Fine-tuning the morphology of self-assembled nanostructures of propargyl ammonium-based amphiphiles

Article abstract of DOI:10.1021/jp104911e

N-Methyl-N-(pentacosa-10,12-diyn)-propargylamine organizes itself into an unusual supramolecular pH- and thermo-responsive system. Studies have showed that submillimetric length hollow laths form this unique structure in the presence of hydrochloric acid. Specific chemical modifications on the initial molecule and small-angle neutron scattering experiments were performed to understand the structure of this system. Our results allow us to suggest a possible structure of the laths.

Full text of DOI:10.1021/jp104911e

J. Phys. Chem. B 2010, 114, 12495–12500
12495
Fine-Tuning the Morphology of Self-Assembled Nanostructures of Propargyl
Ammonium-Based Amphiphiles
Emmanuelle Morin,†,‡ Jean-Michel Guenet,§ David D. D´ıaz,| Jean-Serge Remy,*,‡ and
Alain Wagner*,†
Laboratoire des Systemes Chimiques Fonctionnels, UMR 7199 - CAMB, Faculte´ de Pharmacie, UniVersite´ de
Strasbourg, 74 Route du Rhin, BP24, 67401 Illkirch, France, Laboratoire de Chimie Ge´ne´tique,
UMR 7199 - CAMB, Faculté de Pharmacie, and Institut Charles Sadron, CNRS UPR22, 23 Rue du Loess,
BP84047 F-67034 Strasbourg Cedex 2, France, Institut fu¨r Organische Chemie, UniVersita¨t Regensburg,
UniVersita¨tsstr. 31, D-93040 Regensburg, Germany, and ICMA CSIC-UniVersidad de Zaragoza,
Pedro Cerbuna 12, 50009 Zaragoza, Spain
ReceiVed: May 28, 2010; ReVised Manuscript ReceiVed: August 5, 2010
N-Methyl-N-(pentacosa-10,12-diyn)-propargylamine organizes itself into an unusual supramolecular pH- and
thermo-responsive system. Studies have showed that submillimetric length hollow laths form this unique
structure in the presence of hydrochloric acid. Specific chemical modifications on the initial molecule and
small-angle neutron scattering experiments were performed to understand the structure of this system. Our
results allow us to suggest a possible structure of the laths.
Introduction
and then dried over anhydrous Na2SO4 before being filtered and
evaporated under vacuum to afford 1 as a white solid (4.40 g,
91% yield).
The design of self-assembled architectures is an expanding
area of research and could be applied in many areas of chemistry
and biology.1-7
Under the control of weak interactions such as van der Waals
forces,8 hydrogen bonding,9 and hydrophobic interactions,8
amphiphiles are known to exhibit a broad spectrum of self-
assembling systems in aqueous solutions, including micelles,
bilayers, vesicles, tubes,10-12 or more recently nanoconstructs
on the surface of carbon nanotubes.13
In this work, we describe a new type of self-assembled
nanostructures based on N-methyl-N-(pentacosa-10,12-diyn)-
propargylamine (3), which organized itself into submillimetric
length laths in the presence of hydrochloric acid. The resulting
lattice forms a supramolecular pH- and thermo-responsive
system.
Pentacosa-10,12-diynyl-4-methylbenzenesulfonate (2). To
a stirred solution of pentacosa-10,12-diyn-1-ol (4.40 g, 12.20
mmol) in CH2Cl2 (60 mL) the following chemicals were
successively added: p-toluenesulfonyl chloride (3.49 g, 18.30
mmol), triethylamine (2.55 mL, 18.30 mmol), and catalytic
amounts of 4-dimethylaminopyridine (DMAP). The resulting
solution was stirred at RT overnight. A saturated solution of
NaHCO3 (25 mL) was added, and the aqueous layer was
extracted with CH2Cl2 (2 × 15 mL). The organic phases were
combined, washed with a saturated solution of NaCl (15 mL),
dried over anhydrous Na2SO4, and then filtered and concentrated
under reduced pressure. The residue was submitted to silica-
gel chromatography to afford compound 2 as a white solid (5.58
g, 89% yield).
