniline-derivatives using sodium hydride as the base, followed by alkaline hydrolysis of the dinitrile intermediates (Ia), (Ib), (Ic). A series of poly(amine-amide)s were prepared by the direct phosphorylation polycondensation from the newly synthesized diacid monomers with various aromatic diamines. FTIR, 1H and 13C NMR spectroscopic techniques were used to identify the chemical structures of the dicyano intermediates, the carboxylic acid monomer and the resultant poly(amine-amide)s. These aromatic poly(amine-amide)s were found to be readily soluble in a variety of organic solvents and could afford strong and tough films via solution casting. They exhibited excellent thermal stability associated with high glass transition temperatures (Tg = 248.32-290.46 °C) and 10 % weight loss temperatures in excess of 522 °C in nitrogen. In dilute N-methyl pyrrolidone solution, these polymers exhibited a medium to strong photoluminescence in the blue region at (425-443) nm. Cyclic voltammetry of the poly(amineamide) s films cast onto an ITO-coated glass substrate in dry acetonitrile containing 0.1 M of tetrabutylammonium perchlorate (TBAP) as an electrolyte exhibited one oxidation redox couples (Eonset) at (1.30-1.37) V versus Ag/AgCl and revealed electrochromic characteristics with a colour change from pale yellow to blue at applied potentials switched between 0.0 and 1.6 V.

Full text of DOI:10.14233/ajchem.2014.15331

Asian Journal of Chemistry; Vol. 26, No. 1 (2014), 85-92
http://dx.doi.org/10.14233/ajchem.2014.15331
Synthesis, Characterization, Effect of Triaryl Ring Substituents Groups on Thermal and
Spectral Properties of New Soluble Triphenylamine-Based Aromatic Polyamides
1
1
AZHAR KAMIL RASHID1,2,*, ROSIYA BINTI YAHYA and PHANG SOOK WAI
1Department of Chemistry, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia
2University of Baghdad, Baghdad, Iraq
*Corresponding author: Fax: +60 79674193; Tel: +60 104259265; E-mail: azhar_almasody@yahoo.co.uk
Received: 18 February 2013;
Accepted: 24 June 2013;
Published online: 26 December 2013;
AJC-14479
Three new triphenylamine-containing aromatic diacid monomers, 4,4'-dicarboxy-4'’-isopropyl-triphenylamine (Ma), 4,4'-dicarboxy-2’4'’-
dimethyl-triphenylamine (Mb, 4,4'-dicarboxy-4'’-ethyltriphenylamine (Mc) were successfully synthesized via the aromatic nucleophilic
fluoro-displacement reaction of 4-fluorobenzonitrile with aniline-derivatives using sodium hydride as the base, followed by alkaline
hydrolysis of the dinitrile intermediates (Ia), (Ib), (Ic). A series of poly(amine-amide)s were prepared by the direct phosphorylation
polycondensation from the newly synthesized diacid monomers with various aromatic diamines. FTIR, 1H and 13C NMR spectroscopic
techniques were used to identify the chemical structures of the dicyano intermediates, the carboxylic acid monomer and the resultant
poly(amine-amide)s. These aromatic poly(amine-amide)s were found to be readily soluble in a variety of organic solvents and could
afford strong and tough films via solution casting. They exhibited excellent thermal stability associated with high glass transition temperatures
(Tg = 248.32-290.46 ºC) and 10 % weight loss temperatures in excess of 522 ºC in nitrogen. In dilute N-methyl pyrrolidone solution, these
polymers exhibited a medium to strong photoluminescence in the blue region at (425-443) nm. Cyclic voltammetry of the poly(amine-
amide)s films cast onto an ITO-coated glass substrate in dry acetonitrile containing 0.1 M of tetrabutylammonium perchlorate (TBAP) as
an electrolyte exhibited one oxidation redox couples (Eonset) at (1.30-1.37) V versus Ag/AgCl and revealed electrochromic characteristics
with a colour change from pale yellow to blue at applied potentials switched between 0.0 and 1.6 V.
Keywords: Hole-transporting materials, Triphenylamine, Emitting layer.
transporting materials have been tried for light-emission10.
Most of the hole-transporting materials which contain amine
INTRODUCTION
The field of organic light-emitting devices (OLEDs) has
attracted considerable interests due to their potential appli-
cations in flat panel displays. Materials with hole-transporting
capability have been widely used in polymer light-emitting
devices. They have relatively high mobility’s and low ioniza-
tion potentials1-6 and are easily oxidized to form stable radical
cations7. The use of conjugated polymers in polymer light-
emitting devices (PLEDs), has received a great deal of concern
in industry because of several appealing advantages and the
most efficient devices using PLEDs is architecture with a thin-
film multilayer structure consists of a hole-transporting layer,
an emitting layer and an electron transporting layer sandwiched
between two electrodes8. Charge carriers (holes and electrons)
are injected separately from anode and cathode, recombine in
the emitting layer and thus emit light9. Many emitting materials
have been designed and used in light-emitting devices. However,
high-performance light emitting ones are rare because of the
intrinsic wide band-gap required for such materials. Many hole
functionalities show lack sufficient emission characteristics
due to reductive quenching11. Aromatic polyamides are well
accepted as high-performance polymeric materials for their
excellent mechanical properties, high thermal stability and
good chemical resistance12. They are also known as difficult
processing materials because of high melting or glass transition
temperatures and limited solubility in most organic solvents.
