UNITED STATES DEPARTMENT OF COMMERCE 0 MAURICE H. STANS, Secretary
`
`NATIONAL BUREAU OF STANDARDS - LEWIS
`
`BRANSCOMB, Director
`
`Critical Micelle Concentrations of
`
`Aqueous Surfactant Systems
`
`Pasupati Mukerjee
`University of Wisconsin
`
`School of Pharmacy
`
`Madison, Wisconsin 53706
`
`and
`
`Karol J. Mysels
`
`R. J. Reynolds Tobacco Co.
`W1nston~Sa1em, North Carolina
`
`27102
`
`This compilation was prepared under contract for the
`Oflice of Standard Reference Data
`National Bureau of Standards
`Washington, D.C.
`20234
`
`NSRDS-NBS 36
`
`Nat. Stand. Ref. Data Ser., Nat. Bur. Stand. (U.S.), 36,227 pages (Feb. 1971)
`
`© 1970 by the Secretary of Commerce on Behalf of the United States Government
`
`CODEN: NSRDA
`
`Issued February 1971
`
`For sale by the Superintendent of Documents, U.S. Government Printing Office
`Washington, D.C. 20402 - Price $3.75
`
`HYDRITE EXHIBIT 1009
`
`(1 or 7)
`
`HYDRITE EXHIBIT 1009
`(1 OF 7)
`
`

`
`Critical Micelle Concentrations of Aqueous Surfactant Systems
`
`Pasupati Muker-jee* and Karol J. Myseis**
`
`Critical micelle concentrations (CMC’s), have been collected, organized and evaluated. The litera-
`ture has been scanned for numerical values from 1926 up to and including, 1966. In addition. over 800
`values. hitherto available only in graphical form or implied in experimental data, have been extracted
`from the publications and are included. Close to 5,000 entries, based on 333 references, dealing with
`720 compounds are tabulated in the main tables. Whenever available, the temperattire, any additives
`present, the method of determination and the literature source are given for each CMC value and an
`indication of the apparent quality of the preparation and method used are included. A shorter table
`gives selected values which are believed to be particularly reliable. including highly accurate ones.
`Among these, concordant values from at least two independent laboratories are emphasized.
`Included in the Introduction is a_ general discussion of the importance and significance of CMC
`values and of methods for their determination. as well as a summary of the procedures used in the
`collection, evaluation and presentation of these values in the present work. Extensive indexes are
`provided.
`
`Key words: Association colloid; bibliography; CMC; colloid; colloidal electrolyte; critical con-
`centration; critical micelle concentration; detergent; hydrophobic bonding; Krafft point;
`long chain
`compounds; micelle; paraffin chain salts; selected values; soap; solubilization; standard values; surface
`active agents; surface chemistry; surface tension; surfactant.
`
`Introduction
`1.
`Critical micelle concentrations are here to stay!
`This conclusion is evident from figures l to 3 which
`are based on the literature used in this work. They
`show a continuing growth since the middle thirties
`in the number of articles appearing each year which
`contribute new values and in the number of new
`values reported. The number of new values per
`article seems to have passed its peak, which sug-
`gests more careful and critical work in recent years.
`
`The reason for this growth is that a critical micelle
`concentration (CMC)
`is probably the
`simplest
`means of characterizing the colloid and surface
`behavior of a surfactant solute, which in turn deter-
`mines
`its
`industrial usefulness
`and biological
`activity, and gives a measure of the structurally
`interesting solute-solvent and solute-solute inter-
`actions. However, those published CMC values are
`widely scattered through the literature—we have
`consulted 87
`different publications—and vary
`greatly in quality from clearly erronemis data to
`highly accurate values.
`
`Furthermore, some of the existing values are
`clearly tabulated, but others— often the best ones-
`are hidden in graphs. or even in tabulations of some
`*.Present address: University of Wisconsin. .\-’la(ll5U|1. Wisconsin 53706.
`“Present address: Cull General Atomic. lncr. R0. Box 608. San Diego. California .
`92112.
`
`measured property such as conductivity. These re-
`quire considerable effort and judgment to retrieve.
`Frequently, the quality of the work cannot be judged
`without consultation of
`several
`references and
`
`intercomparison with other pertinent publications.
`‘Hence, much of the literature is not now readily .
