Blending of Polymer Liquid Crystals with Engineering Polymers

Chapter 28

Blending of Polymer Liquid Crystals with Engineering Polymers The Importance of Phase Diagrams 1

2

1,3

Witold Brostow , Theodore S. Dziemianowicz , Michael Hess , and Robert Kosfeld Downloaded by VIRGINIA TECH on February 27, 2015 | http://pubs.acs.org Publication Date: August 24, 1990 | doi: 10.1021/bk-1990-0435.ch028

3

1

Center for Materials Characterization and Department of Chemistry, University of North Texas, Denton, TX 76203-5371 Himont U.S.A., Inc., 800 Greenbank Road, Wilmington, DE 19808 FB6-Physikalische Chemie, University of Duisburg, D-4100 Duisburg 1, Federal Republic of Germany 2

3

We study phase diagrams of polymer l i q u i d c r y s t a l s (PLC) i n function of LC concen t r a t i o n i n copolymers and also phase d i a grams of blends of PLCs with engineering polymers. Most PLC systems are multipha s i c . Moreover, there are some non e q u i librium phases with high longevity; such phases have to be included i n the phase diagrams to make i n t e l l i g e n t processing possible. We report phase diagrams or t h e i r parts for copolymers of poly(ethylene terephthalate) (PET) with p-hydroxybenzoic acid (PHB) i n function of mole f r a c t i o n x of PHB; PET/xPHB + poly(bisphenol-A-carbonate) (PC). Several techniques have to be used, since the diagrams are complex and some techniques are more sensitive to c e r t a i n t r a n s i t i o n s while other techniques will not necessarily show a given a t r a n s i t i o n at all. We know w e l l t h a t m e c h a n i c a l a n d o t h e r p r o p e r t i e s of p o l y m e r - b a s e d m a t e r i a l s c a n be i m p r o v e d b y i n t r o d u c t i o n of reinforcements, f o r i n s t a n c e o f chopped g l a s s f i b e r s i n t o an e p o x y . The r e s u l t i n g c l a s s o f m a t e r i a l s h a s b e e n c a l l e d macroscopic composites (1) or e l s e heterogeneous composites (2.) . The u s e o f s u c h c o m p o s i t e s c a u s e s on occasions serious problems due to insufficient 0097-6156/90/0435-0402$06.00/0 © 1990 American Chemical Society In Liquid-Crystalline Polymers; Weiss, R., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1990.

Downloaded by VIRGINIA TECH on February 27, 2015 | http://pubs.acs.org Publication Date: August 24, 1990 | doi: 10.1021/bk-1990-0435.ch028

28.

BROSTOWETAL.

Blending ofPolymer LCs with Engineering Polymers

a d h e s i o n between t h e f i b e r s and t h e m a t r i x . I n s e r v i c e , under e f f e c t s of e x t e r n a l mechanical f o r c e s , p u l l o u t of individual fibers occurs, and in layer structures delamination of entire layers i s possible. A t l e a s t two g o o d ways o u t e x i s t . One c o n s i s t s o f the d i s p e r s i o n at the m o l e c u l a r l e v e l o f r i g i d polymer molecules between flexible chains the concept of m o l e c u l a r c o m p o s i t e s o f H e l m i n i a k , Hwang e . a . ( 3 . , 4 ) . The other involves the use of polymer liquid crystals ( P L C s ) . As d i s c u s s e d by W i t t (5) , compared t o widely used engineering thermoplastics, PLCs show clear superiority with regard to chemical resistance, low f l a m m a b i l i t y , h i g h m o d u l u s , low i s o b a r i c e x p a n s i v i t y (or even zero, depending on the direction), and often unusual ease of p r o c e s s i n g . Monomers f o r PLC s y n t h e s i s a r e o f t e n a v a i l a b l e in s m a l l q u a n t i t i e s o n l y , w i t h e v i d e n t c o n s e q u e n c e s f o r PLC prices. Hence our o b j e c t i v e : blending of PLCs with o r d i n a r y e n g i n e e r i n g p o l y m e r s i n s u c h a way t h a t good thermophysical, rheological, mechanical and other properties o f PLCs a r e p r e s e r v e d t o a l a r g e extent, w h i l e c o s t s l o w e r e d c o n s i d e r a b l y . P e r t i n e n t work a l o n g t h e s e l i n e s was done b y s e v e r a l g r o u p s , i n c l u d i n g W e i s s and collaborators (6-8) , K i s s (9) , DeMeuse a n d J a f f e (10-11) a n d a l s o i n o u r l a b o r a t o r i e s (2., 12-14) . PLCs typicaly form several phases, as do multicomponent systems containing them (2, 6-25). M u l t i p l i c i t y o f phase t r a n s i t i o n s appears i n t r i n s i c t o a l l l i q u i d c r y s t a l s - monomeric (MLCs) a s w e l l a s P L C s . T h i s work was aimed a t b e t t e r u n d e r s t a n d i n g o f phase diagrams of PLC-containing blends. Complexity of the systems s t u d i e d has brought about a c o l l a b o r a t i o n o f three laboratories. Systems

