Preparation and Properties of Some Cardopolyamides Containing

Phenoxathiin-l0,lO-dioxide and Phenoxaphosphine Units

T. ASHOK REDDY and M. SRINIVASAN, Department of Chemistry, Indian Institute of Technology, Madras-600 036, India

Synopsis

Several new cardopolyamides containing phenoxathiin-10,lO-dioxide and phenoxaphosphine units were prepared by condensing 3,3-bis(4-aminophenyl)-phthalide (PDA), 9,9-bis(4- aminopheny1)fluorene (FDA), and 9,9-bis(4-aminophenyl)-lO-anthrone (ADA) with 2,8-dichloro- formylphenoxathiin-l0,lO-dioxide (PDC) and 2,8-dichloroformyl-l0-phenylphenoxaphosphine-10- oxide (PPDC) in DMAc. A low temperature solution polycondensation technique was employed throughout. The cardopolyamides were obtained in 80-92% yield and showed inherent viscosities in the range 0.41-0.6 dL/g. All the polymers were characterized by IR spectra, density, solubility, crystallinity, and thermal analysis.

INTRODUCTION

Cardopolymers generally hhve better thermal stability and mechanical strength.'.2 The presence of various types of heterochain and carbochain units in the cardopolymers give them specific and useful properties such as a combination of enhanced heat resistance as well as solubility. In most of the cardopolymers the connecting groups are less thermally stable than the rings, with the nature of the connecting groups determining the overall thermal stability. In the present work, with a view to improving the thermal stability without any concommitant loss of solubility, the conventional open-chain groups have been replaced with double-strand heterocyclic systems such as phenoxathiin-10,lO-dioxide and phenoxaphosphine units. In this paper the preparation and properties of six new cardopolyamides containing phen- oxathiin-10,lO-dioxide and phenoxaphosphine units (Scheme 1) are reported.

EXPERIMENTAL

Infrared spectra were obtained on a Perkin-Elmer 781 infrared spectropho- tometer, and x-ray diffractograms were taken on a Philips PW 1050 instru- ment using Ni-filtered CuK o( radiation. Thermogravimetric analysis and differential .thermal analysis were performed on a Stanton-Redcroft thermo- balance in static air. Densities were determined with a small Pyknometer in hexane as the nonsolvent a t 30°C. The intrinsic viscosities were measured using an Ubbelhyde suspended level viscometer.

Journal of Polymer Science: Part A: Polymer Chemistry, Vol. 25, 2327-2334 (1987) 0 1987 John Wiley & Sons, Inc. CCC 0360-3676/87/092327-08$04.00

2328 REDDY AND SRINIVASAN

-?- P ( P D C ) , -:- fl (ppDc) x =

0 Ph

Scheme 1.

Materials

N,N '-Dimethyl acetamide (DMAc) was purified by vacuum distillation. Phenoxathiin was obtained from diphenyl ether and sulfur. 4,4'-Ditolyl ether was prepared from p-bromotoluene and p-cresol. Dichlorophenylphosphine was obtained by the action of phosphorus trichloride on benzene. Aniline was distilled before use. Commercial phthalic anhydride was sublimed before conversion to phthaloyl chloride, whereas fluorenone (BDH) and anthro- quinone (BDH) were recrystallized before use.

Monomers

3,3- Bis(4- aminophenyophthali.de (PDA)

PDA was prepared in 60% yield from phthaloyl chloride and N, N'-di- phenyl urea in the presence of anhydrous aluminium chloride in nitrobenzene as solvent; mp 205°C (Lit. 202-205°C).3

9,9- Bis(4-amimphenyo&orene (FDA)

This cardodiamine was prepared from fluorenone, aniline hydrochloride, and aniline in 70% yield; mp 232°C (Lit. 231-233"C).4

9,9- Bis(4-aminophenyl)anthrone (ADA)

ADA was obtained from anthroquinone by a similar method used for FDA in 62% yield; mp 301°C (Lit. 302-305"C).4

CARDOPOLYAMIDES 2329

2,8-Dichloroformylphmxathiin-1O,lO-dioxide (PDC)

Phenoxathiin after diacetylation with acetyl chloride and aluminium chlo- ride was oxidized to give 2,8-phenoxathiin dicarboxylic acid-10,lO '-dioxide with sodium hypochlorite a t 85°C. The diacid on treatment with thionyl chloride yielded PDC (65%); mp 160°C (Lit. 159-161"C).5 IR(KBr): 1750 cm-l (>CO).