`accessible or useful to those interested in learning
`what has been established mus far.
`
`The primary purpose of this publication is to
`provide a list of values in which the user can
`
`place high confidence. In the process of obtaining
`these, we had to make a survey, as complete as
`possible, of all available values. To present
`the
`results of this survey so as to make both the litera-
`ture and the results contained therein readily
`available became, therefore, a secondary objective.
`Perhaps the best evidence for the usefulness of
`this effort is that nearly two-thirds of the best data
`reported herein were not previously directly avail-
`able in the literature but required at least some,
`and often quite extensive, interpretation of a publica-
`tion or individual correspondence.
`The book itself is divided into four parts:
`(1) The Table of Recommended and Selected
`Values lists the values we believe to be most reliable.
`
`They contain further guides to the quality of the data.
`
`HYDRITE EXHIBIT 1009
`
`(2 or 7)
`
`HYDRITE EXHIBIT 1009
`(2 OF 7)
`
`

`
`Entries/paper 6
`
`En/r/es/year
`
`a yearly TOTCII
`o 3yr_ running average
`
`.
`'25 1930
`
`,1.
`
`.1...
`I940
`
`I J_J:J__J_JJ
`I950
`I960
`19?O
`
`FIGURE 1. Number of entries for the complete tables originating
`within each yearfrom 1927 to 1966.
`There are no entries in 1928, 1931, 1933, 1934-, 1937 and 1945.
`
`all values
`(2) The Complete Table contains
`found which were published through 1966.
`(3) Several
`indexes and lists, particularly the
`compound indexes,
`should permit
`the
`reader
`to find any desired compound or its closest analogs,
`give him the meaning of any abbreviation or symbol,
`and also guide him to the pertinent
`literature.
`(4) The Introduction discusses
`the thoughts
`that went into the collection, evaluation, and presen-
`tation of the data. A glance at “How to Use These
`Tables” may be helpful before consulting them.
`50
`
`0
`
`
`
`Papers/year
`
`GO
`
`'25
`
`.; . .’r_.J_»
`I930
`I940
`
`I950
`
`I960
`
`I970
`
`FIGURE 2. Number of papers containing at least one entry for
`the complete tables originating within a. given year.
`
`'25 I930
`
`I940
`
`1950
`
`I960
`
`I970
`
`FIGURE 3. Average number of entries per paper containing at
`least one entry within a given year and within a three year
`period.
`The largest number of entries from a single paper was 167. from reference 55004.
`
`We hope that this work will make us more friends
`than enemies. We tried to be objective in the evalua-
`tion of the data, but some errors and personal
`prejudices are unavoidable. Our evaluation pro-
`cedure of the individual data is described in the
`
`introduction, which contains also general considera-
`tions about
`the validity and significance of the
`various methods of determination.
`
`We are grateful to many who have helped us in
`this work. Close to a hundred authors have re-
`
`sponded to our request for reprints and many have
`provided additional comments, data, and inter-
`pretations. Dr. Edward L. Brady was most helpful
`in getting us started properly in the task of handling
`this multitude of data. Dr. H. J. White’s patience
`and cooperation are greatly appreciated. The
`extensive computer handling of the data was made
`possible by the free availability of the data process-
`ing facilities of the R. J. Reynolds Tobacco Co.,
`and the programming skill and understanding of
`Mr. Bill Donovan. Several secretaries have been
`involved in the careful verification of the hundreds
`of thousands of bits of information recorded. Mrs.
`
`Jerry Wilson and Miss Judy Tate were particularly
`involved in the final stages. The work leading to
`this publication was begun in 1964 at the University
`of Southern California under contract with the
`National Bureau of Standards and continued there
`until September 1966 when the authors transferred
`to their present connections with the University of
`Wisconsin, where the support of
`the National
`Bureau of Standards continued, and the R. J.
`
`HYDRITE EXHIBIT 1009
`
`(3 or 7)
`
`HYDRITE EXHIBIT 1009
`(3 OF 7)
`
`

`
`the resources of
`Reynolds Tobacco Co. Clearly,
`these three institutions made the completion of our
`work possible.
`
`2. How to Use the Tables
`
`This section presents a brief guide to the ad-
`mittedly complicated arrangement of the tables.
