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The effect of added salt on the interaction between polymer and detergent in aqueous solution
The Effect of Added Salt on the Interaction between Polymer and Detergent in Aqueous Solution S H O J I H O R I N AND H A I ~ U H I K O ARAI
Household Goods Research Laboratories, Kao Soap Co., Ltd., 2-Chome, Bunka, Sumidaku, Tokyo, Japan Received July 25, 1969; accepted September 24, 1969 The effect of added NaC1 on the interaction between polyvinyl acetate (PVAc) and sodium dodecyl sulfate (SDS) has been studied in terms of surface tension, viscosity, and solubilization of Yellow-OB. The surface tension-concentration curve gives two transition points which show the concentration where the adsorption of SDS on PVAc first occurs and where SDS adsorbs totally. The critical micelle concentration (cmc) of SDS and the transition point of PVAC-SDS are lowered by the addition of NaC1. On increasing the concentration of NaCI in the PVAc-SDS solution, the reduced viscosity decreases and the solubilization ability increases. The effect of added NaC1 on the PVAc-SDS complex is discussed in terms of electrostatic repulsion. INTRODUCTION
EXPERIMENTAL
Water-insoluble polymers such as polyvinyl acetate dissolve into a highly concentrated anionic-detergent solution, forming a water-soluble complex resulting from the adsorption of detergent on polymer in aqueous solution (1, 2). I n a previous paper, the adsorption of sodium dodecyl sulfate (SDS) on polyvinyl acetate (PVAo) and its derivatives was studied as a function of the hydrophobicity of the polymer by viscosity, solubilization, and dialysis equilibrium measurements (3). In general, dialysis equilibrium measurements for the study of the interaction between polymer and anionic detergent are made in salt solution so t h a t the Donnan effect may be neglected (4). Therefore, it is important to study the effect of added salt on the interaction between polymer and detergent in order to understand the behavior of the polymer-detergent complex. In this paper the effect of added NaC1 on the interaction between PVAc and SDS was studied in terms of surface tension, viscosity, and solubilization.
Material. Polyvinyl acetate (PVAc), sodium dodecyl sulfate (SDS), and YellowOB were the same materials as described in a previous paper (3). The degree of polymerization of PVAc was 2,000, SDS was purified b y recrystallization and extraction with ethyl alcohol and petroleum ether, and Yellow-OB was purified by recrystallization from 1/2 water/ethyl alcohol solution. PVAc-SDS solution was prepared from solubilized PVAc in a 16 weight per cent solution of SDS by heating and mixing, with a weight ratio of PVAc/SDS equal to 1/3. Procedure. Surface tension was measured by the drop-weight method, with a tip 0.660 cm in diameter, in an air thermostat at 30°C (5). The average age of the water drops was 3.7 sec. Viscosity was measured with an Ostwald viscometer at 30°C. Solubilization of Yellow-OB was measured as described previously (3). RESULTS The surface tension of PVAc-SDS and SDS in pure water is plotted in Fig. 1 as a Journal of Colloid and Interface Science, Vol. 32, No. 3, March 197{)
547
548
tIORIN AND ARAI
7O
%,,
u
~60 "0
\
c: o
~ 50
4
1 T2
® o
~ 40 6 30
' lx10-2 I
0 . 3 3 x 1 0 -2
T2
i l x 1 0 -1 Conc. of S D S ( g / 1 0 0 m l . ) i
0 . 3 3 x 1 0 -1
i 1 i
0.33
Conc. of PVAc (g/10Om[)
