Interfacial assembly of a series of cinnamoyl-containing bolaamphiphiles: Spacer-controlled packing, photochemistry, and odd-even effect

Article abstract of DOI:10.1021/la204653b

A series of bolaamphiphiles with 4-hydroxycinnamoyl head groups and different length of the alkyl spacers (n = 6-12) were designed to investigate their photochemistry in the organized films obtained from the air/water interface. It has been found that both the length and odd-even number of the spacers can finely tune the molecular packing as well as the photochemistry. When the spacer length was changed from 6 to 12 methylene units, the assemblies changed from J aggregate to H aggregate. The molecules with evennumbered polymethylene spacer tend to form three-dimensional nanorod structure at the air/water interface. For the assembly of derivatives with odd-numbered spacers, diverse morphologies such as nanospirals and nanofibers were observed depending on the chain length and the surface pressures. The different packing of bolaamphiphiles could subsequently affect the photochemistry of the cinnamoyl groups in the organized films. The spacer effect in the assembly can be understood from the cooperation between Hbond of the phenolic hydroxyl and the amide groups, ?-? stacking as well as the hydrophobic interactions of the alkyl spacer. A packing model was proposed to explain the phenomenon.

Full text of DOI:10.1021/la204653b

Article
pubs.acs.org/Langmuir
Interfacial Assembly of a Series of Cinnamoyl-Containing
Bolaamphiphiles: Spacer-Controlled Packing, Photochemistry, and
Odd−Even Effect
Xufei Liu, Tianyu Wang,* and Minghua Liu*
Beijing National Laboratory for Molecular Science (BNLMS), CAS Key Laboratory of Colloid, Interface, and Chemical
Thermodynamics, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, People’s Republic of China
S
* Supporting Information
ABSTRACT: A series of bolaamphiphiles with 4-hydroxycinnamoyl
head groups and different length of the alkyl spacers (n = 6−12) were
designed to investigate their photochemistry in the organized films
obtained from the air/water interface. It has been found that both the
length and odd−even number of the spacers can finely tune the
molecular packing as well as the photochemistry. When the spacer
length was changed from 6 to 12 methylene units, the assemblies
changed from J aggregate to H aggregate. The molecules with even-
numbered polymethylene spacer tend to form three-dimensional
nanorod structure at the air/water interface. For the assembly of
derivatives with odd-numbered spacers, diverse morphologies such as
nanospirals and nanofibers were observed depending on the chain length
and the surface pressures. The different packing of bolaamphiphiles could subsequently affect the photochemistry of the
cinnamoyl groups in the organized films. The spacer effect in the assembly can be understood from the cooperation between H-
bond of the phenolic hydroxyl and the amide groups, π−π stacking as well as the hydrophobic interactions of the alkyl spacer. A
packing model was proposed to explain the phenomenon.
the aggregation behaviors of conventional amphiphilic mole-
cules with one polar headgroup at the air/water interface have
been well studied,1−8 there are relatively few investigations on
the interfacial assembly of bolaamphiphiles,2,18e−g particularly,
with the bolaamphiphiles containing π-conjugated functional
headgroups. When π-conjugated functional groups are
introduced into the two ends, their cooperative π−π
interactions together with the spacer length would become an
important issue and affect significantly the assembly behavior as
well as their properties.
Previously, we have investigated the assemblies and the
photochemistry of a series of bolaamphiphiles with the same
dodecamethylene spacer but various cinnamoyl ends at the air/
water interface.25 It was found that the assembly behavior and
photochemistry of the bolaamphiphiles largely depended on the
substituted groups on the cinnamoyl unit. The bolaamphiphile
with 4-hydroxycinnamoyl head groups (HCDA), in particular,
was found to assemble into supramolecular nanotube structure.
Moreover, the formed nanotube from HCDA showed supra-
molecular chirality although the bolaamphiphile itself is achiral.
Interestingly, the chiral nanotube can be stabilized through the
photosewing and can further induce the chirality of an achiral
molecule assembled on it. This result caused our further
1. INTRODUCTION
Nanofabrication through the air/water interface provides a
useful platform to construct functional materilas.1−8 Since
building blocks are confined in a two dimension and a slight
molecular change may affect the interactions at the interface,
unique properties and regulation on the interfacial assemblies
are expected.9−11 In general, amphiphilic molecules with
functional groups at air/water has been extensively inves-
tigated,12 and many functional films were obtained via the
corresponding Langmuir−Blodgett technique.4,5,8 Besides the
layered thin films, other nanostructures, such as nanorods,
nanofibers, vesicles, or nanotubes and their arrays, could be also
very important owing to their unique photophysical and
photochemical properties.13−17 Although conventional amphi-
philes are difficult to form such complex nanostructures in most
case at air/water interface, specially designed molecules will
provide many chances to give and further regulate the
formation of those nanostructrues through two-dimensional
nanofabrication.18g
Bolaamphiphiles are the amphiphilic molecules with two
hydrophilic ends, which covalently connected by hydrophobic
alkyl spacers.18 Compared to the conventional amphiphilic
molecules, bolaamphiphiles with two head groups can self-
organize into the supramolecular assemblies with more diverse
structures and functionality.19−24 During the self-assembly of
bolaamphiphiles, the interactions between both the head
groups and the spacers play very important roles. Although
Received: November 25, 2011
Revised: January 23, 2012
Published: January 24, 2012
© 2012 American Chemical Society
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Article
of triethylamine was added in batches first, and then 1,10-
diaminodecane (0.43 g, 2.5 mmol) and triethylamine (5 mL) in
dry DMF (30 mL) were again added dropwise. The reaction
mixture was stirred 2 h on an ice bath and overnight at room
temperature. The solvent was evaporated, and the residue was
dissolved in CH2Cl2 and washed sequently with 1% HCl,
sodium bicarbonate, and water. The organic phase was then
dried over anhydrous sodium sulfate and concentrated under
vacuum. The obtained residue was again dissolved in 10 mL of
THF, and the corresponding THF solution was poured into
200 mL of water. The suspended solid was collected by
filtration and recrystallized from CH2Cl2/acetone to give
interest in how spacer length of the cinnamoyl bolaamphiphiles
affects the packing of their headgroups as well as the
corresponding photoreaction.
In this paper, we designed a series of bolaamphiphiles, which
have 4-hydroxycinnamoyl headgroups and the spacers contain-
ing different methylene units, and investigated their interfacial
assemblies as well as the photochemistry, which is based on the
photodimerization of cinnamoyl headgroups.26,27 For the
spacer effect, besides the usual even-numbered polymethylene,
we also paid attention to the odd-numbered polymethylene
derivatives to show the odd−even effect.28 Although the
aggregation behavior of bolaamphihiles in bulk solution18b−d
and self-assembled monolayers28a have been found strongly
dependent on the odd or even number of oligomethylene, the
air/water interfacial assemblies of bolaamphiphiles with odd-
numbered connecting chains have not yet been well studied.
When the spacer length was increased, the packing of the
headgroups showed the remarkable changes from J-aggregation
to H-aggregation. With such differences in the packing, the
assemblies showed different morphologies and photochemistry.
