Morphology and Dynamic Viscoelastic Behavior of Blends of Styrene

15 Morphology and Dynamic Viscoelastic Behavior of Blends of Styrene-Butadiene Block

Downloaded by UNIV OF CALIFORNIA SAN DIEGO on July 15, 2016 | http://pubs.acs.org Publication Date: June 1, 1979 | doi: 10.1021/ba-1979-0176.ch015

Copolymers G E R A R D KRAUS, L . M . F O D O R , and K. W . R O L L M A N N Phillips Petroleum Co., Bartlesville, O K 74004

Different

block

length

block copolymers their mixtures

distributions

can cause wide changes

ogy at constant

overall polymers

Block

had the expected

morphology.

Broadening

tion by blending appearance mately,

polymers

of cylindrical

to complex

Polymers

monomer

in domain

composition

of substantially spherical, of different and lamellar

tropy in the storage

structures

modulus

led to

and, ulti

morphologies.

by electron

behavior.

morphology

block distribu

block lengths

polybutadiene-continuous

between

(75 wt %

uniform

block length

and blends were characterized

the polybutadiene

and

morphol

polystyrene-continuous

the styrene

copy and by their viscoelastic established

styrene-butadiene x

styrene). length

in

of the linear SBS or (SB) "star" type

Correlations

on one hand

and

micros were aniso-

and the height and position

tan δ maximum

on the

of

other.

T T T h e n a b l o c k c o p o l y m e r is b l e n d e d with the h o m o p o l y m e r o f o n e o f * * t h e m o n o m e r s o f w h i c h i t is c o m p o s e d , t h e h o m o p o l y m e r w i l l enter the b l o c k p o l y m e r d o m a i n s t r u c t u r e o n l y w h e n its m o l e c u l a r w e i g h t does n o t greatly e x c e e d that o f the b l o c k sequences o f l i k e c o m p o s i t i o n ( 1 , 2 ) . W h e n i t does so, t h e h o m o p o l y m e r forms its o w n , u s u a l l y m u c h larger, d o m a i n s w h i c h m a y a b s o r b some of t h e l i k e - b l o c k sequences i n t h e i r surface regions. I n t h e present s t u d y w e e x a m i n e t h e s i t u a t i o n w h e r e b o t h c o n s t i t u ents o f t h e b l e n d a r e b l o c k c o p o l y m e r s of t h e same t w o m o n o m e r s , b u t w h e r e t h e b l o c k lengths m a y v a r y w i d e l y b e t w e e n constituents. 0-8412-0457-8/79/33-176-277$05.00/0 © 1979 American Chemical Society

Cooper and Estes; Multiphase Polymers Advances in Chemistry; American Chemical Society: Washington, DC, 1979.

As a

278

MULTIPHASE POLYMERS

constraint o n the e n o r m o u s n u m b e r o f s u c h b l e n d s possible, t h e t o t a l c o m p o s i t i o n of t h e b l e n d is h e l d fixed. T h e m o n o m e r s chosen are styrene a n d b u t a d i e n e at a n o v e r a l l b l e n d c o m p o s i t i o n of 7 5 % styrene

(by

w e i g h t ).


