NMR Characterization of a Polymethyldisilylazane - American

Chapter 12

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NMR Characterization of a Polymethyldisilylazane A Precursor to Si—C—N—O Ceramics 1

Jonathan Lipowitz, James A. Rabe, and Thomas M. Carr Dow Corning Corporation, Midland, MI 48640

29

13

Si and C NMR spectroscopy was used to characterize a polymethyldisilylazane polymer, a precursor to Si-C-N-O ceramics. Polymer is prepared by reaction of mixed chloromethyldisilanes with hexamethyldisilazane. The polymer is a low MW (M ~2000), glassy oligomer with a polycyclic, cage-like structure and a broad MW distribution. Si and C NMR spectra give only broad signals. A simplified polymerization reaction using sym-tetrachlorodimethyldisilane was followed by Si NMR to give insight into development of polymer structure. The broad NMR signals were shown to result from a multitude of chemical environments about the Si atoms which develop early in the reaction, not from restricted motion of Si atoms in the polymer molecules or from Ν quadrupole broadening. n

29

13

29

14

Ceramics c a n be p r e p a r e d by p y r o l y s i s o f v a r i o u s o r g a n o s i l i c o n polymers. The advantages o f c e r a m i c f o r m a t i o n from polymers i n c l u d e t h e a b i l i t y t o p r e p a r e shapes d i f f i c u l t t o a c h i e v e by c o n v e n t i o n a l powder p r o c e s s i n g methods, such as f i l m s and f i b e r s ; the u s e o f lower p r o c e s s i n g temperatures than in c o n v e n t i o n a l methods; t h e a b i l i t y t o a c h i e v e v e r y h i g h p u r i t y because r e a g e n t s can be p u r i f i e d by w e l l - e s t a b l i s h e d methods such as d i s t i l l a t i o n and r e c r y s t a l l i z a t i o n ; t h e a b i l i t y t o v a r y ceramic c o m p o s i t i o n by v a r i a t i o n o f polymer c o m p o s i t i o n ; and t h e a b i l i t y t o c r e a t e unique m e t a s t a b l e c e r a m i c c o m p o s i t i o n s which cannot be a c h i e v e d by c o n v e n t i o n a l p r o c e s s i n g (3). T h i s t e c h n o l o g y has been r e v i e w e d r e c e n t l y by s e v e r a l a u t h o r s ( 4 - 1 1 ) .

1

Current address: Technical Center, Owens Corning Fiberglas, Granville, OH 43023

0097-6156/88/0360-0156$06.00/0 © 1988 American Chemical Society In Inorganic and Organometallic Polymers; Zeldin, Martel, et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1988.


12.

LIPOWITZ ET AL.

Characterization of a Polymethyldisilylazane

157

One o f t h e main advantages o f t h e polymer r o u t e t o c e r a m i c s is the p r e p a r a t i o n o f ceramic f i b e r s , a shape d i f f i c u l t t o a c h i e v e by o t h e r methods. Ceramic f i b e r - b a s e d composites a r e becoming an i n c r e a s i n g l y i m p o r t a n t group o f s t r u c t u r a l m a t e r i a l s (12, 13). A c e r a m i c f i b e r w i t h Si-C-N-0 c o m p o s i t i o n c a n be p r e p a r e d by m e l t - s p i n n i n g , c u r e and p y r o l y s i s o f a p o l y m e t h y l d i s i l y l a z a n e polymer p r e c u r s o r (14, 15), which is t h e r e a c t i o n p r o d u c t o f a m i x t u r e o f 50 mol % 1,1,2,2- t e t r a c h l o r o - 1 , 2 - d i m e t h y l d i s i l a n e ( l a ) , 40 mol % 1 , 1 , 2 - t r i c h l o r o - 1 , 2 , 2 - t r i m e t h y l d i s i l a n e ( l b ) and 10 m o l % 1,2-dichloro-l,1,2,2- tetramethyldisilane +1,1-dichloro-l,2,2,2tetramethyldisilane (Ic). T h i s m i x t u r e is r e a c t e d w i t h excess h e x a m e t h y l d i s i l a z a n e (HMDZ) to g e n e r a t e o l i g o m e r i c s p e c i e s ( p o l y m e t h y l d i s i l y l a z a n e "polymer") w i t h t h e approximate c o m p o s i t i o n I I , as determined b y e l e m e n t a l a n a l y s i s and M from GPC a n a l y s i s , [Me

