Synthesis and properties of novel phosphorus-containing thermotropic liquid crystalline copoly(ester imide)s

Article abstract of DOI:10.1002/pola.24344

A series of novel phosphorus-containing polyesterimides were prepared from diolsa mixture of a new aromatic phosphorus-containing bisphenol, namely 1,4-bis[N-(4-hydroxyphenyl)phthalimidyl-5-carboxylate]-2-(6-oxido-6H- dibenz<1,2>oxaphosphorin-6-yl)-n

Full text of DOI:10.1002/pola.24344

Synthesis and Properties of Novel Phosphorus-Containing Thermotropic
Liquid Crystalline Copoly(ester imide)s
DIANA SERBEZEANU, TACHITA VLAD-BUBULAC, CORNELIU HAMCIUC, MAGDALENA AFLORI
‘‘Petru Poni’’ Institute of Macromolecular Chemistry, Aleea Gr. Ghica Voda 41A, Iasi 700487, Romania
Received 14 July 2010; accepted 23 August 2010
DOI: 10.1002/pola.24344
Published online 5 October 2010 in Wiley Online Library (wileyonlinelibrary.com).
ABSTRACT: A series of novel phosphorus-containing polyesteri-
mides were prepared from diols—a mixture of a new aromatic
phosphorus-containing bisphenol, namely 1,4-bis[N-(4-hydrox-
yphenyl)phthalimidyl-5-carboxylate]-2-(6-oxido-6H-dibenz<c,e>
<1,2>oxaphosphorin-6-yl)-naphtalene, with aliphatic diols such
as 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexane-
diol, and 1,12-dodecanediol—and an aromatic diacid chloride
containing two preformed ester groups, namely terephthaloyl-
bis-(4-oxibenzoyl-chloride), via high-temperature polyconden-
sation in o-dichlorobenzene. The structures of monomers and
polymers were verified by means of Fourier transform infrared
(FTIR) spectroscopy and 1H NMR spectroscopy. The molar ratio
of aromatic bisphenol to aliphatic diol was varied to generate
a series of copolyesterimides with tailored physicochemical
properties, structure–properties relationships being estab-
lished. The effect of the phosphorus content on the thermal
properties and the flame retardancy was evaluated by means
of thermogravimetric analysis (TGA), TGA–FTIR, and scanning
electron microscopy. The polymers were stable up to 340 ꢀC
showing a 5% weight loss in the range of 340–395 ꢀC and a
10% weight loss in the range of 370–415 ꢀC. The char yields at
700 ꢀC were in the range of 13.6–38% increasing with the con-
tent of phosphorus-containing bisphenol. The effect of the
aliphatic content on the liquid crystalline behavior was investi-
gated by polarized light microscopy, differential scanning calo-
rimetry, and X-ray diffraction. The transition temperatures from
crystal to liquid crystalline melt were in the range of 209–308 ꢀC.
C
V
2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem
48: 5391–5403, 2010
KEYWORDS: flame retardancy; liquid crystalline polymers
(LCPs); phosphaphenanthrene; structure–property relations;
thermal properties; thermal stability; thermotropic liquid crys-
talline poly(ester imide)s
INTRODUCTION Aromatic polyimides are well known as
high-performance polymers because of their high thermal
and thermooxidative stabilities, high transition temperatures,
and outstanding mechanical, insulating, and chemical resist-
ance properties. Therefore, polyimides have been widely
used in many applications such as aerospace, microelec-
tronics, optoelectronics, and information industries.1–4 How-
ever, wholly aromatic polyimides have usually deficiencies in
solubility, processability, melting or softening behavior, trans-
parency, and dielectric constant. Significant improvements in
the performances of polyimides have been made: fluorina-
tion,2,5 bulky substituents,6,7 incorporation of asymmetric,
noncoplanar, or alicyclic units,8–10 flexible bridging,11,12
copolymerization,13,14 and so forth. From a practical point of
view, the most important copolyimides are poly(ester
imide)s (PEIs), poly(amide imide)s, and poly(ether imide)s,
but other linear copolyimides have also been investigated,
such as poly(anhydride imide)s.15
tives in TLC PEIs research has been to reduce the transition
temperature to a temperature range that is suitable for con-
ventional processing facilities, equal to or less than about
300 ꢀC. Random copolymerization is an effective approach,
which has been used to design TLC PEIs by disturbing the
regular molecular structure of the polymer chain. The lack of
periodicity along the chain inhibits crystallization and, thus,
reduces the crystal size and perfection and depresses the
melting transitions Tm. The introduction of kinked linkages
into the polymer backbone effectively reduces the regularity
of the molecule and lowers the melting temperature. How-
ever, the incorporation of kinked units has an unfavorable
influence on the liquid crystallinity because the kinks disrupt
the molecular linearity. Modification of the p-aromatic back-
bone with flexible segments is another important way to
improve the melt processability. By inserting flexible seg-
ments to separate the mesogenic units along the polymer
chain, the chemical periodicity of the mesogenic molecule is
preserved. The most typical spacer segments used are poly-
methylene units (CH2)n of varying length n. Introducing lat-
eral substituent groups to p-oriented monomers has also
been applied to lower the melting points of LCPs. Grafting
Thermotropic liquid crystalline poly(ester imide)s (TLC
PEIs) have been developed to achieve both good processabil-
ity and good mechanical properties. One of the main objec-
Correspondence to: T. Vlad-Bubulac (E-mail: tvladb@icmpp.ro)
C
V
Journal of Polymer Science: Part A: Polymer Chemistry, Vol. 48, 5391–5403 (2010) 2010 Wiley Periodicals, Inc.
PROPERTIES OF PHOSPHORUS-CONTAINING POLYESTERIMIDES, SERBEZEANU ET AL.
5391

