Donor-Acceptor Complexes in Copolymerization - Advances in

13

Donor-Acceptor

Complexes

in

Copolymerization

XXXI. VI.

Alternating Copolymer Graft Copolymers Synthesis in the A b s e n c e a n d Presence o f

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Complexing

Agents

N O R M A N G. G A Y L O R D Gaylord Research Institute Inc., New Providence, N.J. 07974

Graft copolymers containing alternating copolymer

branches

were prepared by copolymerizing monomers that form alternating copolymers

under conditions necessary for for-

mation of the specific alternating copolymer—i.e., with or without a complexing agent, in either case with or without a radical catalyst, and in the presence of polymers containing

labile

copolymers

or active hydrogen

atoms. Alternating

graft

of styrene-maleic anhydride, isoprene-maleic

anhydride, styrene-methyl methacrylate, and styrene-acrylonitrile were prepared in bulk, solution, or aqueous

me-

dium on one or more of these polymers: polystyrene, poly (butyl acrylate), high- and low-density polyethylene, atactic and

isotactic polypropylene, EPR,

nitrile rubber, cis-1,4-

-polybutadiene, ABS, PVC, and cellulose.

' " p h e c o p o l y m e r i z a t i o n of a strong d o n o r m o n o m e r a n d a strong acceptor

monomer—e.g., styrene

and maleic

anhydride—leads

to

the

f o r m a t i o n of a n e q u i m o l a r a l t e r n a t i n g c o p o l y m e r over a w i d e r a n g e of m o n o m e r f e e d ratios.

A l t h o u g h the p o l y m e r i z a t i o n m a y o c c u r s p o n -

taneously at e l e v a t e d temperatures, cursor

increases the

yield

the a d d i t i o n of a f r e e - r a d i c a l p r e -

of a l t e r n a t i n g

copolymer, independent

of

m o n o m e r charge ( 1 ). T h e c o p o l y m e r i z a t i o n of a d o n o r m o n o m e r w i t h a w e a k e r

acceptor

m o n o m e r , s u c h as m e t h y l m e t h a c r y l a t e or a c r y l o n i t r i l e , i n the presence of a c o m p l e x i n g agent ( a m e t a l h a l i d e or a n o r g a n o a l u m i n u m h a l i d e ) y i e l d s a n e q u i m o l a r , a l t e r n a t i n g c o p o l y m e r , regardless of i n i t i a l m o n o m e r c h a r g e a n d w i t h o r w i t h o u t f r e e - r a d i c a l p r e c u r s o r ( 1 ). 209 Platzer; Polymerization Reactions and New Polymers Advances in Chemistry; American Chemical Society: Washington, DC, 1973.

210

P O L Y M E R I Z A T I O N

Polymerization

of Donor-Acceptor

R E A C T I O N S

Comonomer

A N D N

E

W

P O L Y M E R S

Complexes

T h e f o r m a t i o n of a l t e r n a t i n g c o p o l y m e r is a t t r i b u t e d to t h e h o m o p o l y m e r i z a t i o n of a c o m o n o m e r charge-transfer c o m p l e x .

T h e latter is

f o r m e d spontaneously, subject to e q u i l i b r i u m considerations, w i t h t h e i n t e r a c t i o n of a s t r o n g d o n o r m o n o m e r a n d a s t r o n g acceptor m o n o m e r . D + A ^ ± [D

>A]

T h e f o r m a t i o n of the charge-transfer c o m p l e x is e n h a n c e d b y c o m p l e x i n g a n acceptor m o n o m e r w i t h a m e t a l h a l i d e , as a consequence of


the i n c r e a s e d a b i l i t y of t h e c o m p l e x e d m o n o m e r to a c c e p t electrons. A + M X

> A ...M X

D + A . . . M X ;=± [ D Spontaneous tration

>A . . . M X ]

p o l y m e r i z a t i o n occurs w h e n the e q u i l i b r i u m c o n c e n -

of t h e c o m p l e x

is h i g h

enough.

L o w e r temperatures

favor

c o m p l e x f o r m a t i o n , w h i l e p o l y m e r i z a t i o n m a y r e q u i r e t h e r m a l o r catalytic activation.

Since t h e p o l y m e r i z a t i o n w i t h a n d w i t h o u t t h e r a d i c a l

catalyst f o l l o w s the same course, t h e c o m o n o m e r c o m p l e x is c o n s i d e r e d to b e t h e p o l y m e r i z a b l e species i n either case. Although

t h e f o r m a t i o n of t h e ground-state

comonomer

transfer c o m p l e x occurs spontaneously, i t has b e e n suggested

charge(2,

13)

that p o l y m e r i z a t i o n i n v o l v e s the excited-state c o m p l e x ( e x c i p l e x ) . [D [D

>A] ^ [D+. - A ]

>A . . . M X ] ^± [D+. - A . . . M X ]

>—(DA) — X

> — (DA) — + M X X

T h e e x c i p l e x is a p p a r e n t l y generated spontaneously w h e n t h e c o n c e n t r a t i o n of ground-state complexes is h i g h e n o u g h , p r o b a b l y because of collision.

T h e effect of t h e r m a l a c t i v a t i o n is to increase t h e n u m b e r

of collisions. T h e proposed polymerization mechanism ( 1 ) involves initiation b y a h e a d - t o - h e a d r e a c t i o n of t w o e x c i t e d complexes; d u r i n g t h e r e a c t i o n , h y d r o g e n a b s t r a c t i o n a n d transfer occurs t h r o u g h a s i x - m e m b e r e d c y c l i c t r a n s i t i o n state t o generate a p o l y m e r c h a i n w i t h a n a t t a c h e d t e r m i n a l complex.

T h e propagation reaction

is h e a d - t o - t a i l a n d i n v o l v e s t h e

a d d i t i o n of e x c i t e d complexes to t h e c h a i n e n d t h r o u g h h y d r o g e n transfer via a s i x - m e m b e r e d c y c l i c t r a n s i t i o n state to regenerate the c o m p l e x chain end. T h e role of the f r e e - r a d i c a l i n i t i a t o r w a s earlier c o n s i d e r e d to i n v o l v e h y d r o g e n abstraction

(I).

H o w e v e r , d e c o m p o s i t i o n o f t h e free-

r a d i c a l p r e c u r s o r m a y also result i n excitation of t h e ground-state c o m plexes ( 2 ) .

Platzer; Polymerization Reactions and New Polymers Advances in Chemistry; American Chemical Society: Washington, DC, 1973.

13.

G A Y L O R D

Chlorine

Donor-Acceptor is v i r t u a l l y

211

Complexes

absent i n the

copolymer

produced in

the

a z o b i s i s o b u t y r o n i t r i l e ( A I B N ) c a t a l y z e d c o p o l y m e r i z a t i o n of styrene a n d m a l e i c a n h y d r i d e i n the presence of c h l o r o f o r m or c a r b o n

tetrachloride

(3, 4 ) , or of p - d i o x e n e a n d m a l e i c a n h y d r i d e i n the presence of acrylonitrile i n chloroform (5).

T h i s absence indicates that t r i c h l o r o m e t h y l

r a d i c a l s generated b y the r e a c t i o n of the c h l o r i n a t e d h y d r o c a r b o n s w i t h the r a d i c a l s f r o m A I B N are not i n c o r p o r a t e d into the p o l y m e r c h a i n . S i m i l a r l y , there is l i t t l e or n o c n l o r i n e i n the a l t e r n a t i n g c o p o l y m e r that is f o r m e d i n the c o p o l y m e r i z a t i o n of styrene a n d m e t h y l m e t h a c r y l a t e i n the presence of e t h y l a l u m i n u m s e s q u i c h l o r i d e ( E A S C ) i n the presence of c h l o r o f o r m a n d c a r b o n t e t r a c h l o r i d e , a n d w i t h or w i t h o u t a p e r o x i d e Downloaded by CORNELL UNIV on August 4, 2016 | http://pubs.acs.org Publication Date: June 1, 1973 | doi: 10.1021/ba-1973-0129.ch013

initiator

(6).

