In-Situ Formation of Viscoelastic Wormlike Micelles in Mixtures of Non-Surface-Active Compounds

Article abstract of DOI:10.1007/s11743-014-1586-1

Viscoelastic fluids based on surfactant self-assembled wormlike micelles have been in focus over the past decade. In this work, we report wormlike micellar solutions formed in situ by simply mixing two non-surface-active compounds, N-(3-(dimethylamino)propyl)palmitamide (C16AMPM) and salicylic acid (HSal), without specialized organic synthesis of a surfactant. In the absence of HSal, C16AMPM is poorly soluble in pure water; after introducing HSal, C16AMPM is protonated into quaternary ammonium, behaving like a cationic surfactant with a low critical micellar concentration (0.25 mM) and a small area per molecule, which favors the formation of long cylindrical wormlike micelles. Above the overlapping concentration (～28 mM), the wormlike micelles formed entangle each other into viscoelastic networks, enhancing the viscosity by several orders of magnitude. In contrast to the worms formed by a single ultra-long-chain surfactant, the current system shows the advantages of a smaller flow activation energy and end-cap energy, simpler formulation and lower cost, which make it more suitable for practical use.

Full text of DOI:10.1007/s11743-014-1586-1

J Surfact Deterg (2015) 18:189–198
DOI 10.1007/s11743-014-1586-1
ORIGINAL ARTICLE
In-Situ Formation of Viscoelastic Wormlike Micelles in Mixtures
of Non-Surface-Active Compounds
•
Yongmin Zhang Dapeng Zhou Yujun Feng
•
Received: 8 November 2013 / Accepted: 18 March 2014 / Published online: 3 April 2014
Ó AOCS 2014
Abstract Viscoelastic fluids based on surfactant self-
assembled wormlike micelles have been in focus over the
past decade. In this work, we report wormlike micellar
solutions formed in situ by simply mixing two non-surface-
active compounds, N-(3-(dimethylamino)propyl)palmita-
mide (C16AMPM) and salicylic acid (HSal), without spe-
cialized organic synthesis of a surfactant. In the absence of
HSal, C16AMPM is poorly soluble in pure water; after
introducing HSal, C16AMPM is protonated into quaternary
ammonium, behaving like a cationic surfactant with a low
critical micellar concentration (0.25 mM) and a small area
per molecule, which favors the formation of long cylin-
drical wormlike micelles. Above the overlapping concen-
tration (*28 mM), the wormlike micelles formed entangle
each other into viscoelastic networks, enhancing the vis-
cosity by several orders of magnitude. In contrast to the
worms formed by a single ultra-long-chain surfactant, the
current system shows the advantages of a smaller flow
activation energy and end-cap energy, simpler formulation
and lower cost, which make it more suitable for practical
use.
Keywords Wormlike micelles ꢀ Viscoelastic fluids ꢀ
Rheology ꢀ Surfactant ꢀ Salicylic acid
Introduction
Surfactant self-assemblies are of particular interest in
numerous industrial processes. Above a critical micellar
concentration (CMC), surfactant molecules generally form
small globular micellar aggregates in aqueous solution, and
may continuously grow uniaxially into very long and
highly flexible wormlike micelles under some favorable
physico-chemical conditions [1–3]. Typically, these thread-
like micelles have a diameter of 2–5 nm and contour length
ranging from several nanometers up to several micrometers
[4, 5]. Above a threshold overlap concentration (C*), these
linear micelles entangle into a dynamic transient network,
displaying macroscopically remarkable viscoelastic prop-
erties reminiscent of polymer solutions. However, much
unlike polymer chains connected by covalent bonds
between monomers, wormlike micelles are held together
by weak non-covalent hydrophobic interaction, constantly
breaking and recombining, thus are also called as ‘‘living’’
or ‘‘equilibrium’’ polymers [6].
Y. Zhang (&)
Key Laboratory of Food Colloids and Biotechnology, Ministry
of Education, School of Chemical and Materials Engineering,
Jiangnan University, Wuxi 214122, People’s Republic of China
e-mail: zhangym@jiangnan.edu.cn
Over the past decades, considerable attention from both
a theoretical viewpoint and industrial applications has been
focused on wormlike micelles, due mainly to their unique
aggregate microstructures and rheological responses [7].
