Chain-Propagation and Step-Propagation Polymerization - American

Chapter

12

Chain-Propagation and Step-Propagation Polymerization of

Synthesis and Characterization Poly(oxyethylene)-b-poly(pivalolactone)Telechelomer

Downloaded by FUDAN UNIV on February 16, 2017 | http://pubs.acs.org Publication Date: December 22, 1988 | doi: 10.1021/bk-1988-0364.ch012

Κ. B. Wagener and S. Wanigatunga Department of Chemistry and Center for Macromolecular Science and Engineering, University of Florida, Gainesville, FL 32611

Anionic polymerization and polymer modification coupled with step growth polymerization is being used to prepare segmented copolymers containing polyether and polyester segments having narrow molecular weight distributions for each segment. In this method an alkoxide initiator having a masked alcohol group initiates ethylene oxide polymerization. The resulting polyether alkoxide is modified with succinic anhydride to give a carboxylate anion which polymerizes pivalolactone. When the resulting ma croion is hydrolyzed selectively, a telechelomer, poly(oxyethy lene)-b-poly(pivalolactone) containing hydroxy and carboxylic functionalities at its two ends, is formed. Synthesis of the tele chelomer and the reaction intermediates will be discussed. NMR spectra and gel permeation chromatograms will also be presented to show that the products are pure and have narrow molecular weight distributions. T h e f i e l d of m u l t i p h a s e s e g m e n t e d c o p o l y m e r s , a l t h o u g h s o m e 30 y e a r s o l d , r e m a i n s q u i t e a c t i v e ( 1 - 4 ) in p a r t d u e t o t h e p o s s i b i l i t y o f o b t a i n i n g a variety of useful materials ranging f r o m impact resistant plastics to elas t o m e r s (5,6). P o l y ( u r e t h a n e ethers) a n d p a r t i c u l a r l y p o l y ( e s t e r e t h e r s ) lend t h e m s e l v e s to m e l t extrusion such that these p o l y m e r s c a n be shaped easily, an e x t r e m e l y v a l u a b l e f e a t u r e . A s true e l a s t o m e r s , h o w e v e r , these c o p o l y m e r s lack t h e p h y s i c a l p r o p e r t i e s that a r e d e m a n d e d in many a p p l i c a t i o n s , p a r t i c u l a r l y w h e n t h e y a r e m e l t p r o c e s s e d (5). S p e c i f i c a l l y , t h e e l a s t i c p r o p e r t i e s t h a t a r e d e f i c i e n t in m e l t e x t r u d e d s e g m e n t e d c o p o l y mers a r e stress and r e c o v e r y related, like immediate elastic recovery ( o f t e n less t h a n 9 5 % ) , s t r e s s d e c a y ( o f t e n g r e a t e r t h a n 15%) a n d c o m p r e s s i o n s e t ( m o r e t h a n 10%). T h e s e p r o p e r t i e s a r e d i r e c t m a n i f e s t a t i o n s o f t h e i n e f f i c i e n c y o f t h e p h y s i c a l c r o s s l i n k s in t h e c o p o l y m e r , w h i c h in turn a r e a f u n c t i o n o f h o w w e l l t h e p h a s e s e p a r a t i o n i n t h e c o p o l y m e r is a c h i e v e d . Phase mixing - even to a small degree - adversely affects the properties of the c o p o l y m e r s . Phase mixing c a n be attributed partly to the irregularity of the c o p o l y m e r c h a i n . In t h e c a s e o f p o l y ( e s t e r e t h e r ) c o p o l y m e r s s y n t h e s i z e d by normal step p o l y m e r i z a t i o n reactions, the hard segment has a N O T E : This chapter is part II in a scries. 0097-6156/88/0364-0153S06.00/0 © 1988 American Chemical Society

Benham and Kinstle; Chemical Reactions on Polymers ACS Symposium Series; American Chemical Society: Washington, DC, 1988.


