Chiral discrimination in 1-stearylamine-glycerol monolayers

Article abstract of DOI:10.1021/jp0125294

The effect of the chirality on the thermodynamic behavior, the morphological features, and the 2D crystal structures of 1-stearylamine-glycerol monolayers are studied. The results are based on measurements of the surface pressure-area (??-A) isotherms, fluorescence microscopy, and synchrotron X-ray diffraction at grazing incidence (GIXD). Although the ??-A isotherms of the enantiomeric forms and the racemic mixtures agree largely to each other, the filigree domain patterns show remarkable differences, obviously driven by the chirality. The domains of the R(+) enantiomer are curved clockwise, those of the S(-) enantiomer counterclockwise, whereas those of the racemic mixtures are without a specific sense of direction. Chiral discrimination effects are also found in the lattice structure. The enantiomeric monolayers have an oblique lattice where at compression the tilt direction changes continuously from angles nearly toward NN direction to angles nearly toward NNN direction. The condensed phases of the 1:1 racemic mixtures give rise to rectangular-centered lattices indicating a phase transition accompanied by the change in the tilt direction from NN at 1 mN/m to NNN at 5 mN/m. The filigree domain patterns indicate a comparatively low ordering of the alkyl chains. Correspondingly, a short-range translational order can be concluded from the low position correlation and high tilt angles of the alkyl chains at low surface pressures.

Full text of DOI:10.1021/jp0125294

J. Phys. Chem. B 2002, 106, 4419-4423
4419
Chiral Discrimination in 1-Stearylamine-Glycerol Monolayers
D. Vollhardt* and U. Gehlert
Max-Planck-Institute of Colloids and Interfaces, D-14424 Potsdam/Golm, Germany
ReceiVed: July 3, 2001; In Final Form: October 29, 2001
The effect of the chirality on the thermodynamic behavior, the morphological features, and the 2D crystal
structures of 1-stearylamine-glycerol monolayers are studied. The results are based on measurements of the
surface pressure-area (π-A) isotherms, fluorescence microscopy, and synchrotron X-ray diffraction at grazing
incidence (GIXD). Although the π-A isotherms of the enantiomeric forms and the racemic mixtures agree
largely to each other, the filigree domain patterns show remarkable differences, obviously driven by the
chirality. The domains of the R(+) enantiomer are curved clockwise, those of the S(-) enantiomer
counterclockwise, whereas those of the racemic mixtures are without a specific sense of direction. Chiral
discrimination effects are also found in the lattice structure. The enantiomeric monolayers have an oblique
lattice where at compression the tilt direction changes continuously from angles nearly toward NN direction
to angles nearly toward NNN direction. The condensed phases of the 1:1 racemic mixtures give rise to
rectangular-centered lattices indicating a phase transition accompanied by the change in the tilt direction
from NN at 1 mN/m to NNN at 5 mN/m. The filigree domain patterns indicate a comparatively low ordering
of the alkyl chains. Correspondingly, a short-range translational order can be concluded from the low position
correlation and high tilt angles of the alkyl chains at low surface pressures.
Introduction
Chirality-based phenomena are of permanent interest. Chiral
discrimination arises from differences in the interaction potential
between molecules of the same chirality and that of opposite
chirality. Some general reasons for wanting to understand the
phenomenon of chiral discrimination include the chiral prefer-
ence in nature realized in homochiral evolution and the design
of pharmaceuticals of specific chirality.1
Figure 1. Chemical structure of the enantiomeric R(+) and S(-) form
Chiral monolayers provide favorable systems to study chiral-
ity-dependent interactions under defined conditions. As mono-
layer systems can be investigated over a wide range of specific
states, they have been used as model systems to study chiral
discrimination by comparing the surface pressure (π) versus area
per molecule (A) isotherms of enantiomeric and racemic
of 1-stearylamine-glycerol. The chiral C atom is marked with a star
(*).
Monoglycerol amines are another interesting type where the
chiral R- and S-forms are accessible by a usual chemical
preparation procedure. Therefore, the present work focuses on
the effect of the chirality on the thermodynamic behavior, the
morphological features, and the 2D crystal structures of these
monolayers.