To overcome these limitations, polymer-structure modifica-
tion becomes necessary such as introduction of bulky, packing-
disruptive groups into the polymer backbone13-16. It has been
demonstrated that aromatic polyamides containing three-
dimensional, propeller-shaped triphenylamine unit had good
solubility inorganic solvents while retaining high thermal
stability17-19. Furthermore, triphenylamine-based polymers are
widely used as the hole-transport layer in emitting layer-
devices, but they also show interesting electrochromic
behaviour20-25. The most common method for the preparation
of aromatic polyamides is the reaction of diacid compounds

86 Rashid et al.
Asian J. Chem.
with diamines at high temperatures. The solvents used are polar
aprotic solvents like N,N-dimethyl formamide (DMF), N,N-
dimethylacetamide (DMAc), N-methyl pyrrolidone (NMP)
and HMPA. Salts, such as LiCl, CaCl2 or a mixture of both,
are often used as solubility promoters because the cations
interact with the amide groups, diminishing the strength of
the interchain hydrogen bonds. The method was developed by
Yamazaki et al.26. In this paper we synthesize new poly(amine-
amide)s via phosphorylation polycondensation reaction to form
newly synthesized monomers. The monomers and polymers
characterized structurally by FTIR, 1H and 13C NMR spectro-
scopic techniques. General properties, thermal, spectral, redox
were measured for these poly(amine-amide)s.
Synthesis of 4,4’-dicyano-4"-isopropyltriphenylamine
(Ia): A mixture of 1.40 g (0.02 mol) of sodium hydride and
80 mL of DMF was stirred at room temperature for 0.5 h. To
the mixture, 2.70 g (0.02 mol) of 4-isopropylaniline and 4.84
g (0.02 mol) of 4-fluorobenzonitrile were added in sequence.
The mixture was heated with stirring at 120 ºC for 24 h under
nitrogen and then precipitated into 150 mL of cold water27,28
.
The products were filtered and recrystallized from ethanol to
give pale yellowish solid 3.43 g (yield: 51 %), m.p. =(185-
188) ºC. FTIR: 2211.4 cm-1 (C≡N).1H NMR (400 MHz, CDCl3-
d, δ ppm):7, 42 (d, 4H, Hd), 7.15 (d, 2H, Ha), 7.03 (d, 4H,
Hc), 6.97(d, 2H, Hb), 2.85 (m, 1H, HCH), 1.20(d, 6H, HCH3).
13C NMR (400 MHz, CDCl3-d, δ ppm):150.20 (C5),
147.47(C4), 105.38(C8), 118.92(CN), , 122.54(C6), 126.93(C2),
EXPERIMENTAL
128.21(C3), 133.40(C7), 142.38(C1),. 33.62(CCH), 23.84(CCH ).
3
4-Isopropylaniline (Merck, 99.8 %), 2,4-dimethylaniline
(Acros, 98.7), 2-ethylaniline (Merck, 99.5), 4-fluoro-
benzonitrile (Acros, 98.7 %), sodium hydride (NaH) (Fluka,
60 %), N,N-dimethylformamide (DMF) (Acros, 99.6 %), po-
tassium hydroxide (Fluka, 99.8 %), ethanol (Merck, 99.7 %),
acetic acid (Merck, 98 %), hydrochloric acid (Merck, 36 %),
dimethyl sulfoxide-d6, (DMSO-d6) (Merck, 99.8 %), chloro-
form-D1, (CDCl3) (Merck, 99.8 %), P-phenylenediamine
(Merck, 98 %), 1,5-diaminonaphthalene (Fluka, 98.8 %), py-
ridine (Merck, 97.8 %), triphenylphosphite (Fluka, 99 %), cal-
cium chloride (Merck, 99,6 %), N-methyl pyrolidone (NMP)
(Fluka, 99.6 %) were used without further purification.
The FT-IR spectrum of the synthesizied compounds were
recorded with a Spotlight 400 Perkin Elmer spectrometer. 1H
NMR (400 MHz) and 13C NMR (100 MHz) measurements
were performed with a JEOL spectrometer. UV-visible absor-
ption and photoluminescence spectra were recorded in N-
methyl pyrolidone with concentration (10-5 M) on a Cary 60
UV-visible spectrophotometer. Thermal data were obtained
from a Perkin Elmer DSC6 instrument. The data were recorded
under nitrogen atmosphere at a heating rate of 20 ºC/min with
a SDT Q600 thermogravimetric analyser. The thermal decom-
position data were recorded at a heating rate of 20 ºC/min
under nitrogen atmosphere with a SDT Q600 thermogravi-
metric analyser (TGA Instrument).
4,4’-Dicarboxy-4"-isopropyltriphenylamine (Ma): A
mixture of 15.5 g of potassium hydroxide and 6.74 g (0.02
mol) of the dinitrile compound (1) in 60 mL of ethanol and 60
mL of distilled water was stirred at 100 ºC until no further
ammonia was generated. The time taken to reach this stage
was ca. 24 h. The solution was cooled and the pH value was
adjusted by dilute HCl to near 3. The yellowish precipitate
formed was collected by filtration, washed thoroughly with
water. Recrystallization from acetic acid gave pale yellow
crystals 6.0 g (80 % yield); m.p. = 268-270 ºC. FTIR: 1681
cm-1 (C=O), 2987 cm-1 (O-H). 1H NMR (400 MHz, DMSO-
d6, δ ppm): 7.99 (d, 4H, Hd),7.28(d, 2H, Ha),7.07(d, 2H, (Hb),
7.00 (d, 4H, HC), 2.88 (m, 1H, HCH), 1.21 (d, 6H, HCH ), 12.70
3
(br, 2H, COOH).13C NMR (400MHz,DMSO-d6, δ ppm):166.83
(COOH), 150.44 (C5), 145.82 (C4), 143.22 (C1), 130.97 (C7),
128.01 (C3),124.42 (C2) 126.56 (C8), 121.86 (C6), 23.81 (CH),
23.81 (CH3).