154

CHEMICAL REACTIONS ON POLYMERS

p o l y d i s p e r s i t y r a t i o a p p r o a c h i n g 2, a n d t h i s d i s t r i b u t i o n o f c h a i n l e n g t h s w i t h i n t h e h a r d s e g m e n t a d v e r s e l y a f f e c t s p h a s e s e p a r a t i o n (7). Phase m i x i n g is a l s o i n d u c e d by b r o a d d i s t r i b u t i o n s in t h e s o f t s e g m e n t . T h e l o w m o l e c u l a r w e i g h t f r a c t i o n o f e i t h e r t h e h a r d or s o f t s e g m e n t e s p e c i a l l y p r o m o t e p h a s e m i x i n g (7). D r o s c h e r and c o w o r k e r s ' support the h y p o t h e s i s that high r e g u l a r i t y w i t h i n s e g m e n t s , i.e., m o n o d i s p e r s i t y w i t h i n e a c h s e g m e n t , l e a d s t o e n h a n c e d p h a s e s e p a r a t i o n a n d c r y s t a l l i z a t i o n p h e n o m e n a (8). T h e i r i n v e s t i gations involved monodisperse a r o m a t i c poly(ester ether) copolymers s y n t h e s i z e d in a m u l t i s t e p s c h e m e o f n u c l e o p h i l i c s u b s t i t u t i o n r e a c t i o n s ( 8 1 1). Inoue a n d c o w o r k e r s (12) a l s o h a v e p r e p a r e d l o w m o l e c u l a r w e i g h t versions of poly(ester ether) block c o p o l y m e r s having monodisperse segm e n t s using porphyrin c a t a l y s t s . The m o l e c u l a r weights of these p o l y m e r s a r e up t o a b o u t 5 0 0 0 . O u r g o a l is t o s y n t h e s i z e h i g h l y r e g u l a r p o ! y ( e s t e r e t h e r ) s e g m e n t e d c o p o l y m e r s , t o i n v e s t i g a t e t h e i r p h a s e s e p a r a t i o n b e h a v i o r , a n d t o see h o w the phase s e p a r a t i o n b e h a v i o r a f f e c t s m e c h a n i c a l and s u r f a c e p r o p e r t i e s . T h e p o l y m e r s w i l l be s y n t h e s i z e d using a novel s t r a t e g y w h e r e both c h a i n and step p o l y m e r i z a t i o n s are c o m b i n e d into one s c h e m e . The synthetic s c h e m e w a s o u t l i n e d in a p r e v i o u s c o m m u n i c a t i o n (13). When the two segments have narrow m o l e c u l a r weight distributions and when they are i n c o m p a t i b l e , the p o l y m e r s w i l l e x h i b i t good phase separation and the s u r f a c e o f t h e p o l y m e r w i l l b e r i c h e r in t h e s e g m e n t w h i c h h a s a l o w e r s u r f a c e energy. P r o p e r s e l e c t i o n of m o n o m e r s , t h e r e f o r e , w i l l lead to p o l y m e r s h a v i n g c o n t r o l l e d s u r f a c e p r o p e r t i e s s u c h as b i o c o m p a t i b i l i t y , a d h e sion and w e a t h e r i n g . If o n e s e g m e n t is h a r d a n d t h e o t h e r is s o f t , t h e s e g m e n t lengths c o u l d be v a r i e d to o b t a i n t h e r m o p l a s t i c e l a s t o m e r s h a v i n g good mechanical properties. The surface and m e c h a n i c a l p r o p e r t i e s of these c o p o l y m e r s c o u l d then be c o m p a r e d w i t h those of A B A and A B t y p e block copolymers. In t h i s r e s e a r c h w e h a v e s e t o u t t o p r e p a r e a s e r i e s o f h i g h l y r e g u l a r poly(oxyethylene-co-pivalolactone) segmented copolymers. Our strategy i n v o l v e s s y n t h e s i z i n g a h i g h l y r e g u l a r t e l e c h e l o m e r ( A t e l e c h e l o m e r is a high m o l e c u l a r w e i g h t m o n o m e r , that self p o l y m e r i z e s v i a step p o l y m e r i z a t i o n , w h e r e a s a m a c r o m e r is a h i g h m o l e c u l a r w e i g h t m o n o m e r , t h a t s e l f p o l y m e r i z e s by c h a i n p o l y m e r i z a t i o n . ) , then c o n v e r t i n g it to high p o l y m e r . In o r d e r t o o b t a i n n a r r o w m o l e c u l a r w e i g h t d i s t r i b u t i o n s f o r b o t h s e g m e n t s , t h e t e l e c h e l o m e r h a s b e e n p r e p a r e d by a n i o n i c p o l y m e r i z a t i o n ; t h e t e l e c h e l o m e r t h e n c a n b e c o n v e r t e d t o h i g h p o l y m e r by s t e p p o l y m e r i z a t i o n . T h i s p a p e r d i s c u s s e s t h e s y n t h e t i c s t e p s i n v o l v e d up t o t h e p r e p a r a t i o n o f p o l y (oxyethvlene)-bj-Doly(pivalolactone) t e l e c h e l o m e r using anionic p o l y m e r i z a tion. H and N M R s p e c t r a are presented to support the s t r u c t u r e and purity of the t e l e c h e l o m e r and the r e a c t i o n intermediates. G e l p e r m e a t i o n c h r o m a t o g r a m s ( G P C ) a r e also shown to c o n f i r m their p u r i t y and to i n d i cate that narrow molecular weight distributions exist. Experimental Materials. E t h y l e n e O x i d e ( E O ) a n d p i v a l o l a c t o n e ( P V L ) w e r e d r i e d o v e r c a l c i u m h y d r i d e f o r a d a y b e f o r e u s e . E O w a s f u r t h e r d r i e d on a s o d i u m mirror prior to passing into the r e a c t i o n vessel. D r i e d P V L was sealed into a m p u l e s u n d e r h i g h v a c u u m (10 m m Hg). S u c c i n i c anhydride (SA) was d r i e d in a v a c u u m o v e n f o r a d a y a n d s u b l i m e d u n d e r h i g h v a c u u m i n t o a m p u l e s . D r y T H F w a s o b t a i n e d by r e f l u x i n g T H F on N a / K (1:1) a l l o y f o r s i x h o u r s , d i s t i l l i n g o v e r t h e a l l o y a n d d e g a s s i n g u n d e r h i g h v a c u u m in t h e


