Novel Polybenzoxazinones with Tricyclic Fused-Rings

PREMA SUBRAMANIAM and MAHALINGAM SRINIVASAN, * Department of Chemistry, Indian Institute of Technology, Madras-600 036,

India

Synopsis

A series of polybenzoxazinones containing phenoxathiin and phenoxaphosphine units were prepared from tricyclic diacid chlorides and 4,4diaminobiphenyl-3,3'dicarboxylic acid and 4,4'diamino-3,3'diphenylmethane dicarboxylic acid. The low temperature solution polymer- ization technique afforded polyamic acid which subsequently underwent cyclization along the polymer chain in a solvent mixture of refluxing N,N'dimethylacetarnide, acetic anhydride, and pyridine to give polybenzoxazinones in moderate yields. The polymers thus obtained had inherent viscosities in the range of 0.15-0.23 dLlg, were sparingly soluble in N-methyl-2- pyrrolidone, and were found to be thermally more stable than the corresponding open-chain polymer with diphenylether linkage.

INTRODUCTION Wholly aromatic polybenzoxazinones (PBOs) have good thermal stability

with poor solubility in organic With a view to prepare PBOs with improved solubility and thermal stability, a series of PBOs from tri- cyclic diacid chlorides were synthesized and the properties of the resulting polymers evaluated and compared with the polymer derived from an open- chain diacid chloride [eq. (113

RESULTS AND DISCUSSION

Monomers The bis(aminoacid)s-4,4'-diamino-3,3'-biphenyldi~arboxylic acid [mp

300'C (dec.)] and 4,4diamino-3,3'-diphenylmethane dicarboxylic acid (mp 262"C)-were prepared according to literature procedures. s,6 2,8-Dichloro- formyl-10-phenylphenoxaphosphine-10-oxide (mp 217V was prepared by the procedure reported by Sato' and 2,8-dichloroformylphenoxathiin (mp 154°C) and 2,8-dichloroformylphenoxathiin-10,lO-dioxide (mp 160°C) were prepared by Ueda's procedure.8 All these monomers were also characterized by elemental analysis, IR, and IH-NMR spectroscopy.

Model Reaction As a guide to identify the structure of PBO's a model benzoxazinone (MBO)

was prepared from 4,4'-diamino-3,3'-diphenylmethane dicarboxylic acid and benzoyl chloride. The reaction was carried out in N,N'-dimethylacetamide

'To whom correspondence should be addressed.

Journal of Polymer Science: Part A: Polymer Chemistry, Vol. 24, 2553-2563 (1986) @ 1986 John Wiley & Sons, Inc. CCC 0360-3676/86/102553-11$4.00

2554 SUBRAMANIAM AND SRINIVASAN

+ ClOC- (Ar)- COCl - 1 HOOC x a COOH 1

+ (1) COHN NHCO- Ar

L -'n

X = Nil, CH2 Ar =

(DMAC) at 25°C in the presence of pyridine as the acid acceptor to give the model diamic acid (MDA) quantitatively, which subsequently underwent cyclization readily in a solvent mixture of refluxing DMAC, acetic anhy- dride, and pyridine to give MBO [eq. (211

0 0

MBO

TRICYCLIC RINGS 2555

Dehydration was followed by the disappearance of the broad IR absorption band at 3500-3100 cm-1 (NH, OH) and the amide carbonyl absorption at 1660 cm-'. MBO displayed characteristic absorptions at 1740 cm (lactone carbonyl) and 1250 cm-l (C-0-C) (Fig.1). Figure 2 provides the 'H-NMR spectra of MDA and MBO (see Experimental). The elemental analysis of MBO was in good agreement with the calculated value (see Experimental).