N-Methyl-N-(pentacosa-10,12-diyn)-propargylamine (3).
To a stirred solution of pentacosa-10,12-diynyl-4-methylben-
zenesulfonate (5.58 g, 10.84 mmol) and Na2CO3 (1.26 g,11.92
mmol) in anhydrous CH3CN (150 mL) was added N-methyl-
propargylamine (1.83 mL, 21.68 mmol). The solution was stirred
at 70 °C for 24 h. Then, the solvent was removed under reduced
pressure. and the residue was poured into a saturated solution
of NaHCO3 (60 mL). The aqueous layer was extracted with
CH2Cl2 (4 × 25 mL). The organic layers were combined,
washed with a saturated solution of NaCl (15 mL), dried over
anhydrous Na2SO4, and then filtered and concentrated under
reduced pressure. The residue was purified by silica-gel chro-
matography (eluting with EtOAc/cyclohexane: 2/8) to yield the
compound 3 as a colorless oil (3.54 g, 79% yield).
N-Methyl-N-(pentacosa-10,12-diyn)-allylamine (4). N-Meth-
yl-N-(pentacosa-10,12-diyn)-allylamine (4) was prepared by the
same procedure as compound 3, using pentacosa-10,12-diynyl-
4-methylbenzenesulfonate (377.8 mg, 0.73 mmol), Na2CO3 (85.5
mg, 0.81 mmol) and N-allylmethylamine (104.4 mg, 1.46 mmol)
in CH3CN (20 mL). Purification was by silica-gel chromatog-
Experimental Methods
The syntheses of all compounds were obtained in three steps
starting from commercially available acids and are summarized
in Figure 1.
Pentacosa-10,12-diyn-1-ol (1). To a stirred suspension of
lithium aluminum hydride (0.91 g, 20.02 mmol) in tetrahydro-
furan (THF; 100 mL), a solution of 10,12-pentacosadiynoic acid
(5.00 g, 13.34 mmol) in THF (50 mL) was added at 0 °C under
Ar atmosphere. The resulting mixture was stirred for 1 h 45
min at room temperature (RT). After this time, the reaction was
quenched by adding 1 N HCl solution (25 mL), and the mixture
was concentrated to dryness under reduced pressure. The
aqueous layer was extracted with EtOAc (2 × 30 mL), and the
combined organic layers were washed with 1 N HCl (20 mL)
* To whom correspondence should be addressed. E-mail: remy@
bioorga.u-strasbg.fr, wagner@bioorga.u-strasbg.fr.
† LFCS, CNRS-UdS.
‡ Laboratoire de Chimie Ge´ne´tique.
§ Institut Charles Sadron, CNRS UPR22.
| Universita¨t Regensburg and Universidad de Zaragoza.
10.1021/jp104911e  2010 American Chemical Society
Published on Web 09/14/2010

12496 J. Phys. Chem. B, Vol. 114, No. 39, 2010
Morin et al.
Figure 1. Preparation of compounds.
raphy (eluting with EtOAc/cyclohexane: 2/8), which afforded
compound 4 as colorless oil (181.6 mg, 60% yield).
were combined, washed with a saturated solution of NaCl (2 ×
5 mL), dried over anhydrous Na2SO4, and finally filtrated and
concentrated under reduced pressure. The residue was submitted
to silica-gel chromatography to yield compound 8 as a white
solid (59.3 mg, 35% yield).
N-Methyl-N-(pentacosa-10,12-diyn)-propylamine (5). N-
Methyl-N-(pentacosa-10,12-diyn)-propylamine (5) was prepared
by the same procedure as compound 3, using pentacosa-10,12-
diynyl-4-methylbenzenesulfonate (305 mg, 0.59 mmol), Na2CO3
(69.1 mg, 0.65 mmol), and N-methylpropylamine (86.7 mg, 1.18
mmol) in CH3CN (20 mL). Purification by silica-gel chroma-
tography (eluting with EtOAc/cyclohexane: 2/8) afforded
compound 5 as a colorless oil (169.4 mg, 69% yield).
