Sodium-Initiated Polymerization of Alpha- Methylstyrene in the Vicinity of Its Reported Ceiling Temperature

Western Michigan University ScholarWorks at WMU Dissertations Graduate College 8-1976 Sodium-Initiated Polymerization of Alpha- Methylstyrene in the Vicinity of Its Reported Ceiling Temperature Shuenn-long Ou Western Michigan University Follow this and additional works at: http://scholarworks.wmich.edu/dissertations Part of the Polymer Science Commons Recommended Citation Ou, Shuenn-long, "Sodium-Initiated Polymerization of Alpha-Methylstyrene in the Vicinity of Its Reported Ceiling Temperature" (1976). Dissertations. 2806. http://scholarworks.wmich.edu/dissertations/2806 This Dissertation-Open Access is brought to you for free and open access by the Graduate College at ScholarWorks at WMU. It has been accepted for inclusion in Dissertations by an authorized administrator of ScholarWorks at WMU. For more information, please contact maira.bundza@wmich.edu.

SODIUM-INITIATED POLYMERIZATION OP ALPHA-METHYLSTYRENE IN THE VICINITY OP ITS REPORTED CEILING TEMPERATURE by S h u e n n -lo n g Ou A D i s s e r t a t i o n S u b m itte d t o t h e F a c u l ty o f The G ra d u a te C o lle g e i n p a r t i a l f u l f i l l m e n t o f th e D eg ree o f D o c to r o f P h ilo s o p h y W e ste rn M ic h ig a n U n i v e r s i t y K alam azoo, M ic h ig a n A ugust 1976

ACKNOWLEDGEMENT An e x p r e s s io n o f g r a t i t u d e i s e x te n d e d t o P r o f e s s o r G. G. Low ry f o r h i s c o m p e te n t a d v ic e and u n d e r s ta n d in g d u r in g t h i s r e s e a r c h. I am a l s o v e r y th a n k f u l t o P r o f e s s o r s T. H o u se r, D. C. B e rn d t and G. B. T r i m i t s i s f o r t h e i r h e lp and a d v ic e. T hanks a l s o a re g iv e n t o D rs. J. M. K a n a m u e lle r and D. W. Cooke f o r t h e i r g e n e ro u s a s s i s t a n c e and g u id a n c e. The a u th o r i s g r a t e f u l t o th e D e p a rtm e n t o f C h e m is try f o r i t s f i n a n c i a l s u p p o r t th r o u g h T e a c h in g A s s i s t a n t s h i p s and R e s e a rc h A s s o c i a t e s h i p s. I am in d e b te d t o my w if e, S u e -h u a, f o r s u b s t a n t i a l a i d i n t y p i n g th e m a n u s c r ip t and f o r h e r m o ra l s u p p o r t. S h u e n n -lo n g Ou i i

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7 6-2 8,0 9 8 OU, S h u e n n -lo n g, 1944- SODIUM- INITIATED POLYMERIZATION OF ALPHA-METHYLSTYRENE IN THE VICINITY OF ITS REPORTED CEILING TEMPERATURE. W e ste rn M ich ig an U n i v e r s i t y, P h.d., 1976 C h e m is try, g e n e r a l Xerox University Microfilms, Ann Arbor, Michigan 48106

TABLE OP CONTENTS PAGE INTRODUCTION... 1 HISTORICAL BACKGROUND AND THEORY... 4 EXPERIMENTAL PROCEDURE... 13 S y n th e s is o f O lig o m e rs... 13 M a t e r i a l s... P ro c e d u re... S in g le - S t a g e R e a c t i o n... 15 T w o -S tag e R e a c tio n... 20 A n a l y t i c a l C h ro m a to g ra p h y... 21 G el P e r m e a tio n C h ro m a to g rap h y... 21 F i l t e r s... 25 C olum ns and F i t t i n g s... 25 Column P a c k i n g... 2? A n a l y t i c a l P r o c e d u r e... 31 Q u a n t i t a t i v e M e asu rem e n ts... 32 T h in L a y e r C h ro m a to g ra p h y... 32 P r e p a r a t i v e C h ro m a to g ra p h y... 36 G el P e r m e a tio n C h ro m a to g rap h y... 36 Colum n A d s o r p tio n C h ro m a to g rap h y... 36 C h a r a c t e r i z a t i o n o f O lig o m e rs... 37 E le m e n ta l A n a ly s is... 37 M ass S p e c tro m e try... 37 i i i

TABLE OP CONTENTS (CONTINUED) PAGE I n f r a r e d S p e c tro m e try... 38 N u c le a r M a g n e tic R e s o n a n c e S p e c tro m e try (NMR). 39 DISCUSSION... 44 P r o d u c t D i s t r i b u t i o n... 44 C hrom atogram P eak A s s ig n m e n ts... 44- Q uant i t a t iv e R e s u l t s O b ta in e d fro m C hrom atogram s... 55 C a l i b r a t i o n o f P e a k A re a s... 55 Monomer C o n c e n tr a tio n... 57 E q u ilib r iu m C o n s ta n t s... 62 I n i t i a t o r E f f i c i e n c y... 64 O lig o m er C h a r a c t e r i z a t i o n... 73 O lig o m er F o rm a tio n... 79 P ro p o se d C h a in T r a n s f e r M e c h a n is m... 79 C o m p ariso n w ith P r e v io u s Work... 81 C om peting R e a c tio n s... 82 A d d iti o n a l Q u a n t i t a t i v e C o n s id e r a tio n s....... 83 SUMMARY AND RECOMMENDATIONS... 86 APPENDICES... 88 A. The A mounts o f S t a r t i n g M a t e r i a l s U sed f o r th e S y n th e s is o f < j -M e th y lsty re n e O lig o m er S am p les i n T e tr a h y d r o f u r a n S o l u t i o n and T h e ir F i n a l V olum es a f t e r T e r m in a tin g th e R e a c tio n s w ith E th a n o l... 88 B. G el P e rm e a tio n C h ro m a to g ra p h ic R e t e n tio n T im es o f O lig o m e rs R e l a t i v e t o t h a t o f Monomer.... 91 i v

TABLE OP CONTENTS (CONTINUED) PAGE C. M easu red A re a s o f G el P e rm e a tio n C hrom atogram P e a k s < o D. P a r t i a l M ass S p e c t r a D a ta f o r t h e O lig o m er B o f o -M ethylstyrene» m /e V alues down to 27.. E. P. P a r t i a l M ass S p e c t r a D a ta f o r t h e O lig o m er C o f oc -M ethylstyrene : m /e V alues down to 27.. P a r t i a l M ass S p e c t r a D a ta f o r t h e O lig o m er D o f o ( - M e th y ls ty r e n e : m /e V a lu e s down t o 27 9^ 97 99 102 105 V