2-4
monolayers. Comparison of enantiomeric and racemic mono-
layers revealed chirality-dependent differences in the π-A
isotherms. Homochiral discrimination exists if the interaction
between the same enantiomers is more favorable while hetero-
chiral interaction is indicated if the interaction between the two
different enantiomers is more auspicious.
The experiments were performed with monolayers of the
racemic R(+) and S(-) forms of 1-stearylamine-glycerol; the
chiral nature of them is shown in Figure 1. The CIP system20
was used to characterize the configuration of the chiral
molecules. The -NH- group is admittedly less hydrophil than
the corresponding -O-, -CO-O-, or -CO-NH- groups
of the other monoglycerol types with the consequence of lower
contrast between the monolayer phases. To enhance the contrast,
we used an amine with a rather long alkyl chain (C18H37-) and
fluorescence microscopy for imaging. As amines are able to
form hydrogen bonds, chiral discrimination should be expected.
Recent studies have shown the dominant effect of the amide
group on the monolayer properties. The amide-amide hydrogen
bonding is responsible not only for the high crystallinity of the
With the development of sensitive imaging techniques such
as fluorescence and Brewster angle microscopy (BAM), more
effective methods have been available to visualize the effect of
chirality on the morphology of monolayers on microscopic scale.
Chirality-dependent effects have been found in various
amphiphilic monolayers. This concerns particularly the N-acyl
5
-9
10,11
amino acid amphiphiles,
some phospholipids,
but also
aldonamides1
2,13
14
or tailored amphiphiles.
Monoglycerols are interesting amphiphiles that make possible
the comparison of the enantiomeric and racemic monolayers.
Using fluorescence microscopy, BAM and GIXD chiral dis-
crimination effects have been already found for monoglycerol
1
4,19
1
5-17
18
19
monolayers
but also for the chiral recognition in N-
ethers,
esters, and amides.
2
1
acylamino acid monolayers. Finally, the chirality-dependent
monolayer features can be compared for the four monoglycerol
*
To whom correspondence should be addressed.
1
0.1021/jp0125294 CCC: $22.00 © 2002 American Chemical Society
Published on Web 04/05/2002

4420 J. Phys. Chem. B, Vol. 106, No. 17, 2002
Vollhardt and Gehlert
types with chemically different linking groups between glycerol
and alkyl chain.
Experimental Section
Synthesis of Amphiphile. The R(+) and S(-) enantiomers
of 1-stearylamine-glycerol (3-octadecylamino-1,2-propandiol)
were synthesized with a purity of >99% according to the
following procedure.22 Equimolar amounts of octadecylamine
and R(+)- or R(-)-glycidol were dissolved in dry methanol.
The mixture was refluxed for 30 min, and then the solvent was
removed. For purification, the crude product was recrystallized
six times from n-hexane, and a white powder with a purity of
>
99% was obtained. The chemical purity was confirmed by
elemental analysis and HPLC.
Figure 2. π-A isotherm of the enantiomeric and racemic 1-stearyl-
amine glycerol monolayers at 35 °C.
Experimental Procedures
hk
hk
Q
) Q cosψ tan t
z
xy
hk
The surface pressure-area (π-A) isotherms were measured
using a computer-interfaced film balance with a Wilhelmy type
pressure measuring system. The contrast of the very filigree
nonequilibrium structures was not high enough to be visualized
well by Brewster angle microscopy. Imaging of the monolayer
morphology was performed with a fluorescence microscope
where h,k denotes the order of reflection. The lattice parameters
a,b, and γ were calculated from the lattice spacing dhk and from
these the unit cell area Axy was calculated:
Axy ) ab sin γ.