4,4’-Dicyano-4"-2,4-dimethylaniline(Ib): The synthesis
of this compound was the same to that for Ia. The product was
filtered and recrystallized from ethanol to give pale yellowish
solid 2.31 g (yield: 71.5 %), m.p. = 146-148 ºC. FTIR: 2222.4
cm-1(CN). 1H NMR (400 MHz, CDCl3-d1, δ ppm): 7.71-7.69
(d, 4H, He), 7.53-7.49 (m, 1H, Ha), 7.13-7.09 (m, 5H, Hb,d),
7.05-7.03(m, 1H, Hc), 2.12 (s, 3H, HCH "), 1.29-1.23(m, 3H,
3
13
HCH ’). C NMR (400 MHz, CDCl3-d1, δ ppm): 150.22(C7),
3
Monomer synthesis: The monomers (Ma-Mc) have
synthesized via the route as explained in the Scheme-I.
143.41(C3), 138.68(C1), 136.91 (C6), 135.22 (C9), 134.06(C2),
121.81(C4), 120.51(C8), 119.19 (C5), 118.60 (CCN), 108.36(C10).
CN
CN
NC
NaH
N
COOH
HOOC
N
NH2
1-KOH, H2 O . Ethanol
2
+
Ar
DMF
2-HCl, H2O
Ar
Ar
F
(Ia) -(Ic)
(Ma)-(Mc)
CH2CH3
CH3
Ar :
CH3
H3C
CH3
H
Scheme-I: Synthesis routes of monomers

Vol. 26, No. 1 (2014)
Synthesis and Effect of Triaryl Ring Substituents Groups Triphenylamine-Based Aromatic Polyamides 87
4,4’-Dicarboxy-4"-2,4-dimethyltriphenylamine (Mb):
The synthesis of this compound was the same to that for Ma.
The pale yellow crystals 3.40 g (94.18 % yield); m.p = 276-
is used as an example to illustrate the general synthetic routes.
The typical procedure is as follows. A mixture of 1.14 g (3
mmol) of the dicarboxylic acid monomer (Ma), 0.324 g (3
mmol) of p-phenylenediamine, 0.4 g of calcium chloride, 4.5
mL of triphenyl phosphite (TPP), 1.5 mL of pyridine and 4.5
mL of N-methyl-2-pyrrolidone (NMP) was heated with stirring
at 105 ºC for 3 h. The resulting viscous polymer solution was
poured slowly into 300 mL of stirring methanol giving rise to
a stringy, fiber-like precipitate that was collected by filtration,
washed thoroughly with hot water and methanol and dried at
80 ºC for 24 h. The inherent viscosity of the obtained poly-
(amine-amide) was 0.62 dL/g, measured at a concentration of
0.5 g/dL in dimethyl acetamide. The IR spectrum exhibited
characteristic amide absorption bands at 3309.39 (N-H stretching)
and 1644 cm-1 (amide carbonyl). 1H NMR (400 MHz, DMSO-
d6, δ ppm): 10.25 (S, 1H, HNH-CO), 8.05 (d, 4H, Hd) 7.75 (s, 4H,
He), 7.39 (d, 2H, Ha), 7.20 (d, 4H, Hc), 6.59 (d, 2H, Hb), 3.19
1
278 ºC. FTIR: 1683 cm-1 (C=O), 2710-3321 cm-1 (O-H). H
NMR (400 MHz, DMSO-d6, δ ppm):12.81(s, 2H, HCOOH),
7.98(d, 4H, He), 7.84-7.80(m, 1H, Ha), 7.14-7.12(d, 4H, Hd),
7.02-7.00(d, 1H, Hb), 6.96-6.94(d, 1H, Hc), 2.06(s, 3H, HCH3"),
13
1.20(s, 3H, HCH ’). C NMR (400 MHz, DMSO-d6, δ ppm):
3
166.88(CCOOH), 149.86(C7), 143.47(C3), 132.00(C9),
131.11(C1), 129.00(C2), 128.02(C6), 122.04(C4), 126.76(C10)
120.29 (C5), 118.98(C8), 33.15(CCH "), 23.99(CCH ’).
3
3
4,4’-Dicyano-4"-2-ethylaniline (Ic): The synthesis of this
compound was the same to that for Ia. The product was filtered
and recrystallized from ethanol to give pale yellowish solid
2.80 g (yield: 77.5%), m.p. = 110-112 º. FTIR: 2219 cm-1 (CN).
1H NMR (400 MHz, CDCl3-d1, δ ppm): 7.62-7.60(d, 4H, Hf),
7.43-7.31(m, 3H, Ha,b,c), 7.17-7.09 (dd, 5H, He,d), 2.39-2.32
13
(q, 2H, HCH ), 0.99-0.96 (t, 3H, HCH ), C NMR (400 MHz,
(m, 1H, HCH) 2.07 (s, 6H, HCH ). 13C NMR (400 MHz, DMSO-
2
3
3
CDCl3-d1, δ ppm): 150.48(C7), 142.97(C6), 135.38-135.31
(C1,5), 134.04 (C9), 131.34(C2), 130.59(C3), 129.06(C4),
122.33(C8) 120.54(CCN), 105.51(C10), 24.46(CCH2), 13.86
d6, δ ppm): 166.74 (NHCO), 150.44 (C5), 145.82 (C4), 143.22
(C1), 131.83 (C9), 130.97 (C7), 128.23 (C3), 124.12(C2),
126.12(C8), 121.76C6), 120.02 (C10), 32.91 (CCH), 23.81 (CCH ).