Preparation of Polyamic Acids (PAA's) and Polybenzoxazinones: The tricyclic diacid chlorides were polymerized with the bis(aminoacid)s

in DMAC at 25°C using pyridine as the acid acceptor. Lithium chloride (5 wt %) was added to prevent precipitation of the polymer. After completion of the polymerization reaction, the PAA's were isolated by pouring the polymerization solution into excess of water. Table I summarizes the results of PAA synthesis. The PAA's could be isolated only in moderate yields as most of the low molecular weight fractions got washed out during acetone washings. The inherent viscosities of the polymers were in the range 0.15 to 0.22 dL/g in DMAC at 3WC. The qinh value for the openchain PAA-VII (qjnh = 0.13 dL/g) was found to be lower than other PAA's. This is because, the rigid and bulky heterocyclic group offers more resistance to hydrody- namic flow. Figure 1 provides a comparison of the IR spectra of PAA-I and MDA. As can be seen, the absorptions due to the -NH and the -OH group a t 3500-3100 cm-' and at 1660 cm-1 due to the amide carbonyl absorption in PAA-I is spectroscopically not distinguishable from the ab- sorptions due to MDA. Figure 2 provides a comparison of the IH-NMR spectra of PAA-I and MDA (see Experimental).

PBO-I

/

I I I I I

LO00 3000 2000 1600 1200 BOO

Wavenumber (cm-')

Fig. 1. IR (KBr) spectrum of MDA, PAA-I, MBO and PBO-I.

2556 SUBRAMANIAM AND SRINIVASAN

n

Solvent TFA

1 1 I ' I ~ I I I I I

10 5 0 ppm (6)

lH NMR spectrum of MDA, PAA-I, MBO and PBO-I. Fig. 2.

Cyclization of the PAA's was carried out by heating in a solvent mixture of DMAC, acetic anhydride and pyridine at 150°C for 6 h [eq. (l)]. Table I1 summarizes the results of PBO synthesis. The PBO's could be isolated in good yields. The nitrogen analysis of PBO's agreed reasonably well with their calculated values. Their inherent viscosities were in the range of 0.15- 0.21 dL/g in conc. H,SO, at 30°C. The density values of PBO's indicated that PBO-IV is somewhat more denser than rest of the PBO's. All the PBO's showed absorption due to the lactone carbonyl either at 1750 cm or at 1760 cm-' depending on the structure of the PBO. Figure 1 provides a comparison of the IR spectra of PBO-I and MBO and Figure 2 provides a comparison of their 1H-NMR spectra. To elucidate the effect of the intro- duction of the tricyclic units on the resulting polymer properties, open- chain PBO was prepared from 4,4'-diphenylether dicarboxylic acid chloride and 4,4'-diamino-3,3'-biphenyl dicarboxylic acid.

Properties of Polybenzoxazinones: Crystallinity

The x-ray diffraction diagrams of the polymers are shown in Figure 3. All PBO's exhibited intense amorphous halo patterns. This is to be expected as the tricyclic molecules are known to have folded structures about the axis that combines the hetero atoms thereby inhibiting closer packing. 9~10

TABL

E I

Res

ults

of t

he P

olya

mic

Aci

d Sy

nthe

sis"

ClO

C - (A

x9 - C

OCl

IR b

ands

(cm

-')

qinh

b \

Yie

ld

,c=

o N

H, O

H

Hooc

m

HP

xacoo

H

NH

, (%

I (d

L/g

)

PAA

-I

PAA

-I1

PAA

-I11

PAA

-IV

PAA

-v

PAA

-VI

mom

PA

A-V

I

Nil

CHZ

Nil

CH

,

Nil

CHZ

65

0.22

3100 - 3500

1660

60

0.17

3100 - 3500

1660

66

62

70

73

0.16

0.15

0.18

0.17

3100 - 3500

3100-3500

3100- 3500

3100- 3500

c3

-4 0 rl

1670

0 $

1670

1660

2 1670

Nil

70

0.16

3100-3500

1670

Rea

ctio

n tim

e, 6

hour

s; m

ole

ratio

of t

he r

eact

ants

: 1/1

in D

MA

c. M

easu

red

at a

conc

entr

atio

n of

0.2

g/lOO mL in D

MA

c at

30'C.