LIST OP TABLES TABLE PAGE I E f f e c t o f I n i t i a l C o n c e n tr a tio n s o f I n i t i a t o r and Monomer on D egree o f P o ly m e r iz a tio n o f o -M e th y lsty re n e I n i t i a t e d by Sodium N a p h th a le n e a t 0 C... I I C o n d itio n s f o r th e S y n th e s is o f o (-M e th y l- s ty r e n e O lig o m e rs..... I I I IV V VI V II P h y s i c a l C h a r a c t e r i s t i c s o f P a c k in g M a t e r i a l s U sed i n A n a l y t i c a l G el P e rm e a tio n C h ro m a to g ra p h... R - V a lu e s o fc ^ -M e th y ls ty r e n e O lig o m e rs i n T n in L a y e r C h ro m ato g rap h y on S i l i c a G el 60 F -2 5 4 U sin g Vfo T e tr a h y d r o f u r a n i n P e tr o le u m E th e r ( b. p. 6 0-1 1 0 )... I n f r a r e d S p e c t r a o f th e D im er and T rim e r o f C ^ -M e th y ls ty re n e... E ig h t- P e a k s In d e x o f M ass S p e c t r a o f 0 (-M e th y ls ty re n e D im er Com pared w ith T h a t o f O lig o m er B... E ig h t- P e a k s In d e x o f M ass S p e c t r a o f T rim e r and T e tra m e r o f o -M e th y lsty re n e C om pared w ith T hose o f O lig o m e rs C and D... V I I I NMR A b s o r p tio n P e a k s o f o -M e th y ls ty re n e D im er and T rim e r Com pared w ith T hose o f O lig o m e rs B and C..... IX X XI R e l a t i v e R e t e n ti o n Tim es o f C hrom atogram P e a k s... U V -D e te c to r C a l i b r a t i o n D iv is o r s f o r d-meth y 1 s ty r e n e and O lig o m ers B th r o u g h G... The P r o d u c t D i s t r i b u t i o n o f Monomer and O lig o m e rs..... 12 16 27 35 4-8 50 51 53 56 58 v i

LIST OP TABLES (CONTINUED) TABLE PAGE X II A p p a re n t V a lu e s o f D P -D ependent E q u ilib r iu m C o n s ta n ts D e f in e d by E q u a tio n 19... 63 X I I I The I n i t i a t o r E f f i c i e n c y and M a t e r i a l B a la n c e 70 XIV R a t i o s o f R e l a t i v e A bundance f o r F ra g m e n ts w ith m /e V a lu e s o f 105 and 118 i n th e M ass S p e c t r a o f O l i g o m e r s... 78 v i i

LIST OP FIGURES FIGURE PAGE 1 A p p a ra tu s U sed f o r D i s t i l l i n g S o lv e n t and Monomer and T r a n s f e r r i n g S o lv e n t and Monomer i n t o S to r a g e A m poules... 1^ 2 R e a c tio n D e v ic e U sed f o r th e P r e p a r a t i o n o f P o ly m e r............. 19 3 A l t e r n a t i v e A p p a ra tu s U sed f o r P r e p a r i n g t h e O lig o m e rs o f o d -M e th y ls ty re n e... 20 k L iq u id C h ro m a to g rap h Flow D iagram.......... 22 5 U l t r a v i o l e t A b s o rp tio n D e te c to r C o n n e c tio n s. 23 6 A T y p ic a l Chrom atogram o f Sample 4-5-01 as O b ta in e d w ith t h e M odel 1250 L iq u id C h ro m a to g ra p h... 24-7 Colum n T e r m in a to r f o r GPC Colum ns... 26 8 A p p a ra tu s f o r S l u r r y P a c k in g L iq u id C h ro m a to g ra p h ic Column... 28 9 S p e c i a l U n io n f o r J o i n i n g E x te n s io n t o Column 29 10 S c h e m a tic D iagram o f GPC Column C o n n e c tio n s. 30 11 The GPC D e te c to r C a l i b r a t i o n C urve o f Monomer 33 12 The GPC D e te c to r C a l i b r a t i o n C u rv es o f O lig o m e rs B, C, and D... Jk 13 The I n f r a r e d S p e c tru m o f o C -M e th y lsty re n e O lig o m e r B... 4-0 14- The I n f r a r e d S p e c tru m o f o (-M e th y ls ty r e n e O lig o m er C... 4-1 15 The NMR S p e c tru m o f O lig o m er B... 4-2 16 The NMR S p e c tru m o f O lig o m er C... 4-3 v i i i

LIST OF FIGURES (CONTINUED) FIGURE PAGE 17 E q u ilib r iu m Monomer C o n c e n tr a tio n a s a F u n c tio n o f T e m p e ra tu re o f P o ly m e r iz a tio n.. 61 18 P l o t o f I n K2 - vs R e c ip r o c a l R e a c tio n 19 P l o t o f I n K-ji v s R e c ip r o c a l R e a c tio n fporrmoi* 66 20 P l o t o f I n Kk - v s R e c ip r o c a l R e a c tio n rpprrmpt*fi*hvit»ps. 67 21 P l o t o f I n IC g vs R e c ip r o c a l R e a c tio n ft'omnoy' Q+IIT'DS'^....4.>4iaaaaaaaaaaa 68 22 A verag e C a l c u la te d I n i t i a t o r E f f i c i e n c y as a F u n c tio n o f R e a c tio n T e m p e ra tu re..... 72 23 P o s s ib l e M ass S p e c tru m F r a g m e n ta tio n P a t t e r n f o r S t r u c t u r e X... 77 65 i x

INTRODUCTION F o r any a d d i t i o n p o ly m e r iz a tio n p r o c e s s t h e r e e x i s t s a p r o p a g a t io n s t e p. We may w r i t e t h i s r e a c t i o n s c h e m a ti c a ll y as M + Mn ----- -2 * Mn+ 1 ( 1 ) * i n w h ich M d e n o te s monomer and Mn i s an a c t i v e g ro w in g p o ly m e r m o le c u le c o n t a in i n g n m onom er u n i t s. From th e p r i n c i p l e o f m ic r o s c o p ic r e v e r s i b i l i t y, i t i s e v i d e n t t h a t a r e v e r s e r e a c t i o n, c a l l e d th e d e p r o p a g a tio n r e a c t i o n, s h o u ld a l s o e x i s t s M* + M (2) The d e p r o p a g a tio n r e a c t i o n s t e p i s s lo w a t low te m p e r a t u r e. H ow ever, a s th e c e i l i n g te m p e r a tu r e i s ap p ro a c h e d th e r a t e o f d e p r o p a g a tio n i n c r e a s e s f a s t e r th a n th e r a t e o f p r o p a g a t io n. The c e i l i n g te m p e r a tu r e i s t h e te m p e r a t u r e a t w h ich th e r a t e o f p r o p a g a t io n e q u a ls th e r a t e o f d e p r o p a g a tio n. I n o t h e r w o rd s, th e c e i l i n g te m p e r a t u r e i s t h e te m p e r a tu r e a t w h ich p o ly m e r i s i n e q u i l i b r i u m w ith monomer o f a g iv e n c o n c e n t r a t i o n. S zw arc * s u g g e s te d t h a t i n t h e a b s e n c e o f a i r o r m o i s t u r e, no t e r m i n a t i o n o r t r a n s f e r r e a c t i o n s o c c u r i n a num ber o f a n io n ic p o ly m e r iz a tio n s y s te m s, and th e 1

p o ly m e r ic m o le c u le s l i v e f o r an i n d e f i n i t e p e r i o d o f ti m e. S uch a s y ste m s h o u ld be u s e f u l f o r s tu d y in g 2 p o ly m e r iz a tio n - d e p o ly m e r iz a t io n e q u i l i b r i a. A monomer t h a t seem ed t o s a t i s f y t h e s e c o n d i t i o n s i s o 6 -m e th y ls ty re n e ( 2 - p h e n y l p r o p e n e ), w h ich a p p a r e n tly d o e s n o t p o ly m e riz e above 6 i C 2 ^. B ec a u se o f t h i s low c e i l i n g te m p e r a t u r e, e ( - m e th y ls ty re n e s h o u ld be a good m onom er f o r s tu d y in g e q u i lib r i u m p o ly m e r iz a tio n i n s o l u t i o n. D a in to n and I v i n Il d e s c r i b e d how th e h e a t o f p o ly m e r iz a tio n (AHp ) c o u ld be d e te rm in e d by m e a s u rin g th e e q u i lib r i u m c o n c e n t r a t i o n o f monomer a t v a r i o u s te m p e r a t u r e s a p p ro a c h in g th e c e i l i n g te m p e r a t u r e. R o b e rts and J e s s u p ^ m e a su re d t h e h e a t o f c o m b u stio n f o r f o u r f r a c t i o n s o f p o ly m e r o f o C - m e th y ls ty re n e 311(1 fo u n d t h a t t h e h e a t o f p o ly m e r iz a tio n d e c re a s e d as m o le c u la r w e ig h t i n c r e a s e d, b u t J o s h i and Z w o lin s k i ^ h av e q u e s ti o n e d th e m o le c u la r w e ig h t d e p e n d e n c e o f th e h e a t o f p o l y m e r iz a tio n. When one d is c u s s e s t h e m o le c u la r w e ig h t o f a p o ly m e r, one i s a c t u a l l y d e a l i n g w ith i t s a v e ra g e m o le c u la r w e ig h t. M ost p o ly m e rs a r e d i f f e r e n t fro m s m a l l - s i z e d com pounds i n t h a t th e y a re p o l y d i s p e r s e o r h e te r o g e n e o u s i n m o le c u la r w e ig h t. The r e a s o n f o r t h e i r p o l y d i s p e r s i t y l i e s i n th e s t a t i s t i c a l v a r i a t i o n s p r e s e n t i n t h e p o ly m e r iz a tio n p r o c e s s. I n th e e x p e rim e n ta l w ork r e p o r t e d i n t h i s

