8. Micelle Formation of Non-ionic Surfactants.
Properties
of Aqueous
Rempei
Solution
of Polyoxyethylene
GOTO, Takeo SUGANO and Naokazu
(I)
mono-alkyl
Ether
KOIZUMI*
(Goto Laboratory)
Received July 26, 1953
INTRODUCTION
Ionic surfactants
association
in their aqueous solution are characterized
by a high degree
into colloidal micelles above a certain concentration,
micelle concentration
attributable
(c.m.c.)'>.
Since association
to the contradictory
in solution
solubility relation
Gonick and McBain'> expected
exhibit
similar
properties
critical
of those surfactants
is
exhibited by the polar and nonpolar
groups within the molecules,
colligative
the so-called
of
non-ionic
surfactants
to
to those of the ionic type, and they showed for
the first time that
non-ionic
laurate,
"X" and Triton X-100) form colloidal micelles principally by means
Detergent
surfactants
of ester
type
(nonaethylene
glycol
mono-
of cryoscopic evidence.
In the present
factants
in ether
report, various properties
of the aqueous solutions of non-ionic sur-
type are discribed and discussed with respct to their micelle formation.
EXPERIMENTAL
Materials
: Surfactants
used in the present
work are principally
polyoxyethylene
glycol alkyl ethers, HO(C:H40)„ (CH.)mH, and those used in the previous experiment°>.
In the notation of the kinds of samples, lauryl, oleyl and cetyl are abbreviated to L,
O and C respectivery,
ethylene.
For the standard
ed to PL-6)
carried
and figures represent
the degree of polymerization
sample, pure hexaoxyethylene
was prepared in the authors' laboratory.
of polyoxy-
glycol lauryl ether (abbreviatMost
of the experiments
were
out at room temperature.
RESULTS AND DISCUSSION
1.
Density
Densities of the aqueous solutions were measured
meter
remains
(ca. 30 cc) at 25°C. As shown
almost constant
increases gradually
are plotted
the following
*n
in Fig.
until the concentration
with the concentration.
against
relation
concentration.
with the
1, the density
comes
Ostwald's
type picno-
of the L-6 solution
to a certain
value and then
In Fig. 1, also the partial specific volumes
The partial
:
• dA—
( 305 )
specific volume
V were calculated
by
—
Rempei GOTo, Takeo SUGANOand Naokazu KOIZUMI
[ 6)a~
0.918.
Spacificv•
~cd
{v
Y
I
wDensitoCn•
10 S
p
4N
(m).Axrd; y
0997
0I23a ,2 3 f567
4 8 9100.9s~•
5P
t
Concentrationof Surfactant(%)
Fig. 1. Variationof densityand partial specificvolumewith concentrationin aqueous
surfactantsolution.
v_
1 (w
s—h}
p
h \ p
where h is the weight of the dry surfactant
solution,
in the picnometer,
w the weight of the solvent and p the density
with the specific volume of L-6 (1.02 cc./g.
s the
weight of the
of the solvent.
Comparing
at 25°C) in bulk state, the partial specific
volume of the solute in the aqueous solution is considerably small at low concentrations
and comes nearer to the value in bulk with
solutions
of other surfactants
increase
of the concentration.
Aqueous
gave similar results to L-6.
Such change in density against the concentration
the solution vary their degree
of dispersion
with
suggests
that the surfactants
their concentration.
It seems
in
that
phase separation proceeds in the solution gradually as the concentration
increases.
And the rate of change of the partial specific volume is relatively large at low concentration
and becomes smaller above a certain concentration.
also Vetter')
found similar
facts
in the aqueous
defined the c.m.c. as the concentration
increase.
In comparison
corresponds
starts
and
to
specific
volume
of the non-ionic
Viscosity
solution
were measured
with
Ostwald's
type
As shown in Fig. 2., the increase of r,. becomes noticeable above
the concentration
of ca. 10-3 mole/1.
the concentration
C in Fig. 3.
The reduced viscosity 728n/c are plotted
The plots show generally
decrease with increase of the concentration,
certain concentrations.
surfactants
volume
to the micelle fromation.
The relative viscosities r,. of the
at 31°C.
of ionic
Bury4), and
with the results obtained with respect to the ionic surfactants,
2.
viscometer
solutions
at which the partial specific
it may be deduced that the increase in the partial
surfactants
Davies and
and some
that the reduced
of them increase
Similar behavior has been observed with
several
against
viscosities
again above
colloidal-
or
poly-electrolytes.
Kern6> and Seiyama'> ascribed the decrease of reduced viscosity
to the characteristics of the electrolytes (ionic factor) and its increase to that of mac( 306 )
•
Micelle Formation of Non-ionic Surfactants.(I)
romolecules
(macromolecular
the rsP/^C
of pottasium
factor).