FIQ. 1. The effect of added NaC1 on the surface tension of PVAc-SDS and SDS. (1) --PVAc-SDS in pure water; (2) --PVAc-SDS in 0.01 N NaC1; (S) --PVAe-SDS in 0.1 iV NaC1; (4) --SDS in pure water; (5) --SDS in 0.01 N NaC1; (6) --SDS in 0.1 N NaC1. function of the logarithm of the concentration of SDS. First and second transition points of PVAc-SDS, which are the breaking points of the surface tension-concentration curve, were observed at concentrations lower and higher t h a n the critical micelle concentration (emc) of SDS, and are shown b y the arrow in Fig. 1. At concentrations higher and lower t h a n the second and the first transition points, the surface tension of PVAc-SDS is nearly equal to that of SDS. The effect of added NaC1 on the cmc and the transition points is also plotted in Fig. 1. The cmc and the transition points were lowered with increasing NaC1. The relationship between the concentration of PVAc and the reduced viscosity is shown in Fig. 2. The reduced viscosity of PVAc-SDS in pure water increases with increasing concentration. The rate of increase of the viscosity with the increase in concentration at higher concentrations was smaller than that at lower concentrations (3, 6). Reduced viscosity was decreased by the addition of NaC1. The relationship between concentration and the amount of solubilized Yellow-OB is shown in Fig. 3. The amount of Yellow-OB solubilized b y PVAc-SDS was far larger than that b y SDS (3, 6). Increasing the Journal of Colloid and Interface Science, ¥ o l . 32, N o . 3, M a r c h 1970
concentration of NaC1 in SDS solution results in an increase in the amount of solubilized Yellow-OB and a decrease in the cmc. The solubilizing ability of SDS is not affected by the added NaC1; t h a t is, the amount of Yellow-OB (mole) solubilized by micellar SDS (grams) is 4.8 X 10-5 mole/gin, independent of the concentration of NaC1. On the other hand, the solubilization ability of PVAc-SDS increases with increasing concentration of NaC1, namely, the amount of Yellow-OB (mole) solubilized b y PVAe-SDS (per 1 gm of SDS) is, in pure water: 1.6 X 10 -4 mole/gm of SDS; in 0 . 0 1 N NaCl: 1.8 mole X 10-4 mole/gm of SDS; in 0 . 1 N NaCl: 2.4 X 10-4 mole/gin of SDS. DISCUSSION The first and second transition points of the surface tension curve of PVAc-SDS are considered to be the concentrations where the adsorption of SDS on PVAc occurs and where there is saturation of SDS, respectively. This agrees with the result of Jones (7) on the adsorption of SDS on polyethyl6
1
5
2
24
v 3
~2
I
°0
02
0
0.6
014 o16 08'
11o
1.2
3.0
Conc. o f PVAc ( g / 1 0 0 m l ) 1.8
Conc. of SDS
2.4
(g/10Oml)
FIG. 2. The effect of added NaCI on the reduced viscosity of PVAc-SDS. (1) -- in pure water; (2) - - in 0.01 iV NaC1; (3) -- in 0.1 N NaC1.
INTERACTION BETWEEN POLYMER AND DETERGENT
I O
549
been found that the logarithm of the cme and the logarithm of the total concentration of counter-ion (Ci) bear the following relationship (8),
o~6 E
log (cmc) = - K g log (CO + const.,
v
fl::l
o,~ O
"O N
'-- 3 15 ::3
"5 u) 2
O
E
<
0
0.1
0.2 0.3 0.4 0.5 Conc. o f PVAc ( g / 1 0 0 m [ )
0.3
0.6 0.9 1.2 1.5 Conc. o f SDS (g/100ml)
FIG. 3. The effect of added NaC1 on the amount of solubilized Yellow-OB by PVAc-SDS and SDS. (1) --PVAc-SDS in pure water; (2) -- PVAc-SDS in 0.01 NaC1; (3) -- PVAc-SDS in 0.1 N NaCI; (4) --SDS in pure water; (5) -- in 0.01 N NaCI; (6) --SDS in 0.1 N NaC1. ene oxide. At concentrations lower than the first transition point, the solution of PVAcSDS was transparent for more than 5 days at 30°C as judged b y a spectrophotometer (500 m~, Hitachi Co.), though it is believed t h a t little or no SDS adsorbs on PVAc at these concentrations. PVAc dissolves in SDS solution, forming a water-soluble PVAc-SDS complex at a concentration higher than the first transition point. Upon dilution of this solution, SDS desorbs from PVAc. When most of the SDS desorbs from PVAc, the PVAc molecule may be dispersed in water without precipitation because the concentration of PVAc is very small and the intermolecular interaction between PVAc molecules m a y not occur, or because there is electrorepulsion of a small amount of SDS adsorbed on the disperse. There are several papers on the effect of added salts on the cmc of anionic detergents. As the result of these experiments, it has