JOURNAL OF POLYMER SCIENCE: PART A: POLYMER CHEMISTRY DOI 10.1002/POLA
1
bulky side groups onto the polymer main chain influences
the melting temperature in several ways: it effectively
increases the interchain distance and reduces the interchain
forces so that the efficiency of the chain packing is reduced
and the effect is much enhanced by randomly distributing
the side chain along the polymer backbone. Kricheldorf,
Chung or Lenz have reported investigations on PEIs synthe-
sis, ordered structures, phase transition behavior, morphol-
ogy, rheology, and crystallization behavior.16–20
mixed with KBr and pressed into pellets. H NMR (400 MHz)
spectra were obtained on a Bruker Avance DRX 400 spec-
trometer. The polymer samples were dissolved in DMSO-d6
upon heating and then measured at room temperature or
were dissolved in a mixture of solvents (CDCl3: CF3COOD ¼
9/1, v/v) at room temperature. Elemental analysis was car-
ried out with a CHNS 2400 II Perkin Elmer instrument. Ele-
mental analysis for phosphorus was performed with molyb-
denum blue method.28 Thermogravimetric analysis (TGA)
was performed on 15 mg samples under air atmosphere at a
heating rate of 10 ꢀC/min using a Mettler Toledo model
TGA/SDTA 851 instrument. Pyrolysis residues were collected
at various weight losses in the thermogravimetric experi-
ments and were subsequently analyzed by FTIR spectros-
copy. In these experiments, samples of about 15 mg were
heated to a defined temperature, cooled to room tempera-
ture, transferred to Bruker Vertex 70 instrument, and FTIR
spectrum was recorded for each sample. The differential
scanning calorimetry (DSC) analysis was carried out using a
Perkin-Elmer Pyris Diamond instrument using nitrogen as a
carrier gas at a flow rate of about 10 mL/min. The samples
were first heated from room temperature to 350 ꢀC using
a heating rate of 10 ꢀC/min and then cooled to 20 ꢀC at a
cooling rate of 10 ꢀC/min. A second heating and a subse-
quent cooling were performed in the same conditions. The
melting temperatures and the liquid crystalline phase transi-
tion temperatures of copoly(ester imide)s 4 were taken as
maximum of endothermic peaks. Polarized light microscopy
(PLM) was carried out with an Olympus BH-2 polarized light
microscope fitted with a THMS 600/HSF9I hot stage, at a
magnification of 200ꢂ or 400ꢂ. The mesomorphic transition
temperature and disappearance of birefringence, that is, the
crystal-to-nematic and nematic-to-isotropic transition, were
noted. The wide-angle X-ray diffraction (WAXD) experiments
at room temperature and variable temperature XRD were
performed on a D8 Advance Bruker AXS diffractometer using
a CuKa source with an emission current of 36 mA and a
voltage of 30 kV. Scans were collected over the 2h ¼ 2–40
range using a step size of 0.01ꢀ and a count time of 0.5 s
per step. Scanning electron microscopy (SEM) was per-
formed on a TESLA BS 301 instrument, at 25 kV, with a
magnification of 380–3600. The images were recorded on
film surfaces deposed on Al supports and coated by sputter-
ing with Au thin films using an EK 3135 EMITECH device.
Actually, the development of new polymeric structures hav-
ing excellent combined properties required to meet increas-
ing demands and reduce production costs is an important
topic in the field of polymer science. There is a great deal of
effort in developing less flammable polymer materials. To
protect the environment and human health, researchers are
focused on exploiting environmental friendly halogen-free
fire retardants for plastic materials used in various indus-
tries. Phosphorus-containing compounds have received
significant attention for many years because they are consid-
ered to be the most effective flame retardants, as demon-
strated in recent studies.21–26 Phosphorus-containing poly-
mers tend to char rather than burn; thus, charring provides
a diffusion barrier of gaseous products to the flame, shields
the polymer surface from heat and oxygen, and reduces the
production of combustible gas during polymer degradation.27
In the light of these facts, we decided to perform a compre-
hensive study on the relationship between the aliphatic/aro-
matic ratio, polymer liquid crystalline phase structure, flame
retardancy, and thermooxidative stability of novel synthe-
sized TLC aromatic–aliphatic copoly(ester imide)s based on
a new phosphorus-containing monomer, namely, 1,4-bis[N-
(4-hydroxyphenyl)phthalimidyl-5-carboxylate]-2-(6-oxido-6H-
dibenz<c,e><1,2>oxaphosphorin-6-yl)-naphthalene, a series
of aliphatic diols (1,3-propanediol, 1,4-butanediol, 1,5-penta-
nediol, 1,6-hexanediol, and 1,12-dodecanediol), and tereph-
thaloyl bis-(4-oxybenzoyl-chloride).
EXPERIMENTAL
Materials
9,10-Dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO)
was purchased from Chemos GmbH, Germany. Naphthoqui-
none (NQ), trimellitic anhydride chloride (TMAC), p-amino-
phenol, terephthalic acid, 4-hydroxybenzoic acid, and mono-
mers
1 (1,3-propanediol, 1,4-butanediol, 1,5-pentanediol,
Synthesis of the Monomers and Intermediates
1,6-hexanediol, and 1,12-dodecanediol) were provided from
Aldrich and used as received. All other reagents were used
as received from commercial sources or were purified by
standard methods.
Terephthaloyl-bis-(4-oxybenzoylchloride), 2, was synthesized
by treating the corresponding dicarboxylic acid that resulted
from the reaction between 4-hydroxybenzoic acid (2 mol)
and terephthaloyl chloride (1 mol), with excess thionyl chlo-
ride, at reflux temperature, according to a method presented
Measurements
in the literature.29 m.p.: 223–226 C.
ꢀ
Melting points of the monomers and intermediates were
measured on a Melt-Temp II (Laboratory Devices). The inher-
ent viscosities of the polymers, ginh, were measured using an
Ubbelohde viscometer, at 20 ꢀC by using 0.5 g/dL solutions
in N-methyl-2-pyrrolidone. Fourier transform infrared (FTIR)
spectroscopy was performed on a Bruker Vertex 70 at fre-
quencies ranging from 400 to 4000 cmꢁ1. Samples were
FTIR (KBr, cmꢁ1): 1780 (COCl), 1730 (COO), 1600 (CAC aro-
matic), and 1210 (PhAOAOC).
2-(6-Oxido-6H-dibenz<c,e><1,2>oxaphosphorin-6-yl)-1,4-
naphthalene diol (DOPO-NQ) was synthesized from DOPO
and NQ according to the method previously reported
5392
WILEYONLINELIBRARY.COM/JOURNAL/JPOLA