The other poly(amine-amide)s were prepared by analogous
procedure.
3
(CCH ).
3
4,4’-Dicarboxy-4"-2-ethyltriphenylamine (Mc): The
synthesis of this compound was the same to that for Ma. The
pale yellow crystals 3.40 g (94.2 % yield); m.p. = 273-275 ºC.
FTIR: 1680 cm-1 (C=O), 2713-3332 cm-1 (O-H). 1H NMR (400
MHz, DMSO-d6, δ ppm): 12.76(s, 2H, HCOOH), 7.83-7.81(d,
4H, Hf), 7.42-7.31 (m, 3H, Ha,b,c), 7.15-7.13 (d, 5H, He,d), 2.34-
2.28 (q, 2H, HCH ), 0.96-0.91 (t, 3H, HCH ). 13C NMR (400
Synthesis of poly(amine-amide) (Pb1): The polymer
Pb1 was synthesized by the same method as described in
synthesis of Pa1. The obtained poly(amine-amide) was 0.66
dL/g, measured at a concentration of 0.5 g/dL in DMAc. The
IR spectrum 3304 cm-1 (N-H stretching) and 1644 cm-1 (amide
carbonyl). 1H NMR (400 MHz, DMSO-d6, δ ppm): 10.26 (s,
1H, HNHCO), 8.05-7.90 (d, 5H, He), 7.74 (s, 4H, Hf), 7.20 (s,
4H, Ha,b,d), 6.74 (s, 1H, Hb), 6.74-6.56 (s, 1H, Hc), 1.97(s, 3H,
2
3
MHz, DMSO-d6, δ ppm): 166.81 (CCOOH), 150.86(C7),
143.25(C6), 131.20(C1)131.03(C5), 132.18(C9), 128.50(C2),
13
128.34(C3), 128.17(C4), 126.33(C10), 122.16(C8) 23.15(CCH ),
13.23 (CCH ).
HCH ") 1.21(s, 3H, HCH ’). C NMR (400 MHz, DMSO-d6, δ
3
3
3
ppm): 166.89 (CCO-NH), 149.97 (C7), 142.89 (C3), 131.91(C9),
131.21(C1), 129.04(C2), 128.34(C6), 126.45(C10), 125.22(C11),
123.17(C4), 120.17(C5), 118.12(C8), 117.23(C12), 33.45(CCH ").
3
Polymer synthesis
3
Synthesis of poly(amine-amide) (Pa1): The polymers
(Pa1-Pc1, Pa2-Pc2) have synthesized via the routes as explained
in the Scheme-II. The synthesis of poly(amine-amide) (Pa1)
Synthesis of poly(amine-amide) (Pc1): The polymer Pb1
was synthesized by the same method as described in synthesis
of Pa1. The obtained poly(amine-amide) was 0.63 dL/g,
O
O
COOH
HOOC
N
H
N
H
N
N
Ar
n
R
Pyridine / TPP
CaCl2 , NMP
+
N
H2
N
Ar
H2
Ar
R'
Ar-
Ar-
:
p
-phenylene diamine
(Pa1)
(Pa2
R' H C-CH-CH
=
3
3
:
1,5-diamino naphthalene
Ma
R
0
=
Ar- : 1,5-diamino naphthalene
Ar-: 1,5-diamino naphthalene
(Pb1
(Pb2
R
-CH
=
3
Mb
Mc
R' -CH
=
3
Ar- : 1,5-diamino naphthalene
Ar-: 1,5-diamino naphthalene
(Pc1)
(Pc2)
R = -CH2CH3
R'
=
0
Scheme-II: Synthetic routes of the polymers

88 Rashid et al.
Asian J. Chem.
RESULTS AND DISCUSSION
measured at a concentration of 0.5 g/dL in dimethyl acetamide.
The IR spectrum 3314 cm-1 (N-H stretching) and 1644 cm-1
1
(amide carbonyl). H NMR (400 MHz, DMSO-d6, δ
Monomer synthesis: The new aromatic dicarboxylic acid
having 4-isopropyl substituted triphenylamine unit, 4,4’-
dicarboxy-4"-isopropyltriphenylamine (Ma), was synthesized
by the amination reaction of 4-isopropylaniline with 4-fluoro-
benzonitrile, followed by the alkaline hydrolysis of the inter-
mediate dicyano compound (Ia). According to the synthetic
routes outlined in Scheme-I. FT IR, 1H and 13C NMR spectro-
scopic techniques were used to identify the chemical struc-
tures of the intermediate dicyano compounds (Ia) and the di-
carboxylic acid monomer (Ma).The FTIR spectra of
compound Ia gave a cyano group characteristic band at 2221
cm-1 (C≡N stretching). After hydrolysis, the cyano group
absorption beak disappeared and the carboxylic acid group
showed a typical carbonyl absorption band at 1678 cm-1 (C=O
stretching) together with the appearance of broad bands around
3400-2700 cm-1 (O-H stretching) (Fig. 1).
ppm):10.23(S, 1H, HNHCO), 7.98-7.83 (S, 1H, Hf,a), 7.40-7.34
(S, 1H, Hg,c), 7.13-6.73 (S, 1H, Hb,e,d), 2.06(S, 1H, HCH2), 0.93(S,
1H, HCH ) 13C NMR (400 MHz, DMSO-d6, δ ppm): 166.82
3
(CCO-NH), 150.12 (C7), 142.89(C6), 131.20 (C1), 131.03(C5),
131.91(C9), 129.17(C2), 128.89(C3), 127.16(C4), 126.12(C10),
125.32(C11), 122.23(C8), 121.18(C12), 26.45(CCH2),
13.43(CCH ).