`Space and computer requirements dictated much of
`this complexity; some is inherent in the dissimi-
`larity of the compounds and the variety of conditions
`used for CMC determinations. The guide is arranged
`to answer a series of questions which may be raised
`by readers.
`How do Ifind the compound I am interested in? In
`the tables the compounds are arranged in numerical
`order by arbitrary “Compound Numbers.” To find
`this number you must go through the “Compound
`Index” in which the listed compounds are arranged
`by structure. There are five parts to this index (plus
`an alphabetical one for commercial names) and in
`each the compounds are listed according to different
`structural properties. These arrangements are de-
`scribed on the first page of the compound index
`(p. 23).
`Wfliut can I do if my compound is not listed? The
`indexes will lead you to the most closely related
`compounds that are listed. These should permit
`you to make a good giiess by interpolation and
`extrapolation.
`
`How do I learn about the eflect of an additive ? The
`names of additives are abbreviated (if the abbrevia-
`tion is not clear, its meaning can be found in the
`list on p. 222). Surfactant additives are indicated by
`their “Compound Number." For each compound,
`CMC values in the presence of additives are listed
`after the simple (surfactant-water) system in alpha-
`betical order of the abbreviations. This is followed
`by systems with two additives and then by those
`with three additives.
`
`listed with my
`if the additive is not
`What
`compound? The additive index shows all the com-
`pounds reported for any additive. You may find
`some useful analogies in this way.
`What is the efiect of temperature? Within each
`system (compound-additive(s))
`the
`values
`are
`arranged by increasing temperature. By checking
`the author, or better the reference column, you
`can locate groups of values that were obtained
`specifically to
`show the effect of
`temperature
`(which is often small).
`
`Which are the “good” CMC values? The shorter
`tables beginning on page 51 contain the “Selected”
`and “Recommended” values (15% of all reported
`values). Those that carry a “l” in the last column
`have been independently confirmed and should
`be highly reliable (to 1.5%, keeping in mind that
`different methods can give significantly different
`values—cf. p. 11). Those marked “2” are of the
`same
`apparent quality but
`lack confirmation.
`Among those marked “D” for each system, there
`is probably one that
`is as good as those of the
`preceding categories, but we do not know which.
`The many marked “3” do not seem to be in the same
`class but should be good to 10 percent.
`What do I find in the long tables? These tables
`beginning on page 66 contain all the “Recommended
`and Selected” values plus all
`the others that we
`have located. In a number of cases, indicated by
`“R” in the last column, we make references to the
`literature where
`additional data or calculated
`
`values may be found or to warn the reader that the
`values are duplicates of those already listed or
`are in error. The bulk of the values carry an “L”
`in the last column. These may be useful and some
`may be excellent but we could not “recommend”
`or “select” them for a variety of reasons. Some
`clue to these reasons may be found in the "quality”
`column.
`is the “quality” column? In this column
`What
`the first letter refers to the material and the second
`
`to the measurement. The meaning of the letters may
`be found on page 6. In general the quality decreases
`in alphabetical order.
`It represents our opinion
`after a careful study of the reference.
`Are there more data in the literature? Our
`Search does not cover anything published in 1967
`or later (including the 1964 Congress of Surface
`Activity which did not appear in print until 1968).
`There are also older references that we may have
`overlooked. All
`the references within this field
`that we have scanned are listed in the literature
`
`index starting on page 213 whether they have yielded
`any entries or not. We would like to be informed
`of overlooked articles. Some of
`the literature
`scanned does contain data which, if properly inter-
`pretcd, could lead to a CMC value which is not
`included. We have made such interpretations in
`many hundreds of cases, but not always. However,
`if 2 CMC value was mentioned as such in the article,
`we have tried to include it in all cases.
`
`What are those various “methods”? The “method”
`
`column contains generally an abbreviation of the
`
`HYDRITE EXHIBIT 1009
`
`(4 or 7)
`
`HYDRITE EXHIBIT 1009
`(4 OF 7)
`
`

`
`method by which the CMC value was obtained.
`These methods are discussed briefly (and their
`abbreviations given) on pages 8 to II. The “methods
`index” lists the references which have used each.
`These references should be consulted for details.
`
`Occasionally the methods column contains infor-
`mation about the literature or a cross-reference. This
`
`is only the case when the entry does not give a CMC
`value.