where Ko is an experimental constant. F r o m Fig. 1, log (cmc), log (concentration of the first transition point), and log (concentration of the second transition point) are plotted against log (C~) in Fig. 4. I t is interesting t h a t the relationship between log (C~) and log (concentration of the second transition point) was linear as in the case of SDS alone. The constant Ka of the first and the second transition points agrees with that for the cmc, Kg = 0.52, and is nearly equal to t h a t reported b y Lange (9). Therefore, it is considered t h a t the effect of added NaC1 on the PVAc-SDS complex is the same as that on SDS. At the second transition point, the surface tension of PVAcSDS is almost identical with that of SDS at the cmc. If it is assumed t h a t the concentration of free SDS at the second transition point of PVAc-SDS equals that at the cme of SDS, namely, the total amount of SDS of the second transition point subtracted
._
3
O
J ~-~ E -2'0I c
0
u
-2.5
;5 •
~ 0
r"
~ -3.0 LI
I
-2.0
-1.5
Log. of Conc. of ]on
I
-1.0 Counter
( eq / [ )
FIG. 4. The relationship between the logarithm of the cmc or the logarithm of the transition point concentration and the logarithm of the concentration of counter-ion. (1) -- the cmc; (2) -- the first transition point; (3) -- the second transition point. Journal of Colloid and Interface ~cience, Vol. 32, N o . 3, t ~ a r c h 1970
550
HORIN AND ARAI
from the concentration of cmc adsorbed on PVAc, the amount of SDS adsorbed on PVAc can be calculated. In 0.1 N NaC1 solution, the cmc of SDS is 5.6 × 10-3 gm/100 ml and the concentration of the second transition point is 1.8 X 10-1 gin/ 100 ml. Therefore, 1.8 X 10-1 -- 0.56 X 10-1 = 1.24 X 10-1 gm/100 ml of SDS adsorbed on PVAc out of the total SDS. That is, the ratio of SDS adsorbed on PVAc to the total SDS at the second transition point is 1.24 × 10-1/1.8 X 10-I = 0.69. In a previous paper (3), the amount of adsorbed SDS on PVAc at a weight ratio of PVAc/ SDS of 1/4 in 0.1 N NaCI solution was studied as a function of the concentration of PVAc and SDS by dialysis equilibrium. NaC1 was added to eliminate the Donnan effect. From the results of this study, about 3 gm of SDS adsorbed on 1 gm of PVAc when the concentration of PVAc-SDS was high and total adsorption was attained. Thus, the ratio of SDS adsorbed on PVAc to the total SDS when SDS is totally adsorbed on PVAc, is 3/4 = 0.75, which is in close agreement with the result by surface tension. From a similar calculation against the surface tension-concentration curve in pure water and 0.01 N NaC1 solution, these ratios are 0.51 in pure water and 0.58 in 0 . 0 I N NaC1 solution. Therefore, it is believed that the amount of SDS which adsorbs totally on PVAc increases with the concentration of NaC1. It is believed that the high viscosity of PVAc-SDS in pure water is due to the electrostatic repulsion of adsorbed SDS (6), namely, the elcctroviscous effect. On the other hand, the decrease of viscosity at lower concentration is due to the effect of desorption of SDS from PVAc (3). The amount of adsorbed SDS on PVAe in NaC1 solution may be slightly larger than that in pure water. Therefore, the decrease of the reduced viscosity in NaC1 solution is due to the effect of decreasing electrorepulsion between the adsorbed SDS in NaC1
Journal of Colloidand Interface Science, Vo]. 32, No. 3, March 1970