2,8-Dichloroformyl-lO-phenylphnaxaphosphine-lO-oxide (PPDC)

2,8-Dimethyl-lO-phenylphenoxaphosphine obtained from 4,4'-ditolyl ether and phenyl dichlorophosphine under Friedel-Crafts conditions was oxidized with alkaline KMnO., to give 2,8-dicarboxy-l0-phenylphenoxaphosphine-10- oxide, which on treatment with thionyl chloride gave PPDC (55%), mp 217°C (Lit. 219-221°C).6 IR (KBr): 1740 cm-' (> CO).

General Polymerization Procedure

The cardodiamine (0.002 mol) was dissolved in DMAc (10 mL) and cooled to 0°C. To this the diacid chloride (0.002 mol) dissolved in DMAc (10 mL) was added under nitrogen with constant stirring. After 3 h at 0-10°C it was allowed to warm slowly to room temperature, and the stirring was continued for an additional 4 h. The reaction mixture was then poured into water, and the precipitated polymer was filtered, washed with water and hot methanol, and dried.

RESULTS AND DISCUSSION

A series of cardopolyamides containing phenoxathiin-10,lO-dioxide and phe- noxaphosphine double-strand units was prepared by a low-temperature solu- tion polycondensation method using DMAc as a solvent a t 0-10°C in 80-92% yield (Scheme 1). The yields of polymers and their properties such as inherent viscosity and density are summarized in Table I. Inherent viscosities mea- sured at a concentration of 0.1 g/dL in DMF at 30°C ranged from 0.41 to 0.6 dL/g. The polyamides were characterized by IR (KBr) spectra (Fig. 1). The

TABLE I Preparation of Cardopolyamides* and Their Properties

C ~ d o p o l y - Cardo- Diacid Yield qinh' Density' arnide diamine chloride (W (dL/g) (pm/cm3)

I PDA PDC 90 0.60 1.157 I1 FDA PDC 85 0.46 1.671 I11 ADA PDC 92 0.50 1.289 IV PDA PPDC 80 0.55 1.14 V FDA PPDC 86 0.41 1.32 VI ADA PPDC 86 0.43 1.4

"Mole ratio 1 : 1 in DMAc. bMeasured at a concentration of 0.1 g/100 mL in DMF at 30°C. 'Determined pyknometrically in hexane at 30°C.

2330 REDDY AND SRINIVASAN

CARDOPOLYAMIDES 2331

TABLE I1 Solubility of Cardopolyamides

Cardo- Ace- Conc. poiyarnide DMF DMAc DMSO NMP CDCl, tone H,SO, TFA"

+ + I + + + + + t I1 + + + + + + I11 + + + +

IV + + + + - + + + + V + + + +

VI + + + + + +

- -

- -

- -

~

- -

~ -

Note: +, freely soluble; - , insoluble w/w. a Trifluoroacetic acid.

IR spectra of these polyamides showed absorption bands near 3300,1660, and 1265 cm-' for >NH, amide carbonyl, and ether linkage, respectively. In addition to those absorptions, polyamides I and IV showed absorption bands at 1760 cm-', which corresponded to the phthaloyl carbonyl bending frequency. The polyamides 1-111 had absorption bands owing to (-SO,-) a t 1175 cm-' and 1330 cm-', and polyamides IV-VI had absorption bands owing to (P=O) and (P-Ph) at 1180 cm-' and 1380 cm-', respectively.

Solubility

The solubility of these polymers in excess solvent was tried, and the results are summarized in Table 11. All of these polymers were soluble at room temperature in concentrated sulfuric acid, trifluoroacetic acid, and dipolar aprotic solvents such as DMF, DMAc, DMSO, and NMP, whereas they were insoluble in common organic solvents such as acetone and chloroform. In contrast, the analogous non~ardopolyamides~.~ derived from PDC and PPDC, p-phenylene diamine, and 4,4'-diaminodiphenyl ether were either insoluble or partially soluble in amide solvents such as DMF and DMAc. Such a difference in solubility is probably due to the greater rigidity of these cardopolymers compared with the analogous noncardopolymers and the presence of highly polar groups capable of intermolecular association. I t was found that the polymers (I and IV) containing phthalide cardogroups have higher solubility when compared with the polymers (11,111, V, and VI) containing fluorene and anthrone cardogroups. The higher solubility of polymers with phthalide groups is probably due to the greater polarity and symmetry of the phthalide group. The somewhat lower solubility of the polymers with fluorene and anthrone groups is probably due to their greater symmetry, which at times leads to the crystallization or partial crystallization of such polymers. All these polymers are capable of forming 25-30% solutions in amide solvents. Efforts to obtain films from a good solution were not successful.

