MOLECULAR IXTERACTIOK IN HIGH-POLYMER SOLUTIOKS ASDRIES VOET Research Department, I n k D i v i s i o n , J . M. Huber Corporation, N e w Y o r k , N e w Y o r k Received October $8, 1948 I. INTRODUCTIOS
It has been observed that the dielectric constant of more concentrated liquid lispersions may decrease very considerably as the result of the application of shearing stresses t o the system. An analysis of this phenomenon has shown ,hat a t relatively low concentrations the particles of the dispersion move indeDendently, but a t a value of the concentration higher than a critical value a Lendency to particle agglomeration exists, resulting in the formation of struc;ures (9). Such particle structures, however, are broken up upon the applica.ion of shearing stresses, resulting in particles moving independently at higher :oncentrations in systems under shear. I t had been established that a Sewtonian flow is exhibited by systems in n-hich particle agglomeration was found to be absent, while a plastic flow occurred in systems exhibiting particle agglomeration. Plastic flow appears to be always :onnected with thixotropy in the dispersions investigated, although often the Lime factor involved is too short to be measured rheologically but may be determined by means of the dielectric method. I n view of the similarity of dispersions and solutions of high-molecular,veight substances, the investigation was extended to the latter systems. The naterials investigated were polystyrenes and polyisobutylenes of different nolecular sizes, dissolved in hydrocarbon solvents. They were chosen as eximples of polymers in which random molecular configurations predominate. 11. E X P E R I M E i i T i L
A . Apparatus and rnethod The capacity bridge used to measure the capacity of the solutions was subjtantially the same as that previously described (9). As a cell, however, the :up and bob assembly of a high-shear variable-speed precision rotational vis:ometer was used, basically as described by Buchdahl et al. (2), but redesigned ,o have the bob and cup of the cell electrically insulated from each other.
The iccuracy of the instrument was materially improved by mounting the bob unit, 3y means of brass sleeves, on the cup-retaining cylinder. In addition, a closed init is formed, eliminating solvent evaporation. At the same time the rheoogical characteristics of the solutions were examined by means of torque measirements a t varying rates of shear, while the same cell was also used for conh c t ivity measurements. The instruments allowed capacity measurements with an accuracy of =t 1 per cent. Iiheograms could be obtained a t varying rates of shear up to G5O 597
598
.\
s u li 1 1.:s v 0 1;1'
reciprbcal seconds, for niatt>i,ialsof ;i \iscosity up t o poises, \vith a11 over-all accuracy of =t0.5 per cent in slicuring stresses mid k 1.2 per cent in torque retidingw. For ni:itci,ialb of'ii \iwosity of I w than I poise. hon.evr:r, the :tccuracy is substantially iwiucecl. Tlic tempcraturr \\.as kept constaIit a t :30.OYi. during: the experiment by means of :in e l e c t i ~ i ~ * corit a l l ~idlcti ~ therniostat. Capwit!. 1 ~ i ~ ' ~ ~ ~ ~ i i ' ~\vc~ixl ' i ~ i e iinitially itw made :it different irrqiiencieh. It appeared, lio\vevc~i,,tliat a t .iOOO cycles the maximum L-alues of the dielectric constants \\.ere obtained, outside of the dielectric dispersion range. Conductivity nieasurernc~ntsslio\ved that the systems investigated have a loiv conductivit'y, of the order of 10-" reciprocal ohm. The conductivity is not aff'ected by the application of shearing stressrs. 1he high-moleciilar-\\.ei~~ht substances in\,estigated ivere all noli-polar hydrocarbons. Thus, no complications due to a twiation in the state of orientation of polar molecules in alternitt ing electric fields of 1-arying frequencies could occur. r ,
B. Datu The materials investigated \\-ere polystyrenes of an average molecular \\-eight of 9,900, 31,000, and 73,000, u-hile polyisobutylenes of average molecular weights of 12,530, 37,2W2 77,620, 120,200, and 199,500 were studied.' I n addition, small yuant'ities of polystyrenes of higher molecular weight were obtained, of average molecular \\.eight's 1,100,000 and 500,000, but not enough was available t o complet'e all tests.? These materials, n-hile not strictly monodisperse, \vere believed to have fairly uniform characteristics. Their molecular weights \rere calciilated from the intrinsic viscosities. The solvent used \vas generally toluene, for \\-hich i\ chemically pure material was used; other aromatic hydrocarbons \veixe occasionally used but, the results being entirely equivalent, only the data for t,oluene have been reported. ,
1 . llielectric data
Figure 1 sho\vs tlie dielect,ric constant--conceritration (by volume) relationship for solutions of polystyrenes in toluene at rest, as well as \\-hen subjected to shearing stresses. It may be seen that initially there is n o increase of the dielectric constant \\.it11 increasing concentration, but for each particle size there appears t'o Le :I characteristic. concrntrntion \\-hich may be called tlie critical concentration, above \vhich a very marked increase of t,he dielectric constant is observed. The applicittion of s11e:iring stresses, hoivever, newly completely eliminates this inc i ~ a s e . The minimum shearing stre5.i necessary t u start tlie change in dielectric constant was found, for solutions of ii conwnt~rationjust above t,he critical, to be 1 The polystyrerics re uht:iiried froin the Mo~isaiituChernicd C ~ I I I ~ ~while I I ~ ,the polyisobutylenes were made available t o us by the Standard Oil CompaIiy of S e w ,Jersey, to both of rvhich we \\.ish t o express our appreciatiou. We wish t ( J rhrirrk t h e Polytechnic Institute of Brooklyii for these salnp~es.