12.

WAGENER AND WANIGATUNGA


presence dryness.

Chain and Step Propagation

of the Ν α / Κ alloy and benzophenone

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155 for

Synthesis of Masked Poly(oxyethylene)-b-poly(pivalolactone) C o p o l y m e r i c Salt, 4. T h e s y n t h e s i s o f t h e i n i t i a t o r , J_, w a s r e p o r t e d in a p r e v i o u s c o m m u n i c a t i o n (13). F i g u r e 3 shows a t y p i c a l a p p a r a t u s used for t h e synthesis of 4. The reaction vessel " A " contains an ampule with initiator (approxi m a t e l y 0.005 m o l e ) in T H F a n d a n a m p u l e w i t h e x c e s s S A . A c o a r s e f i l t e r F c o n n e c t s f l a s k s " A " a n d " Β " . " B " c o n t a i n s a n a m p u l e o f P V L (2.5 m L , .04 m o l e ) . T h e a p p a r a t u s w a s b r o u g h t t o 10 m m H g . The initiator was added t o t h e r e a c t i o n v e s s e l f o l l o w e d b y T H F (90 m L ) , t h e n s t i r r i n g w a s s t a r t e d a n d E O (5.5 m L , 0 . I l m o l ) w a s d i s t i l l e d o v e r t h e N a m i r r o r t h r o u g h t h e m a i n l i n e , a n d t h e m i x t u r e w a s s t i r r e d a t 2 5 °C u n d e r d r y a r g o n f o r t h r e e days. A m e r c u r y v a l v e w a s used to r e l e a s e any sudden pressure. S A (2.0 gms, .02 mol) w a s s u b l i m e d into the r e a c t i o n flask, " A " , under v a c u u m and the m i x t u r e was stirred for six hours at 2 5 ° C . The flask " A " was then sealed o f f f r o m the v a c u u m line, the contents filtered through F into flask " B " , a n d " B " s e a l e d o f f a t R. P V L w a s t h e n a d d e d a n d t h e m i x t u r e w a s s t i r r e d v i g o r o u s l y for three hours at 2 5 ° C . T h e p r o d u c t w a s p r e c i p i t a t e d in c o l d e t h e r a n d p u r i f i e d t h r i c e by d i s s o l v i n g in m e t h y l e n e c h l o r i d e a n d reprecipitating in c o l d e t h e r . (Elemental analysis, C a l c u l a t e d for C| | 2 | 9 9 ° 5 0 C 56.39, H 8.42; F o u n d : C 56.50, H 8.43). H