d i s s e r t a t i o n, i t w as o r i g i n a l l y p la n n e d t o s y n t h e s i z e 3 o lig o m e rs o f $ (-m e th y ls ty re n e a t te m p e r a t u r e s n e a r i t s r e p o r t e d c e i l i n g te m p e r a tu r e and t o d e te rm in e t h e i n d i v i d u a l e q u i lib r i u m c o n s t a n t s f o r t h e c o n s e c u t iv e s t e p s o f t h e p o ly m e r iz a tio n p r o c e s s. H o p e fu lly i t m ig h t c l a r i f y t h e q u e s t i o n o f w h e th e r t h e h e a t o f p o ly m e r iz a tio n i s D P -d e p e n d e n t o r n o t. ("DP" i s a s ta n d a r d n o t a t i o n i n p o ly m e r s c ie n c e w h ic h m eans d e g re e o f p o l y m e r iz a tio n, o r th e num ber o f monomer u n i t s a t ta c h e d t o g e t h e r i n th e p o ly m e r m o le c u l e.) U n f o r t u n a t e l y, i t was n o t p o s s i b l e t o o b t a i n th e d e s i r e d in f o r m a tio n b e c a u s e th e p o ly m e r iz a tio n o f o (-m e th y ls ty r e n e i n i t i a t e d by sodium m e ta l i s n o t as s im p le a s y s te m as h ad b e e n th o u g h t. From t h e e x p e r i m e n t a l r e s u l t s r e p o r t e d h e r e, we p ro p o s e t h a t t h i s ty p e o f p o ly m e r iz a tio n in v o lv e s c h a in t r a n s f e r r e a c t i o n s. B ec au se o f th e c h a in t r a n s f e r r e a c t i o n s in v o l v e d, t h i s ty p e o f p o ly m e r iz a tio n i s n o t an e q u i lib r i u m s y s te m. I n o r d e r t o v e r i f y th e p o ly m e r iz a tio n m ech an ism, v a r i o u s s p e c t r o s c o p i c m e th o d s w ere u s e d t o s tu d y th e s t r u c t u r e s o f p u re d im e r, t r i m e r, and t e t r a m e r w h ic h w ere s e p a r a t e d fro m a sam p le o f e ( - m e th y ls ty r e n e o lig o m e r s.

1* HISTORICAL BACKGROUND AND THEORY I t h a s b e e n r e p o r t e d ^ t h a t among v i n y l m o n o m ers, u n s u b s t i t u t e d e t h y le n e h a s a b o u t th e h i g h e s t ( - 2 5.9 k c a l / m o le ), and o (-m e th y ls ty re n e a b o u t th e lo w e s t ( - 8. 8 k c a l / m o le ), h e a t o f p o ly m e r iz a tio n. D i s u b s t i t u t i o n on t h e same v i n y l c a rb o n atom i s a common c a u s e o f s t e r i c i n t e r f e r e n c e, 8 r e s u l t i n g i n a low h e a t o f p o ly m e r iz a tio n. H e a ts o f p o ly m e r iz a tio n ca n be o b ta in e d fro m h e a t s o f c o m b u s tio n o f p o ly m e r and m onom er. The h e a t o f p o ly m e r iz a tio n o f < j(-m e th y lsty re n e h a s b e e n m e a s u re d by t h i s m e th o d. R o b e r ts and J e s s u p ^ fo u n d v a l u e s f o r f o u r d i f f e r e n t m o le c u la r w e ig h t f r a c t i o n s o f p o ly m e r t o be r e p r e s e n t e d by t h e e x p r e s s io n 219^ -AH (k c a l/m o le ) = QAzk + ----- (3 ) p M H e r e, Mn (n u m b e r-a v e ra g e m o le c u la r w e ig h t) i s d e f i n e d as t h e t o t a l w e ig h t o f a l l p o ly m e r m o le c u le s p r e s e n t d iv i d e d b y t h e t o t a l num ber o f m o les p r e s e n t. From th e s tu d y o f h e a t and c o m b u stio n o f h ig h m o le c u la r w e ig h t p o ly m e r, J o s h i and Z w o lin s k i ^ r e p o r t e d th e h e a t o f p o ly m e r iz a tio n t o be - 8.9 6 k c a l/m o le f o r e ( - m e th y ls ty r e n e, and th e y s t a t e d t h a t t h e v a lu e i s in d e p e n d e n t o f m o le c u la r w e ig h t. The v a l u e s o b ta in e d by t h i s m ethod r e p r e s e n t th e e n t h a lp y c h a n g e f o r p o ly m e r iz a tio n o f l i q u i d monomer t o s o l i d p o ly m e r.

M e s ro b ia n and T o b o lsk y ^ show ed t h a t f o r a s o l u t i o n 5 o f s t y r e n e and p o ly s ty r e n e i n t o l u e n e a t 100 C an e q u i l i b r i u m a v e ra g e m o le c u la r w e ig h t e x i s t e d w h ich c o u ld b e a p p ro a c h e d fro m b o th h ig h and low m o le c u la r w e ig h t s i d e s. L a t e r, W o rs fo ld and B y w a te r10 s t u d i e d t h e a n io n ic p o ly m e r iz a tio n o f o (-m e th y ls ty re n e i n i t i a t e d by sodium n a p h t h a le n e. The e q u i lib r i u m monomer c o n c e n t r a t i o n w as m e a s u re d i n a s e r i e s o f e x p e rim e n ts c o n d u c te d a t a r e a c t i o n te m p e r a tu r e o f 0 C. I n one e x p e rim e n t th e r e a c t i o n w as f i r s t h e ld a t -80 C f o r 72 h o u r s. t h i s e x p e rim e n t gav e th e same e q u i lib r i u m monomer S in c e c o n c e n t r a t i o n as was o b ta in e d i n e x p e rim e n ts c o n d u c te d e n t i r e l y a t 0 C, t h e s e a u th o r s c o n c lu d e d t h a t th e e q u i l i b r i u m m u st be q u i t e dynam ic and c o u ld b e a p p ro a c h e d fro m b o th s i d e s. F o r an e q u i lib r i u m p o ly m e r iz a tio n, D a in to n and k 11 I v i n ^,A-L h av e shown t h a t t h e r e i s a c e i l i n g te m p e r a tu r e (T c ) above w h ich no h ig h p o ly m e r c a n b e fo rm e d, and a t w h ic h t h e f r e e e n e rg y o f p o ly m e r iz a tio n v a n i s h e s. T hey f o r m u l a te d th e v a lu e o f TQ as a f u n c t i o n o f th e rm o d y n am ic p a r a m e t e r s, Tc = *Hp / (* S + R I n [ m] ) (4 ) w h ere A Hp, A Sp» and M a re r e s p e c t i v e l y t h e e n t h a lp y and s ta n d a r d e n tr o p y o f p o ly m e r iz a tio n, and t h e e q u i lib r i u m monom er c o n c e n t r a t i o n.