The molecules with even-numbered spacer tend to construct
large scale and three-dimensional nanorod structures, while the
molecules with odd-numbered polymethylene spacer prefer to
form approximate one-dimensional or two-dimensional nano-
structures, such as nanofiber or nanospiral, flat plate, and
twisted ribbons. Various characterization methods such as SEM,
TEM, and AFM measurements and the UV−vis and FT-IR
spectroscopy were employed to understand the structural
formation as well as their functions of the assemblies.
1
ACDA10 as a white solid (yield 28%). H NMR (400 MHz,
DMSO-d6): δ (ppm) 1.27 (s, 12H), 1.45 (m, 4H), 2.27 (s, 6H),
3.13 (m, 4H), 6.59 (d, 2H), 7.16 (d, 4H), 7.40 (d, 2H), 7.58 (d,
4H), 8.06 (t, 2H). MALDI-TOF-MS 549.3 [M + H]+, 571.3
[M + Na]+, calcd 548.7 (C32H40N2O6); elemental analysis calcd
(%) for C32H40N2O6: C 70.05%, H 7.35%, N 5.11%. Found: C
69.99%, H 7.35%, N 5.19%.
Compounds bis(4-acetoxycinnamoyl)-1,6-hexanemethylenediamine
(ACDA6), bis(4-acetoxycinnamoyl)-1,7-heptanemethylenediamine
(ACDA7), bis(4-acetoxycinnamoyl)-1,8-octanemethylenediamine
(ACDA8), bis(4-acetoxycinnamoyl)-1,9-nonanemethylenediamine
(ACDA9), and bis(4-acetoxycinnamoyl)-1,11-undecanemethylenedi-
amine (ACDA11) were synthesized in similar method, with the yield
coming to 38%, 35%, 32%, 33%, and 40%, respectively.
1
ACDA6. H NMR (400 MHz, DMSO-d6): δ (ppm) 1.32 (s, 4H),
1.46 (m, 4H), 2.28 (s, 6H), 3.17 (m, 4H), 6.58 (d, 2H), 7.17 (d, 4H),
7.40 (d, 2H), 7.59 (d, 4H), 8.08 (t, 2H). MALDI-TOF-MS 493.2 [M
+ H]+, 515.2 [M + Na]+, calcd 492.6 (C28H32N2O6); elemental
analysis calcd (%) for C28H32N2O6·0.5H2O: C 67.05%, H 6.63%, N
5.59%. Found: C 67.37%, H 6.64%, N 5.63%.
1
ACDA7. H NMR (400 MHz, DMSO-d6): δ (ppm) 1.30 (s, 9H),
1.45 (m, 4H), 2.27 (s, 6H), 3.16 (m, 4H), 6.58 (d, 2H), 7.16 (d, 4H),
7.40 (d, 2H), 7.58 (d, 4H), 8.07 (t, 2H). MALDI-TOF-MS 507.3 [M
+ H]+, 529.3 [M + Na]+, 545.3 [M + K]+, calcd 506.59 (C29H34N2O6);
elemental analysis calcd (%) for C29H34N2O6: C 68.75%, H 6.76%, N
5.53%. Found: C 68.42%, H 6.91%, N 5.59%.
2. EXPERIMENTAL SECTION
2.1. Materials. trans-4-Hydroxycinnamic acid, 1,6-hexanediamine,
1,7-diaminoheptane, 1,8-diaminooctane, and 1,9-diaminononane were
purchased from Alfa Aesar. 1,10-Diaminodecane was purchased from
Aldrich, 1,11- diaminoundecane was purchased from TCI Fine
Chemicals, and all these compounds were used as received, while
other starting materials and solvents with analytical grade were
purchased from Beijing Chemicals. The dry THF was obtained by
distillation from sodium and benzophenone prior to use. Milli-Q water
(18.2 MΩ cm) was used in all cases.
2.2. Instruments. Measurements of surface pressure−area (π−A)
isotherms, and film depositions were carried out on a KSV minitrough
(Helsinki, Finland). UV lamp (20 W) centered at 254 nm were used as
the irradiation source for the photoreaction in the films. The 1H NMR
spectra were recorded on an ARX400 Bruker (400 MHz)
spectrometer in DMSO-d6 with TMS as an internal standard. TOF-
MS was carried out on the BIFLEXIII mass spectrometer. Elemental
analysis was performed on a Carlo-Erba-1106 instrument. A JASCO
UV-550 spectrometer was used for the UV−vis spectra measurements.
FTIR spectra were obtained with a JASCO FT/IR-660 plus
spectrophotometer. Atomic force microscopy (AFM) was performed
by using Tapping Mode (Nanoscope IIIa, Digital Instruments, Inc.)
with silicon cantilever probes. Scanning electron microscope (SEM)
images were taken on a field emission SEM (Hitachi S-4800, 15 kV).
For transmission electron microscopy (TEM) measurements, a JEOL
1011 system operated at 200 kV was used. X-ray diffraction (XRD)
was achieved on a Rigaku D/Max-2500 X-ray diffractometer (Japan)
with Cu Kα radiation (λ = 1.5406 Å), which was operated at 45 kV,
100 mA.
1
ACDA8. H NMR (400 MHz, DMSO-d6): δ (ppm) 1.29 (s, 8H),
1.45 (m, 4H), 2.28 (s, 6H), 3.16 (m, 4H), 6.58 (d, 2H), 7.16 (d, 4H),
7.39 (d, 2H), 7.58 (d, 4H), 8.06 (t, 2H). MALDI-TOF-MS 521.3 [M
+ H]+, 543.3 [M + Na]+, calcd 520.6 (C30H36N2O6); elemental
analysis calcd (%) for C30H36N2O6: C 69.21%, H 6.97%, N 5.38%.
Found: C 68.83%, H 7.05%, N 5.45%.
1
ACDA9. H NMR (400 MHz, DMSO-d6): δ (ppm) 1.26 (s, 10H),
1.43 (m, 4H), 2.26 (s, 6H), 3.14 (m, 4H), 6.56 (d, 2H), 7.14 (d, 4H),
7.38 (d, 2H), 7.57 (d, 4H), 8.04 (t, 2H). MALDI-TOF-MS 535.3 [M
+ H]+, 557.3 [M + Na]+, calcd 534.64 (C31H38N2O6); elemental
analysis calcd (%) for C31H38N2O6·0.5H2O: C 68.49. %, H 7.23%, N
5.15%. Found: C 68.75%, H 7.29%, N 5.20%.
ACDA11. 1H NMR (400 MHz, DMSO-d6): δ (ppm) 1.27 (s, 14H),
1.45 (m, 4H), 2.28 (s, 6H), 3.16 (m, 4H), 6.59 (d, 2H), 7.17 (d, 4H),
7.40 (d, 2H), 7.59 (d, 4H), 8.08 (t, 2H). MALDI-TOF-MS 563.4 [M
+ H]+, 585.4 [M + Na]+, calcd 562.70 (C33H42N2O6); elemental
analysis calcd (%) for C33H42N2O6: C 70.44%, H 7.52%, N 4.98%.
Found: C 70.10%, H 7.55%, N 5.04%.
Bis(4-hydroxycinnamoyl)-1,10-decanemethylenediamine
(HCDA10). ACDA10 (200 mg, 0.36 mmol) and p-toluenesulfonic acid
monohydrate (367 mg, 1.9 mmol) were dissolved in 50 mL of absolute
ethanol. The solution was refluxed for 40 min, and then about 75% of
the alcohol was distilled within 3 h during the continuous refluxing.