(Zeiss, Axiotron). The spread monoglycerol solution contained
1
.5 mol-% L-R-phosphatidylcholin-â-(NBD-aminohexanoyl)-
The cross section per alkyl chain A0 is related to the unit cell
area Axy (area per molecule parallel to the interface) and the tilt
angle t
γ-palmitoyl (Sigma, Munich) as fluorescence dye. Excitation
of the fluorescence probe was achieved using a high-pressure
mercury lamp. Discrimination of excitation and emission was
regulated by using conventional dichroic mirrors and a standard
blue filter. Details of the method have been described else-
where.23
The GIXD experiments were performed using the liquid-
surface diffractometer on the undulator beamline BW1 at
HASYLAB, DESY, Hamburg, Germany. The beam was made
monochromatic by a beryllium crystal (002). The monochro-
matic synchrotron beam was adjusted to strike the water surface
with a grazing incidence angle RI ) 0.85Rc, where Rc ∼ 0.14°
is the critical angle for total reflection. A linear position-sensitive
detector (PSD) (OED-100-M, Braun, Garching, Germany) was
used to monitor the diffracted intensity as a function of the
vertical scattering angle Rf. A Soller collimator in front of the
PSD provides the resolution for the horizontal scattering angle
A ) A cos t
0
xy
Assuming an exponential decay of positional correlations with
increasing separation within the layer, the full width at half-
maximum of a Bragg peak ∆xy corrected for resolution effects
of the detector is taken to determine the coherence length ê )
2
xy
2
res
2
π/ (∆ - ∆ ), where the second term under the root
x
2
6
represents the resolution of the Soller collimator.
The monolayer material (1-stearylamine-glycerol) was dis-
solved in a 9:1 (v:v) mixture of n-heptane (for spectroscopy,
Merck) and ethanol (p.A., Merck) for spreading on the aqueous
subphase. The fluorescence microscopy studies were performed
with a compression rate of 0.04 nm molecule min . The
subphase water used for the experiments was purified by a
Millipore desktop unit (Millipore, Eschborn).
2
-1
-1
-
1
2
θxy which was approximately 0.01 Å . The wave vectors ki
and kf of the incident and diffracted photons have the same
absolute value because of the quasi-elastic nature of the
scattering. The scattering vector Q ) kf - ki can be written in
terms of an in-plane component Qxy
Results and Discussion
1
-Stearylamine glycerol monolayers undergo a main-phase
transition of first order from a fluidlike (gaseous) state to a
condensed phase at higher temperatures of the accessible range.
Figure 2 shows the π-A isotherm for 35 °C which have the
pronounced nonhorizontal “plateau” region characteristic for the
two-phase coexistence region. The π-A isotherms for the
racemic and enantiomeric monolayers are identical so that
chirality-dependent differences in the thermodynamic behavior
do not occur. The exact coordinates of the main-phase transition
Q ≈ (4π/λ)sin θ
xy
xy
and an out-of-plane component Qz
Q ≈ (2π/λ)sin R
z
f
where λ is the X-ray wavelength. The diffracted intensities were
corrected for polarization, effective area, and Lorentz factor.
The intensities were least-squares fitted to model peaks as
Lorentzian in the in-plane direction and Gaussian in the out-
of-plane direction.
2
point (Ac ) 0.53 nm /molecule, πc ) 4.9 mN/m) cannot be taken
directly from the isotherm, but they result as the intersection
point between the two different slopes. Formation and growth
of condensed-phase patterns can be expected at A e Ac.
Fractal-like domain textures can be seen by Brewster angle
microscopy, but the characterization of the morphology is
difficult as the filigree textures are at the resolution limit. Better
information can be obtained by fluorescence microscopy. Using
this method, it is seen that at low compression rates the
1-stearylamine glycerol monolayers develop fractal-like filigree
The lattice parameters can be obtained from the peak
positions. The lattice repeat spacing dhk, the polar tilt angle t of
the long molecule axis, and the tilt azimuth ψxy were calculated
from the positions of the Qxy and Qz maxima2
4,25
according to
hk
dhk ) 2π/Q
xy

Chiral Discrimination
J. Phys. Chem. B, Vol. 106, No. 17, 2002 4421
TABLE 1: Data of the Lattice Structure of S(-)
a
1
-Stearylamine Monoglycerol Monolayers at 20 °C
π
a
b
γ
[°]
t
A
xy
A
0
2
ψa
[°]
2
[
mN/m] [Å] [Å]
[°] [Å ] [Å ]
td
d
1
0
5
0
5
5
5.22 5.57 104.6 46 28.1 19.7
4.98 5.35 112.7 36 24.5 19.9
4.93 5.19 117.4 28 22.7 20.0
4.91 5.05 118.1 24 21.9 20.0
4.89 5.00 119.2 19 21.3 20.0 NNN 90
4.88 8.73 90.0 19 21.3 20.0 NNN 90
60.2 0.292
74.7 0.162
85.1 0.078
85.0 0.049
1
2
3
3
3
0.031
0.031
a
a, b, γ are lattice constants, t is polar tilt angle, Axy is molecular
area, A is cross-section area of alkyl chain, td is tilt direction, ψ is
0
a
the angle between azimuthal tilt direction and a-axis, d is distortion.