ARTICLE
(1H, s), 7.94 (2H, m), 7.73 (4H, m), 7.62 (2H, m), 7.49 (1H,
m), 7.25 (1H, m), and 7.07 (1H, d). 31P NMR (DMSO-d6,
ppm): d ¼ 27.72. UV–vis (DMF, nm): kabs ¼ 296, 322; PL
(DMF, nm): kem ¼ 401 (kex ¼ 340 nm).
1,4-Bis[N-(4-hydroxyphenyl)phthalimidyl-5-carboxylate]-2-(6-
oxido-6H-dibenz<c,e><1,2>oxaphosphorin-6-yl)-naphtalene,
3, was synthesized according to the following synthetic pro-
cedure: 4-aminophenol (0.219 g, 0.002 mol), 1,4-[2-(6-oxido-
6H-dibenz<c,e><1,2>oxaphosphorin-6-yl)]-naphthalene-bis
(trimellitate)dianhydride (0.722 g, 0.001 mol), and acetic
acid (7 mL) were loaded into a 100-mL three-necked flask,
which was equipped with mechanical stirrer. The mixture
was heated to reflux and stirred for 8 h. After the comple-
tion of the reaction, the mixture was allowed to cool down,
filtered off, and washed several times with water. The
ꢀ
resulted product was filtered off and dried at 100 C for 8 h
in a vacuum oven. The entire synthetic route of 3 is depicted
in Scheme 1.
Yield ¼ 80%. FTIR (KBr, cmꢁ1): 3450 (AOH), 3065 (CAH ar-
omatic), 1780 (C¼¼O, imide carbonyl asymmetric stretching),
1730 (C¼¼O, ester carbonyl and imide carbonyl symmetric
stretching), 1600 (CAC aromatic), 1478 (PAPh), 1368
(CANAC), 1245 (ester CAO), 1205 (P¼¼O), and 1160, 925
(PAOAPh). 1H NMR (DMSO-d6, ppm): d ¼ 9.8 (2H, d), 8.69
(2H, d), 8.45 (2H, m), 8.23 (2H, m), 7.95 (6H, m), 7.62 (4H,
m), 7.49 (1H, m), 7.29 (5H, m), 7.09 (1H, d), and 6.97 (4H,
d). 31P NMR (DMSO-d6, ppm): d ¼ 18.7–16.9.
Synthesis of the Copoly(ester imide)s 4
The polymers 4 were prepared by solution polycondensation
reaction of equimolar amounts of aliphatic diols 1/aromatic
bisphenol 3 with aromatic diacid chloride 2 (Scheme 2). A
typical polycondensation was run as shown in the following
example for the synthesis of homopolymer 4a: In a 100-mL
three-necked flask, which was equipped with nitrogen inlet
and nitrogen outlet and a magnetic stirrer, bisphenol 3
(2.712 g, 0.003 mol), diacid chloride 2 (1.329 g, 0.003 mol),
and o-dichlorobenzene (9.4 mL) were introduced. The reac-
tion mixture was heated to reflux (180 ꢀC) and stirred for
20 h; it was cooled to room temperature and poured into
methanol (20 mL), under stirring, to obtain a precipitate,
which was filtered, washed with methanol, and dried at 100
ꢀC for 10 h in a vacuum oven.
SCHEME 1 Synthetic route of bisphenol 3.
(Scheme 1).29 Itꢀwas recrystallized from ethoxyethanol; m.p.
(DSC): 279–280 C.
FTIR (KBr, cmꢁ1): 3430 (AOH), 1582 (PAPh), 1190 (P¼¼O),
and 1165 and 925 (PAOAPh). 1H NMR (DMSO-d6, ppm): d
¼ 7.9 (2H, m), 7.8 (1H, m), 7.7 (1H, m), 7.5 (4H, m), 7.4
(1H, m), 7.3 (1H, m). 7.2 (1H, t), 7.1 (1H, t), and 6.6 (1H, d).
Yield: 89%. 1H NMR (DMSO-d6, ppm): d ¼ 8.73 (d, 2H, aro-
matic), 8.5–8.16 (m, 8H, aromatic), 8.09–7.85 (m, 6H, aro-
matic), 7.8–7.5 (m, 11H, aromatic), 7.4–7.11 (m, 8H, aro-
matic), and 6.94 (m, 4H, aromatic). The same procedure was
used to synthesize the copoly(ester imide)s 4b–4f by react-
ing 0.114 g (0.0015 mol) 1,3-propanediol, 0.135 g (0.0015
mol) 1,4-butanediol, 0.156 g (0.0015 mol) 1,5-pentanediol,
0.177 g (0.0015 mol) 1,6-hexanediol, and 0.303 g (0.0015
mol) 1,12-dodecanediol, respectively, 1.329 g (0.003 mol)
compound 2 and 1.356 g (0.0015 mol) aromatic bisphenol 3.
Copoly(ester imide)s 4g, 4h, and 4i were synthesized by
using 0.1515 g (0.00075 mol), 0.4545 g (0.00225 mol), and
0.5757 g (0.00285 mol) of 1,12-dodecanediol and 2.034 g
1,4-[2-(6-Oxido-6H-dibenz<c,e><1,2>oxaphosphorin-6-yl)]-
naphthalene-bis(trimellitate)dianhydride was synthesized
from DOPO-NQ and TMAC according to our recently re-
ported procedure (Scheme 1).30 The crude product was
finally recrystallized from anhydrous acetic anhydride.
Yield: 71.8%; m.p.: 295–297 ꢀC; ELEM. ANAL.: Calcd.
40H19O12P (722 g/mol) (%): C, 66.48; H, 2.63. Found: C,
C
65.74; H, 2.39; FTIR (KBr, cmꢁ1): 3067 (CAH aromatic),
1865 and 1791 (COAOACO), 1750 (ester C¼¼O), 1600 (aro-
matic), 1478 (PAPh), 1245 (ester CAO), 1220 (P¼¼O), and
1165 and 928 (PAOAPh); 1H NMR (DMSO-d6, ppm): d ¼
9.05 (2H, s), 8.95 (2H, d), 8.28 (2H, m), 8.09 (1H, d), 8.01
(0.00225 mol), 0.678
g (0.00075 mol), and 0.1356 g
PROPERTIES OF PHOSPHORUS-CONTAINING POLYESTERIMIDES, SERBEZEANU ET AL.
5393

JOURNAL OF POLYMER SCIENCE: PART A: POLYMER CHEMISTRY DOI 10.1002/POLA
SCHEME 2 Synthesis of the polymers 4.
(0.00015 mol) of diol 3, based on the above procedure;
1.329 g (0.003 mol) of compound 2 was added for each
polymer (Scheme 2). The FTIR and H NMR spectra of copo-
ties, phosphorus–nitrogen synergism was expected to induce
a high level of fire resistance, providing a dual mechanism of
degradation associated with the condensed and gas
phases.27,37
1
ly(ester imide)s 4b–4i are almost identical differing only in
relative signal intensities. For example, copolymer 4e: FTIR
(KBr, cmꢁ1): 3066 (¼¼CAH); 2938 and 2856 (ACH2A); 1779
(C¼¼O, imide carbonyl asymmetric stretching); 1734 (C¼¼O,
ester carbonyl and imide carbonyl symmetric stretching);
1604 and 1501 (C¼¼C, aromatic); 1472 (ArAP); 1369
(CANAC); 1267 and 1015 (CAOAC, ester); 1202 (P¼¼O);
1162 and 929 (PAOAC); and 760 and 718 (CAH, aromatic).
Synthesis, Chemical Structure Confirmation, and
Mesomorphic Behavior of Monomer 3
The phosphorus-containing bisphenol 3 was synthesized in
three steps starting from DOPO and NQ. In the second step,
the obtained aromatic diol, DOPO-NQ, was treated with
TMAC to form a new dianhydride, namely, 1,4-[2-(6-oxido-
6H-dibenz<c,e><1,2>oxaphosphorin-6-yl)]-naphthalene-bis
(trimellitate)dianhydride. In the last step, the phosphorus-
containing dianhydride was reacted with p-aminophenol to
form a new bisphenol containing phosphorus and preformed
imide rings. The entire synthetic route of 3 is illustrated in
Scheme 1. Complete procedures for the synthesis of all inter-
mediates and monomers are described in the ‘‘Experimental’’
section.
RESULTS AND DISCUSSION
The concept of achieving thermal stability, flame retardancy,
and liquid crystalline behavior through combination of phos-
phorus-containing monomers and aliphatic moieties into aro-
matic mesogenic moieties was successfully applied for the
control of thermal stability, phase transitions, and crystallin-
ity degree of aromatic–aliphatic phosphorus-containing copo-
lyesters.29,31–33 Recently, Wang and coworkers have paid
attention to the use of phosphorus-containing TLC polymers
for flame retardation on other thermoplastic polymers.34–36
Thermal stability and flame retardancy of these polymers
were excellent, but the mesophase and melting temperatures
need to be more decreased. Thus, our aim here was to syn-
thesize a new phosphorus-containing bisphenol, which has
preformed imide rings. In terms of flame retardant proper-
The chemical structure of the monomer 3 was confirmed by
FTIR, 1H NMR, and 31P NMR spectroscopies. The spectra
were in good agreement with the proposed molecular struc-
ture. Figure 1 shows the FTIR spectrum of bisphenol 3. The
characteristic absorption bands appeared at 3450 cmꢁ1 due
to functional AOH groups and at 1780 and 1730 due to
C¼¼O imide carbonyl asymmetric stretching and C¼¼O ester
carbonyl and imide carbonyl symmetric stretching. Absorp-
tion peaks appeared at 1478 cmꢁ1 due to PAAr, at 925 and
5394
WILEYONLINELIBRARY.COM/JOURNAL/JPOLA