T h e f a i l u r e to i n c o r p o r a t e moieties a r i s i n g f r o m r a d i c a l attack o n the solvent into the a l t e r n a t i n g c o p o l y m e r s , c o u p l e d w i t h the

virtual

absence of catalyst residues i n the c o p o l y m e r w h e n the c o p o l y m e r i z a t i o n of styrene a n d m a l e i c a n h y d r i d e is i n i t i a t e d b y A I B N (3, 4), that

radical

species

may

initiate

the

p o l y m e r i z a t i o n of

indicates comonomer

charge-transfer complexes, b u t they are not i n c o r p o r a t e d into the p o l y mer chain. T h e absence of c h l o r i n e i n the c o p o l y m e r s , as w e l l as the f o r m a t i o n of h i g h - m o l e c u l a r - w e i g h t c o p o l y m e r s i n reactions c a r r i e d out i n c h l o r o f o r m or c a r b o n t e t r a c h l o r i d e , indicates that the p r o p a g a t i n g chains not p a r t i c i p a t e i n chain-transfer h y d r o g e n or c h l o r i n e atoms.

reactions

that result i n abstraction

do of

High-molecular-weight alternating copoly

mers are also o b t a i n e d i n the r a d i c a l - c a t a l y z e d c o p o l y m e r i z a t i o n of p r o p y l e n e a n d m a l e i c a n h y d r i d e i n l i q u i d p r o p y l e n e ( 7 ) , a n d i n the s p o n taneous c o p o l y m e r i z a t i o n of p r o p y l e n e a n d other α-olefins w i t h l o n i t r i l e i n the presence of a n o r g a n o a l u m i n u m h a l i d e

(8).

acry-

This

is

f u r t h e r e v i d e n c e that the p r o p a g a t i n g c h a i n i n the h o m o p o l y m e r i z a t i o n of c o m o n o m e r charge-transfer complexes does not abstract l a b i l e h y d r o gen atoms even f r o m α-olefins, w h i c h u s u a l l y u n d e r g o d e g r a d a t i v e c h a i n transfer i n the presence of free r a d i c a l s .

Grafting

of Alternating

Copolymers

D e s p i t e the absence of b o t h c h a i n transfer b y the p r o p a g a t i n g c h a i n a n d the i n i t i a t i n g r a d i c a l i n the c o p o l y m e r c h a i n , graft c o p o l y m e r s c o n t a i n i n g a l t e r n a t i n g c o p o l y m e r branches c a n b e p r e p a r e d b y c o p o l y m e r i z i n g m o n o m e r s that f o r m a l t e r n a t i n g c o p o l y m e r s i n the presence of p o l y mers c o n t a i n i n g l a b i l e or active h y d r o g e n atoms—e.g., tertiary or a l l y l i c c a r b o n atoms a n d a l d e h y d e groups One

proposal

(I)

(9).

h o l d s that the

h o m o p o l y m e r i z a t i o n of a c o m o n o m e r

propagating

chain end in

the

c o m p l e x is a c o m p l e x , a n d that


212


R E A C T I O N S

A N D N

E

W P O L Y M E R S

bimolecular termination involves polymer-polymer or polymer-complex interaction through carbene formation. w h e n the comonomers

I t is reasonable t o p r o p o s e that

are p o l y m e r i z e d i n t h e presence of a p o l y m e r ,

g r a f t i n g occurs b y t e r m i n a t i o n of a p r o p a g a t i n g a l t e r n a t i n g

copolymer

c h a i n o n a l a b i l e C - H of t h e substrate p o l y m e r , i.e., b y i n s e r t i o n o f t h e p o l y m e r i c c a r b e n e i n t o t h e l a b i l e C - H of t h e substrate. H HC-

HCH

\


/ XCY Η

•'"\

XCY V

Η •C—R \ HCH Η

ι

m ; YCX

/

\

R—C+ H

Ρ

Η HC•

H +C—R

:CH Η

Ρ—Ο

YCX

\

/ •CH Η

R—C Η

ι C H

I

R—CH I HCH

I

YCX

\ HCH

I

R—CH I HCH

I

YCX H Grafting in the Absence of Complexing

Agents

T h e g r a f t i n g o f a n a l t e r n a t i n g c o p o l y m e r o n a substrate p o l y m e r occurs w h e n t h e a l t e r n a t i n g c o p o l y m e r is p r e p a r e d u n d e r c o n d i t i o n s n o r m a l l y u s e d w i t h o u t t h e substrate p o l y m e r . W h e n c o m o n o m e r s that are subject t o spontaneous o r t h e r m a l i n i t i a t i o n a r e p o l y m e r i z e d i n t h e presence of a suitable p o l y m e r , graft c o p o l y m e r s are f o r m e d d e s p i t e t h e absence of a r a d i c a l catalyst (10).


13.

Donor-Acceptor

G A Y L O R D

Table I.

Graft Copolymerization of Poly ( styrene-alt-maleic anhydride ) onto Polystyrene

S - M A n h / P S wt ratio P o l y s t y r e n e ( P S ) , grams M

v


S / M A n h (1/1 m ) , grams Benzene, m l T e m p / T i m e , °C/hr M o n o m e r conversion, % Fractionation " Polystyrene, % G r a f t copolymers Benzene soluble, % P S / S - M A n h , mole % Benzene insoluble, % P S / S - M A n h , mole % α

213

Complexes

0.5 5.0 10,800 1.29/ 1.21 7.5 60/3 26.4

1.0 2.0 10,800 1.03/ 0.97 3.0 60/3 40.8

1.0 20.0 40,500 10.3/ 9.7 30 80/1 70.8

9.0 1.0 40,500 4.63/ 4.36 0 60/3 45.8

0.7

0.2

23.7

0.8

91.9 83/17 7.4 7/93

73.8 87/13 25.9 0/100

43.8 94/6 32.5 8/92

0.0 — 99.2 3/97

Precipitation in 1:2 benzene-petroleum ether from MEK solution. T y p i c a l results i n the graft p o l y m e r i z a t i o n of p o l y (styrene-alt-maleic

anhydride)

onto p o l y s t y r e n e i n s o l u t i o n w i t h o u t a r a d i c a l catalyst

s h o w n i n T a b l e I.

are

A n a l o g o u s results are o b t a i n e d i n the presence of a

r a d i c a l catalyst. T h e m o l e c u l a r w e i g h t of a n a l t e r n a t i n g c o p o l y m e r d e p e n d s o n the concentration

of p o l y m e r i z a b l e species, the c o m o n o m e r

charge-transfer

c o m p l e x , w h i c h i n t u r n depends o n the r e a c t i o n temperature.

A t ele

v a t e d temperatures, the c o p o l y m e r i z a t i o n rate is r a p i d a n d the m o l e c u l a r w e i g h t of the a l t e r n a t i n g c o p o l y m e r is l o w .

W h e n the p o l y m e r i z a t i o n

is c a r r i e d out u n d e r those c o n d i t i o n s i n the presence of a p o l y m e r , the g r a f t e d a l t e r n a t i n g c o p o l y m e r is present as m u l t i p l e short Spontaneous

branches.

c o p o l y m e r i z a t i o n of styrene a n d m a l e i c a n h y d r i d e i n

the presence of a m o l t e n p o l y m e r or a b u l k p o l y m e r u n d e r g o i n g defor m a t i o n at e l e v a t e d

temperatures

carboxylating polymers. m e r at 120° to 2 0 0 ° C .

is a r a p i d a n d c o n v e n i e n t

route

for

T h e r e a c t i o n is c a r r i e d out o n the b u l k p o l y ( d e p e n d i n g u p o n the softening o r m e l t i n g p o i n t

of the p o l y m e r ) b y i n j e c t i n g a n e q u i m o l a r s o l u t i o n of m a l e i c a n h y d r i d e i n styrene i n t o the m o l t e n p o l y m e r

(11,12).

T h e r e a c t i o n is d o n e i n e q u i p m e n t s u c h as a B r a b e n d e r or extruder; it c a n b e a b a t c h or a c o n t i n u o u s process.

Plasticorder

M a l e i c anhy

d r i d e is d i s s o l v e d i n styrene at 6 0 ° C , a n d the s o l u t i o n ( s t i l l at 6 0 ° C )

is

injected i n t o the m o l t e n p o l y m e r w h i c h is b e i n g fluxed or m i x e d at the d e s i r e d temperature.