MOL t;CVL.\R
IT HIGH-POLYMER bOLY'PlOl*S
IXTE.RA('TIOS
599
1 . T i X IO3 clyneh pel q i i w e wntinieter, \\-hile at stresses of 2.9 X lo3 dynes per square centimeter thc decrease is completed. The same values \\-ere found n-ith all sohitions of a c~)ncentrationjust above the critical concenti*ation, rntirely inrlepcntlent of thc niolerulwr \\ eight of the diq*olved polymer.
2.30
J
1
0.10 xi
I
t
0.20
0. LO
0.30
0.50
0.60
FIG 1 D~elrc~tricconstant-coric~ritratioii rrlatioiiship f o r solutions of p o l ~ s t y r c i i e s toluciic Intic,\ I t , .it rrst iiitlr\ 'hrdi. +s
~
P I I L l > T I R &\ E .
0
c A
-
-
__
\IOLECK L I R !\LIGHT
-
76,500 31,000 9 , so0
Figiire 2 s h o i ~ sthe dielectric constant-concentration (by 1-oliinie) relar ion,hip for pol.isobut'vlenes in toluene. Substantially the smic type of relation#hip is ohserved as \\-itli polystyrenes. Belon- the critical cmtcentration t h e lielectrica constant does not differ from the soli-ent niliir3 h i 1 :i s h a r p 1Lr is )hsei.~.rd:it higher concentrat ions. Upon discontinilation of the shwring sti'wseh, the dielecti-ic! constants i,cg:iin heir original, high values? h i t only after ii short period of tirnr c h i ~ r n c ~ r ~iri iofs ~ ach moleciilar size. Ta1)Ics I and 2 sholv t h e appiusimated elas as at ion timcs, the> pi'riotls of time ieressary t o 1diic.e the 1os.s in diclertric ronstwnt t o 37 per ( w i t ( 1 c i of its valiie.
GOO
ANDRIES VOET
DIELECTRIC CONSTANT
2.55
REST 2.50
2.L5
2,LO
2.35 SHEAR
2.3
,
0.10
CONCENTRATION BY VOLUME #
0.20
0.40
0.30
0.60
0.50
FIG.2. Dielectric constant-concentration relationship for polyisobutylenes in toluene. Index R, a t rest; index S, shear.
1 0
A
____---
I__.__
POLYISOBUTYLENE
MOLECULAR WEIGHT
A B
199,500 120,200 77,620 37,260 12,530
V
C D
0
E
0
TABLE 1 Polystyrenes ~ _ _ _ _ _ _ - -- RELAXATION TI=
MOLKCUWB WEIGHT
-
-.
__-
-
seconds
9,800 31,000 76,000
4 5 10
To allow a comparison, the relationship between the square of the refractive index nn, measured at 30.0"C. with the aid of an Abbe type refractometer, and
601
MOLECULAR INTERACTION I N HIGH-POLYMER SOLUTIONS
,he concentration by volume is plotted in figure 3. Linear relationships are Ibtained, but here the characteristics of the materials of different molecular veights are identical. TABLE 2 Polyisobulylenes MOLECULAR WEIGHT
I
RELAXATION TIME
I
seconds
~
12,530 37,260 77,620 120,220 199,500
2.20
-
2.10
-
4 5
7
9 10
CONCEHPRATION BT VOLUME
I
I
0.10
I
0.20
#
0.30
I
I
0.40
0.50
FIG.3. Plot of square of refractive index against concentration. lolyisobutylenes.
