Synthesis, Micellization, and Surface Activity of Novel Linear-Dendritic Carboxylate Surfactants

Article abstract of DOI:10.1002/jsde.12455

Two generations of novel linear-dendritic carboxylate surfactants C₁₈-G₁-(COONa)₂ and C₁₈-G₂-(COONa)₄ have been synthesized by the divergent method and their structures are characterized by ¹H Nuclear Magnetic Resonance and Infrared analysis. The electrical conductivity measurement is used to measure the Krafft temperatures of C₁₈-G₁-(COONa)₂ and C₁₈-G₂-(COONa)₄, which are much smaller than those of the corresponding conventional surfactant sodium stearate. The markedly enhanced solubility of two linear-dendritic surfactants is ascribed to the high hydrophilicity of surfactant headgroups induced by the carboxylate and ester groups. The critical micelle concentration (CMC) values obtained from both the electrical conductivity and surface tension measurements indicate that the micellizations of linear-dendritic surfactants become favorable with the increase in the number of the surfactant headgroup. However, the surface activity parameters including the surface tension at the CMC, maximum surface excess, and minimum surface area reveal that C₁₈-G₁-(COONa)₂ exhibits greater efficiency in absorbing at the air/water interface compared to C₁₈-G₂-(COONa)₄, owing to their different steric repulsions of the surfactant headgroups. In addition, C₁₈-G₁-(COONa)₂ and C₁₈-G₂-(COONa)₄ have higher emulsifying ability than the conventional surfactants sodium stearate and sodium octadecyl sulfate.

Full text of DOI:10.1002/jsde.12455

J Surfact Deterg (2020)
DOI 10.1002/jsde.12455
ORIGINAL ARTICLE
Synthesis, Micellization, and Surface Activity of Novel Linear-
Dendritic Carboxylate Surfactants
1#
1#
1
2
1
1
Yuning Lou · Yajuan Dong · Xiaoyong Wang
· Feirong Gong · Min Zhao · Zongming Rong
Received: 18 January 2020 / Revised: 14 June 2020 / Accepted: 17 July 2020
2020 AOCS
©
Abstract Two generations of novel linear-dendritic car-
absorbing at the air/water interface compared to C -G -
18
2
boxylate surfactants C -G -(COONa) and C -G -
(COONa) , owing to their different steric repulsions of the
1
8
1
2
18
2
4
(
COONa) have been synthesized by the divergent method
surfactant headgroups. In addition, C -G -(COONa) and
C -G -(COONa) have higher emulsifying ability than the
18 2 4
conventional surfactants sodium stearate and sodium
octadecyl sulfate.
4
18
1
2
1
and their structures are characterized by H Nuclear Mag-
netic Resonance and Infrared analysis. The electrical con-
ductivity measurement is used to measure the Krafft
temperatures of C -G -(COONa) and C -G -(COONa) ,
18
1
2
18
2
4
which are much smaller than those of the corresponding
conventional surfactant sodium stearate. The markedly
enhanced solubility of two linear-dendritic surfactants is
ascribed to the high hydrophilicity of surfactant headgroups
induced by the carboxylate and ester groups. The critical
micelle concentration (CMC) values obtained from both
the electrical conductivity and surface tension measure-
ments indicate that the micellizations of linear-dendritic
surfactants become favorable with the increase in the num-
ber of the surfactant headgroup. However, the surface
activity parameters including the surface tension at the
CMC, maximum surface excess, and minimum surface area
reveal that C -G -(COONa) exhibits greater efficiency in
Keywords Linear-dendritic surfactant ꢀ Krafft
temperature ꢀ Micellization ꢀ Electrical conductivity ꢀ
Surface tension
J Surfact Deterg (2020).
Introduction
The possibilities of varying headgroup-tail architecture to
design novel types of surfactants have drawn increasing
attention both in industrial and academic fields (Asadov
et al., 2019a; Mirgorodskaya et al., 2018; Naves
et al., 2013). Dendritic surfactants usually have one hydro-
phobic or hydrophilic chain connecting with the divergent
groups like branches, where the number of branched groups
arranged in a neat way can increase as the surfactant gener-
ation increases (Shavykin et al., 2018). The unique struc-
ture causes dendritic surfactants to have special aggregation
behaviors in the solution and at the interface, together with
varied advantages such as controllable molecular structure,
geometric symmetry of molecular configuration, variable
types, and number of functional groups (Suek and
Lamm, 2008). The surfactants containing the dendritic
polymeric structures have been widely investigated in the
synthesis, aggregation, and application properties (Gosika
et al., 2019; Tian et al., 2019).
18
1
2
*
*
*
1
Xiaoyong Wang
xiaoyong@ecust.edu.cn
Feirong Gong
gongfeirong@ecust.edu.cn
Min Zhao
zhaomin6502@sina.com
School of Chemistry & Molecular Engineering, East China
University of Science and Technology, Shanghai, 200237, China
2
School of Materials Science & Engineering, East China
University of Science and Technology, Shanghai, 200237, China
Present address: Yajuan Dong, Enkun Chemical Co., Ltd. Shanghai,
Shanghai 200444, China
#
These two co-first authors contributed equally to this work.
J Surfact Deterg (2020)

J Surfact Deterg
1
Compared to dendritic polymeric surfactants with rela-
tively high polydispersity, dendritic surfactants with low
molecular weight have the fixed molecular mass, high solu-
bility capacity, and easily controlled aggregation behaviors.
Polypeptides can be thought as dendritic molecules, carry-
ing a long carbon chain on which different functional
groups are grafted (Jacobs et al., 2014). Actually, some sur-
factants commonly studied such as sodium bis(2-
ethylhexyl) sulfosuccinate and Gemini surfactants have
branched structures in their headgroups or hydrophobic
tails, which brings about many unique properties superior
to those of the surfactants carrying one headgroup and one
alkyl chain (Allen et al., 2019; Franke and Rehage, 2019a).
The surfactants with multiple headgroups by grafting a den-
dritic unit of poly(amidoamine) onto an octadecyl chain have
been synthesized, which could spontaneously form vesicles
in aqueous solutions at pH > 5 (Wang et al., 2008). The
branched and multiheaded surfactants can be considered as
the first generation of linear-dendritic surfactants. However,
linear-dendritic surfactants with the strict symmetric configu-
ration have not been reported, most probably due to the lack
of the controlled synthetic procedures.
C -G -(COONa) have been characterized by H NMR and
18
2
4
IR analysis. The electrical conductivity measurement is used
to determine the Krafft temperatures of C -G -(COONa)
and C -G -(COONa) , together with sodium stearate for
comparison. From the critical micelle concentrations (CMC)
determined conductometrically at various temperatures, the
relative changes in Gibbs energy of surfactant micellization
are evaluated. The surface tension measurement is further
employed to study the surface properties of C -G -
18
1
2
18
2
4
18
1
(COONa) and C -G -(COONa) . Finally, the emulsifying
ability of C -G -(COONa) and C -G -(COONa) is mea-
2
18
2
4
18
1
2
18
2
4
sured in comparison with the conventional surfactants
sodium stearate and sodium octadecyl sulfate. These studies
are intended to deeply understand how the dendritic
headgroup influences the solubility, micellization, and sur-
face activity of novel linear-dendritic surfactants.
