Synthesis of Succinic Gemini Surfactants and the Effect of Stereochemistry on Their Monolayer Behaviors

Article abstract of DOI:10.1007/s11743-015-1682-x

In this work, succinic gemini surfactants, dl- and meso-2,3-bis(alkyl)succinic acids (alkyl: C₆H₁₃-C₁₃H₂₇), were successfully synthesized by oxidative coupling of enolates of fatty acid tert-butyl esters with copper(II) bromide followed by treatment with CF₃COOH. Focusing on the influence of stereochemistry (dl- and meso-) of succinic geminis, their monolayer behaviors at the air-water interface were explored using surface pressure-area (Π-A) isotherms, the compression modulus of monolayers (ε_s), and Brewster angle microscope (BAM) analysis. meso-2,3-Bis(undecyl)succinic acid showed a unique isotherm where the surface pressure drastically decreased at A = ～0.56 nm² (Π = 21.9 mN m^-1) regardless of compression rates and subphase temperatures, while dl-isomer showed the common isotherm of gas → liquid-expanded → liquid-condensed phase transitions. BAM analysis on meso-2,3-bis(undecyl)succinic acid films at the air-water interface showed that small islands of aggregates appear just after the maximum pressure (A = ～0.56 nm²), and on further compression needle-shaped assemblies appear that can grow in size. It was reasonably concluded that hydrophobic interactions can operate more effectively in meso-isomers than in dl-isomers, and that meso-molecules can "jump up" to cause a transition from monolayer to bilayer. This is the first finding of the "jumping-up" phenomenon of gemini surfactants having meso-stereochemistry.

Full text of DOI:10.1007/s11743-015-1682-x

J Surfact Deterg
DOI 10.1007/s11743-015-1682-x
ORIGINAL ARTICLE
Synthesis of Succinic Gemini Surfactants and the Effect
of Stereochemistry on Their Monolayer Behaviors
1
1
1
1
Tokuzo Kawase
•
Maiko Kagawa-Ohara
•
Tsunetomo Aisaka
•
Tatsuo Oida
Received: 23 July 2014 / Accepted: 12 March 2015
AOCS 2015
ꢀ
Abstract In this work, succinic gemini surfactants, dl-
and meso-2,3-bis(alkyl)succinic acids (alkyl: C H –
operate more effectively in meso-isomers than in dl-iso-
mers, and that meso-molecules can ‘‘jump up’’ to cause a
transition from monolayer to bilayer. This is the first
finding of the ‘‘jumping-up’’ phenomenon of gemini sur-
factants having meso-stereochemistry.
6
13
C H ), were successfully synthesized by oxidative cou-
13 27
pling of enolates of fatty acid tert-butyl esters with cop-
per(II) bromide followed by treatment with CF COOH.
3
Focusing on the influence of stereochemistry (dl- and
meso-) of succinic geminis, their monolayer behaviors at
the air–water interface were explored using surface pres-
sure–area (P–A) isotherms, the compression modulus of
Keywords Succinic Gemini ꢀ Stereochemistry ꢀ
Monolayer ꢀ Surface pressure–area isotherm ꢀ Brewster
angle microscope ꢀ Compression modulus of monolayer ꢀ
Jumping-up phenomena
monolayers (e ), and Brewster angle microscope (BAM)
s
analysis. meso-2,3-Bis(undecyl)succinic acid showed a
unique isotherm where the surface pressure drastically
2
-1
decreased at A = *0.56 nm (P = 21.9 mN m ) re-
gardless of compression rates and subphase temperatures,
while dl-isomer showed the common isotherm of
gas ? liquid-expanded ? liquid-condensed phase transi-
tions. BAM analysis on meso-2,3-bis(undecyl)succinic acid
films at the air–water interface showed that small islands of
Introduction
Gemini surfactants consist of two surfactants covalently
attached by a spacer group at the level of, or in close
vicinity to, the head groups. It has been widely accepted
that they show higher efficiency in decreasing the surface
tension of water to achieve one to two orders of magnitude
lower critical micelle concentration (CMC) values and
smaller surface tensions at their CMC (cCMC) than the
corresponding monomeric surfactants [1–7]. A lot of
studies on the effects of structural factors such as the length
of hydrophobic chains, head groups, spacers, and counter
ions on their surface properties in aqueous solution
aggregates appear just after the maximum pressure
2
A = *0.56 nm ), and on further compression needle-
shaped assemblies appear that can grow in size. It was
(
reasonably concluded that hydrophobic interactions can
&
Tokuzo Kawase
kawase@kit.ac.jp
(
structure–performance relationship) have been reported so
far [8–10].
From the viewpoint of molecular structure, Gemini
Maiko Kagawa-Ohara
m-kagawa@iml.chem.kit.ac.jp
Tsunetomo Aisaka
t-aisaka@iml.chem.kit.ac.jp
surfactants having asymmetric carbon atoms or chiral
groups represent a new class of twin-tailed and twin-chiral
amphiphiles. With respect to the chirality of the spacer,
Sommerdijk et al. [11] reported the effects on the transition
temperature of liposome bilayers and calcium binding of
synthetic gemini phospholipids. Bello et al. [12, 13] also
reported the role of the spacer stereochemistry on the
Tatsuo Oida
t-oida@iml.chem.kit.ac.jp
1
Department of Chemistry and Materials Technology, Kyoto
Institute of Technology, Hashigamicho 1, Matsugasaki,
Sakyo-ku, Kyoto 606-8585, Japan
1
23