The remaining solvent was evaporated, and the residue was dispersed
in 500 mL of 10% sodium bicarbonate aqueous solution. The mixture
was stirred for 2 h and filtered. The obtained white solid was washed
with water and was recrystallized from CH2Cl2/acetone to give the
2.3. Synthesis. Bis(4-acetoxycinnamoyl)-1,10-decanemethyle-
nediamine (ACDA10). 3-(4-Acetoxyphenyl)propenoic acid (1.24
g, 6 mmol) was prepared according to the method described in
the literature,29 which was again refluxed with thionyl chloride
in dry toluene to give the corresponding acyl chloride. After
evaporation, the acyl chloride was dissolved in 100 mL of dry
THF and stirred on the ice/water bath. To the reaction, 10 mL
1
product (105 mg, yield 62%). H NMR (400 MHz, DMSO-d6): δ
(ppm) 1.27 (s, 12H), 1.43 (m, 4H), 3.13 (m, 4H), 6.38 (d, 2H), 6.78
(d, 4H), 7.25 (d, 2H), 7.37 (d, 4H), 7.90 (t, 2H), 9.80 (s, 2H).
MALDI-TOF-MS 465.1 [M + H]+, 487.1 [M + Na]+, 503.1 [M+K]+,
calcd 464.6 (C28H36N2O4); elemental analysis calcd (%) Calcd for
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Figure 1. Surface pressure−area isotherms of the spreading films of 4-hydroxycinnamoyl-containing bolaamphiphiles with different alkyl chain length
on aqueous subphase at 20 °C: (a) HCDA6-10; (b) HCDA7-11.
C28H36N2O4·0.5H2O: C 71.01%, H 7.87%, N 5.91%. Found: C
70.74%, H 7.88%, N 5.77%.
without any staining. The multilayer films were prepared by the
horizontal Langmuir−Schaefer method through the mini-trough. For
the UV−vis measurement, quartz plates were used. In preparing
samples for XRD measurements, LS films were deposited onto glass
plates. Fresh cleaned silicon wafers were adopted as substrate of
multilayer films for FT-IR spectral measurements.
Compounds bis(4-hydroxycinnamoyl)-1,6-hexanemethylenedi-
amine (HCDA6), bis(4-hydroxycinnamoyl)-1,7-heptanemethylenedi-
amine (HCDA7), bis(4-hydroxycinnamoyl)-1,8-octanemethylenedi-
amine (HCDA8), bis(4-hydroxycinnamoyl)-1,9-nonanemethylenedi-
amine (HCDA9), and bis(4-hydroxycinnamoyl)-1,11-
undecanemethylenediamine (HCDA11) were then synthesized in
similar method, with the yield coming to 72%, 63%, 75%, 73%, and
70%, respectively.
3. RESULTS
3.1. Surface Pressure−Area Isotherms. Figure 1 shows
the surface pressure−area (π−A) isotherms of the 4-
hydroxycinnamoyl-containing bolaamphiphiles with various
spacers spread on pure water subphase. The results show that
the aggregation behaviors of these bolaamphiphiles are
significantly dependent on the spacer length, especially the
even−odd number of polymethylene. The extrapolated
molecular area was obtained by extrapolating the linear part
of the isotherm to zero surface pressure. For the compounds
HCDA6, HCDA8, and HCDA10, the extrapolated molecular
areas are 0.008, 0.033, and 0.022 nm2, respectively (Figure1 and
Table S1). The CPK model shows a vertical arrangement of the
bolaamphiphile on water surface should at least occupy more
than 0.2 nm2; the much smaller molecular area suggests the
formation of 3D structures or multilayer films on water
surface.30
1
HCDA6. H NMR (400 MHz, DMSO-d6): δ (ppm) 1.30 (s, 4H),
1.45 (m, 4H), 3.14 (m, 4H), 6.39 (d, 2H), 6.77 (d, 4H), 7.29 (d, 2H),
7.37 (d, 4H), 7.93 (t, 2H), 9.79 (s, 2H). MALDI-TOF-MS 409.0 [M +
H]+, 431.0 [M + Na]+, calcd 408.5 (C24H28N2O4); elemental analysis
calcd (%) Calcd for C24H28N2O4·0.5H2O: C 69.04%, H 7.00%, N
6.71%. Found: C 68.60%, H 6.99%, N 6.58%.
1
HCDA7. H NMR (400 MHz, DMSO-d6): δ (ppm) 1.29 (s, 6H),
1.44 (m, 4H), 3.15 (m, 4H), 6.38 (d, 2H), 6.77 (d, 4H), 7.29 (d, 2H),
7.36 (d, 4H), 7.92 (t, 2H), 9.79 (s, 2H). MALDI-TOF-MS 423.2 [M +
H]+, 445.2 [M + Na]+, 461.2 [M + K]+, calcd 422.52 (C25H30N2O4);
elemental analysis calcd (%) Calcd for C25H30N2O4·1.25H2O: C
67.47%, H 7.36%, N 6.29%. Found: C 67.57%, H 7.48%, N 6.18%.
1
HCDA8. H NMR (400 MHz, DMSO-d6): δ (ppm) 1.28 (s, 8H),
1.43 (m, 4H), 3.13 (m, 4H), 6.38 (d, 2H), 6.77 (d, 4H), 7.29 (d, 2H),
7.37 (d, 4H), 7.93 (t, 2H), 9.81 (s, 2H). MALDI-TOF-MS 437.3 [M +
H]+, 459.3 [M + Na]+, 475.3 [M+K]+, calcd 436.5 (C26H32N2O4);
elemental analysis calcd (%) Calcd for C26H32N2O4·0.25H2O: C
70.80%, H 7.43%, N 6.35%. Found: C 70.87%, H 7.50%, N 6.40%.
Scheme 1. Molecular Structure of the 4-Hydroxycinnamoyl-
Containing Bolaamphiphiles
1
HCDA9. H NMR (400 MHz, DMSO-d6): δ (ppm) 1.27 (s, 10H),
1.43 (m, 4H), 3.13 (m, 4H), 6.39 (d, 2H), 6.77 (d, 4H), 7.29 (d, 2H),
7.36 (d, 4H), 7.91 (t, 2H), 9.79 (s, 2H). MALDI-TOF-MS 451.3 [M +
H]+, 473.3 [M + Na]+, calcd 450.57 (C27H34N2O4); elemental analysis
calcd (%) Calcd for C27H34N2O4·H2O: C 69.21%, H 7.74%, N 5.98%.
Found: C 68.82%, H 7.74%, N 6.02%.
HCDA11. 1H NMR (400 MHz, DMSO-d6): δ (ppm) 1.23 (s, 14H),
1.40 (m, 4H), 3.10 (m, 4H), 6.35 (d, 2H), 6.74 (d, 4H), 7.26 (d, 2H),
7.33 (d, 4H), 7.88 (t, 2H), 9.80 (s, 2H). MALDI-TOF-MS 479.3 [M +
H]+, 501.4 [M + Na]+, 517.3 [M + K]+, calcd 478.6 (C29H38N2O4);
elemental analysis calcd (%) Calcd for C29H38N2O4·H2O: C 70.13%,
H 8.12%, N 5.64%. Found: C 70.06%, H 7.86%, N 5.50%.
