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TECH. REP. #15-POLYENAMINONICRILES:NOVEL MATERIALS FOR USE IN LECTRONICS-UNCTASSIFIED

12. PCRSONAL AUTHOR(S)J.A. Xoore, Douglas R. Roelo and arag . Kehta

13&. TYPE OF REPORT 13b. TIME COVERED 14. DATE OF REPORT (Year, Month, Oay) IS. PAGE COUNTPublicatio FROM TO June, 199

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19.STRACT (Conrnue on row-e ;f nmssary and identify by block number)

Three new bis(i-chloro-2,2-dicyanovinvli benzene monomers have been synthesized. Poiymerizatioof these monomers with two different diamines led to moderate to high molecular weight pol-enaminonitriles possessing excellent thermal stability. These polymers cure without enissionof volatile byproducts. initial thermal, mechanical and dielectric data of these polymers ispresented. The dielectric constant of a representative polmez was ,ounr to be approximate!-8 before heat treatment and 5 afterward. C.l' tr" '. t . V .C-

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Office of Naval ResearchContract N0014-85-K-0632

R & T Code 413c014

Technical Report No. 15

"Poly(enaminonitriles): Novel Materials for Use in Electronics"

by

J. A. Moore, Douglas R. Robello and Parag G. Mehta

6

To be published inAccession For

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June, 1989

Reproduction in whole or in part is permitted for any purpose of theUnited States Government.

This document has been approved for public release and sale; itsdistribution is unlimited.

Poly(enaminonit'les): Novel Materials for Use in Electronics

byJ. A. Moore*, Douglas R. Robello anOPrgV.MeA

Department of Chemistry log \

Polymer Science and Engineering Program ". 7'Rensselaer Polytechnic Institute

Troy, NY 12180-3590

ABSTRACT functional groups in the polymer backbone

that crosslink upon heating and inflexible

Three new bis(l-chloro-2,2-dicyanovinyl) chains. Aromatic moieties in a molecule

benzene monomers have been synthesized. normally endow the polymers with superior

Polymerization of these monomers with two thermal stability. Because the most

different diamines led to moderate to high common mechanism for the degradation of

molecular weight polyenaminonitriles the polymers is oxidative in nature,

possessing excellent thermal stability, incorporation of heterocyclic units further

These polymers cure without emission of improves thermal stability by increasing

volatile byproducts. Initial thermal, char yield at very high temperatures.

mechanical and dielectric data of these Polymers possessing these structural

polymers is presented. The dielectric features generally are difficult to process

constant of a representative polymer was because of their low solubilities and high

found to be approximately 8 before heat glass transition or melting temperatures.

treatment and 5 afterward. These conflicting trends often lead to aprocessability-thermal stability tradeoff.

1. INTRODUCTION A common approach to solve the problem

of processability is to synthesize a more

The growing need for novel polymer flexible prepolymer which upon subsequent

possessing excellent thermal stability by the treatment ("curing") cyclizes

electronics and aerospace industries has intramolecularly to produce the final

provided researchers with the impetus that thermally stable, rigid rod polymers.

led to the discovery of a variety of Polyimides 3 are a familiar and successfully

polymeric materials 2. The structural applied example of this approach. The

requirements for such polymers include principal drawback to the curing reaction of

incorporation of chemical bonds of high polyimide and other similar polymers is the

dissociation energy, the presence of emission of volatile molecules which are

, trapped in the bulk of high molecular weight brown and then yellow. The mixture waspolymer. The difficulties in removing these heated under nitrogen for 18 hours at 70 'C,small molecules from the bulk polymer cooled to room temperature and poured intowithout causing voids has restricted the use vigorously stirred water. The precipitated

of many polyimides to various thin-film polymer was dissolved in

applications. Besides this result, the N,N-dimethylformamide (DMF) and

intermediate polyamic acid (prepolymer) reprecipitated into methanol.suffers from poor hydrolytic stability. We, Method B: Equimolar quantities of atherefore, reasoned that the presence of particular bis(l-chloro-2,2-dicyarovinyl)

suitable functional groups in a prepolymer benzene monomer and 1 3-big(4-aminowhich can undergo intramolecular phenoxy- 4'-benzoyl)benzene were mixed,cyclization by structural rearrangement will under an argon atmosphere, at 0C in dryyield cured polymer without the emission of NMP in the presence of one equivalent ofvolatile byproducts. Recent work4 from our 1,4-diazabicyclo [2.2.2] octane (DABCO)

laboratory has demonstrated the successful (purified by sublimation prior to use) as acid

application of this approach to the acceptor. The mixture immediately turned

preparation of several new polymers brown and then yellow (ca. 1 minute). Theemploying vinylic nucleophilic substitution mixture was allowed to warm to room

reactions. temperature over 1 hour and then heated at70-75 0C for 24 hours. The viscous solution