J Surfact Deterg
aggregation properties of cationic gemini surfactants.
Furthermore, the stereochemistry at the point of attachment
of spacer group would also be one of the important struc-
tural factors for the surface properties of gemini surfac-
tants. In this decade, several studies on the correlation
between the stereochemistry at the point of attachment of
spacer group, physical properties and self-aggregation be-
havior of gemini surfactants have been reported [14–21],
but more research is needed.
Previously, we reported the synthesis of 2,3-bis(unde-
cyl)succinic acid 3e, hereafter abbreviated as succinic
gemini surfactant, where two vicinal COOH head groups
are also attaching directly to the chiral centers, from co-
rynomicolic acid [34]. We measured the surface tensions of
the meso- and dl-diastereomers in KOH solution and
clarified the effect of stereochemistry of succinic gemini on
their surface tension isotherms. It should be noted that
meso-3e showed two breakpoints in surface tension vs lnC
isotherms, while dl-3e gave the common variation as ex-
pected. We suspected that the first breakpoint may be due
to premicellar aggregate formation in dilute solution, while
the second breakpoint is the critical micelle concentration.
We interpreted this premicellar formation in terms of the
intermolecular interaction between two alkyl groups and
According to our literature searches, Harvey and his
coworkers’ work should be the first report focusing on the
effects of the chirality at the connecting points of dimeric
surfactants on the monolayer behavior at the air–water
interface with the aid of surface pressure–area (P–A)
isotherms [22]. Four pairs of diastereomeric surfactants
were prepared (meso or dl) by joining two pentadecanoic
-
the electrostatic repulsion between two hydrophilic COO
0
0
0
acid units by a carbonyl group at the 3,3 , 6,6 , 9,9 , and
0
groups.
1
2,12 -positions. In all cases the meso monolayers were
In the present work, we report a simple but useful
synthesis of dl- and meso-2,3-bis(alkyl)succinic acids by
the oxidative coupling of enolates of fatty acid tert-butyl
esters with copper(II) bromide followed by treatment with
compressed more easily than their dl diastereomers, which
they attributed to better lateral alignment of the hydrocar-
bon chains about the meso plane of symmetry in compar-
ison with the dl plane. Based on molecular mechanics,
Porter concluded that the dl compounds have a preferred
conformation that resists compression at the air–water in-
terface [23].
CF COOH, and their unique monolayer and self-assem-
3
bling behaviors at the air–water interface as a consequence
of their stereochemistry.
Most chiral gemini surfactants have been derived from
natural chiral resources such as tartaric acid, amino acids,
and alkyl glucosides [24–33]. Nakanishi et al. [31] inves-
tigated the P-A isotherms of stereoisomers of l- and meso-
Experimental Procedures
Materials
0
O,O -dialkanoyl tartaric acid on aqueous CdCl /KHCO
2
3
0
solutions. They found l- and meso- O,O -bis(tetradecanoyl)
All reagents and solvents were purchased from Wako Pure
Chemical Industries. Purification of solvents was done as
usual, THF over Na/benzophenone. Water was prepared by
ultrafiltration of distilled water using an Advantec pure
water system RFU354BA. Infrared spectra were recorded
tartaric acids formed stable monolayers with limited
2
molecular areas of 0.48 and 0.43 nm , respectively, and
succeeded in preparation of LB films as Y-type films from
the meso-isomer and as Z-type film from the l-isomer.
0
1
Similarly, we also measured the P–A isotherms of l-O,O -
on a Nicolet Avator 370 DTGS FTIR spectrometer, the H-
dialkanoyl tartaric gemini amphiphiles on water (pH = 2)
and investigated the effects of the length of the hy-
drophobic alkanoyl chains [32] and their asymmetrical
diversity [33]. A more tightly packed monolayer was
formed at the air–water interface with increase in hy-
drophobic alkanoyl chain length. Aside from those works,
Shankar et al. [16–19] found that enantiomerically pure
tartaric acid-based surfactants form more stable vesicles
and have a lower CMC compared to their racemic mix-
tures. They also reported the monolayer behavior of chiral
gemini, (2R,3R)-(?)-bis(decyloxy)- and (2S,3S)-(-)-
NMR spectra were recorded on a Bruker AC-300 spec-
trometer. The mass spectra were taken on a JEOL Mstation
JMS-700 mass spectrometer in HR-FABMS mode. Ele-
mental analysis was accomplished on a Yanaco CHN
CORDER MT-5 Elemental analyzer with an oxygen de-
termination kit.
Synthesis
Di-tert-butyl 2,3-bis(alkyl)succinate (2)
0
bis(decyloxy)succinic acids (otherwise, l-O,O -bis(decyl)-
0
The succinic Gemini surfactants, dl- and meso-2,3-
bis(alkyl)succinic acids, were synthesized by the oxidative
coupling of enolates of fatty acid esters with copper(II)
bromide according to Quermann et al. [35] and subsequent
deprotection of ester groups. Following is a typical synthesis
and d-O,O -bis(decyl)tartaric acid, respectively), at the air–
water interface [18] and observed the spontaneous
separation of chiral phases in the monolayers of the race-
mate [17].
1
23