From a fundamental perspective, wormlike micelles are
particularly intriguing since they are models of ‘‘living
polymers’’ [2, 8] for complex polymer systems. On the
practical side, these viscoelastic fluids are good candidates
for applications in the oil industry [9–12] including oilwell
drilling, sand control, cleaning fracturing, self-diverting
acidizing, and tertiary oil recovery, and show great
D. Zhou
Zhejiang Zanyu Technology Co., Ltd., Hangzhou 310030,
People’s Republic of China
Y. Feng (&)
Polymer Research Institute, State Key Laboratory of Polymer
Materials Engineering, Sichuan University, Chengdu 610065,
People’s Republic of China
e-mail: yjfeng@scu.edu.cn
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Synthesis of N-(3-(Dimethylamino)Propyl)Palmitamide
potentials in biomedicine [13, 14], drag reduction [15, 16],
home and personal care [17], to name but a few. So far,
wormlike micellar solutions have been formulated with a
wide variety of surfactants such as cationic [18–20],
anionic [21, 22], zwitterionic [23, 24], and nonionic [25]
species, as well as mixed formulations such as cationic–
anionic [26], ionic–nonionic [27], ionic–zwitterionic [28],
and nonionic–zwitterionic [29] systems. To the best of our
knowledge, all the viscoelastic fluids mentioned above
were formulated utilizing synthetic surfactant self-assem-
blies, few efforts have been put into the production of
viscoelastic wormlike micelles through directly mixing two
or more compounds of originally non-surface active agents.
Among the most popular wormlike micelles reported so
far, those formed from the common cationic surfactant ce-
tyltrimethyl ammonium bromide (CTAB) and a hydrotrope
which is the most popular way. According to Hofmeister
sequence [30], with increasing the binding capacity of
counterions, the persistence length (lp) of micelles decreases,
and then the micellar flexibility increases. In other words, the
counterions with strong binding capacity favor the formation
of wormlike micelles. In contrast to non-organic counteri-
ons, organic ones are generally better at inducing the growth
of micelles because they not only screen the electrostatic
repulsion between charged hydrophilic headgroups of ionic
surfactants, but also plug into the aggregates of surfactants
owing to their strong binding ability. From what has been
reported to date, it is confirmed that aryl-organic salts more
readily induce the self-assembly of CTAB into elongated
rod-like micelles than other hydrotropes [18–20]. However,
few attempts have been made to fabricate viscoelastic fluids
in situ utilizing non-surface-active aryl acid and a long-chain
amphiphilic molecule.
(C16AMPM)
50 mmol (12.82 g) palmitic acid, 75 mmol (7.66 g)
DMPDA and 0.15 g NaF were put into a three-necked
flask. The reaction mixture was refluxed 10 h at
155–160 °C under a N2 atmosphere, during which the by-
product H2O was absorbed continuously by Al2O3. The
excess of DMPDA was removed and the residue was
washed with cold acetone (150 ml 9 2) (each time 10 ml
water was added to remove NaF), followed by drying under
a vacuum at -45 °C to obtain 15.8 g C16AMPM (yield
93 %) with a purity of 99.90 % (HPLC).
1H NMR (300 MHz, CD3OD), d/ppm: 0.89 (t, J =
6.18 Hz, 3H), 1.26 (m, 24H), 1.60 (s, 2H), 1.71 (m, 2H),
2.16 (m, 2H), 2.20 (s, 6H), 2.40 (t, J = 7.68 Hz, 2H), 3.18
(t, J = 6.81 Hz, 2H).
Characterizations
1H-NMR spectra of the C16AMPM, HSal and C16AMPM–
HSal were recorded on a Bruker Avance 300 spectrometer
at 300 MHz in CD3OD at room temperature. Chemical
shifts are expressed in ppm downfield from TMS as an
internal standard. HPLC analysis was performed on a
Waters HPLC system equipped with All-tech 2000 ELSD
detector using a reverse phase (C18) column.
Preparation of Solutions
Different concentrations of mixture solutions were
obtained by dissolving a specific amount of C16AMPM
and HSal in triply distilled water with gentle agitation at
25 °C, and then the sample solutions were left for at least
24 h to reach equilibrium prior to measurements. The
molar ratios of all the solutions were fixed at 1:1 unless
otherwise stated, and the concentration of the solutions is
given as the concentration of C16AMPM.
Thus, here we have developed a wormlike micellar
system by simply mixing two non-surface-active precur-
sors: salicylic acid (HSal) and N-(3-(dimethylamino)pro-
pyl)palmitamide (C16AMPM) originated from natural
palmitic acid, and examined the solubility, surface activi-
ties, as well as macroscopic rheological properties of a
binary mixture in pure water.
Surface Tension Measurement
Surface tension (c) of the sample solutions was measured
with a Kru¨ss K100 tensiometer by the automatic Du Nou¨y
ring model at 25 0.1 °C, and a cover was used to min-
imize water evaporation. A set of measurements to obtain
a stable surface tension was repeated until the change
was \0.03 mN m–1 every 3 min.
Experimental Section
Materials
Palmitic acid (Chengdu Kelong Chemical Reagent Factory),
N,N-dimethyl-1,3-propanediamine (DMPDA) (Rhodia Fei-
xiang Specialty Chemicals), salicylic acid (HSal, Sinopharm
Chemical Reagent Co., Ltd.) were used without further
purification. All other chemicals used were of reagent grade,
and were used as received. Triply distilled water by a quartz
water purification system was used in all the measurements.
Rheology Measurement
Rheological properties of mixture solutions were deter-
mined on a Physica MCR 301 (Anton Paar, Austria) rota-
tional rheometer equipped with a concentric cylinder
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191
geometry CC27 (ISO3219), with a measuring bob radius of
13.33 mm and a measuring cup radius of 14.46 mm.