S i n c e the p o l y m e r i z a t i o n a n d g r a f t i n g

reactions

are just a b o u t instantaneous, n o r e a c t i o n t i m e is n e e d e d after m o n o m e r a d d i t i o n is

finished.


214


R E A C T I O N S

A N D N

W h e n the g r a f t i n g r e a c t i o n is d o n e i n the B r a b e n d e r the p o l y m e r is fluxed f o r t w o m i n u t e s . tinuously

injected

into

the molten

E

W

P O L Y M E R S

Plasticorder,

T h e m o n o m e r m i x t u r e is c o n

mass o v e r

one minute,

a n d the

r e a c t i o n m i x t u r e then d i s c h a r g e d f r o m the P l a s t i c o r d e r . When

the r e a c t i o n is d o n e i n a n extruder, t h e rate of m o n o m e r

a d d i t i o n , g e n e r a l l y t h r o u g h a vent into the b a r r e l , is adjusted d e p e n d i n g u p o n the rate of t h r o u g h p u t of the m o l t e n p o l y m e r .

T h e carbox-

y l a t e d p o l y m e r m a y b e e x t r u d e d as r i b b o n , w h i c h is then f o r m e d i n t o pellets or as a fiber o r film. Table

II

shows

t y p i c a l results

obtained

i n t h e c a r b o x y l a t i o n of

l o w - d e n s i t y p o l y e t h y l e n e i n the P l a s t i c o r d e r at 1 5 0 ° C . E x t r a c t i o n of the Downloaded by CORNELL UNIV on August 4, 2016 | http://pubs.acs.org Publication Date: June 1, 1973 | doi: 10.1021/ba-1973-0129.ch013

r e a c t i o n p r o d u c t w i t h acetone at 2 5 ° C f o r 24 hours removes u n r e a c t e d m o n o m e r s a n d u n g r a f t e d styrene-maleic

Table II.

C a r b o x y l a t i o n of L o w - D e n s i t y P o l y e t h y l e n e at 1 5 0 ° C

Monomers

S/AA

S/MAnh

W e i g h t , grams M o l e ratio L D P E , grams R e c o v e r y , grams Monomer Conversion, % Acetone-Extraction Soluble, % Insoluble, % A c i d Value, m g K O H / g Before E x t r a c t i o n After Extraction a

anhydride copolymer.

α

MAnh

S/AA

2.7/6.2

2.7/1.9

1/1 40.0 44.9 92.4

1/1 40.0 41.9 41.3

2.7/3.8 1/2 40.0 43.2 49.2

2.6 — 40.0 41.5 57.7

0.4 99.6

0.6 99.4

0.8 99.2

1.8 98.2

35.4 (70.8) 31.9 (63.8)

11.2

10.9

6.2

5.6

19.7 (39.4) 2.2 (4.4)

Two min in Brabender Plasticorder. T h e a c i d v a l u e is o b t a i n e d b y r e f l u x i n g the p r o d u c t w i t h x y l e n e to

c o n v e r t c a r b o x y l i c a c i d g r o u p s ( f o r m e d b y exposure of the p r o d u c t to air)

into

anhydride

methanolic K O H .

groups,

followed b y refluxing w i t h

anhydrous

T h e c o o l e d m i x t u r e is then t i t r a t e d w i t h 2 - p r o p a n o l i c

H C 1 u s i n g p h e n o l p h t h a l e i n as the i n d i c a t o r . T a b l e I I is the a c t u a l t i t r a t i o n v a l u e .

T h e acid value shown i n

H o w e v e r , since m e t h a n o l converts

the a n h y d r i d e to the h a l f ester, the true a c i d v a l u e , s h o w n i n p a r e n theses, is d o u b l e t h e t i t r a t i o n v a l u e . T h e effectiveness of the r e a c t i o n w i t h styrene-maleic a n h y d r i d e is clear w h e n the results are c o m p a r e d w i t h those o b t a i n e d — u n d e r the same c o n d i t i o n s w i t h o u t a r a d i c a l c a t a l y s t — u s i n g a 1:1 m o l a r m i x t u r e of styrene a n d a c r y l i c a c i d , a 1:2 m o l a r m i x t u r e of styrene a n d a c r y l i c


13.

G A Y L O R D

Table III.

Donor-Acceptor

215

Complexes

Carboxylation of High-Density Polyethylene

Temperature, °C


170

150

2.7/2.6 40.0 43.4 64.2

2.7/2.6 40.0 44.1 77.4

S / M A n h (1/1 m ) , grams H D P E , grams R e c o v e r y , grams Monomer Conversion, % Acetone Extraction Soluble, % Insoluble, % Acid Value, mg K O H / g Before E x t r a c t i o n After Extraction

α

3.2 96.8

3.2 96.8

3 2 . 2 (64.4) 2 0 . 0 (40.0)

3 4 . 0 (68.0) 2 3 . 7 (47.4)

" Two min in Brabender Plasticorder. Table I V .

Carboxylation of Atactic Polypropylene at 1 5 0 ° C

S / M A n h (1/1 m ) , grams A P P , grams Acetone Extraction Soluble, % Insoluble, % A c i d Value, mg K O H / g Before E x t r a c t i o n After Extraction

a

1.4/1.3 40.0

2.7/2.6 40.0

9.8 91.8

5.8 94.2

24.3 21.3

5 9 . 6 (119.2 3 2 . 5 (65.0)

(48.6) (42.6)

° Two min in Brabender Plasticorder. a c i d ( t o give t h e same n u m b e r of c a r b o x y l groups as are a v a i l a b l e i n m a l e i c a n h y d r i d e ) , a n d m a l e i c a n h y d r i d e alone ( T a b l e

II).

T h e m o n o m e r c o n v e r s i o n u s i n g t h e m i x t u r e of styrene a n d m a l e i c a n h y d r i d e is m u c h h i g h e r t h a n i n the other cases.

T h i s v a l u e does n o t

t r u l y represent m o n o m e r c o n v e r s i o n b u t , instead, the a m o u n t of m o n o m e r n o t lost d u r i n g treatment. volatilized monomers

Thus, both reacted monomers a n d n o n -

are present

i n the r e p o r t e d v a l u e .

T h e values

o b t a i n e d w i t h m a l e i c a n h y d r i d e alone represent a large a m o u n t of u n r e a c t e d m a l e i c a n h y d r i d e , as i n d i c a t e d b y the a m o u n t extracted a n d t h e a c i d v a l u e of the p o l y m e r after extraction. w i t h styrene-maleic

I n a n y event, t h e r e c o v e r y

a n h y d r i d e is c o n s i d e r a b l y h i g h e r t h a n i n a l l t h e

other cases. The monomers

acetone-soluble that

fraction representing

unreacted

d i d n o t react w i t h the substrate

a n d reacted

p o l y m e r is also f a r

smaller w i t h the styrene-maleic a n h y d r i d e m i x t u r e . T h e a c i d values, b o t h b e f o r e a n d after extraction w i t h acetone, are at least five times h i g h e r w i t h styrene-maleic a n h y d r i d e t h a n w i t h a n y of t h e other mixtures.

T h e differences are even m o r e d r a m a t i c w h e n t h e

a c i d values are d o u b l e d f o r styrene-maleic a n h y d r i d e .


216


R E A C T I O N S

A N D N E W

P O L Y M E R S

T h e results o b t a i n e d b y c a r b o x y l a t i n g h i g h - d e n s i t y p o l y e t h y l e n e s h o w n i n T a b l e III.

T h e tertiary c a r b o n atoms at b r a n c h points

are are

g r a f t i n g sites.

T h e h i g h a c i d values m a y also i n d i c a t e that the g r a f t e d

styrene-maleic

anhydride copolymer

chains

are

of

higher

molecular

w e i g h t t h a n i n the case of l o w - d e n s i t y p o l y e t h y l e n e . T h e presence of a great n u m b e r of g r a f t i n g sites is s h o w n i n the c a r b o x y l a t i o n of atactic p o l y p r o p y l e n e at 1 5 0 ° C

(Table I V ) .

Isotactic

p o l y p r o p y l e n e requires a temperature of 1 7 0 ° C f o r effective c a r b o x y l a tion (Table V ) .

