Polymer Characterization - American Chemical Society

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Characterization of Polymers by Thermally Stimulated Current Downloaded by UNIV OF ARIZONA on October 17, 2015 | http://pubs.acs.org Publication Date: May 5, 1990 | doi: 10.1021/ba-1990-0227.ch010

Analysis and Relaxation Map Analysis Spectroscopy J. P. Ibar , P. Denning , T. Thomas , A. Bernes , C. de Goys , J. R. Saffell , P. Jones , and C. Lacabanne 1

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Solomat, Glenbrook Industrial Park, Stamford, C T 06906 Solomat S.A., Ballainvilliers 91160, France Solomat Mfg. Ltd., Finnimore Industrial Estate, Ottery St. Mary, Devon, EX11 1AH England Paul Sabatier University, 31062 Toulouse Cédex, France 1

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This chapter presents an overview of thermally stimulated current (TSC) analysis, which reveals the molecular mobility of a material's structure; and relaxation map analysis (RMA), which reveals structural transitions in polymers. Essentially, TSC and RMA are the same technique with two different focuses resulting in two types of analysis. The purpose of this chapter is to show that RMA is an exceptional technique that reveals more about the state of polymeric matter than previous methods. Equations are given for relaxation time, elementary retardation time, and temperature-dependent retardation time. The fully automated TSC/RMA spectrometer is described. Use of TSC/RMA spectroscopy for engineering applications is discussed. The influence of orientation, hydrostatic press, and processing conditions is described. A comparison of differential scanning calorimetric, thermal mechanical, and TSC/RMA spectroscopic characterization of latex copolymers is given.

T H E M O L E C U L A R R E S P O N S E O F M A T E R I A L S to physical or chemical influ-

ences can be analyzed by several techniques. Differential scanning calorim-

0065-2393/90/0227-0167$06.75/0 © 1990 American Chemical Society

In Polymer Characterization; Craver, C., et al.; Advances in Chemistry; American Chemical Society: Washington, DC, 1990.

POLYMER CHARACTERIZATION

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e t r y ( D S C ) a n d differential t h e r m a l analysis ( D T A ) are a m o n g t h e most p o p u l a r choices i n laboratories a n d o n p r o d u c t i o n sites. O t h e r t e c h n i q u e s i n c l u d e t h e r m a l m e c h a n i c a l analysis ( T M A ) , stress relaxation or c r e e p a n a l ysis, t h e r m a l expansion coefficient devices, d i e l e c t r i c constant analysis, a n d d y n a m i c m e c h a n i c a l analysis ( D M A ) .

Thermally Stimulated Current Analysis Downloaded by UNIV OF ARIZONA on October 17, 2015 | http://pubs.acs.org Publication Date: May 5, 1990 | doi: 10.1021/ba-1990-0227.ch010

V e r y special k i n d s o f spectra c a n b e o b t a i n e d b y r e c o r d i n g t h e s h o r t - c i r c u i t c u r r e n t d u r i n g w a r m i n g - u p after a m a t e r i a l sample has b e e n p o l a r i z e d at a constant d i r e c t - c u r r e n t (d.c.) field above a t r a n s i t i o n t e m p e r a t u r e a n d t h e n q u e n c h e d . O r i g i n a l l y this t e c h n i q u e was u s e d to measure charge d e t r a p p i n g i n l o w - m o l e c u l a r - w e i g h t organic a n d i n o r g a n i c c o m p o u n d s . T h i s m e t h o d is c a l l e d t h e r m a l l y s t i m u l a t e d c u r r e n t ( T S C ) analysis. It has also b e e n r e f e r r e d to as t h e r m o s t i m u l a t e d c u r r e n t , t h e r m o c u r r e n t , o r e l e c t r i c d e p o l a r i z a t i o n c u r r e n t analysis. O n l y since 1971 has t h e T S C t e c h n i q u e b e e n a p p l i e d to t h e study o f structural transitions i n p o l y m e r s (1-5). T h e r m o c u r r e n t studies have also b e e n r e p o r t e d for crystals, polycrystals, semiconductors,

and inorganic

glasses; a t h o r o u g h r e v i e w o f T S C c o m m u n i c a t i o n s p u b l i s h e d o v e r t h e past 25 years is s u m m a r i z e d i n ref. 5. T S C is p a r t i c u l a r l y s u i t e d for i n v e s t i g a t i n g the fine structure o f p o l y m e r s : semierystalline p o l y m e r s , c o p o l y m e r s a n d b l e n d s , p o l y m e r complexes,