2 > 6

Si (NH) 2

1 5

(NHSlMe ) 3

0 > 4

Cl

o a 5

],

(II)

1 3

a l o n g w i t h M e ^ S i C l and NH^Cl as b y - p r o d u c t s . The v o l a t i l e s p e c i e s M e ^ S i C l and HMDZ a r e removed by g r a d u a l l y i n c r e a s i n g temperature t o about 250° C d u r i n g r e a c t i o n . The polymer is a g l a s s y m a t e r i a l w i t h a h i g h l y c r o s s l i n k e d presumably c a g e - l i k e p o l y c y c l i c s t r u c t u r e and is r e a d i l y s o l u b l e in a r o m a t i c and a l i p h a t i c h y d r o c a r b o n s . Number average m o l e c u l a r w e i g h t s (R ) o f c a . 2000 a r e found b y GPC. Polymers a r e r e a c t i v e w i t h b o t h oxygen and m o i s t u r e and must be h a n d l e d in a d r y and i n e r t atmosphere. A b r o a d MW d i s t r i b u t i o n is found b y GPC, s u g g e s t i n g t h a t a v a r i e t y o f s t r u c t u r e s a r e p r e s e n t . The m i x t u r e o f c h l o r o d i s i l a n e monomers and t h e i r h i g h average f u n c t i o n a l i t y (f=3.4) suggest a complex h i g h l y c r o s s l i n k e d s t r u c t u r e . The i n t e n t o f t h e e f f o r t d e s c r i b e d in t h i s paper was t o o b t a i n i n s i g h t i n t o t h e s t r u c t u r e o f t h i s complex polymer and t o c h a r a c t e r i z e t h e s t r u c t u r e s p r e s e n t u s i n g NMR. Experimental A p p r o x i m a t e l y 1 g polymer and 0*06 M C r ( a ç a c ) ^ were d i s s o l v e d in CDC1 to prepare s o l u t i o n s f o r S i and C NMR s p e c t r o s c o p y . NMR s p e c t r a were r u n on a V a r i a n XL-200 FT-NMR i n s t r u m e n t . To a i d in o b t a i n i n g q u a n t i t a t i v e d a t a , t h e s o l u t i o n was doped w i t h 0.06 M chromium a c e t y l a c e t o n a t e [ C r ( a c a c ) ) ] t o remove p o s s i b l e s i g n a l a r t i f a c t s r e s u l t i n g from l o n g s p i n - l a t t i c e r e l a x a t i o n times ( T ' s ) and t^ç n u c l e a r ^ O v e r h a u s e r e f f e c t , well-known f e a t u r e s a s s o c i a t e d with S i and C NMR s p e c t r o s c o p y . T h i s p e r m i t s q u a n t i t a t i v e signal acquisition. From t h e l i t e r a t u r e (16) and a d d i t i o n a l work done in t h i s l a b o r a t o r y , i t was e x p e c t e d t h a t C r ( a c a c ) ^ would be an i n e r t s p e c i e s . A s o l u t i o n o f HMDZ (2.04 g, 12.67 mmole), l , l , 2 , 2 - t e t r a c h l o r o - l , 2 - d i m e t h y l d i s i l a n e , l a (0.99 g, 4.34 mmole), 9

g

0

,

3

m

m

o

9

in

C D C 1

t

0

5

m

l

v

u

m

e

w

a

s

Cr ( a c a c ) ^ ( ° 2 § » 3 .° o l p r e p a r e d and S i NMR d a t a were sampled a t 10 minute i n t e r v a l s . 1 , 1 , 2 , 2 - t e t r a c h l o r o - l , 2 - d i m e t h y l d i s i l a n e was p r e p a r e d by t h e method o f S a k u r a i e t a l . ( 1 7 ) . H e x a m e t h y l d i s i l a z a n e e n r i c h e d t o 99% Ν was p r e p a r e d by a N i - c a t a l y z e d r e a c t i o n o f t r i m e t h y l s i l a n e w i t h 99% e n r i c h e d NH . R e a c t i o n was c a r r i e d o u t in a 5 L f l a s k on a 0

In Inorganic and Organometallic Polymers; Zeldin, Martel, et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1988.