J Surfact Deterg
1
of di-tert-butyl 2,3-bis(undecyl)succinate, 2e: first of all,
tert-butyl tridecanoate 1e was prepared from tert-butanol,
tridecanoic acid, dicyclohexyl carbodiimide (DCC) and
DMAP (0.2 equiv) in toluene under stirring at room tem-
perature. In a dry 100 mL flask equipped with a dropping
funnel, septum inlet, and magnetic stirrer, a solution of
meso-2c (R = C H ): yield: 29 %;
9
H
NMR
19
(300 MHz, CDCl ) d = 0.87 [t, 6H, J = 6.4 Hz, –(CH ) –
3
2 8
CH ], 1.25–1.58 [m, 32H, –CH–(CH ) –CH ], 1.42 [s,
2 8
3
3
18H, –COO–C(CH ) ], 2.62 (m, 2H, –CH–CH–): IR (KBr,
3
3
-
1
cm ): m 1720 (C=O).
dl-2d (R = C H ): yield: 32 %; H NMR (300 MHz,
1
1
0 21
1
2.5 mL of lithium diisopropylamide (2.0 M in hexane/
CDCl ) d = 0.86 [t, 6H, J = 6.6 Hz, –(CH ) –CH ],
3
2 9
3
THF) and 30 mL of dry THF were added under nitrogen.
Under cooling at -78 ꢁC, 25 mmol of 1e in 10 mL dry
THF was added dropwise over a period of 30 min, and then
the mixture was stirred for an additional 15 min. With
1.25–1.56 [m, 36H, –CH–(CH ) –CH ], 1.40 [s, 18H,
2 9 3
–COO–C(CH ) ], 2.66 (m, 2H, –CH–CH–): IR (KBr,
3
3
-
1
cm ): m 1733 (C=O).
meso-2d (R = C H ): yield: 28 %;
1
H
NMR
1
0 21
vigorous stirring 5.0 g of anhydrous CuBr powder was
2
(300 MHz, CDCl ) d = 0.88 [t, 6H, J = 6.6 Hz, –(CH ) –
3
2 9
added all at once to the solution. After stirring for 30 min,
the reaction was quenched by adding 50 mL of 1 M HCl at
this temperature, and the mixture was allowed to reach
room temperature. After extracting twice with hexane
CH ], 1.25–1.57 [m, 36H, –CH–(CH ) –CH ], 1.42 [s,
3 2 9 3
18H, –COO–C(CH ) ], 2.62 (m, 2H, –CH–CH–): IR (KBr,
3
3
-
1
cm ): m 1723 (C=O).
dl-2e (R = C H ): yield: 36 %; H NMR (300 MHz,
1
1
1 23
(
75 mL each), the combined organic layer was washed
CDCl ) d = 0.85 [t, 6H, J = 6.6 Hz, –(CH ) –CH ],
3
2 10
3
with water and dried over Na SO . By means of a short-
2
1.22–1.59 [m, 40H, –CH–(CH ) –CH ], 1.41 [s, 18H,
2 10
4
3
path vacuum distillation apparatus, both unreacted ester
–COO–C(CH ) ], 2.68 (m, 2H, –CH–CH–): IR (KBr,
3 3
-
1
and a-bromo ester (5e) were distilled off (*160 ꢁC,
cm ): m 1736 (C=O).
meso-2e (R = C H ): yield: 25 %;
1
1
mmHg). The residue was subjected to column chro-
matography on silica eluting with hexane/diethyl ether
20:1) to separate dl- (dl-2e) and meso-isomers (meso-2e)
H
NMR
1
1 23
(300 MHz, CDCl3) d = 0.85 [t, 6H, J = 6.6 Hz,
–(CH ) –CH ], 1.23–1.59 [m, 40H, –CH–(CH ) –CH ],
(
2
10
3
2 10
3
at the yields of 36 and 25 %, respectively. Other dl- and
meso-isomers of 2a–2g were also prepared in a similar
manner, and diastereomers (dl and meso) were separated by
1.43 [s, 18H, –COO–C(CH ) ], 2.63 (m, 2H, –CH–CH–):
3 3
-
1
IR (KBr, cm ): m 1731 (C=O).
dl-2f (R = C H ): yield: 27 %; H NMR (300 MHz,
1
1
2 25
SiO chromatography.
2
CDCl ) d = 0.88 [t, 6H, J = 6.6 Hz, –(CH ) –CH ],
1.26–1.58 [m, 44H, –CH–(CH ) –CH ], 1.42 [s, 18H,
2 11 3
3
2 11
3
1
dl-2a (R = C H ): yield: 39 %; H NMR (300 MHz,
6
13
CDCl ) d = 0.88 [t, 6H, J = 6.5 Hz, –(CH ) –CH ],
–COO–C(CH ) ], 2.67 (m, 2H, –CH–CH–): IR (KBr,
3 3
3
2 5
3
-
1
1
.26–1.56 [m, 20H, –CH–(CH ) –CH ], 1.41 [s, 18H,
3
cm ): m 1733 (C=O).
meso-2f (R = C H ): yield:25 %;
2
5
1
–
COO–C(CH ) ], 2.67 (m, 2H, –CH–CH–): IR (KBr,
3
H
NMR
3
12 25
-
1
cm ): m 1730 (C=O).
meso-2a (R = C H ): yield: 30 %;
(300 MHz, CDCl3) d = 0.88 [t, 6H, J = 6.6 Hz,
–(CH ) –CH ], 1.26–1.58 [m, 44H, –CH–(CH ) –CH ],
1
H
NMR
6
13
2 11
3
2 11
3
(
300 MHz, CDCl ) d = 0.89 [t, 6H, J = 6.5 Hz, –(CH ) –
1.42 [s, 18H, –COO–C(CH ) ], 2.63 (m, 2H, –CH–CH–):
3 3
3
2 5
-
1
CH ], 1.26–1.58 [m, 20H, –CH–(CH ) –CH ], 1.42 [s,
3
IR (KBr, cm ): m 1724 (C=O).
dl-2g (R = C H ): yield: 31 %; H NMR (300 MHz,
2 5
3
1
1
8H, –COO–C(CH ) ], 2.63 (m, 2H, –CH–CH–): IR (KBr,
3
3
13 27
-
1
cm ): m 1724 (C=O).
dl-2b (R = C H ): yield: 32 %; H NMR (300 MHz,
CDCl ) d = 0.88 [t, 6H, J = 6.6 Hz, –(CH ) –CH ],
3
2 12
3
1
1.25–1.55 [m, 48H, –CH–(CH ) –CH ], 1.43 [s, 18H,
2 12 3
8
17
CDCl ) d = 0.86 [t, 6H, J = 6.1 Hz, –(CH ) –CH ],
–COO–C(CH ) ], 2.67 [m, 2H, –CH–CH–): IR (KBr,
3 3
3
2 7
3
-
1
1
.25–1.55 [m, 28H, –CH–(CH ) –CH ], 1.42 [s, 18H,
3
cm ): m 1732 (C=O).
meso-2g (R = C H ): yield: 26 %;
2
7
1
–
COO–C(CH ) ], 2.67 (m, 2H, –CH–CH–): IR (KBr,
3
H
NMR
3
13 27
-
1
cm ): m 1733 (C=O).
meso-2b (R = C H ): yield: 24 %;
(300 MHz, CDCl3) d = 0.88 [t, 6H, J = 6.6 Hz,
–(CH ) –CH ], 1.25–1.57 [m, 48H, –CH–(CH ) –CH ],
1
H
NMR
8
17
2 12
3
2 12
3
(
300 MHz, CDCl ) d = 0.88 [t, 6H, J = 6.1 Hz, –(CH ) –
1.40 [s, 18H, –COO–C(CH ) ], 2.62 (m, 2H, –CH–CH–):
3 3
3
2 7
-
1
CH ], 1.25–1.57 [m, 28H, –CH–(CH ) –CH ], 1.41 [s,
3
IR (KBr, cm ): m 1724 (C=O).
2 7
3
1
8H, –COO–C(CH ) ], 2.62 (m, 2H, –CH–CH–): IR (KBr,
3 3
-
1
cm ): m 1726 (C=O).
dl-2c (R = C H ): yield: 31 %; H NMR (300 MHz,
2,3-Bis(alkyl)succinic acid (3)
1
9
19
CDCl ) d = 0.87 [t, 6H, J = 6.4 Hz, –(CH ) –CH ],
According to Andr e´ s et al. [36], each isomer (meso- and dl-
3
2 8
3
1
.25–1.57 [m, 32H, –CH–(CH ) –CH ], 1.43 [s, 18H,
3
2e) was treated with CF COOH to remove the tert-butyl
3
2
8
–
COO–C(CH ) ], 2.66 (m, 2H, –CH–CH–): IR (KBr,
3
group: A mixture of meso-2e (0.216 g, 0.4 mmol) and
CF COOH (3 mL) was stirred for 30 min at room
3
-
1
cm ): m 1729 (C=O).
3
1
23