a n d resins. T S C also appears to b e u n i q u e l y

s u i t e d for d e t e r m i n i n g the i n f l u e n c e of a d d i t i v e s , dopants, plasticizers, w a t e r content, a n d c r o s s - l i n k i n g . I n a t y p i c a l T S C e x p e r i m e n t , a high-voltage s t a b i l i z e d d.c. s u p p l y is u s e d for p o l a r i z i n g the sample generally above its m a i n t r a n s i t i o n t e m p e r ature. T h e sample is h e a t e d at constant rate to the p o l a r i z a t i o n t e m p e r a t u r e u n d e r a n e l e c t r i c field of about 4 X 1 0 V p e r m e t e r o f thickness. T h e sample 6

is h e l d at this t e m p e r a t u r e for a specified t i m e a n d t h e n c o o l e d d o w n at a c o n t r o l l e d rate to - 1 5 0 ° C . A t that stage the external field is r e m o v e d , a n d an e l e c t r o m e t e r is c o n n e c t e d to t h e sample to r e c o r d t h e s h o r t - c i r c u i t c u r r e n t w h i l e the sample is h e a t e d at a constant rate. A c u r r e n t is created w h e n t h e m a t e r i a l depolarizes. T h i s t h e r m a l l y s t i m u l a t e d c u r r e n t reveals t h e m o l e c u l a r m o b i l i t y o f t h e material's s t r u c t u r e . T h e rate o f d e p o l a r i z a t i o n is r e l a t e d to t h e relaxation times o f t h e i n t e r n a l motions; this approach p r o v i d e s a n e w o p p o r t u n i t y to study the p h y s i c a l a n d m o r p h o l o g i c a l structure o f materials. T h e c u r r e n t peaks r e c o r d e d this w a y correlate w e l l w i t h t h e t r a n s i t i o n t e m p e r a t u r e s m e a s u r e d b y m e c h a n i c a l relaxation, D S C , o r c o n v e n t i o n a l [alternating-current (a.c.)] d i e l e c t r i c or m e c h a n i c a l spectroscopy.


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TSC and RMA Spectroscopic Characterization

Relaxation Map Analysis (RMA): A New and Powerful Analytical Concept

Downloaded by UNIV OF ARIZONA on October 17, 2015 | http://pubs.acs.org Publication Date: May 5, 1990 | doi: 10.1021/ba-1990-0227.ch010

A l t h o u g h m o r e p o w e r f u l i n its characterizations, T S C technology has not a c q u i r e d the reputation of other analytical methods such as D S C , T M A , or d y n a m i c m e c h a n i c a l analysis ( D M A ) . I n 1974, L a c a b a n n e (3) a n d C h a t a i n (4) a p p l i e d a n e w m e t h o d of " w i n d o w i n g p o l a r i z a t i o n " (also referred to as " t h e r m a l cleaning") to study relaxation p h e n o m e n a b y T S C analysis. Lacabanne's concept of w i n d o w i n g m a d e possible the isolation of e l e m e n t a r y D e b y e - t y p e relaxations of the molecules o v e r the e n t i r e relaxation s p e c t r u m . I n previous w o r k , the T S C o u t p u t consisted of u n r e s o l v e d b r o a d peaks that are the result of the i n t e r a c t i o n b e t w e e n several relaxation modes. Lacabanne's i d e a was to s u b m i t the p o l a r i z e d s p e c i m e n to a w i n d o w i n g treatment ( F i g u r e 1). F i r s t , the sample is p o l a r i z e d at t e m p e r a t u r e T for a t i m e t selected to a l l o w orientation o n l y of a certain fragment of the dipoles. T h e sample is q u e n c h e d to t e m p e r a t u r e T , generally 5 - 1 0 °C b e l o w the polarization t e m perature T . T h e p o l a r i z i n g voltage is t h e n cut off a n d T is m a i n t a i n e d for a t i m e t . T h i s step allows the depolarization of another fragment of the o r i e n t e d dipoles. F i n a l l y , the sample is q u e n c h e d to T < < T . T h e sample is t h e n reheated at constant rate, a n d the c u r r e n t is m e a s u r e d . W h e n t , t , a n d (T - T ) are c o n v e n i e n t l y chosen, the s p e c t r u m of depolarization is " s i m p l e " . T h e s p e c t r u m is d e s c r i b e d b y a single relaxation t i m e that is a function of t e m p e r a t u r e only. B y v a r y i n g the value of T a n d r e p e a t i n g the process, the e l e m e n t a r y modes can be isolated one b y one ( F i g u r e 2) a n d the material's relaxation m a p can be constructed ( F i g u r e 3). p

