J Surfact Deterg (2013) 16:271–278 DOI 10.1007/s11743-012-1389-1

ORIGINAL ARTICLE

Estimation of Micellization Parameters of SDS in the Presence of Some Electrolytes for Emulsion Polymerization Systems Saeed Naderi Miqan • Farshad Farshchi Tabrizi Hossein Abedini • Hossein Atashy Kashi

•

Received: 9 April 2012 / Accepted: 6 July 2012 / Published online: 21 July 2012 Ó AOCS 2012

Abstract The critical micelle concentration and the effective degree of dissociation of micelles (a) of sodium dodecyl sulfate, which is the most extensively used surfactant in emulsion polymerization systems, were determined in the presence of various amounts of sodium carbonate and potassium persulfate, and some monomers, such as methyl methacrylate, butyl acrylate, and styrene by means of the conductometric procedure at 25 °C. In addition, the other micellization parameters, such as aggregation number and number of counter-ions per micelle, were computed directly from the obtained conductivity measurements data. The effect of the combination of sodium carbonate and potassium persulfate, on the critical micelle concentration of the sodium dodecyl sulfate solutions was studied at 60 °C (emulsion reaction temperature). The empirical formulations derived provide an easy way to estimate the critical micelle concentration and the effective degree of dissociation of micelles of a system at a given electrolyte and monomer concentration. Keywords Sodium dodecyl sulfate  Critical micelle concentration  Dissociation degree  Conductivity measurements  Micellization parameters

S. Naderi Miqan  F. Farshchi Tabrizi  H. Atashy Kashi Department of Chemical Engineering, University of Sistan and Baluchestan, Zahedan, Iran H. Abedini (&) Department of Polymerization Engineering, Iran Polymer and Petrochemical Institute, P.O. Box 14965-115, Tehran, Iran e-mail: [email protected]

Introduction Micellization is one of the most important phenomena in industry and nature due to its applications in pharmacy, cosmetic products and for diverse tasks related to environmental protection [1, 2]. One of the most noticeable parameters related to micellar phases is the critical micelle concentration of a surfactant (CMC). Knowledge of this quantity is essential for both scientific and practical grasps of how surfactants act. In addition, it is a favored issue due to its unusual physicochemical properties because of surfactant aggregation. The effective factors, such as the addition of electrolytes, buffer pH, temperature, addition of organic modifiers, ionic strength of the aqueous solution, and presence of additives can change the CMC value from that determined in pure water [3–5]. In the case of ionic surfactants, the influence of added electrolytes on their micellization characteristics is attributed entirely to the counter-ion effect [6]. A comprehensive investigation has been done on the micellization behavior of sodium dodecyl sulfate (SDS) with many electrolytes, such as sodium butyrate (NaBu), sodium acetate (NaAc), and sodium chloride (NaCl) [7], and organic compounds, such as alcohols [8, 9], at 25 °C. All the available literature shows a shortage of data on the micellization behavior of SDS with electrolytes, such as sodium carbonate Na2CO3 and potassium persulfate (KP) at 25 °C and specifically at the emulsion reaction temperature 60 °C. In particular, to the best of our knowledge, no effort has been made to present the semi-empirical relationships for estimating the CMC of SDS solutions with Na2CO3 and KPS electrolytes that are crucial materials in emulsion polymerization systems. It should be noted that Na2CO3 and KPS electrolytes are widely used in emulsion polymerization systems as a buffer and initiator, respectively. For example, the absence

