JOURNAL OF POLYMER SCIENCE: PART A: POLYMER CHEMISTRY DOI 10.1002/POLA
119.90, 116.56, 111.20, 94.65, 85.59, 35.20, 33.52, 28.09,
26.92, 22.66, 14.03, 13.95, 10.53. Mn ¼ 19,000, Mw/Mn ¼ 2.4
(GPC, polystyrene calibration). Td (oC, 5% weight loss): 330.
3:2 molar ratio of the bis-ethynyl monomer (1, 2, 3, or 4)
and tri(4-iodophenyl)amine) (5) were allowed to react in
presence of catalytic amount of (PPh3)2PdCl2 and CuI as
shown in Scheme 1. Initially, the polymerization was carried
out following the procedure routinely used for the synthesis
of linear PAEs.20,11a In this procedure, A2 (0.24 mmol) and
B3 (0.16 mmol) monomers were dissolved in chlorobenzene
(4 mL) to which (PPh3)2PdCl2 (0.0032 mmol), CuI (0.0064
mmol), and diisopropylamine (2 mL) wꢀere added and the
mixture was heated under stirring at 65 C. However, in this
condition, the reaction mixture gelled within 30 min. There-
fore, to avoid gelation, the polymerization was carried out by
taking the B3 monomer along with catalyst and base and a
chlorobenzene solution of A2 was added slowly. For all the
polymerization, chlorobenzene was used as solvent for poly-
merization to obtain high molecular weight as well as more
soluble polymers.18 It was observed that by increasing the
reaction temperature above 50 ꢀC, the color of the reaction
mixture turned dark brown with the formation of insoluble
mass. Therefore, all the polymerization reactions were car-
ried out at room temperature. It was also observed that the
soluble polymers without end capping are found to become
insoluble after Soxhlet extraction and drying. This dark color
and insolubility of the polymers may be attributed to cross-
linking of the polymers. This type of behavior was also
observed by others and described the crosslinking of the
polymers due to the tendency of cyclo- and [4 þ 2] cyclodi-
merization of the remaining ethynyl groups with ene-ethynyl
moieties in the presence of Pd traces or possible Bergman
cyclization of the ene-dieyne moieties in the polymer.21
HB-PAE2
9,9-Bis(2-ethylhexyl)-2,7-diethynyl-9H-fluorene (2) (105.68
mg, 0.24 mmol) was used. Yield: 86%. FTIR (cmꢁ1, KBr):
2954, 2923, 2858, 2361, 2335, 1540, 1514, 1457, 820. 1H
NMR (CDCl3, 300 MHz), d (ppm): 7.65 (Ar-H, fluorene), 7.54
(Ar-H, fluorene), 7.07 (Ar-H, TPA), 6.86 (Ar-H, TPA), 2.17 (CH2),
2.00 (CH), 1.66–0.74 (CH2), 0.55 (CH3). 13C NMR (CDCl3, 125
MHz), d (ppm): 150.91, 146.55, 138.44, 132.74, 131.58, 130.47,
128.04, 127.00, 126.33, 123.35, 121.61, 120.12, 119.90, 94.15,
84.80, 44.54, 34.68, 33.52, 27.99, 26.92, 22.66, 14.03, 13.95,
10.23. Mn ¼ 22,700, Mw/Mn ¼ 3.3 (GPC, polystyrene calibra-
tion). Td (ꢀC, 5% weight loss): 325.
HB-PAE3
1-(2-Ethylhexyloxy)-2,5-diethynyl-4-methoxybenzene (3) (68.25
mg, 0.24 mmol) was used. Yield: 80%. FTIR (cmꢁ1, KBr): 2954,
2925, 2862, 2361, 2335, 1592, 1507, 1488, 1316, 1280, 1215,
1034, 828. 1H NMR (CDCl3, 300 MHz), d (ppm): 7.56 (Ar-H),
7.43 (Ar-H), 7.00 (Ar-H, TPA), 6.86 (Ar-H, TPA), 4.56–3.69
(OCH2), 3.22 (OMe), 1.79 (CH), 1.56–1.35 (CH2), 0.96 (CH3).
13C NMR (CDCl3, 125 MHz), d (ppm): 152.40, 150.91, 146.45,
131.58, 121.61, 119.12, 118.90, 117.60, 112.76, 95.15, 83.90,
70.23, 54.68, 33.56, 28.00, 26.93, 22.76, 14.03, 13.85, 10.21.