p

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d

d

0

p

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p

d

p

A T S C w i t h o u t w i n d o w i n g polarization produces results similar to D S C , T M A , or D M A w o r k i n g at v e r y l o w frequencies (—10" H z ) . It does i n d e e d p r o v i d e i n t e r e s t i n g results at an a c c r u e d sensitivity, b u t perhaps no m o r e i n t e r e s t i n g than results o b t a i n e d f r o m other analytical i n s t r u m e n t s o p e r a t i n g at the same l o w frequency. T h e concept of w i n d o w i n g polarization gives T S C another d i m e n s i o n . T h e relaxation m a p o b t a i n e d w i t h the w i n d o w i n g polarization concept reveals a m a t e r i a l s p h y s i c a l properties established from its e l e m e n t a r y relaxations. 3

F r o m l o w temperatures to the m o l t e n state, R M A seems i d e a l l y s u i t e d to the study of structural transitions i n p o l y m e r s . T h e objective of this chapter is to s h o w that R M A is an exceptional t e c h n i q u e that reveals m o r e about the state of p o l y m e r i c matter t h a n previous methods. It recognizes the fine relaxation differences b e t w e e n a slowly c o o l e d a n d a q u e n c h e d plastic, as w e l l as the r e s u l t i n g influence o n the i n t e r n a l stress a n d o n orientation. R M A has e n o u g h sensitivity to m o n i t o r the influence of external p h y s i c a l p a r a m eters such as the d e g r e e of cooling, pressure, orientation, processing c o n ditions, annealing treatment, c h e m i c a l c o m p o s i t i o n , tacticity, a n d p e r c e n t -




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Figure 2. Deconvolution of global TSC peaks into their elementary Debye relaxation components. Relaxed polystyrene (see also Figure 5).

age of cross-linking. The influence of tacticity, molecular weight, and chemical structure are discussed elsewhere (5). The sensitivity of T S C is also compared to D S C and D M A in the investigation of the microstructure of latex block copolymers.

Principles of TSC and RMA For both the T S C and R M A techniques, the current, I, and the temperature, T, are recorded versus time, t. TSC. To observe the various thermally stimulated current peaks, the mobile units of the sample are oriented by a constant electrostatic field, E,

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TCC)

T(5)

10 T

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2.60

2.70

2.60

ZS0

£40

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Figure 3. Relaxation map for PMMA. The spectral lines are relaxation curves obtained at various polarization temperatures T . p


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at a g i v e n p o l a r i z a t i o n t e m p e r a t u r e ,

W h e n the p o l a r i z a t i o n , P , has

T. p

r e a c h e d its e q u i l i b r i u m v a l u e , the t e m p e r a t u r e is d e c r e a s e d to freeze this configuration. T h e n the f i e l d is cut off. T h e p o l a r i z a t i o n r e c o v e r y is i n d u c e d b y i n c r e a s i n g the t e m p e r a t u r e i n a c o n t r o l l e d m a n n e r . T h e d e p o l a r i z a t i o n c u r r e n t , 1, f l o w i n g t h r o u g h the external c i r c u i t is m e a s u r e d b y an e l e c t r o m eter, a n d allows m e a s u r e m e n t of t h e d i p o l a r c o n d u c t i v i t y , cr. I f the i s o t h e r m a l p o l a r i z a t i o n varies e x p o n e n t i a l l y w i t h t i m e , t h e n its relaxation t i m e , T , is d e d u c e d from the measure o f a :


T =

RMA.

