Structure and Segmental Mobility of Polyester Urethanes Using

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Downloaded by UNIV MASSACHUSETTS AMHERST on June 21, 2013 | http://pubs.acs.org Publication Date: November 30, 1981 | doi: 10.1021/bk-1981-0172.ch017

Structure and Segmental Mobility of Polyester Urethanes Using Photochromic Azobenzene Probes CLAUS D. EISENBACH Institut für Makromolekulare Chemie, Universität Freiburg, Hermann-Staudinger-Haus, Stefan-Meier-Strasse 31, D-7800 Freiburg, West Germany

Photochromic processes in a solid matrix such as polymers gene rally proceed with considerable deviations from solution. This phenomenon is ascribed to particular interactions between the photoreactive molecule and the surrounding matrix (1,2) on a molecu lar scale (3) as will be shortly illustrated below. It can be infered from these findings that photochromic molecules, on the other hand, should be suitable probes to detect, e. g., particu lar motions in solid polymers and changes of the overall chain segmental mobility. This is a challenging technique to be applied in the field of polyurethane elastomers, since quite a few ques tions are still unsolved in this area. For segmented polyurethane elastomers of the (AB) type i t is established that the elastomeric properties are due to physical crosslinks of the urethane hard segments Β via hydrogen bonding (4,5,6), whereas the soft segments A form the continous soft phase. However, the question of 1) how complete the phase separa tion between the soft phase and the hard domains is, 2) of the extent to which single hard segments are dissolved in the soft phase and how much they influence the elastomeric properties via hydrogen bonding to soft segments and 3) of size and shape of the domains and the structure and dimension of the interlayer between soft and hard phase are still not yet solved (7,8,9). For completeness and b e t t e r understanding o f the method des c r i b e d i n t h i s paper and the c o n c l u s i o n drawn, the main r e s u l t s ob t a i n e d with azoaromatic chromophores i n c o r p o r a t e d i n l i n e a r p o l y ( a c r y l a t e s ) and poly(methacrylates) (3,10) a r e f i r s t presented and s h o r t l y d i s c u s s e d ; then the i n v e s t i g a t i o n o f the photochromic polyurethanes w i l l be d e s c r i b e d and evaluated. Experimental The two-phase polyurethanes were s y n t h e s i z e d i n the u s u a l way s t a r t i n g from a p o l y e s t e r d i o l which i s r e a c t e d with a d i i s o c y a nate and f i n a l l y the chain extension r e a c t i o n i s achieved by

0097-6156/81 /0172-0219$05.00/0 © 1981 American Chemical Society

In Urethane Chemistry and Applications; Edwards, K., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