solution. A similar phenomenon is displayed by polyelectrolytes such as sodium polyacrylate and polyvinyl butylpyridinium bromide (10), that is, the high value of the reduced viscosity of a dilute solution of a polyelectrolyte in the absence of added salt decreases with the increase of ionic strength. The solubilization ability of the polymerdetergent solution is affected by the state of adsorption of the detergent (3), whereas the solubilization ability of SDS alone is not changed by the addition of NaC1. Therefore, the increase of the solubilization ability of PVAc-SDS by the addition of NaC1 is due only not to the increase of the amount of adsorbed SDS but also to the change of the state of adsorption of SDS, or to the change of the state of dissolution of the PVAc-SDS complex. ACKNOWLEDGMENT The authors wish to thank Dr. I. Maruta, Director of Household Goods Research Laboratories, for his encouragement and permission to publish this paper. Some of the data reported herein were obtained by Mr. S. Katakura and Miss M. Yamamoto. REFERENCES 1. S2~TA, N., AND SAITO, S., Kolloid-Z. 128, 154 (1952). 2. ISEMURA, T., AND IMANISHI, A., J. Polymer Sci. 16, 92 (1955); ibid. 38,337 (1958). 3. ARAI, H., .~ND HORIN, S., J. Colloid and Interface Sci. 30, 373 (1969). 4. SAITO, S., KolIoid-Z. 154, 19 (1957). 5. S~INODA,K., YAMAOUCHI,AND HOBI, R., Bull. Chem. Soc. Japan 84,237 (1961). 6. M~RUTA, I., J. Chem. Soc. Japan Pure Chem. Sect. 83, 861 (1962). 7. JONES, M. N., J. Colloid and Interface Sei. 23, 36 (1967). 8. SHINODA, K., NAKAGAWA, T., TAMAMUBHI, B., AND ISEMURA, T., "Colloidal Surfactants," p. 58. Academic Press, New York, 1963. 9. I~NGE, H., Kolloid-Z. 121, 66 (1951). 10. FLORY, P. J., "Principles of Polymer Chemistry," p. 635. Cornell University Press, New York, 1953.
Household Goods Research Laboratories, Kao Soap Co., Ltd., 2-Chome, Bunka, Sumidaku, Tokyo, Japan Received July 25, 1969; accepted September 24, 1969 The effect of added NaC1 on the interaction between polyvinyl acetate (PVAc) and sodium dodecyl sulfate (SDS) has been studied in terms of surface tension, viscosity, and solubilization of Yellow-OB. The surface tension-concentration curve gives two transition points which show the concentration where the adsorption of SDS on PVAc first occurs and where SDS adsorbs totally. The critical micelle concentration (cmc) of SDS and the transition point of PVAC-SDS are lowered by the addition of NaC1. On increasing the concentration of NaCI in the PVAc-SDS solution, the reduced viscosity decreases and the solubilization ability increases. The effect of added NaC1 on the PVAc-SDS complex is discussed in terms of electrostatic repulsion. INTRODUCTION
EXPERIMENTAL
Water-insoluble polymers such as polyvinyl acetate dissolve into a highly concentrated anionic-detergent solution, forming a water-soluble complex resulting from the adsorption of detergent on polymer in aqueous solution (1, 2). I n a previous paper, the adsorption of sodium dodecyl sulfate (SDS) on polyvinyl acetate (PVAo) and its derivatives was studied as a function of the hydrophobicity of the polymer by viscosity, solubilization, and dialysis equilibrium measurements (3). In general, dialysis equilibrium measurements for the study of the interaction between polymer and anionic detergent are made in salt solution so t h a t the Donnan effect may be neglected (4). Therefore, it is important to study the effect of added salt on the interaction between polymer and detergent in order to understand the behavior of the polymer-detergent complex. In this paper the effect of added NaC1 on the interaction between PVAc and SDS was studied in terms of surface tension, viscosity, and solubilization.