(1)

E • a

W h e n the p o l a r i z a t i o n is d u e to a d i s t r i b u t i o n of relaxation

t i m e s , the t e c h n i q u e of w i n d o w i n g p o l a r i z a t i o n is u s e d for the e x p e r i m e n t a l r e s o l u t i o n of spectra (5) a n d p r o d u c t i o n o f the relaxation m a p ( F i g u r e 3). F o r a simple behavior described b y a K e l v i n - V o i g t model, the elementary retardation t i m e , 7

h

is g i v e n b y :

T(T) }

= P — J(T)

(2) V

}

w h e r e / ( T ) = P ( T ) , the rate o f d e p o l a r i z a t i o n . T h e analysis o f each r e s o l v e d s p e c t r u m gives a t e m p e r a t u r e - d e p e n d e n t retardation t i m e , T / T ) , that follows e i t h e r an A r r h e n i u s e q u a t i o n : AH T,.(T) = T • exp —

(3)

w

(where T

0 i

is the p r e e x p o n e n t i a l factor, A H is the activation e n t h a l p y , a n d

k is the B o l t z m a n n constant) or a V o g e l e q u a t i o n : rff)

where T

0 i

= T -exp[a *(T 0

s

is the p r e e x p o n e n t i a l factor, a

coefficient of the free v o l u m e , a n d

s

-

T^)]"

(4)

1

is the average t h e r m a l expansion

is the c r i t i c a l t e m p e r a t u r e at w h i c h

the retardation t i m e b e c o m e s i n f i n i t e , that is, w h e r e there is no m o b i l i t y . R M A d e t e r m i n e s t h e v a r i a t i o n of the e l e m e n t a r y enthalpies, p r e e x p o n e n t i a l factors (related to the e n t r o p y o f activation), coefficients of

free-volume

ex-

p a n s i o n , a n d t e m p e r a t u r e s of z e r o m o b i l i t y , w i t h respect to a p a r a m e t e r u n d e r investigation, w h e t h e r it b e the d e p e n d e n c e o n m o l e c u l a r w e i g h t , c h e m i c a l s t r u c t u r e , o r i e n t a t i o n , or t h e r m o d y n a m i c history.


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The TSC/RMA


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Spectrometer: An Automated Instrument

In obtaining a material's relaxation map, a large number of experiments must be performed. Better resolution of the relaxation spectrum requires smaller experiment windows (T - T ) and more experiments. The solution is to automate the R M A process. Solomat has designed a fully automated T S C / R M A spectrometer (Figure 4).


p

d

The spectrometer's hardware features an IBM-type 80286 microprocessor with 1 Mbyte of R A M (random access memory) for high-speed realtime analysis, with a 40-Mbyte hard disk and a 1.2-Mbyte floppy disk. This computer system, connected to the cell head and to the electrometer, is driven by software that makes the instrument easy to use. Once the experiment has begun, the computer systems constantly monitor and control vacuum levels, cooling liquid, helium, and PID temperatures. Automatic analytical functions include digital data collection, data graphing, data transfer, data analysis, and slide preparation. The electrometer measures current with 10" -amp sensitivity. The cell head developed by the researchers at the Laboratory of Physics of Solids in Toulouse is reliable, precise, and simple to use. 16

Figure 4. Solomat TSC/RMA spectrometer.



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Liquid nitrogen, helium, and vacuum supplies are all that are needed for ready-to-run experiments, and a complete family of sample holders can accommodate most solids, liquids, or coatings.

TSC/RMA

Spectroscopy for Engineering Applications

The application of windowing polarization technology (RMA) to the study of amorphous polymers has revealed properties of the glassy state never observed

previously, with investigations

on polystyrene

(PS) (6-10),

poly(methyl methacrylate) ( P M M A ) (11-15), polyvinyl chloride) (PVC) (16),


polycarbonate (17,18), and polyethylene terephthalate) (PET) (19, 20). This new type of T S C analysis brings a new light to the following questions: W h y is polycarbonate so tough? W h y are polystyrene and Plexiglas so brittle? R M A shows that, in most amorphous polymers, the major relaxation modes responsible for internal flow decompose into a variety of elementary mechanisms well described by the activated-state theories (Figure 5). However, in a few instances the molecular processes obey a W i l l i a m s - L a n d e l - F e r r y (WLF)-type equation, which reveals the dominance of a free-volume effect over an activated process for that relaxation mode (upper temperature relaxation curve in Figure 5). Such W L F activities observed for motions below the glass transition temperature seem to dominate in tough polymers (Figure 6). For semicrystalline polymers, the resolution power of R M A ascertains the difference between the macromolecules trapped in the interlamellar regions and those that belong to the true amorphous region (Figure 7). The

150°C

100°C

4

POLYSTYRENE 3

T>Tg 2

3.0

2.5

1000/T(K)

Figure 5. Relaxation map for annealed polystyrene. This map is the result of the analysis of the deconvoluted curves in Figure 2.