I
0.60
I
0.70
I, polystyrenes; 11,
2. Rheological data Rheograms have been established for all solutions investigated for rates of hear varying from 1 to 650 reciprocal seconds. It uas found that for bath
602
AXDRIES VOET
polystyrenes and polyiaohutylenes at concentrations belon- the critical concentration Kewtonian flow is exhibited, but a plastic flow pattern is observed a t higher concentrations.
D
E
1
L.0
3.5
3-0
2.5
2.0
1
1.5
I
I
I
/
I
1.0
t
I 0.5
0
I I
I
I
VC
VC
VC I
I
0.10
A
0
I
I
0.50
I
0.60
0.70
li
1, 100,000 ~~00,000
(
76,000
D E
31,000 9,800
i
0
c
0.hO
0.30
0.20
CS'CENTRATION BY V O L W
,
Plotting t h e logarit him of the 13ingham yieltl \.;iliies, determined from the rheograms. against thc. concentration (by volume). :1 linear idationship is ob. tained. which ends abruptly, hovever, at the critical concentration. In figures 4 and 5 these relationships are shown for. both polystyrenes and pol~risobutylenes of diff'erent molecular weights.
It is thus obvious that the critical concentration is not only dielectrically but rheologically a characteristic point, indicating a basic change in the structure If the liquid. 2150
D 4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5 CONCENTRATION BY VOLUME
0
0.05
0.10
0.15
0.20
0.25
0.30
FIG.5 . Plot of logarithm of Bingharn yield value (d)ries per square centnnrtei) d t $O.O"C. against concentration b l volume. T', = critical concentration. _ _ -~ ~
~
~~
~~
POL\IWBI
r1t.n~
XOLECUL-IK WEIGHT
-
0
-%
199,500
n
B C D
120,200 77,620
0
V
37,260
111. D I S C U S S l O S
Frum the data given it appears that the dielectrical and rheological charac,eristics of the solutions of the substances of higher molecular weight investiCated is quite analogous t o the characteristics of dispersions of solids in liquids. ~n both instances a critical concentration appears t o exist, above which a sud-
604
ANDRIES VOET
den rise in dielectric constant is observed. This increase, however, is substantially eliminated in both systems by the application of shearing stresses. There is no doubt that in either case this phenomenon must be caused by particle interaction leading to agglomeration. A relationship derived by Bruggeman (1) for the dielectric constant e of a dispersion of independently moving spherical particles a t a concentration by volume V , is reduced for particles of a comparatively large dielectric constant to E
=
€,(I
+3 V)
(1)
where E, is the dielectric constant of the medium. The quantitative validity of this equation has been verified experimentally (9). For non-spherical particles moving independently, it higher dielectric constant is observed. It was found that the relationship =
Em(l
+ 3fl')
(2) is valid, in which f is a form factor characteristic of the form of the dispersed particles. The more deviation there is from the spherical form, the larger the experimentally determined form factor. For particles not moving independently, but forming aggregates, the form factor is changed, since the new kinetic unit, the agglomerate, has a form different from the primary particle. A factor a, has heen introduced, indicating the state of agglomeration. Thus, for the dielectric constant E , of the dispersion of a concentration V , the folloTving relation holds: E,. = €,[I 3U"fi';I (3) The higher the value of a,, the more the form of the agglomerates differs from the spherical shape and the higher, in general, the degree of agglomeration. Upon application of shearing stresses, hair-ever, the aggregates are broken up and the factor a, generally reduces to a value not much larger than unity. The time factors involved in breaking up and rebuilding the agglomerates were estimated and found to vary from a fraction of a second to many minutes. In addition, Sewtonian flow was found to exist exclusively in dispersions in which agglomeration of particles was absent, while plastic flow was exhibited when agglomeration occurred. If the dielectric constant of the dispersed phase is of the same order of magnitude as the dielectric constant of the dispersing medium, for independently moving particles the following equation was found to be satisfied in first approximation (10) : E = &[I 3 ( J - li)V] (4) wherein k is a factor dependent upon the dielectric constants of both phases. For a particle of high dielectric constant lc = 0, while for equal values of the dielectric constants of both phases IC = 1. Again, for particles forming agglomerates this effect modifies the form factor by an agglomeration factor a,, and the following relationship is valid: t
