INDUSTRIAL AND ENGINEERING CHEMISTRY
October 1955
2175
b
0 COTTON
I
3 4
IO
8 1.5
16.6 50.0
30
20 ELONGATION
8.3% NO2
SO 27
1
PERCENTAGE OXIDIZED
4%)
Figure 5. Change in moisture regain on oxidation with nitrogen dioxide in carbon tetrachloride
Figure 4. Changes in stress-strain curves of tirecord rayon produced by oxidation under various conditions
LITERATURE CITED
of high accessibility and short times should be chemically most stable and of the highest degree of polymerization after alkaline treatment, Celluloses oxidized in 8.3% nitrogen dioxide in carbon tetrachloride for 100 hours have most of the amorphous material oxidized but are unstable, as the time of reaction is long enough t o produce a considerable amount of side reaction. This oxycellulose is soluble in dilute caustic because of degradation of portions of the amorphous segments of the chains, but it precipitates on addition of either acid or large amounts of base. This solution is probably a suspension of crystallites having highly oxidized fringes whose partially ionized carboxyl groups stabilize the suspension.
(1) Davidson, G. F., J . TestiZeInst., 32, T132 (1941). ( 2 ) Fowler, W. F., Unruh, C. C., McGee, P. A., and Kenyon, W.
(3) (4) (5) (6) (7) (8)
O., J. Am. Chem. Soc., 69, 1636 (1947). Head, F. S., J . Chem. Soc. (London), 1948, p. 1135. Hermans, P. H., “Physics and Chemistry of Cellulose Fibers,’” p. 517, Elsevier, Xew York, 1949. McGee, P. H., Fowler, W. F., Jr., Unruh, C. C . , and Kenyon, W. O . , J.Am. Chem. Soc., 70,2700 (1948). Nevell, T. P., J . TextiZeInst., 42, T91 (1951). Roseveare, W. E., IND. E m . CHEM., 44, 168 (1952). Roseveare, W. E., and Poore, E. L., J . Polymer Sci., 24, 341 (1954).
RECEIVEDfor review January 29, 1955.
ACCEPTED March 31, 1985. Division of Cellulose Chemistry, Symposium on Degradation of Cellulose and Cellulose Derivatives, 127th NIeeting ACS, Cincinnati, Ohio, 1965.
Effect of icellar Size on Physicochemical Properties of Surfactants A. M. MANKOWICH Paint and Chemical Laboratory, Aberdeen Proving Ground, M d .
N A previous paper (6), it was shown that the micellar molecular weights of commercial, 10070 active surfactants differ greatly and that micellar size is a variable in aqueous surfactant solutions. It is important t o know in what way this variable influences physicochemical properties such as micellar solubilization, suspendibility, spreading coefficient, and the boundary tensions. It seems that more fundamental relationships will become apparent if these properties are compared a t fixed micellar sizes. No studies of the subject have been published.
MATERIALS
The sodium dodecyl benzene sulfonate (SDBS) was of the lot previously described ( 6 ) , but a different batch of iso-octyl phenyl nonaethylene glycol ether (IOPNG) was used in this investigation. The difference in micellar size of the two batches of the latter is to be expected in commercial surfactants. T h e builders were technical grade sodium tripolyphosphate and trisodium phosphate monohydrate and reagent grade sodium sulfate, sodium carbonate, sodium chloride, potassium chloride.
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INDUSTRIAL AND ENGINEERING CHEMISTRY 400
I ESTIMATING SURFACTANT PROPERTIES
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Vol. 47, No. 10 1
$ 350 m
; . I (3
may be possible by mathematical relationship based on mice1Ia r size
300
m
4 250
5 II
0 200
z APPARATUS AND MEASUREMENTS
Micellar size was determined by the light-scattering technique using the apparatus described in a former publication (5). Improvements were made in the methods of preparation of test solutions for light-scattering measurements and calculation of micellar molecular weights of built, surfactants.
