CHOESIVE AND TRANSPORT PROPERTIES OF A BINARY ORGANIC GLASS-FORMING SYSTEM CONTAINING CO2+

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CHOESIVE AND TRANSPORT PROPERTIES OF A

BINARY ORGANIC GLASS-FORMING SYSTEM

CONTAINING CO2+

Mady Elias, A. Elias

To cite this version:

JOURNAL DE PHYSIQUE

Colloque C8, supplkrnent au n012, Tome 46, dkcembre 1985 page C8-125

CHOESIVE AND TRANSPCRT PROPERTIES OF A BINARY ORGANIC

GLASS-FORM1 NG SYSTEM CONTAINING

co2+

M.E. Elias and A.M. Elias

Department of Chemistry, Lisbon University, Faculty of Science,

R. EscoZa PoZite'cnica, 1294 Lisbon Codex, Portugal,

R6sume

-

La f o r m a t i o n de v e r r e dans l e c h l o r u r e de c o b a l t e t l e s y s - m c h l o r u r e de a - p i c o l i n i u m

+

c h l o r u r e de y-picolinium] a S t 6

6 t u d i 6 e . Les p r ' o p r i & t & s p h y s i g u e s t e l l e s que l a cohEsion, l a m o b i l i - t 6 i o n i q u e e t l a f l u i d i t e o n t 6 t j a u s s i m e s u r j e s . Le systPme forma- t e u r de v e r r e o r g a n i q u e b i n a i r e p r e s de l a composition e u t e c t i q u e a un T de -42.5OC r r o c h e du T du a-picHC1 p u r . Les t e m p j r a t u r e s de t r a l s i t i o n s v i t r e u s e s T e t

Po

pour l e systame i o n i q u e C O ~ + ne p r E s e n t e n t aucun minimum s q g n i f l c a t i f dans 1' i n t e r v a l l e de concen- t r a t i o n 0

-

10 mole % , c o n t r a i r e m e n t au systgme a-picHC1

+

CoC12. On o b s e r v e cependant une tendence v e r s un maximum de l a c o n d u c t l - v i t 6 S l e c t r i q u e e t de l a f l u i d i t E , a i n s i q u ' u n minimum de Tg e t To,

21 33,3 mole % de c h l o r u r e d e c o b a l t . Ceci p e u t $ t r e dO 2 l a forma- t i o n de s t r u c t u r e s t e t r a s d r i q u e s [CO

c14]

2-.

A b s t r a c t

-

The o c c u r r e n c e of g l a s s e s i n s t r u c t u r a l l y i o n i c c o b a l t c h l o r i d e and ( a - p i c o l i n i u m c h l o r i d e + y - - p i c o l i n i u m c h l o r i d e ) system was s t u d i e d . Also c o h e s i o n , i o n m o b i l i t y and f l u i d i t y - r e l a t e d phy- s i c a l p r o p e r t i e s have been measured. The b i n a r y o r g a n i c g l a s s - f o r - ming system n e a r t h e e u t e c t i c composition w i t h 6 4 , 5 mole % a-?icPCJ- and 3 5 , 5 mole % a-picFIC1 shows a T v a l u e o f - 4 2 , 5 O ~ c l o s e t o p u r e a-picHC1 Tri v a l u e which i s l e s s , 5oQ. The v a l u e s of

lass

t r a n s i - t i o n t e m p e r a t u r e s Tg and To ( u a n d $ ) f o r C O ~ + system d o e s n o t show any s i q n i f i c a n t minimum i n 0-10 mole % c o b a l t c h l o r i d e a s was t h e c a s e w i t h wpicECl+CoC12. However, a t 33,3 mole % c o b a l t c h l o r i d e a maximum tendency i n e l e c t r i c c o n d u c t i v i t y and f l u i d i t y a minimum i n Tc and To i s i n t e r p r e t e d i n t e r m s of [ c o c 1 4 ] 2 - t e t r a h e d r a s t r u t u r e s and c o o r d i n a t i o n number. An a n a l y s i s o f " a c t i v a t i o n e n e r q y " and VTF e q u a t i o n p a r a m e t e r s A , B ( u and 4 ) i s a t t e m p t e d t o c o r r e l a t e d w i t h s i n g u l a r i t i e s found i n t h e o r g a n o m e t a l l i c c h l o r i d e system and t h e i r c o n f i g u r a t i o n a l e n t r o p i e s .

I

-

INTRODUCTION

O r q a n o m e t a l l i c g l a s s - f o r m i n g m a t e r i a l s a r e a r e c e n t a r e a of i n t e - r e s t , f i r s t i n t e r m s o f f r e e a b i l i t y o f o r q a n i c compounds t o form g l a s s /1-3/ and second when t h e s e a r e mixed w i t h t r a n s i t i o n metal-ca t i o n s /4-5/:

The b e h a v i o u r of c o 2 + i n h a l i d e g l a s s forrcinq systems was s t u d i e d r e c e n t l y . I n f a c t , it was found t h a t CoC1.2+ a - p i c o l i n i u m s C 1 ( a - P i c HC1)mixture p r e s e n t s a remarkable d e c r e a s e b o t h i n Tg, and i n To (i- d e a l g l a s s t r a n s i t i o n t e n p e r a t u r e ) , i n t h e range of c o m ~ o s i t i o n from 0 t o 22 mole % CoC12. Between 22 and 40 mole % CoC12 no g l a s s forma- t i o n was d e t e c t e d , however To v a l u e s p r e s e n t a remarkable d e c r e a s e

/6/. These r e s u l t s were w e l l c o r r e l a t e d w i t h maxima v a l u e s found i n c o n d u c t i v i t y measurements.

