Synthesis and characterization of hyperbranched aromatic poly(ether imide)s

Article abstract of DOI:10.1021/ma021620i

The four AB₂ monomers, N-[3- or 4-bis(4-hydroxyphenyl)toluoyl]-4-chlorophthalimide and N-{3- or 4-[1,1-bis(4-hydroxyphenyl)]ethylphenyl}-4-chlorophthalimides, were prepared and used for synthesis of hyperbranched poly(ether imide)s bearing hydr

Full text of DOI:10.1021/ma021620i

Macromolecules 2003, 36, 5537-5544
5537
Synthesis and Characterization of Hyperbranched Aromatic
Poly(ether imide)s
Xiu r u Li a n d Yu esh en g Li*
State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry,
Chinese Academy of Sciences, Changchun 130022, P. R. China
Yu ejin Ton g
Department of Chemistry, Fujian Normal University, Fuzhou 350007, P. R. China
Lin qi Sh i a n d Xia oh a n g Liu
Institute of Polymer Chemistry, Nankai University, Tianjin 300071, P. R. China
Received October 24, 2002; Revised Manuscript Received April 28, 2003
ABSTRACT: The four AB2 monomers, N-[3- or 4-bis(4-hydroxyphenyl)toluoyl]-4-chlorophthalimide and
N-{3- or 4-[1,1-bis(4-hydroxyphenyl)]ethylphenyl}-4-chlorophthalimides, were prepared and used for
synthesis of hyperbranched poly(ether imide)s bearing hydroxyl end groups. These hyperbranched poly-
(ether imide)s had moderate molecular weights with broad distributions and showed glass-transition
temperatures (Tgs) between 177 and 230 °C. The thermogravimetric analytic measurement revealed the
decomposition temperature at 5% weight-loss temperatures (Td5%) ranging from 240 to 281 °C. Analysis
1
using H NMR spectroscopy revealed the four types of hyperbranched poly(ether imide)s to have similar
degrees of branching (ca. 60%). These polymers were modified by acylation or nucleophilic substitution
reaction at the hydroxyl end groups. The conversion effectiveness depended on the type of modification
reaction, modifier, and reaction conditions. The thermal stability and solubility of hyperbranched poly-
(ether imide)s were improved by the modification of the end groups.
In tr od u ction
[di(-tert-butyldimethylsiyloxy)phenyl]-4-fluorphthalim-
ide and modifying end group and revealed that hyper-
branched aromatic poly(ether imide)s had better solu-
bility than their linear analogues. They are soluble in
amide type solvents, even in tetrahydrofuran, and can
be used as specialty additives for other high-perfor-
mance polymer materials.21-24 Hyperbranched aromatic
polyimides exhibiting good solubility or gas separation
property were successfully prepared via polyamic acid
methyl ester precursors19,20 or from dianhydrides (A2)
and triamine monomers (B3) by controlling the concen-
tration and molar ratio of monomers.25,26 Recently,
Kakimoto’s group27 prepared new aromatic hyper-
branched polyimides from 1,4-phenylenediamine (A2)
and tri(phthalic acid methyl ester) (B3) in the presence
of condensation agent. Shu et al.28-30 reported the
synthesis of dendritic poly(ether imide)s from the build-
ing block 1-(4-aminophenyl)-1,1-bis(4-hydroxyphenyl)-
ethane and hyperbranched poly(ether imide)s from AB2
monomer containing a fluoro-substituted phthalimide.
In this paper, we report synthesis and characterization
of various aromatic hyperbranched poly(ether imide)s
with hydroxy, cyanophenyl, aromatic imide, aryl ester,
and alkyl ester end groups from AB2 monomers contain-
ing a chloro-substituted phthalimide. The degree of
branching (DB) of the polymers can be easily deter-
mined without model compounds. The influence of the
chain-end groups on the solubility and glass-transition
temperature of the hyperbranched polymers was inves-
tigated.
Dendritic macromolecules such as dendrimers, den-
drons, and hyperbranched polymers have received
considerable attention due to their unique structure and
properties.1-4 Dendrimers are synthesized by controlling
repetitive reaction sequences;5-8 by contrast, hyper-
branched polymers are generally prepared by a one-step
polymerization. Therefore, they may be suitable for a
large-scale production. Although hyperbranched poly-
mers do not have perfectly defined structures, they
retain many of the important features of dendritic
macromolecules such as higher solubility, lower viscos-
ity, and multiple end groups offering the possibility for
further modification and special applications compared
to their linear analogues.8,9 In 1952, Flory published the
statistical calculation methods for the one-step poly-
merization of AB2-type monomers and copolymerization
of AB and AB2 monomers.10 Thirty years later, Krich-
eldorf synthesized the aromatic polyester copolymers
from AB and AB2 monomers.11 Kim and Webster
reported the synthesis of hyperbranched polyphenylenes
by the one-step polycondensation of AB2 monomers in
1990.12 Since then, a large number of hyperbranched
polymers have been prepared.4,13-20
Aromatic polyimides are well-known for their excel-
lent thermal stability, chemical resistance, and mechan-
ical properties and have been applied widely in modern
industries. However, aromatic polyimides are only
soluble in highly polar solvents such as concentrated
sulfuric acid. Moore’s group synthesized a hyper-
branched poly(ether imide) by self-condensation of 3,5-
Exp er im en ta l Section
Ch em ica ls. N,N-Dimethylacetamide (DMAc), N-methyl-2-
pryolidinone (NMP), and pyridine were distilled from calcium
hydride under reduced pressure. Acetic anhydride was used
after distillation from magnesium. Benzoyl chloride and
* To whom correspondence should be addressed. E-mail: ysli@
ciac.jl.cn.