9 10 12 M ccormick and W o rs fo ld and B y w ate r ' s t u d i e d 6 th e p o ly m e r iz a tio n o f o ( -m e th y ls ty r e n e i n i t i a t e d by sodium n a p h t h a le n e. T h e se w o rk e rs fo u n d a l i n e a r r e l a t i o n s h i p o f I n [M] a g a i n s t l / T a s e x p e c te d fro m e q u a tio n A ) : A H? A S i n [ m] = ptp - r " (5 ) c 2 U sin g t h i s r e l a t i o n s h i p, M ccorm ick c a l c u l a t e d AHp = - 6.9 6 k c a l/m o le a n d A S = - 2 ^.8 c a l/m o le d e g re e ; W o rs fo ld and B y w ate r 10 c a l c u l a t e d AHp = - 8.0 2 k c a l/m o le and a S = - 2 8.7 5 c a l/m o le d e g r e e. T h e se v a l u e s a re f o r p o ly m e r iz a tio n o f monomer i n t e t r a h y d r o f u r a n s o l u t i o n t o p o ly m e r d is s o l v e d i n t h e sam e s o l v e n t. T h is m eth o d h a s a l s o b e e n u s e d t o d e te r m in e th e 14 p o ly m e r iz a tio n th e rm o d y n a m ic s f o r m e th y l m e th a c r y l a te * m e t h a c r y l o n i t r i l e and a lk e n e s u lf o n e s 17 C o tta m, C ow ie, and B y w ate r 1 a p p l ie d c o r r e c t i o n s f o r h e a t o f s o l u t i o n t o th e r e s u l t s o f W o rs fo ld and B y w a te r10 and f o r g l a s s y s t a t e e n t h a lp y t o th e r e s u l t s o f R o b e rts and J e s s u p They c o n c lu d e d t h a t t h e h e a t o f p o ly m e r iz a tio n o f l i q u i d monomer t o h ig h m o le c u la r w e ig h t d i s o r d e r e d p o ly m e r i s b e s t r e p r e s e n t e d by th e v a lu e AHp = - 9.3 t OA k c a l/m o le a t 25 C. S zw arc and c o w o rk e rs h av e p ro p o s e d a m echanism f o r th e p o ly m e r iz a tio n o f v i n y l h y d ro c a rb o n s i n i t i a t e d by c o m p le x e s o f so d iu m w ith p o ly n u c le a r a r o m a tic h y d ro c a rb o n s

i n s o l u t i o n i n some a l i p h a t i c e t h e r s. They show ed t h a t 7 a ro m a tic h y d r o c a rb o n s ( e. g., n a p h th a le n e ) r e a c t w ith m e t a l l i c sodium i n s u i t a b l e s o l v e n t s y i e l d i n g c o lo r e d and s o lu b le c o m p lex es w h ich i n i t i a t e p o ly m e r iz a tio n. The s t r u c t u r e o f th e s e co m p le x e s h a s b e e n e l u c i d a t e d by W eissm an and L ip k in who show ed them t o be com posed o f n e g a tiv e a r o m a tic h y d ro c a rb o n io n s and p o s i t i v e sodium i o n s. A m onom eric r a d i c a l io n ( I ) c a n be fo rm ed by d o n a tio n o f an e l e c t r o n fro m th e n e g a t i v e a r o m a tic h y d ro c a rb o n io n to th e monomer. ch3 Na+ ( 0 10H8 C=CH + Na+ + G10Hg (6) U 6 5 ( I ) T h is i s fo llo w e d by d i m e r i z a t i o n o f r a d i c a l io n s t o g iv e d ic a r b a n io n l i v i n g p o ly m e r. I n s u i t a b l e s o l v e n t s th e s e l i v i n g p o ly m e rs a r e s t a b l e and no te r m i n a t i o n o c c u r s, so t h a t th e c h a in e n d s re m a in a c t i v e e v e n a f t e r th e monomer h a s b e e n consum ed. T h is p r o p e r t y was u s e d i n d e m o n s tra tin g th e r e v e r s i b l e n a t u r e o f t h e p r o p a g a t io n s t e p o f p o ly m e r iz a tio n Sodium a lo n e h a s a l s o b e e n u s e d a s a c a t a l y s t f o r th e 20 21 p o ly m e r iz a tio n o f < /-m e th y ls ty r e n e. S zw arc p ro p o s e d th e f o llo w i n g m ech an ism f o r t h e sodium m i r r o r - i n i t i a t e d

p o ly m e r iz a tio n o f o (-m e th y ls ty re n e i n t e t r a h y d r o f u r a n. 21 S zw arc e t a l, s t a t e d t h a t, " I n t h e a b s e n c e o f a la r g e a l k a l i m e ta l s u r f a c e, d im e r ic r a d i c a l - i o n s ( I I ) d im e riz e i n t o t e t r a m e r i c d ia n io n s ( I I I ), CH. 3 l=ch CH, i 3 + C=CH, I 2 chq 0Ho (7) (I), f 3 s C-CH0-CH0 -C* 2 2 6h5 c6«5 ( I I ) CHf 3 : C-CH0 -CH0 -C, 2 2 c6h5 ( I I ) OH, 6H5 c6h5 ( I I I ) f 3 c6«5 ( 8 ) b u t i n s y s te m s h a v in g a l a r g e m e ta l s u r f a c e, e. g., i n th e p r e s e n c e o f sodium e m u ls io n, t h e d im e r ic r a d i c a l - i o n ( I I ) a c q u ir e s an e l e c t r o n and i s t r a n s f e r r e d i n t o d im e r ic d ia n io n ( I V )." CH0 CH0 :C -CH9 -CHr,-C* + Na i 2 2 6h5 ^6 h5 ( I I ) 0Ho T l C-CH ~-CH9 -C : i 2 2 c6h5 (IV ) c6h5 (9) IV + monomer h ig h polym er ( 1 0 ) I I I + monomer h ig h polym er ( 11)

20 H ow ever, R ic h a r d s and W illia m s h ave show n t h a t th e t e t r a m e r d ia n io n h a s t h e s t r u c t u r e CH, C H, CH, CH, I 3 i 3 i 3 i 3 : C - C H,- C - C H,- C H,- C - C H,- C s 2 2 2 i 2 i 6H5 C6H5 6h5 C6h5 ~ ' ( V ) r a t h e r th a n s t r u c t u r e I I I. T h u s, t h e m echanism f o r i t s f o r m a tio n from t h e m onom eric r a d i c a l io n p r o b a b ly p r o c e e d s by f o r m a tio n o f a d im e r ic r a d i c a l io n ( V I ), f 3 c=ch2 6H5 7 CH, 1 3 + C=CH, < 6h5 CH, CH, _ I I 3 :C -C H 2 - C - 0 H 2. c6h5 c6h5 ( 12) T h is r e a c t i o n s t e p w ould t h e n be f o llo w e d by a s im p le d i m e r i z a t i o n by c o u p lin g o f th e f r e e r a d i c a l c a rb o n ato m s. C H, C H,.1 3 i 3 2 i C - C H.- C - C H,. 2 2 6h5 6h5 ( V I ) CH, CH, I 3 CH, f 3 10 - C H,- 0 - O H,- C H.- 0 - C H,- C t I 2 I 2 2 I 2 I c 6 h 5 c 6 h 5 c6h5 c6h5 (V ) (13) D a in to n and I v i n and R o b e rts and J e s s u p ^ h ave s u g g e s te d t h a t t h e e n th a lp y o f a d d i t i o n o f a monomer m o le c u le t o a p o ly m e r s h o u ld d ep e n d on th e d e g r e e o f p o ly m e r iz a tio n o f th e p o ly m e r, a t l e a s t f o r low DP