2. EXPERIMENTAL was cooled and poured into vigorously

2.1 Monomer Synthesis stirred water and the precipitated polymer

Bis (1-chloro-2,2- dicyanovinyl)benzene was filtered. The polymer was further

monomers4 were readily synthesized from purified by one more precipitation from

the corresponding diacid chlorides as shown NMP into water followed by extraction within Scheme I. methanol in a Soxhlet apparatus for 24

1,3-Bis(4-aminophenoxy-4'-benzoyl)benze hours. The polymers were dried at 130-135ne was prepared according to a literature *C in vacuo for 24 hours.

procedure5 and was purified by two 2.3 C tzatnrecrystallizations from 1-butanol. All six polymers were characterized by IR,

4-Aminophenylether (Gold label quality) 1H NMR and 13C NMR. Viscosities of the

was obtained from the Aldrich Chemical polymer solutions were measured in an

Company and was used as received. Ubbelohde viscometer. Thermal analysis

2.2 Polymer Synthesis (DSC, TGA and TMA) of the polymers wasMethod A: Equimolar quantities of the carried out on a Perkin-Elmer 7 Series

appropriate bis(1-chloro-2,2-dicyanovinyl) Thermal Analysis System. Dynamicbenzene monomer and 4-aminophenylether mechanical analysis was performed using awere mixed, under nitrogen, at 23 *C in dry Rheovibron instrument. Dielectric constantN-methyl pyrrolidone (NMP) in the of polymer F was measured with a GenRadpresence of two equivalents of 1689 Precision RLC Digibridge. Sample4-(dimethylamino)pyridine (DMAP) as an thickness was measured with a Danatron

acid acceptor. The reaction mixture turned .digital electrogauge. Aluminum electrodes

(2000 A') were applied on both sides of the The polymers appeared to possess

polymer film by vacuum deposition. The moderate to high molecular weight, judging

dielectric constant, e, was calculated as from intrinsic viscosity measurements

follows. (Table 1) and the fact that

(Capacitance in pF)(Thickness in Lm) fingernail-creasable films could be cast from

F_ = their solutions in DMF and NMP.

(area in cm 2)(885.4) 3.2 Thermal and Mechanical Properties

3. RESULTS AND DISCUSSION As shown in Table 1, all polymers

3.1 Synthesis possess good to excellent stability in both

There are primarily two reasons for the air and nitrogen (see also Fig. 1 and 2).

choice of bis(1-chloro-2,2- dicyanovinyl) The polymers decompose completely in air

benzene monomers. above 550 'C but retain approximately 70 %

1. The dicyanomethylidene group of their mass at 900 *C in nitrogen.

(--C(CN) 2) and the carbonyl group have Differential scanning calorimetry (DSC) of

similar inductive and resonance effects6. all six polymers showed a somewhat broad

Thus the presence of dicyanomethylidene exotherr, starting near 300 °C and reaching

units imparts sufficient electrophilic maximum intensity near 350 °C. This peak

character to the vinylchloride functionality to was completely absent when the samples

make it reactive toward nitrogen-containing were cooled and rescanned (Fig. 3). This

nucleophiles. phenomenon is believed to indicate the2. The presence of suitably disposed nitrile occurence of a thermally induced cyclization

groups further ensures that an reaction as shown in Scheme MII for

enaminonitrile moiety, the initial product of polymer F.

a vinylic nucleophilic substitution reaction, Polymers F, G and H did not show any

can cyclize to a stable heteroaromatic prominent glass transition in DSC while

aminoquinoline structural unit3a. (Scheme polymers I, J and K showed distinct glass

III) transition temperatures (Fig. 3). This result

An additional advantage of the may be caused by the incorporation of

enaminonitrile structural unit is that it unsymmetrical diamine E, especially theendows the polymer with good thermal and central benzene ring with 1,3- entrainment,hydrolytic stability (as opposed to the which may have resulted in a substantial

hydrolytic sensitivity of polyamic acids in decrease in the ordered arrangement ofthe synthesis of polyimides) as well as polymer chains.