N,N-Diethyl-pentacosa-10,12-diyn-1-amine (6). N,N-Dieth-
yl-pentacosa-10,12-diyn-1-amine (6) was prepared by the same
procedure as compound 3, using pentacosa-10,12-diynyl-4-
methylbenzenesulfonate (7.14 g, 13.86 mmol), Na2CO3 (7.35
g, 69.3 mmol), and diethylamine (5.07 g, 69.3 mmol). Purifica-
tion by alumina-gel chromatography (eluting with EtOAc/
cyclohexane: 5/95) afforded compound 6 as a colorless oil (2.36
g, 41% yield).
Pentacosan-1-ol (7). To a stirred solution of lithium alumi-
num hydride (35.7 mg, 0.94 mmol) in THF (5 mL), a solution
of pentacosanoic acid (200 mg, 0.52 mmol) in anhydrous THF
(10 mL) was added at 0 °C under Ar atmosphere. The resulting
solution was stirred for one night at RT. Then, the reaction was
quenched with 1 N HCl solution (5 mL) and the mixture
concentrated to dryness under reduced pressure. The aqueous
layer was extracted with CH2Cl2 (2 × 5 mL) and the organic
phases combined and washed with 1 N HCl (3 × 5 mL). After,
it was dried over anhydrous Na2SO4, and it was filtered and
concentrated under reduced pressure to afford compound 7 as
a white solid (192.69 mg, 65% yield).
N-Methyl-N-pentacosapropargylamine (9). To a stirred
solution of pentacosa-4-methylbenzenesulfonate (59 mg, 0.11
mmol), and NaH (13.2 mg, 0.33 mmol, 60% dispersion in
mineral oil) was added N-methylpropargylamine (19 µL, 0.22
mmol). The solution was stirred at 80 °C for 48 h. The solvent
was removed under reduced pressure, and the residue was
poured into a saturated solution of NaHCO3 (15 mL). The
aqueous layer was extracted with CH2Cl2 (2 × 10 mL), and the
organic layers were combined, washed with a saturated solution
of NaCl (10 mL), dried over anhydrous Na2SO4, filtered, and
concentrated under vacuum. The residue was purified by silica-
gel chromatography (eluting with EtOAc/cyclohexane: 2/8) to
yield compound 9 as a colorless oil (3.54 g, 79% yield).
Scanning Electron Microscopy (SEM). Samples of the
material were prepared by the freeze-drying (FD) method: A
vial (1 mL) containing the corresponding sample was frozen in
liquid nitrogen or dry ice/acetone, and the sample was im-
mediately evaporated under reduced pressure (0.6 mm Hg)
overnight at room temperature. A fibrous solid was obtained,
which was placed on top of a tin plate and shielded by Pd/Au.
Transmission Electron Microscopy (TEM). Ten microliters
of the samples were allowed to be adsorbed for 1 min onto
copper grids (300 mesh) coated with formar. The excess solvent
was removed by touching the edges with a small piece of
Whatman paper. Samples were stained for 30 s using 2%
aqueous uranyl acetate.
Pentacosa-4-methylbenzenesulfonate (8). To a stirred solu-
tion of de pentacosa-1-ol (120 mg, 0.32 mmol) in CH2Cl2 (15
mL) were successively added p-toluenesulfonyl chloride (93.1
mg, 0.49 mmol), NaH (14.1 mg, 0.35 mmol, 60% dispersion in
mineral oil), and catalytic amounts of DMAP. The resulting
suspension was stirred at 50 °C overnight. Then, a saturated
solution of NaHCO3 (15 mL) was added, and the aqueous layer
was extracted with CH2Cl2 (2 × 10 mL). The organic layers
Differential Scanning Calorimetry (DSC). DSC character-
ization was performed on a Perkin-Elmer Diamond. A heating
rate of 5 °C/min was used. The systems were prepared in test
tubes beforehand, and then approximately 50 mg of material
were transferred into a stainless steel sample. The instrument
was calibrated with indium.