22 6 10 p o ly m e rs. H ow ever, M a th ie s o n and J o s h i and Z w o lin s k i h a v e d is p u te d t h i s s ta t e m e n t. E q u ilib r iu m b e tw e e n l i v i n g c - m e th y ls ty re n e t e t r a m e r and monomer and b etw e en l i v i n g c C -m e th y ls ty re n e d im e r and monomer i n t e t r a h y d r o f u r a n s o l u t i o n o v e r a te m p e r a tu r e ra n g e o f -2 6 C t o +25 C h ave b e e n i n v e s t i g a t e d by V ra n c k e n, Smid and S z w a r c ^. The l i v i n g o 6 -m e th y ls ty re n e d im e r and c C -m e th y lsty re n e t e t r a m e r w e re t h e s t a r t i n g m a t e r i a l s. Monomer was t h e n added t o t h e s e l i v i n g p o ly m e rs, and t h e c o n c e n t r a t i o n o f monom er r e m a in in g w hen e q u i lib r i u m was a c h ie v e d w as d e te r m in e d. T h is m ethod a llo w e d t h e c a l c u l a t i o n o f t h e i n d i v i d u a l e q u i lib r i u m c o n s t a n t s f o r th e c o n s e c u t iv e s t e p s o f th e p r o c e s s, i. e., d im e r + monomer K2. t r i m e r (1 4 ) t e t r a m e r + monomer p e n ta m e r + monomer h ig h polym er + monomer pen tam er (15) K- h ex a m er ( 1 6 ) Kca ; 1 h ig h p o ly m e r (1 7 ) T h e se i n d i v i d u a l e q u i lib r i u m c o n s t a n t s w ere c a l c u l a t e d ol i n d i r e c t l y u s in g a r e l a t i o n s h i p d e r i v e d by T o b o lsk y. The a p p l i c a t i o n o f T o b o lsk y * s r e l a t i o n s h i p assu m es c e r t a i n r e l a t i o n s h i p s among e q u i lib r i u m c o n s t a n t s w h ic h h av e n o t b e e n p ro v e n f o r t h i s s y s te m, so t h e r e l i a b i l i t y o f th e c a l c u l a t i o n s d e p e n d s on an u n t e s t e d h y p o th e s i s w h ich may

o r may n o t be v a l i d. The m o le c u la r w e ig h t d i s t r i b u t i o n o f o ( -m e th y ls ty re n e 11 o lig o m e rs o b ta in e d i n e q u i lib r i u m p o ly m e r iz a tio n s y ste m s h a s n o t b e e n w e ll s t u d i e d. The a n a l y s i s o f t h e o lig o m e r s by g e l p e r m e a tio n c h ro m a to g ra p h y was u n d e r ta k e n i n t h i s w ork t o r e d e te r m in e th e h e a t o f p o ly m e r iz a tio n, and t o r e s o l v e th e q u e s tio n o f w h e th e r i t s v a lu e d e p e n d s on th e d e g re e o f p o ly m e r iz a tio n. G el p e r m e a tio n c h ro m a to g ra p h y (GPC) i s t h e n e w e s t a n a l y t i c a l t o o l a v a i l a b l e f o r t h e f r a c t i o n a t i o n o f m o le c u le s by s i z e. I t c a n be u s e d t o o b t a i n th e e q u i lib r i u m monomer c o n c e n t r a t i o n and t h e m o le c u la r w e ig h t d i s t r i b u t i o n o f p o ly m e rs. The s e p a r a t i o n i s c a r r i e d o u t on colum ns t h a t a re t i g h t l y p a c k e d w ith a g e l o r some o t h e r p o ro u s m a t e r i a l and c o m p le te ly f i l l e d w ith s o l v e n t. S m a ll m o le c u le s d i f f u s e i n t o t h e p o r e s o f t h e g e l, la r g e o n e s a re e x c lu d e d, and o t h e r s o f i n t e r m e d i a t e s i z e p e n e t r a t e some o f th e l a r g e r p o r e s. The m o le c u le s c o n s t a n t l y d i f f u s e b a c k and f o r t h b e tw e e n t h e p o r e s and th e i n t e r s t i c e s. S o lv e n t pumped th r o u g h t h e colum n flo w s o n ly i n th e i n t e r s t i c e s, s w e e p in g a lo n g a l l sam p le m o le c u le s p r e s e n t t h e r e. The m o le c u le s i n th e p o r e s s t a y b e h in d u n t i l th e y d i f f u s e b a c k o u t. The l a r g e m o le c u le s w h ich a r e alw a y s o r m o s tly e x c lu d e d fro m t h e p o r e s a r e, t h e r e f o r e, e l u t e d f i r s t } th e s m a ll o n e s w h ich a r e i n s i d e th e p o r e s much o f th e tim e come o u t l a s t.

12 I t i s known t h a t th e e q u i lib r i u m d e g r e e o f p o ly m e r i z a t i o n i s a f u n c t i o n o f t h e i n i t i a l c o n c e n t r a t i o n s o f 26 monomer and i n i t i a t o r ( s e e T a b le I ). I n o r d e r t o o b t a i n t h e i n d i v i d u a l e q u i lib r i u m c o n s t a n t s d i r e c t l y, th e i n i t i a l monomer c o n c e n t r a t i o n m u st e x c e e d i t s a p p a re n t e q u i lib r i u m v a lu e and t h e i n i t i a t o r c o n c e n t r a t i o n m u st be h ig h enough t o s y n t h e s i z e low o lig o m e r s o n ly. T a b le I E f f e c t o f I n i t i a l C o n c e n tr a ti o n s o f I n i t i a t o r and Monomer on D eg ree o f P o ly m e r iz a tio n o f # - M e th y l s t y r e n e I n i t i a t e d by Sodium N a p h th a le n e a t 0 C Monomer C o n c e n tr a ti o n, m o le s /k g I n i t i a t o r C o n c e n tr a tio n, m o le s /k g D egree o f P o ly m e r iz a tio n 1.1 40 0.0 0 2 0 3 350 1.1 5 9 0.0 0 9 5 2 6 0-1 0 0 1.1 5 9 0.0 0 5 8 4 110 1.1 6 0 0. 003^>1 190 1.7 3 0 0.0 0 3 3 0 580 2.8 7 0.0 0 2 0 0 1,750 2.8 8 0.0 0 3 3 5 800 4.4? 0.0 0 0 7 6 3 14,000 4.5 5 0.00219 3,500 5.1 4 0.0 0 2 8 0 4,4 0 0 5.1 8 0.0 0 3 3 2 1,6 5 0 S o u r c e : R e fe re n c e 2 6.

