Macromolecules, Vol. 36, No. 10, 2003
Hyperbranched Aromatic Polyimides 3527
Syn th esis of Com p ou n d 6. Into a 90 mL autoclave were
added 2 g (0.00266 mol) of 5, 40 mL of THF, 10 mL of
methanol, and 0.2 g of 10% Pd/C catalyst. The mixture was
stirred under 20 atm of hydrogen at room temperature for 48
h and then filtered with Celite to get a clear yellow filtrate.
The filtrate was condensed to one-fourth of its original volume
and poured into water to precipitate the product. The precipi-
tate was collected by filtration and dried under vacuum at
room temperature for 24 h and at 40 °C for 2 h. Compound 6
cm-1): 3073, 2945, 1778, 1725, 1595, 1515, 1479, 1438, 1362,
1267, 1197, 1120, 1004, 837, 789, 745, 695, 670, 593, 529, 419.
F r eeze-E xt r a ct ed Sa m p le P r ep a r a t ion . The freeze-
extracted samples were prepared by dissolving a certain
amount of TEP I in NMP to afford a solution with a concentra-
tion of 0.5 g/L. The solution was then rapidly frozen by
immersion of a vigorously shaken flask in a dry ice-acetone
bath. Then the frozen solution was poured into a large amount
of cold methanol at -20 °C. The powdery TEP I was collected
by filtration, washed with methanol for several times and dried
under vacuum at room temperature. A fluffy powder of TEP I
was obtained and stored at -20° for DSC measurement. Prior
to DSC measurement, the sample was dried again under
vacuum at 40 °C for 2 h.
1
was obtained as a white fluffy powder. Yield: 89%. H NMR
(δ, ppm): 9.93 (s, 1H), 7.85-7.82 (d, 2H), 7.72-7.70 (d, 0.5H),
7.64-7.61 (d, 0.5H), 7.54-7.50 (d, 0.46H), 7.42-7.40 (d, 0.6H),
7.26 (s, 7H), 6.75 (s, 3H), 6.63-6.60 (d, 0.46H), 6.55-6.52 (d,
2.5H), 3.77 (s, 5.3H), 3.72 (s, 3.6H). 13C NMR (δ, ppm): 167.7,
167.6, 166.9, 166.8, 166.5, 166.0, 165.0, 159.3, 158.7, 158.3,
157.7, 157.6, 156.3, 145.3, 144.6, 141.5, 135.9, 135.6, 134.1,
131.1, 130.2, 128.6, 128.2, 125.8, 122.8, 121.4, 119.6, 118.8,
117.3, 116.2, 113.9, 113.5, 52.6, 52.5, 52.4, 52.3. IR (KBr, cm-1):
3446, 3378, 3073, 2956, 2605, 1723, 1593, 1573, 1515, 1491,
1454, 1436, 1278, 1213, 1121, 1067, 1009, 889, 837, 788, 705,
518. Anal. Calcd for C39H30O14N2: C, 62.40; H, 4.03; N, 3.73.
Found: C, 62.10; H, 4.09; N, 3.62.
Mea su r em en ts. Infrared (IR) spectra were recorded on a
Shimadzu FTIR-8100 Fourier transform infrared spectropho-
1
tometer. H and 13C NMR spectra were recorded on a J EOL
J NM-AL 300 MHz spectrometer. Thermogravimetric analysis
(TGA) was carried out with a Seiko TG/DTA 6200 at a heating
rate of 10 °C/min under nitrogen. Differential scanning calo-
rimetry (DSC) was performed on a Seiko DSC 6200 using a
heating rate of 10 °C/min under nitrogen. Thermal mechanical
analysis (TMA) was conducted on a Seiko TMA/SS6000 in a
penetration mode with a 10 g load and 5 °C/min heating rate.
Dynamic mechanical thermal analysis (DMA) was performed
on a dynamic mechanical analyzer DVA-200S in tension mode
at a heating rate of 5 °C/min and a frequency of 10 Hz. Gel
permeation chromatography (GPC) was performed on a J AS-
CO HPLC 880PU fitted with polystyrene-divinylbenzene
columns (two Shodex KD806MS and KD802.5) and a Shodex
RI-71 refractive index detector. DMF containing 0.01 mol L-1
of lithium bromides was used as an eluent. The molecular
weights were determined by laser light scattering measure-
ment using a mini DAWN apparatus (Wyatt Technology Co.).
Specific refractive increments (dn/dc) of polymers were mea-
sured in DMF at 690 nm by using an Optilab 903 apparatus
(Wyatt Technology Co.). Inherent viscosity of TE)P AAMEs
was measured at a concentration of 0.5g dL-1 in NMP at 30
°C by using an Ostwald viscometer. Intrinsic viscosity of
TE)P AAMEs was measured in DMF at 30 °C by utilizing
an Ubbelohde viscometer.