`
`In what units are the CMC’s? We have followed
`the references except for order of magnitude con-
`versions (e.g., from millimoles to moles) and as a
`result have a large number of units. The meaning
`of the abbreviations is given on page 222 and in the
`footnote to the table. For noncommercial com-
`
`pounds, for which a molecular weight is likely to
`have meaning, we have added a value in moles (per
`liter or kg of solution or kg of solvent) when the
`corresponding weight concentration of the compound
`was given. This was done by the computer on the
`basis of the molecular weight listed for the compound
`which in turn was also obtained by the computer
`from a structural or empirical formula of the com-
`pound. The value is printed by itself on a separate
`line below the value given by the author and is
`characterized by “Ni” in the “source” column.
`
`What unitsare usedfor additives ? The same units
`and symbols as for CMC’s plus a number of others,
`including such peculiar ones as pH, again following
`the authors. In addition, we have used the additive
`columns to record certain special conditions such
`as pressure. The meaning of the abbreviations is
`listed on page 222. For additives we have not made
`any conversions to mole units.
`What compound nomenclature is used? We have
`generally followed the first author whom we en-
`countered dealing with the particular compound in
`the hope that this will also be the most common and
`understandable name. In case of ambiguity or some
`exotic names, we have added an alternative name
`or a formula in parentheses.
`Are there any valuesfor solvents other than water?
`If the solvent is a mixed one including water, the
`other components have been considered as addi-
`tives. Nonaqueous systems have not been included
`for reasons discussed on page 18 with the exception
`of D20 which is treated as an additive at 100 mole
`
`percent concentration‘.
`What is the meaning of “source”? This column
`serves to indicate in what way the pertinent CIVIC
`value was obtained by us. The meaning of the abbre-
`viations is listed on page 222. In some cases the
`
`reader can check our listing directly or after carefully
`reading a graph or replotting some numerical data.
`In a few cases, however, our listing is based not
`only on what appears in the article but on corre-
`spondence or conversation with the authors.
`In
`this case an L in the source column is given. We
`have not included, however, values made available
`to us privately which did not have a basis in the
`published literature.
`Where do these CMC’s come from? The exact
`reference may be found in the Reference index
`starting on page 213 through the number in the
`“reference” column of each entry. However, much
`information can be obtained from this number
`
`itself since the first two digits give the year of pub-
`lication and from the “authors” column which car-
`ries the first four letters of the name of the author
`
`or two of the authors of that publication. Particularly
`for those familiar with the field, this should often
`permit identification of the reference.
`Are the numbers of digits
`really significant?
`Not in the great majority of entries. We have again
`followed the authors for the sake of the record
`
`and it is clear that most authors paid no attention
`whatsoever to the rules pertaining to significant
`figures. A better idea of the precision of the values
`is given by our “quality” rating of the method
`(second letter). See page 6 for the approximate
`meaning of these letters. When the value quoted
`is obtained by ourselves from published graphs,
`etc., the significant figures refer to how Well these
`graphs could be read or interpreted without digging
`further into the uncertainties of the experiment.
`
`3. Usefulness of CMC Value
`
`The expression critical micelle concentration
`(CMC), as will be discussed later, is slightly mis-
`leading because of the use of the singular form of
`the noun “concentration.” The formation of micelles
`
`from the constituent monomers involves a rapid,
`dynamic, association-dissociation equilibrium. Ex-
`perimentally,
`it
`is
`found,
`in accord with the
`expectations from such equilibria,
`that
`In-icelles
`are undetectable in dilute solutions of the mono-
`mers, and become detectable over a narrow range of
`concentrations as the total concentration of solute
`
`increased, above which nearly all additional
`is
`solute material forms micelles. The concentration
`at which the micelles become first detectable
`
`the experimental
`depends on the sensitivity of
`probe used. The concentration range over which
`
`4
`
`HYDRITE EXHIBIT 1009
`
`(5 or 7)
`
`HYDRITE EXHIBIT 1009
`(5 OF 7)
`
`

`
`solute which forms
`the fraction of additional
`micelles changes from nearly zero to nearly unity
`depends on such factors as the number of monomers
`in the micelle, the chain length of the monomer,
`the properties of counterions and other details
`affecting the monomer-micelle equilibrium. An
`approximate rule is that the higher the CMC value,
`the broader is the concentration range over which
`this transition takes place,
`in absolute value as
`well as in relative value in comparison to the CMC.
