Synthesis and characterization of soluble poly(ether imide)s based on 2,2 '-bis(4-aminophenoxy)-9,9 '-spirobifluorene

Synthesis and characterization of soluble poly(ether imide)s based

on 2,2

0

-bis(4-aminophenoxy)-9,9

0

-spirobifluorene

D. Sahadeva Reddy

, Chia-Hung Chou

, Ching-Fong Shu

*, Gene-Hsiang Lee

a

Department of Applied Chemistry, National Chiao Tung University, 1001 Ta Hsueh Road, Hsin-Chu 30035, Taiwan, ROC

b

Instrumentation Center, College of Science, National Taiwan University, Taipei, Taiwan, ROC Received 6 September 2002; received in revised form 1 November 2002; accepted 5 November 2002

Abstract

A series of aromatic poly(ether imide)s containing 9,90-spirobifluorene moieties in the main chain have been synthesized via the polycondensation of 2,20-bis(4-aminophenoxy)-9,90-spirobifluorene with a variety of aromatic dianhydrides. In the diamine monomer, the two aminophenoxyfluorene entities are orthogonally arranged and are connected through an sp3carbon atom (the spiro center). The resulting poly(ether imide)s have a polymer backbone which is periodically twisted with an angle of 908 at each spiro center. This structural feature, which restricts the close packing of the polymer chains and reduces inter-chain interactions, leads to amorphous poly(ether imide)s with good solubility in common organic solvents. In addition, the rigidity of the main chain of these polymers appears to be preserved due to the spiro-structure. As a result, these poly(ether imide)s exhibit a high Tgand excellent thermal stability.

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Keywords: Organosoluble; Polyimides; Spirobifluorene

1. Introduction

Aromatic polyimides possess outstanding thermal, mechanical, and electrical properties, as well as excellent chemical resistance. But their poor processability imposes

limitations to their areas of application [1,2]. Therefore,

much research effort has been focused on the synthesis of soluble polyimides without deteriorating their otherwise

excellent properties [3]. Typical approaches include the

introduction of bulky lateral groups[4 – 9], flexible linkages

[10,11], and kinked [12 – 14] or unsymmetrical structures

[15,16]into the polymer backbone.

Previous studies have shown that incorporating a spirobifluorene linkage into the structure of small mol-ecules, as well as polymeric materials, leads to a reduction in crystallization tendency, an enhancement in solubility,

and an increase in glass transition temperature[17 – 25]. In

light of these observations, we aimed to synthesize a series of poly(ether imide)s which contain spiro-skeletal units, along with flexible ether linkages, in the polymer main

chain, based on a new spiro-fused diamine monomer. The spirobifluorene monomer consists of two identical amino-phenoxyfluorene moieties connected through a common tetracoordinate carbon atom (the spiro center). In the spiro-segment, the rings of the connected bifluorene entities are

orthogonally arranged[17,26,27]. The resulting polyimides

would be expected to have a polymer backbone, which is periodically twisted with an angle of 908 at each spiro-center. This structural feature would restrict the close packing of the polymer chains and reduce the probability of interchain interactions, resulting in high polymer solubility. Furthermore, the main chain rigidity of the polyimide would be preserved due to the spiro-structure, which restricts the free segmental mobility.

Herein, we describe the synthesis of the novel

spiro-fused diamine monomer, 2,20-bis(4-aminophenoxy)-9,

90-spirobifluorene (6), starting from 2,20-dihydroxy-9,

90-spirobifluorene [28]. This diamine was subjected to

polymerization with a variety of aromatic dianhydrides, and the properties of the resulting poly(ether imide)s were studied. These polyimides were found to be highly soluble in common organic solvents and possess good thermal stabilities.

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* Corresponding author. Tel.: 712121x56544; fax: þ886-35-723764.