Materials and Methods
Materials
Fatty acids and their salts are surface-active materials,
which are known as the soap components for over
Sodium stearate (C H COONa, purity ≥99%) was pur-
chased from TCI (Shanghai, China) Development Co., Ltd.
18 37
4000 years (Zaidi et al., 2018). Currently, fatty acid com-
Sodium octadecyl sulfate (C H OSO Na, purity ≥99%)
18
37
3
pounds are widely used in daily cosmetics, drug encapsula-
tion, and the construction of high-porosity materials.
However, the application of fatty acid compounds are
somewhat limited by the low solubility especially for the
compounds with the long and saturated alkyl chain
was obtained from Acros Organics (Shanghai, China) Co.,
Ltd. 2,2-Bis(hydroxymethyl)propionic acid (purity ≥99%)
was purchased from Shanghai D&B Biological Scientific
(
Shanghai, China) Co., Ltd. Octadecanol (purity ≥99%),
succinic anhydride (purity ≥99%), and
-dimethylaminopyridine (DMAP, purity ≥99%) were
obtained from J&K Scientific (Shanghai, China) Co., Ltd.
,2-dimethoxypropane (purity ≥99%) and ethanol (C H OH,
(
Khuwijitjaru et al., 2002). Sodium stearate, for example,
4
ꢁ
has a high Krafft temperature over 60 C, and is almost
insoluble in water at room temperature. Some approaches
such as introducing hydrophilic units such as oxyethylene
into the hydrocarbon chain or hydrophilic headgroup pro-
vide good water solubility for fatty acid compounds (Liu
et al., 2008; Voutsas et al., 2002). Recently, Bhattacharya
et al. found that the multiheaded surfactant has the
decreased Krafft temperature, owing to the strong interac-
tion between water and the large surfactant hydrophilic part
2
2
5
purity ≥99%) were obtained from Sinopharm Chemical
Reagent (Shanghai, China) Co., Ltd. p-Toluenesulfonic acid
monohydrate (purity ≥98%) was obtained from Energy
Chemical (Shanghai, China) Co., Ltd. Triethylamine (purity
0
≥
99%), N,N -dicyclohexylcarbondimine (purity ≥99%) and
sodium hydroxide (NaOH, purity ≥96%) was obtained from
Aladdin Chemical (Shanghai, China) Co., Ltd. Silicone oil
was obtained from Hangzhou Sili Organosilicone (Hang-
zhou, China) Co., Ltd. All other chemical reagents used
were of analytical grade, and water was double distilled.
(Bhattacharya and Samanta, 2011).
In order to obtain suitable biodegradable and biocompati-
ble drug carrier, our group previously synthesized a series of
linear-dendritic block copolymers consisting of linear
poly(ethylene glycol) and comb-like poly(L-lactide) (Gong
et al., 2009). Based on the process used for preparing the
linear-dendritic block copolymers, the present work gives a
convenient synthetic route for two generations of novel
linear-dendritic carboxylate surfactants C -G -(COONa)
Synthesis of Linear-Dendritic Surfactants
Two generations of linear-dendritic carboxylate surfactants
C -G -(COONa) and C -G -(COONa) were synthe-
1
8
1
2
18
1
2
18
2
4
and C -G -(COONa) , holding a hydrophobic linear alkyl
sized using an adapted method reported in our previous
work (Gong et al., 2009). As outlined in Scheme 1, the
synthesis procedure is initialized by the key intermediate
18
2
4
chain connected with two and four carboxylate headgroups,
respectively. The structures of C -G -(COONa) and
1
8
1
2
J Surfact Deterg (2020)

J Surfact Deterg
1 2 2 4
Scheme 1 Synthetic route of C18-G -(COONa) and C18-G -(COONa)
compound of 2,2,5-trimethyl-1,3-dioxane-5-carboxylic
anhydride, and followed by grafting with two or four car-
boxylate end groups via the ring-opening reaction.
Synthesis of 2,2,5-trimethyl-1,3-dioxane-5-carboxylic
anhydride. 2,2,5-Trimethyl-1,3-dioxane-5-carboxylic anhy-
dride was obtained by the dehydration of the acetonide-
protected 2,2-bis(hydroxymethyl) propionic acid according
to the method described by Malkoch et al. (Malkoch
et al., 2002). 2,2-Bis(hydroxymethyl)propionic acid was
reacted with 2,2-dimethoxypropane and p-toluenesulfonic
acid monohydrate in acetone for 4 h. Then the mixture was
poured in triethylamine and stirred for 10 min. After
removing the solvent, the dried powders were reacted
0
with N, N -dicyclohexylcarbondimine in CH Cl for 24 h.
2
2
J Surfact Deterg (2020)

J Surfact Deterg
The product of 2,2,5-trimethyl-1,3-dioxane-5-carboxylic
anhydride was finally obtained after the purification. H
on a Thermo Electron Corporation Nicolet 6700 FT-IR
spectrophotometer and KBr pellets of the samples were
used in analysis.
1
NMR (CDCl ) δ: 1.27 (s, 12H), 1.358 (s, 6H), 4.12–3.87
3
(d, J = 12, 8H).
Synthesis of C -G -(OH) and C -G -(OH) . C -G -
Electrical Conductivity Measurement
18
1
2
18
2
4
18
1
(
OH) was prepared by the method described by Würsch
2
et al. (Würsch et al., 2001). Octadecanol and DMAP were
dissolved in the mixture of water and CH Cl , and then
The electrical conductivities of sodium stearate, C -G -
18
1
(COONa) , and C -G -(COONa) solutions were mea-
2
2
2
18
2
4
2
,2,5-trimethyl-1,3-dioxane-5-carboxylic anhydride was
sured as a function of surfactant concentration at different
temperatures. A DDS-307 conductivity meter was used
with a dip-type cell made of platinum black. In all experi-
ments, the cell was partially dipped into the surfactant solu-
tion at the desired temperatures in a water bath.
added. This reaction was kept for 24 h. Then, the interme-
diate compound was further reacted with Dowex H resin
in methanol for 24 h. After cooling, filtering, and concen-
trating, the product of C -G -(OH) was finally obtained
+
1
8
1
2
as white crystals. C -G -(OH) was synthesized in the
1
8
2
4
same way as C -G -(OH) , except the proportion of mate-
Dynamic Light Scattering Measurement
18
1
2
1
rials is different. For C -G -(OH) , H NMR (CDCl ) δ:
1
8
1
2
3
0.88 (t, J = 8, 3H), 1.06 (s, 3H), 1.30 (s, 30H), 3.73 (t,
The particle size distribution of C -G -(COONa) and
18
1
2
J = 10, 2H), 3.89 (d, J = 4, 4H), 4.17 (t, J = 16, 2H). For
C -G -(COONa) micelles was determined using a
18 2 4
1
ꢁ
C -G -(OH) , H NMR (CDCl ) δ: 0.88 (t, J = 8, 3H),
Malvern Zetasizer Nano ZS at 40 C. The samples were fil-
tered with a 0.45 μm syringe filter before test to remove the
dust and other interference factors. The measurement was
carried out in situ by dynamic light scattering with the help
of Malvern Zetasizer Software v.6.34. The data of time-
dependent fluctuations in the scattering intensity were
treated using the cumulant analysis to estimate the diffusion
coefficient, which is finally converted into the hydrody-
namic diameter of the surfactant micelles according to the
Stokes-Einstein equation.