K :

Synthesis o f the T e l e c h e l o m e r , 5 . T h e c o p o l y m e r i c s a l t , 4 , ( 2 . 2 8 g m s ) w a s d i s s o l v e d in m e t h y l e n e c h l o r i d e (12.6 m L ) a n d w a s s h a k e n w i t h 3 N H C I (25.6 m L ) in a s e p a r a t o r y f u n n e l f o r 3 0 m i n u t e s . T h e o r g a n i c l a y e r w a s s e p a r a t e d a n d t h e p r o d u c t w a s p r e c i p i t a t e d in c o l d e t h e r . T h e p r o d u c t w a s p u r i f i e d t h r i c e b y d i s s o l v i n g in m e t h y l e n e c h l o r i d e a n d r e p r e c i p i t a t i n g in c o l d ether. ( E l e m e n t a l analysis, C a l c u l a t e d for CiηοΗιΟΟΟΛΟ: C 57.01, Η 8.52; F o u n d : C 56.94, Η 8.62). Instrumentation. 3 0 0 M H z Ή N M R a n d 7 5 M H z C N M R spectra were obtained using N i c o l e t N T - 3 0 0 S p e c t r o m e t e r operating at a f i e l d of 7 t e l s a . 50 M H z ' ^ C N M R w e r e o b t a i n e d using V a r i a n X L - S e r i e s N M R S u perconducting Spectrometer System. A l l spectra were taken at room t e m p e r a t u r e in C D C I 3 . S u f f i c i e n t r e l a x a t i o n t i m e s w e r e g i v e n in t a k i n g Η s p e c t r a so t h a t t h e i n t e g r a t i o n s a r e a c c u r a t e . A Waters G P C System containing a Model 6000A solvent delivery system coupled w i t h a R-401 D i f f e r e n t i a l R e f r a c t o m e r was used to o b t a i n G P C chromatocjrams (solvent: CHoCI^, f l o w r a t e : I m L / m i n , 10 A y s t y r a g e l c o l u m n a t 2 5 C ) . E l e m e n t a l a n a l y s i s of p r o d u c t s w e r e done by A t l a n t i c M i c r o l a b , Inc. ,

3

Results and Discussion F i g u r e I i n d i c a t e s the a p p r o a c h used t o s y n t h e s i z e p o l y ( o x y e t h y l e n e ) - b poly(pivalolactone) telechelomers. A n acetal capped anionic initiator, J j (13) p o l y m e r i z e s e t h y l e n e o x i d e ( E O ) t o g i v e 2j a p o t a s s i u m a l k o x i d e o f a m a s k e d p o l y e t h e r , a n d t h i s " n e w " i n i t i a t o r is t o b e u s e d t o p o l y m e r i z e pivalolactone (PVL). Since potassium alkoxides are strong nucleophiles, they c a n randomly a t t a c k at both the carbonyl carbon and the 3 - m e t h y l e n e c a r b o n in l a c t o n e s , ( F i g u r e 2 ) ; s u c h a r a n d o m a t t a c k w o u l d r e s u l t in a p i v a l o l a c t o n e s e g m e n t c o n t a i n i n g i r r e g u l a r i t i e s . L e n z (15), a n d H a l l (16), a n d B e a m a n (17) h a v e i n v e s t i g a t e d P V L p o l y m e r i z a t i o n a n d h a v e s h o w n t h a t t h e less n u c l e o p h i l i c c a r b o x y l a t e a n i o n is p r e f e r a b l e i n p o l y m e r i z i n g P V L smoothly. The weaker c a r b o x y l a t e anion w i l l attack only at the methylene


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12.



