Ring-Opening Polymerization

10 Ring-Opening Copolymerization of Some Cyclic Compounds Containing Oxygen and Nitrogen Atoms H. L. HSIEH

Downloaded by UNIV OF ROCHESTER on November 4, 2014 | http://pubs.acs.org Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0059.ch010

Phillips Petroleum Co. Research and Development, Bartlesville, OK 74004

The copolymerization of cyclic polar monomers can be used for the preparation of various classes of linear, hetero-chain co polymers. Cyclic compounds of the same chemical type, differing from one another only in the number of units in the ring or the presence of various substituents, can be copolymerized to form products, some of which find a wide variety of application. The copolymerization of various oxides to form linear polyethers has been extensively studied.^ A number of investigations Jjjaye been made of the copolymerization of lactones- — and lactams™^ to form polyesters and polyamides respectively. Cyclic compounds of different chemical type can also be poly merized to produce copolymers with hetero-bonds in the macromolecular chain derived from both copolymerizing monomers. Lactones can polymerize with cyclic ethers such as epoxides, tetrahydrofuran, oxetans and trioxane as well as imines. The copolymerization of lactones with epoxides, for example, should lead to the formation of copolymers containing ether and ester links in the chain. 1

I t was a l s o reported t h a t l a c t o n e s undergo c o p o l y m e r i z a t i o n w i t h c y c l i c phosphites upon h e a t i n g o r i n the presence o f a b a s i c catalyst.

145

In Ring-Opening Polymerization; Saegusa, T., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

146

RING-OPENING

POLYMERIZATION

The a l t e r n a t i n g c o p o l y m e r i z a t i o n o f epoxides and d i b a s i c a c i d anhydride r i d e r e s u l t e d i n formation o f p o l y e s t e r s i ^ » 8,9,10) R ι

-CHC.H,C00CHRCH 06 4 2


o

A l t e r n a t i n g terpolymers o f epoxides, d i b a s i c a c i d anhydrides and t e t r a h y d r o f u r a n o r oxetane were s u c c e s s f u l l y prepared by u s i n g t r i a l k y l a l u m i n u m as c a t a l y s t : " * This unique f a m i l y o f polymers has r e p e a t i n g e t h e r - e s t e r - e s t e r l i n k a g e s along the c h a i n . CH -CH 2

CH -CH + \ / CH CH \ / 0

2

-CH CH OCH CH CH CH OCOC H COOjx 2

0

2

2

0

2

-co'

0

2

2

2

2

2

2

6

4

Another i n t e r e s t i n g r e a c t i o n i s the c o p o l y m e r i z a t i o n o f a z i r i d i n e s w i t h c y c l i c imides, which leads t o the formation o f c r y s t a l l i n e polyamides5—' CH -CH 2

CH -C0 I 2 >NH-

2

0

\ v Ν Η Aziridine

v

COCH CH CONHCH CH NH 2

CH -C0

2

2

2

2

e

m.p. 300 C Succinimide

High molecular polyurethanes have been prepared by the ring-r opening c o p o l y m e r i z a t i o n o f a z i r i d i n e s w i t h c y c l i c carbonatesr *

CH

2

\

H

- CH / H

2

CH 0 >^ l / 2° 2

+

C

C H

no c a t . η y ^2 ^ > H+0Œ Œ 0C0NHŒ Œ 4-N Ι» ^0Η HO group a l k y l i m i n o group r

0

2

2

2

2

2

There are many other examples o f t h i s type o f copolymeri z a t i o n which i n v o l v e s the ring-opening o f two o r more h e t e r o c y c l i c monomers. For t h i s r e p o r t , I w i l l d i s c u s s the formation o f polyamidoesters by means o f t h i s k i n d o f r e a c t i o n . Experimental e p s i l o n - C a p r o l a c t o n e was d i s t i l l e d , and e p s i l o n - c a p r o l a c t a m was melted and purged w i t h n i t r o g e n , before use. P h t h a l i c