6 2 150 B
m
: (3
100
50
BUILDER NORMALITY
Purified water (redistilled from alkaFigure 1. Micellar size of built 1%sodium dodecyl benzene sulfonate, 26' C. line permanganate solution) was poured into the Selas filter mantle and forced 0 NUPOa. € 1 2 0 builder 0 NazSOa builder + NaaPsOia builder through the filter of 1.2-micron maximum pore size for 2 hours at a rate of approximately 1 drop per 15 seconds. The mantle was washing with purified water for 2 hours. This cleaning proemptied and filled with surfactant solution, which was forced cedure eliminated the former periodic fouling of the filter (as through the filter for 30 minutes a t a rate of 1 drop per 6 to 10 indicated by temporary inability to obtain turbidity checks). seconds, depending on the solution. The mantle was again emptied and refilled with surfactant solution, and filtrate for The reciprocal specific turbidity ( H c j T ) values reported herein light-scattering measurements was collected in a semioctagonal show small differences between the 0.8 and 1.0% surfactant concell placed in a Fisher Scientific Co. filtrator. After a series of centrations of most of the surfactant-buiIder combinations studtests had been completed with a particular surfactant-builder combination, the Selas filter was cleaned as follows: Purified ied. This indicates t h a t for these surfactant-builder combinawater was forced through the filter for 2 hours, followed by tions, and at the builder concentrations investigated, the slopes reverse flushing with absolute ethyl alcohol for 30 minutes, of the lines of H c / T os. C are small and tend to parallel the C reverse flushing with purified water for 10 minutes, and normal axis. Similar tendencies have been reported by other investigators for built cationic surfactants (1). These investigators noted t h a t direct calculation of micellar size from observed values of reciprocal specific turbidity at higher concentrations Table I. Treatment of H c / T Data on Built Iso-octyl Phenyl Nonaethylene Glycol Ether a t 25-26" C. will not differ materially from the value calculated by the classical extrapolation method. This observation, together with Micellar Molecular Weight the possibility t h a t experimental error could exaggerate the value Builder, Extrapolation Modified % (0.4, 0.8, and 1.0%) method deviation of the intercept a t zero concentration when only two concentraNazSO4 tions are used (method formerly used a t this laboratory), led -4.8 76,800 73,100 0.3 -8.2 84,000 77,100 0.6 to the absorption of a modified direct calculation. The latter, + 7 . 1 98,000 105,000 1.5 in which micellar size is obtained from the reciprocal of the avNaCl 0 . 9 74,000 73,300 0.3 erage H c / T value for 0.8 and 1.0% surfactant, was checked 75,600 +0.5 75,200 0.6 78,800 -3.7 81,800 1.5 against the classical extrapolation method using the least squares line for three surfactant concentrations (0.4, 0.8, and 1.0%). -~ Table I shows an average deviation of 4.2% between the modiTable 11. Reproducibility of Data on Iso-octyl Phenyl fied and classical methods of treatment of the H c / T data. T h e Nonaethylene Glycol Ether a t 25-26' C. agreement is considered good enough to justify the use of the Concn., modified method described herein. Table I11 gives micellar % sizes of built sodium dodecyl benzene sulfonate solutions recal(C./lOO CC.) Date Gsao Goo a culated by the modified method. 1.0 6 - 29- 5 4 53.5 95.0 6-29-54 53.0 95.0 Suspendibility and micellar solubilization were determined as 7-1-54 54.0 95.0 7-1-54 54.0 95.0 described previously (4),only slight changes being made in 7-2-64 53.5 95.0 test conditions. Both properties were measured in a constant 7-2-54 54.5 95.0 temperature room a t 25-26" C. 0.8 7-6-54 40.0 95.0
a
7-6-54 8-24-54
Gsoo.
Goo.
40.0 40.0
95.0 95.0
Intensity of light scattered a t 90'. Intensity of incident light.
a Incident light intensity with filters 1 2 and 3. Check data of same date obtained with different Selas filter and different cell.