Morphology of Ammonium-Based Amphiphiles
J. Phys. Chem. B, Vol. 114, No. 39, 2010 12497
Small-Angle Neutron Scattering. Samples were prepared
directly in quartz cells from Hellma with an optical path of 5
mm by using D2O + 0.1 M DCl as solvent. Concentrations of
0.005 g/cm3, 0.01 g/cm3, and 0.015 g/cm3 were prepared.
The experiments were performed with the D11 camera located
at the Institut Laue-Langevin (Grenoble, France). A wavelength
of λm ) 0.6 nm was used with a wavelength distribution
characterized by a full width at half-maximum, ∆λ/λm, of about
9%. Neutron detection was achieved with a built-in two-
dimensional sensitive detector (further details are available at
theILLWebsitehttp://www.ill.fr).Byvaryingthesample-detector
distance (34 m, 10 m, 5 m) the available q-range was 0.03 < q
(nm-1) < 2.1 where q ) (4π/λ) sin(θ/2), θ being the scattering
angle. Detector efficiency correction was achieved by means
of light water. Corrections for transmissions as well as subtrac-
tion from the intensity scattered by the empty cell and
renormalization by the water cross-section were systematically
performed prior to solvent scattering and incoherent background
subtractions.14 The method of Fazel et al.15 was used to subtract
the incoherent scattering caused by the hydrogen atoms of the
molecule:
Figure 2. A: Self-supporting structures of 3 (C ) 0.001 g/cm3 in 1 M
HCl). B: System pictures obtained by optical microscopy (scale bar )
270 µm). C: SEM (scale bar ) 5 µm). D: TEM (scale bar ) 0.5 µm).
TABLE 1: Solubilization Properties of Compound 3 in
Neutral and Acidic Solutions
NH
Iinc ) ꢀ × 8.65
VH
aqueous solutionsa
phaseb,c
water
NaCl
HCl
CH3CO2H
TCA
HCO2H
H2SO4
HF
S
S
lathsd
S
in which ꢀsp is the amphiphile fraction, NH is the number of
proton per monomer, and VH the molar volume of the am-
phiphile. The contrast factor, KN, for the molecule in D2O was
calculated as follows:
S
S
TS
A
2
HBr
HI
HPF6
AgBF4
HClO4
A
A
A
A
V
D2O
NA AH -
× AD O 10-24
(
)
2
VH
KN )
2
mH
A
a 1 M solutions were used. b Compound concentration ) 0.005
g/cm3. c Abbreviations: S ) clear solution; TS ) turbid solution; A
) aggregates. d Laths were formed after 3 h.
where NA is Avogadro’s number, AH and AD O (cm-1) the
scattering amplitudes of the molecule and of 2 heavy water,
respectively, VD O the molar volume of heavy water, and mH
2
the molecular weight of N-methyl-N-(pentacosa-10,12-diyn)-
propargylamine (3).
We investigated the importance of the protonation state and
the nature of counterions on the laths formation, with various
types of acidic and neutral solutions. Results (see Table 1)
showed that the laths only appear with HCl solutions, and this
demonstrates that their structure is strongly correlated to the
presence of ammonium cation, acidic pH, and chloride coun-
terion. Aggregates that were observed with mineral acids did
not show any organized structure.
We then altered the chemical structure of the lipophilic amine
to determine what are parts of the molecules for lath structures.
Alteration on the head groups (allyl, propyl, and diethyl head-
groups) were investigated. Results (see Table 2) showed that
none of these analogues led to the formation of laths.