ARTICLE
FIGURE 1 FTIR spectrum of
bisphenol 3.
1160 cmꢁ1 due to PAOAAr groups, and at 1205 cmꢁ1 due
to P¼¼O groups. Aromatic C¼¼C bands were found at 1600
and 1500 cmꢁ1, whereas aromatic CAH stretching band was
found at 3065 cmꢁ1. The representative 1H NMR of the
monomer 3 is illustrated in Figure 2, with the assignments
for all the protons. The monomer 3 shows the characteristic
resonances of the phosphaphenanthrene bulky group at 7.62
and 7.29 ppm and of the naphthalene unit at 7.95–7.62 ppm
and 7.09 ppm, respectively.30 The protons H1, H2, and H3,
which are characteristic for the TMAC segment, appeared at
higher ppm values (8.69, 8.45, and 8.23 ppm, respectively),
whereas the protons H18, which are closed to the terminal
hydroxyl groups, appeared at the farthest up field region of
the spectrum. The 31P NMR spectrum (Fig. 3) provides fur-
ther information regarding the expected structure of the
monomer 3. The single 31P signal can be observed for 3 at
around 18.7–16.9 ppm, as a split signal (Fig. 3, detailed
view) probably because of the presence of different chiral
centers in the molecule of 3.26
can effectively increase the melting points.38 PLM confirmed
that the bisphenol 3 exhibited liquid crystalline phase after
melting. Under visual observation, the sample melts around
347 ꢀC exhibiting a fine liquid crystalline texture [Fig. 4(c)],
difficult to ascribe but, generally, typical for a nematic phase,
whereas the clearing point was not observed up to 430 ꢀC.
ꢀ
The 430 C value, according to the TGA, represents the tem-
perature at which the sample reaches 5% of weight loss
[Fig. 4(b)]. Because of the partial decomposition at high tem-
perature, only data from the first heating scan were
available.
Synthesis, Chemical Structure Confirmation, and
General Characterization of the Poly(ester imide)s 4
Aromatic–aliphatic copoly(ester imide)s 4 were synthesized
from various ratios of 1,3-propanediol, 1,4-butanediol,
1,5-pentanediol, 1,6-hexanediol, or 1,12-dodecanediol, 1, ter-
ephthaloyl bis-(4-oxybenzoyl-chloride), 2 (TBOC) and DOPO-
containing bisphenol 3, namely 1,4-bis[N-(4-hydroxy-
phenyl)phthalimidyl-5-carboxylate]-2-(6-oxido-6H-dibenz<c,e>
<1,2>oxaphosphorin-6-yl)-naphtalene, by heating the reac-
tion mixture for 20 h at reflux temperature (180 ꢀC) using
Phase characterization of the monomer 3 was performed by
DSC, TGA, and PLM. A typical thermogram obtained by DSC
of phase transitions of the monomer 3 during the first heat-
ꢀ
ing (15 C/min) is presented in Figure 4(a). An endothermic
ꢀ
peak centered at 327.5 C starts at high temperature (above
300 ꢀC) when heating, which correspond to crystal–liquid
crystal transition, due to the fact that the naphthalene ring
FIGURE 2 1H NMR spectrum of bisphenol 3.
FIGURE 3 31P NMR spectrum of bisphenol 3.
PROPERTIES OF PHOSPHORUS-CONTAINING POLYESTERIMIDES, SERBEZEANU ET AL.
5395

JOURNAL OF POLYMER SCIENCE: PART A: POLYMER CHEMISTRY DOI 10.1002/POLA
FIGURE 4 Mesomorphic behavior of monomer 3 [DSC curve, heating scan (a), thermogravimetric analysis (b), and polarized light
microscopy micrograph (c)]. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]
o-dichlorobenzene as reaction medium. The reaction system
got temporarly homogeneous, and then the polymers precipi-
tated during the polycondensation process. The inherent vis-
cosities of the polymers, measured in N-methyl-2-pyrroli-
done, were in the range of 0.17–0.27 dL/g (Table 1)
suggesting moderate molecular weights for this type of PEIs.
Bisphenol 3 contains polar side-chain DOPO groups respon-
sible for the enhanced rigidity and polarity of the polymeric
chains, which can subsequently reduce the reactivity of func-
tional end groups and hindrance further propagation of the
polycondensation process.
aromatic CAH (deformation vibration from aromatic tereph-
thaloyl ring39,40) together with imide ring deformation (725
cmꢁ1). Aromatic C¼¼C bands were found at 1601 and 1501
cmꢁ1. The FTIR spectra also showed a broad weak absorb-
tion peak centered at 3454 cmꢁ1, which is characteristic of
the stretching vibration of unreacted OH groups. A longer
reaction time did not lead to the disappearance of such
weak absorbtion bands. The 1H NMR spectrum of the poly-
mer 4f (recorded in CDCl3: CF3COOD ¼ 9:1, v/v) is pre-
sented in Figure 6 with the assignments for all the protons.
The protons H9, H10, and H11 closed to imide ring appeared
at higher ppm in the 1H NMR spectrum (8.95–8.35 ppm).
The protons coming from DOPO-NQ unit appeared in the
range of 7.90–7.25 ppm. The polymers 4b–4i showed char-
acteristic peaks of the aliphatic protons, one singlet which
corresponds to the methylene groups located in the a-posi-
tion of the ester linkages (OACH2, 4H1, d % 4.35 ppm) and
one singlet which corresponds to the methylene groups
located in the b-position of the ester linkages, respectively
(OACH2ACH2, 2H2 for polymer 4b, or 4H2 for the others,
d % 1.73 ppm). In the case of polymers 4f–4i, the peak
characterizing the other methylene groups of the structural
unit (CH2, 16H3) appeared at d % 1.47–1.24 ppm. From the
1H NMR spectra of the copolymers, it was found that the
The structure of the resulting polymers was investigated by
FTIR and 1H NMR spectroscopies. Figure 5 shows the FTIR
spectrum of polymer 4a, as an example. As can be seen from
FTIR, the most important absorbtion bands are associated
with aromatic CAH (3066 cmꢁ1, stretching vibration), C¼¼O
groups of imide rings and ester linkages (1780 and 1734/
1705 cmꢁ1, asymmetrical and symmetrical stretching vibra-
tions), ester CAOAC (1244 and 1015 cmꢁ1, asymmetric and
symmetric stretching vibrations), PAOAAr (925 and 1160
cmꢁ1, stretching vibrations), PAAr (1470 cmꢁ1), P¼¼O (1203
cmꢁ1), aromatic CAH (756 cmꢁ1, deformation vibration
caused by the 1,2-disubsituted aromatic DOPO rings), and
TABLE 1 The Viscosity and Thermogravimetric Data of Polymers 4
IDTa (ꢀC)
T10 (ꢀC)
Tmax1 (ꢀC)
Tmax2 (ꢀC)
Char Yield at 700 ꢀC (%)
b
c
d
Polymer
ginh (dL/g)
4a
4b
4c
4d
4e
4f
0.17
0.20
0.21
0.22
0.19
0.23
0.27
0.25
0.22
355
340
365
365
360
375
395
375
385
390
370
385
375
370
400
415
385
400
425
410
400
400
385
420
445
400
410
615
645
615
590
595
620
595
585
600
33.6
30
38
30
28.8
27.6
36.4
18.4
13.6
4g
4h
4i
a
c
Initial decomposition temperature ¼ the temperature of 5% weight loss.
First maximum polymer decomposition temperature.
Second maximum polymer decomposition temperature.
b
d
Temperature of 10% weight loss.
5396
WILEYONLINELIBRARY.COM/JOURNAL/JPOLA