Samples were equilibrated at the experimental temperature
for not \20 min prior to the experiments. Dynamic fre-
quency spectra were conducted in the linear viscoelastic
region, as determined from prior dynamic stress sweep
measurements. All measurements were carried out in the
stress-controlled mode, and CANNON standard oil was
used to calibrate the instrument before measurements. The
temperature was controlled by a Peltier device, and a sol-
vent trap was used to minimize water evaporation during
the measurements.
example, when at CC16AMPM/CHSal = 0.1:1, the pH of the
mixture suspension is 2.70. In this case, the solubility of
HSal in water at 25 °C is about 15 mM [31], which is
sufficient to protonate 10 mM C16AMPM molecules.
Upon increasing C16AMPM content, the residual HSal
content decreases and thus the pH value of the solutions
increases slightly (Fig. 1b), indicating more and more that
HSal molecules have been consumed through the proton-
ation of C16AMPM. When the molar ratio of CC16AMPM
/
CHSal goes up to 0.75:1, the HSal solid almost disappears
from the bottom of the test tube, and the pH value starts
rising rapidly (Fig. 1b). The solutions become homogenous
when the molar ratio ranges from 0.75:1 to 1.5:1. If the
C16AMPM concentration is further increased, phase sep-
aration occurs because of excessive C16AMPM. Hence,
the molar ratio of CC16AMPM/CHSal for the following
experiments was fixed at 1:1 to ensure homogeneity of the
solutions for further measurements.
Results and Discussion
Phase Behavior
There is no doubt that solubility or homogeneity of the
mixture solutions is the primary consideration for further
examination. Under a neutral or alkaline state, C16AMPM
is hardly soluble in water due to its long hydrophobic tail
and non-ionic headgroup, and behaves as a waxy solid at
low temperatures or an oily paste at high temperatures,
floating on the water surface. Nevertheless, the terminal
tertiary amine groups in C16AMPM molecules can be
protonated into quaternary species by the H? ionized from
HSal (pKa = 2.98) [31] in aqueous solution, which
improves the solubility of C16AMPM.
1H-NMR Confirmation of C16AMPM Protonation
by HSal
To verify the protonation of C16AMPM in the presence of
1
HSal, comparative H-NMR studies were carried out on
C16AMPM, HSal and the mixture of C16AMPM–HSal in
CD3OD, respectively. As exhibited in Fig. 2, for the mix-
ture ‘‘C16AMPM–NaSal’’, the chemical shifts of the pro-
tons around tertiary amine group show an obvious
downfield shift compared with C16AMPM alone, from
1.68 (peak ‘‘f’’), 2.24 (g) and 2.38 ppm (h) to 1.90 (f1), 2.86
(g1) and 3.09 ppm (h1), respectively, implying the pro-
tonation of tertiary amine group along C16AMPM [32, 33].
Whereas, the chemical shifts of the protons of Sal-1 remain
As shown in Fig. 1a, the quantity of HSal is initially too
excessive to be completely dissolved, thus one can observe
that the aqueous phase of the binary mixture solution and
the solid phase (HSal crystal) coexist in the system. For
Fig. 1 a Snapshots of and b pH variation of binary mixture solutions with varied molar ratios of CC16AMPM/CHSal, where CHSal was fixed at
100 mM
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1
Fig. 2 Comparison of the H-
NMR spectra for C16AMPM,
HSal and C16AMPM–HSal
using CD3OD as the solvent
tensions of C16AMPM–HSal, HSal and C16AMPM
against their concentrations in pure water at 25 °C,
respectively. For C16AMPM or HSal alone, the surface
tension nearly maintains constant with increasing concen-
tration, and the value is comparable to that of pure water,
suggesting that C16AMPM or HSal alone are non-surface-
active. On the contrary, the surface tension of C16AMPM–
HSal exhibits an evident drop with increasing concentra-
tion, and then reaches a plateau of 34.86 mN m–1. The
break point between the slope and plateau, generally taken
as the CMC, is 0.25 mM, which is less than 1/3 that of
CTAB (0.92 mM) [34]. This suggests that C16AMPM–
HSal is surface active, which can dramatically decrease the
surface tension of water with a small dose of C16AMPM–
HSal.
The amount of adsorbed surfactant (C) at the air–water
interface can be calculated using the Gibbs adsorption
ꢀ
ꢁ
Fig. 3 The variation of surface tension with concentration at 25 °C
oc
1
isotherm C ¼ ꢁ , and the area occupied (A) by a
surfactant molecule at the air–solution interface can be
nRT o ln C
1
obtained from the saturated adsorption A ¼
[35],
unvaried by contrast with HSal alone. In other words, the
addition of HSal leads to the ionization of C16AMPM,
transforming it into a cationic surfactant with anionic Sal-1
as the counterion.
