Thermodynamic stability of polyheteroarylene-epoxy resin systems

Thermodynamic stability of polyheteroarylene-epoxy resin systems

Thermodynamic stability of P H A - E R systems 425 9. R. BUCKLEY, M. SZAWEC and A. REMBAUM, J. Chem. Soc., 3442, 1958 10. A. A. BERLIN, A. V. RAGIMO...

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Thermodynamic stability of P H A - E R systems

425

9. R. BUCKLEY, M. SZAWEC and A. REMBAUM, J. Chem. Soc., 3442, 1958 10. A. A. BERLIN, A. V. RAGIMOV, S. I. SADYKII-ZADE and T. A. GADZHIYEVA, Vysokomol. soyed. A17: 111, 1975 (Translated in Polymer Sci. U.S.S.R. 17: 1, 126, 1975) 11. L. BELLAMY, Infrared Spectra of Complex Molecules, p. 263, 1963

Polymer ScienceU.S.S.1L¥ol. 21, pp. 425-431. (~) PergamonPress Ltd. 1979.Printedin Poland

0032-3950/79/0201-0425$07.50/0

THERMODYNAMIC STABILITY OF POLYHETEROARYLENE-EPOXY RESIN SYSTEMS* L. V. ADAMOVA, A. A. TAGER, N. D. KARPOVA, N. T. NERUSH, S. N. SALAZKIN, Yx. S. VYGODSKn and I. A. BULGAKOVA A. M. Gorkii Urals State University (Received 9 February 1978) The concentration dependence of the free energy of mixing polyheteroarylenes and epoxy resins is taken as a basis for determining the thermodynamic compatibility of the components and the thermodynamic stability of the mixtures. The components of most of the systems proved to be thermodynamically compatible and the systems obtained are thermodynamically stable. Light is shed on the role played by the chemical structure of the mixing components in their thermodynamic compatibility: the degree of compatibility is highest in cases where groups that are similar in their chemical structure are present in molecules of the components. Such groups provide simultaneously for strong energy interaction a n d for the formation of compatible structures.

EPoxY resins (ER) have a set of good properties fitting their wide spread applications in industry and technology. However the major disadvantage associated with these materials is their poor heat stability, which may be improved by modification of ER with heat stable and thermally stable polymers, in particular, by means of polyheteroarylenes [1, 2]. No chemical interaction is observed between ER and polyheteroarylenes at temperatures below 100 ° [3, 4], and mixtures are formed. This leads to problems of the thermodynamic stability of such mixtures, and to the matter of the thermodynamic compatibility of the components. In the present work we investigated the effect of the chemical structure of epoxy resins and polyheteroarylenes (PHA) on the thermodynamic stability of the mixtures and on the thermodynamic compatibility of the components esti* Vysokomol. soyed. A21: No. 2, 388-392, 1979.

L. V. ADAMOVA et al.

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m a t e d on the basis of the concentration dependence of the free energy of mixing determined by the method proposed by Tager and #oworkers [5-7]. Three epoxy resins and four polyheteroarylenes, the formulae of which appear in Table 1, were used. Films of the polymers and mixtures of the latter of predetermined composition were prepared from 5 ~ solutions in tetrachloroothano. The films were either TABLE 1. THE POLYMERS UNDER INVESTIGATION Chemical formulae of respecting units

Polymers

ED.20

H,C-ACH --CH ,--[--0--Ar--0--CH ,--CH--CH ,--].--0--

",o/

M ([~]] in tetrachloroethane a t 25 °, dl/g) 450

&

A r - - - O - - C ~ , - - - C H - - C H , ( A r - - d i p h e n y l o l p r o p a n e residue)

430

ERPh

0--CH,~J~, EIP.612

i

o
250

o-~./%/ o95 × 104

F-1

-

~=o

~ CH,

CH,

CH~

(1.2o)

DI~-I

N----N (0.70)

7POD-1

@---- ,,o/ C=O

(0.60)

P01-1

C~O

Thermodynamic stability of PHA-ER systems

427

translucent or opaque (Table 2), depending on the nature of the mixing components and on their ratio. A study was made of the isothermic sorption of chloroform vapours b y the polymers and their mixtures at 25% To do so a thermogravimetric method of sorption together with a spiral of sensitivity 0.2-0.5 mm/mg were used. The shape of the sorption isotherms is typified b y those displayed in Fig. 1. Sorption isotherms obtained for the other systems examined are of similar appearance. TABLE

2.