ARTICLE
FIGURE 5 FTIR spectrum of poly-
mer 4a.
composition of the polymer is similar with the composition
of the reactants used in the synthesis.
polymers 4a, 4f, 4h, and 4i are shown in Figure 7. The most
important TGA data (the initial decomposition temperature,
temperature of DTG peaks, and the yields of char residue at
700 ꢀC) are presented in Table 1. TGA revealed that the
polymers were stable up to 340 ꢀC showing a 5% weight
loss in the range of 340–395 ꢀC and a 10% weight loss in
The solubility of the polymers 4 was tested in various sol-
vents, by using 15 mg polymer/mL solvent, at room temper-
ature. All the polymers 4 were easy soluble in DMAc, in
NMP and DMSO they were soluble after heating the solu-
tions, whereas in solvents such as DMF or CHCl3 they were
only partially soluble. The lower solubility of the polymers 4
can be explained by the high rigidity of the segment coming
from the diacid chloride, which contains three p-phenylene
groups connected by ester units. The macromolecular chains
can have a linear conformation and allowed a strong packing
that reduced the solubility.
ꢀ
the range of 370–415 C.
As can be seen from the differential thermogravimetric
curves (DTG), phosphorus-containing PEIs decomposed in
two-stage weight loss process. The first maximum of decom-
position (Tmax1) was in the range of 385–445 ꢀC and was
due to the decomposition of ester units and aliphatic moi-
eties, which were more sensitive to degradation. The second
maximum of the decomposition (Tmax2) was in the range of
585–645 ꢀC and was due to the degradation of aromatic
polymer chain itself (Table 1). For a better understanding of
the degradation mechanism and fire retardancy, the thermal
Thermal Analysis of the Poly(ester imide)s 4
The thermooxidative stability of the polymers was evaluated
by TGA in air at a heating rate of 10 ꢀC/min; the traces of
FIGURE 6 1H NMR spectrum of polymer 4f.
PROPERTIES OF PHOSPHORUS-CONTAINING POLYESTERIMIDES, SERBEZEANU ET AL.
5397

JOURNAL OF POLYMER SCIENCE: PART A: POLYMER CHEMISTRY DOI 10.1002/POLA
ester units followed by the volatilization of the aliphatic moi-
eties from the macromolecule, can be observed (Fig. 8). Aftꢁe1r
heating the sample up to 500 ꢀC, the 1734–1717 cm
region, which represents two carbonyl peaks [Fig. 8(a)],
transformed into one band with the overall absorption at
1720 cmꢁ1, whereas the imide C¼¼O appeared at 1776 cmꢁ1
in one more intense absorption band, suggesting the destruc-
tion of the ester groups from the macromolecular chains
with an increase of the aromatic (1600 and 1503 cmꢁ1) and
heteroaromatic content. The organophosphorus PAOAC
group incorporated in the solid residue is distinguishable by
the absorption band at 939 cmꢁ1. The characteristic bands
of PAC and P¼¼O were observed at 1467 and 1194 cmꢁ1
,
respectively, indicating the presence of phosphorus in the
solid residue. It can be concluded that in the first step of
degradation, the destruction of aliphatic moieties and ester
groups with an increase of phosphorus content took place,
as the characteristic bands of PAC and P¼¼O are still present
ꢀ
in the solid residue at 500 C. It has been demonstrated that
the inherent flammability of many synthetic polymers can be
decreased by increasing their char-forming tendency.41–43
The residual char reduces the rates at which the formation
of volatile fuels are generated from pyrolysis and subsequent
combustion, acts as a barrier to heat spread and flame pene-
tration, and consequently reduces the flame propagation
rates. Furthermore, the chars of polymers are easily oxidized
ꢀ
in air when they are heated above 500 C; therefore, the re-
FIGURE 7 TG and DTG curves of the polymers 4a, 4f, 4h, and 4i.
sistance of polymeric char to thermal oxidation strongly
affects polymer flammability. A more compact structure of
the generated char led to a better resistance against heat
and oxygen admission to the polymeric substrate.44 The SEM
images of the residues of the polymers 4a and 4e obtained
decomposition behavior of the polymers was studied through
FTIR–TGA and SEM–TGA analysis. The FTIR spectra of the
polymer 4e and the solid residue of the polymer 4e, after
heating the sample up to 500 ꢀC, are presented in Figure 8.
The value of 500 ꢀC represents the temperature of the end
of the first decomposition process from DTG curve, which
corresponds to a 44% weight loss. At this stage, a decrease
in intensity of the aliphatic CAH (2938 and 2856 cmꢁ1) and
the disappearance of CAOAC ester absorption bands (1244
and 1015 cmꢁ1), associated with the decomposition of the
ꢀ
after heating the samples up to 510 and 500 C, respectively,
are shown in Figure 9. The char from 4a displayed a more
compact structure [Fig. 9(a)] when compared with the char
from 4e, supporting the results obtained by FTIR–TGA, which
indicated that the aliphatic content of the polymers 4 was
released after the first step of decomposition process, pene-
trating through the char and, thus, giving a less compact
FIGURE 8 FTIR spectra of polymer 4e, sample at room temperature (a) and sample heated up to 500 ꢀC (b).
5398
WILEYONLINELIBRARY.COM/JOURNAL/JPOLA