Recently,
chloride solution
5
1.4-CIO
N
.o- 08
a1.3L6
Nakamura
decreases
and
linearly
Kubo8) showed that
with 1/e in accordance
C.;• O8
a
Aa53•
12-p
•
1.1 .-RC182
"dI.00I2y
IxConcentration
ofSurfactants
(%)b
Fig.
2. Relation between
~t'
relativel!.C18
viscosity and concentration of--*--<~`
surfactants.0
1v
C 10
1
2
3
4
5
Concentration of Surfactants (%)
Fig. 3. Plots of reduced viscosity against
concentration of surfactants.
with the theory of electrolytes of Falkenhagen.However,
viscosity
has been observed not only with
substance.
ities
such decrease of the reduced
ionic substances
but also with non-ionic
Sata and Tyuzyo°) measured the diffusion constants
of ionic and
reduced
non-ionic surfactants,
and the reduced viscos-
and pointed out that the minimum
viscosity against the concentration
corresponds
6
point
of
to the c.m.c. of the solution.
With respect to the reduced viscosity, similar facts has been observed also in organic
solutions
of surfactants
chloride by Takeda
volume
mentioned
concentration
a certain
the change of partial
micelle
formation
as Fuoss"),
Absorption
Spectrum
and
Rosen,
critical
The aqueous
concentration
As to
there are
of Dye Solution
solution
solution of the dye changes
of the surfactant,
tone of color with the alcoholic solution
with the
Kamath and Eirich1) have
chloride is tinged with purple in its aqueous
solution.
specific
in the solution.
behavior of viscosity in the aqueous solution of surfactants,
3.
in its alcoholic
with
above, the decrease of the reduced viscosity of surfactants
to be discussed further,
Pinacyanol
authors") and in organic solutions of polyvinyl
Comparing
may be closely related with
the characteristic
problems
shown.
by the present
and Tsuruta71>.
where the
of the dye.
solution
and with
blue
its color above
shows
similar
This color change has been ex-
plained in terms of solubilization of the dye into the micelles of the surfactants.
Now, keeping pinacyanol chloride at a constant concentration (ca. I X 10-5 mole/I),
( 307 )
-
Rempei GOTO,Takeo SUGANOand Naokazu KOIZUMi
changes of absorption
surfactants
were
the absorption
spectrum
observed
spectrum
two characteristic
with
of the dye solution
Beckman's
against
the concentration
spectrophotometer.
It was found that
of the dye solution containing the non-ionic surfactant
absorption
bands, a (600mji) and a
Fig. 4 and Fig. 5, while in the
case of anionic
(550mp2) bands
surfactant,
of the
sodium
showed
as shown
lauryl
in
sulfate
(S.L.S.), r band appeared at low concentration range, and above a certain concentration, a and .43bands appeared instead of r bands. Change of instensities of a, (3 and
0.7
e 1.9~x1U3
~pP~l
06 -
/~05 4)-7.92404
id
f
.
~p~f336/104
0.3
-
0.2
-.,
^
INWATER
0.1 -
450
Fig.
500550600
Wave Length
'
650
(my)
4. Absorption spectrum of aqueous solution of pinacyanol
of concentration of non-ionic surfactant
(PL6).
0.8.PL6
chloride
as a function
a
,,
0.7-
00
•0•.6
0.5
.5-4a.A
•
O 0.•3~;.
A
0.2
0.1
00
Fig.
1
2
3
4
5
6
7
8
9
Concentration of Surfactant (10-3-mole. /1. )
5. Relation between concentration of non-ionic surfactant (PL6)
of two characteristic
bands.
( 308 )
10
and optical
density
Miceile Formation
r bands
in the case of anionic
of Non-ionic
surfactant,
Surfactants.
are plotted
2.0 (sL .s.)
against
(I)
the concentration
of the.
d
•
••
N
•
T
4
O
•
•
•
41,A
• •
•
4
••
67
8
9
IO
Concentration of Surfactant (10-3-mole. /1. )
Fig. 6. Relation between concentration of anionic surfactant (S.L.S. ) and optical
density of three characteristic bands.
surfactant
tant,
in Fig. 6.
It seems that at low concentration
a and (3 bands are suppressed
by r band.
vens14>, the medial value of the concentration
the so-called
c.m.c.
Comparing
of the non-ionic surfactants
magintude
tants showed similar results
ionic surfactant,
falls at a concentration
of magnitude
with the non-ionic surfactants
of the anionic
surfacof Kle-
at which a band rises, corresponds
with the results of the
PL-6,
is in the same order
Bain obtained
rang
According to the experiment
with
the
c.m.c.
of about 10-4 mole/1
whose
the results
in ester
with
type.
of
Gonick and Mc-
Other non-ionic
surfac-
with PL-6.
r band at low concentration of the anionic surfactant may be ascribed to the
ionic interaction between the dye and the surfactant.