158

INORGANIC AND ORGANOMETALLIC POLYMERS

vacuum l i n e u s i n g 0.67 atm (0.14 mole) Me^SiH (PCR Research C h e m i c a l s , G a i n e s v i l l e , F L ) and 0.33 atm 10.07 mole) NH (Stohler I s o t o p e C h e m i c a l s , Waltham, MA) and 25 g N i powder, 99.9%, 500-600 urn, s p h e r i c a l (Johnson Matthey, I n c . , Seabrook, NH). N i powder was washed w i t h r e a g e n t grade THF and vacuum degassed b e f o r e use. R e a c t i o n c o n d i t i o n s a r e s i m i l a r t o t h a t d e s c r i b e d in ( 1 8 ) . The bottom s e c t i o n o f t h e f l a s k c o n t a i n i n g N i powder was h e a t e d 96 h r s at 170° C. D i s t i l l a t i o n gave 7.1 g (0.044 mole) (Me S i ) NH o f 98% p u r i t y by gc a n a l y s i s . The o n l y i m p u r i t y found was h e x a m e t h y l d i s i l o x a n e . A nmr experiment t o f o l l o w f o r m a t i o n o f p r o d u c t s and l o s s o f r e a c t a n t s was performed j u s t as d e s c r i b e d f o r u n l a b e l e d HMDZ. F o r m a t i o n o f p r o d u c t s and l o s s o f r e a c t a n t s was v i r t u a l l y i d e n t i c a l t o t h a t shown in F i g u r e 5.


2

Results 13 To g a i n i n s i g h t i n t o the polymer s t r u c t u r e , C NMR s p e c t r o s c o p y was performed. From e x a m i n a t i o n o f the b r o a d s i g n a l s in F i g u r e 1 i t c a n be seen t h a t t h i s e x p e r i m e n t a l approach y i e l d s l i t t l e i n f o r m a t i o n . There is l i t t l e a d d i t i o n a l i n f o r m a t i o n o b t a i n e d from e x a m i n a t i o n o f the b r o a d s i g n a l s in a S i NMR spectrum ( F i g u r e 2) o f t h i s polymer, except f o r the o b s e r v a t i o n o f r e s i d u a l Me^SiÇl b y - p r o d u c t a t c a . + 32 ppm and Me^SiNH groups a t c a . +2 ppm. H NMR^hows o n l y Si-CH^ groups. I t was hoped t h a t the b r o a d , f e a t u r e l e s s S i NMR spectrum c o u l d be s i m p l i f i e d by the u s e o f a pure d i s i l a n e s t a r t i n g m a t e r i a l . S i n c e t h e polymer i t s e l f is h i g h l y c r o s s - l i n k e d and the p u r e , s y m m e t r i c a l 1 , 1 , 2 , 2 - t e t r a c h l o r o - l , 2 - d i m e t h y l d i s i l a n e is l i k e l y t o produce a s i m p l e r polymer o f s i m i l a r s t r u c t u r e , i t was chosen f o r d e t a i l e d s t u d y . Polymer p r e p a r e d from the s y m - t e t r a c h l o r o d i s i l a n e e x h i b i t s s i m i l a r p r o p e r t i e s t o t h a t from the m i x t u r e ( I ) o f chlorodisilanes. Indeed, the s y m - t e t r a c h l o r o d i s i l a n e is t h e predominant m o l e c u l a r s p e c i e s in the m i x t u r e o f d i s i l a n e s ( I ) i s e d . The S i NMR spectrum o f the polymer t h a t r e s u l t s from the r e a c t i o n of HMDZ w i t h s y m - t e t r a c h l o r o d i m e t h y l d i s i l a n e ( C ^ M e S i - S i M e C i p , l o o k s v e r y much l i k e t h a t o f polymer p r e p a r e d from the m i x t u r e o f d i c h l o r o s i l a n e s ( F i g u r e 2 ) . There is no o b s e r v a b l e f i n e s t r u c t u r e t h a t would l e a d t o an i n c r e a s e d u n d e r s t a n d i n g o f t h e c h e m i c a l s t r u c t u r e o f t h i s simpler oligomer. 29 The b r o a d , f e a t u r e l e s s n a t u r e o f t h e S i NMR s i g n a l is l i k e l y due t o one o f t h r e e phenomena t h a t a r e well-known t o cause such e f f e c t s in NMR s p e c t r o s c o p y : a m u l t i p l i c i t y o f c h e m i c a l and p h y s i c a l environments about the s i l i c o n atoms; r e s t r i c t e d segmental motj^n in p o l y c y c l i c o r c a g e - l i k e m o l e c u l e s ; o r j-J e b r o a d e n i n g due to S i magnetic i n t e r a c t i o n s w i t h t h e numerous Ν quadrupoles. To o b t a i n i n f o r m a t i o n on the r e a s o n f o r NMR s i g n a l b r o a d e n i n g and i n s i g h t i n t o the c h e m i c a l n a t u r e o f t h e s e p r e - c e r a m i c polymers, attempts were made t o f o l l o w the r e a c t i o n o f t h e s y m - t e t r a c h l o r o d i s i l a n e and HMDZ by S i NMR s p e c t r o s c o p y . From i n s p e c t i o n o f F i g u r e 3, which is t h e S i NMR spectrum o f the r e a c t i o n m i x t u r e a f t e r 10 m i n u t e s , i t is seen t h a t r e a c t i o n is q u i t e r a p i d and t h a t a s i g n i f i c a n t amount o f the t r i m e t h y l s i l a z a n e monoadduct o f s y m - t e t r a c h l o r o d i s i l a n e has formed, a l o n g w i t h M e ^ S i C l b y - p r o d u c t and a s m a l l amount o f the sym-1,2- d i a d d u c t . As r e a c t i o n p r o c e e d s , r a p i d consumption o f s t a r t i n g m a t e r i a l s w i t h r e s u l t a n t n