Experimental

Block polymers were prepared b y organolithium-initiated polymeri zation i n cyclohexane solution b y using the sequential monomer addition t e c h n i q u e ( 3 ) . P o l y m e r s w e r e b o t h of t h e l i n e a r - S B S a n d " r a d i a l " branched ( S B ) * type. Blends were prepared i n cyclohexane solution, either b e f o r e o r after c o u p l i n g the i n i t i a l l y l i n e a r S B L i p r e c u r s o r . C o u p l i n g agents i n v e s t i g a t e d w e r e e t h y l acetate ( f o r l i n e a r c o u p l i n g ) , e p o x i d i z e d soybean o i l ( E S O ) , a n d S i C l j . B l o c k m o l e c u l a r w e i g h t s w e r e c a l c u l a t e d f r o m m o n o m e r charges a n d i n i t i a t o r levels a n d c o r r e c t e d f o r "scavenger l e v e l , " i.e., the a m o u n t of R L i d e s t r o y e d b y system i m p u r i t i e s . T h e s e n o m i n a l b l o c k lengths w e r e , i n general, i n g o o d a g r e e m e n t w i t h g e l - p e r m e a t i o n c h r o m a t o g r a p h i c molecular weights. B l o c k l e n g t h p o l y d i s p e r s i t y indices* for b l e n d s w e r e c a l c u l a t e d o n t h e a s s u m p t i o n that t h e b l o c k p o l y m e r s , as p r e p a r e d , w e r e c o m p o s e d of m o n o d i s p e r s e b l o c k s . T h i s is ,of course, a n a p p r o x i m a t i o n justified o n l y b y the narrowness o f the m o l e c u l a r w e i g h t d i s t r i b u t i o n i n p o l y m e r i z a t i o n s of t h e present t y p e . T h e b l o c k heterogeneity i n d i c e s g i v e n h e r e s h o u l d , therefore, b e r e g a r d e d as r e l a t i v e measures of b r e a d t h of d i s t r i b u t i o n . Polymers a n d blends were w o r k e d u p b y evaporating the cyclohexane solvent a n d m a s s i n g the p o l y m e r o n a 1 4 0 ° C r o l l m i l l . F i l m s w e r e t h e n p r e p a r e d b y c o m p r e s s i o n m o l d i n g ( 5 m i n at 2 0 0 ° C ) or, i n o n e set o f experiments, b y e x t r u s i o n t h r o u g h a slit d i e . D y n a m i c v i s c o e l a s t i c meas-

Table I.

Blend Compositions Precoupling

Wt

Compo sition

Compo nent

Fraction

A

—

1.00

19

Β

1 2 Blend

0.64 0.36 1.00

30 7.6

120 13.4

1 2 Blend

0.64 0.36 1.00

13 11

137 10

1 2 Blend

0.64 0.36 1.00

1 2 Blend

0.64 0.36 1.00

C

D

Ε

Block Length M /1000 Ms/1000 B

—

—

56

—

—

Styrene (%)

(M /W ) w

n 8

75

1

80 63.8 74.2

2.4

91.3 47.6 75.7

3

6 13.5

144 7.5

96.3 35.9 74.5

3.5

14.9

150 6.1

100 29.1 74.5

3.7

— —, —

—

—


15.

KRAUS

279

Styrene-Butadiene Block Copolymers

urements were m a d e w i t h a R h e o v i b r o n M o d e l D D V - I I viscoelastometer i n the tensile m o d e at 35 H z . U l t r a t h i n sections of p o l y m e r films w e r e prepared b y cryomicrotomy, stained w i t h O s 0 vapor ( 4 ) , a n d examined under a Philips E M - 3 0 0 electron microscope. 4

Results T a b l e I describes five c o m p o s i t i o n s , e a c h of 7 5 %

styrene

content,


p r e p a r e d b y c o u p l i n g d i b l o c k S B L i m o l e c u l e s of v a r y i n g b l o c k l e n g t h w i t h a p o l y f u n c t i o n a l e p o x i d e . T h e d a t a are a r r a n g e d i n o r d e r of i n c r e a s 104,

1

I

1

-120

1

1

-80

1

1

-40

ι o

t C

0

ι

ι 40

ι

ι 80

ι

I .001

Figure 1. Storage modulus and loss tangent (35 Hz) for block polymer with uniform polystyrene blocks (composition A). Compression molded.



280

MULTIPHASE POLYMERS

Figure 2.

Electron micrograph of composition A

i n g p o l y d i s p e r s i t y of ( n o m i n a l ) p o l y s t y r e n e ( P S ) b l o c k lengths.