studied

T h e r e i s a p p r o x i m a t e l y a d o z e n o f c l a s s e s o f PLCs known today, d i f f e r i n g i n l o c a t i o n ( i n the backbone, i n the s i d e - c h a i n , e t c . ) and s h a p e ( r o d , c r o s s , d i s c , e t c . ) of the mesogenic groups. The first comprehensive systematical classification was p r o p o s e d i n (26) and somewhat a m p l i f i e d l a t e r ( B r o s t o w , W. P o l y m e r 1990, in p r e s s ) , s e e a l s o (27.) . Because o f the i m p o r t a n c e o f l o n g i t u d i n a l PLCs c l a s s " a l p h a " a c c o r d i n g t o (2j6) - i n t h e d e v e l o p m e n t o f h i g h - m o d u l u s m a t e r i a l s , a p o l y e s t e r e a s y t o o b t a i n and t o m o d i f y was c h o s e n a s t h e r i g i d - r o d t y p e PLC com p o n e n t : t h e J a c k s o n a n d K u h f u s s (15) copolyester based on poly(ethylene terephthalate) (PET) a n d p - h y d r o x y benzoate (PHB). The p o l y e s t e r can be prepared and

In Liquid-Crystalline Polymers; Weiss, R., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1990.

403

404

LIQUID-CRYSTALLINE POLYMERS

analyzed quite e a s i l y with d i f f e r e n t compositions, that is with different degrees of rigidity. It shows a n e m a t i c mesophase above 30 m o l e % PHB. T h e n o t a t i o n P E T / x P H B w i l l be u s e d where x i s t h e m o l e p e r c e n t o f PHB. The polymer had been k i n d l y s u p p l i e d by Eastman Kodak a n d h a d a w e i g h t - a v e r a g e m o l a r mass ^ 2 . 0 1 0 g / m o l e , v a r y i n g l i t t l e w i t h x, w i t h almost b u t not q u i t e statistical distribution of the PHB-units in the b a c k b o n e . C o n s i d e r a b l e work on t h i s m a t e r i a l h a s been done b e f o r e ( 1 7 , 28-39). A s t h e s e c o n d component i n t h e b l e n d e i t h e r PET f r o m E a s t m a n Kodak o r a b i s p h e n o l - A b a s e d poly(carbonate) (PC) g e n e r o u s l y p r o v i d e d b y t h e B a y e r AG were u s e d . T h e w e i g h t - a v e r a g e m o l a r mass was 3 . 2 1 0 g/mole f o r e a c h . T h e q u o t i e n t / f o r a l l p o l y m e r s studied was / 2. PET a n d PC were c h o s e n f o r two r e a s o n s . F i r s t , b o t h h a v e c e r t a i n f e a t u r e s common t o a l l p o l y e s t e r s . Second there is a difference: PET i s less flexible a n d more easily c r y s t a l l i z a b l e while PC i s more flexible and t y p i c a l l y n e a r l y c o m p l e t e l y amorphous ( £ 0 ) . 4


W

4

W

w

w

n

n

Sample p r e p a r a t i o n It is advantageous to prepare a blend by coprec i p i t a t i o n f r o m a m u t u a l s o l u t i o n i n a common s o l v e n t . V e r y good d i s p e r s i o n i s t h u s a c h i e v e d e v e n when e.g. transesterification or degradation processes during m e c h a n i c a l m i x i n g and i n t h e m e l t a r e p o s s i b l e . PET/xPHB w i t h x b e t w e e n 10% a n d 40% a n d PC a r e s o l u b l e i n C H C 1 . I n t h e s e c a s e s t h e s a m p l e s were p r e p a r e d b y c o p r e c i p i t a t i o n f o l l o w e d by a subsequent a n n e a l i n g a t 2 1 0 ° C / 4 M P a . More i n f o r m a t i o n on t h e s e t y p e s o f t e r n a r y s y s t e m s a n d their phase behavior is given in (13) and w i l l be considered in a later paper in conjunction with theoretical predictions. F o r b l e n d s c o n t a i n i n g P E T / x P H B w i t h x > 40% a m i x e d s o l v e n t c o n s i s t i n g o f 2 0 v o l u m e % C F 3 C O O H a n d C H C I 3 was used. I n a l l c a s e s t h e p o l y m e r s were p r e c i p i t a t e d b y a d d i t i o n of acetone to the s o l u t i o n . 3