3
Synthesis of poly(amine-amide) (Pa2): This polymer
Pa2 was synthesized by the same method as described in
synthesis of Pa1 but used 1,5-diamine naphthalene instead of
p-phenylene diamine.The inherent viscosity of the obtained
poly(amine-amide) was 0.75 dL/g, measured at a concentration
of 0.5 g/dL in DMAc. The IR spectrum exhibited characteristic
amide absorption bands at 3364 cm-1 (N-H stretching) and
1647 cm-1 (amide carbonyl). 1H NMR (400 MHz, DMSO-d6,
δ ppm): 10.42 (s, 1H, HNH-CO), 7.99-7.97(d, 2H, Hg), 7.84-
7.82(d, 4H, Hd), 7.50(s, 2H, Hf), 7.37-7.35(d, 2H, Ha), 7.29-
7.27(d, 2H, He), 7.15-7.13(d, 4H, Hc), 7.03-7.01(d, 2H, Hb),
Ia
2221
Stretch CN
1.92-1.84(m, 1H, HCH), 1.21-1.19(d, 6H, HCH ).13C NMR(400
3
MHz, DMSO-d6, δ ppm): 166.56 (CCONH), 150.47(C5), 145.68
(C4), 143.46(C1), 131.76(C9), 130.36(C7), 128.33(C3),
127.40(C2), 126.11(C8),125.98(C13), 125.68(C11), 121.86(C6),
Ma
2987.07
OH
1678
Stretch
COOH
110.77(C12), 104.24(C10), 32.82(CCH), 23.87(CCH ).
3
Synthesis of poly(amine-amide) (Pb2): This polymer
was synthesized by the same method ass describd in synthesis
of Pa1 but used 1,5-diamine naphthalene instead of p-phenylene
diamine.The inherent viscosity of the obtained poly(amine-
amide) was 0.67 dL/g, measured at a concentration of 0.5
g/dL in DMAc. The IR spectrum exhibited characteristic amide
absorption bands at 3364 cm-1 (N-H stretching) and 1648 cm-1
4000
3500
3000
2500
Wavelength (cm–1)
Fig. 1. FTIR spectrum of compounds (Ia), (Ma)
2000
1500
1000
500
Structures of compounds Ia and Ma were also confirmed
by high-resolution NMR spectra (Figs. 2 and 3). In 1H NMR
spectrum (Fig. 2), a two big doublet peaks at 7.42 (d, 4H, Hd),
7.03 (d, 4H, Hc), due to four phenylene protons(d) and (c),
respectively. Doublet peak at 7.15 (d, 2H, Ha) due to two
protons of (a). Doublet peak at 6.97(d,2H, Hb) for two protons
of (b). Multiplet peak of proton (-CH-). Doublet peak of six
protons for (2CH3). Fig. 3 exhibits very broad singlet peak
due to proton of carboxylic group which is hardly observed
because replacement hydrogen atoms of (COOH) by deuterium
of DMSO solvent and formation of H-bonding. The 13C NMR
spectra (Figs. 4 and 5) confirmed that the chemical shifting of
C-atoms and that the cyano groups were completely converted
into the carboxylic acid groups by the disappearance of the
resonance peak for the cyano carbon at 105.42 ppm and by
the appearance of the carboxylic peak at 166.8 ppm.
1
(amide carbonyl). H NMR (400MHz, DMSO-d6, δ ppm):
10.46 (s, 1H, HNH-CO),8.14 (s, 6H, He,h), 7.94-7.88(d, 2H, Hg),
7.55-7.24(d, 2H, Hf),7.20-7.06(d, 6H, Ha,b,d), 6.68-6.64 (d, 2H,
Hc), 1.98-1.76(s, 3H, HCH "), 1.23-0.92(s, 3H, HCH ’). 13C NMR
3
3
(400 MHz, DMSO-d6, δ ppm): 166.86 (CCONH), 150.54(C7),
143.73(C3), 132.71(C11), 131.75(C9), 131.12(C1), 130.76 (C2),
128.58(C6), 126.67(C10), 125.87(C15), 124.77(C13),
122.57(C4),121.82(C5). 118.82(C8), 110.23(C14), 107.63(C12),
33.07(CCH "), 23.65(CCH ’).
3
3
Synthesis of poly(amine-amide) (Pc2): This polymer
Pc2 was synthesized by the same method as described in
synthesis of Pa1 but used 1,5-diamine naphthalene instead of
p-phenylene diamine.The inherent viscosity of the obtained
poly(amine-amide) was 0.81 dL/g, measured at a concentration
of 0.5 g/dL in DMAc. The IR spectrum exhibited characteristic
amide absorption bands at 3357 cm-1 (N-H stretching) and
1648 cm-1 (amide carbonyl). 1H NMR (400 MHz, DMSO-d6,
δ ppm): 10.43(s, 1H, HNHCO), 8.12-8.08(s, 7H, Hf,a,i), 7.88-7.86
(d, 2H, Hh), 7.64-7.50 (d, 2H, Hg,c), 7.19-7.00(d, 5H, He,d),
6.66-6.64 (d, 1H, Hb), 2.06 (q, 1H, HCH ), 0.97 (t, 1H, HCH .13C
NC
N
CN
CH3
c
d
b
a
2
3
NMR (400 MHz, DMSO-d6, δ ppm): 165.92 (CCONH), 150.24
(C7), 142.56(C6), 132.05(C5), 131.85(C1), 131.24(C11),
130.86(C9), 131.12(C2), 130.76(C3), 128.58(C4), 126.56(C10),
124.06(C15), 121.77(C13), 118.57(C8), 110.32(C14).