Binney and Smith, Super-Spectra brand, carbon powder, with a particle size of 0.01 micron and p H of 4 t o 5, was used in the tests of suspending power of iso-octyl phenyl nonaethylene glycol ether solutions. Carbon suspendibilities were reported as photometric absorption values instead of in terms of the equivalent concentrations of aqueous Nigrosin Black solutions. Waterinsoluble dye, Orange OT, l-o-tolylazo-2-naphthol,was used in
INDUSTRIAL AND ENGINEERING CHEMISTRY
October 1955
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creased t o substantially the same degree by equivalent concentrations of three PO0 types of builders until a builder concenI tration of ca. 0.13N is reached. This P behavior is not unexpected because of its close relationship t o the generalizae 180 tion t h a t the lowering of the critical 4dW micellar concentration of a n ionic sur1l 160 factant is the same for equivalent concentrations of inorganic salts. Above II 0.13N, effects of builder concentration 0 become specific. The sharp increases 140 z in the slopes of the lines of aggregation number us. builder normality fot trisodium phosphate and sodium sulfate 120 suggests that, above 0.13N concentrat(35 tions, these salts tend to produce a dif4 ferent type of micelle, or t h a t the ag100 gregates are no longer micellar ( 2 ) . The 0 0.08 0.16 0.24 0.32 slight influence of polyphosphate builder BUILDER NORMALITY on micellar size at concentrations above Figure 2. Micellar size of built 1% iso-octyl phenyl nonaethylene glycol 0.13N may be due to a nonproportionate ether, 26" C. increase in sodium ion concentration -C NasPaOio 0 NaCl 0 NaaPOa.Hz0 (gegen-ion effect) resulting from low 0 NazSO4 A KC1 -0- XarCOa ionization of concentrated sodium tripolyphosphate. The aggregation number of the as-received condition for the measurement of micellar solusodium dodecyl benzene sulfonate a t builder concentrations of bilization, a 30-minute interaction period being utilized. A 0.13iV is 68. more fundamental unit of micellar solubilization was developed ISO-OCTYL PHENYL NONAETHYLESE GLYCOLETHER.Table during this investigation. The new unit, molecules of dyestuff IV and Figure 2 reveal t h a t uni-univalent salts in concentrations solubilized per micelle of surfactant, was calculated from data on micellar size and Avogadro's number. not exceeding 0.30N and uni-divalent salt not exceeding 0.12h7 Boundary tensions were determined with a D u Nouy interdecrease the micellar size of unbuilt, 1% iso-octyl phenyl nonafacial tensiometer, using the Harkins and Jordan correction ethylene glycol ether solution. It is believed that this decrease factors ( 8 ) . White mineral oil, USP grade, 125/135 Saybolt in the size of the micellar aggregate may be explained as follows: viscosity at 100' F., was used as a nonpolar reference liquid in the tests of interfacial tension. Spreading coefficients were calAs the unit nonionic molecule may be considered t o be a dipole, culated from the following equation: and only attractive forces exist between dipoles, the micelle is probably lamellar ( a group of oriented dipoles); on addition of = so- s, - so, where the builder salts (potassium chloride, sodium chloride, or sodium W = spreading coefficient So = surface tension of oil S, = surface tension of surfactant solution So, = interfacial tension of oil-surfactant solution Table 111. Built Sodium Dodecyl Benzene Sulfonate at 25-26' C. RESULTS AND DISCUSSION I
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0 01
p
P
2
w
Builder Effects. SODIUMDODECYL BENZENE SULFONATE. Figure 1 shows t h a t the micellar size of anionic SDBS is in-
Builder
Conon.,
%
NaiPOd.HzO 0.6
v
0.9 1.5
D 9.0
2.0
w
3 1.6 \
I
//
5 1
IiazSOp 0.3 0.6 0.9 1.5 2.0 NaaPaOia 0.3
0.6 01 50
I
100
150
I
I
PO0
250
1
300
0.9
I
350
400
NO. Figure 3. Solubilization by built 1%sodium dodecyl benzene sulfonate, 26" C . 0 NasPO4.HnO builder 0 NazS04 builder + NarPiOlo builder AGGREGATION
1.5 2.0
Zero
Surfactant Conon., C, G./Ml. 0.008 0.010
Dissym-
Hc/ T
x
106
0.008 0,010 0.008 0.010 0,008 0.010
5.11 5.41 4.55 4.37 1.97 2.49 1.11 1.21
0.008 0.010 0.008 0.010 0 I008 0.010 0.008 0.010 0.008 0.010
5.99 5.92 5.02 4.95 4.80 4.95 2.62 2.73 1.05 1.13
0.008 0,010 0,008 0.010 0,008 0.010 0,008 0,010 0,008 0.010
0.010
metry, 1.0%
Sur-
factant
Micellar AggregaMol. Wt., tion Cor. NO.