P olym er P r ep a r a tion . Syn th esis of P oly(a m ic a cid
m eth yl ester ) (P AAME). A typical procedure for synthesis
of P AAME is described as follows. To a completely dry flask
under N2 were added 0.5 g of 6, 0.21 mL of triethylamine, and
6 mL of NMP. Then 0.697 g of DBOP was added to the
solution. The reaction solution was stirred at 50 °C for 24 h.
Then the solution was poured into methanol containing 1%
LiCl to precipitate the polymer. After the isolation by filtration
and washing with methanol for several times, a white powdery
1
polymer was obtained. P AAME-AB2-5. Yield: 94%. H NMR
(δ, ppm): 10.55 (s, 0.5H), 10.19 (m, 0.5H), 7.99-7.58 (m, 3.8H),
7.47 (m, 7.9H), 7.30 (m, 3.6H), 7.19 (m, 1.3H), 6.81 (m, 3.0H),
3.77-3.70 (d, 4.5H). IR (KBr, cm-1): 3482, 3073, 2956, 1778,
1725, 1594, 1515, 1477, 1438, 1358, 1268, 1198, 1119, 1006,
971, 949, 838, 785, 746, 692, 671, 528.
Syn th esis of An h ydr ide-Ter m in ated P olyim ide (ATP I).
To a solution of 0.12 g of P AAME in 6 mL of NMP were added
2.3 mL of acetic anhydride and 1.7 mL of pyridine. The
reaction was carried out at 115 °C under N2 overnight. Then
polymer was precipitated via pouring the reaction solution into
dry toluene. After isolation by filtration and drying under
vacuum at 60 °C overnight, ATP I was obtained in a brown
Refer en ces a n d Notes
1
(1) (a) Kim, Y. H.; Webster, O. W. Am. Chem. Soc., Div. Polym.
Chem. Polym. Prepr. 1988, 29 (2), 310. (b) Kim, Y. H.;
Webster, O. W. J . Am. Chem. Soc. 1990, 112, 4592.
(2) Turner, S. R.; Voit, B. I.; Mourey, T. H. Macromolecules 1993,
26, 4617.
(3) Tomalia, D. A.; Durst, H. Top. Curr. Chem. 1993, 165, 193.
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powder. ATP I-AB2-5. Yield: 94%. H NMR (δ, ppm): 7.94-
7.82 (m, 2.4H), 7.57 (bs, 6.9H), 7.35-7.25 (m, 4.1H), 6.84-
6.71 (t, 3.0H). IR (KBr, cm-1): 3071, 1777, 1724, 1596, 1514,
1479, 1437, 1365, 1238, 1196, 1080, 1006, 838, 794, 746, 693,
671, 595, 528.
Syn th esis of p-Tolu id in e En d -ca p p ed P oly(a m ic a cid
m eth yl ester ) (TE)P AAME). To a completely empty flask
under N2 were added 0.5 g of P AAME, 0.37 g of p-toluidine,
and 15 mL of NMP. To this solution were added 0.697 g of
DBOP and 0.21 mL of triethylamine. The reaction solution was
stirred overnight at room temperature and then was poured
into methanol to precipitate the polymer. After isolation by
filtration, washing with methanol for several times, and drying
under vacuum, a yellowish-white powder of TE)P AAME was
obtained. TE)P AAME-AB2-5. Yield: 95%. ηinh ) 0.17dL/g.
1H NMR (δ, ppm): 10.49 (s, 0.1H), 10.19 (s, 0.4H), 10,06 (s,
0.2H), 7.94 (m, 2.4H), 7.57 (bs, 5.6H), 7.28 (bs, 4.9H), 7.12 (s,
1.3H), 6.81 (m, 3.0H), 3.78 (s, 2.7H), 2.36 (s, 2.6H). IR (KBr,
cm-1): 3074, 2951, 2882, 1778, 1722, 1594, 1514, 1475, 1455,
1438, 1412, 1357, 1301, 1269, 1208, 1137, 1119, 1090, 1065,
1009, 971, 949, 844, 781, 748, 693, 671, 616, 512, 426.
Syn t h esis of p -Tolu id in e E n d -Ca p p ed P olyim id e
(TEP I). To a solution of 0.39 g of TE)P AAME in 16 mL of
NMP were added 7 mL of acetic anhydride and 5 mL of
pyridine. The reaction solution was stirred at 115 °C overnight
and then was poured into water to precipitate the polymer.
After isolation by filtration, the polymer was washed by water
several times and dried at 40 °C under vacuum overnight. A
yellowish-brown powder of TEP I was obtained. TEP I-AB2-5.
Yield: 97%. 1H NMR (δ, ppm): 7.95-7.83 (m, 2.7H), 7.56 (bs,
6.8H), 7.29 (bs, 5.7H), 6.83 (bs, 3.0H), 2.35 (s, 2.4H). IR (KBr,
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