However, for the bolaamphiphiles with odd-number spacers,
the π−A isotherms of spreading films show relatively larger
molecular areas, as the extrapolated areas were determined as
0.184, 0.058, and 0.140 nm2 for compounds HCDA7, HCDA9,
and HCDA11, respectively. But these areas are still smaller
than the case of a monolayer. These results indicate that the
odd-numbered bolaamphiphiles also form some high level
nanostructures at the air/water interface, but the structures
could be different from the assemblies formed by the
compounds with even number spacer. It is also noted that
HCDA7 gave an isotherm with the largest extrapolated
molecular area and the lowest collapsed surface pressure (ca.
34 mN/m), even though it has the shortest odd-numbered
alkyl spacer. This result means that HCDA7 might form more
flat structures on water surface.
2.4. Procedures. The floating Langmuir films of the investigated
compounds were formed by spreading their chloroform (1 × 10−3
mol/L) solutions onto the surface of pure Milli-Q water (18 MΩ cm)
at 20 °C. After the evaporation of the solvent for 20 min, the π−A
isotherms of the spreading films were recorded by compressing the
barrier with a speed of 5 mm/min. For AFM measurement, the
monolayers of the compounds were transferred onto newly cleaved
mica plates by a vertical lifting method at the selected surface pressure
with the upward dipping speed at 5 mm/min. The sample for scanning
electron microscope (SEM) measurement was prepared by the
horizontal Langmuir−Schaefer method on clean silicon wafer. For
transmission electron microscopy (TEM) measurements, the copper
grid was aslant infixed into the water subphase and was uplifted flatly
and slowly to get the langmuir film, which was dried and checked
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Figure 2. SEM images of the LS films deposited at 10 mN/m from (a) HCDA6, (c) HCDA8, and (e) HCDA10 and TEM images of the LS films
deposited at 10 mN/m of (b) HCDA6, (d) HCDA8, and (f) HCDA10.
3.2. Morphology of the Transferred Films. To get
further insight into the possible nanostructures formed at the
air/water interface, the floating films were transferred onto
solid substrates for further characterizations. We could not
obtain good atomic force microscopy (AFM) images for the
assemblies from even spacer compounds due to their large sized
three-dimensional nanostructures. Therefore, those films
obtained from even-numbered compounds were transferred
onto silicon wafer or copper grid for SEM and TEM
measurements. Figure 2 shows the SEM and TEM images of
one-layer transferred HCDA6, HCDA8, and HCDA10 films.
For their assemblies, nanorod structures with length ranging
from 150 to 300 nm were observed. We measured the size of
HCDA nanorods from the SEM images with statistical methods
and found that the length−diameter ratio (l/d) of the obtained
nanorods increased from to 2.7 to 4.1 when the spacer length of
the molecular building blocks was increased from C6 to C10
(Table S2).
plate, and the height of the film was estimated to be about 1 nm
(Figure 3a). Compound HCDA11 formed nanofibers, which
are aligned in certain directions. The length of the nanofibers
can be estimated as about 600 nm with the height as 4−7 nm
(Figure 3e). The HCDA9 assemblies showed an interesting
morphological change depending on the surface pressures.
Nanofibers with many spiral structures winding in both a
clockwise and an anticlockwise direction were observed for the
film transferred at near zero surface pressure (Figure 3b). When
the deposition surface pressure was increased to 3 mN/m,
densely packed nanofibers were observed (Figure 3c). When
the deposition surface pressure was further increased to 10
mN/m, many curved nanorod-like morphology can be
observed with the height as 8−9 nm (Figure 3d). TEM
observation further revealed that these nanorod-like structures
are twisted ribbons (Figure 3f).
3.3. UV−Vis Spectra of the Transferred Films. Figure 4
shows the UV−vis spectra of transferred multilayer films in
comparison with the compound in ethanol solution. The UV−
vis spectra of all the HCDA ethanol solution showed an
absorption peak at 227 nm and a broaden split band with the
peaks at about 294 and 310 nm, respectively, regardless of the
spacer lengths (Figur 4a and Figure S1). The relatively long
wavelength can be attributed to the contribution of hydroxyl
group, which reduce the energy of corresponding π−π*
transition of cinnamoyl head groups.31 On the other hand,
the UV−vis spectra of the assemblies from the air/water
interface showed remarkable dependence on the spacer length.
For HCDA6 film, the maximum absorption peak appears at
300 nm with a shoulder at 315 nm (Figure 4a), which is 6 nm
red-shifted, indicating the J-like aggregation of HCDA6
assemblies. The maximum absorption peaks of HCDA7,
HCDA8, and HCDA9 films appear at nearly the same
wavelength as the spectra of the corresponding ethanol
solution, although the splitting bands were merged with each
other (Figure 4a and Figure S1). The π−π* transition
absorption band of HCDA10 and HCDA11 films appears at
284 and 269 nm, which are 20 and 35 nm blue-shifted
comparing with the UV−vis spectra of the corresponding
solution (Figure 4a). These results clearly indicate that the
headgroups packed within HCDA10 and HCDA11 assemblies
could be in a head to head manner or H-aggregates.
Considering the previously reported HCDA12 air/water
interfacial assemblies,25 which also showed as an H-aggregate,
it is clear that upon extending the spacers from the C6 to C12,
In contrast, the assemblies from the bolaamphiphiles
containing odd spacers exhibit completely different morphol-
ogies, which are relatively flat and can be measured by AFM, as
shown in Figure 3. Compound HCDA7 assembled as a flat
Figure 3. AFM images of one-layer transferred films: (a) HCDA7
deposited at 10 mN/m; HCDA9 deposited at (b) 0, (c) 3, and (d) 10
mN/m; (e) HCDA11 deposited at 10 mN/m; (f) TEM image of
HCDA9 deposited at 10 mN/m.
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Figure 4. (a) UV−vis spectra of HCDA6 ethanol solution (black) and transferred 10-layer LS films at 10 mN/m: HCDA6 (purple), HCDA8 (red),
HCDA10 (blue), HCDA11 (3 times intensity, green). (b) Relationship between maximum peak and the alkyl chain length from UV−vis spectra of
LS film deposited at 10 mN/m.
Figure 5. FT-IR spectra of 100-layer LS films from a set of bolaamphiphiles deposited at 10 mN/m: (a) HCDA6−10; (b) HCDA7−11.
the headgroups packing of bolaamphiphiles will change from J-
aggregate to the H-aggregate (Figure 4b).
wavenumber. For example, the antisymmetric and symmetric
stretching bands of HCDA6 appeared at 2939 and 2860 cm−1,
respectively, indicating the alkyl chain adopted much gauche
conformation in the assembly.35,36 For HCDA11, they showed
at 2920 and 2849 cm−1 which means that the alkyl spacer
packed more in the all-trans conformation.35,36 When the
spacer length spacer increased, a highly ordered and well-
organized arrangement of the hydrocarbon chains was
obtained.35,36
3.5. Photodimerization in the Organized Molecular
Films. It has been reported that the single-headed cinnamoyl-
containing amphiphiles could undergo photodimerization
under the UV irradiation in LS or LB films.25,26,27c,d,31 It
seems to be true for the present assemblies from bolas. Upon
photoirradiation, the films showed a clear spectral change.
However, depending on the spacer length, these films showed
some different behaviors.