T h e r e l a t i v e l y greater a m o u n t of extractable

material

i n the case of atactic p o l y p r o p y l e n e i n d i c a t e the acetone s o l u b i l i t y of the p o l y p r o p y l e n e or the l i g h t l y g r a f t e d p o l y m e r , or b o t h . Downloaded by CORNELL UNIV on August 4, 2016 | http://pubs.acs.org Publication Date: June 1, 1973 | doi: 10.1021/ba-1973-0129.ch013

C o m p a r i s o n of the c a r b o x y l a t i o n procedures u s i n g a c r y l i c a c i d i n l i e u of m a l e i c a n h y d r i d e is e v e n m o r e s t r i k i n g w i t h isotactic p o l y p r o p y l ene ( T a b l e V ) t h a n w i t h p o l y e t h y l e n e . Table V .

C a r b o x y l a t i o n of Isotactic Polypropylene at 1 7 0 ° C

Monomers

S/MAnh

W e i g h t , grams Mole Ratio I P P , grams R e c o v e r y , grams M o n o m e r Conversion, % Acetone Extraction Soluble, % Insoluble, % Acid Value, mg K O H / g Before E x t r a c t i o n

2.7/2.6

2.7/1.9

1/1 40.0 44.2 79.2

After Extraction a

S/AA

MAnh

1/1 40.0 42.4 52.2

2.7/3.8 1/2 40.0 42.8 43.1

2.6 — 40.0 41.4 53.8

1.4 98.6

2.2 97.8

3.2 96.8

2.6 97.4

27.9 (55.8) 15.9 (31.8)

7.4

6.8

1.3

2.1

24.1 (48.2) 1.9 (3.8)

Two min in Brabender Plasticorder.

Table V I .

Carboxylation of Ethylene-Propylene Rubber

Temperature, °C S / M A n h (1/1 m ) , grams E P R , grams Acetone Extraction Soluble, % Insoluble, % A c i d Value, mg K O H / g After Extraction a

S/AA

α

100 3.6/3.4 35.0

150 3.6/3.4 35.0

8.0 92.0

2.5 97.5

8 . 5 (17.0)

3 8 . 0 (76.0)

a

170 3.6/3.4 35.0 3.8 96.2 12.5

Ten min in Brabender Plasticorder.


(25.0)

13.

Donor-Acceptor

G A Y L O R D

Table V I I .

Carboxylation of A B S , B / A N and cis-l,4-Polybutadiene

P o l y m e r (35 grams)


Butadiene

3.6/3.4 150 6.8 93.2

9.8 90.2

14.8 85.2

1 5 . 5 (31.0)

2 8 . 0 (56.0)

5.4/5.1 120

8 . 0 (16.0)

Ten min in Brabender Plasticorder.

Table V I I I .

Carboxylation of Poly (vinyl chloride) at 1 8 0 ° C

S / M A n h (1/1 m ) , g r a m s P V C ( 1 % T h e r m o l i t e 31), g r a m s Recovery, grams Monomer Conversion, % Acetone Extraction Soluble, % Insoluble, % A c i d Value, mg K O H / g Before E x t r a c t i o n After Extraction a

a

B/AN (75/25) 3.6/3.4 150

ABS

S / M A n h (1/1 m ) , grams T e m p e r a t u r e , °C Acetone Extraction Soluble, % Insoluble, % A c i d Value, m g K O H / g After Extraction α

217

Complexes

a

1.4/1.3 40.0 41.6 59.3

2.7/2.6 40.0 44.1 77.4

35.2 64.8

34.2 65.8

3 4 . 4 (68.8) 1 7 . 1 (34.2)

5 4 . 4 (108.8) 2 7 . 7 (55.4)

Two min in Brabender Plasticorder. T h e c a r b o x y l a t i o n of E P R is s u m m a r i z e d i n T a b l e V I , w h i l e the

carboxylations

of A B S , n i t r i l e r u b b e r ,

and ds-l,4-polybutadiene

are

shown i n Table V I I . T h e presence of s t a b i l i z e r has l i t t l e effect o n p o l y ( v i n y l c h l o r i d e ) carboxylation (Table

VIII).

S i n c e the other p o l y m e r s w e r e also s u b

jected to the c a r b o x y l a t i o n process w i t h o u t r e m o v i n g c o m m e r c i a l a d d i tives

such

as antioxidants,

U V a n d thermal

stabilizers,

antiblocking

agents, e t c . — t h e a d d i t i v e s i n h i b i t neither the p o l y m e r i z a t i o n of the sty r e n e - m a l e i c a n h y d r i d e c o m p l e x n o r the g r a f t i n g reaction. P o l y s t y r e n e , a c r y l i c ester h o m o p o l y m e r s a n d c o p o l y m e r s , a n d other p o l y m e r s c o n t a i n i n g tertiary or a l l y l i c h y d r o g e n atoms h a v e also b e e n r e a d i l y c a r b o x y l a t e d b y the in situ p o l y m e r i z a t i o n of the styrene-maleic a n h y d r i d e c o m p l e x at 120 to 1 8 0 ° C . R a d i c a l - c a t a l y z e d graft c o p o l y m e r i z a t i o n is g e n e r a l l y

accompanied

b y c r o s s l i n k i n g o r scission ( o r b o t h ) of the substrate p o l y m e r .

G e l per

m e a t i o n c h r o m a t o g r a p h i c analysis of p o l y m e r c a r b o x y l a t e d b y the in situ copolymerization

of styrene

a n d maleic

anhydride without a radical

catalyst shows that the m o l e c u l a r size d i s t r i b u t i o n of the c a r b o x y l a t e d


218


R E A C T I O N S

A N D N E W

P O L Y M E R S

p o l y m e r is s i m i l a r to that of t h e o r i g i n a l substrate p o l y m e r ; this

finding

is consistent w i t h the absence of r a d i c a l species. A l t h o u g h a r a d i c a l catalyst is n o t necessary f o r graft p o l y m e r i z a t i o n w h e n the a l t e r n a t i n g c o p o l y m e r forms spontaneously, a r a d i c a l catalyst is r e q u i r e d w h e n a l t e r n a t i n g c o p o l y m e r f o r m a t i o n requires r a d i c a l i n i tiation ( 1 0 ) . T h e t h e r m a l r e a c t i o n of a conjugated yields the cyclic D i e l s - A l d e r adduct.

diene and maleic anhydride

H o w e v e r , alternating copolymers

are r e a d i l y f o r m e d w h e n t h e r e a c t i o n is c a r r i e d out i n t h e presence of a f r e e - r a d i c a l p r e c u r s o r at a temperature w h e r e t h e catalyst h a l f - l i f e is o n e h o u r o r less, o r t h e catalyst a d d i t i o n t i m e is less t h a n o n e h o u r (2, 13). Downloaded by CORNELL UNIV on August 4, 2016 | http://pubs.acs.org Publication Date: June 1, 1973 | doi: 10.1021/ba-1973-0129.ch013

T h e r a d i c a l - c a t a l y z e d c o p o l y m e r i z a t i o n of isoprene a n d m a l e i c a n h y d r i d e i n t h e presence of p o l y s t y r e n e gives t h e c o r r e s p o n d i n g a l t e r n a t i n g c o p o l y m e r graft c o p o l y m e r

(Table

I X ) . S i m i l a r results a r e o b t a i n e d

w i t h other dienes a n d a p p r o p r i a t e substrate p o l y m e r s . Table IX.