10.1021/ma021620i CCC: $25.00 © 2003 American Chemical Society
Published on Web 06/21/2003

5538 Li et al.
Macromolecules, Vol. 36, No. 15, 2003
4-chlorobenzonitrile were distilled under reduced pressure
before use. Other solvents and reagents were used as received.
Mea su r em en ts. 1H NMR spectra (DMSO-d6) were recorded
using a Varian Unity 400 MHz spectrometer using the residual
1H solvent peak as reference. IR spectra were recorded on a
Bio-Rad FTS-135 spectrophotometer. DSC and TG measure-
ments were conducted with Perkin-Elmer Pyris 1 differential
scanning calorimeter and Pyris 1 thermogravimetric analyzer
at a heating rate of 10 °C/min under nitrogen, respectively.
Gel permeation chromatography (GPC) was performed with
a Waters 410 fitted with polystyrene-divinylbenzene columns
(two Shodex KD 806 M and 802) and a Waters 410 refractive
index detector in tetrahydrofuran (THF) or was carried out
using a Waters 410 fitted with Styragel HMW6E column with
dimethylformamide (DMF) containing 0.05 M LiCl as mobile
phase. The inherent viscosities were measured with an
automated Ubbelohde viscometer thermostated at 25 °C.
4,4′-Dih yd r oxy-4′′-n itr otr ip h en ylm eth a n e, 1A. A solu-
tion of p-nitrobenzaldehyde (30.40 g, 0.20 mol) and phenol (37.6
g, 0.40 mol) in acetic acid (100 mL) was stirred and cooled
slowly to 11-12 °C. A cool mixture of sulfuric acid (40 mL)
and acetic acid (60 mL) was added dropwise. The reaction
mixture was kept at 11-12 °C for 18 h and then was poured
into water. The material precipitated was washed with water.
The crude product was purified by recrystallization from
benzene. The product separated from benzene partly as resin
and partly as large, pale yellow prisms of the benzene adduct
(29.5 g, 30%), which melted at 52-57 °C, solidified with a
continued slow rise in temperature, and melted again at 212-
214 °C. IR (KBr): 3373 (O-H); 3089 (Ar3C-H); 3034 (Ar-H);
1611, 1510, 1477, 1438 (CdC); 1595, 1344 (NO2) cm-1. 1H NMR
(DMSO-d6): δ 5.67 (s, 1H), 6.81 (d, 4H), 6.99 (d, 4H), 7.48 (d,
2H), 8.26 (d, 2H), 9.49 (s, 2H).
mixture was purged with nitrogen and then with hydrogen
three times to remove oxygen and stirred vigorously at 35 °C
under hydrogen for 1 week. The reaction mixture was then
filtered, and the filtrate was evaporated to give 4-amino-4′,4′′-
dihydroxytriphenyl methane (8.18 g, 93%). IR (KBr): 3388,
3321 (N-H, O-H); 1596 (N-H), 1612, 1512,1364 (CdC); 1252
(C-N); 1172 (C-O) cm-1. 1H NMR (DMSO-d6): δ 5.00 (s, 2H),
5.24 (s, 1H), 6.58 (d, 2H), 6.76 (d, 4H), 6.82 (d, 2H), 6.96 (d,
4H), 9.29 (s, 2H). Anal. Calcd for C19H17NO2: C, 78.33; H, 5.88;
N, 4.81. Found: C, 78.83; H, 5.79; N, 4.76.
1-(4-Am in op h e n yl)-1,1-b is(4-d ih yd r oxyp h e n yl)e t h -
a n e, 2B. Compound 2B was synthesized by reduction of 1B.
The procedure was similar to that for 2A, as shown in Scheme
1. Yield: 88%. IR (KBr): 3387, 3317 (N-H, O-H); 1587 (N-
H), 1608, 1505,1365 (CdC); 1237 (C-N); 1182 (C-O) cm-1
.
1H NMR (DMSO-d6): δ 2.05 (s, 3H), 5.00 (s, 2H), 6.56 (d, 2H),
6.75 (m, 6H), 6.91 (d, 4H), 9.29 (s, 2H). Anal. Calcd for C20H19
-
NO2: C, 78.66; H, 6.27; N, 4.59. Found: C, 78.05; H, 6.17; N,
4.55.
