Die Angewandte Makromolekulare Chemie 140 (1986) 113 - 125 (Nr. 2275)

Departamento de Quimica Orghnica, Facultad de Quimicas de Tarragona, Universidad de Barcelona, P1. Imperial Tarraco s/n, Tarragona, Spain

Preparation and Reactivity of New 3,3 ' ,4,4 '-Tetracarboxybenzop henone

Dianhydride Glycidyl Ester Derivatives

Angels Serra, Virginia Chdiz*, Pedro-Albert0 Martinez, and Ana Mantecbn

(Received 23 September 1985)

SUMMARY: New diimidediacids coming from 3.3 ',4,4 '-benzophenonetetracarboxylic dianhy-

dride (TBPA) and their corresponding diglycidyl derivatives have been synthesized. Preparation of diglycidyl esters was carried out by reaction with epichlorohydrin (EPC) in excess and using a quaternary ammonium halide as catalyst. The obtained compounds were characterized by spectroscopic methods and employed as starting monomers in a stepwise polymerization. The presence of imide groups in the new epoxy resins confers them higher thermal stability and also acceptable processing possibilities, as they are soluble in high polar organic solvents.

ZUSAMMENFASSUNG: Neue DiimiddicarbonsSLuremonomere und ihre entsprechenden Diglycidylester

wurden aus 3,3 ',4,4 '-Benzophenontetracarbonsluredianhydrid hergestellt. Die Syn- these der Diglycidylester erfolgte durch Umsetzung mit Epichlorhydrin im Uberschul3 mit quaterniiren Ammoniumsalzen als Katalysator. Die synthetisierten Produkte wur- den durch spektroskopische Methoden identifiziert und als Monomere in einer Stu- fenpolymerisation eingesetzt . Die neuen Epoxidharze zeigen durch den Einbau von Imid-Gruppen nicht nur eine hdhere thermische Bestbdigkeit, sondern sie sind auch in polaren Ldsungsmitteln gut 18slich.

Introduction

In line with the actual studies carried out in our laboratory'-2, whose objectives are to prepare new epoxy resins of increased thermal stability, we have planned to use 3,3 ',4,4 '-benzophenonetetracarboxylic dianhydride

* Correspondence author.

0 1986 Huthig & Wepf Verlag, Base1 O003-3146/86/$03.00 113

A. Serra, V. Cadiz, P.-A. Martinez, and A. Mantech

(TBPA) as starting product to develop a series of new compounds, which show a carbonyl group between two aromatic rings. This special arrange- ment allowed us to consider this product as very suitable in order to achieve epoxy resins of low and high molecular weight in which the solubility and processability characteristics might be improved without the thermal prop- erties suffering from serious degradation. So the purpose of this article is to report the succesive synthesis and characterization of diimido-diacids and their respective diglycidyl ester oligomers, which had never been reported in the literature, and their later use as starting materials in the intention of linear polymers with a preformed imide ring, whose properties are of great interest for us. All the reactions involving these products are collected in scheme 1.

Likewise the spectral characterization of new formulations was specially devoted.

Experimental

Reagents

3,3 ',4,4'-Benzophenone tetracarboxylic dianhydride (Fluka) was used without prior purification. Aminoacids were used as submitted by Merck. Epichlorohydrin (Scharlau) and benzyltrimethylammonium chloride (Merck) were used without further purification.

m-Cresol and N-methyl pyrrolidone (Merck) were purified by distilling under vacuum. DMF (Merck) was dried under phosphorous pentoxide and distilled under reduced pressure.

Synthesis of the Diimido-diacids ( I )

6-Aminohexanoic acid (26.2 g, 0.2 mol) was dissolved in DMF (200 ml) and ben- zene (60 ml) in a reaction flask fitted with a stirrer, Dean-Stark system, and thermo- meter, and the mixture was heated to 90°C. Then TBPA (32.2 g, 0.2 mol) was gra- dually added and the solution was heated at reflux until the stoichiometric amount of water was recovered. Benzene was distilled off and the solution was poured into ice water. The yellowish solid was filtered, washed with acetone and sulphuric ether, and recrystallized from ethanol to give 1 a as white product (mp 201 - 3 OC, yield 45 g 82%).

l a (G9H2&C+) calc. 63.50 C 5.11 H 5.11 N found 64.20C 5.35 H 5.10N

114

Preparation and Reactivity of Glycidyl Ester Deriuatiues

Scheme 1

R + 2H2N - R -C-OH

0 0 TBPA

-2Hz0 I

2

2 + 1

6 0 3

.R -C -0 1 3a : R = -(CH215- 3b: R= -(CH2I3- 312: R -CH2 -

115

A. Serra, V. Cbdiz, P.-A. Martinez, and A. Mantecbn

IR: 3600-3400 cm-' (broad band vcc0 acid) 1710 cm-' acid) 1660 cm-' (vcz0 carbonyl) 1780 and 1725 cm-' (symm. and asymm, vc=o imide).