10. HSiEH

Copolymerization

of Cyclic

Compounds

147

anhydride and N - p h e n y l a z i r i d i n e were used as r e c e i v e d . The i n i t i a t o r , R ^ A l L i , was obtained from Foote M i n e r a l and i t s chemical formula f o r the R group i s not known although the molecular weight i s 253. I t i s s o l u b l e i n hydrocarbon s o l v e n t t o give a v i s c o u s s o l u t i o n . Toluene was d r i e d by countercurrent scrubbing w i t h n i t r o g e n . A l l p o l y m e r i z a t i o n s were done i n beverage b o t t l e s . Solid monomers were weighed i n t o the b o t t l e f i r s t and then the b o t t l e was f l u s h e d w i t h n i t r o g e n . Toluene was added and t h e b o t t l e was f l u s h e d w i t h n i t r o g e n again before capping. Caprolactone was then added by hypodermic s y r i n g e . I n i t i a t o r was g e n e r a l l y added a t room temperature. Polymers, i n most o f the runs, were i n s o l u b l e i n toluene and came out o f s o l u t i o n . They were s t i r r e d i n a c i d i f i e d i s o p r o p y l a l c o h o l and d r i e d i n t h e vacuum oven. R e s u l t s and D i s c u s s i o n A. N-Substituted A z i r i d i n e and D i b a s i c A c i d Anhydride. J u s t as a l k y l e n e oxide under a p p r o p r i a t e c o n d i t i o n can a l t e r n a t i n g l y copolymerize w i t h a c i d anhydride t o y i e l d p o l y e s t e r , a z i r i d i n e compounds can a l s o copolymerize s i m i l a r l y w i t h a c i d anhydride t o form polyamidoester.

0

//

0

0

T r i i s o b u t y l a l u m i n u m , a very e f f e c t i v e i n i t i a t o r f o r a l k y l e n e o x i d e - d i b a s i c a c i d anhydride c o p o l y m e r i z a t i o n £L-? was used t o i n i t i a t e the c o p o l y m e r i z a t i o n o f N - p h e n y l a z i r i d i n e and p h t h a l i c anhydride (Table I ) . Both the conversion and the elementary a n a l y s i s i n d i c a t e d the two monomers a r e present i n equal mole r a t i o . Since p h t h a l i c anhydride cannot be h o m o p o l y m e r i z e d , — i t i s concluded t h a t t h e product i s an a l t e r n a t i n g copolymer. S u r p r i s i n g l y , when the same experiment was c a r r i e d out without i n i t i a t o r , the r e s u l t was the same. Obviously, these two monomers copolymerize r e a d i l y by simply h e a t i n g . The low s o f t i n g p o i n t o f t h i s polymer, however,


148

RING-OPENING

POLYMERIZATION

TABLE I N-PHENYLAZIRIDINE AND PHTHALIC ANHYDRIDE COPOLYMERIZATION N-Phenylaziridine P h t h a l i c anhydride Toluene Triisobutylaluminum

0.06 mole (7.1 g) 0.06 mole (9.0 g) 100 ml 4 mmole


Temperature, ° C Time, hours

70 16

Experimental Data Total Monomers Charged, G

Polymer Recovered, G

16.1

Polymer Soft Point, °C

16.5

60

% 0

% Ν 4.6

a

(5.2)

b

18.6

a

(18.0)

1

a - Found b - C a l c u l a t e d based on 1 t o 1 mole r a t i o l i m i t s i t s u s e f u l n e s s . Endic anhydride, c h l o r o e n d i c anhydride and s u c c i n i c anhydride a l s o copolymerize w i t h N - p h e n y l a z i r i d i n e t o form low-melting s o l i d s , but i n much lower y i e l d s . B. e p s i l o n - C a p r o l a c t o n e and epsilon-Caprolactam. Another i n t e r e s t i n g method f o r p r e p a r i n g polyamidoester i s the copolymeri z a t i o n o f a l a c t o n e such as c a p r o l a c t o n e w i t h a l a c t a m such as caprolactam.

c

I r° η (CH )c + 2

_o

ι — r ° η (CEL). |

1

D

NH

r ι > 4-0(CH )cC0NH(CH«),-Co4 9

L

Z

D

Δ

D

J

n

I n the f i r s t experiments, f i v e o r g a n o m e t a l l i c compounds were screened as i n i t i a t o r s . I t i s known t h a t c a p r o l a c t o n e polymerizes r e a d i l y i n the presence o f t r i i s o b u t y l a l u m i n u m , b u t y l l i t h i u m , potassium t e r t - a m y l o x i d e , and l i t h i u m t e t r a a l k y l a l u m i n a t e . However, the mixture o f caprolactone and caprolactam i n toluene formed polymer o n l y i n the presence o f the l a s t compound (Table ID. The f a c t t h a t polymer i n over 50% c o n v e r s i o n was formed i n d i c a t e d both monomers p a r t i c i p a t e d i n t h e r e a c t i o n , and t h a t t h e product seemed homogeneous and i n s o l u b l e i n toluene ( c a p r o l a c t o n e homopolymer i s t o l u e n e - s o l u b l e ) prompted f u r t h e r experimentation w i t h R .4A l L i . The r e s u l t s a r e shown i n Table I I I .