2. Experimental section 2.1. Materials

2,20-Dihydroxy-9,90-spirobifluorene (4) was prepared as

described in the literature[28]. The dianhydrides 3,30,4040

-biphenyltetracarboxylic dianhydride, 4,40-oxydiphthalic

anhydride, 3,30,4,40-benzophenonetetracarboxylic

dianhy-dride, and 4,40-(4,40-isopropylidenediphenoxy)bis(phthalic

anhydride) were recrystallized from acetic anhydride and

dried at 150 8C under reduced pressure prior to use. 4,40

-(hexafluoroisopropylidine)diphthalic anhydride was sub-limed before use. m-Cresol was freshly distilled under reduced pressure and isoquinoline was used as received. 2.2. Characterization

1

H and 13C NMR spectra were recorded with a Varian

Unity 300 MHz or a Bruker-DRX 300 MHz spectrometer. IR spectra were taken with a Nicolet 360 FT-IR spec-trometer. Differential scanning calorimetry (DSC) was performed with a DuPont TA 2000 instrument using a

heating/cooling rate of 20 8C min21. Samples were scanned

from 30 to 400 8C and then cooled to 30 8C and scanned for a second time over the same range. The glass transition

temperature (Tg) was determined from the second heating

scan. Thermogravimetric analysis (TGA) was made with a DuPont TGA 2950 instrument. The thermal stabilities of all samples were determined in nitrogen by measuring weight

loss while heating at a rate of 20 8C min21. Mass spectra

were obtained with a JEOL JMS-SX/SX 102A mass spectrometer. Gel permeation chromatography (GPC) was carried out with a Waters chromatography connected to a Waters 410 differential refractometer. Three, 5 mm Waters

styragel columns (300 £ 7.8 mm2) were connected in series

and in decreasing order of pore size (105, 104and 103A˚ ),

with DMF as the eluent; PMMA standard samples were used for calibration. Wide-angle X-ray diffraction patterns were obtained at room temperature with a Rigaku XRD-RU 200 (Cu Ka, 40 mA, 30 kV) at a sampling step of 0.028 and

a scan rate of 58 min21. X-ray crystal structure

determi-nation was performed with a Bruker SMATER APEX diffractometer using graphite monochromated Mo Ka

radiation ðl¼ 0:7107 AÞ: Structure analyses were

per-formed utilizing the SHELXTL/PC program.

2.3. 2,20-Bis(4-nitrophenoxy)-9,90-spirobifluorene (5)

To a solution of 2,20-dihydroxy-9,90-spirobifluorene (4)

(3.80 g, 10.9 mmol) in DMF (15 ml) was added potassium carbonate (4.52 g, 33.0 mmol) and 4-fluoronitrobenzene (2.50 ml, 23.0 mmol). The mixture was stirred at 60 8C for 8 h under nitrogen. After cooling, the resulting solution was slowly added into 120 ml of water. The precipitated solid was collected by filtration and dried under vacuum. The crude product was recrystallized from acetonitrile to afford

crystalline dinitro compound 5 (5.75 g, 89.3%), mp. 191 8C.

IR (KBr, cm21): 1603, 1588, 1573, 1511, 1475, 1450, 1342, 1260, 1245, 1163, 1112, 871, 845, 753.1H NMR (DMSO-d6):d 6.47 (d, 2H, J ¼ 2.0 Hz), 6.67 (d, 2H, J ¼ 7.5 Hz), 6.98 (d, 4H, J ¼ 9.0 Hz), 7.15 (dd, 2H, J ¼ 7.5, 7.5 Hz), 7.21 (dd, 2H, J ¼ 8.3, 2.0 Hz), 7.41 (dd, 2H, J ¼ 7.5, 7.5 Hz), 8.00 (d, 2H, J ¼ 7.5 Hz), 8.10 (d, 2H, J ¼ 8.3 Hz), 8.12 (d, 4H, J ¼ 9.0 Hz). 13C NMR (DMSO-d6): d 162.8, 154.2, 150.2, 147.8, 142.2, 140.3, 138.7, 128.3, 128.0, 126.0, 123.4, 122.4, 120.7, 120.5, 117.1, 115.7, 65.4. HRMS (m/z ): 590.1478. Calcd 590.1478 for C37H22N2O6. 2.4. 2,20-Bis(4-aminophenoxy)-9,90-spirobifluorene (6)