making the polymer soluble in volatile, To understand further thenon-aqueous solvents. structure-property relationship and to assess

Hergenrother's success in using 1,3-bis- their usefulness for advanced applications, it(4-anminophenoxy-4'-benzoyl)benzene as a is necessary to analyze these polymers

monomer which confers both toughness and under various stress-strain conditions.solvent resistance on a series of polyimides Furthermore, the knowledge of dynamicwhich he studied5 prompted us to try this moduli and other related properties can alsocompound in our system. pave the way for the design of novel

polymers having better properties. Polymer analysis discussed above. It can be readily

F was chosen for preliminary study and seen that such a transition is absent in the

initial data is shown in Fig. 5 which case of the cured polymer. An Instron test

contains the plots of E' (storage modulus) of this polymer gave the following results.

and E" (loss modulus) versus temperature Polymer Average Average

for uncured and cured polymer and Kapton. Breaking Stress Breaking

The glass transition for the uncured polymer Strain

occurs around 270-280 'C as indicated by Uncured 136,000 psi 4.2 %

the decrease in the value of E'. Cured Cured 131,000 psi 2.9 %polymer, as expected, doe. not show any

glass transition when heated to 384 *C. In Cured polymer seems to be slightly more

the glassy state (below the glass transition brittle and less elastic as indicated by the

temperature) molecular motions are largely lower values of average breaking stress and

restricted to vibrations and short range strain. It should be noted that these samples

rotational motions and hence E' does not have not been optimized with respect to

change appreciably over a wide temperature molecular weight or distribution. A detailed

range. Because polymer F starts analysis of the mechanical data will be

undergoing a curing reaction at -300 1C, presented in a future publication.

measurements of E' beyond this range are 3.4 Dielctric Behavio

not meaningful. Under the same Upon interaction with an electric field the

experimental conditions, Kapton appears to charges within the polymer experience

undergo a glass transition at approximately restricted movement giving rise to a net304 "C. dipole moment which, in turn, determines

The transitions evident in the loss modulus the dielectric constant of the material. Thus,

curve are reminiscent of those which have the dielectric property of a polymer is

been attributed to motion about the chain determined by the charge distribution in the

backbone or to the motion of side chains 9. macromolecule. The charge distribution in a

These phenomena could be an outcome of at polymer depends on a number of factors8 :

least two processes which we are studying 1. Polarity of the bonds between the atoms

via dynamic NMR techniques7 : constituting a given structural unit. This

1. Rotation around the double bond of the structural feature translates into the net

vinylidene cyanide group. polarity of the structural units in the

2. Rotation about the vinyl carbon-nitrogen molecule. These dipolar structural units are

single bond in enaminonitrile moieties. easily affected by thermal motion.Polymer F was further investigated by 2. Overall molecular configuration

thermornechanical analysis (TMA). As including symmetry in the molecule.

shown in Fig. 6, the extent of penetration 3. Morphology of a polymer.

was measured as a function of temperature In the case of polyenaminonitriles, there is a

for both cured and uncured polymers. For strong charge asymmetry in the vinylic

an uncured polymer, the glass transition double bond bearing two nitrile groups

temperature was detected around 260-270 (acceptor) and a secondary amino group

°C in accord with the dynamic mechanical .. (donor). This polarization of the double

bond is clearly reflected in the 13C NMR 4. CONCLUSION

spectra of these polymers. Difference in the We have successfully employed

chemical shifts of the two carbon atoms of dicyanovinylidenechloride monomers as

the double bond in question is synthetic equivalents of diacid chlorides to

approximately I 10 ppm. High yield a new class of thermally stable

concentration of these dipolar enaminonitrile materials possessing interesting properties.

structural units (two per repeat unit) results Work to study the dielectric and dynamic

in a dielectric constant as high as 8 for mechanical properties of all the polymers

polymer F. As can be seen in the Table II, further is underway.

the dielectric constant shows very little

frequency dependence. After heat-curing, 5. ACKNOWLEDGEMENT

the dielectric constant decreases to 5. This We thank Paul M. Hergenrother for

change in the dielectric constant can be providing a detailed procedure for the

explained qualitatively. Upon heat-curing, synthesis of monomer E and James Mason,

one of the nitrile groups is consumed. This formerly of Beta Physics Co., Holcomb,

occurrence, coupled with the fact that the NY for determination of dielectric constants.