The lattice parameters based on a rectangular lattice structure at 35
mN/m are presented in italics.
Figure 3. Fluorescence micrograph of the chiral discrimination in the
nonequilibrium domains of 1-stearylamine glycerol monolayers. (a)
S(-)-enantiomer, (b) R(+)-enantiomer, (c) racemate. The bar represents
1
00 µm.
nonequilibrium domains at the beginning of the plateau region.
Chiral discrimination effects are observed in the morphological
shape of the condensed-phase patterns formed in the two-phase
coexistence region at A e Ac. Figure 3 shows fluorescence
microscopic micrographs of the condensed-phase domains of
the enantiomers (Figure 3a and b) and the racemates (Figure
3
c). Dependent on the enantiomeric form, the filigree domains
are curved in opposite directions, namely, clockwise for the
R(+) enantiomer (Figure 3b) and counterclockwise for the S(-)
enantiomer (Figure 3a). The racemic mixtures give rise to
fractal-like domains without a specific sense of direction. Similar
chiral discrimination effects have been observed in other
1
0,11
nonequilibrium domains of phospholipid monolayers.
The spiral growth of condensed-phase domains was theoreti-
cally considered as a result of modulated distributions of tilt
27
angle and free charges in chiral-polarized monolayers. On the
basis of this qualitative approach, it was concluded that the spiral
distributions of small perturbations should be the nuclei for the
condensed phase. However, the approach cannot explain details
of chiral monolayer behavior. The experimental fact that spiral
shapes grow from initially compact domains in the similar
28,29
monogycerol ether monolayers does not support this model.
Recent theoretical calculations can help to understand cur-
vature and handedness of chiral domains formed by amphiphilic
monolayers.3
0,31
In these papers, an effective pair potential
description of the groups attached to the chiral center of amino
acid amphiphiles has been performed. The results suggest that
the observed curvature of the domain shape is due to the twist
at the interface between the condensed and fluid phase of the
monolayer where the inter-residue hydrogen-bond cycle is not
Figure 4. Contour plots of the corrected diffraction intensities as a
function of the in-plane (Q ) and out-of-plane (Q ) components of the
scattering vectors of the S(-) enantiomeric monolayer at 20 °C;
above: π ) 1 mN/m, middle: π ) 10 mN/m, below: π ) 35 mN/m.
30,31
as regular as within the condensed phase.
The theoretically
xy
z
predicted handedness of the amino acid amphiphiles agreed
fairly well with handedness experimentally observed by Brew-
ster angle microscopy.31
GIXD experiments were performed to study whether chiral
discrimination between the enantiomeric and racemic forms also
occurs in the lattice structure of 1-stearylamine monoglycerol
monolayers. The contour plots of the corrected diffraction
intensities as a function of the in-plane (Qxy) and out-of-plane
gives the unit cell parameters a, b, γ, the in-plane lattice area
Axy, the chain tilt angle t, the azimuthal tilt angle ψa, the tilt
direction td, and the lattice distortion for different surface
pressures d.
The cross-section area of the alkyl chains is typical for the
free-rotator phase of n-alkanes. With increasing surface pressure,
the angle between the azimuthal tilt direction and the a-axis
approaches to a value of 90° that is reached at π ) 35 mN/m.
Consequently, at π g 35 mN/m the alkyl chains are tilted toward
next-nearest neighbors (NNN) in agreement with the fact that
the contour plots show only two diffraction maxima (see Figure
4, π ) 35 mN/m). Figure 5 shows the angle between the
azimuthal tilt direction and the a-axis (ψa) in dependence on
the surface pressure. At compression of the monolayer, the tilt
direction changes continuously from angles close to a nearest-
(
Qz) components of the scattering vectors of the monolayer of
the S(-)enantiomers at 20 °C and at 1mN/m, 10 mN/m, and
5 mN/m are presented in Figure 4. Similar results were
3
obtained by the monolayers of the R(+) form.