A mixture of dinitro compound 5 (4.45 g, 7.54 mmol) and 10% Pd – C (225 mg, 5 wt%) in 60 ml of ethanol was stirred under a hydrogen atmosphere for 10 h at room temperature. The resulting solution was filtered through celite to remove the catalyst and the filtrate was concen-trated under reduced pressure to strip off approximately two-thirds of the solvent. On cooling the concentrated solution, white crystalline solid precipitated out. The solid was filtered and dried under vacuum to yield the pure diamine monomer 6 (3.31 g, 82.8%), mp: 232 8C. IR (KBr, cm21): 3457, 3375, 1614, 1578, 1511, 1480, 1455, 1250, 1209, 866, 830, 748, 738.1H NMR (DMSO-d6):d4.96 (br s, 4H), 6.07 (d, 2H, J ¼ 2.4 Hz), 6.48 (d, 4H, J ¼ 8.7 Hz), 6.57 (d, 2H, J ¼ 7.5 Hz), 6.62 (d, 4H, J ¼ 8.7 Hz), 6.86 (dd, 2H, J ¼ 8.4, 2.4 Hz), 7.06 (dd, 2H, J ¼ 7.5, 7.5 Hz), 7.34 (dd, 2H, J ¼ 7.5, 7.5 Hz), 7.86 (d, 2H, J ¼ 7.5 Hz), 7.88 (d, 2H, J ¼ 8.4 Hz). 13C NMR (DMSO-d6): d 159.0, 150.0, 147.9, 145.4, 145.3, 140.8, 135.1, 128.0, 127.1, 123.3, 121.7, 120.6, 120.0, 116.4, 114.7, 111.5, 65.3. HRMS (m/z ): 530.1984. Calcd 530.1994 for C37H26N2O2. 2.5. Polymerization

A typical polymerization procedure is as follows. To a

solution of 2,20-bis(4-aminophenoxy)-9,90-spirobifluorene

(6, 265 mg, 500 mmol) in 2.5 ml of freshly distilled

m-cresol, 4,40-(hexafluoroisopropylidine)diphthalic anhydride

(7a, 222 mg, 500 mmol) and isoquinoline (2 – 3 drops) as a catalyst were added at room temperature and stirred for 30 min under nitrogen atmosphere. The reaction mixture was then stirred at 70 – 80 8C for 4 h, and heated to 220 8C, with stirring, for 8 h. After cooling, the viscous solution was added slowly into methanol (80 ml) and the colorless fibrous solid was collected by filtration, washed thoroughly with methanol and dried under vacuum at 100 8C to afford the corresponding polyimide 8a. The poly(ether imide)s 8a – e were further purified by reprecipitating from DMF into methanol several times.

8a: Yield 94%. IR (KBr, cm21): 1779, 1726, 1598, 1480,

1450, 1374, 1255, 1189, 835, 733.1H NMR (CDCl3):d6.54

(d, 2H, J ¼ 2.2 Hz), 6.74 (d, 2H, J ¼ 7.5 Hz), 6.98 (d, 4H, J ¼ 9.1 Hz), 7.03 (dd, 2H, J ¼ 8.3, 2.2 Hz), 7.08 (dd, 2H,