ARTICLE
FIGURE 9 SEM micrographs of solid residue obtained from polymers 4a at 510 ꢀC (a) and 4e at 500 ꢀC (b).
structure of the char [Fig. 9(b)]. This agreed with the high
char yield at high temperature. The char yields at 700 ꢀC
were in the range of 13.6–38% (Table 1) increasing with the
content of phosphorus-containing bisphenol 3. Therefore, the
efficiency against heat transfer and air access from the sur-
face to the inner substrates of the polymeric residue and the
better inhibition of the effectively flame spread can be con-
trolled by increasing the content of the phosphorus-contain-
ing monomer into the final polymeric matrix.
ferent components of the morphology formed in multiple
stages of crystallization.53 The as-synthesized copolymer 4i
(Fig. 10, H-1 curve) exhibited multiple melting endotherms
(Tꢃ167, 178, 196, and 204 C), a very tiny endotherm (indi-
ꢀ
cated by arrow, 238 ꢀC) corresponding to a smectic-to-ne-
matic transition and finally a broad endothermic peak at 304
ꢀC corresponding to the nematic-to-isotropic transition. Upon
cooling from isotropic state (310 ꢀC) to room tempꢀerature,
the copolymer 4i showed a tiny broad peak (Tꢃ183 C) cor-
responding to a liquid crystal-to-liquid crꢀystal transition and
a sharp crystallization exotherm (Tꢃ138 C) with a shoulder
at 146 ꢀC, whereas the isotropic-to-nematic transition was
not observable (Fig. 10, C-1 curve). Second heating scan of
the copolyester 4i after cooling from the mesomorphic state
transformed the multiple melting peaks into one major endo-
therm (Tꢃ157), whereas the mesomorphic transition and
isotropization transition were not observable. The first heat-
ing run for the copolymer 4h exhibited similar behavior
with multiple melting endotherms and relevant mesomor-
phic smectic-to-nematic transition, but the isotropization
transition was not detected and the first cooling scan did not
show the expected exotherms (Table 2). The disappearance
of the endotherms and exotherms in the second heating–first
cooling scans can be explained by the fact that the different
crystalline structures induced by the solvent used in the
Thermal Transitions Behavior
The thermal properties and the phase transition tempera-
tures of the polymers 4, obtained during the first heating–
cooling cycle, are determined by DSC, and the data for 4a,
4f–4i are summarized in Table 2. The data listed in Table 2
revealed a considerable effect of molecular structure on the
melting temperatures and mesomorphic properties as will
be discussed in this section. Figure 10 shows the DSC heat-
ing–cooling curves of the polymer 4i at a heating rate of
10 ꢀC/min. The DSC curves showed multiple melting endo-
therms. The phenomenon of multiple melting was reported
in many articles as a feature in common for liquid crystalline
polymers.45–48 Multiple melting behavior has previously
attributed to reasons including the presence of different
crystal structures49,50 to crystal reorganization51,52 or to dif-
TABLE 2 Phase Transition Temperatures of Synthesized Polymers 4
Transition Temperature in ꢀCa
First Cooling
Transition Temperatures
in ꢀC, from PLMb
Polymer
First Heating
4a
4f
K293N(ꢁ)I
K1177K2186(189)N(ꢁ)I
K172N(ꢁ)I
K1180K2200(207)Sm239N(ꢁ)I
K1167(178)K2196(204)Sm(238)N304I
I(ꢁ)N(ꢁ)K
K308LC > 400I
K259LC > 400I
K291LC > 400I
K213LC369I
I(ꢁ)N165K
4g
4h
4i
I(ꢁ)N(ꢁ)K
I(ꢁ)N(ꢁ)Sm145K
I(ꢁ)N183Sm146(138)K
K209LC312I
b
K, K1, K2, solids; Sm, smectic phase; N, nematic phase; I, isotropic
phase; LC, liquid crystalline phase; (–), peak temperature not observed
by DSC.
Phase transition temperature taken from PLM observation, first heat-
ing cycle at a heating rate of 10 ꢀC/min.
a
Peak temperatures from DSC were taken as the phase transition
temperature.
PROPERTIES OF PHOSPHORUS-CONTAINING POLYESTERIMIDES, SERBEZEANU ET AL.
5399

JOURNAL OF POLYMER SCIENCE: PART A: POLYMER CHEMISTRY DOI 10.1002/POLA
nematic phases (N, fine textures and schlieren textures),
whereas the copolyesters 4f, 4h, and 4d with a higher con-
tent of long methylene segment as spacer lengths exhibited
enantiotropic mesophase and revealed smectic phases (SmA,
fan-shape texture) because of the increasing of molecular
interaction of the macromolecules. As shown in Table 2,
introduction of laterally attached DOPO bulky groups does
not affect the LC properties in small amounts, but increasing
the content of aromatic diol decreased the ability of the poly-
mers 4a and 4g to form more ordered liquid crystalline
phases. The result suggests that the sterically hindered
DOPO group might decrease the molecular interaction
between macromolecules leading to the appearance of the
less ordered liquid crystalline mesophases.33
Texture Analysis
FIGURE 10 DSC thermogram of polymer 4i, H-1, first heating
Polarizing light microscopy was used to identify the liquid
crystalline phases and to complement the phase transitions
observed by DSC. Optical micrographs of different textures
are shown in Figure 11. The data of the mesomorphic transi-
tion temperatures (K ! LC ! I) are given in Table 2. A suit-
able amount of sample for each polymer was charged
between two clean glass plates. The samples were heated up
to clearing point, which is considered as the liquid crystal-
line to isotropic state transition. The transition temperatures
from crystal to liquid crystalline melt were in the range of
and C-1, first cooling.
synthesis stage can be influenced by thermal treatment.45
The DSC trace of the polymer 4a did not show a multiple
melting behavior, but a melting endotherm appeared at
about 293 ꢀC, and the liquid crystalline to isotropic state
ꢀ
transition did not appeared up to 350 C. The polymers 4a–
4e and 4g that have no or small aliphatic content (n ¼ 3–6,
Scheme 2) exhibited enantiotropic mesophases and revealed
FIGURE 11 Optical micrographs of polymers 4: (a) polymer 4a heating cycle at 365 ꢀC, fine texture; (b) polymer 4i cooling cycle at
288 ꢀC showing fine droplets appearance from the isotropic state; (c) polymer 4i second cooling cycle at 238 ꢀC showing a fan-
shaped texture (SmA phase); and (d) polymer 4i second cooling cycle at 221 ꢀC showing a fingerprint texture.
5400
WILEYONLINELIBRARY.COM/JOURNAL/JPOLA