These findings illustrate the importance of the final alkyne
and suggest the existence of supramolecular interactions between
head groups, like π-hydrogen interactions between final alkynes
and ammoniums.16,17 Such interactions have been described to
be stronger with alkynes than with weaker π-bases like alkenes
and could explain the different behavior observed for compounds
4 and 5.
Results and Discussion
Compound 3 showed the ability to form a self-supporting
structure at 0.1% (w/w) in aqueous HCl (Figure 2A). These
observations were confirmed by optical microscopy, as shown
in Figure 2B, the material is composed of a dense tangle of
straight and long laths.
Laths are well-formed at room temperature and pH 2.
Increasing the temperature to 40 °C, as well as raising the pH
to 7 resulted in the complete dissolution of laths. When they
are returned to the initial conditions, their formation was
observed once again; this shows the reversible properties of the
system. These cycles could be repeated more than ten times
without changing any of its properties.
The formation kinetics are very slow and are strongly cor-
related to amphiphile and acid concentrations. Samples at 0.1%
(w/w) formed laths after one week at 25 °C with aqueous HCl
0.1 M and after 3 days in aqueous HCl 1 M. Increasing the
amphiphile concentration up to 0.5% (w/w) provided laths after
2 days in 0.1 M aqueous HCl and after 3 h in 1 M aqueous
HCl. At 4 °C, formation kinetics was twice as fast.
The diyne group helps solubilization and probably contributes
to the self-organization of the molecules by rigidifying the
hydrophobic tail and providing π-interactions.

12498 J. Phys. Chem. B, Vol. 114, No. 39, 2010
Morin et al.
TABLE 2: Solubilization of Compounds 3, 4, 5, 6, and 9 in
Hydrochloric Acid Solutiona
compoundb
HCl (1 M)c
3
4
5
6
9
lathsd
VS
VS
S
Figure 4. Sketch of the possible chevron-like arrangement of 3
accounting for the 4.9 nm spacing d observed in SANS.
I
a Saturated amphiphile
9
was strongly insoluble in aqueous
solution. b Compound concentration ) 0.005 g/cm3. c Abbreviations:
S ) clear solution; VS ) viscous solution; I ) insoluble. d Laths
were formed at RT after 3 h.
domain of distances. In what is defined as the transitional
domain (0.1 < q (nm-1) < 0.7) the curve varies linearly. For
0.7 < q (nm-1) < 1 a typical Porod regime is observed. For q >
1 nm-1 a maximum is obviously seen at q ) 1.28 nm-1. This
maximum is also observed when plotting I(q) versus q, which
implies the presence of ordered structures. The neutron scattering
outcomes are consistent with the TEM observations that suggest
rather thin laths (see Supporting Information). The maximum
observed at q ) 1.28 nm-1 is clearly related to the organization
of the amphiphile within the laths. Calculating the associated
distance by means of Bragg’s law yields d ) 4.9 nm. A simple
head-to-head or tail-to-tail model can account for this value as
shown in Figure 4. This value stands for the distance between
planes containing the polar heads, provided the molecules are
tilted by approximately 45°.
The fact that the scattering curve increases again for q > 1.28
nm-1 is possibly due to free molecules not being incorporated
in the laths.
Figure 3. Small-angle scattering curves plotted as q4I(q) vs q for
molecule 3 in D2O + DCl for concentrations of C ) 0.015 g/cm3 (b)
and C ) 0.01 g/cm3 (O). The solid lines highlight the different scattering
regimes.
Note that, if the laths are hollow, as may be the case in view
of the TEM and the SEM pictures, this cannot be directly shown
by the present neutron diffraction experiments but suggested
by the absolute intensity calculated. An absolute density of F
) 0.46 g/cm3 is obtained (see Supporting Information). As a
compact packing of such molecules is rather expected to yield
a value around 1 g/cm3, this may suggest the occurrence of
hollow laths as opposed to solid ones.