EXPERIM EN TA L PROCEDURE S y n th e s is o f O lig o m e rs A ll t h e p r e p a r a t i o n s w ere c a r r i e d o u t i n h ig h vacuum, w ith r i g o r o u s l y p u r i f i e d and d r i e d r e a g e n t s, u s in g b r e a k - s e a l s i n t o t a l l y s e a l e d s y s te m s. M a t e r i a l s T e tr a h y d r o f u r a n ( M a l l i n c k r o d t, I n c. ) w as f i r s t d i s t i l l e d w ith a 1 2 - p l a t e b u b b le ca p d i s t i l l a t i o n a p p a r a t u s. The s o lv e n t was th e n t r a n s f e r r e d t o s i x am p o u les u s in g th e d e v ic e shown i n F ig u re 1. The s o l v e n t (a p p r o x im a te ly 500 m l), n a p h th a le n e (6 g, 0.0 ^ 7 m o le, A ld r ic h C h e m ic a l C o.), and sodium (1 g, 0.C 4 4 m o le) w ere p la c e d i n b u lb A. The sodium d is s o lv e d c o m p le te ly t o g iv e a g r e e n - c o lo r e d s o l u t i o n, c h a r a c t e r i s t i c o f e t h e r s o l u t i o n s o f sodium n a p h t h a le n e. The a p p a ra tu s w as s e a l e d a t c o n s t r i c t i o n H u n d e r a h ig h vacuum a t t a i n e d w ith a m e rc u ry d i f f u s i o n pum p. The s o l v e n t was c a r e f u l l y d i s t i l l e d i n t o b u lb B and th e c o n n e c tin g tu b e was s e a l e d a t c o n s t r i c t i o n K. The s o lv e n t i n b u lb B w as b r o u g h t t o room te m p e r a t u r e and th e n t r a n s f e r r e d i n t o s i x am p o u les w h ic h had t h e d e s i r e d volum e m arked on t h e i r o u t s i d e w a ll s by a tu n g s t e n c a r b i d e s c r i b e r. The o ^ -m eth y lsty ren e monomer u sed was com m ercial g rad e 13

m a t e r i a l o b ta in e d fro m The Dow C h em ical Company. d i s t i l l e d o v e r so d iu m u n d e r h ig h vacuum and th e n I t was Ik t r a n s f e r r e d i n t o s i x am p o u les u s in g th e same d e v ic e a s w as u s e d f o r t h e s o l v e n t. A p p r o p r ia te q u a n t i t i e s o f a b s o lu t e e th a n o l (C o m m ercial S o lv e n t s C o r p., u s e d as r e c e iv e d ) w ere s e a l e d 500m l F la s k O o O A m poules F ig u r e 1. A p p a ra tu s U sed f o r D i s t i l l i n g S o lv e n t and Monomer and T r a n s f e r r i n g S o lv e n t and Monomer i n t o S to r a g e A m poules.

in am poules u n d er vacuum. A chunk o f sodium ( a p p r o x im a te ly 100 g ) w as p la c e d 15 i n s i d e a c o n t r o l l e d a tm o s p h e re g lo v e b ox (V acuum / A tm o sp h ere s Co. M odel H E-^93 D r i- T r a i n ) and th e o x id iz e d f a c e s o f th e so d iu m w ere sh a v e d o f f t o r e v e a l th e s h in y m e ta l s u r f a c e. T h is p ie c e o f so d iu m w as s t o r e d i n th e g lo v e b o x, and p i e c e s u s e d i n t h e p r o c e s s w ere c u t and t r a n s f e r r e d i n th e i n e r t a tm o s p h e re. P ro c e d u re I n an a tte m p t t o o b t a i n a v a r i e t y o f o lig o m e rs w ith d i f f e r e n t m o l e c u la r w e ig h t d i s t r i b u t i o n s, th e s y n th e s e s w ere c a r r i e d o u t w ith v a r i o u s in i t i a t o r - t o - m o n o m e r r a t i o s and r e a c t i o n te m p e r a t u r e s ( s e e T a b le I I ). The am ounts o f s t a r t i n g m a t e r i a l s u s e d f o r th e s y n t h e s i s o f a l l th e p o ly m e r s a m p le s, and t h e i r f i n a l v o lu m es a f t e r te r m i n a t i n g t h e r e a c t i o n w ith e t h a n o l, a r e show n i n A p p en d ix A. S in g le - S t a g e R e a c t i o n. To s y n t h e s i z e th e o lig o m e r s, am p o u les c o n t a i n i n g { /- m e th y ls ty r e n e, t e t r a h y d r o f u r a n and e t h a n o l w ere s e a l e d t o th e r e a c t i o n a p p a r a tu s a t th e l o c a t i o n s i n d i c a t e d i n F ig u r e 2. The r e a c t i o n f l a s k C w as pum ped a t 10**^ t o r r f o r t h r e e h o u rs w h ile b e in g h e a te d o c c a s i o n a l l y w ith an e l e c t r i c h e a t g u n. The r e a c t i o n d e v ic e ( c l o s e d u n d e r vacuum w ith a s to p c o c k ) was th e n p la c e d i n s i d e t h e g lo v e b o x. S m a ll p i e c e s o f sodium w ere c u t, w e ig h e d, and in t r o d u c e d i n t o r e a c t i o n f l a s k C. The

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. C o n d itio n s f o r t h e S y n th e s is o f o -M e th y ls ty re n e O lig o m e rs S am ple R e a c tio n C o n d itio n s C o n c e n t r a t i o n s, m o l e s / l i t e r Number Temp., Tim e, I n i t i a t o r I n i t i a l F i n a l K h r Monomer Monomer 0 0-0 1 2 7 3.1 5 24 0.2 2 0 0.9 4 6 0.5 8 4 0 0-0 2 2 7 3.1 5 24 0.2 2 0 1.0 2 0.5 9 1 0 0-0 3 2 7 3.1 5 24 0.2 2 0 1.1 0 0.6 0 8 16-0 1 2 89.15 72 0.14 1 2.5 6 1.17 25-01 298.15 24 0.0 44 2 2.4 3 1.80 2 5-0 2 2 9 8.1 5 72 0.1 3 8 3.3 7 1.7 4 2 5-0 3 2 9 8.1 5 24 0.2 3 7 2.3 0 1.7 3 2 5-0 4 2 9 8.1 5 24 0.2 2 7 2.3 8 1.7 6 2 5-0 5 2 9 8.1 5 24 0.2 2 9 2.5 3 1.7 9 2 5-0 6 2 9 8.1 5 24 0.2 2 8 2.4 5 1.7 4

17 G G h o PuS H 6 P o H C G o H g Table I I. ( C o n tin u e d )

1 8 G G H O Table I I. ( C o n tin u e d ) 0)

19 s to p c o c k w as c l o s e d, t h e f l a s k was a t ta c h e d t o t h e vacuum l i n e and i t was th e n e v a c u a te d f o r tw o h o u r s and s e a l e d a t c o n s t r i c t i o n I. The r e a c t i o n f l a s k w as im m ersed i n a w a te r b a t h c o n t r o l l e d by a T h e rm o n ito r te m p e r a t u r e r e g u l a t o r (E. H. S a r g e n t and C o., M odel ST) t o a p p ro x im a te ly + O.i C o f th e d e s i r e d te m p e r a t u r e. The b r e a k - s e a l SI t o th e s o l v e n t w as c ru s h e d f i r s t, th e n th e b r e a k - s e a l S2 t o m onom er. I t to o k a p p ro x im a te ly f i v e h o u rs f o r a l l th e sodium t o d i s s o l v e. The t o t a l H igh Vacuum S to p c o c k $ 2 ^ A 0 J o i n t T e tr a h y d ro fi ( S o lv e n t) E th a n o l c (-M e th y ls ty re n e (M onomer) F ig u r e 2. R e a c tio n D e v ic e U sed f o r t h e P r e p a r a t i o n o f Polym er

r e a c t i o n tim e w as v a r i e d fro m 12 h o u rs t o 8? h o u r s. The r e a c t i o n was th e n q u en c h ed w ith e t h a n o l by c r u s h in g th e b r e a k - s e a l S3. The c h e r r y r e d c o l o r o f t h e r e a c t i o n s o l u t i o n d is a p p e a r e d im m e d ia te ly a f t e r a d d in g t h e e t h a n o l. T w o-s tage R e a c t i o n. A n o th e r d e v ic e ( F ig u r e 3 ) was u s e d t o p r e p a r e sam p le 3 6-0^. A ll t h e r e a g e n t s w ere in t r o d u c e d i n t o t h e r e a c t i o n sy ste m i n s i d e t h e d r y b o x. I n b u lb A, o (-m e th y ls ty re n e (5 m l, O.0 3 8 m o le ) w as m ixed w ith t e t r a h y d r o f u r a n (5 ^ m l, O.6 6 5 m o le ), and sodium E th a n o l Monomer + S o lv e n t + Sodium F ig u r e 3. A l t e r n a t i v e A p p a ra tu s U sed f o r P r e p a r i n g th e O lig o m e rs o f o (-M e th y ls ty re n e