123

272

of Na2CO3 in the emulsion polymerization of butadiene causes the reaction to progress very slowly and attains to very low conversion. The results show that when persulfates are used as an initiator, the pH tends to reduce because of the formation of H2SO4 [10]. Accordingly, it is necessary to keep the aqueous solution as neutral or basic with buffering materials, especially when the initiator efficiency is low with regard to the polymerization. In consequence of the long reaction times at moderately high polymerization temperature, the emulsion polymerization of butadiene is specifically susceptible to reductions in the pH. As the pH drops, polymerization becomes rigorously retarded. Therefore, it is crucial to use Na2CO3 as a buffer in emulsion polymerization of butadiene with KPS as an initiator. In contrast, many other monomers (e.g., styrene, methyl methacrylate (MMA), butyl acrylate (BA)) can easily be polymerized by emulsion polymerization up to high conversion in the absence of a buffering substance. Also, the reaction can not develop with the lack of KPS. Similarly, MMA, BA, and styrene are used frequently in industry as monomers in emulsion polymerization reactions. The conductivity method is one of the most commonly used methods to estimate the CMC of ionic surfactants [11]. Hence, attempts are intended for the expansion of an acceptable empirical and theoretical approach to approximate the CMC and other micellization parameters of SDS from the conductimetric data. The critical micelle concentration of the surfactant has major effect on particle size distribution of latex produced by emulsion polymerization systems. Particle size distribution (PSD) is a key parameter in the emulsion polymerization process; it directly influences the final latex end-use properties, such as its rheological properties, maximum solid content adhesion, drying time, film-forming characteristics freeze-thaw stability, gloss, pigment binding, hold out, and bond strength. The main goal of this study is to determine the critical micelle concentration (CMC) and the effective degree of dissociation (a) of micelles of sodium dodecyl sulfate in the presence of various amounts of sodium carbonate and potassium persulfate and some monomers that are essential materials in emulsion polymerization systems.

J Surfact Deterg (2013) 16:271–278

A Radiometer CDM210 conductometer with a Radiometer conductivity cell was used. The conductivity cell was calibrated by measuring the conductivity of potassium chloride (KCl) solutions at various concentrations. At first, a certain concentration of SDS solution (for example, a solution with 20 % SDS) was prepared. Then a solution with a certain concentration of salt was prepared at 25 or 60 °C. The experiment took place by adding various amounts of surfactant solution to the fixed volume of electrolyte solution at a constant temperature and measuring the conductivities.

Results and Discussion Effects of Electrolytes and Monomers on CMC of SDS Solutions at 25 °C The specific conductivity of a solution depends on the free surfactant concentration and the temperature of the solution. When the change in conductivity of a solution is measured with increasing concentrations of surfactant, the conductivity–surfactant concentration plots display two straight lines with different slopes. The specific conductivity increases sharply in the pre-micellar zone (when only monomers of the surfactant exist in the solution) with surfactant concentration but is slightly increased at a certain concentration which shows the CMC, (i.e., micelles start to form and the slope change since the conductivity rise in a different manner). The intersection of these two straight lines is taken as the CMC value of the surfactant (Fig. 1) [2, 4]. The values of the CMC obtained in this work for SDS solutions with different concentrations of electrolytes and monomers at 25 °C are presented in Fig. 2. The CMC values reduce with the increase of the electrolyte concentration, which is in agreement with the literature [4].

Experimental Study The salts used in the experimental studies were Na2CO3 (Applichem, 99.5? %) and KPS (Merck, 99? %), and the monomers used were styrene (Merck, 98? %), BA (Merck, 99? %), MMA (Merck, 99? %). SDS (Merck, 99? %) was used as received without further purification. It should be mentioned that distilled water was used to prepare the solutions.

123

Fig. 1 CMC point alteration of SDS solutions with different concentrations of KPS at 25 °C

J Surfact Deterg (2013) 16:271–278

273 Table 1 The values of the coefficients of equation (1) in order to estimate CMC of SDS solutions with electrolytes and monomers at 25 °C Substance

A

B

R2

Na2CO3

-0.96

7.26

0.98

KPS

-1.94

7.82

0.97

MMA BA

-1.32 -0.52

7.84 6.25

0.93 0.92

Styrene

-0.36

7.69

0.97

Effects of Electrolytes and Monomers on a of SDS Solutions at 25 °C The values of effective degree of dissociation of micelles (a) can be calculated from the ratios of slopes of micellar and pre-micellar phases in the conductivity-surfactant concentration (Fig. 1). These values for SDS micelles in the presence of different concentrations of electrolytes and monomers are shown in Fig. 3. The figure explains that the values of a for SDS depend on the type of electrolyte and monomer and their concentrations. These empirical curves at 25 °C were fitted by the following equation: a ¼ AðxÞ þ B Fig. 2 Variation of CMC of SDS with concentration of a electrolytes and b monomers at 25 °C

The reason behind this behavior could be explained by the fact that, the electrolytes can influence micelle formation, which neutralizes the charge at the micelle surface and decrease the thickness of the ionic atmosphere around the surfactant ionic heads. As a result, the electrostatic repulsions between them decrease and consequently the CMC values are reduced [4]. For each electrolyte and monomer, the experimental results obtained at 25 °C were fitted by the following equation: CMC ¼ A lnðxÞ þ B

ð1Þ

where x is the electrolyte or monomer concentration, and it is expressed in mmol dm-3. Equation (1) provides an easy way for researchers to estimate the CMC of a system at a given electrolyte or monomer concentration. The coefficients of equation (1) are given in Table 1. R2 is the coefficient of determination (linear regression). The values of the CMC of SDS in the presence of potassium ions, decline severely in comparison with the decrease in the CMC value in the presence of sodium ions. Dutkiewicz et al. also reported the above trend [1].