1 b - l e were synthetized in a similar manner. For l c - l e m-cresol instead of DMF was employed, not being necessary to pour into ice water, as a large amount of precipitate was ever obtained.

l b mp 232-4°C yield 81% (C&HzoNzQ) calc. found

l c mp 290-3OC yield 98% (~ ,H, ,N,Q) calc. found

Id mp >300"C yield 89% (q1H&Zo$,) calc. found

l e mp > 300°C yield 89% (q1H16NzQ) calc. found

60.97 C 4.06 H 5.69 N 60.56 C 4.21 H 5.56 N 57.80 C 2.75 H 6.42 N 57.50 C 2.87 H 6.33 N 66.42 C 2.86 H 5.00 N 67.01 C 2.96 H 4.82 N 66.42 C 2.86 H 5.00 N 66.03 C 3.05 H 4.91 N

Synthesis of the Diepoxides (2)

All reactions were carried out with diimido-diacids (1) previously described and epichlorohydrin (EPC, molar ratio I : 100, except for 2c = 1 : 200). Owing to their great insolubility 2d and 2e were not prepared. In a typical example 2a was prepared as follows: a mixture of EPC (156 ml, 2 mol) and l a diimido-diacid (10.96 g, 0.02 mol) was heated at 110°C in a three-necked round-bottomed flask equipped with a stirring device and thermometer. The solid benzyltrimethylammonium chloride (BTMA) (0.75 g, 0.002 mol) was added in a batch and the mixture was heated at reflux. The reaction was controlled by thin layer chromatography (TLC), using as eluent system chloroform/acetone (8/2). The process was finished in about 35 min. Then the mixture was cooled to room temperature and washed twice with water (75 ml). The washing waters were discarded and unchanged epichlorohydrin was removed from the organic phase by distillation under nitrogen and at reduced pressure until the temperature of the residue reached 35°C at 1 mm Hg. Toluene (75 ml) was added to the residue and remaining epichlorohydrin was removed as the toluene azeotrope by distillation until the temperature of the residue again reached 35 "C at I mm Hg. The so obtained product (28) was recrystallized from n-butanol. (mp 82 - 4OC); epoxy equivalent (E. E.) 368 g/equiv. (calc. 331 g/equiv.); chlorine content 1.6%.

IR (KBr): 2930 cm-' (different bands), 1710 cm-' ester), 1660 cm-' (vc=o ketone), 905 cm-' (oxirane ring), 725 cm-' (imide ring).

2a (G,H36NZOll) calc. 63.64 C 5.44 H 4.23 N found 63.51 C 5.62H 4.28 N

2b and 2c were synthetized in a similar manner.

116

Preparation and Reactivity of Glycidyl Ester Derivatives

2b mp 112 - 5 OC; E. E. 340 glequiv. (calc. 303 glequiv.); recrystallized from methanol; chlorine content 1.8%.

2b (GlH28%011) calc. 61.38 C 4.62 H 4.62 N found 61.38 C 4.65 H 4.50 N

2c: The crude reaction product was isolated by pouring the organic phase into sulphuric ether. The obtained product was recrystallized from n-butanol; mp 153 - 6OC, E. E. 330 glequiv. (calc. 274 g/equiv.); chlorine content 2%.

2c (G7H20%011) calc. 59.12 C 3.65 H 5.11 N found 58.07 C 3.76 H 5.26 N

These products were also identified by 'H- and I3C-NMR spectroscopy. The existence of the glycidyl group was the most characteristic feature and it was studied on the basis of preceding All the chemical shifts and coupling constants involving this group are listed in Tab. 1.

Polymer Synthesis (3)

The reactions were conducted in N-methyl pyrrolidone (NMP) at IlO'C, using a reaction flask fitted with a stirrer, thermometer, and under & atmosphere. A typical run is as follows: l a (0.05 mol) and 2a (0.1 equivalents of pure diepoxide, on the basis of calculated E. E.) were mixed in NMP (50 mi). The mixture was heated at 110 OC and then benzyltrimethylammonium chloride (BTMA) (0.005 mol) was added in one batch. Disappearance of initial diimide-diacid was controlled by acid index measurements, taking samples at different times. When the acid index values remain- ed constant the mixture was cooled and poured into ice water. The filtered product was washed with water and dried at room temperature in vacuum for 24 h. All the properties of the products prepared in this way are reported in Tab. 2. Polymers were obtained in practically quantitative yields.