Experimental

procedure

Following is a list of the kinds of operations performed: d r y i n g the m a t e r i a l s f o r at l e a s t 4 hours at 160°C in a dehumidyfying, recirculating oven; in jection molding in an E n g e l machine (barrel tempe r a t u r e s 2 7 4 - 2 8 8 ° C , mold temperature 5 2 ° C , o v e r a l l c y c l e time ^ 1 m i n . ) ; mechanical t e s t i n g (flexural modulus


28. BROSTOWETAL.

Blending ofPolymer LCs with Engineering Polymers 405

a c c o r d i n g t o ASTM D790 p r o c e d u r e , t e n s i l e y i e l d s t r e s s and stress elongation according to ASTM D638, Izod impact test according to ASTM D256 C o n d i t i o n A) ; differential scanning calorimetry (DSC, du Pont Thermal A n a l y z e r and P e r k i n - E l m e r D S C - 2 ) ; m e l t r h e o l o g y (Rheometrics System 4 m e c h a n i c a l s p e c t r o m e t e r a t 2 6 0 ° C ) ; e l e c t r o n microscopy of f r a c t u r e surfaces (SEM, J E O L 35C scanning e l e c t r o n microscope); thermomechanical a n a l y s i s (TMA, P e r k i n - E l m e r T M S - 2 ) ; a u t o m a t i c t o r s i o n a l p e n d u l u m (ATP, M y r e n n e A T M - 3 ) ; w i d e a n g l e X - r a y s c a t t e r i n g (WAXS, A = 1 5 4 . 1 8 pm C u - K , 2 5 ° C ) ; 1H-NMR a n d 13C-NMR (Bruker WM-300 s p e c t r o m e t e r w i t h 200 mg o f m a t e r i a l d i s s o l v e d i n C H C 1 + h e x a f l u o r o i s o p r o p a n o l i n t h e r a t i o 40 : 1 ) . Downloaded by VIRGINIA TECH on February 27, 2015 | http://pubs.acs.org Publication Date: August 24, 1990 | doi: 10.1021/bk-1990-0435.ch028

3

Mechanical ties

Testing

and A n i s o t r o p y o f

Mechanical Proper

R i g i d i t y o f t h e mesogens p l a y t h e c e n t r a l r o l e f o r most of the properties of these types of polymers (27.) . J a c k s o n a n d K u h f u s s (15) h a v e shown a l r e a d y i n 1976 how easily acquire PLCs orientation during processing. I n f l u e n c e o f t h e t y p e o f f l o w on o r i e n t a t i o n a n d t e x t u r e o f PLC c o p o l y e s t e r s s u c h a s o u r s was s t u d i e d b y I d e and O p h i r (47) a n d b y V i o l a e . a . (46)Figure 1 v i s u a l i z e s the influence of o v e r a l l chain r i g i d i t y p r o d u c e d by v a r i a t i o n o f t h e P H B - c o n t e n t x i n the copolymer on the elastic modulus parallel and transverse to the a p p l i e d i n j e c t i o n flow. S i n c e P E T / 6 0 P H B shows p a r t i c u l a r y g o o d m e c h a n i c a l properties, i n the f o l l o w i n g we s h a l l focus on this m a t e r i a l and b l e n d s c o n t a i n i n g i t . The tendency to c r y s t a l l i z e i s q u i t e poor i n the p u r e PET/60PHB, as e a s i l y d e m o n s t r a t e d by c a l o r i m e t r i c measurements. Small-angle X-ray investigations on compression-molded samples show that only after annealing f o r s e v e r a l hours at 2 2 0 ° C r e f l e x e s due t o c r y s t a l l i t e s may be i d e n t i f i e d . N e v e r t h e l e s s , a proper estimate of the degree of crystallinity was not possible; t h e p e a k s h a r d l y emerged f r o m t h e amorphous halo. Point-measurements at different areas of the s a m p l e r e v e a l e d t h a t t h e r e was an o r i e n t a t i o n o f the c r y s t a l l i t e s p r e s e n t i n s m a l l a r e a s o f about 1 mm . In g e n e r a l , t h e s e a r e a s were r a n d o m l y o r i e n t e d , h e n c e t h e sum o v e r a l l a r e a s p r e s e n t was v i r t u a l l y z e r o . These r e s u l t s a r e s u p p o r t e d b y SEM a n a l y s i s o f c o r r e s p o n d i n g specimens f r a c t u r e d under l i q u i d n i t r o g e n , showing t h a t compression-molded samples contain randomly oriented thin fibers. The c r y s t a l l i n i t y i s m a i n l y due t o PHB u n i t s r a t h e r t h a n t o PET u n i t s (43). 2




406

6"

100 Mole % PHB F i g u r e 1. E l a s t i c m o d u l u s o f P E T / x P H B c o p o l y m e r s i n f u n c t i o n of x determined i n the d i r e c t i o n p a r a l l e l ( • ) and t r a n s v e r s e t o t h e flow ( • ).