Material. Polyvinyl acetate (PVAc), sodium dodecyl sulfate (SDS), and YellowOB were the same materials as described in a previous paper (3). The degree of polymerization of PVAc was 2,000, SDS was purified b y recrystallization and extraction with ethyl alcohol and petroleum ether, and Yellow-OB was purified by recrystallization from 1/2 water/ethyl alcohol solution. PVAc-SDS solution was prepared from solubilized PVAc in a 16 weight per cent solution of SDS by heating and mixing, with a weight ratio of PVAc/SDS equal to 1/3. Procedure. Surface tension was measured by the drop-weight method, with a tip 0.660 cm in diameter, in an air thermostat at 30°C (5). The average age of the water drops was 3.7 sec. Viscosity was measured with an Ostwald viscometer at 30°C. Solubilization of Yellow-OB was measured as described previously (3). RESULTS The surface tension of PVAc-SDS and SDS in pure water is plotted in Fig. 1 as a Journal of Colloid and Interface Science, Vol. 32, No. 3, March 197{)
547
548
tIORIN AND ARAI
7O
%,,
u
~60 "0
\
c: o
~ 50
4
1 T2
® o
~ 40 6 30
' lx10-2 I
0 . 3 3 x 1 0 -2
T2
i l x 1 0 -1 Conc. of S D S ( g / 1 0 0 m l . ) i
0 . 3 3 x 1 0 -1
i 1 i
0.33
Conc. of PVAc (g/10Om[)
FIQ. 1. The effect of added NaC1 on the surface tension of PVAc-SDS and SDS. (1) --PVAc-SDS in pure water; (2) --PVAc-SDS in 0.01 N NaC1; (S) --PVAe-SDS in 0.1 iV NaC1; (4) --SDS in pure water; (5) --SDS in 0.01 N NaC1; (6) --SDS in 0.1 N NaC1. function of the logarithm of the concentration of SDS. First and second transition points of PVAc-SDS, which are the breaking points of the surface tension-concentration curve, were observed at concentrations lower and higher t h a n the critical micelle concentration (emc) of SDS, and are shown b y the arrow in Fig. 1. At concentrations higher and lower t h a n the second and the first transition points, the surface tension of PVAc-SDS is nearly equal to that of SDS. The effect of added NaC1 on the cmc and the transition points is also plotted in Fig. 1. The cmc and the transition points were lowered with increasing NaC1. The relationship between the concentration of PVAc and the reduced viscosity is shown in Fig. 2. The reduced viscosity of PVAc-SDS in pure water increases with increasing concentration. The rate of increase of the viscosity with the increase in concentration at higher concentrations was smaller than that at lower concentrations (3, 6). Reduced viscosity was decreased by the addition of NaC1. The relationship between concentration and the amount of solubilized Yellow-OB is shown in Fig. 3. The amount of Yellow-OB solubilized b y PVAc-SDS was far larger than that b y SDS (3, 6). Increasing the Journal of Colloid and Interface Science, ¥ o l . 32, N o . 3, M a r c h 1970
concentration of NaC1 in SDS solution results in an increase in the amount of solubilized Yellow-OB and a decrease in the cmc. The solubilizing ability of SDS is not affected by the added NaC1; t h a t is, the amount of Yellow-OB (mole) solubilized by micellar SDS (grams) is 4.8 X 10-5 mole/gin, independent of the concentration of NaC1. On the other hand, the solubilization ability of PVAc-SDS increases with increasing concentration of NaC1, namely, the amount of Yellow-OB (mole) solubilized b y PVAe-SDS (per 1 gm of SDS) is, in pure water: 1.6 X 10 -4 mole/gm of SDS; in 0 . 0 1 N NaCl: 1.8 mole X 10-4 mole/gm of SDS; in 0 . 1 N NaCl: 2.4 X 10-4 mole/gin of SDS. DISCUSSION The first and second transition points of the surface tension curve of PVAc-SDS are considered to be the concentrations where the adsorption of SDS on PVAc occurs and where there is saturation of SDS, respectively. This agrees with the result of Jones (7) on the adsorption of SDS on polyethyl6
1
5
2
24
v 3
~2
I
°0
02
0
0.6
014 o16 08'
11o
1.2
3.0
Conc. o f PVAc ( g / 1 0 0 m l ) 1.8
Conc. of SDS
2.4
(g/10Oml)
FIG. 2. The effect of added NaCI on the reduced viscosity of PVAc-SDS. (1) -- in pure water; (2) - - in 0.01 iV NaC1; (3) -- in 0.1 N NaC1.