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a d d i t i o n o f a d i a m i n e . I n c a s e o f t h e p o l y u r e t h a n e s w i t h chromop h o r i c s o f t segments (11) , t h e s t a r t i n g p o l y e s t e r was o b t a i n e d b y a c o p o l y c o n d e n s a t i o n r e a c t i o n o f a 4,4'-diaminoazobenzene d e r i v a t i v e , 1 , 4 - b u t a n d i o l and a d i p i c a c i d ; 2 , 4 - t o l y l e n e d i i s o c y a n a t e (TDI) was u s e d f o r t h e f o r m a t i o n o f t h e p r e p o l y m e r a n d t h e f i n a l p o l y u r e t h a n e was o b t a i n e d b y a d d i t i o n o f c a r b o h y d r a z i d . The p o l y u r e t h a n e s w i t h p a r t l y c h r o m o p h o r i c h a r d segments (12) were o b t a i n e d b y u s i n g 4 , 4 d i a m i n o a z o b e n z e (DAAB) t o g e t h e r w i t h e t h y l e n e d i a m i n e (EDA) a s c h a i n e x t e n d e r s i n t h e f i n a l r e a c t i o n s t e p , s t a r t i n g w i t h p o l y ( t e t r a m e t h y l e n e a d i p a t e ) a s m a c r o d i o l a n d TDI o r 4 , 4 * - m e t h y l e n e b i s ( 1 , 4 - p h e n y l e n e ) d i i s o c y a n a t e (MDI) a s d i i s o c y a n a t e s . The e x p e r i m e n t a l d e t a i l s f o r t h e s e two t y p e s o f p h o t o c h r o mic p o l y ( e s t e r u r e t h a n e ) s a r e g i v e n e l s e w h e r e (11,12). The s i n g l e p h a s e p o l y u r e t h a n e s were o b t a i n e d b y f i r s t r e a c t i n g a s m a l l amount o f DAAB w i t h MDI o r TDI i n DMF s o l u t i o n a n d subsequent a d d i t i o n o f p o l y ( t e t r a m e t h y l e n e a d i p a t e ) d i o l , i . e., no EDA c h a i n e x t e n d e r was u s e d ( 1 3 ) . The p o l y m e r s were p u r i f i e d b y r e p r e c i p i t a t i o n f r o m DMF/me t h a n o l a n d d r i e d f o r 48 h r s . a t 6 0 C u n d e r v a c u o . C l e a r , t h i n f i l m s o f a l l polymers c o u l d be o b t a i n e d by m e l t i n g t h e p o l y m e r a t 140 c u n d e r c o m p r e s s i o n b e t w e e n t e f l o n c o a t e d s t e e l plates. The s a m p l e s were c h a r a c t e r i z e d b y DSC-measurements a n d b y t o r s i o n a l pendulum e x p e r i m e n t s . F o r t h e p h o t o c h e m i c a l i s o m e r i z a t i o n , a 150 W Xe-lamp o r a 200 W S u p e r P r e s s u r e M e r c u r y Lamp w e r e u s e d . The l i g h t was f i l t e r e d e i t h e r b y u s i n g a monochromator o r a n i n t e r f e r e n c e f i l t e r w i t h t r a n s m i s s i o n i n t h e w a v e l e n g t h r a n g e o f t h e maximum a b s o r p t i o n b a n d o f t h e t r a n s i s o m e r . The o t h e r c o n d i t i o n s were t h e same as p r e v i o u s l y d e s c r i b e d (3). The p r o c e e d i n g o f t h e p h o t o c h e m i c a l and t h e t h e r m a l c i s - t r a n s i s o m e r i z a t i o n was f o l l o w e d b y m e a s u r i n g the change i n t h e a b s o r p t i o n o f t h e t r a n s - i s o m e r i n t h e a r e a o f 370-400 nm.


L

R e s u l t s and D i s c u s s i o n 1) G e n e r a l d i s c u s s i o n o f p h o t o c h r o m i s m i n p o l y m e r m a t r i c e s P h o t o c h r o m i s m means t h e r e v e r s i b l e change o f a s i n g l e c h e m i c a l s p e c i e s b e t w e e n two d i f f e r e n t s t a t e s h a v i n g d i s t i n g u i s h a b l e d i f f e r e n t a b s o r p t i o n s p e c t r a ; t h e change i s i n d u c e d i n a t l e a s t one d i r e c t i o n by the i n t e r a c t i o n w i t h electromagnetic r a d i a t i o n (14). T y p i c a l photochromic molecules which best f u l f i l these r e quirements a r e t h e aromatic azo benzenes :