28. BROSTOWETAL.

Blending of Polymer LCs with Engineering Polymers


In order to control anisotropy and hence pro perties, it is necessary to know w h i c h p h a s e s o c c u r during processing, which r e s u l t after processing has been completed, their stability, and t h e i r structure. C o n s e q u e n t l y , the f i r s t o b j e c t o f i n v e s t i g a t i o n has t o be t h e p h a s e d i a g r a m and t h e p h a s e s t r u c t u r e i f a n i n t e l l i g e n t p r o c e s s i n g h a s t o be c o n d u c t e d . We n o t e t h a t t h e p h a s e d i a g r a m s f o r P L C - c o n t a i n i n g blends are more c o m p l i c a t e d t h a n those of ordinary e n g i n e e r i n g p l a s t i c s . F o r PLCs a d d i t i o n a l p h a s e s h a v e t o be t a k e n i n t o a c c o u n t s i n c e t h e PLCs t h e m s e l v e s may e x h i b i t complex polymorphism. Phase

diagrams

It was expected that the P E T / 6 0 PHB s y s t e m will be relatively easy to interpret, p a r t i c u l a r l y since a number o f p r o p e r t i e s o f PET/60PHB + PET b l e n d s h a d b e e n s t u d i e d b e f o r e (2): c a l o r i m e t r y , melt rheology, several m e c h a n i c a l p r o p e r t i e s , and s c a n n i n g e l e c t r o n m i c r o s c o p y of f r a c t u r e s u r f a c e s . I t t u r n e d out t h a t even t h e phase d i a g r a m f o r PET/xPHB copolymers no b l e n d i n g in function of x is not exactly simple. While phase diagrams of PLC-containing systems have been little i n v e s t i g a t e d s o f a r , we r e c a l l an i m p o r t a n t r e s u l t o f L i n and W i n t e r (2j5) t h a t a PLC f o r m s a h i g h m e l t i n g c r y s t a l from a n e m a t i c m e l t . The p h a s e d i a g r a m o f p u r e P E T / x P H B i n f u n c t i o n o f x r e s u l t i n g f r o m d i f f e r e n t methods a n d d i f f e r e n t authors i s shown i n f i g u r e 2 ; n o n - e q u i l i b r i u m p h a s e s a n d t h e corresponding transitions are included: glass t r a n s i t i o n s w h i c h o c c u r i n t h e s y s t e m s e p a r a t e l y f o r PET and P L C , and a l s o a c o l d c r y s t a l l i z a t i o n c u r v e . We b e l i e v e t h a t i n g e n e r a l n o n - e q u i l i b r i u m phases have t o be i n c l u d e d i n t h e PLC p h a s e d i a g r a m s , s i n c e some s u c h p h a s e s e x h i b i t q u i t e h i g h l o n g e v i t y ; d i s r e g a r d i n g them would have obvious consequences for processing proce d u r e s and f o r p r o p e r t i e s o f t h e p r o d u c t s . M o r e o v e r , from the behavior of glass t r a n s i t i o n temperatures conclu s i o n s c a n be drawn on m i s c i b i l i t y o f t h e s y s t e m s . The d i a g r a m i n f i g u r e 2 c o n t a i n s a t l e a s t one p h a s e such t h a t i t s e x i s t e n c e has been noted o n l y recently (Brostow, W . ; Dziemianowicz, T . S . , Hess, M . , Saboe, J r . , S.H. Liquid Crystals, submitted), namely the quasi-liquid (q-1) . T h i s i s t h e m a t e r i a l w h i c h was i n t h e amorphous s t a t e b e l o w i t s g l a s s t r a n s i t i o n T g , b u t now i s i n the t e m p e r a t u r e range between T g and the melting transition. Thus, q-1 can undergo crystallization - the s o - c a l l e d "cold c r y s t a l l i z a t i o n " i n d i s t i n c t i o n t o an o r d i n a r y l i q u i d w h i c h c a n n o t .