1.09
20,900
1.23
25,900
74
1.20
51,500
148
0.98
86,200
248
60
1.15
18,500
53
1.15
22,100
64
0.93
20,500
59
1.99
73,000
210
1.56
129,000
371
5.94 0.29 5.09 5.45 4.65 4.80 4.19 4.40 3.57 4.03
1.13
17,700
51
1 30
23,200
67
1.17
23,700
68
1.11
25,600
74
1.10
28,900
83
23.84
1.00
1,700
5
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
2178 Table 1V.
Vol. 47, No. 10
B u i l t Iso-octyl P h e n y l N o n a e t h y l e n e Glycol E t h e r Solutions a t 25-26' C. ( S o dissymmetry found)
Builder Concn.,
%
Surfactant Concn., C, G./Ml.
GsoO
GoQ Filters
Surfactant Turbidity, T,Cm.3
x
104
Hc/T X 106
Micellar Mol. Wt. Cor.
Aggregation NO.
NasP0a.H10 0.3 0.6 0.9 1.5
2.0
0,008 0.010 0.008 0.010 0.008 0.010 0.008 0.010 0.008
46.5 57.5 51.0 63.5 55.0 70.0 61.5 75.5 70.0 93.0
1 X 2 X 3
0,008 0,010 0.008 0.010 0.008
42,s 54.5 44.5 58.0 48.0 62.5 61.5 77.5 68.5 86.5
1 X 2 X 3
0.010
18.076 22.438 19.858 24.815 21,444 27.392 24.024 29.573 27.392 37.511
12.90 12.99 11.74 11.74 10.87 10.64 9 70 9.85 8.51 7.77
16.619 21.376 17,394 22.746 18.770 24,518 24.131 30.475 26.907 34.042
13.87 13.48 13.26 12.67 12.28 11.75 9.55 9.46 8.57 8.47
18.578 22.939 19.568 23.139 20.958 23.734 21.154 27.102 22.939 28.887
12.26 12.41 11.64 12.30 10.86 11.99 10.76 10.50 9.93 9.85
1 X 2 X 3
21.124
11.84
1 X 2 X 3
19.113 23,275 18.917 25,260 20.898 26.846 25,060 31.208
12.18 12.61 12.31 11.52 11.14 10.84 9.29 9.33
17.534 20,906 17.930 21,697 18.325 23.282 18,325 23.087 19.715 24.672
13.31 13.96 13.02 13.45 12 74 12: 53 12.74 12.64 11.84 11.83
16.355 20.321 15.760 19,527 16,555 21.312 19.131 24.284
14.17 14.25 14.70 14,83 13.99 13.59 12.11 11.93
1 X 2 X 3 1 X 2 X 3 1 X 2 X 3 1 X 2 X 3
77,200
128
85,200
142
93,000
154
102,000
169
123,000
204
NazSOa 0.3 0.6 0.9 1.5 2.0
0.010
0,008 0.010 0,008 0.010
1 X 2 X 3 1 X 2 X 3 1 X 2 X 3 1 X 2 X 3
73,100
121
77,100
128
83,200
138
105,000
174
117,000
194
NasPsO1o 0.3
0.6 0.9 1.5
2.0
Zero
0.008 0,010 0,008 0.010 0,008 0,010 0.008 0.010 0.008
0.010
48.5 59.5 51.0 60.0 54.5 61.5 55.0 70.0 59.5 74.5
0.010
53.7
0,008 0,010 0.008 0,010 0,008 0.010 0,008 0,010
50.0 60.5 49.5 65.5 54.5 69.5 65.0 80.5
0.008 0.010 0.008 0.010 0.008 0.010 0,008 0,010 0.008 0.010
45.0 53.5 46.0 55.5 47.0 59.5 47.0 59.0 50.5 63.0
0,008 0,010 0.008 0.010 0,008
42.0 52.0 40.5 50.0 42.5 54.5 49.0 62.0
1 X 2 X 3 1 X 2 X 3 1 X 2 X 3 1 X 2 X 3 1 X 2 X 3
81,100
135
83,600
139
87,500
145
94,100
156
101,000
168
81,300
135
81 ,000
135
83,900
139
KnzCO3 0.3 0.6 0.9 1.5
1 X 2 X 3 1 X 2 X 3 1 X 2 X 3
91 ,OOQ
151
107,000
178
73,300
122
75,600
126
79,100
131
78,000
131
84,500
140
70,400
117
67,700
112
72,500
120
83 ,200
138
NaCl 0.3 0.6 0.9 1.5 2.0
1 X 2 X 3 1 X 2 X 3 1 X 2 X 3 1 X 2 X 3 1 X 2 X 3
KC1 0.3
0.6 0.9
15 :
0.010
0,008 0,010
1 X 2 X 3 1 X 2 X 3 1 X 2 X 3 1 X 2 X 3