double bond bearing a nitrile and an amino Dr. H. Baer and Dr. T. T. Wang of AT & T

group now become part of the aromatic Bell Laboratory provided the TMA and

system thereby effectively participating in Rheovibron-Instron analysis, respectively

the electron delocalization in the quinolinering system, results in a net decrease in 6. REFERENCES

charge asymmetry and also interferes with 1. Present Address: Eastman Kodak

the efficiency of electron delocalization Corporate Research Laboratory,

between the amino group and the nitrile Building 82C, Rochester, NY 14650

group. 2. Cassidy, P. E. Thermally stable

3.5 Curin Polymers; Marcel Dekker: New York

All six polymers were cured (Scheme III) 1980.

by heating at approximately 400 C in an 3. Mittal, K. L. Polyimide; Plenum: New

inert atmosphere and the curing was York, 1984; Vol. 1 and 2.

monitored using IR spectroscopy. As 4. (a)Moore, J.A.; Robello, D.R.

shown in Fig. 4, for polymer F, the Macromolecules 1986, 19, 2667. (b)

enamine N-H stretching band at 3260 cm-1 Moore, J.A., Robello, D. R. Polym.

disappeared and was replaced by two new Prepr. (Am. Chem. Soc., Div. Polym.

bands at 3365 and 3480 cm' which are Chem.) 1986, 27(2), 127; 1987,

characteristic of a primary aromatic amine. 28(1), 39. (c) Moore, J. A.; Mehta,

At the same time, the nitrile band near 2210 P. G. Polymeric Materials: Science &

cm -1 decreased to approximately half its Engineering, 1989, 60 , 0000. (d)

original intensity. The above data is Moore, J. A.; Mehta, P. G.

consistent with a rearrangement, at least in Macromolecules, 1988, 21 ,2644.

part, of the enaminonitrile repeat unit into a 5. Hergenrother, P. M.; Wakelyn, N. T.;

4-aminoquinoline unit" (Scheme 3). Havens, S.J. J. Polym. Sci., Polym.

Chem. Ed., 1987, 25, 1093. American Cvanamid Award for Significant

6. (a) Wallenfels, K. Chemia , 1966, 20. Achievement in Synthesis.

303. (b) Wallenfels, K.; friedrich, K.;

Rieser, J.; Ertel, W.; Thieme, K. Douglas R. Robello obtained a B.S.Angew. Chem. Int. Ed. Engl. 1976, degree from Rensselaer Polytechnic Institute

15 ,261. in 1978. After teaching High School

7. Moore, J. A., Mehta, P. G. Chemistry for three years, he joined

Unpublished results. Rensselaer Polytechnic Institute as a

8. Ku, C. C.; Liepins, R. Electrical graduate student in 1982 and received his

Properties of Polymers ; Hanser: Ph.D degree in 1986. He is currently at

Munich, Viena, New York, 1987; Eastman Kodak Corporate Research

chapter 2. Laboratory.

9. Murayama, T. In Encyclopedia of

Polymer Science and Technology , 2nd Parag G. Mehta obtained a B.Sc. degree

ed.; Mark, H. F.; Bikales, N. M.; from Gujarat University, Ahmedabad, India

Overberger, C. G.; Menges, G; in 1982 and an M.Sc degree from Indian

Kroschwitz, J. I., Ed.; Wiley Institute of Technology, Bombay, India in

Interscience: New York, 1986, Vol. 5, 1984. Mr. Mehta is currently a graduate

p 299. student at Rensselaer Polytechnic Institutewhere he expects to receive his Ph.D degree

7. BIOGRAPHY in September 1989. Mr. Mehta is a memberof the American Chemical Society.

James A. Moore obtained a B.S. degre

from St. John's University and a Ph.D

degree from the Polytechnic Institute of

Brooklyn in 1967. Thereafter he was a

National Insitutes of Health Postdoctoral

Fellow at the University of Mainz, West

Germany, and a Research Associate at the

University of Michigan in 1968. In 1969 he

joined the faculty of the Chemistry

Department of Rensselaer Polytechnic

Institute where he is Full Professor of

Organic and Polymer Chemistry. He is a

member of the American Chemical Society,

the Editorial Boards of MacromolecularSyntheses and Chemistry of Materials and is

Associate Editor of Organic Preparations

and Procedures International. Dr. Moore

has more than 130 publications, including 6

books, and in 1985 was awarded the

Scheme I

NC CN NC CNOO~rCQ +KBu 4N'Cr PC I

CN NaOH O Na' -- C1ClOC- Ar - C( + < CN CH 2C12 / H20 Na'O Ar CH 2CI-CH 2CI C1 /At

<PTC> I" .