+
+
E,
=
E,
[I
+ 3(a,f - k ) V ]
(5)
MOLECULAR IXTERACTION I N HIGH-POLYMER SOLUTIONS
605
These equations may now be applied to the solutions of polystyrenes and polyisobutylenes in hydrocarbon solvents. ’I’he polymers considered are all of the “randomly coiling” type, and their average contribution to the dielectric constant will not differ from the contribution of a spherically shaped particle. Thus, for all systems investigated, the fmm factor will not differ much from unity. I n addition, while the dielectric constant of solid polystyrene is somewhat higher than the dielectric constant of toluene, in solution the molecular structures of the substances are quite similar, and very little, if any, difference in dielectric constant is to be expected. The same is true for polyisobutylenes, where differences are even less. Consequently, the factor 1; of equations 4 and 5 will not differ substantially from unity. As a result, for independently moving molecules, equation 4 reduces to: e =
em
a*
AT CONCESTRATIONS
MOLECULAR WEIGHT
9,800 31,000
78,500
,
0.10
0.20
0.30
0.40
0.50
0.60
1.00 1.00
1 .oo 1.00 1.12
1 .oo 1 .oo 1.19
1.01 1.0s
1.06 1.13
1.10
1.00
I
irrespective of the concentration of the polymer. Since figures 2 and 3 show exactly this behavior for concentrations lower than the critical, it is obvious that a t these concentrations the polymer molecules move independently in the solution. For molecules which do not move independently, but which form agglomerates, the form factor is not equal to unity, but has to be multiplied hy the agglomeration factor a,. While it is strictly true that by complete equality of the dielectric constant of solvent and dissolved material no increase of the dielectric constant of the solution is to be expected, regardless of the shape of the particles, it is obvious that such a complete equality does not exist. Even the presence of a thin solvent film with a different dielectric constant, such as a “solvation” layer, will change the direction of the electrical lines of force a t the solvent-particle interface and result in an increased dielectric constant for non-spherical particles. I n accordance with equation 5 the following relationship holds: Eu
= E,[1
+ 3 (a,- l ) V ]
(7)
marking a rise in dielectric constant a t the moment of molecular agglomerations, as a result of the formation of non-spherical compleses. The values of uu for polymer solutions of different molecular weights in varying concentrations are given in table 3 for polystyrenes, and in table 4 for
606
AXDRIES VOET
polyis~butylenes.~From the data, it is obvious that the changes in dielectric constant are caused by relatively small agglomerations of molecules, and no general aggregation of large numbers of molecules is found in the solution. It, appears that the higher the molecular weight, the more pronounced the tendency to form aggregates a t a given concentration, and the lower the critical concentration above which agglomeration occurs. I n addition, it is evident that plastic flow always coincides with agglomeration, while in general, in the systems investigated, solutions in which the particles move independently exhibit Newtonian flow. Consequently, there is experimental evidence to shorn that in these systems plastic flow is not a result of molecular orientation or deformation, but is caused solely by agglomeration of large molecules. There are indications that this conclusion has a much more general validity. I n general, a plastic flow pattern, connected with dielectric changes a t different shearing stresses, points to particle agglomeration or orientation. It was found that orientation is accompanied by a characteristic dielectric constant-concenTABLE 4 Polyisobut yleries WEIGHT
_____
12,530 36,260 77,620 120,200
__-
0 01
1.00 100 100 1 00
___ _
--__ -
0 10
0 15
020
100 100 1 14 1 27
100 105 1 22
1.00 1.07
0 05 I _ - -
100 100 1.00 1 02
,
.
I
-_-_)
.
~
,
-
1 I 1
030
1.00 1 10
050
__ 100
0 60
_ -
1.03
I . .