Characterization and Measurements

The melting points are uncorrected and were determined on a Tottoli capillary mp apparatus. Elemental analyses were carried out on a Perkin-Elmer 240 B device. IR spectra were recorded on a Beckmann IR 4260 spectrometer (KBr pellets). 'H-NMR and "C-NMR spectra were obtained with a Varian XL 200 spectrometer, working at 200 and 50.3 MHz, respectively. Samples were run in CDCh and DMSO-4, with TMS as internal standard.

Viscosity measurements were taken in 0.5% (w/v) solution in DMF at 30.0 f 0.1 "C with an Ostwald type viscometer.

117

L

Y

00

? c

Tab

. 1.

Che

mica

l str

uctu

re a

nd sp

ectr

osco

pic

para

met

ers in

'H- a

nd "

C-N

MR

of t

he g

lyci

dyl g

roup

in th

e ne

w e

poxy

este

rs.

~~~

~ ~

~ ~

~~

~~~

Com

- H

-NM

R sp

ectr

al d

ata

I3C

-NM

R sp

ectr

al d

ata

,pou

nd

chem

ical s

hift

s of

prot

ons

(ppm

) co

uplin

g co

nsta

nts (

Hz)

ch

emic

al s

hift

s of

ca

r-

bons

&

Hb

@

Hd

h

Jab

Jbc

Jac

Jde

Jcd

Jce

c-1

c-2

c-3

2a*

4.41

3.

90

3.21

2.

84

2.64

12

.3

6.3

3.0

4.9

2.6

4.2

44.6

49

.3

64.8

2b

* 4.

43

3.90

3.

21

2.85

2.

65

12.2

6.

3 3.

1 4.

8 2.

6 4.

2 44

.6

49.2

65

.0

2c*

4.53

4.

04

3.24

2.

88

2.61

12

.2

6.4

3.1

4.8

2.6

4.2

44.6

48

.9

66.4

9

* All

spec

tra

wer

e ru

n in

CD

Cl,.

Preparation and Reactivity of Glycidyl Ester Derivatives

Thermogravimetric analyses were carried out using a Perkin-Elmer TGS-2 thermo- balance in

The epoxy content was expressed in g/equivalent and determinated by the Jay and Dijkstra and Dahmen method, variation by Cibas. The determination of the acid index was carried out as

atmosphere and at a heating rate of lO"C/min.

Results and Discussion

Diglycidyl Derivatives

As reported in the experimental part, the synthesis of these compounds needs a great excess of EPC and also the presence of a quaternary ammonium halide, which acts as catalyst6. The use of alkali medium as cyclizing agent was forbidden by the presence of an imide ring in the new structure^^.^.

The different products were obtained in high purity and therefore they were suitable materials in further polycondensation reactions.

Linear Polymerization

As can be seen in Tab. 2, different molar ratios of diglycidyl ester/diimido- diacids were employed in the synthesis of the polymers. From acid index measurements it may be supposed, that residual acid groups remained when the reaction was finished, except for molar ratios equal or higher than 1.3/1. Nevertheless, epoxide groups have almost completely reacted, as it can be seen from the E. E. values.

The course of the reaction could be followed by the measurements of acid index values. The comparison of these reactions with those of pyromellit- imide glycidyl ester derivatives and their respective diimido-diacids, which had been reported in a previous paper', shows this process to be faster, probably owing to the presence of the carbonyl group which furnishes a higher solubility in the starting products (see Fig. 1).

Viscosity values remained unchanged along several weeks of storage. When different molar ratios were used for the synthesis of 3a, the inherent viscosity varied in a linear manner (see Fig. 2), as it was expected.

119

A. Serra, V. Ciidiz, P.-A. Martinez, and A. Mantech

Acid Index

9 4 9 i

8 -

7 -

6 -

5 - L -

3 -

2 -

1 -

0 30 60 90 120 150 t (min)

Fig. 1. Comparison of the reaction course by acid index measurements in the formation of: (V) 3a polymer, (V) pyromellitimide derivative polymer for R = -(CH*k-'.

'I inh

0.12 .

0.11 '

0.10 '

I I I I I

1.1 : 1 1.3-1 1.5~1

Molor r o t i o

Fig. 2. Variation of the inherent viscosity values as a function of the molar ratios of diglycidyl ester: diimido-diacid.

Preparation and Reactiuity of Glycidyl Ester Derivatives

Tab. 2. Preparation and properties of the polymers.