C8-126 JOURNAL

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W r e p r e s e n t s a t r a n s p o r t p r o p e r t y , r e v e a l s an a d e q u a t e d t o o l t o t h e a n a l y s i s of t h e r e s u l t s a s was found i n p r e v i o u s work / 5 - 7 / .

I1

-

EXPERIMENTAL SECTION

a - P i c o l i n i u m C h l o r i d e , r e f e r r e d a s a-PicHC1, was o b t a i n e d b y a d d i t i o n o f c o n c e n t r a t e d aqueous h y d r o c h l o r i d e a c i d e (Mallinkrodt,ACS) to- a s l i g h t e x c e s s of 2 - m e t h y l - p y r i d i n e /4-5/ m.p.90.5°~. y-Picolinium c h l o r i d e h a s been o b t a i n e d i n a s i m i l a r way. I t m e l t s t o a c o l o r l e s s l i q u i d a t 165.2% / 2 / .

C h l o r i d e s a l t s were p u r i f i e d by a low t e m p e r a t u r e s u b l i m a t i o n

m e

t h o d and s t o r e d i n a d e s s i c a t o r under vacuum t o a v o i d c o n t a m i n a t i o n . These s a l t s were p r e p a r e d i n s e e d qeometry.

CoC12 m i x t u r e s f o r s t u d y were p r e p a r e d by a d d i t i o n s o l i d - s o l i d t o t h e o r g a n i c c h l o r i d e g l a s s - f o r m i n s system. A l l h a n d l i n g and measu rement p r o c e s s e s were performed under gaseous d r y n i t r q e n and sam- p l e s p r e p a r e d by w e i a h t i n a g l o v e box.

F o r t h e o r a a n i c m i x t u r e s t h e s o l u b i l i t y l i m i t and decomposition

of t h e samples o c c u r s s l i a h t l y above t h e h i q h e s t c o n c e n t r a t i o n (work c o m u o s i t i o n ) . The D i f f e r e n t i a l Thermal A n a l y s i s method was e s s e n t i a - l l y t h e same a s p r e v i o u s l y described / 6 / . The a l a s s e s were produced by quenching f i x e d m i x t u r e s . C o n d u c t i v i t y o and f l u i d i t y @ measure- ments were performed a s r e f e r r e d e l s e w h e r e /2-6/.

I11

-

RESULTS

A r r h e n i u s p l o t s o f c o n d u c t i v i t y and f l u i d i t y a r e shown i n t h e f i g u r e 1 and f i g u r e 2. I n f i g u r e 3 and f i g u r e 4 a r e shown t h e i s o t h e r - mic r e p r e s e n t a t i o n of c o n d u c t i v i t y and f l u i d i t y

@.

The p a r t i a l phase diagram f o r t h e system a-picHCl+y-picHC1 and v a l u e s of Tg and To a r e shown i n f i g u r e 5. The v a l u e s o f Tg and Tolo

,

T o $ f o r t h e svstem a - -picFCl+y-picHCl+CoC12 a r e shown i n f i g u r e 6 .

I V

-

DISCUSSION

The A r r h e n i a n b e h a v i o u r of c o n d u c t i v i t y and f l u i d i t y , shows so- me dependence w i t h t e m p e r a t u r e a s was e x p e c t e d f o r t h i s t y p e o f com- pounds.

From t h e i s o t h e r m a l p l o t s i n f i g u r e s 3 and 4 we f i n d an i n c r e a s e i n c o n d u c t i v i t y , o , between 0-30 mole % and a d e c r e a s e above 30 mole

% i n CoC12. A d e c r e a s e i n f l u i d i t y , $

,

i s a l s o found. I f v a l u e s f o r a-picHcl+CoC12 / 6 / a r e compared w i t h t h o s e of t h e p r e s e n t system, we f i n d t h a t Aa =a ( a -

+

y -)

-

o ( a - ) i s p o s i t i v e

,

d o e s show an e x p o n e n t i a l i n c r e a s i n g b e h a v i o u r . The i n c r e a s e i n p a r t i c l e m o b i l i t y d e t e r m i n e s t h e f e a t u r e s i n c o n d u c t i v i t y ; The a d d i t i o n of y-picFC1 t o a-picHC1+CoC12 r e s u l t s r e a d i l y a s s o c i a t e d w i t h t h e d i s r u p t i o n o f a s t r u c t u r e d 3 - d i - mensional network l i q u i d by b r e a k i n g up t h e c h l o r o b r i d g e bonds i n p r o p o r t i o n a l i t y t o t h e number o f added c h l o r i d e i o n s .