INTERACTION BETWEEN POLYMER AND DETERGENT
I O
549
been found that the logarithm of the cme and the logarithm of the total concentration of counter-ion (Ci) bear the following relationship (8),
o~6 E
log (cmc) = - K g log (CO + const.,
v
fl::l
o,~ O
"O N
'-- 3 15 ::3
"5 u) 2
O
E
<
0
0.1
0.2 0.3 0.4 0.5 Conc. o f PVAc ( g / 1 0 0 m [ )
0.3
0.6 0.9 1.2 1.5 Conc. o f SDS (g/100ml)
FIG. 3. The effect of added NaC1 on the amount of solubilized Yellow-OB by PVAc-SDS and SDS. (1) --PVAc-SDS in pure water; (2) -- PVAc-SDS in 0.01 NaC1; (3) -- PVAc-SDS in 0.1 N NaCI; (4) --SDS in pure water; (5) -- in 0.01 N NaCI; (6) --SDS in 0.1 N NaC1. ene oxide. At concentrations lower than the first transition point, the solution of PVAcSDS was transparent for more than 5 days at 30°C as judged b y a spectrophotometer (500 m~, Hitachi Co.), though it is believed t h a t little or no SDS adsorbs on PVAc at these concentrations. PVAc dissolves in SDS solution, forming a water-soluble PVAc-SDS complex at a concentration higher than the first transition point. Upon dilution of this solution, SDS desorbs from PVAc. When most of the SDS desorbs from PVAc, the PVAc molecule may be dispersed in water without precipitation because the concentration of PVAc is very small and the intermolecular interaction between PVAc molecules m a y not occur, or because there is electrorepulsion of a small amount of SDS adsorbed on the disperse. There are several papers on the effect of added salts on the cmc of anionic detergents. As the result of these experiments, it has
where Ko is an experimental constant. F r o m Fig. 1, log (cmc), log (concentration of the first transition point), and log (concentration of the second transition point) are plotted against log (C~) in Fig. 4. I t is interesting t h a t the relationship between log (C~) and log (concentration of the second transition point) was linear as in the case of SDS alone. The constant Ka of the first and the second transition points agrees with that for the cmc, Kg = 0.52, and is nearly equal to t h a t reported b y Lange (9). Therefore, it is considered t h a t the effect of added NaC1 on the PVAc-SDS complex is the same as that on SDS. At the second transition point, the surface tension of PVAcSDS is almost identical with that of SDS at the cmc. If it is assumed t h a t the concentration of free SDS at the second transition point of PVAc-SDS equals that at the cme of SDS, namely, the total amount of SDS of the second transition point subtracted
._
3
O
J ~-~ E -2'0I c
0
u
-2.5
;5 •
~ 0
r"
~ -3.0 LI
I
-2.0
-1.5
Log. of Conc. of ]on
I
-1.0 Counter
( eq / [ )
FIG. 4. The relationship between the logarithm of the cmc or the logarithm of the transition point concentration and the logarithm of the concentration of counter-ion. (1) -- the cmc; (2) -- the first transition point; (3) -- the second transition point. Journal of Colloid and Interface ~cience, Vol. 32, N o . 3, t ~ a r c h 1970
550
HORIN AND ARAI