II

hV , Δ* 2

H

TYPICAL WAVE LENGTHS 350-380 nm X » 4 5 0 nm 9



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A r e v e r s i b l e c i s - t r a n s i s o m e r i z a t i o n around the a z o - l i n k a g e o c c u r s upon i r r a d i a t i o n w i t h U V - l i g h t o f t h e a p p r o p r i a t e wave l e n g t h ? the t y p i c a l U V - a b s o r p t i o n s p e c t r a o f t h e s e chromophores incorporated i n a poly(methyl methacrylate) matrix a f t e r d i f f e r e n t p e r i o d s o f i r r a d i a t i o n a r e shown i n F i g . 1. In the f o l l o w i n g the t h e r m a l back r e a c t i o n o f t h e c i s - i s o m e r s t o t h e t h e r m o d y n a m i c a l l y more s t a b l e t r a n s - i s o m e r w i l l be d i s cussed; i n the experiment, the polymer f i l m i s i r r a d i a t e d u n t i l the p h o t o s t a t i o n a r y s t a t e i s reached, then the l i g h t source i s c u t o f f and t h e r e f o r m a t i o n o f t h e t r a n s - i s o m e r w i t h t i m e i s f o l l o w e d by m e a s u r i n g t h e i n c r e a s e o f t h e U V - a b s o r p t i o n a t t h e maximum a b s o r p t i o n b a n d o f t h e t r a n s - f o r m . Whereas t h e t h e r m a l c i s - t r a n s i s o m e r i z a t i o n f o l l o w s s i n g l e f i r s t order k i n e t i c s i n rubbery specimen, t h i s i s not the case i n g l a s s y p o l y m e r s ( F i g . 2 ) . The e x p e r i m e n t a l c u r v e c a n be r e s o l v e d by two s i m u l t a n e o u s f i r s t o r d e r p r o c e s s e s , one o f t h e s e r e a c t i o n s ( l i n e 3) b e i n g much f a s t e r t h a n t h e t h e r m a l b a c k r e a c t i o n i n s o l u t i o n a t t h e same t e m p e r a t u r e (_3) . S i n c e t h e c i s - i s o m e r s c a n o n l y be p r e s e n t a s a s i n g l e s p e c i e s , t h i s phenomenon h a s t o be a t t r i b u t e d t o two d i f f e r e n t r e l a x a t i o n mechanisms. T h i s i s e v i d e n t from t h e r e d u c e d A r r h e n i u s p l o t o f t h e r a t e c o n s t a n t k o f the t h e r m a l c i s - t r a n s back r e a c t i o n i n terms o f a^ ( F i g . 3); a i s the r a t i o of the thermal c i s - t r a n s r e l a x a t i o n t i m e τ (Vk) a t t e m p e r a t u r e Τ t o i t s v a l u e a t Tg. F o r a l l g l a s s y p o l y m e r s i n v e s t i g a t e d , a o f t h e n o r m a l and t h e s o - c a l l e d a n o m a l o u s l y f a s t r e a c t i o n i s g i v e n by two l i n e a r b r a n c h e s . The a p p a r e n t e n e r g i e s o f a c t i v a t i o n as d e t e r m i n e d f r o m t h e s l o p e s a r e 68.7 k J / m o l and 26.8 k J / m o l . T h e s e v a l u e s c o i n c i d e w i t h the c h a r a c t e r i s t i c a c t i v a t i o n energies f o r r o t a t i o n a l (crank s h a f t (15)) and t r a n s l a t i o n a l c h a i n s e g m e n t a l m o t i o n s i n g l a s s y p o l y m e r s ( 3 , 1 0 ) . I t was t h e r e f o r e c o n c l u d e d t h a t o n l y c h a i n s e g m e n t a l r e l a x a t i o n p r o c e s s e s , w h i c h d e p e n d on t h e l o c a l e n v i r o n m e n t of the chromophore, are the c o n t r o l l i n g f a c t o r s f o r the i s o m e r i z a tion. The t e m p e r a t u r e d e p e n d e n c y o f t h e a p p a r e n t e n e r g y o f a c t i v a t i o n o f t h e b l e e c h i n g p r o c e s s as e x h i b i t e d b y t h e c u r v a t u r e i n t h e A r r h e n i u s p l o t ( F i g . 3) i s t y p i c a l l y f o u n d f o r , e. g., d y n a m i c m e c h a n i c a l r e l a x a t i o n p r o c e s s e s (17), which l e a d s t o the connec t i o n w h i t h t h e f r e e volume t h e o r y . The l a t t e r p r o c e s s e s a r e b e s t d e s c r i b e d by t h e W L F - e q u a t i o n (18), l o g a =C ( T - T g ) / ( C + T - T g ) , i . e., a m a s t e r p l o t i s o b t a i n e d when p l o t t i n g t h e l o g a r i t h m o f a v s . T-Tg. The f o r m o f t h e W L F - e q u a t i o n , i n d e e d , i s a l s o v a l i d f o r p h o t o c h r o m i c r e l a x a t i o n p r o c e s s e s ( 3 , 1 0 ) ; t h i s i s shown by t h e c o r r e s ponding WLF-plot o f the r e l a x a t i o n time o f the azochromophore (Fig. 4). I n c o n c l u s i o n i t c a n be s t a t e d f r o m t h e s e g e n e r a l s t u d i e s t h a t p h o t o c h r o m i c p r o c e s s e s i n p o l y m e r m a t r i c e s c a n be d e s c r i b e d by t h e f r e e v o l u m e t h e o r y ; m o r e o v e r , t h e s e p r o c e s s e s a r e c o n t r o l l e d by t h e k i n d o f l o c a l e n v i r o n m e n t a r o u n d t h e p h o t o c h r o m e s , T