Corn- Molar t Acid index %h EPOXY pound ratioa (fin) equivb

beg. end

3a 1.1 : 1 105 8.82 0.33 0.12 12500 1.3:l 105 8.76 0 0.11 4600 1.5:l 1 20 8.30 0 0.10 3000

3b 1.1:l 1 20 7.29 0.72 0.07 31 700 3c 1.1 : 1 520 11.67 5.16 0.09 -*

a Molar ratio diglycidylester to diacid. Epoxy equivalent in g/equivalent. 0.5% solution in DMF at 3 O O C .

* Could not be calculated.

Solubility of Polymers

Solubility measurements are collected in Tab. 3. These compounds were soluble in highly polar solvents and also in chloroform except for 3c. This fact may be explained on the basis of the presence of the polar carbonyl group, which reduces packing due to aromatic rings, increasing the chain flexibility2.

I3C-NMR Data

The identification of the repeat units has been possible by employing 13C- NMR. In a similar manner to the homologous compounds, pyromellitimide derivatives, in this reaction five signals of new appearance have been detect- ed between 55 - 75 ppm, the two more intensive lines corresponding to attack on the less substituted carbon (normal opening), and the other three remaining signals corresponding to the attack on the more substituted carbon (abnormal opening).

121

A. Serra, V. Ciidiz, P.-A. Martinez, and A. Mantech

Tab. 3. Solubility of the polymers.

n-hexane toluene acetone chloro- DMF DMSO NMP form

+ + + + + + + - - + + + + + + +

+ + + + -I-

- - - 3a

3b

3c

- - - - -

- Insoluble; + soluble at room temperature; + soluble by heating; f partially soluble or swelling.

Tab. 4. l3C chemical shifts of carbons of the new formed units.

R C-f c-g C-i C-j C-k

--(CH&-' 65.1 -(CH2&-b 64.8

68.2 62.2 72.2 61.4 66.0 61.8 71.4 58.9

a in CDCl,; in DMSO-4.

122

100

90

80

70 -

60 J P 50 L

7 LO P ' 30

20

Preparation and Reactivity of Glycidyl Ester Derivatives

..., .. - ........, . . ---. ---._

lo 1 4 U , , ~ S , T ~ ~ , l f f l ~ V

90 170 250 330 410 490 570 650

Ternperoture I'CI

Fig. 3. TGA curves of the polymers.

Tab. 5. Decomposition temperatures of the polymers.

Polymer T,, Weight loss at temp. ("C) Weight residue (070) at

("C) 10% 20% 30% 50% 500 "C

3a* 433 395 419 429 445 25 3a** 454 414 438 450 468 31 3b 410 320 392 406 429 43 3c 395 270 373 393 428 44

* Molar ratio diglycidyl to diacid 1.3 : 1. ** Molar ratio diglycidyl to diacid 1.1 : 1.

123

A. Serra, V. Ciidiz, P.-A. Martinez, and A. Mantec6n

90 170 250 330 L10 L90 570 650 Temperature loci

Fig. 4. Comparison of the TGA curves as a function of introduced imidic residue.

Spectral data of 3a and 3b are listed in Tab. 4. Data of 3c are not collect- ed because signals corresponding to abnormal opening were not clearly assignable. Nevertheless, signals due to normal attack clearly appeared at 65.2 ppm and 67.1 ppm, respectively.

Thermal Behaviour

TGA curves of the obtained polymers are shown in Fig. 3 and 4, and the most important parameters, coming from such figures are summarized in Tab. 5 .

It may be observed (see Tab. 5 ) that these compounds are more stable, when they are obtained in molar ratios of 1.1 / l .

In general, they present a good stability explained on the basis of the accumulation of aromatic rings along the backbone. Likewise the variation of the imidic residue gave place to a significant improvement of stability for 3a, as can be observed in Fig. 4.

Preparation and Reactivity of Glycidyl Ester Deriuatiues

' P. A. Martinez, V. Ciidiz, A. Mantech, A. Serra, Angew. Makromol. Chem. 133 (1985) 97 A. Serra, V. Csldiz, P. A. Martinez, A. Mantech, Angew. Makromol. Chem. 138 (1986) 185 A. Serra, V. Ciidiz, A. Mantech, P. A. Martinez, Tetrahedron 41 (1985) 763 P. A. Martinez, V. Ciidiz, A. Serra, A. Mantech, Heterocycles 23 (1985) 3021 B. Dobinson, W. Hofman, B. P. Stark, The Determination of Epoxide Groups, Is' ed., Pergamon Press Ltd., London 1970, p. 40 W. Bradley, J. Forrest, 0. Stephenson, J. Chem. SOC. 1951, 1589

125