ARTICLE
TABLE 3 X-Ray Diffraction Data for Some of the Polymers 4
whereas the polymers with a smaller content of methylene
groups in the structural unit (4b–4g) loose the ability to
organize into more ordered phases and displayed only fine
threaded textures, typical of nematic phases. For example, in
the case of the polymer 4i, upon cooling at a rate of 5 ꢀC/min,
some tiny birefringent droplets start to appear from the iso-
tropic state [Fig. 11(b)]. On continued cooling, these tiny
droplets organize in some Schlieren droplets [Fig. 11(b),
down left corner] or they grow and populate the whole mi-
croscopic view developing interesting fingerprint textures
[Fig. 11(b), down right corner]. On the second cooling run,
when the temperature approaches 238 ꢀC (the temperature
corresponding to smectic-to-nematic transition from DSC, first
heating), under shearing the nematic disclination structures
transforms into more ordered phase showing a fan-shaped
texture, suggestive of a smectic A phase [Fig. 11(c)] or a fin-
gerprint texture [Fig. 11(d)]. The polymer 4h features simi-
larly, whereas the polymers 4a–4g displayed only threaded
nematic textures over the melting temperatures.
Peak
(2y) (ꢀ)
d-Spacing
Intensity
(%)
Crystallinity
(%)
˚
Polymer
(A)
4a
3.6
19.9
23.0
3.6
24
67
100
68
39
36
28
32
4.4
3.9
4e
4f
24.3
4.6
69
19.4
23.3
3.5
100
61
3.8
24.9
4.5
65
19.6
23.3
3.6
61
3.8
39
4g
24.7
4.6
66
19.3
20.9
23.4
2.2
90
4.2
63
3.8
60
4i
39.8
31.5
16.9
4.6
64
43
2.8
79
X-Ray Measurements
5.2
17
The mesophase of the polymers was also characterized
through X-ray diffraction measurements. The XRD data (per-
centage crystallinity, peaks intensity, d-spacing values, and
Bragg angles) of the polymers 4a, 4e, 4f, 4g, and 4i, respec-
tively, obtained at room temperature are summarized in Ta-
ble 3. Representative XRD curve for 4i at room temperature
is shown in Figure 12. The sample 4i showed sharp and
strong peaks at low angle (2h ꢄ 2.2ꢀ, 2.8ꢀ, and 5.2ꢀ, respec-
tively) suggesting d-spacing near 39.8, 31.5, and 16.9 Å,
respectively, and strong sharp peaks in wide angle (2h ꢄ
19.4ꢀ and 23.4ꢀ) indicating d-spacing near 4.6 and 3.8 Å,
respectively, confirming the results obtained from DSC and
PLM investigations. Other studied polymers showed rela-
tively broad reflections at wide angles (associated with the
lateral packing) and only one weak sharp reflection at small
angles (associated with weak smectic layers),57 which evi-
denced the inability to identify smectic organizations under
DSC and PLM observations. Furthermore, the intensity of
sharp reflection at low angle increased with the number of
ACH2A and with increasing the molar ratio of the aliphatic
monomer indicating strengthening smectic layer structure. It
can be concluded that the intermolecular distance of the
polymer chains became smaller by decreasing the content of
19.4
21.4
23.4
100
37
4.2
3.8
75
ꢀ
209–308 C and depended on the aliphatic content, polymer
4a having the highest value for the transition K ! LC (308
ꢀC). The LC ! I transition temperatures for 4i and 4h were
312 and 369 ꢀC, respectively. For the polymers 4a–4g, this
transition cannot be found in PLM investigation because
these PEIs had too high Ti to match the limiting temperature
of the hot stage of PLM (400 ꢀC). Ti greatly depends on the
content of phosphorus-containing bisphenol 3, which has
preformed imide rings. As seen in Table 2, the broad meso-
phase temperature range makes these polymers interesting
from practical point of view.54 The transition temperatures
of the polymers 4 obtained by PLM were compared with
those measured by DSC measurements. These two methods
gave comparable results as seen in Table 2. The observed
differences could be explained by the variation of heating–
cooling rate, amounts of the sample used for the measure-
ments, or the presence of the different atmosphere (nitrogen,
in the case of DSC, and air, in the case of the PLM
investigation).
Upon heating all as-synthesized polymers 4 formed fine tex-
tures [Fig. 11(a)], difficult to ascribe to a smectic or nematic
phase, but similar to those reported for thermotropic poly-
mers based on terephthaloyl-bis(4-oxyphenylene carbonyl)
units.20,55,56 Upon cooling from the isotropic state, the poly-
mers 4 behave different as a function of the aliphatic content.
The flexible methylene spacer groups separate the mesogenic
alignment, thereby reducing the overall rigidity. Thus, the
polymers 4i and 4h containing a higher ratio of 1,12-dodeca-
nediol seem to form textures typical of smectic phases,
FIGURE 12 Wide-angle X-ray diffractogram of polymer 4i.
PROPERTIES OF PHOSPHORUS-CONTAINING POLYESTERIMIDES, SERBEZEANU ET AL.
5401

JOURNAL OF POLYMER SCIENCE: PART A: POLYMER CHEMISTRY DOI 10.1002/POLA
2 Liu, J. G.; Li, Z. X.; He, M. H.; Wang, F. S.; Yang, S. Y. In
Polyimides and Other High Temperature Polymers; Mittal, K.
L., Ed.; VSP BV: Utrecht, 2003; Vol. 2, pp 447–458.
bulky phosphorus-containing groups laterally attached to the
macromolecular chains.33 The percent crystallinity of the
polymers was determined by bisecting the experimental plot
into crystalline domain and amorphous domain by curve fit-
ting. The areas under the crystalline and amorphous domain
are determined computationally, and the percentage crystal-
linity was calculated. The percentage crystallinity varies
from 28 to 43%, for the studied polymers, depending slightly
upon aliphatic segment content in the polymer (Table 3).
The percentage crystallinity decreased by introducing equi-
molecular amounts of 3 and 1,6-hexanediol or 1,12-dodeca-
nediol, respectively, when compared with polymer 4a.
Decreasing the molar ratio of 1,12-dodecanediol in 4g
slightly increased the percentage crystallinity from 28 to
32% (4f vs. 4g, Table 3), illustrating that the molecular pack-
ing is disrupted by difference in the size of comonomer units
and also by random comonomer sequences.58 The polymer
4i that contains the smallest quantity of aromatic bisphenol
3 in the structural unit of the macromolecular chain exhib-
ited the highest value for the percentage crystallinity.
3 Leng, W. N.; Zhou, Y. M.; Xu, Q. H.; Liu, J. Z. Polymer 2001,
42, 9253–9259.
4 Liaw, D. J.; Chang, F. C.; Leung, M. K.; Chou, M. Y.; Muellen,
K. Macromolecules 2005, 38, 4024–4029.
5 Wang, L.; Zhao, Z.; Li, J.; Chen, C. Eur Polym J 2006, 42,
1266–1272.
6 Shang, Y.; Fan, L.; Yang, S.; Xie, X. Eur Polym J 2006, 42,
981–989.
7 Myung, B. Y.; Kim, J. J.; Yoon, T. H. J Polym Sci Part A:
Polym Chem 2002, 40, 4217–4227.
8 Liu, Y. L.; Hsu, C. Y.; Wu, C. S. J Appl Polym Sci 2003, 89,
791–796.
9 Xu, J. W.; Chng, M. L.; Chung, T. S.; He, C. B.; Wang, R. Poly-
mer 2003, 44, 4715–4721.
10 Wakita, J.; Sekino, H.; Sakai, K.; Urano, Y.; Ando, S. J Phys
Chem B 2009, 113, 15212–15224.
CONCLUSIONS
11 Wang, C. S.; Leu, T. S. Polymer 2000, 41, 3581–3591.
A series of main-chain LC PEIs bearing bulky phosphorus-
containing groups were synthesized by using various ali-
phatic diols, the mesogenic terephthaloyl-bis-(4-oxibenzoyl-
chloride), and a new LC phosphorus-containing monomer.
The chemical structures of the monomers and polymers
were characterized with FTIR and 1H NMR spectroscopies.
The liquid crystalline phases were confirmed by DSC and X-
ray diffraction experiments and were also compared with
the PLM observations. The samples 4a–4g exhibited nematic
phases upon heating and cooling, whereas the samples 4h
and 4i displayed both smectic and nematic phases. The mes-
omorphic transition temperatures of the synthesized poly-
mers decreased by increasing the number of methylene units
in the macromolecular chain (polymers 4b–4f). Also, the
mesomorphic transition temperatures decreased with the
increase of the aliphatic molar ratio in the polymer backbone
(polymers 4f–4i). Broad mesophase temperature ranges
were observed for these polymers, making them interesting
from practical point of view. The thermal properties and the
flame retardancy of the polymers were evaluated by means
of TGA, TGA–FTIR, and SEM. The TGA results showed that
5% weight loss temperatures were greater than 340 ꢀC for
all the polymers, and the residue at 700 ꢀC increased with
the increase of phosphorus-containing units in the macromo-
lecular system.
12 Eichstadt, A. E.; Ward, T. C.; Bagwell, M. D.; Farr, I. V.; Dun-
son, D. L.; McGrath, J. E. J Polym Sci Part B: Polym Phys 2002,
40, 1503–1512.
13 Madhra, M. K.; Sharma, M.; Banerjee, S. J Appl Polym Sci
2004, 93, 235–246.
14 Krishnan, P.; Santhana, G.; Veeramani, S. Polym Degrad
Stab 2003, 81, 225–232.
15 De Abajo, J.; De la Campa, J. G. In Handbook of Polymer
Synthesis, 2nd ed.; Kricheldorf, H. R.; Nuyken, O.; Swift, G.,
Eds.; Marcel Dekker: New York, 2005, p 575.
16 Kricheldorf, H. R.; Domschke, A.; Schwarz, G. Macromole-
cules 1991, 24, 1011–1016.
17 Kricheldorf, H. R. Adv Polym Sci 1999, 141, 83–188.
18 Kim, T. K.; Kim, S. O.; Chung, I. J. Polym Adv Technol 1997,
8, 305–318.
19 Reddy, C. R.; Lenz, R. W. J Polym Sci Part A: Polym Chem
1991, 29, 1015–1021.
20 Ignatious, F.; Lenz, R. W.; Kantor, S. W. Macromolecules
1994, 27, 5248–5257.
21 Senthill, S.; Kannan, P. J Polym Sci Part A: Polym Chem
2001, 39, 2396–2403.
22 Wang, X.; Hu, Y.; Song, L.; Xing, W.; Lu, H.; Lv, P.; Jie, G.
Polymer 2010, 51, 2435–2445.
This research was financially supported by European Social
Fund—‘‘Cristofor I. Simionescu’’ Postdoctoral Fellowship Pro-
gramme (ID POSDRU/89/1.5/S/55216) and Sectoral Opera-
tional Programme Human Resources Development 2007–2013.
23 Du, X. H.; Wang, Y. Z.; Chen, X. T. Polym Degrad Stab 2005,
88, 52–56.
24 Wang, C. S.; Lin, C. H.; Chen, C. Y. J Polym Sci Part A:
Polym Chem 1998, 36, 3051–3061.
25 Liu, Y. L.; Wu, C. S.; Hsu, K. Y.; Chang, T. C. J Polym Sci
REFERENCES AND NOTES
Part A: Polym Chem 2002, 40, 2329–2339.
1 Ghosh, M. K.; Mittal, K. L. Polyimides: Fundamentals and
26 Canadell, J.; Mantecon, A.; Cadiz, V. J Polym Sci Part A:
Applications; Marcel Dekker: New York, 1996; pp 7–48, 71–120.
Polym Chem 2007, 45, 1980–1992.
5402
WILEYONLINELIBRARY.COM/JOURNAL/JPOLA