10. HsiEH

Copolymerization

of Cyclic

Compounds

149

TABLE I I CAPROLACTONE AND CAPROLACTAM

COPOLYMERIZATION

WITH ORGANOMETALLIC COMPOUNDS


Caprolactone Caprolactam Toluene Organometallic compound

10 g 10 g 200 ml 2 mmoles

Temperature, °C Time, hours

70 16

Experimental Data Organometallic Compound

% Conversion

(i-BuKAl Et AlCI n-BuLi tert-AmylOK R,AlLi

0 trace 0 0 60

2

a

a - Polymer p r e c i p i t a t e d

TABLE I I I LITHIUM TETRAALKYLALUMINATE AS CATALYST FOR CAPROLACTONE AND CAPROLACTAM COPOLYMERIZATION Capro lactone, Grams

Capro lactam, Grams

100 70 50 30 0

0 30 50 70 100

Polymer, Grams 100° 72 80 0

d

%

a

Solubility i n Toluene

% Ν

b Caprolactam

0 3.7 6.7 9.9

0 30 54 79

Yes Yes No No

—

—

a - I n 1 l i t e r t o l u e n e w i t h 5.1 grams (20 mmoles) R . A l L i i n i t i a t o r . P o l y m e r i z a t i o n was c a r r i e d out a t 70°C f o r 16 hours. b - Based on % Ν i n polymer. c - Waxy s o l i d ; m e l t i n g p o i n t 60°C. d - M e l t i n g p o i n t 180 C. Nylon 6 melts a t 220°-230°C. e



150

RING-OPENING POLYMERIZATION

As was a n t i c i p a t e d , caprolactone was r e a d i l y polymerized by R ^ A l L i t o y i e l d homopolymer which i s low-melting and s o l u b l e i n t o l u e n e , t e t r a h y d r o f u r a n and chloroform. Caprolactam, on t h e o t h e r hand, d i d not homopolymerize. The composition o f t h e copolymers v a r i e d w i t h the charge r a t i o o f the monomers, i n d i c a t i n g i t i s not an e x c l u s i v e l y a l t e r n a t i n g process. Polymers c o n t a i n i n g h i g h lactam content a r e h i g h - m e l t i n g and completely i n s o l u b l e i n the common s o l v e n t s . This leads t o the c o n c l u s i o n t h a t the products a r e not a mixture o f homopolymer s. To f u r t h e r e l u c i d a t e the s t r u c t u r e o f these copolymers, phase t r a n s i t i o n behavior of three copolymers o f caprolactone and capro lactam (see Table IV) were determined. Three methods were used t o determine the phase t r a n s i t i o n behavior o f these polymers. a. C a p i l l a r y d i l a t o m e t r y , u s i n g mercury as the displacement f l u i d , from -38°C t o +65 C. b. Dynamic measurements ( V i b r o n ) , a t 110 Hz, from -80°C t o the upper m e l t i n g p o i n t (120°-240°C). c. D i f f e r e n t i a l scanning c a l o r i m e t r y from 40°C t o 250°C. A l s o i n c l u d e d are r e s u l t s from a p h y s i c a l blend o f p o l y caprolactone and polycaprolactam made i n a Brabender P l a s t o g r a p h at 255°C. From the data on the p h y s i c a l blend i t appears t h a t the two homopolymers a r e i n c o m p a t i b l e i n both the amorphous and c r y s t a l l i n e s t a t e s . Only the expected t r a n s i t i o n s of the two homopolymers were observed. Apparently the three experimental polymers are random copolymers w i t h some homopolymer b l o c k on o r admixed. The polymer near 50/50 i n composition showed a very broad t r a n s i t i o n around 0 C i n both the d i l a t o m e t r i c experiment and i n the V i b r o n . The o n l y other t r a n s i t i o n was a m e l t i n g p o i n t (170°C ( V ) , 192 C [DSC]). The other two experimental polymers had s i m i l a r broad t r a n s i t i o n s near 0 C. I n a d d i t i o n , these polymers d i s p l a y e d d i s p e r s i o n regions which appear t o be a s s o c i a t e d w i t h the t r a n s i t i o n s e