NꢀCCMC
where R is the gas constant (8.314 J mol–1 K–1), T is the
absolute temperature (K), C is the surfactant concentration
(mol L–1), oc=o ln C refers to the slope below the CMC in
the surface tension plot, N is Avogadro’s number, and
CCMC is the maximum surface excess concentration at
CMC. The value of n that stands for the number of species
at the interface was taken as 2 for cationic surfactants [35].
Thus, the obtained value of CCMC is 1.25 9 10–3 mM,
about half of that reported for CTAB [34], while the A is
1.33 nm2, which is 3 times larger than that reported for
Surface Activity
The surface activities of C16AMPM–HSal, HSal and
C16AMPM were measured for comparison to further
confirm the conversion of non-surface-active C16AMPM
into a surfactant. Figure 3 shows the variation in surface
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193
Fig. 4 Effect of C16AMPM–
HSal (molar ratio = 1:1)
concentration on a steady
rheology and b zero-shear
viscosity g0 of C16AMPM–
HSal solutions at 25 °C
CTAB [34]. This difference could be accounted for by the
much larger counterion Sal–1 for C16AMPM–HSal since
their hydrophobic tail length is the same. Compared with
Br–1 in CTAB, the Sal–1 in C16AMPM–HSal has a bigger
steric hindrance, concomitantly resulting in a looser
adsorption layer at the air–water interface, i.e., a smaller
CCMC and a bigger A should obtain in this case.
network entanglements to undergo a structural change when
exceeding a critical shear rate at which shear-thinning starts to
shift to lower values, rendering the alignment of long micelles
along the flow direction, exhibiting shear-thinning behavior
macroscopically.
When CC16AMPM–HSal is continuously increased, the
viscosity of C16AMPM–HSal solutions is further enhanced
due to the increasing network entanglement density and
the critical shear rate decreases. However, when
CC16AMPM–HSal goes up to 150 mM, the apparent viscosity
continuously increases, but the variation is no longer as
dramatic as that in the concentration range of 50–100 mM.
Zero-shear viscosity (g0) of C16AMPM–HSal solutions,
obtained by extrapolation of the shear viscosity along the
Newtonian plateau to zero shear rate, is plotted as a
function of CC16AMPM–HSal to check the dependence of
Concentration Dependence on Rheological Behavior
The shape and size of the micelles rely not only on the
geometry of the surfactant, but also on its surfactant concen-
tration. Shown in Fig. 4 are the steady rheograms of
C16AMPM–HSal solutions with different concentrations but
at a fixed molar ratio of 1:1. As displayed in Fig. 4a, when the
concentration of C16AMPM is \25 mM, the apparent vis-
cosity of the mixture solutions is as small as that of water
(*1 mPaꢀs), andremainsconstantregardlessoftheshearrate,
indicative of a typical Newtonian fluid. When CC16AMPM–HSal
is increased to 50 mM, the C16AMPM–HSal solution still
behaves as a Newtonian fluid, but its apparent viscosity
increases slightly, up to *10 mPaꢀs, suggesting that the
spherical micelles in the solution have evolved into short rod-
like ones. Nevertheless, the dynamic network structures are
not formed yet because the lengths of the rod-like micelles are
still too short to entangle with each other. On further
increasing the concentration to 75 mM, the C16AMPM–HSal
solutiondisplaysadistinctrheologicalresponse,inwhichboth
Newtonian fluid behavior and the shear-thinning response are
shown in low- and high-shear-rate regions, respectively,
which are normally attributed to the formation of flexible
wormlikemicelles[3, 36]. Inthe initiallow-shear-rateregime,
the applied shear stress or strain is not big enough to impart
any effect on the network entanglements, thus Newtonian
behavior appears; whereas in the high-shear-rate region, the
applied shear stress or strain is strong enough to cause the
CC16AMPM–HSal on viscosity. One can see in Fig. 4b that the
g0–C curve is made up of two parts with a clear break-
point, i.e., a critical overlapping concentration C*. Below
C*, g0 increases linearly in accordance with the Einstein
equation [7, 29].
g0 ¼ gwaterð1 þ KCÞ
ð1Þ
where K is on the order of unity; at this moment, the
average micellar length usually increases with surfactant
concentration following a simple power-law model with an
exponent of *1/2 [29]. Above C*, g0 increases exponen-
tially by several orders of magnitude following the scaling
law [7, 29].
g0 / Cp
ð2Þ
where p is the power-law exponent. This implicates that the
wormlike micelles in the solutions start entangling with
each other, forming a dynamic transient network, and then
substantially imparting viscoelasticity to the solutions.
As shown in Fig. 4b, C* of the C16AMPM–HSal sys-
tem appears at around 28 mM, which is much higher than
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Fig. 5 Effect of surfactant
concentration on a dynamic
rheology, b Cole–Cole plots and
c G0 and sR of C16AMPM–
HSal solutions at 25 °C
those of the wormlike micellar solutions formed from
longer chain surfactants, docosyl dimethyl carboxylbetaine
(DDCB *0.68 mM) [23] or sodium erucate (*8 mM)
[21]. This moderate C* of the C16AMPM–HSal worm
solutions can be ascribed to its relative shorter hydrophobic
tail to that of DDCB or sodium erucate. In the semi-dilute
regime (C [ C*), the power-law exponent of g0 against
C16AMPM–HSal concentration is 6.2, slightly higher than
the value predicted by the theoretical model for cationic
worm solutions [37].
increases accompanied with decrease in xc, reflecting that
the viscoelasticity at high concentrations is more pro-
nounced than that at low concentrations.