Graft Copolymerization of Poly(isoprene-alt-maleic anhydride ) onto Polystyrene α

I - M A n h / P S wt ratio Polystyrene (PS), grams M I / M A n h (1/1 m ) , grams tert-BPP ( 7 5 % ) , g r a m s Monomer Conversion, % F r a c t i o n a t i o n (Benzene) P(I-MAnh), % Graft Copolymer, % P S / I - M A n h , mole % v

tert-BPP

a

1.7 10.0 10,800 0.68/0.98 0.5 54

4.1 10.0 10,800 1.7/2.45 1.2 89

0 100 89/11

16 84 87/13

8.3 2.0 40,500 6.8/9.8 4.8 90 71 29 28/72

in I added over 15 min to PS + MAnh in 25 ml dioxane at 65-75°C;

total reaction time, two hr Grafting

in the Presence

of Metal

Halide

Complexing

Agents

A l t e r n a t i n g c o p o l y m e r graft c o p o l y m e r s a r e also p r o d u c e d w h e n comonomers

that y i e l d a l t e r n a t i n g c o p o l y m e r s w i t h b u t n o t w i t h o u t a

c o m p l e x i n g agent are c o p o l y m e r i z e d i n t h e presence of a c o m p l e x i n g agent a n d a suitable

p o l y m e r , either w i t h o r w i t h o u t a f r e e - r a d i c a l

p r e c u r s o r (14). G r a f t i n g occurs w h e n t h e a l t e r n a t i n g c o p o l y m e r is p r e p a r e d u n d e r c o n d i t i o n s n o r m a l l y u s e d i n t h e absence of a substrate p o l y m e r .

Pres

ence of a r a d i c a l catalyst is therefore n o t necessary w h e n t h e r e a c t i o n is c a r r i e d out i n b u l k o r i n a n o r g a n i c m e d i u m , so l o n g as c o n c e n t r a t i o n of t h e c o m p l e x is h i g h e n o u g h .

T h e c o n c e n t r a t i o n of c o m p l e x i n g agent

is 5 t o 5 0 m o l e %, b a s e d o n t h e c o n c e n t r a t i o n o f t h e acceptor m o n o m e r .


13.

Donor-Acceptor

G A Y L O R D

219

Complexes

S o l v e n t c o n c e n t r a t i o n is k e p t at a l e v e l that ensures efficient s t i r r i n g b u t l o w e n o u g h to a v o i d d i l u t i o n ; the t e m p e r a t u r e is g e n e r a l l y k e p t b e l o w 60°C. T a b l e X shows t h e results o b t a i n e d w h e n p o l y s t y r e n e is d i s s o l v e d i n styrene m o n o m e r , f o l l o w e d b y t h e a d d i t i o n of m e t h y l m e t h a c r y l a t e and

EASC.

Depending upon monomer

concentration

a n d after t h e

i n d i c a t e d r e a c t i o n p e r i o d , the r e a c t i o n m i x t u r e is c o n v e r t e d to a h i g h l y s w o l l e n g e l or s o l i d p r o d u c t .

T h e alternating and equimolar composi-

t i o n of t h e p r o d u c t s w a s c o n f i r m e d b y N M R a n d e l e m e n t a r y

analyses,

respectively.


Table X .

G r a f t C o p o l y m e r i z a t i o n of P o l y ( s t y r e n e - a l t - m e t h y l m e t h a c r y l a t e ) onto P o l y s t y r e n e i n B u l k

P S , grams S / M M A , mmoles E A S C , mmoles T e m p / T i m e , °C/hr Monomer Conversion % F r a c t i o n a t i o n (Cyclohexane) Soluble, % P S / S - M M A , weight % Insoluble, % P S / S - M M A , weight % Table X I .

3.0 30/30 15 20/3 81.9

3.0 90/30 15 20/3 88.2

3.0 30/90 45 20/3 95.3

3.0 30/30 15 60/1.67 55.7

32 93/7 68 13/87

32 87/13 68 12/88

29 94/6 71 10/90

38 95/5 62 14/86

G r a f t C o p o l y m e r i z a t i o n of P o l y ( s t y r e n e - a l t - a c r y l o n i t r i l e ) onto P o l y ( b u t y l a c r y l a t e )

P B A , grams S / A N , mmoles Z n C U , mmoles A N / Z n C l mole r a t i o Medium, ml Catalyst T e m p / T i m e , °C/hr Monomer Conversion, % F r a c t i o n a t i o n (Acetone) Soluble, % P B A / S - A N , weight % Insoluble, % P B A / S - A N , weight % 2

8 . 0 (Solid) 125/125 6.25 20/1 T o l u e n e , 60 tert-BPP, 0 . 5 m l 30/20 40.8 18 4/96 82 44/56

8 . 0 (Latex) 125/125 31.25 4/1 water, 1 0 . 8 K P S , 0.4 g 25/20 51.0 25 0/100 75 48/52

T h e use of a r a d i c a l catalyst increases p o l y m e r i z a t i o n rate a n d t h e extent of g r a f t i n g .

W h e n the r e a c t i o n is d o n e i n a n aqueous m e d i u m ,

as w h e n t h e substrate

p o l y m e r is c h a r g e d as a latex, a w a t e r - s o l u b l e

catalyst is necessary, as p r e v i o u s l y o b s e r v e d f o r the p r e p a r a t i o n of altern a t i n g c o p o l y m e r s i n a n aqueous

m e d i u m (15).

A l t h o u g h t h e latex


220


coagulates w h e n the

R E A C T I O N S

A N D N E W

P O L Y M E R S

c o m p l e x i n g agent is a d d e d , efficient s t i r r i n g of

the m i x t u r e gives a smooth r e a c t i o n . T h e c a t a l y z e d graft c o p o l y m e r i z a t i o n of trile)

onto

poly(styrene-alt-acryloni-

p o l y ( b u t y l a c r y l a t e ) i n the presence of z i n c c h l o r i d e , i n

s o l u t i o n , a n d i n a n aqueous m e d i u m , is s u m m a r i z e d i n T a b l e X L T h e c a t a l y z e d graft c o p o l y m e r i z a t i o n of s t y r e n e - m e t h y l l a t e - E A S C a n d α-methylstyrene-methacrylonitrile-EASC ber i n s o l u t i o n is s h o w n i n T a b l e X I I . done

on

ethylene-propylene

I n a d d i t i o n , g r a f t i n g has

copolymers,

polybutadiene,


been

acrylic

c o p o l y m e r s , a n d other p o l y m e r s c o n t a i n i n g l a b i l e h y d r o g e n Table X I I .

methacry-

onto n i t r i l e r u b ester

atoms.

Graft Copolymerization onto Nitrile Rubber ( B / A N = 70/30)

P ( B / A N ) , grams Monomers Moles E A S C , mmoles Medium, ml C a t a l y s t , grams T e m p / T i m e , °C/hr Monomer Conversion, % F r a c t i o n a t i o n (Acetone) Soluble, % P ( B / A N ) , weight % A l t , weight % Insoluble, % P ( B / A N ) , weight % A l t , weight %

5.6 MS/MAN 125/125 25 T o l u e n e , 55 B P , 0.25 40/4 7.5

5.6 S/MMA 125/125 10 Benzene, 55 B P , 0.25 40/4 8.6 44 90 S / M M A 10 56 58 S / M M A 42

40 80 MS/MAN 60 74 MS/MAN

W h e n the p o l y m e r i z a t i o n is c a r r i e d out b e l o w 6 0 ° C , the copolymer branches have an equimolar composition.

20

26

grafted

Above 60°C, and

either w i t h or w i t h o u t a r a d i c a l catalyst, little or no g r a f t i n g occurs a n d n o n e q u i m o l a r u n g r a f t e d c o p o l y m e r is o b t a i n e d — p a r t i c u l a r l y w h e n polymerizing composition (16)

is s t y r e n e - a c r y l o n i t r i l e - E A S C .

Earlier

the

work

has s h o w n that this c o m p o s i t i o n y i e l d s r a d i c a l rather t h a n alternat

i n g c o p o l y m e r at elevated temperatures.

W h e n the p o l y m e r i z i n g c o m p o

s i t i o n is s t y r e n e - a c r y l o n i t r i l e - z i n c c h l o r i d e , temperatures a b o v e 6 0 ° C g i v e grafted

copolymer

rich i n acrylonitrile.

Acrylonitrile-rich copolymers

h a v e b e e n o b t a i n e d at e l e v a t e d temperatures of the A N - A N - Z n C l

2

complex

because of p o l y m e r i z a t i o n

(17).

H i g h e r levels of g r a f t i n g are o b t a i n e d o n p o l y m e r s c o n t a i n i n g p o l a r functionality—e.g.,

ester or n i t r i l e g r o u p — w h e n s u c h p o l y m e r s are c o m -

p l e x e d b e f o r e a d d i n g the comonomers

a n d f r e e - r a d i c a l catalyst

(18).