3-Am in o-4′,4′′-d ih yd r oxytr ip h en ylm eth a n e, 2C. Com-
pound 2C was synthesized by reduction of 1C. The synthesis
procedure was similar to that for 2A, as shown in Scheme 1.
Yield: 93%. IR (KBr): 3373, 3313 (N-H, O-H), 3018 (Ar3C-
H); 1596 (N-H), 1610, 1510,1456 (CdC); 1235 (C-N); 1171
1
(C-O) cm-1. H NMR (DMSO-d6): 5.05 (s, 2H), 5.23 (s, 1H),
6.31 (d, 1H), 6.40 (s, 1H), 6.47 (d, 1H), 6.77 (d, 4H), 6.98 (d,
4H), 7.01 (d, 1H), 9.32 (s, 2H). Calcd for C19H17NO2: C, 78.33;
H, 5.88; N, 4.81. Found: C, 78.83; H, 5.79; N: 4.76.
1-(3-Am in op h e n yl)-1,1-b is(4-d ih yd r oxyp h e n yl)e t h -
a n e, 2D. Compound 2D was synthesized by reduction of 1D.
The synthesis procedure was similar to that for 2A, as shown
in Scheme 1. Yield: 93%. IR (KBr): 3372, 3311 (N-H, O-H),
1593 (N-H), 1609, 1510,1446 (CdC); 1243 (C-N); 1177 (C-
O) cm-1. 1H NMR (DMSO-d6): δ 2.05 (s, 3H), 5.00 (s, 2H), 6.24
(s, 1H), 6.39 (s, 1H), 6.47 (d, 1H), 6.74 (d 4H), 6.94 (d, 4H),
6.98 (m, 1H), 9.37 (s 2H). Calcd for C20H19NO2: C, 78.66; H,
6.27; N, 4.59. Found: C, 78.12; H, 6.49; N, 4.59.
1,1-Bis(4-h yd r oxyp h en yl)-1-(4-n itr op h en yl)eth a n e, 1B.
Zinc chloride (13.6 g, 0.10 mol) was added to a mixture of
p-nitroacetophenone (82.6 g, 0.50 mol) and phenol (188.0 g,
2.0 mol), the apparatus was purged with dry hydrogen chloride
to remove the air, and then the solution was stirred at 81-82
°C under hydrogen chloride for 20 h. The reaction mixture was
poured into 1 L of hot water, and the precipitated product was
recovered by filtration and washed with hot water several
times. The yellow crude product was dissolved in a solution of
sodium hydrogen carbonate (5%, 2.1 L) and then filtered. The
filtrate was acidified with hydrochloric acid, and then the
precipitate was recovered by filtration and washed with water
to give light-yellow product 1B (148 g, 88%). IR (KBr): 3400
(O-H); 3068, 3036 (Ar-H); 1594, 1510, 1479, (CdC); 1595,
1344 (NO2) cm-1. 1H NMR (DMSO-d6): δ 2.17 (s, 3H), 6.79 (d,
4H), 6.93 (d, 4H), 7.40 (d, 2H), 8.24 (d, 2H), 9.47 (s, 2H).
4,4′-Dih yd r oxy-3′′-n itr otr ip h en ylm eth en e, 1C. A solu-
tion of m-nitrobenzaldehyde (15.2 g, 0.10 mol) and phenol (18.8
g, 0.20 mol) in acetic acid (70 mL) was stirred and cooled to
3-4 °C. A cool mixture of sulfuric acid (6 mL) and acetic acid
(30 mL) was added dropwise. The mixture, which turned
orange, was kept at 3-4 °C for 48 h and then poured into
crushed ice and stirred. The resin separated was washed until
free from acid and freed from adhering water. A solution of
the resin in hot benzene deposited some red resin on cooling,
followed by yellow crystals of the benzene adduct (17.9 g, 37%)
which melted at 72 °C, solidified on slowly raising the
temperature, and melted again at 156-157 °C. IR (KBr): 3371
(O-H); 3089 (Ar3C-H); 3034 (Ar-H); 1611, 1509, 1477, (Cd
N-[4-Bis(4-h yd r oxyp h en yl)tolu oyl]-4-ch lor op h th a lim -
id e, Mon om er 3A. A solution of 4-amino-4′,4′′-dihydroxy-
triphenylmethane (4.78 g, 16 mmol) and 4-chlorophthalic
anhydride (3.10 g, 16.98 mmol) was dissolved in dry, deoxy-
genated dimethylacetamide (40 mL), stirred for 24 h at room
temperature under a slow stream of nitrogen, and then was
added xylene (20 mL); the mixture was refluxed to dehydrate
for 10 h. After cooling the reaction mixture was poured into
ethanol (100 mL). The precipitate was isolated by filtration,
washed with n-hexane/ethanol (6/4), and dried in a vacuum
to give 3A (7.49 g, 95%). IR (KBr): 3477, 3231 (O-H), 1778,
1710 (CdO); 1611, 1511 (Ar-H); 1392 (C-N); 1096 (C-Cl)
1
cm-1. H NMR (DMSO-d6): δ 5.55 (s, 1H), 6. 82 (d, 4H), 7.04
(d, 4H), 7.34 (d, 4H), 7.47 (m, 1 H), 8.07 (m, 2H), 9.39 (s, 2H).