While

the p o l y b u t a d i e n e ( P B ) b l o c k s also v a r y i n l e n g t h , t h e i r p o l y d i s p e r s i t y is c o n s i d e r a b l y less. F i g u r e 1 s h o w s storage m o d u l u s a n d loss tangent v s . t e m p e r a t u r e plots f o r c o m p o s i t i o n A , w h i c h is n o t a b l e n d . A s s h o w n b y F i g u r e 2, the m o r p h o l o g y is spheres of P B i n a c o n t i n u u m of P S . T h e loss t a n g e n t c l e a r l y shows t h e P B glass

t r a n s i t i o n at

b r a n c h of t h e P S m a x i m u m n e a r

— 90°C

100°C.

a n d the ascending

T h e results

are e x a c t l y

as

e x p e c t e d f r o m t h e s p h e r i c a l m o r p h o l o g y , except that t h e t e m p e r a t u r e of t h e P B t a n δ m a x i m u m lies s e v e r a l degrees l o w e r t h a n t h a t of p o l y b u t a d i e n e of t h e a p p r o p r i a t e m i c r o s t r u c t u r e and 1 0 % vinyl) for which Τ (tan 8

m a x

) =

-

( c a . 5 0 % trans, 4 0 % cis, 80°C.


15.

KRAus

281


F i g u r e 3 shows t h e s a m e k i n d of d a t a f o r b l e n d C , i n w h i c h P B b l o c k lengths a r e s i m i l a r , b u t t h e P B b l o c k s differ g r e a t l y i n l e n g t h ; F i g u r e 4 shows a n e l e c t r o n m i c r o g r a p h o f this c o m p o s i t i o n .

T h e mor-

p h o l o g y of this b l e n d is c l e a r l y l a m e l l a r , w i t h c o n s i d e r a b l e

orientation

i n one direction.

( T h e u n e v e n spacings of l i g h t a n d d a r k b a n d s

result

f r o m l a m e l l a e s e c t i o n e d at v a r i o u s angles. ) T h e d i r e c t i o n o f o r i e n t a t i o n


is that o f m o l d

flow.

T h e d y n a m i c d a t a a r e e n t i r e l y consistent w i t h this

10 i

1

4

120

80

-40

0

0

.

40

100

Figure 3. Storage modulus and loss tangent (35 Hz) for composition with bimodal polystyrene block length distribution (composition C). Compression molded: (\\) parallel to direction of mold flow; (±) normal to direction of mold flow.



282

MULTIPHASE POLYMERS

Figure 4. morphology.

Electron micrograph of composition C

I n t h e d i r e c t i o n of m o l d

flow,

£ ' a n d tan δ are n o t too

g r e a t l y d i f f e r e n t f r o m F i g u r e 1 b u t n o r m a l t o t h e flow d i r e c t i o n , t h e r e s i n is m u c h softer ( s m a l l e r E ' ), a n d t h e P B t a n δ p e a k is s t r o n g l y a c c e n t u a t e d . T h e above

results a r e f o r c o m p r e s s i o n - m o l d e d

samples.

A closer

i n v e s t i g a t i o n o f these resins i n e x t r u d e d film is s u m m a r i z e d i n F i g u r e s 5 a n d 6. N o t e t h e r e l a t i v e i s o t r o p y i n m e c h a n i c a l p r o p e r t i e s of t h e s p h e r i c a l m o r p h o l o g y f o r the single anisotropy for the b l e n d . £ m a x ) is consistently

characteristic

p o l y m e r a n d the strong

N o t e also t h a t f o r the l a m e l l a r b l e n d Τ ( t a n

— 8 0 ° to — 8 1 ° C , t h e n o r m a l v a l u e f o r p o l y b u t a -

d i e n e i n d e p e n d e n t of o r i e n t a t i o n . T h e reason f o r t h e d e p r e s s i o n of Τ ( t a n 8

) i n t h e s i n g l e p o l y m e r is e v i d e n t l y t h e constraint t h e p o l y b u t a d i e n e

m&x


15.