157

c a r b o n a d j a c e n t to o x y g e n and as such the P V L s e g m e n t w i l l be d e v o i d of any d e f e c t s ( F i g u r e 2). C o n s e q u e n t l y , i t b e c a m e n e c e s s a r y f o r us t o convert the alkoxide anion of the masked polyether into a c a r b o x y l a t e anion. A n o t h e r p r o b l e m c a u s e d by a l k o x i d e anions has been r e p o r t e d by Y a m a s h i t a and H a n e (14). T h e y p o l y m e r i z e d P V L using p o l y s t y r e n e c o n taining an a l k o x i d e ion end group and observed that the h o m o p o l y m e r o f p i v a l o l a c t o n e w a s a l s o f o r m e d in a d d i t i o n t o p o l y ( s t y r e n e ) - b - p o l y ( p i v a l o l a c tone) b l o c k c o p o l y m e r . T h e m e c h a n i s m for the f o r m a t i o n o f h o m o p o l y m e r was unclear. A v a r i e t y o f r e a g e n t s c o u l d b e used t o c a r r y o u t s u c h a c o n v e r s i o n (18,19). We chose to r e a c t the a l k o x i d e ion w i t h s u c c i n i c a n h y d r i d e ( S A ) , b e c a u s e the a l k o x i d e ion c o u l d be c o n v e r t e d q u a n t i t a t i v e l y to the c a r b o x y l a t e i o n w h e n e x c e s s o f S A is u s e d , a n d a l s o b e c a u s e no s i d e r e a c t i o n s a r e r e p o r t e d (19). T h e c a r b o x y l a t e a n i o n , 3, thus f o r m e d w a s used t o p o l y merize P V L giving the masked poly(oxyethylene)-b-po!y(pivalolactone) c o p o l y m e r i c s a l t , 4 . T h e s a l t , 4, w a s c o n v e r t e d t o t h e t e l e c h e l o m e r , 5, b y acid hydrolysis. C a n d Ή N M R o f t h e i n i t i a t o r , I, a n d t h e m a s k e d p o l y e t h e r , 2, h a v e b e e n p r e s e n t e d in a p r e v i o u s c o m m u n i c a t i o n ( 1 3 ) . C N M R of the m a s k e d p o l y e t h e r w i t h a s u c c i n i c a n h y d r i d e e n d g r o u p , 2? is s h o w n i n F i g u r e 4, w h i c h is a n a t t a c h e d p r o t o n t e s t ( A P T ) s p e c t r u m w i t h p r i m a r y a n d t e r t i a r y c a r b o n s a p p e a r i n g as u p w a r d signals and s e c o n d a r y and q u a r t e r n a r y c a r b o n s a p p e a r i n g a s d o w n w a r d s i g n a l s . T h r e e u p w a r d s i g n a l s a t 15.3, 19.3 and 99.5 p p m a r e due to two m e t h y l carbons " a " and " b " and the m e t h i n e c a r b o n " g " c o m i n g f r o m t h e i n i t i a t o r , J_. D o w n w a r d s i g n a l s a t 2 2 . 5 , 2 9 . 5 , and 60.5-65.2 p p m a r e due to " c " , " d " and " e " carbons which also c o m e f r o m t h e i n i t i a t o r , _L T h e m a j o r d o w n w a r d s i g n a l a t 6 9 . 9 p p m is a s s i g n e d t o t h e ethylene oxide repeat units; the small signals surrounding the major signal is a s s i g n e d t o t h e e n d e t h y l e n e o x i d e u n i t s ( 2 0 ) . T h e s e s i g n a l s w e r e p r e s e n t in t h e C N M R s p e c t r u m o f t h e m a s k e d p o l y e t h e r , 2_ ( 1 3 ) . T h e i n c o r p o r a t i o n o f t h e s u c c i n i c a c i d e n d g r o u p is c l e a r l y s e e n b y t h e n e w s i g n a l s " r " a n d " s " a p p e a r i n g a t 173.2 a n d 176.1 p p m . A n e w s e t o f d o w n w a r d signals also appear b e t w e e n 30.2-30.6 p p m ; these are assigned to the methylene carbons " i " of the succinic acid moiety. T h e Ή N M R o f t h i s c a r b o x y l a t e c a p p e d p r e p o l y m e r 3 , ( F i g u r e 5) c o n f i r m the carbon assignments. The " a " , "b", "c", " d " and " g " protons of t h e i n i t i a t o r a r e c e n t e r e d a r o u n d 1.2, 1.3, 1.4, 1.6 a n d 4.6 p p m r e s p e c t i v e l y as a t r i p l e t , d o u b l e t , m u l t i p l e t , and a q u a r t e t . T h e e t h y l e n e o x i d e r e p e a t u n i t s g i v e a m a j o r s i g n a l a t 3.71 p p m . T h e t w o m e t h y l e n e h y d r o g e n s " i " o f t h e s u c c i n i c a c i d m o e i t y o c c u r a t 2.6 p p m . T h e r a t i o o f " i " p r o t o n s t o " g " p r o t o n in t h e s p e c t r a is 2 , s h o w i n g t h a t t h e f u n c t i o n a l i z a t i o n o f t h e m a s k e d p o l y e t h e r b y s u c c i n i c a n h y d r i d e is q u a n t i t a t i v e . T h e s i g n a l a t 4.2 p p m is due to t h e " j " m e t h y l e n e p r o t o n s t h a t b e c a m e d i f f e r e n t f r o m "(h )" m e t h y lene p r o t o n s due to the i n c o r p o r a t i o n o f the s u c c i n i c a c i d m o e i t y . P r o t o n s "(h )" a n d "(h )" o f t h e end e t h y l e n e o x i d e u n i t s g i v e signals c l o s e t o t h e m a j o r s i g n a l a t 3.7 p p m ( 2 0 ) . T h e b r o a d s i g n a l a t 5.4 p p m is d u e t o t h e p r e s e n c e o f s o m e m o i s t u r e in t h e s a m p l e w h i c h is v e r y h y g r o s c o p i c . T h i s c a r b o x y l a t e d c a p p e d p r e p o l y m e r , 2? w h i c h a c t s a s a n e w i n i t i a tor smoothly p o l y m e r i z e s pivalolactone giving poly(oxyethylene)-b-poly(piv a l o l a c t o n e ) c o p o l y m e r i c s a l t , 4 . ' ^ C A P T N M R s p e c t r u m o f ^ ( F i g u r e 6) shows the presence of a l l the signals of the C A P T N M R o f 3_ p l u s a number of signals c o m i n g f r o m the newly incorporated P V L units. The new signals " I " and "k" appearing at 42.9 and 23.0 p p m are due to methylene and m e t h y l c a r b o n s . A l s o t h e t w o n e w s i g n a l s " t " a n d " u " a p p e a r i n g a t 174.1 a n d 178.2 p p m a r e d u e t o c a r b o n y l c a r b o n s o f p i v a l o l a c t o n e u n i t s a n d t h e ,