Figure 6 shows the UV−vis spectral changes of all the
bolaamphiphilic films as a function of UV irradiation time. Two
features are clear. One is that the films, whatever forming H-
aggregates or not, initially underwent a spectral change to the
spectrum with broaden and splitting band around 300 nm, 315
nm, and then the UV−vis spectra of the films started to show a
clear decrease in the intensity upon photoirradiation (Figure 6).
It has been shown that when photodimerization occurred, the
π-conjugate system will be destroyed and caused the decrease
of the absorption maximum. In addition, the cinnamoyl group
could undergo photoisomerization. In the present films, there
underwent a initial spectral shift as well as the intensity change.
Some of them showed increase of the peak intensity. This
implies that there is a reorganization of the molecules in the
film and then proceed photodimerization. Such reorganization
process might be related to the photoisomerization of the
cinnamoyl group and the packing adjustment of the molecules
3.4. FT-IR Spectra of the Transferred LS Films. Figure 5
shows the FT-IR spectra of the LS films of the cinnamoyl-
containing bolaamphiphiles, which were transferred at 10 mN/
m. All of the films showed characteristic vibration bands around
3400, 3300, 2920, 1647−1655, and 1540−1564 cm−1, which
can be ascribed to the stretching vibration of O−H, N−H,
CH2, amide I, and amide II bands, respectively. On the basis of
the vibrational frequencies of these bands, it is clear that either
the amide groups or the phenolic hydroxyl groups are in the
hydrogen-bonding form in the films.32−34
On the other hand, depending on the spacer length,
particularly, the odd−even methylene number of the spacers,
the vibrational bands showed some regular changes. For OH
stretching vibration, the band shifted to the lower wavenumbers
when the spacer length was increased in even or odd systems
(Figure 5), indicating that the H-bond interactions between the
hydroxyl groups become stronger for the assemblies of
molecules with longer spacer.33 In addition, the N−H
stretching band could be separated from the O−H stretching
more distinctly in even system than in odd ones, which means
the H-bonds cooperatively exist in the formation of even
assemblies. Furthermore, as increasing the spacers, amide I
bands from the FT-IR spectra of even bola assemblies shifted to
the lower wavenumbers, indicating the H-bonds between the
amide groups were enhanced.32 However, the contrary
tendency appears in the odd assemblies, which means amide
hydrogen bonding between odd bolas would become weak
when the spacer was enlarged. These spectral changes might be
related to the different packing of the bolaamphiphiles with odd
and even spacers.
As the spacer length increasing, both the antisymmetric and
symmetric stretching vibrations of CH2, shifted to the lower
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Figure 6. Time-dependent UV−vis spectra of 10-layer LS films from (a) HCDA6, (b) HCDA7, (c) HCDA8, (d) HCDA9, (e) HCDA10, and (f)
HCDA11 upon 254 nm UV irradiation. (g, h) Plot of the peak at 315 nm as a function of irradiation time. Hollow circle: HCDA6 (black); HCDA8
(red), HCDA10 (green); solid circle: HCDA7 (black); HCDA9 (red), HCDA11 (green).
Figure 7. Possible packing modes of the bolaamphiphiles with even (HCDA10) and odd (HCDA11) spacers and the photoinduced dimerization. In
the assemblies of the bolaamphiphiles with even-numbered spacer, the amide H-bond aligned antiparallel, while those with odd ones aligned parallel.
For the former, the H-bond between phenolic groups can be extended between layers and caused the formation of large three-dimensional
assemblies. The photoirradiation caused the rearrangement of the cinnamic group and lead to the dimerization.
to facilitate the subsequent photodimerization. The other
feature is that the reaction is clearly different between the
assemblies from even- and odd-numbered bolas. Compared
with the case of even-numbered bolaamphiphiles, the initial
reorganization process of odd-numbered ones was quite fast.
For example, the UV−vis spectra of the as-prepared HCDA11
LS films exhibited the 269 nm peak due to the H-aggregation,
first shifted to a broad double peak after only 2 min irradiation
and then underwent decreasing of the intensity upon further
irradiation (Figure 6f,h). For the LS films obtained from even-
numbered bolas, the photochemical reactions are also different
depending on the spacer length. Moreover, its change to the
photodimerizable spectrum required more time. For example,
the initial band of HCDA6 assemblies decreased at 300 nm and
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the band at 315 nm increased to its maximum after 12 min
irradiation. After 15 min irradiation, both of the peaks began to
decrease, meaning the photodimerization is going on.25,37,38 We
plotted the peak intensity at 315 nm as a function of irradiation
time. For the bolaamphiphiles with even spacer, the peak
reached to the maximum within 15 min and then showed a
decrease. For the bolaamphiphiles with odd spacer, only about
4 min is needed to reorganize into the conformation for
photodimerization.
The photodimerization also could be confirmed by FT-IR
spectra (Figure S2) which showed that the intensity of CC
stretching band (1600−1610 cm−1) and CH deformation band
(974−989 cm−1) of trans-alkenes decreased under UV
irradiation.25,37,38 Since for these bolaamphiphile, the reaction
can take place at the two ends and the final products were
unfortunately not separated.
the phenolic groups could further affect the π−π stacking of the
head cinnamoyl groups and thus we could obtain different
aggregates.
The photochemical reaction between cinnamoyl groups is a
topochemical one.27d,e That is, the reaction is dependent on the
distance and packing of the neighboring parallel double bonds
(3.6−4.2 Å).27d,e The cinnamoyl groups in strong H-
aggregation need to be reorganized to occupy proper distance
for benefiting the photodimerization.27a,d,e This reorganization
could be affected by H-bonding interaction. Therefore, as we
reported previously, when the HCDA assemblies were under
UV irradiation, the H-aggregation of the packed molecules
would be destroyed first, and then the photoreaction could
further proceed.25 On one hand, for the odd-numbered HCDA
molecules, the headgroups tend to aggregate in a loose model
with weaker H-bonding interaction, and the reaction was
favored, which was confirmed by the initial instant reorganiza-
tion (Figure 6). While for the assemblies of bolamphiphiles
with even spacers, due to the relatively stronger 3D H-bond
which seizes the headgroups tightly, the packing modes need to
be modulated by longer irradiation time (Figure 6). After the
initial reorganization, the following photoreactions of HCDA
derivatives with different spacer are similar.
4. DISCUSSION
The above bolaamphiphiles revealed to be good building blocks
for the construction of functional nanostructures at air/water
interface, and their assembly properties are largely dependent
on both the spacer length and the odd−even number. It
seemed that these properties are related to the cooperative
interactions between H bonds of the OH and amide groups,
hydrophobic interactions of the hydrophobic spacer, and the
π−π stacking of the π-conjugated end groups. XRD diffraction
of the assembled interfacial films revealed that the assemblies
have a layered structure (Supporting Information, Figure S3).
On the basis of these data, we proposed a packing model to
explain these differences in the assemblies, as illustrated in
Figure 7.