J ¼ 7.5, 7.5 Hz), 7.26 (d, 4H, J ¼ 9.1 Hz), 7.33 (dd, 2H, J ¼ 7.5, 7.5 Hz), 7.76 (d, 2H, J ¼ 7.0 Hz), 7.78 (d, 2H, J ¼ 8.3 Hz), 7.81 (d, 2H, J ¼ 8.8 Hz), 7.87 (s, 2H), 7.95 (d, 2H, J ¼ 8.8 Hz).13C NMR (CDCl3):d166.2, 166.0, 157.6, 155.9, 150.7, 148.3, 141.0, 139.0, 138.0, 135.8, 132.6, 132.3, 128.0, 127.9, 125.7, 125.3, 124.0, 123.9, 121.1, 119.8, 119.3, 118.3, 115.9, 65.8. 8b: Yield 93%. IR (KBr, cm21): 1777, 1721, 1608, 1511, 1475, 1445, 1368, 1260, 1235, 1081, 851, 738. 1H NMR (CDCl3):d1.71 (s, 6H), 6.53 (d, 2H, J ¼ 2.1 Hz), 6.73 (d, 2H, J ¼ 7.5 Hz), 6.93 (d, 4H, J ¼ 9.0 Hz), 6.97 (d, 4H, J ¼ 8.8 Hz), 7.02 (dd, 2H, J ¼ 8.4, 2.3 Hz), 7.07 (dd, 2H, J ¼ 7.6, 7.6 Hz), 7.23 – 7.35 (m, 14H), 7.74 – 7.78 (m, 6H). 13_{C NMR (CDCl} 3): d 166.8, 163.7, 157.3, 155.9, 152.6, 150.7, 148.3, 147.5, 141.0, 138.0, 134.2, 128.7, 128.0, 127.5, 126.0, 125.6, 125.0, 123.9, 122.8, 121.2, 120.0, 119.9, 119.5, 118.0, 116.0, 111.8, 65.8, 42.5, 31.0. 8c: Yield 95%. IR (KBr, cm21): 1777, 1726, 1603, 1486, 1445, 1368, 1255, 1199, 753, 722, 615.1H NMR (CDCl3):d 6.53 (d, 2H, J ¼ 2.1 Hz), 6.74 (d, 2H, J ¼ 7.6 Hz), 6.95 (d, 4H, J ¼ 8.9 Hz), 7.02 (dd, 2H, J ¼ 8.3, 2.1 Hz), 7.08 (dd, 2H, J ¼ 7.5, 7.5 Hz), 7.26 (d, 4H, J ¼ 8.9 Hz), 7.30 (dd, 2H, J ¼ 7.8, 7.8 Hz), 7.37 (dd, 2H, J ¼ 8.1, 2.0 Hz), 7.43 (d, 2H, J ¼ 2.0 Hz), 7.75 (d, 2H, J ¼ 7.3 Hz), 7.77 (d, 2H, J ¼ 8.3 Hz), 7.89 (d, 2H, J ¼ 8.1 Hz).13C NMR (CDCl3): d 166.3, 166.2, 161.0, 157.4, 155.9, 150.7, 148.3, 141.0, 137.9, 134.5, 128.0, 127.9, 127.5, 127.2, 126.1, 125.8, 124.6, 123.9, 121.2, 119.8, 119.4, 118.1, 115.9, 113.9, 65.8. 8d: Yield 94%. IR (KBr, cm21): 1778, 1726, 1670, 1603, 1511, 1475, 1450, 1373, 1245, 1214, 1158, 1086, 871, 819, 717.1H NMR (CDCl3):d6.55 (d, 2H, J ¼ 1.8 Hz), 6.74 (d, 2H, J ¼ 7.5 Hz), 6.93 (d, 4H, J ¼ 8.8 Hz), 7.03 (dd, 2H, J ¼ 7.9, 2.2 Hz), 7.08 (dd, 2H, J ¼ 7.8, 7.8 Hz), 7.26 (d, 4H, J ¼ 8.8 Hz), 7.33 (dd, 2H, J ¼ 7.8, 7.8 Hz), 7.75 (d, 2H, J ¼ 7.8 Hz), 7.77 (d, 2H, J ¼ 7.9 Hz), 7.95 (d, 2H, J ¼ 8.0 Hz), 8.07 (s, 2H), 8.10 (d, 2H, J ¼ 8.0 Hz). 13C NMR (CDCl3):d166.1, 157.8, 155.6, 150.7, 148.3, 141.6, 141.0, 138.1, 135.7, 135.0, 132.1, 127.9, 127.6, 125.4, 124.5, 123.9, 121.3, 119.9, 117.9, 116.2, 65.8. 8e: Yield 95%. IR (KBr, cm21): 1776, 1724, 1606, 1603, 1501, 1476, 1446, 1372, 1242, 1204, 1168, 1081, 833, 747. 1_{H NMR (CDCl} 3):d6.55 (s, 2H), 6.74 (d, 2H, J ¼ 7.3 Hz), 6.88 (d, 2H, J ¼ 6.8 Hz), 7.02 (d, 2H, J ¼ 7.8 Hz), 7.08 (dd, 2H, J ¼ 7.8, 7.8 Hz), 7.23 – 7.39 (m, 6H), 7.65 – 7.85 (m, 10H). 13C NMR (CDCl3): d 166.6, 157.8, 155.5, 150.7, 148.3, 144.5, 141.0, 138.1, 132.7, 131.4, 128.0, 127.6, 125.5, 124.3, 124.0, 121.8, 121.3, 119.9, 117.6, 116.2, 65.8.