TAB

LE I1

R

esul

ts o

f Po

lybe

nzox

azin

one

Synt

hesi

s ~~

Ele

men

tal a

naly

sis

% N

So

lubi

lityb

(%)

Yie

ld

.))‘n

h D

ensi

ty

IR b

ands

(cm

Po

lym

er

Cal

cd.

Foun

d

PBO

-I

PBO-

111

PBO

-I1

PBO

-IV

PB

O-V

PB

O-V

I PB

O-V

II

63

55

60

58

68

65

67

4.84

4.73

5.74

5.57

5.39

5.30

6.14

4.63

4.50

5.63

5.32

5.12

5.11

5.93

(dL/

g)

0.21

0.16

0.15

0.15

0.17

0.17

0.13

(g/c

m3)

0.951

1.056

1.090

1.120

0.896

0.824

0.956

NM

P C

onc.

H,S

O,

11

100

10

100

10

100

9 100

14

100

16

100

2 100

[lac

tone

C=O

]

1750

1755

1760

1760

1760

1750

1760

‘Mea

sure

d at

a c

once

ntra

tion

of 0.2g/100 m

l in

con

c. H

,SO

, at

30°C.

A w

eigh

ed a

mou

nt o

f PB

O w

as t

aken

and

10

mL

of h

ot N

MP

was

add

ed a

nd w

arm

ed a

t 100°C

for 5

min

. The

sol

utio

n w

as c

oole

d to

room

tem

pera

ture

, an

d th

e w

eigh

t of s

olut

e de

term

ined

.

TRICYCLIC RINGS 2559

PBO-6 b 1 1 I I I I

28

Fig. 3. X-ray diffraction diagrams of the PBO’s.

Solubility

Quantitative solubility tests of amorphous PBO’s were made on powdery samples to determine the effects of heterocyclic tricyclic units on the sol- ubility behavior of aromatic PBO’s. All of the PBO’s were soluble in strong acids such as concentrated sulphuric acid and trifluoroacetic acid (TFA). These PBO’s showed varying degree of solubility in polar organic solvent such as NMP (Table 11). PBO-V and PBO-VI showed somewhat better sol- ubility than other PBO’s. As listed in Table 11, the densities of PBO’s in- creased in the reverse order of solubility. This fact explains the better solubility of PBO-V and -VI over other PBO’s. One explanation for the improved solubility of PBO I-VI over PBO-VII is that the highly folded structures in the main chain interfere with the close packing of the polymer molecules and make the solvation easier. In addition to the folded structure, the two oxygen atoms in the phenoxathiin-10,lOdioxide moiety lies out of the conjugated plane, thereby inhibiting close packing. Hence the solubility of PBO-V and PBO-VI over other PBO’s is better.

. .. --- . . ~ . ~~. .... ... ..

2560 SUBRAMANIAM AND SRINIVASAN

Thermal Properties of the Polybenzoxazinones The thermal properties of PBO's were evaluated by thermogravimetric

analysis (TGA) and differential thermal analysis (DTA) in static air. Typical TGA and DTA curves are illustrated in Figure 4. TGA curve of PBO-VII derived from open-chain 4,4'-diphenylether dicarboxylic acid chloride has been included for comparison. Table I11 shows the thermal behavior data of the PBO's. These data indicate that the polymers hardly degrade until a temperature of about 325°C is reached. However, PBO's reported by Yoda et a1.l have much better thermal stability than those reported here. In- complete conversion of amic acid to benzoxazinone could probably be the reason. The rate of decomposition of PBO-V and PBO-VI is faster than PBO I-IV. All of these PBO's were more stable than the equivalent openchain PBO-VII, which is to be expected from the fused-ring structures. Glasstran- sition temperatures (T,) of PBO's derived from 4,4-diaminobiphenyl-3,3'- dicarboxylic acid were found from their DTA curves. PBO's derived from 4,4'-diaminobiphenyl-3,3'-dicarboxylic acid had no discernible phase tran- sition below the temperatures a t which degradation occurred.