~
~
..
tration relationship (9), by a relaxation time dependent upon the rotary diffusion constant, and by streaming birefringence, allowing differentiation between orientation and agglomeration of particles or molecules. Thus, t>henon-Xewtonian behavior of mineral oils at higher shearing stresses (11) is clearly caused hy the destruction and re-formation of molecular aggregates. It may be observed from the diagrams that the dielectric constant of the solutions at concentrations above the critical concentration subjected to shear does not fully revert back t o the solvent value. While it is possible that the agglomerates are not fully separated, it seems more likely that the difference is due to a change in the “average” shape of the “randomly coiled” molecules, subjected to high stress, forming particles elongated in the direction of the shearing stresses. The presence of such molecules, which are oriented by the shearing stresses, becomes apparent from birefringence measurements at higher shearing stresses. Owing to the time element involved in rebuilding once destroyed molecular aggregates, all plastic systems investigated were found to be thixotropic, ala It must be remarked t h a t equations l to 5 are approximations and only strictly valid in lower concentrations, h u t have i n some instances been used t o calculatc n a t higher concentrations.
MOLECUL.\R
ISTERACTIO&- IK HIGH-POLYMER SOLUTIOSS
607
tliough a t concentrations near the critical point the time element is generally too small to be detected rheologically (see tables 1 and 2). The concept of the coiled, spherically shaped polymer molecule, moving freely in the solution, was found to lead to an understanding of Staudinger's rule, according to which the intrinsic viscosity of the solutions should be proportional to the molecular weight of the polymer (3, 4,5 , 6). This concept makes it equally possible to understand t8he exist'ence of the critical concentration and its dependence on the molecular size of t'he polymer. -Agglomerat,ion, result'ing from molecular attraction, will occur only at relatively higher concentrations, where the average distance between the molecules is small enough to allow the attractive forces to overcome the tendency to prevent agglomeration resulting from the molecular t'liermal energy. The nat,ure of the attractive forces, forniulated by van der Waals, was first t,reated from a fundamental quantum-mechanical standpoint by London (7). From a recent generalization of the London theory (8) it appears that for the attractive London-van der Waals forces acting bet\veen spherical particles, the size of the particle,. is of great importance. For smaller particles, with average diameters of cm. or less, the attractive forces are comparatively small and do not reach beyond cm. Wibh increased particle diameter, however, the London-van der Waals attraction markedly increases and reaches much farther in the solut'ions. Consequently, for the larger, higher-molecular-weight particles the attractive forces are stronger and act at' greater distances than for the smaller, lo\vermolecular-weight part,icles. Thus, molecular agglomeration will occur in polymer solutions at the larger average molecular distance and therefore at the lon-er concentrations the larger the molecule, resulting in a lower critical concentration the higher the molecular \\eight. These vien.s are in complete accord with the observed fact's. It appears that for solutions of polymeric hydrocai.bon particles of an average molecular weight of the order of 10,000, agglomeration is exhibited only in extremely high concentrations (40 per cent or more by volume). Still smaller molecules of the hydrocarbon type of polymer will require still shorter particle distances t o show agglomeration, which cannot be realized physically in general. We must therefore assume that if agglomeration occurs in polymer solutions of molecular weight's substantially loii-er than 10,000, other forces than the Londonvan der Waals forces are responsible for the formation of molecular aggregates. The characteristic rise in dielectric constant of the polymer solution of a concentration above the critical concentration might offer the possibility for a novel method for the det'ermination of the molecular weights of high polymers. The index of refraction, being a measure of the electronic polarization, will be sensit,ive neither t o agglomeration nor to molecular weight, the only difference being in the end groups. The latter, however, are such u small fraction of t'he total in the systems investigated that they will not c,hange the general picture and the relat'ionship given in figure 3 is in cornpletp :~cw)rdv-itli the v i e w expressed ahove.