`Since different experimental methods may reflect
`this transition to different extents, some systematic
`variations
`in operationally defined CMC’s are
`expected, as discussed in more detail later (p. 11).
`Nevertheless, in spite of these various sources of
`uncertainty in defining and pinpointing the CMC
`exactly, the range of uncertainty is often no more
`than i1 to 2 percent of the CMC value. Thus, the
`CMC is a quantity which can be, and often is, deter-
`mined experimentally to a _much higher precision
`and accuracy than nearly any other property which
`is characteristic of solutions of surface-active agents,
`a point we would like to emphasize strongly. For
`comparative purposes, in careful work, the precision
`is often within i 1 percent.
`The usefulness of CMC values in various qualita-
`tive and quantitative investigations involving sur-
`factant solutions arises basically from the fact that
`the surface and interfacial activity of the amphi-
`pathic (polar-nonpolar) monomers is closely reflected
`in the value of the CMC. The tendency to form
`micelles arises mainly from the presence of a hydro-
`phobic part in the amphipathic monomers. The role
`of the hydrophilic part, nonionic, zwitter-ionic, or
`ionic (with associated counterions), which is essen-
`tial for conferring enough of a solubility to the
`hydrocarbon chain so that CMC values can be
`reached or exceeded, is essentially a negative one
`as far as the stability of micelles is concerned. The
`same factors are involved qualitatively in the surface
`activity of the monomers, irrespective of whether
`the surface is an air-water interface, oil-water inter-
`face, or a nonpolar solid-water interface. There is
`thus an excellent correspondence between the
`adsorbability of the monomers, their ability to re-
`duce surface and interfacial tensions, and the value
`of the CMC [1, 2].‘ The more surface active the
`monomer is,
`the higher is the tendency to form
`micelles and the lower the CMC value. Since above
`
`the CMC the monomer activity rises only very
`
`‘Italicized Figures in brackets indicate the literature references on page 20.
`
`slowly, the CMC is also a measure of the concentra-
`tion at which the thermodynamic activity of the
`monomer and,
`therefore,
`its net surface activity
`and adsorbability to various substrates, level off to
`nearly constant values [I-3]. In closely comparable
`systems, particularly if the hydrophilic moiety of
`the monomer is kept the same and the hydrophobic
`part is varied, there is a considerable similarity in
`the amount of adsorption to air-water and oil-water
`interfaces at concentrations close to the CMC. It
`
`is thus often possible to obtain rough estimates of
`equilibrium monolayer concentrations
`from the
`CMC values in homologous systems [I -3].
`
`Since adsorption from surfactant solutions is
`involved in widely rangng systems of technical
`importance
`such as
`foams,
`froths, emulsions,
`suspensions, and surface coatings, CMC values
`are important in a wide variety of industrial opera-
`tions [4, 5].
`
`In striking contrast to monomers, the micelles,
`which have a hydrophilic exterior, are not surface-
`active. As a result, above the CMC, excepting in
`some cases where small micelles form and the
`monomer
`activity
`increases
`appreciably,
`the
`surface and interfacial
`tensions decrease very
`little [1, 2, 6]. The CMC, therefore, indicates the
`concentration at which surface and interfacial
`
`tensions reach, approximately, their lowest values.
`Characteristic values
`at
`room temperature are
`often about 35 dyn/cm for surface tensions and
`5 dyn/cm for interfacial tensions.
`
`is the concentration at
`The CMC, of course,
`which the micelles make their first appearance.
`Micelles provide in many ways one of the most
`convenient systems available to study in depth the
`properties of colloids. As the properties of micelles
`depend on micelle-medium interactions and also
`micelle-micelle
`interactions,
`to nnrlerstanrl
`the
`former without the latter complication, it is neces-
`sary to extrapolate properties of micelles to a point
`where micelle-micelle interactions become negli-
`gible. The corresponding extrapolation of preformed
`colloidal systems, such as polymers or proteins,
`which do not dissociate on extensive dilution,
`is
`made to “infinite dilution." For micellar properties,
`the CMC serves as a convenient point for extrapola-
`tion,
`i.e., “infinite dilution” for micelles. Just as
`interactions
`binary
`pr0tein—protein
`(i.c.,
`those
`involved in second virial coeflicients) are experi-
`mentally determined from the slopes of curves
`as they approach infinite dilution. so in micellar
`
`HYDRITE EXHIBIT 1009
`
`(6 or 7)
`
`HYDRITE EXHIBIT 1009
`(6 OF 7)
`
`

`
`systems, the corresponding concentration range is
`the one just above the CMC [7-10].