There are two kinds of the hydrogen bonds within the
HCDA assemblies. One is the hydrogen bond between the
amide groups, as revealed from the FT-IR spectra in the N−H
vibration, amide I and amide II bands, which could connect
neighboring bolaamphiphiles, as illustrated in Figure 7.39 In
addition, the packing direction of amide H-bond is different for
the even and odd-spacered bolaamphiphiles, as revealed by the
crystal structure of bolaamphiphiles with 1-glucosamide
headgroup by Shimizu et al.21 Generally, for the packing of
bolaamphiphiles within the layer, the even bolas could form
linear hydrogen bonds because two equidistant CO−NH pairs
occur on each edge of the chain. For the assemblies of odd
bolas, both NH groups and CO groups are located on one edge
and the distances are not the same, and linear hydrogen bonds
cannot be formed.23 The other is the hydrogen bond between
phenolic groups. The hydrogen bond of OH groups could be
presented both “inside” or “between” the layers.25,40 The FT-IR
spectra showed that the hydroxyl H-bond within the even bolas
assemblies are stronger than that within the odd bolas
assemblies. Therefore, it seemed that in the assemblies formed
by odd-numbered HCDA molecules the weak hydrogen bond
between hydroxyl groups seemed to be not able to connect the
layers, while the assemblies from even-numbered spacers could,
as verified from their stronger H bond between OH groups.
Because of these combined H-bonds, we obtained relative
larger 3D nanorod for the even-spacered bolaamphiphiles and
one-dimensional nanofiber structure for the odd-spacered ones.
On the other hand, the hydrophobic interaction between the
spacers player also an important role. With the spacer length
increased, the alkyl spacer packed more organized, as verified
from the FT-IR spectra. These hydrophobic interactions
together with the H bonds between the amide groups and
5. CONCLUSION
In summary, we have designed a series of bolaamphiphiles with
4-hydroxycinnamoyl headgroups (HCDA) and various spacer
lengths. Utilizing the delicate balances among different
noncovalent interactions, packing control and fine-tuning of
the supramolecular nanostructures from the air/water inter-
facial aggregation can be achieved. The packing of HCDA
derivative changed from J-aggregation to H-aggregation when
the length of alkyl spacers was increased from C6 to C11. The
bolaamphiphiles with even carbon number spacer were found
to aggregate into nanorods at air/water interface, while those
with odd-numbered spacers could assemble to 1D or 2D
nanostructure. All the assemblies showed photodimerization
upon UV-irradiation after experiencing a reorganization of the
molecular packing. The assemblies from odd-spacered
amphiphiles showed a shorter time of reorganization. The
odd−even spacer effect in HCDA assembly can be understood
from the cooperation between H bond in the headgroups, π−π
stacking, and the alkyl hydrophobic interactions.
ASSOCIATED CONTENT
■
S
* Supporting Information
Data for π−A isotherms; additional UV−vis, FT-IR spectra, and
XRD. This material is available free of charge via the Internet at
http://pubs.acs.org.
AUTHOR INFORMATION
■
Corresponding Author
*Telephone: +86-10-82615803. Fax: +86-10-62569564. E-mail:
liumh@iccas.ac.cn (M.L.); twang@iccas.ac.cn (T.W.).
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
This work was supported by the National Natural Science
Foundation of China (Nos. 91027042, 21021003, and
20873161), the Basic Research Development Program
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metrical Bolaamphiphiles. Langmuir 2004, 20, 5969−5977. (d) Kogiso,
M.; Ohnishi, S.; Yase, K.; Masuda, M.; Shimizu, T. Dicarboxylic
Oligopeptide Bolaamphiphiles: Proton-Triggered Self-Assembly of
Microtubes with Loose Solid Surfaces. Langmuir 1998, 14, 4978−
4986. (e) Liu, M.; Cai, J. Silver(I) Ion Induced Reverse U-Shape
Monolayers of Poly(methylenebis(benzimidazoles)) at the Air/Water
Interface. Langmuir 2000, 16, 2899−2901. (f) Patwardhan, A. P.;
Thompson, D. H. Novel Flexible and Rigid Tetraether Acyclic and
Macrocyclic Bisphosphocholines: Synthesis and Monolayer Properties.
Langmuir 2000, 16, 10340−10350. (g) Gao, P.; Liu, M. Compression
Induced Helical Nanotubes in a Spreading Film of a Bolaamphiphile at
the Air/Water Interface. Langmuir 2006, 22, 6727−6729. (h) Parera,
E.; Comelles, F.; Barnadas, R.; Suades, J. New Surfactant Phosphine
Ligands and Platinum(II) Metallosurfactants. Influence of Metal
Coordination on the Critical Micelle Concentration and Aggregation
Properties. Langmuir 2010, 26, 743−751.
(2007CB808005 and 2009CB930802), and the Fund of the
Chinese Academy of Sciences.
REFERENCES
■
(1) (a) Ulman, A. An Introduction to Ultrathin Organic Films;
Academic Press: Boston, MA, 1991. (b) Petty, M. C. Langmuir-
Blodgett Films: An Introduction; Cambridge University Press: Cam-
bridge, U.K., 1996.
(2) Kuzmenko, I.; Rapaport, H.; Kjaer, K.; Als-Nielsen, J.; Weissbuch,
I.; Lahav, M.; Leiserowitz, L. Design and Characterization of
Crystalline Thin Film Architectures at the Air−Liquid Interface:
Simplicity to Complexity. Chem. Rev. 2001, 101, 1659−1696.
(3) Zasadzinski, J. A.; Viswanathan, R.; Madsen, L.; Garnaes, J.;
Schwartz, D. K. Langmuir-Blodgett films. Science 1994, 263, 1726−
1733.
(4) McCullough, D. H. III; Grygorash, R.; Hsu, J. T.; Regen, S. L.
Insight into the Permeation Barrier of Glued Langmuir−Blodgett
Bilayers. J. Am. Chem. Soc. 2007, 129, 8663−8667.
(5) Punkka, E.; Rubner, M. F. Molecular heterostructure devices
composed of langmuir-blodgett films of conducting polymers. J.
Electron. Mater. 1992, 21, 1057−1063.
(6) Reitzel, N.; Greve, D. R.; Kjaer, K.; Howes, P. B.; Jayaraman, M.;
Savoy, S.; McCullough, R. D.; McDevitt, J. T.; Bjørnholm, T. Self-
Assembly of Conjugated Polymers at the Air/Water Interface.
Structure and Properties of Langmuir and Langmuir−Blodgett Films
of Amphiphilic Regioregular Polythiophenes. J. Am. Chem. Soc. 2000,
122, 5788−5800.
(7) (a) Kim, J.; Swager, T. M. Control of Conformational and
Interpolymer Effects in Conjugated Polymers. Nature 2001, 411,
1030−1034. (b) Ling, M. M.; Bao, Z. Thin Film Deposition,
Patterning, and Printing in Organic Thin Film Transistors. Chem.
Mater. 2004, 16, 4824−4840.
(19) De Rosa, M.; Gambacorta, A. The lipids of archaebacteria. Prog.
Lipid Res. 1988, 27, 153−175.
(20) Song, B.; Wang, Z.; Chen, S.; Zhang, X.; Fu, Y.; Smet, M.;
Dehaen, W. The Introduction of π−π Stacking Moieties for
Fabricating Stable Micellar Structure: Formation and Dynamics of
Disklike Micelles. Angew. Chem., Int. Ed. 2005, 44, 4731−4735.
(21) Shimizu, T.; Masuda, M. Stereochemical Effect of Even−Odd
Connecting Links on Supramolecular Assemblies Made of 1-
Glucosamide Bolaamphiphiles. J. Am. Chem. Soc. 1997, 119, 2812−
2818.