wlfate), sodium or potassium ions are adsorbed by the solvated water at ether linkages; these absorbed cations introduce repulsive effects into the aggregate, reducing micellar size. Micellar Size-Micellar Solubilization. Tables V, VI, and VI1 and Figures 3 and 4 demonstrate the existence of direct proportionality between micellar size and Orange O T solubilization (expressed in molecules of Orange OT per micelle) by 1.070 built solutions. Micellar Size-Suspendibility. Table VI11 and Figure 5 indicate t h a t suspendibility in built 1.0% iso-octyl phenyl nonaethylene glycol ether solutions decreases as micellar size increases, suspendibility at fixed micellar size varying with the builder. These results may be explained as follows: Micellar size is increased by a n increase in builder content; this has a twofold effect of (1) tending t o remove adsorbed unit molecules of the nonionic surfactant from the carbon particles for the formation
of the larger aggregates and ( 2 ) simultaneously increasing the gegen-ion concentration (probably anion in this case); both of these processes tend t o decrease the zeta potential and, hence, the suspendibility. Micellar Size-Boundary Tensions. According to Table I X interfacial films of unbuilt 1.0% sodium dodecyl benzene sulfonate are not close packed. Increasing the size of the micellar aggregates by builder additions causes a lowering of boundary tensions. This effect of micellar size on boundary tensions may be explained by the postulations of other investigators (6). Micelles possess greater mobility than individual detergent ions. The potential barriers at interfacial boundaries exert less repulsion per detergent ion in a micelle than on individual ions. Larger micelles penetrate interfacial films more readily, subsequently decomposing into detergent ions, and causing closer packing and lower tensions. Table X indicates t h a t interfacial
INDUSTRIAL AND ENGINEERING CHEMISTRY
October 1955
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Table VII. Orange OT Solubilization by Built 1.0% Iso-octyl Phenyl Nonaethylene Glycol Ether (0.5-hour interaction, 25-26' C.) Builder Concn.,
l
70
M G Orange OT/G. Surfactant
Mole Orange OT/Mole Surfactant
Molecules Orange OT/Micelle Surfactant
WazC03
f
2.8 O i -
0.3
0
0.6
0.9 1.5 2.0
6.86 7.14 7.22 7.50 7.64
0.01574 0.01639 0.01667 0,01721 0.01753
2.126 2.279 2,503 3.065
5.82 5.94 6.00
6.12 6.22
0.01836 0.01363 0.01377 0.01405 0.01428
1.630 1.718 1.805 1.841 1.999
7.OB 7.44 7.46 7.84 7.96
0.01625 0.01707 0.01712 0.01799 0.01827
2.081 2.426 2.638 3.042 3.728
6.06 6.34 6.30 6.50 6.64
0.01391 0.01455 0.01446 0.01492 0,01524
1.878 2.023 2.097 2.828 2.561
6.00 6.14 6.36 6.54 6.54
0.01377 0.01409 0.01460 0.01501 0.01501
1.667 1.804 2.015 2.613 2.913
6.30
0.01446
1.953
...
NaCl
0.3 0.6
0.9 1.5 2.0
$1
NaaP04.HzO
I
0.3 0.6 0.9 1.5 2.0
v)
8
2.0
NasPaOio
0.3 0.6
I
1
0.9 1.5 2.0
-I
NazSO4
0.3 0.6 100
80
140
120
160
0.9 1.5 2.0
200
I80
AGGREGATION NO.
