Dilute solution properties of bisphenol A polycarbonate—I Osmotic, light scattering and viscosity measurements

Europeaa Polymer Journal, 1969, Vol. 5, p~. 185--193. Pergamon Press. Printed in England.

DILUTE SOLUTION PROPERTIES OF BISPHENOL A POLYCARBONATE--I OSMOTIC, LIGHT SCATTERING AND VISCOSITY MEASUREMENTS W. R. M o o ~

a n d M. UDDIN

School of Polymer Science, University of Bradford, Bradford, England (Received 21 June 1968)

Abstract--Dilute solutions of ten fractions of a bisphenol A polycarbonate (gl, 7000--77,000) have been examined by osmotic, light scattering and viscometric techniques at 25°. Of the seven solvents used three are acidic, three basic and one a theta-solvent mixture. Second virial coefficients and other parameters are obtained. The results suggest the following order of thermodynamic solvent power: chloroform ~ methylene chloride > ethylene chloride ~ dioxan ~ tetrahydrofuran > cyclohexanone > dioxan/cyclohexaae. Viscosities lead to the following Mark-Houwink relationships at 2Y: [n] = 1" 12 x IO-'LI~I,°'a2 in chloroform [~7] -- 1.23 × 10-41~I,°'81s in methylene chloride [rd = 1"42 × 10-4i~,°'~8 in ethylene chloride [71 ----3"09 x 10-4~v ° ' ~ in dioxan [~7l --- 4"90 × 10-'L~v °'n7 in tetrahydrofuran [7] = 7-76 x 10"4I~lv°'nz in cyclohexanone [~.] = 21"4 x 10-4~Iv°'5° in dioxan/cyclohexane. INTRODUCTION THE POLVCARBONATEderived from 4,4'-dihydroxy-diphenyl-2,2-propane (bisphenol A) possesses polar a n d polarizable groups a n d contains b o t h flexible and relatively rigid units in the chains. A p a r t from the work of Sitaramaiah " ) and, to a lesser extent of Berry et al., (2) there have been few systematic studies of the variations of dilute solution properties a n d parameters derived from them with solvent a n d molecular weight. The work described in this paper is part of a study of the interaction of bisphenol A p o l y c a r b o n a t e with solvents. Osmotic, light scattering a n d viscometric m e a s u r e m e n t s have n o w been m a d e o n dilute solutions of fractions in seven solvents. Three of the solvents are acidic, in the Lewis sense, three basic a n d the seventh a b i n a r y mixture behaving as a theta solvent. Estimates are made of the second viral coefficient A 2 a n d other parameters a n d intrinsic viscosity-molecular weight relationships are obtained.

EXPERIMENTAL A commercial sample of bisphenol A polycarbonate was fractionated by stepwise addition of methanol to a 1 per cent solution in chloroform at 25 ±0" 1°. Eleven fractions were obtained of which ten were used in further work. Each was reprecipitated from chloroform solution by excess methanol and dried in vacuo at 50°. Chloroform, methylene chloride, ethylene chloride, dioxan, tetrahydrofuran and cyclohexanone were used as solvents. The first three solvents are acidic, the latter three being basic. A dioxan/cyclohexane mixture containing 63-9 per cent dioxan by weight was also used. This was found by Berry et al. (2) closely to approximate to a theta solvent at 25°. All liquids were further purified and dried by appropriate methods and fractionally distilled before use. Preliminary viscometric examination of dilute solutions of the fractions indicated molecular weights in the range 10,000-70,000.Number-average molecular weights g'l, less than 25,000 were obtained with 185

186

W.R.

M O O R E and M. U D D I N

a Mechrolab vapour pressure osmometer using chloroform solutions at 37 °. Osmotic pressures ,r of dilute solutions of fractions with number-average molecular weights in excess of 25,000 were obtained with each solvent in Pinner-Stabin osmometers, ~*~ using gel cellulose 600 membranes appropriately conditioned to solvent, at 2 5 - 0 - 0 1 ° Membrane permeation was not detected. Values of 1~I, and A2 were obtained from rectilinear plots of ,rio against e, where c is the conceatration~ and the relation: ~r/c = R T ( 1 / ~

+ A2c + . . . ).