1
8
2
4
3
1.05 (s, 3H), 1.27 (s, 30H), 3.72 (t, J = 8, 4H), 3.86 (d,
J = 4, 8H), 4.12 (t, J = 16, 2H), 4.28–4.45 (d, J = 12, 4H).
Synthesis of C -G -(COOH) and C -G -(COOH) .
1
8
1
2
18
2
4
C -G -(COOH) was obtained by the reaction between
1
8
1
2
C -G -(OH) and succinic anhydride with the help of
1
8
1
2
DMAP and triethylamine. The thin layer chromatography
was used to detect the reaction process. C -G -(COOH)
4
1
8
2
was synthesized from C -G -(OH) in the same way as
1
8
2
4
C -G -(COOH) , except the dosage of succinic anhydride
1
8
1
2
1
is different. For C -G -(COOH) , H NMR (CDCl ) δ:
1
8
1
2
3
0
2
.76 (t, J = 8, 3H), 1.15 (s, 3H), 1.19 (s, 30H), 1.51 (s, 2H),
.50 (t, J = 4, 8H), 4.05 (s, 2H), 4.14 (s, 4H). For C -G -
Surface Tension Measurement
18
2
1
(COOH) , H NMR (CDCl ) δ: 0.76 (t, J = 8, 3H), 1.08 (s,
The surface tensions of C -G -(COONa) and C -G -
4
3
18
1
2
18
2
9H), 1.23 (s, 30H), 1.52 (s, 2H), 2.50 (t, J = 4, 16H), 4.04
(COONa) solutions were measured as a function of surfac-
4
(
t, J = 8, 2H), 4.12 (s, 8H).
tant concentration by a Sartorius DCAT11 tensiometer
using the Wilhelmy plate method at 40 C. Before each
ꢁ
Synthesis of C -G -(COONa) and C -G -(COONa) .
18
1
2
18
2
4
C -G -(COOH) and sodium hydroxide were first dis-
measurement, the plate was firstly rinsed with double dis-
tilled water and then burned to red. For the comparability
of equilibrium surface tension, the measurements were
stopped when the standard deviation of the surface tension
1
8
1
2
solved in ethanol, respectively. Then, the solution of
sodium hydroxide was added to C -G -(COOH) solution
1
8
1
2
drop by drop. C -G -(COONa) was finally precipitated
18
1
2
−
1
out from the solution. C -G -(COONa) is synthesized in
values was less than 0.01 mN m .
1
8
2
4
the same way as C -G -(COONa) , except the dosage of
1
8
1
2
sodium hydroxide is twice as much as C -G -(COONa) .
Emulsification Test
1
8
1
2
The structures of C -G -(COONa) and C -G -(COONa)
4
1
8
1
2
18
2
1
were characterized by H NMR and IR measurements.
The emulsifying ability of C -G -(COONa) and C -G -
18
1
2
18
2
(
COONa) was measured in comparison with sodium stea-
4
Structural Characterization
rate and sodium octadecyl sulfate. About 20 mL aqueous
surfactant solution and 10 mL silicone oil were mixed
under magnetic stirring for 30 min in 40 C water bath.
Then, the emulsions were prepared through the high-speed
homogenization at 10,000 rpm for 5 min using a Fluko
FA25 homogenizer. The stability of emulsions was tested
by observing the time for the separation of 5 mL aqueous
phase from the emulsion layer.
1
ꢁ
The H NMR spectra were recorded on a Bruker Avance
1
4
00 spectrometer ( H, 400.00 MHz) at room temperature.
The tested samples were prepared in deuterium chloroform,
and tetramethylsilane was used as the internal standard. All
chemical shifts (δ) values downfield from the signal of
tetramethylsilane were given. IR spectra were obtained
J Surfact Deterg (2020)

J Surfact Deterg
Statistical Analysis
the complete reaction of 2,2,5-trimethyl-1,3-dioxane-
-carboxylic anhydride with octadecanol and C -G -(OH) .
5
18
1
2
Data are presented as mean and standard deviations. For all
measurements, a minimum of three replicates was taken for
data analysis.
While C -G -(COOH) and C -G -(COOH) were syn-
18 1 2 18 2 4
thesized by reacting C -G -(OH) and C -G -(OH) with
18
1
2
18
2
4
succinic anhydride, respectively, two linear-dendritic car-
boxylate surfactants C -G -(COONa) and C -G -
18
1
2
18
2
(
(
COONa) were finally obtained by the reaction of C -G -
4 18 1
COOH) and C -G -(COOH) with sodium hydroxide in
2
18
2
4
1
Results and Discussion
ethanol, respectively. Figure 2 gives the H NMR spectra
of C -G -(COONa) and C -G -(COONa) , which are
18
1
2
18
2
4
Synthesis and Characterization of C -G -(COONa)
almost same as those of C -G -(COOH) and C -G -
18 1 2 18 2
1
8
1
2
and C -G -(COONa)
(COOH) due to nearly same chemical environments of
1
8
2
4
4
their hydrogens. The characteristic peaks attributed to the
quaternary carbon of linear-dendritic structures are reserved
for C -G -(COONa) and C -G -(COONa) . Compared
The linear-dendritic carboxylate surfactants C -G -
18
1
(
COONa) and C -G -(COONa) have been synthesized
2 18 2 4
18
1
2
18
2
4
1
from the compound of 2,2,5-trimethyl-1,3-dioxane-
-carboxylic anhydride, which was then grafted with two
to the H NMR spectra of C -G -(OH) and C -G -
18 1 2 18 2
5
(OH) , the presence of two new peaks at 2.3–2.5 ppm for
4
or four carboxylate end groups (Gong et al., 2009; Malkoch
et al., 2002). Octadecanol was reacted with 2,2,5-trimethyl-
C -G -(COONa) and C -G -(COONa) may give the
18
1
2
18
2
4
indication of the conversion from the hydroxyl group into
carboxylate group. Carboxylate and ester groups make two
CH2 groups in the linkage have different chemical envi-
ronments (Satyarthi et al., 2009; Wang et al., 2016), lead-
1
,3-dioxane-5-carboxylic anhydride to obtain C -G -(OH) ,
18 1 2
which can further react with 2,2,5-trimethyl-1,3-dioxane-
1
5
-carboxylic anhydride to obtain C -G -(OH) . H NMR
18 2 4
1
spectra of C -G -(OH) and C -G -(OH) are given in
ing to two different H NMR peaks at 2.3–2.5 ppm.