from the concentration of cmc adsorbed on PVAc, the amount of SDS adsorbed on PVAc can be calculated. In 0.1 N NaC1 solution, the cmc of SDS is 5.6 × 10-3 gm/100 ml and the concentration of the second transition point is 1.8 X 10-1 gin/ 100 ml. Therefore, 1.8 X 10-1 -- 0.56 X 10-1 = 1.24 X 10-1 gm/100 ml of SDS adsorbed on PVAc out of the total SDS. That is, the ratio of SDS adsorbed on PVAc to the total SDS at the second transition point is 1.24 × 10-1/1.8 X 10-I = 0.69. In a previous paper (3), the amount of adsorbed SDS on PVAc at a weight ratio of PVAc/ SDS of 1/4 in 0.1 N NaCI solution was studied as a function of the concentration of PVAc and SDS by dialysis equilibrium. NaC1 was added to eliminate the Donnan effect. From the results of this study, about 3 gm of SDS adsorbed on 1 gm of PVAc when the concentration of PVAc-SDS was high and total adsorption was attained. Thus, the ratio of SDS adsorbed on PVAc to the total SDS when SDS is totally adsorbed on PVAc, is 3/4 = 0.75, which is in close agreement with the result by surface tension. From a similar calculation against the surface tension-concentration curve in pure water and 0.01 N NaC1 solution, these ratios are 0.51 in pure water and 0.58 in 0 . 0 I N NaC1 solution. Therefore, it is believed that the amount of SDS which adsorbs totally on PVAc increases with the concentration of NaC1. It is believed that the high viscosity of PVAc-SDS in pure water is due to the electrostatic repulsion of adsorbed SDS (6), namely, the elcctroviscous effect. On the other hand, the decrease of viscosity at lower concentration is due to the effect of desorption of SDS from PVAc (3). The amount of adsorbed SDS on PVAe in NaC1 solution may be slightly larger than that in pure water. Therefore, the decrease of the reduced viscosity in NaC1 solution is due to the effect of decreasing electrorepulsion between the adsorbed SDS in NaC1
Journal of Colloidand Interface Science, Vo]. 32, No. 3, March 1970
solution. A similar phenomenon is displayed by polyelectrolytes such as sodium polyacrylate and polyvinyl butylpyridinium bromide (10), that is, the high value of the reduced viscosity of a dilute solution of a polyelectrolyte in the absence of added salt decreases with the increase of ionic strength. The solubilization ability of the polymerdetergent solution is affected by the state of adsorption of the detergent (3), whereas the solubilization ability of SDS alone is not changed by the addition of NaC1. Therefore, the increase of the solubilization ability of PVAc-SDS by the addition of NaC1 is due only not to the increase of the amount of adsorbed SDS but also to the change of the state of adsorption of SDS, or to the change of the state of dissolution of the PVAc-SDS complex. ACKNOWLEDGMENT The authors wish to thank Dr. I. Maruta, Director of Household Goods Research Laboratories, for his encouragement and permission to publish this paper. Some of the data reported herein were obtained by Mr. S. Katakura and Miss M. Yamamoto. REFERENCES 1. S2~TA, N., AND SAITO, S., Kolloid-Z. 128, 154 (1952). 2. ISEMURA, T., AND IMANISHI, A., J. Polymer Sci. 16, 92 (1955); ibid. 38,337 (1958). 3. ARAI, H., .~ND HORIN, S., J. Colloid and Interface Sci. 30, 373 (1969). 4. SAITO, S., KolIoid-Z. 154, 19 (1957). 5. S~INODA,K., YAMAOUCHI,AND HOBI, R., Bull. Chem. Soc. Japan 84,237 (1961). 6. M~RUTA, I., J. Chem. Soc. Japan Pure Chem. Sect. 83, 861 (1962). 7. JONES, M. N., J. Colloid and Interface Sei. 23, 36 (1967). 8. SHINODA, K., NAKAGAWA, T., TAMAMUBHI, B., AND ISEMURA, T., "Colloidal Surfactants," p. 58. Academic Press, New York, 1963. 9. I~NGE, H., Kolloid-Z. 121, 66 (1951). 10. FLORY, P. J., "Principles of Polymer Chemistry," p. 635. Cornell University Press, New York, 1953.