2

T



222


1,0

λ/ΠΓΤΊ Die Makromolekulare Chemie

Figure 1. The UV absorption of afilmof methylmethacrylate/4-methacrylaminoazobenzene-copolymer after different periods of irradiation (\ — 355 nm) (3).


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[ τ . ] - [ τ ] - [ ο '

Ν

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0

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ν CURVE 2

+

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[ ε

Α

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]

ο

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ν CURVE 3

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Die Makromolekulare Chemie

Figure 2. Resolution of the experimentally obtained time-conversion curve by simultaneousfirst-orderreactions (3).


224



Figure 3. Reduced Arrhenius plot of a (ratio of the relaxation time at tempe ture Τ and T j for the thermal cis-trans isomerization of azoaromatic chromoph in bulk polymers (3). T

g


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17.

Figure 4. The WLF plot of a for the thermal cis-trans isomerization of azo~ aromatic chromophores in bulk polymers (3, 10). T


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p a r t i c u l a r l y the m o b i l i t y o f c h a i n segments. As a consequence, a photochromic molecule can be expected t o probe polymer propert i e s on a molecular s c a l e what w i l l be shown i n the f o l l o w i n g with the example o f polyurethanes. 2) Photochromism i n polyurethanes As o u t l i n e d b e f o r e , the q u e s t i o n o f i n t e r e s t now i s f i r s t , how the photochrome would r e a c t when i n c o r p o r a t e d i n the backbone o f amorphous and s e m i c r y s t a l l i n e polymers such as segmented polyurethanes and i f the i s o m e r i z a t i o n behaviour o f the photochrome would allow c o n c l u s i o n s on the s t r u c t u r e , morphology, and segmental m o b i l i t y of t h i s matrix. The segmented s t r u c t u r e o f polyurethane elastomers and the chain o r g a n i z a t i o n i n the s o l i d polymer i s s c h e m a t i c a l l y shown i n F i g . 5a and b. These polymers are u s u a l l y made by subsequent a d d i t i o n p o l y m e r i z a t i o n r e a c t i o n s : a h i g h molecular weight macrod i o l (e.g., poly(tetramethylene adipate) or poly(tetramethylene o x i d e ) , molecular weight between 1000 and 2000) i s reacted with a d i i s o c y a n a t e (TDI o r MDI) t o form a s o - c a l l e d macrodiisocyanate and by the a d d i t i o n o f a low molceular weight d i o l o r diamine the chain extension r e a c t i o n t o the f i n a l segmented elastomer (Fig.5a) takes p l a c e . Due t o the i n c o m p a t i b i l i t y o f th,e hard and s o f t segments i n the temperature range o f a p p l i c a t i o n , phase s e p a r a t i o n occurs r e s u l t i n g i n a domain s t r u c t u r e ( F i g . 5b); The hard segment aggregates a c t as p h y s i c a l c r o s s l i n k s and t h i s thermoreversible three - dimensional network formation accounts f o r the p r o p e r t i e s o f these t h e r m o p l a s t i c elastomers. T h i s b a s i c view o f the s t r u c t u r e and morphology o f segmented polyurethane elastomers i s w e l l e s t a b l i s h e d (19), but as mentioned b e f o r e , on a m i c r o s c o p i c l e v e l these polymer systems are f a r from being f u l l y understood; the key questions are l i n k e d t o the phase s e p a r a t i o n (e. g., sharpness o f i n t e r l a y e r between hard and s o f t phase, f r a c t i o n and e f f e c t o f i s o l a t e d hard segments i n the s o f t phase) and t o the r e s u l t i n g chain segmental m o b i l i t y o f hard and s o f t segments i n the regions o f d i f f e r e n t morphology. The approache u f u s i n g a photochromic probe f o r the study o f these problems was undertaken with three types o f photochromic segmented polyurethanes (one-phase and two-phase systems) with an aromatic azochromophore i n c o r p o r a t e d i n d i f f e r e n t s e c t i o n s o f the polymer chain; t h i s i s s c h e m a t i c a l l y represented i n F i g . 6. In the two-phase systems the chromophore i s s t a t i s t i c a l l y i n c o r p o r a t e d e i t h e r i n the s o f t segment or i n the hard segment; i n the s i n g l e phase system , which i s obtained by a p o l y a d d i t i o n r e a c t i o n o f macrodiol and d i i s o c y a n a t e without u s i n g a p a r t i c u l a r chain extender except f o r a small amount o f DAAB, the azochromophore i s p a r t o f an i s o l a t e d hard segment u n i t . Thus, the azochromophore i s l o c a t e d i n a v a r i e t y o f r e p r e s e n t a t i v e regions and segments i n these polymers, a l l o w i n g a general study o f the i n f l u e n c e o f s t r u c t u r a l and morphological changes o f the matrix on the photochromism as w e l l as o f the use o f a photochromic probe i n m u l t i phase polymer systems. In Urethane Chemistry and Applications; Edwards, K., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.