J Surfact Deterg
temperature. After removal of CF COOH under reduced
3
J = 6.7 Hz, –(CH ) –CH ], 1.25–1.54 [m, 48H,
2 12
3
pressure, the residue was extracted with ether
–(CH ) –CH ], 2.46–2.49 (m, 2H, –CH–CH–); IR (KBr,
2 12 3
-
1
(
10 mL 9 3), washed with water, and dried over Na SO .
2
cm ): m 3446 (OH), 1695 (C=O); mass (HR-FABMS) m/z:
[M?H] 483.4419 (calc. for C H O : 483.4413); anal.
4
?
After evaporation of ether, the residue was washed with
3
0 59 4
cold CHCl and recrystallized from THF/hexane to afford
3
calc. for C H O : C, 74.63; H, 12.11; O, 13.26. Found: C,
30 58 4
meso-3e (0.109 g, 64 %). In the case of dl-2e, after similar
operation, CHCl filtrate was concentrated, and the residue
74.71; H, 12.18; O, 13.11.
Methods
3
was recrystallized from THF/hexane to afford dl-3e
(
0.099 g, 58 %).
1
dl-3e (R = C H ): mp 87.9–88.7 ꢁC; yield: 58 %; H
Surface Pressure–Area (P–A) Isotherm
1
1 23
NMR (300 MHz, CDCl ) d = 0.86 [t, 6H, J = 6.6 Hz,
3
–
(CH ) –CH ], 1.23–1.64 [m, 48H, –(CH ) –CH ], 2.64
2
Surface pressure–area (P–A) isotherms were obtained us-
ing a KSV Minitrough 2000 kept in a dust shield enclosure.
2
The total trough surface area was 364 9 75 mm with a
10
3
2 10
3
-
1
(m, 2H, –CH–CH–); IR (KBr, cm ): m 3231 (OH), 1707
(C=O); mass (HR-FABMS) m/z: [M?H] 427.3797 (calc.
?
for C H O : 427.3787); anal. calc. for C H O : C,
2
trough volume *170 mL. The trough area was robotically
controlled by two hydrophobic barriers that compressed the
spread film symmetrically and bilaterally at a rate of
6
51
4
26 50 4
7
1
3.19; H, 11.81; O, 15.00. Found: C, 73.31; H, 11.92; O,
4.77.
-
1
-4
2
-1
meso-3e (R = C H ): mp 134.7–135.3 ꢁC; yield:
10 mm min (7.5 9 10 m min ). A roughened plat-
inum Wilhelmy plate, which was flame-cleaned prior to
each measurement, was placed in the middle of the trough
facing (parallel to) the moving barriers. Spreading solu-
1
1 23
1
6
4 %; H NMR (300 MHz, d -MeOH) d = 0.87 [t, 6H,
4
J = 6.7 Hz, –(CH ) –CH ], 1.26–1.58 [m, 48H,
2
10
3
–
(CH ) –CH ], 2.48 (m, 2H, –CH–CH–); IR (KBr,
2 10 3
-
1
-3
-1
cm ): m 3408 (OH), 1698 (C=O); mass (HR-FABMS) m/z:
tions of 1.60 9 10 mol L in Benzene/THF (3/2, v/v)
(spectra grade) were prepared 24 h prior to use and were
used within 2 days. Prior to each measurement, the sub-
phase surface was cleaned by aspiration, such that the
?
[
M?H] 427.3791 (calc. for C H O : 427.3787); anal.
26 51 4
calc. for C H O : C, 73.19; H, 11.81; O, 15.00. Found: C,
26 50 4
7
3.11; H, 11.94; O, 14.95.
-
1
Other dl- and meso-isomers of 3c (R = C H ) and 3g
9 19
measured surface pressure remained\0.20 mN m over a
full compression. A 20–25 lL volume of gemini solution
was deposited in 10 drops uniformly distributed onto the
0.001 M HCl surface (pH = 3.0) using a gas-tight
Hamilton syringe, and left to evaporate and spread evenly
over a period of 30 min at the subphase temperature of
25.0 ꢁC. Unless otherwise noted, all measurements were
made at 15.0 ꢁC and at the barrier moving speed of
(
R = C H ) were also prepared in a similar manner.
13 27
1
dl-3c (R = C H ): mp 72.2–73.0 ꢁC; yield: 68 %; H
9
19
NMR (300 MHz, CDCl ) d = 0.86 [t, 6H, J = 6.8 Hz,
3
–
(CH ) –CH ], 1.27–1.66 [m, 32H, –(CH ) –CH ],
2 8 3 2 8 3
-
1
2
.62–2.64 (m, 2H, –CH–CH–); IR (KBr, cm ): m 3235
?
(
OH), 1712 (C=O); mass (HR-FABMS) m/z: [M?H]
71.3160 (calc. for C H O : 371.3164); anal. calc. for
3
2
2 43 4
-
1
C H O : C, 71.31; H, 11.42; O, 17.27. Found: C, 71.40;
22 42 4
10 mm min . In the compression rate dependency ex-
H, 11.38; O, 17.22.
periments, the barrier moving speed was varied from
-1
-
3.8 9 10 m min
4
2
-3
to 2.3 9 10 m min
2
-1
meso-3c (R = C H ): mp 118.9–120.3 ꢁC; yield:
8 %; H NMR (300 MHz, d -MeOH) d = 0.87 [t, 6H,
at
9
19
1
6
T = 15.0 ꢁC. In subphase temperature dependency ex-
periments, after spreading 3e over 0.001 M HCl subphase
at 25.0 ꢁC and maintained for 30 min, the subphase tem-
perature was adjusted to the target temperature
(5.0–25.0 ꢁC), and maintained for at least 30 min before
measurements. Measurements were made at a compression
4
J = 6.8 Hz, –(CH ) –CH ], 1.26–1.54 [m, 32H, –(CH ) –
2
8
3
2 8
1
-
CH ], 2.46–2.49 (m, 2H, –CH–CH–); IR (KBr, cm ): m
3
3
428 (OH), 1694 (C=O); mass (HR-FABMS) m/z:
?
[
M?H] 371.3169 (calc. for C H O : 371.3164); anal.
22 43 4
calc. for C H O : C, 71.31; H, 11.42; O, 17.27. Found: C,
22 42 4
-
4
2
-1
7
1.56; H, 11.28; O, 17.16.
dl-3g (R = C H ): mp 96.6–97.7 ꢁC; yield: 58 %; H
rate of 7.5 9 10 m min . Each measurement was re-
peated at least three times to check the reproducibility of
the isotherms, which in all cases was reproducible with
standard deviations for molecular surface area and surface
1
1
3 27
NMR (300 MHz, CDCl ) d = 0.85 [t, 6H, J = 6.3 Hz,
3
–
(CH ) –CH ], 1.23–1.64 [m, 48H, –(CH ) –CH ], 2.63
2 12 3 2 12 3
-
1
2
-1
(m, 2H, –CH–CH–); IR (KBr, cm ): m 3228 (OH), 1708
(C=O); mass (HR-FABMS) m/z: [M?H] 483.4408 (calc.
pressure, *0.1 nm and *0.1 mN m , respectively.
?
for C H O : 483.4413); anal. calc. for C H O : C,
4
Relaxation Behavior in P–A Isotherm
3
0
59
30 58 4
7
1
4.63; H, 12.11; O, 13.26. Found: C, 74.36; H, 11.98; O,
3.66.
Relaxation behaviors (hysteresis) of 3e in P–A isotherms
were investigated by the iterative measurements of com-
pression to the first-specified surface pressure P1st (first
meso-3g (R = C H ): mp 132.6–133.7 ꢁC; yield:
1
3 27
1
6
1 %; H NMR (300 MHz, d -MeOH) d = 0.87 [t, 6H,
4
1
23