Calcd for C27H18ClNO2: C, 71.13; H, 3.98; N, 3.07. Found: C,
71.25; H, 4.04; N, 3.17.
N-{4-[1,1-Bis(4-h yd r oxyp h en yl)]et h ylp h en yl}-4-ch lo-
r op h th a lim id e, Mon om er 3B. Monomer 3B was synthesized
by condensation of 2B and 4-chlorophthalic anhydride. The
synthesis procedure was similar to that for monomer 3A, as
shown in Scheme 1. Yield: 90%. IR (KBr): 3046 (O-H), 1775,
1708 (CdO); 1609, 1507 (Ar-H); 1376 (C-N); 1091 (C-Cl)
1
cm-1. H NMR (DMSO-d6): δ 2.18 (s, 3H), 6.80 (d, 4H), 6.98
(d, 4H), 7.28 (d, 2H), 7.44 (d, 2H), 8.07 (m, 2H), 8.16 (s, 1H),
9.42 (s, 2H). Calcd for C28H20ClNO2: C, 71.57; H, 4.29; N, 2.98.
Found: C, 71.59; H, 4.30; N, 2.85.
1
C); 1595, 1529, 1344 (NO2) cm-1. H NMR (DMSO-d6): δ 5.70
(s, 1H), 6.82 (d, 4H), 7.01 (d, 4H), 7.65 (m, 2H), 7.99 (s, 1H),
8.18 (d, 1H), 9.48 (s, 2H).
N-[3-Bis(4-h yd r oxyp h en yl)tolu oyl]-4-ch lor op h th a lim -
id e, Mon om er 3C. Monomer 3C was synthesized by conden-
sation of 2C and 4-chlorophthalic anhydride. The synthesis
procedure was similar to that for monomer 3A, as shown in
Scheme 1. Yield: 90%. IR (KBr): 3460 (O-H), 1772, 1713 (Cd
1,1-Bis(4-h yd r oxyp h en yl)-1-(3-n itr op h en yl)eth a n e, 1D.
Compound 1D was synthesized by condensation of m-nitroac-
etophenone and phenol. The synthesis procedure was similar
to that for 1B, as shown in Scheme 1. Yield: 90%. IR (KBr):
3373 (O-H); 1611, 1510, 1477, (CdC); 1594, 1525, 1352 (NO2)
O); 1612, 1512 (Ar-H); 1383 (C-N); 1100 (C-Cl) cm-1 1H
.
NMR (DMSO-d6): δ 5.55 (s, 1H), 6.82 (d, 4H), 7.04 (d, 4H),
7.34 (d, 4H), 7.47 (m, 1H), 8.07 (m, 2H), 8.16 (s, 2H), 9.39 (s,
2H). Calcd for C27H18ClNO2: C, 71.13; H, 3.98; N, 3.07.
Found: C, 71.35; H, 3.95; N, 3.20.
N-{3-[1,1-Bis(4-h yd r oxyp h en yl)]et h ylp h en yl}-4-ch lo-
r op h th a lim id e, Mon om er 3D. Monomer 3D was synthesized
1
cm-1. H NMR (DMSO-d6): δ 2.22 (s, 3H), 6.80 (d, 4H), 6.94
(d, 4H), 7.67 (m, 2H), 7.89 (s, 1H), 8.18 (d, 1H), 9.48 (s, 2H).
4-Am in o-4′,4′′-dih ydr oxytr iph en ylm eth an e, 2A. 5% Pd/C
(1.60 g) was added to a solution of 4,4′-dihydroxy-4′′-nitro-
triphenylmethane (13.76 g) in 80 mL of ethanol. The resulting

Macromolecules, Vol. 36, No. 15, 2003
Hyperbranched Aromatic Poly(ether imide)s 5539
Sch em e 1. Syn th esis of Mon om er s
by condensation of 2D and 4-chlorophthalic anhydride. The
synthesis procedure was similar to that for monomer 3A, as
shown in Scheme 1. Yield: 97%. IR (KBr): 3421 (O-H), 1776,
1716 (CdO); 1610, 1511 (Ar-H); 1375 (C-N); 1102 (C-Cl)
and removed. Stirring and heating were then continued for
11 h. After cooling, N-phenyl-4-chlorophthalimide (0.85 g) and
potassium carbonate (0.26 g) were added. The procedure was
carried out as described above. After cooling, the reaction
mixture was poured into water (1 L). The precipitated polymer
was dried and heated at ca. 240 °C under vacuum to remove
excess N-phenyl-3-chlorophthalimide to afford the imide-
terminated polymers.
cm-1 1H NMR (DMSO-d6): δ 2.03 (s,3H), 6.65 (d, 4H), 6.84
.