ð2Þ

where x is concentration of electrolyte or monomer, and it is expressed in mmol dm-3. The coefficients of equation (2) are presented in Table 2. Figure 3 shows two types of dependence of a on the electrolyte and monomer concentration. For styrene and KPS solution, a decreased monotonously but for MMA, BA, and Na2CO3 systems, a increased with the increase of concentration of electrolyte or monomer. Dutkiewicz et al. [1] also reported the above trend. They mentioned that the decrease or increase in a for SDS depends on the concentration range of the electrolyte added. For example, an increase in a observed for a lower concentration range of NaCl and NaF electrolytes and a decrease in a observed for lower concentration range of KCl and MgCl2. As stated by Dutkiewicz et al. [1], the increase of a with increasing Na2CO3 concentration could be explained either by an increased charge screening at higher ionic strength or by micelle growth in the presence of the electrolyte added. This growth can cause a reduction in the micelle charge density and, accordingly, the liberation of counter-ions. In the case of KPS, the reduction of a may be attributed to the stronger interaction of SDS micelles with K? ions than with Na? ions. The K? ions are less hydrate than the Na? ions and, therefore, the K? charges are less screened than Na? charges [1]. The effect of monomers concentrations on the CMC and a can be explained as below: the inclusion of hydrophobic compounds in micelles will decrease the CMC and increase

123

274

J Surfact Deterg (2013) 16:271–278

where [Na?]aq is the molar concentration of Na? ions in the aqueous phase created by SDS or both SDS and added salt. In this relationship, the unit of [Na?]aq is mol dm-3, and K and c are constants and they are sensitive to the alkyl chain length [12]. For SDS, Quina et al. [13] estimated the values of K and c from experimental data. In this work, the values k = 164 and c = 0.25 were used for the experiments. Also Bales et al. [12] used these values. The relationship between [Na?]aq and the surfactant and the added salt concentration can be found using the following equation [1, 12]. ½Naþ aq ¼ að½SDS  ½free surfactantÞ þ ½free surfactant þ ½Naþ ad ¼ a½SDS þ b½free surfactant þ 2½Na2 CO3 

ð4Þ

where [SDS] is the total molar SDS concentration, [free surfactant] is the molar concentration of monomeric surfactant that equals the CMC. b = 1 - a, and [Na?]ad is the molar concentration of added Na? ions, which is equal to 2 [Na2CO3]. Dutkiewicz et al. assumed that the Eq. (4) might apply not only for Na? but also for any univalent counter-ions. In this work, we also used this assumption. Therefore, Eq. (4) can be rewritten as follows [1]: Fig. 3 Effects of a electrolytes and b monomers on the degree of dissociation of micelles, a, for SDS at 25 °C Table 2 The calculated coefficients of equation (2) in order to determined a of SDS solution with electrolytes and monomers at 25 °C Substance Na2CO3 KPS MMA BA Styrene

A

B

R2

0.005

0.39

0.99

-0.030

0.41

0.96

0.032 0.023

0.36 0.42

0.98 0.91

-0.055

0.40

0.87

a, this latter because the isomers intercalate between the polar headgroups thus reducing the surface charge density. Electrolyte Effects on the Other Micellization Parameters of SDS Solutions at 25 °C In this section, the other micellization parameters of SDS solutions with KPS and Na2CO3 electrolytes are calculated. Firstly, the values of the aggregation numbers (n) were determined, according to the following relationship [1, 12, 13]: n ¼ Kð½Naþ aq Þc

123

ð3Þ

½counterionþ aq ¼ a½SDS þ ð1  aÞCMC þ ½counterionþ ad :