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IBAR ET AL.



100°C

2.7

175

150°C

2.6

2.5

2.4

2.3 1000/T(K)

Figure 6. Relaxation map for polycarbonate annealed for 5 min at 235 °C.

40 i

T(scc)

44

-30 - 2 0 -10 0 10 20 30 40 50 60 708090 i 1 1—i—i—i—i—i—i—r—r T «C

Η

3d

>

ρ

184


zation i n w h i c h b o t h m o n o m e r s are fed r a n d o m l y i n a s e m i c o n t i n u o u s m a n n e r (23). B l o c k c o p o l y m e r s are p r e p a r e d b y step e m u l s i o n c o p o l y m e r i z a t i o n of A first, t h e n S, to f o r m A . S . S . b l o c k c o p o l y m e r s ,

or S first, t h e n A , to

synthesize the S . A . S . b l o c k c o p o l y m e r s . O u r objective was to characterize a n d c o m p a r e the m i c r o s t r u c t u r e s of these t h r e e latices. D S C , T M A , a n d T S C / R M A spectroscopy a l l w e r e used. It w i l l be s h o w n that for these latices, the p o w e r o f r e s o l u t i o n a n d characterization of t h e T S C / R M A t e c h n i q u e far exceeds the o t h e r m e t h o d s . DSC.

F i g u r e 15 displays the t h r e e traces of heat capacity C

p

versus


t e m p e r a t u r e (the h e a t i n g rate was 20 ° C / m i n ) r e c o r d e d o n a differential s c a n n i n g c a l o r i m e t e r ( D u p o n t 990) for the S C , A . S . S . , a n d S . A . S . samples. T h e t h e r m o g r a m for the statistical c o p o l y m e r (SC) is characteristic of a q u a s i h o m o g e n e o u s s t r u c t u r e , w i t h o n l y one T

g

drop-off o b s e r v e d at 20 ° C , a

t e m p e r a t u r e located b e t w e e n the T values o f the polyacrylate a n d p o l y s t y g

r e n e h o m o p o l y m e r i c phases. T h i s b e h a v i o r indicates t h e presence o f a single h o m o g e n e o u s phase for this c o p o l y m e r . T h e drop-off of the b a s e l i n e for the A . S . S . b l o c k c o p o l y m e r spreads o v e r 70 ° C , a n d a k i n k is v i s i b l e a r o u n d 15 ° C , w h i c h m i g h t b e a n i n d i c a t i o n o f the presence of a heterogeneous m i c r o s t r u c t u r e . H o w e v e r , i t is difficult to assess w h e r e the T s of the t w o g

phases are l o c a t e d , perhaps - 2 1 a n d + 1 5 ° C . T h e alternate b l o c k c o p o l y m e r S . A . S . is e v e n m o r e t r o u b l e s o m e analyze. A g a i n the drop-off at T

g

to

is v e r y b r o a d , o v e r 85 ° C , b u t there is

a p p a r e n t l y no i n d i c a t i o n o f the presence o f t w o T s. I n s u c h a case, w e c a n g

o n l y guess that t h e r e are two segregated phases, b u t w e have no i n d i c a t i o n of the m i c r o s t r u c t u r a l differences b e t w e e n the S . A . S . a n d A . S . S . samples. F i g u r e 16 is a r e p r e s e n t a t i o n of the storage m o d u l u s E'

DMA.

and

loss m o d u l u s E" for the t h r e e latices S C , A . S . S . , a n d S . A . S . as f u n c t i o n of t e m p e r a t u r e . F i g u r e 16 does not r e v e a l m u c h at a l l . T h e case of the statistical r a n d o m c o p o l y m e r S C is the o n l y c o n c l u s i v e one: the s e m i c o n t i n u o u s i n t r o d u c t i o n of m o n o m e r gives a r e l a t i v e l y h o m o g e n e o u s phase w i t h a single T . T h e o t h e r c u r v e s ( F i g u r e 16) d o not i n d i c a t e the i n f l u e n c e o f p o l y m e r g

ization c o n d i t i o n s o n the m i c r o s t r u c t u r e of those b l o c k c o p o l y m e r s . A s for D S C , o n l y v e r y vague statements o n t h e presence o f at least t w o phases can be m a d e . TSC.

