Determination of Critical Micelle Concentration
`(CMC) of Nonionic Surfactants by Donor–Acceptor
`Interaction with Iodine and Correlation of CMC
`with Hydrophile–Lipophile Balance and Other
`Parameters of the Surfactants
`Samik Kumar Hait and Satya Priya Moulik*
`Centre for Surface Science, Department of Chemistry, Jadavpur University, Calcutta 700 032,West Bengal, India
`
`ABSTRACT: The nonionic surfactants form donor–acceptor
`complexes with iodine in aqueous medium. The spectral ab-
`sorption and the shift in the λ
`max of I2 upon complexation have
`been exploited to determine the critical micelle concentration
`(CMC) of Tweens, Brijs, and Triton X-100. The CMC values ob-
`tained closely agree with those determined by other meth-
`ods, including measurements of static surface tension, differ-
`ential refractive index, and iodine solubilization. The spectral
`characteristics of the complex salt KI3 can be utilized as well
`to derive similar information. The CMC and the spectral shift
`can be correlated with the weight fraction of the polyoxyeth-
`ylene groups and the hydrophile–lipophile balance (HLB) in
`various ways, with the parameters in these relationships de-
`pending on the series to which the surfactant belong. Because
`both CMC and HLB depend on temperature, the results and
`the relations obtained are temperature-dependent; those
`presented are with reference to 298 K.
`Paper no. S1214 in JSD 4, 303–309 (July 2001).
`
`KEY WORDS: CMC, Donor–acceptor complex, CMC, HLB,
`iodine, nonionic surfactants.
`
`Amphiphiles consisting of nonpolar and polar sections in
`their molecules have dual affinity for water and oil (1).
`Under specific environmental conditions, they may self-or-
`ganize or associate to form “micelles.” Nonionic am-
`phiphiles (surfactants), viz., Tweens, Brijs, Spans, Myrjs, and
`Triton Xs, have a vast array of chemical, biochemical, and
`pharmaceutical applications. With the exception of the
`Spans, they usually have a distinct hydrophobic (HP) tail
`consisting of a polymethylene chain and a hydrophilic (HF)
`head consisting of varying numbers of polyoxyethylene
`(POE) groups. Depending on the molecular structure and
`type, a balance between hydrophilicity and hydrophobicity
`exists in surfactant molecules. This is called the hydrophile–
`lipophile balance or HLB, which is important in categoriz-
`ing surfactants as emulsifiers, detergents, etc. (2) (Table 1).
`
`Surfactants having greater hydrophobicity are more sur-
`face-active and vice versa. With increasing hydrophobicity
`in a homologous series, micelle formation becomes easier.
`Thus, HLB may be one of the fundamental properties of
`surfactants, especially of nonionic surfactants, in relation to
`their self-association. HLB was estimated from the chemical
`formulas of surfactants by Griffin (3). Hydrophilic surfac-
`tants having high water solubility are good stabilizers for oil-
`in-water (o/w) emulsions and have higher HLB values.
`Those with low water solubility have lower HLB and they are
`good stabilizers for water-in-oil (w/o) emulsions. For non-
`ionic surfactants with polyoxyethylene groups, the HLB can
`be obtained from Equation 1 (3):
`
`HLB = (mol% of hydrophilic group)/5
`
`[1]
`
`In such a scheme, the maximum HLB of an unsubstituted
`nonionic surfactant would be 20. Semiempirical ways of de-
`termining HLB (4) have shown that ln Co [Co is the critical
`micelle concentration (CMC) of a nonionic surfactant, ex-
`pressed in g/dL × 104] is linearly related to the number of
`carbon atoms in the surfactant molecule.
`The CMC of surfactants can be determined by a number
`of methods, including tensiometry, conductometry, viscom-
`etry, light scattering, fluorimetry, calorimetry, spectropho-
`tometry, and nuclear magnetic resonance (NMR) spec-
`troscopy (1). The most frequently used methods are ten-
`siometry, fluorimetry, and spectrophotometry. When the
`
`TABLE 1
`Uses of Surfactants in Terms of the Range of Hydrophile–
`Lipophile Balance (HLB) Valuesa
`
`HLB ranges
`
`Uses
`
`3 – 6
`7 – 9
`8 – 15
`13 – 15
`15 – 18
`
`Water-in-oil emulsions
`Wetting agents
`Oil-in-water emulsions
`Detergents
`Solubilizers
`
`* To whom correspondence should be addressed.