Figure 4 shows three diffraction peaks for π ) 1 mN/m and
π ) 10 mN/m. Up to a surface pressure of 30 mN/m, three
diffraction maxima clearly separable can be observed. This
indicates an oblique lattice. The data of the in-plane and out-
of-plane scattering vector components are listed in Table 1 which

4422 J. Phys. Chem. B, Vol. 106, No. 17, 2002
Vollhardt and Gehlert
Figure 5. Angle between the azimuthal tilt direction and the a-axis
(
ψ ) in dependence on the surface pressure of the monolayer of S(-)
a
enantiomeric 1-stearylamine glycerol at 20 °C.
Figure 7. Contour plots of the corrected diffraction intensities as a
function of the in-plane (Qxy) and out-of-plane (Q ) components of the
z
scattering vectors of the 1:1 racemic 1-stearylamine glycerol monolayer
at 20 °C; above: π ) 1 mN/m, below: π ) 10 mN/m.
TABLE 2: Data of the Lattice Structure of 1:1 Racemic
a
1-Stearylamine Monoglycerol Monolayers at 20 °C
Figure 6. Intensity as function of the vertical component of the wave
-1
π
a
[Å]
b
[Å]
t
[°]
A
xy
A0
vector Q
z
at 35 mN/m (for Qxy between 1.44 and 1.45 Å and between
-
1
[mN/m]
[Å
2
]
[Å
2
]
td
d
1
.50 and 1.51 Å ). The extended full width at half-maximum of the
-
1
diffraction peak suggests two reflexes at Qz1 ) 0.29 Å and Qz2
)
1
5
0
5
6.36
4.83
5.00
4.91
8.49
10.21
10.00
8.58
43
36
35
18
27.0
24.7
25.0
21.0
19.9
19.9
19.9
19.9
NN
0.256
0.196
0.143
0.0996
-
1
0
.50 Å .
NNN
NNN
NNN
1
3
neighbor (NN) direction at π ) 1 mN/m to that of NNN
direction at π ) 35 mN/m. As seen in Figure 4, the diffraction
maxima are close together. At high surface pressures (π ) 35
mN/m), the diffraction peaks overlap each other by the high
full width at half-maximum of the Bragg peak ∆xy. The overlap
can be better seen if the Bragg rod intensities are plotted in
dependence on the vertical component of the scattering vector.
Figure 6 shows the extended peak at π ) 35 mN/m that can be
a
a and b are lattice constants, t is polar tilt angle, Axy is molecular
area, A is cross-section area of alkyl chain, td is tilt direction, and d
is distortion.
0
data of the racemic and enantiomeric forms (see Tables 1 and
2) shows, besides some agreement in the data, remarkable
differences caused by chirality. The lattice type undergoes
striking chiral discrimination that is apparent in the transition
of the oblique lattice of the enantiomeric forms into the
rectangular lattice of the racemic mixture. Accordingly, the
lattice structure data (a, b, γ, td, and d) are completely different.
As to expect, the cross-sectional area A0 of the alkyl chains of
the enantiomeric and racemic forms agree with each other. The
-
1
-1
spitted in two reflexes (Qz1 ) 0.29 Å , Qz2 ) 0.50 Å ).
According to the overlap of the reflexes, the position correlations
obtained from the full width at half-maximum represent only
approximate values. The correlation lengths ê are relatively
small: ê < 100 Å perpendicular to the tilt direction of the
chains, ê < 35 Å parallel to the tilt direction of the chains.
Corresponding GIXD measurements of 1:1 racemic 1-stearyl-
octadecylamine monoglycerol monolayers reveal that chiral
discrimination exists also in the lattice structure. Racemic
monolayers produce only two diffraction peaks at all surface
pressures investigated. Consequently, in the studied surface
pressure region of π e 35 mN/m, the 1:1 racemic monolayers
have rectangular-centered lattice. Two characteristic contour
plots of the corrected diffraction intensities obtained at 1 mN/m
and 10 mN/m are shown in Figure 7. In the first case, the
maximum of the degenerate diffraction peak is at Qz ) 0 so
that the alkyl chains are tilted toward NN direction. At π ) 10
mN/m, the two reflexes are at Qz > 0 indicating chain tilt in
NNN direction. The structure data calculated for the different
surface pressures are listed in Table 2.