Mn ¼ 18,600, Mw/Mn ¼ 2.9 (GPC, polystyrene calibration). Td
(ꢀC, 5% weight loss): 302.
HB-PAE4
4-Bis(2-ethylhexyloxy)-2,5-diethynylbenzene (4) (91.82 mg,
0.24 mmol) was used. Yield: 84%. FTIR (cmꢁ1, KBr): 2955,
2926, 2862, 2361, 2335, 1509, 1487, 1316, 1271, 829. 1H
NMR (CDCl3, 300 MHz), d (ppm): 7.54 (Ar-H), 7.02 (Ar-H,
TPA), 6.85 (Ar-H, TPA), 4.46–3.65 (OCH2), 1.79 (CH), 1.56–
1.35 (CH2), 0.96 (CH3). 13C NMR (CDCl3, 125 MHz), d (ppm):
151.48, 146.05, 131.58, 122.61, 118.90, 117.60, 112.56,
95.95, 83.90, 72.23, 41.68, 32.56, 28.96, 23.93, 22.76, 13.85,
11.21. Mn ¼ 19,500, Mw/Mn ¼ 3.4 (GPC, polystyrene calibra-
tion). Td (ꢀC, 5% weight loss): 298.
To compare with the linear analog, two linear polymers were
synthesized as shown in Scheme 1 (part 2). The polymeriza-
tions were carried out by reacting equimolar ratio of 4-iodo-
N-(4-iodophenyl)-N-phenylaniline (6) and bisethynylene
monomers (1 or 2) in similar conditions as for HB polymers.
After the successive polymerization and end capping, it was
found that the fluorene-containing polymer (L-PAE2) was
soluble in most of the organic solvents where as the carba-
zole-containing polymer (L-PAE1) was insoluble. This could
be because of the more rigid structure of the linear PAEs
when compared with its HB analog. The higher solubility of
L-PAE2 when compared with L-PAE1 is because of the pres-
ence of two 2-ethylhexyl group which enhances the solubil-
ity. As L-PAE1 was insoluble, no characterizations of the
polymer could carry out.
L-PAE2
4-Iodo-N-(4-iodophenyl)-N-phenylaniline (6) (100 mg, 0.20
mmol) and 9,9-bis(2-ethylhexyl)-2,7-diethynyl-9H-fluorene
(2) (88.13 mg, 0.20 mmol) were used. Yield: 79%. 1H NMR
(CDCl3, 300 MHz), d (ppm): 7.67 (Ar-H, fluorene), 7.54 (Ar-H,
fluorene), 7.48 (Ar-H, fluorene), 7.36 (Ar-H, TPA), 7.19 (Ar-H,
TPA), 7.12 (Ar-H, TPA), 6.93, 6.86 (Ar-H, TPA), 2.08 (CH2), 1.58
(CH), 1.26–0.74 (CH2), 0.55 (CH3). 13C NMR (CDCl3, 125 MHz),
d (ppm): 150.94, 147.11, 138.24, 132.60, 129.52, 126.07,
125.39, 125.11, 124.00, 123.35, 122.94, 119.76, 44.54, 34.62,
33.51, 27.98, 26.98, 22.67, 14.03, 10.29. Mn ¼ 34,200, Mw/Mn
¼ 3.8 (GPC, polystyrene calibration). Td (ꢀC, 5% weight loss):
314.
The number-average molecular weights (Mn) of the polymers
estimated by GPC were in the range of 18,600–34,200 with
polydispersity index of 2.4–3.8. The yield and molecular
weights of the polymers are summarized in Table 1. In HB
polymer series, the polymers HB-PAE2 and HB-PAE4 had
higher molecular weight when compared with HB-PAE1 and
HB-PAE3. This could be attributed to the presence of the
two 2-ethylhexyl groups which enhance the solubility. How-
ever, comparing with the HB polymers, the linear polymer
was found to possess much higher molecular weight in GPC
probably because of larger hydrodynamic volume. All the
synthesized polymers were analyzed by FTIR and 1H NMR
RESULTS AND DISCUSSION
Synthesis and Characterization
The HB polymers were synthesized by A2 þ B3 approch
using Sonagashira polycondensation reaction. In this method,
834
WILEYONLINELIBRARY.COM/JOURNAL/JPOLA