`E-mail: cssju@yahoo.co.uk
`
`aReference 2.
`
`Copyright © 2001 by AOCS Press
`
`Journal of Surfactants and Detergents, Vol. 4, No. 3 (July 2001)
`
`303
`
`Page 1 of 7
`
`SENJU EXHIBIT 2047
`INNOPHARMA v. SENJU
`IPR2015-00903
`
`

`
`A (for 286 nm)
`
`304
`
`S.K. HAIT AND S.P. MOULIK
`
`A(for 346 and 460 nm)
`
`values of the measured physical properties are plotted
`against concentration, there are usually breaks in the plots,
`which are considered as the CMC points for the surfactants
`under investigation. Plotting the derivatives of the values
`may also be a convenient way of precisely locating the CMC
`(5).
`In this work, a detailed investigation of the spectral behav-
`ior of nonionic surfactant/iodine system has been made. The
`surfactants employed in this study include Tweens, Brijs, and
`Triton X-100 (TX-100). The spectral shifts of I2 and the KI3
`complex in the surfactant solutions have been exploited to
`derive information on the CMC. The possible correlations
`among the CMC, HLB, and other useful physicochemical pa-
`rameters, relevant to the systems, have been investigated. Al-
`though studies dealing with I2/nonionic surfactant systems
`have been reported in the literature (6–10), there has been
`only limited investigation of the determination of CMC by the
`method described here.
`
`MATERIALS AND METHODS
`
`The iodine used was the resublimed product of May and
`Baker Ltd. (Dagenham, England). The nonionic surfac-
`tants Tween-20, -40, -60, -80, and Triton X-100 were prod-
`ucts of Sigma Chemical Co. (St. Louis, MO), Brij-35 and -56
`of E. Merck (Darmstadt, Germany), and Brij-76 of Aldrich
`Chemical Co. (Milwaukee, WI). Triply distilled water was
`employed in the preparation of solutions.
`Spectral measurements were taken with a temperature-
`compensated ultraviolet (UV)-visible recording spectropho-
`tometer (UV-160A; Shimadzu, Kyoto, Japan) using a
`matched pair of quartz cells having a pathlength of 1 cm.
`In one set of experiments, 2.5 mL of a saturated aqueous
`solution of iodine was placed in each of a number of stop-
`pered and calibrated test tubes, and varying amounts of sur-
`factant solution were added. The solutions were made up
`to a volume of 10 mL by adding water. Their spectra were
`recorded after temperature equilibration at 298 K, and the
`absorbances at 286, 346, and 460 nm were measured. The
`absorbance maximum (λ
`max) of I2 in each solution, which
`showed a blue shift from 460 nm with increasing concentra-
`tion of the nonionic surfactant, was also measured.
`In another set of experiments, 0.5 mL of 0.01 M KI3 so-
`lution (prepared by adding KI to a saturated iodine solu-
`tion) was placed in several graduated test tubes and the vol-
`ume was brought to 10 mL by addition of both surfactant
`solution and water in requisite amounts. The absorbances
`of each solution at 286, 320, 346, and 460 nm were mea-
`sured. All measurements were taken at a temperature of 298
`± 0.2 K.
`
`[TX-100] × 104
`FIG. 1. Absorbance vs. concentration plot for Triton X-100 (TX-100)
`and I2 (33.46 × 10-5 M) at 286, 346, and 460 nm at 298 K. The break in
`each plot is the critical micelle concentration (CMC) point.
`
`containing both I2 and KI3. It has similarity with the plots
`reported by Ross and Oliver (11).