T h e T S C spectra of the c o p o l y m e r s w e r e r e c o r d e d after p o l a r -

ization ( £ = 3 M V / m ) for 2 m i n at the t e m p e r a t u r e s i n d i c a t e d b y the arrows i n F i g u r e 17. T h e v a r i a t i o n of the d y n a m i c c o n d u c t i v i t y i n the t e m p e r a t u r e range - 1 5 0 to + 1 5 0 °C shows a single T S C peak for the S C c o p o l y m e r a n d two r e s o l v e d peaks for b o t h A . S . S . a n d S . A . S . T h e l o w - t e m p e r a t u r e peak o b s e r v e d i n b o t h A . S . S . a n d S . A . S . is associated w i t h the glass transition of b u t y l acrylate


IBAR ET AL.


d

^dt

185

S.A.S.

|(0.2mcay ) s

\

Endo


10.

T(°C)

i 100

-50

50

100

Figure 15. DSC traces for the statistical (SC) and block (A.S.S. and S.A.S.) copolymers. sequences, and the high-temperature peak with the glass transition of styrene sequences. Comparison of Figures 15, 16, and 17 clearly reveals the superior sensitivity of the T S C method. RMA. The T S C analysis revealed the global microstructure of the materials under investigation: S C is a relatively homogeneous statistical random copolymer with a T located between the T s of the homopolymers. Both S. A . S. and A . S. S. are block copolymers with segregation of two phases, g

g



186


Figure 16. DMA storage and loss moduli for S C , A . S . S . , and S.A.S. one rich in the styrene component, and the other rich in aery late sequences. The amount of styrene in acrylate (or acrylate in styrene) is, however, unknown. The technique of "window polarization" can be employed to answer this important question.

Compensation Point and Compensation Search.

When several

Arrhenius lines converge into a single point, this point is called a compensation point. In such a case, the entropy (the negative or mirror image of the intercept of the Arrhenius line) and the enthalpy (the slope of the A r rhenius line) are linearly related to each other. Hence, a very simple and practical way to see whether a set of Arrhenius lines obtained at various T

p

values converge is to plot intercept versus slope for these lines and to try to draw a straight line through the points (Figure 18). This drawn line is the compensation line. The coordinates of the compensation point are calculated from the slope and intercept of the compensation line. This type of analysis is called a compensation search. In general, for amorphous polymers, the behavior at T is characterized by a compensation phenomenon, as clearly g

demonstrated for oriented polystyrene under internal stress (Figure 8).



10.

IBAR ET AL.


-100

0

187

100

Figure 17. TSC traces for SC, A.S.S., and S.A.S. To resolve the global T S C spectra of Figure 17, the technique of windowing polarization is applied in the temperature range -45 to +75 °C, with a temperature window of 5 °C. The electrical voltage applied has the same intensity as for the global T S C thermogram (Figure 17). Figure 19 shows, for A . S . S . , the deconvolution of the global peaks into elementary Debye peaks for the two T s , and Figure 18 is a compensation search, a plot of intercept versus slope for all Arrhenius lines obtained for all copolymers studied. Table I presents the results of the analysis of the Arrhenius lines. g

For the S C copolymer (the straight line in the middle of Figure 18), the single compensation line corresponds to one T , one single phase, but for the A . S . S . and S.A.S. copolymers, two compensation lines are observed. They correspond to the low A and high S temperature peaks observed with T S C (Figure 17). This behavior is characteristic of a biphasic structure. g

The microstructure of the two phases in A . S . S . and S.A.S. is different, as shown in Table I for the value of the compensation parameters: 1. The relaxation modes associated with the A and S phases are significantly different in the A . S . S . and S.A.S. copolymers from those in the homopolymers.




188

Figure 19. Deconvolution of the two main peaks found by TSC into elementary Debye components (S.A.S.).


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189

Table I. Compensation Parameters for Copolymers S Line

A Line T Sample (°C) c

SC A.S.S. S.A.S.

64

— —

M

T (°C)

0.035 — —

— 32 28

T

c

c A

TcA

(>) 6.0 x IO" 4.5 x IO"

3 3

T S C

T cS

(°C)

(s)

105 104

0.045 0.55

NOTE: Subscript A refers to the A phase, S to the S phase. The A and S lines are those of Figure 18.