ð5Þ

Thus, [counterion?]ad in this work is 2[Na2CO3] or 2[KPS]. The values of n obtained for Na2CO3 and KPS are presented in Tables 3 and 4, respectively. The results show that the values of, n, rise with increases in the electrolyte concentration because of decreasing the repulsive interactions between the head groups in the micelles [1]. After determining n and a, the charge (or m = na, number of counter-ions per micelle [2, 14–16]) and the radius r, of the micelles can be computed. It is supposed that the shape ˚ of the micelle is spherical. Therefore, r was evaluated in A (Angstrom) using the following relationship [1, 2, 17, 18]: r ¼ ½3=ð4pÞð27:4 þ 26:9nc Þn1=3

ð6Þ

where nc is the number of carbon atoms in the hydrocarbon chain of the used surfactant (i.e., for SDS nc is equal to 12). As it is obvious, the radius of the micelle increases with increasing of the electrolyte concentration. In addition, the surface area per head group Ao, in the micelle can be calculated from Eq. 7 [1, 17]. ˚ 2 Ao ¼ 3t=r½ðAÞ

ð7Þ

where m is the volume of the hydrophobic tail [17] (i.e., the volume of an individual chain in the micelle [1]) and calculated according to the Tanford equation [1, 12, 17].

J Surfact Deterg (2013) 16:271–278

275

Table 3 Micellization parameters for different concentrations of Na2CO3 at 25 °C Concentration (mmol dm-3)

n

m = n* a

˚) r (A

˚ )3 V (A

˚ )2 Ao (A

Pm

˚ )3 Vp (A

4.71

57.97

24.21

16.92

350.20

62.07

0.33

411.06

5.66

59.62

25.48

17.08

350.20

61.49

0.34

406.23

7.07

61.69

27.13

17.28

350.20

60.79

0.34

400.41

28.3

81.89

45.06

18.99

350.20

55.31

0.37

355.80

47.17

92.21

59.93

19.75

350.20

53.17

0.39

338.82

Table 4 Micellization parameters for different concentrations of KPS at 25 °C Concentration (mmol dm-3)

n

m = n* a

˚) r (A

˚ )3 V (A

˚ )2 Ao (A

Pm

˚ )3 Vp (A

1.85

52.67

18.35

16.39

350.20

64.084

0.327

428.08

2.77

54.29

17.69

16.56

350.20

63.44

0.330

422.60

3.33

55.03

17.53

16.63

350.20

63.15

0.332

420.19

4.62

57.24

15.16

16.85

350.20

62.33

0.336

413.26

˚ 3 t ¼ ð27:4 þ 26:9nc Þ½ðAÞ

ð8Þ

The values of Ao decrease with an increase in the concentration of electrolytes, showing a good agreement with the previously reported data [1, 17]. These equations can be applied in order to compute the critical packing parameter, which controls the shape of the micelle [17]. Pm ¼ t=ðAo lÞ

ð9Þ

where l is the critical chain length and it is equal to ˚ )]. It is known that, Pm = 0.33 for [1.5 ? 1.26 nc(A spherical micelles, 0.50 for cylindrical micelles, and 1.00 for disks or bilayers [1]. As based on Tables 3 and 4, Pm of the SDS micelles is directly related to the electrolyte concentration. This means that, by increasing the electrolyte concentration, the larger pseudo-spherical micelles will be formed. In this study, as presented in Tables 3 and 4, for KPS (0.322 \ Pm \ 0.326) and for Na2CO3 (0.328 \ Pm \ 0.374) that means in Na2CO3 electrolytes, larger pseudo-spherical micelles are formed which is due to that the Na2CO3 concentrations used were much higher than the KPS concentrations used. ˚ 3) per surfactant molecule in the polar The volume (A shell of the spherical micelle, Vp, is given by [1, 12, 17]: ˚ 3  r3  Vp ¼ ½4p=3n½ðr þ 5ðAÞÞ