`A blue shift of the λ
`max of I2 from 460 nm was observed
`in nonionic surfactant medium. Fluorescence measure-
`ments in micellar media of certain dyes also show blue shifts
`(12). The observed blue shift is attributed to the ability of
`the ether oxygen of the POE groups in the surfactant mole-
`cules to donate electrons to the vacant σ* orbital of I2 (13),
`resulting in the formation of a surfactant–iodine donor–ac-
`ceptor type complex. The extent of the blue shift depends
`on the nature of the nonionic surfactant. The spectra of I2
`between 300 and 600 nm in the absence and in the pres-
`ence of TX-100 are presented in Figure 2. With increasing
`
`A
`
`RESULTS AND DISCUSSION
`
`The critical micellar concentration. Figure 1 shows plots of ab-
`sorbance at different wavelengths vs. surfactant concentra-
`tion for TX-100 solutions containing both I2 and KI3. The
`plots show breaks in the region of the CMC for solutions
`
`λ(nm)
`FIG. 2. Absorption spectra of TX-100 and I2 (33.46 × 10-5 M) at 298 K.
`Curve 1 I2; curves 2–4, [TX-100] = 5 × 10-5, 10 × 10-5, and 20 × 10-5 M,
`respectively (below CMC curve 5, [TX- 100] = 25 × 10-5 M (around
`CMC) ; curve 6, [TX-100] = 30 × 10-5 M (above CMC). See Figure 1 for
`abbreviation.
`
`Journal of Surfactants and Detergents, Vol. 4, No. 3 (July 2001)
`
`Page 2 of 7
`
`

`
`DETERMINATION OF (CMC)
`
`305
`
`TABLE 2
`Critical Micelle Concentration (CMC) of Nonionic Surfactants
`Obtained by Surface Tension (ST) and Spectral Measurements
`in the Presence of I2 at 298 K
`CMC × 105 (mol dm–3)
`Absorbanceb
`
`Surfactant
`
`STa
`
`b
`
`Shift in λ
`max
`5.57
`2.10
`1.96
`1.15
`4.75
`0.43
`0.38
`22.5
`
`Tween 20
`Tween 40
`Tween 60
`Tween 80
`Brij 35
`Brij 56
`Brij 76
`Triton X-100
`aReference 3.
`bThis study.
`
`4.88
`2.26
`2.06
`0.99
`6.00
`0.20
`0.30
`24.0
`
`5.50
`2.30
`2.09
`1.05
`3.80
`0.40
`0.38
`24.0
`
`dm−3 at 298 K for TX-100 and Tween-20, respectively. These
`minima are considered to correspond to the respective CMC.
`The CMC of the nonionic surfactants determined by spectral
`measurements of their interaction with I2 are listed in Table 2,
`together with tensiometric literature data (6). The results ob-
`tained in this study closely agree with the data available in the
`literature.
`The characteristic plots of absorbance (A) vs. [TX-100]
`at 286, 346, and 460 nm (Fig. 1) have crossing points at 23
`× 10−5, 23 × 10−5, and 24 × 10−5 mol dm−3, respectively. These
`CMC values agree nicely with the literature value of 24 ×
`10−5 mol dm−3 (6). The spectra of I2 at [TX-100] > CMC be-
`come symmetrical, with no further shift of λ
`max at 280 nm
`(Fig. 5). Plots of the absorbance of KI3 at 286 and 346 nm
`against concentration of nonionic surfactants show distinct
`intersection points that are considered to correspond to
`their CMC. A representative plot is shown in Figure 6. The
`derivative plots to determine the CMC (inset, Figs. 3 and 4)
`are according to Zhao et al. (14).
`Rationalization of spectral observations. The nonionic sur-
`factants are referred to as iodophores or I2 carriers and re-
`
`[TX-100] × 104 (M)
`
`max(nm)
`
`λ
`
`[TX-100] × 104 (M)
`FIG. 3. Dependence of λ
`max of TX-100-I2 system on [TX-100] at 298 K.
`Inset: Second degree differential plot of the variation of λ
`max with [TX-
`100]; Gaussian fit, showing the minimum as CMC. See Figure 1 for ab-
`breviations.