(d, 4H), 7.06 (d, 1H), 7.17 (s, 1H), 7.20 (d, 1H), 7.40 (m, 1H),
7.92 (s, 2H), 7.99 (s, 1H), 9.29 (s, 2H). Calcd for C28H20ClNO2:
C, 71.57; H, 4.29; N, 2.98. Found: C, 71.59; H, 4.03; N, 2.96.
Gen er a l P r oced u r e for th e Syn th esis of Hyp er -
br a n ch ed P oly(eth er im id e)s, 4A-D. Dry NMP (20 mL)
and dry toluene (15 mL) were added to a mixture of AB2
monomer (13 mmol) and potassium carbonate (2.90 g). The
reaction mixture was then heated at reflux in nitrogen for 10
h, with the water being collected in a Dean-Stark trap. The
distillate was collected and removed when the temperature of
the reaction mixture had reached ca. 180 °C. After stirring
and heating for 3 h, the reaction mixture was poured into
water (1.6 L), and the precipitate was collected and reprecipi-
tated twice from THF into methanol to give a white solid
hyperbranched poly(ether imide).
Gen er a l P r oced u r e for Acyla tion of Hyp er br a n ch ed
P oly(eth er im id e)s. Acetic anhydride (in excess) and pyridine
were added to a solution of hyperbranched poly(ether imide)
in dry DMAc. The reaction mixture was then refluxed under
an atmosphere of nitrogen for 30 h. After cooling, the reaction
mixture was poured into water, and the precipitate was
collected and reprecipitated twice from THF into methanol to
give the ester-terminated hyperbranched poly(ether imide)s.
On e-P ot P r oced u r e for Syn th esis of Im id e-Ter m in a t-
ed Hyp er br a n ch ed P oly(eth er im id e)s. Dry DMAc or NMP
(15 mL) and dry toluene (15 mL) were added to a mixture of
AB2 monomer (5 mmol) and potassium carbonate (0.6 g). The
mixture was then refluxed in nitrogen for 10 h, with the water
being collected in a Dean-Stark trap. The toluene was distilled
Resu lts a n d Discu ssion
Mon om er Syn th esis. The synthesis of monomers
3A-D was accomplished in three steps from nitroben-
zaldehyde or nitroacetophenone (Scheme 1). The syn-
thesis of 2A or 2C was performed by the sulfuric acid-
catalyzed condensation reaction of p- or m-nitrobenzalde-
hyde with phenol in cold acetic to give compound 1A or
1C,31 followed by the reaction of the nitro group of 1A
or 1C with H2 catalyzed by Pd/C. Condensation of p- or
m-nitroacetophenone and excess phenol in the presence
of a mixture of zinc chloride and hydrogen chloride at
60-70 °C afforded 1,1-bis(4-dihydroxyphenyl)-1-(4-ni-
trophenyl)ethane or 1,1-bis(4-dihydroxyphenyl)-1-(3-ni-
trophenyl)ethane (1B or 1D) in good yields. Compounds
2B-D were easily prepared by hydrogenation of corre-
sponding compounds 1B-D in the presence of Pd/C
catalyst. Reactions of 2A-D with 4-chlorophthalic
anhydride followed by imidizations in refluxing xylene
afforded the corresponding monomers 3A-D. The yields
of these reactions were above 95%. The structure of
1
3A-D was characterized by H NMR and IR spectra
and confirmed by elemental analysis.

5540 Li et al.
Macromolecules, Vol. 36, No. 15, 2003
Sch em e 2. Syn th esis of Hyp er br a n ch ed P oly(eth er im id e)s
Syn th esis a n d P r op er ties of Hyp er br a n ch ed
P oly(eth er im id e)s w ith Hyd r oxy En d Gr ou p s.
Dendritic poly(ether imide)s can be prepared from 2B
and 3-nitro-N-phenylphthalimide having high reactivity
at room temperature.28 Preliminary experiments, how-
ever, suggested that hyperbranched poly(ether imide)s
cannot be obtained under the same condition from
corresponding monomers, 3A-D, due to low reactivity.
Poly(ether imide)s, 4A-D, were prepared by self-
condensation of corresponding monomers, 3A-D, at
high temperature and in the presence of potassium
carbonate, as shown in Scheme 2.