(I)

Measurements of light scattering of dilute solutions of the fractions in chloroform were made at 30±0" 1° with a Brice-Phoenix universal light scattering photometer c5' (1000 series). A wave length of 5461 A was used. The instrument was calibrated with a standard polystyrene sample. Solvent and solutions were filtered through fine sintered filters. The value of the Rayleigh ratio for benzene (30 °, 5461 A) was Rgo = 18"15 x 10 -6 cm -1, somewhat higher t h a n t h e value of 16"46 × 10 -6 cm - t given by Kratohvil et al. ~ Scattered light intensities were measured at angles of 45 °, 900 and 135 ° to the primary beam. Weight-average molecular weights i~1,, and values o f Az were obtained from: Kc/Rgo = (l/M,,) + 2Azc

(2)

K -----2~r2 no2(dn/dc)2/;~'N,t

(3)

where in which no is the refractive index of chloroform, ,Xthe wavelength of the light and Na the Avogadro number. The value of the refractive index increment dn/dc was obtained using a Brice-Phoenix differential refractometer at 300.2-0 • 1° and found to be 0" 156 ° at 5461 .~, in chloroform. This is somewhat less than the value of 0.162 ° obtained by Sitaramaiah. tt) No dissymmetry correction was applied to the scattering data as values of intrinsic dissymmetry were close to unity. Low ia'~ensities of scattering by solutions of the three fractions of lowest molecular weight precluded determination of their weightaverage molecular weights. Viscosities of dilute solutions of the fractions in each solvent were measured at 25 ° :k0" 01 ° by means of Ubbelohde suspended level capillary viscometers. Kinetic energy corrections, although small, were made where applicable. Shear dependence was not observed. All solvents and solutions were filtered before use. Intrinsic viscosities It/] were obtained by extrapolation of rectilinear least squares plots of r/sp/c against ¢ using: ,I s p / c =

[~7] + k ' [~7]'c.

(4)

RESULTS Figure 1 shows typical plots of ~r/c against c. Those for the dioxan/cyclohexane mixture are parallel to the c axis. Values of ~ in this mixture tended to be a little less than in other solvents, perhaps because of slight degradation, but in no case did values of 1~71~for any fraction in all solvents differ by more than 5 per cent, implying no associa tion of polymer. TABLE I. VALUES OF 1~I., /~I,, and l~l,,/l~l. Fraction 1 2 3 4 5 6 7 8 9 10

1~I. x 10"-* ~I,, x 10 ~ 7"69 5"63 5"48 3"28 3" 16 2" 85 2" 14 I "62 0"95 0"69

8"80 6"50 5-89 4-19 4-05 3.73 2- 76

1V, i,*/l~I. 1"15 1"15 1-07 1"25 1 "28 1" 30 I" 29

Dilute Solution Properties of Bisphenol A Polycarbonate--I

II 0

rio

187

Dioxan

90

i

70 T

f

I

T

Tetrahyclro furan

I1"0

o

T

/

- IO0

90 t

7O

,

~

i

T

i

i

.100 Cy/~.~_clohexanon~/:>"~

IlO

90

¸

9 0

Dioxan

-

r

t

i

i

Icyclohexone

o---

~

70

.'tO T

r

00

i

0'5

I

110

i

i

05

I0.

g/dt.

Concentration,

Fzo. I. =/c against c plots for fraction 4 at 25°. i 5

6-0

2 I

~,.0

O0

I

T

I

T

0-25

0.50

0.75

t-0

Concentration,

g/dt.

Fzo. 2. Kc[Re against c plots for chloroform solutions at 30°. Figures denote ffaetiom. Figure 2 shows plots of Kc/Rgo against c for chloroform solutions. Table 1 gives values of/Vl, from the osmotic and vapour pressure results for chloroform solutions, with values of 1"9I,,and lqI,/IVl.. These results are similar to those of Sitaramaiah. m Table 2 gives osmotic values of A2 and includes those derived from the light scattering results. For solvents other than the dioxan/cyclohexane mixture, A2 tends to decrease with increasing molecular weight in a~eement with theory c7) but in contrast to the results of Sitamaraiah. ~I) eoL~

$/1--o

188

W.R.