`
`concentration of TX-100, the 460-nm peak of I2 is increasingly
`blue-shifted and the absorbance increases. A plot of λ
`max vs.
`surfactant concentration shows a sharp decline in the CMC
`region. When the derivative of a function consisting of two dif-
`ferent linear segments is plotted, a step function is obtained.
`The second derivative (5) of the original function would show
`a positive or negative peak, the position of which corresponds
`to the intersection point of the two nearly linear segments of
`the original function. The estimation of the break, herein the
`CMC, thus becomes less ambiguous. The blue shift of the λ
`max
`of I2 from 460 nm and the second-degree differential plots for
`TX-100 and Tween-20 are presented in Figures 3 and 4, re-
`spectively. The second-degree differential plots exhibit sharp
`minima at concentrations of 22.5 × 10−5 and 5.57 × 10−5 mol
`
`[TX-20] × 105 (M)
`
`A
`
`max(nm)
`
`λ
`
`[TX-20] × 105 (M)
`FIG. 4. Dependence of λ
`max of Tween-20-I2 system on [Tween-20] at
`298 K. Inset: Second degree differential plot of the variation of λ
`max
`with [Tween-20]; Gaussian fit, showing the minimum as CMC is shown
`in inset. See Figure 1 for abbreviation.
`
`λ (nm)
`FIG. 5. Absorption spectra of TX-100 solutions treated with I2 at 298
`K. Curves 1–6 represent [TX-100] = 0.0, 50 × 10−5, 75 × 10−5, 100 × 10−5,
`125 × 10−5, and 150 × 10−5 M, respectively. All the concentrations are
`above the CMC. See Figure 1 for abbreviations.
`
`Journal of Surfactants and Detergents, Vol. 4, No. 3 (July 2001)
`
`Page 3 of 7
`
`

`
`S.K. HAIT AND S.P. MOULIK
`
`306
`
`A
`
`[Tween-60] × 105 (M)
`FIG. 6. Absorbance at 346 and 460 nm of Tween-60 and KI3 (19.7 ×
`10−5 M) vs. [Tween 60] at 298 K. The break points in each plot are the
`CMC point. See Figure 1 for abbreviation.
`
`tain their surfactant properties when complexed with I2.
`The nature of the nonionic surfactant–iodine bond is not
`completely understood. Complexation by POE oxygen has
`been considered to be a plausible mechanism (15–18),
`which is supported by the failure of solvents such as CCl4 to
`extract I2 from the complex. In solution, the dissolved I2 is
`in equilibrium with I2 in micelles or I2-micelle complexes.
`An NMR study in CCl4 provided evidence that a donor–ac-
`ceptor type complex is formed between TX-100 and I2 (19).
`In a nonaqueous medium such as CCl4, a charge-transfer
`type complex between TX-100 and I2 has been reported
`(13). A distinct isosbestic point corresponding to the for-
`mation of a 1:1 complex was observed. Such complexes with
`the ether oxygen as electron donor and I2 as electron ac-
`ceptor are also formed by other nonionic surfactants. In our
`laboratory, a solid donor–acceptor complex between Brij
`–35 and I2 has been isolated and spectroscopically charac-
`terized. The results of this work are not presented for here
`because they are not in line with the objectives of this paper.
`CMC, HLB, and ∆λdata correlation. The general formulas
`of the nonionic surfactants of the Tween, Span, Brij, and
`TX-series are presented in Figure 7. It has been shown (6)
`that the weight fraction (W ) of POE groups in the molecule
`is directly proportional to the HLB of nonionic surfactants.
`We have found that the following relationship holds:
`
`HLB ≈ 20.00
`W
`
`[2]
`
`where W is given by the relation (3)
`
`[3]
`
`= 44R
`44R
`W =
`44R + M1
`M 0
`
`where M1, M0, and R are, respectively, the molecular weight
`of the lipophilic moiety, the molecular weight of the surfac-
`tant, and the polyoxyethylene mole ratio in the molecule.