J Surfact Deterg
compression), decompression to the initial spreading area
esters with copper(II) bromide to afford dimethyl esters of
dialkylated succinic acid. As their synthesis is only one
step (oxidative coupling), we also examined their technique
under similar conditions (Scheme 1). Results of oxidative
coupling of methyl and tert-butyl esters were summarized
in Table 1. For example, the coupling of methyl tride-
canoate afforded a mixture of meso- and dl-isomers of
dimethyl 2,3-bis(undecyl)succinate 2e, methyl 2-undecyl-
3-oxo-pentadecanoate (Claisen condensation product), and
a-bromo methyl tridecanoate (33:40:9:8) with recovery of
unreacted methyl tridecanoate (10 %). Quermann also re-
ported the production of both a-bromo ester and the Clai-
sen condensation product. Though unreacted ester and a-
bromo ester were easily removed by distillation, the Clai-
sen condensation product, which may be unavoidable when
methyl esters were used, made it more cumbersome to
separate and purify meso- and dl-isomers by column
chromatography.
(
expansion), and immediate recompression to the measur-
able limit area. Compression and decompression rate was
-1
-
kept at 7.5 9 10 m min
4
2
.
Brewster Angle Microscope (BAM)
The monolayer was directly visualized by a Brewster angle
microscope (KSV Optrel BAM 300, KSV Instruments Ltd.,
Finland) coupled to KSV Minitrough. The application of a
2
0 mW He–Ne laser emitting p-polarized light of 632.8 nm
wavelength and a 10 9 objective lens (M Plan Apo, Mit-
sutoyo, Japan). The angle of the incident beam to the air/
water interface was fixed at the Brewster angle (53.1ꢁ) at
2
88.2 K. The reflected beam was recorded with a high
grade charge coupled device (CCD) camera (EHDkam-
Pro02, EHD Imaging GmbH, Germany), and the BAM
images were digitally saved to a computer hard disk.
It has been known that enolate of tert-butyl ester is more
stable than those of methyl and ethyl esters, and self-Claisen
condensation of tert-butyl ester is often unlikely to occur.
Thus, to suppress the Claisen condensation product, tert-
butyl esters of fatty acids were employed in place of methyl
esters. As can be seen in Table 1, steric hindrance by tert-
butyl group worked well to afford no Claisen condensation
products as might have been expected, but with higher yields
of dl-isomers (*1.4:1) over meso-isomers in comparison
with the case of methyl esters (*1.2:1).
Compression Modulus of Monolayer
The compression modulus of the monolayer (e ) on the
water surface was calculated from the P–A isotherm using
Eq. (1) [37–39].
s
es ¼ ꢁAðdP=dAÞT
ð1Þ
The e (max) was defined as the maximum of e , and the
s
s
collapsing point in this work was defined as the point on
the isotherm where e reaches e (max).
The coupling products, dl- and meso-succinic esters,
were successfully separated by column chromatography on
silica eluting with hexane/diethyl ether (20:1), and they
were hydrolyzed separately. Surprisingly, 2,3-bis(unde-
cyl)succinic acid dimethyl esters were quite resistant to
usual hydrolysis by acids and base as shown in Table 2,
which might be the reason why Quermann did not report
the conversion of COOMe to the corresponding COOH. In
contrast, we previously succeeded in the conversion of CN
group to COOH using the extreme conditions, namely
75 % H SO at 190 ꢁC [34]. Similarly, we carried out
s
s
Results and Discussion
Synthesis
In our previous work [34], 2,3-bis(undecyl)succinic acid,
succinic Gemini surfactant, 3e was successfully synthe-
sized from corynomicolic acid by the functional intercon-
version of OH of corynomicolic acid to COOH. However,
this synthetic route consists of multiple reaction steps in-
cluding synthesis of corynomicolic acid, mesylation of syn-
OH, dimethanesulfonic acid to E-a,b-unsaturated ester,
2
4
hydrolysis of 2 using 50 % H SO at 190 ꢁC, and 2,3-
2
4
dialkylsuccinic acids 3 were successfully obtained together
with acid anhydrides of dl-isomers. However, as the hy-
drolysis conditions were somewhat radical, both meso- and
dl-isomers were always obtained even when one pure di-
astereomer was used. To the contrast, in the case of tert-
butyl ester, the hydrolysis conditions could be lowered
such as 50 % H SO at 130 ꢁC or 35 % H SO at 190 ꢁC,
-
Michael addition of CN, separation of syn- and anti-iso-
mers, and hydrolysis of CN to COOH. Though all steps
proceeded at good yields, the last hydrolysis step required
extraordinary condition, such as 75 % H SO at 190 ꢁC,
and dl-2,3-bis(undecyl)succinic acid was predominately
obtained as its anhydride even from the syn-isomer. We
were not successful in selective synthesis of meso-2,3-
bis(undecyl)succinic acid, which was separated by column
chromatography of a mixture of dl- and meso-anhydrides.
Aside from our synthesis, Quermann et al. [35] reported
the oxidative coupling of enolates of fatty acid methyl
2
4
2
4
2
4
and no acid anhydride was produced. In addition, accord-
ing to Andr e´ s et al. [36], tert-butyl esters can be smoothly
converted to their COOH by treatment with CF COOH.
3
Indeed, both meso- and dl-3e were obtained from the cor-
responding tert-butyl esters without any production of an-
other diastereomer.
1
23

J Surfact Deterg
Scheme 1 Synthesis of 2,3-
bis(alkyl)succinic acids
Table 1 Results of oxidative coupling of fatty acid esters
sequence: gas (G) ? liquid expanded (LE) ? liquid
condensed (LC). After passing the maximum pressure of
Compounds
Yield (%)
Me ester
meso
-
3 mN m at A = 0.44 nm , the pressure decreased to 38
1
2
4
tert-Bu ester
-1
mN m and reached the plateau region. In our previous
0
Abbrev.
R
dl
meso
dl
study on the monolayers of l-O,O -bis(alkanoyl)tartaric
acids, the maximum values of e , es(max), were
*
for LE, LC and solid states, respectively. As shown in
s
2
2
2
2
2
2
2
a
b
c
d
e
f
C
C
C
C
C
C
C
6
8
9
H
H
H
13
17
19
32
29
35
37
29
30
28
41
35
38
41
38
37
33
30
24
29
28
25
25
26
39
32
31
32
36
27
31
-
1
-1
50 mN m , 80–100 mN m , and over 200 mN m
-1
-1
Fig. 1b, e (max) of dl-3e was *130 mN m , which
indicates that the monolayer collapses in the condensed
s
10
11
12
13
H
21
23
25
27
H
H
H
liquid region. The zero-pressure molecular area (A ) ob-
0
tained by extrapolating the condensed region to zero
2
pressure is 0.70 nm for dl-3e.
g
Shankar et al. [17, 18] reported similar isotherms for
(2R,3R)-(?)-bis(decyloxy)succinic acid, (2S,3S)-(-)-
bis(decyloxy)succinic acid and (± )-bis(decyloxy)succinic
Surface Properties
As previously reported [34], we studied the surface tension
isotherms of succinic Geminis (meso- and dl-3e) in KOH
solution and clarified the effect of stereochemistry on
surface tension isotherms. In this work, the effects of
stereochemistry on monolayer formation behavior of suc-
cinic gemini were studied from surface pressure–area (P–
A) measurements.
acid, but there were no maximum on their isotherms. Their
2
values of A were all *0.7 nm . Furthermore, with opti-
0
mizing the geometry of (2R,3R)-(?)-bis(decyloxy)succinic
acid to an upright orientation at the air–water interface,
they also calculated the Connolly surface with a head group
2
area of *0.72 nm . Good consistency with A of dl-3e
0
would indicate that dl-3e also adopts an upright orientation
at the air–water interface.
Surface Pressure–Area (P–A) Isotherm
On the contrary, meso-3e showed a quite different and
interesting monolayer behavior. On compression, the iso-
2
therm lifted off at the area of 0.77 nm , which was almost
The surface pressure–area (P–A) isotherms of meso- and
dl-2,3-bis(undecyl)succinic acids 3e at a subphase tem-
perature of 15.0 ꢁC are shown in Fig. 1a. In addition, the
compression modulus of meso- and dl-3e monolayers are
plotted against A (Fig. 1b). As can be seen, the effects of
same to that of dl-3e, and surface pressure increased
-
1
similar to the dl-isomer. However, at P = 21.9 mN m
which was the maximum surface pressure for meso-3e, the
,
-
1
isotherm varied drastically decreasing to *8 mN m (at
2
stereochemistry on their P–A and e -A curves are striking.
A = *0.3 nm ), and again began to increase slowly.
s
In the case of dl-3e, the isotherm lifted off at the area of
0
Similar to dl-3e, e (max) of meso-3e was *100 mN/m,
which would also indicate that the monolayer can reach the
s
2
.78 nm and showed evidence of the following behavior
1
23