12.

LIPOWITZ ET AL.


U


CDCI

159

3

Intensity

Π

— ι

Γ

90 p p m

1 40

1

Τ 0

Γ

r -10

C h e m i c a l Shift, δ (ppm)

13 F i g u r e 1. CDC1 .

C NMR Spectrum o f P o l y m e t h y l d i s i l y l a z a n e Polymer in

3

Intensity

30

—ι 10

20

1 c

-10

-20

C h e m i c a l Shift, δ (PPm) 29 F i g u r e 2. S i NMR Spectrum o f P o l y m e t h y l d i s i l y l a z a n e Polymer in CDC1 ; 0.06 M in C r ( a c a c ) 3

3



160


f o r m a t i o n o f monoadduct and d i a d d u c t s p e c i e s is seen. About 40 m i n u t e s a f t e r i n i t i a l m i x i n g , f o r m a t i o n o f the t r i a d d u c t s p e c i e s is o b s e r v e d , which remains as a minor component throughout the c o u r s e o f the r e a c t i o n . A c o m p i l a t i o n o f t h e S i NMR c h e m i c a l s h i f t s o f t h e s e low m o l e c u l a r weight s p e c i e s is shown in T a b l e I . A f t e r 80 minutes i t was o b s e r v e d t h a t the o n l y s i g n i f i c a n t changes were the n e a r - t o t a l consumption o f t h e [ M e C ^ S i ] ^ starting m a t e r i a l and the monoadduct s p e c i e s , a l o n g w i t h i n c r e a s e d d i a d d u c t formation. I n a d d i t i o n , t r i a d d u c t c o n t e n t is a t i t s maximum c o n c e n t r a t i o n , w i t h o n l y s m a l l amounts o f t h i s s t r a i n e d s p e c i e s w i t h [Me«Si] -SiMe- l i n k a g e s formed. From i n s p e c t i o n o f F i g u r e 4, o b t a i n e d a f t e r 10 h o u r s , i t can be seen t h a t , a l o n g w i t h M e ^ S i C l and HMDZ s p e c i e s , a p p r e c i a b l e amounts o f h i g h e r o r d e r o l i g o m e r s w i t h [ = S i N H ] S i M e - t y p e l i n k a g e s a r e formed. These o b s e r v a t i o n s l e a d t o t h e f o l l o w i n g c o n c l u s i o n s r e g a r d i n g the r e a c t i o n scheme o f [ M e C ^ S i L and HMDZ. The i n i t i a l s t e p i n v o l v e s t h e f a s t l i g a n d exchange r e a c t i o n o f HMDZ w i t h [ M e C ^ S i K t o c r e a t e the monoadduct and Me S i C l b y - p r o d u c t . A s i m i l a r f a s t r e a c t i o n o c c u r s a t the o t h e r S i atom t o c r e a t e the s y m m e t r i c a l 1,2-diadduct and a d d i t i o n a l M e ^ S i C l . Steric h i n d r a n c e causes f o r m a t i o n o f two t r i m e t h y l s i l y l a z a n e groups on a s i l i c o n atom t o y i e l d [Me^SiNH] ~SiMe-type s p e c i e s t o be slow. This would account f o r the p r e s e n c e o f o n l y minor amounts o f t r i a d d u c t and t h e f a c t t h a t t h e 1,1-diadduct is n o t o b s e r v e d . The f o r m a