MOORE

a n d M. U D D I N

¢)

o -

2o

o

O

6666~ ,)

%

6 ed o

o

x ._> t~ O

o

°

°

°

°

.o

°

z~ e4 e~ °

°

o

°

°

,-'7

~J tll eo •

°

°

g,.

o .o e-, 0

°

,

o

°

°

O

o

Dilute Solution Properties of Bisphenol A Polycarbonate--I

6

66

66

6

66

66

o~

6

o~

6

-g 66666

666666

O0 e-

666666

g,

O0 e~

N~ 666666

,..~Q

;> ,.4

N Q

66

66666

0

66

66666

0

6

6666

6

6666

N -

6666666666

~666666666

189

190

W.R. MOORE and M. UDDIN DISCUSSION

The values of A2 suggest the following order of thermodynamic solvent power: chloroform -~ methylene chloride > ethylene chloride ~ dioxan ~ tetrahydrofuran > cyclohexanone > dioxan/cyclohexane. Chloroform is thus a good solvent, in agreement with the result of others (I" 2) but in contrast to those of de Chirico c8) which suggest it to be a theta-solvent at 25 °. The zero values of A 2 for the dioxan/cyclohexane mixture show that this does behave as a theta-solvent at 25 °. Acidic solvents seem to be

16 I-5

Y

t.4 D i o x ~ ~ , , , ~

I0

.08

16

I

I

I

l

t

I

-I.4 Cyclohexanone

1.3 I.O ~'~ I-4

•0.6 I

I

Oioxan/cyclohexane

18 T

e

t

r

~

-0.9

1.4 I.I i

O0

0.50

o15 l.O Concentration, g/dL.

I

,:o

Fxc. 3. ~,~/c against ¢ plots at 25°. Figures denote fractions. better, in a thermodynamic sense, than basic ones. Solvation, possibly involving specific interaction between acidic hydrogen atoms of the solvent and basic carbonyl groups of the polymer, may enhance solvent power. ¢9) At higher molecular weights, the variation of [-q]with solvent is similar to that of A2. At the lowest molecular weights, however, the variation is very small if it exists at all. Stockmayer and Fixman el°) have suggested that the intrinsic viscosities of impermeable coils should be represented by: [,71 -~ K* M ~ -b K**M

(5)

where K** is proportional to A2 so that it vanishes for theta solvents and increases with solvent power. The first term on the right of Eqn. (5) may become dominant at low molecular weights of polymer and ['d should then become less sensitive to the nature

Dilute Solution Properties of Bisphenol A Polycarbonate--I

191

ofthe solvent. Such effects have also been observed for polystyrene, (zz, z2) polymethyl methacrylateCt3.14) and polyethylene terephthalate, c15) Values of the slope constant k' tend to increase with decreasing solvent power, in agreement with other results. (z' 2) Values of k' for the dioxan/cyclohexane mixture exceed 0-5. Similar values have been obtained with other polymers in poor or thetasolvents, cz6) Values of ~ , for the fractions in the mixture suggest that the high values of k' are not a consequence of association of polymer (zv) unless this occurs in the process of flow. (zs) Figure 4 shows least squares plots of log [7/] against log 1Q,, these being preferred to those of log ['7] against log I~I, in view of the greater number of values of 1Q.. There is a little scatter but no real evidence for an increase of slope at low molecular weights as observed by Berry e t al. c2) who ascribed it to partial draining effects. Similarly, there is no evidence for a decrease of slope at low molecular weights as might perhaps be expected if the first term on the right of Eqn. (5) becomes sufficiently dominant.

0.0

T.6

oo y Tetrahydrofuron

-76

T2 i

I

Dioxan

I

.'T'8

0.0

T6

-1"4

0

Cyclohexanone -7.8

1.2 T

[

T

Ethylene chloride

~

0.0

-7.4

r

.T'8

I

~

Dioxan/cyclohexone

T.6

i.2

t

_~

.T.4 I

4'0

4!4

4J8

4.0

4.4

4.8

log, Mn

FIG. 4. log [7/] against log l~I, plots at 25 °.

Table 4 gives values of the Mark-Houwink exponent a. These, and values of 1Q,, and 1Q,, have been used to obtain values of the viscosity-average molecular weight 19I, from:(~9) 5 , --- 0-5 (a + 1) l~w - 0.5 (a - 1) ~ , .