18
1
2
18
2
4
Fig. 1. Two characteristic peaks at about 1.06 and 3.73 ppm
are observed, which are respectively attributed to the signals
Moreover, the ratios of peak areas at about 0.88, 1.06, and
2.3–2.5 ppm of C -G -(COONa) and C -G -(COONa)
4
18
1
2
18
2
from the hydrogens in CH and CH2 groups linked to
are in well agreement with their linear-dendritic structures.
The structures of C -G -(COONa) and C -G -
3
the quaternary carbon of linear-dendritic surfactants. The
quaternary carbon can be considered as the important bifur-
cation group for C -G -(OH) and C -G -(OH) , which is
18
1
2
18
2
(COONa) can be further demonstrated by comparing their
4
18
1
2
18
2
4
IR spectra together with that of sodium stearate, as shown
in Fig. 3. All three surfactants have C H stretching vibra-
1
generally seen in the H NMR curves of the dendritic poly-
meric molecules (Würsch et al., 2001). Furthermore, the
peak at about 4.17 ppm, corresponding to the CH2 group
connected with the ester group formed newly, may prove
−1
tion bands in the region from 2800 to 3000 cm and high-
−
1
intensity band at ~1570 cm , which is ascribed to the
stretching vibration from C O group of carboxylates. This
result is generally observed in the IR spectra of carboxylate
1
1
Fig 1 H NMR spectra of C18-G
1
-(OH)
2
and C18-G
2
-(OH)
4
. The peak
Fig 2 H NMR spectra of C18-G
1
-(COONa)
2
and C18-G
2 4
-(COONa) .
at 7.26 ppm is originated from the solvent CDCl
3
The peak at 7.26 ppm is originated from the solvent CDCl
3
J Surfact Deterg (2020)

J Surfact Deterg
Fig 3 IR spectra of sodium stearate, C18-G
COONa)
1
-(COONa)
2
, and C18-G
2
-
Fig 5 Variations of the maximum solubility (circular point) and CMC
(
4
(square point) of sodium stearate, C18-G
COONa) as a function of temperature
1 2 2
-(COONa) , and C18-G -
(
4
et al., 2004), beyond which the surfactant is no longer dis-
solved in water and the electrical conductivity does not
increase anymore. Because the ionic surfactants have the
significantly improved solubility above the Krafft tem-
perature, the electrical conductivity continues to increase
with increasing surfactant concentration even after the
turning point. At high temperatures, the turning point in
the electrical conductivity curve corresponds to the CMC
of the surfactant (Chauhan et al., 2012). While surfactant
molecules are completely ionized below the CMC, the
counterions are bound to surfactant micelles above the
CMC, which subsequently causes a reduction in the
slope of the electrical conductivity relative to the surfac-
tant concentration.
Fig 4 Variations of the electrical conductivity as a function of the
concentration of C18-G -(COONa) at various temperatures
1
2
Figure 5 gives the variations of the maximum solubility
and CMC of sodium stearate, C -G -(COONa) , and C -
compounds of fatty acids (Bani-Jaber et al., 2012; Vaisman
18
1
2
18
−1
et al., 2013). Two new peaks at ~1740 cm are observed
only for C -G -(COONa) and C -G -(COONa) , which
G -(COONa) as a function of temperature. Determined
2
4
18
1
2
18
2
4
from the interception of the two lines of maximum solubil-
ity and CMC, the Krafft temperatures of sodium stearate,
C -G -(COONa) , and C -G -(COONa) are 65.2, 33.2,
are resulted from the stretching vibration from C O in the
ester group. The existence of these two special bands fur-
ther illustrates that the two generations of linear-dendritic
surfactants have been successfully synthesized.
1
8
1
2
18
2
4
ꢁ
and 28.4 C, respectively. Sodium stearate carrying an alkyl
chain with 18 carbons has high hydrophobicity, leading to
the low solubility and high Krafft temperature (Nardello
et al., 2006). Compared to sodium stearate, sulfate surfac-
tant sodium octadecyl sulfate with the same alkyl chain has
a smaller Krafft temperature (56.0 C), whereas sodium
pentadecyl sulfate (31.5 C) and sodium tetradecyl sulfate
(30.0 C) with shorter alkyl chain have much smaller Krafft
Solubility and Micellization of Linear-Dendritic
Carboxylate Surfactants
ꢁ
ꢁ
The solubility and micellization properties of C -G -
18
1
ꢁ
(
COONa) and C -G -(COONa) as well as sodium stea-
2
18
2
4
rate have been investigated using the electrical conductivity
method. Figure 4 gives the representative plots of electrical
conductivity against the surfactant concentration of C -G -
temperatures (Li et al., 2005). It is clear that the Krafft tem-
peratures of C18-G -(COONa) and C18-G -(COONa) are
1 2 2 4
much lower than sodium stearate and sodium octadecyl sul-
fate, but roughly equivalent to sodium pentadecyl sulfate
and sodium tetradecyl sulfate. The decreased Krafft temper-
18
1
(
COONa) at different temperatures. At low-surfactant con-
2
centrations, the electrical conductivity increases linearly
with the increase of C -G -(COONa) concentration at all
atures of C18-G -(COONa) and C18-G -(COONa) corre-
1 2 2 4
1
8
1
2
investigated temperatures. However, after a turning point,
the electrical conductivity curve gives different changes at
low and high temperatures. At low temperatures, the almost
unchanged electrical conductivity values suggest that the
maximum solubility is reached at the turning point (Bakshi
spond to the superior solubilities, which could be a
consequence of their two and four headgroups containing
carboxylate and ester groups. This result is consistent with
the observation by Holmberg et al., who found the
enhanced solubility for the surfactants upon increasing the
J Surfact Deterg (2020)

J Surfact Deterg
number of cationic headgroup linked with ester group
ΔG = RTð1 + 4βÞlnCMC + 4RTβln4
ð3Þ
(Tehrani-Bagha and Holmberg, 2010).
where CMC is expressed in molarity, R is the gas constant,
and T is temperature on the Kelvin scale. β is the degree of
dissociation of the micelles, which is determined from the
ratio of the post-micellar slope to the pre-micellar slope in
the electrical conductivity curve.