t i o n o f h i g h e r o r d e r s p e c i e s than t r i a d d u c t i n v o l v e s s e l f - r e a c t i o n o f monoadduct and d i a d d u c t s p e c i e s as w e l l as r e a c t i o n between t h e s e s p e c i e s t o c r e a t e a m u l t i p l i c i t y o f l i n e a r and c y c l i c s p e c i e s w i t h S i - S i - N H - S i - S i - t y p e l i n k a g e s . No s i n g l e h i g h e r o r d e r s p e c i e s t h a n t r i a d d u c t is formed in s u f f i c i e n t c o n c e n t r a t i o n t o s t a n d out from the m u l t i p l i c i t y o f s p e c i e s p r o d u c e d . The v a l i d i t y o f t h e c o n c l u s i o n r e g a r d i n g the r e a c t i o n scheme can be v e r i f i e d from F i g u r e 5, which p l o t s r e l a t i v e moles o f each s p e c i e s vs time. There is a r a p i d r i s e in monoadduct and d i a d d u c t content i n i t i a l l y . S h o r t l y a f t e r i n i t i a l mixing, a r a p i d decrease in monoadduct w i t h a s i g n i f i c a n t l y s l o w e r d e c l i n e in d i a d d u c t c o n t e n t is seen. T r i a d d u c t is slow t o form and slow t o r e a c t . A r a p i d d e c r e a s e in HMDZ c o n t e n t f o l l o w e d by a g r a d u a l i n c r e a s e in HMDZ is found due t o t h e f o l l o w i n g c o n d e n s a t i o n r e a c t i o n s : 2

2

=Si-NH-SiMe

3

+ Me SiNH-Si= - 2 ^ > =Si-NH-Si= + [ M e ^ i ^ N H 3

(III)

I t is o b s e r v e d t h a t t h e l o n g - t e r m i n c r e a s e in HMDZ is s i g n i f i c a n t l y l e s s t h a n the s h o r t - t e r m d e c r e a s e in t h e i n i t i a l r e a c t i o n p e r i o d . T h i s is s i g n i f i c a n t b e c a u s e , in terms o f the proposed r e a c t i o n scheme ( F i g u r e 6 ) , i t would be d i f f i c u l t t o e n v i s i o n f o r m a t i o n o f p o l y c y c l i c o r c a g e - l i k e s t r u c t u r e s w i t h o u t r e g e n e r a t i o n o f HMDZ t h a t is n e a r l y e q u a l in magnitude t o t h a t o f t h e i n i t i a l consumption o f HMDZ, l o n g b e f o r e l a r g e r m o l e c u l e s o f r e s t r i c t e d segmental m o t i o n a r e p r o d u c e d . However, b r o a d s i g n a l s a r e f o r m i n g as shown by t h e r e d u c t i o n in t o t a l i n t e g r a t e d i n t e n s i t y o f sharp s i g n a l s . No s i l i c o n r e s o n a n c e from a m o l e c u l e w i t h more than 5 S i atoms ( t r i a d d u c t ) can be d i s t i n g u i s h e d from the m u l t i t u d e o f S i environments p r o d u c e d . W i t h t h i s e v i d e n c e , i t would seem t h a t b r o a d


12.

LIPOWITZ ET AL.