Crystallinity

The x-ray diffractogrm of the polyamides I-VI are shown in Figure 2. The polymides 1-111 containing phenoxathiin-10,10-dioxide units were found to be partially crystalline; this can be attributed to the rigid orientation of the

2332 REDDY AND SRINIVASAN

10 20 30 40 50 60

Fig. 2. X-ray diffraction diagrams of cardopolyamides. ze

polymer chains. Among the polymers containing phenoxaphosphine units, polyamide IV showed an amorphous pattern, whereas polyamide V was found to be partially crystalline, and polyamide VI was found to be crystalline. The crystalline pattern in polyamides V and VI might be due to the symmetry of the fluorene and anthrone cardogroups.

Thermal Stability

The typical TGA and DTA curves of the cardopolyamides in static air are shown in Figure 3, and the thermal data is summarized in Table 111. The

CARDOPOLYAMIDES 2333

100

90

80

- 3 70 - c 3 0

t 60 - r 0 .- ' 50

LO

30

I I I GI 4 00 500 600

Temperature ('C) Fig. 3. TGA and DTA curves for the cardopolyamides in static air. Heating

rate = 10"C/min; sample form was powder.

DTA curves of polyamides did not show any endothermic peaks owing to Tg, indicating that the polyamides have a fairly high Tg and that decomposition occurs even before Tg is reached. All these polymers exhibited endothems owing to thermal decomposition in the temperature range 548-580°C. A polyamide derived from 3,3-bis-(4-aminophenyl)phthalide (PDA) and di-( p - carboxyphenyl)-ether1n2 has a Tg of 340°C in a nitrogen atmosphere. In

TABLE 111 Thermal Stabilities of the Cardopolyamides in Static Air

Temperature at various percent of decomposition ("C) Cardo- Tmax"

polyamide 10 20 30 40 70 ("C)

I 492 516 530 543 566 548 I1 501 550 566 578 620 570 111 524 561 570 584 624 566 IV 462 535 566 580 633 580 V 488 516 546 575 628 570 VI 480 530 560 580 645 563

Note: Rate of heating = 10"C/min. aTemperature of maximum endothermal peak observed in DTA.

2334 REDDY AND SRINIVASAN

contrast, the polyamides (I and IV) containing double-strand heterocyclic units did not show a Tg even up to 500°C in air.

The temperature at which 10% polymer loss of the original weight of polymer was observed by TGA was selected as a measure of thermal stability. The polyamides containing phenoxaphosphine units were found to be less thermally stable when compared with the polyamides having phenoxathiin- 10,lO-dioxide units. Similarly the polyamides (I and IV) with phthalide cardogroups were thermally less stable in comparison with the polyamides (11, 111, V, and VI) having fluorene and anthrone cardogroups. This difference in the thermal stability is probably due to the structural differences between cardogroups that affect the intermolecular interactions. Polyamides IV-VI had a 10% weight loss at 462, 488, and 480"C, respectively, whereas a similar noncardopolymer derived from 4,4'-diaminodiphenylmethane and PPDC showed a decomposition at 456°C. The higher thermal stability of the cardopolymers is due to the hindered rotation about the methylene linkage, which is responsible for the rigid coiling of the polymer chains. These results suggest that the cardopolyamides containing phenoxathiin-10,lO-dioxide and phenoxaphosphine double-strand units are thermally more stable than the cardopolyamides having open-chain linkages and their analogous noncardo- polyamides.

The authors express their gratitude to the Department of Science and Technology, Government of India for sponsoring this project.

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3. M. H. Hubacher, J . Am. C h m . Soc., 73, 5885 (1951). 4. P. R. Srinivasan, M. Srinivasan, and V. Mahadevan, J. Polym. Sci. Polym. Chem. Ed., 19,

5. M. Ueda, T. Aizawa, and Y. Imai, J. Polym. Sci. Polym. Chem. Ed., 15, 2739 (1977). 6. M. Sato and M. Yokoyarna, Eur. Polym. J., 15, 733 (1979).

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2275 (1981).

Received April 10, 1986 Accepted September 11, 1986