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SEGMENTED POLYURETHANE ELASTOMERS SCHEME OF THE CHAIN STRUCTURE: HARD

SOFT

HARD SEGMENT: WÊm: - C O N H - ^ ) - C H - < ^ - N H C O O ( C H ) , O O C N H - < P > - C H - ^ - N H C O 2

2

/

2

SOFT SEGMENT: r^rv:

{ 0 ( C H l^OOC ( C H ) 0 θ } 0 ( C H ) 0 2

2

4

η

2

4

SCHEMATIC REPRESENTATION OF DOMAIN STRUCTURE:

Figure 5. Scheme of primary chain structure of segmented polyurethane ela mers and chain segment organization.


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2a) Two-phase polyurethanes with chromophoric segments (11)

soft

The b a s i c s t r u c t u r e of these p o l y ( e s t e r urethane)s with a DAAB de r i v a t i v e randomly i n c o r p o r a t e d i n the p o l y e s t e r s o f t segment i n v a r i o u s c o n c e n t r a t i o n s i s shown i n F i g . 7. The photochemical c i s - t r a n s i s o m e r i z a t i o n of the azochromophore can be achieved by i r r a d i a t i o n at the maximum a b s o r p t i o n band of the t r a n s isomer a t λ = 3 7 8 nm; the change i n the absorp t i o n s p e c t r a o f a polymer f i l m before and a f t e r i r r a d i a t i o n i s given i n F i g . 8. S i m i l a r f r a c t i o n s o f c i s - i s o m e r s can be ob t a i n e d i n samples quenched from the melt ( i . e . , from above the m e l t i n g temperature Τ of the s o f t phase ; Τ =45 C) and i n samples annealed a t temperature some degrees below Ç of the s o f t phase, by which some s o f t segment c r y s t a l l i z a t i o n was caused. In c o n t r a s t to t h i s , d i s t i n c t d i f f e r e n c e s were observed f o r the thermal c i s - t r a n s i s o m e r i z a t i o n depending on the samples t h e r mal h i s t o r y ; the i n c r e a s e i n the trans-isomer content was f o l lowed by measuring the change i n the a b s o r p t i o n a t λ = 3 7 8 nm (Fig. 8). At temperatures above Τ , s i n g l e f i r s t order k i n e t i c s were found f o r the thermal back r e a c t i o n as one would expect f o r t h i s r e a c t i o n i n an amorphous m a t r i x / i n agreement with the r e s u l t s obtained f o r , e. g., the p o l y a c r y l a t e systems (_3) (s. above). The same behaviour i s a l s o found a t temperatures below Τ i n samples quenched from the melt with s t i l l completely amorphous s o f t phase ( F i g . 9, l i n e 4), and the r a t e constants k^ of the thermal back r e a c t i o n i n these samples were s i m i l a r to those found i n s o l u t i o n over the whole temperature range. In c o n t r a s t to t h i s , the k i n e t i c s do not f o l l o w s i n g l e f i r s t order k i n e t i c s i n the annealed samples ( F i g . 