In agreement with the Krafft temperature data, C -G -
18
1
(
COONa) and C -G -(COONa) give much smaller CMC
2
18
2
4
values than sodium stearate, indicating much better tendency
for forming micelles. The formation of micelles is not only
affected by the hydrophobic interaction between surfactant
alkyl chains, but also by the intermolecular force such as the
electrostatic repulsion between the surfactant headgroups,
the hydrogen bonding between the surfactant headgroups
and water molecules in the solution. Given that C -G -
The ΔG values of sodium stearate, C -G -(COONa) ,
18
1
2
and C -G -(COONa) at high temperatures beyond the
18
2
4
lowest point in the CMC curves have been obtained. The
average ΔG values are 32.1, 64.3, and 100.4 KJ mol ,
−1
18
1
ꢁ
corresponding to sodium stearate at 70–80 C, C -G -
18
1
(
COONa) , C -G -(COONa) , and sodium stearate share
2 18 2 4
ꢁ ꢁ
COONa) at 45–55 C, and C -G -(COONa) at 45–55 C,
2 18 2 4
(
the same linear alkyl chain, the structure of headgroup part
should be the major determining factor for the micelle for-
mation. Although the headgroups of linear-dendritic surfac-
tants have the enhanced electrostatic repulsion compared to
sodium stearate, the increase in the hydrophilicity of linear-
dendritic surfactants may cause the micelle formation to be
more favorable. This result is in well agreement with previ-
ous result from Garofalo et al. (2014), where a decrease of
CMC by increasing the hydrophilicity of copolymers was
reported. Bhattacharya et al. discussed that the ester linkages
at the hydrocarbon chain-charged headgroup connection,
located at the micellar stern layer region, may facilitate inter-
molecular association of the surfactants through dipole-
induced dipolar interactions and therefore probably enhances
the tendency to aggregate into surfactant micelles
respectively. All three surfactants give the negative ΔG
values, which indicate the spontaneous characteristics of
the micellization process. Moreover, it is noted that the
absolute values of ΔG have the order of C -G -
18
2
(
COONa) > C -G -(COONa) > sodium stearate. Previ-
4 18 1 2
ously, Holmberg et al. found that the surfactants had
smaller CMC values upon increasing the number of cat-
ionic headgroup linked with ester group (Tehrani-Bagha
and Holmberg, 2010). The thermodynamic calculation
from Rosen et al. also suggested that the ΔG value
becomes more negative upon the introduction of oxy-
ethylene units into surfactant molecule (Dahanayake
et al., 1986). Consistent with these reported work, our
result reveals that the dendritic headgroup composed of the
carboxylate and ester groups can increase the driving force
for the formation of micelles, which leads to the most nega-
tive ΔG value for C -G -(COONa) .
(Bhattacharya and Haldar, 2004). Therefore, the CMC
values are more affected by the branching degree of
headgroup: the CMC value of C -G -(COONa) with four
18
2
4
18
2
4
As shown in Fig. 6, dynamic light scattering has been
headgroups is lower than that of C -G -(COONa) with two
18
1
2
used to measure the particle size distribution of C -G -
18
1
headgroups. Additionally, the CMC values of three surfac-
tants decrease first and then increase with increasing temper-
ature. This result is generally observed for the ionic
surfactants (González-Pérez et al., 2001), owing to the differ-
ent influences of temperature on the hydrations of surfactant
hydrophobic and hydrophilic parts.
(
COONa) and C -G -(COONa) micelles at the surfactant
2 18 2 4
The formation of surfactant micelles is a spontaneous
process, which is usually evaluated by the relative change
in Gibbs energy of micellization (ΔG). ΔG is one important
thermodynamic parameter of the surfactant system, which
can be calculated based on the CMC and electrical conduc-
tivity data. There are different equations to calculate ΔG
values of surfactant micellization, depending on the num-
bers of surfactant headgroup and alkyl chain (Franke and
Rehage, 2019b; Zana, 1996). Considering the structures of
headgroups, the ΔG values of sodium stearate, C -G -
18
1
(
COONa) , and C -G -(COONa) can be calculated
2 18 2 4
according to the Eqs 1–3, respectively.
Fig 6 Particle size distribution of C18-G
.10 mM; b, 0.15 mM; c, 0.25 mM) and C18-G
d, 0.10 mM; e, 0.15 mM; f, 0.25 mM)
1
-(COONa)
2
micelles (a,
micelles
ΔG = RTð1 + βÞlnCMC
ð1Þ
ð2Þ
0
(
2
-(COONa)
4
ΔG = RTð1 + 2βÞlnCMC + 2RTβln2
J Surfact Deterg (2020)

J Surfact Deterg
concentrations of 0.10, 0.15, and 0.25 mM above the CMC
values. When the surfactant concentration increases from
samples are clear solutions without any precipitate, which
are prepared at the concentrations quite lower than their
maximum solubilities. Moreover, these samples were care-
0
1
.10 to 0.25 mM, the mean particle size increases from
0 to 15 nm for C -G -(COONa) and from 6 to 16 nm
ꢁ
fully maintained at 40 C above the Krafft temperatures of
1
8
1
2
for C -G -(COONa) , respectively. The slightly fast
C -G -(COONa) and C -G -(COONa) . Figure 7 gives
18
2
4
18
1
2
18
2
4
increase in the mean particle size for C -G -(COONa)
4
the plots of surface tension (γ) versus logarithm of surfac-
tant concentration (C) for C -G -(COOH) , C -G -
1
8
2
micelles may support the above discussion about the stron-
ger tendency of the micelle formation for C -G -
18
1
2
18
2
(COOH) , C -G -(COONa) , and C -G -(COONa) at
18
2
4
18
1
2
18
2
4
ꢁ
(
COONa)4 than C -G -(COONa) . On the other hand,
40 C. For four compounds, as the surfactant concentration
increases, the surface tension values decrease gradually and
finally achieve a relative stable value. This result suggests
that both carboxylic and carboxylate types of linear-
dendritic compounds can adsorb at the air/water interface.
However, C -G -(COONa) and C -G -(COONa) gener-
18
1
2
many people have observed the so-called sphere-to-rod
micelle transition when the surfactant concentration reaches
a threshold value (Christov et al., 2004; Miyagishi
et al., 1996). In fact, the relatively small values of the mean
particle size of C -G -(COONa) and C -G -(COONa)
18
1
2
18
2
4
18
1
2
18
2
4
micelles are not as large compared with nonspherical
micelles. Meanwhile, it is seen that there is no significant
change in the width of particle size distribution peaks of
C -G -(COONa) and C -G -(COONa) micelles. These
ally have lower surface tension values than those of C -
18
G -(COOH) and C -G -(COOH) , which indicates higher
1
2
18
2
4
surface activity of two linear-dendritic carboxylate surfac-
tants (Atrafi and Pawlik, 2016). It is noted that C -G -
1
8
1
2
18
2
4
18
1
results may indicate that C -G -(COONa) and C -G -
(COONa) and C -G -(COONa) give nonlinear changes
2 18 2 4
1
8
1
2
18
2
(
COONa) form spherical micelles at low surfactant con-
in the whole surfactant concentration range below the break
point in the curves of γ-logC, which is generally observed
for the surfactant systems and can be fitted by Szyszkowski
equation (Daniel and Berg, 2002). According to the com-
mon method used by other investigators (Xu et al., 2015),
the CMC values of C -G -(COONa) and C -G -
4
centrations (Kuperkar et al., 2010).