161

(Me Si) NH 3

2

Me

CI Me|H]SiNHSiMe3 2

CI

Me Me CI MeSiSiNH[|j]Me CI

Intensity

2

CI M*Si[|i]NHSiMe3 CI 2

3

Me SiCI


3

Me dUNHSiMeaJa CI —Γ 20

-T30

Γ™ 40

"I -20

-10

10 0 C h e m i c a l Shift, Ô (ppm)

29 F i g u r e 3. S i NMR Spectrum o f 10-Minute R e a c t i o n P r o d u c t o f ( M e S i ) NH, 2.5 M, and ( M e C l S i ) 0.87 M, in CDC1 ; 0.06 M in Cr(acac; . 3

2

2 >

3

3

on TABLE I . of

S i NMR C h e m i c a l S h i f t s in t h e R e a c t i o n ( M e S i ) N H and ( M e C l S i ) 3

2

6 (

Starting Materials (Me S i ) NH (MeOl Si) 2

2

2

By-Product Me SiCl

2 9

2

S i ) in ppm R e l a t i v e t o Me^Si 2.24 17.45

30.08

3

Monoadduct 7.48 1.91 21.61

Me„Si NH-ClMeSi,-Si Cl.Me 3 a b c l

(a) (b) (c)

1,2-Diadduct [Me Si -NHClMeSi l 3

a

b

6.60 (a) 2.20 ( b ) *

2

Triadduct [Me„Si NH] -MeSL - S i MeCl-NHSi,Me 3 a 2 b e α 5 0

0

3.42 17.65 3.97 5.65

(a) (b) (c) (d)

* D o u b l e t o b s e r v e d ( c a . 0.1 ppm s e p a r a t i o n ) due t o t h e p r e s e n c e o f e r y t h r o and t h r e o d i a s t e r e o m e r s .



162

x10


Intensity

Γ"

20

30

40

—Γ" -10

10

-30

-20

Chemical Shift, δ (ppm) 29„. F i g u r e 4. S i NMR Spectrum o f 10-Hour R e a c t i o n P r o d u c t o f ( M e S i ) N H and ( M e C l S i ) in CDC1 ; 0.06 M in C r ( a c a c ) . 3

2

2

2

3

3

4η

Me SiCI

3H

3

Total Signal Due to Sharp Lines (x 1/3) Moles

2Η (Me Si) NH 3

(CI MeSi) 2

2

^ - - ^

Monoadduct

1 VI

Ί 2 10

F i g u r e 5.

3

2

4

Ν

tria-Adduct

M II I 5 6 789 100 T i m e (min)

sym-Diadduct = 5

1 2

Γ Γ 3

I M l 11 4

R e a c t i o n o f ( M e S i ) N H and ( M e C l S i ) 3

2

2

2

5 6 7 89 1000

in CDC1 .


3

12.

LIPOWITZ ET AL.


Me Me CISI-SiCI CI CI

163

Me Me RNHSi-SiCI + RCI CI CI

R NH 2

fast

mono-adduct + RCI

fast J R NH 2

Me Me R NH RNHSi-SiNHR slow NH CI R tris-adduct R = Me Si


2

Me Me RNHSi-SiNHR + RCI CI CI 1,2-di-adduct

3

Further reactions include primarily mono- anddi-adduct reactions:

(

linear SiSiNHSiSi cyclic dimers Si—Si—NH

Self-condensations and cross-condensations

dimers

I NH-Si/ and /Si-Si NH NH \ Si-Si' N

F i g u r e 6.

R e a c t i o n Scheme.

s i g n a l s a r e n o t due t o r e s t r i c t e d segmental motiojj in c a g e - l i k e moieties. I n s t e a d , i t would appear t h a t e i t h e r Ν quadrupolar i n t e r a c t i o n s o r p r o d u c t i o n o f numerous S i - N speçies would cause t h i s lack of spectral d e t a i l . S u b s t i t u t i o n o f 99% N - e n r i c h e d HMDZ, w h i c h has no q u a d r u p o l a r n u c l e i , in t h e r e a c t i o n m i x t u r e r e s u l t s in the same s i g n a l b r e a d t h . T h i s i n d i c a t e s t h a t t h e r e a c t i o n o f HMDZ and [MeCl Si]« r e s u l t s in a continuum o f s p e c i e s t h a t ^ g a n n o t be r e s o l v e d By The Ν chemical 5y NMR tteecc hh n i q u e s a t t h e p r e s e n t t i m e . s h i f t s a r e shown in T a b l e I I .

15 N-NMR C h e m i c a l

TABLE I I .