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ι—ι—ι—I—I—I—I—J—I—I—ι—I—J—I— 100 50 0 PPM

F i g u r e 4. 75 M H z C N M R spectrum of the masked polyether with suc c i n i c a c i d e n d g r o u p , 3> u s i n g a t t a c h e d p r o t o n t e s t s e q u e n c e ( C H , C H o , P o s . ; C H , C, neg.) in C D C I 3 a t 25°C. l

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F i g u r e 6. 50 M H z C N M R s p e c t r u m of the masked poly(oxyethylene)b - p o l y ( p i v a l o l a c t o n e ) c o p o l y m e r i c s a l t , 4, u s i n g a t t a c h e d p r o t o n t e s t s e q u e n c e ( C H , C H 3 , P o s . ; C H , C , neg.) in C D C I 3 a t 2 5 ° C . ,

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|b jg | t ' t * rM t' J i f Î 3 )-, CH CH-0-CH CH CH CH CH -0-CH CH D- (CH CH 0î pH CH 0 - C- (CH^C-O-JCH- 0- COO j e c i \ CH > CHXH-0 1* 'k i I α e d

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CH, II II / I \ I HO - C H 2 C H C H C H C H 2 - 0 -( CHgCHjO),,- C - ( C H fe- Ç - 0 - ^ C H - Ç - COOJ^jCHg- Ç - C 0 0 H 3

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CH, 0 0 II II H 0 - C H 2 C H C H C H C H - 0 - C H C H 0 - ( C H C H 0).-^H CH 0-C-(CH )-C-0-[CH C-C00-] 2