`On the basis of this rationale, the HLB value of Myrj 59 is
`18.8. We have observed that, for the nonionic surfactants,
`plots of ln C0 (where C0 is the CMC of the surfactant, in
`units of g/dL × 104) vs. HLB are linear,
`
`ln C0 = A + B(HLB)
`[4]
`When the CMC values are in units of mole dm−3, similar lin-
`ear plots should be obtained with different magnitudes of
`
`FIG. 7. Structural formulas of nonionic surfactants: A, Tween; B, Span;
`C, Brij; D, Triton X.
`
`the constants A and B. The values of W, HLB, HLB/W, and
`CMC for four series of nonionic surfactants are presented
`in Table 3. The values of the constants A and B are given in
`Table 4. The maximum HLB value of nonionic surfactants
`is 20 (3). The results in Table 3 show that all the HLB/W
`values are also around 20 except in the case of Tweens, for
`which the average value is 23. The W value of a nonionic
`surfactant is therefore related to its HLB. Low values of
`HLB, as in the case of Triton X-15 and Triton X-35, corre-
`spond to low values of W. Values of HLB close to 20 corre-
`spond to values of W close to unity.
`By using the above relation, the CMC of the nonionic
`surfactants can be predicted. Thus, the CMC of Triton X-
`15, Triton X-35, and Triton X-705 at 298 K [not available in
`the literature (20)] are predicted to be 0.015, 0.048, and
`1.04 mM, respectively. In Table 3, the CMC values normally
`unavailable in the literature are enclosed in parentheses.
`We are not aware of any report of the self-aggregation be-
`havior of Myrjs in aqueous solution except for that of Sul-
`tana et al. (21) on Myrj 45. The CMC at 298 K obtained by
`extrapolation of the results at different temperatures re-
`ported by Sultana et al. (21) is presented in Table 3. Because
`CMC values for one or two other Myrjs are not available,
`evaluation of CMC values for Myrjs using Equation 4 has not
`been possible. Because Spans have a sorbitan head group,
`rather than a POE head group in the molecules, the rela-
`
`Journal of Surfactants and Detergents, Vol. 4, No. 3 (July 2001)
`
`Page 4 of 7
`
`

`
`DETERMINATION OF (CMC)
`
`307
`
`TABLE 3
`Physicochemical Parameters of Nonionic Surfactant Series
`
`Chemical nameb
`
`Trade name
`
`Molecular weight
`
`W
`
`HLB
`
`HLB/W
`
`Tween series
`POE(20) sorbitan monolaurate
`POE(20) sorbitan monopalmitate
`POE(20) sorbitan monostearate
`POE(20) sorbitan monooleate
`POE(20) sorbitan tristearate
`POE(20) sorbitan trioleate
`
`Myrj series
`POE(8) stearate
`POE(40) stearate
`POE(50) stearate
`POE(100) stearate
`
`Triton X (TX) series
`p-t-O-P-POE(1)E
`p-t-O-P-POE(3)E
`p-t-O-P-POE(5)E
`p-t-O-P-POE(7.5)E
`p-t-O-P-POE(9.5)E
`p-t-O-P-POE(12.5)E
`p-t-O-P-POE(16)E
`p-t-O-P-POE(30)E
`p-t-O-P-POE(40)E
`p-t-O-P-POE(70)E
`
`Tween 20
`Tween 40
`Tween 60
`Tween 80
`Tween 65
`Tween 85
`
`Myrj 45
`Myrj 52
`Myrj 53
`Myrj 59
`
`TX-15
`TX-35
`TX-45
`TX-114
`TX-100
`TX-102
`TX-165
`TX-305
`TX-405
`TX-705
`
`1227.54
`1283.65
`1311.70
`1309.68
`1899.54
`1838.60
`
`635
`2043
`2483
`4683
`
`250
`338