Figure 4.
0
0
2' V
NaaPO4. IlzO NazCOa ~ a z ~ 0 4 NaiPaOlo NaCl
films of unbuilt 1.0% iso-octyl phenyl nonaethylene glycol ether are saturated with detergent molecules. Increased micellar size has no effect on the boundary tensions, as closer packing of the interfacial films is impossible. Mathematical Estimation of Physicochemical Properties. iinalysis of the solubilization data indicates that the differing Orange OT values in built 1.0% iso-octyl phenyl nonaethylene glycol ether solutions of fixed micellar sizes are not a function of the builder or ionic concentrations. Figure 6 illustrates that solubilization in solutions containing the alkaline builders is significantly larger than in solutions built with sodium sulfate or sodium tripolyphosphate (NabP301O). Also, solubilization in solutions of fixed micellar sizes containing the latter two salts is substantially the same. This suggests (Figure 6) that, below pH of ca. 10, solubilization in iso-octyl phenyl nonaethylene glycol ether solution of fixed micellar size is independent of the builder; above p H 10, solubilization is proportional t o builder pH. Because the slopes of the lines of solubilization vs. builder pH are nearly equal, simple mathematical relationships can be derived for the calculation of Orange OT solubilization in built solutions of fixed micellar size, provided the builder p H is known. T h e "constants" (0.379, 0.711, and 1.084) of the solubilizationbuilder p H lines are directly proportional to aggregation numbers. The least squares equation connecting them is:
Table V. Orange OT Solubilization by Built 1.0% Sodium Dodecyl Benzene Sulfonate (0.5-hour interaction, 25-26' C.) Builder Concn.,
%
NaaPOa.Hz0 0.6
0.9 1.5 2.0
Molecules Orange OT/Micelle Surfactant
M G Orange OT/G. Surfactant
Mole Orange OT/Mole Surfactant
4.30 4.50 4.62 4.97
0.00570 0.00587 0.00613 0.00659
0.342 0.442 0,097 1.635
3.62 3.90 3.97 4.a5 4.43
0.00480 0.00517 0.00527 0.00564 0.00588
0.255 0.331 0.311 1.184 2.180
3.64 3.77 ... 3.97 4.07
0.00483 0.00500
0.246 0.335
0.00527 0.00540
0:390
3.26
0.004R1
0.022
XazSOa
0.3 0.6 0.9 1.5 2.0 ?iaEPaOlo
0.3 0.6 0.9 1.5
2.0
Zero
Solubilization by built 1% iso-octyl phenyl nonaethylene glycol ether, 26" C.
Zero
Constant = (0.02127 X aggregation S o . ) - 2.494
0.448
.~
~~
Table VI.
Orange OT Solubilization by Built 1.0% Sodium Dodecyl Benzene Sulfonate
Molecules Orange OT /Minelle- -, AggregaBuilt Built ' tion with with Xo. YaaPOa.Hz0 NazSOa
100 148 200 248
0.605 0.907 1.286 1.635
0.541 0.822 1.126 1.419
(0.5-hour interaction, 25-26' Total Na Mo l.~ s ~7 .. ,/Lit Ratio Built Built Col. 2/ with Col. 3 Sa~P0a.Hz0 NaaSOa 0.145 1.12 0.212 1.10 0.276 0.192
+
~
1.14 1.15
C.)
~
0.319 0.358
0.231 0.257
Ratio
col.51 Col. 6 1.47 1.44 1.38 1.40
Anion Concn. Equiv./Liter' PO4 Son ' 0.183 0.116
0.247 0.290 0.330
0.163 0.203 0.228
Ratio, POa/SOr
1.58 1.52 1.43 1.45
INDUSTRIAL AND ENGINEERING CHEMISTRY
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Vol. 47, No. 10
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7 3.0 -
I100 O8
I
a
f
0
-
Y -1 -1 Y
92
f=!
0
2-. 2.6 6
84
4 -
!i
t,
z
62 4
76
68 1.8
i
I
6
I
I
I
I
1
12
10
8
BUILDER pH
F i g u r e 6. 52
,
Effect of pH on built 1% s u r f a c t a n t solution
NQrSo&
/y4c?
1