407

408

LIQUID-CRYSTALLINE POLYMERS T °C


3 50-

250

q-l • c r y s t a l l i n e

J

150-

high T

g

quasi-liquid crystalline

low T„ gla

50

mole

P H B

F i g u r e 2. The phase d i a g r a m ( e s s e n t i a l p a r t ) for PET/xPHB copolymers i n f u n c t i o n o f x. The s o u r c e s of t h e r e s u l t s a r e denoted as f o l l o w s : o - our r e s u l t s , independently of the technique used (see above) and i n d e p e n d e n t l y of location (U.S.A., Germany); • Meesiri e.a. (28); • J e z i o r n y ( 2 9 ) ; O - Chou e.a. (10); A - Benson and Lewis (32); V Gedde e . a . (33); • Hedmark ( M ) ? O - J a c k s o n a n d K u h f u s s (15) ; a n d H K r i c h e l d o r f and Schwarz ( 3 5 ) . In Liquid-Crystalline Polymers; Weiss, R., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1990.


28. BROSTOWETAL.


Further, the presence o f a n o t h e r component b e l o w its glass t r a n s i t i o n and/or of c r y s t a l l i t e s prevents the quasi-liquid from flowing like a liquid does; the mobility is fairly low. Moreover, the notion of a "liquid" brings about a mental association of a material w h i c h upon h e a t i n g can only undergo vapo rization, or, if it is a polymer melt, no further t r a n s i t i o n a t a l l . By c o n t r a s t , t h e m a t e r i a l c o n t a i n i n g a q-1 phase has t o undergo a t l e a s t two more phase t r a n s i t i o n s : m e l t i n g and i s o t r o p i z a t i o n a t t h e c l e a r i n g point. I f more t h a n one l i q u i d - c r y s t a l l i n e p h a s e is f o r m e d , s a y s m e c t i c A a n d n e m a t i c , t h e n t h e r e w i l l be e v e n more t r a n s i t i o n s . We now go on t o t h e P E T / 6 0 P H B + PC p h a s e d i a g r a m . A q u i t e s i g n i f i c a n t p a r t o f i t i s shown i n f i g u r e 3 . I n p a r t i c u l a r , we w o u l d l i k e t o draw a t t e n t i o n t o a s m a l l approximately t r i a n g u l a r region just below t h e glass t r a n s i t i o n o f PC ( 1 5 4 ° C ) i n t h e r a n g e b e t w e e n 80% a n d 90 mole % P C . S t a r t i n g from p u r e p o l y c a r b o n a t e and g o i n g i n s i d e t h e d i a g r a m , we f i n d a b i f u r c a t i o n o f t h e g l a s s t r a n s i t i o n l i n e , c o n f i r m e d by e x p e r i m e n t s by b o t k U . S . and German g r o u p s . Hence i n t h i s c o n c e n t r a t i o n r a n g e we o b s e r v e t h r e e g l a s s t r a n s i t i o n l i n e s , t h e t h i r d f o r PET a t 5 4 ° C . The t o p l i n e c o r r e s p o n d s e v i d e n t l y t o a phase dominated by P C . The r a p i d fall of the middle line b e t w e e n 10% a n d 20% P E T / 6 0 P H B d e m o n s t r a t e s considerable m i s c i b i l i t y of constituents. PET i s n o t a p a r t n e r i n t h e miscibility occurrence; if it were, given its low concentration in this range, the separate PET g l a s s t r a n s i t i o n w o u l d n o t show. Hence t h e p a r t n e r s must be PHB a n d P C ; t h e r e i s enough o f PC t o show i t s own g l a s s t r a n s i t i o n a n d s i m u l t a n e o u s l y t o m i x i n p a r t w i t h PHB. The i n t e r a c t i o n b e t w e e n PHB a n d PC h a s c o n s e q u e n c e s not only for glass transitions but also for c r y s t a l l i z a t i o n as w e l l as f o r m e c h a n i c a l p r o p e r t i e s . In f i g u r e 4 we show a p r o j e c t i o n o f a t h r e e - d i m e n s i o n a l WAXS s u r f a c e i n f u n c t i o n o f b o t h s c a t t e r i n g a n g l e and t e m p e r a t u r e f o r x = 80%. I t a p p e a r s t h a t PHB a n d PC a i d each other to crystallize, and t h e effect increases a l o n g w i t h t e m p e r a t u r e i n c r e a s e . I n f i g u r e 5 we show t h e f l e x u l a r m o d u l u s E i n f u n c t i o n o f c o n c e n t r a t i o n f o r two different preparation conditions (annealing times of t h e samples) . S t a r t i n g as b e f o r e from p u r e P C , i n b o t h c a s e s we s e e a clear increase i n m o d u l u s b e y o n d 10% P E T / 6 0 P H B , t h a t i s a t t h e c o n c e n t r a t i o n s where we h a v e o b s e r v e d m i s c i b i l i t y i n t h e g l a s s y phase and c o - c r y s t a l l i z a t i o n o f PHB and P C . T h e c o n n e c t i o n b e t w e e n t h e p h a s e s t r u c t u r e s , t h e phase d i a g r a m and p r o p e r t i e s i s c l e a r l y operative. F