106.81(C12), 26.43(CCH ), 13.63 (CCH ).
H2O
H3C
CH3
H
–CH–
8
7
6
5
4
3
2
1
cm–1
Fig. 2. 1H NMR spectrum of compound (Ia) in CDCl3-D1
2
3

Vol. 26, No. 1 (2014)
Synthesis and Effect of Triaryl Ring Substituents Groups Triphenylamine-Based Aromatic Polyamides 89
by the direct polycondensation reactions of the dicarboxylic
acid monomer (Ma) with various aromatic diamines, p-phenyl-
HOOC
N
COOH
c
d
enediamine, 1,5-diamino naphthalene using triphenylphosphite
(TPP) and pyridine as condensing agents (Scheme-II).All the
polymerizations proceeded homogeneously throughout the
reaction and afforded clear, highly viscous polymer solutions.
b
a
H3C
CH3
H
These polymers precipitated in a tough, fiber-like form when
the resulting polymer solutions were slowly poured with stirring
into methanol. These poly(amine-amide)s were obtained in
almost quantitative yields, with ηCinh values in the range of
0.62-0.81 dL/g (Table-2). All the polymers can be solution-
cast into flexible and tough films. Structural features of these
poly(amine-amide)s were verified by FTIR and NMR spectro-
scopy. The characteristic absorption bands observed around
3309.39 (N-H stretching) and 1644 cm-1 (C=O stretching of
amide group). Fig. 6 illustrates a typical FTIR spectrum of the
representative poly(amine-amide) (pa1). Typical set of 1H and
13C NMR spectra of polyamide in DMSO-d6. Assignments of
each proton and the spectra agree well with the proposed
molecular structure of pa1.
8.5
7.5
6.5
5.5
4.5
ppm
3.5
2.5
1.5
0.5
Fig. 3. 1H NMR spectrum of compound (Ma) in CDCl3-D1
6
7
5
8
NC
N
CN
4
3
2
1
CH3
H3C
CH3
CHCl3
H
–CH–
3309.39
NH
180
160
140
120
100
ppm
80
60
40
20
0
Fig. 4. 13C NMR spectrum of compound (Ia) in CDCl3-D1
6
7
1644
(CO-NH-)
5
8
HOOC
N
COOH
4
3
4000
3500
3000
2500
2000
1500
1000
500
0
2
1
Fig. 6. FTIR spectrum of poly(amine-amide) (pa1)
DMSO
H3C
CH3
e
e
O
C
O
C
H
H
N
H
N
N
CH3
–CH–
c
d
CH3
n
b
a
COOH
160
DMSO
H2O
180
140
120
100
ppm
80
60
40
20
0
H3C
CH3
Fig. 5. 13C NMR spectrum of compound (Ma) in DMSO-d6
TABLE-1
POLYMER CODES
CH
Polymer diamine
Monomer code
10.5
8.5
6.5
4.5
2.5
0.5
ppm
Fig. 7. 1H NMR of compound poly(amine-amide) (pa1)
1
1
1
2
2
2
pa1
pb1
pc1
pa2
pb2
pc2
Ma
Mb
Mc
Ma
Mb
Mc
O
O
H
N
H
N
5
N
9
8
4
6
10
7
n
3
2
Other important evidence of this change is the shifting of
1
the carbon resonance signals of C8 adjacent to the cyano or
carboxyl group. The C8 of dinitrile (Ia) resonated at a higher
field (105.4 ppm) than the other aromatic carbons because of
the anisotropic shielding by the π-electrons of Ca≡N. After
hydrolysis, the resonance peak of C8 shifted to a lower field
(126.56 ppm) because of the lack of an anisotropic field.
Polymer synthesis:A series of new aromatic poly(amine-
amide)s with aryltriphenylamine (ATPA) units were prepared
H3C
CH3
DMSO
CH3
-CH-
NH-CO
180
160
140
120
100
ppm
80
60
40
20
Fig. 8. 13C NMR of poly(amine-amide) (Pa1) in DMSO-d6

90 Rashid et al.
Asian J. Chem.
TABLE-2
SOLUBILITY OF AROMATIC POLYAMIDES
Solventsa
Polymer
code
η
inhb (dl/g)
NMP
++
DMAc
++
DMF
++
DMSO
++
m-Cresol
THF
CHCl3
pal1
pb1
pcl1
pa2
pb2
pc2
0.62
0.66
0.63
0.75
0.67
0.81
–
–
–
+
+
+
–
–
–
–
–
–
–
–
–
–
–
–
++
++
++
++
++
++
++
++
++
++
++
++
++
++
++
++
++
++
++
++
aSolubility: ++, soluble at room temperature, +: soluble on heating, -, insoluble even on heating. bMeasured at a polymer concentration of 0.5 g/dL
in DMAc at 30 ºC.
Also, the monomer Ma reacts with 1,5-diamino naphtha-
lene to form polyamide with more solubility in the polar solvent.