(22) Masuda, M.; Vill, V.; Shimizu, T. Conformational and Thermal
Phase Behavior of Oligomethylene Chains Constrained by Carbohy-
drate Hydrogen-Bond Networks. J. Am. Chem. Soc. 2000, 122, 12327−
12333.
(23) Schneider, J.; Messerschmidt, C.; Schulz, A.; Gnade, M.; Schade,
B.; Luger, P.; Bombicz, P.; Hubert, V.; Fuhrhop, J.-H. Odd−Even
Effects in Supramolecular Assemblies of Diamide Bolaamphiphiles.
Langmuir 2000, 16, 8575−8584.
(8) Sakakibara, K.; Hill, J. P.; Ariga, K. Thin-Film-Based Nano-
architectures for Soft Matter: Controlled Assemblies into Two-
Dimensional Worlds. Small 2011, 7, 1288−1308.
(24) Bohme, P.; Hicke, H.-G.; Bottcher, C.; Fuhrhop, J.-H. Reactive
̈
̈
and Rigid Monolayers of Bisaroyl Azide Diamide Bolaamphiphiles on
Polyacrylonitrile Surfaces. J. Am. Chem. Soc. 1995, 117, 5824−5828.
(25) Liu, X.; Wang, T.; Liu, M. Interfacial assembly of cinnamoyl-
terminated bolaamphiphiles through the air/water interface: head-
group-dependent assembly, supramolecular nanotube and photo-
chemical sewing. Phys. Chem. Chem. Phys. 2011, 13, 16520−16529.
(26) (a) Quina, F. H.; Whitten, D. G. Photochemical reactions in
organized monolayer assemblies. 4. Photodimerization, photoisomeri-
zation, and excimer formation with surfactant olefins and dienes in
monolayer assemblies, crystals, and micelles. J. Am. Chem. Soc. 1977,
99, 877−883. (b) Zhao, X.-M.; Perlstein, J.; Whitten, D. G. Aggregate
Formation and Photoreactivity in Phospholipid Vesicles and
Langmuir-Blodgett Multilayers: Topologically Controlled Photo-
dimerization of Amphiphilic Styrenes. J. Am. Chem. Soc. 1994, 116,
10463−10467.
(9) Yuan, J.; Liu, M. Chiral Molecular Assemblies from a Novel
Achiral Amphiphilic 2-(Heptadecyl) Naphtha[2,3]imidazole through
Interfacial Coordination. J. Am. Chem. Soc. 2003, 125, 5051−5056.
(10) Huang, X.; Li, C.; Jiang, S.; Wang, X.; Zhang, B.; Liu, M. Self-
Assembled Spiral Nanoarchitecture and Supramolecular Chirality in
Langmuir−Blodgett Films of an Achiral Amphiphilic Barbituric Acid. J.
Am. Chem. Soc. 2004, 126, 1322−1323.
(11) Guo, P.; Zhang, Li.; Liu, M. A Supramolecular Chiroptical
Switch Exclusively from an Achiral Amphiphile. Adv. Mater. 2006, 18,
177−180.
(12) Gaines, G. L., Jr. Insoluble Monolayers at Liquid-Gas Interfaces;
Interscience: New York, 1966.
(13) Chi, L.; Jacobi, S.; Anczykowski, B.; Overs, M.; Schafer, H.-J.;
̈
Fuchs, H. Supermolecular Periodic Structures in Monolayers. Adv.
Mater. 2000, 12, 25−30.
(27) (a) Cohen, M. D.; Schmidt, G. M. Topochemistry. Part I. A
survey. J. Chem. Soc. 1964, 86, 1996−2000. (b) Weissbuch, I.;
Bouwman, W.; Kjaer, K.; Als-Nielsen, J.; Lahav, M.; Leiserowitz, L.
Two-dimensional crystalline structures and photochemial behavior of
cinnamate monolayers on water surfaces. Chirality 1998, 10, 60−65.
(c) Yan, Y.; Guo, S.; Xiong, W.; Huang, J.; Li, Z.; Ma, J. Molecular
Arrangement and Recognition of a New Bolaform Cinnamic acid
Derivative in LB Films. Acta Phys.-Chim. Sin. 2005, 21, 550−555.
(d) Xu, L.; Yan, C.; Wan, L.; Jiang, S.; Liu, M. Light-Induced Structural
Transformation in Self-Assembled Monolayer of 4-(Amyloxy)-
cinnamic Acid Investigated with Scanning Tunneling Microscopy. J.
Phys. Chem. B 2005, 109, 14773−14778. (e) Fan, H.; Zhu, X.; Gao, L.;
Li, Z.; Huang, J. The Photodimerization of a Cinnamoyl Moiety
Derivative in Dilute Solution Based on the Intramolecular Chain
Interaction of Gemini Surfactant. J. Phys. Chem. B 2008, 112, 10165−
10170.
(14) Guo, L.; Wu, Z.; Liang, Y. Nanotubes of poly(phenylene
vinylene) derivative at the air/water interface. Chem. Commun. 2004,
1664−1665.
(15) Shankar, B. V.; Patnaik, A. Surface Pressure Driven Supra-
molecular Architectures from Mixed H-Aggregates of Dye-Capped
Azobenzene Derivative. Langmuir 2006, 22, 4758−4765.
(16) Yao, P.; Wang, H.; Chen, P.; Zhan, X.; Kuang, X.; Zhu, D.; Liu,
M. Hierarchical Assembly of an Achiral π-Conjugated Molecule into a
Chiral Nanotube through the Air/Water Interface. Langmuir 2009, 25,
6633−6636.
(17) Ghosh, A.; Choudhury, S.; Das, A. Vesicle formation from an
amphiphilic porphyrin derivative at air water interface. Chem.Asian J.
2010, 5, 352−358.
(18) (a) Fuhrhop, J.-H.; Wang, T. Bolaamphiphiles. Chem. Rev. 2004,
104, 2901−2937. (b) Shimizu, T. Bottom-Up Synthesis and
Morphological Control of High-Axial-Ratio Nanostructures through
Molecular Self-Assembly. Polym. J. 2003, 35, 1−22. (c) Masuda, M.;
Shimizu, T. Lipid Nanotubes and Microtubes: Experimental Evidence
for Unsymmetrical Monolayer Membrane Formation from Unsym-
(28) (a) Tao, F.; Bernasek, S. L. Understanding Odd−Even Effects in
Organic Self-Assembled Monolayers. Chem. Rev. 2007, 107, 1408−
1453. (b) Popovitz-Biro, R.; Wang, J. L.; Majewski, J.; Shavit, E.;
3481
dx.doi.org/10.1021/la204653b | Langmuir 2012, 28, 3474−3482

Langmuir
Article
Leiserowitz, L.; Lahav, M. Induced freezing of supercooled water into
ice by self-assembled crystalline monolayers of amphiphilic alcohols at
the air-water interface. J. Am. Chem. Soc. 1994, 116, 1179−1191.
(c) Gavish, M.; Popovitz-Biro, R.; Lahav, M.; Leiserowitz, L. Ice
Nucleation by Alcohols Arranged in Monolayers at the Surface of
Water Drops. Science 1990, 250, 973−975.
Chains and Their Ability To Regulate Liquid Crystal Alignment.