Hbl, and that of Hat equals half of that of Hbt. The
monomer 3A shows a single peak of Ar3C-H (Ha) at
5.50 ppm and a single peak of OH (Hb) at 9.30 ppm, as
shown in Figure 1. Polymer 4A shows three peaks of
Ha at 5.30 (a1, H integration, Hi ) 0.74), 5.50 (a2, Hi )
0.60), and 5.70 ppm (a3, Hi ) 0.57) and two peaks of Hb
at 9.30 ppm (b1, Hi ) 1.20) and 10.30 ppm (b2, Hi )
0.75). According to the chemical environment of 3A and
4A, Hat of 4A is similar to Ha of 3A, and Hbt of 4A is
similar to Hb of 3A. Hence, the chemical shift of NMR
of these protons should be similar, too. Thus, as Figure
1 shows, a2 must be at, and b1 must be bt, so the other
(b2) must be bl. On the other hand, the integration of
Ha2 (Hat) almost equals half Hb1 (Hbt); this is just
agrees with theoretic analysis as mentioned above.
Hence, it can be deduced that a1 must be al due to the
integration of Ha1 almost equal to Hb2 (Hbl), and
another peak (a3) must be ad.
As Scheme 3 shows, poly(ether imide) 4A possesses
three constructional units, linear units with Hal and Hbl,
dendritic units with Had, and terminal units with Hat
and Hbt. Obviously, the number of Hal equals that of
Hbl, and the number of Hat equals half of that of Hbt in
4A. It is expected that the proton NMR signal of Ha or
Hb in each type unit is different from that of others.
Thus, the NMR signal intensity of Hal equals that of
DB of hyperbranched polymer was defined as the ratio
of the sum of dendritic and terminal units vs total units

Macromolecules, Vol. 36, No. 15, 2003
Hyperbranched Aromatic Poly(ether imide)s 5541
F igu r e 2. 400 MHz 1H NMR spectra (d6-DMSO, TMS, 20 °C)
of monomer 3C, polymer 4C, and modified polymer 4Ca by
acylation for 10 h.
by calculating the integration ratio of these three peaks.
The methine of 4C also shows triplet at 5.30, 5.50, and
5.70 ppm (Figure 2) assigned to the dendritic units,
terminal units, and linear units, respectively. Hence,
the DB of 4C was calculated to be 0.68 from integrated
intensities of the distinct proton resonance of the
methane similar to the case of 4A. The DB of 4B was
determined to be 0.64 from integrated intensities of the
distinct proton resonance of the methyl (triplet at D
2.18, T 2.08, L 2.00 ppm), as shown in Figure 3.
Unfortunately, it was unsuccessful to determine the DB
of 4D using this method because of the overlapping of
the1H NMR signals of methyl (1.96-2.09 ppm), as
shown in Figure 1.
F igu r e 1. 400 MHz 1H NMR spectra (d6-DMSO, TMS, 20 °C)
of 3A, 4A, 3D, and 4D.
Sch em e 3. Str u ctu r e of Mon om er 3A a n d Th r ee
Con str u ction a l Un its in P olym er 4A
On the other hand, the degree of branching (DB) of
one hyperbranched polymer based on AB2 monomer can
be estimated by another equation according to Frey’s
definition,32 when the molecular weight of the hyper-
branched polymer is high enough.
DB ) 2T/(2T + L)
(1)
where T and L are the fractions of terminal and linear
incorporated monomers in a hyperbranched polymer
based on AB2 monomer. As shown in Scheme 3, one
linear unit has one Hal and one Hbl; one terminal unit
possesses two Hbt. Hence, the DB can be calculated by
the following equation:
DB ) ITb/(ITb + ILb
)
(2)
where ITb and ILb are the signal intensity of Hbt and Hbl,
respectively. The DB of hyperbranched poly(ether imide)
4A using the integration of terminal Hbt (1.20) and
linear proton Hbl (0.75) gives a value of 0.62, according
to eq 2. Similar to 4A, the DB of 4B, 4C, and 4D are
estimated to be 0.63, 0.61, and 0.60, respectively.
Comparing these results with those (0.61, 0.64, and
1
0.68) calculated from H NMR of the methane or methyl
(linear, dendritic, and terminal units) by Fre´chet.33 As
described before, the three peaks of methine of 4A, Had,
Hat, and Hal (Figure 1), can be assigned to the dendritic
units, terminal units, and linear units of 4A, respec-
tively. Therefore, DB of 4A was determined to be 0.61
of the polymers, it can be found that the difference
between the two values of DB of the same hyper-
branched polymer calculated from two distinct methods
increase with the decrease of the molecular weight of
polymers (see Table 1), indicating the DB calculated by

5542 Li et al.
Macromolecules, Vol. 36, No. 15, 2003
1
F igu r e 3. 400 MHz H NMR spectra (d6-DMSO, TMS, 20 °C) of 3B and 4B.