9, l i n e 1), but the experimental curve i s given by two e x p o n e n t i a l s ( l i n e 2 and 3, F i g . 9), s i m i l a r t o what was a l r e a d y found i n g l a s s y polymers. As could be shown by DSC-measurements of annealed samples, p a r t i a l c r y s t a l l i z a t i o n of s o f t segments occurs due to the annealing procedure a t about 5 Κ below Τ of the s o f t phase ; t h e r e f o r e the phenomenon o f two simultaneous ? i r s t order processes i n these samples with sem i c r y s t a l l i n e s o f t phase as compared to only one s i n g l e f i r s t order process i n samples w i t h completely amorphous s o f t phase c l e a r l y shows the s e n s i t i v i t y o f the photochrome t o changes i n the morphology o f the surrounding matrix. The r a t e constants k obtained f o r t h e r m a l l y d i f f e r e n t l y t r e a ted polyurethanes are represented i n the Arrhenius p l o t , F i g . 10. The apparent energy of a c t i v a t i o n Ε f o r the thermal c i s - t r a n s i s o m e r i z a t i o n , as determined from the slopes i n F i g . 10, i s about 80 kJ/mol (k^) i n polymers with completely amorphous s o f t phase, a s i m i l a r f i g u r e as found i n s o l u t i o n ; i n samples with p a r t i a l l y c r y s t a l l i z e d s o f t segments, values of about 60 kJ/mol (k^) and 19 kJ/mol (k^) are found f o r the two simultaneous f i r s t order processes ( l i n e 2 and 3, F i g . 10). The o c c u r i n g of these two apparent energies of a c t i v a t i o n , which are s i m i l a r to the energies r e q u i r e d f o r r o t a t i o n a l (crankshaft (15) ) and t r a n s l a t i o n a l (3)


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PHOTOCHROMIC SEGMENTED POLYURETHANES TWO-PHASE SYSTEM; (MACRODIOL+DIIS^


1)PHOTOCHROME(t)IN THE SOFT SEGMENT(

)·

2)PHOTOCHROME (§)IN THE HARD SEGMENT! • ) ·

SINGLE-PHASE SYSTEM: ( M AC RODIO L+Dl I SOC YA Ν AT Ε, NO CHAIN EXTEND Ε R ) P H O T O C H R O M E ( · ) IN THE "HARD SEGMENTS —

):

Figure 6. Scheme of the primary chain structure of photochromic segment polyurethanes with aromatic azochromophores built in the polymer chain.

PHOTOCHROMIC POLY(ESTER URETHANES) Soft Segment A -^0(CH ) OCO(CH )^CO ^ 0 ~ R - O C O ( C H ) ^ C O ^ O i C H ^ 0 — 2

4

2

30-N=N-«-NH mol ratio

Figure 13.

R1 /gH

b

2

or

B

R / 22 B

=100

Molecular structure of a single-phase polyurethane containing a jew chromophoric hard segments.


17.