3. Results and discussion 3.1. Monomer synthesis

In order to introduce the spiro-skeletal units into the polyimide backbone, the novel spiro-diamine monomer,

2,20-bis(4-aminophenoxy)-9,90-spirobifluorene (6) was

syn-thesized. The precursor, 9,90-spirobifluorene (1) was

prepared by following the Clarkson and Gomberg method, which involves coupling of a Grignard reagent obtained

from 2-iodo-biphenyl with 9-fluorene [29], followed by

dehydrative ring closure of the resulting carbinol in acetic acid, which on acylation and oxidation, followed by alkaline

hydrolysis, afforded the 2,20-dihydroxy-9,90-spirobifluorene

(4)[28], as shown inScheme 1. Nucleophilic substitution of

4-fluoronitrobenzene with 4 in DMF/K2CO3 medium

furnished 2,20-bis(4-nitrophenoxy)-9,90-spirobifluorene (5)

in quantitative yields, which on catalytic reduction over 10% Pd – C afforded the desired spiro-diamine monomer 6. The structures of compounds 5 and 6 were confirmed by IR,

1_{H, and} 13_{C NMR spectroscopy, as well as by mass}

spectroscopy. The dinitro compound shows characteristic

absorptions at 1342 and 1588 cm21, associated with nitro

group stretching, whereas the diamine lacks these two absorption bands. The latter displays new absorptions at

3457, 3375 (N – H stretching) and 1613 cm21 (N – H

deformation). Fig. 1 shows the 1H NMR spectra of

compounds 5 and 6. Based on the reported 1H NMR data

of 2,20-disubstituted-9,90-spirobifluorene [25] and with

auxiliary 2D1H –1H correlation spectroscopy, the positions

of the chemical shifts for protons in compounds 5 and 6 are

readily assigned. In the13C NMR spectra, the central spiro

carbon (C-9) signal resonates at d 65.4 and 65.3,

respectively, indicative of the presence of a spiro skeleton in 5 and 6. The molecular structure of compound 5 in the solid state was also elucidated by X-ray crystallographic analysis. Single crystals of 5 were obtained from acetonitrile

solution by slow evaporation of the solvent.Fig. 2shows the

ORTEP plot of 5 accomplished by X-ray diffraction at 295 K. The spiro-molecule consists of two identical 4-nitrophenoxyfluorene moieties connected through a com-mon tetra coordinate carbon atom (the spiro center). In the spiro-segment, the arrangement of the connected bifluorene entities is nearly orthogonal (dihedral angle ¼ 88.68). This structure agrees with the proposed one.

Scheme 1. Reagents: (i) CH3COCl, AlCl3/CS2, (ii) m-chloroperoxybenzoic

acid/CHCl3; (iii) NaOH(aq )/MeOH; (iv) 4-fluoronitrobenzene,

3.2. Polymer synthesis

For the synthesis of poly(ether imide)s 8a – e, the one-step polymerization method was employed. The one-step method provides some advantages over the conventional two-step method. Polyimides in bulk are more easily produced; further, this method is useful for unreactive diamines and dianhydrides, which cannot form high molecular weight polyamic acids by the

two-step method [30]. However, the disadvantage of the

one-step method is that insoluble polyimides cannot form high molecular weight polymers because of premature precipitation. We have chosen the one-step solution method, envisaging that the resulting poly(ether

imide)s from the 2,20-bis(4-aminophenoxy)-9,90

-spirobi-fluorene (6) could be soluble in m-cresol. The spiro-diamine and a series of dianhydrides 7a – e were reacted in m-cresol in the presence of a catalytic amount of

isoquinoline (Scheme 2). Fortunately, no premature

precipitation was observed during the polymerization. At ambient temperature, after 30 min, a homogeneous and clear solution formed. The temperature was then raised to 70 – 80 8C, then slowly increased to 220 8C and maintained there for 8 h. Polymers were isolated in

quantitative yields by precipitating into methanol and drying under vacuum. In the IR spectra of the obtained polymers, the absence of amic acid absorptions (, 3350