EXPERIMENTAL

Measurements Infrared (IR) spectra were recorded using a Perkin-Elmer-257 spectro-

photometer in KBr. IH-NMR spectra were recorded with Varian EM 390 spectrophotometer using TMS as internal standard. The inherent viscosities

I I 1 I 300 400 500 600

Temperature ( 'C)

Fig. 4. TGA and DTA curves for the PBOs in air. (Heating rate 10"C/min).

TABL

E I1

1 Th

erm

al B

ehav

ior

Dat

a of

PB

O's

in A

ir

Tem

pera

ture

at

vari

ous

% w

eigh

t lo

sses

" ("

C)

pe

w

F#

r3

Po

lym

er

10

20

30

40

50

80

('C)

PBO

-I 41

0 47

6 52

0 55

3 56

0 63

5 53

0 -

PBO

-I1

339

466

503

539

553

619

555

6.38

2 PB

O-11

1 36

5 44

7 51

5 55

0 56

6 61

0 56

6 .-

E: PB

O-V

41

9 46

6 50

3 51

2 53

0 55

1 52

1 -

z PB

O-V

I 39

9 50

3 51

2 51

8 51

8 53

5 53

9 43

9 z $2 d

PBO

-IV

37

5 47

5 51

2 53

0 53

9 56

4 54

8 43

6

PBO

-VII

I 35

0 40

9 41

9 43

8 44

7 48

4 41

9 -

a R

ate

of h

eatin

g 10

"C/m

in.

Tem

pera

ture

of m

axim

um e

xoth

erm

al p

eak

obse

rved

in

DTA

(he

atin

g ra

te l

WC

/min

). Fr

om D

TA.

2562 SUBRAMANIAM AND SRINIVASAN

were measured using a Ubbelohyde suspended level viscometer. The x-ray diffractograms were taken using Ni-filtered CuK, radiation on a Philips PW 1140 instrument. The TGA and DTA measurements were done in air using a Stanton Red Croft thermobalance at a heating rate of 10"C/min. The densities were determined with a small pycnometer in hexane at 30°C. The sample size was 30-50 mg.

Materials

4,4'-Diamino-3,3'-biphenyldicarboxylic acid (yield 90%, mp 300°C) and 4,4'- diaminodiphenylmethane-3,3'-dicarboxylic acid (yield 70%, mp 262°C) were prepared according to literature procedures. 5,6 2,8-Dichloroformyl-lO-phenyl- phenoxaphosphine-10-oxide (mp 217"C, yield 55%), 2,8-dichloroformylphen- oxathiin (yield 70%, mp 1 5 4 0 , and 2,8-dichloroformylphenoxathiin-l0, 10-dioxide (yield 76%, mp 160°C) were also prepared according to literature procedure^.^^^ DMAC was refluxed over Pz05 and distilled under reduced pressure. Pyridine, thionyl chloride, and benzoyl chloride were purified by the usual methods. The other reagents were of commercial origin and used without purification.

Preparation of Model Diamic Acid (MDA)

To a stirred solution of 4,4'-diamino-3,3'-diphenylmethanedicarboxylic acid (1.4 g, 5 mmol) and pyridine (2 drops) in DMAC (5 mL) at 25°C was added benzoyl chloride (1.4g, 10 mmole) in one portion. A colorless solid precipitated instantly. The reaction mixture was stirred at room temper- ature for 30 min, then poured into excess of water, filtered, washed thor- oughly with methanol, and dried. Yield 93%, mp 265°C.