Concerning the change of a
and
(3 band above the c.m.c.,
and non-ionic surfactants.
there seems to be no essential
difference between
From this fact, it is suggested that
itself is not affected essentially
by the ionic character
pointed out, but rather it may be dependent
4.
Solubilization
of the surfactants
upon the surfactant
of Sudan
III
in alcohol. Alco-
of this dye is tinged with red orange and its characteristic
is shown at 490 mg.
Now, change of intensity
of the characteristic
to Sudan III was observed with the aqueous solution of non-ionic
at various concentrations.
surfactant,
as Philipoff15>
molecules.
The dyestuff Sudan III is almost insoluble in water but soluble
holic solution
The results are shown
sodium lauryl sulfate (S.L.S.),
in Fig.
solubilization
ionic
the micelle formation
absorption
absorption
due
or ionic surfactants
7. In the case of anionic
of Sudan III was
recognized
above ca. 6 x10-3 mole/1. which is somewhat lower than the c.m.c. obtained by another
method. For the non-ionic surfactant,
PL-6, it was found that solubilization
( 309 )
•
occurs at
Rempei
GOTO, Takeo
SUGANO and Naokazu
KOIZUMI
2.0
(f)
Rs 1.0 -
o.o S
U
.L.S.---t. •
• •
•
••
0 i 2 3 4 5 6 7 8 8
Concentration of Surfactants (mole. /4. x 103)
Fig. 7, Comparison of solubilization curves for non-ionic and anionic surfactant.
concentration
range far lower than in the case of the ionic surfactant.
with other experimental
micelle formation
not determined
results shown above, such solubilization
of the non-ionic surfactant
In comparison
may be ascribed
in the solution, though the c.m.c.
to
was
accurately.
SUMMARY
Concerning
the aqueous solutions of non-ionic
surfactants,
it was °observed
that
partial specific volume, reduced viscosity and solubilization of dyes against their
concentrations showed relatively large rate of change at low concentration range (ca.
10-1 mole/1.) and such behaviours were ascribed to the micelle formation in the
solution in comparison
not detemined
necessarily
dependent
and non-polar
formation
with the case of ionic surfactants,
accurately.
And it was suggested
upon the ionic character
constitution
of the surfactant
that
though
the micelle
of the surfactants
their c.m.c.
were
formation
is not
but upon
the polar
molecules by the reason that the micelle
can be recognized not only in the aqueous solution of non-ionic surfactants
but also in the organic solution of surfactants
as reported
by Askin and Single terry")
or others").
ACKNOWLEDGEMENTS
The authors are indebted to Mr. T. Kariyone of Kao Soap Co. for the sufactant
samples and to Mr. T. Yano of Mitsubishi
Paper Mills Ltd. for the dyes used herein.
Their thanks are also due to Mr. N. Hayama
who carried out the viscosity and density
measurements.
REFERENCES
(1) J.W.McBain,
"Colloid Sceince" D.C.Heath
( 310 )
& Co. (1950).
Micelle Formation
(2)
(3)
(4)
(5)
(6)
(7)
(8)
(9)
(10)
(11)
(12)
(13)
(14)
(15)
(16)
of Oon-ionic
Surfactants.
(I)
E.Gonick and J.W.McBain,
J. Am. Chem. Soc., 69,334 (1947).
R.Goto, N.Koizumi, N.Elayama and T.Sugano,
This Bulletin ,31,285 (1953).
D.G.Davies and C.R.Bury,
J. Chem. Soc., 2263 (1930).
R. J. Vetter, J. Phys. & Coll. Chem., 15,262 (1947).
W. Kern, Z. Phys. Chem., A 181 283 (1938).
T.Seiyama. J. Chem. Soc. Japan, (Ind. Chem. Section)., 25,300 (1949).
S. Nakamura and S. Kubo, J. Chem. Soc. Japan,
(Pure Chem. Section).,
47,392
(1953).
N. Sata and S. Tyuzyo, 5th and 6th Annual Meeting of Chem. Soc. Japan, April
(1952) and April (1953), Bull. Chem. Soc. Japan, 26,177 (1953).
R. Goto, N. Koizumi and T. Sugano, Symposium on Colloid Chemistry, Chem. Soc.
Japan, Nov. (1951).
M. Takeda and E. Turuta, Bull. Chem. Soc. Japan, 25,80 (1952).
R. M. Fuoss, Faraday Soc. Discussions, No. 11 p. 125 (1951).
B.Rosen, P.Kamath and F.Eirich,
ibid., No. 11 p. 135 (1951).
H. B. Klevens, J. Phys & Coll. Chem., 15,1143 ( 1947 ) .
W. Philipoff, Faraday Soc. Discussions. No. 11 p. 96 (1951).
L. Askin and C. R. Singleterry, J. Coll. Sci., 4,537 (1949).
( 311 )