2
A0 value of approximately 20 Å corresponds to the free-rotator
phase of n-alkanes. Both forms have also nearly the same polar
tilt angle so that they have approximately the same molecular
area. This is demonstrated in Figure 7 that shows the change
of the tilt angle of the enantiomeric and racemic form in
dependence of the surface pressure at 20 °C. Both forms agree
in the strong dependence of the tilt angle on the surface pressure
resulting finally in a complete erection of the alkyl chains at
π ≈ 45 mN/m. The perpendicular orientation of the alkyl chains
is corroborated by the disappearance of the optical contrast at
the BAM studies as well as the kink in the π-A isotherm.
The chiral discrimination in the lattice structure between the
enantiomeric and racemic monolayers has been discussed on
the assumption that different interactions of the molecules
2
6
It is seen that a phase transition accompanied by a change in
the tilt direction from NN to NNN takes place between 1mN/m
and 5 mN/m. This phase transition corresponds to the L2d/Ov
transition at fatty acids.32 Comparison of the characteristic lattice
compensate each other. For the case that the racemic mixture
experiences a discontinuous transition between NN and NNN
tilted states which corresponds to the L2d/Ov transition in fatty
acid monolayers, the interactions controlling the tilt azimuth

Chiral Discrimination
J. Phys. Chem. B, Vol. 106, No. 17, 2002 4423
been found in the condensed phases of the monoglycerol ethers
that also give rise to oblique lattices in the enantiomeric
monolayers and rectangular lattices, dependent on temperature
an abrupt NN-NNN transition at medium surface pressure
between 15 and 20 mN/m, in the racemic mixtures.
Acknowledgment. The authors thank Dr. R. Wagner for the
preparation of the enantiomeric substances and are grateful to
Drs. G. Brezesinski and K. Kjaer for help with setting up the
X-ray experiments.
References and Notes
Figure 8. Tilt angle of alkyl chains of 1-stearylamine glycerol
monolayers in dependence of surface pressure at 20 °C. b racemate,
O enantiomer, 2 obtained by BAM.
(1) Vollhardt, D.; Emrich, G.; Melzer, V.; Weidemann, G.; Gehlert,
U. In Short and Long Chains at Interfaces; Daillant, J., Guenoun, P.,
Marques, C., Muller, P., Eds.; Frontiers: Cedex, France, 1995.
(2) Arnett, E. M.; Chao, J.; Kinzig, B.; Stewart, M.; Thompson, O.;
Verbiar, R. J. Am. Chem. Soc. 1982, 104, 309.
are compensated. Consequently, the monolayer structure of the
enantiomer should differ from that of the racemate. The tilt
azimuth of the enantiomer varies continuously in the surface
pressure region near the transition point in the racemate and
adopts structures close to those of the racemate more far from
the transition.
(3) Arnett, E. M.; Harvey, N. G.; Rose, P. L. Acc. Chem. Res. 1989,
2, 131.
2
(
(
4) Heath, J. G.; Arnett, E. M. J. Am. Chem. Soc. 1992, 114, 4500.
5) Stine, K. J.; Uang, J. Y.-J.; Dingman, S. D. Langmuir 1993, 9,
2112.
(6) Parazak, D. P.; Uang, J. Y.-J.; Turner, B.; Stine, K. J. Langmuir
994, 10, 3787.
7) Uang, J. Y.-J.; Parazak, D. P.; Stine, K. J. Chem. Phys. Lipids 1995,
5, 163.
(8) Parazak, D. P.; Uang, J. Y.-J.; Whitt, S. A.; Stine, K. J. Chem.
Phys. Lipids 1995, 75, 155.
9) Nassoy, P.; Goldmann, M.; Bouloussa, O.; Rondelez, F. Phys. ReV.
Lett. 1995, 75, 457.
1
(
7
Conclusions
The absence of differences in the π-A isotherms of the
enantiomeric forms and the racemic mixtures indicates that at
most, small energetic effects occur at the complete mixing of
the two enantiomers. The characteristic curvatures of the filigree
domain patterns are obviously driven by the chirality of the
molecules concerned. The curvature of the R(+) enantiomeric
domains is clockwise whereas that of the S(-) enantiomeric
domains is counterclockwise. Chiral discrimination of different
kind but having the same sense of curvature has been found in
(
(10) Weidemann, G.; Vollhardt, D. Thin Solid Films 1995, 264, 94.