ð10Þ

˚ is the thickness of the polar micelle shell [1]. As where 5 A can be seen from Tables 3 and 4, the values of Vp has an indirect relation with the concentration of the added electrolyte, which is in good agreement with the literature [1, 17]. In this work, the effects of the kinds of electrolytes on CMC and a as the important SDS micellization parameters,

are shown. However, the aggregation number, n, does not depend on the kind of electrolyte added because in Eq. (3) (in combination with Eqs. 4 or 5), the electrolyte concentration suppresses the effect of a on [counter-ions?] and n (a[SDS] ? (1 - a)CMC  [electrolyte]), especially in high concentrations of electrolyte. Also the micellization parameters of SDS, r, Ao, Pm, and Vp, depend on n only (Eqs. 6, 7, 9, 10). Therefore, these parameters do not depend on the kind of electrolyte added [1]. Estimation of CMC of SDS Solutions with KPS and Na2CO3 Electrolytes at 60 °C Effect of Single Electrolyte on CMC at T = 60 °C Since all the emulsion polymerizations occur at temperatures higher than 25 °C, and most of them are developed at 60 °C, such as emulsion polymerization of styrene and butadiene, it was decided to estimate CMC values of such systems at 60 °C. Also, it is important to have a knowledge of the CMC values of these systems at this temperature for modeling and simulating purposes. The experimental results of CMC values obtained at 60 °C are shown in Fig. 4. As it can be seen from this figure, the CMC value again decreases as the concentration of electrolytes increases which complies with the reasons explained in the ‘‘Effects of Electrolytes and Monomers on CMC of SDS Solutions at 25 °C’’ section. Similarly, the dependence of the CMC of the SDS on the electrolyte concentration can be explained using Eq. (1) but with different coefficients, and these coefficients are as follows: for Na2CO3, A = - 2.12 and B = 10.70 with R2 = 0.90, and for KPS A = - 2.18 and B = 10.21 with R2 = 0.95.

123

276

J Surfact Deterg (2013) 16:271–278

to the high temperature. As a matter of fact, at high temperature conductometric titration exhibits a lack of sensitivity, specially at a high concentration of electrolytes and SDS, when values of CMC are low. Hence, it caused some inaccuracy in the results, although an effort was made to do each experiment more than once. Effect of a Combination of Electrolytes on the CMC at T = 60 °C

Fig. 4 Variation of CMC of SDS versus the concentration of electrolytes at 60 °C

Since all of the polymerization systems include these electrolytes simultaneously at 60 °C (temperature of reaction), it is necessary to study the effect of the combination of these electrolytes with various concentrations on the CMC of the SDS electrolyte solutions at this temperature and correlate an acceptable empirical formula to estimate the CMC of such systems. Therefore, experiments were carried out on SDS solutions with different concentrations of these electrolytes at 60 °C to determine the CMC values. Then, MATLAB software was used to derive a semiempirical formula with reasonable coefficients by using the least squares method. The derived equation is as follows: CMC ¼ AðXÞf ðYÞg

Fig. 5 Variation of a of SDS versus the concentration of electrolytes at 60 °C

Effect of a Single Electrolyte on a at T = 60 °C It is necessary to calculate the exact value of a from the slopes of the conductivity-concentration curve. To remove the data uncertainty, each experiment was carried out twice and the results are shown in Fig. 5. As it is obvious from the figure, in SDS solutions with KPS, there is a monotonous decrease in a, while in the case of Na2CO3, a increased with the increase in concentration and is compatible with the variation of a with the electrolyte concentration at 25 °C mentioned in ‘‘Effects of Electrolytes and Monomers on a of SDS Solutions at 25 °C’’ section. In a similar way, the variations of a of SDS with the electrolyte concentration obey the equation obtained at 25 °C but with the diverse coefficients which are as follow: for Na2CO3, A = 0.005 and B = 0.43 with R2 = 0.90, and for KPS A = -0.007and B = 0.45 with R2 = 0.89. As it can be seen from Fig. 5 and the R2 values, this equation with these constants at 60 °C, are not as accurate as at 25 °C. It is thought that this phenomenon is attributed

123

ð11Þ

where X, Y are the Na2CO3 concentration and KPS concentration (in mmol dm-3), respectively. Equation (11) provides an easy way for researchers to estimate the CMC of a combined system at given electrolyte concentrations at 60 °C. The obtained coefficients for this equation are: A ¼ 0:004; f ¼ 0:33; and g ¼ 0:17: Complete information on various concentration combinations of these two electrolytes, experimental CMC and CMC obtained from this formula are presented in Table 5. Equation (11) represents a reasonable estimation of the CMC at different concentrations. It should be noted that the relative error is equal to CMCðmodelÞCMCðEXPÞ . CMCðEXPÞ In Table 5, five sets of experiments including five different concentrations of Na2CO3 with diverse concentrations of KPS are given. All the relative errors in Table 5 are less than 9 %, which is a good error in engineering when estimating parameter. As it has been mentioned before, at high temperatures like 60 °C, conductometric titration is not sensitive. Hence, it caused some inaccuracy in the results and increased the errors. Therefore, experiments in this study were carried out at concentrations of less than 32.90 (mmol dm-3) of the concentration combination of these electrolytes. Since there is always continued search for empirical formulations with specific properties for various applications, the present results in this paper will be useful in