e

e

e

TABLE IV SUMMARY OF STUDIES OF PHASE TRANSITION BEHAVIOR OF COPOLYMERS Caprolactam, % 30 54 79

Copolymer 60 100 40-50

0

Composition, % Polycaprolactone

Polycaprolactam

40 0 0

0 0 50-60

a - Based on % Ν i n polymer. b - From the s o l u b i l i t y d a t a , i t seems most l i k e l y the homopolymers a r e present i n the form o f b l o c k , c - About 50-50 composition.


10.

HSiEH

Copolymerization

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Compounds

151


o f the major components. The r e s u l t s would support t h e i d e n t i f i c a t i o n o f t h e experimental polymers as copolymers o f ca. 50-50 composition p l u s excess homopolymer ( p o s s i b l y block)· I n c o n c l u s i o n , N - s u b s t i t u t e d polyamidoesters can be r e a d i l y formed by h e a t i n g N - s u b s t i t u t e d a z i r i d i n e s w i t h d i b a s i c a c i d anhydrides. The low s o f t i n g p o i n t o f these polymers l i m i t s t h e i r u s e f u l n e s s . Copolymerization o f caprolactam and caprolactone leads to very i n t e r e s t i n g products. They a r e g e n e r a l l y h i g h m e l t i n g and by a d j u s t i n g monomer charge r a t i o e i t h e r p o l y e s t e r o r polyamide b l o c k copolymer can be produced. ABSTRACT N - P h e n y l a z i r i d i n e and p h t h a l i c anhydride copolymerize in a l t e r n a t i n g order t o g i v e polyamidoesters upon initiation with t r i i s o b u t y l a l u m i n u m o r by h e a t i n g . The low softing p o i n t o f this polymer limits its u s e f u l n e s s . e p s i l o n - C a p r o l a c t o n e and epsilon-Caprolactam copolymerize in the presence o f R A1Li. The composition o f the copolymers v a r i e d w i t h the feed ratios o f the monomers. Polymers c o n t a i n i n g over 50 p e r cent lactam are h i g h - m e l t i n g and completely i n s o l u b l e in common s o l v e n t s . From t h e results o f s t u d y i n g the phase transi tion behavior o f these polymers it was concluded t h a t they a r e about o f 50/50 composition p l u s excess homopolymer p o s s i b l y in b l o c k form. 4

LITERATURE CITED Furukawa, J. and Saegusa, T. " P o l y m e r i z a t i o n o f Aldehydes and O x i d e s " , John W i l e y & Sons, New Y o r k , 1963. 2. Tada, K., Numata, Y., Saegusa, T., and Furukawa, J . , Makromol. Chem. 77, 220 (1964). 3. Y a m a s h i t a , Y., Tsuda, T., I s h i k a w a , J ., and H i m i d y , T., J . Chem. Soc. Japan, I n d . Chem. S e c t . , 66, 1493 (1963). 4. G l i c k m a n , S.M. and Miller, E. S., U.S. P a t e n t 3,016,367 (1962). 5. H e d r i c k , R. Μ., M o t t e r s , Ε. Η., and B u t l e r , Τ. Μ., U.S. P a t e n t 3,120,503 (1964). 6. McConnel, R.L. and Coover, H. W., U.S. P a t e n t 3,062,788 (1962). 7. F i s h , W., Hoffman, W., and K o s k i k a l l i o , J ., Chem. and I n d . , 756 (1956). 8. F i s h e r y R. F., J. Polymer Sci., 44, 155 (1960). 9. T s u r u t a , T., Matsumura, Κ., and I n o u e , S., Makromol. Chem. 75, 211 (1964). 10. H s i e h , H. L., J. Macromol. Sci-Chem., A7 ( 7 ) , 1525 (1973). 11. K a g i u a , T., N a r i s a w a , S., Manobe, Κ., and K o b a t a , M., J . Polymer Sci., A1, 2081 (1966). 12. D r e c k s e l , Ε. Κ., U.S. P a t e n t 2,824,857 (1958). 1.


Ring-Opening Polymerization

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