J Surfact Deterg
Table 2 Results of hydrolysis of 2,3-bis(undecyl)succinic acid diesters
Entry
Diester
Acid or base
Solvent
Temp. (ꢁC)
Time
Yields (%)
a
Recovery of 2
3e
Other
dl
meso
(dl)
1
2
3
Me (dl)
H
2
SO
4
Dioxane/H
2
O
O
Reflux
Reflux
Reflux
2 days
1 day
80
60
30
5
–
–
–
–
(
5/1)
Dioxane/H
5/1)
EtOH/H
5/1)
HCl
2
30
30
–
(
KOH
2
O
2 days
10
(
4
5
6
7
50 % H
50 % H
2
SO
4
4
150 ? 190
130
3 h
4
50
60
58
10
32
–
33
\1
–
tert-Bu (dl)
Me (meso)
2
SO
3 h
2
CF COOH
3
rt
30 min
2 days
–
H
2
SO
4
Dioxane/H
5/1)
Dioxane/H
5/1)
EtOH/H
5/1)
2
O
O
Reflux
No reaction
(
8
9
HCl
2
Reflux
Reflux
2 days
2 days
No reaction
95
(
KOH
2
O
Not detected
(
1
1
1
a
0
1
2
50 % H
50 % H
2
SO
4
4
150 ? 190
3 h
6
6
–
35
35
–
17
45
64
7
–
tert-Bu (meso)
2
SO
130
rt
3 h
CF
3
COOH
30 min
Acid anhydride
2
-1
condensed liquid phase but collapses soon after. The A for
0
23 cm min at T = 15.0 ꢁC. At any compression rate,
their monolayer behaviors remained essentially undis-
turbed except the small variations in lift-off area for dl-3e
and the values of minimum surface pressure for meso-3e.
Therefore, it can be concluded that the relaxation against
the compression would not be a significant factor for the
difference in P–A isotherms of dl-3e and meso-3e.
2
meso-3e was determined to be 0.73 nm . Quite similar lift-
off area and A of meso-3e to those of dl-3e would also
0
mean that meso-3e assumes an upright orientation at the
air–water interface.
Harvey obtained a very analogous appearance of an
0
optimum on P–A isotherm for dl-3,3 -keto-pentadecanoic
acid dimer, while its meso-isomer showed an ordinary
isotherm [22]. They interpreted the different monolayer
behaviors of meso- and dl-isomers in terms of the relative
stereochemistry at the point of attachment of two chains of
the carbonyl bridge, but there were no explanations for the
drastic decrease in P–A isotherm. However, our results on
the effect of the stereochemistry on isotherms were com-
pletely opposite to their observation.
Effect of Subphase Temperature on P–A Isotherm
It has been widely accepted that P–A isotherms are often
influenced by the subphase temperature as well as the
compression rate. The P–A isotherms were also recorded
at several subphase temperatures ranging from
T = 5–25 ꢁC. Results show the lifting-off areas of dl-3e
shifted to smaller ones with increase in temperature, but
their collapse pressures were almost unchanged. In the
case of meso-3e, the lifting-off areas were inherently the
same and the maximum in isotherms appeared at
Though not gemini surfactants, Andersson et al. [40]
reported significant differences between monolayers con-
sisting of enantiomerically pure polyhydroxy surfactants as
well as between diastereomers, where racemate showed
pronounced sinuous curvature at the phase transition region
of a liquid-expanded to a liquid-condensed phase. They
assigned the differences to the slower relaxation speed of
the molecules in the monolayer in comparison with the
compression speed of the barrier. To verify whether their
concept of slower relaxation speed can be applicable to our
case, the P–A isotherms of dl-3e and meso-3e were
recorded by changing the compression rate from 3.8 to
2
A = *0.55 nm for all temperatures, while the maximum
pressure decreased with increase in temperature.
BAM Image Analysis
Simultaneous observation of the morphology of the meso-
and dl-3e films at the air–water interface during the P–
A isotherm measurement was also performed. The BAM
1
23

J Surfact Deterg
Fig. 1 a P-A isotherms of dl-3e (dashed line) and meso-3e (solid
line) and b compression modulus of monolayers (e ) of dl-3e (open)
and meso-3e (closed) at a constant compression rate of 7.5 cm min
s
2
-1
at T = 15.0 ꢁC. Subphase: 0.001 M HCl (pH = 3.0)
images at the designated points a–c for dl-3e and points
d–h for meso-3e are shown in Fig. 2. In the case of dl-3e,
before arriving at the collapse pressure, where es of
monolayer gave e (max), there are no obvious BAM im-
s
ages attributable to the formation of a self-assembling
structure. However, at point-a, just after the collapse
pressure, small domain structures began to appear. At
point-b, images of 3D-aggregate structures clearly ap-
peared. At point-c, in the plateau region, the size and
number of aggregates increased, throughout which the
aggregates seemed amorphous or less ordered. Likewise,
meso-3e did not give any BAM images of self-assembling
structure until the maximum pressure. However, at point-d
just after the maximum pressure, a small island structure
appeared. With further compression, the island structure
grew and needle-shaped structures were observed. The
needle-shaped structure grew up ramifying and threading
to fibrous structures similar to crystallization. At the
minimum of isotherm (point-g), 3D-shaggy structures were
Fig. 2 BAM images of dl-3e and meso-3e after collapse pressure
-1
2
c
(P ) obtained for compression at 7.5 cm min . Subphase: 0.001 M
HCl (pH = 3.0), 15 ꢁC. The letters a–c and d–h on the isotherms of
dl-3e (dashed line) and meso-3e (solid line), respectively, correspond
2
to the 4.8 9 6.4 mm BAM images: a A = 0.477 nm molecule
2
-1
-
1
2
-1
(P = 40.5 mN m ), b A = 0.423 nm molecule (P = 40.4 mN
-
1
2
-1
-1
m
), c A = 0.292 nm molecule (P = 38.0 mN m ), d A =
2 -1 -1 2
0.529 nm molecule
molecule
(P = 21.4 mN m ), e A = 0.492 nm
-1 2 -1
-1
(P = 18.4 mN m ), f A = 0.436 nm molecule
-1 2 -1
(
m
P = 15.0 mN m ), g A = 0.356 nm molecule (P = 10.5 mN
-1
2
-1
-1
), and h A = 0.220 nm molecule (P = 8.8 mN m )
1
23

J Surfact Deterg
observed, and it is noted that small but definite solids on
the subphase surface were visually recognized.
chains of the meso-isomer than that of the dl-isomer.
Therefore, even at the liquid condensed state, meso-isomer
molecules would be arranged with higher regularity in
comparison with dl-isomer. Additional compression leads
to the accession of molecules, and at the same time, the
intermolecular interactions between hydrophobic chains of
adjacent molecules as well as the intramolecular hy-
drophobic interaction come into play.
As shown in Fig. 2, both meso- and dl-3e gave BAM
images consistent with 2D monolayer ?3D aggregates
above the collapse pressure. However, with respect to the
organizing degree of 3D aggregates, meso-3e gave the more
structured threads while dl-3e gave rather amorphous
structures, which would indicate that meso-3e molecules
have a more ordered alignment in the monolayer than dl-3e.
2
On further compression to A = *0.56 nm , the surface
-
1
pressures rose to *25 mN m for both meso- and dl-
isomers, and the effects of stereochemistry on the P–
Conformational Illustration During Compression
2
A isotherms came in focus. At A = *0.56 nm , the ap-
parent area per one hydrophobic chain can be estimated as
The differences in film formation of meso- and dl-3e can be
illustrated in terms of the hydrophobic interaction. Initially,
both isomers spread at the air–water interface with the two
hydrophilic COOH groups dousing in water. As shown in
Fig. 3, at the lifting-off point, the two hydrophobic groups
are standing upright, and all hydrophobic and hydrophilic
groups should be set in eclipsed arrangement relative to the
carbon–carbon spacer bond. Under such a circumstance,
the two hydrophobic alkyl chains of the meso-isomer are
set in parallel array as shown in Fig. 3a, while those of the
dl-isomer should be set in skew position as shown in
Fig. 3b. However, the lifting-off area would be determined
mainly by the area of the head groups, which would ex-
plain why the lift-off area of the meso-isomer was almost
the same as the dl-isomer.
2
*0.28 nm . In line with the isotherm for pentadecanoic
acid on 0.01 M HCl subphase, the monolayer shows the
liquid expanded ? liquid condensed and liquid con-
-
1
densed ? solid phase transitions at 8 mN
(A = 0.34 nm ) and at *20 mN m
m
2
-1
2
(A = 0.23 nm ),
respectively. Also, in our previous work on the P–
0
A isotherm of l-O,O -bis(tridecanoyl)tartaric acid at
25.0 ꢁC [32], only the monolayers of liquid condensed
-
1
0
state was obtained even at P = 20 mN m while l-O,O -
bis(alkanoyl)tartaric acids having longer hydrophobic
chains ([C H ) showed the phase transition of liquid
1
6 33
-
1
condensed (LC) ? solid state at P = *30 mN m
.
Therefore, including Shankar’s work [17, 18], it is rea-
sonably presumed that l- (or d-) stereochemistry of gemini
surfactants with short hydrophobes attached at the carbon
atom adjacent to COOH lead to only the monolayers of
liquid condensed state probably because of weak hy-
drophobic intramolecular interaction between short alkyls.
To the contrast, as suspected easily from Fig. 3, both
hydrophobic intra- and intermolecular interactions between
adjacent alkyl chains in the meso-isomer can operate more
effectively than the dl-isomer at the same molecular area,
It is obvious that the hydrophobic interaction between
alkyl chains depends on both the length of alkyl chains and
their distance. The length of alkyl chains in meso- and dl-
3
e is the same, but the distances between the two alkyl
chains on the adjacent carbon atoms of the spacer are
different. This would cause the larger degree of in-
tramolecular hydrophobic interaction between two alkyl
2
and at A = *0.56 nm some meso-molecules would jump
up to cause the phase transition to bilayer from the
monolayer, which would be induced by the intermolecular
interactions. During further compression, though the
monolayer compaction should be promoted simultaneously
with the ‘‘jumping-up’’ transition, the latter transition must
be stimulated to bring the drop of surface pressure and 3D
aggregates as shown in BAM images.
Relaxation Behaviors in P–A Isotherms
For each isomer of 3e, iterative measurements of com-
pression to the first-specified surface pressure P1st (first
compression), decompression to the initial spreading area
(expansion), and successive immediate recompression
were carried out. Results for meso-3e are shown in Fig. 4.
First, film formations of meso-3e were analyzed in
several patterns. After first compression to P1st = 10.1
Fig. 3 Schematic illustration of jumping-up of a meso-molecule just
adjacent in a monolayer at the air/water interface due to the
hydrophobic interaction on compression
1
23