Ta ble 1. P r op er ties of Hyp er br a n ch ed P oly(eth er im id e)s w ith Hyd r oxyl En d Gr ou p s
solubilitye
react react
temp time yeild
DBFrey
2T/
DBFre´chet
(D + T)/
a
b
c
5% d
ηinh
Mh w
Tg
Td
polymer
(°C)
(h)
(%)
(dL/g) (kDa) PDIb (2T + L) (D + L + T) (°C)
(°C)
EtOAc CHCl3 THF DMAc NMP
4A
4B
4C
4D
180
170
162
175
12
11
24
10
85
92
82
88
0.16
0.12
0.14
0.15
8.03
7.87
6.93
5.69
3.95
3.81
3.21
2.69
0.62
0.63
0.61
0.60
0.61
0.64
0.68
230
190
202
177
281
245
275
240
- -
- -
- -
- -
- -
+ -
- -
- -
+ +
+ +
+ -
+ +
+ +
+ +
+ +
+ +
+ +
+ +
+ +
+ +
a
b
Measured at 25 °C with c ) 0.5 g/dL in DMAc. The molecular weight was measured by GPC with DMF containing 0.05 M LiCl as
eluent solvent. c DSC measurements with a heating rate of 10 °C/min in nitrogen. TGA measurements with a heating rate of 10 °C/min
d
in nitrogen. e Solubility studies were performed by adding 20 mg of polymer to 5 mL of the corresponding solvent: + + ) soluble; - - )
insoluble; + - ) partially soluble.
the former method is more accurate than that calculated
by the latter.
acetic anhydride was used for the acetylation of polymer
4C, and the reaction temperature was limited to 140
°C. After 10 h, a product with conversion of phenolic
hydroxyl to acetate of ca. 65% was obtained according
The properties of hyperbranched poly(ether imide)s
with hydroxyl end groups are summarized in Table 1.
In general, the polyimides from meta-oriented diamines
have denser polymer chain packing and lower chain-
segment mobility than those from the corresponding
para-oriented diamines because of the larger conforma-
tional entropy of the meta-oriented chain. Furthermore,
the former (meta-oriented) has lower glass transition
temperature (Tg) than the latter.34 Consequently, 4C
and 4D possessing a meta-oriented chain have lower
Tg than the corresponding polymers 4A and 4B pos-
sessing para-oriented chain, respectively. The polymers
containing triphenylmethane units, 4A and 4C, have
much higher Tg than the corresponding polymers con-
taining triphenylethane units, 4B and 4D, respectively,
as a consequence of the same packing density effect. The
same trend was observed in the thermal decomposition
temperature of these hyperbranched poly(ether imide)s
(see Table 1).
Mod ifica tion of Hyp er br a n ch ed P oly(eth er im i-
d e)s. Although all the hyperbranched poly(ether imide)s
with hydroxyl end group, 4A-D, have high Tgs, their
thermal decomposition temperatures are very low be-
cause hydroxyl is not a thermally stable group. To
improve their thermal stability, the hydroxyl end groups
of the polymers were modified by acylation or nucleo-
philic substitution reaction.
1
to the analysis of the H NMR spectra (Figure 2). The
second acetylation experiment was conducted using a
50% excess of acetic anhydride for 24 h and gave a
conversion around 85%. An attempt to further increase
the conversion of acetylation by increasing the amount
of acetylation agent and extending the reaction time was
not successful. The higher boiling point of benzoyl
chloride allowed a higher reaction temperature of 190
°C. Using an excess of 50% benzoyl chloride in combina-
tion with a reaction time of 24 h gave more than 90%
acylation.
The nucleophilic substitution reactions of hyper-
branched poly(ether imide)s with electrophiles were
conduced by a “one-pot” procedure. The poly(ether
imide) with hydroxyl end groups was prepared by self-
condensation of corresponding AB2 monomers. After
cooling, an excess of 20% electrophilic agent and potas-
sium carbonate (excess) were added and then were
heated for several hours. A high conversion could be
obtained easily in the case of 4-chlorophthaliimide.
Nearly 100% conversion was achieved when polymer 4D
was reacted with N-phenyl-4-chlorophthaliimide at 200
°C for 10 h. However, only a low conversion was
obtained when 4-chlorobenzonitrile was used as a
modifying agent, although forcing conditions were uti-
lized. The N-phenyl-4-chlorophthaliimide molecule is
much bulkier than 4-chlorophthaliimide, but the con-
version, using chlorobenzonitrile, was lower than that
using N-phenyl-4-chlorophthaliimide. This fact is con-
sistent with the proposal that the main factor affecting
The hyperbranched poly(ether imide) with hydroxyl
end groups was dissolved in NMP. An acylation agent
(in excess) and pyridine as a catalyst were added and
heated at different temperatures according to the boiling
point of acylation agent. The first acylation experiment
was conducted with acetic anhydride. A 20% excess of

Macromolecules, Vol. 36, No. 15, 2003
Hyperbranched Aromatic Poly(ether imide)s 5543
Ta ble 2. P r op er ties of Mod ified Hyp er br a n ch ed P oly(eth er im id e)s
solubilityf
THF
b
c
d
5% e
react temp
(°C)
react
time (h)
conva
(%)
ηinh
Mh w
Tg
Td
(°C)
polymer
(dL/g)
(kDa)
PDIc
(°C)
EtOAc
CHCl3
DMAc
NMP
4Aa
4Ba
4Bb
4Bc
4Bd
4Ca
4Da
4Db
4Dc
4Dd
140
140
190
170
170
140
140
190
200
200
29
24
24
11/21
11/12
24
24
18
87
85
94
63
96
86
86
92
76
98
0.11
0.08
0.08
0.11
0.14
0.09
0.08
0.08
0.10
0.15
7.61
4.23
4.68
5.42
3.92
2.53
2.65
2.61
196
165
185
178
207
168
163
172
301
251
256
257
408
286
257
295
297
315
+ +
+ +
+ -
+ -
- -
+ +
+ +
+ -
- -
- -
+ +
+ +
+ +
+ -
- -
+ +
+ +
+ +
+ -
- -
+ +
+ +
+ +
+ -
- -
+ +
+ +
+ +
+ +
- -
+ +
+ +
+ +
+ +
+ +
+ +
+ +
+ +
+ +
+ +
+ +
+ +
+ +
+ +
+ +
+ +
+ +
+ +
+ +
+ +
7.10
4.45
4.80
5.34
3.79
2.56
2.62
2.58
10/18
10/10
214
a
b
Transform yield of end group was measured by 1H NMR. Measured at 25 °C with c ) 0.5 g/dL in DMAc. c The molecular weight was
measured by GPC with THF as eluent solvent. DSC measurements with a heating rate of 10 °C/min in nitrogen. e TGA measurements
d
with a heating rate of 10 °C/min in nitrogen. f + + ) soluble; - - ) insoluble; + - ) partially soluble.