MIXTURES

:FILMS

OF

POLYHETEROARYI~NE--EPOXY

RESII~

CAST F R O M SOLUTIONS I N TETRACHILOROETHANE

System F- 1-t-ED-20

Weight ratio of External appear, component ante of the film 1:3

Translucent

1:1 F- 1q- ERPh PM-1 q-ED-20

3:1 8:2 6:4 2:8 1:3

1:1 POD- 1-b EPPh

POD-l-bED-20

3:1 8:2 6:4 5:5 4:6 2:8 1:3

9~

t~ 9~

Opaque

1:1 POD-I-bUP-612

POI- 1q- ERPh

3:1 8:2 6:4 5:5 4:6 2:8

Translucent

1:3 1:1 3:1

Translucent

Opaque

The isotherms of chloroform sorption b y polyheteroarylenes are of a sigmoid t y p e having a convex initial portion in the region of low relative vapour pressures, which is characteristic of loosely packed polymers [8]. Sorption isotherms obtained for the E R specimens have the concave shape associated with polymers in the elastic state or in the flow state [8] and comes about as a result of sorbate molecules changing places with flexible chain units. Concave isotherms are likewise obtained for the P H A - E R mixtures owing to the plasticizing action of E R . Using the sorption isotherms and the equation A/II=(l/Mx) RT In pips we

L . V . ADAMOVA et al.

428

c a l c u l a t e d t h e chemical p o t e n t i a l differences of t h e solvent A/z1 a n d t h e G i b b s D u h e m e q u a t i o n w a s u s e d for t h e chemical p o t e n t i a l differences of t h e polym e r i c c o m p o n e n t A#~, while t h e e q u a t i o n Agra~-oPiAlh+o~2Alt2 g a v e t h e a v e r a g e free energies o f m i x i n g for each of t h e c o m p o n e n t s w i t h chloroform. T h e conc e n t r a t i o n d e p e n d e n c e of Ag m for t h e s y s t e m F - 1 - E D - 2 0 is d i s p l a y e d in Fig. 2. S i m i l a r l y s h a p e d curves were p l o t t e d for t h e o t h e r s y s t e m s . T h e free energies o f m i x i n g were f o u n d for t h e p o l y h e t e r o a r y l e n e A GI a n d for t h e e p o x y resin

x/m

I

l

2'0

ED-20

.041

0"8 F-!

!

y o

o.ep,/p7

o., ~(~. 1

@ FiG. 2

FIG. 1. Sorption isotherms for chloroform vapours by mixtures of F-1 and ED-20. Weight ratio of F-1 : E D - 2 0 = I : 0 (1), 1 : 3 (2), 1 : 1 (3), 3 : 1 {4), 0 : 1 (5). I~G. 2. Plots of the average free energy of mixing zigm vs. the composition of solutions of F-I, ED-20 and ~heir mixtures in chloroform:/--F-I; 2-4--F-lq-ED-20 (F-1 : ED-20=3 : 1 (2), 1 : 1 {3), 1 : 3 (4)), 5--ED-20.

Thermodynamic stability of PHA-ER systems

42~

AG~ and their mixtures AGm using 1 g of polymer or 1 g of mixture with chloroform. The values obtained were substituted in equation (1) -

(i)

Agz ---- A G~Iz-- (~o1AGI + ~o2AG~ )

-

-

-

where Agx is the average free energy of mixing of the polymers, and col, 0)2 are weight fractions of polymers in the mixture [7]. Figure 3 shows plots of the average free energies of mixing vs. the composition of the polymeric mixtures. I t can be seen t h a t the plots of Agx vs. composition of the mixture are located for most of ~he systems in the negative region and are convex downwards (Agx<0; ~2gx/~>O). This means t h a t the components intermingle spontaneously, i.e. are thermodynamically compatible, and the resulting systems are thermodynamically stable. Exceptions are observed in the ease of mixtures of polyoxadiazole POD-1 with two epoxy resins, for which, with a high content of ER, the curves are convex upwards (Agx>O; a~gx/aw~
5RPh

0.#

O'8

F-I EO-20 POD-/ POI-I

0.¢

O8 '

2

a

~,.q:r, cal/g _ -2"0

PliA

-l.g

-l.O !

'

b

[email protected]

ERPh ED -20

POP-/

UP-G12

-I'0 0

call5

FIG. 3. Plots of the average free energy of mixing of polymers vs. the composition of the polymeric mixture for the systems: a: 1 -- F- 1-~ERPh; 2-- POD- 1~-ERPh; 3--POI- 1TERPh; b: 1--DM-I~ED-20; 2--F-ITED-20; c: 1--POD-I~-ERPh; 2--POD-I~ED-20; 3--POD-I ~UP-612.