J Surfact Deterg
-
1
2 -1
(A = 0.65 nm molecule ),
-1
Fig. 4 Iterative P-A measurements of compression, expansion and
recompression of meso-3e obtained for the barrier speed of
m
b
P
1st = 16.9 mN
m
2
-1
-1
2
(A = 0.58 nm molecule ), c P1st = 16.9 mN m (A = 0.58 nm
molecule
2
-1
-1
-1
7
.5 cm min . Subphase: 0.001 M HCl (pH = 3.0), 15 ꢁC. Solid
) and hold-time 30 min, d P1st = 16.5 mN m
2
-1
line is the isotherm of the first compression, and dashed line the
second compression. The letters a–e correspond to P1st (the first-
specified surface pressure of first compression): a P1st = 10.1 mN
(A = 0.45 nm molecule ) and hold-time 30 min, e P1st = 9.4
-1
2
mN m (A = 0.23 nm molecule
-1
)
-
1
mN m , where no aggregates were observed in the BAM
analysis, an immediate opening (decompression) showed
no hysteresis behavior, and the second compression passed
through the same isotherm (Fig. 4a), which indicates that
, liquid expanded film is reversible. When compressed to
-1 2
P
= 17 mN m (A = 0.58 nm ), where the compres-
st
1
sion modulus was maximum and some aggregation was
observed in the BAM analysis, an immediate opening
showed a small hysteresis with a little smaller landing area
than the first lifting-off, and the second lifting-off started
-
1
in this region of P = 0–10 mN m meso-3e exists in the
monomolecular state, and the transition from gaseous film
1
23

J Surfact Deterg
from that landing area of the first opening and after then a
similar isotherm was observed (Fig. 4b). Additionally,
-
1
after the first compression to P1st = 17 mN m , the area
was maintained for 30 min. The surface pressure gradually
decreased and at the end the surface pressure was around
-
1
*
2 mN m (Fig. 4c). Such a low surface pressure could
be attributed to the partial jumping-up of molecules to a
bimolecular film or 3D aggregates and the reduction of the
number of molecules in the monomolecular state. Also, in
this case, the second lifting-off position shifted to the end
area of the first compression and after that a similar iso-
therm was observed, which may also mean that only
molecules remaining in the monolayer would be reversibly
parted to the gaseous state and recompressed again.
2
Furthermore, when compressed to the area of 0.45 nm ,
passing through the maximum of the isotherm and held at
that area, the surface pressure decreased rapidly to
-
mN m within only a few minutes. In this case, the
1
0
second lifting-off point shifted to quite small area (less than
2
.4 nm ), and a second monolayer formation was observed
0
(
Fig. 4d). However, when compressed to the measurement
2
limit (A = 0.23 nm ) and decompressed immediately, the
second compression did not show the obvious isotherm (no
surface pressure) (Fig. 4e). It can be concluded that a
strong compression induces the growth of 3D aggregates
with robust microcrystalline structure not easily parted to
the monomolecular state.
Similar
compression–decompression–recompression
measurements on dl-3e were also examined. After the first
-
1
compression to P1st = 10 mN m , an immediate decom-
pression showed no hysteresis behavior. Next, the first
Fig. 5 P-A isotherms of dl-2,3-bis(alkyl)succinic acids (a) and meso-
,3-bis(alkyl)succinic acids (b) having C 19 (dashed line), C11
(solid line) and C H (dash-dot-dot line) as hydrophobic alkyl
2
9
H
H
23
-
1
compression was executed to P1st = 25 mN m , where the
compression modulus of dl-3e monolayer was just below
es(max), and an immediate decompression showed a slight
but definite hysteresis behavior, and as expected the second
lifting-off started from the landing area of the first decom-
pression. When the first compression exceeded the collapse
13
27
2
-1
groups at a constant compression rate of 7.5 cm •min
T = 15.0 ꢁC. Subphase: 0.001 M HCl (pH = 3.0)
for
15 ꢁC). Clearly, regardless of chain lengths, meso- and dl-
isomers gave different P–A isotherms.
In the case of dl-isomers (Fig. 5a), common monolayer
2
point of monolayer (A = 0.35 nm ) and the area was
maintained for 5 min, the surface pressure rapidly decreased
behaviors were observed as expected. Judging from the
2
-
to 14 mN m . After decompression, the second lifting-off
1
values of e (max), which appeared at around A = 0.6 nm ,
s
started from the area identical with that of first compression
the formed films were all in the liquid-condensed states
-
1
at P1st = 14 mN m , and the second isotherm moved in
parallel to the smaller area. Similar to the case of meso-3e, it
may mean that 3D aggregates of dl-3e would be formed
beyond the collapse point, and the aggregates would not
revert to the monomolecular gaseous film.
with the zero-pressure molecular areas of 0.64 (C H ),
13
27
2
0.67 (C H ), and 0.78 nm (C H ). With respect to the
1
1
23
9 19
collapse of films, 3c did not show the concrete maximum
surface pressure attributable to 3D aggregation. On the
other hand, 3g (C H ) showed an intermediate region and
1
3 27
2
the formation of solid film from A = 0.38 nm [e (-
s
-
max) = 190 mN m , A = 0.46 nm ]. Interestingly, this
1
2
Effect of Hydrophobic Chain Length
0
A value is twice that of a typical long chain fatty acid
0
2
The influence of hydrophobic chain length on the mono-
layer formation was also studied on gemini surfactants 3c
and 3g with hydrocarbon chain length of C H and
(*0.21 nm ). Thus, it can be concluded that the increase in
hydrophobic chain length would lead to the increase of the
inter- and intramolecular hydrophobic interactions to attain
tight-packing at the air/water interface.
9
19
C H , respectively. The results are shown in Fig. 5 (at
13 27
1
23