J Surfact Deterg (2013) 16:271–278

277

Table 5 Complete information for predicting the CMC of combined electrolytes with different concentrations in SDS solutions with their relative errors at 60 °C Na2CO3 (mmol dm-3)

KPS (mmol dm-3)

CMC (mmol dm-3) EXP

CMC (mmol dm-3) Model

Relative error (%)

4.72

0.29

6.88

7.14

3.77

4.72

0.52

6.64

6.54

1.50

4.72 4.72

0.74 2.60

6.24 5.64

6.21 5.15

0.48 8.68

4.72

2.96

5.28

5.05

4.35

4.72

4.44

5.10

4.75

6.86

4.72

5.00

4.99

4.67

6.41

4.72

7.02

4.33

4.44

2.54

9.44

0.26

5.76

5.81

0.86

9.44

0.52

5.10

5.24

2.74

9.44

10.00

3.65

3.37

7.67

9.44

13.00

3.41

3.25

4.69

14.16

0.26

5.00

5.10

2.00

14.16

0.52

4.71

4.60

2.33

14.16

5.00

3.49

3.29

5.73

14.16

7.50

3.26

3.09

5.21

14.16

10.00

2.76

2.96

7.24

18.89 18.89

0.37 0.52

4.26 4.12

4.42 4.20

3.75 1.94

18.89

1.11

4.06

3.75

7.63

18.89

1.48

3.82

3.59

6.02

18.89

8.14

2.85

2.79

2.10

23.61

5.00

3.01

2.79

7.30

23.61

7.50

2.68

2.63

1.86

23.61

9.25

2.35

2.55

8.51

Mean relative error

determining the CMC of SDS solutions with these electrolytes at 25 and 60 °C.

Conclusion Since the CMC of SDS has a major effect on particle size distribution of latex produced by emulsion polymerization systems, the critical micelle concentrations of sodium dodecyl sulfate were measured in the presence of various amounts of sodium carbonate and potassium persulfate, which are widely used materials in these systems, at 25 and 60 °C. Similarly, the CMC of SDS were determined in the presence of some monomers that are essential materials in emulsion polymerization systems at 25 °C. In these cases, the values of the degree of dissociation a were obtained, as well. Moreover, the other micellization parameters of SDS such as r, Ao, Pm, and Vp were calculated at 25 °C which are reported.

4.49

In addition, due to the importance of the presence of sodium carbonate and potassium persulfate simultaneously, in the reaction media of emulsion polymerization, the effects of the combination of these electrolytes with various concentrations on the CMC of the SDS were determined at 60 °C (temperature of reaction). In all cases, acceptable empirical formulas for estimation of the CMC were derived which allow the prediction of the CMC at a given electrolyte or monomer concentration. The values of the CMC and a of SDS solutions have been shown to depend on the kind and concentration of the electrolyte and monomer, this is represented in Figs. 2, 3, 4, 5. In all cases, the reduction in the CMC with increasing electrolyte and monomer concentration, were observed. For KPS and styrene, it was found that the degree of dissociation decreases with increasing concentration; however, for Na2CO3, MMA, and BA, a increases with increases in the concentrations of electrolytes and monomers. Conductometric titration provides a simple and swift

123

278

way to compute CMC values, but has the disadvantage of the lack of sensitivity at high temperature, where the values of the CMC are low.