T h e c o m p l e x i n g agent is a d d e d to the p o l y m e r , either i n s o l u t i o n or d i s p e r s e d or e m u l s i f i e d i n a nonsolvent.

R e a c t i o n t i m e varies f r o m


13.

Donor-Acceptor

G A Y L O R D

221

Complexes

five m i n u t e s to 48 hours, d e p e n d i n g u p o n t h e specific f u n c t i o n a l g r o u p , its

concentration

a n d accessibility,

a n d the reaction

medium.

c o m o n o m e r s a n d t h e f r e e - r a d i c a l p r e c u r s o r are then a d d e d . ogeneous

The

I n a heter-

system s u c h as a p o l y m e r latex, the f r e e - r a d i c a l catalyst is

u s u a l l y a d d e d after the m o n o m e r s have h a d a c h a n c e to diffuse i n t o t h e precomplexed polymer. T h e t e m p e r a t u r e at w h i c h the c o m p l e x is f o r m e d m a y b e t h e same or different f r o m that u s e d f o r the c o p o l y m e r i z a t i o n of t h e m o n o m e r . T h e results s h o w n i n T a b l e X I I I

were obtained when solid zinc

chloride was m i x e d w i t h solid poly ( b u t y l acrylate)

a n d the m i x t u r e

s t i r r e d o r h o m o g e n i z e d v i g o r o u s l y f o r one h o u r at 5 0 ° C Downloaded by CORNELL UNIV on August 4, 2016 | http://pubs.acs.org Publication Date: June 1, 1973 | doi: 10.1021/ba-1973-0129.ch013

parent y e l l o w - b r o w n gel was obtained).

( u n t i l a trans-

T h e g e l w a s d i s s o l v e d i n 50

m l of toluene a n d t h e m i x t u r e s t i r r e d at 5 0 ° C f o r six hours.

T h e sty-

r e n e - a c r y l o n i t r i l e m i x t u r e w a s a d d e d at 2 5 ° C , f o l l o w e d b y the o r g a n i c p e r o x i d e catalyst. hours.

This reaction

w a s c a r r i e d o u t at 2 5 ° C

f o r three

After precipitation w i t h methanol, the product was fractionated

b y Soxhlet extraction, as s u m m a r i z e d i n T a b l e X I I I .

Table

X I I I . G r a f t C o p o l m e r i z a t i o n of P o l y ( s t y r e n e - a l t - a c r y l o n i t r i l e ) onto P r e c o m p l e x e d P o l y ( b u t y l a c r y l a t e ) - Z n C l 2

Polymerization

Precomplexation P B A , grams Z n C l , grams Temp/Time, Toluene, m l Temp/Time, 2

(mmoles) (mmoles) °C/hr °C/hr

6 . 5 (50) 3 . 4 (25) 50/1 50 50/6

A N , grams (mmoles) S, grams (mmoles)

6 . 6 (125) 1 3 . 0 (125) 0.5 25/3

M P P (50%), m l T e m p / T i m e , °C/hr

Monomer Conversion 53.0% Fractionation

Solvent Hexane E t h y l Acetate Residue

%

BA/S/AN Mole Ratio

S/AN Mole Ratio

20.0 7.5 72.5

100/0/0 32/36/32 11/44.5/44.5

— 52/48 50/50

T h e results i n T a b l e X I V w e r e o b t a i n e d b y a d d i n g a n aqueous z i n c c h l o r i d e s o l u t i o n to a p o l y ( b u t y l a c r y l a t e ) latex.

After precomplexation

at 3 0 ° C , the m o n o m e r m i x t u r e a n d the r e d o x catalyst w e r e a d d e d , a n d the p o l y m e r i z a t i o n w a s c a r r i e d o u t at 3 0 ° C .

B e c a u s e of the hetero-

geneity of the r e a c t i o n m i t x u r e , a l a r g e a m o u n t of a l t e r n a t i n g c o p o l y m e r a c c o m p a n i e d t h e a l t e r n a t i n g c o p o l y m e r graft c o p o l y m e r .


222


R E A C T I O N S

A N DN E W

P O L Y M E R S

Table X I V . Graft Copolymerization of Poly(styrene-alt-acrylonitrile) onto Precomplexed Poly (butyl a c r y l a t e ) - Z n C l Latex 2

Polymerization

Precomplexation

A N , g r a m s (mmoles)

P B A L a t e x (42.5%), grams P B A , grams (mmoles) Z n C l , grams (mmoles) T e m p / T i m e , °C/hr

6 . 6 (125)

18.8 S, g r a m s (mmoles)

1 3 . 0 (125)

K S 0 /Na S 0 , grams T e m p / T i m e , °C/hr

0.27/0.19 30/3

8 . 0 (62.5)

2

2

1.70(12.5) 30/24

2

8

2

2

3


Monomer Conversion 69.5% Fractionation Solvent Hexane Acetone Residue

%

BA/S/AN Mole Ratio

S/AN Mole Ratio

7.1 47.1 45.8

100/0/0 2/49/49 64/18/18

50/50 50/50

Table X V . Graft Copolymerization of Poly(styrene-alt-acrylonitrile) onto Precomplexed Poly (butyl acrylate)—ZnCl Latex 2

Polymerization

Precomplexation P B A latex (42.5%) grams P B A , grams (mmoles) Styrene, grams (mmoles) T e m p / T i m e , °C/hr Z n C l , grams (mmoles) T e m p / T i m e , °C/hr

A N , g r a m s (mmoles)

6 . 6 (125)

18.8 K S 0 , grams 2

2

0.4

8

8 . 0 (62.5) 1 3 . 0 (125) 30/24

T e m p / T i m e , °C/hr

50/20

2

4 . 2 6 (31.25) 42/5 M o n o m e r conversion 8 8 . 4 % Fractionation

Solvent Hexane Acetone Residue

% 8.7 7.3 84.0

BA/S/AN Mole Ratio 100/0/0 1/46.5/52.5 25/40/35

S/AN Mole Ratio — 47/53 53/47


13.

G A Y L O R D

Donor-Acceptor

223

Complexes

T h e y i e l d of graft c o p o l y m e r w a s i n c r e a s e d b y m i x i n g t h e latex w i t h styrene f o r 24 hours before a d d i n g s o l i d z i n c c h l o r i d e . easier d i f f u s i o n of t h e latter i n the p o l y m e r .

This permitted

A s a result (see T a b l e X V ) ,

m o n o m e r c o n v e r s i o n w a s increased, y i e l d of u n g r a f t e d a l t e r n a t i n g c o p o l y m e r w a s r e d u c e d , a n d y i e l d of graft c o p o l y m e r w a s increased. P r e c o m p l e x a t i o n is n o t as effective i n a homogeneous system, w h e r e the c o m p l e x i n g agent has a n o p p o r t u n i t y to diffuse a w a y f r o m the p o l y m e r a n d c o m p l e x w i t h the a c c e p t o r m o n o m e r .

T h i s is p a r t i c u l a r l y true


w h e n p r e c o m p l e x a t i o n t i m e is short ( T a b l e X V I ) . T a b l e X V I . G r a f t C o p o l y m e r i z a t i o n of P o l y ( s t y r e n e - a l t - a c r y l o n i t r i l e ) onto P r e c o m p l e x e d P o l y ( b u t y l a c r y l a t e ) — E A S C Precomplexation P B A , grams (mmoles) E A S C , m l (mmoles) Toluene, m l T e m p / T i m e , °C/hr

Polymerization 8 . 0 (62.5) 3 . 5 (15.7) 50 25/0.5

A N , grams (mmoles) S, grams (mmoles) M P P (50%), m l T e m p / T i m e , °C/hr

6 . 6 (125) 1 3 . 0 (125) 0.5 22/3

M o n o m e r conversion 5 5 . 6 % Fractionation

%

B A /S/AN Mole Ratio

S/AN Mole Ratio

3.6 64.9 31.5

100/0/0 2/52.5/45.5 67/18/15

— 54/46 54/46

Solvent Hexane E t h y l acetate Residue

T a b l e X V I I shows the g r a f t i n g of p o l y ( s t y r e n e - a l t - a c r y l o n i t r i l e ) o n nitrile rubber precomplexed w i t h E A S C .