IR(KBr: 3100-3500 cm-' (NH, OH), 1660 cm-' (C=O). 'H-NMR (TFA) : 6 3.8(s, 2H, -CH,-), 6 7.1-7.9 (m,16H, ArH). -

ANAL. Calcd for CBH2,N,O,: N, 5.66%.=und: N, 5.43%.

Preparation of Model Benzoxazinone (MBO)

MDA was heated at 150°C for 2 h in a solvent mixture of DMAC (2 mL), acetic anhydride (4 mL), and pyridine (2 mL). The hot solution was cooled and the solid was filtered, washed with methanol, and dried.Yield 90%, mp 290'C.

IR(KBr) : 1740 cm-1 (lactone C=O>, 1250 cm-l (-C-0-C-). lH-NMR(TFA): 6 4.3 (s, 2H, -CH2), 6 7.2-8.1 (m, 16H, ArH). -

ANAL. Calcd for C,H,,N,O,: N, 6.12%yound : N, 5.96%.

Preparation of Polyamic Acid PAA-I

To a stirred solution of 4,4'-diamino-3,3'-diphenylmethane dicarboxylic acid 0.14 g (0.5 mmol) and pyridine (2 drops) in DMAC (4 mL) that contained 5 wt % of lithium chloride a t 25'C was added 2,8dichloroformyl-lO-phen- ylphenoxaphosphine-10-oxide 0.21g (0.5 mmol) in one portion. The mixture was stirred at room temperature for 6 h and then poured into a large excess of water. The precipitated PAA was filtered, washed thoroughly with hot acetone, and dried to give a green powder. Yield 65%.

TRICYCLIC RINGS 2563

IR(KBr): 3100-3500 cm-' (NH, OH), 1660 cm-l (C=O). 'H-NMR(TFA): 6 4.0 (s, 2H, -CH,-), 6 6.9-8.2 (m, 17H, ArH). -

ANAL. Calcd for C36H23N208P N, 4.294rFound N, 4.03%.

Preparation of Polybenzoxazinone (PBO-I)

The polyamic acid PAA-I was heated in a solvent mixture of DMAC (4 mL), acetic anhydride (8 mL), and pyridine (4 mL) at 150°C for 6 h. The solution was cooled and the solid was filtered, washed with hot acetone, and dried. Yield 63%.

IR(KBr): 1750 cm-1 (lactone C=O), 1250 cm-' (-C-O-C-). lH-NMR(TFA): 6 4.0 (s, 2H, -CH,-), 6 7.1-8.0 (m, 17H, ArH).

ANAL. Calcd for CS5H19N206P N, 4.844TFound: N, 4.63%.

The authors are indebted to the Department of Science and Technology and the department of Atomic Energy for their financial assistance.

References 1. N. Yoda, EncyZ. Polym. Sci. Technol., 10, 682 (1969). 2. M. Kurihara and N. Yoda, J. Macromol. Sci. Chem., 1069 (1967). 3. R. Takatsuka, T. Unishi, and I. Honda, J. Polym. Sci. Polym. Chem. Ed., 15,1985 (1977). 4. R. Takatauka, K. Uno, F. Toda, and Y. Iwakura, J. Polym. Sci. Polym. Chem. Ed., 15.,

5. N. Yoda, M. Kurihara, M. Ideda, S. Tohyama, and R. Nakanishi, J. Polym. Sci. B, 4,551

6. E. I. Khofbaver and T. A. Leonova, Zh. Prikl. Chem., 44, 699 (1971); Chem. Abstr., 74,

7. M. Sat0 and M. Yokayama, Eur. Polym. J., 15, 733 (1979). 8. M. Ueda, T. Aizawa and Y. Imai, J. Polym. Sci. Polym. Chem. Ed., 15, 2739 (1977). 9. J. P. Malrieu, J. Chim. Phys., 62 , 485 (1964).

1985 (1977).

t1966).

125086s (1971).

10. R. J. Wratten and M. A. Ali, Mol. Phys., 13, 233 (1967).

Received October 26, 1984 Accepted December 9, 1985