~30

L.V. ADAm"OVAeta/.

attributable to two factors: the low molecular weight of the latter (it is known that oligomers are as a rule readily compatible with polymers of a chemically different nature [9]) and the strong energy interaction between functional groups # f components of the foregoing systems. It is clear from the data presented above to what extent the chemical structure of the mixing components affects their thermodynamic compatibility. Thus all the PHA whose molecules contain phthalide rings are readily compatible w~th an epoxy resin whose molecule likewise contains phthalide groups (ERPh). Moreover the thermodynamic affinity is influenced by the remaining portion of the PHA molecule. Thus on going from polyarylate F-1 to polyoxadiazole POD-1 a n d polyimide POI-1 a lower degree of affinity towards ER is observed for the latter polymers (Fig. 3a). ED-20 epoxy resin containing the isopropylidene group has greater affinity towards DM-1 polyarylate, likewise containing the isopropylene group, than towards F-1 polyarylate containing the phthalide ring (see Fig. 3b). The role played by the chemical structure of the components is also apparent from an analysis of Fig. 3o showing A g z = f (co2) plots for POD-1 polyoxadiazole with three different epoxy resins. The value of Ag~ was most negative for the system POD-I-~ERF, i.e. the case where the molecules of both components contain phthalide rings. Less readily compatible with POD-1 is the resin containing the isopropylidene group (ED-20), while still less affinity is observed between POD-1 and the UP-612 cycloaliphatic resin. The absence of thermodynamic compatibility is observed when the content of the latter resins in a mixture is high. Thus it is clear from the data considered above that the highest degree of compatibility between polymers and oligomers appears in those cases where groups having a similar chemical structure are found in molecules of the components. The authors thank D. R. Tur for trlndiy providing the poly-l,3,4-oxadiazole specimen. Translated by R. J. A. HEyDay REFERENCES

1. L. N. BET.KINA, A. A. ASKADSKII and V. Y. KORSHAK, Voprosy radioelektron~]~i, seriya obshchetekhnichoskaya(Problems of Radio Electronics, General Technical Series). No. 12, p. 120, 1975 2. L. N. B]~IJ]gTNA,A. A. ASKADSKII and V. V, KORSHAK, Voprosy radioelektroniki, seriya obshehetekhnicheskaya(Problems of Radio Electronics, General Technical Series). No. 12, p. 127, 1975 3. L. I. KOMAROVA,S. N. SALAZKINe~ed., Vysokomol.soyed. BI6: 718, 1974 (Not translated in Polymer Sci. U.S.S.R.) 4. L. I. KOMAROVA, I. A. BULGAKOVA and S. N. SALASKIN, Polymer Letters 14: 179, 1976 5. A. A. TAGER, Vysokomol.soyed. AI4: 2690, 1972 (Translated in Polymer Sci. U.S.S.R. 14: 12, 3129, 1972)

Poly(arylate organosiloxane) polyblock copolymer

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6. A. A. TAGER, T. I. TSHOLOKORICH and L S. BESSONOV, Europ. Polymer J. 7: 321, 1974 7. A. A. TAGER, T. I. SHOLOKHOVICH eta/., Vysokomol. soyed. A17: 2766, 1975 (Translated in Polymer Sci. U.S.S.R. 17: 12, 3178, 1975) 8. A. A. TAGER and M. V. TSIIJPOTKINA, Uspekhi khimii 47: 152, 1978 9. V. N. KULEZNEV, L. S. KROKHINA eta/., Kolloidn. zh. 33: 98, 1971

PolymerScienceU.S.S.R.Vol.21, pp. 431-446. (~) PergamonPress Ltd. 1970.Printed In Poland

0032-3950/79/0201-0431 $07.50/0

STRUCTURE, PROPERTIES AND THE, PROCESS OF PHASE CONVERSION IN THE, POLY(ARYLATE ORGANOSILOXANE) POLYBLOCK COPOLYMER* L. Z. ROGOV~A, A. YE. CHALYKH,P. M. VALETSKII,YE. A. NEKKAYKI~O) YA. V. GE~TIN, N. I. Z~]~wAROVA, YE. I. LEvI~, S. B. DOLGOPLOSK, S. V. VINOGRADOVA, G. L. SLO~mSK~ a n d V. V. KORSHAK Het~ro-organie Compounds Institute, U.S.S.R. Academy of Sciences Physical Chemistry Institute, U.S.S.R. Academy of Sciences

(Received 13 February 1978) Using the methods of electron microscopy and low angle X-ray scattering a comparative analysis has been carried out on the structure .and properties (glass transition temperature, mechanical properties, sorption and diffusion of selective solvent in the poly(arylate dimethylsfloxane) polyblock copolymer in relation to the chemical structure of the chain and the selectivity of the solvent. I t is shown that the main features of the polyblock copolymer are: the phase conversion process taking place over a wide range of block copolymer composition, the presence of several levels of segregation, and phase organization that is less regular than in t w o and three block copolymers.

VI~.ws currently accepted by investigators regarding segregation of thermodynamically incompatible blocks in block copolymers and concerning the formation of phase structure and its evolution with change in the copolymer composition have mainly been formed in the light of investigations of two and three block copolymers of styrene with dienes [1-3]. V. A. Kargin and coworkers were the first to realize that where block copolymer components manifested their individual properties this must mean that separation of each of the components into individual micro regions takes place, i.e. the concept of segregation processes * Vysokomol. soyed. A21: No. 2, 393-405, 1979.