409

410



T

weight^ PET/60 PHB F i g u r e 3. The phase d i a g r a m ( e s s e n t i a l p a r t ) for P E T / 0 . 6 P H B + p o l y c a r b o n a t e (PC) i n f u n c t i o n o f PC concentration.



28.


BROSTOW ET AL.

29 Grad F i g u r e 4. T w o - d i m e n s i o n a l p r o j e c t i o n f r o m a WAXS surface i n function of the s c a t t e r i n g a n g l e and temperature for PET/0.8 PHB s h o w i n g independent crystallization of the different crystalline phases.

flexural modulus GPa

2 J

0

20

40

60

weight % PC

100

80

^

F i g u r e 5. F l e x u r a l m o d u l u s f o r b l e n d s o f P E T / 0 . 6 P H B w i t h p o l y c a r b o n a t e (PC) i n f u n c t i o n o f PC c o n c e n tration.


411

412


To conclude this Section, let us return to the e x p e r i m e n t a l p r o c e d u r e s f o r the d e t e r m i n a t i o n o f phase d i a g r a m s . We f i n d t h a t t r a n s i t i o n t e m p e r a t u r e s deter mined by d i f f e r e n t techniques approximately coincide. H o w e v e r , some t e c h n i q u e s a r e more s e n s i t i v e t h a n o t h e r for c e r t a i n p h a s e s , and a l s o f o r c e r t a i n c o n c e n t r a t i o n r e g i o n s . In r e l a t i v e l y i n f r e q u e n t but dangerous c a s e s , a technique might miss a t r a n s i t i o n e n t i r e l y . In p a r t i c u l a r , d y n a m i c m e c h a n i c a l t e s t i n g ( G a n d G") seems t o be o v e r a l l more s e n s i t i v e t h a n D S C . I n a d d i t i o n , it turned out that the quite simple analysis of the thermomechanical behaviour i s a v e r y u s e f u l t o o l : the p e n e t r a t i o n of a quartz rod with a f l a t t i p under a s m a l l l o a d g i v e s an a d d i t i o n a l , independent i n f o r m a t i o n w h i c h v e r y o f t e n a p p e a r e d t o be e s s e n t i a l for proper i n t e r p r e t a t i o n of the r e s u l t s o b t a i n e d from t h e other methods m e n t i o n e d a b o v e , a s t h i s method seems most s e n sitive to a l l types of thermal t r a n s i t i o n s . In other words, the thermomechanical a n a l y s i s v e r y q u i c k l y g i v e s an overview on almost all transitions occuring. Additional application of dynamic-mechanical analysis and calorimetry helps to identify the types of transitions and confirms the results. Therefore, a c o m b i n a t i o n o f t e c h n i q u e s i s recommended.


1

Solubility

i n o r g a n i c l i q u i d s and t e r n a r y p h a s e

diagrams

We a l s o h a v e a n i n t e r e s t i n s o l u t i o n p r o c e s s i n g , t h a t i s i n t e r n a r y p h a s e d i a g r a m s o f t h e t y p e PLC + e n g i n e e r i n g polymer + s o l v e n t . A statistical mechanical theory of rigid-rod systems has been developed by Flory; he s t a r t e d t h e work i n 1956 (44) when most o f t h e p r e s e n t a p p l i c a t i o n s o f PLCs were unknown a n d c o n t i n u e d i t more t h a n two d e c a d e s l a t e r ( 4 5 ) . T h e F l o r y c o n f i g u r a t i o n a l partition function is Z

M

=

z

z

comb' orient

1

C )