The viscoelastic behavior of wormlike micellar solu-
tions at low shear frequency often follows the Maxwell
model with single relaxation time, which can be usually
described by a semicircular shape of the Cole–Cole plots
[29]:
ꢂ
ꢃ
ꢂ
ꢃ
2
2
G0
G0
G002
þ
G0 ꢁ
¼
ð3Þ
2
2
The shear frequency dependence of the storage and loss
moduli (G0 and G00) on the concentration of the
C16AMPM–HSal solutions is depicted in Fig. 5a. For all
the solutions in the concentration range of 100–250 mM,
G0 crosses and prevails over G00 when exceeding a critical
shear frequency (xc). Namely, at low shear frequencies, the
solutions show an evident viscous behavior, while a typical
elastic response at high shear frequencies, implying that the
C16AMPM–HSal solutions are viscoelastic and their
relaxation times sR (*1/xc) are finite. Furthermore, when
CC16AMPM–HSal is increased from 100 to 250 mM, the
plateau modulus G0 (storage modulus at high frequencies)
in which the imaginary part G00 is plotted against the real
part G0. As shown in Fig. 5b, for the Cole–Cole plots of
C16AMPM–HSal solutions, G0 and G00 have been nor-
malized by the plateau modulus G0. At low frequencies,
they fit the semicircle well over a majority of frequencies
and deviations occurring at high frequencies owing to non-
repetitive effects [38, 39]. This suggests that the dynamic
rheologic behavior of the C16AMPM–HSal solutions can
be described by the single-mode Maxwell constitutive
equation over a frequency range, indicative of the forma-
tion of wormlike micelles [37]. Moreover, the radius of the
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195
semicircle and consequently the shear modulus increase
steadily with concentration, which is generally attributed to
the increase in G0 and viscoelasticity [29].
Additionally, a similar temperature effect is also
observed for the oscillatory spectra of the C16AMPM–
HSal solution (Fig. 6b). With increasing temperature, the
critical shear frequency xc at which G0 starts to cross and
prevail over G00 shifts to higher values. In other words, the
relaxation time of the solution deceases with increasing
temperature, and thus the reversible breaking–recombining
process of wormlike micelles becomes faster. However, the
plateau modulus G0 remains nearly constant since it is
independent of temperature, as is usually found in worm-
like micellar solutions [39].
To gain insight into the wormlike micelles formed by
C16AMPM–HSal, the rheological parameters, G0 and sR
(estimated via 1/xc), were further investigated as a func-
tion of CC16AMPM–HSal. From the results shown in Fig. 5c,
one can see that G0 and sR both rise steadily with
increasing CC16AMPM–HSal, and both display power-law
behavior as G0 * Ca and sR * Cb with a = 2.2 and
b = 1.0, respectively, very close to the theoretical forecast
values 2.25 and 1.25 for entangled linear wormlike
micelles [1, 6]; the power-law exponent of G0 is also
comparable to the value obtained for wormlike micelles of
DDCB (2.1) [23].
Generally, the key rheological parameters such as g0 and
sR of the C16AMPM–HSal solutions can be empirically
described by the Arrhenius equation [1].
g0 ¼ G0AeE =RT
ð4Þ
ð5Þ
a
According to Cates et al. [1] reptation or diffusion of
wormlike micelles along their own contour network con-
forms to the stress relaxation mechanism. Thus the mag-
nitude of G0 is related to the density number of
entanglement or mesh size in the network, and only
depending on the surfactant concentration, whereas sR is
linked with the average length of the wormlike micelles,
which is relevant to the concentration of both surfactant
and hydrotrope. In the present system, only the surfactant
concentration of C16AMPM–HSal varies. Hence, the
increase in these rheological parameters with increasing
CC16AMPM–HSal can be interpreted as the growth in the
length of the wormlike micelles [40]. As C16AMPM–HSal
concentration increases, the length and flexibility of the
micelles rise concomitantly, and then the elongated
micelles promote the increase of g0 and sR. Furthermore,
the growth of the micelles leads to an increase in the
density number or mesh size of the aggregates, and thus the
G0 increases with increasing surfactant concentration.
sR ¼ AeE =RT
a
where Ea is the flow activation energy in J mol–1, and A is a
pre-exponential factor. According to Eq. (4), G0 is inde-
pendent of temperature, which is also confirmed by the
experimental results shown in Fig. 6b. However, the plots
of g0 and sR against 1,000/T both lie on straight lines with
nearly the same slope (Fig. 7), indicative of Arrhenius
behavior. Thus the Ea can be obtained from the temperature
dependence of either g0 or sR, and was found to
95 kJ mol–1, which is comparable to that of wormlike
micelles formed from CTAB–KBr (113 kJ mol-1) [19],
but is far less than those of wormlike micelles based on
C22-tailed surfactants (160–198 kJ mol-1) [22, 39].