( o.4 g, 0.0 1 7 m o le) was ad d e d. The r e s t o f t h e monomer (50 m l, 0. 38^ m o le) w as s t o r e d i n b u lb B. A f te r th e 2 1 r e a c t i o n s y ste m was e v a c u a te d and s e a l e d, t h e s o l u t i o n in b u lb A was s t i r r e d w ith a m a g n e tic s t i r r e r f o r f o u r t e e n h o u rs a t room te m p e r a t u r e. Then i t was im m ersed i n th e t h e r m o s ta t and th e b r e a k - s e a l b e tw e e n b u lb s A and B was c r u s h e d, The monomer i n b u lb B w as p o u re d i n t o b u lb A. A f te r th e p o ly m e r iz a tio n had p ro c e e d e d 2k h o u r s a t 36 C, th e r e a c t i o n was q u e n c h ed w ith e t h a n o l (fro m b u lb C) by c r u s h in g th e b r e a k - s e a l B l. A n a l y t i c a l C h ro m a to g rap h y G el P e rm e a tio n C h ro m a to g rap h y A ll th e o lig o m e r s a m p le s w ere a n a ly z e d by g e l p e r m e a tio n c h ro m a to g ra p h y u s in g a P e r k in - E lm e r M odel 1250 L iq u id C h ro m a to g ra p h. A s c h e m a tic d ia g ra m o f th e a p p a r a tu s i s shown in F ig u r e k. The b a s i c in s tr u m e n t c o n s i s t s o f f o u r e le m e n ts : (1 ) a pump t o move t h e s o l v e n t c a r r i e r th r o u g h t h e s y ste m ; ( 2 ) an i n j e c t o r f o r d e p o s i t i n g t h e sam p le a t th e h e a d o f th e co lu m n ; ( 3 ) th e colum n f i l l e d w ith a p a c k in g m a t e r i a l ; and (k) a d e t e c t o r t o v i s u a l i z e t h e e l u t e d c o m p o n e n ts. As sam p le co m p o n en ts em erge fro m th e co lu m n, th e y p a s s th r o u g h an u l t r a v i o l e t a b s o r p ti o n d e t e c t o r w h ich p r o v id e s a m eans o f m e a s u rin g c o n c e n t r a t i o n s o f u l t r a v i o l e t - a b s o r b i n g m a t e r i a l s. The d e t e c t o r l i g h t

s o u r c e i s a m e rc u ry lam p w ith f i l t e r s t o s e l e c t th e 2 5 3.7 nm w a v e le n g th. Flow c e l l s a r e h ig h p r e s s u r e s t a i n l e s s s t e e l u n i t s w ith S u p r a s i l I I end w indow s and T e f lo n s e a l s. The r e f e r e n c e and sam p le flo w c e l l s a re c o n n e c te d as shown i n F ig u r e 5» w h ich p r o v id e s a d o u b le beam c o n f i g u r a t i o n o f t h e s p e c t r o m e tr i c d e t e c t o r. M oving P h a s e S o lv e n t R e s e r v o i r Pump I n j e c t o r P ack e d Colum ns W aste F r a c t i o n C o l l e c t o r U.V D e te c to r F ig u r e *J-. L iq u id C h ro m a to g ra p h Flow D iagram

A Beckman t e n - i n c h r e c o r d e r (1 mv f u l l s c a l e ) was 2 3 u s e d t o r e c o r d t h e d e t e c t o r o u tp u t as a c h ro m ato g ram. A t y p i c a l c h ro m ato g ram (s a m p le ^ 5-0 1 ) i s shown i n F ig u re 6. I n t h e f o ll o w i n g p a g e s, e a c h o lig o m e r i s i d e n t i f i e d by th e l e t t e r u s e d t o i d e n t i f y t h e GPC p e a k a t w h ich th e p a r t i c u l a r s p e c i e s a p p e a r s. I n o r d e r t o o b t a i n s a t i s f a c t o r y s e p a r a t i o n o f o lig o m e r s, some m o d i f i c a t i o n s o f t h e o r i g i n a l a p p a ra tu s w ere m ade. Pump " 7 K > 0 R e fe re n c e I n U R e fe re n c e O ut V Sam ple I n Y S am ple O ut W aste o r F r a c t i o n C o l l e c t o r F ig u r e 5. U l t r a v i o l e t A b s o r p tio n D e te c to r C o n n e c tio n s

2 4 $ rl Os 3 o x: -=> d> rh a M O d Model 1250 Liquid C hrom atograph I

F i l t e r s. P a r t i c u l a t e m a t e r i a l i n t h e s o lv e n t may c a u s e e v e n tu a l b lo c k a g e o f n a r r o w - b o r e t u b i n g, i n j e c t i o n d e v i c e s, colum n end f i t t i n g s, o r t h e colum n p a c k in g 25 i t s e l f. To a v o id t h i s th e pum ping s y ste m in c lu d e s a b u i l t - i n f i l t e r, w h ich i s s e a l e d by a r u b b e r 0 - r i n g. The r u b b e r i s a tta c k e d by t e t r a h y d r o f u r a n, le a d i n g t o le a k a g e, b lo c k a g e, and an u n s t a b l e b a s e l i n e. The o r i g i n a l r u b b e r O - r in g w as t h e r e f o r e r e p l a c e d by a T e f lo n O - r in g. To m in im iz e r e l i a n c e on t h e b u i l t - i n f i l t e r s y s te m, a f i l t e r m a n u fa c tu re d by th e M i l l i p o r e C o r p o r a t io n was c o n n e c te d b e tw e e n th e s o lv e n t r e s e r v o i r and th e b u i l t - i n s y s te m. The M ill ip o r e f i l t e r c o n s i s t e d o f a c o a rs e m em brane ( C a t. No. A P2002200) f o llo w e d by a f i n e m em brane ( C a t. No. LSW P02500), b o th m ounted i n a s t a i n l e s s s t e e l f i l t e r h o ld e r ( C a t. No. X X ^502500). B o th f i l t e r m em branes w ere changed ev e ry week. Colum ns and F i t t i n g s. C olum ns f o r l i q u i d c h ro m a to g ra p h y m u st be i n e r t, h av e sm ooth i n t e r n a l w a l l s, be o f u n ifo rm c r o s s s e c t i o n, and be a b le t o w ith s ta n d h ig h p r e s s u r e s. S o - c a l le d " p r e c i s i o n b o re s t a i n l e s s s t e e l " ( ty p e 3 1 6 ) h a s b e e n s u g g e s te d a s t h e b e s t tu b i n g f o r l i q u i d c h ro m a to g ra p h y co lu m n s b u t t h e r e i s a p p a r e n tly l i t t l e d i f f e r e n c e in e f f i c i e n c y b e tw e e n t h i s and o r d in a r y s e a m le s s s t a i n l e s s s t e e l t u b i n g. N ine 6 - f o o t lo n g p i e c e s o f 0.1 8 in c h I. D., 0,2 5 in c h 0.D, ty p e 30*fS s t a i n l e s s s t e e l t u b i n g w ere u s e d. The