608
ANDRIES VOET
Finallg, t,he time factor observed in destroying and rebidding moleciilar agglomerates must be considered as resulting from a particle diffusion process, charact,erixcd by a molecul:tr motion toivards union, caused by the attractive forces. LVhile the London-van der Waals forces act.ing between molecules are stronger for higher molecular weights, the effect of the greater average molecular distances a t lower critical concentration and the markedly slower rate of diffusion of the larger moleciiles overshadow their stronger mutual attraction, resulting in an increased relaxation time for the polymers of higher molecular weight. SUJIhIARY
The dielectric constants of solutions of lower concentrations of polystyrenes and polyisobutylenes in hydrccarbon solvents appear to be constant a t rest as well as n hen subjected to shear, and equal to the solvent value, for concentrations up to a critical concentration. For higher concentrations the dielectric constants rapidly increase with increasing concentration in the solutions at rest, but in solutions subjected to shearing stresses the dielectric constants decrease to a much lower value, approaching the dielectric constant of the solvent. It was found that the higher the molecular weight, the lower the critical concentration. In addition, rheograms showed that the linear relationship valid a t higher Concentrations between the logarithm of the Bingham yield value and the concentration by volume ends abruptly a t the critical concentration. A Kewtonian flow is found below the critical concentration. Since at higher concentrations the flow is always plastic, the critical concentration may also be determined rheologically. From the experimental facts it was derived that in the solutions investigated the molecules move independently a t concentrations below the critical, but agglomeration occurs a t higher concentrations, resulting in an increased dielectric constant and a plastic type of flow. The dielectric changes resulting from the molecular agglomeration have been explained on the basis of extended theoretical views of Bruggeman, combined with the London-van der Waals cmcept of molecular attraction. The author wishes to express his thanks t o Louis R. Suriani for his capable assistance in carrying out the experiments and to the J. M. Huber Corporation icr their \villir.gness to release this part of the investigations. REFERESCES (1) (2) (3) (4) (5) (6) (7)
DRUGGEMAN, D. A . G.: Ann. Physik 29, 636 (1935). BUCHDAHI., R., el a[.: Rev. sci. Instruments 18, 163 (1947). D E B Y EP.: , J . Chem. Phys. 14, 636 (19.26). H E R M A N SJ., J.: l’hysictt 10, 777 (1943). K I R K W O OJ. D ,C . : J . Chem. Phys. 14, 153 (1946). KRAMERS, 11, A , : J . Chem. Phys. 14, 415 (1946). LONUON, F.: Z. Physik 63, 245 (1930).
FORMATION OF LIQUID CRYSTALS IN SOLUTION
609
(8) VERWEY,E. ,J. W., A Y D OVERBEEK,J. TH.G . : T h e o r y of the Slnbilitv of T,?jophobic Cc I l o d s . ElscLier Publishing Company, New York and Amsterdam (1948). (9) \’OET, A , : J . P h w . Colloid Chem. 61, 1037 (1947). (10) V O E T , A , , A N I ) S U R I A X1,. I . R.:7’0 be published. (11) W ’ E L r b i m x , R. S . I n d . Eng. Chern., Anal. E L 16, 424 (1913).
T H E FIRST APPROXIMATE COKDITIONS FOR THE FORMATION OF
LIQUID CRYSTALS IN SOLUTION STASLEY H. JURY AND ROBERT C. ERR’ST
Department of Chemical Engineering, University of Louisville, Louisville, Kentucky Received M a y 11, 1948
The peculiar optical properties and apparent phase transformation in aqueous solutions of the two dyes Amaranth and Naphthol Yellow S suggest that these solutions are liquid crystalline. Xoreover, the concentration range of phase transformation appears to be specific for each substance. T’5;hile a search of the literature did not confirm these observations, it did materially adJ to the belief that liquid crystals in solution might be the counterpart of coacervates in colloidal solution. Furthermore, it revealed ten different substances for which the conditions for liquid crystal formation in solution might be correlated, to a first degree of approximation, by application of theory already applied to coacervation. It is therefore the purpose of this paper first to present the results of experimentation nith the two dyes, and second to attempt to correlate these results with those reported in the literature using the medium of correlation just mentioned. I n the interest of clarity, a brief historical review is appropriate. Hitherto the distinction between liquid crystallinity and coacervation has been one of principle rather than degree; consequently the study of each has been quite independent of the other. These studies may be grouped as follows: ( a ) coacervation of colloids, ( b ) liquid crystalline melts, and (c) liquid crystalline solutions. Bungenberg de Jong and Kruyt (3) discovered a sort of “unmixing” in certain solutions of colloids and later in supersaturated solutions of inorganic salts. In 1930 they proposed the name “coacervation” for the process of separation acd “coacervate” for the denser solution which separated from the original. Two types of coacervates were recognized. The simple coacervate, which came from colloidal particles of like charge, was distinguished from the complex coacervate arising from bipolar lyophilic colloidal solution. A hydration theory was proposed to explain complex coacervation phenomena. Mme. Dobry ( 5 ) demonstrated that cellulose acetate and chloroform can form a coacervated system, the stability being due to nearly identical densities of coacervated and liquid phases. With cellulose acetate, ethyl alcohol, and chloroform the compounds of high molecular weight are in the coacervated phase