According to Granek and Cates [38], if the entanglement
length le is known, the micellar contour length L can be
estimated from rheological results through the following
equation [38].
00
min
G
le
ꢀ
L
Effect of Temperature on Rheological Behavior
ꢂ
ð6Þ
G0
00
min
where G is the value of G00 at its minimum. As displayed
As temperature also plays an important role in the practical
applications of wormlike micellar solutions, it is necessary
to investigate the influence of temperature on the micellar
system formed by C16AMPM and HSal. Plotted in Fig. 6a
is the temperature dependence of the steady rheological
behavior of C16AMPM–HSal solutions with a fixed con-
centration of 150 mM. Within the temperature scope of
25–70 °C, the C16AMPM–HSal solution exhibits the
coexistence of Newtonian fluid behavior at low shear rates
and shear-thinning behavior at high shear rates, and the
critical shear rate shifts to higher values and g0 decreases
monotonically with increasing temperature. Upon further
increasing the temperature (80–90 °C), the shear-thinning
behavior of the C16AMPM–HSal solution disappears in
the shear rate range investigated here, and g0 continues to
decrease monotonically.
00
min
in Fig. 6b, with increasing temperature, G also increases
while G0 maintains constant, signifying the increase in
00
min
G
/G0, or equivalently, the decrease of L/le with tem-
perature. Since G0 is relatively independent of temperature,
which is also confirmed by the experimental results
(Fig. 6b), the mesh size and hence the entanglement length
le are also independent of temperature [39]. Thus, as
expected, the contour length L decreases with increasing
temperature, and the variation in L with temperature can be
quantified utilizing the mean-field theory [1].
L ꢃ u1=2eE =2kT
ð7Þ
c
where u is the volume fraction of surfactant, Ec is the end-
cap energy (J mol-1) that is the energy required to create
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Fig. 6 Effect of temperature on
a steady rheology and
b dynamic rheology of 150 mM
C16AMPM–HSal solution
Fig. 7 Zero-shear viscosity g0 and relaxation time sR plotted as a
function of the inverse of temperature for the 150 mM C16AMPM–
HSal solution
Fig. 8 The ratio of contour length L and entanglement length le,
plotted as a function of the inverse of temperature for the 150 mM
C16AMPM–HSal solution
two end caps by breaking a micelle, k is Boltzmann con-
stant, 1.38 9 10-23 J K-1
.
Thus, Ec can be readily obtained from the slope of a
semilogarithmic plot of G0/G00 : L/le vs 1/T, even
in rheological properties such as g0. Whereas within a low
temperature range (25–40 °C), the wormlike micelles are
presumably still long enough to entangle with each other so
that the volume fraction of the giant entanglements remains
constant, this is why G0 remains constant throughout
temperature increases.
min
without knowing the precise values of L. From the results
shown in Fig. 8, one can find that the plot of L/le against
1,000/T falls on a straight line as well, thus the Arrhenius
relationship for L is confirmed, and the slope yields a value
for Ec of 91 kJ mol-1, which is more close to the Ec
obtained for wormlike micelles formed from C16-tailed
surfactants (ca. 50 kJ mol-1) [19], but rather low compared
to those reported for ultra-long-chain surfactant worms
Conclusions
(160 kJ mol-1
) [39] or gemini surfactants systems
Although it is well known that surfactants can self-
assembly into wormlike micelles under appropriate con-
ditions, displaying a viscoelastic response analogous to
polymer solutions, most of the surfactants are obtained by
organic synthesis prior to the experiments. Here, in
(98–170 kJ mol-1) [41].
The low Ec value denotes low energy cost for micellar
scission; that is to say, the length of micelles is readily
influenced by heating, leading to an exponential decrease
123

J Surfact Deterg (2015) 18:189–198
197
12. Li L, Nasr-El-Din HA (2010) Rheological properties of a new
class of viscoelastic surfactant. SPE Prod Oper 25:355–366
13. Afifi H, Karlsson G, Heenan RK, Dreiss CA (2011) Solubilization
of oils or addition of monoglycerides drives the formation of
wormlike micelles with an elliptical cross-section in cholesterol-
based surfactants: a study by rheology, SANS, and cryo-TEM.