(NH and OH) and 1650 cm21 (amide, CyO)) and the

presence of cyclic imide carbonyl absorptions (1779 –

1776 and 1726 – 1721 cm21) confirmed the complete

cyclodehydration of the corresponding amide intermedi-ate. In addition, DSC and TGA measurements did not show any transition corresponding to imidization, indicating that the resulting polyimides were fully imidized. The structure of the poly(ether imide)s was

characterized by 1H NMR. Fig. 3 shows the 1H NMR

spectra of polymers 8a – e. In addition to the distinct features associated with the spirobifluorene diamine component, resonances corresponding to the aromatic protons of the dianhydride component are clearly

present. 13C NMR spectra provides complementary

information. Resonances associated with the carbonyl carbons of the imide ring appear in the relatively

downfield region (d 166) [31]. The molecular weights

of the polymers were determined by GPC with DMF as the eluent, calibrated against PMMA standards. The

molecular weights and polydispersities (Mw/Mn) are

presented in Table 1.

3.3. Properties of the poly(ether imide)s

Transparent, flexible films of the poly(ether imide)s can be obtained by solution casting. The crystallinities of the polyimides 8a – e were evaluated by wide-angle X-ray diffraction experiments. All the polymers display amorphous diffraction patterns as a result of the

presence of the kinked 9,90-spirobifluorene structure.

The amorphous character of the polyimides is also reflected in their high solubility. The solubilities of poly(ether imide)s 8a – e were tested in a variety of organic solvents and the results are summarized in Fig. 1.1_{H NMR spectra in the aromatic region of compounds (a) 5 and (b) 6}

in DMSO-d6.

Fig. 2. ORTEP diagram of compound 5 determined by X-ray crystal-lography. All hydrogens are omitted for clarity.

Table 2. All the poly(ether imide)s exhibit good solubility in polar aprotic solvents, such as NMP, DMF, DMAc and pyridine, the phenolic solvent m-cresol, as well as chlorinated solvents like chloroform and methylene chloride. The poly(ether imide)s, except polyimide 8e, are also soluble in less polar THF solvent. The poor solubility of 8e in THF is possibly

due to the rigid nature of its dianhydride moiety. The highly soluble nature of these poly(ether imide)s may be attributed to the presence of linked spirobifluorene units, with flexible aryl ether linkages along the polymer backbone. The orthogonally arranged polymer branches would restrict the close packing of the polymer chains and thereby lessen the probability of interchain inter-actions, resulting in the high solubility of the poly(ether imide)s. It has been demonstrated that the incorporation of a cyclic cardo side group, such as fluorene, into the polymer backbone affords aromatic polyimides high

solubility, as well as good thermal stability [32 – 34].

For comparison, the reported solubility data of fluorene-based cardo poly(ether imide)s 9d and 9e are included in Table 2 [33]. Comparison of polymer solubilities

indicates that the 9,90-spirobifluorene-containing

poly(-ether imide)s, 8d and 8e, exhibit better solubility than their cardo analogues 9d and 9e. This observation reveals that the placement of the orthogonal arrange-ment of each bifluorene moiety in the polymer chain plays an important role in enhancing the solubilities of Fig. 3.1_{H NMR spectra in CDCl}

3of poly(ether imide)s (a) 8a, (b) 8b, (c)

8c, (d) 8d, and (e) 8e. p indicates a signal arising from CHCl3.