15 Ν Chemical

Compound (Me Si) 3

1 5 2

-351.4

1 5

3

2

-350.3

1 5

(Me S i N H S i C l M e ) (1,2-diadduct)

J

1 5

2

1 5

N H S i C l M e S i M e ( N HSiMe ) (triadduct) a

* ppm r e l a t i v e

Shift*

-358.4

NH

Me Si NHSiClMeSiCl Me (monoadduct)

Me S i

Shifts

b

5

t o CH N0 3

1

-349.2 (a) -352.2 (b) d o u b l e t

2



164 Conclusions


As a r e s u l t o f the above work, the f o l l o w i n g has been a c h i e v e d . A proposed r e a c t i o n scheme f o r f o r m a t i o n o f p o l y m e t h y l d i s y l a z a n e o l i g o m e r , a c e r a m i c p r e c u r s o r , has been d e v e l o p e d , g i v i n g some i n s i g h t i n t o s t r u c t u r a l f e a t u r e s o f t h i s type of r e s i n - l i k e molecule. I n a d d i t i o n , the cause f o r b r o a d f e a t u r e l e s s s i g n a l s in the NMR s p e c t r o s c o p y o f t h e s e polymers has been d e t e r m i n e d t o be the m u l t i p l i c i t y o f environments about the S i atoms w h i c h d e v e l o p e a r l y in t h e r e a c t i o n b e f o r e a p p r e c i a b l e p o l y m e r i z a t i o n o c c u r s . Acknowledgments T h i s work was made p o s s i b l e by s u p p o r t from the D e f e n s e Advanced R e s e a r c h P r o j e c t s Agency (DARPA) and the A i r F o r c e Wright A e r o n a u t i c a l L a b o r a t o r i e s (AFWAL) under C o n t r a c t F33615-83-C-5006 t o Dow C o r n i n g C o r p o r a t i o n . The a u t h o r s g r a t e f u l l y acknowledge t h e encouragement o f t h e C o n t r a c t managers S. Wax (DARPA) and A. K a t z (AFWAL).

Literature Cited 3. Lipowitz, J., Freeman, Η. Α., Chen, R. T., and Prack, E. R. Adv. Ceram. Mater. 1987, 121. 4. Rice, R. W. Am. Ceram. Soc. Bull. 1983, 62, 889. 5. Yajima, S. ibid., 893. 6. West, R., David, L. D., Durovich, P. I., Yu, Η., and Sinclair, R. ibid., 899. 7. Wills, R., Markle, R. Α., and Mukherjee, S. P. ibid., 904. 8. Schilling, Jr., C. L., Wesson, J. P., and Williams, T. C. ibid., 912. 9. Walker, Jr., Β. E., Rice, R. W., Becher, P. F., Bender, Β. Α., and Coblenz, W. S. ibid., 916. 10. Baney, R. H. Division of Industrial and Engineering Chemistry, I. Structural, Electronic and Refractory Ceramics, ACS Symposium on Materials in Emerging Technologies, 1985. 11. K. J. Wynne and R. W. Rice. An. Rev. Mater. Sci. 1984, 14, 297. 12. Mah, T., Mendiratta, M. G., Katz, A. P. and Mazdiyasni, K. S. Am. Ceram. Soc. Bull. 1987, 66, 304. 13. Marshall, D. B. and Ritter, J. E. ibid. 1987, 66, 309. 14. Gaul, Jr., J. H. U.S. Patent 4 340 619, 1982. 15. Baney, R. H. In Ultrastructure Processing of Ceramics, Glasses, and Composites. Ed. Hench, L. L. and Ulrich, D. R. Wiley, J. New York, 1984, Chapter 20.


12. 16.

17. 18.

LIPOWITZ ET AL.


165

Harris, R. K. Kennedy, J. D., McFarlane, W. In NMR and the Periodic Table. Ed. Harris, R. K. and Mann, Β. E., Academic Press, London, 1978, 309-340. Sakurai, H., Watanabe, T. and Kumada, M. J. Organometal. Chem. 1967, 7,15. Kotzsch, H. J., Draese, R., and Vahlensieck, H. J. U.S. Patent 4 115 427, 1978.


RECEIVED September 1, 1987


NMR Characterization of a Polymethyldisilylazane - American

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