T h i s system is

heterogeneous

since a d d i t i o n of E A S C to t h e p o l y m e r s o l u t i o n causes the p o l y m e r to agglomerate o r p r e c i p i t a t e . A n effective m e t h o d of p r e p a r i n g p r e c o m p l e x e d p o l y m e r is to h o m o p o l y m e r i z e a p o l a r m o n o m e r i n the presence of a c o m p l e x i n g agent u s i n g l i g h t , a s m a l l a m o u n t of o x y g e n , or a f r e e - r a d i c a l catalyst f o r initiation.

The homopolymer

contains

W h e n a m i x t u r e of c o m o n o m e r s

complexed

complexing

agent.

is a d d e d to the c o m p l e x e d p o l y m e r ,

f o l l o w e d b y a d d i t i o n of a f r e e - r a d i c a l catalyst ( i f n e c e s s a r y ) ,

alternating

c o p o l y m e r a n d graft c o p o l y m e r are o b t a i n e d . Similarly, an alternating copolymer containing complexed complexing agent m a y b e p r e p a r e d f r o m a c o m o n o m e r with

different

comonomers

to f o r m

mixture a n d then m i x e d

an alternating

copolymer

copolymer.


graft

224


Table X V I I .

R E A C T I O N S

A N D N E W

P O L Y M E R S

Graft Copolymerization of Poly(styrene-alt-acrylonitrile) onto Precomplexed Nitrile R u b b e r - E A S C

Precomplexation

Polymerization

P ( B / A N ) (70:30), grams E A S C , mmoles Toluene, m l T e m p / T i m e , °C/hr

4.0 22 40 40/1

A N , grams (mmoles) S, grams (mmoles) B e n z o y l P e r o x i d e , grams T e m p / T i m e , °C/hr

4 . 1 (77) 8 . 0 (77) 0.36 40/5

M o n o m e r conversion 8 7 %


Fractionation

Solvent Benzene Acetone Residue Grafting

on Cellulose

%

B/AN/S Mole Ratio

S/AN Mole Ratio

19 12 69

64/27/9 0/50/50 40/39/21

9/0 50/50 49/51

and Polyvinyl

Alcohol

F o r m a t i o n of a l t e r n a t i n g c o p o l y m e r graft c o p o l y m e r s f r o m b i n a r y m o n o m e r mixtures suggests that cellulose acts as a m a t r i x a n d promotes the f o r m a t i o n of c o m o n o m e r c h a r g e transfer complexes (19).

T h i s is i n

spite of the fact that graft c o p o l y m e r i z a t i o n of a c r y l i c m o n o m e r s cellulose i n aqueous

on

suspension, either w i t h o u t a catalyst, u n d e r i r r a

d i a t i o n , or i n the presence of o x i d i z i n g agents is c o n s i d e r e d to i n v o l v e a r a d i c a l m e c h a n i s m c o m p l i c a t e d b y d i f f u s i o n effects s t e m m i n g f r o m the r e a c t i o n mixture's heterogeneity a n d h i g h viscosity. T h e c o p o l y m e r i z a t i o n of styrene a n d m e t h y l m e t h a c r y l a t e molar ratio) catalyst

(90/10

i n the presence of w o o d p u l p at 9 0 ° C u s i n g N a C 1 0

2

as

gives e q u i m o l a r g r a f t e d a n d u n g r a f t e d c o p o l y m e r s at a l o w

conversion.

H o w e v e r , w h i l e the g r a f t e d c o p o l y m e r c o m p o s i t i o n is s t i l l

e q u i m o l a r at a h i g h e r c o n v e r s i o n , the u n g r a f t e d c o p o l y m e r c o m p o s i t i o n approaches

that

expected

w i t h a radical mechanism

f r o m the c o m o n o m e r

charge

in

accordance

(20).

W h e n a m i x t u r e of b u t a d i e n e a n d m e t h y l m e t h a c r y l a t e is h e a t e d at 90 ° C w i t h a n aqueous suspension of k r a f t w o o d p u l p c o n t a i n i n g a s m a l l a m o u n t of n o n i o n i c surfactant a n d i n the absence of a catalyst, essen t i a l l y e q u i m o l a r a l t e r n a t i n g b u t a d i e n e - m e t h y l m e t h a c r y l a t e c o p o l y m e r is g r a f t e d o n the cellulose w h e n the m o n o m e r charge contains 2 0 - 5 0 m o l e % methyl methacrylate

(21).

T h e m u t u a l γ-irradiation

of viscose r a y o n i m m e r s e d i n a m e t h a n o l

s o l u t i o n c o n t a i n i n g b u t a d i e n e a n d a c r y l o n i t r i l e at 3 0 ° C y i e l d s u n g r a f t e d


13.

Donor-Acceptor

G A Y L O R D

225

Complexes

c o p o l y m e r s h a v i n g t h e c o m p o s i t i o n s expected f o r a n o r m a l r a d i c a l c o p o l y m e r i z a t i o n o v e r a w i d e range of m o n o m e r charge ratios.

However,

the g r a f t e d c o p o l y m e r s are essentially e q u i m o l a r w h e n t h e a c r y l o n i t r i l e content i n t h e m o n o m e r charge is f r o m 30 to 90 m o l e %

(22).

U n d e r s i m i l a r c o n d i t i o n s , graft p o l y m e r i z a t i o n of a m i x t u r e o f sty rene a n d a c r y l o n i t r i l e o n viscose r a y o n y i e l d s e q u i m o l a r g r a f t e d c o p o l y mers a n d u n g r a f t e d c o p o l y m e r s w i t h a r a d i c a l c o m p o s i t i o n w h e n t h e m o n o m e r c h a r g e contains 25 to 70 m o l e % a c r y l o n i t r i l e . S i m i l a r results are o b t a i n e d i n the r a d i a t i o n - i n d u c e d graft c o p o l y m e r i z a t i o n of b u t a d i e n e - a c r y l o n i t r i l e a n d s t y r e n e - a c r y l o n i t r i l e onto p o l y


vinyl alcohol

fibers

(22).

C e l l u l o s e - w a t e r m a y act as a m a t r i x a n d p r o m o t e t h e d e v e l o p m e n t of arrays of c o m o n o m e r c h a r g e transfer complexes (19).

T h e cellulose

acts n o t o n l y as a substrate f o r s u c h a l i g n m e n t b u t also as a c o m p l e x i n g agent.

T h e m a t r i x of complexes

(styrene-methyl

methacrylate)

m a y b e represented

a n d II

as s h o w n i n I

(butadiene-acrylonitrile).

The

r a d i c a l - , t h e r m a l - , a n d r a d i a t i o n - i n d u c e d graft p o l y m e r i z a t i o n s i n v o l v e h o m o p o l y m e r i z a t i o n of c o m o n o m e r complexes r a t h e r t h a n c o p o l y m e r i z a t i o n of u n c o m p l e x e d m o n o m e r s .

H φ—C -CH +

H φ—C+-CH

2

Il H C2

H φ—C+-CH

2

II

-CCH

2

I

X

3

X

2

H C- CCH

3

2

I

C—OCH

H

II

H C- CCH

3

I

C—OCH

2

II

H C- CCH

3

H φ—C+-CH

2

I

X

C—OCH

3

H.

3

X

C—OCH

3

3

H

H

Ο

H

-CH

H

cellulose I


-CH

cellulose

226


H C+

H C+

2

HC

/

II 1 II 1 HC CH / 1

H C2

C

HC

2

/

I

/ C

P O L Y M E R S

2

2

-

A N D N E W

H C+

H C+

2

~CH

R E A C T I O N S

/ ~CH

HC

2

II HC

/

H C2

ι C^H C-

C

2

/

H C-

C

2


Ν

Η

Η

Η

Η

υ

-CH

Η

-CH

Η

cellulose

cellulose

II W h e n the c o p o l y m e r i z a t i o n of styrene a n d a c r y l o n i t r i l e i n the pres ence of z i n c c h l o r i d e is c a r r i e d out at 4 0 ° - 5 0 ° C

i n the presence of

cellulose u n d e r c o n d i t i o n s that n o r m a l l y y i e l d an a l t e r n a t i n g c o p o l y m e r (i.e., i n a n aqueous system i n the presence of p o t a s s i u m persulfate or a persulfate-bisulfite redox s y s t e m ) , the a l t e r n a t i n g c o p o l y m e r is a c c o m p a n i e d b y cellulose graft c o p o l y m e r i n w h i c h the g r a f t e d chains h a v e a n equimolar, than

when

alternating the

structure.

reaction

The

is c a r r i e d

monomer

out

c o n v e r s i o n is

w i t h o u t cellulose,

and

higher both

u n g r a f t e d a n d g r a f t e d c o p o l y m e r s (60-80% of the t o t a l c o p o l y m e r ) are of very high molecular weight ( T a b l e X V I I I ) .