T h e r e e x i s t s a l s o a t h e o r y o f M a i e r a n d Saupe (.46/ 47) which takes into account the stability of aligned m o l e c u l e s , f o r i n s t a n c e i n t h e n e m a t i c s t a t e , due t o t h e anisotropy of the d i s p e r s i o n f o r c e s . The F l o r y t h e o r y covers this as w e l l , but i n a d d i t i o n i t takes into a c c o u n t two f u r t h e r e f f e c t s : a n i s o t r o p y o f t h e m o l e c u l a r s h a p e , and t h e i n f l u e n c e o f t h a t a n i s o t r o p y on m o l e c u l a r packing. The s e p a r a b i l i t y o f f a c t o r s i n equation (1) has been w e l l justified by subsequent results (48.) , ( F l o r y , P . J . p r i v a t e communication t o W.Brostow, August 20, 1985). The F l o r y t h e o r y has been a p p l i e d , among o t h e r s , t o t e r n a r y systems o f the type r i g i d r o d polymer


28. BROSTOWETAL.


+ f l e x i b l e polymer + solvent (spherical molecules). If we a p p l y t h i s v e r s i o n o f t h e t h e o r y t o o u r b l e n d s w i t h c h l o r o f o r m as t h e s o l v e n t , we o b t a i n o n l y qualitative and n o t q u a n t i t a t i v e a g r e e m e n t w i t h t h e e x p e r i m e n t . T h i s i s c l e a r l y due t o t h e f a c t t h a t o u r PLC i s n o t a r i g i d rod polymer, but consists of rigid sequences i n t e r c a l a t e d w i t h f l e x i b l e o n e s . Work on e x t e n s i o n of t h e F l o r y t h e o r y t o s u c h s y s t e m s i s o n g o i n g . We e x p e c t to report l a t e r theoretical results i n conjunction with t h e a p p r o p r i a t e e x p e r i m e n t a l phase diagrams.


A c k n o w l edcrment s PLC s a m p l e s were k i n d l y p r o v i d e d b y D r . W . J . J a c k s o n , Jr. o f E a s t m a n Kodak C o . , K i n g s p o r t , T N . W . B . b e g a n work on this problem at the Department of Materials Engineering of D r e x e l U n i v e r s i t y i n P h i l a d e l p h i a and appreciates discussions there with Prof. Marvin Garfinkle. Financial support was provided by the Deutsche Forschungsgemeinschaft, Bonn, f o r t h e r e s e a r c h as w e l l as t h e s t a y o f M . H . a t t h e U n i v e r s i t y o f N o r t h Texas and by the National Science Foundation, Washington, DC. M . H . i s indebted to the M i n i s t e r fur Wissenschaft und F o r s c h u n g , Nordrhein-Westfalen, for approving a sabbatical leave; to t h e HASYLAB a t the DESY, Hamburg, for providing some time on their e q u i p m e n t ; a n d t o t h e c o w o r k e r s o f P r o f . H . - G . Zachmann, U n i v e r s i t y o f Hamburg, f o r t e c h n i c a l s u p p o r t .

Literature Cited 1. Krause, S.J.; Haddock, T . ; Price, P . G . ; Lehnert, P.G; O'Brien, J.F.; Helminiak, T.E.; Adams, W.W. J. Polymer S c i . 1986, 24, 1991 2. Brostow, W.; Dziemianowicz, T . S . ; Romanski, J.; Werber, W. Polymer Eng. & S c i . 1988, 28, 785. 3. Husman, G . ; Helminiak, T . ; Adams, W.; Wiff, D . ; Benner, C. Am. Chem. Soc. Symp. Ser.1980, 132, 203. 4. Hwang, W . - F . ; Wiff, D.R.; Benner, C.L.; Helminiak, T . E . J. Macromol. S c i . Phys. 1983, B22, 231. 5. Witt, W. Kunststoffe-German Plastics 1988, 78, 795. 6. Huh, W.; Weiss, R . A . ; Nicolais, L . Polymer Eng.& Sci. 1983, 23, 779. 7. Weiss, R . A . ; Huh, W.; Nicolais, L . Polymer Eng.& Sci. 987, 27, 684. 8. Kohli, A . ; Chung, N . ; Weiss, R.A. Polymer Eng.& S c i . 1989, 29, 573. 9. Kiss, G. Polymer.Eng.& S c i . 1987, 27, 410.


413

414 10. 11. 12. 13. 14. 15.


16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27.

28. 29. 30. 31. 32. 33.