(6)

192

w . R . MOORE and M. UDDIN

Plots of log [r/] against log l~v are also linear and Table 4 gives values o f K, and K~ defined by:

[,71 = K. ~°+ = Xo ~ ¢ .

(7)

The value of a m a y be regarded as a measure of solvent power and the values in Table 4 give a similar order to those o f A2. Values of K, and a for chloroform, ethylene chloride and tetrahydrofuran are in reasonable agreement with those o f Sitaramaiah31) Schulz and H o r b a c h (2m give a = 0.70 for tetrahydrofuran and Berry et al. ~2) give a = 0 . 8 0 for methylene chloride at 25 °. The value o f a = 0.50 for the dioxan/cyclohexane mixture is, o f course, that expected for a theta-solvent. The d a t u m point for the fraction of ~ . 6900 does fall slightly below the straight line corresponding to a = 0.50 but there is no other evidence for an increase in slope for M < 10 + as observed by Berry et aL (2) TABt~ 4. VALUESOF K,, Kv A~',a9 a AT 25° Solvent Chloroform Methylene chloride Ethylene chloride Dioxan Tetrahydrofuran Cyclohexanone Dioxan/cyclohexane

K~ × 10+

Ko × 10+

a 4-0"02

1"27 1" 37 1" 63 3.55 5" 46 8" 51 22- 7

1" 12 1" 23 1" 42 3" 09 4" 90 7.76 21" 4

0" 82 0" 81 0" 78 0' 71 0.67 0" 62 0" 50

It is perhaps worth noting that a plot o f log K, against a for the other solvents is linear and extrapolation to a = 0 . 5 leads to K = 23.4 × 10+ in fair agreement with the experimental value. Similar results have been obtained with polyacenaphthylene, u 9)

REFERENCES (1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) (15) (16) (17) (18) (19) (20)

G. Sitaramaiah, J. Polym. ScL A3, 2743 (1965). G. C. Berry, H. Nomura and K. G. Mayhan, J. Polym. Sci. A2, 5, 1 (1967). M. J. R. Cantow, R. S. Porter and F. J. Johnson, J. Polym. ScL AP,, 2547 (1964). S. H. Pinner and J. V. Stabin, J. Polym. Sci. 9, 575 (1952). B. A. Brice, M. Halwer and H. Speiser, J. opt. Soc. Am. 40, 768 (1950). J. K.ratohvil, G. Dezelic and E. Matijevic, J. Polym. Sci. 57, 59 (1962). T. A. Orofino and P. J. Flory, J. chem. Phys. 27, 1067 (1957). A. de Chirico, Chim. Ind. 42, 248 (1960). H. Daoust and M. Rinfret, J. Coll. Sci. 7, 11 (1952). W. H. Stockmayer and M. Fixrnan J. Polym. Sci. C1, 137 (1963). C. Rossi, U. Bianchi and E. Bianchi, Makromolek. Chem. 41, 31 (1960). R. Okada, Y. Toyoshima and H. Fujita, Makromolek. Chem. 59, 137 (1963). E. Cohn-Ginsberg, T. G. Fox and H. F. Mason, Polymer 3, 97 (1962). T. G. Fox, J. B. K,dnsinger, H. F. Mann and E. M. Scheule, Polymer 3, 71 (1962). W. R. Moore and D. Sanderson, Polymer 9, 153 (1968). W. R. Moore, Progress in Polymer Science (edited by A. J. Jenkins, Pergamon, p. 3 (1967). R. Simha and J. L. Zakin, d'. chem. Phys. 33, 1791 (1960). A. Peterlin, C. Quan and D. T. Turner, J. Polym. ScL 133, 521 (1965). J. H. Barrales-Rienda and D. C. Pepper, Polymer 8, 337 (1967). G. V. Schulz and A. Horbach, Makromolek. Chem. 29, 93 (1959).