W h e n the r e a c t i o n i n the

presence of cellulose is c o n d u c t e d above 6 0 ° C , n o r m a l r a d i c a l c o p o l y m e r is p r o d u c e d

(23).

T h e c o m o n o m e r complexes m a y be a n c h o r e d o n the cellulose, ana logous to structures I a n d II, or t h r o u g h the i n t e r a c t i o n of z i n c c h l o r i d e a n d the c e l l u l o s i c h y d r o x y l g r o u p s ; aqueous solutions of the m e t a l h a l i d e are k n o w n to b r e a k the h y d r o g e n b o n d s i n cellulose a n d r e d u c e c r y s t a l l i n i t y . A l t h o u g h radicals generated o n the cellulose as the result of r e a c t i o n w i t h the catalyst m a y initiate p o l y m e r i z a t i o n of the c o m o n o m e r


13.

Donor-Acceptor

G A Y L O R D

Table X V I I I .

227

Complexes

C o p o l y m e r i z a t i o n of Styrene a n d A c r y l o n i t r i l e i n P r e s e n c e of Z n C l a n d C e l l u l o s e 2


T e m p e r a t u r e , °C Time, hr Monomer Conversion, % Add-on, % Grafted copolymer % of T o t a l A N , mole %

40 3 22 221

M dl/g Ungrafted Copolymer % of T o t a l A N , mole % M dl/g

50 1 16 146

40 5 32 353

63.9 50.0 5.4

66.7 49.0 5.3

58.6 50.2 5.2

36.1 50.0 5.1

33.3 50.2 4.3

41.4 52.0 3.2

[S] = [AN] = 1.0 mole; [ZnCl ] = 0.5 mole; [K S 0sl = 0.05 mole; H 0, 157 grams; wood pulp, 10 grams; [η] DMF, 30°C. 2

charge-transfer

2

2

2

complexes, they are not the sites for the attachment

of

g r a f t e d a l t e r n a t i n g c o p o l y m e r chains. T h e r e is a m a x i m u m of one g r a f t e d c h a i n per cellulose or p o l y v i n y l a l c o h o l m o l e c u l e , i n d e p e n d e n t of the i n i t i a t i o n m e t h o d (24). t i o n s h i p b e t w e e n the a l d e h y d e content also b e e n d e m o n s t r a t e d

A rela

a n d the extent of g r a f t i n g has

(19).

It is therefore reasonable to assume that g r a f t i n g occurs b y t e r m i n a tion

of

a propagating alternating

c o p o l y m e r c h a i n o n the

CH OH

CH OH

H

Η

2

2

OH

OH

CH OH 2

Η

OH


substrate

228


2

I I I

OH

2

OH

OH

2

I

A N D N E W

P O L Y M E R S

H ~CH CHCH CH + .CCH CH CH~

~CH CHCH CH—CHCH CH CH~ 2

R E A C T I O N S

2

OH

2

I

— *

OH

II

2

I

0

2

OH

I

OH

PM * X

Ψ ~CH CHCH C—M P 2

polymer, presumably


groups. erated

X

II

OH

Ο

b y insertion of the generated

i n t o the C - H of an a l d e h y d e g r o u p . a terminal

2

I

g r o u p generated

by

terminal

carbene

I n cellulose, the latter is a p p a r e n t l y

c l e a v a g e of the

terminal

hemiacetal

I n p o l y v i n y l a l c o h o l , the a l d e h y d e is a t e r m i n a l g r o u p b y c l e a v a g e of the v i c i n a l g l y c o l r e s u l t i n g f r o m

addition.

gen

head-to-head

A l t h o u g h a l d e h y d e groups are also generated b y c l e a v a g e of

the v i c i n a l g l y c o l i n the a n h y d r o g l u c o s e units of cellulose, these groups are r e l a t i v e l y inaccessible bonded

cellulose,

a n d are b u r i e d i n the c r y s t a l l i n e h y d r o g e n -

compared

p r o b a b l y i n d i s o r d e r e d areas. mers

with

the

terminal

aldehydes

which

are

T h e a l t e r n a t i n g c o p o l y m e r graft c o p o l y

o n cellulose a n d p o l y v i n y l a l c o h o l are thus a c t u a l l y

alternating

copolymer block copolymers. Acknowledgment T h e a u t h o r is p l e a s e d to a c k n o w l e d g e the e x p e r i m e n t a l

contribu

tions of L . C . A n a n d , H . A n t r o p i u s o v a , R. G u z z i , S. K i k u c h i , E . O i k a w a , Β. K . Patnaik, M . Stolka, and A . Takahashi.

Literature

Cited

1. Gaylord, N. G., J. Polym. Sci., Part C (1970) 31, 247. 2. Gaylord, N. G., Maiti, S., J. Polym. Sci., Part Β (1971) 9, 359. 3. Tsuchida, E., Ohtani, Y., Nakadai, H., Shinohara, I., Kogyo Kasaku Zasshi (1967) 70, 573. 4. Tsuchida, E., Tomono, T., Nishide, H., Kogyo Kagaku Zasshi (1970) 73, 2037. 5. Iwatsuki, S., Yamashita, Y., J. Polym. Sci., Part A-1 (1967) 5, 1753. 6. Gaylord, N. G., Antropiusova, H., J. Polym. Sci., Part Β (1969) 7, 145. 7. Frank, H. P.,Makromol.Chem. (1968) 114, 113. 8. Hirooka, M., Yabuuchi, H., Iseki, J., Nakai, Y., J. Polym.Sci.,Part A-1 (1968) 6, 1381. 9. Gaylord, N. G., U.S. patent pending. 10. Gaylord, N. G., Oikawa, E., Takahashi, Α., J. Polym. Sci., Part Β (1971) 9, 379 11. Gaylord, N. G., Belgian Patent 762,854 (1971). 12. Gaylord, N. G., Takahashi, Α., Kikuchi, S., Guzzi, R., J. Polym. Sci. Part Β (1972) 10, 95.


13.

G A Y L O R D

Donor-Acceptor

Complexes

229


13. Gaylord, N . G., Stolka, M., Takahashi, Α., Maiti, S.,J.Macromol. Sci. (Chem.) (1971) A5, 867. 14. Gaylord, N. G., Antropiusova, H., Patnaik, Β. K.,J.Polym. Sci., Part Β (1971) 9, 387. 15. Gaylord, N . G., Takahashi, Α., Anand, L . C.,J.Polym. Sci. Part Β 16. Gaylord, N. G., Patnaik, Β. K.,J.Polym. Sci., Part Β (1970) 8, 411. 17. Gaylord, N. G., Antropiusova,H.,J.Polym.Sci.,Part Β (1970) 8, 183. 18. Gaylord, N . G., Patnaik, Β. K., Stolka, M.,J.Polym. Sci., Part Β (1971) 9, 923. 19. Gaylord,N.G.,J.Polym.Sci.,Part C (1972) 37, 153. 20. Rebek, M., Schurz, J.,Stöger,W.,Popp, W., Monatsh. Chem. (1969) 100, 532. 21. Nara, S., Matsuyama, K., Kobunshi Kagaku (1968) 25, 840. 22. Sakurada, I., Okada, T., Hatakeyama, S., Kimura,F.,J. Polym.Sci.,Part C (1963) 4, 1233. 23. Gaylord, N . G., Anand, L . C.,J.Polym. Sci., Part Β (1971) 9, 617. 24. Sakurada,I.,Ikada, Y., Uehara, H., Nishizaki, Y., Horii, F., Makromol. Chem. (1970) 139, 183. R E C E I V E D April 1, 1972.


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