Langmuir 27:7480–7492
14. Afifi H, Karlsson G, Heenan RK, Dreiss CA (2012) Structural
transitions in cholesterol-based wormlike micelles induced by
encapsulating alkyl ester oils with varying architecture. J Colloid
Interface Sci 378:125–134
15. Zakin JL, Zhang Y, Ge W (2007) In: Zana R, Kaler EW (eds) Giant
micelles: properties and applications. CRC Press, Boca Raton
16. Shi HF, Wang Y, Fang B, Talmon Y, Ge W, Raghavan SR, Zakin
JL (2011) Light-responsive threadlike micelles as drag reducing
fluids with enhanced heat-transfer capabilities. Langmuir 27:
5806–5813
17. Yang J (2002) Viscoelastic wormlike micelles and their appli-
cations. Curr Opin Colloid Interface Sci 7:276–281
18. Kern F, Zana R, Candau SJ (1991) Rheological properties of
semidilute and concentrated aqueous solutions of cetyltrimeth-
ylammonium chloride in the presence of sodium salicylate and
sodium chloride. Langmuir 7:1344–1351
19. Candau SJ, Hirsch E, Zana R, Delsanti M (1989) Rheological
properties of semidilute and concentrated aqueous solutions of
cetyltrimethylammonium bromide in the presence of potassium
bromide. Langmuir 5:1225–1229
20. Shikata T, Hirata H, Kotaka T (1989) Micelle formation of
detergent molecules in aqueous media. 3 Viscoelastic properties
of aqueous cetyltrimethylammonium bromide-salicylic acid
solutions. Langmuir 5:398–405
contrast, we developed a wormlike micellar system sim-
ply by mixing C16AMPM and HSal. Before introducing
HSal, C16AMPM is non-surface-active and poorly soluble
in water. However, in the presence of HSal, C16AMPM is
protonated into quaternary ammonium, behaving like a
cationic surfactant with an anionic counterion Sal-1. Due
to a strong electrostatic screening capacity and binding
ability of such a counterion, C16AMPM–HSal has a
lower CMC and a smaller area per molecule than those of
CTAB, and this favors the formation of long cylindrical
wormlike micelles. With increasing concentration above
C* (*28 mM), the viscosity jumps by several orders of
magnitude due to the formation of entangled wormlike
micellar networks. Compared to ultra-long-chain surfac-
tant worms, the current system shows some advantages
such as lower Ea and Ec, simpler formulation and lower
cost, which enable it to be an attractive candidate for
some special applications particularly in oil and gas
production.
Acknowledgments The financial support from the Fundamental
Research Funds for the Central Universities (JUSRP11421) and the
Natural Science Foundation of China (21173207) is gratefully
acknowledged.
21. Zhang Y, Han Y, Chu Z, He S, Zhang J, Feng Y (2013) Ther-
mally induced structural transitions from fluids to hydrogels with
pH-switchable anionic wormlike micelles. J Colloid Interface Sci
394:319–328
References
1. Cates ME, Candau SJ (1990) Statics and dynamics of worm-like
surfactant micelles. J Phys Condens Matter 2:6869–6892
2. Rehage H, Hoffmann H (1991) Viscoelastic surfactant solutions:
model systems for rheological research. Mol Phys 74:933–973
3. Dreiss CA (2007) Wormlike micelles: where do we stand? Recent
developments, linear rheology and scattering techniques. Soft
Matter 3:956–970
22. Han Y, Feng Y, Sun H, Li Z, Han Y, Wang H (2011) Wormlike
micelles formed by sodium erucate in the presence of a tetraal-
kylammonium hydrotrope. J Phys Chem B 115:6893–6902
23. Zhang Y, Luo Y, Wang Y, Zhang J, Feng Y (2013) Single-
component wormlike micellar system formed by a carboxylbe-
taine surfactant with C22 saturated tail. Colloid Surf A 436:
71–79
4. Magid LJ (1998) The surfactant-polyelectrolyte analogy. J Phys
Chem B 102:4064–4074
5. Hoffmann H, Ebert G (1988) Surfactants, micelles and fascinat-
ing phenomena. Angew Chem Int Ed 27:902–912
6. Cates ME (1988) Dynamics of living polymers and flexible sur-
factant micelles-scaling laws for dilution. J Phys Fr 49:1593–1600
7. Berret J-F (2006) In: Weiss RG, Terech P (eds) Molecular gels.
Springer, Dordrecht
24. Chu Z, Feng Y, Su X, Han Y (2010) Wormlike micelles and
solution properties of a C22-tailed amidosulfobetaine surfactant.
Langmuir 26:7783–7791
¨
¨
25. Ericsson CA, Soderman O, Garamus VM, Bergstrom M,
Ulvenlund S (2005) Effects of temperature, salt, and deuterium
oxide on the self-aggregation of alkylglycosides in dilute
solution.