ARTICLE
27 Lu, S.-Y.; Hamerton, I. Prog Polym Sci 2002, 27, 1661–1712.
28 Merz, W. Microchim Acta 1959, 47, 456–465.
43 Horrocks, A. R.; Anand, S. C.; Sanderson, D. Polymer 1996,
37, 3197–3206.
44 Deng, Y.; Zhao, C.-S.; Wang, Y.-Z. Polym Degrad Stab 2008,
29 Vlad-Bubulac, T.; Hamciuc, C. Polymer 2009, 50, 2220–2227.
93, 2066–2070.
30 Hamciuc, C.; Hamciuc, E.; Serbezeanu, D.; Vlad-Bubulac, T.
45 Lin, L. L.; Hong, J. L. Polymer 2000, 41, 4501–4512.
46 Lin, L. L.; Hong, J. L. Polymer 2001, 42, 1009–1016.
47 Cheng, S. Z. D. Macromolecules 1988, 21, 2475–2484.
Polym Adv Technol, DOI: 10.1002/pat.1784.
31 Vlad-Bubulac, T.; Hamciuc, C.; Petreus, O. Mater Plast (Bu-
charest) 2007, 44, 199–203.
32 Vlad-Bubulac, T.; Hamciuc, C. Polym Eng Sci 2010, 50,
48 Schneggenburger, L. A.; Osenar, P.; Economy, J. Macromo-
1028–1035.
lecules 1997, 30, 3754–3758.
33 Serbezeanu, D.; Vlad-Bubulac, T.; Hamciuc, C.; Aflori, M.
49 Lovering, E. G.; Wooden, D. C. J Polym Sci Part A-2: Polym
Macromol Chem Phys 2010, 211, 1460–1471.
Phys 1969, 7, 1639–1649.
34 Zhao, C. S.; Chen, L.; Wang, Y.-Z. J Polym Sci Part A: Polym
50 Samuel, R. J. J Polym Sci Polym Phys Ed 1975, 13,
Chem 2008, 46, 5752–5759.
1417–1466.
35 Huang, H.-Z.; Chen, L.; Wang, Y.-Z. J Polym Sci Part A:
51 Alfonso, G. C.; Pedemonte, E.; Ponzetti, L. Polymer 1979, 20,
Polym Chem 2009, 47, 4703–4709.
104–112.
36 Bian, X.-C.; Chen, L.; Wang, J.-S.; Wang, Y.-Z. J Polym Sci
52 Lee, Y.; Porter, S. R.; Lin, J. S. Macromolecules 1989, 22,
Part A: Polym Chem 2010, 48, 1182–1189.
1756–1760.
37 Dufton, P. Flame Retardants for Plastics; Rapra Technology
53 Basset, D. C.; Olley, R. H.; Al Raheil, I. A. M. Polymer 1988,
Limited: Shawbury, Shrewsbury, Shropshire, 2003; p 73.
29, 1745–1754.
38 Zhang, L.-Y.; Guan, X.-L.; Zhang, Z.-L.; Chen, X.-F.; Shen, Z.;
54 Chen, B. K.; Tsay, S. Y.; Chen, J. Y. Polymer 2005, 46,
Fan, X.-H.; Zhou, Q.-F. Liq Cryst 2010, 37, 453–462.
8624–8633.
39 Socrates, G. Infrared and Raman Characteristics Groups Fre-
55 McCarthy, T. F.; Lenz, R. W.; Kantor, S. W. Macromolecules
quencies: Tables and Charts, 3rd ed.; Wiley: Chichester, 2004.
1997, 30, 2825–2838.
40 Thomas, L. C. Interpretation of the Infrared Spectra of Orga-
56 Skovby, M. H. B.; Lessel, R.; Kops, J. J Polym Sci Part A:
nophosphorus Compounds; Heyden: London, 1974.
Polym Chem 1990, 28, 75–87.
41 Hamciuc, C.; Vlad-Bubulac, T.; Petreus, O.; Lisa, G. Eur
57 Meng, F.-B.; Cui, Y.; Chen, H.-B.; Zhan, B.-Y.; Jia, C. Polymer
Polym J 2007, 43, 980–988.
2009, 50, 1187–1196.
42 Horrocks, A. R. Polym Degrad Stab 1996, 54, 143–154.
58 Jin, J.-I.; Kang, C.-S. Prog Polym Sci 1997, 22, 937–973.
PROPERTIES OF PHOSPHORUS-CONTAINING POLYESTERIMIDES, SERBEZEANU ET AL.
5403