Surface Activity of Linear-Dendritic Carboxylate
Surfactants
18
1
2
18
2
(
COONa) are determined from the interceptions of two
Surface tension measurement is employed to evaluate
the surface activity of C -G -(COONa) and C -G -
4
furnished straight lines from the linearly changed data
below and above the break point, as shown in the insert in
1
8
1
2
18
2
(
COONa) , in comparison with their corresponding carbox-
4
Fig. 7. The CMC values of C -G -(COONa) and C -G -
ylic acids C -G -(COOH) and C -G -(COOH) . All
18
1
2
18
2
18
1
2
18
2
4
ꢁ
COONa) at 40 C are 0.025 and 0.017 mM respectively,
4
(
as listed in Table 1. The CMC value of C -G -(COONa)
4
18
2
is smaller than that of C -G -(COONa) , which are highly
18
1
2
consistent with the result obtained from the electrical con-
ductivity measurement.
As shown in Table 1, the surface tension value at the
CMC (γCMC) of C -G -(COONa) is higher than that of
18
2
4
C -G -(COONa) . The ability of a surfactant to reduce the
18
1
2
surface tension of water depends on what group it can sub-
stitute for the water at the surface and to what extent it can
replace it in its ultimate adsorption. Thus, the composition
of surfactant headgroup and its maximum adsorption
capacity are decisive factors for reducing surface tension.
Although there are more hydrophilic headgroups for C -
18
Fig 7 Surface tension values of C18-G
COOH) (b), C18-G -(COONa) (c), and C18-G
function of surfactant concentration. The inset shows the determina-
tion of CMC using C18-G -(COONa) as an example
1
-(COOH)
2
2
(a), C18-G -
G -(COONa) , the adsorption of C -G -(COONa) mole-
2
4
18
2
4
(
4
1
2
2 4
-(COONa) (d) as a
cules at the air/water interface is somewhat hampered due
to higher steric hindrance. So C -G -(COONa) is less
2
4
18
2
4
Table 1 Surface activity parameters of C18-G
1 2 2 4
-(COONa) and C18-G -(COONa)
CMC (mN m−
1
)
Γ
max (μmol m−2
)
A
min (nm )
2
Surfactant CMC (mM)
γ
C
C
18-G
18-G
1
-(COONa)
-(COONa)
2
4
0.025
0.017
31.38
34.36
3.39
0.99
0.49
1.67
2
J Surfact Deterg (2020)

J Surfact Deterg
capable of reducing surface tension than C -G -
Emulsifying Ability of Linear-Dendritic Carboxylate
Surfactants
18
1
(
COONa) . This result together with the CMC data indi-
2
cates that C -G -(COONa) molecules are more inclined
18
2
4
to aggregate into micelles in the solution than to adsorb at
the air/water interface (Alexander et al., 2014; Tan
et al., 2019).
The maximum surface excess (Γmax) and the area occu-
pied by a surfactant molecule (Amin) at the air/water inter-
face are two important parameters for reflecting the
adsorption amount and packing density of surfactant mole-
cules at the air/water interface. Based on Gibbs adsorption
isotherm theory (Asadov et al., 2019b), the values of Γmax
and Amin can be calculated by Eqs 4 and 5.
Surfactant molecules can be absorbed at oil/water inter-
face to create a protective barrier for reducing the physical
contact between the droplets and decreasing the potential
for coalescence (Noori et al., 2014). The separation time
of the aqueous phase from the emulsion layer is used to
measure the emulsifying ability of C -G -(COONa) and
1
8
1
2
C -G -(COONa) in comparison with sodium stearate
1
8
2
4
and sodium octadecyl sulfate. The stability of emulsion
composed of silicone oil and water in the presence of sur-
ꢁ
factant was investigated at 40 C. When sodium stearate
ꢀ
ꢁꢀ
ꢁ
and sodium octadecyl sulfate are added, it takes 52 and
77 s, respectively, for separation of the aqueous layer
from the emulsion, whereas for C -G -(COONa) and
1
dγ
Γmax = −
ð4Þ
2
:303nRT
dlogC
T
18
1
2
024
C -G -(COONa) the times taken are 84 and 106 s,
18 2 4
1
Amin
=
ð5Þ
respectively. The tested four surfactants have the same
alkyl chain except the headgroup structure. Sodium
octadecyl sulfate gives better emulsifying property than
sodium stearate, which is resulted from higher charge den-
sity of sulfate headgroup of the former. Compared to two
conventional surfactants, C -G -(COONa) and C -G -
N Γ
A
max
−
2
where Γ
is expressed in μmol m , A is expressed
max
min
2
in nm , R is the gas constant, T is temperature on the Kel-
−1
vin scale, γ represents the surface tension in mN m , dγ/
dlogC is the slope of the linear line used for the determina-
tion of the CMC value below the break point in the γ-logC
curve, NA is Avogadro’s number. The value of n is the
number of ionic species whose adsorption amount at the
interface changes along with the surfactant concentration.
Considering the headgroup numbers of linear-dendritic car-
boxylate surfactants (Azum et al., 2016; Zana, 2002), 2 and
1
8
1
2
18
2
(
COONa) have higher emulsifying ability owing to their
4
special dendritic headgroups carrying the carboxylate and
ester groups (Zhang et al., 2017).
Conclusions
4
are adopted for n values of C -G -(COONa) and C -
18 1 2 18
G -(COONa) , respectively.
Table 1 gives the values of Γmax and Amin of C -G -
2
4
The linear-dendritic carboxylate surfactants from genera-
tion one to generation two have been synthesized and stud-
ied with respect to their solubility, micellization, and
surface activity. C -G -(COONa) and C -G -(COONa)
4
18
1
(
COONa)2 and C -G -(COONa) . While the values of
18 2 4
Γmax of C -G -(COONa) and C -G -(COONa) are 3.39
18
1
2
18
2
4
18
1
2
18
2
−
2
and 0.99 μmol m respectively, C -G -(COONa) and
1
8
1
2
show high solubility capacity, indicated by their much
smaller Krafft temperatures compared to the corresponding
conventional surfactant sodium stearate. The values of
CMC and ΔG indicate that the micellizations of linear-
dendritic carboxylate surfactants become more favorable
with the increase in the headgroup number. On the con-
trary, compared to C -G -(COONa) , the surface activity
2
C -G -(COONa) have A values of 0.49 and 1.67 nm ,
1
8
2
4
min
respectively. It is noted that C -G -(COONa) has bigger
1
8
1
2
Γmax value than C -G -(COONa) , but the A values
min
18
2
4
show the contrary variation for two linear-dendritic carbox-
ylate surfactants. This result is consistent with the Γmax and
Amin results of other surfactant system (Azum et al., 2016).