The v a l u e s of To,o and T o , @ w i t h c o n s t r a i n e d v a l u e s of (B=770K) and (B=940K) f o r c o n d u c t i v i t y and v i s c o s i t y r e s p e c t i v e l y show a slow i n c r e a s e i n c o m p o s i t i o n r a n g e 0-10.4 mole % CoC12, a f t e r which t e n d t o d e c r e a s e q u a s i - s h a r p l y t o 30%, t h e v a l u e s & T g show i d e n t i c a l l y f a n i n c r e a s e between 0-10.4

mole

% CoC12 c o m p o s i t i o n .

f o r o a t 30 mole % CoCl2 a r e e x p l a i n e d b y t h e l i g a n d f i e l d s t a b i l i z a - t i o n e n e r g y o f Co (11); i n f a c t C o b a l t (11) h a s t h e t e n d e n c y t o form t e t r a h e d r a l s t r u c t u r e w i t h C1-environment and f o r t h e c o m p o s i t i o n we a r e n e a r t h e optimum Td s t o i c h j o m e t r y 3 3 . 3 mole % CoC12.

The d e c r e a s e i n To and To,$ f o r X>30 mole % CoCl i s o r i e n t e d d u e t o t h e i n c r e a s e i n t h e c o n f i g u r a t i o n a l e n t r o p y SC / 7 3 . A l s o , SC i n c r e a s e s a s T i n c r e a s e s . I n f a c t , t h e f o r m a t i o n o f a n a n i o n i c complex o f t a n s i t i o n m e t a l c o n s i d e r i n g t h e c h l o r i d e t r a n s f e r r e a c t i o n , [Co

Cia]

'-

from .-picPC1 and p r o b a b l y from y-picHC1, t o t h e s t r o n g Lewis a c i d , i s d u e t o a - p i c o l i n i u m and y - p i c o l i n i u m s m a l l e f f e c t i v e i o n i c p o t e n t i a l . U n f o r t u n a t e l y t h e p a r t i a l c r y s t a l f o r m a t i o n above 20 mole

% CoCl2 i n h i b i t s e x t e n s i o n o f T, and o f o u r d i s c u s s i o n . The Tg/To va- l u e s l i e s between 1 . 2

-

1 . 3 a s e x p e c t e d s i n c e t h e t e r n a r y g l a s s f o r -

ming s y s t e m s a r e composed t o s i m p l y c o n s t i t u t e d o r g a n i c i o n i c l i q u i d and B+n,BO1.2 which c o n f i r m s a b o v e c o m p a r i s o n .

"Energy o f A c t i v a t i o n " ( E o ,

E

$ ) f o r t r a n s p o r t , f i g u r e 7 a n d f i - g u r e 8 , show a r e m a r k a b l e l i n e a r i t y w i t h f ( T o / T ) which a r e b e s t f i t v a l u e s / 8 / t h i s c o n f i r m s VTF e q u a t i o n a s

an..

i m w o r t a n t model t o ex- p l a i n t h o s e p r o p e r t i e s i n G l a s s f o r m i n g m a t e r i a l s , and u s i n g B v a l u e s o f f i g u r e 6 a u n i q u e l i n e r e p r e s e n t a t i o n i s f o u n d .

V

-

CONCLUSION

JOURNAL

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Fig.2

-

Arrhenius plot of

-

.A

' 2

fluidity for a-picHCl+y-picHCl+ $ +CoC12 system.

-

C

Fig.4

-

Fluidity for isotherms a-picHCl+Y-picHC1+CoCl2 system.

for 2 o o 0 c

a 180

t 160

1 4 0 Fig.3

-

Conductivity isotherms

.

I 2 0 for a -picHCl+y -picHCl+CoC12

Fig.5

-

Partial phase diagram and Fig.6

-

T

,

To ,and T vaiues T values for a-picHCl+y-picHC1. for u - p i c ~ ~ l + u ~ p i c ~ ~ l ? ' ~ o ~ 1 2

? system.

Fig.7

-

Representation of "Activg Fig.8

-

Representation of "Activa- tion Energy" for conductivity vex tion Energy" for fluidity versus

JOURNAL

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REFEPENCES

/1/ Lesikar, A.V., J.Chem.Phys.,

63

(1975) 2297.

/2/ Elias, A.PI. and Elias, II.E., paper presented at 2nd Heetina of Pla

terial Portuguese Society, PORTO, (19P5).

/3/ Xanno, F., Shimada, K. and Yoshino, K., Chem.Phys.Letters.

112

(1984) 242.

/4/

Angell, C.A., Hodge, I.M. and Cheeseman, P.A., in "Pblten Salts", Edited by J.P.Pemsler (The Electrochemical Society, 1976), p.138. /5/ Angell, C.A., and Elias, A . M . , J. hys. Chem., 8 7 (1983) 4704.

/6/ Elias, A.M. and Anyell, C.A., to be published

/7/

Angell, C.A. and Ploynihan, C .T., in "Pflolten Salts", Ed.G.Mamantov, Parcel Deklcer,

Mew

York, N.Y. (1969), p.315.