(11) Weidemann, G.; Vollhardt, D. Colloids Surf., A 1995, 100, 187.
(12) Vollhardt, D.; Gutberlet, T.; Emrich, G.; Furhop, H.-J. Langmuir
1995, 11, 2661.
13) Vollhardt, D.; Emrich, G.; Gutberlet, T.; Fuhrhop, H.-J. Langmuir
996, 12, 5659.
14) Melzer, V.; Weidemann, G.; Vollhardt, D.; Brezesinski, G.; Wagner,
(
1
(
R.; Struth, B.; M o¨ hwald, H. J. Phys. Chem. B 1997, 101, 4752.
(15) Scalas, E.; Brezesinski, G.; M o¨ hwald, H.; Kaganer, V. M.;
Bouwman, W. G.; Kjaer, K. Thin Solid Films 1996, 285, 56.
2
8,29
the domain morphology of the monoglycerol ethers.
Here,
(
16) Gehlert, U.; Vollhardt, D. Prog. Colloid Polym. Sci. 1994, 97, 302.
spiral shapes grow from initially compact domains at the end
of the plateau region of the π-A isotherm. In enantiomeric
monolayers, they are chirality-dependent curved in the same
sense, but the racemic monolayers develop spirals curved in
both directions.
(17) Brezesinski, G.; Rietz, R.; Kjaer, K.; Bouwman, W. G.; M o¨ hwald,
H. NuoVo Cimento 1994, 16, 1487.
18) Gehlert, U.; Vollhardt, D.; Brezesinski, G.; M o¨ hwald, H. Langmuir
996, 12, 4892.
19) Gehlert, U.; Weidemann, G.; Vollhardt, D.; Brezesinski, G.;
Wagner, R.; M o¨ hwald, H. Langmuir 1998, 14, 2112.
20) Cahn, R. S.; Ingold, C. K.; Prelog, V. Angew. Chem. 1992, 104,
012.
21) Stine, K. J.; Leventhal, A. R.; Parazak, D. P.; Uang, J. Y.-J.
(
1
(
(
The lattice structure of the 1-stearylamine monoglycerol
monolayers is also affected by the chirality of the molecules.
The enantiomeric monolayers have an oblique lattice where at
compression the tilt direction changes continuously from angles
nearly toward NN direction to angles nearly toward NNN
direction. In opposite, the condensed phases of the racemic
mixtures give rise to rectangular-centered lattices. Here, a phase
transition occurs that is accompanied by a change in the tilt
direction from NN at 1 mN/m to NNN at 5 mN/m. Both the
enaniomeric monolayers and their racemic mixtures have highly
tilted molecules at low surface pressures. In agreement with
the low position correlation, it allows the conclusion of low
ordering of the alkyl chains in the filigree domain structure.
Similar chiral discrimination effects on the lattice structure have
1
(
Enantiomer 1989, 1, 41.
(22) Ulsperger, E.; Dehns, R. J. Prakt. Chem. 1965, 27, 195. 155.
(
23) L o¨ sche, M.; M o¨ hwald, H. ReV. Sci. Instrum. 1984, 5, 1968.
(24) Als-Nielsen, J.; Kjaer, K. In Phase Transitions in Soft Condensed
Matter; Riste, T., Sherrington, D., Eds.; NATO ASI Series B.; Plenum
Press: New York, 1989; Vol. 211, p 113.
(
25) Kjaer, K. Physica B 1989, 198, 100.
(26) Kaganer, V. M.; M o¨ hwald, H.; Dutta, P. ReV. Mod. Phys. 1999,
7
1, 779.
(27) Pikin, S. A. Physica A 1992, 191, 139.
(28) Gehlert, U.; Vollhardt, D. Prog. Colloid Polym. Sci. 1994, 97, 302.
(
(
(
29) Vollhardt, D.; Gehlert, U. Tenside 1996, 33, 197.
30) Nandi, N.; Vollhardt, D. Colloids Surf., A 2001, 183-185, 67.
31) Nandi, N.; Vollhardt, D. Colloids Surf., A 2002, 207-221, 198.
(32) Peterson, I. R.; Kenn, R. M. Langmuir 1994, 10, 4645.