Table 1

Molecular weights, inherent viscosities and thermal properties of poly(ether imide)s 8a – e Polymer Mwa ( £ 104₎ Mw/Mn hinhb (dl/g) DSC, Tgc TGAd Yc (%)e T5% T10% 8a 3.2 2.2 0.39 278 564 592 64 8b 9.4 2.0 0.75 243 581 590 63 8c 4.0 2.4 0.41 279 608 625 69 8d 3.5 1.9 0.41 281 581 607 64 8e 6.0 1.9 0.55 293 588 616 69 a

Molecular weight (g/mol) was determined by GPC in DMF based on PMMA standards.

b

Measured at 0.5 g/dl in DMAc at 30 8C.

c

Tg(8C) was determined by DSC at a heating rate of 20 8C min21under

nitrogen.

d

Temperatures (8C) at which 5 and 10% weight losses were determined at a heating rate of 20 8C min21_{under nitrogen.}

e _{Char yield at 900 8C in nitrogen.}

Fig. 4. DSC thermograms of poly(ether imide)s (a) 8a, (b) 8b, (c) 8c, (d) 8d, and (e) 8e.

Fig. 5. TGA curves for poly(ether imide)s (a) 8a, (b) 8b, (c) 8c, (d) 8d, and (e) 8e at a heating rate of 20 8C min21_{in N}

the poly(ether imide)s 8a – e:

The thermal properties of the poly(ether imide)s were investigated by DSC and TGA, with the results tabulated in

Table 1. The incorporation of rigid spirobifluorene units in the polymer backbone results in poly(ether imide)s with

high glass transition temperatures (Tg).Fig. 4displays DSC

thermograms for polymers 8a – e The Tgs of polyimides 8a –

e were in the range of 243 – 293 8C and varied with the

structure of the dianhydride component. The comparatively

lower Tg value of polymer 8b can be attributed to the

presence of a larger number of flexible ether linkages in its polymer chain. Polyimide 8e, containing a stiff biphenyl

group, exhibits a higher Tgvalue. The thermal stabilities of

polymers 8a – e were evaluated by TGA. Fig. 5 shows

typical TGA curves for these poly(ether imide)s. All the polyimides showed similar patterns of decomposition, without any significant weight loss up to 500 8C in nitrogen; the residual weights at 800 8C were all above 60%. Temperatures corresponding with 5 and 10% weight loss in nitrogen were in the range of 564 – 608 and 590 – 625 8C, respectively. The high thermal stabilities of these poly-imides reflect the rigid nature of spiro-segment unit in the polymer main chain.

4. Conclusions

In summary, a new spiro-fused diamine monomer has been synthesized, whose polymerization with various anhydrides leads to highly soluble and thermally stable

poly(ether imide)s. The excellent solubility nature of these poly(ether imide)s can be attributed to the presence of spiro-fused orthogonal bifluorene segments along the polymer chain. High thermal stabilities are due to the rigid spirobifluorene units. Further studies concerning the incorporation of a spirobifluorene unit into the polymer backbone, which may produce novel, soluble and proces-sable high-performance polymeric materials, are in progress.

Acknowledgements

We thank the National Science Council of the Republic of China for financial support.

References

[1] Wilson D, Stenzenberger HD, Hergenrother PM, editors. Polyimides. New York: Blackie; 1990.

[2] Mittal KL, editor. Polyimides: synthesis, characterization, and applications, vols. 1/2. New York: Plenum Press; 1984.

[3] de Abajo J, de la Campa JG. In: Kricheldorf HR, editor. Advances in polymer science. Berlin: Springer; 1999. p. 23 – 59 and references therein.

[4] Lin SH, Li F, Cheng SZD, Harris FW. Macromolecules 1998;31: 2080.

[5] Liaw DJ, Liaw BY, Li LJ, Sillion B, Mercier R, Thiria R, Sekiguchi H. Chem Mater 1998;10:734.

[6] Yang CP, Hsiao SH, Yang HW. Macromol Chem Phys 2000;201:409. [7] Liaw DJ, Liaw BY, Chung CY. Macromol Chem Phys 2000;201:

1887.

[8] Liou GS, Wang JSB, Tseng ST, Tsiang RCC. J Polym Sci, Part A: Polym Chem 1999;37:1673.

[9] Liaw DJ, Liaw BY, Lai SH. Macromol Chem Phys 2001;202:807. [10] Eastmond GC, Paprotny J, Irwin RS. Macromolecules 1996;29:1382. [11] Wang CS, Leu TS. Polymer 2000;41:3581.