`426
`536
`625
`756
`910
`1526
`1966
`3286
`
`0.7168
`0.6855
`0.6708
`0.6719
`0.4632
`0.4786
`
`0.5543
`0.8614
`0.8860
`0.9395
`
`0.1761
`0.3905
`0.5164
`0.6156
`0.6688
`0.7275
`0.7736
`0.8650
`0.8952
`0.9373
`
`16.7
`15.6
`14.9
`15.0
`10.5
`11.0
`
`11.1
`16.9
`17.9
`18.8
`
`3.6
`7.8
`10.4
`12.4
`13.5
`14.6
`15.8
`17.3
`17.9
`18.7
`
`23.29
`22.75
`22.21
`22.32
`22.66
`22.98
`
`20.024
`19.617
`20.202
`20.011
`
`20.45
`19.97
`20.14
`20.14
`20.19
`20.06
`20.42
`20.00
`20.00
`19.95
`
`CMCa
`(mM)
`
`0.050
`0.023
`0.021
`0.010
`(0.00018)
`(0.00029)
`
`0.373
`
`(0.0145)
`(0.047)
`0.100
`0.168
`0.240
`0.350
`0.439
`0.720
`0.810
`(1.0413)
`
`Brij series
`362
`Brij 30
`POE(4) lauryl ether
`1198
`Brij 35
`POE(23) lauryl ether
`330
`Brij 52
`POE(2) cetyl ether
`682
`Brij 56
`POE(10) cetyl ether
`1120
`Brij 58
`POE(20) cetyl ether
`358
`Brij 72
`POE(2) stearyl ether
`710
`Brij 76
`POE(10) stearyl ether
`1096
`Brij 78
`POE(20) stearyl ether
`356
`Brij 92
`POE(2) oleyl ether
`710
`Brij 97
`POE(10) oleyl ether
`1094
`Brij 99
`POE(20) oleyl ether
`4670
`Brij 700
`POE(100) stearyl ether
`1194
`Brij 721
`POE(21) stearyl ether
`aCMC at 298 K; values in parentheses are normally unavailable in the literature.
`bPOE, polyoxyethylene; p-t-O-P-POE(x)E = p-tert-octyl phenoxy polyoxy(x) ether; where x is the number of POE groups. W, weight fraction; for other
`abbreviations see Tables 1 and 2.
`
`0.4862
`0.8447
`0.2666
`0.6452
`0.7857
`0.2458
`0.6197
`0.8029
`0.2472
`0.6197
`0.8043
`0.9421
`0.7738
`
`9.7
`16.9
`5.3
`12.9
`15.7
`4.9
`12.4
`15.3
`4.9
`12.4
`15.3
`18.8
`15.5
`
`19.95
`20.01
`19.88
`20.00
`19.98
`19.93
`20.01
`19.01
`19.82
`20.01
`19.02
`19.95
`20.03
`
`0.004
`0.060
`(0.000067)
`0.002
`0.007
`(0.00025)
`0.003
`(0.0057)
`(24.845)
`0.940
`0.265
`0.020
`0.0039
`
`tion in Equation 2 is not applicable to them. They have very
`low solubility in water and do not form normal micelles.
`Consequently, the parameters W and HLB/W are not
`meaingful in their case.
`The CMC values of nonionic surfactants depend on the
`length of both the lipophilic and hydrophilic parts of their
`
`TABLE 4
`The Values of the Constants A and B in Equation 4 for the
`Tween, Brij, and Triton X Series at 298 K
`
`Series
`
`Tween
`Brij (lauryl)
`Brij (cetyl)
`Brij (xtearyl)
`Brij (oleyl)
`Triton X
`aCorrelation coefficients.
`
`A
`
`–10.49
`–14.10
`–16.96
`–16.18
`0.86
`–10.65
`
`B
`
`0.88
`0.54
`0.625
`0.59
`–0.29
`0.48
`
`r a
`
`0.9804
`0.9990
`0.9990
`0.9528
`0.9990
`0.9945
`
`molecules. The CMC decreases with increasing length of
`the hydrophobic moiety for a fixed hydrophilic group. The
`CMC of nonionic surfactant decreases with decreasing POE
`content in the molecule. These results may be correlated by
`plotting ln ∆λ vs. HLB, where ∆λ is the shift in the λ
`max of
`I2 in the surfactant solution in the CMC region for the dif-
`ferent surfactant series. Thus,
`ln ∆λ = C + D ln (HLB)
`[5]
`where C and D values are appropriate constants given in
`Table 5. The plots of ln ∆λ vs. ln HLB are shown in Figure 8.