The size and morphology of the objects were studied by
scanning electron microscopy (SEM). As shown in Figure 2C,
these objects appear to be straight and hollow laths. These
unusual structures are up to 1 mm long and about 0.5-2 µm
wide and display a smooth surface. These dimensions were
confirmed by TEM, which also revealed that the laths are hollow
(Figure 2D). Additional pictures are available in Supporting
Information (Figures S1-S3).
Diacetylenic amphiphiles are well-known to self-assemble
into cylindrical systems, by twisting the amphiphile bilayer.18
In this case, the fibers do not show any tubular or helical
systems, but are a rectangular and straight structure.
Differential scanning calorimetry (DSC) experiments were
also performed. The laths were analyzed at two concentrations
diluted in water/HCL 0.1 M, namely C ) 0.001 g/cm3 and C
) 0.005 g/cm3 (see Supporting Information). Only one endot-
herm is seen on heating that peaks at T ) 39 ( 1 °C. This
clearly shows that these objects result from a first-order
transition. The laths formation proceeds in two days as no
exotherm was detected on cooling at 10 °C/min. The melting
enthalpy associated with the compound is about to 10 ( 4 J/g
once the DSC value is rescaled by concentration (namely for
100% amphiphile compound), which suggests the occurrence
of rather weak interactions between molecules within the object.
This value is typical of what is found for liquid crystalline
systems or thermoreversible polymer gels.19 Small-angle neutron
scattering (SANS) experiments gave an insight on laths struc-
tures. Typical scattering curves are displayed in Figure 3. There
is no significant change of the scattering pattern with concentra-
tion, except some discrepancy at the largest q-values. This
pattern displays several features of interest. In the very low-q
range (q < 0.1 nm-1) the curve is monotonously increasing,
which implies that no remarkable organization is present in this
Conclusion
We have shown the formation of new supramolecular
nanostrutures based on the self-arrangement of N-methyl-N-
(pentacosa-10,12-diyn)-propargylamine (3) at low concentrations
into micrometric laths. Our results have shown importance of
the chemical structure for system formation, in particular the
final alkyne group and chloride counterion. DSC experiments
confirmed a first-order transition, which is the result of an
organized structure. Visualization by electronic microscopy and
SANS experiments suggest possible structures of hollow laths.
Such a metastable system, which is on the threshold between
crystallization and solubilization, could be improved to exhibit
gel-base material properties. Moreover, the final alkyne groups
allow easy chemical modifications to create cross-linked gel-
like systems in the future.
Appendix
The N-methyl-N-(pentacosa-10,12-diyn)-propargylamine (3)
of chemical formula C29H50N possesses a very high neutronic
contrast in the mixture D2O/DCl due to the large number of
hydrogen atoms. As a result, a very high signal/noise ratio is
expected particularly for low-concentrated systems for which
the incoherent background due to hydrogen atoms will be low
enough.
As SEM has revealed lath-like structures, we shall attempt
to account for these results by using a model derived by
Mittelbach and Porod,14 while also considering dispersion
in lath dimensions, particularly thickness dispersion. Let us

Morphology of Ammonium-Based Amphiphiles
J. Phys. Chem. B, Vol. 114, No. 39, 2010 12499
consider a lath of length Lc, width lc, and thickness δc. On