References 1. Dutkiewiez E, Jakubowska A (2002) Effect of electrolytes on physiochemical behavior of sodium dodecyl sulfate micelles. Colloid Polym Sci 280:1009–1014 2. Shah SS, Jamroz NU, Sharif QM (2001) Micellization parameters and electrostatic interactions in micellar solution of sodium dodecyl sulfate (SDS) at different temperatures. Colloids Surf A 178:199–206 3. Behara K, Pandy S (2007) Modulating properties of aqueous sodium dodecyl sulfate by adding hydrophobic ionic liquid. J Colloid Interface Sci 316:803–814 4. Fuguet E, Rafols C, Roses M, Bosch E (2005) Critical micelle concentration of surfactants in aqueous buffered and unbuffered systems. Anal Chim Acta 548:95–100 5. Carswell ADW, Lowe AM, Wei X, Grady BP (2003) CMC determination in the presence of surfactant-adsorbing inorganic particulates. Colloids Surf A 212:147–153 6. Umlong IM, Ismail K (2007) Micellization behavior of sodium dodecyl sulfate in different electrolyte media. Colloids Surf A 299:8–14 7. Umlong IM, Ismail K (2006) Micellization behavior of sodium dodecylsulfate and dioctyl sulfosuccinate in the presence of sodium salicylate. J Surface Sci Technol 22:101–117 8. Bravo C, Leis JR, Pena ME (1992) Effect of alcohols on catalysis by dodecyl sulfate micelles. J Phys Chem 96:1957–1961 9. Gharibi H, Razavizadeh BM, Rafati AA (1998) Electrochemical studies associated with the micellization of dodecyltrimethyl ammonium bromide (DOTAB) in aqueous solutions of ethanol and 1-propanol. Colloids Surf A136:123–132 10. Weerts PA (1990) Emulsion polymerization of butadiene: a kinetic study, Ph.D. Thesis, Eindhoven University of Technology 11. Paul BC, Islam SS, Ismail K (1998) Effect of acetate and propionate co-ions on the micellization of sodium dodecyl sulfate in water. J Phys Chem B 102:7807–7812 12. Bales BL, Messina L, Vidal A, Peric M (1998) Precision relative aggregation number determinations of SDS micelles using a spin probe. A model of micelle surface hydration. J Phys Chem B 102:10347–10358 13. Quina FH, Nassar PM, Bonilha JBS, Bales BL (1995) Growth of sodium dodecyl sulfate micelles with detergent concentration. J Phys Chem 99:17028–17031

123

J Surfact Deterg (2013) 16:271–278 14. Moroi Y, Otonishi A, Yoshida N (1999) Micelle formation of sodium 1-decanesulfonate and change of micellization temperature by excess counterion. J Phys Chem B 103:8960–8964 15. Moroi Y, Sakamoto Y (1988) Solubility and micelle formation of p-n-alkylbenzoic acids. J Phys Chem 92:5189–5192 16. Moriyama E, Lee J, Moroi Y, Abe Y, Takahashi T (2005) Micelle formation of N-(1,1-dihydroperfluorooctyl)- and N-(1,1-dihydroperfluorononyl)-N,N,N-trimethylammonium chlorides. Langmuir 21:13–18 17. Bhat MA, Dar AA, Amin A, Rather GM (2008) Co- and counterion effect on the micellization characteristics of dodecylpyridinium chloride. J Dispersion Sci Technol 29:514–520 18. Gunaseelan K, Ismail K (2003) Estimation of micellization parameters of sodium dodecyl sulfate in water ? 1-butanol using the mixed electrolyte model for molar conductance. J Colloid Interface Sci 258:110–115

Author Biographies Saeed Naderi Miqan is a chemical engineer who graduated in the field of thermodynamic and kinetics from the University of Sistan and Baluchestan in 2010. His M.Sc. degree is on the investigation of the mathematical modeling of kinetics of the nucleation and growth of nano-particles during emulsion polymerization using conductimetry. He has been working on this issue since 2010. Farshad Farshchi Tabrizi received his Ph.D. in 2004 from the University Claude Bernard, Lyon-France for his study on the online monitoring of emulsion polymerization by conductimetry and calorimetry. He then returned to the University of Sistan and Baluchestan, Zahedan-Iran, as an assistant professor in chemical engineering and became an associate professor in 2010. Hossein Abedini is an assistant professor in chemical engineering in the process modeling and control group in the Polymerization Engineering Department of the Iran Polymer and Petrochemical Institute. He received his M.Sc. and Ph.D. from the Sharif University of Technology, in 2001 and 2008, respectively. His areas of interest are modeling, simulation, and control of polymerization processes. Hossein Atashi is a full professor in chemical engineering. He received his B.Sc., M.Sc., and Ph.D. from the Technische Universita¨t Vienna, Austria in 1972, 1974 and 1978, respectively. In 1978, he joined the University of Sistan and Baluchestan. His areas of interest are kinetics and reactor design, catalyst and nano-catalyst preparation.