`
`4. Evaluation
`
`In systems involving solubilization of an addi-
`tional component or its distribution between the
`bulk solution and the micelle, the CMC again is a
`measure of
`the
`concentration at which such
`
`phenomena become first apparent. It will be dis-
`cussed later that
`the addition of the third com-
`ponent may modify the CMC itself to some extent
`and, therefore, the CMC of the system in presence
`of the third component is the value to be used.
`The change in the CMC, however, is often small.
`
`In situations where a quantitative estimate of
`the amount or concentration of micelles is desired,
`for example,
`in estimating solubilizing powers,
`
`An important part of this work is the evaluation
`of the data presented. We hope to guide the reader
`to those data that are most useful and reliable in
`
`our considered judgment and also to show him other
`values that exist in the literature so that he may
`make more easily his own evaluation. We also tried
`to indicate the relevant literature and data that we
`have considered but not used in final listings.
`We divided our evaluation into two steps: one,
`which we may call the individual or preliminary
`evaluation;
`the other, the comparative evaluation.
`The former represents our opinion on the basis of
`the individual paper (and its references or related
`papers of the same author); the latter is based on
`intercomparison of all the available data for a given
`
`estimate 0
`
`t e monomer concentration in t e
`
`solution. The micelle concentration in equivalents,
`therefore, can be closely approximated as the total’
`\:u11cei1u'a.t.ion uiinus the CMC.
`
`For the quantitative study of the thermodynamics
`of the interactions involved in the monomer-micelle
`
`equilibrium, the CMC is of paramount importance
`[l6—21]. Although considerable uncertainties still
`exist with regard to the proper means of estimating
`the charge effects in ionic micelles, for uncharged
`systems
`the CMC itself gives an approximate
`quantitative measure of the s.ta.ndarri free energy
`of formation of micelles. These free energies and
`other derived thermodynamic quantities are of
`great potential and actual use in understanding
`hydrophobic interactions in general [22—24]. Such
`interactions are involved in a wide variety of bio-
`chemical phenomena, e.g., the stability, structure,
`conformation, and activity of proteins, enzymes, and
`membranes. With ionic micelles, as mentioned
`before, the calculation of thermodynamic quantities
`characterizing the various interactions is not on
`sure ground as yet. For comparison of related sys-
`tems, however, e.g., in noting the effect of varying
`the chainlength, salt concentrations, or cnlinterirms,
`the CMC provides quite a good quantitative measure
`of the changes as they affect the monomer-micelle
`equilibrium [8, 18, 25].
`
`collected. and sorted by the computer.
`Individual evaluation. A preliminary separation
`involved the question whether Fl given CMC value
`should be reported in detail or not. Values which
`are indicated in the article as being duplicates of
`other published values are omitted completely.
`Others, however, which are clearly duplicates but
`not explicitly indicated as such by the authors, are
`mentioned as “VALUES FROM REF IN CMC,”
`with the article from which they are taken listed in
`the column in which the CMC is normally found.
`Values which could not be retrieved profitably,
`c.g.,
`those in the form of small-scale graphs or
`summarizing equations, are indicated as “GRAPH
`DATA NOT RETRIEVED” and “SUMMARIZING
`EON ONLY” for the reader who wishes to examine
`them himself. There are 41 entries in the former
`category and 22 in the latter.
`Once a value was included explicitly, we at-
`tempted to evaluate the purity of the materials and
`the accuracy and precision of the method used.
`These were noted separately as reported in the
`“Quality” Rating columns. The meaning of the
`symbols is as follows:
`'
`
`MATERIAL
`
`METHOD
`
`A Highest purity—not likely to
`be significantly improved in
`the future
`
`precise to about 1%
`accurate to 1.5%
`
`HYDRITE EXHIBIT 1009
`
`(7 or 7)
`
`HYDRITE EXHIBIT 1009
`(7 OF 7)