KRAUS

283


d o m a i n s find themselves

u n d e r as t h e r e s u l t o f differences i n t h e r m a l

c o n t r a c t i o n of t h e phases as t h e y c o o l f r o m T ( p o l y s t y r e n e ) . g

T h e smaller

coefficient of e x p a n s i o n of glassy p o l y s t y r e n e causes t h e cavities a c c o m modating

the polybutadiene

i n c l u s i o n s t o s h r i n k less t h a n

the free

c o n t r a c t i o n of p o l y b u t a d i e n e , p l a c i n g the latter p h a s e i n a state of h y d r o static tens ion a n d l o w e r i n g T . I n t h e l a m e l l a r m o r p h o l o g y t h e r e is n o g

the p o l y b u t a d i e n e l a m e l l a e m e r e l y t h i n o u t a n d t h e


s u c h constraint;

Figure 5. Effect of orientation on E ' and tan δ in extrudedfilm(35 Hz) of composition A. Direction of measurement with respect to extrusion direction: (O) 0% f Φ) 22.5% (A) 45°, (Π) 67.5% (X) 9 0 ° .



284

MULTIPHASE POLYMERS

Figure 6.

normal T

g

Effect of orientation on E ' and tan δ in extruded film (35 Hz) of composition C . Notation as in Figure 5.

is o b s e r v e d .

C o m p a r i s o n of Figures 3 a n d 6 indicates the

d e g r e e o f o r i e n t a t i o n t o b e greater i n t h e c o m p r e s s i o n - m o l d e d s a m p l e . R e t u r n i n g n o w to composition B , i n w h i c h the P S block distribution is less severe t h a n i n C , w e n o t e that e v i d e n t l y b o t h r o d - l i k e a n d l a m e l l a r morphologies are about equally probable. Figures

7 a n d 8 were

obtained

T h e morphologies shown i n

on presumably

identically

prepared

s a m p l e s ; t h e y a p p e a r t o b e t h e result o f s m a l l a d v e n t i t i o u s v a r i a t i o n s i n m o l d i n g technique and/or thermal history. T h e data of T a b l e I I , w h i c h


15.

KRAUS

285


is a s u m m a r y of t h e p r i n c i p a l m o r p h o l o g y - r e l a t e d features of t h e d y n a m i c v i s c o e l a s t i c d a t a , c l e a r l y c o n f i r m t h e different m o r p h o l o g i e s . T h e r o d - l i k e P B d o m a i n s of F i g u r e 7 cause o n l y m o d e s t a n i s o t r o p y since P S r e m a i n s c o n t i n u o u s i n b o t h d i r e c t i o n s of o r i e n t a t i o n . Τ ( t a n δ ) is a g a i n d e p r e s s e d , as c y l i n d r i c a l P B d o m a i n s c a n n o t contract f r e e l y u n d e r the constraint of the glassy c o n t i n u u m . E l e c t r o n m i c r o g r a p h s of c o m p o s i t i o n s D a n d Ε are s h o w n i n F i g u r e s


9 a n d 10. I t is e v i d e n t that i n Ε p o l y b u t a d i e n e is t h e c o n t i n u o u s ( w i t h some r u b b e r i n t h e p o l y s t y r e n e d o m a i n s )

phase

w h i l e D represents

t r a n s i t i o n f r o m l a m e l l a r to p o l y b u t a d i e n e - c o n t i n u o u s m o r p h o l o g y .

a

Again

the d y n a m i c m e c h a n i c a l d a t a ( T a b l e I I ) a r e consistent w i t h these obser-

Figure 7.

Composition Β in rod-like form


286

MULTIPHASE POLYMERS

Table II.

Resin


A B C D Ε α

b

c

(M /M ) w

n

s

Continuous Phase

1.0 2.4

Morphology and

Discrete Phase

PS PS

P B (spheres) P B (rods) alternating lamellae alternating lamellae P B P S (complex PB P S (ellipsoids)

3 3.5 37

d

Compression-molded samples. E'20 = storage modulus at 20°C.