`In a nonionic surfactant series, the number of carbon
`atoms in the lyophilic and lyophobic parts of the molecule may
`essentially control its physicochemical nature, which is re-
`flected in the spectral behavior of the complex with I2. A rela-
`tion of the form
`ln ∆λ = L + M ln (NC
`Journal of Surfactants and Detergents, Vol. 4, No. 3 (July 2001)
`
`head – NC
`
`tail)
`
`[6]
`
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`S.K. HAIT AND S.P. MOULIK
`
`308
`
`ln ∆λ
`
`tion and discussion. The financial support from University Grants
`Commission, Government of India, in the form of a Junior Re-
`search Fellowship to S.K.Hait is thankfully acknowledged.
`
`REFERENCES
`1. Moulik, S.P., Micelles: Self-Organized Surfactant Assemblies,
`Curr. Sci. 71:5 (1996).
`2. Becher, P., Emulsions: Theory and Practice; 2nd edn. Reinhold
`Publishing Corp., New York, 1965; Myers, D., Surfactant Science
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`3. Becher, P., Nonionic Surfactants, Marcel Dekker, New York,
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`celle Concentrations of Water Soluble Ether-Alcohols, J. Phys.
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`5. Mosquera, V., A Comparative Study of the Determination of
`the Critical Micelle Concentration by Conductivity and Dielec-
`tric Measurements, Langmuir 14:4422 (1998).
`6. Schick, M.J., Nonionic Surfactants, Lever Bros. Co. Research
`Centre, Edgewater, New Jersey, 1969.
`7. Elworthy, P.H., The Critical Micelle Concentration of Ce-
`tomacrogol 1000, J. Pharm. Pharmacol. 12:293 (1960).
`8. Matsumoto, T., and T. Kenjo, The Interaction of Nonionic Sur-
`factants with Iodine. “Iodine Number” of Polyethoxy Deriva-
`tives, J. Jpn. Oil Chem. Soc. 16:48 (1961).
`9. Matsumoto, T., and T. Kenjo, The Interaction of Nonionic Sur-
`factants with Iodine. Displacement of Absorption Maximum
`Spectrum of Aqueous Polyethoxy Ether–Iodine Solution, J.
`Jpn. Oil Chem. Soc. 16:418; 683 (1961).
`10. Carless, J.E., R.A. Challis, and B.A. Mulley, Nonionic Surface
`Active Agents Part V. The Effect of the Alkyl and the Polygly-
`col Chain Length on the Critical Micelle Concentration of
`Some Monoalkyl Polyethers, J. Colloid Sci. 19:201 (1964).
`11. Ross, S., and J.P. Olivier, A New Method for the Determination
`of Critical Micelle Concentrations of Un-ionized Association
`Colloids in Aqueous or in Non-Aqueous Solution, J. Phys. Chem.
`63:1671 (1959).
`12. Bhattacharyya, K., and A. Nag, Fluorescence Enhancement of
`p-Toluidino Naphthalenesulphonate in a Micellar Environ-
`ment, J. Photochem. Photobiol. 47:97 (1989).
`13. Rohatgi Mukherjee, K.K., S.C. Bhattacharya, and B.B.
`Bhowmik, Charge Transfer Interaction of Micelle and Re-
`versed Micelle of Triton X-100 with Iodine, Indian J. Chem.
`22a:911 (1983).
`14. Zhao, J., S.D. Christian, and B.M. Fung, Mixtures of
`Monomeric and Dimeric Cationic Surfactants, J. Phys. Chem. B.
`102:39 (1998).
`15. Hugo, W.B., and J.H. Newton, The Solubility of Iodine in
`Aqueous Solutions of Nonionic Surface Active Agents, J.
`Pharm. Pharmacol. 15:731 (1963).
`16. Hugo, W.B., and J.H. Newton, The Adsorption of Iodine from
`Solution by Micro-organisms and by Serum, J. Pharm. Pharma-
`col. 16:49 (1964).