NIIC CN NC CN

A Ar=

B Ar=

C Ar S 02

0 0N / \A

E

Fig. 1 TGA of polymer I in air and nitrogen atmosphere.

I110.0

to.. o

100.0 300.0

90.0 , Nitrogen 90.0

80.0. am a

700 70.0

60.0 u0.o ,

So. aOM

S40.0 -40.0

30.0 -30.0

20. 0 ,-O 20.0

IAir 10. 0

l0.0.

0.0 0.0

-30.0-10.0

.

200.0 200.0 300.0 400.0 500.0 600.0 700.0 00. 0 900.0 2000.0

Tworatwure 0C)

Scheme II

NCCAr

+ H2N-Ar'-NH2N C CI

CN

DABCO

~ NCAr

" C N

N C /HN-Ar'-NH]ON

Polymer Monomers

F A DG B DH C DI A EJ B EK C E

Scheme m

NC CN CN

14000 °C

NH 2

NC . i 0 NH 2 i

I I-

n

Fig. 2 Isothermal aging of polymer I at 300 'C in air.100. 0 -Kapion

00 100.0

90.0 90.0

80.0 80.0

70.0 70.0

60.0 60.0

50.0 50.0

40.0 40.0

0 0

30.0 NC" CN C 30.0

20.0 20.0

10.0 - 10.0

0.0 I I 0.00.0 250.0 500.0 750.0 1000.0 1250.0

TIm (mnutes)

Fig. 3 DSC of polymer K.

10.0~ - 0.0

9.0- so 9.0

NH O O N7

.0- 8.0

3 7. CN K NC CN .

J 5 0 -.0 ,,

U

4.0 8 .0L.

3.0 - 3.0

2.0- 2.0

0.0 - 1.0

0.1 I 1 -0.0#

S0.0 10.0a 120.0 200.0 2M.0 30j. 0 350.0

T tur (C)

Fig. 4 IR spectra of Polymer F at 400 0C

Uncured

I h

1 hours

4 hours

4O00cm 1 3500 N000 2w0 2000

Fig. 6 Thermomechanical Analysis of polymer F.

105.0 FILM AFTER 3HRS AT 350" 1'. 0

900.0

90.0 95.0

gOLOo

801.0 "5.0

~7. NC CN 0 NNC CN .70.0

. H H Io.

T O n 55.0

30.0 a I5I.050.0 lam. a 5lima 20M 0 M2a0.0 a. 10.0 400.0 £10.0a

Topwvutswe (0

FigY. 5 Dynamic Mechanical Analysis of Polymer F

-- A-- -&ato

Oil -9

~~iiii~ ..___ _ . ** .- .. ... . .

4-

Temperature (0C _Q__ -

p _ __A_

Table I: Characterization of Polymers

Polymer [11 50% wt. loss Residual wt. % Tg(dL/g) temp.0 C(air) 900 0C (N2) (OC)

F 0.84a 505 73 260-270 d

G 0.39a 477 71

H 0.68a 484 68 -

I 0.60b 569 73 164.3 (film)

J 1.99b 531 70 240.4 (powder)

K 1.83c 525 62 184.21 (powder)237.35 (film)

a: In DMF at 25 'Cb: In DMAC at 25 'Cc :rlinh at conc. of 0.41g/dL in DMAC at 25 OCd: Determined by TMA.

Table IIDielectric Measurements for Films of Polymer F

test freq, Hz capacitance. pF f Dissipation FactorBefore Heat Curing4

10' 474.5 8.452 0.0437l0, 456.9 8.146 0.0106104 448.5 7.996 0.0089106 446.9 7.968 0.0145

After Heat Curinge103 696.9 5.178 0.0042104 689.9 5.126 0.0095106 676.6 5.027 0.0368106 658.7 4.894 0.2509

"Sample thickness 20.0 um. Electrode area 1.27 cm 2; 24.0 *C.bSaMple thickness 7.5 1&m. Electrode area 1.14 cm'; 24.9 *C.