C -G -(COONa) has a large molecule volume with four
18
1
2
1
8
2
4
parameters of γCMC, Γmax, and Amin reveal that C -G -
18
2
headgroups to increase the steric hindrance during packing
in the adsorption layer, which results in the decrease of sur-
face adsorption amount and the increase of the area per
molecule (Alexander et al., 2014). Meanwhile, when there
are more hydrophilic groups in the headgroup, the surfac-
tant can get in contact with water directly, be lying and
stretching more at the air/water interface. Therefore, it is
(
COONa) molecules have lower tendency to adsorb at the
4
air/water interface. This result suggests that the increase in
the number of headgroup results in lower intermolecular
packing density of linear-dendritic surfactant molecules at
the air/water interface, mainly due to the steric repulsions
of the dendritic structure of surfactant headgroups. This
work on the solubility, micellization, and surface activity of
linear-dendritic carboxylate surfactants may urge us to
design novel types of surfactants with special structural
properties and aggregation behaviors.
likely that C -G -(COONa) molecules are not closely
18
2
4
packed and have lower packing density at the air/water
interface.
J Surfact Deterg (2020)

J Surfact Deterg
Acknowledgement This work is supported by the National Natural
Science Foundation of China (Grant 21573071).
architecture on the micelle formation and cellular uptake. Bio-
macromolecules, 15:403–415.
Gong, F., Cheng, X., Wang, S., Wang, Y., Gao, Y., & Cheng, S.
(2009) Biodegradable comb-dendritic tri-block copolymers con-
sisting of poly(ethylene glycol) and poly(L-lactide): Synthesis,
characterizations, and regulation of surface morphology and cell
responses. Polymer, 50:2775–2785.
Conflict of Interest The authors declare that they have no conflict
of interest.
González-Pérez, A., del Castillo, J. L., Czapkiewicz, J.,
&
References
Rodríguez, J. R. (2001) Conductivity, density, and adiabatic com-
pressibility of dodecyldimethylbenzylammonium chloride in aque-
ous solutions. The Journal of Physical Chemistry. B, 105:
1720–1724.
Gosika, M., Sen, S., Kundagrami, A., & Maiti, P. K. (2019) Under-
standing the thermodynamics of the binding of pamam dendrimers
to graphene: A combined analytical and simulation study. Lang-
muir, 35:9219–9232.
Jacobs, J., Byrne, A., Gathergood, N., Keyes, T. E., Heuts, J. P. A., &
Heise, A. (2014) Facile synthesis of fluorescent latex nanoparticles
with selective binding properties using amphiphilic glycosylated
polypeptide surfactants. Macromolecules, 47:7303–7310.
Khuwijitjaru, P., Adachi, S., & Matsuno, R. (2002) Solubility of satu-
rated fatty acids in water at elevated temperatures. Bioscience, Bio-
technology, and Biochemistry, 66:1723–1726.
Alexander, S., Smith, G. N., James, C., Rogers, S. E., Guittard, F.,
Sagisaka, M., & Eastoe, J. (2014) Low-surface energy surfactants
with branched hydrocarbon architectures. Langmuir, 30:
3
413–3421.
Allen, F. J., Truscott, C. L., Gutfreund, P., Welbourn, R. J. L., &
Clarke, S. M. (2019) Potassium, calcium, and magnesium bridging
of AOT to mica at constant ionic strength. Langmuir, 35:
5
753–5761.
Asadov, Z. H., Ahmadova, G. A., Rahimov, R. A.,
Hashimzade, S.-Z. F., Ismailov, E. H., Asadova, N. Z., …
Agamaliyeva, D. B. (2019a) Micellization and adsorption proper-
ties of new cationic gemini surfactants having hydroxyisopropyl
group. Journal of Chemical & Engineering Data, 64:952–962.
Atrafi, A., & Pawlik, M. (2016) Surface tension and gas dispersion
properties of fatty acid solutions. Minerals Engineering, 85:
Kuperkar, K., Abezgauz, L., Prasad, K., & Bahadur, P. (2010) Forma-
tion and growth of micelles in dilute aqueous CTAB solutions in
1
38–147.
3 3
the presence of NaNO and NaClO . Journal of Surfactants and
Azum, N., Rub, M. A., & Asiri, A. M. (2016) Micellization and inter-
facial behavior of the sodium salt of ibuprofen–BRIJ-58 in
aqueous/brine solutions. Journal of Solution Chemistry, 45:
Detergents, 13:293–303.
Li, Y., Xu, G., Luan, Y., Yuan, S., & Xin, X. (2005) Property predic-
tion on surfactant by quantitative structure-property relationship:
Krafft point and cloud point. Journal of Dispersion Science and
Technology, 26:799–808.
Liu, X., Piao, X., Wang, Y., & Zhu, S. (2008) Liquid-liquid equilib-
rium for systems of (fatty acid ethyl esters + ethanol + soybean oil
and fatty acid ethyl esters + ethanol + glycerol). Journal of Chemi-
cal & Engineering Data, 53:359–362.
7
91–803.
Bakshi, M. S., Kaura, A., Miller, J. D., & Paruchuri, V. K. (2004)
Sodium dodecyl sulfate–poly(amidoamine) interactions studied by
AFM imaging, conductivity, and Krafft temperature measurements.
Journal of Colloid and Interface Science, 278:472–477.
Bani-Jaber, A., Hamdan, I., & Alkawareek, M. (2012) The synthesis
and characterization of fatty acid salts of chitosan as novel matrices
for prolonged intragastric drug delivery. Archives of Pharmacal
Research, 35:1159–1168.
Malkoch, M., Malmström, E., & Hult, A. (2002) Rapid and efficient
synthesis of aliphatic ester dendrons and dendrimers. Macromole-
cules, 35:8307–8314.
Bhattacharya, S.,
micellization of multiheaded single-chain cationic surfactants.
Langmuir, 20:7940–7947.
Bhattacharya, S., & Samanta, S. K. (2011) Surfactants possessing
multiple polar heads. A perspective on their unique aggregation
behavior and applications. Journal of Physical Chemistry Letters,
&
Haldar, J. (2004) Thermodynamics of
Mirgorodskaya, A. B., Valeeva, F. G., Lukashenko, S. S.,
Kushnazarova, R. A., Prokopéva, T. M., Zubareva, T. M., …
Zakharova, L. Y. (2018) Dicationic hydroxylic surfactants: Aggre-
gation behavior, guest-host interaction and catalytic effect. Journal
of Molecular Liquids, 250:229–235.