the conversion of end groups is the reactivity of the
electrophile but not its steric bulk.
values of ca. 0.6 and exhibited good solubility in NMP,
DMAc, THF, and CHCl3. The Tgs and thermal stability
of these hyperbranched poly(ether imide)s depend on
the chain structure and the nature of the end groups.
The polymers from N-[3- or 4-di(4-hydroxyphenyl)-
toluoyl-4-chlorophthalimide possess higher Tgs and
thermal decomposition temperatures than those from
N-{3- or 4-[1,1-di(4-hydroxyphenyl)ethylphenyl-4-chlo-
rophthalimides. Furthermore, the polymers based on
monomers derived from para-isomers have higher Tgs
and thermal decomposition temperatures than those
based on corresponding meta-isomers. The thermal
stability of hyperbranched poly(ether imide)s could be
improved through acylation of their hydroxyl end groups.
The maximum conversion of acetylation and benozyla-
tion of the hydroxyl end groups was greater than 85 and
90%, respectively. The hyperbranched poly(ether imi-
de)s can also be modified by nucleophilic substitution
reaction. The main factor affecting conversion of hy-
droxyl end groups is the reactivity of the electrophile,
not its steric bulk. When N-phenyl-4-chlorophthalimide
with high reactivity is used as the electrophile, more
than 98% conversion was achieved. Among the hyper-
branched poly(ether imide)s studied, the polymers
modified by N-phenyl-4-chlorophthalimide possess the
highest inherent viscosity and the best thermal stabili-
ties.
The modified polymers 4Bd and 4Dd were purified
by sublimation of the excess 4-chlorophthaliimide, and
the other modified polymers were purified by reprecipi-
tation several times from THF into methanol. In all
these experiments the conversion was checked by 1H
NMR spectroscopy of modified hyperbranched poly-
(ether imide)s. The signal intensity ratios of the protons
in residual hydroxyl to aromatic protons were used to
calculate conversion.
The solubility of hyperbranched poly(ether imide)s,
except for 4Bd and 4Dd , were improved by end-group
modification, as shown in Tables 1 and 2. Among the
modified polymers, those with ester end groups show
the lowest weight-average molecular weight (Mh w) and
the narrowest PDI, while those with cyanophenyl, which
were prepared by one-pot procedure at higher temper-
ature, exhibit the highest Mh w and the broadest PDI in
the polymers possessing same chain backbone. 4Ba -c
and 4Da -c have a PDI of about 2.60, and 4Aa and 4Ca
possess a broader PDI of above 3.70 (Table 2). This
agreed with Flory’s prediction of very large PDIs for AB2
polymers.10 The Mh w and PDI of the hyperbranched poly-
(ether imide)s, 4Bd and 4Dd , were not obtained because
they are not soluble in THF. They have higher inherent
viscosities than the other polymers. This indicates that
they probably possess higher molecular weight than the
others.
Refer en ces a n d Notes
The two hyperbranched poly(ether imide)s with imide
end groups (4Bd and 4Dd ) show higher Tgs than the
parent polymers, and the other modified polymers
exhibit much lower Tgs than the parent polymers due
to both loss of H-bonding and the plasticization of the
more flexible end groups. All of the modified hyperbra-
nhced poly(ether imide)s exhibit much higher thermal
decomposition temperature than the parent polymers.
In other words, the thermal stability of hyperbranched
poly(ether imide)s was improved by the modification of
end groups. The two imide modification products, 4Bd
and 4Dd , have the highest thermal stability among the
polymers studied.
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