Dilute Solution Properties o f Bisphenol A P o l y c a r b o n a t e - - I

193

R~sum6----On a soumis ~ des mesures osmom~triques, viscosim~t_riques et de diffusion de la lumi~re ~. 25 °, les solutions dilutes de dix fractions d'un bisph6nol A polycarbonate (I~= 7000-77,000). On a utilis~ sept solvants diff~rents dont trois sont acides trois basques et le d e m i e r est un m~lange solvant th~ta. On a d~termin~ les seconds coeificients du viriel et d'autres param~tres. D'apr~s les r6sultats on peut classer de la mani~re suivante les solvants par ordre de pouvoir solvant thermodynamique dc~croissant: chloroforme ~ chlorure de m~thyl~ne > chlorure d'~thyl~ne ~ dioxane ~ tetrahydrofuranne > cyclohexanone > dioxane/cyclohexane. Les relations M a r k - H o u w i n k suivantes ont 6t~ 6tablies ~ 25°: [7] [r/] [7] [71 [7] [7] [7]

= = = = = = =

1"12 1.23 1.42 3-09 4.90 7.76 21.4

× x x x × × ×

10 -4 10 -4 10 -'~ 10 -'~ 10 -4 10 -4 10 -4

I ~ °'8-' ~oO.81s l~fo°'T8 ~oo.~1 ~oO.~: l~i~°'~2 1~ TM

dans darts darts darts darts dans dans

le chloroforme le chlorure de m~thyl6ne le chlorure d'6thyl6ne le dioxane le tetrahydrofuranne le cyclohexanone le dioxane-cyclohexane.

Somm,rio---Sono state esaminate soluzioni diluite di 10 frazioni di un policarbonato di bisfenolo A ( ~ = 7000-77,000) con tecniche osmotiche, di diffusione della luce e viscosimetriche a 25 °. Dei sette solventi impiegati, tre sono acidi, tre basici e uno 6 una misce[a di solvente 8. Sono staff ottenuti secondi coefficienti del viriale e altri parametri. I risultati suggeriscono il seguente ordine eli potere solvente termodinamico: cloroformio ~ cloruro di metilene > cloruro di etilene ~ diossano tetraidrofurano > cicloesanone > diossano/cicloesano. La viscositY, h a n n o c o n d o t t o alle seguenti realzioni di M a r k - H o u w i n k a 25°: [7] [7] [7] [7] [7] [7] [~]

= 1,12 = 1,23 = 1,42 = 3,09 -----4,90 -- 7,76 = 21,4

× × × × × x ×

10~ ffi, T M 10 ~ I~i, °'815 10"~/~I, ° . ~ I0 -'~ IVI,°'~t 10~ I~I,°,sv 10--~ l~i,T M 10 -~ ~4, °'~°

in in in in in in in

cloroformio cloruro di metilene cloruro di etilene diossano tetraidrofurano cicloesanone diossano/cicloesano.

Zusammenfassung--Verdtinnte LSsungen von zehn F r a k t i o n e n eines Bisphenol A Polycarbonats (fifo 7000-77,000) wurden durch osmotische, Streulicht- und viskosimetrische M e t h o d e n bei 25 ° untersucht. Yon den sieben verwendeten L6sungsmitteln waren drei sauer, drei basisch und eines eine Theta-Mischung. Es wurden die zweiten Virialkoeffizienten und andere Parameter bestimmt. Aus den Ergebnissen erhtilt m a n for die thermodynamischen L6sungseigenschaften folgende Reihe: Chloroform ~ Methylenchlorid > .~.thylenchlorid ~ Dioxan ~ Tetrahydrofuran > Cyclohexanon > Dioxan/Cyclohexan. Aus den Viskosit~.ten ergeben sich for die M a r k - H o u w i n k Beziehung bei 25 ° folgende Gleichungen: [7] [7] [7] [7] [7] [7] [7]

= 1,12 --- 1,23 = 1,42 = 3,09 = 4,90 -- 7,76 = 21,4

× × × × x × ×

10 ~ 10 ~ 10 -4 10 "~ 10 -4 10 ~4 10 ~

~o,~ 1~4,° , s ~ ~o.~ 1~, °.v~ l~i,°.s~ I~, ° . ~ I~i, °.~°

in Chloroform in Methylenchlorid in Athylenchlorid in Dioxan in Tetrahydrofuran in Cyclohexanon in Dioxan/Cyclohexan