[12] Mi Q, Gao L, Ding M. Polymer 1997;38:3663.

[13] Liou GS, Maruyama M, Kakimoto MA, Imai Y. J Polym Sci, Part A: Polym Chem 1998;36:2021.

[14] Matsumoto T, Kurosaki T. Macromolecules 1997;30:993. [15] Zheng HB, Wang ZY. Macromolecules 2000;33:4310. Table 2

Solubility of aromatic poly(ether imide)s Polymer Solventa

CH2Cl2 CHCl3 Pyridine THF DMF DMAc NMP Acetone m-Cresol

8a þ þ þ þ þ þ þ þ þ þ þ þ þ þ 2 2 þ þ 8b þ þ þ þ þ þ þ þ þ þ þ þ þ þ 2 2 þ þ 8c þ þ þ þ þ þ þ þ þ þ þ þ þ þ 2 2 þ þ 8d þ þ þ þ þ þ þ 2 þ þ þ þ þ þ 2 2 þ þ 8e þ þ þ þ þ þ 2 þ þ þ þ þ þ þ 2 2 þ þ 9db _{2 þ þ þ 2 þ þ þ 2 þ} 9eb þ þ þ 2 2 þ þ þ 2 2

Solubility: (þ þ ) soluble at room temperature; (þ 2 ) soluble on heating; (2 þ ) partially soluble or swollen; (2 2 ) insoluble.

a _{THF, tetrahydrofuran; DMF, N,N-dimethylformamide; DMAc, N,N-dimethylacetamide; NMP, N-methyl-2-pyrrolidinone.} b _{Data fromRef. [33].}

[16] Chung IS, Kim SY. Macromolecules 2000;33:3190.

[17] Salbeck J, Yu N, Bauer J, Weisso¨rtel F, Bestgen H. Synth Met 1997; 91:209.

[18] Salbeck J, Bauer J, Weisso¨rtel F. Macromol Symp 1997;125:121. [19] Johansson N, dos Santos DA, Guo S, Cornil J, Fahlman M, Salbeck J,

Schenk H, Arwin H, Bre´das JL, Salenek WR. J Chem Phys 1997;107: 2542.

[20] Kim YH, Shin DC, Kim SH, Ko CH, Yu HS, Chae YS, Kwon SK. Adv Mater 2001;13:1690.

[21] Katsis D, Geng YH, Ou JJ, Culligan SW, Trajkovska A, Chen SH, Rothberg LJ. Chem Mater 2002;14:1332.

[22] Yu WL, Pei J, Huang W, Heeger AJ. Adv Mater 2000;12:828. [23] Marsitzky D, Murray J, Scott JC, Carter KR. Chem Mater 2001;13:

4285.

[24] Chiang CL, Shu CF. Chem Mater 2002;14:682.

[25] Reddy DS, Shu CF, Wu FI. J Polym Sci, Part A: Polym Chem 2002; 40:262.

[26] Weisburger JH, Weisburger EK, Ray FE. J Am Chem Soc 1950;72: 4250.

[27] Jeffry RW, Schumm S, Pearson DL, Tour JM. J Org Chem 1996;61: 6906.

[28] Prelog V, Bedekovic D. Helv Chim Acta 1979;62:2285. [29] Clarkson RG, Gomberg M. J Am Chem Soc 1930;52:2881. [30] Harris FW. In: Wilson D, Stenzenberger HD, Hergenrother PM,

editors. Polyimides. New York: Blackie; 1990. p. 1 – 37.

[31] White DM, Takekoshi T, Williams FJ, Relles HM, Donahue PE, Klopfer HJ, Loucks GR, Manello JS, Matthews RO, Schluenz RW. J Polym Sci, Polym Chem Ed 1981;19:1635.

[32] Korshak VV, Vinogradova SV, Vygodskii YS. J Macromol Sci, Rev Macromol Chem, Part C 1974;11:45.

[33] Yang CP, Lin JH. J Polym Sci, Part A: Polym Chem 1993;31:2153. [34] Hsiao SH, Li CT. J Polym Sci, Part A: Polym Chem 1999;37:1403.