2. T h e phase segregation is not c o m p l e t e i n t h e block

copoly-

mers. 3. T h e compensation d i a g r a m ( F i g u r e 18) quantifies t h e difference b e t w e e n the structure of the amorphous phases i n A . S. S. a n d S . A . S . T h e p r e e x p o n e n t i a l factors are h i g h e r for A . S . S . (the compensation l i n e is situated above), a n d , because t h e e n t r o p y o f activation is t h e m i r r o r o f the l o g o f the p r e e x p o n e n t i a l factor, the activation entropies are l o w e r i n A . S. S. than in S.A.S. 4. T h e phase segregation is l o w e r i n A . S . S . than i n S . A . S . These results indicate a core s h e l l structure a n d suggest a m o r p h o l o g y i n w h i c h latex particles have a (butyl acrylate)-rich core a n d a s t y r e n e - r i c h s h e l l for b o t h A . S . S . a n d S . A . S . T h e s e results also suggest that t h e phase segregation is m o r e p r o n o u n c e d for S . A . S . T h e s e conclusions are consistent w i t h those d r a w n f r o m other results p u b l i s h e d separately (21, 22).

References 1. Vanderschueren, J . , Ph.D. Thesis, University of Liege, Belgium. 2. van Turnhout, J. Thermally Stimulated Discharge of Polymer Electrets; Elsevier: New York, 1975. 3. Lacabanne, C., Ph.D. Thesis, University of Toulouse, France, 1974. 4. Chatain, D., Ph.D. Thesis, University of Toulouse, France, 1974. 5. Bernes, A.; Boyer, R. F.; Chatain, D . ; Lacabanne, C.; Ibar, J. P. In Order in the Amorphous State of Polymers; Keitnath, S. E., E d . ; Plenum: New York, 1987; pp 305-326. 6. Diaconu, I.; Dumitrescu, S. V. Eur. Polym. J. 1978, 14, 971-975. 7. Goyaud, P., M.S. Thesis, University of Toulouse, France, 1979. 8. Lacabanne, C.; Goyaud, P.; Boyer, R. F. J. Polym. Sci. Polym. Phys. Ed. 1980, 18, 277-284. 9. Shrivastava, S. K.; Ranade, J. D . ; Srivastava, A. P. Thin Solid Films 1980, 67, 201-206. 10. Jeszka, J. K.; Ulanski, J.; Glowacki, I.; Kryszewski, M. J. Electrost. 1984, 16, 89-98. 11. Kryszewski, M . ; Zielinski, M . ; Sapieha, S. Polymer, 1976, 17, 212-216. 12. Ohara, K.; Rehage, G. Colloid Polym. Sci. 1981, 259, 318-325.



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13. Biros, J.; Larina, T.; Trekoval, J.; Pouchly, J. Colloid Polym. Sci. 1982, 260, 27-30. 14. Gourari, A . , M.S. Thesis, University of Algeria, 1982. 15. Gourari, A.; Bendadaoud, M . ; Lacabanne, C.; Boyer, R. F. J. Polym. Sci. Polym. Phys. Ed. 1985, 23, 889-916. 16. Barandiaran, J. M . ; Del Val, J. J . ; Colmenero, J . ; Lacabanne, C.; Chatain, D.; Millan, J.; Martinez, G . J. Macromol. Sci. Phys. Ed. 1984, B22, 645-663. 17. Aoki, Y.; Brittain, J. O. J. Polym. Sci. Polym. Phys. Ed. 1976, 14, 1297-1304. 18. Guerdoux, L . ; Marchal, E . Polymer, 1981, 22, 1199-1204. 19. Sawa, G.; Nakamura, S.; Nishio, Y.; Ieda, M . Jpn. J. Appl. Phys. 1978, 17, 1507-1511. 20. Belana, J . ; Colomer, P.; Pujal, M . ; Montserrat, S. J. Macromol Sci. in press. 21. Ibar, J. P. Polym. Plast. Technol. Eng. 1981, 17, 1, 11. 22. Cebeillac, P., Ph.D. thesis, Paul Sabatier University, 31062 Toulouse, France, 1989. 23. Materials were synthesized by Rhone-Poulenc Recherches, Aubervilliers, France. R E C E I V E D for review February 14, 1989. A C C E P T E D revised manuscript July 26, 1989.


Polymer Characterization - American Chemical Society

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