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163

e n d c a r b o x y l a t e a n i o n , r e s p e c t i v e l y . Ή N M R s p e c t r u m ( F i g u r e 7) c o n f i r m s t h e i n c o r p o r a t i o n o f P V L i n t o 3_ w h i l e f o r m i n g 4 . T h e o n l y d i f f e r e n c e s b e t w e e n t h e p r o t o n s p e c t r a o f 3^ a n d k_ a r e t h e n e w s i g n a l s " k " a n d " I " a p p e a r i n g a t 1.2 a n d 4 . 6 p p m in t h e s p e c t r a o f 4 j t h e s e a r e a s s i g n e d t o t h e m e t h y l e n e and m e t h y l p r o t o n s of the p i v a l o l a c t o n e units in 4. T h e c o n v e r s i o n o f t h e s a l t , 4, t o t h e t e l e c h e l o m e r , 5, w a s d o n e u s i n g aqueous H C I (3M) under homogeneous conditions. H e r e the polymer d i s s o l v e d in m e t h y l e n e c h l o r i d e w a s s h a k e n w i t h a q u e o u s H C I ( 3 M ) f o r 3 0 m i n u t e s . T h i s p r o c e s s s h o u l d r e m o v e t h e a c e t a l m a s k , a n d t h i s is w h a t is o b s e r v e d in t h e C A P T N M R s p e c t r a o f 5_ ( F i g u r e 8 ) . T h e s i g n a l s " g " , " a " a n d " b " c o m i n g f r o m t h e a c e t a l g r o u p a r e a b s e n t h e r e . It is a l s o i n t e r e s t i n g t o n o t e t h e c h a n g e s in " e " s i g n a l s . In 4 , t h r e e " e " s i g n a l s w e r e p r e s e n t a t 6 5 . 1 , 6 3 . 8 a n d 6 0 . 6 p p m . In s t r u c t u r e 5, h o w e v e r , o n l y t w o s i g n a l s a r e s e e n in t h i s r e g i o n , o n e a t 6 3 . 6 p p m a n d t h e o t h e r a t 6 2 . 3 p p m . T h e s i g n a l a t 65.1 p p m h a s d i s a p p e a r e d a n d t h e s i g n a l a t 6 0 . 6 p p m h a s m o v e d t o 6 2 . 3 p p m a s a r e s u l t o f h y d r o l y s i s . O n t h i s b a s i s , t h e s i g n a l a t 6 2 . 3 p p m is a s s i g n e d t o t h e e n d a l c o h o l c a r b o n i n t h e t e l e c h e l o m e r . P r o t o n N M R o f 5> ( F i g u r e 9) c o n f i r m s t h e loss o f a c e t a l m a s k ; h e r e t h e q u a r t e t a t 4.7 p p m a n d t h e d o u b l e t a t 1.3 p p m c o r r e s p o n d i n g t o t h e " g " a n d " b " p r o t o n s h a v e d i s a p p e a r e d . T h e loss o f " a " p r o t o n s c o u l d n o t b e s e e n d u e t o t h e l a r g e " k " s i g n a l a t 1.2 p p m . T h e p o s s i b i l i t y e x i s t s t h a t t h e a c i d u s e d in h y d r o l y s i s c o u l d c a t a l y z e t h e h y d r o l y s i s o f t h e s u c c i n i c ester, xjroup in t h e m i d d l e o f t h e t e l e c h e l o m e r itself. Even though N M R ( Ή and '^C) cannot easily e l i m i n a t e this possibi lity, w e have evidence that such a hydrolysis did not take place. F o r i n s t a n c e , h y d r o l y s i s s h o u l d r e s u l t in t h e f o r m a t i o n o f p o l y ( p i v a l o l a c t o n e ) w h i c h is i n s o l u b l e b o t h in m e t h y l e n e c h l o r i d e a n d w a t e r , b u t n o i n s o l u b l e s were evident. A l s o , the G e l P e r m e a t i o n C h r o m a t o g r a m s do not show i m p u r i t i e s in t h e p r o d u c t . G e l P e r m e a t i o n C h r o m a t o g r a m s of the t e l e c h e l o m e r and the inter m e d i a t e s a r e s h o w n in F i g u r e 10. T h e n u m b e r a v e r a g e m o l e c u l a r w e i g h t s ( M ) w e r e d e t e r m i n e d by H NMR. S u f f i c i e n t l y large relaxation times w e r e u s e d in o b t a i n i n g s p e c t r a so t h a t i n t e g r a t i o n s a r e r e a s o n a b l y a c c u r ate. The molecular weight distributions of the polystyrene and poly(oxye t h y l e n e ) s t a n d a r d s a r e 1.06 a n d 1.07 r e s p e c t i v e l y . S o m e a b s o r p t i v e e f f e c t i v e e f f e c t s a r e s e e n in t h e p o l y m e r s i n c l u d i n g t h e p o l y o x y e t h y l e n e s t a n d ard; but they show narrow m o l e c u l a r w e i g h t distributions. T h e t e l e c h e l o m e r h a s a c a r b o x y l i c a c i d e n d g r o u p in a d d i t i o n t o t h e a l c o h o l e n d g r o u p and t h e r e f o r e the a b s o r p t i v e e f f e c t s a r e more e v i d e n t . B a s e d on the a t o m ic r a t i o s o b t a i n e d f r o m N M R , p e r c e n t a t o m i c r a t i o s w e r e c a l c u l a t e d . These values agree w i t h those obtained f r o m e l e m e n t a l analysis. Our f u t u r e work includes the synthesis of highly regular segmented c o p o l y m e r s v i a step p o l y m e r i z a t i o n o f the t e l e c h e l o m e r and investigating their structure-property relationships. ,