1515
2 n-Tetradecyl-b-D-maltoside. Langmuir 21:1507–
8. Cates ME (1987) Reputation of living-polymers-dynamics of
entangled polymers in the presence of reversible chain-scission
reactions. Macromolecules 20:2289–2296
26. Raghavan SR, Fritz G, Kaler EW (2002) Wormlike micelles
formed by synergistic self-assembly in mixtures of anionic and
cationic surfactants. Langmuir 18:3797–3803
9. Chase B, Chmilowski W, Marcinew R, Mitchell C, Dang Y,
Krauss K, Nelson E, Lantz T, Parham C, Plummer J (1997) Clear
fracturing fluids for increased well productivity. Oilfield Rev
9:20–33
27. Acharya DP, Hattori K, Sakai T, Kunieda H (2003) Phase and
rheological behavior of salt-free alkyltrimethylammonium bro-
mide/alkanoyl-N-methylethanolamine/water systems. Langmuir
19:9173–9178
10. Al-Anzi E, Al-Mutawa M, Al-Habib N, Al-Mumen A, Nasr-El-
Din H, Alvarado O, Brady M, Davies S, Fredd C, Fu D, Lungwitz
B, Chang F, Huidobro E, Emmali M, Samuel M (2003) Positive
reaction carbonate reservoir stimulation. Oilfield Rev 15:28–45
11. Kefi S, Lee J, Pope TL, Sullivan P, Nelson E, Hernandez AN,
Olsen T, Parlar M, Powers B, Roy A, Wilson A, Twynam A
(2004) Expanding applications for viscoelastic surfactants. Oil-
field Rev 16:10–23
28. Hoffmann H, Rauscher A, Gradzielski M, Schulz SF (1992)
Influence of ionic surfactants on the viscoelastic properties of
zwitterionic surfactant solutions. Langmuir 8:2140–2146
29. Hoffmann H (1994) Structure and flow in surfactant solutions.
American Chemical Society, Washington
30. Lo Nostro P, Ninham BW, Ambrosi M, Fratoni L, Palma S,
Allemandi D, Baglioni P (2003) Hofmeister effect in coagels of
ascorbic acid based surfactants. Langmuir 19:9583–9591
123

198
J Surfact Deterg (2015) 18:189–198
31. (2014) http://en.wikipedia.org/wiki/Salicylic_acid. Accessed 6
Jan 2014
32. Zhang Y, Chu Z, Dreiss CA, Wang Y, Fei C, Feng Y (2013)
Smart wormlike micelles switched by CO2 and air. Soft Matter
9:6217–6221
41. Kern F, Lequeux F, Zana R, Candau SJ (1994) Dynamical
properties of salt-free viscoelastic micellar solutions. Langmuir
10:1714–1723
Yongmin Zhang received his Ph.D. in polymer chemistry and
physics from Chengdu Institute of Organic Chemistry, Chinese
Academy of Sciences in 2013, and is now serving as an assistant
professor at the School of Chemical and Material Engineering,
Jiangnan University, People’s Republic of China. His research
interest lies in viscoelastic fluids and stimuli-responsive assemblies.
33. Zhang Y, Feng Y, Wang Y, Li X (2013) CO2-switchable visco-
elastic fluids based on a ‘‘pseudo’’ gemini surfactant. Langmuir
29:4187–4192
34. Rosen MJ (2004) Surfactants and interfacial phenomena. Wiley,
Hoboken
35. Rosen MJ, Cohen AW, Dahanayake M, Hua X (1982) Rela-
tionship of structure to properties in surfactants. 10 Surface and
thermodynamic properties of 2-dodecyloxypoly(ethenoxyetha-
nol)s, C12H25(OC2H4)xOH, in aqueous solution. J Phys Chem
86:541–545
36. Candau SJ, Oda R (2001) Linear viscoelasticity of salt-free
wormlike micellar solutions. Colloid Surf A 183:5–14
37. Hassan PA, Candau SJ, Kern F, Manohar C (1998) Rheology of
wormlike micelles with varying hydrophobicity of the counter-
ion. Langmuir 14:6025–6029
Dapeng Zhou earned her master’s degree in applied chemistry from
China Research Institute of Daily Chemical Industry in 2009, and
then joined Zhejiang Zanyu Technology Co., Ltd. as an engineer.
Currently, she is working on surfactants and olein chemistry.
Yujun Feng is a professor at the Polymer Research Institute, State
Key Laboratory of Polymer Materials Engineering, Sichuan Univer-
sity, People’s Republic of China. After earning his Ph.D. in applied
chemistry from the Southwest Petroleum University, China, in 1999,
he moved to France performing his two post-doctoral researches at a
38. Granek R, Cates ME (1992) Stress relaxation in living polymers:
results from
96:4758–4767
a Poisson renewal model. J Chem Phys
´
joint laboratory of CNRS/Universite de Pau and at Institut Franc¸ais du
Petrole (IFP). In 2004, he returned to the Chengdu Institute of
39. Raghavan SR, Kaler EW (2001) Highly viscoelastic wormlike
micellar solutions formed by cationic surfactants with long
unsaturated tails. Langmuir 17:300–306
40. Clausen TM, Vinson PK, Minter JR, Davis HT, Talmon Y, Miller
WG (1992) Viscoelastic micellar solutions—microscopy and
rheology. J Phys Chem 96:474–484
´
Organic Chemistry, Chinese Academy of Sciences, and then to
Sichuan University in September, 2012. Professor Feng has been
focusing recently on self-assemblies of surfactants and amphiphilic
polymers, as well as their applications in oil and gas productions.
123