`17. Hugo, W.B., and J.H. Newton, The Antibacterial Activity of a
`Complex of Iodine and a Nonionic Surface-Active Agent, J.
`Pharm. Pharmacol. 16:189 (1964).
`18. Hugo, W.B., and J.H. Newton, The Stability Staining and Cor-
`rosive Properties of an Iodine–Nonionic Surface-Active Agent
`Complex, J. Pharm. Pharmacol. 16:273 (1964).
`19. Rakshit, A.K., and S. Dixit, Proton NMR Study of Triton X-100
`Reverse Micellar System in CCl4, J. Surf. Sci. Technol. 2:97
`(1986).
`20. http : //www. Sigma sial. Com/sigma/proddata/
`21. Sultana, S.B., S.G.T. Bhat, and A.K. Rakshit, Thermodynamics
`of Micellization of a Nonionic Surfactant Myrj 45: Effect of Ad-
`ditives, Colloids Surf. A 111:57 (1996).
`
`Received August 10, 2000; accepted March 15, 2001]
`
`ln HLB
`FIG. 8. Dependence of ln ∆λ on ln HLB for Tweens and Brijs at 298
`K. HLB, hydrophile–lipophile balance.
`
`ln ∆λ
`
`tail)
`head – NC
`ln (HC
`FIG. 9. Dependence of ln ∆λ on ln(NC
`head – NC
`Brijs at 298 K.
`
`tail) for Tweens and
`
`TABLE 5
`The Values of the Constants C and D in Equation 5 and L and M
`in Equation 6 for Tweens and Brijs at 298 K
`
`Series
`
`Tween
`Brij
`
`C
`
`–7.47
`3.647
`
`D
`
`0.607
`–0.079
`
`L
`
`–24.280
`5.602
`
`M
`
`9.570
`–1.167
`
`has been observed to be obeyed, where L and M are con-
`tail represent the number of car-
`head and NC
`stants, and NC
`bon atoms in the POE head and the hydrocarbon tail, re-
`spectively. The validity of the relation is exemplified in Fig-
`ure 9. The evaluated constants L and M are presented in
`Table 5. The shift in the λ
`max of the donor–acceptor com-
`plex of I2 with the nonionic surfactants is thus found to be
`a useful parameter in the study of their solution behavior.
`
`ACKNOWLEDGMENTS
`We thank Professor B.B. Bhowmik, Center for Surface Science, De-
`partment of Chemistry, Jadavpur University, for necessary informa-
`
`Journal of Surfactants and Detergents, Vol. 4, No. 3 (July 2001)
`
`Page 6 of 7
`
`

`
`DETERMINATION OF (CMC)
`
`309
`
`Samik K. Hait is a UG C junior research fellow of the University
`Grants Commission, Government of India at the Department of
`Chemistry, Jadavpur University. He received his B.Sc. (Chemistry
`Hon’s.) and M.Sc. (Physical Chemistry) degree from the Jadavpur
`University. He has interest in the field of surface science and bio-
`physical chemistry, and is working on problems related to the micel-
`lization of surfactants and interaction of surfactants and model
`drugs with natural and synthetic biopolymers.
`Satya P. Moulik is a Professor of Chemistry and the Co-ordina-
`tor of the Centre for Surface Science at Jadavpur University, Cal-
`
`cutta. He is a fellow of the Indian National Science Academy. He
`was the Chief Editor of the journal of Surface Science and Technol-
`ogy, and presently he is its editorial advisor. He held the position of
`James Chair professor at St. Francis Xavier University, Nova Sco-
`tia, Canada, and is the president of the Indian Society for Surface
`Science and Technology. His research interests are in surface and
`biophysical chemistry with special reference to micelles, microemul-
`sions, liposomes and interaction of polymers and biopolymers with
`small molecules especially drugs and surfactants. He has published
`10 review articles and 190 research papers.
`
`Journal of Surfactants and Detergents, Vol. 4, No. 3 (July 2001)
`
`Page 7 of 7