Figure 8.

Composition Β in lameUar form


15.

KRAus

287


Dynamic Viscoelastic Properties" Parallel to Flow* Tftan B J (°C) ma


tarifa* 0.021 0.024 0.061 0.030 0.181 0.296 c d

-

9 9 8 8 7 7

4 0 4 0 6 9

Normal to Flow* E ' (MPa) M

1760 1550 1260 1850 330 140

Tftan B ) (°C)

E'„ (MPa)

-94 -90 -83 -80 -76 -78

1680 1300 520 530 170 130

max

tan$

mas

0.026 0.044 0.137 0.120 0.244 0.300

This composition has been observed in two distinct morphologies ; see text. Predominantly.

Figure 9.

Morphology of composition D



288

MULTIPHASE POLYMERS

Figure 10.

Morphology of composition Ε

v a t i o n s , s h o w i n g m u c h s m a l l e r storage m o d u l i a n d l a r g e t a n δ m a x i m a n e a r — 8 0 ° C f o r t h e P B d o m a i n s . M e c h a n i c a l a n i s o t r o p y is a b s e n t i n E . T h e a b o v e results

s h o w c l e a r l y that, i n the s y s t e m

at

hand,

the

b r o a d e r the d i s t r i b u t i o n of P S b l o c k l e n g t h , the greater the t e n d e n c y the m i n o r P B p h a s e to b e c o m e c o n t i n u o u s .

It is also o b v i o u s that

d y n a m i c m e c h a n i c a l d a t a t e l l a great d e a l a b o u t the m o r p h o l o g y .

of the The

h e i g h t of the P B loss m a x i m u m increases as the r u b b e r b e c o m e s increas i n g l y l o a d b e a r i n g w h i l e at the same t i m e E' decreases.

Mechanical

anisotropy

p r o n o u n c e d f o r the l a m e l l a r s t r u c t u r e . butadiene

tan δ peak

is d e p r e s s e d

p o l y s t y r e n e is the c o n t i n u o u s

( b e t w e e n the transitions )

resulting from

orientation

is

most

F i n a l l y , t h e p o s i t i o n of the p o l y f o r those m o r p h o l o g i e s

in which

phase.


15.

KRAUS

289


S o m e seventy b l e n d s w e r e e x a m i n e d b y d y n a m i c v i s c o e l a s t i c meas urements o n l y . T h e y d i f f e r e d i n m o l e c u l a r w e i g h t of t h e constituents, l i n e a r i t y of t h e constituent b l o c k p o l y m e r m o l e c u l e s , ( S B S v s . [ S B ] * ) , t y p e a n d s t o i c h i o m e t r y of c o u p l i n g , o r d e r of c o u p l i n g ( b e f o r e a n d after b l e n d i n g ) , c o m p o s i t i o n of t h e fractions, a n d b l e n d r a t i o — a l w a y s , h o w ever, subject to t h e constraint of 7 5 % styrene content.

A l t h o u g h differ

ences i n viscoelastic b e h a v i o r w e r e o b s e r v e d , t h e most d e c i s i v e v a r i a b l e Downloaded by UNIV OF CALIFORNIA SAN DIEGO on July 15, 2016 | http://pubs.acs.org Publication Date: June 1, 1979 | doi: 10.1021/ba-1979-0176.ch015

b y f a r w a s b l o c k - l e n g t h heterogeneity.