This polymer characterized by FTIR, H and 13C NMR as
shown in Figs. 9-11.
presence of introduced triphenylamine unit. Polymers (pa2),
(pb2), (pc2) have more solubility than others because the more
bulky pendent naphthalene group chromophores in the repea-
ting unit leading to increase in free volume in the polymer
chains to allow more solvent to come in. Further more, poly-
mers (pb2)-(pc2) are more flexibility. The excellent solubi-
lity makes these polymers convenient to process into articles
by spin-coating.
1
3264
N-H stretch
Thermal properties: DSC thermograms of all the
poly(amine-amide)sare as shown in Fig. 12. The thermal
behaviour data of these polymers are summarized in Table-3.
They showed high glass transition temperatures Tg in the range
of (289.60-248.32) ºC. The Tg values of these poly(amine-
amide)s generally decreased with decreasing stiffness of the
diamine component. So polymers with phenylene diamine
exhibited high Tg value due to more rigidity than of polymers
with 1,5-diamine.The lowest Tgvalue of poly(amine-amide)s
can be explained in terms of the flexibility and low rotation
barrier of its diamine moiety. Poly(amine-amide) (pb1) exhibited
the highest Tg value (289.60 ºC) in this series polymers because
of the presence of rigid phenylene diamine and methyl groups
segment in the main chain.
O
1647
C
4000
3500
3000
2500
2000
1500
1000
500
cm–1
Fig. 9. FTIR spectrum of poly(amine-amide) (pa2)
e
f
O
O
H
N
g
N
c
d
H
N
b
a
n
CH3
H2O
H3C
CH3
CH3
NH
Onset = 281 °C
12
10
8
Tg = 289.60 °C
12
10
8
6
4
2
ppm
1
Fig. 10. H NMR of compound poly(amine-amide) (pa2)
Onset = 238.01 °C
Tg = 248.32 °C
6
7
6
11
10
O
O
4
H
N
5
9
8
N
12
13
4
2
H
N
3
n
2
0
200
1
220
240
260 280
Temperature (°C)
300
320
340
H3C
CH3
CH3
DMSO
Fig. 12. DSC of poly(amine-amide)s (pa1), (pc1)
CH3
20
-CH-
Fig. 13 shows the TGA curves of poly(amine-amide) (pa1).
The decomposition temperatures (Td) at 5 and 10 % weight
losses in nitrogen atmosphere are given in Table-3. All the
poly(amine-amide)s exhibited good thermal stability with
insignificant weight loss up to 300 ºC in nitrogenand the 5 %
weight-loss temperatures in nitrogen were recorded in the range
of (410-460 ºC) and (451-522 ºC) for 10 % weight. Due to
their high aromatic content, these polymers revealed high char
yields in nitrogen, more than 60 % at 800 ºC.
160
140
120
100
ppm
80
60
40
Fig. 11. 13C NMR of poly(amine-amide) (Pa2)
Polymer properties
Solubility: The qualitative solubility properties of poly-
(amine-amide)s in several organic solvents at 10 % (w/v) are
also summarized in Table-2. All the polymers exhibited
excellent solubility in polar organic solvents such as NMP
and DMAc. The enhanced solubility can be attributed to the
Spectral properties: The optical properties of poly-
(amine-amide)s were investigated by UV-visible and photo-

Vol. 26, No. 1 (2014)
Synthesis and Effect of Triaryl Ring Substituents Groups Triphenylamine-Based Aromatic Polyamides 91
TABLE-3
Polymer code (ºC)
(pb1)
Onseta (ºC)
265.45
281.00
230.01
243.32
246.92
238.30
Tbb (ºC)
283.32
289.60
248.32
260.00
265.45
248.32
Onsetc (ºC)
383.76
364.84
367.37
357.04
361.43
370.21
Td 5 % (ºC)
Td 10 % (ºC)
Peak (%)
444.04
443.72
437.20
421.22
411.04
405.23
Char.e
460
522
63
(pc1)
410
480
65
(pa1)
400
475
67
(pa2)
400
475
61
(pb2)
430
472
65
(pc2)
420
451
65
a: onset temp,recorded by DSC. b: The midpoint temperature of baseline shift on the subsequent DSC trace ( from 30-350 ºC at heating rate 20
ºC/min) was defined as Tg. C: onset temp. Recorded by TGA. Td: Decomposition temperature at which a 5% or 10% weight loss was recorded by
TGA at a heating rate of 20 ºC/min. Peak: The midpoint temperature of baseline shift on the subsequent TGA trace (from 50-800 ºC at heating rate
20 ºC/min) was defined as peak(ºC). e: Residual weight percentages at 800 ºC under nitrogen flow.
1.2
110
1.0
0.8
0.6
0.4
0.2
0
100
90
80
70
60
50
40
280
330
380
430
Wavelength (nm)
480
530
580
200
300
400 500
Temperature (°C)
600
700
800
Fig. 14. UV-visible absorption spectra of poly(amine-amide)s in
concentration (10-5 M) in NMP
Fig. 13. TGA of Poly(amin-amide) (pa1)
luminescence spectroscopy. The results are summarized in
Table-4. The dilute solutions of these poly(amine-amide)s in
NMP exhibited strong UV-VIS absorption bands at (318-355)
nm, assignable to the (n-π*) transition resulting from the conju-
gation between the aromatic rings and nitrogen atoms and transi-
tion from the characteristic (π-π*) transitions of naphthalene
chromophore29. Their spectra in NMP solution showed photo-
luminescence emission maxima bands around (425-443) nm
in the blue region. Figs. 14 and 15 shows the UV-visible
absorption and photoluminescence spectra for poly(amine-
amide)s. Fig. 16 showed the strong fluorescence emissions
inthe blue region which can be explained from the decreased
intra- and intermolecular electronic interactions. The bulky,
crank effective in decreasing charge transfer formation within
or between polymer chains through steric hindrance. The UV-
visible transmittance spectra of these poly(amine-amide)s films
and cut-off wavelengths (absorption edge λo) in the range of
(412-430) nm are also indicated in Fig. 16.