Macromolecules 1997, 30, 903−911.
(38) Chae, B.; Lee, S. W.; Ree, M.; Jung, Y. M.; Kim, S. B.
Photoreaction and Molecular Reorientation in a Nanoscaled Film of
Poly(methyl 4-(methacryloyloxy)cinnamate) Studied by Two-Dimen-
sional FTIR and UV Correlation Spectroscopy. Langmuir 2003, 19,
687−695.
(29) Kiviranta, P. H.; Leppanen, J.; Rinne, V. M.; Suuronen, T.;
̈
(39) Masuda, M.; Shimizu, T. Multilayer structure of an unsym-
metrical monolayer lipid membrane with a ‘head-to-tail’ interface.
Chem. Commun 2001, 2442−2443.
Kyrylenko, O.; Kyrylenko, S.; Kuusisto, E.; Tervo, A. J.; Jarvinen, T.;
̈
́
Salminen, A.; Poso, A.; Wallena, E. A. A. N-(3-(4-Hydroxyphenyl)-
propenoyl)-amino acid tryptamides as SIRT2 inhibitors. Bioorg. Med.
Chem. Lett. 2007, 17, 2448−2451.
(40) (a) Popovitz-Biro, R.; Majewski, J.; Margulis, L.; Cohen, S.;
Leiserowitz, L.; Lahav, M. Self-Aggregation of α,ω-Alkanediols into 3-
D Crystallites As Studied at Interfaces: The System of α,ω-
Docosanediol. J. Phys. Chem. 1994, 98, 4970−4972. (b) Majewski,
J.; Edgar, R.; Popovitz-Biro, R.; Bouwman, W. G.; Als-Nielsen, J.;
Lahav, M.; Leiserowitz, L. Structure Determination in the Twilight
Region Between Monolayers and 3-D Crystals; a Grazing Incidence X-
Ray Diffraction Study of Nanocrystalline Aggregates of α,ω-
Docosanediol at the Air−Water Interface. Angew. Chem., Int. Ed.
Engl. 1995, 34, 649−652. (c) Ajayaghosh, A.; George, S. J. First
Phenylenevinylene Based Organogels: Self-Assembled Nanostructures
via Cooperative Hydrogen Bonding and π-Stacking. J. Am. Chem. Soc.
2001, 123, 5148−5149.
(30) Bohm, C.; Leveiller, F.; Jacquemain, D.; Mohwald, H.; Kjaer, K.;
̈
̈
Als-Nielsen, J.; Weissbuch, I.; Leiserowitz, L. Packing Characteristics of
Crystalline Monolayers of Fatty Acid Salts, at the Air-Solution
Interface, Studied by Grazing Incidence X-ray Diffraction. Langmuir
1994, 10, 830−836.
(31) Hu, W.; Werner, C.; Hesse, M. The Photoisomerization
Behavior of the (4-Hydroxycinnamoyl)-spermidines. Helv. Chim. Acta
1998, 81, 342−352.
(32) (a) Du, X.; Liang, Y. Detection of NH Stretching Signals from
the Monolayers of Amino Acid Amphiphiles at the Air−Water
Interface and Change of Hydrogen Bond Depending on Metal Ion in
the Subphase: Infrared Reflection−Adsorption Spectroscopy. J. Phys.
Chem. B 2004, 108, 5666−5670. (b) Clegg, R. S.; Hutchison, J. E.
Hydrogen-Bonding, Self-Assembled Monolayers: Ordered Molecular
Films for Study of Through-Peptide Electron Transfer. Langmuir
1996, 12, 5239−5243.
(41) Shimizu, T.; Masuda, M.; Minamikawa, H. Supramolecular
Nanotube Architectures Based on Amphiphilic Molecules. Chem. Rev.
2005, 105, 1401−1444.
(33) (a) Brune, B. J.; Koehler, J. A.; Smith, P. J.; Payne, G. F.
Correlation between Adsorption and Small Molecule Hydrogen
Bonding. Langmuir 1999, 15, 3987−3992. (b) Hill, D. J. T.;
Whittaker, A. K.; Wong, K. W. Miscibility and Specific Interactions
in Blends of Poly(4-vinylphenol) and Poly(2-ethoxyethyl methacry-
late). Macromolecules 1999, 32, 5285−5291.
(34) (a) Fournier, J.-H.; Maris, T.; Simard, M.; Wuest, J. D.
Molecular Tectonics. Hydrogen-Bonded Networks Built from
Tetraphenols Derived from Tetraphenylmethane and Tetraphenylsi-
lane. Cryst. Growth Des. 2003, 3, 535−540. (b) Venkataramanan, B.;
James, W. L. G.; Vittal, J. J.; Suresh, V. Synthesis and Solid-State Self-
Assembly of Polyphenols. Cryst. Growth Des. 2004, 4, 553−561.
(c) Cheng, X.; Das, K.; Baumeister, M.; Diele, U. S.; Tschierske, C.
Liquid Crystalline Bolaamphiphiles with Semiperfluorinated Lateral
Chains: Competition between Layerlike and Honeycomb-Like
Organization. J. Am. Chem. Soc. 2004, 126, 12930−12940.
(35) Sapper, H.; Cameron, D. G.; Mantsch, H. H. The thermotropic
phase behavior of ascorbyl palmitate: an infrared spectroscopic study.
Can. J. Chem. 1981, 59, 2543−2549.
(36) (a) Miyahara, M.; Kawasaki, H.; Fukuda, T.; Ozaki, Y.; Maeda,
H. Effects of alkyl chain length on the solid state phase behaviors of
alkyldimethylamine oxide hydrochlorides and hemihydrochlorides.
Colloids Surf., A 2001, 183, 475−485. (b) Du, X.; Shi, B.; Liang, Y. N-
Octadecanoyl-l-alanine Amphiphile Monolayer at the Air/Water
Interface and LB Film Studied by FTIR Spectroscopy. Langmuir
1998, 14, 3631−3636. (c) Wang, Y.; Nichogi, K.; Iriyama, K.; Ozaki,
K. Y. Thermal Behavior of Mixed-Stack Charge Transfer Films of 2-
Octadecyl-7,7,8,8-tetracyanoquinodimethane and 3,3′,5,5′-Tetrame-
thylbenzidine Prepared by the Langmuir−Blodgett Technique and
Donor Doping. 2. Morphology and Annealing Effects of the Films
Investigated by Atomic Force Microscopy and Ultraviolet−Visible−
Near Infrared and Infrared Spectroscopies. J. Phys. Chem. 1996, 100,
17238−17242. (d) Guo, Z. X.; Jiao, T. F.; Liu, M. H. Effect of
Substituent Position in Coumarin Derivatives on the Interfacial
Assembly: Reversible Photodimerization and Supramolecular Chirality.
Langmuir 2007, 23, 1824−1829.
(37) (a) Xia, Q.; Feng, X.-S.; Mu, J.; Yang, K.-Z. Monolayer
Behaviors of 4-Octadecanoxycinnamic Acid and the Photodimerization
Kinetics in Its Langmuir−Blodgett Films. Langmuir 1998, 14, 3333−
3338. (b) Ichimura, K.; Akita, Y.; Akiyama, H.; Kudo, K.; Hayashi, Y.
Photoreactivity of Polymers with Regioisomeric Cinnamate Side
3482
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