F i g u r e 11 s h o w s a p l o t o f t h e

h e i g h t of t h e t a n δ m a x i m u m v s . ( M / M „ ) . w

ranges of b l o c k heterogeneity be expected.

s

O n e c a n easily spot t h e

i n w h i c h different m o r p h o l o g i e s are t o

T h i s p a t t e r n is c o n f i r m e d b y F i g u r e 12 i n w h i c h t h e h e i g h t

of t a n δ is p l o t t e d against its p o s i t i o n . T h e r e are several reasons, aside f r o m e x p e r i m e n t a l error, f o r t h e v a r i a b i l i t y i n properties at e q u a l ( M / w

M ) . n

s

O n e is that M / M „ is o n l y o n e of m a n y p o s s i b l e , n o n e q u i v a l e n t w

w a y s of expressing b l o c k l e n g t h heterogeneity a n d is n o t necessarily t h e most relevant o n e to t h e present s i t u a t i o n . A l s o , as i n T a b l e I, i n t h e e x p a n d e d s t u d y the P B b l o c k s d o v a r y i n size, e v e n i f m u c h less t h a n t h e P S b l o c k s . L a c k of m o r p h o l o g i c a l u n i q u e n e s s , as i n b l e n d B , c o m p l i c a t e s the p i c t u r e i n t h e o v e r l a p r e g i o n near M / M w

n

=

2.5. F i n a l l y , there is a

tendency for abnormally h i g h Γ (tan 8 ) i n the compositions w i t h the mMX

b r o a d e s t P S b l o c k d i s t r i b u t i o n . A t t a i n m e n t of s u c h d i s t r i b u t i o n s r e q u i r e s use of s u b s t a n t i a l a m o u n t s o f p o l y m e r w i t h P S b l o c k s of less t h a n 10,000 .40

INVERTED·Ε (S IN Β)

ο BRANCHED Δ LINEAR .30

.20 c

B' .10

. -

CYL. (Β IN S ) ^ SPHERICAL (Β IN S)

Δ

*

r

- ^ LAMELLAR ο o_4

-il (M /M ) w

n

$

Figure 11. Maximum low temperature loss tangent (35 Hz) measured normal to mold flow vs. styrene block length heterogeneity. Circles— branched polymers, triangles—linear polymers, solid symbols—electron micrographs displayed.


290

MULTIPHASE POLYMERS

.40

o BRANCHED

_INVERTED| (S IN B)

Δ LINEAR .30 h


H

E

.20

c

CO

ο α ·Β'

.10

°

ο

ο ο

Δ

Q

-100 12.

Figure

-90 Height

T(tanÔ

x

m a x

.)

c°

ο

i-o ο ο °LAMELLAR

CYLINDRICAL — Û _ ° — 2 ^ SPHERICAL (Β IN S ) J °£ (B IN S ) " " A

-70

-80

and position of low temperature Notation as in Figure 11.

loss

maximum.

m o l e c u l a r w e i g h t (5000 w a s t h e shortest b l o c k u s e d i n this w o r k ) .

In

this r a n g e o f b l o c k m o l e c u l a r w e i g h t s , interphase effects b e g i n to h a v e a n effect o n t h e p o s i t i o n of t h e P B loss m a x i m u m ( 5 ) . E x t r e m e differences i n P B b l o c k l e n g t h c u r i o u s l y a p p e a r to e x t e n d the r a n g e

i n P S block heterogeneity

morphologies

are possible.

i n which

F o r example,

polystyrene-continuous

F i g u r e 13 shows

a

straight

b l e n d of linear S B S polymers i n w h i c h b o t h kinds of blocks v a r y tenfold in length ( composition F ) :

Wt Fraction Component 1 Component 2 Blend

S/B/S 150000/100000/150000 15000/10000/15000

0.60 0.40 1.00

I n spite of ( M / M ) w

n

Styrene (%)

8

=

_ (M /M ) w

75 75 75

n

(1) (1) 2.9

2.9, t h e m o r p h o l o g y appears to b e b a s i c a l l y

s p h e r i c a l , a l b e i t w i t h c o n s i d e r a b l e c o n n e c t i v i t y of p o l y b u t a d i e n e d o m a i n s . M o r e o v e r , f o r this b l e n d t a n 8

m a x

= 0.028, T ( t a n S

m a x

) =

-

88°C, with

v i r t u a l l y n o a n i s o t r o p y i n storage m o d u l u s , consistent w i t h s p h e r i c a l o r short r o d - s h a p e d p o l y b u t a d i e n e d o m a i n s .