DeMeuse, M . T . ; Jaffe, M. Molec. Cryst. L i q . Cryst. 1988, 157, 535. DeMeuse, M . T . ; Jaffe, M. in the present volume. Kosfeld, R.; Hess, R . M . ; Friedrich, K. Mater.Chem. & Phys. 1987, 18, 93. Schubert, F . ; Friedrich, K . ; Hess, M . ; Kosfeld,R. Molec. Cryst. L i q . Cryst. 1988, 155, 477. Friedrich, K . ; Hess, M . ; Kosfeld, R. Makromol.Chem. Symp. 1988, 16, 251. Jackson, Jr., W . J . ; Kuhfuss, H.F. J. Polymer S c i . Phys. 1976, 14, 2043. Menczel, J.; Wunderlich, B. J. Polymer S c i . Phys. 1980, 18, 1433. Menczel, J.; Wunderlich, B. Polymer 1981, 22, 778. Meesiri, W.; Menczel, J.; Gaur, U . ; Wunderlich, B. J. Polymer S c i . Phys. 1982, 20, 719. Noel, C. In Polymeric Liquid Crystals; Blumstein, A. (Ed.) Plenum: New York 1985; p.21. Freidzon, Y a . ; Boiko, N . I . ; Shibaev, V . P . ; Tsukruk, V . V . ; Shilov, V.V; Lipatov, Yu.S. Polymer Commun. 1986, 27, 19 Sawyer, L.C.; Jaffe, M. J. Mater. S c i . 1987 , 21, 1897 P e l z l , G . ; L a t i f , I . ; Diele, S.; Novak, M . ; Demus, D.; Sackmann, H. Molec. Cryst. L i q . Cryst. 1986, 139, 333 L i n , Y . G . ; Winter, H.H. Macromolecules 1988, 21, 2439 George, E . R . ; Porter, R . S . ; J.Polymer S c i . Phys. 1988, 26, 83. Buchner, S.; Chen, D . ; Gehrke, R.; Zachmann,H.-G, Molec. Cryst. L i q . Cryst. 1988, 155, 357. Brostow, W., Kunststoffe - German Plastics 1988, 78, 411. Brostow, W. In: Polymer Liquid Crystals: From Struc tures to Applications; Collyer, A.A.(Ed.) Elsevier Applied Science, London - New York, to appear in 1990; Chapter 1. Meesiri, W.; Menczel, J.; Gaur, U . ; Wunderlich, B. J. Polymer S c i . Phys. 1982, 20, 719. Jeziorny, A . ; Polimery 1989, 34, 210. Chou, C h . ; Clough, S.B. Polymer Eng.& S c i . 1988, 28, 65. Viney, C . ; Windle, A.H. J. Mater. S c i . 1982, 17, 2661. Benson, R . S . ; Lewis, D.N. Polymer Commun. 1987, 28, 289. Gedde, U.W.; Buerger, D . ; Boyd, R.H. Macromolecules 1987, 20, 988.


28.

Blending ofPolymer LCswtih Engineering Polymers

BROSTOWETAL.

34. Hedmark, P. Ph.D.Thesis, Royal Institute of Techno logy, Stockholm, 1988. 35. Kricheldorf, H.R.; Schwarz, G. Makromol.Chem. 1983, 184,

475.

36. Lenz, R.W.; J i n , 1983,

24,

J.I.;

Feichtinger, K.A. Polymer

327.

37. Nicely, V . A . ; Dougherty, J.T.; Renfro, L.W. Macromolecules 1987, 20, 573. 38. Zachariades, A . E . ; Economy, J.; Logan, J.A. J.Appl.Polymer

Sci.

1982,

27,

2009.

39. Krigbaum, W.R.; Salaris, F. J.Polymer Sci.Phys.Ed. Downloaded by VIRGINIA TECH on February 27, 2015 | http://pubs.acs.org Publication Date: August 24, 1990 | doi: 10.1021/bk-1990-0435.ch028

1978,

16,

883.

40. Saechtling, H . J . Kunststofftaschenbuch Carl Hanser Verlag: München-Wien 1979, p.290. 41. Ide, Y . ; Ophir, Z. Polymer Eng.& Sci. 1983, 23, 261. 42. Viola, G.G.; Baird, D . C . ; Wilkes, G.L. Polymer Eng.& Sci. 1985, 25, 888. 43. Schubert, F . ; PH.D. thesis, University of Duisburg, Duisburg, 1989. 44. Flory, P . J . Proc. Royal Soc. A 1956, 234, 60. 45. Flory, P . J . e.a., Macromolecules 1978, 11, 1119, 1122,

1126,

1134,

1138,

1141.

46. Maier, W.; Saupe, A. Z. Naturforschung A 1959, 14, 882.

47. Maier, W.; Saupe, A. Z. Naturforschung A 1960, 15, 287.

48.

Flory, P . J . In: Polymer Liquid Crystals; C i f f e r i , A . , (Ed.) Academic Press: New York, 1982; Chap. 4.

RECEIVED April 3, 1990


415

Blending of Polymer Liquid Crystals with Engineering Polymers

Recommend Documents