J

p

A c k n o w iedq men ts We would like to thank A r m y R e s e a r c h O f f i c e for its f i n a n c i a l support. We also thank D r . T. E. H o g e n - E s c h for helpful suggestions and D r . H . E. H a l l f o r s e n d i n g us a p i v a l o l a c t o n e s a m p l e .

Literature Cited ( 1) Cooper, S. L.; Miller, J. Α.; Lin, S. E.; Hwang, Κ. K. S.; Wu, K. S.; Gibson, P. E. Macromolecules, 1985, 18, 32.


CHEMICAL REACTIONS O N POLYMERS


164

( 2) McGrath, J. E.; Sheridan, M. M.; Hoover, J. M.; Ward, T. C. Polymer Preprints, 1985, 26(1), 186. ( 3) Franta, E.; Reibel, L. Polymer Preprints, 1985, 26(1), 55. ( 4) Ogata, S.; Kakimoto, M.; Imai, Y. Macromolecules, 1985, 18, 851. ( 5) Wolfe, J., Jr. Polymer Preprints, 1978,19(1),5. ( 6) Wolfe, J., Jr. Rubber Chem. Technol. 1977, 50(1), 230. ( 7) Wegner, G.; Fujii, T.; Meyer, W. H.; Lieser, G. Angew. Makromol. Chem., 1978, 74, 295. ( 8) Droescher, M.; Bandara, U.; Schmidt, F. Macromol. Chem. Phys. Suppl., 1984,7,107. ( 9) Droescher, M.; Schmidt, F. Makromol. Chem., 1983,184,2669. (10) Droescher, M.; Hasslin, H. Makromol. Chem., 1980,181,301. (11) Droescher, M.; Bill, R.; Wegner, G. Makromol. Chem., 1981, 182, 1033. (12) Inoue, S.; Yasuda, T.; Aida, T. Macromolecules, 1984,17,2217. (13) Wagener, K. B.; Wanigatunga, S. Polymer Preprints, 1986, 27(1), 105. (14) (15) (16) (17) (18) (19) (20)

Yamashita, Y.; Hane, T. J. Polym. Sci. Chem. Ed., 1973,11,425434. Lenz, R.; Bigdelli, E. Macromolecules, 1978,11,493. Hall, H. Macromolecules, 1969,2, 488. Wilson, D. R.; Beaman, R. G. J. Polym. Sci., A-1, 1970, 8, 2161. Young, R. N.; Quirk, R. P.; Fetters, L. J. Adv. Polym. Sci., 1984,56,70. Harris, J. M. Macromol. Chem. Phys. Rev., 1985, C25(3), 341-345. Hashimoto, K.; Sumitomo, H.; Yamanori, H. Polymer J., 1985, 17(5), 682.

RECEIVED August

27, 1987


Chain-Propagation and Step-Propagation Polymerization - American

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