J Surfact Deterg
In contrast, all meso-isomers lifted off at almost the
2
same area (A = 0.78 nm ) regardless of hydrophobic chain
Series 117, Marcel Dekker, New York. doi:10.1201/9780
203913093
. Hana Y, Wang Y (2011) Aggregation behavior of gemini sur-
factants and their interaction with macromolecules in aqueous
solution. Phys Chem Chem Phys 13:1939–1956. doi:10.1039/
c0cp01196g
6
7
lengths. They also showed the maximum of isotherm at
2
-1
around A = *0.57 nm (P = 20 mN m ), but the sub-
sequent reductions in the surface pressure of 3c and 3g
were moderate in comparison with 3e (Fig. 5b).
. Kumara N, Tyagi R (2014) Industrial applications of dimeric
surfactants: a review. J Disper Sci Technol 35:205–214. doi:10.
From BAM observation on meso-3g, no obvious images
were observed between the lifting-off and the first e (max)
1
080/01932691.2013.780243
s
8. Zhu Y-P (2004) Structure-performance relationships in gemini
surfactants. Surfactant Science Series 117, Marcel Dekker, New
York, pp 281–300. doi:10.1201/9780203913093
. Franses EI, Prosser AJ, Infante MR, Perez L, Pinazo A (2004)
Adsorption and surface tension behavior of gemini surfactants at
air–water, oil–water, and solid–water interfaces. Surfactant Sci-
ence Series 117, Marcel Dekker, New York, pp 65–92. doi:10.
points, but just after the maximum surface pressure, little
structured aggregates appeared due to the jumping-up
phenomena of molecules similar to meso-3e. In addition,
on further compression the aggregate grew larger. At the
minimum surface pressure point, the structure of the ag-
gregate changed to needle-like crystal form, and at final
compression cancellous (netted) structure was attained.
Moreover, meso-3c showed similar variation in the BAM
9
1
201/9780203913093
1
0. Tyagi P, Tyagi R (2009) Synthesis, structural properties and
applications of gemini surfactants: a review. Tenside Surf Det
46:373–382. doi:10.3139/113.110045
images. Just after the e (max) point, small round aggregates
11. Sommerdijk NAJM, Hoeks THL, Synak M, Feiters MC, Nolte
RJM, Zwanenburg B (1997) Stereodependent fusion and fission
of vesicles: calcium binding of synthetic gemini phospholipids
s
began to appear, and at the maximum surface pressure 3D
aggregates developed. In comparison with 3e and 3g,
however, 3c has shorter alkyl chain and the hydrophobic
intra- and intermolecular interactions would be smaller,
which would result in the smaller jumping-up of molecules.
Considering these results, it can be reasonably con-
cluded that the film formation behaviors are quite different
depending on the meso- and dl-stereochemistry, and in the
same stereochemistry the hydrophobic chain length would
lead to the difference in the strength of the intra- and in-
termolecular hydrophobic interactions, aggregate forma-
tion and probably rigidity of films.
containing two phosphate groups.
119:4338–4344. doi:10.1021/ja962303s
J
Am Chem Soc
12. Bello C, Bombelli C, Borocci S, di Profio P, Mancini G (2006)
Role of the spacer stereochemistry on the aggregation properties
of cationic gemini surfactants. Langmuir 22:9333–9338. doi:10.
1
021/la061230f
13. Caracciolo G, Pozzi D, Mancini G, Caminiti R (2007) Role of the
spacer stereochemistry on the structure of solid-supported gemini
surfactants aggregates. Langmuir 23:10040–10043. doi:10.1021/
la7014995
1
4. Luchetti L, Mancini G (2000) NMR investigation on the various
aggregates formed by a gemini chiral surfactant. Langmuir
16:161–165. doi:10.1021/la990713z
1
5. Sugiyasu K, Tamaru S, Takeuchi M, Berthier D, Huc I, Oda R,
Shinkai S (2002) Double helical silica fibrils by sol-gel tran-
scription of chiral aggregates of gemini surfactants. Chem
Commun 2002:1212–1213. doi:10.1039/B202799M
To further explore the influence of gemini surfactant
stereochemistry on monolayer behaviors, we are now in-
vestigating the glutaric acid type gemini surfactants, dl-
and meso-2,4-bis(alkyl)glutaric acids. Details will be re-
ported in the near future.
16. Shankar BV, Patnaik A (2007) A new pH and thermo-responsive
chiral hydrogel for stimulated release. Phys Chem
11:9294–9300. doi:10.1021/jp073275a
J
B
1
1
7. Shankar BV, Patnaik A (2007) Chiral discrimination of a Gemini-
type surfactant with rigid spacer at the air–water interface. J Phys
Chem B 111:11419–11427. doi:10.1021/jp074279i
8. Shankar BV, Patnaik A (2008) Equilibrium structure and dy-
namics of (2R,3R)-(?)-bis(decyloxy)succinic acid at the air–
water interface. Langmuir 24:758–766. doi:10.1021/la701998c
Acknowledgments Mr. Mitsuya Kouno at the Advanced Tech-
nology Center of the Kyoto Institute of Technology is thanked for
performing the elemental analysis.
1
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Tokuzo Kawase is currently a professor at the Graduate School of
Chemistry and Materials Technology, Kyoto Institute of Technology.
He received his D. Eng. in synthetic organic chemistry at Kyoto
University and Ph.D. at Osaka City University, Japan. His research
interests include organic synthesis, surfactants chemistry, fluorine
chemistry and surface modification.
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disaccharide spacer. J Am Chem Soc 123:875–885. doi:10.1021/
ja0033178
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bolaamphiphiles and gemini surfactants based on carbohydrates.
Langmuir 13:6857–6860. doi:10.1021/la970681k
Maiko Kagawa-Ohara is a master’s degree student at the Graduate
School of Chemistry and Materials Technology, Kyoto Institute of
Technology. Her research deals with the synthesis and the properties
of surfactants.
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2. Kawase T, Saito I, Oida T (2011) Effects of hydrophobic chain
length on temperature dependence of monolayer behavior of
ester-type tartaric geminis. J Oleo Sci 60:61–69. doi:10.5650/jos.
Tsunetomo Aisaka is a master’s degree student at the Graduate
School of Chemistry and Materials Technology, Kyoto Institute of
Technology. His research deals with the synthesis and the properties
of surfactants.
6
0.61
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3. Kawase T, Saito I, Oida T (2013) Monolayer behavior of
asymmetrical ester type tartaric gemini. J Oleo Sci 62:371–380.
doi:10.5650/jos.62.371
Tatsuo Oida is currently an associate professor at the Graduate
School of Chemistry and Materials Technology, Kyoto Institute of
Technology. He received his M. Eng. in organic chemistry at the
Kyoto Institute of Technology and his Ph.D. in synthetic organic
chemistry at Kyoto University, Japan. His research interests include
synthesis and application of gemini surfactants and polyglycerine
based surfactants.
3
4. Aisaka T, Oida T, Kawase T (2007) A novel synthesis of succinic
acid type Gemini surfactant by the functional group intercon-
version of corynomicolic acid. J Oleo Sci 56:633–644. doi:10.
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1
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