the basis of the SEM observations it turns out that the
following conditions are fulfilled: qLc . 1 and qlc . 1. The
form factor of a lath of length Lc, width lc, and thickness δc,
for qLc . 1, Lc . lc, and lc > δc has been derived by
Mittelbach and Porod:20
sections, the following distribution had been chosen on the
basis of experimental results:
w(δc) ∝ 1/δc
(8)
considering the transitional regime defined by Guenet,22
wherein there are no conditions on the product qδ, and using
the same procedure for calculating eq 8, one eventually
obtains:
P(q) ≈
π/2 sin2(ql cos θ/2) sin2(qδc sin θ/2)
π
2
π
c
×
×
sin θ dθ
∫
(qlc cos θ/2)2
(qδc sin θ/2)2
0
qLc
2
1
q4IA(q) ≈ 2πF qπ -
(9)
(1)
(
)
δmax log(δmax/δmin
)
if lc . δc and qlc . 1 then the above equation can be
rewritten:
by means of a q4I(q) versus q plot, a linear variation should
be obtained in the so-called transitional regime. Then,
defining qo for q4I(q) ) 0 δmax can be calculated through:
sin2(qδc/2)
(qδc/2)2
2
qLc
P(q) ≈
×
×
2
qo )
(10)
sin2(qlc cos θ/2)
(qlc cos θ/2)2
πδmax
π/2
× sin θ dθ (2)
∫
0
[
]
for qδmin . 1, the intensity reaches the Porod regime for
solid objects,23,24 and considering that the average value of
sin2X oscillates around 1/2 for Xf∞, it is written:
since under these conditions the term
sin2(qlc cos θ/2)
(qlc cos θ/2)2
b
2πF
2
δc
I(q) ≈
×
× w(δc) dδc b w(δ ) dδ
∫
∫
c
c
(3)
q4
a
a
/
(11)
(12)
rapidly equals zero except for qlc cos θ ≈ 0, that is, for θ ≈
π/2 as highlighted by Pringle and Schmitt.21 This term is
actually reminiscent of a Dirac function. Integration of eq 2
then yields:
which eventually yields:
q4I(q) ≈
4πF
δ
〉
c n
〈
sin2(qδc/2)
2π
where 〈δc〉n is the number averaged value of δc. A simple
calculation eventually shows that:
P(q) ≈
×
(4)
q2lcLc
(qδc/2)2
1
1
δmin
1
δmax
1
the intensity for a lath of mass M is therefore:
)
-
×
(13)
[
]
δ
log(rmax/rmin)
〈
〉
c n
sin2(qδc/2)
2π
I(q) ≈ M ×
×
(5)
as a result, the scattering vector q* at which the transitional
regime and the Porod regime intersect in a q4I(q) versus q
representation is expressed as:
q2lcLc
(qδc/2)2
which can be written by introducing the density of the lath
F:
2
q* )
(14)
πδmin
sin2(qδc/2)
2πF
I(q) ≈
×
(6)
interestingly, the ratio qo/q* is:
q4
δc/4
qo
δmin
Now, if there is some dispersity of δc (a collection of laths
with different thicknesses), then one has to take the average
value of the intensity:
)
(15)
q*
δmax
It is worth stressing that all of these relations are identical to
those calculated for fibrils with a circular cross-section.20
These equations pertain to the present case. As seen in
Figure 5, the extrapolation to q4I(q) ) 0 in the transitional
regime yields δmax ≈ 6.5 nm. This value is independent of
concentration and is therefore a characteristic of the laths.
The intersection between the transitional regime and the
b sin2(qδ /2)
× w(δc)dδc b w(δ ) dδ
(7)
2πF
c
∫
∫
c
c
q4
a
a
δc/4
/
where a ) δmin and b ) δmax are, namely, the lowest and the
largest thicknesses. In the case of fibrils with circular cross

12500 J. Phys. Chem. B, Vol. 114, No. 39, 2010
Morin et al.
of the material by DSC experiments and visualization of the
material by SEM and TEM. This material is available free of
charge via the Internet at http://pubs.acs.org.
References and Notes
(1) Fyfe, M. C. T.; Stoddart, J. F. Acc. Chem. Res. 1997, 30, 393.
(2) Yagai, S.; Kitamura, A. Chem. Soc. ReV. 2008, 37, 1520.
(3) Ryu, J.-H.; Hong, D.-J.; Lee, M. Chem. Commun. 2008, 1043.
(4) Yamamoto, Y.; Fukushima, T.; Suna, Y.; Ishii, N.; Saeki, A.; Seki,
S.; Tagawa, S.; Taniguchi, M.; Kawai, T.; Aida, T. Science 2006, 314, 1761.