80
70
60
50
40
30
20
10
0
350
400
450
500
550
600
Wavelength (nm)
Fig. 15. UV-visible photoluminescence emission of poly(amine-amide)s in
concentration (10-5 M) in NMP
100
80
60
40
20
0
Electrochemical properties:The redox behaviour of poly-
(amine-amide)s was investigated by cyclic voltammetry for
TABLE-4
Polymer
code
Onset
(nm)b
λabs,max
(nm)a
λabs
(nm)a
λPLλo
(nm)c
(pa1)
(pb1)
(pc1)
(pa2)
(pb2)
(pc2)
355(352)
354(356)
350(350)
328(327)
318(319)
320(321)
422(420)
436(438)
418(417)
427(422)
423(419)
421(423)
431
439
425
438
443
427
427
420
418
410
405
414
a: UV-VIS absorption measurements in NMP (1 × 10-5 M) at room
temperature. Values in the parentheses were measured in polymer film.
b: PL spectra measurements in NMP (1 × 10-5 M). c: the cutoff
wavelengths (λo) from the transmission.
250
300
350
400
450
500
550
600
650
Wavelength (nm)
Fig. 16. UV-visible transmittance spectra of poly(amine-amide)s with a
concentration (10-5 M) in NMP

92 Rashid et al.
Asian J. Chem.
TABLE-5
abs, onset HOMOa
(eV)
Eonset/V(vs. Ag/AgCl) in
CH3CN (nm)
LUMOb
(eV)
HOMO-LUMO gapc
(eV)
λ
Polymer code
pa1
pb1
pc1
pa2
pb2
pc2
1.35
1.31
1.27
1.37
1.34
1.30
422(420) 5.74
436(438) 5.70
418(417) 5.66
421(423) 5.76
423(419) 5.73
27(422) 5.69
2.79
2.87
2.69
2.83
2.78
2.76
2.95
2.83
2.97
2.93
2.95
2.93
a: The HOMO energy levels were calculated from cyclic voltammetry and were referenced to ferrocene (4.8 eV). b: LUMO = HOMO – gap. c:
Energy gap data were calculated of thin film by the equation: Energy gap = 1240/λonset of polymer film.
the cast film on an ITO-coated glass substrate as working
electrode in dry acetonitrile containing 0.1 M of tetrabutyl-
ammonium perchlorate as an electrolyte, under nitrogen
atmosphere.All the poly(amine-amide)s showed an reversible
oxidation process. Fig. 17 shows the typical cyclic voltammogram
for poly(amine-amide) (pa1) recorded at scanning rate of 0.1
V/s. One reversible oxidation redox couple with half- wave at
E1/2 = 1.35V (vs.Ag/Ag/Cl) in the oxidative scan was observed.
Because of electrochemical stability of the films and good
adhesion between the polymer and ITO substrate, the poly-
amide (pa1) exhibited good reversibility of electrochromic
characteristics by continuous five scans between 0.0-1.60 V
changing colour from original pale yellowish to blue. The
energy of the HOMO and LUMO levels of the corresponding
poly(amine-amide)s can be determined from the oxidation
onset (Eonset) and the onset absorption wavelength of the UV-
VIS absorption of thin films30 and the results are listed in Table-
5. The external ferrocene/ferrocenium (Fc/Fc+) redox standard
Eonset is 0.41 V versus Ag/AgCl in CH3CN and the HOMO
energy for the Fc/Fc + standard is 4.80 eV with respect to the
zero vacuum level. Therefore, the HOMO energy for (pa1)
has been evaluated to be 5.74 EV as follows: E1/2 (onset)=
(EPC + Epa)/2 where pc and pa are potentials of cathode and
anode, respectively.
Conclusion
A series of new poly(amine-amide)s bearing derived-
triphenylamine units in the polymer main chain have been
successfully prepared from a newly synthesized aromatic
derived triphenylamine dicarboxylic acid, 4,4'-dicarboxy-4"-
triphenylamine with two different aromatic diamines by
phosphorylation polyamidation technique.All the poly(amine-
amide)s were amorphous with high Tg and exhibited excellent
thermal stability and useful redox stability. These polymers
exhibited blue photoluminescence both in film and in solution.
Thus, these novel triphenylamine-containing polyamides may
find applications in electroluminescent devices as hole-trans-
porting or blue-light-emitting polymeric materials.
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Working electrode
Oxidation
-0.05
-0.10
-0.15
-0.20
-0.25
-0.30
10 µA
Ferrocene/ferrocenium
(Fc/Fc+) redox standard
(a)
(b)
1.0
0.5
Potential (V vs. / AgCl)
0.0
pa
2.0 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2
0
Potential (V vs. / AgCl)
Fig. 17. Cyclic voltammograms of (a) ferrocene as reference and (b) the
cast film of poly(amine-amide) (pa1) on the indium-tin oxide(ITO)-
coated glass substrate in CH3CN containg 0.1 M TBAP, with a scan
rate of 0.1 V/s