Miyagishi, S., Suzuki, H., & Asakawa, T. (1996) Microviscosity and
aggregation number of potassium N-acylalaninate micelles in
potassium chloride solution. Langmuir, 12:2900–2905.
Nardello, V., Chailloux, N., Joly, G., & Aubry, J.-M. (2006) Prepara-
tion, amphiphilic properties and lyotropic phase behaviour of new
surfactants based on sodium monoalkyl α,ω-dicarboxylates. Col-
loids and Surfaces, A: Physicochemical and Engineering Aspects,
288:86–95.
Naves, A. F., Palombo, R. R., Carrasco, L. D. M., & Carmona-
Ribeiro, A. M. (2013) Antimicrobial particles from emulsion poly-
merization of methyl methacrylate in the presence of quaternary
ammonium surfactants. Langmuir, 29:9677–9684.
Noori, S., Naqvi, A. Z., Ansari, W. H., Akram, M., & Kabir-ud-Din
(2014) Synthesis and investigation of surface active properties of
counterion coupled gemini surfactants. Journal of Surfactants and
Detergents, 17:409–417.
2
:914–920.
Chauhan, S., Sharma, K., Rana, D. S., Kumar, G., & Umar, A. (2012)
Conductance, apparent molar volume and compressibility studies
of cetyltrimethylammonium bromide in aqueous solution of leu-
cine. Journal of Molecular Liquids, 175:103–110.
Christov, N. C., Denkov, N. D., Kralchevsky, P. A.,
Ananthapadmanabhan, K. P., & Lips, A. (2004) Synergistic sphere-
to-rod micelle transition in mixed solutions of sodium dodecyl sul-
fate and cocoamidopropyl betaine. Langmuir, 20:565–571.
Dahanayake, M., Cohen, A. W., & Rosen, M. J. (1986) Relationship
of structure to properties of surfactants. 13. Surface and thermody-
namic properties of some oxyethylenated sulfates and sulfonates.
The Journal of Physical Chemistry, 90:2413–2418.
Daniel, R. C., & Berg, J. C. (2002) Dynamic surface tension of poly-
disperse surfactant solutions:
A
pseudo-single-component
approach. Langmuir, 18:5074–5082.
Satyarthi, J. K., Srinivas, D., & Ratnasamy, P. (2009) Estimation of
free fatty acid content in oils, fats, and biodiesel by H NMR spec-
troscopy. Energy & Fuels, 23:2273–2277.
Shavykin, O. V., Leermakers, F. A. M., Neelov, I. M., &
Darinskii, A. A. (2018) Self-assembly of lysine-based dendritic sur-
factants modeled by the self-consistent field approach. Langmuir,
34:1613–1626.
1
Franke, M. E., & Rehage, H. (2019a) Effects of chirality on the aggre-
gation properties of amide-bonded pyridinium gemini surfactants.
Langmuir, 35:8968–8976.
Garofalo, C., Capuano, G., Sottile, R., Tallerico, R., Adami, R.,
Reverchon, E., … Pappalardo, D. (2014) Different insight into
amphiphilic PEG-PLA copolymers: Influence of macromolecular
J Surfact Deterg (2020)

J Surfact Deterg
Suek, N. W., & Lamm, M. H. (2008) Computer simulation of archi-
tectural and molecular weight effects on the assembly of amphi-
philic linear-dendritic block copolymers in solution. Langmuir, 24:
Wang, W., Lu, W., & Jiang, L. (2008) Influence of pH on the aggre-
gation morphology of a novel surfactant with single hydrocarbon
chain and multi-amine headgroups. The Journal of Physical Chem-
istry. B, 112:1409–1413.
3
030–3036.
Tan, J., Xiong, X., He, Z., Cao, F., & Sun, D. (2019) Aggregation
behavior of polyether based siloxane surfactants in aqueous solu-
tions: Effect of alkyl groups and steric hindrance. The Journal of
Physical Chemistry. B, 123:1390–1399.
Tehrani-Bagha, A. R., & Holmberg, K. (2010) Cationic ester-
containing gemini surfactants: Physical−chemical properties. Lang-
muir, 26:9276–9282.
Würsch, A., Möller, M., Glauser, T., Lim, L. S., Voytek, S. B.,
Hedrick, J. L., … Hilborn, J. G. (2001) Dendritic-linear AxBx
block copolymers prepared via controlled ring-opening polymeriza-
tion of lactones from orthogonally protected multifunctional initia-
tors. Macromolecules, 34:6601–6615.
Xu, W., Gu, H., Zhu, X., Zhong, Y., Jiang, L., Xu, M., … Hao, J.
2
(2015) CO -controllable foaming and emulsification properties of
Tian, F., Lin, X., Valle, R. P., Zuo, Y. Y., & Gu, N. (2019) Poly
the stearic acid soap systems. Langmuir, 31:5758–5766.
(
amidoamine) dendrimer as a respiratory nanocarrier: Insights from
experiments and molecular dynamics simulations. Langmuir, 35:
364–5371.
Zaidi, A., Alsvik, I. L., Øpstad, C. L., Martin, D., Rebman, E.,
Voss, G., … Partali, V. (2018) Forgotten fatty acids—Surface prop-
erties supply conclusive evidence for including carotenoic acids.
Chemistry and Physics of Lipids, 216:48–53.
Zana, R. (1996) Critical micellization concentration of surfactants in
aqueous solution and free energy of micellization. Langmuir, 12:
5
Vaisman, B., Ickowicz, D. E., Abtew, E., Haim-Zada, M.,
Shikanov, A., & Domb, A. J. (2013) In vivo degradation and elimi-
nation of injectable ricinoleic acid based poly(ester-anhydride).
Biomacromolecules, 14:1465–1473.
Voutsas, E. C., Tsavas, P., Magoulas, K., Tassios, D., Ferrer, M.,
Plou, F. J., & Ballesteros, A. (2002) Solubility measurements of
fatty acid glucose and sucrose esters in 2-methyl-2-butanol and
mixtures of 2-methyl-2-butanol with dimethyl sulfoxide. Journal of
Chemical & Engineering Data, 47:1517–1520.
Wang, H., Hamilton, M., & Rempel, G. L. (2016) Hydrogenation of
sodium oleate in aqueous emulsion with the hoveyda−grubbs
second-generation catalyst. Organic Process Research and Devel-
opment, 20:1252–1257.
1
208–1211.
Zana, R. (2002) Dimeric and oligomeric surfactants. Behavior at inter-
faces and in aqueous solution: A review. Advances in Colloid and
Interface Science, 97:205–253.
Zhang, R., Cai, Y., Wang, J., Zhao, Z., Mao, X., & Peng, Z. (2017) A
star-shaped anionic surfactant: Synthesis, alkalinity resistance,
interfacial tension and emulsification properties at the crude oil-
water interface. Journal of Surfactants and Detergents, 20:
1027–1035.
J Surfact Deterg (2020)