(5) Akihiro, K.; Aya, K.; Kensuke, O.; Yuichi, Y.; Kazunori, K. Angew.
Chem., Int. Ed. 2007, 46, 6085.
(6) Lin, C.; Liu, Y.; Yan, H. Biochemistry 2009, 48, 1663.
(7) Hill, J. P.; Jin, W.; Kosaka, A.; Fukushima, T.; Ichihara, H.;
Shimomura, T.; Ito, K.; Hashizume, T.; Ishii, N.; Aida, T. Science 2004,
304, 1481.
(8) Fuhrhop, J. H.; Boettcher, C. J. Am. Chem. Soc. 1990, 112, 1768.
(9) Debapratim, D.; Antara, D.; Sangita, R.; Rajendra Narayan, M.;
Sisir, D.; Prasanta Kumar, D. Chem.sEur. J. 2006, 12, 5068.
(10) Chen, D.; Jiang, M. Acc. Chem. Res. 2005, 38, 494.
(11) Shimizu, T.; Masuda, M.; Minamikawa, H. Chem. ReV. 2005, 105,
1401.
(12) Zhou, Y.; Shimizu, T. Chem. Mater. 2007, 20, 625.
(13) Thauvin, C.; Rickling, S.; Schultz, P.; Celia, H.; Meunier, S.;
Mioskowski, C. Nat. Nano 2008, 3, 743.
(14) Neutron, X-ray and light scattering; Cotton, J. P., Ed.; Elsevier:
Amsterdam, 1991.
(15) Fazel, N.; Brulet, A.; Guenet, J.-M. Macromolecules 1994, 27, 3836.
(16) Laurence, C.; Graton, J.; Berthelot, M.; Besseau, F. O.; Le Questel,
J.-Y.; Luca˜sson, M.; Ouvrard, C.; Planchat, A.; Renault, E. J. Org. Chem.
2010, 75, 4105.
(17) Viswamitra, M. A.; Radhakrishnan, R.; Bandekar, J.; Desiraju, G. R.
J. Am. Chem. Soc. 1993, 115, 4868.
(18) Zhou, W.; Li, Y.; Zhu, D. Chem. Asian J. 2007, 2, 222.
(19) Guenet, J. M. Polymer-SolVent Molecular Compounds; Elsevier:
London, 2008.
(20) Mittelbach, P.; Porod, G. Acta Phys. Austriaca 1961, 14, 405.
(21) Pringle, O. A.; Schmidt, P. W. J. Appl. Crystallogr. 1971, 4, 290.
(22) Guenet, J.-M. J. Phys. II 1994, 4, 1077.
Figure 5. Small-angle scattering curves plotted as q4I(q) vs q for
compound 3 in D2O + DCl for a concentration of C ) 0.015 g/cm3
The solid line highlights the linear variation expected in the transitional
regime when the thickness distribution is of the type w(δ) ∼ δ-1
.
Porod21 regime provides q*. From 14 and 15 one obtains
δmin ≈ 1 nm, and 〈δ〉n ) 2.21 nm are derived. Note that q*,
and correspondingly δmin, are independent of concentrations.
As far as δmin and δmax are concerned, the neutron scattering
outcomes are consistent with the SEM observations that
suggest rather thin laths.
Acknowledgment. We would like to thank Dr. Nadia
Messaddeq and Christine Ruhlmann from the Imaging Center
of IGBMC for help with SEM and TEM images. The SANS
experiments have been performed at Institut Laue-Langevin
(Grenoble, France) on the D11 camera under the greatly
appreciated technical assistance of Dr. Ralph Schweins. E.M.
received a grant from MESR. D.D.D. is an Experienced
Research Fellow of the Alexander von Humboldt Foundation.
(23) Porod, G. Kolloid Z. 1951, 124, 83.
(24) Porod, G. Kolloid Z. 1952, 125, 51.
Supporting Information Available: Characterization and
NMR spectra of compounds 1-9 and thermal characterization
JP104911E