colum n en d s w ere sm oothed and d e b u r r e d. 26 A colum n te r m i n a t o r end f i t t i n g ( F ig u r e 7) was u s e d t o k eep th e p a c k in g i n th e co lu m n. C o m m ercial colum n t e r m i n a t o r s a re g e n e r a l l y v e ry e x p e n s i v e. I t was fo u n d t h a t s a t i s f a c t o r y te r m i n a t o r s c o u ld b e made fro m c o m m e rc ia lly a v a i l a b l e p o ro u s m e ta l f r i t (11 t o 25 m ic ro n ra n g e s i n t e r e d s t a i n l e s s s t e e l f i l t e r e l e m e n t ), and a colum n r e d u c in g u n io n. S om etim es s m a ll p a r t i c l e s o f p a c k in g m a t e r i a l p lu g g e d th e p o ro u s m e ta l f r i t, as i n d i c a t e d by i n c r e a s i n g gauge p r e s s u r e. When t h i s h a p p e n e d, th e m e ta l f r i t was c l e a n e d by r e v e r s i n g th e S. S. U nion ( d r i l l e d o u t) P o ro u s M e ta l F r i t S. S. N ut S. S. F e r r u l e Chromatographic Colum n F ig u r e 7. Column T e r m in a to r f o r GPC Colum ns

s o l v e n t flo w th ro u g h th e colum n t e r m i n a t o r. 27 Colum n P a c k i n g. P r i o r t o p a c k in g, t h e co lu m n s w ere c le a n e d w ith 50% n i t r i c a c id, d i s t i l l e d w a te r, a c e to n e, c h lo r o f o rm, and a c e to n e and th e n w ere d r i e d w ith a s tr e a m o f n i t r o g e n. A s m a ll wad o f c l o t h w as p u s h e d th r o u g h th e colum n t o rem ove p a r t i c l e s w h ich c lu n g t o th e i n s i d e o f th e tu b e. C le a n li n e s s was c h e c k e d by h o ld i n g a tu b e up t o a b r i g h t l i g h t and v ie w in g th e i n t e r n a l l y r e f l e c t e d l i g h t on th e w a l l s. Two d i f f e r e n t k in d s o f p a c k in g m a t e r i a l w ere u s e d, n am ely B io -B e a d s S-X2 (B io -R a d L a b o r a t o r i e s ) and P o r a g e l / 100 A (W a te rs A s s o c i a t e s ). T h e ir p h y s i c a l c h a r a c t e r i s t i c s a r e shown i n T a b le I I I. T h e se p a c k in g m a t e r i a l s a re s o f t T a b le I I I P h y s i c a l C h a r a c t e r i s t i c s o f P a c k in g M a t e r i a l s U sed i n A n a l y t i c a l G el P e r m e a tio n C h ro m a to g rap h Type P a r t i c l e E x c lu s io n S e p a r a t io n S iz e L im it Range (D ry) M ol. Wt. M ol. Wt. B io -B eads ZOO-kOO Mesh 2700 100-2 7 0 0 P o r a g e l 37-7 5 1300 1 0 0-1300

2 8 g e l s w h ic h s w e ll a p p r e c ia b l y i n t e t r a h y d r o f u r a n, th u s r e q u i r i n g a s l u r r y p a c k in g t e c h n iq u e. S l u r r y p a c k in g w as p e rfo rm e d u s in g th e a p p a r a tu s shown s c h e m a ti c a ll y i n F ig u r e 8. S o lv e n t R e s e r v o i r P r e s s u r e Gauge [Column T e r m in a to r E x te n s io n Colum n U n io n Pump P a c k in g Colum n Colum n T e r m in a to r B e a k e r F ig u r e 8. A p p a ra tu s f o r S l u r r y P a c k in g L iq u id C h ro m a to g ra p h ic Column

29 The p a c k in g m a t e r i a l was s o a k e d i n t e t r a h y d r o f u r a n f o r one d a y. A 5-1 0 cm e x t e n s io n was jo i n e d t o t h e colum n b y a u n io n o f t h e ty p e shown i n F ig u r e 9. T h is u n io n j o i n s t h e e x t e n s io n and th e colum n w ith o u t u n e v e n e d g e s o r o v e r l a p. T hen th e colu m n and i t s e x t e n s io n w ere f i l l e d w ith a s l u r r y o f s o l v e n t and p a c k in g m a t e r i a l u s i n g a s y r in g e c o n n e c te d t o a l e n g th o f T e flo n tu b i n g. The e x c e s s p a c k in g i n th e e x t e n s io n in s u r e d t h a t t h e co lu m n re m a in e d f u l l ev e n w hen s e t t l i n g o c c u r r e d. T h is co lu m n e x t e n s i o n w as rem oved a f t e r s o lv e n t had b e e n pum ped th r o u g h t h e p a c k in g f o r one d a y. F ig u r e 9. S p e c i a l U n io n f o r J o i n i n g E x te n s io n t o Colum n

A f te r p a c k in g, n in e colum ns w ere c o n n e c te d t o g e t h e r 3 0 b y n a r r o w - b o r e s t a i n l e s s s t e e l t u b i n g ( l / l 6 " O.D., 0.0 1 5 " I. D. ) i n t h e m anner shown i n F ig u r e 1 0. The f i r s t tw o c o lu m n s w ere p a c k e d w ith P o r a g e l, and th e r e m a in in g c o lu m n s w ere p a c k e d w ith B io -B e a d s. S o lv e n t I n W V VT O ut t o D e te c to r F ig u r e 1 0. S c h e m a tic D iagram o f GPC Colum n C o n n e c tio n s

31 A n a l y t i c a l P r o c e d u r e. T e tr a h y d r o f u r a n s o lv e n t fro m a f r e s h s to c k b o t t l e was d i s t i l l e d o v e r sodium th ro u g h a 12- p l a t e b u b b le ca p d i s t i l l a t i o n a p p a ra tu s and was u s e d im m e d ia te ly. B ec au se o f t h e lo n g colum n sy ste m and th e slo w flo w r a t e, i t to o k a b o u t s i x h o u r s t o r e a c h a good s t a b l e r e c o r d e r b a s e l i n e. The s o l v e n t r e s e r v o i r was f i l l e d w ith f r e s h s o l v e n t e v e ry tw o d a y s. A ir i n th e s o lv e n t s y ste m may i n t e r f e r e w ith h ig h p r e s s u r e l i q u i d c h ro m a to g ra p h y o p e r a t i o n. W hile p r e s s u r e s o f s e v e r a l h u n d re d pounds p e r s q u a re in c h a r e r e q u i r e d t o a c h ie v e r a p i d flo w th r o u g h th e n a rro w b o re co lu m n s, th e r e l a x a t i o n o f p r e s s u r e on t h e d o w n stream s id e o f th e colum n may a llo w e x p a n s io n o f th e e n t r a i n e d a i r, r e s u l t i n g in b u b b le f o r m a tio n. When t h e s e b u b b le s p a s s th ro u g h th e d e t e c t o r, th e y p ro d u c e s p ik e s on th e r e c o r d e r t r a c e. T h is i s p r e v e n te d by s t i r r i n g and h e a t i n g th e s o lv e n t b e f o r e pum ping. I n th e c a s e o f t e t r a h y d r o f u r a n, a s a t i s f a c t o r y s o l v e n t r e s e r v o i r te m p e r a tu r e i s aro u n d 55 c. S o lv e n t r e c o v e r e d fro m th e w a s te d id n o t g iv e as s t a b l e a b a s e l i n e as d id f r e s h s o l v e n t. T h is a p p a r e n tly i s due t o th e f o r m a tio n o f i m p u r i t i e s in th e t e t r a h y d r o f u r a n w h ich a re n o t e a s i l y rem oved e v e n by r e d i s t i l l a t i o n o v e r so d iu m. S o lu ti o n s o f e a c h o f th e o lig o m e r m ix tu r e s w ere p r e p a r e d a t v a r i o u s c o n c e n t r a t i o n s. A fix e d -v o lu m e lo o p