EiSENBACH

Polyester Urethanes

237


Conclusion I t i s c l e a r l y e v i d e n t from the data d i s c u s s e d above t h a t the i s o m e r i z a t i o n o f the aromatic azochromophore i n c o r p o r a t e d i n the backbone o f polyurethanes i s markedly a f f e c t e d by i t s p o s i t i o n i n the backbone o f the polyurethanes and a l s o by the morphology o f the polymer matrix. The k i n e t i c s o f the p h o t o i s o m e r i z a t i o n and the thermal c i s - t r a n s i s o m e r i z a t i o n both r e f l e c t the s t r u c t u r e , morphology and segmental m o b i l i t y o f the surrounding polymer. In part i c u l a r i t was shown that the s o f t segment m o b i l i t y i s h i g h l y r e s t r i c t e d i n o r d i n a r y two-phase polyurethanes with a d d i t i o n a l s o f t phase c r y s t a l l i z a t i o n , that the segmental m o b i l i t y o f hard segments i n the hard domains i s n e g l e c t a b l y small compared t o the segmental m o b i l i t y o f s o f t segments i n the s o f t phase and f i n a l l y t h a t the m o b i l i t y o f i s o l a t e d hard segments i n the s o f t phase i s comparable t o t h a t o f s o f t segments. In c o n c l u s i o n i t can be s t a t e d t h a t , based on the already pos i t i v e r e s u l t s and new f i n d i n g s d i s c u s s e d above, photochromic molecules can be used as probes f o r the study o f some o f the open questions i n the area o f polyurethanes mentioned a t the beginning; t h i s technique w i l l f u r t h e r be employed i n f u t u r e work with photochromic polyurethane elastomers o f known segment length d i s t r i butions.

Literature Cited 1) 2) 3) 4) 5) 6) 7) 8) 9) 10) 11) 12) 13) 14) 15) 16) 17)

G. Smets, Pure Appl. Chem. 30, 1 (1972) C. S. Paik, H, Morawetz, Macromolecules 5, 171 (1972) C. D. Eisenbach, Makromol. Chem. 179, 2489 (1978) R. Bonart, Angew. Makromol. Chem. 58/59, 259 (1977) R. Bonart, Polymer 20, 1389 (1979) R. W. Seymour, G. M. Estes, S. L. Cooper, Macromolecules 3, 579 (1970) R. Bonart, E. H. Müller, J. Macromol. Sci., Phys. Β 10, 345 (1974) G. M. Estes, R. W. Seymour, S. L. Cooper, Macromolecules 4, 452 (1971) J. W.C. van Bogart, J. C. West, S. L. Cooper, Am. Chem. Soc., Div. Org. Coat. Plast. Chem., Prepr. Vol. 37 (2), 503 (1977) C. D. Eisenbach, Ber. Bunseng. Physikal. Chem. 84, 680 (1980) C. D. Eisenbach, Polym. Bull. 1, 517 (1979) C. D. Eisenbach, Makromol. Chem. Rapid. Commun. 1, 287 (1980) C. D. Eisenbach, Polym. Bull.,in preparation G. H. Brown, Techniques of Chemistry, Vol. III, "Photochromism", Wiley Interscience, New York 1971 T. Schatzki, J. Polym. Sci. 57, 496 (1963); Polym. Prepr., Am Chem. Soc., Div. Polym. Chem. 6, 646 (1965) C. D. Eisenbach, Europhys. Conf. Abstr., Europ. Phys. Soc., Vol. 4A, 212 (1980) N. G. McCrum, Β. Ε.Read, G. Williams, Anelastic and Dielectric Effects in Polymeric Solids, John Wiley and Sons, London 1967 In Urethane Chemistry and Applications; Edwards, K., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.


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URETHANE CHEMISTRY AND APPLICATIONS

18) M. L. Williams, R. F. Landel, J. D. Ferry, J. Am. Chem. Soc. 77, 3701 (1955) 19) S. L. Cooper, G. M. Estes, Multiphase Polymers, Advanc. in Chem. Ser. 176, Am Chem. Soc., Washington, D. C. 1979 20) F. Agolini, F. P. Gay, Macromolecules 3, 349 (1970) 21) D. Ta-Li Chen, H. Morawetz, Macromolecules 9, 463 (1976) 22) C. S. Paik Sung, L. Lamarre, Μ. Κ. Tse, Macromolecules 12, 666 (1979) 23) J. J. de Lange, J. M. Robertson, I. Woodward, Proc. Roy Soc., Ser. A 171, 398 (1939); G. V. Hampson, J. M.Robertson, J. Chem. Soc 1941, 409 RECEIVED June

23, 1981.


Structure and Segmental Mobility of Polyester Urethanes Using

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