15.

KRAUS

291


Figure 13.

Morphology of composition

F

Discussion T h e o b s e r v a t i o n t h a t b r o a d , b i m o d a l styrene, b l o c k l e n g t h d i s t r i b u tions t e n d to f a v o r c o n t i n u i t y of t h e p o l y b u t a d i e n e phase is n o t c o n f i n e d to 7 5 % styrene content.

T h u s , a l i m i t e d s t u d y at 5 0 % styrene

showed

that p o l y b u t a d i e n e - c o n t i n u o u s c o m p o s i t i o n s c o u l d b e p r e p a r e d b y b r o a d b l e n d i n g i n p l a c e of the n o r m a l a l t e r n a t i n g l a m e l l a r structures characteristic of this c o m p o s i t i o n . S i n c e s i m p l e b l e n d i n g of t h e finished b l o c k p o l y m e r s a n d c o u p l i n g b l e n d s of S B L i d i - b l o c k p o l y m e r s d i d n o t p r o d u c e m a r k e d l y

different

results, i t seems c l e a r t h a t t h e b l o c k l e n g t h d i s t r i b u t i o n p e r se is m o r e


292

MULTIPHASE POLYMERS

i m p o r t a n t i n g o v e r n i n g m o r p h o l o g y t h a n the d i s p o s i t i o n of these b l o c k s over i n d i v i d u a l molecules. E x t e n s i v e use is m a d e i n this w o r k of the effects of o r i e n t a t i o n o n m e c h a n i c a l properties i n b l o c k p o l y m e r s w i t h c y l i n d r i c a l a n d l a m e l l a r structures.

T h e s e effects are,

i n general,

k n o w n f r o m earlier

( 6 , 7 ) ; t h e y a d d c o n v i n c i n g e v i d e n c e to the m o r p h o l o g i c a l

studies

assignments

made.


It s h o u l d b e clear that t h e conclusions of this w o r k are l i m i t e d to b l o c k p o l y m e r s i s o l a t e d f r o m the p o l y m e r i z a t i o n solvent ( c y c l o h e x a n e ) by

evaporation

and

subsequently

m i x i n g a n d shaping techniques.

processed

by

O b v i o u s l y , other

conventional

thermal

morphologies

could

b e r e a l i z e d i n m a n y instances b y c a s t i n g films f r o m solvents of v a r y i n g q u a l i t y f o r the t w o b l o c k sequences. Conclusions Different block length distributions i n SBS a n d ( S B )

X

block polymers

a n d t h e i r m i x t u r e s c a n cause w i d e changes i n d o m a i n m o r p h o l o g y a t constant o v e r a l l m o n o m e r c o m p o s i t i o n , w h i c h l e a d to

characteristically

different l i n e a r v i s c o e l a s t i c p r o p e r t i e s . Acknowledgment T h e authors are i n d e b t e d to J . O . G a r d n e r f o r the e l e c t r o n m i c r o graphs d i s p l a y e d i n this r e p o r t . Literature

Cited

1. Inoue, T., Soen, T., Hashimoto, T., Kawai, H . , Macromolecules (1970) 3, 87. 2. Niinomi, M . , Akovali, G . , Shen, M . , J. Macromol.Sci.,(1977) B13, 133. 3. Zelinski, R. P., Childers, C. W., Rubber Chem. Technol. (1968) 41, 161. 4. Kato, K., Polym. Eng.Sci.,(1967) 7, 38. 5. Kraus, Gerard, Rollmann, K. W., J. Polym.Sci.,Polym. Phys. Ed. (1976)

14, 1133.

6. Charrier, Jean-Michel, Ranchoux, Robert J. P., Polym. Eng. Sci., (1971) 11,

381.

7. Folkes, M . J., Keller, Α., Polymer (1971) 12, RECEIVED

April

222.

14, 1978.


Morphology and Dynamic Viscoelastic Behavior of Blends of Styrene

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